Evaluation of Gross Alpha
and Uranium Measurements
for MCL Compliance
Subject Area: Water Quality
Evaluation of Gross Alpha
and Uranium Measurements
for MCL Compliance
©2010 Water Research Foundation. ALL RIGHTS RESERVED
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Evaluation of Gross Alpha
and Uranium Measurements
for MCL Compliance
Prepared by:
Michael F. Arndt
Wisconsin State Laboratory of Hygiene
2601 Agriculture Drive, Madison, WI 53718
Jointly sponsored by:
Water Research Foundation
6666 West Quincy Avenue, Denver, CO 80235-3098
and
U.S. Environmental Protection Agency
Washington, D.C.
Published by:
©2010 Water Research Foundation. ALL RIGHTS RESERVED
DISCLAIMER
This study was jointly funded by the Water Research Foundation (Foundation) and the U.S.
Environmental Protection Agency (USEPA) under Cooperative Agreement No. CR-83110401. The
Foundation or USEPA assume no responsibility for the content of the research study reported in this
publication or for the opinions or statements of fact expressed in the report. The mention of trade
names for commercial products does not represent or imply the approval or endorsement of the
Foundation or USEPA. This report is presented solely for informational purposes.
Copyright © 2010
by Water Research Foundation
ALL RIGHTS RESERVED.
No part of this publication may be copied, reproduced
or otherwise utilized without permission.
ISBN 978-1-60573-096-7
Printed in the U.S.A.
©2010 Water Research Foundation. ALL RIGHTS RESERVED
CONTENTS
TABLES ........................................................................................................................................ xi
FIGURES ...................................................................................................................................... xv
LIST OF SYMBOLS .................................................................................................................. xxv
FOREWORD .......................................................................................................................... xxxvii
ACKNOWLEDGMENTS ....................................................................................................... xxxix
EXECUTIVE SUMMARY ........................................................................................................ xliii
CHAPTER 1: INTRODUCTORY CONCEPTS ........................................................................... 1
Introduction: Necessity of and Objectives of the Study ..................................................... 1
Organization of the Report.................................................................................................. 5
Measurement of the GAA ................................................................................................... 6
Radioactive Decay .............................................................................................................. 7
Radionuclide Populations ................................................................................................. 11
Alpha-Particle Range and Energy and Self-Absorption ................................................... 12
Ingrowth, Secular Equilibrium, and Decay Chains .......................................................... 14
Supported and Unsupported Activity................................................................................ 16
Chemistry of the Natural Radionuclides ........................................................................... 18
Disequilbrium: Recoil Enrichment ................................................................................... 20
A Survey of the Occurrence of the Radionuclides............................................................ 21
Some Common Misconceptions Concerning the GAA .................................................... 21
CHAPTER 2: VARIOUS FACTORS THAT AFFECT THE GAA ........................................... 23
Introduction ....................................................................................................................... 23
Dependence of the GAA on the Efficiencies of the Alpha Emitters and the Calibration
Standard ...................................................................................................................... 23
Geometry of Actual Sample Residues and the Dependence of the GAA on the Residue
Geometry..................................................................................................................... 26
Time Intervals that Affect the GAA ................................................................................. 29
Grab Samples and Quarterly Composite Samples ............................................................ 30
CHAPTER 3: METHODS ........................................................................................................... 31
Introduction ....................................................................................................................... 31
Materials and Instruments ................................................................................................. 31
Preparation of Ba(Ra)SO4 Residues for the Determination of the Efficiencies of the
224
Ra and 226Ra Decay Chains..................................................................................... 32
Preparation of Ba(Am)SO4 Residues for the Determination of 241Am Efficiencies ......... 33
Experiments to Qualitatively Characterize the Volatility of Polonium in Sample
Residues ...................................................................................................................... 33
v
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vi | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
Collection and Analysis of Groundwater Samples ........................................................... 34
Radiochemical Methods.................................................................................................... 34
Inorganic Methods ............................................................................................................ 35
CHPATER 4: GROSS ALPHA-PARTICLE ACTIVITY OF THE DECAY CHAINS ............. 37
Introduction ....................................................................................................................... 37
Geometry of the Residues: Uniform, Smooth, and Patch Residues ................................. 39
An Outline of the Determination of the GAA .................................................................. 39
Factors that Contribute to the Variablity of the GAA....................................................... 40
Notation Used ................................................................................................................... 40
The 238U Decay Chain....................................................................................................... 41
The 234U Decay Chain....................................................................................................... 42
The 226Ra Decay Chain ..................................................................................................... 42
The 210Po Decay Chain ..................................................................................................... 44
The 210Pb Decay Chain ..................................................................................................... 46
The 228Ra Decay Chain ..................................................................................................... 49
The 224Ra Decay Chain ..................................................................................................... 52
The 212Pb Decay Chain ..................................................................................................... 54
The GAA for Samples Containing Both 224Ra and 226Ra ................................................. 55
CHAPTER 5: CALCULATION OF THE GAA FOR A HYPOTHETICAL
EXAMPLE .............................................................................................................................. 57
Introduction ....................................................................................................................... 57
The GAA Due to the 238U Decay Chain ........................................................................... 58
The GAA Due to the 234U Decay Chain ........................................................................... 59
The GAA Due to the 226Ra Decay Chain .......................................................................... 59
The GAA Due to the 210Po Decay Chain .......................................................................... 60
The GAA Due to the 210Pb Decay Chain .......................................................................... 61
The GAA Due to the 228Ra Decay Chain .......................................................................... 63
The GAA Due to the 224Ra Decay Chain .......................................................................... 64
The GAA Due to the 212Pb Decay Chain .......................................................................... 65
The Total GAA ................................................................................................................. 65
CHAPTER 6: EFFECT OF OTHER ERRORS ON THE GAA AND THE URANIUM
CONCENTRATION............................................................................................................... 69
Introduction ....................................................................................................................... 69
Effect of Counting Error on the GAA............................................................................... 69
Problems with Uranium Methods and how They Affect the Uranium Concentration and
the Adjusted GAA....................................................................................................... 72
Miscellaneous Sources of Error in the GAA .................................................................... 75
CHAPTER 7: RADIOCHEMICAL COMPOSITION OF THE GROUNDWATER
SAMPLES............................................................................................................................... 77
Introduction ....................................................................................................................... 77
Violations and Potential False-Postive Violations ............................................................ 78
Uranium Results................................................................................................................ 79
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Contents | vii
Radium Results ................................................................................................................. 81
210
Po and 210Pb Results...................................................................................................... 85
CHAPTER 8: GROSS ALPHA-PARTICLE ACTIVITY OF THE GROUNDWATER
SAMPLES............................................................................................................................... 89
Introduction ....................................................................................................................... 89
Review of the Decay Chain’s Contribution to the GAA .................................................. 89
Sample Preparation ........................................................................................................... 90
Presentation of GAA Data ................................................................................................ 91
Group (1): Radium-Containing Samples .......................................................................... 93
Group (2):Uranium-Containing Samples .......................................................................... 95
Group (3): Radium-and-Uranium-Containing Samples.................................................. 100
Group (4): 210Po-Containing Samples ............................................................................. 100
Group (5): Samples that Contain Less than 2 pCi/L of Alpha Activity.......................... 101
Variability of the GAA Due to Variabilty of the Residue Geometry ............................. 101
Conclusions ..................................................................................................................... 105
CHAPTER 9: THE GROSS RADIUM ACTIVITY OF THE GROUNDWATER
SAMPLES............................................................................................................................. 129
Introduction ..................................................................................................................... 129
Experimental and Theoretical Calculation of the GRA .................................................. 130
Presentation of the GRA Data......................................................................................... 132
Experimental Results ...................................................................................................... 133
Conclusions ..................................................................................................................... 135
CHAPTER 10: METHODOLOGY ISSUES AND RECOMMENDATIONS ......................... 157
Introduction ..................................................................................................................... 157
Problems With Analyzing Radium-Containing Samples ............................................... 157
Problems With Uranium-Containing Samples................................................................ 158
Problems Due to Residue Geometry ............................................................................... 159
Problems Due to Residue Mass ...................................................................................... 159
Problems Due to Counting Error .................................................................................... 160
Problems With Long Sample Holding Times and Quarterly Composite Samples ......... 160
Problems With Ingrowth Periods .................................................................................... 160
Problems With Calibration Standards............................................................................. 161
Problems With Hard- and Soft-Water Samples .............................................................. 161
Inconsistencies Between GAA Method Types ............................................................... 161
Problems With Uranium Methods .................................................................................. 162
Factors Affecting Evaporation Methods That Require Further Research ...................... 163
REFERENCES ............................................................................................................................165
ABBREVIATIONS .....................................................................................................................171
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viii | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
APPENDIX A: CURRRENT NATIONAL PRIMARY DRINKING WATER
REGULATIONS FOR RADIONUCLIDES IN WATER .................................................... 173
Introduction ..................................................................................................................... 173
Maximum Contaminant Levels....................................................................................... 174
Monitoring Baseline........................................................................................................ 175
Compliance Flowcharts .................................................................................................. 176
Information Public Water Systems Must Supply Customers ......................................... 179
Consumer Confidence Reports ........................................................................... 179
Public Notification .............................................................................................. 180
Laboratory Certification and EPA-Approved Analytical Methods ................................ 181
Best Available Technologies for Water Treatment ........................................................ 182
APPENDIX B: WATER TREATMENT OPTIONS .................................................................. 185
Reverse Osmosis for Removal of Uranium, Thorium, Radium, and Polonium ............. 185
Electrodialysis for Removal of Radionuclides ............................................................... 186
Water Softening to Remove Hardness, Radium, and Uranium ...................................... 188
Cation-Exchange to Remove Hardness and Radium .......................................... 188
Lime-Soda Softening to Remove Hardness, Radium, and Uranium .................. 189
Anion-Exchange for Uranium and Polonium Removal .................................................. 190
Iron/Aluminum Coagulation-Filtration for Iron, Uranium, and Polonium Removal. .... 190
Preformed Hydrous MnO2 Process for Iron, Manganese, and Radium .......................... 191
Removal of Radium By Manganese Greensand Filtration ............................................. 191
Coprecipitation of Radium With Barium Sulfate ........................................................... 192
Adsorption of Radium on MnO2-Impregnated Resins and Acrylic Fibers ..................... 192
Removal of Urnanium, Radium, Lead, and Polonium With Granular Activated Carbo
Filtration.................................................................................................................... 192
Removal of Uranium, Radium, Lead, and Polonium by Nanofiltration ......................... 193
Removal of Uranium and Arsenic by Hydrous Iron Oxide Nanoparticulate Resin ....... 194
APPENDICES C–P INCLUDED ON A CD WITH THE PRINTED REPORT
APPENDIX C: DETECTOR EFFICIENCIES IN BA(RA)SO4 RESIDUES ............................ 195
Introduction ..................................................................................................................... 195
Efficiencies of the 226Ra Decay Chain ............................................................................ 195
Efficiencies of the 224Ra Decay Chain ............................................................................ 198
Efficiency of 228Th .......................................................................................................... 202
Efficiency of 210Po .......................................................................................................... 202
Efficiencies of 234U and 238U........................................................................................... 204
APPENDIX D: EFFICIENCIES IN RESIDUES OF ARBITRARY COMPOSITION............. 205
APPENDIX E: EFFICIENCIES IN RESIDUES OF ARBITRARY GEOMETRY .................. 207
APPENDIX F: EQUATIONS FOR THE CALCULATION OF THE CONTRIBUTION OF
ALPHA EMITTERS TO THE GROSS ALPHA-PARTICLE ACTIVITY ......................... 209
Introduction ..................................................................................................................... 209
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Contents | ix
Some Preliminaries ......................................................................................................... 209
Calculation of the Efficiency of the 230Th Calibration Standard .................................... 210
The GAA Due to the 234U Decay Chain ......................................................................... 211
The GAA Due to the 238U Decay Chain ......................................................................... 213
The GAA Due to the 226Ra Decay Chain ........................................................................ 213
The GAA Due to 210Po Decay Chain .............................................................................. 214
The GAA Due to the 210Pb Decay Chain ........................................................................ 214
The GAA Due to the 224Ra Decay Chain ........................................................................ 215
The GAA Due to the 212Pb Decay Chain ........................................................................ 216
The GAA Due to the 228Ra Decay Chain ........................................................................ 216
APPENDIX G: EFFICIENCY OF THE BOTTOM LAYER OF THE SAMPLE RESIDUE ... 221
APPENDIX H: ESTIMATION OF THE EXTENT OF THE DETECTOR
CONTAMINATION BY 220RN ........................................................................................... 223
APPENDIX I: THE CONVERSION FACTOR BETWEEN URANIUM ACTIVITY AND
CONCENTRATION............................................................................................................. 225
APPENDIX J: ESTIMATE OF THE COUNTING ERROR ..................................................... 227
APPENDIX K: ALPHA SPECTROCOPY METHOD FOR 210PO ........................................... 229
APPENDIX L: ALPHA SPECTROSCOPY METHOD FOR 224RA ......................................... 231
Introduction ..................................................................................................................... 231
Equipment ....................................................................................................................... 231
Reagents .......................................................................................................................... 231
Preparation of the BaSO4 Seeding Suspension ............................................................... 232
Experimental Method...................................................................................................... 232
Calculations..................................................................................................................... 233
APPENDIX M: GROSS ALPHA-PARTICLE ACTIVITY DATA .......................................... 239
APPENDIX N: GROSS RADIUM ACTIVITY DATA............................................................. 271
APPENDIX O: RADIOCHEMICAL DATA ............................................................................. 283
Uranium Data .................................................................................................................. 283
Radium Data ................................................................................................................... 285
Thorium Data .................................................................................................................. 287
210
Pb and 210Po Data ........................................................................................................ 289
APPENDIX P: INORGANIC DATA ......................................................................................... 293
Metal Concentrations of the Samples ............................................................................. 293
Concentrations of Some of the Anions of the Samples .................................................. 295
Alkalinity, pH, Conductivity, Turbidity, and Dissovled Silica (SiO2) ........................... 297
©2010 Water Research Foundation. ALL RIGHTS RESERVED
©2010 Water Research Foundation. ALL RIGHTS RESERVED
TABLES
1.1
Range-energy characteristics of alpha emitters .................................................................13
3.1
Radiochemical methods .....................................................................................................35
3.2
Inorganic methods ..............................................................................................................36
4.1
Decay chains of the 238U decay series................................................................................38
4.2
Decay chains of the 232Th decay series ..............................................................................38
5.1
Radiological composition of the sample ............................................................................57
5.2
Time intervals ....................................................................................................................58
5.3
Sample with a 60-mg residue and 2 pCi/L of 238U ............................................................59
5.4
Sample with a 60-mg residue and 5 pCi/L of 234U ............................................................59
5.5
Grab and composite sample with a 60-mg residue and 3 pCi/L of 226Ra ..........................60
5.6
Grab sample with a 60-mg residue and 5 pCi/L of 210Po ...................................................61
5.7
Quarterly Composite sample with a 60-mg residue and 5 pCi/L of 210Po .........................61
5.8
Grab sample with a 60-mg residue and 5 pCi/L of 210Pb ...................................................62
5.9
Quarterly composite with a 60-mg residue and 5 pCi/L of 210Pb ......................................62
5.10
Grab sample with a 60-mg residue and 3 pCi/L of 228Ra ..................................................63
5.11
Quarterly composite sample with a 60-mg residue and 3 pCi/L of 228Ra ..........................63
5.12
Grab sample with a 60-mg residue and 4 pCi/L of 224Ra ..................................................64
5.13
Composite sample with a 60-mg residue and 4 pCi/L of 224Ra .........................................65
5.14
Grab and composite sample with a 60-mg residue and 4 pCi/L of 212Pb ..........................65
5.15
The total GAA for a grab sample with a patch residue......................................................67
5.16
The total GAA for a grab sample with a smooth residue ..................................................67
5.17
The total GAA for a quarterly composite sample with a patch residue .............................67
xi
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xii | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
5.18
The total GAA for a quarterly composite sample with a smooth residue ..........................67
6.1
Percent chance of observing the decay in four atoms ........................................................70
6.2
Percent chance of observing decay in 1000 atoms ............................................................70
6.3
The error in the GAA .........................................................................................................71
6.4
EPA-approved methods for uranium .................................................................................73
7.1
Classification of Some of the samples ...............................................................................78
7.2
Classification of Some of the samples ...............................................................................79
8.1
Samples Groups .................................................................................................................93
8.2
Group (1): Radium-containing samples (44 samples) .......................................................94
8.3
Samples that may have a GAA violation at 30 days but not at 3 hours for Standard
Methods 7110C ......................................................................................................95
8.4
Samples predominately containing uranium decay chains (19 samples)...........................96
8.5
Samples with a GAA violation where there is no uranium violation. ...............................99
8.6
Samples that contain significant amounts of uranium and radium decay chains (9
samples). ..............................................................................................................100
8.7
Samples that predominately contain either uranium and 210Po decay chains or just the
210
Po decay chain (5 samples) ..............................................................................101
9.1
Fit of the GRA data to the model curves (78 samples) ....................................................135
A.1
NPDWR; Radionuclides; final rule; 200 .........................................................................175
A.2
Uranium methods .............................................................................................................178
A.3
Standard Health Effects Language for CCR and Public Notification..............................180
A.4
List of BAT along with Water Quality Range and Limitations and Operator Skill for
PWSs serving 25-10,000 People ..........................................................................182
A.5
Limitations in BAT for PWS that serve 25-10,000 people ..............................................183
A.6
BAT according to PWS Size. Numbers correspond to those technologies listed in
Table A.4..............................................................................................................183
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Tables | xiii
C.1
Fit parameters to Eqn. (C.6) .............................................................................................198
D.1
The composition of a groundwater sample (Stumm and Morgan 1970) .........................205
L.1
Full energy peaks of 133Ba ...............................................................................................233
M.1
Gross alpha-particle activity data for samples .................................................................239
N.1
Gross radium activity data for samples ............................................................................271
O.1
238
U, 235U, and 234U activities of the samples...................................................................283
O.2
224
Ra, 226Ra, and 228Ra activities of the samples ..............................................................285
O.3
228
Th, 230Th, and 232Th activities of the samples ..............................................................287
O.4
210
Pb and 210Po activities of the samples ..........................................................................289
P.1
Metal concentrations of the samples ................................................................................293
P.2
Concentrations of the anions of the samples....................................................................295
P.3
Alkalinity, pH, conductivity, turbidity, and dissolved silica (SiO2) of the samples .......297
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©2010 Water Research Foundation. ALL RIGHTS RESERVED
FIGURES
1.1
Sample-detection system .....................................................................................................7
1.2
The 238U decay series ...........................................................................................................8
1.3
The 232Th decay series .........................................................................................................9
1.4
Radionuclide populations corresponding to 1 pCi of activity ...........................................12
1.5
Secular equilibrium between 226Ra and 222Rn ....................................................................15
1.6
Ingrowth of 228Ra progeny .................................................................................................17
1.7
Ingrowth of 210Po from 210Pb .............................................................................................19
1.8
Recoil of 234Th and enrichment of 234U relative to 238U ....................................................20
2.1
Mass-efficiency curve for 230Th .........................................................................................24
2.2
Picture of a sample with a patch residue ............................................................................27
2.3
Plot of σ/σmax versus x contoured with values of e. ...........................................................28
4.1
The GAA due to 238U in a grab or quarterly composite sample ........................................41
4.2
The GAA due to 234U in a grab or quarterly composite sample ........................................42
4.3
The GAA for grab and quarterly composite samples containing 226Ra and having a
smooth residue .......................................................................................................43
4.4
The GAA for grab and quarterly composite samples containing 226Ra and having a patch
residue ....................................................................................................................43
4.5
The GAA for a 210Po-containing grab sample with a smooth residue ...............................44
4.6
The GAA for a 210Po-containing grab sample with a patch residue ..................................45
4.7
The GAA for a 210Po-containing composite sample with a smooth residue ......................45
4.8
The GAA for a 210Po-containing composite sample with a patch residue .........................46
4.9
The GAA for a grab sample with unsupported 210Pb and a smooth residue ......................47
4.10
The GAA for a grab sample with unsupported 210Pb and a patch residue .........................48
xv
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xvi | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
4.11
The GAA for a composite sample with unsupported 210Pb and a smooth residue ............48
4.12
The GAA for a composite sample with unsupported 210Pb and a patch residue................49
4.13
The GAA for a grab sample containing 228Ra and having a smooth residue .....................50
4.14
The GAA for a grab sample containing 228Ra and having a patch residue ........................50
4.15
The GAA for a composite sample containing 228Ra and having a smooth residue ...........51
4.16
The GAA for a composite sample containing 228Ra and having a patch residue ..............51
4.17
The GAA for a grab sample containing 224Ra and having a smooth residue .....................52
4.18
The GAA for grab sample containing 224Ra and having a patch residue...........................53
4.19
The GAA for grab sample containing 212Pb and having a smooth residue ........................54
4.20
The GAA for a grab sample containing 212Pb and having a patch residue ........................55
4.21
The GAA for a grab sample containing 224Ra and 226Ra and with T1 = 1 d ......................56
6.1
Plot of C versus A1/A2 ........................................................................................................74
6.2
Volatility of polonium........................................................................................................76
7.1
Map of sample collection sites in the Continental United States. A circle (●) indicates a
site where one sample was taken, a square (■) indicates a site where two samples
were taken, and triangle (▲) indicates a site where three samples were taken. ....77
7.2
234
7.3
Histogram of the ratio of the 234U activity to the 238U activity ..........................................80
7.4
226
Ra activity versus 228Ra activity ....................................................................................81
7.5
224
Ra activity versus 228Ra activity ....................................................................................82
7.6
Histogram of the ratio of the 224Ra activity to the 228Ra activity .......................................84
7.7
Plot of 226Ra versus the total uranium activity ...................................................................84
7.8
Histogram showing the 210Po distribution in the samples..................................................86
7.9
Histogram showing the 210Pb distribution in the samples..................................................86
U activity versus 238U activity........................................................................................80
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Figures | xvii
7.10
Plot of the 210Po activity versus the 210Pb activity .............................................................87
7.11
Plot of the 210Po activity versus the total uranium activity ................................................88
8.1
Example of a GAA plot for sample 8 (RR093663) ...........................................................92
8.2
Three distributions of uranium in sample residues ............................................................96
8.3
Ratio of GAA to uranium activity versus mol fraction of Ca and Mg ..............................97
8.4
Values of σ2/GAA plotted in increasing order ................................................................103
8.5
A plot of σ1/GAA versus residue mass for all sample points where GAA > 3.75
pCi/L ....................................................................................................................104
8.6
A plot of σ1/GAA versus residue mass for all sample points where GAA > 3.75 pCi/L
and σ2/GAA < 0.06. .............................................................................................104
8.7
GAA plot for sample 1 (RQ091434) ...............................................................................108
8.8
GAA plot for sample 2 (RQ091435) ...............................................................................108
8.9
GAA plot for sample 3 (RQ091436) ...............................................................................108
8.10
GAA plot for sample 4 (RQ091437) ...............................................................................108
8.11
GAA plot for sample 5 (RQ091438) ...............................................................................109
8.12
GAA plot for sample 6 (RQ091439) ...............................................................................109
8.13
GAA plot for sample 7 (RQ091440) ...............................................................................109
8.14
GAA plot for sample 8 (RQ091441) ...............................................................................109
8.15
GAA plot for sample 9 (RQ091442) ...............................................................................110
8.16
GAA plot for sample 10 (RQ091444) .............................................................................110
8.17
GAA plot for sample 11 (RQ091713) .............................................................................110
8.18
GAA plot for sample 12 (RQ091720) .............................................................................110
8.19
GAA plot for sample 13 (RQ091721) .............................................................................111
8.20
GAA plot for sample 14 (RQ091722) .............................................................................111
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xviii | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
8.21
GAA plot for sample 15 (RQ091723) .............................................................................111
8.22
GAA plot for sample 16 (RQ091724) .............................................................................111
8.23
GAA plot for sample 17 (RQ091725) .............................................................................112
8.24
GAA plot for sample 18 (RQ091726) .............................................................................112
8.25
GAA plot for sample 19 (RQ091751) .............................................................................112
8.26
GAA plot for sample 20 (RQ091992) .............................................................................112
8.27
GAA plot for sample 21 (RQ091993) .............................................................................113
8.28
GAA plot for sample 22 (RQ091994) .............................................................................113
8.29
GAA plot for sample 23 (RQ091995) .............................................................................113
8.30
GAA plot for sample 24 (RQ091996) .............................................................................113
8.31
GAA plot for sample 25 (RQ091997) .............................................................................114
8.32
GAA plot for sample 26 (RQ091998) .............................................................................114
8.33
GAA plot for sample 27 (RQ091999) .............................................................................114
8.34
GAA plot for sample 28 (RQ092000) .............................................................................114
8.35
GAA plot for sample 29 (RQ092001) .............................................................................115
8.36
GAA plot for sample 30 (RQ092029) .............................................................................115
8.37
GAA plot for sample 31 (RQ092250) .............................................................................115
8.38
GAA plot for sample 32 (RQ092251) .............................................................................115
8.39
GAA plot for sample 33 (RQ092252) .............................................................................116
8.40
GAA plot for sample 34 (RQ092253) .............................................................................116
8.41
GAA plot for sample 35 (RQ092254) .............................................................................116
8.42
GAA plot for sample 36 (RQ092255) .............................................................................116
8.43
GAA for plot sample 37 (RQ092256) .............................................................................117
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Figures | xix
8.44
GAA plot for sample 38 (RQ092257) .............................................................................117
8.45
GAA plot for sample 39 (RQ092258) .............................................................................117
8.46
GAA plot for sample 40 (RQ092847) .............................................................................117
8.47
GAA plot for sample 41 (RQ092848) .............................................................................118
8.48
GAA plot for sample 42 (RQ092849) .............................................................................118
8.49
GAA plot for sample 43 (RQ092850) .............................................................................118
8.50
GAA plot for sample 44 (RQ092851) .............................................................................118
8.51
GAA plot for sample 45 (RQ092852) .............................................................................119
8.52
GAA plot for sample 46 (RQ092853) .............................................................................119
8.53
GAA plot for sample 47 (RQ092854) .............................................................................119
8.54
GAA plot for sample 48 (RQ092855) .............................................................................119
8.55
GAA plot for sample 49 (RQ092856) .............................................................................120
8.56
GAA plot for sample 50 (RQ093078) .............................................................................120
8.57
GAA plot for sample 51 (RQ093079) .............................................................................120
8.58
GAA plot for sample 52 (RQ093080) .............................................................................120
8.59
GAA plot for sample 53 (RQ093081) .............................................................................121
8.60
GAA plot for sample 54 (RR093082) ..............................................................................121
8.61
GAA plot for sample 55 (RR093083) ..............................................................................121
8.62
GAA plot for sample 56 (RR093084) ..............................................................................121
8.63
GAA plot for sample 57 (RR093085) ..............................................................................122
8.64
GAA plot for sample 58 (RR093373) ..............................................................................122
8.65
GAA plot for sample 59 (RR093374) ..............................................................................122
8.66
GAA plot for sample 60 (RR093375) ..............................................................................122
©2010 Water Research Foundation. ALL RIGHTS RESERVED
xx | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
8.67
GAA plot for sample 61 (RR093376) ..............................................................................123
8.68
GAA plot for sample 62 (RR093377) ..............................................................................123
8.69
GAA plot for sample 63 (RR093378) ..............................................................................123
8.70
GAA plot for sample 64 (RR093660) ..............................................................................123
8.71
GAA plot for sample 65 (RR093661) ..............................................................................124
8.72
GAA plot for sample 66 (RR093662) ..............................................................................124
8.73
GAA plot for sample 67 (RR093663) ..............................................................................124
8.74
GAA plot for sample 68 (RR093664) ..............................................................................124
8.75
GAA plot for sample 69 (RS095390) ..............................................................................125
8.76
GAA plot for sample 70 (RS095391) ..............................................................................125
8.77
GAA plot for sample 71 (RS095392) ..............................................................................125
8.78
GAA plot for sample 72 (RS095393) ..............................................................................125
8.79
GAA plot for sample 73 (RS095394) ..............................................................................126
8.80
GAA plot for sample 74 (RS095395) ..............................................................................126
8.81
GAA plot for sample 75 (RS095396) ..............................................................................126
8.82
GAA plot for sample 76 (RS095397) ..............................................................................126
8.83
GAA plot for sample 77 (RS095398) ..............................................................................127
8.84
GAA plot for sample 78 (RS095399) ..............................................................................127
8.85
GAA plot for sample 79 (RS095400) ..............................................................................127
9.1
Example of gross radium plot ..........................................................................................133
9.2
GRA plot for sample 1 (RQ091434) ................................................................................137
9.3
GRA plot for sample 2 (RQ091435) ................................................................................137
9.4
GRA plot for sample 3 (RQ091436) ................................................................................137
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Figures | xxi
9.5
GRA plot for sample 4 (RQ091437) ................................................................................137
9.6
GRA plot for sample 5 (RQ091438) ................................................................................138
9.7
GRA plot for sample 6 (RQ091439) ................................................................................138
9.8
GRA plot for sample 7 (RQ091440) ................................................................................138
9.9
GRA plot for sample 8 (RQ091441) ................................................................................138
9.10
GRA plot for sample 9 (RQ091442) ................................................................................139
9.11
GRA plot for sample 10 (RQ091444) ..............................................................................139
9.12
GRA plot for sample 11 (RQ091713) ..............................................................................139
9.13
GRA plot for sample 12 (RQ091720) ..............................................................................139
9.14
GRA plot for sample 13 (RQ091721) ..............................................................................140
9.15
GRA plot for sample 14 (RQ091722) ..............................................................................140
9.16
GRA plot for sample 15 (RQ091723) ..............................................................................140
9.17
GRA plot for sample 16 (RQ091724) ..............................................................................140
9.18
GRA plot for sample 17 (RQ091725) ..............................................................................141
9.19
GRA plot for sample 18 (RQ091726) ..............................................................................141
9.20
GRA plot for sample 19 (RQ091751) ..............................................................................141
9.21
GRA plot for sample 20 (RQ091992) ..............................................................................141
9.22
GRA plot for sample 21 (RQ091993) ..............................................................................142
9.23
GRA plot for sample 22 (RQ091994) ..............................................................................142
9.24
GRA plot for sample 23 (RQ091995) ..............................................................................142
9.25
GRA plot for sample 24 (RQ091996) ..............................................................................142
9.26
GRA plot for sample 25 (RQ091997) ..............................................................................143
9.27
GRA plot for sample 26 (RQ091998) ..............................................................................143
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xxii | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
9.28
GRA plot for sample 27 (RQ091999) ..............................................................................143
9.29
GRA plot for sample 28 (RQ092000) ..............................................................................143
9.30
GRA plot for sample 29 (RQ092001) ..............................................................................144
9.31
GRA plot for sample 30 (RQ092029) ..............................................................................144
9.32
GRA plot for sample 31 (RQ092250) ..............................................................................144
9.33
GRA plot for sample 32 (RQ092251) ..............................................................................144
9.34
GRA plot for sample 33 (RQ092252) ..............................................................................145
9.35
GRA plot for sample 34 (RQ092253) ..............................................................................145
9.36
GRA plot for sample 35 (RQ092254) ..............................................................................145
9.37
GRA plot for sample 36 (RQ092255) ..............................................................................145
9.38
GRA for plot sample 37 (RQ092256) ..............................................................................146
9.39
GRA plot for sample 38 (RQ092257) ..............................................................................146
9.40
GRA plot for sample 39 (RQ092258) ..............................................................................146
9.41
GRA plot for sample 40 (RQ092847) ..............................................................................146
9.42
GRA plot for sample 41 (RQ092848) ..............................................................................147
9.43
GRA plot for sample 42 (RQ092849) ..............................................................................147
9.44
GRA plot for sample 43 (RQ092850) ..............................................................................147
9.45
GRA plot for sample 44 (RQ092851) ..............................................................................147
9.46
GRA plot for sample 45 (RQ092852) ..............................................................................148
9.47
GRA plot for sample 46 (RQ092853) ..............................................................................148
9.48
GRA plot for sample 47 (RQ092854) ..............................................................................148
9.49
GRA plot for sample 48 (RQ092855) ..............................................................................148
9.50
GRA plot for sample 49 (RQ092856) ..............................................................................149
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Figures | xxiii
9.51
GRA plot for sample 50 (RQ093078) ..............................................................................149
9.52
GRA plot for sample 51 (RQ093079) ..............................................................................149
9.53
GRA plot for sample 52 (RQ093080) ..............................................................................149
9.54
GRA plot for sample 53 (RQ093081) ..............................................................................150
9.55
GRA plot for sample 54 (RR093082) ..............................................................................150
9.56
GRA plot for sample 55 (RR093083) ..............................................................................150
9.57
GRA plot for sample 56 (RR093084) ..............................................................................150
9.58
GRA plot for sample 57 (RR093085) ..............................................................................151
9.59
GRA plot for sample 58 (RR093373) ..............................................................................151
9.60
GRA plot for sample 59 (RR093374) ..............................................................................151
9.61
GRA plot for sample 60 (RR093375) ..............................................................................151
9.62
GRA plot for sample 61 (RR093376) ..............................................................................152
9.63
GRA plot for sample 62 (RR093377) ..............................................................................152
9.64
GRA plot for sample 63 (RR093378) ..............................................................................152
9.65
GRA plot for sample 64 (RR093660) ..............................................................................152
9.66
GRA plot for sample 65 (RR093661) ..............................................................................153
9.67
GRA plot for sample 66 (RR093662) ..............................................................................153
9.68
GRA plot for sample 67 (RR093663) ..............................................................................153
9.69
GRA plot for sample 68 (RR093664) ..............................................................................153
9.70
GRA plot for sample 69 (RS095390) ..............................................................................154
9.71
GRA plot for sample 70 (RS095391) ..............................................................................154
9.72
GRA plot for sample 71 (RS095392) ..............................................................................154
9.73
GRA plot for sample 72 (RS095393) ..............................................................................154
©2010 Water Research Foundation. ALL RIGHTS RESERVED
xxiv | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
9.74
GRA plot for sample 73 (RS095394) ..............................................................................155
9.75
GRA plot for sample 74 (RS095395) ..............................................................................155
9.76
GRA plot for sample 75 (RS095396) ..............................................................................155
9.77
GRA plot for sample 76 (RS095397) ..............................................................................155
9.78
GRA plot for sample 77 (RS095398) ..............................................................................156
9.79
GRA plot for sample 78 (RS095399) ..............................................................................156
9.80
GRA plot for sample 79 (RS095400) ..............................................................................156
A.1
Flowchart for radium compliance ....................................................................................177
A.2
Flowchart for GAA and uranium compliance .................................................................177
B.1
Schematic diagram of RO system ....................................................................................186
B.2
Schematic diagram of an electrodialysis assembly. ATM is an anion-transfer
membrane, and CTM is a cation-transfer membrane...........................................187
B.3
Schematic diagram of the HMO process .........................................................................191
C.1
Plot for the determination of ε1 and Kεave .....................................................................196
C.2
The efficiencies of 226Ra and its progeny, ε1, and Kεave ................................................197
C.3
Plot for the determination of k1 and k2 ...........................................................................201
C.4
The efficiencies of the 224Ra decay chain ........................................................................201
C.5
Efficiencies of 241Am and 210Po .......................................................................................203
C.6
Efficiencies of 238U as interpolated from 226Ra efficiencies ............................................203
F.1
Efficiency eS versus residue mass ....................................................................................211
G.1
Coordinate system employed in the derivation of the constraint .....................................221
G.2
Plot of η(l) versus residue mass for 241Am .....................................................................222
©2010 Water Research Foundation. ALL RIGHTS RESERVED
LIST OF SYMBOLS
Chapter 1
Variable
Definition
t1/2
Half-life of a radionuclide
λ
Decay constant of a radionuclide
t
Time
N
Number of radionuclide atoms at time t
N0
Number of radionuclide atoms at time t = 0
A
Activity of a radionuclide at time t at time t
A0
Activity of a radionuclide at time t = 0
A1
Activity of 226Ra
A2
Activity of 222Rn
λ2
Decay constant of 222Rn
Ai
Activity of the ith radionuclide
Chapter 2
Variable
Definition
e
Efficiency of an alpha emitter
C
Detector count rate due to an alpha emitter
A
Activity due to an alpha emitter
ei
Efficiency of the ith radionuclide
CT
Detector count rate due to all alpha emitters
Ci
Detector count rate due to the ith alpha emitter
GAA
Gross alpha-particle activity
V
Sample volume
eS
Average efficiency of the calibration standard
Ai
Activity due to the ith alpha emitter
AT
Total alpha activity
σ
Measure of radial uniformity of residue
σmax
Maximum value of σ
ξ(r)
Radial distribution function of the residue
xxv
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xxvi | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
Chapter 2 (continued)
Variable
Definition
x
Fraction of the planchet covered by patches
r1
Radius of the central disc of a nonuniform residue
r2
Inside radius of the outer ring of a nonuniform residue
r3
Planchet radius and outside radius of the outer ring of a nonuniform residue
e
Measure of radial nonuniformity of the residue
D
Percent difference between εN and the efficiency εU
εD
Efficiency of the central disc-shaped part of the residue (r < r1)
εR
Efficiency of the outer ring-shaped part of the residue (r2 < r < r3)
εN
Efficiency of a nonuniform residue
εU
Efficiency of a uniform residue
T1
Time between sample collection and preparation
T2
Time between sample preparation and analysis
T3
Time between sample collection and analysis
Chapters 4 and 5
Variable
Definition
GAA
Gross alpha-particle activity
A1
Parent activity of a radionuclide that does not decay appreciably over the
sample’s lifetime
A1,0
Parent activity of a radionuclide that decays appreciably over the sample’s
lifetime
T1
Time between sample collection and preparation
T2
Time between sample preparation and analysis
T3
Time between sample collection and analysis
Chapter 6
Variable
Definition
ΔT
Count time interval in minutes
N
Number of counts accumulated in time T
σN
Error or standard deviation in N
GAA
Gross alpha-particle activity in pCi/L
σGAA
Error or standard deviation in GAA in pCi/L
©2010 Water Research Foundation. ALL RIGHTS RESERVED
List of Symbols | xxvii
Chapter 6 (continued)
Variable
Definition
eS
Average efficiency of the calibration standard
V
Sample volume in liters
C
Conversion factor from uranium activity (pCi/L) to concentration (μg/L)
A2
238
U activity
A1
234
U activity
Chapter 7
Variable
Definition
t
Time
A1
228
Ra activity at time t
A1,0
228
Ra activity at time t =0
A4
224
Ra activity at time t
λ1
Decay constant of 228Ra
λ3
Decay constant of 228Th
c41, c43
Coefficients in the Bateman equations
Chapter 8
Variable
Definition
T1
Time between sample collection and preparation
T2
Time between sample preparation and analysis
T3
Time between sample collection and analysis
GAA
Gross alpha-particle activity
eS
Average efficiency of the calibration standard
V
Volume of the sample in liters
ΔTS
Sample count interval in minutes
NS
Number of alpha counts detected in count interval ΔTS
ΔTB
Background count interval in minutes
⎯
C
Background count rate in min−1
σ1
Total error in the GAA
GAAi
The ith value of the GAA in a triplicate of values
〈GAA〉
Average among a triplicate of GAA data all taken at the same time T2
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xxviii | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
Chapter 8 (continued)
Variable
Definition
σ2
Counting error in the GAA
Chapter 9
Variable
Definition
GRA
Gross radium activity in pCi/L
V
Volume of the sample in liters
γ
Gravimetric yield of BaSO4
ε1
Efficiency of 226Ra in BaSO4
λ2
Decay constant of 222Rn
T2
Time between sample preparation and analysis
CT
Number of alpha counts per unit time minus the background count rate
Appendix C
Variable
Definition
Ai
Activity of ith radionuclide in the sample residue
κi
Fraction of ith radionuclide that remains in the sample residue
cj
jth coefficient in the Bateman equations for the decay of 226Ra
εi
Efficiency of ith radionuclide in the sample residue
λi
Decay constant of ith radionuclide
t
Time elapsed since the ingrowth of 226Ra progeny began
Δt
An increment in t
ΔN
Number of alpha counts in time interval Δt
εave
Weighted average of the efficiencies of the 222Rn, 218Po and 214Po
K
Average among κ2, κ3, and κ6 [K = (κ2 + κ3 + κ6)/3]
m
Mass of the sample residue
f(m)
Function used to fit to a curve to the efficiency versus residue mass data
ai, b
For i = 0 to 5, adjustable parameters in the function f (m)
m1
Transition mass from “thin” to “thick” residues
D
Fractal dimension of the residue surface (D = 3 – n)
©2010 Water Research Foundation. ALL RIGHTS RESERVED
List of Symbols | xxix
Definition
t
Time elapsed since the ingrowth of 224Ra progeny began
Ai
Activity of ith radionuclide in the sample residue
A1,0
224
βi
Branching ratio at the ith radionuclide
κi
Fraction of ith radionuclide that remains in the sample residue
λi
Decay constant of ith radionuclide
cij
ijth coefficient in the Bateman equations for the decay of 224Ra
dN/dt
Instantaneous alpha count rate due to 224Ra and its progeny
εi
Efficiency of ith radionuclide in the sample residue
k1
A constant defined as k1 = ε1 + κ2ε2 + κ3ε3 + β5c51κ5ε5 + (1 − β5)c51κ6ε6
k2
A constant defined as k2 = −β5c54κ5ε5 + (1 − β5)c54κ6ε6
Δt
An increment in time t
ΔN
Number of counts in the time period Δt
Ii
Integral of the factor exp(−λit) between t = t and t = t + Δt
εave,1
Weighted average of the efficiencies of 224Ra, 220Rn and 216Po
εave,2
Weighted average of the efficiencies of 212Bi and 212Po
K1
Average among κ1 (= 1) κ2, and κ3 [K1 = (1 + κ2 + κ3)/3]
K2
Average among κ5 and κ6 [K2 = β5κ5 +(1 − β5)κ6]
ε
Efficiency of an alpha emitter
E
Alpha particle energy of an alpha emitter
a, b
Fit parameters in the equation ε = aE + b
Ra activity in the sample residue at t = 0
Appendix D
Variable
Definition
ε
Efficiency of an alpha emitter in a BaSO4 residue
e
Efficiency of an alpha emitter in a sample residue of arbitrary composition
SP
Planchet area
R1
Range of an alpha particle in BaSO4 (mg/cm2)
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xxx | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
Appendix D (continued)
Variable
Definition
R2
Range of an alpha particle in a sample residue (mg/cm2)
wi
Weight fraction of ith element in a residue
ri
Range of ith element in a residue
Ai
Atomic weight of ith element in a residue
Appendix E
Variable
Definition
e
Efficiency of an alpha emitter in a sample residue of arbitrary composition
〈e〉
Value of e averaged over the residue geometry
SP
Planchet area
τ
“Thickness” of a sample residue (τ = m/SP)
τ0
Average value of τ for a sample residue
ϕ (τ )
ϕ (τ )dτ is the probability of a residue having a thickness between τ toτ + dτ
R1
Range of an alpha particle in BaSO4 (mg/cm2)
R2
Range of an alpha particle in a sample residue (mg/cm2)
δ
Dirac delta function
〈G〉
Value of G averaged over the residue geometry
〈ΔN〉
Value of ΔN averaged over the residue geometry
Appendix F
Variable
Definition
ei
Efficiency of ith alpha emitter in a sample residue
Ni
Number of counts due to ith alpha emitter detected in time interval Δt
Ai
Activity of ith alpha emitter in a sample residue
Δt
Sample count interval
AT
Total activity of all alpha emitters in a sample residue
V
Sample volume
G
Gross alpha-particle activity (GAA) of a sample
ΔN
Total number of alpha counts collected by the detector in time interval Δt
eS
Average efficiency of the calibration standard
〈G〉
Value of G averaged over the residue geometry
©2010 Water Research Foundation. ALL RIGHTS RESERVED
List of Symbols | xxxi
Appendix F (continued)
Variable
Definition
〈Ni〉
Value of Ni averaged over the residue geometry
〈ΔN〉
Sum of all of the 〈Ni〉; i.e., 〈ΔN〉 = 〈ΔN1〉 + 〈ΔN2〉 + 〈ΔN3〉 + . . .
eS
Average efficiency of the calibration standard
e1,P
Efficiency of the calibration standard in a patch residue
e1,S
Efficiency of the calibration standard in a smooth residue
〈G〉
Value of G due to 234U averaged over the residue geometry
A1
234
〈e〉
Value of the 234U efficiency, e, averaged over the residue geometry
eS
Average efficiency of the calibration standard
V
Volume of a sample
e1,P
Efficiency of the calibration standard in a patch residue
e1,S
Efficiency of the calibration standard in a smooth residue
e1
234
U efficiency in a patch residue
e2
234
U efficiency in a smooth residue
〈G〉
Value of G due to 238U averaged over the residue geometry
A1
238
〈e〉
Value of the 238U efficiency, e, averaged over the residue geometry
eS
Average efficiency of the calibration standard
V
Volume of a sample
T2
Time between sample preparation and analysis
ΔT2
An increment in T2
ΔN
Number of alpha counts in time interval ΔT2
〈ΔN〉
ΔN averaged over the residue geometry
A1
226
λ2
Decay constant of 222Rn
〈e1〉
226
Ra efficiency, e1, averaged over the residue geometry
〈K1eave,1〉
226
Ra progeny efficiency, K1eave,1, averaged over the residue geometry
〈G〉
G due to 226Ra and progeny averaged over the residue geometry
eS
Average efficiency of the calibration standard
U activity
U activity
Ra activity
©2010 Water Research Foundation. ALL RIGHTS RESERVED
xxxii | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
Appendix F (continued)
V
Sample volume
T3
Time between sample collection and analysis
A1
210
Po activity at time T3
A1,0
210
Po activity at time T3 = 0
λ1
Decay constant of 210Po
〈G〉
Value of G due to 210Po averaged over the residue geometry
〈e1〉
Value of the 210Po efficiency, e1, averaged over the residue geometry
eS
Average efficiency of the calibration standard
V
Sample volume
T3
Time between sample collection and analysis
A3
210
Po activity
A1,0
210
Pb activity at T3 = 0
λ1
Decay constant of 210Pb
λ2
Decay constant of 210Bi
λ3
Decay constant of 210Po
cij
Constants in the Bateman equations for the decay of 210Pb
〈G〉
Value of G due to 210Po averaged over the residue geometry
〈e3〉
Value of the 210Po efficiency, e3, averaged over the residue geometry
eS
Average efficiency of the calibration standard
V
Sample volume
T3
Time between sample collection and analysis
ΔT3
An increment in T3
〈ΔN〉
Value of ΔN averaged over the residue geometry
A1,0
224
〈k1〉
Value of k1 averaged over the residue geometry
〈k2〉
Value of k2 averaged over the residue geometry
λi
Decay constant of the ith radionuclide
Ii
Integral of the factor exp(−λit) between t = t and t = t + Δt
cij
Coefficients of the Bateman equation for the decay of 224Ra
Ra activity at T3 = 0
©2010 Water Research Foundation. ALL RIGHTS RESERVED
List of Symbols | xxxiii
Appendix F (continued)
Variable
Definition
〈K1eave,1〉
Value of the K1eave,1 averaged over the residue geometry
〈K2eave,2〉
Value of the K2eave,2 averaged over the residue geometry
〈G〉
Value of G due to 224Ra and its progeny averaged over the residue geometry
eS
Average efficiency of the calibration standard
V
Sample volume
T3
Time between sample collection and analysis
ΔT3
An increment in T3
〈G4〉
Value of G due to 212Pb progeny averaged over the residue geometry
A4,0
212
〈K2eave,2〉
Value of the K2eave,2 averaged over the residue geometry
q
A constant equal to 1.105
eS
Average efficiency of the calibration standard
V
Sample volume
T3
Time between sample collection and analysis
ΔT3
An increment in T3
Ai
Activity of ith radionuclide in the sample residue
A1,0
228
κi
Fraction of ith radionuclide that remains in the sample residue
βi
Branching ratio of ith radionuclide
λi
Decay constant of ith radionuclide
cij
ijth coefficient in the Bateman equations for the decay of 224Ra
〈ΔN1〉
Number of 228Th alpha counts in time interval ΔT3 averaged over residue
geometry
〈ΔN2〉
Number of 224Ra, 220Rn, and 216Po alpha counts in the time interval ΔT3 averaged over residue geometry
〈ΔN3〉
Number of 212Bi and 212Po alpha counts in the time interval ΔT3 averaged
over residue geometry
〈ΔN〉
Number of alpha counts due to 228Ra progeny 〈ΔN〉= 〈ΔN1〉 + 〈ΔN2〉 + 〈ΔN3〉
〈K1eave,1〉
Value of the K1eave,1 averaged over the residue geometry
〈K2eave,2〉
Value of the K2eave,2 averaged over the residue geometry
Pb activity at T3 = 0
Ra activity at T3 = 0
©2010 Water Research Foundation. ALL RIGHTS RESERVED
xxxiv | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
Appendix F (continued)
〈G〉
Value of G due to 228Ra progeny averaged over the residue geometry
eS
Average efficiency of the calibration standard
V
Sample volume
Appendix G
Variable
Definition
ε
Efficiency of the sample residue
l
Thickness of the sample residue
z
The z-coordinate of a point in the sample residue
η(z)
Function that gives the efficiency of the residue at the plane z = z.
m
Mass of the residue
Appendix H
Variable
Definition
N 2D
Number of 220Rn atoms in the detector region
t
Time elapsed since sample was placed in the instrument
Δt
An increment in t
F
Rate at which 220Rn atoms escape from the BaSO4 residue
A1,0
Activity of 224Ra at t = 0
e
Proportionality constant between F and the 224Ra activity of the residue
λi
Decay constant of ith radionuclide
f
Fraction of the 220Rn atoms that remain in the detector region
ΔND
Number of alpha counts detected in time interval Δt
cij
Coefficients in the Bateman equations for the decay of 224Ra
ε
Efficiency with which the contaminating alpha emitters register detector
counts
Appendix I
Variable
Definition
AT
Total activity of 234U and 238U in a sample
mT
Total mass of 234U and 238U in a sample
C
Conversion factor between uranium activity (pCi/L) and concentration
(μg/L)
λ1
Decay constant of 234U
©2010 Water Research Foundation. ALL RIGHTS RESERVED
List of Symbols | xxxv
λ2
Decay constant of 238U
N1
Number of 234U atoms
N2
Number of 238U atoms
A1
234
U activity
A2
238
U activity
Appendix J
Variable
Definition
G
The gross-alpha-particle activity in pCi/L
ΔTS
Sample count interval in minutes
ΔTB
Background count interval in minutes
NS
Number of alpha counts detected in count interval ΔTS
NB,i
For the ith background count, the number of counts in the count interval ΔTB
⎯
C
Background count rate in min−1
σ2
Counting error in the GAA in pCi/L
σ NS
Standard deviation or error in NS
σC⎯
Standard deviation or error in C in min−1
V
Volume of the sample in liters
eS
Efficiency of the calibration standard
⎯
©2010 Water Research Foundation. ALL RIGHTS RESERVED
©2010 Water Research Foundation. ALL RIGHTS RESERVED
FOREWORD
The Water Research Foundation (Foundation) is a nonprofit corporation that is dedicated
to the implementation of a research effort to help utilities respond to regulatory requirements and
traditional high-priority concerns of the industry. The research agenda is developed through a
process of consultation with subscribers and drinking water professionals. Under the umbrella of
a Strategic Research Plan, the Research Advisory Council prioritizes the suggested projects
based upon current and future needs, applicability, and past work; the recommendations are forwarded to the Board of Trustees for final selection. The Foundation also sponsors research
projects through the unsolicited proposal process; the Collaborative Research, Research Applications, and Tailored Collaboration programs; and various joint research efforts with organizations
such as the U.S. Environmental Protection Agency, the U.S. Bureau of Reclamation, and the Association of California Water Agencies.
This publication is a result of one of these sponsored studies, and it is hoped that its findings will be applied in communities throughout the world. The following report serves not only
as a means of communicating the results of the water industry's centralized research program but
also as a tool to enlist the further support of the nonmember utilities and individuals.
Projects are managed closely from their inception to the final report by the Foundation's
staff and large cadre of volunteers who willingly contribute their time and expertise. The Foundation serves a planning and management function and awards contracts to other institutions
such as water utilities, universities, and engineering firms. The funding for this research effort
comes primarily from the Subscription Program, through which water utilities subscribe to the
research program and make an annual payment proportionate to the volume of water they deliver
and consultants and manufacturers subscribe based on their annual billings. The program offers
a cost-effective and fair method for funding research in the public interest.
A broad spectrum of water supply issues is addressed by the Foundation's research agenda: resources, treatment and operations, distribution and storage, water quality and analysis, toxicology, economics, and management. The ultimate purpose of the coordinated effort is to assist
water suppliers to provide the highest possible quality of water economically and reliably. The
true benefits are realized when the results are implemented at the utility level. The Foundation's
trustees are pleased to offer this publication as a contribution toward that end.
David E. Rager
Chair, Board of Trustees
Water Research Foundation
Robert C. Renner, P.E.
Executive Director
Water Research Foundation
xxxvii
©2010 Water Research Foundation. ALL RIGHTS RESERVED
©2010 Water Research Foundation. ALL RIGHTS RESERVED
ACKNOWLEDGMENTS
The author would like to acknowledge the Water Research Foundation and the United
State Environmental Protection Agency for their generous financial support. The author would
like to acknowledge the patient and enthusiastic support and of the project officer and the Project
Advisory Committee (PAC). On several occasions permission was granted to significantly alter
the original scope of the proposal. These scope changes added significantly to the understanding
of the problem, and it is the author’s opinion that these scope changes were made only because
the project manager and PAC members had a thorough grasp of the intricacies of the problems
that were to be addressed.
Project Manager:
Alice Fulmer, Water Research Foundation, Denver, CO
PAC Members:
Patrick Churilla, USEPA Region V, Chicago, IL
Joseph A. Drago, Kennedy/Jenks Consultants, San Francisco, CA
Michael Delaney, Massachusetts Water Res. Auth, Winthrop, MA
Miguel del Toral, USEPA Region V, Chicago, IL
Zoltan Szabo, USGS, NJ Water Science Center, W. Trenton, NJ
The author would like to thank all of the members in the Radiochemistry at the Wisconsin State
Laboratory of Hygiene.
Radiochemistry:
Michael F. Arndt, Associate Scientist
Lynn E, West, Laboratory Supervisor
Yuliya Henes, Senior Chemist
Gary Krinke, Senior Chemist
Jennifer Leete, Project Chemist
Lynn West supervised and coordinated much of the effort, dealt with complex administrative problems performed the 210Pb analyses and many of the gross alpha-particle analyses,
counted planchet at all hours, including nights and weekends, helped perform experiments to obtain alpha-emitter’s efficiencies, and designed a database to hold the myriad of data generated by
this project.
Gary Krinke performed all of the analyses by alpha spectrometry, including isotopic uranium, isotopic thorium, 224Ra, and 210Po; and occasionally he assisted with the 226Ra and 228Ra
analyses. Yuliya Henes performed gross alpha-beta analyses, the 210Pb analyses, and much of the
data entry and data checking. Jennifer Leete performed 226Ra and 228Ra analyses.
The author would like to thank the United States Geological Survey, the South Carolina
Geological Survey, the South Dakota Geological Survey, the South Dakota Department of Environment and Natural Resources and the water utilities operators and private well owners who
participated in this project. Individuals from these organizations kindly volunteered to collect the
groundwater samples for this study. The collection procedure required significant attention to
detail and a considerable investment of time. A list of the participants is given below:
Town of Clio
Clio, AL
Chloride, AZ
Chloride Domestic Water Improvement
District
Southern California Water Company
Anaheim, CA
xxxix
©2010 Water Research Foundation. ALL RIGHTS RESERVED
xl | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
Golden State Water Company
Apple Valley, CA
Charles County Department of Utilities
La Plata, MD
City of Kerman
Kerman, CA
Taneytown Utilities Department
Taneytown, MD
South Tahoe Public Utility District
South Lake Tahoe, CA
Woodstock Job Corps Center
Woodstock, MD
Valencia Heights Water Company
West Covina, CA
Village of Chatham
Chatham, MI
May Valley Water Association
Wiley, CO
Mason Department of Public Works
Mason, MI
Palm and Pine RV Park
Felda, FL
City of Arlington
Arlington, MN
Oak Park Mobile Home Village
Saint Alva, FL
City of Claremont Water Department
Claremont, MN
Petross Water System
Vidalia, GA
New Richland Maintenance Department
New Richland, MN
North Georgia Water Systems, Inc.
Watkinsville, GA
City of Taconite
Taconite, MN
s
City of Fromberg
Fromberg, MT
Fairways Home Owners Association
Caldwell, ID
Joliet Public Works and Utilities Department
Joliet, IL
Romeoville Public Works
Romeoville, IL
Lehigh City Water Plant
Lehigh, IA
Columbia Water and Light Department
Columbia, MO
McCaul, McCaul, and Associates
Potosi, MO
Grand Island Utilities Department
Grand Island, NE
Alliance Water Resources
Maquoketa, IA
City of Burdett
Burdett, KS
Municipal Light & Water
North Platte, NE
F. X. Lyons, Inc. Water & Pump Service
Intervale, NH
Stonington Water Company
Stonington, ME
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Acknowledgments | xli
Waukesha Water Utility
Waukesha, WI
GPM Associates
Cherry Hill, NJ
U. S. Geological Survey
New Jersey Water Science Center
West Trenton, NJ
Sierra Estates GID
Carson City, NV
United States Geological Survey
Nevada Water Science Center
Carson City, NV
South Carolina Department of Health and
Environmental Control
Columbia, SC
South Dakota Department of Environment and
Natural Resources
Pierre, SD
South Dakota Geological Survey
Rapid City, SD
South Dakota Geological Survey
Vermillion, SD
South West Water Company
Houston, TX
United States Geological Survey
Texas Water Science Center
Shenandoah, TX
Allouez Village Water Department
Village of Allouez, WI
City of Fond du Lac Water Utility
Fond du Lac, WI
Gresham Waterworks
Village of Gresham, WI
City of Thorp Public Works & Utilities
Thorp, WI
©2010 Water Research Foundation. ALL RIGHTS RESERVED
©2010 Water Research Foundation. ALL RIGHTS RESERVED
EXECUTIVE SUMMARY
BACKGROUND
Radioactive minerals in an aquifer are the source of radionuclides (radioactive isotopes)
in groundwater. In all aquifers, radionuclides can reside in the water, in the solids, and on the
solid surfaces. Some isotopes, like 224Ra, may reside in all three phases; some isotopes, like
228
Th, mainly reside in the solids and on the solid surfaces and are virtually absent in the water.
The radiological composition of a groundwater sample at the time of collection reflects the composition of the groundwater in the aquifer. Once groundwater is removed from an aquifer and is
no longer in contact with the minerals, its radiological composition can change substantially over
time. Some radionuclides, like 224Ra, decay away in about three weeks. Some, like 228Th, which
were absent in the sample at collection time, are produced by other radionuclides, like 228Ra, and
can accumulate to a significant level in the sample. Thus, with the passage of time, a sample’s
radiological composition can progressively diverge from its composition at collection time.
The gross alpha-particle activity (GAA) of a water sample is intended to approximate the
total alpha activity of the sample. However, the GAA is subject to various sources of bias and
error (discussed in detail in Chapters 2, 4, 5, 6 and 8) that can cause a sample’s GAA to be substantially higher or lower than the sample’s actual alpha activity and can cause duplicate measurements to differ significantly from one another. Water samples are commonly analyzed for
the alpha emitters 226Ra, 234U, and 238U. Frequently, it is believed that the sum of the 226Ra, 234U,
and 238U activities should be equal to the GAA, but there is often a large discrepancy between
this sum and the GAA.
Two types of methods are used to measure a sample’s GAA: evaporation methods and
coprecipitation methods. In an evaporation method, like EPA Method 900.0 (U.S EPA 1980a),
an aliquot of a water sample is evaporated to dryness leaving a relatively thin, solid residue on
the bottom of a shallow dish, called a planchet. The residue contains the non-volatile radionuclides of the aliquot. In a coprecipitation method, like Standard Methods 7110C (SM 1998c), the
non-volatile radionuclides of an aliquot of water are coprecipitated with a mixture of barium sulfate and ferric hydroxide. The precipitate is collected on a filter, which is placed in a planchet. In
either method, the collection of solids in the planchet is called the sample residue. A detector is
used to measure the rate at which alpha-particles are emitted from the residue, and the alphaparticle emission rate is used to calculate the GAA.
Two types of samples are used in GAA analyses: grab samples and quarterly composite
samples. For a grab sample, the water source is sampled once. For a quarterly composite sample,
equal aliquots of water are combined in each of four consecutive three-month periods. The sample holding time for both types of sample is six months. For a quarterly composite sample, the
holding time begins when the fourth aliquot is added.
Over the course of the six-month holding time, the radiological composition of a grab
sample can vary appreciably and at times bears little resemblance to the original composition.
The radiological composition of a quarterly composites sample can vary more than that of a grab
sample because the first three aliquots could have been added to the composite sample by as
much as nine months prior the fourth aliquot. The graphs of Chapter 4 and the example of Chapter 5 show how the variation of a sample’s radiological composition over time affects its GAA,
xliii
©2010 Water Research Foundation. ALL RIGHTS RESERVED
xliv | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
and show the extent to which the GAA can differ between a grab sample and the corresponding
quarterly composite sample.
All of a sample’s alpha emitters contribute to its GAA; however, many common alpha
emitters are not routinely quantified. Often, a radionuclide, called a parent, produces a series of
relatively short-lived radionuclides called its progeny. The parent and progeny constitute a decay
chain. The activities of a decay chain’s members are not independent but are fixed by the laws of
radioactive decay. The following is an example of a decay chain:
226
Ra ⎯α
→ 222Rn ⎯α
→ 218Po ⎯α
→ 214Pb ⎯β→ 214Bi ⎯β→
214
Po ⎯α
→ 210Pb,
where 226Ra is the parent and the subsequent radionuclides are the progeny. Here, “α” denotes an
alpha emitter, a radionuclide that emits an alpha particle, and “β” denotes a beta emitter, a radionuclide that emits a beta particle. 222Rn, 218Po, and 214Po are relatively short-lived, alpha-emitting
progeny whose contribution to the GAA is frequently ignored; however, whenever the parent,
226
Ra, is present, it continually produces progeny, and, in such cases, the short-lived progeny can
substantially contribute to the GAA. All of the decay chains of importance in this study are enumerated in Chapter 1.
Any sample that contains a significant 228Ra activity will usually contain a comparable
224
Ra activity at the time of collection. 224Ra, a parent, in turn, produces four alpha emitters—
220
Rn, 216Po, 22Bi, and 212Po—that all contribute to the GAA. The 224Ra activity of a sample is rarely determined and often ignored, but if a sample has a significant 228Ra activity and is analyzed
within one week of collection, 224Ra and its progeny often account for most of the sample’s GAA.
Even when all of a sample’s alpha emitters have been accounted for, the sum of the alpha
activities rarely equals the GAA. An alpha emitter’s contribution to the GAA is measured by its
efficiency, which is the fraction of its alpha particles that reach the detector. The efficiency increases as the alpha-particle energy increases. Many high-energy alpha emitters—like 226Ra
progeny, 224Ra and its progeny, and 228Ra progeny—are not routinely quantified but often account for most of the GAA. If a sample contains significant amounts of the high-energy alpha
emitters, its GAA often exceeds its alpha activity.
The GAA is equal to the sample residue’s alpha-particle count rate divided by the efficiency of a calibration standard:
GAA =
alpha count rate
.
standard efficiency
Natural uranium and 230Th are commonly used as calibration standards. In addition, 241Am is
used in some coprecipitation methods. The alpha-particle energies, and efficiencies, of the calibration standards are not equal but increase in the order
natural uranium <
230
Th < 241Am.
Thus, a sample’s GAA will depend on which calibration standard was used, and the GAA will
increase in the order
241
Am < 230Th < natural uranium.
A sample’s GAA could be under the maximum contaminant level (MCL) when
and over the MCL when 230Th is used.
©2010 Water Research Foundation. ALL RIGHTS RESERVED
241
Am is used
Executive Summary | xlv
It is frequently stated that a sample’s GAA is the sum of the activities of its alpha emitters excluding uranium and radon. This statement often causes confusion because the way in
which radon is “excluded” differs from the way in which uranium is “excluded.” Radon is purportedly excluded because it does not precipitate with the sample residue. However, once the residue forms, the radon isotopes 220Rn and 222Rn, produced by 224Ra and 226Ra, are trapped in the
residue. The 220Rn activity is maximized within 10 minutes of residue formation, making it impossible to exclude. While the initial 222Rn activity is negligible, once the residue forms, the
222
Rn activity steadily increases until it equals the 226Rn activity, which takes about 23 days. Frequently, both 220Rn and 222Rn contribute to the GAA and both produce additional alpha emitters
that contribute to the GAA. Thus, in radium-containing samples, radon is never entirely excluded
from the GAA.
A sample’s uranium activity is “excluded” from its GAA by subtracting its uranium activity concentration (pCi/L) from its GAA to get the adjusted GAA:
Adjusted GAA = GAA − uranium activity concentration.
The MCL for the adjusted GAA is 15 pCi/L.
Some uranium methods, like fluorometric, laser phosphorimetric, and ICP-MS methods,
give an accurate uranium mass concentration but tend to underestimate the uranium activity concentration, which may cause the adjusted GAA to be overestimated and lead to a false-positive
GAA violation. A uranium MCL violation occurs when the mass concentration of the uranium
isotopes—234U, 235U, and 238U—exceeds 30 μg/L. Some uranium methods, like radiochemical
methods, give an accurate uranium activity concentration (pCi/L) but tend to overestimate the
uranium mass concentration (μg/L), which may cause a false-positive uranium violation; Some
uranium methods, like alpha spectroscopy and some ICP-MS methods, can accurately measure
both; however, none of these ICP-MS methods have as yet been approved by the EPA. Problems
with uranium methods are discussed in detail in Chapter 6.
The GAA, like any radiological measurement, is subject to counting error. Counting error
is inherent in the measurement and can cause the measured value of the GAA to be greater than
or less than the true value. If the true value is near the 15 pCi/L MCL, counting error can cause
the GAA to exceed or to be less than the MCL. A detailed discussion of the counting error is presented in Chapter 6.
OBJECTIVES
The objectives of this project were to determine and quantify the source of bias and error
that affect the gross alpha-particle activity (GAA) and the uranium concentration of drinking water
samples, to determine conditions under which the GAA and the uranium concentration can exceed
their true values and cause false-positive violations, to provide guidance to water utility, regulatory
and laboratory personnel on how to identify the source of a GAA violation and on how to identify
and respond to a false-positive violation, and to suggest ways of modifying some of the current radiological methods to improve inter-laboratory consistency. Much experimental and theoretical
effort was devoted to the factors affecting the GAA measurement. Less effort was devoted to the
factors affecting the uranium measurement, since these are generally well understood.
©2010 Water Research Foundation. ALL RIGHTS RESERVED
xlvi | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
APPROACH
Theoretical models, presented in Appendices C through J, were developed to calculate
each decay chain’s contribution to the GAA. The total GAA is the sum of contributions from all
of the decay chains. In the experimental part of this project, groundwater samples, collected from
throughout the continental United States, were analyzed for the GAA using EPA Method 900.0
and were analyzed for most of the long-lived radionuclides of the 238U and 232Th decay series.
The data provided information on the frequency of occurrence of radiological contaminants, and,
in Chapter 8, the GAA data are compared to predictions made by the theoretical models to determine the relative importance of the factors that affect the GAA.
SUMMARY OF RESULTS
The most common radiological contaminants were the radium isotopes—224Ra, 226Ra,
and 228Ra—and the uranium isotopes—234U and 238U. There are no EPA approved analyses for
224
Ra, but several methods exist that can measure the 224Ra activity of water (SM 2005a, Parsa et
al 2004, and ASTM 2003a). Samples that contained 228Ra also contained a comparable activity
of 224Ra at the collection time. 210Pb and 210Po were the next most common contaminants. 210Po
often co-occurred with uranium, but it was the major alpha emitter in three samples. A significant 210Pb activity (>2 pCi/L) was found in a seven groundwater samples. Currently, 210Pb and
210
Po are unregulated, but they were listed under the Unregulated Contaminant Monitoring Rule
(U.S. EPA 1999) and may be regulated by the EPA in the future. None of the samples contained
a significant activity of any thorium isotope—228Th, 230Th, and 232Th—at collection time. Currently, 228Th and 230Th are unregulated, but 232Th is listed as a contaminant in the EPA’s third
Contaminant Candidate List (U.S. EPA. 2009).
The work of Chapters 4 and 8 shows that for radium-, 210Po- and 210Pb-containing samples, the GAA can increase significantly with residue mass. Evaporation methods, like EPA Method 900.0, require that the residue mass be in the range from 0 to 100 mg, but within this range
(40 to 100 mg), the residue mass can significantly elevate the GAA. A high residue mass can be
avoided by using a coprecipitation method, like Standard Methods 7110C, where the residue
mass can be kept to about 20 mg.
Chapter 2 and Chapter 4 show that a sample’s GAA depends markedly on the geometry
of the sample’s residue. For evaporation methods, like EPA Method 900.0, the residue can range
from being of uniform thickness to being composed of relatively thick patches that cover less
than half of the planchet. Uniform residues give a relatively high GAA; patch residues give a relatively low GAA. The disparity between uniform and patch residues increases as the residue
mass increases. Characterizing a residue’s geometry and its effect on the GAA is very difficult.
Thus, for evaporation methods, variability in the GAA due to residue geometry must be tolerated. Alternatively, coprecipitation methods produce residues that are often more uniform and
reproducible.
As discussed above, alpha-emitting progeny often make a major contribution to the GAA.
The parents and all alpha emitters of each decay chain are listed in Table ES.1. All progeny of
the 234U, 348U, and 210Po decay chains are beta emitters, long-lived alpha emitters, or stable lead
isotopes and do not make a significant contribution to the GAA. Table ES.1 also shows whether
the average alpha-particle energy of the decay chain is lower, the same, moderately higher, or
much higher than that of the calibration standard, which is assumed to be 230Th. The higher the
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Executive Summary | xlvii
alpha-particle energy is relative to that of the calibration standard, the higher is the alpha emitter’s contribution to the GAA. The discussion in Chapter 4 shows how to estimate a sample’s
GAA when all of the parent activities are known or can be estimated.
Table E.S. 1
An alpha emitter’s energy and GAA contribution relative to 230Th
U
234
U
Alpha-particle energy relative to
the calibration standard, 230Th
Same as 230Th
238
U
238
U
Lower than 230Th
210
Po
210
Po
Moderately higher than 230Th
226
Ra
226
Ra
Same as
226
Ra
222
210
Pb
228
Ra
224
Ra
Parent
234
Alpha emitters
Rn,
210
218
Po and
214
230
Th
Moderately higher than 230Th
Po
Po
Moderate higher than 230Th
228
Th, 224Ra, 220Rn, 216Po, 212Bi, 212Po
Much higher than 230Th
224
Ra, 220Rn, 216Po, 212Bi, and 212Po
Much higher than 230Th
Table E.S. 2
Time dependence of an alpha emitter’s or a group’s contribution to the GAA
234
U
Time interval
of importance
No dependence
Constant
Effect on
Composite
Same as grab
238
U
226
No dependence
Constant
Same as grab
Ra
Preparation to analysis
Increases over 23 days
Same as grab
210
Po
Collection to analysis
Decreases over 3-6 months
Less than grab
228
Ra
Collection to analysis
Increases over 3-6 months
More than grab
210
Pb
Collection to analysis
Increases over 3-6 months
More than grab
224
Ra
Collection to analysis
Decreases over 21 days
Less than grab
Decay chain
Timescale
The first three decay chains in Table ES.1 contain a single alpha emitter, which is the decay chain’s parent. The fourth and fifth rows in Table ES.1 are the alpha emitters of the 226Ra
decay chain. 226Ra, the parent, is listed separately from its progeny—222Rn, 218Po, and 214Po—
because the contribution of 226Ra to the GAA is considerably less than that of its progeny. The
alpha emitters of the 224Ra decay chain are the parent, 224Ra, and the progeny 220Rn, 216Po, 212Bi,
and 212Po. The alpha emitters of the 228Ra decay chain consist of 228Th and all of the alpha emitters of the 224Ra decay chain, so that the 224Ra and 228Ra decay chains overlap. By convention, all
224
Ra activity in a sample at collection time is assigned to the 224Ra decay chain; the 224Ra activity of the 228Ra decay chain at collection time is taken to be zero. Similarly, 210Po is the single alpha emitter of both the 210Po and 210Pb decay chains. By convention, all 210Po activity in a sample at collection time is assigned to the 210Po decay chain; the 210Po activity of the 210Pb decay
chain at collection time is taken to be zero
©2010 Water Research Foundation. ALL RIGHTS RESERVED
xlviii | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
The 234U and 238U decay chain’s contribution to the GAA is virtually constant because
neither decays to any significant extent, and neither is produced to any significant extent by other
radionuclides. The other decay chain’s contribution to the GAA depends on one of two time intervals: (1) the time between collection and analysis, and (2) the time between preparation and
analysis. The preparation time is when the sample residue forms; the analysis time is when the
alpha-particle emission rate of the residue is measured with a detector. Table ES.2 gives which
time interval that affects a decay chain’s contribution to the GAA, gives the timescale over
which the GAA changes, and indicates whether the decay chain’s contribution to a grab sample’s
GAA is greater than, less than, or equal to its contribution to the corresponding quarterly composite sample’s GAA.
The 226Ra decay chain’s contribution to the GAA depends on the time between sample
collection and analysis. Just after preparation, the 226Ra decay chain’s contribution to the GAA is
due solely to 226Ra because 222Rn is quantitatively lost during preparation. Once the residue
forms, 222Ra atoms, produced by 226Ra, are trapped in the residue, and 222Rn, in turn, produces
the alpha emitters 218Po and 214Po. Thus, after sample preparation, the 226Ra decay chain’s contribution to GAA increases with time and attains it maximum value after about 23 days. If each
aliquot of a quarterly composite sample had the same 226Ra activity (pCi/L) as the grab sample,
then the 226Ra decay’s chain’s contribution to the GAA would be the same for both the grab and
composite samples.
The 224Ra decay chain’s contribution to the GAA is near its maximum value at the time
of sample collection. However, as Table ES.2 shows, this contribution decreases with time and
becomes negligible at 21 days after collection. The 224Ra decay chain’s contribution to the GAA
of a quarterly composite would be much less than that of a grab sample, because by the time that
the fourth aliquot had been added, the 224Ra and the 224Ra progeny in the first three aliquots
would have decayed away.
The 228Ra decay chain’s contribution to the GAA is negligible at collection time, but, as
Table ES.2 shows, this contribution continually increases and can have a significant effect on the
GAA at three to six months following collection. The 228Ra decay chain’s contribution to the
GAA will always be greater for a quarterly composite sample than for the corresponding grab
sample because at the time that the last aliquot is added, production of 228Ra progeny in the first
three aliquots would have been occurring for many months. A radium MCL violation occurs
when the combined activities of 226Ra and 228Ra exceeds 5 pCi/L. In Chapter 4, it is shown that a
sample can have radium levels too low to cause a radium violation but high enough to be the sole
cause of a GAA violation. Such a GAA violation would be a false-positive GAA violation.
The 210Po decay chain’s contribution to the GAA is at a maximum at the time of collection and steadily decreases thereafter, declining to one-half of its original value after 4.6 months.
The decrease in the 210Po activity is more pronounced in quarterly composite samples than in
grab samples. A grab sample could have a GAA violation when the corresponding composite
sample would have no GAA violation.
By convention, the 210Pb decay chain’s contribution to the GAA is zero at collection.
However, 210Pb steadily produces 210Po, and after three months, the 210Po activity will be about
36% of the 210Pb activity. It would take about 2.3 years for the 210Po activity to attain its maximum value; thus, as is indicated in Table ES.2, the 210Po activity continues to increase beyond
three months. The increase in the 210Po activity is more pronounced in quarterly composite samples than in grab samples. Thus, a composite sample could have a GAA violation when the corresponding grab sample would have no violation.
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Executive Summary | xlix
For radium-containing samples prepared just after collection, the GAA frequently varies
significantly with time for a period of about three weeks. The time dependence of the GAA depends on the ratio of the 224Ra activity to the 226Ra activity. If the ratio is less than one, the GAA
will increase, if the ratio is greater than one, the GAA will decrease, and if the ratio is about
equal to one, the GAA will remain approximately constant. A radium-containing sample’s GAA
can be minimized by preparing the sample about three weeks after collection, when 224Ra and its
progeny will have decayed away and when the activity of 228Ra progeny will still be low, and by
analyzing the sample just after preparation, when the activity due to the 226Ra progeny is negligible. EPA Method 900.0 requires that there be at least three days between preparation and analysis; Standard Methods 7110C requires that there be at least three hours between preparation and
analysis.
For some uranium-containing samples, prepared by EPA Method 900.0, the experimental
values of the GAA were significantly elevated above the theoretical values. This elevation is an
unresolved problem, but could be due to uranium preferentially distributing towards the top of
the sample residue. The data of Chapter 8 shows that two samples had no uranium violation but
had an adjusted GAA elevated high enough to cause a GAA violation. Such a GAA violation is a
false-positive GAA violation.
RECOMMEDATIONS ON HOW TO FIND THE SOURCE OF A GAA VIOLATION AND ON HOW TO RECOGNIZE AND RESPOND TO A
FALSE-POSITIVE URANIUM OR GAA VIOLATION
In this section, guidance is provided to water utility, regulatory, and laboratory personnel
on how to determine the cause of a GAA violation and on how to determine whether a GAA or
uranium violation could be a false-positive violation. If the adjusted GAA is near its 15 pCi/L
MCL or if the uranium concentration is near its 30 μg/L MCL, the violation could be a falsepositive violation. Some parameters, like preparation and analysis times, that are needed to assess the possibility of a false-positive violation are not reported with the analytical result but can
often be obtained from the laboratory. If a false-positive violation is suspected, the recommendations below should be performed with the consent of the pertinent regulatory personnel.
1. False-positive uranium violation due to uranium method used. The uranium mass
concentration (μg/L) can be overestimated when it is obtained from a uranium activity
concentration (pCi/L) using the EPA mandated conversion factor of 0.67 pCi/μg.
Recommendation: If a sample has a uranium violation (>30 μg/L), one should determine
which uranium method was used. If a radiochemical method was used, then the uranium
mass concentration could have been significantly overestimated, and the uranium mass
concentration should be re-determined using a fluorometric, laser phosphorimetric, ICP-MS,
or alpha spectroscopic method.
2. False-positive GAA violation due to uranium method. The uranium activity concentration
(pCi/L) can be overestimated when it is obtained from a uranium mass concentration (μg/L)
using the EPA mandated conversion factor of 0.67 pCi/μg.
Recommendation: If the adjusted GAA of a sample exceeds the 15 pCi/L MCL, one should
determine which uranium method was used. If the uranium activity concentration was
determined by a fluorometric, a laser phosphorimetric, or an ICP-MS method, which cannot
measure activity, then it could have been significantly underestimated, and it should be re-
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l | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
3.
4.
5.
6.
7.
determined using a radiochemical or an alpha spectroscopic method and the adjusted GAA
should be recalculated.
Contribution of 224Ra to a GAA violation. Samples that contain 228Ra usually contain a
comparable 224Ra activity at collection time. If such a sample were analyzed within one week
of collection, the contribution of 224Ra, and its progeny, to the GAA could be substantial; if
such a sample were analyzed more than 21 days after collection, the contribution of 224Ra to
the GAA would be negligible.
Recommendation: To determine whether 224Ra may have contributed to the GAA, one
should obtain the sample collection and analysis times from the laboratory. If the sample
contains 228Ra (≥2 pCi/L) and was analyzed within one or one weeks of collection, then the
contribution of 224Ra to the GAA could be significant.
Contribution of 226Ra progeny to a GAA violation. The contribution of 226Ra progeny to
the GAA is usually negligible at the time of preparation, but after preparation, the
contribution will increase continually and reach its maximum value after 23 days. In EPA
method 900.0, it is stipulated that there must be at least three days between preparation and
analysis, and in Standard Methods 7110C, it is stipulated that there must be at least three
hours between preparation and analysis. Allowing more time will only increase the 226Ra
progeny’s contribution to the GAA.
Recommendation: If a sample has a GAA violation (>15 pCi/L) and a 226Ra activity above 2
pCi/L, the sample preparation and analysis times should be obtained from the laboratory. If
the time between preparation and analysis significantly exceeded three days for an
evaporation method or three hours for a coprecipitation method, then it is advisable to have
the laboratory re-prepare and reanalyze the sample, keeping the time between preparation
and analysis near the minimum allowed by the method.
Contribution of 228Ra progeny to a GAA violation. In grab samples, 228Ra progeny can
significantly contribute to the GAA at three to six months after collection. The contribution
for quarterly composite samples will exceed that of a grab sample.
Recommendation: If a grab sample has a GAA violation (>15 pCi/L), has a 228Ra activity
above 3 pCi/L, and was analyzed several months after collection, another grab sample should
be collected and analyzed within a month of collection. If a quarterly composite sample has a
GAA violation and a substantial 228Ra activity, a grab sample should be collected and
analyzed within a month of collection.
False-positive GAA violation due to artificially elevated uranium. For some uraniumcontaining samples analyzed in this study by EPA Method 900.0, the experimental GAA was
significantly higher than the theoretical GAA, which caused a false-positive GAA violation
(>15 pCi/L) in two samples.
Recommendation: If a uranium-containing sample has a GAA violation that cannot be
ascribed to any alpha emitter besides the uranium isotopes, the GAA of the sample should be
re-analyzed using a coprecipitation method, like Standard Methods 7110C.
False-positive GAA violation due to an excessive residue mass. The GAA often increases
with residue mass. For evaporation methods, like EPA Method 900.0, a high residue mass
can be difficult to avoid when the level of dissolved solids is high. In such cases, a
coprecipitation method, like Standard Methods 7110C, may be preferable because the residue
mass can be kept to about 20 mg.
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Executive Summary | li
Recommendation: If a sample has a GAA violation (>15 pCi/L), if the GAA was measured
using an evaporation method, and if the residue mass exceeded 40 mg, then it is advisable to
re-determine the GAA using a coprecipitation method, like Standard Methods 7110 C.
8. Contribution of 210Pb progeny to a GAA violation. 210Pb, a beta emitter, is not a common
contaminant; however, if 210Pb is present at a significant level (5 pCi/L), it would produce a
significant activity of 210Po, an alpha emitter, over three to six months. The 210Po activity,
produced by 210Pb, of a quarterly composite sample would be significantly higher than that of
the corresponding grab sample.
Recommendation: If a grab sample held for three to six months or a quarterly composite
sample has a GAA violation that cannot be attributed to any radium or uranium isotopes or
any 210Po initially present in the sample, the GAA violation could be due to 210Po produced
by 210Pb. In such a case, a grab sample should be re-collected and analyzed within a month of
collection. If the new GAA were significantly less than the old, the elevated GAA could be
due to 210Pb. In addition, a 210Pb test could be performed on the grab or quarterly composite
sample.
RECOMMENDATIONS TO IMPROVE INTER-LABORATORY CONSISTENCY
1. Residue mass. The 224Ra, 226Ra, 228Ra, 210Pb, and 210Po decay chains can contribute
disproportionately to the GAA when the residue mass is high (40 to 100 mg). If a sample has
a GAA violation and a high residue mass, and if the sample is either a grab sample that was
held for at least three months and contained a significant a 224Ra, 228Ra, or 210Po activity or a
composite sample that contained a significant 226Ra, 228Ra, 210Pb, or 210Po activity, then it is
recommended that one be allowed to re-determine the GAA either by an evaporation method,
using a lesser sample volume, or by a coprecipitation method, which would yield a 20 mg
residue.
2. Residue geometry. For evaporation methods, variability in residue geometry causes
significant variability in GAA, especially at high residue masses (40 to 100 mg). The GAA
could be biased high or low. Thus, the recommendation here, like the previous one, is that
one be allowed to re-determine the GAA using a lesser residue mass.
3. Sample holding time and quarterly composite samples. If either a grab sample held for
three to six months or a quarterly composite sample held for any length of time has a
significant 228Ra activity (≥2 pCi/L), but no radium violation, and has a GAA violation, it is
recommended that one be allowed to re-determine the GAA by collecting a new grab sample
and having it analyzed within a month of collection to eliminate the contribution of 228Ra
progeny to the GAA. 210Pb, a beta emitter, can produce a substantial 210Po activity in three
months, which can contribute to a GAA violation. If 210Pb is regulated in the future, a GAA
analysis would not be an appropriate test to imply its presence.
4. Characterization of homogeneity of sample residues. Some recommendations of the
previous section offered coprecipitation methods as an alternative to evaporation methods to
determine the GAA. One conclusion of this study is that uranium may not be uniformity
distributed throughout sample residues prepared by evaporation methods. The residue of a
coprecipitation method is a heterogeneous mixture of barium sulfate, ferric hydroxide, and
paper pulp, and there is no guarantee that all radionuclides are uniformly distributed
throughout these residues. Further, the heterogeneity and the occurrence of barium or iron in
some samples makes the practice of using the residue mass to obtain a chemical yield
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lii | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
questionable. Research should be undertaken to characterize the distribution of radionuclides
in residues for both evaporation and coprecipitation methods for a variety of water matrices.
5. Three calibration standards. The allowed use of three calibration standards for GAA
analyses sets three standards by which the GAA is measured. One standard should be used
for all methods. The one selected is, to some extent, arbitrary. Assuming a uniform
distribution, which is questionable, 241Am would give the lowest GAA, natural uranium
would give the highest GAA, and 230Th would give an intermediate GAA. Some samples
would be under the MCL if 241Am were used and over the MCL if natural uranium or 230Th
were used. If one standard is to be selected, it is recommended that research be conducted to
determine whether it distributes uniformly in residues that are derived from a variety of water
matrices.
6. Two time intervals. When a sample contains 226Ra, the contribution of 226Ra progeny to the
GAA increases with the time between preparation and analysis. EPA Method 900.0 stipulates
that there be at least three days between preparation and analysis, and Standard Methods
7110C stipulates that there be at least three hours between preparation and analysis. The use
of two time intervals sets two standards by which the GAA is measured. One time interval
should be chosen for all methods.
224
7.
Ra and its progeny. If the contribution of 224Ra and its progeny is to be included in the
GAA, samples should be analyzed within two to three days of collection. The rapid decay of
224
Ra in combination with the many factors that affect the GAA would make it impracticable
to quantify 224Ra by a GAA analysis. The trend in the GAA over time can give some
qualitative information about the ratio of 224Ra to 226Ra, but any uranium activity in the
samples would make a constant contribution to the GAA, which would cause the ratio to be
underestimated. EPA Method 900.1, which is selective for radium and lead, would be a better
screening test for the radium isotopes.
©2010 Water Research Foundation. ALL RIGHTS RESERVED
CHAPTER 1
INTRODUCTORY CONCEPTS
INTRODUCTION: NECESSITY OF AND OBJECTIVES OF THE STUDY
The objectives of this study were to elucidate the sources of bias and error that affect the
gross alpha-particle activity (GAA) and the uranium concentration of drinking water samples; to
determine conditions under which the GAA and the uranium concentration can exceed their true
values and cause false-positive maximum contaminant level (MCL) violations; to provide
guidance to water utility and regulatory personnel on how to identify the source of a GAA
violation and on how to identify and respond to a false-positive violation; and to suggest ways of
modifying some of the current radiological methods to improve inter-laboratory consistency.
The gross alpha activity (GAA) of a water sample is intended to approximate the total
alpha activity of the sample. However, the GAA is subject to various sources of bias and error
that can cause a sample’s GAA to be substantially higher or lower than the sample’s actual alpha
activity and can cause duplicate measurements of a sample’s GAA to differ significantly from
one another. A sample is commonly analyzed for the alpha emitters 226Ra, 234U, and 238U.
Frequently, it is believed that the sum of the 226Ra, 234U, and 238U activities should be equal to
the GAA, but there is often a large discrepancy between this sum and the GAA. In many cases,
other unquantified alpha emitters are present in the sample; however, even when all alpha
emitters have been accounted for, the sum of their activities rarely equals to GAA.
Two types of methods are commonly used to measure the GAA: evaporation methods
and coprecipitation methods. In an evaporation method, like EPA Method 900.0 (U.S EPA
1980a), an aliquot of a water sample is evaporated to dryness leaving a relatively thin, solid
residue on the bottom of a shallow dish, called a planchet. The residue contains the non-volatile
radionuclides (radioactive isotopes) of the aliquot. In a coprecipitation method, like Standard
Methods 7110C (SM 1998c), the non-volatile radionuclides of an aliquot of a water sample are
coprecipitated with a mixture of barium sulfate and ferric hydroxide. The precipitate is collected
on a filter, which is placed in a planchet. In either method, the collection of solids in the planchet
is referred to as the sample residue. A gas proportional counter is used to measure the rate at
which alpha-particles are emitted from the residue, and the alpha-particle emission rate is used to
calculate the GAA.
Three types of radiological maximum contaminant levels (MCL) violations will be
discussed in this report: (1) radium MCL violations, (2) uranium MCL violations, and (3) GAA
MCL violations. A drinking water source has a radium MCL violation if the sum of the 226Ra and
228
Ra activities exceeds 5 pCi/L, a uranium MCL violation if the uranium mass concentration
exceeds 30 µg/L, and a GAA MCL violation if the adjusted GAA exceeds 15 pCi/L. In many
places in this report, an MCL violation is simply called a violation.
Every water source must be sampled at its point of entry into the water system, and the
GAA and the 228Ra activity of the sample must be determined. If the 228Ra activity exceeds 5
pCi/L, the water source has a radium violation. In such a case, the 226Ra activity must still be
determined to establish the extent of the radium violation. If the GAA is less than 5 pCi/L, the
GAA can be substituted for the 226Ra activity. Whenever the GAA exceeds 5 pCi/L, the 226Ra
activity must be determined, regardless of the 228Ra activity. Frequently, both the uranium mass
concentration (µg/L) and the uranium activity concentration (pCi/L) are needed. EPA regulations
1
©2010 Water Research Foundation. ALL RIGHTS RESERVED
2 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
allow one to subtract the uranium activity (pCi/L) from the GAA: the result is called the adjusted
GAA. If the adjusted GAA exceeds 15 pCi/L, the drinking water source has a GAA violation.
The current National Primary Drinking Water Regulations are discussed in more detail in
Appendix A.
Two types of samples are used in radiological analyses: grab samples and quarterly
composite samples. For a grab sample, the water source is sampled once. For a quarterly
composite sample, equal aliquots of water are combined in each of four consecutive three-month
periods. The sample holding time for both types of sample is six months. For a quarterly
composite sample, the holding time begins when the fourth aliquot is added.
To establish a monitoring baseline, a new water source must be sampled in each of four
consecutive three-month periods. One grab sample can be taken in each period or a quarterly
composite sample can be substituted for the four grab samples. Using a quarterly composite
sample can substantially reduce analytical costs, but, as is discussed in the rest of this section,
and in Chapters, 2, 4, 5, and 10, under some circumstances, a quarterly composite sample will
have a GAA violation when none of the corresponding grab samples would have had a violation.
In the rest of this section, for the sake of simplicity it is assumed that the first, second, and third
aliquots of a quarterly composite sample were added at 270, 180, and 90 days prior to the fourth
aliquot. Although an analysis of radium methods is probably warranted, this report focuses on
GAA and uranium methods.
Both GAA and uranium methods are subject to various sources of bias and error. Major
contributors to bias and error in the GAA include variability in residue mass and geometry. A
high residue mass often biases a sample’s GAA high, and variability in the residue geometry—
which can range from being of uniform thickness across the planchet to being composed of
relatively thick patches that cover less than 50% of the planchet—can cause substantial
variability in the GAA, especially at high residue masses. The effects of residue mass and
geometry on the GAA are discussed in Chapters 2, 4, 5, and 8.
Depending on a sample’s initial radiological composition, the GAA of a sample held for
six months could be significantly greater than, significantly less than, or approximately equal to
the GAA of a sample that is prepared and analyzed soon after collection. Over time, the 234U and
238
U activities of a sample, and their contributions to the sample’s GAA, are constant because
neither decays to any significant extent and neither is produced by other radionuclides to any
significant extent. The radiological composition of samples that contain 224Ra, 226Ra, 228Ra,
210
Po, and/or 210Pb can vary substantially over time. The variation depends on the sample
collection time, the time at which the sample residue is prepared, and the time at which the
alpha-particle count rate of the residue is measured, which is called the sample analysis time. A
short account of the variation of a sample’s radiological composition is given here. A more
detailed and more quantitative account is given in Chapters 1, 2, 4, 5, and 8. Other studies have
shown that short-lived radionuclides can cause the GAA to depend markedly on the time
between sample collection and analysis (Parsa 1998, Focazio et al 2001, Szabo et al 2005).
Additional sources of bias and error in the GAA are discussed in Chapter 6. Some of the sources
of bias and error can be controlled and minimized, some are extremely difficult to control, and
some are inherent in the method.
In samples that contain 226Ra, 222Rn is volatilized during sample preparation, and just
after preparation, the activities of the alpha-emitters 222Rn, 218Po, and 214Po are relatively low.
Once the residue forms, 222Rn, produced by 226Ra, is trapped in the residue, and 222Rn, in turn,
produces the alpha emitters 218Po and 214Po. The total alpha activity, and the GAA, due to 222Rn,
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Chapter 1: Introductory Concepts | 3
218
Po, and 214Po increases with time and attains its maximum value at about 23 days after
preparation. The GAA due to 226Ra and its progeny is the same for both a grab sample and a
quarterly composite sample whose aliquots all had the same 226Ra activity (pCi/L) as the grab
sample.
Samples that contain 228Ra usually contain a comparable activity of 224Ra at the sample
collection time. 224Ra is an alpha emitter and it produces the alpha-emitting progeny 220Rn, 216Po,
212
Bi, and 212Po. The total activity of 224Ra and its progeny, originally present in the sample, is
greatest near the sample collection time. If a sample is analyzed within a week of collection,
224
Ra, and its progeny, can make a significant contribution to the GAA; if the sample is analyzed
three or more weeks after collection, any 224Ra that was originally present in the sample will
have decayed away. The contribution of 224Ra, and its progeny, to the GAA of a quarterly
composite sample will be considerably less than that of the corresponding grab sample, because
by the time that the last aliquot has been added to the composite, the 224Ra and the 224Ra progeny
originally present in first three aliquots will have decayed away.
228
Ra is a beta emitter that over a period of three or more months, can produce significant
amounts of the alpha emitters 228Th, 224Ra. 220Rn, 216Po, 212Bi, and 212Po. If a grab sample is
analyzed within a month of collection, the alpha activity, and the GAA, due to 228Ra progeny
will be small. If a grab sample is analyzed three or more months after collection, or if a
composite sample is analyzed at any holding time, the alpha activity, and the GAA, due to 228Ra
progeny can be significant. The contribution of 228Ra progeny to the GAA of a quarterly
composite sample will be considerable higher than that of the corresponding grab sample,
because at the time that the last aliquot is added to the composite sample, 228Ra will have been
producing progeny in the first, second, and third aliquots for 270, 180, and 90 days, respectively.
210
Po is an alpha emitter that is occasionally found in samples at significant levels (>2
pCi/L). 210Po has a half-life of 138 d; thus, the contribution of 210Po to the GAA is greatest at the
sample collection time and declines to one-half of its original value at 138 days after collection.
It would take about 2.3 years for the 210Po to decay away. Thus, the activity of 210Po, and its
contribution to the GAA, will decrease over the lifetime of a sample and will be greater for a
grab sample than for the corresponding quarterly composite sample.
210
Pb is a beta emitter that is sometimes found in samples at significant levels (>2 pCi/L).
210
Pb produces 210Po, an alpha emitter. After three months, the activity of 210Po, produced by
210
Pb, will be 36% of the 210Pb activity. The 210Po activity would continue to increase and reach
its maximum value after about 2.3 years, when the 210Po activity would equal the 210Pb activity.
Thus, the activity of 210Po, and its contribution to the GAA, will increase over the lifetime of the
sample and will be greater for a quarterly composite sample than for the corresponding grab
sample.
Frequently, 224Ra and its progeny, 226Ra progeny, and 228Ra progeny account for most of
a sample’s GAA; however, these alpha emitters are often given no consideration when
accounting for a sample’s GAA. Even when all of a sample’s alpha activity has been account for,
there is usually a discrepancy between the sample’s GAA and the sample’s alpha activity. Part of
the discrepancy can be due residue mass and geometry. However, an alpha emitter’s contribution
to the GAA can be greater than, less than, or approximately equal to its own activity depending
on whether the its alpha-particle energy is greater than, less than, or approximately equal to the
alpha-particle energy of the calibration standard, which is usually natural uranium or 230Th for
evaporation methods or natural uranium 230Th, or 241Am for coprecipitation methods. Highenergy alpha emitters include 224Ra and its progeny, 226Ra progeny, 228Ra progeny, and 210Po.
©2010 Water Research Foundation. ALL RIGHTS RESERVED
4 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
Thus, the GAA of radium-, 210Po-, or 210Pb-containing samples frequently exceeds the total alpha
activity of such samples.
Most sources of bias and error affect both evaporation and coprecipitation methods;
however, variability in residue mass and geometry typically have a larger affect on evaporation
methods than coprecipitation methods. For an evaporation method, the residue mass, which must
be kept in a range from 0 to 100 mg, depends on the sample volume used and on the level of
dissolved solids in the sample, and a high residue mass (40 to 100 mg) can be difficult to avoid;
for a coprecipitation method, the residue mass, which is usually about 20 mg, depends mainly on
the amount of barium and iron carrier added to the sample and has little to do with the level of
dissolved solids. Further, the residue geometry for an evaporation method is typically more
variable than that for a coprecipitation method, which usually produces residues that appear to be
of relatively uniform thickness. Since residue mass and geometry have a larger effect on
evaporation methods than coprecipitation methods, EPA Method 900.0, an evaporation method,
was analyzed in detail in this study.
In the first phase of this study, theoretical models were developed to determine the
contribution of the each of the commonly occurring alpha emitters to the GAA. The models
account for the residue mass and geometry, for the radiological composition of the sample, and
for the variation of the sample’s radiological composition over time. The theory is presented in
Appendices C through H. Results from the theory are presented in Chapters 4 and 5.
In the second phase of the study, 79 groundwater samples, most with well-established
GAA, uranium, or radium violations, were collected from throughout the continental United
States and were analyzed for their initial radiological and inorganic compositions, and were
prepared in triplicate for GAA analysis on two occasions: the first occasion was as soon as
possible after collection, which was usually within three days of collection; the second occasion
was one month or more after sample collection. These two preparation times were chosen
because in radium-containing samples, it was anticipated that the difference in the GAA between
these two preparations times would be close to the maximum observable value. At the time of
the first preparation, the 224Ra activity would be relatively large, whereas at the time of the
second preparation, any 224Ra activity originally present in the sample would have decayed away
to a negligible level. The GAA of each prepared sample was determined at three points in time:
(1) just after residue preparation, (2) about three days after the residue preparation, and (3) 30 or
more days after residue preparation. These three points in time were chosen because it was anticipated that the contribution of 226Ra progeny to the GAA would be relatively small just after
preparation but would increase with time and be at its maximum value at about 23 days
following preparation. Samples were prepared in triplicate to assess the effect of variable residue
geometry on the GAA.
The experimental results for the GAA analyses are presented in Chapter 8. Each sample’s
radiological composition is used to theoretically predict its GAA. Comparison between the
experimental and theoretical results helped establish the relative importance of the various
sources of bias and error that affect the GAA and helped identify a problem with the GAA
measurement of uranium-containing samples that remains unresolved.
An analysis of EPA-approved uranium methods is given in Chapter 6.3. Most EPAapproved uranium methods give accurate results when they are applied as originally intended.
However, some methods only measure the uranium activity concentration (pCi/L) accurately,
some only measure the uranium mass concentration (μg/L) accurately, and some can measure
both accurately. Significant error can arise when a uranium mass concentration is converted to a
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Chapter 1: Introductory Concepts | 5
uranium activity concentration, or vice versa. Such conversion errors can lead to false-positive
uranium violations and can cause the uranium activity concentration to be underestimated and
the adjusted GAA—the GAA minus the uranium activity concentration—to overestimated,
which could cause a false-positive GAA violation (>15 pCi/L).
EPA Method 900.1 (U.S. EPA 1980b) is a coprecipitation method that uses barium
sulfate to coprecipitate all radium isotopes—224Ra 226Ra, and 228Ra—and lead isotopes—210Pb
and 212Pb—but insignificant amounts of the uranium isotopes—234U, 235U, and 238U—and 210Po.
EPA Method 900.1 is intended to measure the gross radium activity (GRA) of a water sample.
The term “gross radium activity” suggests that the total activity of all of a sample’s radium
isotopes is measured, but the method’s calculations clearly show that the method is intended to
measure a sample’s 226Ra activity. In general, a sample’s GRA is only an accurate measure of its
226
Ra activity when the sample is prepared several weeks after collection, when 224Ra and 212Pb
will have decayed away, and when the alpha activity produced by 228Ra will still be quite small.
For radium-containing samples, the GRA typically varies significantly with the time
between sample collection and analysis and the time between sample preparation and analysis in
much the way as the GAA varies. EPA Method 900.1 is subject to most of the same kinds of bias
and error that affect GAA methods; however, like most coprecipitation methods, EPA Method
900.1 is less affected than evaporation methods by variability in the residue mass and geometry.
Because of the similarities between EPA Method 900.1 and other coprecipitation
methods, samples were prepared by EPA Method 900.1 and the results were compared with the
GAA results obtained by EPA Method 900.0. The sample preparation and analysis schedule
coincided with that of EPA Method 900.0. Each sample was prepared for GRA analysis by EPA
Method 900.1 on two occasions—just after collection and 30 or more days after collection. On
both occasions, the GRA was determined at three points in time—just after residue preparation,
about three days after residue preparation, and 30 or more days after residue preparation. The
experimental results for the GRA are presented and compared to the GAA analyses in Chapter 9.
Each sample’s radiological composition was used to theoretically predict its GRA. Comparison
between the experimental and theoretical results helped establish the relative importance of the
various sources of bias and error that affect the GRA. Because EPA method 900.1 is selective for
radium isotopes and yields a low residue mass (∼20 mg), EPA method 900.1 has a greater
potential to accurately measure the 224Ra activity shortly after sample collection than EPA
method 900.0.
ORGANIZATION OF THE REPORT
Chapter 2 discusses various factors that affect the GAA. These include the alpha-particle
energies of the alpha emitters, the geometry of the sample residue, the time at which certain steps
in the analysis are performed, and whether the sample is a grab sample or a quarterly composite
sample. Chapter 3 gives the experimental methods employed in this work.
In Chapter 4, the contributions of the alpha emitters in the 238U and 232Th decay series to
the GAA are determined. The foundation for this work is somewhat mathematical, and the
mathematical details can be found in Appendices C through J for the interested reader. In
Chapter 4, it will be shown that the contribution of each decay series can be simplified by
considering one portion of the decay series at a time. One of these portions, called a decay chain,
consists of a sequence of radionuclides from the decay series. Each decay series contains several
decay chains, which may overlap. In Chapter 4, the contribution of each decay chain to the GAA
©2010 Water Research Foundation. ALL RIGHTS RESERVED
6 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
is quantified. Once all contributions of all decay chains are determined, they can be added
together to get the total GAA. In Chapter 5, a hypothetical example is given that demonstrates
how one can estimate the total GAA of a sample from its constituent radionuclides.
In Chapter 4, several factors that cause variability and error in the GAA are taken into
account. These factors include the radiological composition of the sample, the residue mass and
geometry, the time between sample collection and analysis, and the time between sample
preparation and analysis. In Chapter 6, other factors that cause variability and error in the GAA
are discussed. These other factors can be difficult to quantify or can be difficult to include in the
graphs of Chapter 4. In Chapter 6, problems encountered with EPA-approved methods for
uranium are discussed. Such problems can lead to false-positive uranium violations and falsepositive GAA violations.
In Chapter 7, a short discussion of the radiological composition of the samples is given.
In Chapter 8, the results of the GAA analyses are presented. The experimental GAA data are
compared with the GAA calculated from the model presented in Chapter 4. The comparison
between the experimental and theoretical values of the GAA will help establish which factors
affect the GAA and their relative importance. In Chapter 9, the results of the gross radium
analyses, by EPA Method 900.1, are presented and compared with EPA Method 900.0. In
Chapter 10, some recommendations are given for water utility operators, regulators, and analysts
and for future research, which draw upon the results of Chapters 8 and 9.
In Appendix A, the current National Primary Drinking Water Regulations are discussed.
In Appendix B, water treatment options for removing radium, uranium, polonium, and gross
alpha-particle activity from water are discussed. Appendices C through J provide the
mathematical and physical foundation for this work. Appendix L gives the 224Ra method that was
developed for this study.
MEASUREMENT OF THE GAA
In EPA Method 900.0, the residue is often hygroscopic due to the presence of salts like
Ca(NO3)2 and Mg(NO3)2. In this case, the planchet is heated over a flame to decompose these
nitrates to CaO and MgO, which produces a residue that is less hygroscopic. Hygroscopic
residues increase in mass over time, which is undesirable, since some parameters used to
calculate the GAA depend on residue mass. While being heated the residue usually melts and
solidifies either during the heating process or after the planchet cools. During the evaporation
and heating steps, radon—222Rn and 220Rn—is quantitatively lost from the residue. Once the
residue solidifies, it traps most of the radon produced by the decay of 226Ra and 224Ra. Similarly,
in the coprecipitation methods, radon does not precipitate with the other alpha emitters, but once
formed, the residue traps radon produced by the decay of 226Ra and 224Ra. The time at which a
sample is heated over a flame, for an evaporation method, or the time at which the precipitate
forms, for a coprecipitation method, is called the sample preparation time.
It is often stated that a water sample’s GAA is its total alpha activity excluding radon and
uranium. EPA regulations allow one to subtract the uranium activity of a water sample from its
GAA. However, as noted above, the residue traps radon isotopes, produced by the decay of 226Ra
and 224Ra, and the trapped radon often contributes substantially to the GAA. Thus, in many
cases, radon is not rigorously excluded from the GAA.
After sample preparation, the alpha-particle emission rate of the residue is measured
using a type of detector called a gas proportion counter. The time at which this measurement is
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Chapter 1: Introductory Concepts | 7
made is called the sample’s analysis time. Figure 1.1 is a schematic diagram of the sample and
detector. The planchet is about 5 cm in diameter. There is a 1-cm air gap between the planchet
and the detector. The detector has a thin entrance window that is a Mylar sheet with a thin
coating of aluminum. Alpha particles that cross the entrance window ionize molecules in the P10 gas (10% methane in argon), producing electrons and ions. Electrons created in the ionization
process are collected at the detector’s anode, and positive ions are collected on the housing of the
detector. This burst of electrons and ions produces an electrical pulse, which is counted by the
electronics of the instrument. During the course of a measurement, the gas proportional counter
tallies up the number of alpha particles that have reached the detector.
EPA Method 900.0 stipulates that the sample holding time—the time between sample
collection and analysis—can be up to six months and that the time between sample preparation
and analysis be at least three days. The times at which the various steps are performed can
significantly affect the value of the GAA. Some radionuclides are decaying away and others are
being produced. As a consequence, a sample’s radiological composition and its GAA can change
substantially over time.
The GAA also depends on the geometry of the sample residue. The residue can vary from
being of nearly uniform thickness to being composed of relatively thick patches. The uniform
residues tend to give a high GAA; the patch residues tend to have a low GAA. Thus, two results
for samples prepared in duplicate can be quite different, not because of any differences in their
radiological composition, but because of differences in the geometry of their residues. The affect
that all of these factors have on the GAA will be discussed in detail in latter sections.
57 mm
detector
9 mm
sample residue
Entrance window
a
b
c
10 mm
planchette
51 mm
Figure 1.1. Sample-detection system
The theory required to understand the GAA is somewhat mathematical but cannot be
avoided if one desires a full understanding of the phenomena involved. However, most of the
mathematics is presented in the appendices, and a minimal amount of mathematics is presented
in the main body of this work. Before discussing the theory of the GAA measurement in detail,
some fundamental principles of radioactive decay and radiochemistry are discussed.
RADIOACTIVE DECAY
Most naturally occurring alpha emitters are members of one of the three natural decay
series: the 238U, 232Th, and 235U decay series. The activities of the members of the 235U decay
series are usually negligible when compared to the activities of the members of other two; thus,
in this work, only members of the 238U and 232Th decay series are considered. Schematic
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8 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
diagrams of the two decay series are given in Figure 1.2 and Figure 1.3. These figures include
the half-lives of the radionuclides, and, for the alpha emitters, their major alpha-particle energy.
All data was taken from a database of the National Nuclear Data Center (NNDC 2004).
An atom is radioactive if its nucleus has so much energy that it is unstable and can
spontaneously disintegrate into a new atom and one or more particles. The original atom is called
the parent, and the new atom is called the progeny. Any radioactive atom is called a
radionuclide. The disintegration process is called radioactive decay. In this work two types of
radioactive decay processes are considered: (1) alpha decay in which the parent disintegrates into
a progeny nucleus and an alpha particle, and (2) beta decay in which the parent disintegrates into
a progeny nucleus, a beta particle, and an antineutrino. An alpha particle is a high-energy helium
nucleus, a beta particle is a high-energy electron, and an antineutrino is an uncharged elementary
particle with a mass that is much less than that of an electron.
U-238
4.47×109 y
4.20 MeV
Pa-234
6.70 h
α
Th-234
24.1 d
β
U-234
2.46×105 y
4.78 MeV
β
α
Th-230
7.54×104 y
4.69 MeV
α
Ra-226
1622 y
4.78 MeV
α
Rn-222
3.823 d
5.49
α
Po-218
3.05 m
6.00 MeV
Bi-214
19.7 m
α
Pb-214
26.8 m
β
Po-214
164 μs
7.69 MeV
β
Bi-210
5.01d
α
Pb-210
22.2 y
β
Figure 1.2. The 238U decay series
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β
Po-210
138.4 d
5.31 MeV
α
Pb-206
(stable)
Chapter 1: Introductory Concepts | 9
Th-232
1.41×1010 y
4.01 MeV
Ac-228
6.15 h
α
β
Ra-228
5.75 y
β
Th-228
1.91 y
5.42 MeV
α
Ra-224
3.63 d
5.68 MeV
α
Rn-220
55.6 s
6.29 MeV
α
Po-216
145 ms
6.78 MeV
α
Pb-212
10.64 h
β
Bi-212
60.55 m,
6.05 MeV
β
α (0.3594)
Tl-208
3.053 m
Po-212
0.299 μs
8.78 MeV
α
Pb-208
(stable)
β
Figure 1.3. The 232Th decay series
An example of alpha decay is given by the decay of
progeny. This is symbolized by the equation
226
226
Ra, the parent, to
222
Rn, the
Ra → 222 Rn + α ,
where α is an alpha particle. This equation can also be written as
226
α
Ra ⎯→
222
Rn.
In alpha decay, the alpha particle and progeny move in opposite directions. The kinetic
energy of the alpha particle is typically in the range from 4.5 to 8.0 MeV. (Here MeV stands for
million electron volts. One MeV is the kinetic energy acquired by an electron that is accelerated
through one million volts.) In the example given above, the progeny, 222Rn, is also radioactive
and, in time, alpha decays to 218Po:
222
Rn → 218 Po + α
Here 222Rn is the parent and 218Po is the progeny. 226Ra is often referred to as the parent of both
222
Rn and 218Po.
In alpha decay, the mass of the progeny’s nucleus is four atomic mass units less than that
of the parent’s nucleus, and the atomic number of the progeny’s nucleus is two elementary
charges less than that of the parent’s nucleus. Because of the change in the atomic number, the
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10 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
chemistry of the progeny is often significantly different than the chemistry of the parent. For
example, 226Ra is a group II metal whose solubility depends in complex way on the composition
of the water and the solids in the aquifer. The progeny of 226Ra, 222Rn, is a gas, which is
relatively soluble in water. 222Rn is also highly volatile, and much of a sample’s radon is lost to
the air.
An example of beta decay is given by the decay of 228Ra, the parent, to 228Ac, the
progeny:
228
Ra ⎯→ 228Ac + β + ν,
where β is the beta particle and ν is the antineutrino. This equation can also be written as
228
β 228Ac,
Ra ⎯→
where the antineutrino is omitted. In beta decay, a neutron in the nucleus decays into a proton, an
electron, and an antineutrino. The electron and the antineutrino are ejected from the nucleus; the
proton remains in the nucleus, which increases the atomic number of the nucleus by 1 unit. Most
of the decay energy shows up as kinetic energy that is distributed between the beta particle and
the antineutrino; a small portion of the decay energy shows up as kinetic energy of the progeny’s
nucleus. The mass of the progeny’s nucleus is slightly less than the parent. Since the progeny has
an atomic number that is one unit greater than the parent, the chemistry of the parent and the
progeny are often very different. In the above equation, the progeny, 228Ac, is also radioactive
and, in time, beta decays to 228Th. In Figure 1.2 and Figure 1.3 an arrow pointed downward
represents alpha decay, and an arrow pointed upward and to the right represents beta decay.
The SI unit of radioactivity is the Becquerel, which is abbreviated Bq. One Bq is 1 decay
per second. Another common unit of radioactivity is the picoCurie, which is abbreviated pCi. 1
pCi is 0.037 decays per second, so that
1 Bq = 27 pCi.
The Bq unit is now preferred over the pCi unit; however, the U.S. EPA still uses the pCi unit in
regulation, so that the pCi unit will be used when discussing EPA regulations.
The alpha activity of a water sample is the number of alpha decays per unit time
occurring in the sample. Thus, if there are 3 alpha decays per second in a water sample, its alpha
activity is 3 Bq or 81 pCi. One usually divides the sample activity by the sample volume to get
the specific alpha activity—if the sample has an activity of 3 Bq, or 81 pCi, and has a volume of
0.5 L, then its specific alpha activity is 6 Bq/L, or 162 pCi/L. The GAA is an estimate of the
specific alpha activity of a water sample. Frequently, both here and in other works, the specific
alpha activity of the water sample is simply called the alpha activity of the water sample.
Radioactive decay is by its very nature a random phenomenon. It is not possible to
predict when an atom will decay, it is only possible to give a probability that the atom will decay
during some time interval. Radioactive decay is characterized by the parameter λ, which is called
the decay constant. Each radionuclide has a unique value of λ. The average time that a
radioactive atom survives before it decays is 1/λ. A related parameter is its half-life t1/2 given by
t1 / 2 =
0.69
λ
.
(1.1)
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Chapter 1: Introductory Concepts | 11
A radioactive atom has a 50% chance of decaying before t1/2 and a 50% chance of decaying after t1/2. A collection of atoms is called a population of atoms. If there are N0 atoms in a
population of radioactive atoms, then, on average, 50% of them (0.5N0) will decay before t1/2,
and 50% of them (0.5N0) will decay after t1/2.
If there are N0 radioactive atoms at time t = 0, the average number N of atoms at time t is
given by
N = N 0 exp(−λt ) .
(1.2)
Because of the randomness of radioactive decay, the actual number of atoms at time t will
usually be somewhat more or fewer than N. Because of the functional form of Eqn. (1.2), a
population of radionuclides is said to decay away exponentially with time.
Usually, multiple radionuclides are present in a sample, and some radionuclides are
producing a series of progeny. In the simplest case, the alpha activity of a sample would be due
to a single alpha emitter that decays to a stable progeny. An example of such an alpha emitter is
210
Po, which decays to stable 206Pb. In such a case, the activity A, given by λN, is obtained by
multiplying both sides of Eqn. (1.2) by λ to give
A = A0 exp(−λ t),
(1.3)
where A0 = λN0, and A0 is the activity at time t = 0
Usually, more than one alpha emitter contributes to a sample’s alpha activity. A sample’s
alpha activity often changes with time, as the populations of its alpha emitters change. Some
alpha emitters are decaying away, some are being produced, and some are decaying and being
produced simultaneously. Thus, in many cases, the activity of an alpha emitter over time is
significantly more complicated than that given by equation (1.3).
RADIONUCLIDE POPULATIONS
The half-lives of the radionuclides from the 238U decay series (Figure 1.2) and the 232Th
decay series (Figure 1.3) range over about 24 orders of magnitude. At the low end of the range is
212
Po, which has a half-life of 0.299 μs, or 3.5 ×10−12 d; at the high end of the range is 232Th,
which has a half-life of 1.4 ×1010 y, or 5.1 ×1012 d. This is an enormous range. A comparable
example is given by the mass of 6 liters of water, which is 6 Kg, and the mass of the entire Earth,
which at 6.0 ×1024 Kg, is 24 orders of magnitude more massive than 6 liters of water.
The number N of atoms of a given radionuclide population is directly proportional to its
half-life, t1/2 and its activity A:
t
N = 1/ 2 A ,
0.69
Thus, for a given activity, A, this equation shows that the number of atoms, N, also ranges
over 24 orders of magnitude. Figure 1.4 is a log-log plot of the number of atoms versus the halflife, in days, for 1 pCi of activity. The half-lives of various radionuclides are indicated by an
arrow.
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12 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
238U
20
234U
16
226Ra
log10(N)
12
8
220Rn
4
230Th
228Ra
210Po
0
-4
232Th
224Ra
222Rn
212Po
212Pb
-8
-12
-12
216Po
214Po
-8
-4
0
4
log10(t1/2)
8
12
Figure 1.4. Radionuclide populations corresponding to 1 pCi of activity
For 1 pCi of activity, Figure 1.4 shows the number of 212Po atoms is 1.6 ×10−8, the
number of 210Po atoms is 6.4 ×105, and the number of 232Th is 2.4 ×1016. These numbers are
averages. Due to the random nature of radioactive decay, the actual number fluctuates somewhat
about the average. The extremely small number for 212Po indicates that a 212Po atoms decays
within microseconds of being formed.
ALPHA-PARTICLE RANGE AND ENERGY AND SELF-ABSORPTION
When an alpha emitter emits an alpha particle, the alpha particle travels in a relatively
straight line until it loses all of its energy and comes to rest. The alpha particle primarily loses its
energy through collisions with electrons of the atoms that make up the material that the alpha
particle is moving through. In a given material, an alpha particle has a well-defined range, which
is just the distance that an alpha particle travels in the material. The range of an alpha particle
depends on its energy. The higher the alpha-particle’s energy, the longer is the range of the alpha
particle. Table 1.1 gives the major alpha-particle energies and ranges in CaF2 for the alpha
emitters of the 238U and 232Th decay series. The number in parentheses, after each alpha-particle
energy, is the fraction of alpha particles emitted at that energy. This fraction is called the
branching ratio at that energy. The calibration standards for EPA Method 900.0 are 230Th and
natural uranium, which is mostly 234U and 238U. These are shown in bold. In addition, 241Am, a
calibration standard for some of the coprecipitation methods, is shown in bold. The ranges for
CaF2 were taken from the National Institute of Standards ASTAR database (Coursey et al 2005).
CaF2 was chosen because it has range-energy characteristics similar to CaO, a common
constituent in the residue of samples prepared by EPA Method 900.0.
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Chapter 1: Introductory Concepts | 13
The data in Table 1.1 show that the energies and ranges for most of the alpha emitters
exceed those of the calibration standards for EPA Method 900.0. For example, the ranges of the
progeny of 226Ra—222Rn (19.7 μm), 218Po (22.6 μm), 214Po (33.3 μm)—all exceed those of the
calibration standards. And the range of 212Po (41.2 μm) is almost three times that of the
calibration standards.
Table 1.1 shows that the alpha emitters with the shortest half-lives have the highest
alpha-particle energies. Many of the short-lived alpha emitters are progeny of the radium
isotopes 224Ra and 226Ra, and whenever these isotopes are present, their progeny will be present
at some level. Consequently, radium-containing samples often have relatively high GAAs.
Even when the path of an alpha particle is pointed towards the detector, the alpha particle
may lose all of its energy in the sample residue or the air gap and never reach the detector (like
path b in Figure 1.1). In this case, the alpha particle is said to be absorbed by the residue or the
air gap. The process of being absorbed before reaching the detector is called self-absorption.
Since an alpha particle’s path length increases with its energy, an alpha particle from a highenergy alpha emitter, like 212Po, has a better chance of reaching the detector than an alpha
particle from a low-energy alpha emitter, like 238U. Thus, the high-energy alpha emitters
contribute more to the GAA than the low-energy alpha emitters.
Table 1.1
Range-energy characteristics of alpha emitters
Alpha
emitter
Decay
series
Half-life
Alpha-particle energies
(MeV)
Alpha-particle range in
CaF2 (microns)
238
U
238
U
4.47×109 y
4.15 (0.21), 4.20 (0.79)
13.0, 13.3
234
U
238
U
2.46×105 y
4.72 (0.28), 4.78 (0.71)
15.7, 16.0
230
Th
238
U
7.54×104 y
4.62 (0.23), 4.69 (0.76)
15.3, 15.6
226
Ra
238
U
1622 y
4.60 (0.06), 4.78 (0.94)
15.2, 16.0
222
Rn
238
U
3.823 d
5.49 (1.00)
19.7
218
Po
238
U
3.05 m
6.00 (1.00)
22.6
214
Po
238
U
164 μs
7.69 (1.00)
33.3
210
Po
238
U
138.4 d
5.31 (1.00)
18.7
232
Th
232
Th
1.41×1010 y
3.95 (0.22), 4.01 (0.78)
12.2, 12.4
228
Th
232
Th
1.91 y
5.34 (0.27), 5.42 (0.72)
18.9, 19.4
224
Ra
232
Th
3.63 d
5.45 (0.05), 5.68 (0.95)
19.5, 20.9
220
Rn
232
Th
55.6 s
6.29 (1.00)
24.3
216
Po
232
Th
145 ms
6.78 (1.00)
27.3
212
Bi
232
Th
60.55 m
6.30 (0.26), 6.34 (0.35)
24.4, 24.6
212
Po
232
Th
0.299 μs
8.78 (1.00)
41.2
241
Am
—
432.6 y
5.44 (0.13), 5.49 (0.85)
19.5, 19.7
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14 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
INGROWTH, SECULAR EQUILIBRIUM, AND DECAY CHAINS
Often, to understand the alpha activity of a sample, one must consider one or more decay
chains rather than a single radionuclide. A decay chain consists of a group of radionuclides that
decay from one to another. A rigorous definition of a decay chain will be given below after some
examples are given. In this work, all of the decay chains will comprise a part of either the 238U or
the 232Th decay series.
In a water sample, all radionuclides are decaying, but some radionuclides are being
produced, by parent decay, at a faster rate than they decay. The process in which the activity of a
radionuclide increases with time is called ingrowth.
In many cases, the ingrowth of a progeny proceeds until the progeny’s activity is
approximately equal to the parent’s activity. At this point the parent and progeny are said to be in
secular equilibrium. Secular equilibrium can occur when the parent’s half-life exceeds the
progeny’s half-life by a factor of about 10 or more. If this condition is fulfilled, then after about 6
progeny half-lives, the parent and progeny activities will be approximately equal. A good
example is that of 226Ra and its progeny, 222Rn. Let A1 be the 226Ra activity, and let A2 be the
222
Rn activity. Suppose that at time t = 0, the 222Rn activity is zero. Then at some latter time (t >
0), the 222Rn activity produced by 226Ra is given by
A2 = A1[1 − exp(−λ2t)],
(1.4)
where λ2 is the decay constant of 222Rn. A plot of A2 versus t for A1 = 1 is given in Figure 1.5.
The 222Rn activity increases with time until after about 6 of its half-lives, or 23 d, the 222Rn and
226
Ra activities are approximately equal. At this point, 226Ra and 222Rn are said to be in secular
equilibrium, and the rate at which 222Rn is produced by 226Ra equals the rate at which 222Rn
decays to 218Po. In EPA Method 900.0, when a sample residue is heated over a flame, most of the
222
Rn is volatilized and lost. However, after the residue solidifies, most of the 222Rn, produced by
226
Ra, is trapped in the residue, and the 222Rn activity increases over a period of 23 days until
222
Rn and 226Ra are in secular equilibrium.
Eqns. (1.1) and (1.4) show that it takes about one progeny half-life for a parent to
produce a significant progeny activity. Thus, 224Ra produces a significant activity of 220Rn (t1/2 =
55.6 s) within a period of a few minutes, but 234U cannot produce a significant activity of 230Th
(t1/2 = 7.54×104 y) over the lifetime of a sample. Thus, if there is no 230Th activity in a sample at
the collection time, then no significant 230Th activity will be appear in the sample over its sixmonth holding time.
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Chapter 1: Introductory Concepts | 15
Activity (arb. units)
1.0
Ra-226
(α, 1600 y)
0.8
Rn-222 (α, 3.82 d)
Po-218 (α, 3.10 m)
Pb-214 (β , 26.8 m)
Bi-214 (β , 19.9 m)
Po-214 (α, 0.16 ms)
0.6
0.4
0.2
0.0
0
5
10
15
20
25
30
Time (day)
Figure 1.5. Secular equilibrium between 226Ra and 222Rn
The concept of secular equilibrium can be extended to include a parent and several of its
succeeding progeny. When a parent half-life exceeds those of its succeeding progeny by a factor
of 10 or more, then, eventually, the activity of each progeny will equal the activity of the parent,
and the parent and all of the progeny are said to be in secular equilibrium. An example is given
by the following decay chain:
222
Rn ⎯α→ 218Po ⎯α→ 214Pb ⎯β→ 214Bi ⎯β→ 214Po ⎯α→ 210Pb ⎯β→ 210Bi ⎯β→ 210Po ⎯α→ 206Pb.
Figure 1.2 shows that the half-life of 222Rn, the parent, exceeds that of the progeny 218Po,
214
Pb, 214Bi, and 214Po by a factor of 10 or more, and after about 4 hr, which is six times time
half-life of 214Pb, the activities of these progeny will be approximately equal to that of 222Rn.
Since the half-live of 210Pb is 22 y, 210Pb and its progeny, 210Bi and 210Po, can never be in secular
equilibrium with 222Rn, when 222Rn is the parent. Since the half-life of 210Pb is 22 y, there is very
little ingrowth of 210Pb over the six-month holding time of a sample, so that 222Rn produces an
insignificant amount of 210Pb and an insignificant amount of the 210Pb progeny, 210Bi and 210Po.
Since a sample has a six-month holding time, one can terminate a decay chain either at the first
progeny that has a half-life that is significantly greater than six months or at the first progeny that
is stable. Thus, the decay chain above can be terminated at 210Pb:
222
Rn ⎯α→ 218Po ⎯α→ 214Pb ⎯β→ 214Bi ⎯β→ 214Po ⎯α→ 210Pb.
(1.5)
One could omit 210Pb from this decay chain, but it is left in to show that its presence
limits the activities of all the progeny that follow it. Consequently, in the decay chains
considered below, the last member is either a radionuclide with a half-life that is much longer
than six months or a stable lead isotope.
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16 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
From Figure 1.2, it is seen that the half-life of 226Ra significantly exceeds all of the halflives of radionuclides in decay chain (1.5). Thus, if one considers the decay chain
226
Ra ⎯α→ 222Rn ⎯α→ 218Po ⎯α→ 214Pb ⎯β→ 214Bi ⎯β→ 214Po ⎯α→ 210Pb,
(1.6)
it is seen that the activities of 222Rn, 218Po, 214Pb, 214Bi, and 214Po will be equal after about 4 hr,
and then these activities will grow over a period of about 23 d, at which point they will be equal
to the 226Ra activity. Then all of the progeny 222Rn, 218Po, 214Pb, 214Bi, and 214Po are in secular
equilibrium with the parent 226Ra.
A more complicated example of secular equilibrium occurs in the 224Ra decay chain:
224
Ra ⎯α→ 220Rn ⎯α→ 216Po ⎯α→ 212Pb ⎯β→ 212Bi ⎯β→ 212Po ⎯α→ 208Pb,
(1.7)
where 208Pb is a stable isotope. Since the half-lives of 220Rn (55.6 s) and 216Po (145 ms) are more
than factor of 10 less than 224Ra (3.6 d), 220Rn and 216Po will be in secular equilibrium with 224Ra
in a matter of minutes. Because of the length of its half-life, several days would be required for
the 212Pb (10.6 hr) to have an activity comparable to 224Ra. However, 212Pb will come into
secular equilibrium with its alpha-emitting progeny 212Po (60.55 min) and 212Bi (0.299 μs) within
about six hours. Thus, in the above decay chain there are two sets of alpha emitters in secular
equilibrium with one another: (1) 224Ra, 220Rn, and 216Po and (2) 212Bi and 212Po.
A decay chain will be named after the first member, or parent. Thus, the decay chain
given by Eqn. (1.6) is called the 226Ra decay chain, and the decay chain given by Eqn. (1.7) is
called the 224Ra decay chain.
SUPPORTED AND UNSUPPORTED ACTIVITY
The activity of a radionuclide in a water sample can often be divided into a supported and
an unsupported component. In an aquifer, progeny atoms can be produced by parent atoms that
reside both in the groundwater and in the solid phases. When a water sample is removed from an
aquifer, parent atoms of the solid phases no longer contribute progeny atoms to the water sample.
Consequently, the progeny activity of a sample is sometimes greater than the activity that could
have been produced by the parent atoms of the sample. The portion of the progeny activity that
could have been produced by the parent atoms is called the supported activity. The rest of the
activity is called the unsupported activity. Most of the 224Ra activity of a groundwater sample is
unsupported because its parent, 228Th, is insoluble. 228Th residing in a solid or on a solid’s
surface can decay to 224Ra, some of which goes into solution. When water is removed from the
aquifer, 228Th remains behind, and the 224Ra activity in the sample is unsupported, and the
unsupported 224Ra activity decays away with its characteristic 3.6-d half-life. Thus, a sample’s
unsupported 224Ra activity is usually equal to its 224Ra activity at the time of collection, and, in
this work, the terms unsupported 224Ra activity and the 224Ra activity at the time of collection
will be used synonymously.
There is often a large unsupported component of 222Rn in water soon after collection. It is
not unusual for a water sample to have a 222Rn activity of 100 to 200 pCi/L and to have a 226Ra
activity of 1 to 2 pCi/L. Thus, in this case, only 1 to 2 pCi/L of 222Rn is supported; the rest is
unsupported.
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Chapter 1: Introductory Concepts | 17
Unsupported 212Po (232Th decay series) would decay away within a few microseconds.
However, 212Po often contributes to the GAA because its activity is supported by other
radionuclides like 228Ra, 224Ra or 212Pb. For example, 212Po is a member of the 228Ra decay chain:
228
Ra β⎯→ 228Ac β⎯→ 228Th α
⎯→
220
Ra α
⎯→
Rn α
⎯→
216
212
208
Po α
⎯→
Pb β⎯→ 212Bi β⎯→ 212Po α
⎯→
Pb,
224
(1.8)
212
Po never comes into secular equilibrium with 228Ra, because the lifetime of the interceding
Th, 1.91 y, is not a factor of 10 less than 228Ra.
In samples that contain a significant 228Ra activity, a substantial 228Th activity can grow
in over the six-month holding time of the sample, as is shown in Figure 1.6. (228Th is soluble in
the acidified sample.) Since the half-life of 228Th is at least a factor of 10 greater than those of all
succeeding radionuclides in Eqn. (1.8), all succeeding radionuclides will come into secular
equilibrium with 228Th within about 21 days of sample collection, or six times the half-life of
224
Ra. Figure 1.6 shows that 1 pCi of 228Ra would produce about 0.2 pCi of 228Th at six months
after sample collection. Since all alpha emitters in Eqn. (1.8) are in secular equilibrium,
Figure 1.6 shows that 1 pCi of 228Ra would produce a total alpha activity of about 1.0 pCi in six
months. It should noted that the 212Bi nuclei emit alpha particles about 36% of time and emit beta
particles about 64% of the time and that 212Bi beta decays into 212Po. Thus, in six months, 1 pCi
of 228Ra produces about 0.072 pCi of 212Bi alpha activity and about 0.128 pCi of 212Po alpha
activity.
228
Ra-228 Activtiy (Arb. units)
1.0
0.8
Ra-228 (β, 5.75 y)
Po-212 (0.64α, 0.30 μs)
Bi-212 (0.36α, 0.64β, 60.6 m)
Pb-212 (β, 10.6 h)
Po-216 (α, 0.145 s)
Rn-220 (α, 55.6 s)
Ra-224 (α, 3.63 2d)
Th-228 (α, 1.91 y)
0.6
0.4
0.2
0.0
0
50
100
150
200
250
300
350
Time (days)
Figure 1.6. Ingrowth of 228Ra progeny
Although the concepts of supported and unsupported activities are important in
understanding the radiological composition of many ground waters, a radionuclide’s initial
©2010 Water Research Foundation. ALL RIGHTS RESERVED
18 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
activity, the activity at the time of sample collection, is used in all of the calculations of this
work. Sometimes a radionuclide’s initial activity is completely supported, like 212Po, is
completely unsupported, like 224Ra, or is partly supported and partly unsupported, like 222Rn.
CHEMISTRY OF THE NATURAL RADIONUCLIDES
2+
Uranium has two common oxidation states: the +4 state (U4+) and the +6 state (UO2 ).
2+
U4+ is insoluble in water and precipitates from solution. UO2 , the uranyl ion, is formed from U4+
under aerobic conditions:
U 4 + + 1 / 2 O 2 + 2 OH − ←
⎯→ UO 22 + + H 2 O
The uranyl ion is frequently complexed by carbonate forming uranyl carbonate complexes:
UO 22+ (aq) + nCO 32− (aq) ←
⎯→ UO 2 (CO 3 ) n2− 2 n (aq) n = 1, 2, 3.
Uranyl carbonate complexes are soluble, and water that is aerobic and that contains carbonate
often has high levels of uranium. In anaerobic water, the uranyl carbonate complexes are reduced
to U4+, which precipitates from solution. Langmuir (1978) provides a comprehensive discussion
of uranium speciation under various conditions and of equilibria between dissolved uranium and
sedimentary ore deposits.
Radium is a group II, or alkaline earth, metal, and has only one common oxidation state:
the +2 state. Radium often coprecipitates with other group II metal sulfates and carbonates. For
example, radium coprecipitates with BaSO4:
Ba 2+ (aq) + Ra 2+ (aq) + SO 24− (aq) ←
⎯→ Ba(Ra)SO 4 (s),
where the parentheses around Ra indicate that the radium is a minor constituent of the solid.
Radium has a tendency to adsorb onto the surface of oxides and hydroxyoxides of iron
and manganese, insoluble salts like BaSO4, and clays. The presence of high levels of other group
II metals, like Mg2+, Ca2+, Sr2+, and Ba2+ can displace radium from these solids by competitive
ion exchange. For example Ca2+ may displace Ra2+:
Ra 2 + ( ad ) + Ca 2 + ( aq ) ←
⎯→ Ra 2 + ( aq ) + Ca 2 + ( ad ) .
Thus, high levels of group II metals in an aquifer can increase the radium level. This is called the
common-ion effect. Langmuir and Riese (1985) provide a comprehensive discussion of the
speciation of radium in water and in minerals from thermodynamic data of radium and from
extrapolating the properties of other group II metals to radium.
Thorium has a single oxidation state (+4) and is usually insoluble in water at near neutral
pH. Thus, levels of thorium isotopes in water just after collection are typically very low. If
thorium is present at the time of collection, it will almost invariably be complexed by inorganic
species like fluoride, chloride, or phosphate or, more probably, by organic species or material
(Langmuir and Herman 1980). Thorium is very soluble in acidic solutions, and since water
samples for GAA analysis are acidified to a pH of 2 or less, any thorium produced in the sample
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Chapter 1: Introductory Concepts | 19
will stay in solution. Over the a sample’s six-month holding time, a substantial 234Th activity can
be produced by 238U decay, and a substantial 228Th activity can be produced by 228Ra decay.
Radon is a noble gas and is relatively soluble in water, so that the radon activity in a
water sample often far exceeds the levels of all other radionuclides. The unsupported 222Rn
activity of a water sample can be as high as 1000 to 2000 pCi/L or more. The unsupported 220Rn
activity of a water sample decays away with a 56-s half-life; thus, any unsupported 220Rn activity
in a sample decays away within 10 minutes.
Most polonium isotopes are very short-lived, with a half-life of 1 hr or less, and
unsupported populations of these isotopes decay away very quickly. An exception is 210Po,
which has a half-life of 138 d. Polonium is typically insoluble in water at near neutral pH.
However, high levels of 210Po are sometimes found in water samples, and in these samples 210Po
is often present in a colloidal form often called radiocolloids. These may be colloidal particles or
may be small clusters of polonium atoms bridged by oxygen or sulfur atoms. The alpha emitter
210
Po comes after 226Ra in the 238U decay series, but little 210Po activity is produced by 226Ra
decay over the six-month sample holding time. The reason for this is that 210Pb comes after 226Ra
but precedes 210Po in the 238U decay series. Because of its 22-y half-life, very little 210Pb, and,
hence, very little 210Po, is formed by 226Ra over a six-month period. For example, in six months,
1 pCi of 226Ra will only produce about 5×10−3 pCi of 210Po. On the other hand, a substantial 210Po
activity can be produced in water samples that contain a substantial unsupported 210Pb activity.
For example, as is shown in Figure 1.7, 1 pCi of 210Pb produces 0.57 pCi of 210Po in six
months.
1.0
Activity (pCi)
0.8
Bi-210 (β , 5 d)
Pb-210 (β, 22)
0.6
Po-210 (α, 138 d)
0.4
0.2
0.0
0
50
100
150
200
250
300
350
Time (days)
Figure 1.7. Ingrowth of 210Po from 210Pb
Even when water samples contain no unsupported polonium, the short-lived polonium
isotopes often substantially contribute to the GAA. For example, 226Ra supports the activities of
the short-lived 218Po and 214Po isotopes; and 224Ra supports the activities of the short-lived 216Po
and 212Po isotopes.
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20 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
DISEQUILBRIUM: RECOIL ENRICHMENT
In the previous section, differences in the solubility between the parent and progeny led
to unsupported progeny activities. In this section a simplified discussion is presented of another
process that can lead to an unsupported progeny activity, even when the parent and progeny are
isotopes of the same element. This process is called recoil enrichment. Osmond and Cowart
(1976 and 1992) and Osmond, Cowart, and Ivanovich (1983) provide a comprehensive
discussion of this phenomenon.
As an example consider the following decay chain:
238
U ⎯α→ 234Th ⎯β→ 234Pa ⎯β→
234
U.
When all sources of uranium—aquifer solids, the solid surfaces, and water—are taken into
account, 234U is in secular equilibrium with 238U. However, in water it is often observed that the
234
U activity exceeds the 238U activity. The reason for this cannot be accounted for by differences
in chemistry, since 234U and 238U are both uranium isotopes. The explanation lies in the fact that
in the alpha decay process both the emitted alpha particle and the progeny atom recoil in
opposite directions with a significant amount of energy. Thus, suppose that a 238U atom is near
the surface of a solid as is shown in Figure 1.8. When the 238U atom decays, the 234Th atom may
recoil through the solid and reach the water. The 234Th atom will precipitate and reside on the
surface of the solid. Then the 234Th atom beta decays to a 234Pa atom, which, in turn, beta decays
to a 234U atom. The 234U atom produced in this way resides on the surface of the solid, and can
go into solution. Without the initial recoil of the 234Th atom, the 234U atom would have still been
in the solid, and could not have ended up in the water. This process enriches water in 234U
relative to 238U, and 234U and 238U are said to be in disequilibrium. Disequilibrium can occur
between other pairs of isotopes, like 224Ra and 228Ra.
234U
234Th
234U
β
234Pa
β
Water
234Th
Surface
α
238U
Figure 1.8. Recoil of 234Th and enrichment of 234U relative to 238U
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Solid
Chapter 1: Introductory Concepts | 21
A SURVEY OF THE OCCURRENCE OF THE RADIONUCLIDES
In this study, the activities of most of the radionuclides in the 238U and 232Th decay series
with a half-life of 3 days or longer were measured. Some exceptions include beta emitters, like
234
Th, which do not produce a significant amount of alpha activity over a six-month period. Also,
the 222Rn activity was not measured because it is volatile, and any unsupported 222Rn in a sample
is lost when the sample is prepared using EPA Method 900.0. 212Pb, a beta emitter, has a half-life
of 10.6 hr, so that if a sample is prepared and analyzed within 2.5 days of collection, the alphaemitting progeny of unsupported 212Pb (212Bi and 212Po) can contribute to the gross alpha-particle
activity (GAA). The 212Pb activity was not measured in this study, and if the GAA of a sample
analyzed within 2.5 days of collection significantly exceeded the expected value, the excess may
be due to 212Pb. The unsupported components of the short–lived radionuclides (with a half-life of
4 hr or less) usually decay away before the sample can be analyzed; however, some short-lived
alpha emitters are produced and supported by a parent that is present in the sample, and, as a
consequence, some short-lived alpha emitters significantly contribute to the GAA. In such cases,
there in no need to experimentally quantify the activity of the short-lived alpha emitters: the
activity of the short-lived alpha emitters can be calculated from the activity of their parents.
In this study, the most common long-lived radionuclides found in samples just after
collection were the radium isotopes—224Ra, 226Ra, and 228Ra—and the uranium isotopes—234U
and 238U. Unsupported 224Ra decays away with a 3.6-d half-life, and several weeks after
collection, its contribution to the GAA is negligible. The next most common radionuclides in
order were 210Po and 210Pb. Both 228Ra and 210Pb are beta emitters, but over the six-month
holding time of a sample, they can produce a significant amount of alpha-emitting progeny. The
activities of the thorium isotopes (232Th, 230Th, and 228Th) were measured, but were typically less
than 0.2 pCi/L, which, for the purposes of this study, is not significant. It should be noted that
one cannot prove that all samples encountered in practice will contain no thorium. For example,
it would be possible for thorium to be attached to colloids suspended in solution. Thus, when the
GAA of a sample cannot be accounted for, a test for thorium may be warranted.
SOME COMMON MISCONCEPTIONS CONCERNING THE GAA
The author has found that, among some water utility operators and personnel involved in
regulation and enforcement, there are several common misconceptions concerning the GAA.
Often it is believed that the GAA should equal the sum of the activities of 226Ra, 234U, and 238U.
However, this is rarely the case. If 226Ra is present, then its alpha-emitting progeny 222Rn, 218Po,
and 214Po will also be present at some level. In addition, samples that are analyzed soon after
collection often contain unsupported 224Ra and its alpha-emitting progeny 220Rn, 216Po, 212Bi and
212
Po. Sometimes samples contain unsupported 210Po, an alpha emitter, and 212Pb, which rapidly
produces the alpha-emitting progeny 212Bi and 212Po.
Because there is a six-month holding time for samples analyzed by EPA Method 900.0,
substantial amounts of alpha emitters can grow into a sample that would not ordinarily be present
just after collection. Thus, when a sample contains a substantial 228Ra or 210Pb activity, their
decay over a six-month period will produce substantial amounts of alpha emitting progeny,
which can significantly contribute to the GAA.
Even when the activities of all alpha emitters in a sample are known, the sum of their
activities rarely equals the GAA. The alpha emitters that emit high-energy alpha particles
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22 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
contribute disproportionately to the GAA. These include the alpha-emitting progeny of 226Ra,
224
Ra and its alpha-emitting progeny, the alpha-emitting progeny of 228Ra, and 210Po.
It is often assumed that the GAA should be reproducible over time; however, this is
frequently not the case. If a sample is prepared twice, the GAA can differ because of differences
in the geometry and mass of the sample residue. This is discussed in more detail in Chapter 2.
Even when a single sample residue is analyzed by the gas proportional counter on two occasions,
the GAA often changes because some alpha emitters are decaying away and some are growing
in, and, in general, the GAA varies in a rather complicated manner with time. The next section
addresses some of the factors that affect the GAA. Although any meaningful analysis of the
GAA must utilize a significant amount of mathematics, in the next section, an effort has been
made to minimize the mathematical content.
©2010 Water Research Foundation. ALL RIGHTS RESERVED
CHAPTER 2
VARIOUS FACTORS THAT AFFECT THE GAA
INTRODUCTION
Ideally, a sample’s gross alpha-particle activity (GAA) would be equal to the total activity of its alpha emitters divided by its volume; however, this is frequently not the case. The contribution of an alpha emitter to the GAA depends on its alpha-particle energy, the residue mass,
the geometry of the residue, and the time at which certain steps in the GAA method are performed. Varying any of these parameters causes the value of the GAA to vary, often substantially. The effect of these parameters on the GAA is discussed in the next three sections. Other
sources of variability and error are addressed in Chapter 6
DEPENDENCE OF THE GAA ON THE EFFICIENCIES OF THE ALPHA EMITTERS
AND THE CALIBRATION STANDARD
For the benefit of the reader, a simplified discussion of the dependence of the GAA on
the alpha-particle energy and on the residue mass is given here. A more comprehensive discussion is given in Appendices C through F. Not all alpha particles emitted in the residue reach the
detector. Some alpha particles miss the detector (like path c in Figure 1.1), and others lose all of
their energy before reaching the detector, being absorbed in either the residue or the air gap (like
path b in Figure 1.1). The higher the residue mass, the higher is the fraction of alpha particles
that are absorbed in the residue. Absorption of alpha particles by the residue and air gap is called
self-absorption.
Because of self-absorption, those alpha particles with the longest ranges have a better
chance of reaching the detector than those with the shortest ranges. Since an alpha particle’s
range increases with its energy (Table 1.1), alpha emitters with high-energy alpha particles—like
224
Ra and its progeny, the 226Ra progeny, the 228Ra progeny and 210Po—contribute more to the
GAA than alpha emitters with low-energy alpha particles—like 234U, 238U, and 226Ra.
The main parameter used to determine an alpha emitter’s contribution to the GAA is its
efficiency, denoted by e. The alpha emitter’s efficiency is just the fraction of its alpha particles
that reach the detector. That is,
number of alpha particles that reach the detector
e=
.
number of alpha particles that are emitted
The efficiency can also be expressed as
(2.1)
C
e= ,
A
where C is the part of the detector’s count rate that is due to the alpha emitter and A is the activity of the alpha emitter in the sample residue. In this equation, the count rate is expressed in
counts per second, and the activity is expressed in decays per second or Becquerels.
As discussed above, the efficiency of an alpha emitter increases with its alpha-particle
energy. However, in EPA Method 900.0, and other GAA methods, it is assumed that the efficiencies of all alpha emitters are equal to the calibration standard’s efficiency. It will be seen that
23
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24 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
this assumption often leads to a GAA that significantly overestimates the alpha activity of the
sample residue.
In evaporation methods, like EPA Method 900.0, either 230Th or natural uranium (mostly
234
U and 238U) are allowed as calibration standards. Before a sample can be analyzed, one must
prepare a mass-efficiency curve for the calibration standard, which is a plot of the calibration
standard’s efficiency versus the residue mass. Sample residues are prepared from a water matrix
that contains a known amount of the calibration standard. The volume of the water matrix used is
varied to produce residues that range in mass from 0 to 100 mg. Once a residue is prepared, its
alpha-particle emission rate is measured using a gas proportional counter; then the efficiency is
calculated using Eqn. (2.1).
Figure 2.1 is a mass-efficiency curve for 230Th. The solid curve is a double exponential
function that was fit to the data. There is considerable scatter in the data, which is largely due to
variations in the geometry of the residues. Some residues are of relatively uniform thickness
across the planchet; others are composed of thick patches that cover less than 50% the planchet.
Most residues have geometries that fall somewhere between these two extremes.
For a given residue mass, uniform residues absorb fewer alpha particles than residues
composed of patches; consequently, uniform residues have higher alpha-particle emission rates,
and higher efficiencies, than patch residues. For a given mass, the higher points in Figure 2.1
correspond to residues that are relatively uniform; the lower points correspond to residues composed of patches. The decrease in the efficiency with residue mass is due to an increased level of
self-absorption as the mass increases.
0.20
Efficiency
0.16
0.12
0.08
0.04
0.00
0
20
40
60
80
100
Residue mass (mg)
Figure 2.1. Mass-efficiency curve for 230Th
©2010 Water Research Foundation. ALL RIGHTS RESERVED
120
Chapter 2: Various Factors that Affect the GAA | 25
Once the calibration standard’s mass-efficiency curve has been prepared, the GAA of
samples can be determined. The GAA of a sample is given by
(2.2)
C
GAA = T
eSV
where V is the sample volume, CT is the residue’s alpha-particle count rate, measured by a gas
proportional counter, and eS is the calibration standard’s efficiency.
The calibration standard’s efficiency is taken from the curve that is fit to the efficiency
data. The scatter in the data of Figure 2.1 shows that there is considerable error in the calibration
standard’s efficiency. This is an inherent problem with the method and does not imply any deficiency on the part of an analyst who prepares a mass-efficiency curve.
The alpha-particle count rate, CT, of a sample residue is the sum of the alpha-particle
count rates due to the individual alpha emitters. Thus, CT is given by
C T = C1 + C 2 + C 3 + . . . ,
where each term on the right corresponds to a distinct alpha emitter. A gas proportional counter
measures the total count rate, CT, and not the count rate of the individual alpha emitters. From
Eqn. (2.1), the total count rate, CT, is given by
C T = e1 A1 + e2 A2 + e3 A3 + . . . ,
(2.3)
where there is an efficiency and an activity for each alpha emitter in the sample residue.
Substituting Eqn. (2.3) into Eqn. (2.2) yields.
(2.4)
1
(e1 A1 + e2 A2 + e3 A3 + . . .) ,
GAA =
eSV
which can be rearranged to give
(2.5)
⎞
e
e
1⎛e
GAA = ⎜⎜ 1 A1 + 2 A2 + 3 A3 + . . .⎟⎟ .
V ⎝ eS
eS
eS
⎠
The purpose of this rearrangement is to express the GAA in terms of the ratios between
an alpha emitter’s efficiency and the calibration standard’s efficiency. These ratios are weighting
factors that determine how much each alpha emitter contributes to the GAA. For high-energy
alpha emitters, these ratios, or weighting factors, are greater than one; i.e.
e
e1
e
> 1, 2 > 1, 3 > 1, . . . .
eS
eS
eS
and Eqn. (2.5) shows that
(2.6)
1
GAA > ( A1 + A2 + A3 + . . .) .
V
or
(2.7)
A
GAA > T .
V
where AT is the total alpha activity of the residue and is given by
(2.8)
AT = A1 + A2 + A3 + . . . ,
©2010 Water Research Foundation. ALL RIGHTS RESERVED
26 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
Eqn. (2.7) shows that the GAA overestimates a sample residue’s alpha activity whenever
the alpha emitters have higher efficiencies (or higher alpha-particle energies) than the calibration
standard’s. Table 1.1 shows that this includes the majority of the alpha emitters in the 238U and
the 232Th decay series. Samples residues containing radium isotopes typically have numerous
progeny that emit high-energy alpha particles, and, consequently, radium-containing samples
often have a GAA that significantly exceeds the sample residue’s alpha activity. (For specific
examples see Appendix C.
GEOMETRY OF ACTUAL SAMPLE RESIDUES AND THE DEPENDENCE OF THE
GAA ON THE RESIDUE GEOMETRY
Much of the scatter in the data of Figure 2.1 can be attributed to variability in the geometry of the sample residue. Residue geometry has two effects on the GAA. First, alpha particles
that are emitted near the center of a planchet (like path a in Figure 1.1) have a higher probability
of reaching the detector than alpha particles emitted near the edge of the planchet (like path c in
Figure 1.1). This is often called the “edge effect.” As a consequence, in some cases, when the
residue is preferentially distributed towards the center of the planchet, the GAA will be higher
than when the residue is preferentially distributed near the edge of the planchet.
Second, the residues can vary from being almost uniform in thickness across the planchet
to being composed of relatively thick patches that cover less than half of the planchet. For a given residue mass, the level of self-absorption by thick patches is higher than the level of selfabsorption by uniformly thick residues. Consequently, for a given residue mass, the GAA of a
patch residue is lower than the GAA of a uniform residue.
In all calculations of the GAA in this work, it is assumed that the radial distribution of the
residues is uniform. This just means that probability that a residue is near the center of the planchet is the same as the probability that the residue is near the edge of the planchet. Uniformity in
the radial distribution is difficult to demonstrate for residues that completely cover the planchet.
The residue could be thicker at the center than near the edge, but this is not always visually obvious. However, for residues composed of patches, photographic images can be used to quantify
the radial distribution of the patches. This is the subject of the rest of this section. Readers who
desire can skip to the next section with little loss of understanding.
Let x be the fraction of the planchet covered by patches, r3 be the radius of the planchet, r
be the distance of a point from the center of the planchet, and let ξ(r) be a distribution function
that gives the fraction of the planchet that is covered by patches between the radii r and r + dr. If
the radial distribution of a residue in the planchet were entirely uniform, then one would have
ξ(r) = x for all r; if a residue were preferentially distributed toward the center of the planchet,
then one would have ξ(r) > x near r = 0 and ξ(r) < x near r = r3; and if a residue were preferentially distributed toward the edge of the planchet, then one would have ξ(r) < x near r = 0 and
ξ(r3) > x near r = r3. If a residue deviates from radial uniformity at some radius r, one would
have that ξ(r) ≠ x. Thus, a measure of this deviation, denoted by σ, is given by
(2.9)
2 r
σ 2 = 2 ∫ 3 [ξ (r ) − x] 2 rdr .
0
r3
Here σ is just the standard deviation of ξ(r). When the radial distribution of the patches is
uniform, σ = 0, and when the radial distribution deviates from uniformity, σ > 0. The highest degree of non-uniformity occurs when one disc-shaped patch occupies the center of the planchet or
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Chapter 2: Various Factors that Affect the GAA | 27
when one ring-shaped patch occupies the outer edge of the planchet. In either case, σ attains a
2
maximum its value σmax, which is given by σmax
= x (1 − x). Thus, σ can be used as measure of
the uniformity of the radial distribution, the higher the value of σ, the more that the distribution
deviates from uniformity. Since the maximum value of σ depends on x, the relative standard deviation σ /σmax, which ranges from zero to one, will be used a measure of non-uniformity.
Figure 2.2. Picture of a sample with a patch residue. An example of a grayscale photograph
(left) and the corresponding threshold image (right). Residue mass = 39.9 mg; x = 0.353;
σ/σmax = 0.247.
Source: Arndt and West 2007. An Experimental Analysis of Some of the Factors Affecting
Gross Alpha-Particle activity with an Emphasis on 226Ra and its Progeny. Health Phys. 92:148156.
The value of σ/σmax was determined for a variety of residues with the aid of ImageJ 1.35q
software (Rasband 1997-2006). A 7.2 megapixel camera was used to take an 8-bit, grayscale image of the residues. Figure 2.2 (left) is an example. A threshold was determined visually for each
image such that pixels exceeding the threshold coincided with the patches. In Figure 2.2 (right),
the pixels exceeding the threshold are shown in white for the image on the left. The integral in
Eqn. (2.9) was evaluated numerically using 100 radial intervals of equal area. The number of
pixels exceeding the threshold in each interval was used to determine ξ(r). Figure 2.3 is a plot of
σ/σmax versus x for 22 samples.
©2010 Water Research Foundation. ALL RIGHTS RESERVED
28 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
Figure 2.3. Plot of σ/σmax versus x contoured with values of e.
Source: Arndt and West 2007. An Experimental Analysis of Some of the Factors Affecting
Gross Alpha-Particle activity with an Emphasis on 226Ra and its Progeny. Health Phys. 92:148156.
To be useful, it is necessary to correlate σ/σmax with the deviation of the efficiency from
that of a radially uniform residue. For a gas proportional counter, the geometry that gives an efficiency with the largest negative deviation from radial uniformity occurs when the residue has a
disc-shaped region in the center with zero coverage (ξ(r) = 0) and a ring of residue around the
perimeter of the planchet with unit coverage (ξ(r) = 1). Let the area of the central disc be eSP,
where e is measure of radial nonuniformity and SP is the area of the planchet. For a given e and x,
this geometry has the function
⎧0 if r < r1 ,
⎪
(2.10)
ξ (r ) = ⎨ x if r1 < r < r2 ,
⎪1 if r < r < r ,
2
3
⎩
2
2
2
2
2
= e/(1 − x).
where r1 = er3 , r2 = [1 − ex/(1 − x)]r3 , and 0 ≤ e ≤ 1 − x. For this function, σ2/σmax
The curves in Figure 2.3 correspond to various values of e. An expression similar to Eqn. (2.10)
holds when the central disc has unit coverage and the outer ring has zero coverage.
For a given e and x, the percent difference D between the efficiency εN of a residue given
by Eqn. (2.10) and the efficiency εU of a radially uniform residue of the same thickness is given
by
ε −εU
e (ε R − ε D )
× 100 =
× 100 ,
D= N
εU
εU
where εD is the efficiency of the central disc-shaped part of the uniform residue (r < r1) and εR is
the efficiency of the outer ring-shaped part of the uniform residue (r2 < r < r3).
For 226Ra, εU = 0.229 for a residue of zero mass (Table C.1). Approximate values for εD
(≈ 0.280) and εR (≈ 0.161) were estimated by spotting 230Th on the center and at the rim of a
planchet. (230Th has an alpha-particle energy nearly equal to that of 226Ra.) From this data ⏐D⏐ ≤
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Chapter 2: Various Factors that Affect the GAA | 29
52e%, so that for e = 0.15, ⏐D⏐ ≤ 7.8%. In Figure 2.3 it is seen that all except one point lie below the e = 0.15 curve, showing that, for these samples, the radial distributions of the thick
patches were relatively uniform. If there were a thin uniform residue of material between the
patches, then the deviation from a uniform residue would be even smaller.
TIME INTERVALS THAT AFFECT THE GAA
In many samples, the GAA is not a constant, but changes with time. For example, one
might measure the GAA of a sample and get a value of 18 pCi/L. One may wish to verify this
value and measure the GAA of the same sample residue several days later to find that it is still 18
pCi/L, that it has increased to 25 pCi/L, or that it has decreased to 10 pCi/L. Depending on the
radiological composition of the sample, all three of these situations are possible. Over the course
of the two measurements, radionuclides with long half-lives do not decay substantially, unsupported radionuclides with short half-lives partially or completely decay away, and the progeny of
some radionuclides grow in and produce a substantial alpha activity.
To understand why the GAA of some samples can change substantially with time, one
must know what the radiological composition of the sample residue is at the time that the sample
is prepared and how the activities of the radionuclides evolve with time. In this effort, it is necessary to consider three important points in time: (1) the sample collection time, (2) the sample
preparation time, which is the time at which the residue is heated over a flame, and radon is
quantitatively lost, and (3) the sample analysis time, which is the time at which the alpha-particle
emission rate of the residue is measured with a gas proportional counter. Further, it will be useful
to define three time intervals: (1) the time between sample collection and sample preparation,
which will be denoted by T1, (2) the time between sample preparation and analysis, which will be
denoted by T2, and (3) the time between sample collection and analysis, which will be denoted
by T3, where T3 = T1 + T2.
The uranium isotopes 234U and 238U have extremely long half-lives (Figure 1.2), and neither isotope produces a significant amount of alpha-emitting progeny over the six-month holding
time of a water sample. Consequently, their contributions to the GAA do not vary with time.
226
Ra has an extremely long half-life (Figure 1.2), and its contribution to the GAA does
not vary with time. The 226Ra progeny, 222Rn, is quantitatively lost when a residue is heated over
a flame; however, once the residue solidifies, it traps most of the 222Rn, produced by 226Ra.
Moreover, 222Rn, in turn, produces the alpha emitters 218Po and 214Po, and, as shown in
Figure 1.5, the activities of 222Rn, 218Po, and 214Po grow over time until they attain their maximum values at about 23 days following preparation. Thus, the contribution of the 226Ra progeny
to the GAA depends on the time between sample preparation and analysis, T2.
Like 222Rn, 220Rn, in the 224Ra decay chain [Eqn. (1.7)], is quantitatively lost when the residue is heated over a flame. However, secular equilibrium between 220Rn and 224Ra is established in a matter of minutes, and the loss of 220Rn has virtually no effect on the GAA. Since the
half-life of 224Ra is 3.6 d, with those of its progeny being less, the contribution of unsupported
224
Ra and its progeny to the GAA can be substantial shortly after sample collection; however,
this contribution decreases over time and is negligible after about three weeks. Thus, the contribution of 224Ra and it progeny depends on the time between sample collection and analysis, T3.
210
Po has a half-life of 138 d, and its contribution to the GAA decreases exponentially
with the time between sample collection and analysis, T3. 228Ra and 210Pb are beta emitters, but
they can produce a significant amount of alpha activity over the six-month holding time of a
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30 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
sample. The amount of alpha activity they produce depends on the time between sample collection and analysis, T3.
Some samples contain a complex mixture of radionuclides, with some decaying, some
growing in, and some remaining relatively constant in activity. Specific examples are presented
in Chapter 4. Many factors that affect the GAA also affect the gross beta activity. Welch et al
(1995) discussed the dependence of the gross beta activity of a sample on the sample holding
time and on the method of preparation. As with the GAA, the gross beta activity can change over
time as some beta emitters decay and as others grow in. Further, tritium is volatized during sample preparation and does not contribute to gross beta activity.
GRAB SAMPLES AND QUARTERLY COMPOSITE SAMPLES
There are two common types of samples used in testing water for radionuclides: grab
samples and quarterly composite samples. For a grab sample, the water source is sampled once.
For a quarterly composite sample, equal aliquots of water are combined in each of four consecutive three-month periods. A quarterly composite sample is intended to represent an average sample composition over the course of a year in water sources where there may be some annual variation in the composition. In EPA Method 900.0, a sample holding time of six months is allowed,
which for grab samples begins when the sample is collected and for quarterly composite samples
begins when the fourth aliquot is added (U. S. EPA 2007).
The GAA of a grab sample and a quarterly composite sample may differ substantially,
even when the aliquots added to the quarterly composite sample are of the same radiological
composition as the aliquot used for the grab sample. In a quarterly composite sample, 210Po,
224
Ra, and 224Ra progeny in the first three aliquots will have partially or completely decayed
away by the time that the fourth aliquot has been added, and 228Ra and 210Pb in the first three aliquots will have been producing alpha–emitting progeny for as long as nine months by the time at
which the fourth aliquot had been added. Thus, the radiological composition of a grab sample
and a quarterly composite sample can differ significantly; and the radiological composition of a
grab sample held for many months or the radiological composition of a quarterly composite
sample of any holding time can differ substantially from the radiological composition of a sample at the time of collection.
©2010 Water Research Foundation. ALL RIGHTS RESERVED
CHAPTER 3
METHODS
INTRODUCTION
One of the main objects of this study was to quantify each decay chain’s contribution to
the gross alpha-particle activity (GAA). To accomplish this, the efficiencies of the alpha emitters
of the 238U and 232Th decay series had to be determined. It can be difficult to accurately determine the efficiencies in actual sample residues. First, the geometries of such residues are highly
variable and difficult to characterize, which would cause the uncertainties in the efficiencies to
be unacceptably large. Second, the radionuclide of interest is often part of a decay chain, where
there is a parent and a series of its progeny, and it would be difficult to measure the efficiency for
one radionuclide when many are present simultaneously. Often, a group of alpha emitters come
into secular equilibrium with one another within a matter of minutes or of a few hours. In such
cases, for purposes of this study, all that is required is the average efficiency of the group. For
some decay chains, like the 226Ra decay chain, one needs the efficiency of the parent, which is a
group that contains one alpha emitter, and the average efficiency of the progeny—222Rn, 218Po,
and 214Po—which is a group that contains three alpha emitters. For the 224Ra decay chain, there
are two groups (the first being 224Ra 220Rn, and 216Po; the second being 212Bi and 212Po) of alpha
emitters in secular equilibrium with one another, and one needs the average efficiency for both
groups. To obtain the group efficiencies, two conditions must hold at some initial point in time:
(1) the activities of the members of each group must be known, and (2) any two groups must not
be secular equilibrium with one another. These conditions allow for the determination of each
group’s average efficiency from the measurement of the total alpha activity of the residue as a
function of time.
The 224Ra and 226Ra decay chains efficiencies can be determined by coprecipitating the
parent in a BaSO4 residue and using EDTA to chelate the progeny, preventing the progeny from
coprecipitating with BaSO4. The time dependence of the alpha activity of the BaSO4 residues can
be used to obtain the efficiencies of the two decay chains. It is also relatively easy to coprecipitate 241Am with BaSO4 residues to obtain 241Am efficiencies. Although 241Am does not occur naturally, the 228Th (of the 228Ra decay chain) efficiencies are virtually equal to the 241Am efficiencies, because both alpha emitters have nearly identical alpha-particle energies. The 210Po efficiencies will be obtained by interpolation between the 226Ra and 241Am efficiencies. Another advantage of using BaSO4 is that it is relatively easy to prepare BaSO4 residues that are visibly uniform. Once the efficiencies are determined in BaSO4, they can be determined in residues of
another composition using the Bragg-Kleeman rules, and they can be determined in residues of
nonuniform geometry. These techniques are discussed in detail in Appendices C through F.
MATERIALS AND INSTRUMENTS
All chemicals were ACS reagent grade. The radioactive standards were NIST traceable
(ANSI 1995) and purchased from Analytics, Inc. (1380 Seaboard Industrial Blvd., Atlanta, GA
30318) or Isotope Products Laboratories (24937 Avenue Tibbitts, Valencia, CA 91355). Gamma
spectroscopy was performed with Canberra Model GC4519 high-purity germanium detectors
using Genie 2000 2.1A software for data acquisition and analysis (800 Research Parkway, Meri-
31
©2010 Water Research Foundation. ALL RIGHTS RESERVED
32 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
den, CT 06450. Gas proportional counting was done with a Protean Instruments Corporation
model MPC 9604 gas proportional counter (231 Sam Rayburn Parkway, Lenoir City, TN 37771).
The stainless steel planchets were 2 in. (50 mm) in diameter and had a series of seven ridges on
the bottom (Coy Laboratory Products Inc., 14500 Coy Drive, Grass Lake, MI 49240).
PREPARATION OF BA(RA)SO4 RESIDUES FOR THE DETERMINATION OF THE
EFFICIENCIES OF THE 224RA AND 226RA DECAY CHAINS
Ba(Ra)SO4 residues were prepared by coprecipitating radium with BaSO4. The method
used to prepare Ba(Ra)SO4 residues for the determination of the efficiencies of the 224Ra and
226
Ra decay chains has been described by Arndt and West (2008a). The method is based on that
of Goldin (1961), except that the precipitation of the mixed lead-barium sulfate from a basic citrate solution is replaced by a precipitation of BaSO4 from an EDTA solution, the dissolution of
the precipitate, and the re-precipitation of the BaSO4, which allows radium to coprecipitate but
reduces the activity of all radium progeny to negligible levels. Reagents containing sodium (e.g.,
H2Na2EDTA) led to Ba(Ra)SO4 residues that were hygroscopic, which is undesirable, since the
efficiencies depend on residue mass. Thus, no reagents containing sodium were used. This method usually gave Ba(Ra)SO4 residues that appeared to be of uniform thickness and gave
Ba(Ra)SO4 residues that initially had negligible amounts of thorium, polonium, bismuth, and
lead. The time of the second coprecipitation step corresponded to the start of the ingrowth of the
progeny of 224Ra and 226Ra (time t = 0), defined in Appendix C.
A 226Ra standard was used as a source of 226Ra. To measure the two efficiencies of the
226
Ra decay chain, using the model of the Appendix C, two conditions had to hold for the
Ba(Ra)SO4 residues: (1) the initial progeny activities had to be negligible, and (2) the 226Ra activity in the residue had to be well-defined. The amount of radon that coprecipitates with BaSO4
is negligible (Sill and Williams 1969), and as was discussed above, the activities of all other
progeny were negligible, so that condition (1) was fulfilled. The 226Ra activity in the Ba(Ra)SO4
was determined by gamma spectroscopy using the 186.2 keV full-energy peak thus meeting condition (2). The complete method for the determination of the efficiencies has been described
elsewhere (Arndt and West 2007) and is presented, in part, in Appendix C.
A description of the determination of the efficiencies of 224Ra and its progeny has been
described elsewhere (Arndt and West 2008a) and is presented, in part, in Appendix C. Because
of the short half-life of 224Ra, it proved useful to use an aged 228Ra standard as a source of 224Ra.
The 224Ra activity in the 228Ra standard was determined by gamma spectroscopy using 228Ac
(which was in secular equilibrium with 228Ra) in the standard to generate an energy-efficiency
calibration curve. Then the full-energy peaks of 224Ra and its progeny, 212Pb and 208Tl, were used
to determine the 224Ra activity. The 224Ra activity determined in this way was in good agreement
(within 2%) with the 224Ra activity determined by calculation using the Bateman equations. Consequently, the Bateman equations were used to determine the initial 224Ra activity in the efficiency experiments.
To measure the two efficiencies of the 224Ra decay chain, using the model of the Appendix C, three conditions had to hold for the Ba(Ra)SO4 residues: (1) the initial 228Th, 212Pb, and
212
Bi activities had to be negligible, (2) the 228Th activity that grows in had to be negligible during the course of the experiment, and (3) the initial 224Ra activity had to be well-defined. As has
already been discussed, condition (1) is fulfilled. Condition (2) is fulfilled because, due to its 1.9y half-life, the production of 228Th from 228Ra over the course of a 24-h experiment is negligible.
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Chapter 3: Methods | 33
(After 24 hr, 6.5×10−4 Bq of 228Th activity grows in for each Becquerel of 228Ra activity.) Condition (3) can be satisfied by using 228Ra—from the 228Ra standard—as a tracer for 224Ra. If at least
40 hours have passed since the coprecipitation, the 228Ra and 228Ac activities in the Ba(Ra)SO4
will be equal (in secular equilibrium), and the 228Ac activity can be determined by gamma spectroscopy. The chemical yield γ of radium—the ratio of the 228Ra activity in the residue to that
used in the coprecipitation—was used to determine the 224Ra activity in the Ba(Ra)SO4 residues.
It should be mentioned that the methods discussed here resemble other methods in which
BaSO4 is used to coprecipitate radionuclides from water samples and gamma spectroscopy is
used to determine the activity of certain radionuclides in BaSO4 (Parsa et al 2004 and SM
2005a). However, the objective here was to measure the efficiencies of the alpha emitters of various decay chains for a gas proportional counter, and the objective of the other works were to use
gamma spectroscopy too analyze water samples for various radionuclides including 212Pb, 224Ra,
226
Ra, and 228Ra. Here, 228Ra is used as a tracer to determine the 224Ra yield; in the other methods, the gravimetric yield of BaSO4 is used to determine the 224Ra and 228Ra yields. Here, the
initial 224Ra activity in the BaSO4 is determined from the 228Ra yield and a calculation using
Bateman equations; in other methods, gamma spectroscopy is used to determine the 224Ra activity in the BaSO4. Here, EDTA is used to prevent the coprecipitation of radium progeny with BaSO4; in the other methods, there in no need to prevent the coprecipitation of radium progeny—
the coprecipitation of 212Pb (the progeny of 224Ra) is necessary to determine the unsupported
212
Pb activity of the sample.
PREPARATION OF BA(AM)SO4 RESIDUES FOR THE DETERMINATION OF 241AM
EFFICIENCIES
The method used to prepare Ba(Am)SO4 residues was based on that of Sill, Puphal, and
Hindman (1974). Over the course of an experiment, 241Am does not decay to any significant extent because of its 430-y half-life, and 241Am does not produce a significant progeny activity because its direct progeny, 237Np, has a half-life of 2.14 × 106 y. The 241Am yield in the
Ba(Am)SO4 residues was determined by gamma spectroscopy using its 59.54 keV full-energy
peak. Further details on the determination of the 241Am efficiencies have been described elsewhere (Arndt and West 2008b) and are presented, in part, in Appendix C. The determination of
210
Po efficiencies from 241Am and 226Ra efficiencies have been described elsewhere (Arndt and
West 2008c), and are presented, in part, in Appendix C.
EXPERIMENTS TO QUALITATIVELY CHARACTERIZE THE VOLATILITY OF
POLONIUM IN SAMPLE RESIDUES
To qualitatively determine the volatility of polonium, a solution was prepared containing
45 mg of NaNO3 and 55 mg of KNO3 per mL of solution. Samples were prepared by adding an
aliquot of the NaNO3-KNO3 matrix, about 0.8 Bq of 210Po standard, and 10 mL of 16 M HNO3 to
a 50-mL centrifuge tube and pouring the contents into a 50-mm planchet. The contents of the
planchet were dried under a heat lamp, the planchets were weighed to obtain the residue masses,
and the planchets were counted on the gas proportional counter in alpha-beta mode for 1 hr. The
planchets were heated over a flame for about 30 s, reweighed, and recounted. The planchets were
then heated over a flame for an additional 60 s, reweighed, and recounted. The results of these
experiments are discussed in Chapter 6.
©2010 Water Research Foundation. ALL RIGHTS RESERVED
34 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
COLLECTION AND ANALYSIS OF GROUNDWATER SAMPLES
Samples were collected from around the continental United States by volunteers from
water utilities and private wells and personnel from the South Carolina Department of Health and
Environmental Control, the South Dakota Department of Environment and Natural Resources,
the South Dakota Geological Survey, and the United States Geological Survey.
The sampling kit consisted of four containers: (1) a 2.5-gallon polyethylene container,
(2) a 1-L polyethylene bottle, (3) a 250-mL wide-mouth bottle, and (4) a 100-mL wide-mouth
bottle. The sampling kit included a pH strip and color indicator to measure the water’s pH. About
50 mL of 8 M nitric acid was added to the 2.5-gallon container; the container was filled to about
one-half of its volume and agitated; and then the container was filled nearly to capacity, capped,
and agitated again. Water from this container was used for the following analyses: the gross alpha-particle activity (GAA), gross radium activity (GRA), isotopic uranium, isotopic thorium,
224
Ra, 226Ra, 228Ra, 210Pb, and the metal analyses (Na, K, Mg, Ca, Ba, Mn, Fe).
The 1-L container was filled to a mark on the side of the bottle that allowed enough headspace so that 50 mL of 16 M nitric acid and about 20 pCi of 209Po tracer could be added to the
container upon receipt by the laboratory. After addition of the acid and tracer, the contents of the
bottle were mixed, and the bottle was allowed to stand for two weeks before preparation was initiated to assure that the 210Po had desorbed from the container wall.
The 250-mL container was filled and placed on ice in a Styrofoam cooler in the field.
Aliquots from this container were used to perform the following analyses: nitrate concentration,
sulfate concentration, chloride concentration, dissolved silica concentration, pH, conductivity,
alkalinity, and turbidity. In three cases where the participants made mistakes in collecting this
sample, chloride and sulfate were determined by ion chromatography using an aliquot from the
2.5 gallon container, and the other analyses were not performed.
The 100-mL container was filled to a mark placed on the bottle, then 40 mL of 6 M
NaOH solution and 100 mg of ascorbic acid were placed in the container, and the contents were
shaken to mix its contents. The contents of this container were used to determine the sulfide concentrations of the water samples. In four cases, the volunteers made mistakes in collecting this
sample, and the sulfide concentration was not determined.
RADIOCHEMICAL METHODS
The radiochemical methods used in this research are given in Table 3.1. The methods for
the gross-alpha particle activity (GAA), the gross radium activity (GRA), 226Ra, 228Ra, are all
EPA-approved methods. The methods for isotopic uranium, isotopic thorium, and 210Pb, which
employ proprietary resins, are available from Eichrom Technologies, LLC (Eichrom Technologies, LLC, 8205 S. Cass Ave., Suite 106, Darien, IL 60561, www.eichrom.com). The 210Po and
224
Ra methods were developed in this laboratory and are described in Appendices K and L, respectively. The isotopic uranium and thorium are alpha spectroscopic methods that employ a cerium fluoride microprecipitate (Sill and Williams 1981) to prepare the sample for counting. The
224
Ra is an alpha spectroscopic method that employs a barium sulfate microprecipitate, which is
described in Appendix L. The alpha spectrometer is an Ortec Octete-Plus Alpha Spectrometer
(Advanced Measurement Technology Inc., 801 South Illinois Avenue, Oak Ridge, TN 37830)
with vacuum modulation and an applied bias between sample and detector to prevent recoil contamination of the detector (Sill and Olson 1970).
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Chapter 3: Methods | 35
Table 3.1
Radiochemical methods
Radionuclide(s)
Method
Reference
234
U, 235U, 238U
Eichrom Method ACW02
Eichrom 2001
228
Th,230Th, 232Th
Eichrom Method ACW10
Eichrom 1999
224
Ra
See Appendix L
See Appendix L
226
Ra
EPA Method 903.1
U.S EPA 1980d
228
Ra
EPA Method 904.0
U.S EPA 1980e
210
Pb
Eichrom Method OTW01
Eichrom 2005
210
Po
See Appendix K
See Appendix K
GAA
EPA Method 900.0
U.S EPA 1980a
GRA
EPA Method 900.1
U.S EPA 1980b
INORGANIC METHODS
Table 3.2 gives a summary of the inorganic methods used in this work. The main purpose
in determining the inorganic composition of the samples was to estimate the composition of the
sample residues produced by EPA Method 900.0. The method for estimating the composition of
a residue from the composition of the water sample is described in Appendix D. There are two
methods for the determination of chloride in Table 3.2. The reason for this is that the analysis of
some samples for chloride by EPA Method 325.2 was not performed by mistake. Consequently,
some samples were analyzed for chloride by EPA Method 300.0 using an aliquot from the 2.5gallon polyethylene container that was preserved with nitric acid. Because of the large nitrate
level of these samples, the nitrate peak was exceedingly large and interfered with the chloride
peak in the undiluted samples. Consequently, the samples were diluted by a factor of 10 to alleviate this problem. It should be mentioned that a sample’s chloride concentration is not required
to determine the composition of a residue because during preparation of the residues, chloride is
quantitatively volatilized using concentrated nitric acid.
©2010 Water Research Foundation. ALL RIGHTS RESERVED
36 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
Table 3.2
Inorganic methods
Analyte(s)
Method
Reference
Na, K, Mg, Ca, Ba, Fe, Mn
EPA Method 200.7
U.S. EPA 1994a
Chloride
EPA Method 325.2
U.S. EPA 1978
Chloride
EPA Method 300.0
U.S. EPA 1993a
Nitrate
EPA Method 353.2
U.S. EPA 1993b
Sulfate
EPA Method 375.2
U.S. EPA 1983
Sulfide
Standard Methods 4500-S2− G
SM 1998a
Dissolved silica
Standard Methods 4500-Si F
SM 1992a
Alkalinity
Standard Methods 2320
SM 1992b
Conductivity
Standard Methods 2510
SM 1992c
pH
Standard Methods 4500-H+
SM 1992d
Turbidity
Standard Methods 2130B
SM 1998b
©2010 Water Research Foundation. ALL RIGHTS RESERVED
CHAPTER 4
GROSS ALPHA-PARTICLE ACTIVITY OF THE DECAY CHAINS
INTRODUCTION
The object of this chapter is to provide a starting point for the calculation of a sample’s
gross alpha-particle activity (GAA) from the known or estimated radiological composition of the
sample. For this calculation, it is not necessary to consider the 238U or 232Th decay series as a
whole. Instead, each decay series can be partitioned into several decay chains, some of which
may overlap, and each decay chain’s contribution to the GAA can be determined from the parent
activity at the time of sample collection. Then the contributions of the decay chains can be added
together to get the total GAA. The GAA for each decay chain is plotted for both smooth and
patch residues and for both grab and quarterly composite samples for residues with the inorganic
composition given in Table D.1, which is typical of groundwater from a sandstone aquifer. For
the quarterly composite sample, it will be assumed that the second, third, and fourth aliquots
were added to the sample at 90, 180, and 270 days, respectively, after the first aliquot was added.
In Chapter 5, the GAA of a hypothetical sample is calculated using the graphs presented in this
chapter.
Table 4.1 gives the decay chains for the 238U decay series; Table 4.2 gives the decay
chains for the 232Th decay series. A decay chain starts with a parent and ends with a radionuclide
that is either a stable lead isotope or a radionuclide with a relatively long half-life, which does
not produce a substantial amount of activity over the six-month holding time of a sample. In Table 4.1 and Table 4.2, the half-life of the last member of a decay chain is given in parentheses, if
it is not a stable lead isotope. The use of decay chains is necessary because whenever the parent
of a decay chain is present, the progeny grow in at a predicable rate, so that the parent and progeny cannot be treated separately. A decay chain will be identified by its parent; for example, the
decay chain starting with 224Ra is called the 224Ra decay chain.
The use of decay chains often allows one to treat short sections of the decay series, which
simplifies the analysis of the decay series considerably. In order to calculate the contribution of a
decay chain to the GAA, the activity of the parent must be known at some point in time, which,
in this work, is taken to be the sample collection time. For the 238U, 234U, and 226Ra decay chains,
the activity of the parent does not change significantly over the holding time of a sample. For the
210
Pb and 228Ra decay chains, the extent of parent decay is small, but measurable, for the 210Po
decay chain, there is substantial parent decay over the six-month holding time of a sample, and
for 224Ra decay chain, all members of the decay chain completely decay away after about three
weeks following collection. For the 238U, 234U, and 210Po decay chains, the parent is the sole contributor to the GAA; however, even in these cases, it is still instructive to use the concept of a
decay chain to indicate that the parent does not produce a significant amount of any alpha emitter
beyond the last member of the decay chain.
In the 232Th decay series, the three decay chains overlap. The 228Ra decay chain includes
the members of the 224Ra decay chain, and the 224Ra decay chain includes the members of the
212
Pb decay chain. If the activities of 228Ra, 224Ra, and 212Pb in a sample at collection time are all
nonzero, then all three decay chains must be included in the calculation of the GAA. Frequently,
not all of the parent activities at the time of sample collection are known and they must be approximated. For example, most laboratories do not routinely analyze samples for 224Ra, but, to a
37
©2010 Water Research Foundation. ALL RIGHTS RESERVED
38 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
first approximation, the 224Ra activity can be taken to be equal to the 228Ra activity. Most laboratories do not analyze for 212Pb, but since its half-life is quite short (10.6 h), the contribution of
the 212Pb decay chain to the GAA is negligible at 2.5 days following sample collection.
Table 4.1
Decay chains of the 238U decay series
Parent
Decay chains
238
U
238
α→234Th ⎯
β→234Pa β
234
5
U ⎯
⎯→ U (2.46×10 y)
234
U
234
α→ 230Th (7.54 × 104 y)
U ⎯
226
Ra
226
222
α 218 α 214 β 214 β 214Po α
210
Ra α
⎯→ Rn ⎯→ Po ⎯→ Pb ⎯→ Bi ⎯→
⎯→ Pb (22 y)
210
Pb
210
206
Pb β⎯→ 210Bi β⎯→ 210Po α
⎯→ Pb
210
Po
210
206
Po α
⎯→ Pb
Table 4.2
Decay chains of the 232Th decay series
Parent
Decay chain
β→228Ac ⎯
β→228Th α
224
α 220
α 216 α 212 β 212 β 212Po α
208
Ra ⎯
⎯→ Ra ⎯→ Rn ⎯→ Po ⎯→ Pb ⎯→ Bi ⎯→
⎯→ Pb
228
Ra
228
224
Ra
224
212
220
216
208
Ra α
⎯→
Rn α
⎯→
Po α
⎯→
Pb β⎯→212Bi β⎯→ 212Po α
⎯→
Pb
212
Pb
212
208
Pb β⎯→212Bi β⎯→ 212Po α
⎯→
Pb
In several decay chains, all of the progeny, except the last, eventually come into secular
equilibrium with the parent, and in some decay chains, secular equilibrium between the parent
and progeny is not possible. For some decay chains, the situation is considerably more complex.
For example, in the 224Ra decay chain, there are two groups of alpha emitters that are in secular
equilibrium with one another. The first group consists of 224Ra, 220Rn, and 216Po; the second
group consists of 212Bi and 212Po. The activities of the members of the two groups approach one
another, but secular equilibrium between the two groups is not established because the half-life
of 224Ra is not at least ten times greater than 212Pb. The 228Ra decay chain contains the members
of the 224Ra decay chain. Thus, it might be expected that the relationship among the alpha emitters of the 228Ra decay chain would be at least as complex as that of the 224Ra decay chain; however, this is not the case. 228Th is the third member of the 228Ra decay chain, but the first alpha
emitter. The half-life of 228Th, at 1.91 years, is more than a factor of 10 greater than the half-lives
of all of the progeny that follow it (Figure 1.3). Thus, all of the alpha emitters of the 228Ra decay
chain eventually come into secular equilibrium with 228Th. In fact, secular equilibrium is established within 21 days, which is six times the half-life of 224Ra.
In principle, any radionuclide could be the parent of a decay chain, and not every possible
decay chain is treated in this report. Since thorium is insoluble in most ground waters, none of
the decay chains for the calculation of the GAA considered in this report has a thorium isotope as
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Chapter 4: Gross Alpha-Particle Activity of the Decay Chains | 39
the parent. However, once a sample is collected and acidified, any thorium produced by a decay
chain will stay in solution. For example, the 228Ra decay chain can produce a substantial 228Th
activity over the lifetime of a sample. 212Bi, in the 228Th decay series, could serve as the parent of
a decay chain, but 212Bi and its progeny 212Po decay away within six hours of collection, and, under most circumstances, the 212Bi decay chain be neglected.
GEOMETRY OF THE RESIDUES: UNIFORM, SMOOTH, AND PATCH RESIDUES
In Chapter 2, it was seen that variations in the geometry of a sample residue could cause
relatively large variations in the GAA. In this section, a qualitative discussion of the residue
geometry is given. A mathematical discussion of residue geometry and its effect on the GAA can
be found in Appendix E. In all of the calculations in this report, it is assumed that the radial distributions of residues are uniform, as was discussed in Chapter 2.
Residues that are of uniform thickness across the planchet will be called uniform residues. Most residues are not uniform. Even when a residue completely covers a planchet, its
thickness will usually vary to some degree from one point to another on the planchet. Sometimes, the nonuniformity of a residue is obvious from its appearance. Such is the case when the
when the bulk of the residue is composed of relatively thick patches separated by areas with little
or no material. Residues that consist of patches that cover 38% of the planchet will be called
patch residues. Sometimes the nonuniformity of a residue is less apparent. The residue may
completely cover the planchet but have relatively small variations in its thickness. Such residues
will be called smooth residues. Exact mathematical definitions of a patch and smooth residues
are given in Appendix E.
The thick areas of a residue absorb a higher fraction of alpha particles than the thin areas.
Thus, the GAA for a patch residue is relatively low and the GAA for a uniform residue of the
same mass is relatively high. The GAA for a smooth residue is intermediate between that of a
patch and a uniform residue of the same mass, although it is usually closer to the GAA of a uniform residue than the GAA of a patch residue.
AN OUTLINE OF THE DETERMINATION OF THE GAA
Eqn. (2.4) of Chapter 2 shows that the GAA of a sample can be calculated if the efficiencies and activities of all of the alpha emitters of the samples are known and if the efficiency of
the calibration standard is known. The efficiency of an alpha emitter is not constant, but depends
markedly on its alpha-particle energy and on the mass and geometry of the sample residue. Thus,
it is not possible to understand how the GAA of a sample depends on factors like residue mass
and geometry without first understanding how the efficiencies of its alpha emitters depend on
these parameters. Thus, much of the theoretical work in this report was devoted to the determination of the dependence of the efficiencies on the various parameters.
In EPA Method 900.0., either 230Th or natural uranium can be used as the calibration
standard. In all of the calculations in this work, it is assumed that 230Th is the calibration standard. The calibration standard’s efficiency, denoted by eS, will be taken to be the average between the 230Th efficiency for a smooth residue and a patch residue. A detailed discussion of this
calculation is given in Appendix F, where Figure F.1 gives a plot of eS versus residue mass.
The determination of an alpha emitter’s efficiency is mathematically involved and is presented in detail in Appendices C through E. In these Appendices, the efficiencies are first deter-
©2010 Water Research Foundation. ALL RIGHTS RESERVED
40 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
mined in uniform BaSO4 residues, and then the BaSO4 efficiencies are used to obtain efficiencies
for sample residues of arbitrary composition and arbitrary geometry using Eqn. (E.2). The efficiencies are initially determined in BaSO4 residues because the BaSO4 residues are visibly uniform, and for some of the decay chains of interest in this work, it is relatively easy to control the
radiological composition of BaSO4, and, as a consequence, to determine the alpha emitter efficiencies in the BaSO4 residues.
When the parent activity at the time of sample collection is known, the amount of progeny activity that it produces can be calculated from the Bateman equations. (The Bateman equations constitute the solution of the differential equations that determine the activities of the members of a decay chain.) Once the activities and efficiencies of all alpha emitters in a decay chain
are known, the calibration standard’s efficiency and Eqn. (2.4) can be used to calculate the decay
chain’s contribution to the GAA.
FACTORS THAT CONTRIBUTE TO THE VARIABLITY OF THE GAA
Some of the factors that contribute to the variability of the GAA are the radiological
composition of the residue, the residue mass and geometry—like uniform, smooth, or patch—
and, for some decay chains, as defined in Chapter 2, the time interval between certain steps—T1,
the time between collection and preparation; T2, the time between preparation and analysis; and
T3 = T1 + T2. It can be difficult to quantify a residue’s geometry. Visual inspection of the residue
may allow one conclude that the geometry is closer to a patch residue than a smooth residue, or
vice versa, but an exact characterization is usually not feasible. In this chapter, the GAA is calculated for both patch and smooth residues. The patch geometry will give a GAA that is less than
the GAA for most resides and the smooth geometry will give a GAA that is greater than that for
most residues. Thus, the object of this chapter is to determine a range for the GAA that will encompass the GAAs of most samples. Other factors, like the counting error, cause random variations in the GAA, and others—like the spatial distribution of a radionuclide in the residue or the
inorganic composition of the residue—can be either be difficult to quantify or are not routinely
determined. Thus, although some of these factors can have a significant effect on the GAA, they
are not treated in this chapter, but are discussed in more detail in Chapter 6.
Each decay chain’s (Table 4.1 and Table 4.2) contribution to the GAA is presented in the
plots later in the chapter. These plots account for the radiological composition of the sample residue, for the residue mass and geometry, and for the time intervals T1, T2, and T3.
NOTATION USED
The variable that is used to represent the GAA will be denoted by “GAA”. This is somewhat unsatisfactory from a notational point of view, since “GAA” is used as both an acronym
and a variable, but it is hoped that it will make the plots in this chapter clearer. The parent activity of a decay chain at the time of sample collection will be denoted by A1,0. The subscript “1” is
used to show that A1,0 is the activity of parent, the first member of the decay chain; the subscript
“0” is used to show that A1,0 is the activity at the time of sample collection. When the half-life of
the parent is long enough such that it does not decay substantially over the sample holding time,
then A1 will be used instead of A1,0. Such is the case for 226Ra, 234U, and 238U.
The ordinate in the plots below is either GAA/A1,0 or GAA/A1, which is just the ratio of
the GAA to the initial parent activity. These ratios are dimensionless factors that facilitate the
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Chapter 4: Gross Alpha-Particle Activity of the Decay Chains | 41
calculation of a decay chain’s contribution to the GAA. For example, if the initial parent activity,
A1,0, of a decay chain is 3.2 pCi/L, and if the value of GAA/A1,0 taken from the decay chain’s plot
is 6.0, then the decay chain’s contribution to the GAA is given by GAA = 6.0 × 3.2 pCi/L or
GAA = 19.2 pCi/L. The abscissa of the plots is the residue mass for the 234U and 238U decay
chains, the time between sample preparation and analysis, T2, for the 226Ra decay chain, and the
time between sample collection and analysis, T3, for all other decay chains.
1.1
1.0
Smooth
GAA /Α1
0.9
0.8
0.7
Patch
0.6
0.5
0
20
40
60
80
100
Residue mass (mg)
Figure 4.1. The GAA due to 238U in a grab or quarterly composite sample
THE 238U DECAY CHAIN
Figure 4.1 is a plot of GAA/A1 versus residue mass for the 238U decay chain for both
smooth and patch residues. The calculations used to construct the plots are given Appendix F.
Figure 4.1 shows that the estimated range of GAA/A1 increases with residue mass and shows
that, on average, GAA/A1 is less than one, so that in most cases, the contribution of 238U to the
GAA will be less than its own activity. The reason for this is that the alpha-particle energy of
238
U is less than that of the calibration standard, 230Th (Table 1.1). For smooth residues with a
mass of 30 mg and above, GAA/A1 is slightly greater than one due to the relatively low level of
self-absorption in a smooth residue. The contribution of 238U to the GAA is the same for both
grab and quarterly composite samples, because 238U neither decays significantly nor produces a
significant amount of alpha-emitting progeny over the course of a sample’s lifetime. Thus, for
any particular residue, the 238U contribution to the GAA is independent of time. The increase in
the GAA in going from a patch to a smooth residue is due solely to residue geometry.
©2010 Water Research Foundation. ALL RIGHTS RESERVED
42 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
THE 234U DECAY CHAIN
Figure 4.2 is a plot of GAA/A1 versus residue mass for the 234U decay chain for both
smooth and patch residues. The calculations used to construct the plots are given Appendix F.
Figure 4.2 shows that the estimated range of GAA/A1 increases with residue mass, and shows
that, on average, GAA/A1 is close to one, so that the contribution of 234U to the GAA is approximately equal to its own activity. The reason for this is that the alpha-particle energy of 234U is
nearly the same as that of the calibration standard, 230Th (Table 1.1). The contribution of 234U to
the GAA is the same for both grab and quarterly composite samples, because 234U neither decays
significantly nor produces a significant amount of alpha-emitting progeny over the course of a
sample’s lifetime. Thus, for any particular residue, the 234U contribution to the GAA is independent of time. The increase in the GAA in going from a patch to a smooth residue is due solely to
residue geometry.
1.4
1.3
1.2
Smooth
GAA /Α1
1.1
1.0
0.9
0.8
Patch
0.7
0.6
0
20
40
60
80
100
Residue mass (mg)
Figure 4.2. The GAA due to 234U in a grab or quarterly composite sample
THE 226RA DECAY CHAIN
Figure 4.3 is a plot of GAA/A1 versus T2 for the 226Ra decay chain for grab samples with
smooth residues ranging from 20 to 100 mg. The calculations used to construct the plot are given
in Appendix F The dashed line corresponds to the total alpha activity—due to 226Ra, 222Rn, 218Po,
and 214Po—divided by A1. Just after preparation, the 222Rn activity is nearly zero because 222Rn is
lost to volatilization, and the two alpha emitting progeny of 222Rn (218Po and 214Po) decay away
within a few hours. Thus, initially, the GAA is due to 226Ra. However, once the sample residue
forms, the alpha-emitting progeny—222Rn, 218Po and 214Po—produced by 226Ra are trapped in the
residue. The progeny’s contribution to the GAA continually increases as T2 increases and reaches
a maximum after about T2 = 23 d, when the progeny are in secular equilibrium with 226Ra. The
contribution of the 226Ra decay chain to the GAA is the same for both grab and quarterly compo-
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Chapter 4: Gross Alpha-Particle Activity of the Decay Chains | 43
site samples, because 226Ra does not decay significantly over the lifetime of a sample and because at the time of sample preparation, when T2 = 0, the progeny activity in the residue is negligible regardless of the time between sample collection and preparation, T1.
Figure 4.3 shows that the GAA overestimates the alpha activity of the residue at all residue masses. As T2 increases, the proportion of the alpha activity due to the high-energy progeny
(222Rn, 218Po, and 214Po) increases, which causes the overestimate in the GAA to increase with
T2. As the residue mass is increased, the efficiencies of the high-energy progeny decrease at a
slower rate than the efficiency of the calibration standard, which causes the increase in the GAA
with residue mass.
10
100 mg smooth
80
8
60
GAA/Α1
40
6
20
4
2
alpha activity
0
0
5
10
15
20
25
30
T2 (d)
Figure 4.3. The GAA for grab and quarterly composite samples containing 226Ra and having a smooth residue
5
GAA /Α1
4
3
20-100 mg patch
2
alpha activity
1
0
0
5
10
15
20
25
30
T2 (d)
Figure 4.4. The GAA for grab and quarterly composite samples containing 226Ra and having a patch residue
©2010 Water Research Foundation. ALL RIGHTS RESERVED
44 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
Figure 4.4 is a plot of GAA/A1 versus T2 for both grab and quarterly composite samples
with patch residues. The GAA is approximately independent of residue mass because the highly
absorptive patch residues cause the efficiencies of the progeny to decrease at about the same rate
as the efficiency of the calibration standard. (Recall that the efficiency of the calibration standard
is an average between that of a patch residue and that of a smooth residue.) When T2 exceeds
three days, the GAA overestimates the alpha activity of the residue, but, because of the high
level of self-absorption, the overestimate is less than that of a smooth residue. Figure 4.3 and
Figure 4.4 show that the estimated range of GAA/A1 increases with both residue mass and T2.
THE 210PO DECAY CHAIN
Figure 4.5 is a plot of GAA/A1,0 versus T3 for grab samples with smooth residues ranging
from 20 to 100 mg. The calculations used to construct the plot are given in Appendix F. The
range of the T3-axis is 180 d, which corresponds to the six-month holding time of a sample. The
dashed line corresponds to the 210Po alpha activity of the residue divided the 210Po alpha activity
at the time of collection, A1,0. GAA/A1,0 overestimates the alpha activity of the residue by as
much as a factor of 2 for the 100 mg residue. Since 210Po decays to stable 206Pb, the GAA decays
away exponentially with the half-life of 210Po.
Figure 4.6 is a plot of GAA/A1,0 versus T3 for grab samples with patch residues of 20 and
100 mg. There is little variation in the GAA/A1,0 with the residue mass because the 210Po efficiency
for the highly-absorptive patch residues decreases with residue mass at about the same rate as the
efficiency of the 230Th calibration standard. For any patch residue, the 210Po activity divided by A1,0
is approximately equal to GAA/A1,0 for the 100 mg residue. Figure 4.5 and Figure 4.6 show that
the possible range of GAA/A1 increases with residue mass but decreases with T3.
2.0
1.8
1.6
100
80
60
GAA/Α1,0
1.4
1.2
1.0
40
20 mg
0.8
0.6
alpha activity
0.4
0.2
0
20
40
60
80 100 120 140 160 180
T3 (d)
Figure 4.5. The GAA for a 210Po-containing grab sample with a smooth residue
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Chapter 4: Gross Alpha-Particle Activity of the Decay Chains | 45
1.1
1.0
GAA/Α1,0
0.9
20 mg
0.8
0.7
0.6
100 mg
0.5
0.4
0
Figure 4.6. The GAA for a
20
210
40
60
80 100 120 140 160 180
T3 (d)
Po-containing grab sample with a patch residue
1.2
GΑΑ/Α1,0
1.0
100
80
60
0.8
40
20 mg
0.6
0.4
alpha activity
0.2
0
Figure 4.7. The GAA for a
20
210
40
60
80 100 120 140 160 180
T3 (d)
Po-containing composite sample with a smooth residue
©2010 Water Research Foundation. ALL RIGHTS RESERVED
46 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
0.6
GAA /Α1,0
0.5
0.4
20
100 mg
0.3
0.2
0
20
40
60
80 100 120 140 160 180
T3 (d)
Figure 4.8. The GAA for a
210
Po-containing composite sample with a patch residue
Figure 4.7 is a plot of GAA/ A1,0 versus T3 for quarterly composite samples with smooth
residues ranging from 20 to 100 mg. The dashed line corresponds to the 210Po activity in the residue divided A1,0. The GAA of a quarterly composite sample is always less than that of a corresponding grab sample. The reason for this is that by the time that the fourth aliquot is added to the
composite, 210Po in the first, second, and third aliquots will have been decaying for 270, 180, and
90 days, respectively. For example, because of the 138-d half-life of 210Po, about one-fourth of
the 210Po activity in the first aliquot will be present at the time that the fourth aliquot is added.
Figure 4.8 is a plot of GAA/ A1,0 versus T3 for quarterly composite samples with patch residues. The 210Po alpha activity divided by A1,0 is approximately equal GAA/ A1,0 for the 100 mg
residue. Figure 4.7 and Figure 4.8 show that the estimated range of GAA/ A1,0 increases with
residue mass but decreases with T3.
THE 210PB DECAY CHAIN
Figure 4.9 is a plot of GAA/A1,0 versus T3, the time between sample collection and analysis, for grab samples with smooth residues ranging from 20 to 100 mg. The range of the T3-axis
is 180 days, which corresponds to the six-month holding time of a sample. The calculations used
to construct the plot are given in Appendix F. By convention, all of the 210Po activity in a sample
at the time of collection is taken assigned to the 210Po decay chain, which was treated in the previous section; the initial 210Po activity of the 210Pb decay chain is taken to be zero. 210Pb continually produces 210Po, and the GAA continually increases over the sample holding time. The
dashed line is the 210Po activity divided by the initial 210Pb activity. Eventually 210Po would be in
secular equilibrium with 210Pb, but this would require 2.3 years. Figure 4.9 shows that GAA/A1,0
overestimates the alpha activity of the residue by as much as a factor of 2 for the 100 mg residue.
The overestimate is due to the relatively low level of self-absorption by smooth residues and by
the relatively high alpha-particle energy of 210Po.
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Chapter 4: Gross Alpha-Particle Activity of the Decay Chains | 47
Figure 4.10 is a plot of GAA/A1,0 versus T3 for grab samples with patch residues. The
Po activity divided by A1,0 is not plotted but is approximately equal to GAA/A1,0 for the 100
mg residue. As with the 226Ra decay chain, the GAA for patch residues is approximately independent of the residue mass because the 210Po efficiency for the highly-absorptive patch residues
decreases with residue mass at about the same rate as the efficiency of the 230Th calibration standard. Figure 4.9 and Figure 4.10 show that the estimated range of GAA/A1 increases with both
residue mass and T3.
Figure 4.11 is a plot of GAA/A1,0 versus T3 for quarterly composite samples with smooth
residues ranging from 20 to 100 mg. The GAA of a quarterly composite sample is always greater
than that of the corresponding grab sample. The reason for this is that by the time that the fourth
aliquot is added to the composite, 210Pb in the first, second, and third aliquots will have been
producing 210Po for 270, 180, and 90 days, respectively. Consequently, the value of GAA/A1,0 at
the time that the last aliquot is added, T1 = 0, is not zero but ranges from 0.55 to 0.80.
Figure 4.12 is a plot of GAA/A1,0 versus T3 for quarterly composite samples with patch residues
of 20 and 100 mg. Figure 4.11 and Figure 4.12, show that the estimated range of GAA/A1,0 increases with residue mass and T3.
210
1.2
1.0
100 mg
80
GAA /Α1,0
0.8
60
40
20
0.6
0.4
alpha activity
0.2
0.0
0
20
40
60
80 100 120 140 160 180
T3 (d)
Figure 4.9. The GAA for a grab sample with unsupported 210Pb and a smooth residue
©2010 Water Research Foundation. ALL RIGHTS RESERVED
48 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
0.6
20 mg
GAA/Α1,0
0.5
0.4
0.3
100 mg
0.2
0.1
0.0
0
20
40
60
80 100 120 140 160 180
T3 (d)
Figure 4.10. The GAA for a grab sample with unsupported 210Pb and a patch residue
1.4
100 mg
80
1.2
GAA /Α1,0
60
40
20
1.0
0.8
0.6
alpha activity
0.4
0
20
40
60
80 100 120 140 160 180
T3 (d)
Figure 4.11. The GAA for a composite sample with unsupported 210Pb and a smooth residue
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Chapter 4: Gross Alpha-Particle Activity of the Decay Chains | 49
0.80
0.75
0.70
GAA /Α1,0
0.65
0.60
0.55
20
0.50
100 mg
0.45
0.40
0
20
40
60
80 100 120 140 160 180
T3 (d)
Figure 4.12. The GAA for a composite sample with unsupported 210Pb and a patch residue
THE 228RA DECAY CHAIN
Figure 4.13 is a plot of GAA/A1,0 versus T3 for grab samples with smooth residues ranging from 20 to 100 mg. The calculations used to construct the plot are given in Appendix F. The
range of the T3-axis is 180 days, which corresponds to the six-month holding time of a sample.
The dashed line corresponds to the total alpha activity of the 228Ra progeny—228Th, 224Ra, 220Rn,
216
Po, 212Bi, and 212Po—in the residue divided by A1,0. At the time of sample collection, the total
alpha activity of the progeny is zero, but 228Ra continually produces progeny and the alpha activity increases continually with T3. Although the activity of each alpha emitter is relatively low
(about GAA/A1,0 0.16 for 228Th at 180 days), since there are six alpha emitters in the decay chain,
the sum of their activities can be substantial. GAA/A1,0 overestimates the alpha activity in the
residue. The overestimate is due to the relatively low level of self-absorption by smooth residues
and by the relatively high alpha-particle energies of the 228Ra progeny relative to that of the calibration standard, 230Th. Figure 4.13 shows that GAA/A1,0 is less than 0.2 when the sample is analyzed within 3 weeks of collection and is as high as 2.2 when the sample is analyzed 6 months
after collection. Although 228Ra may not often cause a GAA violation, it can make a significant
contribution to the GAA in samples held for three to six months.
Figure 4.14 is a plot of GAA/A1,0 versus T3 for grab samples with patch residues. In this
case, GAA/A1,0 overestimates the alpha activity of the patch residue. Because patch residues are
highly absorptive, the overestimate is less than that of smooth residues. Figure 4.13 and
Figure 4.14 show that the estimated range of GAA/A1 increases with residue mass and T3.
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50 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
2.4
GAA /Α1,0
2.0
100 mg
80
1.6
40
1.2
60
20
0.8
0.4
alpha activity
0.0
0
20
40
60
80 100 120 140 160 180
T3 (d)
Figure 4.13. The GAA for a grab sample containing 228Ra and having a smooth residue
1.2
GAA /Α1,0
1.0
100 mg
0.8
20 mg
0.6
0.4
alpha activity
0.2
0.0
0
20
40
60
80 100 120 140 160 180
T3 (d)
Figure 4.14. The GAA for a grab sample containing 228Ra and having a patch residue
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Chapter 4: Gross Alpha-Particle Activity of the Decay Chains | 51
3.5
GAA/Α1,0
3.0
2.5
20
2.0
40
100 mg
80
60
1.5
1.0
alpha activity
0.5
0
20
40
60
80
100 120 140 160 180
T3 (d)
Figure 4.15. The GAA for a composite sample containing 228Ra and having a smooth residue
2.00
1.75
100 mg
GAA /Α1,0
1.50
1.25
20 mg
1.00
alpha activity
0.75
0.50
0
20
40
60
80
100 120 140 160 180
T3 (d)
Figure 4.16. The GAA for a composite sample containing 228Ra and having a patch residue
Figure 4.15 is a plot of GAA/A1,0 versus T3 for quarterly composite samples with smooth
residues ranging from 20 to 100 mg. The dashed line corresponds to the total alpha activity in the
residue divided by A1,0. The GAA of a quarterly composite sample is always greater than that of
the corresponding grab sample. The reason for this is that by the time that the fourth aliquot is
©2010 Water Research Foundation. ALL RIGHTS RESERVED
52 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
added to the composite, 228Ra in the first, second, and third aliquots will have been producing
alpha-emitting progeny for 270, 180, and 90 days, respectively. Figure 4.16 is a plot of GAA/A1,0
versus T3 for quarterly composite samples with patch residues. Again, GAA/A1,0 overestimates
the alpha activity, but to a lesser extent than in the smooth residues, because of the relatively
high level of self-absorption by patch residues. For composite samples, Figure 4.15 and
Figure 4.16 show GAA/A1,0 increases with residue mass and T3.
THE 224RA DECAY CHAIN
Figure 4.17 is a plot of GAA/A1,0 versus T3, the time between sample collection and analysis, for samples with smooth residues ranging from 20 to 100 mg. The calculations used to construct the plot are given in Appendix F. The dashed line corresponds to the total alpha activity—
due to 224Ra, 220Rn, 216Po, 212Bi, and 212Po—divided by A1,0. The initial rise in GAA/A1,0 is due to
the ingrowth of the alpha emitters 212Bi and 212Po. 212Bi and 212Po are produced by the beta emitter 212Pb. Since 212Pb has a half-life of 10.6 hr, several hours are required to produce a substantial
212
Pb activity. The 212Pb, in turn, produces 212Bi and 212Po. At T3 > 1 day, the GAA declines because the 212Bi and 212Po activities are ultimately supported by 224Ra, which decays away with a
3.6-d half-life. Figure 4.17 shows that soon after collection, GAA/A1,0 can be as high as 5 to 10.
At three or more weeks after collection, all of the initial, or unsupported, 224Ra activity will have
decayed away, and GAA/A1,0 will be virtually zero.
10
100 mg
80
8
GAA/A1,0
60
6
40
20
4
2
alpha activity
0
0
3
6
9
12
T3 (d)
15
Figure 4.17. The GAA for a grab sample containing 224Ra and having a smooth residue
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Chapter 4: Gross Alpha-Particle Activity of the Decay Chains | 53
6
100 mg
5
20
GAA/A1,0
4
3
2
alpha activity
1
0
0
3
6
9
12
15
T3 (d)
Figure 4.18. The GAA for grab sample containing 224Ra and having a patch residue
Figure 4.18 is a plot of GAA/A1,0 versus T3 for samples with patch residues. The dashed
curve is the total alpha activity divided by A1,0. GAA/A1,0 overestimates the alpha activity, but to
a lesser extent than the corresponding smooth residues. Figure 4.17 and Figure 4.18 show that
the estimated range in GAA/A1,0 increases with residue mass but peaks at about 1 day and subsequently decreases as T3 increases.
Similar plots could be constructed for quarterly composite samples. However, if the time between the addition of third and fourth aliquots exceed three weeks, then at T3 = 0, all of the unsupported 224Ra in the first three aliquots will have decayed away, and only unsupported 224Ra from the
last aliquot contributes to the GAA. Thus, at T3 = 0, the 224Ra activity of the composite is one-fourth
of the 224Ra activity of the last aliquot, and Figure 4.17 and Figure 4.18 will give GAA/A1,0 for a
composite sample if A1,0 is taken to be one-fourth of the 224Ra activity of the last aliquot.
©2010 Water Research Foundation. ALL RIGHTS RESERVED
54 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
3.2
2.8
100 mg
GAA/A1,0
2.4
80
2.0
60
40
20
1.6
1.2
alpha activity
0.8
0.4
0.0
0.0
0.5
1.0
1.5
2.0
2.5
3.0
T3 (d)
Figure 4.19. The GAA for grab sample containing 212Pb and having a smooth residue
THE 212PB DECAY CHAIN
Figure 4.19 is a plot of GAA/A1,0 versus T3 for samples with smooth residues ranging
from 20 to 100 mg. The calculations used to construct the plot are given in Appendix F. The
dashed line corresponds to the total alpha activity—due to 212Bi and 212Po—divided by the initial
212
Pb activity, A1,0. The initial rise in GAA/A1,0 is due to the ingrowth of 212Bi and 212Po. Eventually, GAA/A1,0 decays as the 212Pb decays away. GAA/A1,0 overestimates the alpha activity,
and the overestimate increases with residue mass because as residue mass increases, the efficiencies of 212Bi and 212Po decrease at a lesser rate than the efficiency of the calibration standard.
Figure 4.19 shows that after 3 days, the contribution of the initial 212Pb activity to the GAA is
negligible. It should be noted that A1,0 is the activity of 212Pb at the time of collection and not the
activity of unsupported 212Pb, which is often defined as the activity of 212Pb in excess of the 224Ra
activity (Parsa et al 2004).
Figure 4.20 is a plot of GAA/A1,0 versus T3 for samples with patch residues. GAA/A1,0
overestimates the total alpha activity of the residue but to a lesser extent than the smooth residues. Figure 4.19 and Figure 4.20 show that the estimated range of GAA/A1,0 increases with residue mass but peaks within one day of collection and subsequently decreases as T3 increases. As
with the 224Ra decay chain, Figure 4.19 and Figure 4.20 can be used to obtain GAA/A1,0 for a
composite sample if A1,0 is taken to be one-fourth of the initial 212Pb activity of the last aliquot.
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Chapter 4: Gross Alpha-Particle Activity of the Decay Chains | 55
2.0
1.8
1.6
100 mg
GAA/A1,0
1.4
40
1.2
20
1.0
0.8
alpha activity
0.6
0.4
0.2
0.0
0.0
0.5
1.0
1.5
2.0
2.5
3.0
T3 (d)
Figure 4.20. The GAA for a grab sample containing 212Pb and having a patch residue
THE GAA FOR SAMPLES CONTAINING BOTH 224RA AND 226RA
Before proceeding to the hypothetical sample in the next chapter, it is useful to consider
how the GAA of a sample containing both 226Ra and unsupported 224Ra develops with time when
the sample is prepared and analyzed shortly after collection. The results presented here apply to
many radium-containing samples and demonstrate a phenomenon that is discussed frequently in
this work.
Most radium-containing samples contain substantial activities of both 226Ra and unsupported 224Ra, but the relative proportions of these two isotopes can vary significantly from one
sample to the next. If the sample is analyzed soon after collection, the contribution of the 224Ra
decay chain to the GAA can be substantial; if the sample is analyzed at least three weeks after
collection, the contribution of the 224Ra decay chain to the GAA will be negligible.
©2010 Water Research Foundation. ALL RIGHTS RESERVED
56 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
9
224
226
Ra: Ra = 0:4
8
GAA (arb. units)
7
1:3
6
5
2:2
4
3
3:1
2
1
0
4:0
0
5
10
15
20
25
30
T2 (d)
Figure 4.21. The GAA for a grab sample containing 224Ra and 226Ra and with T1 = 1 d
Let the combined activity of 226Ra and unsupported 224Ra in the sample at collection time
be 1 in arbitrary units. It will be assumed that the samples are prepared one day after collection,
at which time the residues are heated over a flame and 222Rn is quantitatively lost. Figure 4.21
shows the GAA versus the time between sample preparation and analysis, T2, for samples with a
50-mg smooth residue for various ratios of 224Ra to 226Ra. It is seen that when the sample contains approximately equal activities of 224Ra and 226Ra, the GAA is approximately constant over
time. The reason for this is that the decrease in the contribution of the 224Ra decay chain to the
GAA is approximately offset by the increase in the contribution of the 226Ra decay chain to the
GAA. The contribution of the 224Ra decay chain decreases with a time constant that is approximately equal to the 3.6-d half-life of 224Ra; the contribution of the 226Ra decay chain increases
with a time constant equal to the 3.8-d half-life of 222Rn.
Figure 4.21 demonstrates an important point for radium-containing samples: the GAA
can be minimized by allowing the unsupported 224Ra to decay away before the sample is prepared. One might surmise that the GAA could be minimized by analyzing the sample three or
more weeks after collection when the contribution of the 224Ra decay chain to the GAA is negligible; however, this is not the case for samples that also contain 226Ra. If a sample is prepared
within a few days of collection and analyzed three weeks or more after collection, the contribution of the 224Ra decay chain to the GAA will be negligible, but the contribution of the 226Ra decay chain will be at its maximum value. One would obtain a lower GAA if the sample were prepared about three weeks after collection, when the unsupported 224Ra would have decay away,
and analyzed soon after preparation, when the contribution of the 226Ra decay chain is still relatively small. (For EPA Method 900.0, the U.S. EPA requires that there be at least three days between preparation and analysis.) In addition, if the sample contains 228Ra, the contribution of the
228
Ra decay chain can contribute significantly to the GAA if time between collection and analysis is several months or more. Thus, in general, for radium-containing samples, the minimum in
the GAA is obtained when the sample it prepared about three weeks after collection and analyzed about three days after preparation.
©2010 Water Research Foundation. ALL RIGHTS RESERVED
CHAPTER 5
CALCULATION OF THE GAA FOR A HYPOTHETICAL EXAMPLE
INTRODUCTION
In this chapter, the gross alpha-particle activity (GAA) of a hypothetical sample analyzed
by EPA Method 900.0 will be determined. The purpose of this calculation is to demonstrate how
to use the graphs of Chapter 4 to calculate a sample’s GAA. The sample will be assumed to have
the radiological composition given by Table 5.1 at the time of collection. The radiological composition of this hypothetical sample is relatively complex and is not representative of the radiological composition of the samples analyzed in this study whose GAAs are often determined by
two or three parent radionuclides.
The eight unsupported radionuclides of Table 5.1 correspond to the eight parents of the
decay chains in Table 4.1 and Table 4.2. EPA Method 900.0 requires a minimum of three days
between sample preparation and analyses. Since the radionuclides of the 212Pb decay chain decay
away within 2.5 d of collection, its contribution to the GAA is usually negligible. However, the
State of New Jersey requires that samples be analyzed within 48 hr of collection (NJAC 2004),
and within this timeframe, the 212Pb decay chain can make a significant contribution to the GAA.
Some groundwater samples have very high levels of unsupported 222Rn at the time of sample collection. In such samples, the short-lived, alpha-emitting progeny of 222Rn—214Po and 218Po—can
make a significant contribution to the GAA when the sample is analyzed within 6 hr. of collection (Parsa et al 2000). In this study, no samples were analyzed within six hours of collection,
and the contribution of the unsupported 222Rn progeny was not determined.
Table 5.1
Radiological composition of the sample
Radionuclide
Decay series
Activity (pCi/L)
238
U
234
U
238
226
Ra
210
Pb
210
Po
228
Ra
224
Ra
238
U
U
238
U
232
Th
232
Th
3
5
5
3
4
212
232
4
238
Pb
U
U
2
5
238
Th
The GAA will be determined for a 60-mg sample residue with both smooth and patch residue geometries (which are qualitatively defined in Chapter 4 and quantitatively defined in Appendix E). Calculations are performed for both grab and quarterly composite samples. For the
quarterly composite sample, it is assumed that equal aliquots of water are combined in each of
four consecutive three-month periods. The times at which the second, third, and fourth aliquots
of the water were added to the composite sample will be assumed to be at 90, 180, and 270 days,
57
©2010 Water Research Foundation. ALL RIGHTS RESERVED
58 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
respectively, after the first aliquot, which is the same assumption that was made in Chapter 4.
Further, it is assumed that the radiological composition of each aliquot at the time of addition is
given by Table 5.1. The GAA of a composite sample can differ significantly from the GAA of
the corresponding grab sample. The activity due to the 210Po, 224Ra and 212Pb decay chains in the
first three aliquots will have partially or completely decayed away by the time that the last aliquot had been added, and the activity due to the 210Pb and 228Ra decay chains in the first three
aliquots will have produced a substantial amount of alpha activity by the time that the last aliquot
had been added. Thus, the radiological composition of a composite sample is often substantially
different than the radiological composition of the corresponding grab sample.
The calculations are performed for the four sets of the time intervals T1, T2, and T3 given
in Table 5.2. Here, as in Chapter 2, T1 is the time between sample collection and preparation, T2
is the time between sample preparation and analysis, and T3 = T1 + T2 is the time between sample
collection and analysis. All four sets of time intervals are well within the time requirements of
EPA Method 900.0. For samples that contain radium isotopes, 210Pb, or 210Po, the estimated
range of the GAA will demonstrate the marked dependence of the GAA on these time intervals.
The sources of variability in the GAA included in this hypothetical example are the radiological composition, the residue geometry, and the time intervals T1, T2, and T3. It should be kept
in mind that the residue mass, as seen in the graphs of Chapter 4, counting error (Chapter 6), and
various other sources of error and variation (Chapter 6) are not included here, so that the variability of the GAA could be significantly larger than what is indicated in this example. Once the
reader is familiar with this hypothetical example, it should not be difficult to apply this method
to actual samples. One problem in applying this method is that laboratories usually do not report
the sample preparation and analysis times; however, laboratories should be able to furnish this
information.
Table 5.2
Time intervals
Set of time
intervals
1
2
3
4
T1 (d)
T2 (d)
T3 (d)
1
30
30
120
3
3
30
3
4
33
60
123
THE GAA DUE TO THE 238U DECAY CHAIN
Because of its long half-life, 238U does not substantially decay and does not produce a
significant amount of alpha-emitting progeny between the time of sample collection and analysis, T3. Thus, the 238U decay chain’s contribution to the GAA is independent of the time intervals
T1, T2, and T3 and is the same for both grab and quarterly composite samples. To calculate the
238
U decay chain’s contribution to the GAA for a patch residue, one multiplies the factor
GAA/A1 = 0.5, taken from Figure 4.1, for a 60-mg patch residue, by the sample’s 238U activity, 2
pCi/L, to obtain GAA = 1.0 pCi/L. This corresponds to the lower limits in Table 5.3. To calculate the 238U decay chain’s contribution to the GAA for a smooth residue, one multiplies the fac-
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Chapter 5: Calculation of the GAA for a Hypothetical Example | 59
tor GAA /A1 = 1.1, taken from Figure 4.1 for a 60-mg smooth residue, by the sample’s
tivity to obtain GAA = 2.2 pCi/L. This corresponds to the upper limits in Table 5.3.
Set of time
intervals
1
2
3
4
Table 5.3
Sample with a 60-mg residue and 2 pCi/L of 238U
T1 (d)
T2 (d)
T3 (d)
GAA /A1
1
30
30
120
3
3
30
3
4
33
60
123
0.5-1.1
0.5-1.1
0.5-1.1
0.5-1.1
238
U ac-
GAA
(pCi/L)
1.0-2.2
1.0-2.2
1.0-2.2
1.0-2.2
THE GAA DUE TO THE 234U DECAY CHAIN
Because of its long half-life, 234U, like 238U, does not substantially decay and does not
produce a significant amount of alpha-emitting progeny between the time of sample collection
and analysis, T3. Thus, the 234U decay chain’s contribution to the GAA is independent of the time
intervals T1, T2, and T3 and is the same for both grab and quarterly composite samples. To calculate the 234U decay chain’s contribution to the GAA for a patch residue, one multiplies the factor
GAA/A1 = 0.6, taken from Figure 4.2 for a 60-mg patch residue, by the sample’s 234U activity, 5
pCi/L, to obtain GAA = 3.0 pCi/L. This corresponds to the lower limits in Table 5.4. To calculate the 234U decay chain’s contribution to the GAA for a smooth residue, one multiplies the factor GAA/A1 = 1.4, taken from Figure 4.2 for a 60-mg smooth residue, by the sample’s 234U activity to obtain GAA = 7.0 pCi/L. This corresponds to the upper limits in Table 5.3. Since the total
uranium (234U and 238U) activity is 7 pCi/L and the GAA due to both uranium isotopes can range
from 4.0 to 9.2 pCi/L, it is clear that subtracting the uranium activity from the GAA can undercompensate or overcompensate for uranium’s contribution to the GAA.
Table 5.4
Sample with a 60-mg residue and 5 pCi/L of 234U
Set of time
intervals
1
2
3
4
T1 (d)
T2 (d)
T3 (d)
GAA /A1
1
30
30
120
3
3
30
3
4
33
60
123
0.6-1.4
0.6-1.4
0.6-1.4
0.6-1.4
GAA
(pCi/L)
3.0-7.0
3.0-7.0
3.0-7.0
3.0-7.0
THE GAA DUE TO THE 226RA DECAY CHAIN
For a given residue mass and geometry, the 226Ra decay chain’s contribution to the GAA
depends solely on the 226Ra activity of the sample and on the time between sample preparation
and analysis, T2. Because of its long half-life, 226Ra does not substantially decay over the lifetime
of a sample. However, at the time of sample preparation, 222Rn is quantitatively lost from the
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60 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
sample, but once the residue forms, the progeny 222Rn, 218Po, and 214Po are trapped by the residue, and their activities increase with time until they come into secular equilibrium with 226Ra,
which takes about 23 days. Thus, at the time of sample preparation, 226Ra is the sole contributor
to the GAA, but as T2 increases, the progeny’s contribution steadily increases and reaches a maximum after about 23 days. Since the progeny are high-energy alpha emitters, their contributions
to the GAA frequently exceed their activities. Since the 226Ra decay chain’s contribution to the
GAA does not depend on the time between sample collection and preparation, the GAA of a grab
sample and the corresponding quarterly composite sample are equal.
To calculate the 226Ra decay chain’s contribution to the GAA for a 60-mg patch residue
at T2 = 3 days, one multiplies the factor GAA/A1 = 2.3, taken from Figure 4.4, by the sample’s
226
Ra activity, 3 pCi/L, to obtain GAA = 6.9 pCi/L. This corresponds to the lower limits in Table 5.5 for T2 = 3 days. Similarly, the lower limit for T2 = 30 days is 13.8 pCi/L. To calculate the
226
Ra decay chain’s contribution to the GAA for a 60-mg smooth residue at T2 = 3 days, one
multiplies the factor GAA/A1 = 4.3, taken from Figure 4.4, by the 226Ra activity to obtain GAA =
12.9 pCi/L. This corresponds to the upper limits in Table 5.5 for T2 = 3 days. Similarly, the upper
limit for T2 = 30 days is 25.2 pCi/L. The entries in Table 5.5 demonstrate the extent to which the
226
Ra progeny contribute to the GAA. Between T2 = 3 days and T2 = 30 days, the GAA increases
by more than a factor of 2.
The data in Table 5.5 show that 3 pCi/L of 226Ra can cause a GAA violation by itself. If the
sample contained 4 pCi/L of 226Ra, the GAA for the smooth residue at T2 = 3 days would be 17.2
pCi/L, and the GAA for the smooth residue at T2 = 30 days would be 33.6 pCi/L. Thus, it is possible that 226Ra could be the sole cause of a GAA violation (> 15 pCi/L) for samples that do not have
a radium violation (> 5 pCi/L). Such a violation would be a false-positive GAA violation.
Table 5.5
Grab and composite sample with a 60-mg residue and 3 pCi/L of 226Ra
Set of time
GAA
T1 (d)
T2 (d)
T3 (d)
GAA /A1,0
intervals
(pCi/L)
1
2
3
4
1
30
30
120
3
3
30
3
4
33
60
123
2.3-4.3
2.3-4.3
4.6-8.4
2.3-4.3
6.9-12.9
6.9-12.9
13.8-25.2
6.9-12.9
THE GAA DUE TO THE 210PO DECAY CHAIN
210
Po is an alpha emitter that decays into stable 206Pb. The activity of 210Po decreases as
the time between sample collection and analysis, T3, increases. Since the half-life of 210Po is 138
days, the 210Po activity and its contribution to the GAA will both decrease substantially over a
period of several months. The contribution of 210Po to the GAA will be lower in quarterly composite samples than in grab samples because at the time that the fourth aliquot is added to the
composite, the 210Po in the first, second, and third aliquots will have been decaying for a period
of 270, 180, and 90 days, respectively.
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Chapter 5: Calculation of the GAA for a Hypothetical Example | 61
To calculate the GAA for a sample with a 60-mg patch residue at T3 = 4 days, one multiplies the factor GAA/A1,0 = 1.0, from Figure 4.6, by the initial 210Po activity, 5 pCi/L, to obtain
GAA = 5.0 pCi/L. This is the lower limit for the first entry in Table 5.6. The other lower limits
are computed in a similar way. To calculate the GAA of the corresponding sample with a smooth
residue, one multiplies the factor GAA/A1,0 = 1.9, from Figure 4.5, by the initial 210Po activity to
obtain GAA = 9.5 pCi/L. This is the upper limit for the first entry in Table 5.6. The other upper
limits can be computed in a similar way.
Table 5.6
Grab sample with a 60-mg residue and 5 pCi/L of 210Po
Set of time
intervals
1
2
3
4
T1 (d)
T2 (d)
T3 (d)
GAA/A1,0
1
30
30
120
3
3
30
3
4
33
60
123
1.0-1.9
0.8-1.6
0.7-1.4
0.5-1.0
GAA
(pCi/L)
5.0-9.5
4.0-8.0
3.5-7.0
2.5-5.0
Table 5.7
Quarterly Composite sample with a 60-mg residue and 5 pCi/L of 210Po
Set of time
GAA
T1 (d)
T2 (d)
T3 (d)
GAA/A1,0
intervals
(pCi/L)
1
1
3
4
0.6-1.1
3.0-5.5
2
30
3
33
0.5-1.0
2.5-5.0
3
30
30
60
0.4-0.8
2.0-4.0
4
120
3
123
0.3-0.6
1.5-3.0
To calculate the contribution of 210Po to a quarterly composite sample for a 60-mg patch
residue at T3 = 4 days, one multiples the factor GAA/A1,0 = 0.6, from Figure 4.8, by the initial
210
Po activity, 5 pCi/L, to obtain GAA = 3.0 pCi/L. This is the lower limit of the first entry in
Table 5.7. The other lower limits can be computed in a similar way. To calculate the contribution
to the GAA for the corresponding smooth residue at T3 = 4 days, one multiplies the factor
GAA/A1,0 = 1.1, from Figure 4.7, by the initial 210Pb activity to obtain GAA = 5.5 pCi/L. This is
the upper limit for the first entry of Table 5.7. The other upper limits can be computed in a similar way. Table 5.6 and Table 5.7 show that the 210Po contribution to the GAA for a quarterly
composite sample is about 60% of that for a grab sample with the same holding time.
THE GAA DUE TO THE 210PB DECAY CHAIN
210
Pb is a beta emitter that continually produces the alpha emitter 210Po. The 210Po activity, produced by 210Pb, and its contribution to the GAA, increases as the time between sample collection and analysis, T3, increases. Since about 2.3 years are required for 210Po to come into secular equilibrium with 210Pb, the 210Po activity increases continually over the lifetime of a sample.
The 210Pb decay chain’s contribution to the GAA will be higher in quarterly composite samples
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62 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
than in grab samples because at the time that the fourth aliquot is added to the composite, 210Pb
in the first, second, and third aliquots will have been producing 210Po for a period of 270, 180,
and 90 days, respectively.
For a grab sample, the 210Pb decay chain’s contribution to the GAA for a 60-mg patch residue at T3 = 4 days is clearly negligible. To calculate the GAA for the same sample at T3 = 33
days, one multiplies the factor GAA/A1,0 = 0.1, from Figure 4.10, by the initial 210Pb activity, 5
pCi/L, to obtain GAA = 0.5 pCi/L. This is the lower limit for the second entry in Table 5.8. The
other lower limits can be computed in the same way. To calculate the GAA for a smooth residue
at T3 = 33 days, one multiplies the factor GAA/A1,0 = 0.2, from Figure 4.9, by the initial 210Pb
activity to obtain GAA = 1.0 pCi/L. This is the upper limit for the second entry in Table 5.8. The
other upper limits in can be computed in a similar way.
Table 5.8
Grab sample with a 60-mg residue and 5 pCi/L of 210Pb
Set of time
intervals
1
2
3
4
T1 (d)
T2 (d)
T3 (d)
GAA /A1,0
1
30
30
120
3
3
30
3
4
33
60
123
0
0.1-0.2
0.2-0.4
0.4-0.8
GAA
(pCi/L)
0
0.5-1.0
1.0-2.0
2.0-4.0
Table 5.9
Quarterly composite with a 60-mg residue and 5 pCi/L of 210Pb
Set of time
GAA
T1 (d)
T2 (d)
T3 (d)
GAA /A1,0
(pCi/L)
intervals
1
1
3
4
0.4-0.8
2.0-4.0
2
30
3
33
0.5-0.9
2.5-4.5
3
30
30
60
0.6-1.0
3.0-5.0
4
120
3
123
0.7-1.2
3.5-6.0
For a quarterly composite sample, the 210Pb decay chain’s contribution to GAA is
significant for all values of T3. To calculate the contribution for a 60-mg patch residue at T3 = 4
days, one multiples the factor GAA/A1,0 = 0.4, from Figure 4.12, by the initial 210Pb activity, 5
pCi/L, to obtain GAA = 2.0 pCi/L. This is the lower limit for the first entry in Table 5.9. The
other lower limits can be computed in a similar way. To calculate the contribution to the GAA
for the corresponding smooth residue at T3 = 4 days, one multiplies the factor GAA /A1,0 = 0.8,
from Figure 4.11, by the initial 210Pb activity to obtain GAA = 4.0 pCi/L. This is the upper limit
for the first entry in Table 5.9. The other upper limits can be computed in a similar way.
Table 5.8 and Table 5.9 show that 5 pCi/L of 210Pb cannot by itself cause a GAA violation. However, if a sample had 5 pCi/L of 210Pb activity, and if its GAA soon after collection was
in the range from 10 to 14 pCi/L, then over a period of several months, it would possible for the
210
Pb to elevate the GAA of the sample above the 15 pCi/L MCL. The magnitude of this elevation is clearly larger for quarterly composite samples than for grab samples.
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Chapter 5: Calculation of the GAA for a Hypothetical Example | 63
THE GAA DUE TO THE 228RA DECAY CHAIN
The contribution of the 228Ra decay chain to the GAA depends on the time between sample
collection and analysis, T3. Although 228Ra is a beta emitter, it decays into a series of six alpha
emitters, which, over a period of several months, can significantly contribute to the GAA. Figure 4.13 and Figure 4.14 show that shortly after collection, for a grab sample, the 228Ra decay
chain’s contribution to the GAA is negligible. To calculate the contribution for a grab sample with
a 60-mg patch residue at T3 = 33 days, one multiplies the factor GAA/ A1,0 = 0.2, from Figure 4.14,
by the initial 228Ra activity, 3 pCi/L, to obtain GAA = 0.6 pCi/L. This is the lower limit for the
second entry in Table 5.10. The other lower limits can be determined similarly. To calculate the
contribution of the corresponding smooth residue, one multiplies the factor GAA/ A1,0 = 0.3, from
Figure 4.13, by the initial 228Ra activity to obtain GAA = 0.9 pCi/L. This is the upper limit for the
first entry in Table 5.10. The other upper limits can be determined similarly.
To calculate the 228Ra decay chain’s contribution to the GAA for a quarterly composite
sample with a 60-mg patch residue at T3 = 4 days, one multiples the factor GAA/ A1,0 = 0.9, from
Figure 4.16, by the initial 228Ra activity, 3 pCi/L, to obtain GAA = 2.7 pCi/L. This is the lower
limit for the first entry in Table 5.11. The other lower limits can be determined similarly. To calculate the contribution of the 228Ra decay chain for the corresponding smooth residue, one multiples the factor GAA/ A1,0 = 1.4, from Figure 4.15, by the initial 228Ra activity to obtain GAA =
4.2 pCi/L. This is the upper limit of the first entry in Table 5.11. The other upper limits can be
determined similarly.
Table 5.10 and Table 5.11 show that 3 pCi of 228Ra cannot cause a GAA violation by itself. However, for long holding times, 228Ra could elevate the GAA above the MCL (>15 pCi/L)
in samples that would have no GAA violation had they been analyzed within a month of collection. Such a violation can be considered to be a false-positive GAA violation.
Table 5.10
Grab sample with a 60-mg residue and 3 pCi/L of 228Ra
Set of time
intervals
1
2
3
4
T1 (d)
T2 (d)
T3 (d)
GAA/A1,0
1
30
30
120
3
3
30
3
4
33
60
123
0
0.2-0.3
0.4-0.6
0.8-1.3
GAA
(pCi/L)
0
0.6-0.9
1.2-1.8
2.4-3.9
Table 5.11
Quarterly composite sample with a 60-mg residue and 3 pCi/L of 228Ra
GAA
Set of time
T2 (d)
T3 (d)
GAA /A1,0
T1 (d)
(pCi/L)
intervals
1
1
3
4
0.9-1.4
2.7-4.2
2
3
4
30
30
120
3
30
3
33
60
123
1.0-1.7
1.2-2.0
1.5-2.5
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3.0-5.1
3.6-6.0
4.5-7.5
64 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
THE GAA DUE TO THE 224RA DECAY CHAIN
The contribution of the 224Ra decay chain to the GAA depends on the time between sample collection and analysis, T3. Since the 224Ra decay chain contains the radon isotope 220Rn, it
might be thought that, like the 226Ra decay chain, the GAA due to the 224Ra decay chain would
also depend on the time between preparation and analysis T2. However, although a significant
amount of 220Rn is lost at the time of sample preparation, secular equilibrium between 224Ra and
220
Rn is reestablished within a matter of a few minutes, and any loss of 220Rn can be neglected.
Thus, for all practical purposes, the contribution of the 224Ra decay chain to the GAA is independent of T2.
Since the half-life of 224Ra is 3.6 days, with those of its progeny being shorter, the 224Ra
decay chain’s contribution to the GAA decreases to about half of its original value in about 3 or
4 days and becomes negligible after three weeks. Thus, all entries in Table 5.12 and Table 5.13
corresponding to T3 ≥ 30 days are zero.
To calculate the 224Ra decay chain’s contribution to the GAA for a grab sample with a
60-mg patch residue at T3 = 4 days, one multiples the factor GAA/A1,0 = 3.4, from Figure 4.18,
by the initial 224Ra activity, 4 pCi/L, to obtain GAA = 13.6 pCi/L. This is the lower limit of the
first entry in Table 5.12. For the corresponding smooth residue, one multiplies the factor
GAA/A1 = 5.3, from Figure 4.17, by initial 224Ra activity to obtain GAA = 21.2 pCi/L. This is the
upper limit of the first entry in Table 5.12.
For a quarterly composite sample, the unsupported 224Ra in the first three aliquots will
have decayed away by the time that the last aliquot had been collected. Thus, only unsupported
224
Ra activity of the last aliquot can contribute to the GAA of the composite sample. At T1 = 0,
the 224Ra activity of the composite will be one-fourth of the 224Ra activity of the last aliquot. If
the 224Ra activity of last aliquot was 4 pCi/L, then the 224Ra activity of the composite sample at
time T1 = 0 would be 1 pCi/L, and the values of the GAA for the composite samples in
Table 5.13 are just be one-fourth of the corresponding values for the grab samples in Table 5.12.
Table 5.12
Grab sample with a 60-mg residue and 4 pCi/L of 224Ra
Set of time
T1 (d)
intervals
T2 (d)
T3 (d)
GAA /A1,0
GAA
(pCi/L)
1
1
3
4
3.4-5.3
13.6-21.2
2
30
3
33
0
0
3
30
30
60
0
0
4
120
3
123
0
0
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Chapter 5: Calculation of the GAA for a Hypothetical Example | 65
Table 5.13
Composite sample with a 60-mg residue and 4 pCi/L of 224Ra
Set of time
GAA
T1 (d)
T2 (d)
T3 (d)
GAA /A1,0
intervals
(pCi/L)
1
1
3
4
0.9-1.3
3.4-5.3
2
30
3
33
0
0
3
30
30
60
0
0
4
120
3
123
0
0
Table 5.12 and Table 5.13 show that the 224Ra decay chain’s contribution to the GAA can
be extremely high soon after collection and will be virtually zero when the sample is analyzed
three weeks or more after collection. Table 5.12 shows that even at four days after collection, the
unsupported 224Ra activity, which is slightly less than 2 pCi/L, could cause a GAA violation by
itself. The relatively large contribution of the 224Ra decay chain to the GAA is due to the fact that
all five of the chain’s alpha emitters are high-energy alpha emitters.
Table 5.14
Grab and composite sample with a 60-mg residue and 4 pCi/L of 212Pb
Set of time
GAA
T1 (d)
T2 (d)
T3 (d)
GAA/A1,0
(pCi/L)
intervals
1
1
3
5
0
0
2
30
3
33
0
0
3
30
30
60
0
0
4
120
3
123
0
0
THE GAA DUE TO THE 212PB DECAY CHAIN
The 212Pb decay chain’s contribution to the GAA depends on the time between sample
collection and analysis, T3. Figure 4.19 and Figure 4.20 show that for T3 ≥ 3 days, the GAA due
to the 212Pb decay chain is virtually zero, and all entries for GAA/A1,0 and GAA in Table 5.14 are
zero. The State of New Jersey requires that the GAA of water samples from private and public
wells be analyzed within 48 hours of collection (NJAC 2004). Under these conditions, the
contribution of the 212Pb decay chain to the GAA can be significant, and can be estimated from
Figure 4.19 and Figure 4.20, provided that the initial 212Pb activity is known or can be estimated.
THE TOTAL GAA
The total GAA of the hypothetical sample, whose radiological composition is given in
Table 5.1, is a sum of the contributions of each decay chain, which were determined in previous
sections. Table 5.15 gives the total GAA for the grab sample with a patch residue, Table 5.16
gives the total GAA for the grab sample with a smooth residue, Table 5.17 gives the total GAA
for the quarterly composite sample with a patch residue, and Table 5.18 gives the total GAA for
the quarterly composite sample with a smooth residue. For each set of parameters, the adjusted
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66 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
GAA, which equals the GAA minus the total uranium activity (7 pCi/L), is also tabulated, and
last column of each table indicates whether the sample has a GAA violation (adjusted GAA > 15
pCi/L).
Since all four sets of time intervals, given in Table 5.2, satisfy the time requirements of
EPA Method 900.0, the total GAAs tabulated in Table 5.15 through Table 5.18 all represent
feasible experimental results. These data clearly demonstrate the effect of residue geometry on
the GAA. For a grab sample, Table 5.15 shows that two sets of parameters yield GAA violations
for the patch residues, whereas Table 5.16 shows that all four sets of parameters yield GAA violations for smooth residues. For the quarterly composite samples, Table 5.17 shows that one set
of parameters yields a GAA violation for patch residues; whereas, Table 5.18 shows that in all
four sets of parameters yield GAA violations for smooth residues.
The GAA violation for the first entry in Table 5.15 is largely due to unsupported 224Ra
and its progeny, and the GAA violation for the third entry is largely due to the ingrowth of the
alpha-emitting progeny of the 226Ra decay chain. There are three reasons for the relatively low
value of the GAA for the second entry (9.0 pCi/L). First, the sample was prepared 30 days after
collection, at which point, the unsupported 224Ra would have decayed away. Second, the sample
was analyzed three days after preparation, at which point, the activities of the alpha-emitters of
the 226Ra decay chain would have been minimal. Finally, the sample was analyzed just 33 days
after collection, at which point, the alpha activities due to the 210Pb and 228Ra decay chains would
have still been quite small. The increase in efficiencies in going from patch to smooth residues
causes the two non-violations of Table 5.15 to be elevated to violations in Table 5.16.
For the quarterly composite samples, the increase in efficiencies in going from patch to
smooth residues causes the three non-violations in Table 5.17 to be elevated to violations in Table 5.18. The 210Pb decay chain’s and 228Ra decay chain’s contribution to the GAA increase as
the time between sample collection and analysis increases. Their combined contributions cause
the last three entries of Table 5.17 and Table 5.18, for the composite samples, to exceed those of
Table 5.15 and Table 5.16, for the grab samples. Although, the 210Po decay chain’s contribution
to the GAA decreases as the time between sample collection and analysis increases, in this example, the decrease due to the 210Po decay chain is outweighed by the increase due to the 210Pb
and 226Ra decay chains.
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Chapter 5: Calculation of the GAA for a Hypothetical Example | 67
Set of time
intervals
1
2
3
4
Table 5.15
The total GAA for a grab sample with a patch residue
Adjusted
GAA
GAA
T1 (d) T2 (d) T3 (d)
(pCi/L)
(pCi/L)
1
3
4
32.6
22.5
30
3
33
16.0
9.0
30
30
60
23.5
16.5
120
3
123
17.8
10.8
GAA violation?
Yes
No
Yes
No
Table 5.16
The total GAA for a grab sample with a smooth residue
Adjusted
GAA
GAA violaSet of time
GAA
T1 (d) T2 (d) T3 (d)
(pCi/L)
tion?
intervals
(pCi/L)
1
1
3
4
52.8
45.8
Yes
2
30
3
33
32.0
25.0
Yes
3
30
30
60
45.2
38.2
Yes
4
120
3
123
35.0
28.0
Yes
Table 5.17
The total GAA for a quarterly composite sample with a patch residue
Adjusted
Set of time
GAA
GAA violaT1 (d) T2 (d) T3 (d)
GAA
(pCi/L)
tion?
intervals
(pCi/L)
1
1
3
4
22.0
15.0
No
2
30
3
33
18.9
11.9
No
3
30
30
60
26.4
19.4
Yes
4
120
3
123
20.4
13.4
No
Table 5.18
The total GAA for a quarterly composite sample with a smooth residue
Adjusted
Set of time
GAA
GAA violaT1 (d) T2 (d) T3 (d)
GAA
intervals
(pCi/L)
tion?
(pCi/L)
1
1
3
4
41.1
34.1
Yes
2
30
3
33
36.7
29.7
Yes
3
30
30
60
49.4
42.4
Yes
4
120
3
123
38.6
31.6
Yes
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68 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
©2010 Water Research Foundation. ALL RIGHTS RESERVED
CHAPTER 6
EFFECT OF OTHER ERRORS ON THE GAA AND THE URANIUM
CONCENTRATION
INTRODUCTION
The plots of Chapter 4 and the hypothetical example of Chapter 5 show that the gross alpha-particle activity (GAA) is, in general, highly variable, and depends on such parameters as
the radiological composition of the samples, the time at which certain steps in the method are
performed, the residue mass, and the residue geometry. In this chapter, other sources of bias and
error in GAA methods are discussed, and sources of bias and error in the uranium methods are
discussed.
EFFECT OF COUNTING ERROR ON THE GAA
During the course of a GAA analysis, a gas proportional counter is used to count the
number of alpha particles that are emitted from a sample residue over a period of time, called the
count time. Since radioactive decay is a random process, the number of alpha particles emitted
by the residue, and, thus, the number of counts collected, cannot be determined with infinite precision. If one had two samples that were identical in every respect, and if one were to count both
samples for equal periods of time, then the two count totals would usually differ, sometimes significantly. The uncertainty in the number of counts is called counting error.
The origin of the counting error is due to the random nature of radioactive decay. Over
the count time, it is impossible to predict, with certainty, whether any particular atom will decay:
one can only give the probability p that the atom will decay. Thus, the decay of an atom is directly analogous to flipping a coin and observing whether heads comes up. Before the coin is
flipped, the most one can say is that there is a probability of 0.5 that heads will come up. Analogously, before an atom decays, the most one can say is that there is a probability p that it will decay over the count time.
The probability p increases as the radionuclide’s half-life decreases and increases as the
count time increases. For the sake of simplicity, an example is given in which it is assumed that
the probability that an atoms decays is 0.5, the same as the probability of observing heads in a
coin flip. First, it will be assumed that there are only four atoms in the sample. Since p = 0.5, on
average, one would expect 50% of the atoms to decay. However, any number of decays from zero to four is possible. Table 6.1 gives the overall probability of observing zero to four decays.
The most probable outcome is that two atoms decay, which has a 37.5% chance of occurring.
However, there is still a 62.5% chance that some other outcome will occur. Each outcome in Table 6.1 is possible, and the number of decays over the count period can range from zero to four.
The combined probability at the extreme ends, that is, for zero or four decays, is 12.5%, which is
small but still significant.
For a larger numbers of radioactive atoms, the number of possible outcomes increases,
and the number of counts detected increases. However, the probability that the outcome will be
close to the expected value of 50% becomes much higher, and the probability that an outcome
will be close to one of the two extremes will become much lower. This does not mean that an
outcome of exactly 50% decay is highly likely, but that an outcome that lies within a small inter-
69
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70 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
val about 50% becomes highly probable. For example, for 1000 atoms, the probability that 500
atoms will decay is just 2.5%, but, as Table 6.2 shows, the probability that from 476 to 524
atoms decay is 87.8%. Thus, there is an 87.8% chance that the number of decays will fall within
the middle 5% of the entire range from 0 to 10000. At the lower extreme, the probability that
from 0 to 200 atoms decay, which covers 20% of the entire range, is just 8.2×10−84 %, which is
virtually zero. Thus, as the number of atoms increases, the probability that the percentage of decays will deviate from the expected value of 50% decreases. It can also be shown that when the
half-life of an alpha emitter is much longer than the count interval, then the counting error can be
reduced by collecting more counts, which is done by counting the sample for a longer period of
time.
Table 6.1
Percent chance of observing the decay in four atoms
Number of heads or
% chance of observaPercent of range
number of decays
tion
0
1
2
3
4
6.25
25
37.5
25
6.25
20
20
20
20
20
Table 6.2
Percent chance of observing decay in 1000 atoms
Number of heads or
% chance of observaPercent of range
number of decays
tion
0-200
201-400
401-475
476-524
525-599
600-800
801-1000
8.2×10−84
1.4×10−8
20
20
6.1
87.8
6.1
7.5
5.0
7.5
20
1.4×10−8
8.2×10−84
20
For a given count time ΔT, let N be the number of counts that are detected. In calculations, N is usually assumed to be the most probable number n of counts, but Table 6.1 and
Table 6.2 show that N and n are usually not identical. Such an assumption introduces error into
the calculation. Probability theory (see. e.g., Currie 1968) shows that an estimate of this error,
denoted by σ1, is given by
σ1 = N .
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Chapter 6: Effect of Other Errors on the GAA and the Uranium Concentration | 71
(In this equation, background counts are ignored, which would further increase the value of σ1.)
There is approximately a 95% chance that n will fall between N − 2σ1 and N + 2σ1. Once N is determined, the GAA is calculated with the following equation:
(6.1)
N
GAA = 0.45
,
eSVΔT
where eS is the efficiency of the calibration standard and V is the sample volume. The factor of
0.45 is required when ΔT is expressed in minutes, V is expressed in liters, and the GAA is expressed in picoCuries per liter. Probability theory estimates that the part σ2 of the error in the
GAA due to counting error is given by
(6.2)
1
σ 2 = 0.45
σ1 .
eSVΔT
Since, in this case, N is proportional to ΔT, the factor σ1 /ΔT decreases as the count interval, ΔT, increases. Thus, the longer the count interval, the more counts that are collected and the
lower is the relative counting error, given by 2σ2/GAA. It might be thought that one could simply increase the count interval, ΔT, to make the relative error as small as desired; however, in any
laboratory, there are a limited number of detectors, and one must place a practical upper limit on
the count interval.
Residue mass
(mg)
20
20
20
20
30
30
30
30
90
90
90
90
eS
0.15
0.15
0.15
0.15
0.1
0.1
0.1
0.1
0.05
0.05
0.05
0.05
Table 6.3
The error in the GAA
T
N
GAA
(min)
(pCi/L)
100
100
15
200
200
15
300
300
15
400
400
15
100
67
15
200
133
15
300
200
15
400
266
15
100
33
15
200
67
15
300
100
15
400
133
15
2σ2
(pCi/L)
2.3
1.6
1.3
1.1
2.8
2.0
1.6
1.4
3.9
2.8
2.3
2.0
Percent
GAA error
15.0
10.5
8.5
7.5
18.5
13.0
10.5
9.0
26.0
18.5
15.0
13.0
In Table 6.3, an example is presented for a 200-mL sample that has 15 pCi/L of alpha activity, which is the MCL for the adjusted GAA. For the sake of simplicity, it is assumed that all
of the alpha emitters have the same efficiency as the calibration standard, eS. The table gives
three values of the residue mass, and the corresponding values of the calibration standard’s efficiency, eS, taken from Figure F.1, and gives four different count times for each efficiency. In Table 6.3, the efficiencies, eS, and count times, ΔT, allow one to calculate N, given by
1
N=
eS AΔTV ,
450
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72 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
where A = 15 pCi/L, ΔT is the count time in minutes, and V = 200 mL. Then N and Eqns. (6.1)
and (6.2) can be used to calculate GAA, the GAA error, σ2, and the percent error in the GAA,
given by
% GAA Error = 150σ2/GAA,
at the 95 % confidence limit.
The data in Table 6.3 show that σ2 increases as the number of detected counts, N, increases, but the percent error decreases as N increases. Since the efficiency, eS, decreases as residue mass increases, for a given value of the count time, ΔT, the number of counts collected, N,
decreases and the percent error decreases as the residue mass increases. The counting error can
be quite large, even for samples that contain 15 pCi/L of alpha activity. Table 6.3 shows that for
an efficiency of 0.05, which approximately corresponds to the efficiency of a 90-mg residue, the
sample must be counted for 300 min. to reduce the percent error to 20 %, and if the sample is
counted for an additional 100 min., the percent error is only reduced to 17 %. Thus, in this case,
even reducing the counting error to 10 % is not feasible. The data in Table 6.3 show that when
the GAA of a sample is close to the 15 pCi/L MCL, it is, to some extent, a matter of chance
whether the GAA will be above or below the MCL. Many laboratories only report the part of the
GAA error due to counting error. Other sources of error, which were either discussed above or
are discussed in the next two sections, can cause the GAA error to be significantly larger.
PROBLEMS WITH URANIUM METHODS AND HOW THEY AFFECT THE URANIUM CONCENTRATION AND THE ADJUSTED GAA
The amount of uranium in water is commonly measured in either units of activity concentration (pCi/L) or units of mass concentration (µg/L). Two types of regulatory violations are affected by the presence of uranium. A GAA violation occurs when a sample has an adjusted
GAA—the GAA minus the uranium activity concentration—of more than 15 pCi/L, and a uranium violation occurs when a sample has a total uranium mass concentration of more than 30
μg/L (U. S. EPA 2000a). Frequently, both the uranium mass and activity concentration are
needed.
Ideally, a method for analyzing uranium would accurately measure both the uranium activity and mass concentration; however, some of the EPA-approved methods can only accurately
measure one or the other. Many methods are used to quantify uranium in drinking water and
most yield reliable results when they are applied as intended. EPA-approved methods for the determination of uranium can be classified according to three types: (1) methods that accurately
measure the uranium activity concentration (pCi/L) but not the uranium mass concentration, (2)
methods that accurately measure the uranium mass concentration (μg/L) but not the uranium activity concentration, and (3) methods that accurately measure both the uranium activity concentration and the uranium mass concentration. Type (1) methods include radiochemical methods;
type (2) methods include fluorometric, laser phosphorimetric, and inductively coupled mass
spectroscopic (ICP-MS) methods; and type 3 methods include alpha spectroscopic methods. The
capability of each type of the EPA-approved method, along with an example of each method, is
summarized in Table 6.4.
[It should be mentioned that in 2004, the U.S. EPA (U. S. EPA 2004) approved of three
ICP-MS methods for uranium analyses (U.S EPA 1994b, SM 2005b, ASTM 2003b). Each of
these methods derives the 234U mass concentration from the measured 238U mass concentration
assuming natural abundance. Currently, there are ICP-MS methods, which are not EPA ap-
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Chapter 6: Effect of Other Errors on the GAA and the Uranium Concentration | 73
proved, that are capable of determining the 234U mass concentration directely. Such methods
would be type (3) uranium methods. It is anticipated that the EPA will approve some of these
ICP-MS methods in the near future.]
Errors frequently arise when a type (1) uranium method is used to the estimate uranium
mass concentration or when a type (2) uranium method is used to estimate the uranium activity
concentration. The EPA allows one to convert from uranium activity concentration to uranium
mass concentration, or vice versa, using a mandated conversion factor of 0.67 pCi/μg. The derivation of this conversion factor is based on the assumption that the 234U and 238U activities are
equal; however, as discussed in Chapter 1, groundwater is frequently enriched in 234U relative to
238
U, which causes the mandated conversion factor to underestimate the true conversion factor.
Table 6.4
EPA-approved methods for uranium
Example
Measures mass
conc. (μg/L)
Measures act.
Conc. (pCi/L)
Radiochemical
EPA Method 908.0
No
Yes
Fluorometric
EPA Method 908.1
Yes
No
ASTM Method D5174-97
Yes
No
EPA Method 200.8
Yes
No
Standard Methods 7500U C
Yes
Yes
Type of Uranium method
Laser phosphorimetry
ICP-MS
Alpha spectroscopy
Using the mandated conversion factor will frequently cause one to underestimate a uranium activity concentration obtained from a uranium mass concentration that was determined by
a type (2) uranium method, which can lead to a false-positive GAA violation. Further, using the
mandated conversion factor will frequently cause one to overestimate a uranium mass concentration obtained from a uranium activity concentration that was determined using a type (1) uranium method, which can lead to a false-positive uranium violation.
The following equation for the true conversion factor C is derived in Appendix I:
⎛
A ⎞
(6.3)
C = 0.336⎜⎜1 + 1 ⎟⎟ ,
A2 ⎠
⎝
where A1 is the 234U activity and A2 is the 238U activity. It is seen that C increases linearly with
A1/A2 and that C only equals the mandated conversion factor when A1/A2 = 1. A plot of C versus
A1/A2 is given in Figure 6.1. The dashed line in the figure corresponds to the mandated conversion factor (0.67 pCi/μg). The U.S. EPA is aware of the inaccuracy of the mandated conversion
factor for some samples and has stated that the true conversion factor can be as high as 1.5
pCi/μg (U. S. EPA 2000a), which corresponds to A1/A2 = 3.5 in Eqn. 6.3. In Chapter 7, it will be
seen that 22 samples in this study had a value of A1/A2 that was greater than 3.5, which corresponds to a conversion factor that is more than twice the mandated factor.
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74 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
4.0
3.5
C (pCi/μg)
3.0
2.5
2.0
1.5
1.0
0.5
0.0
0
2
4
6
8
10
A1/A2
Figure 6.1. Plot of C versus A1/A2
As an example of a false-positive GAA violation, suppose that a water sample was found
to contain 10 μg/L of uranium using a type (2) uranium method, had a GAA of 30.0 pCi/L, and
had A1/A2 = 5. Then using the EPA-mandated conversion factor, the uranium activity concentration is estimated to be 10 μg/L × 0.67 pCi/μg = 6.7 pCi/L, and the adjusted GAA is 30.0−6.7 pCi
= 23.3 pCi/L, which is a GAA violation. However, Figure 6.1 shows that for A1/A2 = 5, the true
conversion factor is 2.0 pCi/μg. Using the true conversion factor, the uranium activity concentration is found to be 10 μg/L × 2.0 pCi/μg = 20 pCi/L, and the true adjusted GAA is 30.0 − 20.0
pCi/L = 10.0 pCi/L, which is not a GAA violation. Thus, underestimating the conversion factor
has lead to a false-positive GAA violation. If a false-positive GAA violation is suspected due to
an inaccurate conversion error, the uranium activity concentration should be re-determined using
a type (1) or (3) uranium method.
As an example of a false-positive uranium violation, suppose that a water sample has
25.0 pCi/L of uranium, determined using a type (1) uranium method, and that A1/A2 = 5. Then
using the EPA-mandated conversion factor, the uranium mass concentration is estimated to be
25.0 pCi/L × 1.5 μg/pCi = 37.5 μg/L, which is a uranium violation. From Figure 6.1, it is seen
that, when A1/A2 = 5, the true conversion factor is 2.0 pCi/μg. Using the true conversion factor,
the uranium mass concentration is found to be 25.0 pCi/L × 0.5 μg/pCi = 12.5 μg /L, which is
not a uranium violation. Thus, underestimating the conversion factor has lead to a false-positive
uranium violation. If a false-positive uranium violation is suspected due to an inaccurate conversion error, then the uranium mass concentration should be re-determined using a type (2) or (3)
uranium method.
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Chapter 6: Effect of Other Errors on the GAA and the Uranium Concentration | 75
MISCELLANEOUS SOURCES OF ERROR IN THE GAA
Other parameters can contribute significantly to the bias and error in the GAA. First, in
all of the calculations in this report, it is assumed that the radial distribution of a residue on a
planchet was uniform. Evidence was presented in Chapter 2 to support this assumption in the
case of patch residues, but even for these residues, this assumption is only approximately true.
The degree of uniformity of the radial distribution may depend on a particular analyst’s technique, and may vary from one analyst to another. Owing to the edge effect, discussed in Chapter
2, a radial distribution biased towards the center of the planchet can give a relatively high GAA
and a radial distribution biased towards the edge of the planchet can give a relatively low GAA.
Second, there is no guarantee that the sample residue is homogeneous or that an alpha
emitter is homogeneously distributed throughout the sample residue. It is known that, under
some conditions, uranium is not homogeneously distributed in the residue (Zikovsky 2000). If an
alpha emitter is preferentially distributed towards the top of a residue, its contribution to the
GAA will be larger than if it is preferentially distributed towards the bottom of the residue,
which increases the amount of self-absorption. The results presented in Chapter 8 suggest that,
under some conditions, uranium may distribute towards the top of the residue.
Third, EPA Method 900.0 allows one to use either 230Th or natural uranium as the calibration standard. Because the average alpha-particle energy of natural uranium is less than that
of 230Th (Table 1.1), the efficiency of natural uranium is less than that of 230Th, and, as shown in
Eqn. (2.2), the GAA is less when 230Th is used as the calibration standard than when natural uranium is used as the calibration standard.
Fourth, the aqueous matrix that is used to prepare samples for the calibration curve can
have a marked effect on the geometry of the sample residue. A soft-water matrix, which contains
mostly sodium and potassium and only minor amounts of other metals, yields a sample residue
that stays molten when it is heated over a flame and wets the planchet, so that when the residue
cools, it covers the planchet and appears to be of relatively uniform thickness. A hard-water matrix often yields samples with patchy residues. Thus, one would expect less self-absorption for
soft-water residues than for hard-water residues, and, therefore, one would expect a calibration
standard’s efficiency for soft-water residues to be, on average, higher than that for hard-water
residues. Eqn. (2.2) shows that a high bias in the calibration standard’s efficiency, eS, results in a
GAA with a low bias. Ideally, the composition of the calibration standard’s matrix and the sample matrix would be similar, but this would require one to prepare multiple calibration curves and
to analyze the inorganic constituents of each sample, which is not feasible.
Finally, it is known that polonium and some of its compounds are relatively volatile, especially at elevated temperatures (Figgins 1961). When a sample is heated over a flame, it is
likely that some 210Po is lost to volatilization, which can cause one to underestimate the GAA
and which can cause the GAA to vary with the amount of 210Po that is lost. In EPA Method
900.0, residues are heated over a flame to a dull red glow if they are deemed to be hygroscopic.
In the present work, an attempt was made to quantify the volatility of polonium in the sample
residues, but, for technical reasons, the results were unsatisfactory. Rather, qualitative experiments were performed as described in Chapter 3.
©2010 Water Research Foundation. ALL RIGHTS RESERVED
76 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
10
flame time (s)
0
30
90
Count rate (cpm)
8
6
4
2
0
0
20
40
60
80
100
Residue mass (mg)
Figure 6.2. Volatility of polonium
Source: Arndt and West 2008c. An Experimental Analysis of the Contribution of 210Pb and 210Po
and Progeny to the Gross Alpha-Particle Activity of Water Samples. Health Phys. 95:310-316;
2008.
Six samples were spiked with 0.8 Bq of 210Po and various amounts of the NaNO3-KNO3
solution to give a range of residue masses. The samples were counted on the gas proportional
counter before being flamed, after being flamed for 30 s, and after being flamed for an additional
60 s. The count rate versus the residue mass is plotted in Figure 6.2 for non-flamed residues, for
the same residues flamed for 30 s, and for the same residues flamed for an additional 60 s. There
is a nearly quantitative loss of 210Po at a residue mass of 0 mg, while after flaming for 90 s, the
activity of 210Po in the 20 mg residue is reduced to about 25% of its original activity. It is seen
that there is discernable, loss of 210Po activity at all residue masses. It should be mentioned that
the reduction in the count rate could also be due to adsorption of 210Po on the planchet-residue
interface, which would increase the level of self-absorption.
Figure 6.2 shows that the contribution of 210Po to the GAA decreases with the length of
time that the sample is flamed and that the percent decrease in the GAA depends on the residue
mass. Thus, the volatility of 210Po can contribute significantly to the variability of the GAA.
©2010 Water Research Foundation. ALL RIGHTS RESERVED
CHAPTER 7
RADIOCHEMICAL COMPOSITION OF THE GROUNDWATER SAMPLES
INTRODUCTION
Some 79 groundwater samples were collected from 5 private wells and 74 public wells
from around the continental United States. The geographical location of the sampling sites is indicated in the map of Figure 7.1. Samples were collected from 24 states and from all nine U.S
Census Bureau areas including 5 from the New England States, 4 from the Mid-Atlantic States,
15 from the East North Central States, 21 from the West North Central States, 16 from the South
Atlantic States, 1 from the East South Central States, 2 from the West South Central States, 9
from the Mountain States, and 6 from the Pacific States.
Wells were selected to include several representatives of each of the five principal types
of aquifer, by rock type, as classified by the U. S. Geological Survey: sand and gravel, sandstone,
sandstone and carbonate, carbonate rock, and igneous and metamorphic rock. The majority of
wells had well-established radium, uranium, or GAA MCL violations. Most of the other wells
had uranium, radium, or GAA levels that were either near an MCL or were sometimes greater
and sometimes less than an MCL. Each well was sampled once. Some participants indicated that
the GAA of their wells were quite variable in the past. Some of the variation could be temporal,
but much was probably due to the sources of bias and error that affects the GAA, which were
discussed in Chapters 2, 4, and 5.
Figure 7.1. Map of sample collection sites in the Continental United States. A circle (●) indicates a site where one sample was taken, a square (■) indicates a site where two samples
were taken, and triangle (▲) indicates a site where three samples were taken.
77
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78 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
VIOLATIONS AND POTENTIAL FALSE-POSTIVE VIOLATIONS
Of the 79 samples in this study, 16 had uranium violations (>30 μg/L), 38 had radium violations (combined 226Ra and 228Ra >5 pCi/L), 4 had both and uranium and a radium violations,
1 had enough 210Po activity (>15 pCi/L) to cause a GAA violation, and 24 had no violation. Of
the 24 samples with no violation, 4 had a total uranium concentration between 20 and 30 μg/L, 7
had a combined radium activity between 3 and 4 pCi/L, and 6 had a combined radium activity
between 4 and 5 pCi/L. Of the 4 samples with a uranium activity between 20 and 30 μg/L, 2 had
a false-positive uranium violation when its uranium mass concentration (μg/L) was determined
using its uranium activity concentration (pCi/L) and the EPA-mandated conversion factor of 1.5
μg/pCi (see Chapter 6). Of the 6 samples with a combined radium activity between 4 and 5
pCi/L, 5 had a 226Ra activity that was close to or in excess 3 pCi/L and 1 had a 226Ra activity of
2.2 pCi/L. Of the 7 samples with combined radium activity between 3 and 4 pCi/L, 1 had a 226Ra
activity of 2.2 pCi/L and 1 had a 226Ra activity of 2.8 pCi/L. As was shown in Chapter 4, as little
as 2 pCi/L of 226Ra activity can, under some conditions, cause a false-positive GAA violation.
Thus, out of the 79 samples analyzed in this study, 10 could potentially have yielded a falsepositive uranium and GAA violation. These data are summarized in Table 7.1.
Classification
of samples
U violation
Table 7.1
Classification of Some of the samples
226
Ra+ 228Ra
U conc.
GRA
No. of
activity
(pCi/L) samples
(μg/L )
(pCi/L)
—
—
16
> 30
No. of violations
Potential
violations
16
—
Ra violation
U and Ra
Violation
GAA violation
—
>5
—
38
38
—
> 30
>5
—
4
4
—
—
—
> 15
1
1
—
High U
20-30
—
—
4
—
2
High Ra
—
4-5
—
6
—
6
Moderate Ra
—
3- 4
—
7
—
2
Of the 7 samples that had no MCL violation, that had no combined radium activity above
2 pCi/L, and that had no uranium concentration above 20 μg/L, 1 had been treated to remove radium. One had a recent history of a GAA that fluctuated above and below the 15 pCi/L MCL.,
and one had a well documented but variable GAA violation that was due to 210Po. The 210Po activity of the latter sample was 2.1 pCi/L
224
Ra is currently unregulated, but as shown in Chapter 4, as little as 2 pCi/L of 224Ra can
cause a GAA violation if the sample were prepared and analyzed within 3 days of collection.
There were 49 samples that had a 224Ra activity in excess of 2 pCi/L. Of these 49, 20 had a 224Ra
activity in excess of 10 pCi/L, 16 had a 224Ra activity between 5 and 10 pCi/L, 5 had a 224Ra activity between 3 and 5 pCi/L, and 8 had a 224Ra activity between 2 and 3 pCi/L. These data are
summarized in Table 7.2.
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Chapter 7: Radiochemical Composition of the Groundwater Samples | 79
Table 7.2
Classification of some of the samples by 224Ra activity
224
Classification of samples
No of samples
Ra activity (pCi/L)
Very High 224Ra activity
High
224
Ra activity
Moderate
Low
224
224
Ra activity
Ra activity
>10
20
5-10
16
3-5
5
2-3
8
A brief overview of the radiochemical results for the 79 groundwater samples is given in
the following Sections. Comprehensive studies that discuss the radiochemical composition of
groundwater and its relationship to aquifer geology include those of Focazio et al (2001) and
Szabo et al (2005).
URANIUM RESULTS
As discussed in Chapter 1, due to recoil enrichment, it would be expected that the 234U
activity would exceed the 238U activity in many samples. Figure 7.2 is a log-log plot of the 234U
activity versus the 238U activity. The line in Figure 7.2 corresponds to points where the 234U and
238
U activities are equal. Data points to the right of the line correspond to samples in which the
234
U activity exceeds the 238U activity. It is seen that, within experimental error, all samples
points lie either on or to the right of this line. The 234U activities range from approximately zero
up to about 3000 pCi/L; the 238U activities range from approximately zero up to about 1800
pCi/L.
The level of recoil enrichment in Figure 7.2 is difficult to assess because the uranium activities range over many orders of magnitude. A better measure of the level of recoil enrichment
is given by the ratio of the 234U activity to the 238U activity. Figure 7.3 is a histogram of this ratio
for all samples points where the relative error of the ratio was less than 25%, which comprised
58 samples out of the 79 samples. The points at the left side of the histogram are, to within experimental error, equal to 1, so that there were no samples where the 238U activity exceeded the
234
U activity. There were 26 samples where the ratio was 2 or more, there were 11 samples
where the ratio was 10 or more, and there was 1 sample where the ratio was about 20.
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80 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
10000
−1
U activity (pCi L )
1000
100
10
238
1
0.1
0.01
0.01
0.1
1
10
100
1000
10000
−1
234
U activity (pCi L )
Figure 7.2. 234U activity versus 238U activity
24
No. of samples
20
16
12
8
4
0
0
2
4
6
Ratio of
8
234
10 12 14 16 18 20 22
U activity to
238
U activity
Figure 7.3. Histogram of the ratio of the 234U activity to the 238U activity
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Chapter 7: Radiochemical Composition of the Groundwater Samples | 81
As discussed in Chapter 6, the conversion factor between the uranium activity concentration (pCi/L) and the uranium mass concentration (µg/L), or vice versa, depends on the ratio of
the 234U activity to the 238U activity. In the derivation of the EPA-mandated conversion factor
0.67 pCi/μg, it is assumed that 234U and 238U are in secular equilibrium, i.e., that the 234U and
238
U activities are equal. Figure 7.3 shows that this ratio is often substantially greater than one,
and, therefore, that the true conversion factor is often substantially larger than 0.67 pCi/μg. The
use of the EPA-mandated conversion factor often causes one to overestimate a uranium mass
concentration (μg/L) obtained from a uranium activity concentration (pCi/L), which could yield
a false-positive uranium violation (>30 μg/L) and often causes one to underestimate a uranium
activity concentration obtained from a uranium mass concentration, which could yield a falsepositive GAA violation (>15 pCi/L).
RADIUM RESULTS
Figure 7.4 is a plot of the 226Ra activity versus the 228Ra activity for all 79 samples. It is
seen that there is little correlation between these two activities, which is not surprising since
226
Ra is a member of the 238U decay series and 228Ra is a member of the 232Th decay series.
Figure 7.4 shows that some samples with a significant 226Ra activity (≥1 pCi/L) contain little
228
Ra activity, but that all samples that contain a significant 228Ra activity (≥1 pCi/L) also contain
a substantial 226Ra activity (≥1 pCi/L).
30
228
−1
Ra activity (pCi L )
25
20
15
10
5
0
0
5
10
226
15
20
25
−1
Ra activity (pCi L )
Figure 7.4. 226Ra activity versus 228Ra activity
©2010 Water Research Foundation. ALL RIGHTS RESERVED
30
82 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
32
24
228
−1
Ra activity (pCi L )
28
20
16
12
8
4
0
0
4
8
12
224
16
20
24
28
32
−1
Ra activity (pCi L )
Figure 7.5. 224Ra activity versus 228Ra activity
Figure 7.5 is a plot of the 224Ra activity versus the 228Ra activity for all 79 samples. The
line in Figure 7.5 corresponds to points where the 224Ra activity equals the 228Ra activity. Sample
points that lie to the right of the line correspond to points where the 224Ra activity exceeds the
228
Ra activity. All samples points except one lie either on or to the right of this line. If all sources
of 224Ra and 228Ra in an aquifer (in the groundwater, in the solids, or on the surfaces of solids)
were accounted for, both 224Ra and 228Ra would be found to be in secular equilibrium with their
parent, 232Th, so that the 224Ra and 228Ra activities would be equal. There are at least two reasons
why the 224Ra can exceed 228Ra activity in the ground waters. First, since there is an alpha decay
step between 228Ra and 224Ra, there may be some recoil enrichment in 224Ra relative to 228Ra, like
the recoil enrichment between 234U and 238U. 228Ra undergoes a beta decay step to form 228Ac,
which, within about 36 hours, beta decays to form 228Th. If the original 228Ra atom had been in
solution, the 228Th would likely precipitate or adsorb onto the surface of a solid. If the 228Ra was
in the solid matrix, the two beta decays would impart little recoil energy to the progeny, and the
228
Th atom would occupy a position in close proximity to its parent, 228Ra. A 228Th atom alpha
decays to a 224Ra atom and imparts a significant amount of recoil energy to the 224Ra atom. If
228
Th atom were in a solid but within the recoil distance to the water, the 224Ra progeny atom
could be ejected into the water. Without the recoil step, the 224Ra would have remained in the
solid. In the case of either the pair 224Ra and 228Ra or the pair 234U and 238U, there is one alpha
decay step and two beta decays steps between parent and progeny and there is one thorium isotope between parent and progeny. For 224Ra and 228Ra, the thorium isotope, 228Th, is an alpha
emitter; for 234U and 238U, the thorium isotope, 234Th, is a beta emitter.
Second, if 228Ra in the groundwater moves away from its insoluble 232Th source, it would
be unsupported and the decay of unsupported the 228Ra could eventually produce a 224Ra activity
that exceeds the 228Ra activity. In water that contains unsupported 228Ra, the ratio of the 224Ra
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Chapter 7: Radiochemical Composition of the Groundwater Samples | 83
activity to the 228Ra activity is readily determined. Let t be the length of time that 228Ra was separated from the 232Th parent, A1, 0 be the 228Ra activity at t = 0, A1 be the 228Ra activity at t = t, A4
be the 224Ra activity at t = t, λ1 be the decay constant of 228Ra, and λ3 be the decay constant of
228
Th. Then, the ratio is obtained by dividing the 224Ra activity, given by Eqn. (F.19) with i = 4
and all of the κij equal to 1, by the 228Ra activity, given by
A1 = A1,0exp(−λ1t),
to obtain
A4
= [c 41 + c 43 exp[(λ1 − λ3 )t ] ,
A1
where c41 = 1.501 and c43 = −1.506. This equation shows that as time evolves, the ratio of the
224
Ra activity to the 228Ra activity in the water approaches an upper limit of 1.5. At 11.5 y, or two
half-lives of 228Ra, this ratio is 1.4. Since 228Th precipitates, the degree to which the ratio in actual water would approach 1.5 would depend on the flow rate of the water, and, undoubtedly,
many other factors.
Figure 7.6 is a histogram of the ratio of the 224Ra activity to the 228Ra activity for all samples points where the relative standard deviation of the ratio was less than 25%, which comprised
43 out of the 79 samples. Of these samples only 5 have ratios that were significantly above 1.5,
which suggest that, at least for these 5 samples, there may be some level of recoil enrichment in
224
Ra relative to 228Ra.
Comparison between Figure 7.3 and Figure 7.6 shows that enrichment is more significant
between the uranium isotopes than between the radium isotopes. The reason for this is that the
half-life of 234U is extremely long compared to the radium isotopes, so that disequilibrium between the uranium isotopes can persist for thousands of years, but unsupported 228Ra decays
away in about 10 years and unsupported 224Ra decays away in about three weeks. Near a 232Th
source there could be a high level of recoil enrichment between the radium isotopes, but as the
water moves away from the source, the radium isotopes decay away in a relatively short period
of time.
Figure 7.7 is a plot of the total uranium (234U and 238U) activity versus 226Ra activity. This
figure shows that samples that have high levels of 226Ra tend to have low levels of uranium, and
samples that have high levels of uranium tend to have low levels of radium. This may not be surprising since carbonate tends to increase the solubility of uranium, and radium tends to coprecipitate with certain metal carbonates (Chapter 1). Thus, in the analysis of the GAA data in Chapter 8, most of the samples are categorized as either radium-containing samples or uraniumcontaining samples.
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84 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
12
No. of samples
10
8
6
4
2
0
0.0
0.5
1.0
Ratio of
1.5
2.0 2.5
224
Ra activity to
3.0
3.5
4.0
4.5
228
Ra activity
Figure 7.6. Histogram of the ratio of the 224Ra activity to the 228Ra activity
30
226
−1
Ra activity (pCi L )
25
20
15
10
5
0
0
10
20
234
U+
30
238
40
50
−1
U activity (pCi L )
Figure 7.7. Plot of 226Ra versus the total uranium activity
©2010 Water Research Foundation. ALL RIGHTS RESERVED
60
70
Chapter 7: Radiochemical Composition of the Groundwater Samples | 85
210
PO AND 210PB RESULTS
The results for the 210Po activity were corrected for the 210Po activity that grew in from
Pb decay and were decay corrected back to the sample collection time. After the uranium and
radium isotopes, the next most common radionuclides found in the samples were 210Po and 210Pb.
The 210Po activity exceeded 1 pCi/L in 14 of 79 samples; the 210Pb activity exceeded 1 pCi/L in
10 out of 79 samples. Figure 7.8 is a histogram showing the number of samples versus the 210Po
activity. (Three samples having about 25, 31, and 55 pCi/L of 210Po were excluded from this plot
in order to clearly display the results near origin of the plot.) Studies have estimated that a person’s average daily dietary intake of 210Po ranges from 1 to 10 pCi (Hill 1965, Holtzman 1963).
For most of the groundwater samples in this study, the potential daily intake of 210Po would be
comparable to the average daily dietary intake.
Figure 7.9 is a histogram showing the number of samples versus the 210Pb activity. The
chemistries of lead and calcium are similar, and it has been found that lead competes with calcium for deposition sites in bone (Legget 1993). Although the metabolism of lead is very complex, the retention time of lead in bone is similar to the retention time of the alkaline earth elements (Legget 1993). Unsupported 210Po has a 138-d half-life and will decay away in about 2.3
years. Since 210Pb has a 22-y half-life, it will support a steady activity of 210Po for many decades.
Thus, the 210Po dose an individual receives due to 210Pb decay could be significantly higher than
the dose due to unsupported 210Po.
Although the chemistries of 210Pb and 210Po differ substantially, since 210Po is the progeny
210
of Pb, it was of interest to determine whether the activities of these two radionuclides were
correlated. A plot of the 210Pb activity versus the 210Po activity is given in Figure 7.10. Most
samples contained small amounts of the two radionuclides; only eight samples contained significant amounts of both (≥ 1 pCi/L). One of the eight had a 210Pb activity (14.4 pCi/L) that was significantly higher than the 210Po activity (4.4 pCi/L), one had a 210Po activity (27.4 pCi/L) that
was significantly higher than the 210Pb activity (4.6 pCi/L), and the remaining six had comparable activities of 210Po and 210Po. The relatively small size of the data set does not allow one to
draw general conclusions.
Although there was a significant activity of 210Po (≥1 pCi/L) in a number of the samples,
the 210Po activity was sometimes a small fraction of the total alpha activity. For example,
Figure 7.11 is a log-log plot of the total uranium activity versus the 210Po activity. The line in
Figure 7.11 corresponds to points where the 210Po is 10% of the total uranium activity. For sample points that lie above of the line, 210Po is more than 10% of the total uranium activity. Out of
the 14 samples that contained more than 1 pCi/L of 210Po, only 6 of the samples had a 210Po activity that was more than 10% of the total uranium activity. Figure 4.5 shows that for a 100-mg
smooth residue, the contribution of 210Po to the GAA is about twice the 210Po activity. Three
samples had a 210Po activity that was in excess of 8 pCi/L, so that in these three samples, the
210
Po could, by itself, have caused a GAA violation.
210
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86 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
40
No. of Samples
30
20
10
0
0
2
4
6
8
10
−1
210
Po activity (pC L )
Figure 7.8. Histogram showing the 210Po distribution in the samples
No. of Samples
50
40
30
20
10
0
0
2
4
6
8
10
12
14
210
Pb activity (pCi/L)
Figure 7.9. Histogram showing the 210Pb distribution in the samples
©2010 Water Research Foundation. ALL RIGHTS RESERVED
16
Chapter 7: Radiochemical Composition of the Groundwater Samples | 87
60
210
−1
Po activity (pCi L )
50
40
30
20
10
0
0
3
6
210
9
12
−1
Pb activity (pCi L )
Figure 7.10. Plot of the 210Po activity versus the 210Pb activity
©2010 Water Research Foundation. ALL RIGHTS RESERVED
15
88 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
10
210
−1
Po activity (pCi L )
100
1
0.1
0.01
0.1
1
10
100
−1
210
Pb activity (pCi L )
1000
210
−1
Po activity (pCi L )
100
10
1
0.1
0.01
0.01
0.1
1
234
U+
10
238
100
1000
10000
−1
U activity (pCi L )
Figure 7.11. Plot of the 210Po activity versus the total uranium activity
©2010 Water Research Foundation. ALL RIGHTS RESERVED
CHAPTER 8
GROSS ALPHA-PARTICLE ACTIVITY OF THE GROUNDWATER
SAMPLES
INTRODUCTION
In this chapter, the experimental values of the gross alpha-particle activity (GAA) of the
79 groundwater samples are plotted and are compared with values of the GAA that were determined using the theoretical model presented in Appendices C through F. The theoretical model
takes the following factors into account: the sample’s collection, preparation, and analysis times;
the sample’s radiological and inorganic composition; and the sample residue’s mass. The counting error was estimated from the alpha-particle count rate of the sample residues. In applying the
theoretical model, it was assumed that the spatial distributions of the alpha emitters in the sample
residues were uniform and that the radial distributions of the residue masses in the planchets
were uniform. Since residue geometry is difficult to quantify, the experimental values of the
GAA are compared to the theoretical values of the GAA for uniform, smooth, and patch residues. Although the factors considered in Chapter 6 may, in some cases, be important, they are
difficult to quantify and were not included in the calculations.
Comparison between the experimental and theoretical values of the GAA helped established the relative importance of the factors included in the theoretical model, quantified the effect of some factors and qualitatively characterized the effect of others, and, for some uraniumcontaining samples, showed that the theoretical model did not accurately predict the experimental GAA. For these samples, one or more of the model’s assumptions had to be incorrect. By separating assumptions that were likely to be correct from ones that could be incorrect, some qualitative conclusions were deduced regarding these samples.
REVIEW OF THE DECAY CHAIN’S CONTRIBUTION TO THE GAA
Here, as in Chapter 2, T1 is the time between sample collection and preparation, T2 is the
time between sample preparation and analysis, and T3 = T1 + T2 is the time between sample collection and analysis. Neither 234U nor 238U significantly decays over a sample’s lifetime, and neither produces a significant amount of alpha-emitting progeny. Thus, the contributions of the 234U
and 238U decay chains to the GAA are constant.
The 226Ra decay chain’s contribution to the GAA depends on the time between sample
preparation and analysis, T2. At the time of sample preparation, T2 =0, when the sample residue
is heated over a flame, 222Rn is quantitatively lost. Since 222Rn supports 218Po and 214Po, the 218Po
and 214Po activities both decay substantially over a period of a few hours. Thus, near the sample
preparation time, most of the 226Ra decay chain’s contribution to the GAA is due to 226Ra. After
preparation, 222Rn is trapped in the residue, and 222Rn, in turn, produces 218Po, and 214Po. In a
matter of several hours, 222Rn, 218Po, and 214Po come in to secular equilibrium with another, and
their activities gradually increase with a 3.8-d time constant (the half-life of 222Rn) and attain
their maximum values at about 23 days after preparation, when 222Rn, 218Po, and 214Po are in secular equilibrium with 226Ra.
The 224Ra decay chain’s contribution to the GAA depends on the time between collection
and analysis, T3. 24Ra has a 3.6-d half-life, with those of its progeny being less. Thus, the 224Ra
89
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90 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
decay chain’s contribution to the GAA is frequently substantial when the sample is analyzed
with one week of collection, T3 ≤ 7 d, but would be negligible when the sample is analyzed three
or more weeks after collection, T3 ≥ 21 d.
The 212Pb decay chain’s contribution to the GAA depends on the time between collection
and analysis, T3. 212Pb has a 10.6-h half-life, with those of its progeny being less. Thus, the 212Pb
decay chain’s contribution to the GAA could be substantial if the sample were analyzed within
24 hours of collection, T3 ≤ 24 h, but will be negligible if analyzed more than 2.5 days of after
collection, T2 ≥ 2.5 d.
The 228Ra decay chain’s contribution to the GAA depends on the time between collection
and analysis, T3. At the time of collection, the 228Ra decay chain’s contribution is negligible, but
it continuously produces alpha-emitting progeny, and over the course of several months, can
make a substantial contribution to the GAA. The 228Ra decay chain’s contribution to the GAA
will continually increase over the six-month holding time of a sample.
The 210Po decay chain’s contribution to the GAA depends on the time between collection
and analysis, T3. 210Po has a half-live of 138 d. Thus, the 210Po activity will decrease to half of its
original value in 4.6 months but will not decay away completely until 2.3 years have passed.
Thus, the 210Po activity of a sample decreases exponentially but never completely decays away
over a sample’s six-month holding time.
The 210Pb decay chain’s contribution to the GAA depends on the time between collection
and analysis, T3. The 210Pb decay chain’s contribution to the GAA is negligible at the sample collection time. However, 210Pb continually produces 210Po, and its contribution to the GAA increases over the six-month holding time of a sample. The 210Pb activity is about 36% of the 210Pb
activity after three months and about 60% of the 210Po activity after six months.
SAMPLE PREPARATION
The samples in the study were prepared on two occasions. The first preparation was as
soon as possible after sample collection, typically within three days of collection, when the 224Ra
decay chain’s contribution to the GAA would still be significant. The second preparation was at
least 30 days after collection, when the 224Ra decay chain’s contribution would be negligible. On
each occasion, the samples were prepared in triplicate. Since residue geometry is not highly reproducible, the variability in the GAA among the triplicates was used to help assess the affect of
variability of the residue geometry on the GAA.
For both preparations, the triplicate of samples was analyzed with the gas proportional
counter at three analysis times: (1) as soon as possible following preparation, (2) about three
days following preparation, and (3) at least 30 days following preparation. The first analysis time
was chosen because for the first preparation, the 224Ra decay chain’s contribution to the GAA
would be near its maximum value, and for both preparations, the 226Ra decay chain’s contribution to the GAA would be near its minimum value. The third analysis time was chosen because
for first (and second) preparation, the 224Ra decay chain’s contribution to the GAA would be
negligible, and for both preparations, the 226Ra decay chain’s contribution to the GAA would be
near its maximum value. The second analysis time was chosen, in part, because EPA Method
900.0 stipulates that there must be at least three days between sample preparation and analysis,
and was chosen, in part, because it was expected that the GAA at the second analysis time would
be intermediate between the GAA of first and third analysis times. For radium-containing sam-
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Chapter 8: Gross Alpha-Particle Activity of the Groundwater Samples | 91
ples, it was anticipated that these sample collection, preparation, and analysis times would exhibit the widest possible range for the GAA.
PRESENTATION OF GAA DATA
Figure 8.1 shows how the GAA data for each sample will be presented. The figure consists of two plots. The plot on the left corresponds to the first preparation; the plot on the right
corresponds to the second preparation. In both plots, the points are the experimentally determined GAA data plotted against the time between sample preparation and analysis, T2. Error bars
are not included with the data points because this made for plots that were excessively cluttered.
Also indicated in the legend of each plot is the time between sample collection and preparation,
T1, and the average residue mass of the triplicate of samples. The time between sample collection
and analysis, T3, is just the sum of T1 taken from the legend and T2 taken from the T2-axis.
In each plot, there are three points for each of the three values of T2, which correspond to a
triplicate of sample points. In some cases, there is significant overlap among a triplicate of points,
and not all three can be distinguished. The three curves in each plot correspond to the theoretical
GAA model curves for uniform, smooth, and patch residues that were calculated by the methods of
Appendix F. The residue masses within each triplicate were very close to the average value because, within a triplicate, each residue was prepared using the same sample volume.
In Figure 8.1, the top solid curve is the model curve for a uniform residue, the middle solid curve is the model curve for a smooth residue, and the bottom solid curve is the model curve
for a patch residue. Counting error can cause data points to range outside of the area between the
uniform and patch residue curves. In Figure 8.1, the top dashed curve is the upper limit for the
uniform residue with the two-sigma counting error added to it; the bottom dashed curve is the
lower limit for the patch residue with the two-sigma counting error subtracted from it. The counting error was taken to be the average of the two-sigma counting errors of the nine data points in
the plot.
Errors due to uncertainties in the radionuclide’s activities were not taken into account because this caused excessive clutter in the plots. There are undoubtedly other sources of errors that
have not been taken into account, which were discussed in Chapter 6. Some of these will be discussed below. It had been estimated that about 80% of the GAA data for the calibration standard
fell between the curves for smooth and patch residues (Arndt and West 2007); thus, it will be assumed that the experimental GAA data fit the theoretically derived plots, if 7 out of 9 of the data
points fall between the two dashed curves.
The figures for all 79 samples are presented at the end of this section. In the caption of
each figure, the samples are numbered from 1 to 79, and the Wisconsin State Laboratory of Hygiene’s sample number is given parentheses. In Figure 8.1, the sample number is RR093663.
This number is used to identify sample data in the appendices. Below each figure at the end of
the chapter is a table showing the radiological composition of each sample.
©2010 Water Research Foundation. ALL RIGHTS RESERVED
60
uniform + counting error
uniform
50
smooth
50
40
40
30
30
nd
patch
20
10
20
patch − counting error
mass = 90 mg
T1 = 5.18 d
0
0.01
0.1
GAA for 2 prep (pCi/L)
60
st
GAA for 1 prep (pCi/L)
92 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
1
T2 (d)
10
10
mass = 31 mg
T1 = 44 d
0.1
1
10
0
100
T2 (d)
Figure 8.1. Example of a GAA plot for sample 8 (RR093663)
(Here, a comment is in order concerning the negative values of some of the radionuclide’s activities in these tables. In the course of calculating a radionuclide’s activity, one subtracts a background signal from the signal due to a sample. When the sample contains a nondetectable amount of a radionuclide, the signal due to a sample will be comparable to the signal
due to the background. Thus, owing to counting error, the sample signal can either be greater
than or less than the background signal, and the corresponding calculated radionuclide activity
can be greater than or less than zero. One may be inclined to set the negative activity values
equal to zero, but, in doing so, one introduces bias into the calculations. When the sample and
background signals are comparable, one should expect approximately equal numbers of positive
and negative results. Thus, when there are a significant number of samples with radionuclide activities below the detection limit, the absence of such negative values would make the data set
suspect. The magnitudes of the negative values are relatively small, and setting them equal to
zero would, in actuality, produce a negligible amount of bias in the GAA calculations.)
The time-dependent characteristics of a sample’s GAA plots depend most significantly
on the sample’s radiological composition. In samples that contain predominately uranium isotopes, the GAA is relatively constant over time in both the first and second plots. In samples that
predominately contain radium isotopes, the GAA usually varies significantly with time in both
plots. However, the time-dependent behavior of the first plot is often significantly different than
that of the second plot because unsupported 224Ra contributes to the GAA in the first plot but not
the second. Many samples contain both uranium and radium isotopes, but when uranium predominates, the GAA is relatively constant with time in both plots, and when radium predominates,
there is significant variation of the GAA with time in both plots.
Samples that contained mainly radium or uranium or both and whose 210Po activity was
less than 10% of the sample’s total alpha activity are placed in three groups based on the appearance of the GAA plots: (1) radium-containing samples in which the unsupported 224Ra activity
and/or the 226Ra activity exceeded the total uranium activity, (2) uranium-containing samples in
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Chapter 8: Gross Alpha-Particle Activity of the Groundwater Samples | 93
which the combined activity of unsupported 224Ra and 226Ra was less than 10% of the total uranium activity, and (3) radium-and-uranium-containing samples that predominately contained radium and uranium isotopes but did not fit into either of the first two categories. Although these
groups are, to some extent, arbitrary, one or both plots of a group (1) sample showed significant
variation in the GAA over a period of 30 days; both plots of a group (2) sample had a minimal
time dependence; and one or both plots of a group (3) sample had a time dependence over a period of 30 days that was less pronounced than that of a group (1) sample.
Two other groups of sample groups are defined: (4) 210Po-containing samples in which
210
the Po activity was at least 10% of the sample’s alpha activity, and (5) samples that contained
only a minor amount of alpha activity (< 2 pCi/L). Although the activity of 210Po in some 210Pocontaining samples was less than half of the total activity, this amount of 210Po was sufficient to
cause a significant decrease in the GAA between the first and second preparations. The properties of the sample groups are summarized in Table 8.1.
Table 8.1
Samples Groups
Group
Samples
Ra activity ≥ uranium activity or unsupported 224Ra activity ≥ uranium activity
1
226
2
Sum of unsupported 224Ra and 226Ra activities ≤ 10% uranium activity
226
3
Ra activity < uranium activity or unsupported 224Ra activity < uranium activity
and sum of unsupported 224Ra activity and 226Ra activity and > 10% uranium activity
4
210
5
Total alpha activity < 2 pCi/L
Po > 10% of the total alpha activity
GROUP (1): RADIUM-CONTAINING SAMPLES
Table 8.2 places the radium-containing samples in one of three categories according to
whether the ratio of the 224Ra activity to the 226Ra activity at the time of sample preparation was
greater than one, approximately equal to one, or less than one. The first column indicates the
224
Ra:226Ra activity ratio, the second column indicates whether the experimental data fit the theoretical model curves for the first preparation (left plot) and the second preparation (right plot),
and the third column lists which samples satisfied the conditions of the first two columns. The
224
Ra activity data in the tables below Figure 8.7 through Figure 8.85 were decay corrected to the
sample collection time and not to the sample preparation time.
After about 23 days, the GAAs for both preparations (left and right plots) of most samples were approximately equal because by this time, unsupported 224Ra and its progeny would
have completely decayed away for both preparations, the alpha activity of the 226Ra progeny
would be at its maximum value for both preparations, and the 228Ra decay chain’s contribution to
the GAA would still be relatively small for the first preparations and for most of the second
preparations.
When the ratio of the unsupported 224Ra activity to the 226Ra activity exceeded one, the
GAAs for the first preparation decreased over about 23 days following preparation, and the
GAAs for the second preparation increased over a period of about 23 days following preparation.
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94 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
Good examples of this behavior are provided by samples 5, 16, 19 and 23. The decrease in the
GAAs for the first preparations (left plots) were due to the decay of unsupported 224Ra and its
alpha-emitting progeny—220Rn, 216Po, 212Bi, and 212Po—which was not compensated for by the
ingrowth of the alpha-emitting 226Ra progeny—222Rn, 218Po, and 214Po. At the time of the second
preparation (right plots), all of the unsupported 224Ra would have decayed away, and the increase
in the GAAs were due to the ingrowth of the alpha-emitting 226Ra progeny.
Table 8.2
Group (1): Radium-containing samples (44 samples)
224
Ra to 226Ra
activity ratio
Data fits plot
Left
Samples
Right
>1
>1
Yes
Yes
5, 9, 11, 12, 15, 16, 19, 23, 28, 47, 52, 53, 54, 55, 56
Yes
No
63
>1
No
Yes
36
≈1
Yes
Yes
1, 2, 3, 4, 8, 10, 27, 29, 57, 67, 69
>1
Yes
Yes
14, 17, 18, 24, 25, 26, 32, 33, 51, 66, 68, 70, 71, 72
<1
No
Yes
39
<1
No
No
62
When the ratio of the unsupported 224Ra activity to the 226Ra activity was near one, the
GAA for the first preparation (left plots) was roughly constant over 23 days following preparation, and the GAA for the second preparation (right plots) increased significantly for a period of
about 23 days following preparation. Good examples of this behavior are provided by samples 1,
8, 9, and 27. The GAAs for the first preparation (left plots) changed very little over time because
the decay of 224Ra and its alpha-emitting progeny that was compensated for by the ingrowth of
the alpha-emitting 226Ra progeny. At the time of the second preparation (right plots), all of the
unsupported 224Ra would have decayed away, and the increase in the GAAs were due to the ingrowth of the alpha-emitting 226Ra progeny.
When the ratio of the unsupported 224Ra activity to the 226Ra activity was less than one at
the time of the first sample preparation, the GAAs for both the first (left plot) and second (right
plot) preparations increased over a period of about 23 days following preparation. Good examples of this behavior are provided by samples 14, 18, 32, and 33. In general, the GAAs at the
time of the first sample preparation were higher than those at the time of the second preparation
because, in many samples, some unsupported 224Ra was present at the time of the first preparation, but would have decayed away by the time of the second preparation.
Table 8.2 shows that the model curves provided a good fit to the sample data for 40 out
of 44 for radium-containing samples. For samples 36 and 39, it would seem that the 224Ra activities of the samples were overestimated, because the model curves of the first preparation (left
plots) exceeded the experimental data. For sample 62, it would seem that the 226Ra activity of the
sample was underestimated, because the experimental data of both the first (left plot) and second
(right plot) preparations exceeded the model curves. A higher 226Ra activity would have raised
and flattened the model curves of the left plots and would have raised the model curves of the
right plots, which would give a better fit to the data. For sample 63, the data for one sample in
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Chapter 8: Gross Alpha-Particle Activity of the Groundwater Samples | 95
the set of the triplicates lies within the model curves in the right plot. A higher 226Ra activity
would raise the model curves; however, the large spread in the experimental data for the triplicates of the second preparation of sample 63 would make it difficult to fit the data to any set of
model curves.
The radium-containing samples show that whenever a sample contains unsupported
224
Ra, the GAA can be minimized by preparing the sample about 30 days after collection when
the unsupported 224Ra would have decayed away but before a significant amount of 228Ra progeny would have grown in. The right plots of the radium-containing samples show that the ingrowth of the alpha-emitting progeny of 226Ra substantially elevates the GAA between 3 and 30
days following preparation. Thus, a sample may have no GAA violation when analyzed at 3 days
after preparation, but may have a substantial GAA violation when analyzed at 30, or more, days
after preparation. These data show that this situation would be more pronounced for samples
prepared by a coprecipitation method, like Standard Methods 7110C, where the minimum time
between sample preparation and analysis is three hours. The experimental data and/or the model
curves of the second preparations (right plots) show that for the 35 samples listed in Table 8.3,
there would not be a GAA violation if the sample were analyzed three hours after preparation,
but there would be a GAA violation if the sample were analyzed 30 days after preparation.
Table 8.3
Samples that may have a GAA violation at 30 days but not at 3 hours for Standard Methods 7110C
Samples which may have a GAA violation at 30 d after preparation
but not at 3 h for Standard Methods 7110C
2, 3, 4, 5, 8, 9, 10, 11, 12, 17, 18, 19, 24, 25, 26, 27, 28, 55 56
29, 32, 33, 36, 39, 51, 54, 55, 56, 57, 60, 68, 69, 70, 71, 77
Before this study was designed, it was not appreciated that the 228Ra decay chain could
significantly contribute to the GAA of radium-containing grab samples that were analyzed near
the end of the six-month holding time or composite samples held for any length of time. The
number of samples that were analyzed near the end of the six-month holding time was relatively
few. However, the third analyses of the first preparation of samples 3 (Figure 8.9) and 4
(Figure 8.10) were about 500 days after sample preparation (which is roughly the time from the
first aliquot in a quarterly composite sample to the end of the six-month holding time). In both
cases, it is clear that a significant portion of the GAA is due to the alpha-emitting progeny of the
228
Ra decay chain, which is the cause of the upward increase of the GAA at right side of these
plots.
GROUP (2):URANIUM-CONTAINING SAMPLES
Table 8.4 is a summary of the uranium-containing samples. Of the 19 samples categorized as such, only 9 samples fit the model curves well for both preparations. In 4 samples, the
experimental GAA data for first preparation was within the model curves while the GAA data
for the second preparation was above the model curves. For these 4 samples, the two preparation
times were about 30 days apart, and it is unlikely that any ingrowth process could have elevated
the GAA between these two preparations in such a discontinuous manner, since such an in-
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96 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
growth process should have been evident in the first preparation. It would seem more likely that
the differences between the two preparations were due to non-radiological factors. A higher than
expected GAA could be due to a distribution of the sample residue that is not radially uniform,
but is biased towards the center of the planchet. For patch residues, the results of Chapter 2
would argue against the magnitude of the effect seen in these samples.
Another possibility is that the distribution of uranium atoms in the residues of the second
preparation was not homogeneous but was biased towards the top of the residue. (In all of the
theoretical model curves, the uranium distribution was assumed to be uniform.) Since the chemical properties of the uranyl ion are not the same as those of the major ionic constituents of the
2−
−
residue—Na+, K+, Ca2+, Mg2+, SO4 , NO3 , O2−—it does not follow that uranium should be homogeneously distributed throughout the residue.
The uranium distribution in a residue would clearly affect the value of the GAA. Figure 8.2 shows three types of uranium distributions. In this figure, the distribution of uranium
coincides with the intensity of the shading. In the residue on the left, the distribution is uniform;
in the residue in the middle, the distribution is nonuniform and is biased towards the bottom; and
in the residue on the right, the distribution is nonuniform and is biased towards the top. If all
three residues had the same uranium activity, then the residue in the middle would have the lowest GAA because a large percentage of the alpha particles originate near the bottom of the residue and would be absorbed before reaching the detector, the residue on the right would have the
highest GAA because a large percentage of the alpha particles originate near the top of the residue and would reach the detector before being absorbed, and the residue on the left would have a
GAA that would be intermediate between the other two.
Zikovsky (2000) reported that uranyl nitrate precipitated before other common nitrate
salts and distributed towards the bottom of the residue. This would increase the level of selfabsorption and decrease the value of the GAA relative to a uniform distribution. He found that
reheating the residues to 400 °C caused a redistribution of uranium atoms in the residues resulting in uranium distributions that were much closer to being uniform.
Table 8.4
Samples predominately containing uranium decay chains (19 samples)
Data fits plot
Left
Sample numbers
Right
Yes
Yes
7, 21, 22, 31, 38, 45, 50, 64, 75
Yes
No
44, 58, 59, 61
No
Yes
6
No
No
40, 41, 48, 49, 76
Uniform
Medium GAA
Biased towards bottom
Low GAA
Biased towards top
High GAA
Figure 8.2. Three distributions of uranium in sample residues
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Chapter 8: Gross Alpha-Particle Activity of the Groundwater Samples | 97
In this work, the temperatures of the residues were not carefully controlled. All planchets
were heated over a Meeker burner to a dull red glow, so that their temperatures were higher than
500 °C, the temperature of incipient red heat. Moreover, gravimetric measurements suggested
that Mg(NO3)2 decomposed to MgO, which occurs at 450 °C, and that Ca(NO3)2 decomposed to
CaO, which occurs at 530 °C. Thus, the temperatures employed in this work were significantly
higher than those used in Zikovsky’s work. In this work, the conditions under which the sample
residues were heated were not carefully controlled, and it does not follow that the uranium distributions between any two replicates of a sample would be reproducible.
In five cases, the GAA data from both preparations were significantly higher than predicted by the model curves. In all five cases, the GAA data were relatively constant over the 30day time frame for both preparations. Thus, neither 224Ra nor 226Ra could have made a significant
contribution to the GAA, which is consistent with the 224Ra and 226Ra analyses of these samples.
Additional alpha activity due to the thorium isotopes, 230Th and 232Th would be consistent with
the sample data, but the isotopic thorium analyses showed that none of the five samples contained a significant activity of any thorium isotope. Alpha activity due to any member of the 235U
decay series is unlikely, since, in terms of activity, the relative abundances of 234U, 235U, and
238
U are 48.9%, 2.2%, and 48.9%, respectively. Error in the uranium analyses is possible; however, the five samples were prepared in three separate batches, and there was no indication of
significant error for any of the other groundwater or quality control samples. Thus, it would seem
that the cause of the elevation of the GAA above the model curves was non-radiological.
3.6
GAA/total uranium activity
3.2
2.8
2.4
2.0
1.6
1.2
0.8
0.4
0.0
0.2
0.4
0.6
0.8
1.0
Mol fraction of Ca and Mg
Figure 8.3 Ratio of GAA to uranium activity versus mol fraction of Ca and Mg
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98 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
The elevation of the GAA data above the model curves did not seem to correlate with the
inorganic composition of the samples. Plots of the ratio of the GAA to the total uranium activity
versus factors like the mole fraction of calcium, magnesium, sulfate ion, or dissolved silica
showed no clear trend. Such an example is shown in Figure 8.3, where the plot gives the ratio of
the GAA to the total uranium activity versus the combined mole fraction of calcium and magnesium. The plot includes 18 samples where the 226Ra activity was less than 3% of the total uranium activity. Each vertical band of sample points correspond to the 18 data points for a single
sample. Some of these bands are relatively short, like the ones below 0.3 and above 0.6, while
others are relatively long, like some of the bands between 0.3 and 0.6. Although the long bands
in Figure 8.3 are confined to the region between 0.3 and 0.6, because of the relative scarcity of
data, one cannot conclude that there are no long bands outside of this region.
The technique used to prepare the samples would undoubtedly vary among analysts and
for a given analyst, may vary significantly from one set of samples to the next. Heating a residue
over a flame is an optional step, performed if the sample is deemed to be hygroscopic; however,
EPA Method 900.0 gives no guidelines for characterizing the hygroscopicity of a residue and no
conditions for heating the residue over a flame. Many residues expels gases—like water vapor or
NO2 as CaNO3 and MgNO3 decompose—while being heated and solidify during the heating
step. Residues composed mainly of sodium nitrate and potassium nitrate usually do not solidify
until the residue cools. An analyst may be inclined to heat a residue until it solidifies, but the
time required for solidification varies from one sample to the next and some residues never solidify while being heated. Moreover, the temperature at which the residue is heated is poorly controlled, and the work of Zikovsky (2000) implies that temperature is an important parameter in
controlling the uranium distribution.
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Chapter 8: Gross Alpha-Particle Activity of the Groundwater Samples | 99
Table 8.5
Samples with a GAA violation where there is no uranium violation.
Sample Prep. Count Replicate Adjusted
Uranium
No.
GAA
conc.
(pCi/L)
(μg/L)
40
1
1
1
15.28
26.67
40
1
1
2
16.70
26.67
40
1
1
3
15.61
26.67
40
1
2
2
15.11
26.67
40
1
2
3
15.55
26.67
40
1
3
3
15.76
26.67
40
2
1
3
21.45
26.67
40
2
2
1
17.17
26.67
40
2
2
3
20.89
26.67
40
2
3
1
17.14
26.67
40
2
3
3
22.60
26.67
42
1
1
1
36.38
10.91
42
1
1
2
29.91
10.91
42
1
1
3
31.12
10.91
42
1
2
1
33.41
10.91
42
1
2
2
35.12
10.91
42
1
2
3
36.28
10.91
42
1
3
1
31.18
10.91
42
1
3
2
28.38
10.91
42
1
3
3
24.66
10.91
42
2
1
1
27.49
10.91
42
2
1
2
31.86
10.91
42
2
1
3
25.91
10.91
42
2
2
1
30.41
10.91
42
2
2
2
33.73
10.91
42
2
2
3
27.89
10.91
42
2
3
1
31.80
10.91
42
2
3
2
32.87
10.91
42
2
3
3
33.44
10.91
In samples where uranium’s contribution to the GAA is disproportionately high, subtracting the uranium activity from the GAA will not eliminate uranium’s contribution to the GAA. If
the disparity between the uranium contribution and the total uranium activity exceeds 15 pCi/L,
then uranium, by itself, will cause a GAA violation. If a sample’s GAA is due solely to uranium
isotopes, if the disparity exceeds 15 pCi/L, and if the total uranium concentration is below the 30
μg/L MCL, then the sample would purportedly have a GAA violation, but would no uranium violation. Since subtracting the uranium activity from the GAA is intended to exclude its contribution from the GAA, such a violation would be a false-positive GAA violation. In this study,
samples 40 and 42 had such false-positive GAA violations. The data for these samples are given
in Table 8.5. For sample 40, 11 data points out of 18 had false-positive GAA violations; for sample 42, all 18 data points had false-positive GAA violations. The long bands in Figure 8.3 show
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100 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
that the GAAs of some uranium-containing samples are not very reproducible. These results
suggest that if a sample has a GAA violation that can only be attributed to uranium, and if the
uranium concentration is below the 30 μg/L MCL, then the GAA may be artificially elevated due
to a biased distribution of uranium or some other factor.
GROUP (3): RADIUM-AND-URANIUM-CONTAINING SAMPLES
Table 8.6 is a summary of the radium-and-uranium-containing samples. There were relatively few samples that contained substantial activities of both elements. Solubility of uranium is
positively correlated with the oxygen and carbonate concentrations of groundwaters. Solubility
of radium is not affected by the oxygen content, but radium coprecipitates with some metal carbonates. Thus, some conditions that would favor uranium solubility would hinder radium solubility, and vice versa.
The time-dependent behavior of the GAA data for the first (left plots) and second preparations (right plots) resemble the data for the radium-containing samples, except that the minimum GAA, which occurs at the first analysis of the second preparation, is less pronounced than
that of radium-containing samples because in the radium-and-uranium-containing samples, a
large component of the GAA is due to the uranium activity, which is independent of time.
Although the sample and model data of the left plot of sample 35 agree within experimental error, the plot suggests that the sample’s 224Ra activity was significantly overestimated,
which would cause the model curves of the left plot to be too high. For the method used in this
work, an accurate quantification of the 224Ra activity required that the 226Ra activity also be accurately quantified. The 226Ra activity of sample 35 was 0.14 ± 0.07 pCi/L, which was responsible
for the relatively large error in the 224Ra activity. A more accurate value of the 224Ra activity
would probably cause sample 35 to be re-categorized as a uranium-containing sample.
Table 8.6
Samples that contain significant amounts of uranium and radium decay chains (9 samples).
Data fits plot
Left
Sample numbers
Right
Yes
Yes
13, 34, 46, 60, 74, 77, 78, 79
No
Yes
35
GROUP (4): 210PO-CONTAINING SAMPLES
Table 8.7 gives a summary of the 210Po-containg samples. In these samples, there is a noticeable decline in the experimental data and in the theoretical model curves with time as the
210
Po decays. The third analysis of the first preparation was at 30 or more days after collection,
and the first analysis of the second preparation was at 30 or more days after collection. Over 30
days, the 210Po activity decreases by about 14%.
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Chapter 8: Gross Alpha-Particle Activity of the Groundwater Samples | 101
Table 8.7
Samples that predominately contain either uranium and 210Po decay chains or just the
210
Po decay chain (5 samples)
Data fits model
Left
Sample numbers
Right
Yes
Yes
30, 37, 73
Yes
No
No
No
42
43
For samples 30, 37, and 73, the experimental and model data were in agreement for both
left and right plots, but the GAA data were relatively high relative to the model curves, indicating that the amount of polonium volatilization was minimal. Figure 6.2 shows that polonium volatilization decreases with increasing mass. Since the residue masses for the first and second
preparations of samples 30, 37, and 73 were, on average, 26 and 14 mg, 15 and 13 mg, and 26
and 11 m, respectively, the amount of polonium volatilization for these samples could have been
substantial, which is inconsistent with Figure 6.2. The relatively high GAA is probably due, in
part, to the relatively high softness of the water, which tends to yield relatively uniform residues.
For example, of their metallic elements, the sum of the mole fractions of sodium and potassium
in samples 30, 37, and 73 were 1.0, 0.9, and 1.0, respectively. The somewhat poor fit of sample
42 in the left and right plots could be due to the GAA being disproportionately elevated by uranium, as was discussed in previous sections.
GROUP (5): SAMPLES THAT CONTAIN LESS THAN 2 PCI/L OF ALPHA ACTIVITY
Samples 20 and 65 only contained minor amounts of alpha emitters (< 2 pCi/L). In both
cases there is considerable scatter about the model curves because the counting error accounts for
a large part of the error in the GAA. Figure 8.26 and Figure 8.71 show that the counting error
causes relatively large random variations in the GAA, and, for these samples, it is, to a large degree, a matter of chance whether the GAA exceeds the 5 pCi/L limit, where a 226Ra analysis is
required. If counted for a long enough period of time, the GAA of both of these samples would
be below 5 pCi/L, but, because of limited instrumentation, long count times are not feasible.
VARIABILTIY OF THE GAA DUE TO VARIABILTY OF THE RESIDUE GEOMETRY
In Chapter 4, it was predicted that the error in the GAA, due to residue geometry, would
increase with residue mass because the difference in the GAA between smooth and patch residues increases with residue mass. One of the objects in preparing the samples in triplicate was to
quantify how variability of the residue geometry contributed to the variability of the GAA, and
this is the object of this section. Since it is difficult to characterize the geometry of a residue by
visual inspection, statistical methods will be employed to determine the extent to which the GAA
depends on residue mass.
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102 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
The GAAs of the samples were calculated from the following equation:
⎞
0.45 ⎛ N S
⎜⎜
− C ⎟⎟ ,
eSV ⎝ ΔTS
⎠
GAA =
where ΔTS is the sample count interval in min., NS is the number of counts accumulated in the
⎯
count interval ΔTS, C is the background count rate in min−1, eS is the efficiency of the calibration
standard, V is the sample volume in liters, and the factor of 0.45 is included so that the GAA is in
⎯
units of pCi/L. The determination of C is discussed below.
All samples were prepared in triplicate on two occasions. On both occasions each sample
was analyzed at three different times: the first analysis was just after preparation (T2 = 0 days),
the second analysis was about three days after preparation (T2 ≈ 3 days), and the third analysis
was at least 30 days after preparation (T2 ≥ 30 days). An estimate of the error σ1 in the GAA can
be obtained from the triplicate of GAA data for each T2.
3
σ1 =
∑ (GAA
i =1
i
− 〈GAA〉 ) 2
.
2
Here GAAi is one of the three GAA data points in a triplicate, all at the same T2, and 〈GAA〉 is
the average of the triplicate. Thus, for each sample preparation, there are three values of σ1: one
each for the first, second, and third analysis times. This expression for σ1 includes all sources of
error including counting error, error due to variability in the residue geometry, error due to variability in the distribution of radionuclides in the residue, and other errors. Thus, σ1 will be referred to as the total GAA error. The residue mass corresponding to each σ1 will be taken to be
the average mass for the triplicate of residues. Since equal volumes of sample were used to prepare all samples in a triplicate, one residue mass of a triplicate did not deviate far from the average for the triplicate.
As discussed in Chapter 6, counting error always contributes to the variability in GAA.
Thus, when counting error is relatively large, the effect of the residue geometry on the variability
of the GAA can be quite small. An estimate of the counting error, denoted by σ2, is given bye
Eqn J.4 in Appendix J. Eqn. (J.4) is reproduced below:
σ2 =
0.45 N S
C
+
.
2
eSV ΔTS 20ΔTB
Here ΔTB = 100 min. is the background count interval. The factor 20 in this equation is present
⎯
because C was determined from the average of 20 successive 100-min. count intervals on sequential days. It should be emphasized that the data used to calculate σ2 are from a single sample
point and not from the triplicate of sample points. Thus, there are three values of σ2 for every
value of σ1.
Since σ1 and σ2 are estimates, both of which can have considerable uncertainties, one
cannot simply use a formula like
σ 22 − σ 12
to subtract the counting error from the total GAA error. Instead, trends in large data sets are required to determine whether the variability of the GAA increases with residue mass. The GAA
data, and the values of σ1 and σ2, range over several orders of magnitude. To compare data
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Chapter 8: Gross Alpha-Particle Activity of the Groundwater Samples | 103
among samples whose GAAs differ by orders of magnitude, it is useful to use the relative errors
σ1/〈GAA〉 and σ2/GAA.
For samples with small values of GAA, the counting error, σ2, often accounts for most of
the GAA error. Thus, somewhat arbitrarily, values of 〈GAA〉 less than 3.75 pCi/L were discarded
from consideration, which resulted in discarding 14 values out of 474 values. Since each triplicate of points gives rise to one value of σ1/〈GAA〉 and three values of σ2/GAA, only one value of
σ2/GAA in each triplicate was retained, which was taken to be the first one in the database. The
460 values of σ2/GAA are plotted in Figure 8.4 in order of increasing value.
0.25
σ2/GAA
0.20
0.15
0.10
0.05
0.00
0
50 100 150 200 250 300 350 400 450
Samples
Figure 8.4. Values of σ2/GAA plotted in increasing order
Figure 8.5 is a plot of σ1/〈GAA〉 versus average residue mass for all 460 samples from
Figure 8.4. In Figure 8.5, there is a minimal dependence of σ1/〈GAA〉 on the residue mass. This
result may be unexpected since, it was argued that σ1/〈GAA〉 should increase with residue mass;
however, for some of the data in Figure 8.5, the counting error, σ2, and the total error, σ1, are
comparable, and, in such cases, much of the variability in σ1 is due to random counting error. To
minimize these random variations, one must discard values of σ1/〈GAA〉 where the corresponding relative counting error σ2/GAA is less than some prescribed small value. Figure 8.6, is a plot
of σ1/〈GAA〉 versus residue mass for 245 values of σ1/〈GAA〉 where the relative counting error
σ2/GAA was less than 0.06. Figure 8.6 shows that the maximum value of σ1/〈GAA〉 increases
with residue mass, as expected, and that the increase in σ1/〈GAA〉 with residue mass only becomes apparent when the counting error, σ2/GAA, is relatively small (σ2/GAA < 0.06).
On the left side of Figure 8.6, where the residue mass is close to 0 mg, much of the variability of σ1/GAA is probably due to counting error, σ2, for which σ2/GAA < 0.06. The increase
in σ1/GAA is already apparent for the 20 mg residues, where the largest value of σ1/GAA is
nearly twice the largest value for residues close to 0 mg. For residue masses ranging from 80 to
100 mg, the largest values of the total error, σ1/GAA, are more than three times the upper limit
of the counting error, σ2/GAA < 0.06. For any set of triplicates where σ2/GAA < 0.5(σ1/GAA),
much of the variability in the GAA is due to sources other than counting error.
©2010 Water Research Foundation. ALL RIGHTS RESERVED
104 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
0.6
σ2/GAA < 0.29
0.5
σ1/GAA
0.4
0.3
0.2
0.1
0.0
0
20
40
60
80
100
120
Residue mass (mg)
Figure 8.5. A plot of σ1/GAA versus residue mass for all sample points where GAA > 3.75
pCi/L
0.35
σ2/GAA < 0.06
0.30
σ1/GAA
0.25
0.20
0.15
0.10
0.05
0.00
0
20
40
60
80
100
120
Residue mass (mg)
Figure 8.6. A plot of σ1/GAA versus residue mass for all sample points where GAA > 3.75
pCi/L and σ2/GAA < 0.06.
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Chapter 8: Gross Alpha-Particle Activity of the Groundwater Samples | 105
It should be mentioned that the data of Figure 8.6 only show that the variability in the
GAA increases with residue mass and do not prove that the increase in the variability is due to an
increase in the variability of the residue geometry. For example, variability in the spatial distribution of a radionuclide can contribute to the variability in the GAA, and this component of the variability would also increases with residue mass because the degree of self-absorption would increase with residue mass.
Since 215 data points (with values of σ2/ GAA ≥ 0.6) out of the 460 data points in
Figure 8.5 had to be discarded to show the trend in Figure 8.6, it is clear that counting error,
σ2/GAA, is often the most significant contributor to the total GAA error, σ1/GAA. These results
suggest that the error in the GAA can be minimized by reducing the residue mass and by increasing the count time to lower the counting error, which is not always feasible. For EPA Method
900.0, the residue mass can only be reduced by reducing the volume of sample used. Reducing
the sample volume reduces the amount of alpha activity in the residue and can reduce the alphaparticle emission rate of the residue, which can increase the counting error. Thus, for samples
with a high level of dissolved solids, a coprecipitation method, like Standard Methods 7110C, is
preferable, because the residue mass is independent of the level of dissolved solids.
CONCLUSIONS
The experimental GAA data and the model curves show that in many radium-containing
samples, 226Ra and unsupported 224Ra can cause the GAA to vary by more than an order of magnitude over a 23-day time interval following sample preparation. If a sample is analyzed within
one week of collection, the 224Ra decay chain’s contribution to the GAA can be significant; if a
sample is analyzed three weeks after collection, the 224Ra decay chain’s contribution to the GAA
will be negligible. The alpha-emitting progeny of 226Ra—222Rn, 218Po, and 214Po—begin to grow
in at the time of sample preparation and their contribution to the GAA continually increases and
reaches its maximum value after about 23 days. For EPA Method 900.0, it is stipulated that there
must be at least three days between preparation and analysis, but allowing longer times only increases the contribution of the 226Ra progeny to the GAA.
For radium-containing samples, the time dependence of the GAA just after collection depended on the ratio of the unsupported 224Ra activity to the 226Ra activity. The GAA increased,
decreased, or was approximately constant if the ratio was less than one, greater than one or about
equal to one. The time dependence of the radium-containing samples is consistent with the work
of Chapter 4. When the ratio is less than one, the decrease in the 224Ra decay chain’s contribution
to the GAA is greater than the increase in the 226Ra decay chain’s contribution to the GAA; when
the ratio is greater than one, the decrease in the 224Ra decay chain’s contribution to the GAA is
less than the increase in the 226Ra decay chain’s contribution to the GAA; and when the ratio is
about one, the decrease in the 224Ra decay chain’s contribution to the GAA is approximately
equal to the increase of the 226Ra decay chain’s contribution to the GAA.
For the radium-containing samples and the radium-and-uranium containing samples, the
228
Ra decay chain’s contribution to the GAA was negligible at the time of sample collection but
became significant for samples analyzed several months after collection. To reduce the 228Ra decay
chain’s contribution to the GAA, the sample should be analyzed within one month of collection.
EPA Method 900.0 stipulates that there must be at least three days between sample preparation and analysis. Thus, for radium-containing samples and for radium-and-uranium containing samples, the minimum GAA is obtained when the sample is prepared at about one month fol-
©2010 Water Research Foundation. ALL RIGHTS RESERVED
106 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
lowing collection, at which time unsupported 224Ra will have decayed away and the activity of
228
Ra progeny will still be small; and when the sample is analyzed three days after preparation, at
which time the alpha activity of the 226Ra progeny is at the minimum allowed by the method. For
the radium-containing samples and for the radium-and-uranium containing samples, the minimum GAA is clearly evident in the plots of the second preparation.
For the uranium-containing samples, the experimental GAA data sometimes exceeded the
model curves. This may be an indication that, in these samples, the uranium is preferentially distributed towards the top of the residue, which would decrease the level of self-absorption and
increase the GAA relative to the GAA for a residue with a uniform uranium distribution. Irrespective of the cause, the elevated GAA can sometimes lead to false-positive GAA violations.
Further work is required to determine why there is such a significant discrepancy between the
model curves and the experimental data for some samples and what experimental conditions
would minimize this discrepancy. For the radium-containing samples, the experimental data fell
within the model curves for the majority of samples, which indicates that the radium atoms are,
to a first approximation, homogeneously distributed throughout the sample residues.
Natural uranium and 230Th are the allowed calibration standards for EPA Method 900.0.
Since the alpha-particle energies of the uranium isotopes are, on average, lower than those of
230
Th, natural uranium would yield lower efficiencies than 230Th, provided that uranium and thorium are both uniformly distributed throughout the sample residues. Thus, the value calculated
for the GAA would be higher when natural uranium is used as the calibration standard than when
230
Th is used.
This study provides no direct evidence that either uranium or thorium is uniformly distributed throughout the residues. However, it is clear that the GAA due to uranium was anomalously high for some sample residues. Thus, natural uranium should probably be discontinued as a
calibration standard until the conditions under which its sporadically elevated contribution to the
GAA is understood.
The model curves, Chapter 6, and Figure 8.5 show that in many samples the counting error can be significant, and may determine whether the sample exceeds the 5 pCi/L limit, which
requires a 226Ra analysis, or whether the adjusted GAA exceeds the 15 pCi/L regulatory limit,
which requires that the water be treated. This error is inherent in the method, and can only be reduced by counting samples for a longer period of time, which is often not practical. Since the
counting error is, to a large degree, random, for samples near the 5 or 15 pCi/L MCLs, it is, to
some extent, a matter of chance as to whether the sample will exceed the MCL.
It was demonstrated that the error in the GAA, other than counting error, generally increased with a sample’s residue mass. Much of this error was probably due to variability in the
residue geometry, which ranges from being patchy to being almost uniform. For EPA Method
900.0, the effect of the residue geometry could be reduced by decreasing the sample volume,
which could decrease the alpha activity of the residue and cause the counting error to be larger.
Thus, for samples with a high level of dissolved solids, a coprecipitation method, like Standard
Methods 7110C, would be preferable because the residue mass depends on the amounts of barium and iron carrier that are added to the sample.
Since the 224Ra decay chain’s contribution to the GAA is negligible at about three weeks
after sample collection, and since the 228Ra decay chain’s contribution will still be quite small at
about three weeks after collection, it might be assumed that the GAA of radium-containing samples could be minimized by analyzing them about one month after collection. However, in Chapter 4, it was shown that the 226Ra decay chain’s contribution to the GAA is at a minimum just
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Chapter 8: Gross Alpha-Particle Activity of the Groundwater Samples | 107
after sample preparation, when the activity of the 226Ra progeny is close to zero, and increases
over a period of 23 days as the 226Ra progeny grow in. Thus, to minimize the GAA of radiumcontaining samples, the samples should be prepared at about one month after collection, when
the contributions of the 224Ra and 228Ra decay chains to the GAA will be quite small, and analyzed immediately following preparation, when the contribution of the 226Ra progeny to the GAA
is at a minimum. However, since EPA Method 900.0 stipulates that there must be three days between sample preparation and analysis, the minimum GAA that is consistent with the method is
obtained when the sample is prepared about one month following collection and is analyzed
three days after preparation.
©2010 Water Research Foundation. ALL RIGHTS RESERVED
108 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
Figure 8.7. GAA plot for sample 1
(RQ091434)
140
120
120
100
100
80
80
60
60
40
T1 = 2.46 d
20
0.01 0.1
T1 = 2.63 d
0
1
10
1
10
Activity
(pCi/L)
0.21
3.24
14.53
0.23
0.03
12.61
17.13
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
0
0.01 0.1
T2 (d)
T2 (d)
Nuclide
Error
(pCi/L)
0.03
0.20
0.74
0.47
0.09
1.00
2.10
80
60
70
nd
60
40
40
20
20
0
1
10 100
1
10
T2 (d)
Nuclide
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
100
Error
(pCi/L)
0.04
0.13
0.36
0.47
0.07
0.57
1.33
Error
(pCi/L)
0.03
0.18
0.39
0.56
0.11
0.57
1.01
mass = 71 mg
90
T1 = 29.6 d
80
60
70
50
60
50
40
40
30
30
20
20
mass = 68 mg
10
10
T1 = 2.60 d
0
0.01 0.1
T2 (d)
Activity
(pCi/L)
0.23
1.92
5.73
-0.09
0.10
4.16
7.28
Activity
(pCi/L)
0.19
2.84
6.36
0.10
-0.01
4.19
6.11
Figure 8.10. GAA plot for sample 4
(RQ091437)
Q
100
80
0
0.01 0.1
10
80
GAA for 2 prep (pCi/L)
T1 = 29.5 d
st
GAA for 1 prep (pCi/L)
T1 = 2.46 d
1
T2 (d)
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
120
mass = 82 mg
10 100
Nuclide
120
mass = 100 mg
1
T2 (d)
Figure 8.8. GAA plot for sample 2
(RQ091435)
100
mass = 78 mg
20
st
0
mass = 101 mg
40
GAA for 1 prep (pCi/L)
20
60
nd
140
T1 = 29.6 d
80
GAA for 2 prep (pCi/L)
160
1
0
10 100
1
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
100
T2 (d)
T2 (d)
Nuclide
10
Activity
(pCi/L)
0.10
1.69
4.73
0.41
0.11
3.98
6.07
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Error
(pCi/L)
0.02
0.12
0.33
0.53
0.08
0.57
0.92
nd
180
120
110
100
90
80
70
60
50
40
30
20
10
0
100
GAA for 2 prep (pCi/L)
T1 = 29.5 d
160
st
180
mass = 80 mg
GAA for 1 prep (pCi/L)
200
100
nd
200
40
Q
220
mass = 83 mg
GAA for 2 prep (pCi/L)
st
GAA for 1 prep (pCi/L)
220
Figure 8.9. GAA plot for sample 3
(RQ091436)
Chapter 8: Gross Alpha-Particle Activity of the Groundwater Samples | 109
Figure 8.11. GAA plot for sample 5
(RQ091438)
Figure 8.13. GAA plot for sample 7
(RQ091440)
Q
120
120
7000
7000
100
6000
6000
5000
5000
4000
4000
3000
3000
mass = 51 mg
20
20
nd
40
2000
T1 = 2.67 d
0
1
10
1
Activity
(pCi/L)
0.08
0.66
3.87
0.23
0.03
9.61
12.60
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
3000
2500
2500
2000
2000
1500
10
1
10
T2 (d)
Nuclide
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
T2 (d)
Activity
(pCi/L)
1342
1556
1.84
2.40
2.41
0.40
2.62
Error
(pCi/L)
77
89
0.18
0.69
0.26
0.34
1.87
60
60
50
50
T1 = 29.7 d
40
40
30
30
20
20
10
mass = 93 mg
10
T1 = 2.71 d
1000
1
Error
(pCi/L)
77
130
0.08
0.64
0.13
0.36
0.17
st
3000
T1 = 29.5 d
T2 (d)
Figure 8.14. GAA plot for sample 8
(RQ091441)
Q
GAA for 1 prep (pCi/L)
3500
mass = 21 mg
10
mass = 93 mg
nd
3500
T1 = 2.52 d
1
Activity
(pCi/L)
1784
3000
0.09
0.83
0.12
0.48
0.19
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
GAA for 2 prep (pCi/L)
4000
st
GAA for 1 prep (pCi/L)
4000
mass = 20 mg
10
Nuclide
Error
(pCi/L)
0.02
0.07
0.27
0.48
0.07
0.86
2.00
2000
1000
1
T2 (d)
Figure 8.12. GAA plot for sample 6
(RQ091439)
Q
1000
0.1
T1 = 29.6 d
T2 (d)
Nuclide
1500
mass = 27 mg
T1 = 2.57 d
1000
0.1
10
T2 (d)
mass = 27 mg
nd
0
0.1
GAA for 2 prep (pCi/L)
40
GAA for 2 prep (pCi/L)
60
st
60
nd
80
st
GAA for 1 prep (pCi/L)
80
GAA for 1 prep (pCi/L)
T1 = 29.7 d
100
GAA for 2 prep (pCi/L)
mass = 50 mg
0
0.1
0
1
10
0.1
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
10
T2 (d)
T2 (d)
Nuclide
1
Activity
(pCi/L)
0.61
0.78
4.02
0.26
−0.02
3.24
5.27
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Error
(pCi/L)
0.07
0.08
0.28
0.39
0.08
0.56
0.99
110 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
Figure 8.15. GAA plot for sample 9
(RQ091442)
Figure 8.17. GAA plot for sample 11
(RQ091713)
Q
Q
40
30
30
20
20
mass = 66 mg
10
10
0.1
1
T2 (d)
Nuclide
10
10
mass = 15 mg
5
0
0.1
10
5
0
1
10
0.01
Error
(pCi/L)
0.02
0.12
0.36
0.36
0.06
0.72
2.42
Nuclide
mass = 53 mg
70
mass = 29 mg
60
20
15
15
10
10
st
mass = 54 mg
5
5
T1 = 2.63 d
0
0.1
0
1
10
0.1
1
T2 (d)
Nuclide
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
10
T2 (d)
Activity
(pCi/L)
1.14
7.08
1.79
−0.18
0.14
0.68
1.66
Error
(pCi/L)
0.07
0.32
0.18
0.43
0.09
0.36
1.35
st
25
20
GAA for 1 prep (pCi/L)
25
nd
30
GAA for 2 prep (pCi/L)
30
Error
(pCi/L)
0.01
0.02
0.27
0.36
0.05
0.65
0.97
70
35
T1 = 29.6 d
10
Figure 8.18. GAA plot for sample 12
(RQ091720)
Q
40
35
1
T2 (d)
Activity
(pCi/L)
0.03
0.06
3.44
−0.05
0.07
3.27
5.47
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
Figure 8.16. GAA plot for sample 10
(RQ091444)
Q
40
0.1
T2 (d)
T2 (d)
Activity
(pCi/L)
0.11
1.65
5.92
0.07
0.12
5.24
9.167
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
GAA for 1 prep (pCi/L)
15
T1 = 2.56 d
0
1
15
10
T1 = 2.76 d
0
0.1
20
nd
40
20
GAA for 2 prep (pCi/L)
50
60
T1 = 32.4 d
50
50
40
40
30
30
20
20
mass = 33 mg
10
10
T1 = 2.55 d
0
0.1
0
1
10
0.01
0.1
T2 (d)
Nuclide
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
1
10
T2 (d)
Activity
(pCi/L)
0.04
0.03
4.62
0.01
0.10
6.20
9.83
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Error
(pCi/L)
0.01
0.01
0.31
0.38
0.05
0.66
1.19
nd
60
50
25
T1 = 32.4 d
st
60
nd
70
GAA for 1 prep (pCi/L)
25
T1 = 29.7 d
70
mass = 15 mg
80
GAA for 2 prep (pCi/L)
st
GAA for 1 prep (pCi/L)
80
30
30
90
mass = 64 mg
GAA for 2 prep (pCi/L)
90
Chapter 8: Gross Alpha-Particle Activity of the Groundwater Samples | 111
Figure 8.19. GAA plot for sample 13
(RQ091721)
Figure 8.21. GAA plot for sample 15
(RQ091723)
60
40
40
mass = 33 mg
mass = 34 mg
T1 = 2.40 d
T1 = 32.3 d
20
0
10
0.01
0.1
T2 (d)
1
Activity
(pCi/L)
16.16
49.88
3.61
2.66
2.91
1.54
1.30
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
0.1
100
80
80
60
60
40
40
mass = 7.6 mg 20
T1 = 32.3 d
0
0.01
0.1
Nuclide
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
1
10
T2 (d)
Activity
(pCi/L)
0.21
0.19
26.89
0.51
0.02
16.09
10.88
Error
(pCi/L)
0.04
0.04
1.23
0.42
0.06
1.10
1.23
nd
100
10
1
10
100
T2 (d)
Error
(pCi/L)
0.03
0.04
0.18
0.39
0.05
0.59
1.74
Figure 8.22. GAA plot for sample 16
(RQ091724)
Q
20
20
GAA for 2 prep (pCi/L)
st
GAA for 1 prep (pCi/L)
120
T2 (d)
0.1
Activity
(pCi/L)
0.09
0.13
1.41
-0.18
0.03
4.99
7.47
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
140
T1 = 2.45 d
10
Nuclide
Error
(pCi/L)
0.85
2.48
0.29
0.48
0.25
0.40
0.34
120
mass = 7.2 mg
0
T2 (d)
140
1
1
10
Figure 8.20. GAA plot for sample 14
(RQ091722)
Q
0
0.1
5
mass = 2.8 mg
T1 = 2.33 d
T2 (d)
Nuclide
20
10
15
15
mass = 4.1 mg
T1 = 32.2 d
10
10
nd
1
st
0
0.1
10
5
GAA for 1 prep (pCi/L)
20
15
nd
80
60
GAA for 2 prep (pCi/L)
80
15
5
5
mass = 3.5 mg
0
GAA for 2 prep (pCi/L)
100
20
mass = 3.7 mg
T1 = 32.2 d
20
st
100
GAA for 1 prep (pCi/L)
120
nd
120
25
GAA for 2 prep (pCi/L)
140
st
GAA for 1 prep (pCi/L)
25
140
0
T1 = 2.34 d
1
10
0.1
T2 (d)
Nuclide
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
1
10
100
T2 (d)
Activity
(pCi/L)
0.07
0.12
1.30
−0.07
0.11
6.03
5.92
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Error
(pCi/L)
0.02
0.03
0.17
0.34
0.05
0.67
1.34
112 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
Figure 8.23. GAA plot for sample 17
(RQ091725)
Figure 8.25. GAA plot for sample 19
(RQ091751)
Q
40
35
30
30
25
25
20
20
15
15
10
5
0
0.1
mass = 53 mg
10
T1 = 2.40 d
5
100
10
0.1
1
T2 (d)
Nuclide
60
60
40
40
20
T1 = 1.40 d
0
10
0.1
1
Nuclide
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
10
T2 (d)
T2 (d)
Error
(pCi/L)
0.008
0.02
0.29
0.34
0.05
0.45
0.48
40
20
mass = 72 mg
1
10
Figure 8.24. GAA plot for sample 18
(RQ091726)
Activity
(pCi/L)
0.27
1.53
4.50
-0.02
0.29
12.38
12.21
Error
(pCi/L)
0.03
0.09
0.31
0.34
0.06
0.95
1.96
Figure 8.26. GAA plot for sample 20
(RQ091992)
Q
40
6
20
15
15
st
10
10
mass = 47 mg
5
5
T1 = 2.40 d
0
0.1
3
2
2
0
mass = 66 mg
mass = 67 mg
1
T1 = 2.57 d
T1 = 37.2 d
0
0
1
10
0.1
1
T2 (d)
T2 (d)
Nuclide
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
10
Activity
(pCi/L)
0.07
0.35
3.94
0.43
-0.04
2.62
2.26
Error
(pCi/L)
0.02
0.04
0.28
0.35
0.05
0.46
0.39
0.1
1
10
0.01
0.1
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
10
-1
100
T2 (d)
T2 (d)
Nuclide
1
Activity
(pCi/L)
0.00
0.01
0.14
0.35
1.91
−0.07
−0.01
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Error
(pCi/L)
0.01
0.01
0.05
0.39
0.24
0.35
0.08
nd
20
4
4
st
25
nd
25
5
GAA for 1 prep (pCi/L)
30
GAA for 2 prep (pCi/L)
30
6
35
T1 = 32.3 d
GAA for 2 prep (pCi/L)
mass = 47 mg
35
GAA for 1 prep (pCi/L)
80
T2 (d)
Activity
(pCi/L)
0.010
0.12
4.03
−0.05
0.03
2.57
2.99
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
80
0
0
1
100
T1 = 31.3 d
nd
T1 = 32.3 d
35
GAA for 2 prep (pCi/L)
40
120
mass = 70 mg
st
45
GAA for 1 prep (pCi/L)
mass = 53 mg
nd
45
GAA for 2 prep (pCi/L)
st
GAA for 1 prep (pCi/L)
120
50
50
Chapter 8: Gross Alpha-Particle Activity of the Groundwater Samples | 113
Figure 8.29. GAA plot for sample 23
(RQ091995)
30
50
50
40
40
30
30
20
20
30
25
0
0.1
mass = 89 mg
mass = 90 mg
T1 = 2.60 d
T1 = 37.2 d
10
10
0.01
0.1
Activity
(pCi/L)
13.21
19.21
0.31
0.21
-0.07
0.67
1.04
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
20
15
nd
15
10
10
5
mass = 3.6 mg
5
0
0.1
10
1
T2 (d)
T2 (d)
Nuclide
1
T1 = 36.8 d
20
T1 = 2.50 d
0
1
mass = 3.5 mg
st
nd
GAA for 1 prep (pCi/L)
10
GAA for 2 prep (pCi/L)
st
GAA for 1 prep (pCi/L)
25
0
10
0.1
1
Error
(pCi/L)
0.62
0.88
0.07
0.39
0.18
0.43
0.75
Nuclide
Activity
(pCi/L)
0.12
0.14
1.77
0.11
-0.01
6.00
6.79
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
Figure 8.28. GAA plot for sample 22
(RQ091994)
10
100
T2 (d)
T2 (d)
Error
(pCi/L)
0.02
0.02
0.17
0.40
0.20
0.69
1.28
Figure 8.30. GAA plot for sample 24
(RQ091996)
50
50
mass = 21 mg
40
20
10
0
0.1
mass = 80 mg
mass = 87 mg
T1 = 2.62 d
T1 = 36.9 d
10
0
1
10
0.01
0.1
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
10
T2 (d)
T2 (d)
Nuclide
1
Activity
(pCi/L)
8.14
12.32
0.27
−0.21
0.17
0.47
0.97
Error
(pCi/L)
0.39
0.57
0.07
0.35
0.18
0.35
0.72
st
20
T1 = 37.0 d
40
GAA for 1 prep (pCi/L)
30
nd
30
GAA for 2 prep (pCi/L)
st
GAA for 1 prep (pCi/L)
40
40
30
30
20
20
10
10
mass = 21 mg
T1 = 2.56 d
0
0.1
0
1
10
0.1
T2 (d)
Nuclide
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
1
10
T2 (d)
Activity
(pCi/L)
0.15
0.58
6.25
1.62
0.46
6.07
4.99
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Error
(pCi/L)
0.03
0.06
0.38
0.55
0.29
0.70
0.68
nd
60
GAA for 2 prep (pCi/L)
60
GAA for 2 prep (pCi/L)
Figure 8.27. GAA plot for sample 21
(RQ091993)
114 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
Figure 8.31. GAA plot for sample 25
(RQ091997)
Figure 8.33. GAA plot for sample 27
(RQ091999)
RQ091999
80
80
20
20
10
10
mass = 21 mg
T1 = 2.55 d
0
0.1
0
1
10
0.1
1
Nuclide
Activity
(pCi/L)
0.03
0.11
7.20
2.55
3.17
0.22
0.85
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
50
40
40
30
30
nd
50
20
20
mass = 60 mg
10
0
0.1
10
10
T1 = 2.58 d
0
1
T2 (d)
T2 (d)
10
0.1
1
Error
(pCi/L)
0.01
0.02
0.40
0.60
0.41
0.33
0.25
Nuclide
Activity
(pCi/L)
0.32
3.19
6.42
0.13
0.00
4.23
6.88
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
10
T2 (d)
T2 (d)
Figure 8.32. GAA plot for sample 26
(RQ091998)
60
Error
(pCi/L)
0.04
0.19
0.39
0.34
0.17
0.60
1.57
Figure 8.34. GAA plot for sample 28
(RQ092000)
Q
70
70
mass = 83 mg
50
30
30
20
20
st
10
10
mass = 68 mg
0
0.1
T1 = 2.61 d
1
0
10
0.1
1
Nuclide
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
10
T2 (d)
T2 (d)
Activity
(pCi/L)
0.14
1.85
3.91
−0.02
0.11
2.32
2.51
Error
(pCi/L)
0.03
0.13
0.27
0.32
0.16
0.46
0.85
st
40
nd
40
GAA for 1 prep (pCi/L)
60
T1 = 37.0 d
GAA for 1 prep (pCi/L)
mass = 73 mg
GAA for 2 prep (pCi/L)
50
60
T1 = 37.1 d
50
50
40
40
30
30
20
20
mass = 59 mg
10
10
T1 = 2.66 d
0
0.1
0
1
10
0.1
T2 (d)
Nuclide
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
1
10
T2 (d)
Activity
(pCi/L)
0.07
0.90
4.23
0.42
−0.20
6.39
7.86
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Error
(pCi/L)
0.01
0.06
0.29
0.40
0.20
0.72
1.36
nd
30
70
T1 = 37.0 d
60
st
30
GAA for 1 prep (pCi/L)
40
70
nd
40
st
GAA for 1 prep (pCi/L)
T1 = 37.0 d
mass = 72 mg
GAA for 2 prep (pCi/L)
50
GAA for 2 prep (pCi/L)
50
GAA for 2 prep (pCi/L)
mass = 23 mg
Chapter 8: Gross Alpha-Particle Activity of the Groundwater Samples | 115
Q
35
35
80
T1 = 37.4 d
80
30
30
25
25
20
20
15
15
60
50
50
40
40
30
30
20
mass = 76 mg
20
10
T1 = 2.72 d
10
0
0.1
10
0.1
1
T2 (d)
Nuclide
10
T1 = 4.59 d
T1 = 50.2 d
0.1
35
35
mass = 59 mg
mass = 88 mg
T1 = 1.57 d
2
0
0.1
2
T1 = 36.0 d
0
1
10
0.1
1
T2 (d)
Nuclide
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
10
T2 (d)
Activity
(pCi/L)
0.010
0.022
0.080
0.40
4.11
0.01
0.08
Error
(pCi/L)
0.008
0.013
0.070
0.42
0.39
0.31
0.14
st
st
4
4
Error
(pCi/L)
0.45
0.49
0.06
0.31
0.25
0.32
0.86
Figure 8.38. GAA plot for sample 32
(RQ092251)
Q
GAA for 1 prep (pCi/L)
6
6
nd
8
GAA for 2 prep (pCi/L)
8
10
T2 (d)
mass = 57 mg
30
10
1
Activity
(pCi/L)
10.24
11.32
0.20
-0.09
0.13
0.40
1.07
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
10
12
10
Nuclide
Error
(pCi/L)
0.02
0.09
0.44
0.38
0.20
0.83
1.44
5
0
1
T2 (d)
Figure 8.36. GAA plot for sample 30
(RQ092029)
Q
GAA for 1 prep (pCi/L)
mass = 69 mg
T2 (d)
Activity
(pCi/L)
0.09
1.54
7.93
−0.16
0.12
8.12
9.18
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
5
mass = 94 mg
0
0.1
0
1
10
10
30
T1 = 50.0 d
25
25
20
20
15
15
10
10
mass = 57 mg
5
0
0.1
5
T1 = 4.57 d
1
10
0
0.1
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
10
T2 (d)
T2 (d)
Nuclide
1
Activity
(pCi/L)
0.25
1.85
2.81
0.15
−0.04
0.18
1.30
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Error
(pCi/L)
0.04
0.12
0.22
0.33
0.26
0.32
0.29
nd
60
st
70
nd
st
GAA for 1 prep (pCi/L)
70
nd
40
90
GAA for 1 prep (pCi/L)
40
mass = 77 mg
GAA for 2 prep (pCi/L)
100
90
100
GAA for 2 prep (pCi/L)
Figure 8.37. GAA plot for sample 31
(RQ092250)
GAA for 2 prep (pCi/L)
Figure 8.35. GAA plot for sample 29
(RQ092001)
116 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
55
80
50
mass = 92 mg
50
45
T1 = 50.0 d
45
50
50
40
40
30
30
20
20
mass = 77 mg
T1 = 4.54 d
1
10
0.1
1
Nuclide
Activity
(pCi/L)
0.12
0.54
7.74
0.29
−0.20
0.60
1.75
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
10
Error
(pCi/L)
0.02
0.04
0.44
0.37
0.30
0.32
0.43
25
20
20
15
15
10
10
mass = 83 mg
mass = 85 mg
T1 = 4.59 d
T1 = 50.0 d
T2 (d)
5
0
10
T2 (d)
Activity
(pCi/L)
8.84
8.66
0.12
0.00
0.10
0.29
1.56
0.1
1
Error
(pCi/L)
0.39
0.38
0.05
0.33
0.27
0.29
1.17
10
T2 (d)
Activity
(pCi/L)
7.62
7.98
0.14
0.07
0.05
0.21
4.83
Error
(pCi/L)
0.37
0.35
0.07
0.35
0.29
0.29
3.83
Figure 8.42. GAA plot for sample 36
(RQ092255)
35
35
30
nd
25
1
0
10
mass = 26 mg
GAA for 2 prep (pCi/L)
30
st
GAA for 1 prep (pCi/L)
35
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
1
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
30
0.1
5
T1 = 4.53 d
Nuclide
35
10
10
mass = 96 mg
T2 (d)
40
Nuclide
15
10
0
0.1
40
1
20
15
0
Figure 8.40. GAA plot for sample 34
(RQ092253)
Q
0
0.1
25
20
T2 (d)
T2 (d)
5
30
25
5
st
0
0.1
35
30
10
GAA for 1 prep (pCi/L)
10
40
35
nd
60
40
30
T1 = 50.1 d
25
25
20
20
15
15
10
10
mass = 27 mg
5
5
T1 = 4.59 d
0
0.1
0
1
10
0.1
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
10
T2 (d)
T2 (d)
Nuclide
1
Activity
(pCi/L)
0.04
0.25
2.95
0.14
-0.05
2.01
7.04
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Error
(pCi/L)
0.01
0.03
0.23
0.35
0.28
0.45
1.00
nd
60
55
GAA for 2 prep (pCi/L)
70
st
70
T1 = 50.0 d
90
GAA for 1 prep (pCi/L)
mass = 78 mg
nd
80
GAA for 2 prep (pCi/L)
st
GAA for 1 prep (pCi/L)
90
Figure 8.41. GAA plot for sample 35
(RQ092254)
GAA for 2 prep (pCi/L)
Figure 8.39. GAA plot for sample 33
(RQ092252)
Q
Chapter 8: Gross Alpha-Particle Activity of the Groundwater Samples | 117
Figure 8.45. GAA plot for sample 39
(RQ092258)
Q
80
80
60
60
40
40
20
0
0.1
mass = 32 mg
mass = 35 mg
T1 = 4.62 d
T1 = 50.1 d
20
st
0
1
10
0.1
1
Activity
(pCi/L)
21.86
34.26
0.74
4.60
27.40
0.72
3.72
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
20
15
15
10
10
5
5
Error
(pCi/L)
0.95
1.45
0.11
0.72
1.91
0.36
3.00
0
1
10
Nuclide
1
10
T2 (d)
Activity
(pCi/L)
0.05
0.07
4.42
0.48
−0.18
0.22
4.31
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
Error
(pCi/L)
0.02
0.02
0.29
0.37
0.35
0.27
0.57
Figure 8.46. GAA plot for sample 40
(RQ092847)
50
360
45
45
320
320
40
40
280
280
35
35
240
240
30
30
200
200
25
25
160
160
20
20
120
120
80
40
0
0.01
mass = 70 mg
mass = 62 mg
80
T1 = 5.18 d
T1 = 50.1 d
40
0
0.1
1
10
0.1
T2 (d)
Nuclide
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
1
10
T2 (d)
Activity
(pCi/L)
95.72
139.94
1.51
3.40
5.72
2.22
4.72
Error
(pCi/L)
4.12
5.93
0.16
0.63
0.83
0.46
3.47
nd
st
GAA for 1 prep (pCi/L)
50
360
GAA for 2 prep (pCi/L)
st
20
T2 (d)
Figure 8.44. GAA plot for sample 38
(RQ092257)
GAA for 1 prep (pCi/L)
30
25
T2 (d)
T2 (d)
Nuclide
T1 = 50.0 d
25
0
0.1
10
T1 = 5.07 d
nd
100
30
mass = 25 mg
15
15
10
5
0
0.1
mass = 15 mg
mass = 17 mg
10
T1 = 3.51 d
T1 = 34.2 d
5
0
1
10
0.1
T2 (d)
Nuclide
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
1
10
T2 (d)
Activity
(pCi/L)
8.97
10.99
0.08
3.70
0.89
0.18
0.12
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Error
(pCi/L)
0.43
0.52
0.05
0.69
0.98
0.28
0.12
nd
100
35
mass = 25 mg
GAA for 2 prep (pCi/L)
120
GAA for 1 prep (pCi/L)
120
nd
140
GAA for 2 prep (pCi/L)
st
GAA for 1 prep (pCi/L)
35
140
GAA for 2 prep (pCi/L)
Figure 8.43. GAA for plot sample 37
(RQ092256)
118 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
80
80
16
16
60
60
12
12
40
40
8
8
0.1
1
T2 (d)
Nuclide
50
50
40
40
30
30
20
mass = 25 mg
T1 = 3.62 d
10
T1 = 34.3d
0
1
10
0.1
1
T2 (d)
T2 (d)
Nuclide
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
10
Activity
(pCi/L)
3.67
15.48
2.23
0.72
8.03
1.62
2.57
Error
(pCi/L)
0.22
0.78
0.20
0.45
0.90
0.42
0.58
nd
60
GAA for 2 prep (pCi/L)
st
60
0
0.1
10
0.1
1
10
T2 (d)
Activity
(pCi/L)
3.89
4.58
0.11
0.53
2.66
0.48
0.19
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
70
4
0
1
Nuclide
70
mass = 22 mg
T1 = 34.3d
T2 (d)
Error
(pCi/L)
0.99
1.20
0.06
0.47
0.62
0.34
0.19
20
mass = 22 mg
T1 = 3.67 d
0
0.1
Figure 8.48. GAA plot for sample 42
(RQ092849)
Q
10
st
nd
0
100
T2 (d)
Activity
(pCi/L)
22.67
27.88
0.11
0.49
0.70
0.63
0.23
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
10
mass = 16 mg
Error
(pCi/L)
0.23
0.26
0.07
0.45
0.70
0.33
0.16
Figure 8.50. GAA plot for sample 44
(RQ092851)
Q
20
20
16
16
12
12
8
8
4
0
0.1
mass = 23 mg
mass = 30 mg
T1 = 3.69 d
T1 = 34.4d
4
0
1
10
0.1
T2 (d)
Nuclide
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
1
10
T2 (d)
Activity
(pCi/L)
3.14
4.25
0.07
-0.03
0.25
0.01
0.18
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Error
(pCi/L)
0.19
0.24
0.07
0.42
0.59
0.26
0.16
nd
10
4
GAA for 2 prep (pCi/L)
1
20
mass = 20 mg
T1 = 34.1 d
st
mass = 16 mg
T1 = 3.45 d
GAA for 1 prep (pCi/L)
20
nd
20
GAA for 2 prep (pCi/L)
20
GAA for 1 prep (pCi/L)
100
0
0.1
GAA for 1 prep (pCi/L)
Figure 8.49. GAA plot for sample 43
(RQ092850)
100
GAA for 2 prep (pCi/L)
st
GAA for 1 prep (pCi/L)
Figure 8.47. GAA plot for sample 41
(RQ092848)
Chapter 8: Gross Alpha-Particle Activity of the Groundwater Samples | 119
350
300
300
250
250
200
200
150
150
25
25
50
mass = 23 mg
mass = 30 mg
T1 = 3.41 d
T1 = 34.1d
100
50
0
10
1
10
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
350
300
300
250
250
200
200
150
150
mass = 24 mg
mass = 25 mg
100
T1 = 3.43 d
T1 = 34.1d
50
0
0.01
0.1
T2 (d)
Nuclide
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
1
10
nd
350
10
5
0
0
10
0.1
Error
(pCi/L)
5.12
7.27
0.56
1.45
2.50
0.46
0.82
1
10
T2 (d)
Activity
(pCi/L)
0.07
0.09
0.57
0.35
0.53
1.86
4.91
Error
(pCi/L)
0.01
0.02
0.09
0.41
0.59
0.42
3.72
120
120
mass = 90 mg
T1 = 3.67 d
100
80
80
mass = 116 mg
T1 = 34.4d
60
60
40
40
20
20
0
0
1
T2 (d)
Activity
(pCi/L)
117.91
169.72
10.65
14.39
4.39
2.56
6.15
0.01
Figure 8.54. GAA plot for sample 48
(RQ092855)
100
GAA for 2 prep (pCi/L)
st
400
1
5
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
400
0
0.1
10
Nuclide
450
50
10
Error
(pCi/L)
5.00
6.43
0.07
0.44
0.65
0.31
0.31
450
100
15
T2 (d)
Figure 8.52. GAA plot for sample 46
(RQ092853)
20
st
Activity
(pCi/L)
115.00
149.38
0.35
0.53
1.86
0.21
0.40
T1 = 34.5d
1
GAA for 1 prep (pCi/L)
Nuclide
T1 = 3.77 d
15
T2 (d)
T2 (d)
GAA for 1 prep (pCi/L)
st
0
1
mass = 36 mg
nd
100
GAA for 1 prep (pCi/L)
nd
GAA for 2 prep (pCi/L)
st
GAA for 1 prep (pCi/L)
20
mass = 33 mg
nd
400
350
GAA for 2 prep (pCi/L)
400
Figure 8.53. GAA plot for sample 47
(RQ092854)
GAA for 2 prep (pCi/L)
Figure 8.51. GAA plot for sample 45
(RQ092852)
10
0.01
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
1
10
T2 (d)
T2 (d)
Nuclide
0.1
Activity
(pCi/L)
13.61
22.50
0.48
0.05
0.01
0.34
0.65
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Error
(pCi/L)
0.59
0.95
0.11
0.36
0.51
0.37
0.50
120 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
Figure 8.57. GAA plot for sample 51
(RQ093079)
Q
70
70
80
mass = 108 mg
T1 = 34.3d
60
40
40
20
20
60
T1 = 46.2 d
50
50
40
40
30
st
nd
60
GAA for 1 prep (pCi/L)
GAA for 2 prep (pCi/L)
60
80
mass = 46 mg
mass = 45 mg
T1 = 3.10 d
30
20
20
10
nd
100
mass = 83 mg
T1 = 3.65 d
st
GAA for 1 prep (pCi/L)
100
GAA for 2 prep (pCi/L)
Figure 8.55. GAA plot for sample 49
(RQ092856)
10
0
1
10
0.01
0.1
T2 (d)
Nuclide
0.1
10
1
Nuclide
Error
(pCi/L)
0.57
0.74
0.07
0.42
0.59
0.30
0.35
60
60
50
50
40
40
30
30
1
10
100
1
10
Nuclide
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
10
Activity
(pCi/L)
14.94
20.39
0.33
0.29
−0.22
0.75
0.48
0
100
T2 (d)
Error
(pCi/L)
0.03
0.06
0.38
0.65
0.56
0.37
1.10
24
mass = 46 mg
mass = 32 mg
T1 = 3.19 d
20
T1 = 36 d
16
16
12
12
nd
st
nd
10
8
8
4
4
0
100
T2 (d)
T2 (d)
1
24
GAA for 1 prep (pCi/L)
20
mass = 47 mg
T1 = 46.1 d
GAA for 2 prep (pCi/L)
st
GAA for 1 prep (pCi/L)
20
0
0.1
0.1
Figure 8.58. GAA plot for sample 52
(RQ093080)
20
10
100
Activity
(pCi/L)
0.07
0.17
6.29
0.34
0.35
1.50
2.34
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
Figure 8.56. GAA plot for sample 50
(RQ093078)
mass = 47 mg
T1 = 3.07 d
10
T2 (d)
T2 (d)
Activity
(pCi/L)
12.05
15.82
0.23
-0.10
0.27
−0.09
0.43
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
1
Error
(pCi/L)
0.65
0.87
0.09
0.96
0.94
0.32
0.39
GAA for 2 prep (pCi/L)
0
0.1
1
10
100
0.1
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
10
0
100
T2 (d)
T2 (d)
Nuclide
1
Activity
(pCi/L)
0.09
1.79
0.99
0.55
-0.44
2.14
3.16
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Error
(pCi/L)
0.02
0.12
0.14
0.64
0.63
0.48
0.89
Chapter 8: Gross Alpha-Particle Activity of the Groundwater Samples | 121
100
180
90
mass = 85 mg
90
160
160
80
T1 = 46.2 d
80
120
100
80
80
60
60
40
40
mass = 34 mg
T1 = 3.22 d
10
100
1
10
T2 (d)
Nuclide
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
Activity
(pCi/L)
0.22
3.42
7.51
0.60
−0.53
27.45
32.85
Error
(pCi/L)
0.044
0.23
0.44
0.60
0.59
1.64
3.45
T1 = 46.2 d
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
20
10
10
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
Figure 8.62. GAA plot for sample 56
(RR093084)
80
20
0
100
Error
(pCi/L)
0.04
0.23
0.44
0.60
0.59
1.64
3.45
Error
(pCi/L)
0.01
0.04
0.34
0.49
0.52
0.70
1.73
90
30
Activity
(pCi/L)
0.22
3.42
7.51
0.60
−0.53
27.45
32.85
Activity
(pCi/L)
0.03
0.35
5.26
0.37
-0.34
6.35
9.21
T1 = 46.1 d
30
Nuclide
T2 (d)
80
70
T2 (d)
0
100
80
40
T2 (d)
10
mass = 96 mg
40
10
1
90
50
1
100
100
50
100
10
90
60
0
10
Nuclide
nd
st
mass = 90 mg
60
10
20
mass = 83 mg
T1 = 3.12 d
T2 (d)
GAA for 2 prep (pCi/L)
mass = 92 mg
T1 = 3.13 d
1
30
20
T2 (d)
90
70
40
30
1
Figure 8.60. GAA plot for sample 54
(RR093082)
80
50
40
0
0
100
st
1
60
50
10
20
GAA for 1 prep (pCi/L)
0
0.1
nd
100
70
60
nd
T1 = 46.3 d
GAA for 2 prep (pCi/L)
120
70
100
70
70
60
60
50
50
40
40
30
30
20
20
mass = 95 mg
T1 = 3.08 d
10
0
1
10
10
100
1
T2 (d)
Nuclide
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
10
0
100
T2 (d)
Activity
(pCi/L)
0.08
0.35
4.61
0.31
−0.30
7.77
10.17
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Error
(pCi/L)
0.02
0.04
0.31
0.43
0.46
0.77
2.36
nd
140
100
GAA for 2 prep (pCi/L)
mass = 36 mg
st
140
GAA for 1 prep (pCi/L)
200
180
20
GAA for 1 prep (pCi/L)
Figure 8.61. GAA plot for sample 55
(RR093083)
200
GAA for 2 prep (pCi/L)
st
GAA for 1 prep (pCi/L)
Figure 8.59. GAA plot for sample 53
(RQ093081)
122 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
30
T1 = 46.2 d
30
25
20
20
15
15
10
10
st
nd
25
mass = 53 mg
T1 = 3.18 d
5
0
0.1
1
10
5
100
1
T2 (d)
Nuclide
60
50
50
40
40
30
30
20
20
10
0
0.1
T2 (d)
Activity
(pCi/L)
0.08
0.76
2.71
0.30
−0.27
2.28
3.48
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
0
100
10
60
nd
35
st
mass = 55 mg
GAA for 1 prep (pCi/L)
35
GAA for 2 prep (pCi/L)
40
40
GAA for 1 prep (pCi/L)
Figure 8.65. GAA plot for sample 59
(RR093374)
mass = 85 mg
T1 = 3.25 d
1
10
Nuclide
0.1
1
Figure 8.64. GAA plot for sample 58
(RR093373)
70
10
0
100
T2 (d)
Activity
(pCi/L)
10.22
15.68
0.15
−0.15
0.22
0.19
0.30
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
10
mass = 86 mg
T1 = 37.2 d
T2 (d)
Error
(pCi/L)
0.02
0.06
0.23
0.49
0.52
0.54
0.90
GAA for 2 prep (pCi/L)
Figure 8.63. GAA plot for sample 57
(RR093085)
Error
(pCi/L)
0.45
0.67
0.06
0.3
0.37
0.32
0.22
Figure 8.66. GAA plot for sample 60
(RR093375)
70
50
50
60
50
50
40
40
30
30
20
20
T1 = 37.1 d
10
0
0.1
mass = 36 mg
T1 = 3.24 d
1
10
T1 = 37.2 d
0.1
1
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
10
0
100
T2 (d)
T2 (d)
Nuclide
10
Activity
(pCi/L)
12.97
14.93
0.14
0.27
0.17
0.19
0.19
Error
(pCi/L)
0.57
0.65
0.08
0.3
0.38
0.30
0.16
st
nd
GAA for 1 prep (pCi/L)
mass = 35 mg
GAA for 2 prep (pCi/L)
st
GAA for 1 prep (pCi/L)
40
40
30
30
20
20
10
10
mass = 37 mg
T1 = 3.20 d
0
1
10
0.1
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
10
0
100
T2 (d)
T2 (d)
Nuclide
1
Activity
(pCi/L)
2.02
3.15
4.11
0.24
0.22
0.40
0.86
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Error
(pCi/L)
0.11
0.16
0.30
0.33
0.41
0.34
0.22
nd
60
GAA for 2 prep (pCi/L)
mass = 47 mg
Chapter 8: Gross Alpha-Particle Activity of the Groundwater Samples | 123
30
30
20
20
mass = 106 mg
T1 = 3.24 d
10
0
1
mass = 111 mg
T1 = 37.2 d
10
0.1
1
T2 (d)
Nuclide
0
10
160
140
140
120
120
100
100
80
80
60
60
40
mass = 113 mg
T1 = 3.17 d
20
0.1
1
10
0
100
st
180
0
Activity
(pCi/L)
0.01
0.05
13.97
0.29
-0.03
0.66
9.06
10
Error
(pCi/L)
0.01
0.01
0.72
0.27
0.34
0.36
1.40
100
T2 (d)
Activity
(pCi/L)
0.02
0.03
3.76
0.16
−0.18
7.95
7.72
Error
(pCi/L)
0.01
0.02
0.28
0.31
0.39
0.80
1.54
100
100
80
80
60
60
40
40
20
0
0.1
mass = 23 mg
mass = 52 mg
T1 = 5.31 d
20
T1 = 143 d
0
1
10
0.1
Nuclide
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
1
10
100
T2 (d)
T2 (d)
T2 (d)
T2 (d)
1
Figure 8.70. GAA plot for sample 64
(RR093660)
GAA for 1 prep (pCi/L)
T1 = 37.1 d
160
nd
180
GAA for 2 prep (pCi/L)
st
200
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
20
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
220
Nuclide
20
Nuclide
mass = 117 mg
10
40
1
Error
(pCi/L)
0.56
0.81
0.07
0.32
0.40
0.30
0.32
200
1
40
T2 (d)
220
20
60
0
0
100
Figure 8.68. GAA plot for sample 62
(RR093377)
Q
40
60
T2 (d)
Activity
(pCi/L)
13.00
19.23
0.09
0.14
−0.03
0.10
0.44
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
10
10
80
nd
40
80
Activity
(pCi/L)
11.05
36.77
1.19
1.02
1.32
1.17
1.14
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Error
(pCi/L)
0.56
1.68
0.24
0.38
0.38
0.55
0.45
nd
40
100
T1 = 37.2 d
st
50
GAA for 1 prep (pCi/L)
50
mass = 89 mg
mass = 87 mg
T1 = 3.24 d
100
nd
60
GAA for 2 prep (pCi/L)
70
60
st
GAA for 1 prep (pCi/L)
70
120
120
GAA for 2 prep (pCi/L)
80
80
GAA for 1 prep (pCi/L)
Figure 8.69. GAA plot for sample 63
(RR093378)
GAA for 2 prep (pCi/L)
Figure 8.67. GAA plot for sample 61
(RR093376)
124 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
4
4
0
0
-4
0.1
50
50
40
40
30
30
20
20
st
nd
8
GAA for 1 prep (pCi/L)
T1 = 143 d
8
60
nd
12
GAA for 2 prep (pCi/L)
st
GAA for 1 prep (pCi/L)
mass = 16 mg
mass = 17 mg
T1 = 5.42 d
12
60
10
0
0.01
-4
1
10
0.1
1
T2 (d)
10
100
Activity
(pCi/L)
0.07
0.11
0.34
−0.23
0.24
0.14
0.13
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
mass = 31 mg 10
T1 = 44 d
mass = 90 mg
T1 = 5.18 d
0.1
0
1
10
0.1
1
T2 (d)
T2 (d)
Nuclide
Nuclide
Error
(pCi/L)
0.02
0.04
0.12
0.30
0.27
0.54
0.18
10
100
T2 (d)
Activity
(pCi/L)
0.05
0.23
3.54
−0.01
0.08
7.17
6.73
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
Figure 8.72. GAA plot for sample 66
(RR093662)
Error
(pCi/L)
0.02
0.04
0.28
0.34
0.31
0.77
1.20
Figure 8.74. GAA plot for sample 68
(RR093664)
70
60
40
40
20
20
nd
60
0
0.1
0
1
10
0.1
1
Nuclide
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
10
100
T2 (d)
T2 (d)
Activity
(pCi/L)
0.50
1.24
9.52
0.54
0.07
2.96
2.39
Error
(pCi/L)
0.04
0.08
0.53
0.40
0.37
0.50
0.49
st
80
GAA for 1 prep (pCi/L)
80
60
T1 = 143 d
GAA for 2 prep (pCi/L)
mass = 64 mg
T1 = 5.13 d
70
mass = 93 mg
T1 = 5.29 d
100
mass = 31 mg
st
GAA for 1 prep (pCi/L)
100
GAA for 2 prep (pCi/L)
16
mass = 73 mg
T1 = 143 d
60
50
50
40
40
30
30
20
20
10
10
0
0.01
0
0.1
1
10
0.1
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
10
100
T2 (d)
T2 (d)
Nuclide
1
Activity
(pCi/L)
1.66
2.91
4.62
0.07
-0.02
0.27
0.97
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Error
(pCi/L)
0.11
0.16
0.33
0.35
0.32
0.33
0.37
nd
Q
16
Figure 8.73. GAA plot for sample 67
(RR093663)
GAA for 2 prep (pCi/L)
Figure 8.71. GAA plot for sample 65
(RR093661)
Chapter 8: Gross Alpha-Particle Activity of the Groundwater Samples | 125
Figure 8.75. GAA plot for sample 69
(RS095390)
60
20
10
10
0.1
1
10
0.01
0.1
T2 (d)
Nuclide
10
0
100
50
40
40
30
30
20
20
10
10
0
0.01
mass = 61 mg
T1 = 76.0 d
10
0.1
1
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
0
100
T2 (d)
T2 (d)
Nuclide
10
Activity
(pCi/L)
0.20
3.11
6.92
0.18
−0.06
4.11
4.53
Error
(pCi/L)
0.02
0.15
0.42
0.42
0.42
0.63
0.74
0
100
T2 (d)
Error
(pCi/L)
0.02
0.14
0.38
0.42
0.37
0.56
0.75
12
mass = 35 mg
T1 = 3.50 d
mass = 28 mg
T1 = 77.1 d
10
8
8
6
6
4
4
2
2
0
0
nd
20
10
st
20
1
1
12
GAA for 1 prep (pCi/L)
40
nd
40
GAA for 2 prep (pCi/L)
80
60
0.1
0.1
Figure 8.78. GAA plot for sample 72
(RS095393)
10
60
0
0.01
10
Activity
(pCi/L)
0.15
2.76
5.72
0.47
−0.28
2.74
4.59
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
100
mass = 74 mg
T1 = 3.06 d
1
Nuclide
Error
(pCi/L)
0.03
0.10
0.30
0.39
0.39
0.74
0.63
100
80
0.1
T2 (d)
Figure 8.76. GAA plot for sample 70
(RS095391)
st
50
T2 (d)
Activity
(pCi/L)
0.08
1.05
4.05
0.10
−0.05
5.02
4.11
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
1
60
nd
20
mass = 46 mg
T1 = 76.0 d
GAA for 2 prep (pCi/L)
30
st
30
GAA for 1 prep (pCi/L)
40
nd
40
0
0.01
mass = 55 mg
T1 = 3.08 d
60
50
st
GAA for 1 prep (pCi/L)
50
mass = 43 mg
T1 = 76.0 d
GAA for 2 prep (pCi/L)
mass = 49 mg
T1 = 3.06 d
GAA for 2 prep (pCi/L)
60
GAA for 1 prep (pCi/L)
Figure 8.77. GAA plot for sample 71
(RS095392)
0.01
0.1
1
10
0.01
0.1
T2 (d)
Nuclide
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
1
10
100
T2 (d)
Activity
(pCi/L)
0.02
0.04
1.09
0.38
-0.17
1.62
0.61
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Error
(pCi/L)
0.01
0.01
0.13
0.52
0.52
0.55
0.40
126 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
Figure 8.79. GAA plot for sample 73
(RS095394)
Figure 8.81. GAA plot for sample 75
(RS095396)
100
100
100
80
80
80
80
60
60
60
60
40
40
40
40
0.01
0.1
Activity
(pCi/L)
0.22
0.29
0.11
0.32
55.57
1.00
0.18
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
10
0
0.01
0
100
Nuclide
Error
(pCi/L)
0.02
0.03
0.05
0.41
3.32
0.44
0.17
60
60
40
40
20
20
0
0.01
0.1
1
10
0.01
0.1
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
10
T2 (d)
T2 (d)
Nuclide
1
0
100
Activity
(pCi/L)
6.67
6.06
7.07
0.87
−0.50
0.59
0.67
Error
(pCi/L)
0.30
0.27
0.40
0.44
0.45
0.39
0.28
0.01
0.1
1
10
0
100
T2 (d)
Error
(pCi/L)
1.22
1.58
0.08
0.63
0.69
0.45
0.08
Figure 8.82. GAA plot for sample 76
(RS095397)
80
nd
st
GAA for 1 prep (pCi/L)
mass = 53 mg
T1 = 77.5 d
10
Activity
(pCi/L)
28.18
36.94
0.28
4.17
3.14
1.11
0.04
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
GAA for 2 prep (pCi/L)
mass = 56 mg
T1 = 3.91 d
1
T2 (d)
Figure 8.80. GAA plot for sample 74
(RS095395)
80
0.1
T2 (d)
T2 (d)
Nuclide
1
20
40
40
35
35
30
30
25
25
20
20
mass = 91 mg
T1 = 76.5 d
mass = 91 mg
T1 = 4.26 d
15
nd
10
mass = 32 mg
T1 = 76.0 d
15
10
10
5
5
0
0.01
0.1
1
10
0.01
0.1
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
10
0
100
T2 (d)
T2 (d)
Nuclide
1
Activity
(pCi/L)
5.55
9.12
0.09
0.32
−0.03
0.17
0.13
©2010 Water Research Foundation. ALL RIGHTS RESERVED
GAA for 2 prep (pCi/L)
1
mass = 41 mg
T1 = 2.42 d
20
st
0.1
20
mass = 63 mg
T1 = 76.1 d
GAA for 1 prep (pCi/L)
0
0.01
mass = 73 mg
T1 = 2.49 d
st
nd
20
nd
100
GAA for 2 prep (pCi/L)
120
GAA for 1 prep (pCi/L)
120
GAA for 2 prep (pCi/L)
120
st
GAA for 1 prep (pCi/L)
Q
120
Error
(pCi/L)
0.25
0.40
0.07
0.42
0.37
0.31
0.19
Chapter 8: Gross Alpha-Particle Activity of the Groundwater Samples | 127
Figure 8.83. GAA plot for sample 77
(RS095398)
Figure 8.85. GAA plot for sample 79
(RS095400)
30
25
25
20
20
15
15
10
10
mass = 91 mg
T1 = 4.05 d
5
0
0.1
1
5
10
0.1
1
Activity
(pCi/L)
0.92
3.15
2.97
0.03
0.36
1.05
3.61
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
160
140
140
120
120
100
100
80
80
60
60
40
0
0.01
0
100
0.1
1
10
Nuclide
Error
(pCi/L)
0.06
0.16
0.23
0.45
0.40
0.42
0.86
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
Activity
(pCi/L)
27.08
35.07
6.46
0.77
−0.09
3.85
7.78
80
60
60
40
40
20
mass = 69 mg
T1 = 5.67 d
1
10
0.1
1
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
0
100
T2 (d)
T2 (d)
Nuclide
10
nd
st
GAA for 1 prep (pCi/L)
80
GAA for 2 prep (pCi/L)
100
mass = 59 mg
T1 = 72.4 d
0.1
1
20
10
0
100
T2 (d)
Q
100
0
0.01
0.1
T2 (d)
Figure 8.84. GAA plot for sample 78
(RS095399)
20
40
mass = 54 mg
T1 = 72.4 d
mass = 67 mg
T1 = 5.70 d
20
T2 (d)
T2 (d)
Nuclide
10
160
st
30
GAA for 1 prep (pCi/L)
35
nd
35
40
GAA for 2 prep (pCi/L)
st
GAA for 1 prep (pCi/L)
40
Activity
(pCi/L)
11.81
18.12
4.58
0.06
0.342
1.79
2.80
Error
(pCi/L)
0.54
0.80
0.31
0.40
0.36
0.44
0.72
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Error
(pCi/L)
1.18
1.51
0.39
0.40
0.40
0.55
1.27
nd
45
mass = 102 mg
T1 = 76.3 d
GAA for 2 prep (pCi/L)
Q
45
128
©2010 Water Research Foundation. ALL RIGHTS RESERVED
CHAPTER 9
THE GROSS RADIUM ACTIVITY OF THE GROUNDWATER SAMPLES
INTRODUCTION
Seventy nine samples in this study were analyzed for gross radium activity (GRA) using
EPA Method 900.1 (U.S. EPA 1980b), a coprecipitation method. In EPA Method 900.1, the radium isotopes of a sample are coprecipitated with barium sulfate (BaSO4), and the BaSO4 is
placed in a planchet and counted with a gas proportional counter. EPA Method 900.1 is intended
to measure the total alpha activity of the radium isotopes 223Ra, 224Ra, and 226Ra and was designed to be used on samples with high levels of dissolved solids. EPA Method 903.0 (U.S. EPA
1980c) is an alternate method for measuring the GRA. In EPA Method 903.0, barium and lead
carriers are added to the sample, and a citrate buffer is used to allow the radium, barium and lead
ions to uniformly distribute throughout the solution before radium is coprecipitated with a barium-lead sulfate precipitate. Without the citrate buffer, the naturally occurring sulfate of a sample could cause the barium-lead sulfate precipitate to form before the barium and lead carrier solutions were thoroughly mixed with the sample, which may result in a precipitate with an inhomogeneous distribution of radium. Since no citrate buffer is used in EPA Method 900.1, the radium distribution in the BaSO4 may be inhomogeneous for some samples.
In this study, four alterations were made to EPA Method 900.1. First, the BaSO4 precipitate was not collected on a filter but was slurried with deionized water, poured into a planchet,
and dried under a heat lamp. The BaSO4 residues produced in this way appeared to be relatively
uniform but were sometimes pockmarked with small depressions that seemed to coincide with
places where gas bubbles had formed during the evaporation process. (It was later found that the
pockmarks could be eliminated if 16 M nitric acid was used to transfer BaSO4 to the planchets
rather than deionized water. However, for the sake of consistency, deionized water was used
throughout this study.) Second, the gravimetric yield of BaSO4 was determined, and the calculation of the GRA was modified to take the yield into account. Third, the determination of the
226
Ra efficiency presented in Appendix C differs from EPA Method 900.1. The discussion of
Appendix C shows that these radium efficiencies should be more accurate than those determined
by EPA Method 900.1. Fourth, the average progeny efficiency 3Kεave, as determined in Appendix C, was used in place of the usual factor of 3ε1, where ε1 is the 226Ra efficiency, in the calculation of the GRA.
EPA Method 900.1 was chosen to compare with EPA Method 900.0, an evaporation method, because in EPA Method 900.1, parameters like residue mass and geometry are more easily
controlled than in EPA Method 900.0. In EPA Method 900.0, the level of dissolved solids and
the sample volume determine the residue mass; in EPA Method 900.1, the amount of barium carrier added to the sample determines the residue mass, which was usually about 20 mg. In EPA
Method 900.0, the residues can range from being patchy to being uniform; in EPA Method
900.1, the residues, composed of BaSO4, appeared to be relatively uniform across the planchet.
In EPA Method 900.0, the residues were sometimes hygroscopic, despite having decomposed
Ca(NO3)2 and Mg(NO3)2 to CaO and MgO; in EPA Method 900.1, the BaSO4 sulfate residues
were not hygroscopic.
In EPA Method 900.0, the ingrowth of 226Ra progeny begins when the sample residue solidifies after being heated over a flame; in EPA Method 900.1, the ingrowth of 226Ra progeny
129
©2010 Water Research Foundation. ALL RIGHTS RESERVED
130 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
begins when the BaSO4 precipitate forms Thus, if the sample preparation time is taken to be the
time at which the BaSO4 forms, the determination of a decay chain’s contribution to a sample
residue’s alpha-particle count rate is the same for both EPA Method 900.0 and EPA Method
900.1
Each sample was prepared for GRA analysis on two occasions: the first preparation was
performed as soon as possible after sample collection; the second preparation was performed 30
or more days following sample collection. On each occasion, the samples were counted as soon
as possible after preparation, about three days after preparation, and at least 30 days after preparation. These preparation and analysis times coincided with the preparation and analysis times
for the GAA, but the samples for the GRA analyses were prepared singly rather than in triplicate,
as was done for the GAA analyses. The samples were counted in the alpha-only mode of the gas
proportional counter rather than in the alpha-beta mode, which was used for the GAA analyses.
The background for the alpha-only mode is lower than in alpha-beta mode; thus, it was expected
that the GRAs obtained using the alpha-only mode would be more accurate than the GRAs obtained using the alpha-beta mode.
EXPERIMENTAL AND THEORETICAL CALCULATION OF THE GRA
In this section, as in Appendix C, T1 is the time between sample collection and preparation, T2 is the time between sample preparation and analysis, and T3 = T1 + T2 is the time between
sample collection and analysis.
In EPA Method 900.1, 226Ra is used as the calibration standard; thus, it is implicitly assumed that all of the alpha emitters in the BaSO4 residues have the same efficiency as 226Ra. In
EPA Method 900.1, the 226Ra efficiency, ε1, is determined by measuring the alpha-particle emission rate of a BaSO4 residue that contains a known 226Ra activity. The alpha-particle emission
rate is measured just after preparation to minimize the contribution of 226Ra progeny to the GRA.
In this study, the 226Ra efficiency, ε1, and the average progeny efficiency, 3Kεave, were determined using the method discussed in Appendix C. The GRA was calculated using the following
equation:
(9.1)
CT
GRA =
Vγ {ε 1 + 3Kε ave [1 − exp(−λ 2T2 )]}
,
where CT is the net number of residue counts per unit time, V is the sample volume, γ is the gravimetric yield of BaSO4, which ranges from zero to one, ε1 is the 226Ra efficiency, 3Kεave is the
sum of the three progeny efficiencies, λ2 is the decay constant of 222Rn, and T2 is the time between the sample preparation and analysis. (The symbol T2 is used both here and in the previous
section because; in both cases, T2 = 0 is the point in time at which the ingrowth of 226Ra progeny
begins.) Ordinarily, in EPA Method 900.1, it is assumed that that the BaSO4 yield is 100%, so
that γ = 1. However, it was found to be difficult to consistently attain a yield of 100%, so the factor γ was included in the equation.
In Eqn. (9.1), the following factor
(9.2)
ε 1 + 3Kε ave[1 − exp(−λ2T2 )]
is used to account for the ingrowth of the three alpha-emitting 226Ra progeny—222Rn, 218Po, and
214
Po—and to make the value of the GRA independent of T2 and approximately equal to the
226
Ra activity in samples with minimal 223Ra and 224Ra activities. In EPA Method 900.1, the preexponential factor in Eqn. (9.1) is usually 3ε1, which undercompensates for the progeny in-
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Chapter 9: The Gross Radium Activity of the Groundwater Samples | 131
growth; the factor 3Kεave (>3ε1) completely accounts for the ingrowth of the progeny, so that
there is no need to measure the GRA right after preparation.
In addition to the experimental values of the GRA, the GRA for each sample was theoretically modeled using the sample’s radiological data. The calculation of CT in Eqn. (9.1), for the
GRA, is very similar to the calculation of CT in Eqn. (2.2), for the GAA. The theoretical value of
the GRA depends on the radiological composition of the BaSO4 residue at the time of sample
preparation. The radiological composition of a BaSO4 residue produced by EPA Method 900.1
can differ significantly from the radiological composition of a residue produced by EPA Method
900.0. When BaSO4 is precipitated from a hydrochloric acid solution, as in Method 900.1, not all
radionuclides coprecipitate. Under these conditions, about 99% of the hexavalent uranium (U. S.
EPA 1980b, Sill and Williams 1969); more than 99% of polonium and bismuth (Sill 1977, Sill
and Willis 1977), and quantitative amounts of radon (Sill and Williams 1969) remain in the supernatant, while thorium (Sill 1977) and radium (U. S. EPA 1980b) coprecipitate with BaSO4. In
addition, lead coprecipitates with barium sulfate, even in the presence of a citrate chelating agent
(Goldin 1961). Thus, to a first approximation, it was assumed that no uranium, polonium, bismuth, or radon coprecipitated with BaSO4 and that thorium, radium, and lead quantitatively coprecipitated with the BaSO4. Consequently, all of the decay chains of the previous chapter, except for the 234U, 238U, and 210Po decay chains are required in the theoretical calculation of the
GRA. Just after preparation, the 210Pb decay chain’s contribution to the GRA will be insignificant however; several months after preparation, 210Pb can produce a significant amount of 210Po,
and the 210Pb decay chain’s contribution to the GRA can be significant.
One month after collection, any unsupported 224Ra or 212Pb would have decayed away,
and any 212Bi activity in the sample would be due to the 228Ra decay chain; i.e., 212Bi would be in
secular equilibrium with 228Th. Since 212Bi has a half-life of about 1 hr. and was assumed not to
coprecipitate with BaSO4, just after sample preparation (T2 ≈ 0 hr.), the 212Bi activity was assumed to be negligible, but at six or more hours after preparation (T2 ≥ 6 hr.), 212Bi would be in
secular equilibrium with 228Th, and the initial loss of 212Bi could be neglected. Many of the samples in this study had a significant 228Ra activity, and some of these samples were prepared several months after collection and analyzed just after preparation, when the 212Bi activity was assumed to be negligible. Since 212Bi only accounts for about 13% of the alpha activity of the 228Ra
decay chain, the difference between neglecting and accounting for the initial loss of 212Bi would
not have a large effect on the GRA. However, since it is not difficult to account for the initial
loss of 212Bi activity, this loss was included in the theoretical calculation of the GRA, which is
discussed in the next paragraph. (In the 226Ra decay chain, 214Pb coprecipitates with BaSO4 and
has a half-life of 28.6 min. Thus, to be consistent, the 214Pb decay chain should be employed in
the calculation of the GRA; however, the efficiencies of the 214Pb decay chain were not determined in this work, but the effect of the 214Pb decay chain on the GRA would be negligible after
about 3 hr.)
Any decay chain can be broken down into component decay chains such that the parent
and each progeny, called a component parent, have a decay chain, and the collective contribution
of the component decay chains to the GRA is equal to the original decay chain’s contribution.
The activities of the component parents are equal to their activites at the point in time at which
the original decay chain is broken down into components. To calculate the GRA, the 228Ra decay
chain is broken down into components at the time of sample preparation, when the BaSO4
precipitate forms. The activities of the component parents can be calculated from the sample’s
228
Ra activity at the time of sample collection and from the time between sample collection and
©2010 Water Research Foundation. ALL RIGHTS RESERVED
132 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
preparation, T1. Although, each 228Ra progeny has its own component decay chain, some
progeny—220Rn, 216Po, and 212Po—decay decay away rapidly on the time scale of interest, and
their component decay chains can be neglected. The 212Bi activity in the residue at the time of
sample preparation is assumed to be zero; therefore, the contribution of the component 212Bi decay chain to the GRA is neglected, which accounts for the loss of 212Bi at the time of sample
preparation. Thus, the 228Ra decay chain must be broken down into four component decay
chains: the 228Ra, 228Th, 224Ra, and 212Pb decay chains. The 228Th decay is given by
224
220
216
212
208
Th α
⎯→
Ra α
⎯→
Rn α
⎯→
Po α
⎯→
Pb β⎯→ 212Bi β⎯→ 212Po α
⎯→
Pb.
Since the parent activity of each decay chain is taken to be its activity at the time of sample
preparation, the contribution of each component decay chain will depend on the time between
sample preparation and analysis, T2. If 228Ra, 228Th, and 224Ra quantitatively coprecipitate with
BaSO4, then just after preparation (T2 ≈ 0 hr.), the contribution of 212Bi to the GRA will be negligible, but at T2 = 6 hr, 212Bi will be in secular equilibrium with all of the alpha emitters of the
228
Ra decay chain, and at this time, the collective contribution of the four component decay
chains to the GRA would be equal to the contribution of the original 228Ra decay chain to the
GRA.
Since the 228Ra decay chain has been broken down into component decay chains, in the
GRA model calculations, there are two types of 224Ra and 212Pb decay chains: the first corresponds to unsupported 224Ra and unsupported 212Pb at the time of sample collection; the second
corresponds to 224Ra and 212Pb that was produced by the 228Ra decay chain at the time of sample
preparation. The first type of decay chain can only be significant for the first sample preparation,
and the second type of decay chain can only be significant for the second sample preparation.
The progeny of the 226Ra decay chain—222Rn, 218Po, 214Pb, and 214Po—either do not coprecipitate or decay away within a few hours of preparation. Thus, for the purpose of calculating
the GRA, the activities of the 226Ra progeny are taken to be zero at T2 = 0. Then, as with the
GAA calculations, the 226Ra progeny grow in with the characteristic 3.8-day time constant and
attain their maximum activities at about T2 = 23 days.
Each sample’s radiological composition was used to calculate its GRA. The calculation of each
decay chain’s contribution to C T in Eqn. (9.1) is identical to the calculation of each decay chain’s
contribution to C T in Eqn. (2.2), except that the efficiencies for the BaSO4 residues are different
than the efficiencies for the actual sample residues. Since the BaSO4 residues appeared to be uniform, with the occasional appearance of pockmarks, it was assumed that the BaSO4 residues
were of uniform thickness (rather than having smooth or patch geometries), so that the factor
R1/R2 in Appendix D was set equal to one.
228
PRESENTATION OF THE GRA DATA
Figure 9.1 shows how the GRA data for each sample will be presented. Like the GAA data, the GRA data for first preparation is displayed in the left plot, and the GRA data for the
second preparation is displayed in the right plot. The time between sample collection and preparation, T1, and the BaSO4 residue mass is indicated on each plot. The first preparation was as
soon as possible after collection (T1 < 2 d.); the second preparation was at 30 or more days after
collection (T1 ≥ 30 d.).]. In each plot, the points are the experimentally determined GRA data
plotted against the time between sample preparation and analysis, T2, at three analysis times: (1)
as soon as possible after preparation (T2 ≈ 0 d.), (2) about three days after preparation (T2 ≈ 3 d.),
and (3) 30 or more days after preparation (T2 ≥ 30 d.). The GRA data points have error bars that
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Chapter 9: The Gross Radium Activity of the Groundwater Samples | 133
correspond to a 95% confidence interval. The solid middle curve in each plot of Figure 9.1 is the
GRA model curve that was calculated using the sample’s radiological composition. The error in
each GRA model curve at the 95% confidence interval was calculated using the uncertainties in
the radiological data. The upper dashed curve in Figure 9.1 corresponds to the GRA curve with
the error added to it; the lower dashed curve corresponds to the GRA curve with an error subtracted from it.
45
35
calc. GRA
mass = 21.9 mg
40
T1 = 37.3 d
35
30
30
25
25
20
20
15
15
10
5
0
0.1
10
mass = 25.8 mg
T1 = 2.24 d
5
nd
calc. GRA minu error
Gross radium for 2 prep (pCi/L)
st
Gross radium for 1 prep (pCi/L)
40
45
calc. GRA plus error
0
1
10
T2 (d)
1
10
T2 (d)
Figure 9.1. Example of gross radium plot
The figures for all 79 samples are at presented at the end of this chapter. In the caption of
each figure, the samples are labeled from 1 to 79, and the Wisconsin State Laboratory of Hygiene’s sample number is given in parentheses. Below each figure is a table showing the radiological composition of each sample.
EXPERIMENTAL RESULTS
Many of the GRA plots have the same appearance. In many of the left plots, there is a decrease in the GRA data with T2 due to the decay of unsupported 224Ra and its alpha-emitting
progeny. In many of the right plots, unsupported 224Ra has decayed away, and the GRA data for
many samples are approximately constant for about 23 days, because the rate of increase of the
ingrowth factor of Eqn. (9.2) is equal to the rate of increase of the 226Ra decay chain’s contribution to the sample residue’s alpha-particle count rate.
The 224Ra decay chain’s contribution to the GRA declines over a period of about 21 days,
but the ingrowth factor of Eqn. (9.2) causes the 224Ra decay chain’s contribution to the GRA to
decrease at a faster rate than the 224Ra decay chain’s contribution to the sample residue’s alphaparticle count rate. Thus, a large decrease in the GRA of the first preparation over 21 days indicates the presence of a significant activity of unsupported 224Ra. The lack of such a decrease
would indicate the absence of unsupported 224Ra. For samples prepared soon after collection, the
time dependent behavior of the GRA and the efficiency data of Appendix E could be used to estimate the unsupported 224Ra activity and the 226Ra activity of the sample.
©2010 Water Research Foundation. ALL RIGHTS RESERVED
134 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
If the second preparation occurs many months after collection, the contribution of the
Ra decay chain to the GRA could be substantial at the time of preparation. Since the contribution of the 228Ra decay chain would be virtually constant over 23 days, the factor of Eqn. (9.2)
would cause this contributions to decrease over 23 days, after which, this contribution would begin to increase as the activity of the alpha-emitting progeny continue to increase. Such a decrease
for the second preparation is seen in sample 67, for which T1 = 268 d and for which the initial
228
Ra activity was 7.17 pCi/L.
For sample 73, a sample with a significant 210Po activity, the agreement between the experimental data and the model curves was not very good, but the amount of alpha activity in the
residue was relatively low. The initial alpha activity in the first preparation was about 3 pCi/L.
Over 10 days, the GRA decreased to about 1.2 pCi/L, which is consistent with an alpha emitter
with a half-life that is significantly longer than the 3.8-d half-life of 222Rn. This sample contained
relatively low levels of the radium isotopes and 210Pb, which had been accounted for in the model curves. The only other long-lived alpha emitters in the sample were relatively low levels of
234
U and 238U and 55.6 pCi/L of 210Po. Whether 210Po could have coprecipitated the BaSO4 is not
known. It is unlikely that the GAA was due to 210Po in solution that was included in the BaSO4
because the volume of solution that could be included would be too small to account for the alpha activity. Often, 210Po is present in samples in a colloidal form. It is possible that colloidal
210
Po could have been collected with the BaSO4. The second preparation of sample 73 shows a
small amount of alpha activity growing in over a period of several months. All of the radionuclides that could have caused such an ingrowth were accounted for in the model curves. It is possible that the 228Ra or 210Pb activities could have been underestimated, but if this were the case, it
should have been evident in the first preparation.
As with samples prepared for GAA analysis, the GRA of radium-containing samples can
be minimized by preparing the sample at about one month after collection, to eliminate unsupported 224Ra. Since the ingrowth factor of Eqn. (9.2) completely compensates for the ingrowth of
the 226Ra progeny, the GRA at T2 = 30 days for the first preparation is approximately equal the
GRA at T2 = 0 days for the second preparation, so that, unlike the GAA, the minimal GRA appears in both the first and second preparations.
In Table 9.1, the GRA plots were classified according to whether the experimental GRA
data fit the theoretical model curves for the first preparations (left plots) and second preparations
(right plots). The GRA data were considered to fit the model curves if the error bars of the
experimental data overlapped the region between the upper and lower model curves. It should be
mentioned that the first preparation for sample 39 was not performed by mistake, so that
Table 9.1 contains 78 entries. Table 9.1 shows that the data of 33 samples fit the model curves
for both preparations, that the data of 20 samples fit the model curves for the first preparation
(left plot) but did not fit the model curves for the second preparation (right plot), that the data of
11 samples did not fit the model curves for the first preparation (left plot) but did fit the model
curves for the second preparation (right plot), and that the data of 14 samples did not fit either set
of model curves.
Of the 45 samples whose GRA data did not fit one or both model curves, 23 samples—1,
2, 5, 6, 8, 10, 11, 12, 14, 17, 23, 27, 30, 33, 41, 45, 51, 54, 61, 62, 63, 64, 66—had GRA data that
came close to fitting the model curves in that the GRA data error bars fell just outside of the region between the upper and lower model curves and in that the trend in the GRA data was the
same as the trend in the model curves. Thus, 56 samples out of 78 either fit the model curves or
came close to fitting the model curves.
228
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Chapter 9: The Gross Radium Activity of the Groundwater Samples | 135
Table 9.1
Fit of the GRA data to the model curves (78 samples)
Data fits plot
Left
Samples
Right
Yes
Yes
4, 8, 13, 15, 16, 18, 19, 20, 21, 22, 26, 28, 29, 31, 32, 36, 42, 44, 47,
48, 50, 52, 53, 55, 56, 57, 60, 68, 69, 70, 71, 72, 74
Yes
No
1, 2, 5, 6, 11, 14, 23, 30, 34, 40, 41, 43, 46, 49, 51, 54, 58, 59, 63, 64
No
Yes
7, 10, 12, 25, 33, 35, 61, 65, 75, 78, 79
No
No
3, 9, 17, 24, 27, 37, 38, 45, 62, 66, 67, 73, 76, 77
For some samples, the experimental data and the model curves disagreed substantially.
There are several possible reasons for this. First, the assumption that radium, lead, and thorium
completely coprecipitate with BaSO4 and that uranium, radon, polonium, and bismuth do not coprecipitate with BaSO4 is approximate. EPA Method 900.1 is intended to characterize the radium
activity, but in samples that contain negligible amounts of radium, small amounts of other alpha
emitters, like the uranium isotopes, may be the main contributors the GRA. Second, the actual
errors in some of the radiological data may be larger than the computed errors, which would underestimate the error in the model curves. Third, some of the BaSO4 residues were pockmarked,
and, therefore, deviated somewhat from uniformity. Such deviations would tend to reduce the
GRA, but the magnitudes of these deviations were not quantified.
Samples 6, 7, 37, 38, 43, 45, 46, 49, 58, 59, 64, and 75 all contained a substantial uranium activity, and it is seen that in either the left or the right plot, the GRAs for these samples
was higher than the model curves. This may be due to the inclusion of some uranium in the BaSO4 residues, either in the BaSO4 or in pockets of solution included in the BaSO4, which would
tend to elevate the GRAs. Since the contributions of the 234U and 238U decay chains to the alpha
activity of a BaSO4 residue are constant, the component of the GRA due to the uranium decay
chains would decrease with the 3.8-d time constant of the ingrowth factor in Eqn. (9.2) and become constant at about 23 days after preparation (T2 = 23 days).
In some samples, it seems likely that there was a significant error made in the determination of one of the radium isotopes. For example, in sample 3, it appears that the 226Ra activity
was overestimated; in samples 9, 78, and 79, it appears that the 224Ra activity was overestimated;
and in sample 24 it appears that the 224Ra activity was underestimated. Overall, taking error into
consideration, the agreement between the experimental GRA data and the theoretical GRA model curves was quite good.
CONCLUSIONS
Comparison between the model curves and experimental data for the GAA plots
(Figure 8.7 through Figure 8.85) and the GRA plots (Figure 9.2 through Figure 9.80) shows that,
in general, the GRA error is less than the GAA error. There are several reasons for this, which
illustrate the differences between evaporation methods, like EPA Method 900.0 for the GAA,
and coprecipitation methods, like EPA Method 900.1 for the GRA. First, the residue mass of the
©2010 Water Research Foundation. ALL RIGHTS RESERVED
136 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
coprecipitation methods, which is about 20 mg, can be significantly less than the residue mass of
evaporation methods, which can range from 0 to 100 mg. Since the efficiency of the 230Th calibration standard decreases at a higher rate with residue mass than the efficiencies of many alpha
emitters—226Ra progeny, 224Ra and its progeny, 228Ra progeny and 210Po—the GAA due to evaporation methods often significantly overestimates the GAA of samples when the residue mass is
greater than 40 mg, whereas the overestimate of GRA is limited by the 20-mg upper bound on
the residue mass.
Second, as was shown in Chapter 4 and Chapter 8, the lower the residue mass, the lower
is the amount of error incurred by variations in the residue geometry. The residue geometries of
the samples prepared by EPA Method 900.1 were usually about 20 mg and were usually visibly
uniform; the residue geometries of samples prepared by EPA Method 900.0 ranged from 0 to 100
mg and had geometries that appeared to range from being relatively uniform to being composed
of patches that covered less than 50 % of the planchet.
Third, the GAA results for the uranium-containing samples prepared by EPA Method
900.0 suggested that, in some sample residues, the uranium was not homogenously distributed
throughout the residue, and that variability in the spatial distribution of uranium contributed to
the variability in the GAA. In for EPA Method 900.1, one would expect a more homogenous distribution of those radionuclides that coprecipitate with BaSO4, although in this study, radionuclide distributions in BaSO4 were not characterized. In some coprecipitation methods, like Standard Methods 7110C, two precipitates, BaSO4, and Fe(OH)3, and paper pulp comprise the sample residue, and, under these circumstances, it is not obvious that the residue is comprised of a
homogeneous mixture of BaSO4, Fe(OH)3, and paper pulp.
Fourth, in an evaporation method, the residues are often hygroscopic, even when the nitrates of calcium and magnesium are decomposed to the corresponding oxides over a flame. This
presents two problems; (1) the residue masses are changing with time so that variability in the
GAA due to variations in residue mass can be a problem, and (2) the amount of radon that emanates from a material is often positively correlated with the material’s moisture content (Strong
and Levins 1982), and variability in the amount of radon that emanates increases the variability
in the GAA. In coprecipitation methods, the sample residues contain little water and are usually
not hygroscopic, so that the residue masses are stable, and variability of the GRA or GAA due to
variability of the residue’s moisture content is usually negligible.
Finally, most of the errors that afflict samples prepared by evaporation methods also afflict the mass-efficiency curve for the calibration standard. Consequently, for evaporation methods, the error in the GAA is compounded by the error in the mass-efficiency curve. For coprecipitation methods, error in the mass-efficiency curve should be significantly less than that of an
evaporation method.
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Chapter 9: The Gross Radium Activity of the Groundwater Samples | 137
Figure 9.2. GRA plot for sample 1
(RQ091434)
Figure 9.4. GRA plot for sample 3
(RQ091436)
Q
T1 = 1.08 d
0
0.01
0.1
1
0.01
0.1
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
Activity
(pCi/L)
0.21
3.24
14.53
0.23
0.03
12.61
17.13
nd
T1 = 1.25 d
0
0.01
5
0
0.1
1
10
Nuclide
Error
(pCi/L)
0.03
0.20
0.74
0.47
0.09
1.00
2.10
0.01
30
30
25
20
20
15
15
10
10
mass = 16.7 mg
5
T1 = 1.08 d
0.1
1
0
10
0.01
0.1
T2 (d)
Nuclide
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
1
st
25
Error
(pCi/L)
0.03
0.18
0.39
0.56
0.11
0.57
1.01
Figure 9.5. GRA plot for sample 4
(RQ091437)
Gross radium for 1 prep (pCi/L)
30
nd
30
10
mass = 22.9 mg
Gross radium for 2 prep (pCi/L)
35
T1 =37.0 d
0
0.01
1
T2 (d)
40
35
0.1
Activity
(pCi/L)
0.19
2.84
6.36
0.10
-0.01
4.19
6.11
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
mass = 15.0 mg
st
10
mass = 20.8 mg
T2 (d)
40
Gross radium for 1 prep (pCi/L)
15
5
10
Figure 9.3. GRA plot for sample 2
(RQ091435)
5
15
T2 (d)
T2 (d)
Nuclide
1
20
10
0
10
20
T1 = 37.1 d
25
25
20
20
15
15
10
10
5
mass = 23.3 mg
5
T1 = 1.23 d
0
0.01
0
0.1
1
10
0.01
0.1
10
T2 (d)
T2 (d)
10
1
T2 (d)
Activity
(pCi/L)
0.23
1.92
5.73
-0.09
0.10
4.16
7.28
Error
(pCi/L)
0.04
0.13
0.36
0.47
0.07
0.57
1.33
Gross radium for 2 prep (pCi/L)
mass = 19.5 mg
25
Nuclide
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
Activity
(pCi/L)
0.10
1.69
4.73
0.41
0.11
3.98
6.07
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Error
(pCi/L)
0.02
0.12
0.33
0.53
0.08
0.57
0.92
nd
20
25
Gross radium for 2 prep (pCi/L)
20
30
T1 =37.2 d
st
40
Gross radium for 1 prep (pCi/L)
40
nd
60
st
Gross radium for 1 prep (pCi/L)
60
mass = 19.8 mg
30
80
T1 =37.0 d
Gross radium for 2 prep (pCi/L)
mass = 17.0 mg
80
138 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
Figure 9.8. GRA plot for sample 7
(RQ091440)
6
20
20
10
10
mass = 23.1 mg
T1 = 1.29 d
0
0.01
0.1
0
1
10
0.01
0.1
1
Nuclide
T1 = 1.19 d
T1 = 37.1 d
0.1
12
10
10
8
6
4
2
0
0.01
0.1
1
10
T2 (d)
T2 (d)
Activity
(pCi/L)
1342
1556
1.84
2.40
2.41
0.40
2.62
10
0.01
0.1
Error
(pCi/L)
77
89
0.18
0.69
0.26
0.34
1.87
-2
1
10
T2 (d)
Activity
(pCi/L)
1784
3000
0.09
0.83
0.12
0.48
0.19
Error
(pCi/L)
77
130
0.08
0.64
0.13
0.36
0.17
25
25
mass = 18.9 mg
T1 = 37.2 d
20
20
15
15
10
10
st
14
10
1
-1
Figure 9.9. GRA plot for sample 8
(RQ091441)
Gross radium for 1 prep (pCi/L)
T1 = 37.1 d
Gross radium for 2 prep (pCi/L)
T1 = 1.15 d
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
mass = 13.2 mg
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
nd
st
Gross radium for 1 prep (pCi/L)
mass = 20.6 mg
Nuclide
mass = 21.6 mg
Nuclide
20
mass = 20.0 mg
1
0
Error
(pCi/L)
0.02
0.07
0.27
0.48
0.07
0.86
2.00
20
0.1
1
0
T2 (d)
Figure 9.7. GRA plot for sample 6
(RQ091439)
Q
0
0.01
2
-2
0.01
10
Activity
(pCi/L)
0.08
0.66
3.87
0.23
0.03
9.61
12.60
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
16
3
2
T2 (d)
T2 (d)
18
4
5
5
mass = 18.5 mg
T1 = 1.27 d
0
0.01
0.1
1
0
10
0.01
0.1
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
10
T2 (d)
T2 (d)
Nuclide
1
Activity
(pCi/L)
0.61
0.78
4.02
0.26
−0.02
3.24
5.27
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Error
(pCi/L)
0.07
0.08
0.28
0.39
0.08
0.56
0.99
nd
30
5
4
Gross radium for 2 prep (pCi/L)
30
st
40
Gross radium for 1 prep (pCi/L)
40
nd
st
Gross radium for 1 prep (pCi/L)
T1 = 37.2 d
Gross radium for 2 prep (pCi/L)
50
nd
6
mass = 23.4 mg
50
Gross radium for 2 prep (pCi/L)
Figure 9.6. GRA plot for sample 5
(RQ091438)
Chapter 9: The Gross Radium Activity of the Groundwater Samples | 139
15
25
20
10
15
10
5
5
10
0.01
0.1
T2 (d)
Nuclide
9
6
6
3
3
Error
(pCi/L)
0.02
0.12
0.36
0.36
0.06
0.72
2.42
mass = 25.4 mg
T1 = 1.20 d
T1 = 37.1 d
6
nd
6
3
3
0
0.1
0
0.01
0.1
T2 (d)
Nuclide
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
1
10
T2 (d)
Activity
(pCi/L)
1.14
7.08
1.79
−0.18
0.14
0.68
1.66
0.1
Error
(pCi/L)
0.07
0.32
0.18
0.43
0.09
0.36
1.35
1
10
Activity
(pCi/L)
0.03
0.06
3.44
−0.05
0.07
3.27
5.47
Error
(pCi/L)
0.01
0.02
0.27
0.36
0.05
0.65
0.97
Figure 9.13. GRA plot for sample 12
(RQ091720)
12
9
10
0.01
T2 (d)
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
9
1
10
Nuclide
Gross radium for 2 prep (pCi/L)
mass = 19.0 mg
0
1
T2 (d)
st
Gross radium for 1 prep (pCi/L)
9
10
Figure 9.11. GRA plot for sample 10
(RQ091444)
12
18
12
T2 (d)
Activity
(pCi/L)
0.11
1.65
5.92
0.07
0.12
5.24
9.17
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
1
21
15
0
0.1
st
1
T1 = 17.0 d
12
0
0.1
T1 = 2.24 d
15
Gross radium for 1 prep (pCi/L)
0
0.01
18
mass = 25.4 mg
nd
30
mass = 22.4 mg
Gross radium for 2 prep (pCi/L)
35
st
20
24
21
Gross radium for 1 prep (pCi/L)
T1 = 37.2 d
nd
mass = 26.7 mg
Gross radium for 2 prep (pCi/L)
st
Gross radium for 1 prep (pCi/L)
T1 = 1.32 d
40
24
25
mass = 22.6 mg
45
39
36
33
30
27
24
21
18
15
12
9
6
3
0
0.1
24
mass = 24.8 mg
mass = 20.3 mg
T1 = 2.23 d
T1 = 37.2 d
21
18
15
12
9
6
3
0
1
10
0.1
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
10
T2 (d)
T2 (d)
Nuclide
1
Activity
(pCi/L)
0.04
0.03
4.62
0.01
0.10
6.20
9.83
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Error
(pCi/L)
0.01
0.01
0.31
0.38
0.05
0.66
1.19
nd
50
Figure 9.12. GRA plot for sample 11
(RQ091713)
Q
Gross radium for 2 prep (pCi/L)
Figure 9.10. GRA plot for sample 9
(RQ091442)
140 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
Figure 9.14. GRA plot for sample 13
(RQ091721)
Figure 9.16. GRA plot for sample 15
(RQ091723)
Q
10
mass = 17.7 mg
T1 = 2.08 d
T1 = 37.1 d
0
10
0.1
1
Nuclide
Activity
(pCi/L)
16.16
49.88
3.61
2.66
2.91
1.54
1.30
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
40
40
30
30
20
20
mass = 14.8 mg
mass = 22.7 mg
T1 = 2.14 d
T1 = 37.1 d
0
0.1
1
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
10
T2 (d)
T2 (d)
Nuclide
10
Activity
(pCi/L)
0.21
0.19
26.89
0.51
0.02
16.09
10.88
Error
(pCi/L)
0.04
0.04
1.23
0.42
0.06
1.10
1.23
nd
50
Gross radium for 2 prep (pCi/L)
50
st
Gross radium for 1 prep (pCi/L)
60
10
10
10
5
5
0
1
10
0.1
1
10
T2 (d)
Activity
(pCi/L)
0.09
0.13
1.41
-0.18
0.03
4.99
7.47
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
60
1
15
Nuclide
70
0
0.1
15
Error
(pCi/L)
0.85
2.48
0.29
0.48
0.25
0.40
0.34
70
10
20
T2 (d)
Figure 9.15. GRA plot for sample 14
(RQ091722)
25
20
0
0.1
10
T2 (d)
T2 (d)
T1 = 37.0 d
Error
(pCi/L)
0.03
0.04
0.18
0.39
0.05
0.59
1.74
Figure 9.17. GRA plot for sample 16
(RQ091724)
Q
20
mass = 12.7 mg
mass = 25.7 mg
T1 = 2.02 d
T1 = 37.0 d
20
15
15
10
10
5
5
nd
1
2
T1 = 2.01 d
st
0
0.1
mass = 23.9 mg
Gross radium for 1 prep (pCi/L)
2
25
mass = 16.2 mg
nd
4
st
4
Gross radium for 1 prep (pCi/L)
6
nd
6
Gross radium for 2 prep (pCi/L)
8
st
Gross radium for 1 prep (pCi/L)
8
mass = 15.2 mg
Gross radium for 2 prep (pCi/L)
30
30
Gross radium for 2 prep (pCi/L)
10
0
0.1
0
1
10
0.1
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
10
T2 (d)
T2 (d)
Nuclide
1
Activity
(pCi/L)
0.07
0.12
1.30
−0.07
0.11
6.03
5.92
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Error
(pCi/L)
0.02
0.03
0.17
0.34
0.05
0.67
1.34
Chapter 9: The Gross Radium Activity of the Groundwater Samples | 141
Figure 9.18. GRA plot for sample 17
(RQ091725)
Figure 9.20. GRA plot for sample 19
(RQ091751)
Q
15
6
6
3
3
0
10
0.1
1
Activity
(pCi/L)
0.010
0.12
4.03
−0.05
0.03
2.57
2.99
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
20
20
10
T1 = 1.08 d
0
0.01
10
0.1
0
1
10
0.1
T2 (d)
Error
(pCi/L)
0.008
0.02
0.29
0.34
0.05
0.45
0.48
Activity
(pCi/L)
0.27
1.53
4.50
-0.02
0.29
12.38
12.21
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
12
0.8
6
6
4
4
mass = 22.1 mg
2
T1 = 2.08 d
0
0.1
0
1
10
0.1
1
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
0.6
T1 = 37.1 d
Activity
(pCi/L)
0.07
0.35
3.94
0.43
-0.04
2.62
2.26
Error
(pCi/L)
0.02
0.04
0.28
0.35
0.05
0.46
0.39
0.6
0.4
0.4
0.2
0.2
0.0
0.0
-0.2
-0.2
mass = 18.9 mg
-0.4
0.1
-0.4
T1 = 2.09 d
1
10
1
T2 (d)
T2 (d)
T2 (d)
Nuclide
10
st
8
nd
10
Gross radium for 1 prep (pCi/L)
mass = 17.9 mg
8
2
Error
(pCi/L)
0.03
0.09
0.31
0.34
0.06
0.95
1.96
0.8
Gross radium for 2 prep (pCi/L)
st
Gross radium for 1 prep (pCi/L)
T1 = 37.1 d
10
Figure 9.21. GRA plot for sample 20
(RQ091992)
mass = 24.2 mg
10
1
T2 (d)
Nuclide
Figure 9.19. GRA plot for sample 18
(RQ091726)
12
10
mass = 18.8 mg
T2 (d)
T2 (d)
Nuclide
30
Nuclide
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
10
T2 (d)
Activity
(pCi/L)
0.00
0.01
0.14
0.35
1.91
−0.07
−0.01
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Error
(pCi/L)
0.01
0.01
0.05
0.39
0.24
0.35
0.08
nd
1
30
Gross radium for 2 prep (pCi/L)
0
0.1
40
nd
9
nd
9
T1 = 36.1 d
40
Gross radium for 2 prep (pCi/L)
12
st
T1 = 37.1 d
mass = 21.6 mg
Gross radium for 1 prep (pCi/L)
T1 = 2.08 d
50
50
Gross radium for 2 prep (pCi/L)
12
mass = 16.2 mg
mass = 20.2 mg
st
Gross radium for 1 prep (pCi/L)
15
142 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
5
4
4
3
3
2
2
1
1
0
0.1
10
1
10
T2 (d)
Nuclide
T1 = 37.1 d
5
0
1
10
1
T2 (d)
Nuclide
Error
(pCi/L)
0.62
0.88
0.07
0.39
0.18
0.43
0.75
10
T2 (d)
Activity
(pCi/L)
0.12
0.14
1.77
0.11
-0.01
6.00
6.79
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
Figure 9.23. GRA plot for sample 22
(RQ091994)
20
10
10
T2 (d)
Activity
(pCi/L)
13.21
19.21
0.31
0.21
-0.07
0.67
1.04
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
T1 = 2.02 d
15
0
0.1
0
1
20
mass = 21.0 mg
nd
T1 = 37.2 d
mass = 14.7 mg
st
T1 = 2.12 d
Gross radium for 1 prep (pCi/L)
mass = 28.8 mg
nd
5
mass = 22.3 mg
Gross radium for 2 prep (pCi/L)
st
25
6
6
Gross radium for 1 prep (pCi/L)
Figure 9.24. GRA plot for sample 23
(RQ091995)
Gross radium for 2 prep (pCi/L)
Figure 9.22. GRA plot for sample 21
(RQ091993)
Q
Error
(pCi/L)
0.02
0.02
0.17
0.40
0.20
0.69
1.28
Figure 9.25. GRA plot for sample 24
(RQ091996)
Q
3
2
2
nd
3
1
1
0
0.1
0
1
10
1
10
T2 (d)
Nuclide
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
T2 (d)
Activity
(pCi/L)
8.14
12.32
0.27
−0.21
0.17
0.47
0.97
Error
(pCi/L)
0.39
0.57
0.07
0.35
0.18
0.35
0.72
mass = 21.5 mg
T1 = 2.08 d
T1 = 37.1 d
25
20
20
15
10
10
5
0
0.1
0
1
10
1
T2 (d)
Nuclide
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
10
T2 (d)
Activity
(pCi/L)
0.15
0.58
6.25
1.62
0.46
6.07
4.99
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Error
(pCi/L)
0.03
0.06
0.38
0.55
0.29
0.70
0.68
nd
4
mass = 14.8 mg
st
T1 = 37.2 d
Gross radium for 1 prep (pCi/L)
T1 = 2.14 d
30
30
Gross radium for 2 prep (pCi/L)
mass = 25.7 mg
st
Gross radium for 1 prep (pCi/L)
4
mass = 21.6 mg
Gross radium for 2 prep (pCi/L)
5
5
Chapter 9: The Gross Radium Activity of the Groundwater Samples | 143
9
6
6
Gross radium for 1 prep (pCi/L)
9
3
0
0.1
mass = 17.7 mg
mass = 19.9 mg
T1 = 2.07 d
T1 = 37.1 d
3
10
1
Nuclide
20
15
15
10
10
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
mass = 28.1 mg
5
0
0.1
5
T1 = 2.10 d
0
1
T2 (d)
Activity
(pCi/L)
0.03
0.11
7.20
2.55
3.17
0.22
0.85
10
1
T2 (d)
Error
(pCi/L)
0.01
0.02
0.40
0.60
0.41
0.33
0.25
Nuclide
10
T2 (d)
Activity
(pCi/L)
0.32
3.19
6.42
0.13
0.00
4.23
6.88
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
Figure 9.27. GRA plot for sample 26
(RQ091998)
25
20
10
T2 (d)
30
T1 = 37.2 d
25
0
1
mass = 25.9 mg
30
st
st
nd
12
Gross radium for 2 prep (pCi/L)
12
35
35
nd
15
15
Gross radium for 1 prep (pCi/L)
Figure 9.28. GRA plot for sample 27
(RQ091999)
Gross radium for 2 prep (pCi/L)
Figure 9.26. GRA plot for sample 25
(RQ091997)
Error
(pCi/L)
0.04
0.19
0.39
0.34
0.17
0.60
1.57
Figure 9.29. GRA plot for sample 28
(RQ092000)
6
3
0
0.1
mass = 23.2 mg
mass = 28.1 mg
T1 = 2.13 d
T1 = 37.2 d
3
0
1
10
1
10
T2 (d)
Nuclide
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
T2 (d)
Activity
(pCi/L)
0.14
1.85
3.91
−0.02
0.11
2.32
2.51
Error
(pCi/L)
0.03
0.13
0.27
0.32
0.16
0.46
0.85
mass = 25.5 mg
25
25
T1 = 37.2 d
20
20
15
15
10
10
5
0
0.1
5
mass = 17.7 mg
T1 = 2.18 d
1
0
10
1
T2 (d)
T2 (d)
Nuclide
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
10
Activity
(pCi/L)
0.07
0.90
4.23
0.42
−0.20
6.39
7.86
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Error
(pCi/L)
0.01
0.06
0.29
0.40
0.20
0.72
1.36
nd
6
30
Gross radium for 2 prep (pCi/L)
9
st
9
Gross radium for 1 prep (pCi/L)
12
nd
12
30
Gross radium for 2 prep (pCi/L)
15
st
Gross radium for 1 prep (pCi/L)
Q
15
144 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
T1 = 37.3 d
30
25
25
20
20
15
15
10
10
mass = 25.8 mg
T1 = 2.24 d
1
10
1
1.0
1.0
0.5
0.5
0.0
Nuclide
T2 (d)
Error
(pCi/L)
0.45
0.49
0.06
0.31
0.25
0.32
0.86
Figure 9.33. GRA plot for sample 32
(RQ092251)
0.2
0.2
0.0
0.0
-0.2
1
st
0.4
Gross radium for 1 prep (pCi/L)
0.4
nd
0.8
T1 = 36.2 d
0.6
6
5
4
4
3
3
2
2
mass = 21.2 mg
T1 = 2.23 d
1
Error
(pCi/L)
0.008
0.013
0.070
0.42
0.39
0.31
0.14
1
0
0
1
10
0.1
T2 (d)
T2 (d)
Activity
(pCi/L)
0.010
0.022
0.080
0.40
4.11
0.01
0.08
5
T1 = 37.2 d
10
T2 (d)
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
10
6
Gross radium for 2 prep (pCi/L)
mass = 14.2 mg
0.6
Nuclide
1
mass = 13.3 mg
mass = 26.1 mg
T1 = 1.17 d
10
0.1
Activity
(pCi/L)
10.24
11.32
0.20
-0.09
0.13
0.40
1.07
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
1.0
1
0.0
10
T2 (d)
Error
(pCi/L)
0.02
0.09
0.44
0.38
0.20
0.83
1.44
1.0
st
1.5
1
Figure 9.31. GRA plot for sample 30
(RQ092029)
Gross radium for 1 prep (pCi/L)
1.5
10
Activity
(pCi/L)
0.09
1.54
7.93
−0.16
0.12
8.12
9.18
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
-0.2
0.1
2.0
T2 (d)
Nuclide
2.5
T1 = 37.2 d
2.0
0
T2 (d)
0.8
2.5
mass = 23.7 mg
Nuclide
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
1
10
T2 (d)
Activity
(pCi/L)
0.25
1.85
2.81
0.15
−0.04
0.18
1.30
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Error
(pCi/L)
0.04
0.12
0.22
0.33
0.26
0.32
0.29
nd
0
0.1
5
3.0
mass = 24.1 mg
T1 = 2.25 d
Gross radium for 2 prep (pCi/L)
5
st
30
3.0
Gross radium for 1 prep (pCi/L)
35
nd
mass = 21.9 mg
nd
40
35
Gross radium for 2 prep (pCi/L)
st
Gross radium for 1 prep (pCi/L)
40
Figure 9.32. GRA plot for sample 31
(RQ092250)
Q
Gross radium for 2 prep (pCi/L)
Figure 9.30. GRA plot for sample 29
(RQ092001)
Chapter 9: The Gross Radium Activity of the Groundwater Samples | 145
6
6
4
4
mass = 26.3 mg
T1 = 37.1 d
mass = 23.7 mg
T1 = 2.19 d
2
0
0
0.1
1
T2 (d)
Nuclide
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
3
2
2
1
1
0
0
1
10
T2 (d)
T2 (d)
Activity
(pCi/L)
8.84
8.66
0.12
0.00
0.10
0.29
1.56
Error
(pCi/L)
0.39
0.38
0.05
0.33
0.27
0.29
1.17
nd
4
3
0.1
1
10
T2 (d)
Error
(pCi/L)
0.37
0.35
0.07
0.35
0.29
0.29
3.83
Figure 9.37. GRA plot for sample 36
(RQ092255)
15
15
Gross radium for 2 prep (pCi/L)
st
Gross radium for 1 prep (pCi/L)
mass = 24.5 mg
T1 = 37.2 d
mass = 24.0 mg
T1 = 2.25 d
0.1
Activity
(pCi/L)
7.62
7.98
0.14
0.07
0.05
0.21
4.83
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
5
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
0
10
Nuclide
Error
(pCi/L)
0.02
0.04
0.44
0.37
0.30
0.32
0.43
5
Nuclide
3
T2 (d)
6
10
3
T2 (d)
6
1
6
1
Figure 9.35. GRA plot for sample 34
(RQ092253)
4
6
0
10
Activity
(pCi/L)
0.12
0.54
7.74
0.29
−0.20
0.60
1.75
9
mass = 19.1 mg
T1 = 37.2 d
mass = 25.6 mg
T1 = 2.22 d
12
12
9
9
6
6
3
3
st
10
Gross radium for 1 prep (pCi/L)
1
9
nd
2
12
mass = 24.7 mg
T1 = 37.1 d
mass = 24.5 mg
T1 = 2.15 d
nd
8
12
Gross radium for 2 prep (pCi/L)
8
15
Gross radium for 2 prep (pCi/L)
10
15
st
10
Figure 9.36. GRA plot for sample 35
(RQ092254)
Q
Gross radium for 1 prep (pCi/L)
12
nd
14
12
Gross radium for 2 prep (pCi/L)
14
st
Gross radium for 1 prep (pCi/L)
Figure 9.34. GRA plot for sample 33
(RQ092252)
0
0
1
10
0.1
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
10
T2 (d)
T2 (d)
Nuclide
1
Activity
(pCi/L)
0.04
0.25
2.95
0.14
-0.05
2.01
7.04
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Error
(pCi/L)
0.01
0.03
0.23
0.35
0.28
0.45
1.00
146 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
6
6
3
3
10
0.1
1
T2 (d)
Nuclide
nd
st
3
3
0
0
0.1
1
10
T2 (d)
Activity
(pCi/L)
95.72
139.94
1.51
3.40
5.72
2.22
4.72
Error
(pCi/L)
4.12
5.93
0.16
0.63
0.83
0.46
3.47
1
10
T2 (d)
Error
(pCi/L)
0.02
0.02
0.29
0.37
0.35
0.27
0.57
st
Figure 9.41. GRA plot for sample 40
(RQ092847)
1.2
1.2
0.9
0.9
0.6
0.6
0.3
0.3
st
12
6
T2 (d)
0.1
Activity
(pCi/L)
0.05
0.07
4.42
0.48
−0.18
0.22
4.31
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
9
6
10
Nuclide
Gross radium for 1 prep (pCi/L)
9
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
0
1
T2 (d)
Gross radium for 2 prep (pCi/L)
mass = 14.3 mg
T1 = 37.2 d
mass = 16.5 mg
T1 = 2.27 d
Nuclide
2
mass = 12.4 mg
T1 = 37.1 d
0.1
15
10
2
Error
(pCi/L)
0.95
1.45
0.11
0.72
1.91
0.36
3.00
15
1
4
10
Figure 9.39. GRA plot for sample 38
(RQ092257)
12
4
T2 (d)
Activity
(pCi/L)
21.86
34.26
0.74
4.60
27.40
0.72
3.72
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
6
nd
1
6
0
0
0
8
nd
9
nd
9
8
Gross radium for 2 prep (pCi/L)
12
Gross radium for 1 prep (pCi/L)
mass = 14.8 mg
T1 = 2.25 d
12
st
Gross radium for 1 prep (pCi/L)
mass = 12.7 mg
T1 = 37.2 d
Gross radium for 2 prep (pCi/L)
15
15
Gross radium for 1 prep (pCi/L)
Figure 9.40. GRA plot for sample 39
(RQ092258)
Gross radium for 2 prep (pCi/L)
Figure 9.38. GRA for plot sample 37
(RQ092256)
0.0
0.0
mass = 15.3 mg
T1 = 37.1 d
mass = 16.0 mg
T1 = 2.02 d
-0.3
-0.6
0.1
-0.3
-0.6
1
10
0.1
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
10
T2 (d)
T2 (d)
Nuclide
1
Activity
(pCi/L)
8.97
10.99
0.08
3.70
0.89
0.18
0.12
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Error
(pCi/L)
0.43
0.52
0.05
0.69
0.98
0.28
0.12
Chapter 9: The Gross Radium Activity of the Groundwater Samples | 147
Figure 9.44. GRA plot for sample 43
(RQ092850)
0.0
0.0
-0.3
mass = 21.1 mg
T1 = 37.0 d
mass = 21.2 mg
T1 = 1.95 d
-0.3
-0.6
-0.6
0.1
1
10
0.1
1
Nuclide
Activity
(pCi/L)
22.67
27.88
0.11
0.49
0.70
0.63
0.23
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
4
4
2
2
0
1
T2 (d)
Nuclide
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
10
T2 (d)
Activity
(pCi/L)
3.67
15.48
2.23
0.72
8.03
1.62
2.57
0.0
-0.5
-0.5
-1.0
1
10
0.1
1
Error
(pCi/L)
0.22
0.78
0.20
0.45
0.90
0.42
0.58
10
T2 (d)
Activity
(pCi/L)
3.89
4.58
0.11
0.53
2.66
0.48
0.19
Error
(pCi/L)
0.23
0.26
0.07
0.45
0.70
0.33
0.16
Figure 9.45. GRA plot for sample 44
(RQ092851)
1.4
st
Gross radium for 1 prep (pCi/L)
6
nd
10
6
0.1
0.0
1.4
mass = 25.2 mg
T1 = 37.2 d
mass = 15.3 mg
T1 = 2.20 d
1.2
Gross radium for 2 prep (pCi/L)
st
Gross radium for 1 prep (pCi/L)
mass = 13.4 mg
T1 = 37.2 d
8
10
0.5
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
8
1
0.5
Nuclide
12
0
0.1
1.0
Error
(pCi/L)
0.99
1.20
0.06
0.47
0.62
0.34
0.19
12
10
1.0
T2 (d)
Figure 9.43. GRA plot for sample 42
(RQ092849)
mass = 15.5 mg
T1 = 2.12 d
1.5
-1.0
0.1
10
T2 (d)
T2 (d)
1.5
nd
0.3
2.0
Gross radium for 2 prep (pCi/L)
0.3
2.0
mass = 24.8 mg
T1 = 37.2 d
1.0
1.2
1.0
0.8
0.8
0.6
0.6
0.4
0.4
0.2
0.2
0.0
0.0
-0.2
-0.2
-0.4
0.1
-0.4
1
10
0.1
T2 (d)
Nuclide
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
1
10
T2 (d)
Activity
(pCi/L)
3.14
4.25
0.07
-0.03
0.25
0.01
0.18
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Error
(pCi/L)
0.19
0.24
0.07
0.42
0.59
0.26
0.16
nd
0.6
2.5
mass = 14.5 mg
T1 = 2.18 d
st
0.6
Gross radium for 1 prep (pCi/L)
0.9
nd
0.9
Gross radium for 2 prep (pCi/L)
1.2
st
Gross radium for 1 prep (pCi/L)
2.5
1.2
Gross radium for 2 prep (pCi/L)
Figure 9.42. GRA plot for sample 41
(RQ092848)
148 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
Figure 9.48. GRA plot for sample 47
(RQ092854)
Q
1.6
1.2
1.2
0.8
0.8
0.4
0.4
0.0
0.1
10
0.1
1
Nuclide
10
5
5
0
0.1
20
15
15
10
10
mass = 17.7 mg
T1 = 37.0 d
5
0
0.1
1
Nuclide
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
10
T2 (d)
Activity
(pCi/L)
117.91
169.72
10.65
14.39
4.39
2.56
6.15
Error
(pCi/L)
5.12
7.27
0.56
1.45
2.50
0.46
0.82
10
T2 (d)
Error
(pCi/L)
0.01
0.02
0.09
0.41
0.59
0.42
3.72
5
st
20
10
1
Figure 9.49. GRA plot for sample 48
(RQ092855)
Gross radium for 1 prep (pCi/L)
25
nd
25
Gross radium for 2 prep (pCi/L)
30
st
30
T2 (d)
0.1
Activity
(pCi/L)
0.07
0.09
0.57
0.35
0.53
1.86
4.91
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
35
mass = 14.2 mg
T1 = 1.94 d
10
Nuclide
Error
(pCi/L)
5.00
6.43
0.07
0.44
0.65
0.31
0.31
35
1
0
1
T2 (d)
Figure 9.47. GRA plot for sample 46
(RQ092853)
Q
Gross radium for 1 prep (pCi/L)
10
10
Activity
(pCi/L)
115.00
149.38
0.35
0.53
1.86
0.21
0.40
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
0
0.1
15
T2 (d)
T2 (d)
5
15
0.0
1
20
nd
2.0
1.6
20
5
mass = 25.2 mg
T1 = 37.2 d
mass = 25.3 mg
T1 = 2.18 d
4
4
3
3
2
2
1
1
0
0
-1
0.1
-1
1
10
0.1
T2 (d)
Nuclide
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
1
10
T2 (d)
Activity
(pCi/L)
13.61
22.50
0.48
0.05
0.01
0.34
0.65
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Error
(pCi/L)
0.59
0.95
0.11
0.36
0.51
0.37
0.50
nd
2.0
nd
2.4
mass = 21.3 mg
T1 = 37.3 d
mass = 26.5 mg
T1 = 2.29 d
st
2.8
2.4
Gross radium for 1 prep (pCi/L)
3.2
Gross radium for 2 prep (pCi/L)
2.8
mass = 25.1 mg
T1 = 36.9 d
st
Gross radium for 1 prep (pCi/L)
mass = 17.2 mg
T1 = 1.91 d
Gross radium for 2 prep (pCi/L)
25
25
3.2
Gross radium for 2 prep (pCi/L)
Figure 9.46. GRA plot for sample 45
(RQ092852)
Chapter 9: The Gross Radium Activity of the Groundwater Samples | 149
0
0
mass = 22.3 mg
T1 = 2.16 d
10
0.1
1
T2 (d)
10
2
2
1
1
0
mass = 19.2 mg
T1 = 44.2 1
mass = 15.3 mg
T1 = 2.14 d
-1
10
0.1
1
T2 (d)
10
T2 (d)
Activity
(pCi/L)
14.94
20.39
0.33
0.29
−0.22
0.75
0.48
Error
(pCi/L)
0.65
0.87
0.09
0.96
0.94
0.32
0.39
nd
3
0
mass = 14.3 mg
T1 = 44.1
nd
0
1
10
0.1
1
10
T2 (d)
Activity
(pCi/L)
0.07
0.17
6.29
0.34
0.35
1.50
2.34
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
Gross radium for 2 prep (pCi/L)
st
Gross radium for 1 prep (pCi/L)
mass = 17.4 mg
T1 = 2.18 d
Nuclide
3
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
4
4
Error
(pCi/L)
0.57
0.74
0.07
0.42
0.59
0.30
0.35
Figure 9.51. GRA plot for sample 50
(RQ093078)
Q
Nuclide
8
T2 (d)
Error
(pCi/L)
0.03
0.06
0.38
0.65
0.56
0.37
1.10
Figure 9.53. GRA plot for sample 52
(RQ093080)
Q
12
12
st
Activity
(pCi/L)
12.05
15.82
0.23
-0.10
0.27
−0.09
0.43
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
1
8
T2 (d)
Nuclide
-1
0.1
12
0
0.1
-1
1
Gross radium for 1 prep (pCi/L)
-1
0.1
mass = 23.6 mg
T1 = 37.2 d
12
Gross radium for 2 prep (pCi/L)
1
16
mass = 17.7 mg
T1 = 44.2
mass = 17.2 mg
T1 = 2.27 d
9
9
6
6
3
3
0
0.1
0
1
10
0.1
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
10
T2 (d)
T2 (d)
Nuclide
1
Activity
(pCi/L)
0.09
1.79
0.99
0.55
-0.44
2.14
3.16
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Error
(pCi/L)
0.02
0.12
0.14
0.64
0.63
0.48
0.89
nd
1
16
Gross radium for 2 prep (pCi/L)
2
st
2
Figure 9.52. GRA plot for sample 51
(RQ093079)
Gross radium for 1 prep (pCi/L)
3
nd
3
Gross radium for 2 prep (pCi/L)
st
Gross radium for 1 prep (pCi/L)
Figure 9.50. GRA plot for sample 49
(RQ092856)
Q
150 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
Figure 9.56. GRA plot for sample 55
(RR093083)
36
20
20
10
0.1
1
T2 (d)
Nuclide
20
16
16
12
12
8
8
4
4
0
0.1
0
0.1
1
T2 (d)
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
10
T2 (d)
Activity
(pCi/L)
0.22
3.42
7.51
0.60
−0.53
27.45
32.85
Error
(pCi/L)
0.04
0.23
0.44
0.60
0.59
1.64
3.45
nd
28
20
Nuclide
8
4
4
nd
12
8
0
1
10
0.1
1
10
T2 (d)
Activity
(pCi/L)
0.03
0.35
5.26
0.37
-0.34
6.35
9.21
Error
(pCi/L)
0.01
0.04
0.34
0.49
0.52
0.70
1.73
Figure 9.57. GRA plot for sample 56
(RR093084)
Q
40
40
Gross radium for 2 prep (pCi/L)
st
Gross radium for 1 prep (pCi/L)
32
24
10
12
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
24
1
16
Nuclide
36
mass = 20.5 mg
T1 = 44.2
mass = 24.5 mg
T1 = 2.20 d
28
20
16
T2 (d)
Figure 9.55. GRA plot for sample 54
(RR093082)
32
24
Error
(pCi/L)
0.044
0.23
0.44
0.60
0.59
1.64
3.45
36
28
20
T2 (d)
Activity
(pCi/L)
0.22
3.42
7.51
0.60
−0.53
27.45
32.85
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
10
st
1
32
24
0
0.1
0
Gross radium for 1 prep (pCi/L)
0
0.1
28
mass = 24.6 mg
T1 = 44.1
mass = 21.1 mg
T1 = 2.14 d
35
35
30
30
25
25
20
20
15
15
10
10
5
5
0
0.1
0
1
10
0.1
T2 (d)
Nuclide
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
1
10
T2 (d)
Activity
(pCi/L)
0.08
0.35
4.61
0.31
−0.30
7.77
10.17
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Error
(pCi/L)
0.02
0.04
0.31
0.43
0.46
0.77
2.36
nd
40
40
st
nd
60
60
Gross radium for 1 prep (pCi/L)
80
80
36
mass = 25.0 mg
T1 = 44.1
mass = 21.4 mg
T1 = 2.17 d
32
Gross radium for 2 prep (pCi/L)
100
Gross radium for 2 prep (pCi/L)
st
Gross radium for 1 prep (pCi/L)
mass = 17.6 mg
T1 = 44.3
mass = 17.7 mg
T1 = 2.28 d
100
Gross radium for 2 prep (pCi/L)
Figure 9.54. GRA plot for sample 53
(RQ093081)
Chapter 9: The Gross Radium Activity of the Groundwater Samples | 151
3
10
0.1
1
Activity
(pCi/L)
0.08
0.76
2.71
0.30
−0.27
2.28
3.48
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
2.0
1.5
1.5
1.0
1.0
0.5
0.5
0.0
0.1
1
T2 (d)
10
T2 (d)
Activity
(pCi/L)
12.97
14.93
0.14
0.27
0.17
0.19
0.19
Error
(pCi/L)
0.57
0.65
0.08
0.3
0.38
0.30
0.16
st
2.0
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
0.5
0.5
0.0
1
10
0.1
1
10
T2 (d)
Activity
(pCi/L)
10.22
15.68
0.15
−0.15
0.22
0.19
0.30
Error
(pCi/L)
0.45
0.67
0.06
0.3
0.37
0.32
0.22
Figure 9.61. GRA plot for sample 60
(RR093375)
Gross radium for 1 prep (pCi/L)
mass = 16.0 mg
T1 = 38.2
nd
2.5
T1 = 2.18 d
Nuclide
1.0
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
Gross radium for 2 prep (pCi/L)
mass = 15.5 mg
10
1.0
Nuclide
3.0
1
1.5
Error
(pCi/L)
0.02
0.06
0.23
0.49
0.52
0.54
0.90
3.0
0.0
0.1
1.5
T2 (d)
Figure 9.59. GRA plot for sample 58
(RR093373)
2.5
2.0
T2 (d)
T2 (d)
Nuclide
10
2.5
2.0
0.0
0.1
0
1
T1 = 2.19 d
nd
3
2.5
Gross radium for 2 prep (pCi/L)
6
3.0
mass = 20.8 mg
T1 = 38.2
mass = 19.6 mg
8
10
7
9
8
6
7
5
6
4
5
3
4
3
2
mass = 19.9 mg
T1 = 38.2
mass = 17.1 mg
1
T1 = 2.14 d
0
0.1
2
1
0
1
10
0.1
T2 (d)
Nuclide
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
1
10
T2 (d)
Activity
(pCi/L)
2.02
3.15
4.11
0.24
0.22
0.40
0.86
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Error
(pCi/L)
0.11
0.16
0.30
0.33
0.41
0.34
0.22
nd
6
st
9
nd
9
Gross radium for 1 prep (pCi/L)
12
Gross radium for 2 prep (pCi/L)
12
st
Gross radium for 1 prep (pCi/L)
mass = 26.4 mg
T1 = 44.2
mass = 14.8 mg
T1 = 2.24 d
0
0.1
st
3.0
15
15
Gross radium for 1 prep (pCi/L)
Figure 9.60. GRA plot for sample 59
(RR093374)
Gross radium for 2 prep (pCi/L)
Figure 9.58. GRA plot for sample 57
(RR093085)
Q
152 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
1.0
1.0
0.5
0.5
0.0
0.0
-0.5
0.1
10
0.1
1
Activity
(pCi/L)
13.00
19.23
0.09
0.14
−0.03
0.10
0.44
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
10
mass = 18.3 mg
T1 = 2.10 d
0
0.1
1
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
10
T2 (d)
T2 (d)
Nuclide
5
5
0
1
Activity
(pCi/L)
0.01
0.05
13.97
0.29
-0.03
0.66
9.06
10
0.1
Error
(pCi/L)
0.01
0.01
0.72
0.27
0.34
0.36
1.40
1
10
T2 (d)
Activity
(pCi/L)
0.02
0.03
3.76
0.16
−0.18
7.95
7.72
Error
(pCi/L)
0.01
0.02
0.28
0.31
0.39
0.80
1.54
Figure 9.65. GRA plot for sample 64
(RR093660)
6
6
st
Gross radium for 1 prep (pCi/L)
nd
20
Gross radium for 2 prep (pCi/L)
20
st
Gross radium for 1 prep (pCi/L)
40
30
10
10
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
30
1
10
Nuclide
50
mass = 17.0 mg
T1 = 38.2
0
0.1
15
Error
(pCi/L)
0.56
0.81
0.07
0.32
0.40
0.30
0.32
50
10
15
T2 (d)
Figure 9.63. GRA plot for sample 62
(RR093377)
40
20
T2 (d)
T2 (d)
Nuclide
10
25
20
0
0.1
-0.5
1
25
mass = 16.5 mg
T1 = 38.2
nd
1.5
30
mass = 20.0 mg
T1 = 2.17 d
Gross radium for 2 prep (pCi/L)
1.5
st
2.0
Gross radium for 1 prep (pCi/L)
T1 = 2.17 d
nd
2.0
mass = 19.8 mg
T1 = 38.2
Gross radium for 2 prep (pCi/L)
st
Gross radium for 1 prep (pCi/L)
30
2.5
mass = 20.7 mg
mass = 17.2 mg
T1 = 268 d
5
5
4
4
3
3
2
2
1
1 mass = 24.0 mg
0
0.1
T1 = 2.22 d
1
0
10
0.1
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
10
T2 (d)
T2 (d)
Nuclide
1
Activity
(pCi/L)
11.05
36.77
1.19
1.02
1.32
1.17
1.14
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Error
(pCi/L)
0.56
1.68
0.24
0.38
0.38
0.55
0.45
nd
2.5
Figure 9.64. GRA plot for sample 63
(RR093378)
Gross radium for 2 prep (pCi/L)
Figure 9.62. GRA plot for sample 61
(RR093376)
Chapter 9: The Gross Radium Activity of the Groundwater Samples | 153
1.0
1.0
0.5
0.5
st
st
10
0.1
1
8
8
4
4
0
0.1
10
12
12
8
8
Gross radium for 2 prep (pCi/L)
16
st
10
mass = 25.9 mg
T1 = 268 d
4
0
0.1
1
10
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
10
Activity
(pCi/L)
0.05
0.23
3.54
−0.01
0.08
7.17
6.73
Error
(pCi/L)
0.02
0.04
0.28
0.34
0.31
0.77
1.20
10
10
8
8
6
6
4
4
2
mass = 17.7 mg
T1 = 3.20 d
0
0.1
mass = 24.1 mg
T1 = 268 d
10
0.1
T2 (d)
1
10
T2 (d)
T2 (d)
Activity
(pCi/L)
0.50
1.24
9.52
0.54
0.07
2.96
2.39
Error
(pCi/L)
0.04
0.08
0.53
0.40
0.37
0.50
0.49
2
0
1
Nuclide
Nuclide
1
Figure 9.69. GRA plot for sample 68
(RR093664)
nd
16
T2 (d)
0.1
T2 (d)
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
20
mass = 23.2 mg
T1 = 3.03 d
10
Nuclide
Error
(pCi/L)
0.02
0.04
0.12
0.30
0.27
0.54
0.18
20
1
0
1
T2 (d)
Figure 9.67. GRA plot for sample 66
(RR093662)
Gross radium for 1 prep (pCi/L)
12
nd
Activity
(pCi/L)
0.07
0.11
0.34
−0.23
0.24
0.14
0.13
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
0
0.1
12
st
Nuclide
4
16
T2 (d)
T2 (d)
20
16
0.0
1
Gross radium for 1 prep (pCi/L)
0.0
0.1
20
Gross radium for 2 prep (pCi/L)
1.5
nd
1.5
mass = 22.7 mg
T1 = 268 d
mass = 24.1 mg
T1 = 3.09 d
nd
2.0
Gross radium for 1 prep (pCi/L)
T1 = 3.33 d
2.0
Gross radium for 2 prep (pCi/L)
mass = 22.9 mg
T1 = 268 d
mass = 26.9 mg
24
24
2.5
2.5
Gross radium for 1 prep (pCi/L)
Figure 9.68. GRA plot for sample 67
(RR093663)
Gross radium for 2 prep (pCi/L)
Figure 9.66. GRA plot for sample 65
(RR093661)
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
Activity
(pCi/L)
1.66
2.91
4.62
0.07
-0.02
0.27
0.97
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Error
(pCi/L)
0.11
0.16
0.33
0.35
0.32
0.33
0.37
154 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
8
4
4
mass = 26.8 mg
T1 = 2.18 d
0
0.1
10
0.1
1
16
12
12
8
8
mass = 27.1 mg
T1 = 2.21 d
4
Activity
(pCi/L)
0.08
1.05
3.65
0.10
−0.05
5.02
4.11
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
1
10
0.1
Activity
(pCi/L)
0.15
2.76
5.72
0.47
−0.28
2.74
4.59
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
6
6
12
8
8
mass = 25.3 mg
4
4
T1 = 2.18 d
0
0.1
0
1
10
0.1
1
T2 (d)
Nuclide
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
10
T2 (d)
Activity
(pCi/L)
0.20
3.11
6.92
0.18
−0.06
4.11
4.53
Error
(pCi/L)
0.02
0.15
0.42
0.42
0.42
0.63
0.74
st
12
Gross radium for 1 prep (pCi/L)
16
nd
16
Gross radium for 2 prep (pCi/L)
20
Error
(pCi/L)
0.02
0.14
0.38
0.42
0.37
0.56
0.75
Figure 9.73. GRA plot for sample 72
(RS095393)
24
mass = 14.3 mg
T1 = 84 d
10
T2 (d)
Nuclide
Figure 9.71. GRA plot for sample 70
(RS095391)
20
1
T2 (d)
Error
(pCi/L)
0.03
0.10
0.26
0.39
0.39
0.74
0.63
24
4
0
0
0.1
10
T2 (d)
Nuclide
20
16
0
1
T2 (d)
st
20
nd
8
mass = 12.6 mg
T1 = 84 d
mass = 11.7 mg
T1 = 84 d
5
5
4
4
3
3
2
2
1
1 mass = 15.7 mg
0
T1 = 2.22 d
0.1
1
0
10
0.1
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
10
T2 (d)
T2 (d)
Nuclide
1
Activity
(pCi/L)
0.02
0.04
1.09
0.38
-0.17
1.62
0.61
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Error
(pCi/L)
0.01
0.01
0.13
0.52
0.52
0.55
0.40
nd
12
nd
12
st
16
Gross radium for 1 prep (pCi/L)
Gross radium for 2 prep (pCi/L)
16
24
24
st
Gross radium for 1 prep (pCi/L)
mass = 14.2 mg
T1 = 84 d
Gross radium for 2 prep (pCi/L)
20
20
Gross radium for 1 prep (pCi/L)
Figure 9.72. GRA plot for sample 71
(RS095392)
Gross radium for 2 prep (pCi/L)
Figure 9.70. GRA plot for sample 69
(RS095390)
Chapter 9: The Gross Radium Activity of the Groundwater Samples | 155
2
2
1
1
0
10
0.1
1
Activity
(pCi/L)
0.22
0.29
0.11
0.32
55.57
1.00
0.18
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
nd
4
4
mass = 24.6 mg
T1 = 2.63 d
mass = 23.5 mg
T1 = 84 d
2
0
10
0.1
1
10
T2 (d)
T2 (d)
Activity
(pCi/L)
6.67
6.06
7.07
0.87
−0.50
0.59
0.67
Error
(pCi/L)
0.30
0.27
0.40
0.44
0.45
0.39
0.28
0.1
1
10
T2 (d)
Activity
(pCi/L)
28.18
36.94
0.28
4.17
3.14
1.11
0.04
Error
(pCi/L)
1.22
1.58
0.08
0.63
0.69
0.45
0.08
Figure 9.77. GRA plot for sample 76
(RS095397)
3.5
3.5
Gross radium for 2 prep (pCi/L)
st
Gross radium for 1 prep (pCi/L)
6
6
10
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
8
8
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
0
1
Nuclide
10
Nuclide
1
Error
(pCi/L)
0.02
0.03
0.05
0.41
3.32
0.44
0.17
10
1
1
T2 (d)
Figure 9.75. GRA plot for sample 74
(RS095395)
0.1
2
0.1
st
Nuclide
0
2
T2 (d)
T2 (d)
2
3
10
Gross radium for 1 prep (pCi/L)
1
3
0
0
0.1
4
nd
3
4
mass = 10.7 mg
T1 = 83 d
3.0
mass = 15.3 mg
T1 = 3.14 d
mass = 12.1 mg
T1 = 84 d
3.0
2.5
2.5
2.0
2.0
1.5
1.5
1.0
1.0
0.5
0.5
0.0
0.0
-0.5
-0.5
0.1
1
10
0.1
T2 (d)
Nuclide
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
1
10
T2 (d)
Activity
(pCi/L)
5.55
9.12
0.09
0.32
−0.03
0.17
0.13
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Error
(pCi/L)
0.25
0.40
0.07
0.42
0.37
0.31
0.19
nd
3
mass = 16.1 mg
T1 = 1.14 d
st
4
nd
5
4
5
5
Gross radium for 1 prep (pCi/L)
mass = 11.1 mg
T1 = 83 d
Gross radium for 2 prep (pCi/L)
6
mass = 26.1 mg
5 T = 1.21 d
1
Gross radium for 2 prep (pCi/L)
st
Gross radium for 1 prep (pCi/L)
6
Figure 9.76. GRA plot for sample 75
(RS095396)
Gross radium for 2 prep (pCi/L)
Figure 9.74. GRA plot for sample 73
(RS095394)
156 Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
Figure 9.80. GRA plot for sample 79
(RS095400)
24
8
8
6
6
4
4
2
2
1
10
0.1
1
Nuclide
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
Activity
(pCi/L)
0.92
3.15
1.85
0.03
0.36
1.05
3.61
12
12
8
8
4
4
0
1
10
Nuclide
Error
(pCi/L)
0.06
0.16
0.21
0.45
0.40
0.42
0.86
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
Activity
(pCi/L)
27.08
35.07
6.46
0.77
−0.09
3.85
7.78
10
8
8
6
6
4
4
2
2
nd
st
Gross radium for 1 prep (pCi/L)
10
mass = 12.1 mg
T1 = 81 d
Gross radium for 2 prep (pCi/L)
12
12
0
0
0.1
1
10
0.1
1
T2 (d)
Nuclide
U-238
U-234
Ra-226
Pb-210
Po-210
Ra-228
Ra-224
10
T2 (d)
Activity
(pCi/L)
11.81
18.12
4.58
0.06
0.342
1.79
2.80
1
10
T2 (d)
Figure 9.79. GRA plot for sample 78
(RS095399)
mass = 17.4 mg
T1 = 4.24 d
0.1
T2 (d)
T2 (d)
T2 (d)
16
0.1
10
20
16
0
0
0.1
20
mass = 11.7 mg
T1 = 81 d
Error
(pCi/L)
0.54
0.80
0.31
0.40
0.36
0.44
0.72
156
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Error
(pCi/L)
1.18
1.51
0.39
0.40
0.40
0.55
1.27
nd
10
st
12
10
0
24
mass = 19.3 mg
T1 = 4.27 d
14
Gross radium for 1 prep (pCi/L)
12
mass = 13.9 mg
T1 = 84 d
nd
mass = 22.4 mg
T1 = 2.93 d
Gross radium for 2 prep (pCi/L)
st
Gross radium for 1 prep (pCi/L)
14
Gross radium for 2 prep (pCi/L)
Figure 9.78. GRA plot for sample 77
(RS095398)
CHAPTER 10
METHODOLOGY ISSUES AND RECOMMENDATIONS
INTRODUCTION
Before beginning with methodology issues and recommendations, some fundamental definitions are reiterated. Much of this work is devoted to an analysis of EPA Method 900.0, which
is an evaporation method. In an evaporation method, a volume of sample is evaporated to dryness, and the residue is placed in a planchet. The residue contains the non-volatile radionuclides
of the sample. Some of this work was devoted to an analysis of EPA Method 900.1, which is a
coprecipitation method that attempts to quantify the alpha-emitting radium isotopes. In a coprecipitation method, some or most of the radionuclides of the sample are coprecipitated with barium sulfate, for EPA Method 900.1, or a mixture of barium sulfate, ferric hydroxide, and wood
pulp, as a binder, for Standard Methods 7110C, a method used for GAA analysis.
In an evaporation method, it can be difficult to control the geometry of the sample residue. At one extreme, the residues may be of uniform thickness across the planchet; at the other
extreme, the residues may consist of relatively thick patches that cover less than one-half of the
planchet. A residue that consists of patches that cover 38% of the planchet is called a patch residue. Some residues completely cover the planchet but are not of uniform thickness. They vary
slightly in thickness from one point to another. These residues are called smooth residues. The
uniform, smooth, and patch residues are given rigorous mathematical definitions in Appendix E.
For evaporation methods, like EPA Method 900.0, or a coprecipitation methods, like
Standard Methods 7110C, there are three important points in time in that affect a sample’s GAA:
(1) the sample collection time, (2) the sample preparation time, and (3) the sample analysis time,
which is the time at which the alpha-particle emission rate of the residue is measured. For evaporation methods, the preparation time is the time at which the residue is heated over a flame; for
coprecipitation methods, the sample preparation is the time at which the precipitate forms. For
both methods, radon is quantitatively lost from the sample at the preparation time.
Frequently, a parent produces short-lived, alpha-emitting progeny, and if the parent were
not present, then the short-lived progeny would rapidly decay away. Thus, the progeny activities
often depend on the parent activity, and it is useful to group the parent and its progeny together
into a unit called a decay chain. If the parent activity is known at some initial time, then the
progeny activities that it produces at some latter time can be calculated using the Bateman equations. In this work, the initial time was always taken to be the sample collection time. Table 4.1
and Table 4.2 give the decay chains of the 238U and 232Th decay series that were used in this
work. A decay chain is named after the parent. For example, the decay chain that has 226Ra as the
parent is called the 226Ra decay chain.
PROBLEMS WITH ANALYZING RADIUM-CONTAINING SAMPLES
Samples that contain any one of radium isotopes 226Ra, 228Ra or 224Ra often contain significant amounts of both 226Ra and 228Ra and a significant amount of unsupported 224Ra at the
time of sample collection. The production of alpha emitters by the 224Ra, 226Ra, and 228Ra decay
chains can cause a sample’s GAA to vary significantly over time. The time dependence of the
GAA can appear to be very complex because the 224Ra, the 226Ra, and 228Ra decay chains all con-
157
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158 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
tribute to the GAA simultaneously. However, each decay chain’s contribution to the GAA is unaffected by the other two decay chains, and the GAA is simply the sum of the contributions of
the three decay chains. Thus, if one understands the time dependence of each decay chain’s contribution to the GAA separately, then the overall time dependence of the GAA is found by summing the three contributions. A radium violation occurs when the combined activity of 226Ra and
228
Ra exceeds 5 pCi/L; a GAA violation occurs when the adjusted GAA—the GAA minus the
uranium activity concentration—exceeds 15 pCi/L.
In Chapter 4, it was shown that the 226Ra decay chain’s contribution to the GAA depended on the time between preparation and analysis. When the time between sample preparation and analysis exceeds 23 days, as little as 2 pCi/L of 226Ra activity in a sample can cause a
GAA violation when the residue is uniform and has a high mass (∼100 mg). Higher levels of
226
Ra activity can cause GAA violations under at less extreme conditions. Thus, it is quite possible for a sample to have no radium violation but to have a GAA violation due solely to 226Ra.
Such a violation would be a false-positive GAA violation.
In Chapter 4, it was shown that the 224Ra decay chain’s contribution to the GAA depended on the time between sample collection and analysis. When a sample residue is uniform
and has a high mass (∼100 mg), as little as 2 pCi/L of unsupported 224Ra activity at the time of
sample analysis can cause a GAA violation. Higher levels of 224Ra activity can cause a GAA violation under at less extreme conditions. Since 224Ra is not included in the radium MCL, a sample can have a GAA violation, due solely to 224Ra, but have no radium violation.
In Chapter 4, it was shown that the 228Ra decay chain’s contribution to the GAA depends
on the time between sample collection and analysis. In grab samples, the 228Ra decay chain’s
contribution to the GAA is very low within one month of collection. However, over time, 228Ra
decays into a series of alpha emitters—228Th, 224Ra, 220Rn, 216Po, 212Bi, and 212Po−which are in
secular equilibrium with one another at about 21 days following collection. Although the contribution of each alpha emitter may be small, since there are six of them, the sum of their alpha activities can be substantial. Consequently, if a grab sample is held for three to six months, the contribution of the 228Ra decay chain to the GAA could cause a GAA violation when there would
have been no GAA violation had the sample been analyzed within a month of collection.
PROBLEMS WITH URANIUM-CONTAINING SAMPLES
Many of the samples in this study predominately contained 234U and 238U, and minor
amounts of other alpha emitters. Neither 234U nor 238U decay to any significant extent over the
lifetime of a sample, neither produces significant amounts of alpha-emitting progeny, and neither
is produced to any significant extent by other radionuclides. Thus, the alpha activity due to the
234
U and 238U decay chains is constant. The contributions of 234U and 238U decay chains to the
GAA are affected by residue mass and geometry, counting error, the spatial distribution of uranium in the residue, and the spatial distribution of residue in the planchet.
As discussed in Chapter 8, the GAAs of some of the uranium-containing samples, analyzed by EPA Method 900.0, were significantly higher than that which was predicted by the
model curves. The cause of the elevated GAA for these samples is not known, but a possible explanation is that the spatial distribution of uranium atoms was biased towards the top of the residues. The fraction of alpha particles emitted near the top of a biased residue would be higher
than for a uniform distribution, causing the level of self-absorption to be lower for the biased distribution than for the uniform distribution. The adjusted GAA—the GAA minus the total ura-
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Chapter 10: Methodology Issues and Recommendations | 159
nium activity—is intended to eliminate the uranium’s contribution to GAA; however, if the GAA
is excessively elevated due to a biased distribution of uranium, then subtracting the uranium activity from the GAA will not eliminate uranium’s contribution to the GAA. If the disparity between the total uranium activity and the biased contribution of uranium to the GAA is large
enough, then a sample could have a uranium concentration below the 30 µg/L MCL but have an
adjusted GAA above the 15 pCi/L MCL, which is due solely to uranium. Such a violation would
be a false-positive GAA violation. In Chapter 8, two such uranium-containing samples had falsepositive GAA violations.
PROBLEMS DUE TO RESIDUE GEOMETRY
The geometry of sample residues can range from being of nearly uniform thickness
across the planchet to being composed of relatively thick patches that cover less than one-half of
the planchet. The fraction of alpha particles absorbed by a uniform residue is less than the fraction absorbed by a patch residue of the same mass. Thus, even when their radiological compositions are identical, a uniform residue will always have a higher GAA than a patch residue of the
same mass. The theoretical graphs of Chapter 4 show that the disparity in the GAA between the
two types of residues is relatively small at low residue masses (∼20 mg) but increases as the residue mass increases. Figure 8.6 showes that in samples where the counting error was a small part
of the GAA error, the range of GAA values for the samples analyzed in this study increased with
residue mass. Thus, if a sample has a GAA close to the MCL (15 pCi/L), a uniform residue could
elevate the GAA above the MCL and a patch residue could drop the GAA below the MCL.
For an evaporation method, the residue mass can be reduced by decreasing the sample
volume. However, a lower sample volume yields a residue with a lower alpha activity, and, as a
result, the required count time could be too long to be practical. For samples with high levels of
dissolved solids, a coprecipitation method would be preferable because the residue mass is limited by the amount of barium and iron carrier added to the sample and not by the level of dissolved solids.
PROBLEMS DUE TO RESIDUE MASS
Chapter 4 shows that some decay chains’ contribution to the GAA can increase substantially with residue mass. The alpha-particle count rate of a residue always decreases when the
residue mass increases. However, for some decay chains, the calibration standard’s alpha-particle
count rate decreases faster with residue mass than the alpha-particle count rate of the decay
chain, which causes the decay chain’s contribution to the GAA to increase with residue mass.
This residue-mass effect, which depends to some extent on the residue geometry, is most pronounced for decay chains with very high-energy alpha emitters like the 212Pb, 224Ra and 228Ra
decay chains. The residue-mass effect is often seen with decay chains that have moderately highenergy alpha emitters like the 226Ra, 210Pb, and 210Po decay chains. All of the above decay chains
can contribute disproportionately to the GAA. In cases where a high residue mass (40-100 mg)
cannot be avoided, a coprecipitation method may be preferable.
©2010 Water Research Foundation. ALL RIGHTS RESERVED
160 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
PROBLEMS DUE TO COUNTING ERROR
As discussed in the Chapter 6, the part of the GAA error due to counting error cannot be
avoided. In general, the longer that a sample is counted, the lower will be the counting error. In
many cases, it is impractical to increase a sample’s count time to the point where the counting
error is negligible. Thus, in some samples, it is, to some degree, a matter of chance whether the
GAA will be above the 5 pCi/L limit that requires a 226Ra analysis or whether the adjusted GAA
will be above the 15 pCi/L MCL that requires the water treatment.
PROBLEMS WITH LONG SAMPLE HOLDING TIMES AND QUARTERLY COMPOSITE SAMPLES
The contributions of the 210Pb and 228Ra decay chains to the GAA are negligible at the
time of sample collection. However, as shown in Chapter 4 and Chapter 8, their contributions
continually grow and can become significant for grab samples held for three to six months or for
quarterly composite samples held for any length of time. In some cases, a grab sample may have
no GAA violation (>15 pCi/L) when analyzed within a month of collection but could have its
GAA elevated above 15 pCi/L MCL when analyzed three to six months after collection. For a
quarterly composite sample, the 210Pb and 228Ra decay chains will have been producing alpha
emitters for as much as one year by the time that the fourth aliquot has been added. Thus, for
samples containing 210Pb and 228Ra, the quarterly composite sample could have a GAA violation
when the corresponding grab sample would have no violation.
The health effects of 228Ra have already accounted for by the radium MCL (>5 pCi/L).
Thus, whenever a sample has no radium violation but has a GAA that, over time, has been elevated
from a level below the MCL to a level above the MCL by the 228Ra decay chain, then the sample
has a false-positive GAA violation. Similarly, the 210Pb decay chain can elevate the GAA from a
level below the MCL to a level above the MCL. Currently, 210Pb is unregulated, but since it is a
beta emitter, a GAA analysis should not be used to determine its presence in water samples.
The contribution of 210Po to the GAA can be substantial at the time of sample collection,
but, because of its 138-d half-life, the contribution will decline to about one-half of its original
level at about 4.6 months following collection. Thus, if the 210Po contribution is to be included in
GAA, a grab sample should be analyzed within a month of collection.
PROBLEMS WITH INGROWTH PERIODS
In EPA Method 900.0, it is stipulated that the time between sample preparation and analysis be at least three days, to allow for the partial ingrowth of the 226Ra progeny. This stipulation
is conservative in the sense that the contribution of the 226Ra decay chain to the GAA increases
with time. If a sample is allowed to sit for three days between preparation and analysis, 0.42
pCi/L of each of the alpha emitters 222Rn, 218Po, and 214Po will be produced for every 1 pCi/L of
226
Ra, and a false-negative GAA violation will be less likely. Figure 4.3 and Figure 4.4 show that
the 226Ra decay chain’s contribution to the GAA continues to increase for a period of about 23
days after preparation. Thus, to avoid an excessive contribution of the 226Ra progeny to the GAA,
the time between preparation and analysis should not be much longer than three days.
In Standard Methods 7110C, the time between preparation and analysis must be at least
three hours. When there are exactly three hours between preparation and analysis, the
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Chapter 10: Methodology Issues and Recommendations | 161
unsupported 218Po and 214Po will decay away, and the 222Rn, 218Po, and 214Po activities that grow
in will be minimal (0.022 pCi/L of each for every 1 pCi/L of 226Ra). Thus, in contrast to EPA
Method 900.0, Standard Methods 7110C can be used to minimize the contribution of 226Ra
progeny to the GAA.
PROBLEMS WITH CALIBRATION STANDARDS
For EPA Method 900.0, either natural uranium or 230Th can be used as the calibration
standard. For Standard Methods 7110C, 241Am can also be used. The scatter in the 230Th efficiency data of Figure 2.1 shows that the residue geometry contributes to the error in the 230Th
efficiencies. Eqn. (2.2) shows that the GAA increases as the calibration standard’s efficiency decreases. A calibration standard’s efficiency depends on its alpha-particle energy, the higher the
alpha-particle energy (Table 1.1), the higher the efficiency. Thus, if the calibration standards are
uniformly distributed in the sample residues, which is questionable for uranium, 241Am would
have the highest efficiency, natural uranium would have the lowest efficiency, and 230Th would
have an intermediate efficiency. Thus, it is certain that some samples would have a GAA violation (>15 pCi/L) when 230Th is used as the calibration standard but would have no violation
when 241Am is used as the calibration standard. The calibration standard that is used has no bearing on the radiological composition of the sample. One calibration standard should be chosen for
all GAA methods.
PROBLEMS WITH HARD- AND SOFT-WATER SAMPLES
The residues of soft-water samples, which are composed mainly of NaNO3 and KNO3,
remain molten when heated over a flame and tend to wet the planchet, so that upon cooling, the
residues appear to be relatively uniform. Uniform residues yield values of the GAA that are
higher than non-uniform residues like smooth and patch residues.
When the residues of hard-water samples are heated over a flame, they frequently melt,
but as MgNO3 and CaNO3 decompose to MgO and CaO, the residues often solidify before cooling and often gather into patches. Thus, for a given radiological composition, one would expect
the GAAs of soft-water residues to be generally higher than the GAAs of hard-water residues,
but this was not investigated in this study.
INCONSISTENCIES BETWEEN GAA METHOD TYPES
In this section, EPA Method 900.0, an evaporation method, is compared to Standard Methods 7110C, a coprecipitation method. There are several inconsistencies between EPA Method
900.0 and Standard Methods 7110C. First, EPA Method 900.0 requires that there be at least three
days between preparation and analysis and Standard Methods 7110C requires that there be at
least three hours between preparation and analysis. As discussed in previous sections, Standard
Methods 7110C can be used to minimize the contribution of 226Ra progeny to the GAA, whereas
EPA Method 900.0 guarantees that the contribution of 226Ra progeny to the GAA will be significant in any samples that have a significant 226Ra activity. To improve inter-laboratory consistency, one ingrowth period should be chosen for all GAA methods.
Second, EPA Method 900.0 does not allow 241Am to be use as a calibration standard,
whereas Standard Methods 7110C allows the use of 241Am. As discussed in previous sections,
©2010 Water Research Foundation. ALL RIGHTS RESERVED
162 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
the value of the GAA depends on which calibration standard is used. Since the calibration standard has no bearing on the radiological composition of a sample, to improve inter-laboratory
consistency, one calibration standard should be chosen for all GAA methods
Third, for some types of matrices, EPA Method 900.0 produces residues with highly variable geometries, which, as shown in Chapter 4, can cause large variations in the GAA. Standard Methods 7110C produces residues that appear to be relatively uniform and reproducible.
Thus, the variability in residue geometry for Standard Methods 7110C is probably less than that
for EPA Method 900.0, although Standard Methods 7110C was not investigated in this study.
Finally, EPA Method 900.0 frequently produces residues with a high mass (40-100 mg).
As discussed in previous sections, a high residue mass can elevate the GAA far above the value
it would have at 20 mg. Standard Methods 7110C consistently produces residues that are about
20 mg. Thus, for samples with a high level of dissolved solids, a Standard Methods 7110C is preferable to EPA Method 900.0.
PROBLEMS WITH URANIUM METHODS
As was discussed in Chapter 6, there are two types of problems that can arise from misapplying the uranium methods: one can lead to a false-positive uranium violation; the other can
lead to a false-positive GAA violation. There are three types of uranium methods: (1) methods
that only measure the uranium activity concentration (pCi/L) accurately, (2) methods that only
measure the uranium mass concentration (μg/L) accurately, and (3) methods, like alpha spectroscopy, that measure both the uranium activity and mass concentrations accurately. Table 6.4 of
Chapter 6 lists the types of uranium methods and their capabilities.
Problems arise because the first and second methods do not discriminate among the three
uranium isotopes—234U, 235U, and 238U. To obtain both the uranium activity concentration and
the uranium mass concentration, a method must be able to measure either the mass concentration
or the activity concentration of each uranium isotope separately. Then one can convert from the
mass concentration of each uranium isotope to its activity concentration, and vice versa. Alpha
spectroscopy can measures the activity concentration of each uranium isotope separately; some
mass spectroscopy methods can measure the mass concentration of each uranium isotope separately, although none of these methods have as yet been approved by the EPA.
If one uses a type (1) or (2) uranium method, some assumptions must be made to make
the conversion from activity concentration to mass concentration, or vice versa. The EPA has
mandated the use of the conversion factor 0.67 pCi/μg. In deriving this conversion factor, it was
assumed that the 234U and 238U activities are equal; however, as discussed in Chapters 1, 6, and 7,
in many groundwaters, the 234U activity significantly exceeds the 238U activity, which results in a
conversion factor that significantly exceeds 0.67 pCi/μg.
One type of problem arises when a uranium activity concentration determined by a type
(1) uranium method is used to estimate the uranium mass concentration. If a sample’s 234U activity exceeds its 238U activity, then the estimate of a sample’s uranium mass concentration will
exceed its true value. If the estimate exceeds the 30 μg/L MCL, when the true value is less than
MCL, then the sample has a false-positive uranium violation. If a false-positive uranium violation is suspected, the uranium mass concentration should be re-determined using one a type (2)
or (3) uranium method.
Another type of problem arises when a uranium mass concentration determined by a type
(2) uranium method is used to estimate the uranium activity concentration. If the sample’s 234U
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Chapter 10: Methodology Issues and Recommendations | 163
activity exceeds its 238U activity, the estimate of a sample’s uranium activity concentration will
be less than its true value. Since the uranium activity concentration is subtracted from the GAA
to obtain the adjusted GAA, underestimating a sample’s uranium activity concentration will
cause its adjusted GAA to be overestimated. If the overestimate exceeds the 15 pCi/L MCL,
when the true value is less than the 15 pCi/L MCL, then the sample has a false-positive GAA
violation. If a false-positive GAA violation is suspected, the uranium activity concentration
should be re-determined using one a type (1) or (3) uranium method. Numerical examples of
conversion factor errors are given in Chapter 6.
FACTORS AFFECTING EVAPORATION METHODS THAT REQUIRE FURTHER
RESEARCH
A major problem with EPA Method 900.0, an evaporation method, is that the geometries
of the sample residues are highly variable. Some residues are uniform and yield relatively high
GAAs; other residues are patchy and yield relatively low GAAs. Residue geometry is difficult to
characterize, and, therefore, it is not feasible to account for its effect on the GAA. EPA Method
900.0 could be significantly improved if it could be modified to yield reproducible residue geometries. Semkow et al (2004) have, for some sample matrices, developed a method that yields
relatively uniform residues. However, some of these residues were hygroscopic; to account for
the increase in the residue mass over time, the samples were weighed just before and just after
analysis, and the residue mass at the time of analysis was taken to be to the average of the two. In
this laboratory, when 230Th was used as a spike, it was found that Semkow’s method yielded
anomalously high values of the GAA for some sample matrices, which suggests that the spatial
distribution of 230Th was biased towards the top of some sample residues.
In some uranium-containing samples in this study, the experimental GAA was significantly higher than the theoretical model curves. This phenomenon was not observed for the radium-containing samples. The cause of the elevated GAA for the uranium-containing samples is
unknown but could be due to a spatial distribution of uranium that is biased toward the top of the
residue. In two uranium-containing samples, the GAA was elevated to the point where the adjusted GAA—the GAA minus the uranium activity concentration—exceeded the 15 pCi/L MCL,
but the uranium mass concentration was less than the 30 μg/L MCL. Thus, these two samples
had false-positive GAA violations. Systematic research should be performed to determine the
cause of the elevated GAA and to determine whether it can be eliminated.
The conditions under which a sample residue is heated over a flame are poorly controlled. The rate of temperature increase, the highest temperature achieved, the length of time
maintained at the highest temperature, and the rate of temperature decrease would certainly vary
from one sample to another, from one analyst to another, and from one laboratory to another.
Soft-water residues typically remain molten when heated and wet the planchet, so that upon solidifying, they appear to relatively uniform. Hard-water residues usually melt when heated, but as
Mg(NO3)2 and Ca(NO3)2 decompose to their respective oxides, the residues often gather into
patches and solidify before cooling. Research should be performed to determine whether the parameters of the heating step can be controlled and adjusted to reproducibly yield sample residues
with a higher degree of uniformity.
For the evaporation methods, variability in the GAA due to variability in the residue
geometry increases as the residue mass increases. Further, when a sample contains high-energy
alpha emitters, the GAA overestimates the sample’s alpha activity, and the overestimate
©2010 Water Research Foundation. ALL RIGHTS RESERVED
164 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
increases with residue mass. For an evaporation method, the residue mass, which ranges from 0
to 100 mg, is determined by the sample volume and the total dissolve solids of the sample. The
residue mass can be decreased by reducing the sample volume; however, reducing the sample
volume also reduces the residue’s alpha activity, which may require excessively long count
times. One advantage of evaporation methods is that one can be reasonably assured that the
chemical yield of all radionuclides is near 100%.
For a coprecipitation method, like Standard Methods 7110C, the residue mass depends on
the amount of barium carrier, iron carrier, and paper pulp added to the sample and is typically
about 20 mg. A coprecipitation method may be superior to an evaporation method; however, the
sample residue of a coprecipitation method is a heterogeneous mixture of BaSO4, Fe(OH)3, and
paper pulp, and there is no guarantee that the spatial distribution of a radionuclide in such a residue is uniform. Further, the heterogeneity of the precipitate makes the practice of using the residue mass to obtain the chemical yield of radionuclides somewhat questionable. There is no guarantee that the yields of BaSO4, Fe(OH)3, and paper pulp are equal. Thus, although the residue
mass for a coprecipitation method is more easily controlled than that of an evaporation method,
further research of coprecipitation methods is required to determine whether the chemical yields
of all of the radionuclides of interest are near 100%, whether the spatial distributions of radionuclides in the residues are uniform, and whether the residue mass is reliable measure of the
chemical yield of all of the radionuclides.
For evaporation methods, samples residues are sometimes hygroscopic. The hygroscopicity of some residues is often eliminated when the residue is heated over a flame, which decomposes Mg(NO3)2 and Ca(NO3)2 to their respective oxides. Sometimes, the hygroscopicity of a
residue persists after being heated over a flame. The hygroscopicity of a residue causes its mass
to increase with time and its alpha-particle emission rate to decrease with time. It is the usual
practice of many laboratories to measure the residue mass after the residue is heated over a
flame. If the residue mass subsequently increases and is not re-measured before analysis, the alpha-particle emission rate of the residue will decrease and the GAA will be underestimated.
Some research should be performed to determine what conditions contribute to the hygroscopicity of residues and whether the hygroscopicity can be eliminated. For coprecipitation methods,
the residues are composed of BaSO4, Fe(OH)3, and paper pulp and are not hygroscopic. Thus,
when hygroscopicity is a problem, a coprecipitation method would be preferable to an evaporation method.
©2010 Water Research Foundation. ALL RIGHTS RESERVED
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©2010 Water Research Foundation. ALL RIGHTS RESERVED
ABBREVIATIONS
BAT
Best Available Technologies
CA
CCR
CWS
Cellulose Acetate
Consumer Confidence Report
Community Water System
ED
EDR
EPA
Electrodialysis
Electrodialysis Reversal
Environmental Protection Agency
GAA
GAC
GRA
Gross-Alpha Particle Activity
Granular Activated Carbon
Gross Radium Activity
ICP-MS
Inductively Coupled Plasma Mass Spectroscopy
MCLG
MCL
MWCO
Maximum Contaminant Level Goal
Maximum Contaminant Level
Molecular Weight Cutoff
NF
NPDWR
Nanofiltration
National Primary Drinking Water Regulation
POE
POU
RO
Point of Entry
Point of Use
Reverse Osmosis
SDWA
Safe Drinking Water Act
TT
Treatment Technique
UCMP
Unregulated Contaminant Monitoring Program
171
©2010 Water Research Foundation. ALL RIGHTS RESERVED
172
©2010 Water Research Foundation. ALL RIGHTS RESERVED
APPENDIX A
CURRENT NATIONAL PRIMARY DRINKING WATER REGULATIONS
FOR RADIONUCLIDES IN WATER
INTRODUCTION
The Safe Drinking Water Act (SDWA) was originally passed by the U.S. Congress in
1974 to protect public health by regulating the nation’s public drinking water supply against both
naturally-occurring and man-made contaminants including radionuclides, inorganic and organic
agents, and biological agents. The law was amended in 1986 and 1996. The SDWA authorizes
the United States Environmental Protection Agency (EPA) to set national health-based standards
for drinking water. Drinking water sources include rivers, lakes, reservoirs, springs, and groundwater wells. The EPA, States, Tribes, and other water systems work together to ensure that these
standards are met.
A public water system provides water for human consumption through pipes or other
constructed conveyances to at least 15 service connections or serves an average of at least 25
people for at least 60 days a year. A community water system (CWS) is a public water system
that supplies water to the same population year-round. Currently, only CWSs are regulated by
the SDWA for radionuclides. CWSs can be privately owned, such as those in trailer parks, or can
be publicly owned by State, Tribal, Local, and Federal Governments. The SDWA does not regulate private wells that serve fewer than 25 individuals.
As proscribed by the SDWA, the EPA must determine or estimate the maximum level at
which a contaminant may be present with no adverse health effects. This level is called the
Maximum Contaminant Level Goal (MCLG). The EPA employs a no-threshold linear cancer
risk model to determine the incidence of cancer in populations when ionizing radiation is ingested. The model assumes that the risk of cancer increases linearly with the amount of radiation
ingested, and the “no-threshold” part of the model makes the assumption that there is some, possibly very small, cancer risk for any dose of radiation. Because of the of the “no-threshold” assumption, the EPA has set the MCLG for all radiological contaminants to zero. The EPA recognizes uranium as both a radiological contaminant and a kidney toxin.
For each radiological contaminant, the EPA Administrator is required to set the
maximum contaminant level (MCL) as close to the MCLG as is feasible using the best technology, treatment techniques, and other means available that are demonstrated for efficacy under
field conditions, taking cost into consideration. The EPA’s usual upper limit of acceptable cancer
incidence (morbidity) in drinking water is one case in ten thousand people. The EPA Administrator has the discretionary authority to set an MCL that is higher than the feasible level if (1) there
are practical difficulties in measuring small quantities of a contaminant, (2) there are a lack of
available treatment technologies for the removal of the contaminant, or (3) the EPA
Administrator has determined that the treatment costs outweigh the potential public health
benefits. For example, the feasible level for total uranium concentration was determined to be 20
μg/L, but, using a cost-benefit analysis, the EPA Administrator set the MCL for total uranium
concentration at 30 μg/L. The MCL is legally enforceable; the MCLG is not.
For some contaminants, the EPA establishes a treatment technique (TT) instead of an
MCL. TTs are enforceable procedures that drinking water systems must follow in treating their
water for a contaminant. Currently, there are no TTs for radiological contaminants. The
173
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174 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
collection of MCLs and TTs are known jointly as National Primary Drinking Water Regulations
(NPDWRs), or primary standards. In addition, there are a set of secondary standards that apply to
the aesthetic qualities of the water. None of the secondary standards apply to radiological
contaminants.
Among other things, the NPDWR also establishes a standard monitoring framework for
CWSs, lists approved test methods for the radionuclides, lists the best available technologies
(BAT) for treatment of both small and large CWSs, establishes the kind of information that water
utilities must make available to customers on a routine basis and in the event that the utility has
an MCL violation or other problem that can adversely affect customer’s health, and puts forth
requirements for States and Tribes to apply for primacy, which allows them to enforce the
NPDWR in their jurisdictions.
MAXIMUM CONTAMINANT LEVELS
In 1976, National Interim Primary Drinking Water Regulations (NIPDWR) were promulgated for combined 226Ra and 228Ra, for gross alpha-particle activity (GAA), and for beta particle
and photon radioactivity (U.S. EPA 1976b). The 1986 reauthorization of the SDWA required the
EPA to promulgate maximum contaminant level goals (MCLGs) and NPDWR for the previously
regulated radionuclides, and for radon and uranium. In 1991, the EPA proposed new radionuclide regulations (U.S. EPA 1991), but these were never implemented. The current NPDWR were
promulgated by the EPA on December 7, 2000 (U.S. EPA 2000b) and took legal effect on December 8, 2003, three years after promulgation. The NPDWR established MCLs for the uranium
concentration (30 μg/L), the combined activity of 226Ra and 228Ra (5 pCi/L), the GAA (15
pCi/L), and the beta and photon radioactivity (4 mrem/year). An MCL has not been finalized for
radon. The MCLs for each radionuclide are given in Table A.1.
Associated with each radionuclide is a detection limit given in Table A.1. The detection
limit is a measure of the lowest contaminant level that a method can be used to reliably identify a
contaminant. In most analyses the detection limit varies somewhat from one analysis to the next.
Laboratories analyzing samples must meet these detection limits, and should quote the detection
limits in their reports. The reported detection limits should be equal to or less than the required
detection limits.
Table A.1 also includes radionuclides in the Unregulated Contaminant Monitoring Program (UCMP), as required by the 1996 Amendments to the Safe Drinking Water Act. Unregulated contaminants include 210Pb and 210Po. Also included in the table is 224Ra, since both it and
its progeny are common, albeit relatively short-lived, contaminants in groundwater. Although
these radionuclides are not specifically regulated, 210Pb and some 224Ra progeny (212Pb, 212Bi,
208
Tl) contribute to the beta and photon radioactivity, and the 210Po and 224Ra, and some 224Ra
progeny (220Rn, 216Po, 212Bi, 212Po) contribute to the GAA. Thus, these contaminants are indirectly regulated. For example, if the only significant contaminant of a water source were 210Po, and if
there were enough 210Po to elevate the GAA above 15 pCi/L, then the water would have to be
treated to reduce the 210Po activity low enough so that the GAA would be less than 15 pCi/L. As
a part of the UCMP, data will be collected and used by the EPA to evaluate and prioritize the unregulated contaminants for possible future regulation.
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Appendix A: Current National Primary Drinking Water Regulations for Radionuclides in Water | 175
Table A.1
NPDWR; Radionuclides; final rule; 2000
Radionuclide(s)
MCLG
MCL
Detection
limit
Comment
Combined radium
(226Ra and 228Ra)
Zero
5 pCi/L
1 pCi/L
—
Total uranium
Zero
30 μg/L
1 μg/L
—
GAA
Zero
15 pCi/L
3 pCi/L
May subtract uranium activity.
Beta/Photon Radioactivity
Zero
4 mrem/y
4 pCi/L
—
210
Po
210
Pb
224
Ra
—
—
—
—
—
—
—
Not regulated. Currently in the
UCM Program. 210Po contributes to
the GAA, so it is implicitly regulated.
—
Not regulated. Currently in the
UCM Program. 210Pb contributes to
the Beta/Photon radioactivity, so it
is implicitly regulated.
—
Not regulated. Can contribute to the
GAA in quarterly composite samples or in sample analyzed within a
few weeks of collection
MONITORING BASELINE
At a minimum, the standard monitoring framework requires that a CWS measure the
gross alpha-particle activity (GAA) and the 228Ra activity at each point of entry (POE) to the water system. Results of the GAA determine whether additional testing must be performed. If the
GAA is less than 5 pCi/L, the GAA may be substituted for the 226Ra activity; if the GAA exceeds
5 pCi/L, the 226Ra activity must be determined. If the GAA is less than 15 pCi/L, the GAA may
be substituted for the total uranium activity; if the GAA exceeds 15 pCi/L, the total uranium activity and concentration must be determined. Some systems, with surface water designated as
vulnerable by the State, must measure the gross beta and photon radioactivity, which is not the
focus of this work, so its discussion here will be limited.
To establish a monitoring baseline for each POE, the standard monitoring framework requires that a sample be analyzed in each of four consecutive quarters. To reduce analysis costs,
the regulations allow one to substitute a quarterly composite sample for four consecutive samples. In a quarterly composite sample, equal volumes of sample are added to the sample container in each of four consecutive three-month periods. The use of quarterly composite samples can
substantially reduce the cost of the sample analysis. However, the use of quarterly composite
samples can substantially elevate the GAA in some samples containing 228Ra and 210Pb, which
was discussed in Chapter 5.
The EPA allows States, and any primacy agency, the discretion to use historical data
from a POE to be used to establish a monitoring baseline. Not all historical data is useful for this
purpose because regulations prior to those promulgated in 2000 did not require that water from
©2010 Water Research Foundation. ALL RIGHTS RESERVED
176 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
each POE be analyzed. In addition, uranium was not regulated prior to 2000, so few utilities
probably had such data.
To establish a monitoring baseline, one uses either the average analytical result from the
four consecutive quarters or the analytical result of the quarterly composite sample. These results
determine the future sampling schedule for each POE. If the analytical result is greater than onehalf of the MCL but less than the MCL, then the water from the POE must be analyzed once
every three years. If the average analytical result is greater than the detection limit but less than
one-half of the MCL, then water from the POE must be analyzed once every six years. If the average analytical result is less than the detection limit, then water from the POE must be analyzed
once every nine years.
COMPLIANCE FLOWCHARTS
The determinations of the combined radium activity, the GAA, and the total uranium
concentration are somewhat more complicated than the discussion above indicates. A flowchart
to determine whether a sample has a radium violation is given in Figure A.1. One begins by
measuring the GAA and the 228Ra activity. If the 228Ra activity exceeds 5 pCi/L, the POE has a
radium violation. One must still determine the 226Ra activity to determine the extent of the radium violation. If the GAA is less than 5 pCi/L, the GAA can be substituted for the 226Ra activity. Even when this is the case, one may want to analyze the 226Ra activity directly, since the
226
Ra activity often, if not usually, is less than the GAA. Whenever the GAA exceeds 5 pCi/L,
the 226Ra activity must be determined, regardless of the 228Ra activity.
If the GAA is less than 5 pCi/L, the GAA can be substituted for the 226Ra activity. And if
the combined 226Ra and 228Ra activity is less than 5 pCi/L, then there is no radium violation.
However, if the combined activity exceeds 5 pCi/L, it may be advisable to determine the 226Ra
activity, which is often less than the GAA. Then the combined activity may still fall under the 5
pCi/L limit. As mentioned above, whenever the GAA exceeds 5 pCi/L, the 226Ra activity must be
determined.
A flowchart to determine whether a sample has a GAA and/or a uranium violation is given in Figure A.2. If the GAA is less than 15 pCi/L, the total uranium concentration need not be
determined. Under these conditions, there are no GAA or uranium violations, and one may assume that the total uranium concentration equals the GAA multiplied by 1.5 μg/pCi (the reciprocal of 0.67 pCi/μg).
If the GAA exceeds 15 pCi/L, the total uranium activity and/or concentration (one may
be estimated from the other) must be determined. Then the total uranium activity is subtracted
from the GAA to get the adjusted GAA. If the adjusted GAA is less than or equal to 15 pCi/L,
there is no GAA violation; otherwise there is a GAA violation. If the uranium concentration exceeds 30 μg/L, there is a uranium violation.
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Appendix A: Current National Primary Drinking Water Regulations for Radionuclides in Water | 177
Measure 226Ra
Measure GAA
No
226
Yes
228
Ra act.
< 5 pCi/L?
Measure
Ra activity
226
Ra = GAA
Yes
GAA
or measure
< 5 pCi/L?
226
Ra activity
No
Calc. comb.
Ra activity
No
226
Measure
Ra activity
Comb.
Ra act. < 5
pCi/L?
Calc. comb.
Ra activity
No
Radium
violation
Yes Comb.
Radium
Ra act. < 5
compliance
pCi/L?
Yes
Yes
No
Yes
GAA
< 5 pCi/L?
226
Comb.
No
Ra act. < 5
pCi/L?
Ra = GAA
226
Measure
Ra activity
Calc. comb.
Ra activity
Calc. comb.
Ra activity
Figure A.1. Flowchart for radium compliance
Measure GAA
Yes
GAA
< 15 pCi/L?
No
Measure total
uranium activity
and/or concentration
If necessary,
convert uranium
conc. to activity
Adj.
GAA< 15
pCi/L?
Calculate
adjusted GAA
If necessary,
convert uranium
activity to conc.
No
Yes
Uranium
conc. < 30
μg/L?
No
Yes
Uranium
violation
Uranium
compliance
Uranium = GAA × 1.5 μg/pCi
Figure A.2. Flowchart for GAA and uranium compliance
©2010 Water Research Foundation. ALL RIGHTS RESERVED
GAA
violation
GAA
compliance
178 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
At this point, it should be mentioned that most analytical results are quoted with an error.
For example, the 226Ra activity might be quoted as 2.3 ± 0.3 pCi/L. It is the EPA’s interpretation
of the SDWA that it is the analytical result, in this case, 2.3 pCi/L, that should be used for compliance and in determining the monitoring schedule and not the analytical result with the error
either added or subtracted from it.
It is often written that the GAA excludes uranium and radon. This means that the uranium
activity is subtracted from the GAA to obtain the adjusted GAA. However, it does not mean that
the radon activity can be subtracted from the GAA. The radon activity of groundwater samples is
sometimes thousands of pCi/L, whereas the GAA is typically much less than 100 pCi/L. Radon
is excluded from the GAA because radon is a gas, which is quantitatively lost from the sample
during preparation. Nonetheless, if a sample contains 226Ra, a significant amount of 222Rn, which
arises from 226Ra decay, can contribute to the GAA, so it is not strictly true that all radon is excluded from the GAA. The radon contribution to the GAA is discussed in more detail in Chapters 4 and Appendix F.
In Figure A.2, both the total uranium concentration and the total uranium activity are
used. Alpha spectroscopy is the only EPA-approved method that measures both total uranium
activity (pCi/L) and total uranium concentration accurately (μg/L). All other EPA-approved methods accurately measure one but not the other. Radiochemical methods accurately measure the
total uranium activity; fluorometric methods, laser phosphorimetry, and inductively coupled
plasma mass spectroscopy (ICP-MS) accurately determine the total uranium concentration. This
is summarized in Table A.2.
If one uses a method that only accurately quantifies the total uranium concentration and
then converts it to the total uranium activity, using the factor 0.67 pCi/μg, which is required by
the EPA, one will typically underestimate the total activity. (The conversion factor is typically
too small because it assumes that the 234U and 238U activities are equal, which is typically not
true because of the phenomenon of disequilibrium discussed in Chapter 1) This can be a problem
because the adjusted GAA is obtained by subtracting the total uranium activity from the GAA,
which can give an adjusted GAA that is artificially high, possibly leading to a false-positive
GAA MCL violation (> 15 pCi/L). If a false-positive GAA violation is suspected, the total uranium activity should be re-determined using a radiochemical method or alpha spectroscopy. An
example of false-positive GAA violation is given in Chapter 6.
Table A.2
Uranium methods
Uranium method
Radiochemical
Fluorometric
Laser phosphorimetry
ICP-MS
Alpha spectroscopy
Measures concentration
(μg/L)
Measures activity
(pCi/L)
No
Yes
Yes
Yes
Yes
Yes
No
No
No
Yes
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Appendix A: Current National Primary Drinking Water Regulations for Radionuclides in Water | 179
If one uses a method that only accurately quantifies the total uranium activity and then
converts it to the total uranium concentration, using the factor 1.5 μg /pCi, which is required by
the EPA, one will typically overestimate the total uranium concentration. (As above, the conversion factor is typically too large because of disequilibrium.) This can be a problem because the
overestimate may exceed the 30 μg/L MCL while the true value may be less than the MCL, leading to a false-positive uranium violation. If a false-positive violation is suspected, the total uranium concentration should be determined directly using a fluorometric method, laser phosphorimetry, ICP-MS, or alpha spectroscopy. An example of a false-positive uranium violation is given
in Chapter 6.
INFORMATION PUBLIC WATER SYSTEMS MUST SUPPLY CUSTOMERS
There are two types of information that a CWS is required to provide to its customers.
The first is an annual water quality report, called a consumer confidence report (CCR); the
second, called a public notification, is only required when there is an MCL violation, when the
PWS violates a regulation, or when any other situation develops in which the water supply may
adversely affect consumer health. Much of the following discussion was taken from two EPA
web sites (U. S. EPA 2008a, U. S. EPA 2008b).
Consumer Confidence Reports
CWSs are required to provide CCRs—also called annual water quality reports or drinking
water quality reports—to their customers each year by July 1. While CWSs are free to enhance
their CCR in any useful way, each CCR must provide consumers with the following fundamental
information about their drinking water:
•
•
•
•
•
•
•
•
•
•
the lake, river, aquifer, or other source of the drinking water;
a brief summary of the susceptibility to contamination of the local drinking water source,
based on the source water assessments by states;
how to get a copy of the water system's complete source water assessment;
the level (or range of levels) of any contaminant found in local drinking water, as well as
EPA's health-based standard (maximum contaminant level) for comparison;
the likely source of that contaminant in the local drinking water supply;
the potential health effects of any contaminant detected in violation of an EPA health
standard, and an accounting of the system's actions to restore safe drinking water;
the water system's compliance with other drinking water-related rules;
an educational statement for vulnerable populations about avoiding Cryptosporidium;
educational information on nitrate, arsenic, or lead in areas where these contaminants
may be a concern; and
phone numbers of additional sources of information, including the water system and
EPA's Safe Drinking Water Hotline (800-426-4791).
The SDWA requires that specific language be included in the CCR for the likely source
of a contaminant and the potential health effects of any detected contaminant. The language,
which must be included in the CCR verbatim, is given in A.3. To make the process of generating
the CCR easier, the EPA has developed software, called CCR iWriter (U. S. EPA 2008c). CCR
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180 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
iWriter allows one to quickly create a CCR. It takes users through all of the sections of a CCR,
converts laboratory results into the units that must be used in the CCR, and allows users to insert
and edit the EPA's recommended text. CCR iWriter is an on-line application and is free to use. It
can be accessed at the web site:
http://www.ccriwriter.com/
To use CCR iWriter, one must create an account at this web site so that information can
be saved when the user logs out. CCRWriter (v3) is also available as a desktop application that
runs on computers that use Microsoft Windows 95/98/Me/2000/NTv4. It can be ordered on CDROM by calling the Safe Drinking Water Hotline at 1-800-426-4791.
Table A.3
Standard Health Effects Language for CCR and Public Notification
Contaminant
Standard health effects language for CCR and public notification
Beta/photon emitters
Certain minerals are radioactive and may emit forms of radiation known as photons and beta radiation. Some people who drink water containing beta and photon emitters in excess of the MCL over many years may have an increased risk
of getting cancer.
Alpha Emitters
Certain minerals are radioactive and may emit a form of radiation known as
alpha radiation. Some people who drink water containing alpha emitters in
excess of the MCL over many years may have an increased risk of getting cancer
Combined radium
Some people who drink water containing radium 226 or 228 in excess of the
MCL over many years may have an increased risk of getting cancer.
Uranium
Some people who drink water containing uranium in excess of the MCL over
many years may have an increased risk of getting cancer and kidney toxicity.
Public Notification
A CWS must notify its customers when water it provides exceeds an MCL, when it
violates EPA or State drinking water regulations, including monitoring requirements, or
otherwise provides drinking water that may pose a risk to consumer’s health. The public notice
requirements of the SDWA require the PWS to provide this notice. The EPA sets strict
requirements on the form, manner, content, and frequency of public notices. Public notices must
contain:
•
•
•
•
•
•
•
A description of the violation that occurred, including the potential health effects
The population at risk and if alternate water supplies need to be used
What the water system is doing to correct the problem
Actions consumers can take
When the violation occurred and when the system expects it to be resolved
How to contact the water system for more information
Language encouraging broader distribution of the notice
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Appendix A: Current National Primary Drinking Water Regulations for Radionuclides in Water | 181
The EPA specifies three categories, or tiers, of public notification. Depending on what
tier a violation or situation falls into, water systems have different amounts of time to distribute
the notice and different ways to deliver the notice:
•
•
•
Immediate Notice (Tier 1): Any time a situation occurs where there is the potential for
human health to be immediately impacted, water suppliers have 24 hours to notify people
who may drink the water of the situation. Water suppliers must use media outlets such as
television, radio, and newspapers, post their notice in public places, or personally deliver
a notice to their customers in these situations.
Notice as soon as possible (Tier 2): Any time a water system provides water with levels
of a contaminant that exceed EPA or state standards or that has not been treated properly,
but that doesn't pose an immediate risk to human health, the water system must notify its
customers as soon as possible, but within 30 days of the violation. Notice may be
provided via the media, posting, or through the mail.
Annual Notice (Tier 3): When water systems violate a drinking water standard that does
not have a direct impact on human health (for example, failing to take a required sample
on time) the water supplier has up to a year to provide a notice of this situation to its
customers. The extra time gives water suppliers the opportunity to consolidate these
notices and send them with consumer confidence reports.
The public notification rule lists MCL violations as being subject to Tier 2 public notice
requirements, and lists violations of the monitoring requirements and testing requirements as being subject to ‘‘Tier 3’’ public notice requirements.
LABORATORY CERTIFICATION AND EPA-APPROVED ANALYTICAL METHODS
EPA’s Office of Water implements the Drinking Water Laboratory Certification Program
in partnership with EPA Regions and States. Laboratories must be certified by the EPA or the
State to analyze drinking water samples for compliance monitoring. Certified laboratories must
successfully analyze proficiency testing samples annually, use EPA-approved methods, and
successfully pass periodic on-site audits. EPA recommends that water utility operators use state
certified laboratories for water testing. A list of EPA offices and State agencies that can provide
water utility operators with a list of certified laboratories can be obtained from the following web
site: http://www.epa.gov/safewater/labs/index.html
In general, the water utility operator will order a sampling kit, which typically contains
one or more sample containers, possibly a preservative, like nitric acid, and sampling instructions. In some cases, more than one kind of test can be run on water from one container. The
sampling instructions describe how to collect, preserve, and store the sample. If the water utility
operator is unsure of the instructions, he or she should call the laboratory for clarification, since
noncompliance with sampling instructions may make the sample unsuitable for analysis.
The number of EPA-approved analytical methods for radionuclides is too numerous to
mention here. The complete list can be found at the following web site:
http://www.epa.gov/ogwdw/methods/pdfs/methods/methods_radionuclides.pdf
This web site includes methods for both manmade and naturally occurring radionuclides.
Not all laboratories offer each method listed. Water utility operators should be aware of the methods offered by a laboratory, since, as discussed in previous sections, not all uranium methods
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182 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
give the same information. Sometimes attempts to save costs in the short run lead to more expense in the long run.
Table A.4
List of BAT along with Water Quality Range and Limitations and Operator Skill for PWSs
serving 25-10,000 People
No.
Unit technology
Raw water quality
range and considerations (NRC 1997)
Limitations
(Table A.5)
Operator skill level
required
(NRC 1997).
1
Ion exchange (IE)
All ground waters
A
Intermediate
2
Point of use (POU) IE
All ground waters
B
Basic
3
Reverse osmosis (RO)
Surface waters usually
require pre-filtration
C
Advanced
4
POU RO
Surface waters usually
require pre-filtration
B
Basic
5
Lime softening
All waters
D
Advanced
6
Green sand filtration
E
Basic
7
Co-precipitation with barium
sulfate
Ground waters with
suitable water quality
F
Intermediate to Advanced
8
Electrodialysis/electrodialysis
reversal
All ground waters
9
Pre-formed hydrous manganese oxide filtration
All ground waters
10
Activated alumina
All ground waters;
competing anion concentrations may affect
regeneration frequency
A, H
Advanced
11
Enhanced coagulation/filtration
Can treat a wide range
of water qualities
I
Advanced
—
Basic to Intermediate
G
Intermediate
BEST AVAILABLE TECHNOLOGIES FOR WATER TREATMENT
Under the SDWA, the EPA is required to specify one or more best available technologies
(BAT) for complying with each MCL violation according to the size of the CWS (U.S. EPA
2000b). A BAT is a treatment technology, treatment technique, or other means for removing a
contaminant from drinking water. A BAT is selected by the EPA Administrator taking into account both its efficacy in the field and its cost. A CWS is not allowed to use bottled water to
comply with an MCL violation. Bottled water may only be used on a temporary basis to avoid
unreasonable risks to health as, e.g., negotiated with the State or other primacy agency as part of
the compliance schedule period for an exemption or variance (U. S. EPA 1998). The BATs are
reviewed in Appendix B.
Table A.4 is a compilation of the BATs for each radiological contaminant (U.S. EPA
2000b). The limitations and operator skills are intended as a guide for CWSs that serve 10,000 or
fewer people. The table also lists the raw water quality ranges for each BAT. The limitations are
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Appendix A: Current National Primary Drinking Water Regulations for Radionuclides in Water | 183
given in Table A.5. Point-of-use (POU) technology is a treatment device installed at a single tap
used for the purpose of reducing contaminants in drinking water at that one tap. POU devices are
typically installed at the kitchen tap and are only intended for PWSs serving 25-10,000 people.
Table A.6 lists BATs for water systems according to size of the population served for
combined radium activity, GAA, total uranium concentration, and beta particle and photon
radioactivity. The numbers under each category correspond to the number of the BAT in
(Table A.4).
Table A.5
Limitations in BAT for PWS that serve 25-10,000 people.
Letter
Limitation
A
The regeneration solution contains high concentrations of the contaminant ions. Disposal
options should be carefully considered before choosing this technology.
B
When POU devices are used for compliance, programs for long-term operation, maintenance,
and monitoring must be provided by water utility to ensure proper performance.
C
Reject water disposal options should be carefully considered before choosing this technology.
See other RO limitations described in the SWTR Compliance Technologies Table.
D
The combination of variable source water quality and the complexity of the water chemistry
involved may make this technology too complex for small surface water systems.
E
Removal efficiencies can vary depending on water quality.
F
This technology may be very limited in application to small systems. Since the process requires static mixing, detention basins, and filtration, it is most applicable to systems with sufficiently high sulfate levels that already have a suitable filtration treatment train in place.
G
This technology is most applicable to small systems that already have filtration in place.
H
Handling of chemicals required during regeneration and pH adjustment may be too difficult
for small systems without an adequately trained operator.
I
Assumes modification to a coagulation/filtration process is already in place.
Table A.6
BAT according to PWS Size. Numbers correspond to those technologies listed in Table A.4.
System
Size
No. of people
served
Contaminant and Corresponding BAT (Table A.4)(Table A.4)
Combined radium
activity
GAA
Total uranium
concentration
Beta particle activity
and photon activity
Very small
25-500
1, 2, 3, 4, 5, 6, 7, 8, 9
3, 4
1, 2, 4, 10, 11
1, 2, 3, 4
Small
501-3,300
1, 2, 3, 4, 5, 6, 7, 8, 9
3, 4
1, 2, 3, 4, 5,
10, 11
1, 2, 3, 4
Medium
3,301-10,000
1, 2, 3, 4, 5, 6, 7. 8, 9
3, 4
1, 2, 3, 4, 5,
10, 11
1, 2, 3, 4
Large
10,001-100,000
1, 3, 5
3
1, 3, 5, 11
1, 3
Very Large
> 100,001
1, 3, 5
3
1, 3, 5, 11
1, 3
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184 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
©2010 Water Research Foundation. ALL RIGHTS RESERVED
APPENDIX B
WATER TREATMENT OPTIONS
Treatment options for removal of radionuclides from water will be reviewed. Some information concerning radium removal is taken from a review by Kosarek (1979). In water with a
turbidity that exceeds 10 NTU, about 20% of the total radium is associated with the solids. Equilibrium is established between radium in the water and radium adsorbed on the suspended solids.
When radium is removed from the water, some radium desorbs from the solids and goes into solution. Thus, removal of suspended solids is often a necessary preliminary treatment step.
Often water is treated to remediate both a radionuclide violation and some other problem.
For example, water may be excessively hard or may have high levels of manganese or iron. In general, there are treatments that can address both problems simultaneously. Currently, 210Po is an alpha emitter that is indirectly regulated by its affect on the gross alpha-particle activity (GAA). If
the 210Po activity of a water supply causes the GAA to exceed the 15 pCi/L MCL, then the water
must be treated to remove enough 210Po to bring the water supply into compliance. 210Po is usually
not present in water in a molecular form, but is usually part of a colloid, sometimes called radiocolliod, or is adsorbed onto the surfaces of particles suspended in the water. There are no treatments
designed specifically to remove 210Po, but reverse osmosis indiscriminately removes radionuclides
and can be effective treatment option for 210Po. Some studies, discussed below, suggest that activated carbon filtration or Iron/Aluminum coagulation-filtration can be effective, but in these cases,
the authors suggest that the removal of 210Po depends on the nature of the colloid or particulate,
which contains the 210Po, and not on the particular chemistry 210Po.
REVERSE OSMOSIS FOR REMOVAL OF URANIUM, THORIUM, RADIUM, AND
POLONIUM
In reverse osmosis (RO) a semipermeable membrane is used to remove solutes from the
water. A schematic diagram of an RO system is given in Figure B.1. Water can pass through the
membrane, represented by arrows through the semipermeable membrane in Figure B.1, while the
amount of most solutes that can pass is very low. Pressure in excess of the osmotic pressure of
the feedwater is applied across the membrane to force the water through the membrane
The water that passed through the membrane is called the permeate, and the remaining
feedwater is called the brine. The brine is a byproduct, and may have to be treated before it can
be disposed of. RO indiscriminately removes solutes from water, and, therefore, may be used to
remove uranium, radium, polonium, and lead. It also lowers the hardness and the salinity of the
water. RO removes >99% of the radium and uranium. RO has been successfully used to remove
over 90% of 210Po at two POE-RO installations in the field (Annmäki and Turtianen 2000). Reverse osmosis is a highly effective treatment but is relatively expensive.
In general, a prefiltration step using multimedia, cartridge, and/or sand filtration is necessary to remove components that might foul the membranes. Components that foul the membranes include particles, organic matter, bacteria, oil, and grease. The turbidity of the feedwater
is typically reduced to less than 0.2 NTU. Chlorine, hypochlorite, monochloramine, or other antibacterial agents can be added to reduce bio-fouling. The chlorine can be added at the front of
the plant, and a de-chlorinating agent can be added before the feedwater reaches the membrane
to reduce oxidative damage. Calcium, magnesium, and dissolved silica are of particular concern,
185
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186 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
since they can cause scaling of the membranes. Acid and antiscalents are often added to the
feedwater. The permeate may be treated to reduce its corrosiveness, by adding chemicals like
carbon dioxide or soda ash (Duranceau 2001).
Semipermeable
membrane
Permeate
Pressure
−
+
−
+
+
+
+
−
−
Figure B.1. Schematic diagram of RO system
There are two types of membranes used for RO: cellulose acetate (CA) membranes and
non-cellulose acetate membranes. The CA membranes are relatively smooth and resistant to
fouling. Non-CA membranes, often called “thin-film composite membranes,” include aromatic
polyamide membranes and composite membranes using materials such as polysulfone. Compared to CA membranes, the non-CA membranes produce a higher volume of permeate per unit
area of membrane, allow a lower concentration of salt to pass through the membrane, and are
more stable over a wider pH range, but are more susceptible to degradation by chlorine (ElDessouky and Ettouney 2002).
The recovery rate is the volume of permeate produced per volume of feedwater used. The
recovery rate depends on the osmotic pressure of the water (which is correlated with total dissolved solids of the water), the pressure used, and other factors. Typical recovery rates are from
30 to 80% (Younos and Tulou 2005).
ELECTRODIALYSIS FOR REMOVAL OF RADIONUCLIDES
Removal of radionuclides by electrodialysis (ED) is similar in principle to RO. A schematic diagram of an ED assembly is given in Figure B.2. The system has two electrodes: an
anode and a cathode. Between the electrodes are two or more pairs of membranes called cell
pairs, which consist of a cation-transfer membrane and an anion-transfer membrane. The cationtransfer membrane allows cations to pass, and the anion-transfer membrane allows anions to
pass. A cell pair is arranged so that the cation-transfer membrane is closest to the anode and the
anion-transfer membrane is closest to the cathode. A DC potential is applied between the electrodes, with the anode positive with respect to the cathode. This creates an electric field across
the whole assembly that drives anions towards the anode and cations towards the cathode.
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Appendix B: Water Treatment Options | 187
The feedstream, which flows between adjacent cell pairs, is called the diluate (D) stream.
The water between the two membranes of a cell pair is called the brine or concentrate (C) stream.
The layer of water adjacent to the cathode and anode is called the electrode (E) stream. The E
stream contains an electrolyte like sodium chloride or sodium sulfate.
−
+
cell pair
cell pair
cell pair
Cl2
H2 + 2OH−
2Cl−
4H+ + O2
2H20
Na+
Na+
Cl−
2H2O
Cl−
Cl−
cathode
ATM
CTM
E stream
ATM
CTM
D stream
C stream
C stream
Na+
ATM
CTM
D stream
anode
E stream
C stream
Figure B.2. Schematic diagram of an electrodialysis assembly. ATM is an anion-transfer
membrane, and CTM is a cation-transfer membrane.
When a potential is applied to the assembly, cations from the D stream migrate through
the cation transfer membrane but are blocked from moving further by the anion transfer membrane. Thus, cations from the D stream are captured between the membranes of a cell pair, the C
stream. Charge neutrality requires that the charge of the cations be balanced by the charge of
anions. If the cell pair is adjacent to the cathode, the charge is balanced by the movement of sulfate or chloride across the anion transfer membrane into the cell pair. Otherwise the charge is
balanced by anions from the D stream. Similarly, anions from the D stream are captured between
the membranes of a cell pair, and their charge is balanced either by sodium from the E stream or
cations from the D stream. Thus, the result of applying a potential across the assembly is to reduce the concentration of ions in the D stream and increase the concentration of ions in the C
stream.
As ions migrate through the assembly, current passes from cathode to anode. To maintain
charge neutrality in the E stream, an electrochemical reaction occurs at the surface of the electrodes. At the surface of the cathode the following reduction reaction occurs
2H2O(l) + 2e− ⎯→ H2(g) + 2OH−(aq).
At the surface of the anode either of the following oxidation reaction occurs:
H2O(l) ⎯→ 2H+(aq) + 1/2O2(g) + 2e−
©2010 Water Research Foundation. ALL RIGHTS RESERVED
188 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
2Cl−(aq) ⎯→ Cl2(g) + 2e−
Thus, small amounts of hydrogen gas are generated at the cathode, and small amounts of
oxygen or chlorine gas are generated at the anode. These gases are usually dissipated in the E
stream effluent. The effluents from the two E streams are typically combined in a tank to maintain a neutral pH, and are often recirculated back to the electrodes. The effluent from the C
stream is discarded. The working of the ED assembly shows that electrical energy is consumed
in desalinating the water.
ED does not remove neutral species, like UO2CO3, and removes relatively small amounts
of ions that have low mobilities. ED typically removes 75 to 98% of the total dissolved solids
from the feedwater. As with RO, fouling and scaling of the membranes can be a problem, and a
prefiltration step and addition of chemical agents may be necessary.
In electrodialysis reversal (EDR), the polarity between the two electrodes is reversed periodically, typically four times an hour, which reduces scaling and fouling of the membranes. In
this case D streams become C streams, C streams not adjacent to E streams become D streams,
and C streams adjacent to E streams effectively become E streams. ED and EDR require little
labor, and maintenance costs are typically low (AWWA 1999).
The City of Washington, Iowa has installed EDR systems to treat groundwater for elevated radium. An account of this system is given by Hays (2000). Electrodialysis systems are
offered by Ionics, Inc. (65 Grove Street Watertown, Watertown, MA 02472-2882), GE Osmonics (GE Water & Process Technologies, 4636 Somerton Rd., Trevose, PA 19053-6783) and EET
Corporation (3106 Roane State Highway, Harriman, TN 37748).
WATER SOFTENING TO REMOVE HARDNESS, RADIUM, AND URANIUM
Water softening is used to remove calcium and magnesium. Radium is a divalent group
IIA metal, like calcium and magnesium, and is removed to a large extent during the softening
process. There are two common water treatments that both soften and simultaneously remove
radium: (1) cation-exchange and (2) lime-soda softening.
Cation-Exchange to Remove Hardness and Radium
In the cation-exchange process, radium ions (as well as calcium and magnesium ions) in
the water are exchanged for sodium ions in the ion-exchange medium. An example is given by
zeolites. Sodium ions are bound to sites in the zeolite by an electrostatic interaction with a negatively charged oxygen atom. This interaction can be symbolized by zeolite-O−Na+. The sodium
can be replaced by other cations. This occurs when radium and other cations are removed from
water. Since radium is a divalent cation, it must displace two adjacent sodium ions in the zeolite.
This is represented by the following reaction:
2 (zeolite-O−Na+) + Ra2+(aq) ⎯→ (zeolite-O−)2 Ra2+ + 2Na+(aq).
The radium ions are retained by the cation-exchange medium, and sodium ions are released, so
that the salinity of the water increases in the cation-exchange process. A cation-exchange medium has a maximum capacity to remove ions from water. After the capacity is depleted, the cation-exchange medium must be regenerated, typically using a brine solution containing a sodium
salt. The brine solution that exits the cation-exchange medium contains the waste radium.
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Appendix B: Water Treatment Options | 189
Examples of inorganic cation-exchange media include Decalso (Permutit Co. 1866-9268420), a synthetic zeolite, and clinoptilolite, a natural zeolite. Examples of organic cationexchange media, also called cation-exchange resins, which contain sulfonic acid groups, are
Amberlite IR-120+ (Rohm Ultramar Diamond Shamrock Corporation Haas Co., 100 Independence Mail West, Philadelphia, PA 19106), Duolite C20 (Rohm and Haas Company, 100 Independence Mall West, Philadelphia, PA 19106-2399), Purolite C100 (The Purolite Co., 150 Monument Road, Bala Cynwyd, PA 19004), and Dowex HCR-S (Dow Water & Process Solutions,
P.O. Box 1206, Midland, MI 48642). The cation-exchange process can remove up to 95% of the
radium. The treated water may be blended with the raw water in a proportion such that the blend
does not exceed the 5 pCi/L limit.
Lime-Soda Softening to Remove Hardness, Radium, and Uranium
2−
Water hardness due Ca2+ and CO3 is called temporary hardness because these ions can
be precipitated by boiling the water according to the following reaction:
−
Ca2+(aq) + 2HCO3 (aq) ⎯→ CaCO3(s) + H2CO3(aq).
When the water is heated the H2CO3 dissociates into water and carbon dioxide, which drives the
above reaction to the right. This causes deposits in pipes, which diminishes the flow of water
over time. Hardness not removed by boiling is called permanent hardness. Thus, salts like calcium sulfate, calcium chloride, magnesium sulfate, and magnesium chloride contribute to permanent hardness.
In lime-soda softening, hydrated lime, Ca(OH)2, is added to the water, which decreases
the temporary hardness according to the following reaction:
−
Ca2+(aq) + 2HCO3 (aq) + Ca(OH)2(s) ⎯→ 2CaCO3(s) + 2H2O(l).
It may seem illogical to add hydrated lime to water to reduce temporary hardness; however, in
the above reaction the calcium from the hydrated lime ends up as insoluble CaCO3. Adding more
hydrated lime to the water increases its pH to about 10 or more and precipitates magnesium as
the hydroxide according to the reaction:
Mg2+(aq) + Ca(OH)2(s) ⎯→ Mg(OH)2(s) + Ca2+(aq).
This reaction increases the amount of permanent hardness due to calcium. This calcium is removed by the addition of sodium carbonate according to the reactions:
2−
Na2CO3(s) ⎯→ 2Na+(aq) + CO3 (aq),
2−
Ca2+(aq) + CO3 (aq) ⎯→ CaCO3(s).
The water that results from these steps is caustic, and its pH is reduced by carbonating the water,
which neutralizes carbonate according to the reactions:
CO2(g) + H2O(l) ⎯→ H2CO3(aq),
2−
−
H2CO3(aq) + CO3 (aq) ⎯→ HCO3 (aq).
Typically, lime-soda softening of groundwater systems only need to be jar tested to determine
the quantities of reagents needed. Surface water systems with variable composition need to be
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190 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
pilot tested. The above equations show that the salinity of the water increases in the lime-soda
softening.
Much of the radium and uranium coprecipitates with the Mg(OH)2 and Ca(OH)2(s). The
activity of radium can be reduced by 75 to 95%. The amount of uranium removed increases with
pH, from 80 to 90%, and above a pH of 10.6 the uranium removed increases with the amount of
magnesium added (Kosarek 1979).
ANION-EXCHANGE FOR URANIUM AND POLONIUM REMOVAL
2+
The uranyl ion, UO 2 , is typically complexed by one to three carbonates ions giving
uranyl carbonate complexes (see Chapter 1). Uranium can be removed with the hydrogen form
2+
of a strong acid resin, by converting all uranium species to UO2 , but the pH of the exiting water
is unacceptably low. Above a pH of 6, uranyl carbonate complexes form, which have a strong
affinity for strong-base anion resins like Ionac A-642 (LANXESS Corp., 111 RIDC Park West
Drive Pittsburgh PA, 15275-1112), Purolite A-500 (The Purolite Co., 150 Monument Road, Bala
Cynwyd, PA 19004), and Amberlite IRA 900 (Polysciences, Inc., 400 Valley Road, Warrington,
PA 18976).
Chloride ions are bound to sites on the anion-exchange resin by an electrostatic interaction with a positively charged trimethylamine group. This interaction can be symbolized by [re+
sin-N(CH3)3 Cl −]. The chloride can be replaced by other anions. This occurs when uranyl carbonate complexes and other anions are removed from water. This is represented by the following
reaction:
2 [resin-N(CH3)3 Cl−] + UO2(CO3) 2 (aq)
+
2−
→ [resin-N(CH3)3 ]2 UO2(CO3) 2 + 2Cl−(aq)
+
2−
The anion-exchange process typically removes >95% of the uranium. After the anion-exchange
resin is depleted, it must be regenerated with a brine solution. The brine exiting the anionexchange resin contains the waste uranium. Naturally occurring anions, like sulfate, can occupy
sites on the anion-exchange resin, and can reduce the capacity of the resin, requiring that the resin be regenerated more frequently.
In one study (Annmäki and Turtianen 2000), polonium was found to be removed most efficiently by the strong and weak basic anion resins; however, polonium removal was highly variable and the amount of salt applied to regenerate the resins has no influence on the regeneration
efficiency for polonium. The authors concluded that polonium is in particulate or colloidal form,
and that these particles are essentially filtered by the resin and no ion exchange occurs.
IRON/ALUMINUM COAGULATION-FILTRATION FOR IRON, URANIUM, AND POLONIUM REMOVAL.
When water has uranium and iron contamination, the uranium can be removed by first
oxidizing the iron, which then coagulates:
2Fe2+(aq) + 1/2O2(g) + H2O(l) ⎯→ 2Fe3+(aq) + 2OH−(aq).
Fe3+(aq) + 3OH−(aq) ⎯→.Fe(OH)3(s).
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Appendix B: Water Treatment Options | 191
Sometimes iron and aluminum are added to the water. The aluminum coagulates with the
iron
Al3+(aq) + 3OH−(aq) ⎯→.Al(OH)3(s).
The uranium then adsorbs on the surface of the Fe(OH)3/Al(OH)3, which is filtered from solution. The amount of uranium removed depends on the pH, and is near a maximum at a pH of 6
and 10, where 50 to 90% of the uranium is removed (Kosarek 1979). In any step that involves
aeration, pollution due to radon gas and effluent mists can be a problem. One study showed that
Iron/Aluminum coagulation-filtration removed more than 90% of polonium (Gäfvert et al 2002).
It was concluded that the polonium was probably adsorbed onto particles in the raw water; the
polonium removal was due to the separation of the particulates from the water.
KMnO4
MnSO4
MnO2 slurry
Radium-containing
backwash
feedwater
Oxidation of ferrous
iron by O2, Cl2,
or KMnO4
Product
mixing
Filtration
Figure B.3. Schematic diagram of the HMO process
PREFORMED HYDROUS MNO2 PROCESS FOR IRON, MANGANESE, AND RADIUM
A schematic diagram of the preformed hydrous MnO2 (HMO) process is given in Figure B.3. In the HMO process, ferrous iron, Fe(II), in the water is oxidized with air, chlorine, or
KMNO4 to ferric iron, Fe(III), which precipitates as the hydroxide:
2Fe2+(aq) + 1/2O2(g) + H2O(l) ⎯→ 2Fe3+(aq) + 2OH−(aq).
Fe3+(aq) + 3OH−(aq) ⎯→.Fe(OH)3(s).
Potassium permanganate and manganese sulfate are premixed in a separate reaction chamber
forming a slurry of MnO2:
−
2MnO4 (aq) + 3Mn2+(aq) + 4OH−(aq) ⎯→ 5MnO2(s) +2H2O(l).
The MnO2 suspension is mixed with the water. Radium adsorbs onto the surface of the Fe(OH)3
and MnO2, which are filtered from the water. The backwash from the filter contains the Fe(OH)3
and the MnO2. The HMO process can remove from 20 to 80% of the radium from water (Kosarek 1979).
REMOVAL OF RADIUM BY MANGANESE GREENSAND FILTRATION
Greensand is an olive-green sandstone rock, which is mainly glauconite. The glauconite
is first stabilized and then coated with manganese oxide. The resulting product is called manga-
©2010 Water Research Foundation. ALL RIGHTS RESERVED
192 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
nese greensand. The manganese oxide coating can exist in an oxidized form and a reduced form.
The oxidized form of the coating oxidizes ferrous iron to ferric iron, which precipitates as the
hydroxide.
As the manganese oxide coating reacts with iron and manganese, it is converted to the reduced form and its capacity to react with these metals is depleted. The oxidized form of the coating must be regenerated with oxidizing agents like KMnO4, chlorine, or a combination of the
two. The regeneration process can be carried out continuously or intermittently. In continuous
regeneration the oxidizing agents are added to the feedstream. This mode of operation is used
where removal of iron is the main consideration.
In the intermittent mode the feedstream is stopped, and the greensand is regenerated by
passing a dilute KMnO4 solution through the bed of greensand. The KMnO4 solution is allowed
several minutes to react with the greendsand. The greensand is rinsed to remove excess KMnO4.
This mode of operation is used when removal of manganese is the main consideration.
Radium in the water is believed to be adsorbed onto the higher oxides of manganese in
the greensand. It removes up to 56% of the radium (Kosarek 1979). This process generates waste
in the form of sludge and dissolved radium from the filter backwash, and eventually the radiumcontaminated greensand must be discarded.
COPRECIPITATION OF RADIUM WITH BARIUM SULFATE
In this process a soluble barium salt is added to water containing radium and sulfate. Insoluble barium sulfate (BaSO4) forms. Radium is chemically similar to barium, and the radium
both coprecipitates with the BaSO4 and adsorbs onto the surface of the BaSO4 crystals. This
treatment may leave the water with barium levels that are too high for consumption and is primarily used for the treatment of wastewater. This process can remove up to 95% of the radium
(Kosarek 1979).
ADSORPTION OF RADIUM ON MNO2-IMPREGNATED RESINS AND ACRYLIC
FIBERS
MnO2-impregnated resins and fibers have been shown experimentally to remove radium
from various types of water in small-scale bench top experiments. The EPA has conducted research on the removal of radium from groundwater using MnO2-impregnated acrylic resins (U.S.
EPA 1987). The conclusion was that the method was unsuccessful and no further research was
recommended. A three-month pilot study was carried out on site using Dowex RSC resin (Shuguang 2005). The absorption capacity of the resin was characterized as being exceptionally high,
but the adsorbent mass transfer zone extended with the progress of pilot test. It was concluded
that the adsorption capacity of the resin was so high that it may not be suitable due to radiation
safety concerns and waste disposal limits.
REMOVAL OF URNANIUM, RADIUM, LEAD, AND POLONIUM WITH GRANULAR
ACTIVATED CARBON FILTRATION
Granular activated carbon (GAC) is a form of activated carbon with a particle size that is
significantly larger than powdered activated carbon. GAC can be produced from coconut shells
or coal. The particle size of GAC is designated by the notation n×m, where the particles that will
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Appendix B: Water Treatment Options | 193
pass through a U.S. Standard Mesh Size No. n sieve but be retained on a U.S. Standard Mesh
Size No. m sieve. GAC for liquid applications can be obtained from Siemens Water
Technologies (181 Thorn Hill Rd, Warrendale, Pa. 15086) under the brand names AquaCarb®
and BevCarb®, from Jacobi Carbons, Inc.(1518 Walnut Street, Suite 1350, Philadelphia, PA
19102) under the brand name AquaSorb®, and from Calgon Carbon Corp. (P.O. Box 717, Pittsburgh, PA USA 15230) under the brand name Filtrasorb®.
GAC is typically used to remove radon from water. Tests for the removal of other radionuclides, including radon, were conducted on private wells using GAC columns equipped with
sediment filters (Annmäki and Turtianen 2000). Granular sizes of 0.5-1 mm and >1 mm were
used, which resulted in flow rates of 15 and 30 L/hr., respectively. Sampling for radionuclides
was carried out in three-month intervals, and the service time of the columns ranged from 8 to 27
months.
Uranium removal was only observed when the bed volume of water passed through the
column was less than 200. For large bed volumes, the uranium concentration in the effluent was
the same or slightly higher than in the influent. Radium removal rates for two filters were 53 and
67%. The authors speculated that part of the radium retention might be due to the formation of
radium complexes with humus and fulvic acids, which had collected on the column, and to the
absorption of radium onto ferric hydroxide precipitates, which had formed on the column during
filtration (since the highest radium removal coincided with the well with the highest iron concentration). Depending on the location, lead removal ranged form 30 to 100%. Polonium removal
was typically greater than 80%).
REMOVAL OF URANIUM, RADIUM, LEAD, AND POLONIUM BY
NANOFILTRATION
Nanofiltration (NF) is similar to reverse osmosis (RO) in that a membrane separates a
feedstream from a permeate. In nanofiltration, the pore size of the membrane is nominally one
nanometer, which allows more solutes to cross an NF membrane than a RO membrane; however,
the pressure differential between the feedstream and the permeate is less in NF than in RO. A
membrane for NF is typically characterized by the minimum molecular weight of a solute that
can pass through the membrane. Thus, NF membranes are usually characterized by the minimum
molecular weight, called the molecular weight cutoff (MWCO), rather than by the pore size.
An NF pilot plant experiment using five flat sheet NF membranes with a total area of
1800 cm2 was operated to determine the uranium removal efficiency (Raff O and Wilken RD
1999). The NF membranes used were Desal 5 DK, Desal 5KL, and Desal 52 HL from Ge Osmonics (GE Water & Process Technologies, 4636 Somerton Rd., Trevose, PA 19053-6783) and
NF 90 and NF 45 from Dow Chemical Co. (Dow Water & Process Solutions, P.O. Box 1206,
Midland, MI 48642). The permeate flux across the membranes ranged fro 3.5 to 7.0
L/(m2⋅hr⋅bar). The feedstream consisted of 1 mg/L of uranium and variable amounts of NaHCO3
in DI water with the pH adjusted to 5.9, 7.3, and 8.3., The uranium removal for most experiments
ranged from 81 to 90%, but was usually above 95%.The pH dependence of uranium removal
showed that not all uranium species were excluded equally by the NF membranes. Removal of
2−
4−
the two negative uranyl complexes UO2(CO2) 2 and UO2(CO3) 3 , which are predominant at pH
0
7.3 and 8.3, were 95% or more; removal of the neutral complex UO2CO 3, which is a major species at ph 6.7, was less than 95%.
©2010 Water Research Foundation. ALL RIGHTS RESERVED
194 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
In another study (Favre-Re´guillon et al 2008), experiments were carried out using commercial mineral waters of varying ionic strengths and chemical compositions with 2 mg/L of
uranium. The rejection of uranium by the NF membranes depended on the uranyl species in and
the ionic strength of the water. Rejection was found to be due to charge interactions between the
uranyl carbonate complexes and membrane’s pores. It was found that mineral water containing
up to 20 ppb of uranium could be reduced to 0.8 ppb. As with other membranes, NF membranes
are subject to irreversible fouling and must be chemically cleaned periodically (Koš utić K and
Kunst 2002).
REMOVAL OF URANIUM AND ARSENIC BY HYDROUS IRON OXIDE NANOPARTICULATE RESIN
ArsenXnp (SolmeteX, 50 Bearfoort Road, Northborough MA 01532) is a nanoparticlebased, hydrous iron oxide selective ion-exchange resin that is designed to remove arsenic. ArsenXnp also removes uranium from water. In study conducted by the EPA (U.S. EPA 2008d), a
treatment system achieved a run length of 33,100 bed volumes at 10-μg/L arsenic breakthrough
and reduced 26.6 to 38.9 μg/L of uranium below the method detection limit of 0.1 μg/L throughout the entire study period from October 13, 2005 through August 3, 2006, treating approximately 6,693,700 gallons of water. Silica at a level of 43.4 mg/L (as SiO2) had little or no effect on
ArsenXnp performance and was only removed for the initial 1,000 BV. Parameters like pH, alkalinity, sulfate, fluoride, nitrate, and hardness were not affected.
©2010 Water Research Foundation. ALL RIGHTS RESERVED
APPENDIX C
DETECTOR EFFICIENCIES IN BA(RA)SO4 RESIDUES
INTRODUCTION
In the following sections, the theory and experiments are presented to determine alpha
emitter efficiencies in BaSO4 residues. The BaSO4 efficiencies will be denoted by the symbol
“ε.” The method used to prepare the BaSO4 residues gives visibly uniform residues, so, in all that
follows, the BaSO4 residues will be assumed to be of uniform thickness across the planchet.
While the equations in the next two sections are derived for a uniform Ba(Ra)SO4 residue, they
could be applied to a residue of any composition or geometry. Because of the large number of
variables needed, the same symbol is sometimes used for two different variables in two or more
different sections.
EFFICIENCIES OF THE 226RA DECAY CHAIN
In this section it is shown how the 226Ra efficiency and the average efficiency of 226Ra
progeny may be determined experimentally (Arndt and West 2007, Arndt and West 2008a). The
five progeny— 222Rn, 218Po, 214Pb, 214Bi, and 214Po—of 226Ra decay chain in Eqn. (1.6) must be
considered, three of which are alpha emitters. The next progeny in the chain, 210Pb, need not be
considered because, due to its half-life of 22 y, the 210Pb activity that grows in over the allowed
six-month holding time (U. S. EPA 2007) of the sample is negligible (over six months, 1 pCi of
226
Ra produces about 0.015 pCi of 210Pb). The same considerations show that the activities of
210
Bi and 210Po are negligible.
Let the quantities associated with 226Ra, 222Rn, 218Po, 214Pb, 214Bi, and 214Po be denoted
by subscripts 1, 2, 3, 4, 5, and 6, respectively. When 226Ra decays, the recoiling 222Rn nucleus
may travel far enough to leave the BaSO4 residue and be lost to volatilization. Let κ2 be the fraction of 222Rn that remains in the residue. More generally, let κi be the fraction of ith radionuclide
produced by 226Ra decay that remains in the residue, and let A1 be the 226Ra activity in the residue. Then the activity Ai of the ith radionuclide at time t due to 226Ra decay is given by the
Bateman equations:
i
Ai = κ i A1 ∑ c j exp( −λ j t ) (2 ≤ i ≤ 9) ,
(C.1)
j =1
where λj is the decay constant of the jth radionuclide and
λ λ . . . λi −1λi
c j = 2i 3
∏ (λ k − λ j )
k =1
k≠ j
For i = 3 to 6, the half-life of the longest-lived radionuclide, 214Pb, is 26.8 minutes. Consequently, for i = 1 to 6, if at least 3 hours have passed since the coprecipitation of 226Ra, then all
of the exponential terms in Eqn. (C.1) are negligible except for the first two. Since exp(−λ1t) ≈ 1
and λ2 >> λ1, and since λi >> λ1 and λi >> λ2 when 3 ≤ i ≤ 6; Eqn. (C.1) shows that after 3 hours
(C.2)
Ai = κiA1[1 − exp(−λ2t)] (2 ≤ i ≤ 6).
195
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196 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
Thus, the number of alpha counts per unit time, ΔN/Δt, induced in the detector is given by
ΔN
= ε 1 A1 + ε 2 A2 + ε 3 A3 + ε 6 A6 .
Δt
(C.3)
Substituting Eqn.(C.2) into Eqn. (C.3) yields
ΔN
= 3Kε ave [1 − exp(−λ 2 t )] + ε 1 ,
ΔtA1
(C.4)
where K = (κ2 + κ3 + κ6)/3, and
ε ave =
κ 2 ε 2 + κ 3ε 3 + κ 6 ε 6
,
κ2 + κ3 + κ6
(C.5)
which is a weighted average of the progeny efficiencies. The 226Ra activity is given by A1 = γA1,S,
where A1,S is the 226Ra activity used in the coprecipitation and γ is the chemical yield of 226Ra.
Time t is taken as the time between the coprecipitation of 226Ra and the midpoint of the counting
interval Δt. Eqn. (C.4) shows that a plot of ΔN/(ΔtγA1,S) versus 1 − exp(−λ2t) should yield a
straight line with slope 3Kεave and intercept ε1. Figure C.1 is such a plot for four samples with
the BaSO4 residue masses indicated above the corresponding line. Values of ΔN/(ΔtγA1,S) were
determined on four occasions, and the lines in Figure C.1 are fits to the four data points.
Values of the 226Ra efficiencies, ε1, and the average progeny efficiencies, Kεave, were
determined from the slopes and intercepts of plots like those in Figure C.1 using Eqn. (C.4).
Figure C.2 is a plot of ε1 and Kεave versus BaSO4 residue mass. The solid squares are values of ε1
and the solid triangles are values of Kεave.
0.8
0.7
3.3 mg
ΔN/(γ A1,SΔt)
0.6
81.8 mg
0.5
136.8 mg
0.4
0.3
0.2
277.9 mg
0.1
0.0
0.0
0.2
0.4
0.6
0.8
1.0
1 − exp(−λ2t)
Figure C.1. Plot for the determination of ε1 and Kεave
Source: Arndt and West 2007. An Experimental Analysis of Some of the Factors Affecting Gross
Alpha-Particle activity with an Emphasis on 226Ra and its Progeny. Health Phys. 92:148-156.
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Appendix C: Detector Efficiencies in Ba(RA)So4 Residues | 197
0.25
0.20
Efficiency
ε1
K ε ave
0.15
0.10
0.05
0.00
0
100
200
300
400
500
600
Ba(Ra)SO4 residue mass (mg)
Figure C.2. The efficiencies of 226Ra and its progeny, ε1, and Kεave
Source: Arndt and West 2007. An Experimental Analysis of Some of the Factors Affecting Gross
Alpha-Particle activity with an Emphasis on 226Ra and its Progeny. Health Phys. 92:148-156.
From the high alpha-particle energies of the 226Ra progeny (Figure 1.2), it might be expected that Kεave would greatly exceed ε1. This is true for most residue masses; however, Figure C.2 shows that at the lowest masses Kεave is comparable to ε1. This is partly due to the fact
that, because of edge effects, all efficiencies approach an upper limit as the residue mass goes to
zero. It is probably also due, in part, to some loss of 222Rn by volatilization, since this loss would
be most prominent at the lowest residue masses.
In EPA Method 900.0 either 230Th or natural uranium (mostly 234U and 238U) can be used
as calibration standards. Figure 1.2 shows that the alpha-particle energy of 226Ra is about the
same as that of 230Th and is somewhat greater, on average, than that of natural uranium. Consequently the efficiency of 230Th will be approximately equal to that of 226Ra, and the efficiency of
natural uranium will be somewhat less than that of 226Ra. Thus, the average progeny efficiency,
Kεave, will significantly exceed the calibration standard’s efficiency at most residue masses. And,
from Eqn. (2.5), it is expected that the contribution of the progeny to the GAA will substantially
exceed the total activity of the progeny.
In Appendix F the efficiencies ε1 and Kεave will be used to calculate the contribution of
226
Ra and its progeny to the GAA. To do this, it is necessary to have functions giving ε1 and
Kεave in terms of the residue mass m. In Figure C.2 the curves through ε1 and Kεave are fits to the
⎧⎪a 0 + a1 m + a 2 m 2 + a3 m 3 + a 4 m 4 if m ≤ m1 ,
f ( m) = ⎨
function:
⎪⎩b / m n if m > m1 ,
(C.6)
where a0, a1, a2, a3, a4, m1, and b are adjustable parameters. The function and its first derivative
were constrained to be continuous at m1, leaving five independent parameters. The factor m1 was
taken approximately to be the transition from “thin” to “thick” residues (Semkow et al 2005).
©2010 Water Research Foundation. ALL RIGHTS RESERVED
198 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
The parameter m1 was adjusted a little so that the efficiency of the bottom layer of the residue,
η(l) from Appendix G, decreased monotonically. A summary of the parameters is given in Table C.1. Semkow et al (2005) showed that the fractal dimension D of the residue’s surface is
given by
D = 3 – n,
where n is one of the parameters in Eqn. (C.6). The value of D can range from 2 to 3. For residues with a smooth surface D = 2. Values of D greater than 2 indicate that the surface has some
roughness. The rougher the surface, the closer the value of D is to 3. The values of D for ε1 and
Kεave are 2.09, which is close to 2, but indicates that the surface has some roughness.
Table C.1
Fit parameters to Eqn. (C.6)
226
Ra and progeny
224
ε1
Kεave
K1εave,1
K2εave,2
a0
0.2292
0.2364
0.2518
0.2716
0.2345 0.2334 0.1810
a1 × 104
−11.04
−5.698
−4.978
−6.323
−10.85 −11.45
-9.325
a2 × 106
−11.96
−1.832
−4.391
0.4805
0.2260 −1.359
-7.015
a3 × 108
9.222
0.6875
1.625
0
0.3609
1.635
5.072
m1
89
205
173
288
115
120
75
B
6.141
13.24
7.913
11.43
7.207
6.942
4.738
N
0.9145
0.9144
0.8154
0.7912
0.8864 0.8760 0.9104
D
2.09
2.09
2.18
2.21
Radionuclide(s)
Efficiency
Ra and progeny
241
Am
ε1
2.11
210
238
Po
ε1
2.14
U
ε1
2.09
EFFICIENCIES OF THE 224RA DECAY CHAIN
In this section it is shown how the two efficiencies of the 224Ra decay chain of Eqn. (1.7)
may be determined experimentally (Arndt and West 2008a). Let the quantities associated with
224
Ra, 220Rn, 216Po, 212Pb, 212Bi, and 212Po be denoted by subscripts 1, 2, 3, 4, 5, and 6, respectively.
At time t = 0, let the 224Ra activity be A1,0 and let the 224Ra progeny activities be zero in the
Ba(Ra)SO4 residue. Then the ith progeny activity at time t is given by the Bateman equations:
i
Ai = κ i β i A1,0 ∑ cij exp(−λ j t ) (2 ≤ i ≤6)
j =1
©2010 Water Research Foundation. ALL RIGHTS RESERVED
(C.7)
Appendix C: Detector Efficiencies in Ba(RA)So4 Residues | 199
where the factor κi (≤ 1) accounts for volatilization and recoil loss from the residue, λj is the decay constant of the jth radionuclide, βi is the alpha-decay branching ratio, and
cij =
λ2 λ3 . . . λi −1λi
i
∏ (λ
k
.
− λj)
k =1
k≠ j
If about 10 minutes have passed since t = 0, then the second and third exponential terms in Eqn.
(C.7) are negligible relative to the first, fourth, fifth, and sixth terms, and
Ai = κ i A1,0 exp(−λ1t ) (i = 1, ...,3) ,
(C.8)
A5 = β 5κ 5 A1,0 [c51 exp(−λ1t ) +c 54 exp(−λ 4 t )+ c55 exp(−λ5 t )] ,
(C.9)
A6 = (1 − β 5 )κ 6 A1,0 [c51 exp(−λ1t ) +c 54 exp(−λ 4 t )+ c55 exp(−λ5 t )] ,
(C.10)
where κ1 = 1, β5 = 0.3594, c51 = 1.153, c54 = −1.260, and c55 = 0.1077.
The number of alpha counts dN induced in the detector in time dt is given by
dN
= ε 1 A1 + ε 2 A2 + ε 3 A3 + ε 5 A5 + ε 6 A6 ,
dt
(C.11)
where εi is the efficiency of the ith alpha emitter in the Ba(Ra)SO4 residue. Substituting Eqns.
(C.8), (C.9), and (C.10) into Eqn. (C.11) yields
⎡
⎛
⎞⎤
c
dN
= A1,0 ⎢k1 exp(−λ1t ) − k 2 ⎜⎜ exp(−λ 4 t ) + 55 exp(−λ5 t ) ⎟⎟⎥ ,
c54
dt
⎝
⎠⎦
⎣
(C.12)
k1 = ε 1 + κ 2 ε 2 + κ 3ε 3 + β 5 c51κ 5ε 5 + (1 − β 5 )c51κ 6 ε 6 ,
(C.13)
k 2 = − β 5 c54κ 5ε 5 − (1 − β 5 )c54κ 6ε 6 ,
(C.14)
where
Integrating both side of Eqn. (C.12) with respect to t from t to t + Δt gives
⎡
⎞⎤
⎛
c
ΔN = A1,0 ⎢k1 I 1 − k 2 ⎜⎜ I 4 + 55 I 5 ⎟⎟⎥ ,
c54 ⎠⎦
⎝
⎣
(C.15)
where ΔN is the number of alpha counts accumulated from t to t + Δt and
Ii =
1
λi
{exp(−λi t ) − exp[−λi (t + Δt )]} .
Rearranging terms in Eqn. (C.15) gives
⎞
c
1⎛
ΔN
= k1 − k 2 ⎜⎜ I 4 + 55 I 5 ⎟⎟ .
A1, 0 I 1
I1 ⎝
c54 ⎠
©2010 Water Research Foundation. ALL RIGHTS RESERVED
(C.16)
200 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
In the coprecipitation experiments, A1,0 = γA1,S, whereγ is the chemical yield of radium in
Ba(Ra)SO4 and A1,S is the 224Ra activity used in the coprecipitation. Eqn. (C.16) shows that a plot
of ΔN/A1,0I1 versus [I4 + (c55/c54)I5]/I1 should be a line with slope −k2 and intercept k1.
The parameters k1 and k2 can be related to the two efficiencies:
ε + κ 2 ε 2 + κ 3ε 3
ε ave,1 = 2
,
(C.17)
1+ κ2 + κ3
βκ 5ε 5 + (1 − β )κ 6 ε 6
,
(C.18)
ε ave,2 =
βκ 5 + (1 − β )κ 6
which are weighted averages of the efficiencies for 224Ra, 220Rn, and 216Po and the efficiencies
for 212Bi and 212Po, respectively. Let
1
K 1 = (1 + κ 2 + κ 3 ), K 2 = β 5κ 5 + (1 − β 5 )κ 6 .
3
Then the ε i in Eqns. (C.17) and (C.18) can be eliminated using Eqns. (C.13) and (C.14) to give
⎞
c
1⎛
(C.19)
K 1ε ave,1 = ⎜⎜ k1 + 51 k 2 ⎟⎟ ,
3⎝
c54 ⎠
k2
.
(C.20)
c54
The quantities K1εave,1 and K2εave,2 will be referred to as the two efficiencies of the 224Ra
decay chain, since these are the quantities that can be measured experimentally. Eqns. (C.19) and
(C.20) can be solved simultaneously to give
k1 = 3K 1ε ave,1 + c51 K 2 ε ave, 2 ,
(C.21)
K 2 ε ave, 2 = −
(C.22)
k 2 = −c54 K 2 ε ave, 2 .
Experiments were carried out to determine k1 and k2 (Arndt and West 2008a). Figure C.3
is plot of ΔN/A1,0I1 versus [I4 + (c55/c54)I5]/I1 for various BaSO4 residue masses. The k1 and k2
were determined from the slopes and intercepts of the lines as describe above, and the corresponding values of K1εave,1 and K2εave,2 were determined using Eqns. (C.19) and (C.20). The values of K1εave,1 and K2εave,2 versus residue mass are plotted in Figure C.4. The solid squares are
values of K1εave,1 and the solid triangles are values of K2ε2,ave. In Figure C.4 the curves through
K1εave,1 and K2εave,2 are fits to the function in Eqn. (C.6). A summary of the fit parameters are
given in Table C.1. In Appendix F the efficiencies K1εave,1 and K2εave,2 will be used to determine
the contribution of the members of 224Ra decay chain [Eqn. (1.7)] to the GAA.
Kε ave and K1εave,1 in Figures C.2 and C.4 are nearly equal because the average energies of
the alpha emitters contributing to Kεave and K1εave,1 are 6.39 and 6.25 MeV, respectively. K2εave,2
significantly exceeds K1εave,1 at the higher masses. This is because 64% of the contribution to
K2εave,2 is from 212Po, whose alpha-particle energy, 8.78 MeV, exceeds that of all other alpha
emitters by 1 MeV or more.
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Appendix C: Detector Efficiencies in Ba(RA)So4 Residues | 201
1.0
4.1 mg
0.9
0.8
66.0 mg
ΔN/(γ1A1,SI1)
0.7
140.6 mg
0.6
0.5
253.2 mg
0.4
0.3
571.4 mg
0.2
0.1
0.0
0.0
0.2
0.4
0.6
0.8
1.0
[I4 + (c55/c54)I5]/I1
Figure C.3. Plot for the determination of k1 and k2
Source: Arndt and West 2008a. An Experimental Analysis of the Contribution of 224Ra and 226Ra
and Progeny to the Gross Alpha-Particle Activity of Water Samples. Health Phys. 94:459-470.
0.25
K1ε1,ave
K2ε2,ave
Efficiency
0.20
0.15
0.10
0.05
0.00
226
Ra
0
100
200
300
400
500
600
Ba(Ra)SO4 residue mass (mg)
Figure C.4. The efficiencies of the 224Ra decay chain
Source: Arndt and West 2008a. An Experimental Analysis of the Contribution of 224Ra and 226Ra
and Progeny to the Gross Alpha-Particle Activity of Water Samples. Health Phys. 94:459-470.
©2010 Water Research Foundation. ALL RIGHTS RESERVED
202 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
The dotted line in Figure C.4 is the 226Ra efficiency data from Figure C.2. Since the efficiencies of the calibration standards are about equal to or slightly less than the 226Ra efficiencies,
Eqn. (2.4) and Figure C.4 show that, at most residue masses, the contribution of the alpha emitters of the 224Ra decay chain to the GAA will substantially exceed the total activity of the alpha
emitters in the 224Ra decay chain. Their contribution to the GAA is calculated in Appendix F.
During these experiments it was evident that there was detector contamination by 220Rn
and its progeny. In Appendix H it is shown that radon emanation from the Ba(Ra)SO4 residues is
relatively low. This is not unexpected since, up to a point, radon emanation increases with the
moisture content of materials (Strong and Levins 1982) due to the presence of bulk water between sample grains (Sasaki et al 2004), and the Ba(Ra)SO4 residues presumably contain little
water. Actual residues are sometimes hygroscopic, despite being heated over a flame, and radon
emanation from such samples could be significant.
EFFICIENCY OF 228TH
To determine the GAA due to the ingrowth of alpha emitters produced by the decay of
Ra, it is necessary to obtain the efficiency of 228Th and the efficiencies of 224Ra and its alphaemitting progeny. The efficiency data from the previous section will be used for 224Ra and its progeny. It would be difficult to measure the efficiency of 228Th because it has no gamma peak of sufficient intensity to measure its activity and because it would be difficult to coprecipitate 228Th with
BaSO4 without coprecipitating its progeny. However, it is feasible to determine 241Am efficiencies
in BaSO4 because (1) 241Am is readily coprecipitated with BaSO4, (2) the 241Am standard has no
significant progeny activity, and (3) 241Am has a full-energy peak in the gamma spectrum (59.54
keV) that can be used to determine its activity. The 241Am efficiencies can be used in place of 228Th
efficiencies because the alpha-particle energies of 241Am [5.44 MeV (13 %) and 5.49 MeV (85 %)]
are similar to those of 228Th [5.34 MeV (27 %) and 5.42 MeV (72 %)].
Ba(Am)SO4 residues were prepared as outlined in Chapter 3. The efficiency ε1 of 241Am
is just the ratio of the net number of alpha counts per unit time, C, measured by the gasproportional counter over the activity A of 241Am in the Ba(Am)SO4; i.e., ε1 = C/A. In Figure C.5
the solid squares are the 241Am efficiency data versus BaSO4 residue mass. The curve though the
data is a fit to Eqn. (C.6). The fit parameters are compiled in Table C.1.
228
EFFICIENCY OF 210PO
The efficiency of 210Po is needed to determine its contribution to the GAA. It would be
difficult to measure the efficiency of 210Po directly because it has no gamma peak of sufficient
intensity to measure its activity. Consequently, the efficiency of 210Po was determined by a linear
interpolation between the 226Ra efficiency data and the 241Am efficiency data using the following
equation:
ε = aE + b ,
(C.23)
where, for a given residue mass, ε is the efficiency, E is the alpha-particle energy, and a and b
are constants. The linear interpolation is an approximation and is not based on any theoretical
model. The 226Ra efficiencies are plotted in Figure C.5, and the dashed curve is the 210Po efficiencies determined using the above equation. The 210Po efficiencies in Figure C.5 were fit to
Eqn. (C.6), and the fit parameters are given in Table C.1.
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Appendix C: Detector Efficiencies in Ba(RA)So4 Residues | 203
0.25
Efficiency
0.20
0.15
241
Am
0.10
226
0.05
Ra
210
Po
0.00
0
100
200
300
400
500
600
BaSO4 Residue mass (mg)
Figure C.5. Efficiencies of 241Am and 210Po
Source: Arndt and West 2008c. An Experimental Analysis of the Contribution of 210Pb and 210Po
and Progeny to the Gross Alpha-Particle Activity of Water Samples. Health Phys. 95:310-316;
2008.
0.24
0.20
Efficiency
0.16
0.12
0.08
0.04
0.00
0
100
200
300
400
500
BaSO4 mass (mg)
Figure C.6. Efficiencies of 238U as interpolated from 226Ra efficiencies
©2010 Water Research Foundation. ALL RIGHTS RESERVED
600
204 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
EFFICIENCIES OF 234U AND 238U
Because the alpha-particles energies of 226Ra and 234U are similar (Table 1.1), the 234U
efficiency in BaSO4 will be assumed to be equal to the 226Ra efficiency in BaSO4, which is
plotted in Figure C.6. The 238U efficiencies in BaSO4 are needed for the GAA calculations. These
were not measured but will be estimated from the 226Ra efficiencies in BaSO4. An alpha
particle’s energy must be at least about 2.0 MeV to cause a pulse in the detector. Consequently, it
will be assumed that the efficiency corresponding to an alpha-particle energy of 2.0 MeV is zero,
and the 238U efficiencies in BaSO4 will be obtained from a linear interpolation between the 226Ra
efficiencies in BaSO4 and zero efficiency at 2 MeV using Eqn. (C.23), which is an
approximation that is not based on any theoretical model. The 238U efficiencies in BaSO4 are
plotted in Figure C.6. The 238U efficiency data was fit to Eqn. (C.6). The fit parameters are
summarized in Table C.1.
©2010 Water Research Foundation. ALL RIGHTS RESERVED
APPENDIX D
EFFICIENCIES IN RESIDUES OF ARBITRARY COMPOSITION
In Appendix C, it proved advantageous to determine an alpha emitter’s efficiency in BaSO4 residues. However, it is now necessary to determine the alpha emitter’s efficiency in a sample residue of arbitrary composition. Let e be an efficiency in a sample residue, and let ε be an
efficiency in a Ba(Ra)SO4 residue. And for a given alpha-particle energy, let R1 be the range (in
mg/cm2) in BaSO4 and let R2 be the range in an arbitrary residue (in mg/cm2). Thus, if SP is the
planchet area, a sample residue of mass SPR2 will have about the same efficiency as a BaSO4 residue of mass SPR1; i.e.
e(SPR2) ≈ ε (SPR1)
or
e(m) ≈ ε [(R1/ R2)m)],
(D.1)
where m = SPR2 is the mass of the sample residue. In this equation it should be noted that the
term ε [(R1/ R2)m)] means that ε is a function of (R1/ R2)m, and not that ε is multiplied by (R1/
R2)m. Next, the factor R1/R2 is estimated for a sample residue in which the water sample has a
composition given in Table D.1, which is typical for a sample from a sandstone aquifer (Stumm
and Morgan 1970).
In EPA Method 900.0, samples are prepared using 16 M HNO3 to drive off chloride,
which is corrosive to the planchet. It will be assumed that during sample evaporation, sulfate
precipitates with calcium and that all other residue salts are nitrates. Further, it will be assumed
that the nitrates of calcium and magnesium decompose to oxides and that silicic acid decomposes
to SiO2 when the residue is heated over a flame. The functions R1 and R2 can be determined using the Bragg-Kleeman rule:
n
w
1
=∑ i ,
R i =1 ri
(D.2)
where wi is the weight fraction and ri is the range of the ith element.
Table D.1
The composition of a groundwater sample (Stumm and Morgan 1970)
Species
Conc. (M)
Conc. (mg/L)
−3.3
Na
12
10
−4
4
K
10
−3.5
8
Mg
10
−3
Ca
40
10
−3.9
8
H4SiO4
10
−3.2
SO4
61
10
The functions ri were determined from the database of Coursey et al (2005) either from
the element itself or if elemental data were unavailable, from the Bragg-Kleeman rule:
205
©2010 Water Research Foundation. ALL RIGHTS RESERVED
206 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
r1 / r2 =
A1 / A2 ,
where A is atomic weight, using the average of two determinations with elements of atomic
weights greater and less than the element of interest. Using Eqn. (D.2) the value of R1/R2 for the
residue composition of Table D.1 was determined at 200 equidistant points in range of alphaparticle energies from 2 to 9 MeV. These points were averaged and it was found that R1/R2 =
1.42 (σ = ±1.3%). This value of R1/R2 will be used in all calculations of Chapter 4.
©2010 Water Research Foundation. ALL RIGHTS RESERVED
APPENDIX E
EFFICIENCIES IN RESIDUES OF ARBITRARY GEOMETRY
In this section it is shown how the efficiencies of a sample residue of arbitrary composition and of nonuniform thickness can be calculated from the efficiency data of the BaSO4 residues. In Appendix C, the efficiency of a radionuclide in a BaSO4 residue was designated by the
letter “ε “ with a subscript. In this section, the efficiency of a radionuclide in a residue of arbitrary composition is designated by a letter “e” with a subscript, and the average efficiency of a
collection of alpha emitters, in secular equilibrium with each other, is designated by Keave, where
K is a factor that accounts for loss of alpha emitters from the sample, either by recoil loss or volatilization, and eave is the average efficiency of the alpha emitters. K and eave may have subscripts. The efficiencies of uniform residues are used in Eqn. (E.2) to obtain the efficiencies of
smooth or patch residues. These efficiencies are denoted by 〈e〉 or 〈Keave〉. The brackets “〈〉” indicate that e and Keave are being averaged over the geometry of the residue.
Let τ = m/SP, where m is the residue mass and SP is the planchet area (20.4 cm2). Arndt
and West (2007) defined the residue geometry by a density function ϕ (τ ) such that ϕ (τ )dτ is a
probability of the residue having a thickness between τ toτ + dτ. Accordingly, if the radial distribution of the residue is uniform, the efficiency 〈e〉 averaged over ϕ (τ ) is given by
1 τ
〈 e〉 = ∫ 2 τ ϕ (τ ) e ( S Pτ ) dτ
τ 0 τ1
(E.1)
where τ 0 is the average of τ ; τ ranges from τ 1 to τ 2, and e is an efficiency in a uniform residue.
Substituting Eqn. (D.1) into Eqn. (E.1) gives
1 τ
(E.2)
〈 e〉 = ∫ 2 τ ϕ (τ ) ε [( R1 / R2 )S Pτ ] dτ ,
τ 0 τ1
where ε stands for an efficiency in a BaSO4 residue: e.g., ε1, Kεave, K1εave,1, or K2εave,2,. In the
previous section, it was estimated that R1/R2 = 1.42 for a residue of a groundwater sample with
the composition given in Table D.1.
Arndt and West (2007) defined two types of limiting residues: (1) a “smooth” residue
with
ϕ (τ ) = 1/(2τ 0),
(E.3)
whose thickness varies continuously from 0 to 2τ 0 and whose mass completely covers the planchet bottom; and (2) a “patch” residue with
ϕ (τ ) = 0.38δ (τ − τ R),
(E.4)
where δ is the Dirac delta function. The patch residue consists of patches of uniform thickness τ
R that cover 38% of the planchet bottom. A smooth residue has an efficiency near the maximum
of those encountered in practice. Although the smooth residue covers the bottom of the planchet,
it is not of uniform thickness and, therefore, has an efficiency that is somewhat less than that of a
residue of uniform thickness. A patch residue has an efficiency near the minimum of those encountered in practice.
207
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208
©2010 Water Research Foundation. ALL RIGHTS RESERVED
APPENDIX F
EQUATIONS FOR THE CALCULATION OF THE CONTRIBUTION OF
ALPHA EMITTERS TO THE GROSS ALPHA-PARTICLE ACTIVITY
INTRODUCTION
In the following sections the GAA is determined for (1) the 226Ra decay chain, (2) the
Ra decay chain, (3) the 212Pb decay chain, (4) the 228Ra decay chain, (5) the 210Po decay chain,
(6) the 210Pb decay chain, (7) the 234U decay chain, and (8) the 238U decay chain. Because of the
large number variables needed, it is necessary to reuse some of the same symbols in more than
one section. Thus, it should be remembered that the same symbol used in two different sections
may have two different meanings.
224
SOME PRELIMINARIES
Before deriving the equations for the GAA due to the various decay chains, two
equations [Eqns. (F.3) and (F.4)] are needed that are common to several of the derivations. In
this section, a short derivation of these equations is presented.
The efficiency ei of the ith alpha emitter in a uniform residue is defined by
ei =
Ni
ΔtAi
i = 1, 2, 3, . . .
where Ai is the activity of the ith alpha emitter in the sample residue and Ni is the number of
alpha counts of the ith alpha emitter detected in the time interval Δt. Rearranging the above
equation gives
Ai =
Ni
ei Δt
i = 1, 2, 3, . . .
(F.1)
Thus, if there are n alpha emitters in the sample residue, the total alpha activity AT of the residue
divided by the sample volume V is given by
AT
1
=
V
ΔtV
n
Ni
∑e
i −1
.
i
Ideally, the GAA would be equal to AT/V; however, unless the radiological composition,
the inorganic composition, and the geometry of the residue of the sample are known, it is not
possible to determine the Ni and ei from a measurement of the GAA. Instead, in EPA Method
900.0, the efficiencies of all alpha emitters are approximated by the efficiency of a calibration
standard, either 230Th or natural uranium. Let the calibration standard’s efficiency be denoted by
eS, and let the GAA be denoted by G. Then G is the approximation to AT/V that is obtained by
setting all of the efficiencies in the above equation equal to the calibration standard’s efficiency:
That is
G=
n
1
∑ Ni .
e S VΔt i =1
(F.2)
209
©2010 Water Research Foundation. ALL RIGHTS RESERVED
210 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
When Ai and ei are known, Ni can be obtained by rearranging Eqn. (F.1) to yield
N i = Ai ei Δt i = 1, 2, 3, . . ., n .
Typically, sample residues are nonuniform, and in such residues the efficiency is denoted by 〈ei〉
to show that the efficiency was derived from the efficiencies of the BaSO4 residues, the inorganic
composition of the sample residue (through the factor R1/R2.), and the function ϕ (τ ) using the
methods of Appendix E. In this case, the corresponding number of counts in time interval Δt will
be denoted by 〈Ni〉. Then the above equation becomes
〈 N i 〉 = Ai 〈 ei 〉 Δt i = 1, 2, 3, . . ., n .
(F.3)
The GAA derived from these values of 〈Ni〉 will be denoted by 〈G〉. Then Eqn. (F.2) becomes
n
1
〈G 〉 =
〈Ni 〉 .
∑
e S VΔt i =1
Carrying out the summation in this equation yields the following equation for the GAA of a
sample residue:
〈 ΔN 〉
〈G 〉 =
.
(F.4)
eS VΔt
where
n
〈 ΔN 〉 = ∑ 〈 N i 〉 .
i =1
There are no angle brackets around eS in the above equation because this quantity is determined
in a separate measurement using a calibration standard.
CALCULATION OF THE EFFICIENCY OF THE 230TH CALIBRATION STANDARD
The efficiency of the 230Th calibration standard, eS, must be determined before Eqn. (F.4)
can be used to calculate the GAA. Since 230Th and 226Ra have similar alpha-particle energies, the
226
Ra efficiencies will be used in place of the 230Th efficiencies. Since the smooth residues give
efficiencies near the upper range and patch efficiencies give efficiencies near the lower range of
efficiencies encountered in practice, as described previously (Arndt and West 2007), the
efficiency of the calibration standard, eS, will be taken to be the average between the 226Ra
efficiency for a smooth residue, denoted by e1,S, and the 226Ra efficiency for a patch residue,
denoted by e1,P, so that
eS =
1
(e1,P + e1,S ) .
2
The efficiencies e1,S and e1,P were calculated using Eqn. (E.2) and the 226Ra parameters of
Table C.1. Figure F.1 is a plot of these efficiencies and eS versus residue mass. In all GAA
calculations which follow, it is assumed that this function is used for eS in Eqn. (F.4).
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Appendix F: Equations for the Calculation of the Contribution of Alpha Emitters | 211
0.24
0.20
Efficiency
0.16
e1,S
0.12
0.08
e1,P
0.04
eS
0.00
0
20
40
60
80
100
Residue mass (mg)
Figure F.1. Efficiency eS versus residue mass
Source: Arndt and West 2008a. An Experimental Analysis of the Contribution of 224Ra and 226Ra
and Progeny to the Gross Alpha-Particle Activity of Water Samples. Health Phys. 94:459-470.
The x-axis in Figure F.1 only goes up to 100 mg because EPA Method 900.0 stipulates
that the “thickness” of the residue must be less than or equal to 5 mg cm−2. Since the area of the
planchet, SP, is about 20 cm2, the upper limit for a residue is about 100 mg. It should be noted
that thickness of the residue is an average. For example, the thickness of the patches for a 100mg patch residue is 260 mg cm−2.
THE GAA DUE TO THE 234U DECAY CHAIN
Because of its 2.5 × 105-y half-life, the 234U activity in a sample is virtually constant—
there is not significant ingrowth or decay of 234U. Moreover, because its progeny, 230Th, has a
half-life of 7.5 × 104 y, no significant alpha activity will be produced by 234U decay over the sixmonth holding time of a sample. Thus, the GAA of a sample due to 234U is independent of the
time between sample collection and preparation, T1, the time between sample preparation and
analysis, T2, and the time between sample collection and analysis, T3. And the GAA is the same
for grab samples and quarterly composite samples. Thus, from Eqn. (F.2), the GAA is simply
given by
〈G〉 〈 e〉
,
=
A1 VeS
(F.5)
where A1 is the 234U activity and e is the 234U efficiency.
The function ϕ (τ) from Eqn. (E.3) was used to obtain the averages in Eqn. (F.5) giving
〈G〉/A1 for samples with a smooth residues. Figure 4.2 is a plot of 〈G〉/A1 versus residue mass for
©2010 Water Research Foundation. ALL RIGHTS RESERVED
212 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
grab or quarterly composite samples, where the variable 〈G〉/A1 was relabeled as GAA/ A1. The
function ϕ (τ) from Eqn. (E.4) was used to obtain the averages in Eqn. (F.5) giving 〈G〉/A1 for
patch residues. Figure 4.2 is also a plot of 〈G〉/A1 versus residue mass for patch residues, where
the variable 〈G〉 /A1 was relabeled as GAA/A1. The alpha activity divided by A1 in Figure 4.2 is
just 1. This, of course, is constant, since there is no substantial decay or ingrowth of any alpha
emitter.
Figure 4.2 shows that there can be a considerable amount of variability in the GAA even
when the alpha-particle activity of the alpha emitter, 234U, and the calibration standard, 230Th, are
the same. The reason for this is that the geometries of the residues range from being patch
residues to being smooth residues. The patch residues have a relatively large level of selfabsorption and a low GAA, and the smooth residues have a relatively low level of self absorption
and a high GAA. At zero mass, the GAA of patch and smooth residues are the same, since the
patches have no thickness at zero mass. The difference between the patch and smooth residues
increases with mass, as is shown in Figure 4.2. Thus, at 100 mg the GAA ranges from about 0.6
to 1.4.
Since A1 = 1, Figure 4.2 shows that the adjusted 〈G〉/A1—the value of 〈G〉/A1 minus the
uranium activity— for a samples containing mostly 234U, can range from −0.38 to +0.38 for the
100 mg residue. Figure 4.2 suggest that there is symmetry about the line A1 = 1. The reason for
this is that the efficiency of the calibration standard, 230Th, is given by
eS =
1
(e1 + e2 ) ,
2
where e1 is the efficiency for a patch residue and e2 is the efficiency for a smooth residue The
〈G〉 /A1 for a patch residue is obtained by dividing the efficiency of the patch residue by the
efficiency of the calibration standard giving
e
〈G 〉
=2 1
A1
e1 + e2
(patch) ,
Subtracting 1 from this equation gives
e −e
〈G 〉
−1 = − 2 1
A1
e1 + e2
(patch) ,
(F.6)
The 〈G〉 /A1 for a smooth residue is obtained by dividing the efficiency of the smooth residue by
the efficiency of the calibration standard giving
e2
〈G 〉
=2
A1
e1 + e2
(smooth) .
Subtracting 1 from this equation gives
e −e
〈G 〉
−1 = 2 1
A1
e1 + e2
(smooth) .
(F.7)
Eqns. (F.6) and (F.7) show that the two deviations of 〈G〉/A1 from unity are of the same
magnitude, but are of opposite signs for patch and smooth residues. Ideally, 〈G〉 would equal the
234
U activity, but Eqns. (F.6) and (F.7) show that 〈G〉 can overestimate or underestimate the 234U
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Appendix F: Equations for the Calculation of the Contribution of Alpha Emitters | 213
activity, which shows that the adjusted GAA can overcompensate or under compensate for the
amount of 234U activity present.
THE GAA DUE TO THE 238U DECAY CHAIN
Because of its 4.5 × 109-y half-life, the 238U activity in a sample is virtually constant—
there is not significant decay of 238U. Moreover, because its first alpha-emitting progeny, 234U,
has a half-life of 2.5 × 105 y, no significant alpha activity will be produced by 238U decay over
the six-month holding time of a sample. Thus, the part of the GAA of a sample due to 238U is
independent of the time between sample collection and preparation, T1, the time between sample
preparation and analysis, T2, and the time between sample collection and analysis, T3. And the
GAA is the same for grab samples and quarterly composite samples. Thus, from Eqn. (F.2), the
GAA is simply given by
〈G 〉 〈 e〉
,
=
A1 Ve S
(F.8)
where A1 is the 238U activity and e is the 238U efficiency.
The function ϕ (τ) from Eqn. (E.3) is used to obtain the averages in Eqn. (F.8) giving 〈G〉
/A1 for samples with a smooth residues. Figure 4.1 is a plot of 〈G〉/A1 versus residue mass for
grab or quarterly composite samples, where the variable 〈G〉/A1 was relabeled as GAA/A1. Using
ϕ (τ) from Eqn. (E.4) to obtain the averages in Eqn. (F.9) gives 〈G〉/A1 for patch residues.
Figure 4.1 is also a plot of 〈G〉/A1 versus residue mass for patch residues, where the variable
〈G〉/A1 was relabeled as GAA/A1. The alpha activity divided by A1 in Figure 4.1 is just 1. This, of
course, is constant, since there is no substantial decay or ingrowth of any alpha emitter.
Figure 4.1 shows that there is considerable amount of variability in the GAA due to 238U,
although the variability is somewhat less than that due to 234U.
THE GAA DUE TO THE 226RA DECAY CHAIN
The activity of 226Ra and its progeny in actual sample residues is a function of T2, the
time between sample preparation and analysis. Eqn. (C.4) was applied to calculate the number
ΔN of counts due to 226Ra and its progeny in a uniform BaSO4 residue in the time from t to t +
Δt, where t was the time after the coprecipitation. The time t corresponds to the time T2 because
the ingrowth of the progeny begins at time t = 0 in the BaSO4 residues and the time T2 = 0 for
actual sample residues. Thus, the GAA of 226Ra and its progeny in actual samples as a function
of T2 is obtained by replacing t in Eqn. (C.4) by T2 and averaging the result over ϕ (τ ) using
Eqn. (E.1) to give
〈 ΔN〉 = {〈e1 〉 + 3〈 Keave 〉[1 − exp(−λ2T2 )]}ΔT2 A1 .
(F.9)
Eqn. (D.1) gives the relationship between ε1 and e1 and between Kεave and Keave. Substituting
Eqn. (F.9) into Eqn. (F.4) and dividing the result by A1 gives
〈G 〉
1
=
{〈 e1 〉 + 3〈 Keave 〉[1 − exp(−λ 2T2 )]}
A1 VeS
©2010 Water Research Foundation. ALL RIGHTS RESERVED
(F.10)
214 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
The function ϕ (τ) from Eqn. (E.3) is used to obtain the averages in Eqn. (F.10), which
gives the GAA for smooth residues. Figure 4.3 is a plot of 〈G〉/A1 versus T2 for grab and
quarterly composite samples with smooth residues ranging from 20 to 100 mg. In Figure 4.3, the
variable 〈G〉/A1 was relabeled as GAA/A1.
The function ϕ (τ) from Eqn. (E.4) is used to obtain the averages in Eqn. (F.10), which
gives 〈G〉 /A1 for patch residues. Figure 4.4 is a plot of 〈G〉/A1 versus T2 for grab and quarterly
composite samples having a patch residue. In Figure 4.4, the variable 〈G〉/A1 was relabeled as
GAA/A1. The curve in Figure 4.4 is approximately independent of residue mass in the range
from 20 to 100 mg.
THE GAA DUE TO 210PO DECAY CHAIN
The activity due to the 210Po decay chain depends on the time between sample collection
and analysis, T3. Let the quantities associated with 210Pb, 210Bi, and 210Po be denoted by
subscripts 1, 2, and 3. Further, let the activity of 210Po at time T3 = 0 be A1,0. Then its activity A1
at a later time is given by
A1 = A1,0exp(−λ1T3),
where λ1 is the decay constant of
result by A1,0 gives
210
Po. Substituting this result into Eqn. (F.2), and dividing the
〈G〉 〈 e1 〉
=
exp(−λ1T3 ) ,
A1, 0 VeS
(F.11)
Here e1 is the efficiency of 210Po. The efficiency of 210Po in BaSO4 was determined in Appendix
C. These two efficiencies are related by Eqn. (D.1).
The function ϕ (τ) from Eqn. (E.3) is used to obtain the averages in Eqn. (F.11) giving the
GAA for smooth residues. Figure 4.5 is a plot of 〈G〉/A1,0 versus T3 for grab samples with smooth
residues ranging from 20 to 100 mg. In Figure 4.5, the variable 〈G〉/A1,0 was relabeled as
GAA/A1,0.
The function ϕ (τ) from Eqn. (E.4) is used to obtain the averages in Eqn. (F.11) giving the
GAA for patch residues. Figure 4.6 is a plot of 〈G〉/A1,0 versus T3 for grab samples with patch
residues of 20 and 100 mg. In Figure 4.6, the variable 〈G〉/A1,0 was relabeled as GAA/A1,0.
The calculations for the quarterly composite samples were very similar. For the quarterly
composite samples, it was assumed that equal aliquots of water were added to the sample at
intervals of 90 days apart. Each aliquot was assumed to have the same 210Po activity, A1,0, at the
time of the addition. Figure 4.7 is a plot of GAA/A1,0 versus T3 for a quarterly composite sample
with smooth residues ranging from 20 to 100 mg; Figure 4.8 is a plot of GAA/A1,0 versus T3 for a
quarterly composite sample with patch residues of 20 to 100 mg.
THE GAA DUE TO THE 210PB DECAY CHAIN
It will be assumed that negligible amounts of 210Bi and 210Po are lost to recoil. Then given
that the 210Pb activity in the sample is A1,0 at T3 = 0, the 210Po at time T3 arising from 210Pb decay
is given by,
(F.12)
A3 = A1,0 [c31 exp(−λ1T3 ) + c32 exp(−λ2T3 ) + c33 exp(−λ3T3 )] ,
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Appendix F: Equations for the Calculation of the Contribution of Alpha Emitters | 215
where λj is the decay constant of the jth radionuclide, c31 = 1.018, c32 = 0.03759, and c33 =
−1.056. Substituting this result into Eqn. (F.2) and dividing by A1,0 gives
〈G〉 〈e3 〉
=
[c31 exp(−λ1T3 ) + c32 exp(−λ2T3 ) + c33 exp(−λ3T3 )] .
(F.13)
A1, 0 VeS
The function ϕ(τ) from Eqn. (E.3) is used to obtain the averages in Eqn. (F.13) giving the
GAA for patch residues. Figure 4.9 is a plot of 〈G3〉/A1,0 versus T3 for grab samples with smooth
residues ranging from 20 to 100 mg. In Figure 4.9, the variable 〈G3〉/A1,0 was relabeled as
GAA/A1,0.
The function ϕ(τ) from Eqn. (E.4) is used to obtain the averages in Eqn. (F.13) giving the
GAA for patch residues. Figure 4.10 is a plot of 〈G3〉/A1,0 versus T3 for grab samples with patch
residues of 20 and 100 mg. In Figure 4.10, the variable 〈G3〉/A1,0 was relabeled as GAA/A1,0.
The calculations for the quarterly composite samples were very similar. For the quarterly
composite samples, it was assumed that equal aliquots of water were added to the sample at
intervals of 90 days apart. Each aliquot was assumed to have the same 210Pb activity, A1,0, at the
time of the addition. Figure 4.11 is a plot of GAA/A1,0 versus T3 for a quarterly composite sample
with smooth residues ranging from 20 to 100 mg; Figure 4.12 is a plot of GAA/A1,0 versus T3 for
a quarterly composite sample with patch residues of 20 to 100 mg.
THE GAA DUE TO THE 224RA DECAY CHAIN
The activity of 224Ra and its progeny in actual sample residues is a function of T3, the
time between sample collection and analysis. Eqn. (C.15) was applied to calculate the number
ΔN of counts due to 224Ra and its progeny in a uniform BaSO4 residues in the time from t to t +
Δt, where t was the time after the coprecipitation. The time t corresponds to the time T3 because
the ingrowth of the progeny begins at time t = 0 in the BaSO4 residues and at the time T3 = 0 for
actual sample residues Thus, the GAA of 224Ra and its progeny in actual samples as a function of
T3 is obtained by replacing t in Eqn. (C.15) by T3, and if the result is averaged over ϕ (τ ) using
Eqn. (E.1), then
⎡
⎞⎤
⎛
c
〈 ΔN 〉 = ⎢〈 k1 〉 I 1 − 〈 k 2 〉 ⎜⎜ I 4 + 55 I 5 ⎟⎟⎥ A1, 0 .
c54 ⎠⎦
⎝
⎣
(F.14)
where
〈 k1 〉 = 3〈 K 1eave,1 〉 + c51 〈 K 2 eave , 2 〉 ,
〈 k 2 〉 = −c54 〈 K 2 eave, 2 〉 ,
Ii =
1
λi
{exp(−λi T3 ) − exp[−λi (T3 + ΔT3 )]}
Eqn. (D.1) gives the relationship between K1eave,1 and K1εave,1 and between K2eave,2 and K2εave,2.
Substituting Eqn. (F.14) into Eqn. (F.4) and dividing by A1,0
©2010 Water Research Foundation. ALL RIGHTS RESERVED
216 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
gives
〈G 〉
1
=
A1, 0 VeS ΔT3
⎡
⎛
c55 ⎞⎤
I 5 ⎟⎟⎥ .
⎢〈 k1 〉 I 1 − 〈 k 2 〉 ⎜⎜ I 4 +
c
54
⎝
⎠⎦
⎣
(F.15)
A count time of 1 hr (i.e., ΔT3 = 1 h) is used in all of the calculations in this section.
The function ϕ (τ) from Eqn. (E.3) is used to obtain the averages in Eqn. (F.15), which
gives 〈G〉/A1,0 for smooth residues. Figure 4.17 is a plot of 〈G〉/A1,0 versus T3 for samples with
smooth residues ranging from 20 to 100 mg. In Figure 4.17, the variable 〈G〉/A1,0 was relabeled
as GAA/A1,0.
The function ϕ (τ) from Eqn. (E.4) is used to obtain the averages in Eqn. (F.15) giving
〈G〉/A1,0 for patch residues. Figure 4.18 is a plot of 〈G〉/A1,0 versus T3 for samples with patch
residues of 20 and 100 mg. In Figure 4.18, the variable 〈G〉/A1,0 was relabeled as GAA/A1,0.
THE GAA DUE TO THE 212PB DECAY CHAIN
The GAA due to unsupported 212Pb can be derived in a similar way to Eqn. (F.15). If the
amount of radon that emanates from the residues is near zero, the values of κ 1 through κ 6, and K1
and K2 will be close to one, and it can be shown that the GAA due to 212Pb is given by
〈G 4 〉
1
=
〈 K 2 eave, 2 〉 q ( I 4 − I 5 ),
A4, 0 VeS ΔT3
(F.16)
where A4,0 is the initial 212Pb activity and q = 1.105.
The function ϕ (τ) from (E.3) is used to obtain the averages in Eqn. (F.16) giving the
GAA for smooth residues. Figure 4.19 is a plot of 〈G4〉/A1,0 versus T3 for samples with smooth
residues ranging from 20 to 100 mg. In Figure 4.19, the variable 〈G4〉/A1,0 was relabeled as
GAA/A1,0.
The function ϕ (τ) from (E.4) is used to obtain the averages in Eqn. (F.16) giving the
GAA for patch residues. Figure 4.20 is a plot of 〈G4〉/A4,0 versus T3 for a sample with a patch
residue. In Figure 4.20, the variable 〈G4〉/A1,0 was relabeled as GAA/A1,0.
THE GAA DUE TO THE 228RA DECAY CHAIN
In this section the GAA arising from the decay of 228Ra is considered. To understand the
effect of 228Ra decay on the GAA, the following decay chain must be considered:
β
β
α
α
α
228
Ra → 228Ac → 228Th → 224Ra → 220Rn →
216
α
β
, β 212Po α
Po → 212Pb → 212Biα⎯→
→ 208Pb.
The first alpha emitter in this chain is 228Th. If it is assumed that the initial 228Th activity in a
sample is negligible, since it is insoluble, then, since 228Th has a 1.9-y half-life, its activity will
only be significant in samples that have been stored for many months or for quarterly composite
samples. Even under these conditions, the 228Th activity might be considered to be negligible,
except that 228Th decays into a series of five alpha emitters: 224Ra, 220Rn, 216Po, 212Bi, and 216Po.
Thus, although the activity of each alpha emitter might be relatively low, since there are six
alpha emitters, the sum of their activities may be substantial. Of the 228Th progeny, 224Ra has the
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Appendix F: Equations for the Calculation of the Contribution of Alpha Emitters | 217
longest half-life of 3.6 d. Thus, after about 22 day, all of the alpha emitters of the 228Ra decay
chain are in secular equilibrium. This in contrast to the 224Ra decay chain, where there were two
groups of alpha emitters in secular equilibrium with one another. The difference between these
two situations is that in the present case, the parent, 228Th, has a half-life that exceeds that of all
succeeding progeny by more than a factor of 10. Because of the 5.8-y half-life of 228Ra and the
1.9-y half of 228Th, the GAA due to the 228Ra decay chain continues to increase over the sixmonth holding time of grab samples and quarterly composite samples.
The activity of 228Ra and its progeny in samples is a function of T3, the time between
sample collection and analysis. Let the quantities associated with 228Ra, 228Th, 224Ra, 220Rn, 216Po,
212
Pb, 212Bi, and 212Po be denoted by subscripts 1, 2, 3, 4, 5, 6, 7, and 8, respectively. Let the
228
Ra activity at the time of sample collection be A1,0. It is assumed that the initial 228Th activity
is negligible, which is approximately true because thorium is highly insoluble at near-neutral pH.
Then the activity of the ith progeny at time T3 arising from 228Ra decay is given by the Bateman
equations:
i
Ai = κ i β i A1, 0 ∑ cij exp(−λ j T3 ) (2 ≤ i ≤ 9) ,
(F.17)
j =1
where the factor κi (≤ 1) is included to account for volatilization and recoil loss from the residue,
λj is the decay constant of the jth radionuclide, βi is the alpha-decay branching ratio, and
cij =
λ2 λ3 . . . λi −1λi
i
∏ (λ
k
.
− λj )
k =1
k≠ j
After about 3 days have elapsed since T3 = 0, all but the first, third, and fourth terms in Eqn.
(F.17) are negligible relative to the first, and the activities of the alpha emitters are given by
A3 = κ 3 A1, 0 [c 31exp( −λ1T3 ) + c33 (−λ3T3 )] ,
Ai = κ i A1, 0 [c 41 exp(−λ1T3 )
+ c 43 exp(−λ3T3 ) + c 44 exp(−λ4T3 )] (i = 4,5,6),
A8 = βκ 8 A1,0 [c81 exp(−λ1T3 ) + c83 exp(−λ3T3 ) + c84 exp(−λ4T3 )] ,
A9 = (1 − β )κ 9 A1, 0 [c81 exp(−λ1T3 )
+ c83 exp(−λ3T3 ) + c84 exp(−λ4T3 )],
(F.18)
(F.19)
(F.20)
(F.21)
whereβ5 = 0.3594 is the alpha-decay branching ratio for 212Bi, and c31 = 1.498, c33 = −1.499, c41
= 1.501, c43 = −1.506, c44 = 0.005636, c81 = 1.501, c83 = −1.507, c84 = 0.006420. Eqns. (F.18),
(F.19), (F.20), and (F.21) show that after about 6 half-lives of 224Ra, or 22 d, all of the alpha
emitters are in secular equilibrium with one another.
Let the efficiency of 228Th in BaSO4 residues be denoted by ε3. Then Eqns. (E.2), (F.3),
and (F.18) show that the number of counts 〈ΔN1〉 due to 228Th in the count time ΔT3 is given by
〈 ΔN 1 〉 = 〈κ 3 e3 〉 A1, 0 [c 31 exp( −λ1T3 ) + c33 ( −λ3T3 )]ΔT3 ,
©2010 Water Research Foundation. ALL RIGHTS RESERVED
(F.22)
218 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
where Eqn. (D.1) gives the relationship between κ3ε3 and κ3e3. As discussed in Appendix C, it
will be assumed that the 228Th efficiency, ε3, equals the 241Am efficiency because these two alpha
emitters have similar alpha-particle energies. Further, it will be assumed that κ3 = 1. This is just
the assumption that there is no recoil loss of the parent of 228Th, 228Ac, from the residue. This is
likely to be a good assumption since 228Ac is not volatile and it is formed from 228Ra by a beta
decay.
Let ε4 be the efficiency of 224Ra, ε5 be the efficiency of 220Rn, and ε6 be the efficiency of
216
Po in BaSO4 residues; and let κ4 be the fraction of 224Ra, κ5 be the fraction of 220Rn, κ6 be the
fraction of 216Po that remains in the residue. Then Eqns. (E.2), (F.3), and (F.19) show that the
number of counts 〈ΔN2〉 due to 224Ra, 220Rn, and 216Po in the count time ΔT3 is given by
〈 ΔN 2 〉 = 〈 K 1 e1,ave 〉[c 41 exp( −λ1T3 ) + c 43 exp( −λ3T3 )
+ c 44 exp( −λ 4 T3 )] A1, 0 ΔT3 ,
(F.23)
where K1 = κ4 + κ5 + κ6 and
ε ave,1 =
κ 4ε 4 + κ 5ε 5 + κ 6ε 6
,
κ4 + κ5 + κ6
and Eqn. (D.1) gives the relationship between K1eave,1 and K1εave,1. If κ4 = 1, then the value of
〈K1eave,1〉 derived here is the same as that derived in Appendix C. This is probably a good
assumption since the parents of 224Ra are nonvolatile.
Let ε8 be the efficiency of 212Bi and let ε9 be the efficiency of 212Po in BaSO4 residues.
Then Eqns. (E.2), (F.3), (F.20), and (F.21) show that the number of counts 〈ΔN3〉 due to 212Bi and
212
Po in the count time ΔT3 is given by
〈 ΔN 3 〉 = A1, 0 〈 K 2 e2,ave 〉[c81 exp(−λ1T3 )
+ c83 exp(−λ3T3 ) + c84 exp(−λ4T3 )]ΔT3 ,
(F.24)
where
K2 = βκ8 + (1 − β)κ9
and
ε ave,2 =
βκ 8ε 8 + (1 − β )κ 9 ε 9
,
βκ 8 + (1 − β )κ 9
and Eqn. (D.1) gives the relationship between K2eave,2 and K2εave,2. Again, if κ4 = 1, then the
value of 〈K2eave,2〉 derived here is the same as that derived in Appendix C. The total number of
counts, ΔN, in Eqn. (F.4) is given by
〈ΔN〉 = 〈ΔN1〉 + 〈ΔN2〉+〈ΔN3〉.
(F.25)
Substituting this result into Eqn. (F.4) and dividing the result by A1,0 gives
〈G 〉
1
=
(〈 ΔN1 〉 + 〈 ΔN 2 〉 + 〈 ΔN 3 〉 ) .
A1,0 eSVΔT3
©2010 Water Research Foundation. ALL RIGHTS RESERVED
(F.26)
Appendix F: Equations for the Calculation of the Contribution of Alpha Emitters | 219
Using ϕ (τ) from Eqn. (E.3) to obtain the averages in Eqn. (F.26) gives the GAA for
smooth residues. Figure 4.13 is a plot of 〈G〉/A1,0 versus T3 for grab samples with smooth
residues ranging from 20 to 100 mg. In Figure 4.13, the variable 〈G〉/A1,0 was relabeled as
GAA/A1,0.
Using ϕ (τ) from Eqn. (E.4) to obtain the averages in Eqn. (F.26) gives the GAA for patch
residues. Figure 4.14 is a plot of 〈G〉 /A1,0 versus T3 for grab samples with patch residues of 20
and 100 mg. In Figure 4.14, the variable 〈G〉/A1,0 was relabeled as GAA/A1,0.
The calculations for the quarterly composite samples were very similar. For the quarterly
composite samples, it was assumed that equal aliquots of water were added to the sample at
intervals of 90 days apart. Each aliquot was assumed to have the same 228Ra activity, A1,0, at the
time of the addition. Figure 4.15 is a plot of GAA/A1,0 versus T3 for a quarterly composite
samples with smooth residues ranging from 20 to 100 mg; Figure 4.16 is a plot of GAA/A1,0
versus T3 for a quarterly composite samples with patch residues of 20 to 100 mg.
©2010 Water Research Foundation. ALL RIGHTS RESERVED
220 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
©2010 Water Research Foundation. ALL RIGHTS RESERVED
APPENDIX G
EFFICIENCY OF THE BOTTOM LAYER OF THE SAMPLE RESIDUE
The fit of a curve to the efficiency data in the plots in Appendix C cannot be done without constraints. In this section, an equation is derived that imposes a constraint on any curve that
is used to fit the efficiency data. Let the residue be of uniform thickness l, and let a coordinate
system be employed in which the origin is at the planchet-residue interface and the positive zaxis goes through the air gap between the residue and the detector as shown in Figure G.1.
Let the efficiency of the layer of the residue that is coincident with the plane z = z be given by η(z). Then the overall efficiency ε of the residue is given by
1 l
ε = ∫ η ( z )dz .
l 0
Differentiating this equation with respect to l and rearranging terms gives
dε
η (l) = l
+ε .
dl
Assuming that the residue thickness, l, is proportional to the residue mass, m (i.e., assuming l ∝
m), gives
η (l) = m
dε
+ε .
dm
(G.1)
This equation relates the efficiency of the bottom layer of a sample residue to the efficiency ε
and its derivative dε /dm. Since increasing l requires that more mass be placed above the bottom
layer, which would increase the level of self-absorption of alpha particles emitted from the bottom layer, it is clear that η(l) decreases monotonically with l. Thus, one constraint on any curve
that is fit to a set of efficiency data is that η(l) decrease monotonically with increasing m.
+z
air
z=l
residue
l
z=0
Figure G.1. Coordinate system employed in the derivation of the constraint
As an example, in Appendix C, the function of Eqn. (C.6) was fit to the efficiency data
for 241Am in BaSO4. The 241Am data is reproduced in Figure G.2, and the fit parameters are given in Table C.1. The solid curve is the fit to the 241Am data. The dotted curve in the figure is a
221
©2010 Water Research Foundation. ALL RIGHTS RESERVED
222 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
plot of η(l) that was calculated using Eqn. (G.1). The fit parameter m1 in Eqn. (C.13) is the transition from “thin” to “thick” residues (Semkow et al 2005).
In Figure G.2, it is seen that, initially, η(l) decreases rapidly with m until the point where
m1 = 125 mg is reached. If the residue were completely non-porous and uniform in thickness,
η(l) would go to zero at m1 because, at this mass, all of the alpha particles emitted from the bottom of the residue would be absorbed before reaching the detector. However, since η(l) is greater
than zero, it is clear that these BaSO4 residues have some structural features that allow alpha particles from the bottom of the residue to reach the detector. These features may be small channels
or pores in the residue or places where the residue is still thin enough to allow alpha particles to
reach the detector, in which case, the residues are nonuniform to a small degree. All of these
structural features contribute to roughness of the surface of the residue. A measure of the surface
roughness, derived by Semkow et al (2005), is given by the parameter D, where
D = 3 – n.
The parameter D is the fractal dimension of the surface of the residue. It can vary between 2 and 3. For a surface with no roughness features, D = 2. As the surface becomes rougher,
D increases. For the BaSO4 residues, Table C.1 shows that D = 2.11, which indicates that the
surface has some roughness, but D is still close to 2, indicating that the degree of roughness is
relatively small.
0.24
0.20
241
Am data points
Fit to data points
η(l)
Efficiency
0.16
0.12
0.08
0.04
0.00
0
100
200
300
400
500
Residue mass (mg)
Figure G.2. Plot of η(l) versus residue mass for 241Am
©2010 Water Research Foundation. ALL RIGHTS RESERVED
600
APPENDIX H
ESTIMATION OF THE EXTENT OF THE DETECTOR
CONTAMINATION BY 220RN
During the experiments for the determination of the efficiencies of the 224Ra decay chain,
it was evident that some 220Rn volatilized and contaminated the detector. After counting samples
for 3 days, the detector background counts were elevated from the normal ≤ 0.2 cpm to < 6 cpm.
The elevated background decayed away with a half-life approximately equal to that of 212Pb.
Let it be assumed that the rate F at which 220Rn atoms escape the residue and contaminate
the detector is proportional to the 224Ra activity in the residue:
F = eA1,0 exp(−λ1t ) ,
where t is time, A1,0 is the 224Ra activity at t = 0, when the sample is placed in the instrument, λ1
is the decay constant of 224Ra, and e, a proportionality constant, is technically not the emanation
coefficient. If a fraction f of the radon atoms remain in the detector region, then the number N 2D
of radon atoms in the detector region is given by
dN 2D
= feA1,0 exp(−λ1t ) − λ 2 N 2D
dt
It is seen that the solution of this equation and subsequent ones in the decay chain are given by
D
= feA1,0.
the Bateman equations for the decay of 224Ra with λ1N1,0
If the efficiencies of all of the alpha emitters are assumed to be of the same value, denoted by ε, and if it is assumed that 24 hr have passed since t = 0 (allowing the term corresponding to λ5 to be neglected in the equation below), then, given that the sample and detector are in
contact shortly after t = 0, the total number ΔND of counts in time interval Δt in the detector region due to radon contamination is given by
ΔN D = εfeA1, 0 {(2 + c51 ) exp(−λ1t ) + c 54 exp(−λ 4 t )]}Δt .
(H.1)
If t = 3 d, Δt = 30 m, and ΔN D < 180, then efεA1,0 < 0.057. Thus, this equation shows that
at 24 hr, ΔN D < 240 for Δt = 30 m. The minimum number of counts in any time interval was
about 10,000, so that detector contamination would affect ΔN by less than 2.4%.
223
©2010 Water Research Foundation. ALL RIGHTS RESERVED
224
©2010 Water Research Foundation. ALL RIGHTS RESERVED
APPENDIX I
THE CONVERSION FACTOR BETWEEN URANIUM ACTIVITY AND
CONCENTRATION
It is useful to have an equation that shows how that conversion factor between uranium
activity and concentration depends on the ratio of the 234U activity to the 238U activity. The combined activity of 234U and 238U in a sample is given by
AT = 27.03(λ1 N 1 + λ 2 N 2 ) ,
where N1 is the number of 234U atoms, N2 is the number of 238U atoms, λ1 is the decay constant of
234
U, λ 2 is the decay constant of 238U, and the factor of 27.03 is included so that AT is in units of
picoCuries (pCi) when the decay constants are in units of inverse seconds (s−1). The combined
mass of 234U and 238U in a sample is given by
⎛
N
N ⎞
mT = ⎜⎜ 234 1 + 238 2 ⎟⎟10 6 ,
N0
N0 ⎠
⎝
where N0 is Avogadro’s number, 234 is the atomic weight of 234U, 238 is the atomic weight of
238
U, and the factor of 106 is included so that the mass is expressed in micrograms (μg). The
conversion factor C (in pCi/μg) is just the ratio of AT to mT or
A
λ N + λ2 N 2
C = T = 1.628 × 1019 1 1
.
mT
234 N 1 + 238 N 2
The half-life of 234U is a factor of 5.5 × 10−5 less than the half-life 238U; thus, from the
discussion in Chapter 1, it is clear that when 234U and 238U are in secular equilibrium, N1 is a factor of 5.5 × 10−5 less than N2. And even if the 234U activity exceeded the 238U activity by a factor
of 100, N1 would still be a factor of 5.5 × 10−3 less than N2. Consequently, the first term in the
denominator of the above equation is negligible compared to the second term so that
λ N + λ2 N 2
C = 1.628 × 1019 1 1
.
238 N 2
Multiplying the top and bottom of this equation by λ 2 (= 4.914 × 10−18 s−1) yields
⎛
A ⎞
(I.1)
C = 0.336⎜⎜1 + 1 ⎟⎟ ,
A
2 ⎠
⎝
where A1 ( = λ1N1) is the 234U activity and A2 ( = λ2N2) is the 238U activity.
225
©2010 Water Research Foundation. ALL RIGHTS RESERVED
226
©2010 Water Research Foundation. ALL RIGHTS RESERVED
APPENDIX J
ESTIMATE OF THE COUNTING ERROR
The standard deviation due solely to counting error can be estimated from a single sample
point. The GAA, denoted by the variable G, is given by
N − C ΔTS
G = 0.45 S
eSVΔTS
where ΔTS is the sample count interval in minutes, NS is the number of counts accumulated in the
⎯
count interval ΔTS, C is the background count rate in min−1, eS is the efficiency of the calibration
standard, V is the sample volume in liters, and the factor of 0.45 is included so that the GAA is in
units of pCi/L. From probability theory, an estimate of the standard deviation or error in the
GAA due solely to counting error, denoted by σ2, is given by
⎛ ∂G
σ 2 = ⎜⎜
⎝ ∂N S
2
⎞ 2
∂G ⎞ 2
⎟ σ N + ⎛⎜
⎟ σC .
⎟
S
⎝ ∂C ⎠
⎠
2
(J.1)
⎯
where σNS is the standard deviation in NS, σC⎯ is the standard deviation in C , and the partial derivatives are given by
∂G
0.45
∂G
0.45
=
,
=−
.
∂N S eSVΔTS
∂C
eSV
From probability theory, an estimate of σNS is given by
σ NS = N S .
(J.2)
The background was obtained by averaging the twenty 100-min backgrounds taken on
sequential days. Thus,
1 1 20
C =
∑ N B, i ,
ΔTB 20 i =1
where ΔTB is the background count interval in minutes and NB,i is the number of background
counts in the ith background count. From probability theory, an estimate of σ C⎯ is given by
2
⎛ ∂C ⎞ 2
⎟ σN ,
σ C = ∑ ⎜⎜
⎟
B, i
∂
N
i =1 ⎝
B, i ⎠
where the partial derivatives are given by
∂ (GAA)
∂ (GAA)
0.45
0.45
=
=−
.
,
eSVΔTS
eSV
∂N S
∂C
Substituting these derivatives into Eqn. (J.3) gives
20
σC =
1
400ΔTB2
20
∑N
i =1
B, i
,
or
σC =
C
.
20ΔTB
227
©2010 Water Research Foundation. ALL RIGHTS RESERVED
(J.3)
228 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
And substituting this equation and Eqn. (J.2) into Eqn. (J.1) gives
σ2 =
0.45 N S
C
+
.
2
eSV ΔTS 20ΔTB
©2010 Water Research Foundation. ALL RIGHTS RESERVED
(J.4)
APPENDIX K
ALPHA SPECTROSCOPY METHOD FOR 210PO
Samples to be analyzed for radionuclides are typically acidified with nitric acid to a pH
of 2 or less either in the field or upon receipt by the laboratory. A pH of 2 keeps most naturally
occurring radionuclides in solution; however, this pH does not guarantee that polonium will stay
in solution (Figgins 1961). An acid concentration of about 1 M is required to keep polonium in
solution. Polonium also tends to adsorb onto the surface of containers, particularly glass. Consequently, samples to be analyzed for polonium were collected in the field using pre-weighed 1-L
polyethylene bottles. The bottles were filled to a mark placed on the outside of the bottle, which
provided about 100 mL of headspace. When the bottles arrived at the laboratory, they were
weighed. Then 50 mL of 16 M nitric acid and about 20 pCi of a 209Po tracer were added to the
bottle, and the contents were thoroughly mixed and allowed to stand for at least 2 weeks before
further preparation.
The samples were transferred to 2-L glass beakers and reduced in volume on a hotplate to
about 200 mL. The samples were transferred to 400-mL Teflon beakers, and 20 mL of 48% HF
was added to each beaker. The contents of the Teflon beakers were evaporated to dryness on a
hotplate. The purpose of adding hydrofluoric acid was to digest silicic acid, which polymerizes
under acidic conditions to form to silica gel. The residue in the Teflon beaker was dissolved by
adding 100 mL of a solution that was 1 M in boric acid and 0.6 M in HCl, and warming the solution on a hotplate. This solution dissolves insoluble fluoride salts, but in samples high in sulfate,
there is often an insoluble calcium sulfate residue. The presence of calcium sulfate does not seem
to adversely affect the yield of polonium, but, in any case, any loss of 210Po would be accounted
for by the 209Po tracer. The samples were allowed to warm until the sample volume was reduced
to about 50 mL.
Next 100 mg of ascorbic acid and a 1-cm Teflon coated magnetic stir bar were placed in
a 60-mL polyethylene bottle. The sample is then transferred to the bottle, a 1-cm diameter nickel
disc is placed on the lip of the bottle, a rubber septum is placed on the disc, and the cap of the
bottle is screwed on. The bottle is inverted, and a hot glass stir rod is used to melt a hole in the
bottom of the bottle. The bottle is placed in a 200-mL beaker which has water that has been
warmed to 80 °C. The beaker is placed on a combination magnetic stirrer-hotplate, and the solution is stirred at 80 °C for 4 hours.
The nickel disc is removed and rinsed with DI water followed by methanol. To prevent
contamination of the detector by volatilization of polonium, the polonium on the nickel disc is
oxidized by heating the disc at 300 °C for 5 minutes on a hotplate. After the disc cools, it is
counted with the alpha spectrometer. The 210Po activity A1 is given by
A N − B1
A1 = 2 1
exp(λ1t ),
V N 2 − B2
229
©2010 Water Research Foundation. ALL RIGHTS RESERVED
230 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
where A2 is the activity of the 209Po tracer, V is the sample volume, N1 is the total number of counts
and B1 is the number of background counts in the 210Po channels, N2 is the total number of counts
and B2 is the number of background counts in the 209Po channels, λ1 is the decay constant of 210Po,
and t is the time elapsed between sample collection and counting. The error in A1 is given by
⎛σ 2 σ 2
N 1 + B1
N 2 + B2 ⎞
⎟,
σ 2 = A12 ⎜⎜ 22 + V2 +
+
2
( N 1 − B1 )
( N 2 − B2 ) 2 ⎟⎠
⎝ A2 V
where σ 2 is the error in A2 and σ V is the error in V.
©2010 Water Research Foundation. ALL RIGHTS RESERVED
APPENDIX L
ALPHA SPECTROSCOPY METHOD FOR 224RA
INTRODUCTION
The main contribution made by this laboratory was the development of a method to prepare a barium sulfate (BaSO4) seeding suspension. The seeding suspension is required to coprecipitate radium with BaSO4. Trying to form BaSO4 in situ leads to excessively large crystals,
which degrade the alpha spectra of samples to the point that very little useful information can be
obtained from them.
Initially, a 133Ba tracer was used to obtain the radium yield. The rationale for this is that
radium and barium are both group II metals and that their chemistry and, hence, their chemical
yields should be nearly identical. Several methods have been published that claim that 133Ba is a
good tracer for 226Ra (Valentini Ganzerli 1999, Morvan 2001, Bojanowski et al 2005). This may
be the case since these methods deposit the radium and barium on hydrous manganese dioxide or
basic lead rhodizonate and tend to require a relatively long time for the radium and barium to
deposit. In this study, the deposition of radium and 133Ba on the BaSO4 seeding suspension was,
of necessity, relatively short because the 224Ra activities of the samples were needed, and excessively long deposition times would have caused excessive decay of the unsupported 224Ra. A typical deposition time was about 30 min, and the recoveries of 133Ba, denoted by γ1, ranged from
about 5% to nearly 100%, although all samples were counted until at least 500 133Ba counts were
obtained.
The alpha spectra also contained 226Ra, and a separate measurement of the 226Ra activity
was determined using EPA Method 903.1. Knowing the 226Ra counts in the alpha spectrum, over
a given period of time, and the activity of the 226Ra by EPA Method 903.1 allowed one to determine the radium yield for this method.
EQUIPMENT
•
•
•
Alpha spectrometer
Gamma spectrometer
Gelman filter funnel assembly for 25 mm filters with polycarbonate base, metal screen,
polysulfide funnel, and 100 mL polypropylene flask
REAGENTS
•
•
•
Cation-exchange resin 50W × 8, 100−200 mesh- Eichrom Technologies, Inc., part number: C8−B500−M−H.
80% ethanol solution-Place 800 mL of ethanol in a 1-L volumetric flask and dilute to 1 liter with polished water. Mix thoroughly.
15% (w/v) Na2SO4-0.72 M sodium acetate solution-Place 150 g of anhydrous sodium sulfate and 59.06 g of anhydrous sodium acetate in a 1-L beaker, and add about 900 mL of
polished water. Place a Teflon magnetic stir bar in the beaker, and place the beaker on a
magnetic stirrer-hotplate. Set the hotplate to a low heat so that the solution does not boil.
Allow the solution to stir until complete dissolution. Filter the solution through a Milli231
©2010 Water Research Foundation. ALL RIGHTS RESERVED
232 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
•
pore Durapore 0.45 μm HV membrane filter. Quantitatively transfer the solution to a 1-L
volumetric flask and dilute to the mark. Mix thoroughly.
0.1 M EDTA solution-Place 37.22 g of disodium EDTA in a 2-L beaker, and add about
900 ml of polished water. Place a Teflon magnetic stir bar in the beaker, and place the
beaker on a magnetic stirrer. Allow the solution to stir until complete dissolution. Adjust
the pH of the solution to about 5 using nitric acid and sodium hydroxide. Filter the solution through a Millipore Durapore 0.45 μm HV membrane filter. Quantitatively transfer
the solution to a 1000-mL volumetric flask and dilute to the mark. Mix thoroughly.
PREPARATION OF THE BASO4 SEEDING SUSPENSION
It should be mentioned that the proper preparation of the seeding suspension is of utmost
importance in order to obtain peaks in the alpha spectrum that are sharp and well resolved. First,
a pyrosulfate fusion is prepared. When the fusion solidifies, small crystals of solid barium sulfate
are present throughout the volume of the solid cake. Then the solid cake is dissolved to obtain
the seeding suspension.
Place 125 μL of 20.5 mM barium chloride solution, 0.28 g of anhydrous sodium sulfate,
and 0.5 mL of concentrated sulfuric acid in the bottom of a 10-mL borosilicate tests tube. Heat
the tube over a Meeker burner until white fumes appear and the fusion is clear. This should take
1 minute or less. Allow the sulfuric acid to reflux for about 1 minute, so that any solids on the
side of the tube are rinsed into the solution at the bottom of the tube. Allow the tube to cool to
room temperature. Typically, the fusion will supercool and not solidify. If this happens, place the
tube in an ice-water bath. If the fusion still does not solidify, touch the fusion with a stir rod. This
usually causes the fusion to solidify.
Measure out 100 mL of 15% (w/v) Na2SO4-0.72 M sodium acetate solution. Add about 8
mL of the 15% (w/v) Na2SO4-0.72 M sodium acetate solution to the cake and break it apart with
the stir rod. The cake should dissolve. Transfer the contents of the tube to a 250-mL Erlenmeyer
flask. Rinse the tube with 8 mL of the 15% (w/v) Na2SO4-0.72 M sodium acetate solution, and
transfer the rinse to the flask. Place the rest of the 15% (w/v) Na2SO4-0.72 M sodium acetate solution in the Erlenmeyer flask. Place a Teflon stir rod in the flask, and allow the contents to stir.
EXPERIMENTAL METHOD
Pour 1 L of sample into a 1-L beaker. Add about 200 pCi of 133Ba tracer to the sample.
For each sample prepare a column containing 20 grams of cation-exchange resin. Condition the
column with 150 mL of 0.1 M nitric acid solution. Allow the sample to drain through the column. Allow 150 mL of 0.1 M nitric acid solution to drain through the column. Elute the metals
on the column with 150 mL of 8 M nitric acid solution. Collect the eluent in a pre-weighed 250mL beaker. If the eluent from step contains resin beads, then filter the eluent through 0.45 μm
PVC filters, and discard the resin beads.
Evaporate the eluent to dryness on a hot plate. In this step it is important that all of the nitric acid be evaporated so that it does not alter the pH of the buffer in the following steps. Weigh
the beaker and determine the weight of the residue. Add 60 mL of 0.1 M EDTA solution and a
few drops of methyl red indicator to the beaker. Adjust the pH of the solution in the beaker with
3 M ammonium hydroxide and 0.5 M nitric acid solution to bring the solution to the orange endpoint of the indicator. It may be necessary to increase the pH to the yellow endpoint of the indi-
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Appendix L: Alpha Spectroscopy Method for 224RA | 233
cator to dissolve all of the EDTA. Then 0.5 M nitric acid solution can be added drop wise to get
to the orange endpoint. Allow enough time for the residue to dissolve and the solution to become
clear. This may take 5 minutes and the rate of dissolution may be increased by covering the
beaker with a watch glass and gently heating the beaker. If the amount of residue is too large,
more 0.1 M EDTA solution must be used.
Filter the solution from the previous step through a 0.1 μm filter into a 150-mL beaker. In
this step particulate matter is removed from the solution so that it does not add bulk to the microprecipitate. In addition, 210Po adsorbs onto particulate matter and shows up in the alpha spectrum
if the particulate matter is not removed.
Place a Teflon stir bar in the beaker. Prepare the barium sulfate seeding suspension. Add
20 mL of the seeding suspension to the 150-mL beaker. Stir the contents of the beaker thoroughly. Record the time at which this step was performed. This is the time at which 226Ra progeny
begin to grow in. Let the beaker stand for at least ½ hour.
Assemble the Gelman filter funnel with a 0.1 micron polypropylene filter, and apply a
vacuum to the filter funnel. Place a few milliliters of 80% ethanol in the filter funnel, and allow
the solution to drain through the filter. Rinse down the side of the filter funnel with a few milliliters of polished water. Allow the polished water to drain through the filter. Stir the contents of
the 150-mL beaker, and pour the contents in the filter funnel. Rinse down the sides of the filter
funnel with a few milliliters of 80% ethanol solution. Allow the solution to drain. Rinse down the
sides of the filter funnel with a few milliliters of ethanol from a squirt bottle. Allow the ethanol
to drain. Remove the filter from the funnel, and place it under a heat lamp to dry. Mount the filter
on a 25-mm stainless steel planchet with double-sided tape.
Place the planchet in the alpha spectrometer. Record the time at which the alpha spectrum
was initiated and the time duration of the alpha spectrum. These times are needed later in calculations to account for the decay of 224Ra between the sample collection time and the time at
which the alpha spectrum was initiated. Place the sample in a gamma spectrometer and record
the number of counts in the full energy peaks of 133Ba in Table L.1 for a sufficient period of time
such that the relative counting error is less than 2%.
Table L.1
Full energy peaks of 133Ba
Percent
Energy (keV)
intensity
80.9971
34.1
276.3997
7.164
302.8510
18.33
356.0134
62.05
383.8480
8.94
CALCULATIONS
Because of the long half-life of 226Ra (1622 years), the decay of 226Ra between sample
collection and analysis with the alpha spectrometer does not have to be taken into account. The
activity A1 of 226Ra per unit volume in a sample is given by
©2010 Water Research Foundation. ALL RIGHTS RESERVED
234 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
A1 =
N T,1 / Δt S − N B,1 / Δt B
γθV
,
(L.1)
where NT,1 is the number of counts in the 226Ra peak during time ΔtS, NB,1 is the number of background counts in the 226Ra peak during time interval ΔtB, V is the volume of sample used, γ is the
chemical recovery of the 133Ba tracer expressed as a fraction, and θ is the detector efficiency of
the alpha spectrometer expressed as a fraction. In the above equation, A1 will be in Bq/L if the
time intervals are in seconds and the volume is in liters. The corresponding error is given by
σ A1
⎛ 1
= ⎜⎜
⎝γ θV
⎞
⎟⎟
⎠
2
⎛σ 2 σ 2 σ 2 ⎞
⎛ N T,1 N B,1 ⎞
⎜⎜ 2 + 2 ⎟⎟ + A12 ⎜ γ2 + θ2 + V2 ⎟ ,
⎜γ
θ
Δt B ⎠
V ⎟⎠
⎝ Δt S
⎝
where σγ is the error in the chemical recovery of
ciency. This error can also be written as
σ A21
133
(L.2)
Ba and σθ is the error in the detector effi-
σ C2
σ θ2 σ V2
= 2 + 2 + 2 ,
A12
C1 θ
V
1
where C1 is the net number of 226Ra counts given by
C1 =
N T,1
Δt S
−
N B,1
Δt B
,
(L.3)
and
σ C1 =
N T,1
Δt S2
+
N B,1
.
Δt B2
(L.4)
The chemical yield of 133Ba is given by
γ =
N S /(Δt γ ,1 AS )
N D /(Δt γ , 2 AD )
=
N S Δt γ , 2 AD
N D Δt γ ,1 AS
,
where AS is the activity of 133Ba added to the sample, NS is the number of 133Ba counts of the
sample measured in the time interval Δtγ,1 with the gamma spectrometer, AD is the activity of
133
Ba added on the standard disc, and ND is the number of 133Ba counts of the standard disc
measured in the time interval Δtγ,2 with the gamma spectrometer. The above activities should be
corrected for the decay of 133Ba so that
γ =
N S Δt γ , 2 AD,0 exp(−λ3 ΔTD )
N D Δt γ ,1 AS,0 exp(−λ3 ΔTS )
,
(L.5)
where λ3 is the decay constant of 133Ba, AS,0 is the activity of the 133Ba added to the sample at the
calibration date, ΔTS is the time between the measurement of NS and the calibration date, AD,0 is
the activity of 133Ba on the disc at the calibration date, and ΔTD is the time between the measurement of ND and the calibration date. The error σγ in γ is given by
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Appendix L: Alpha Spectroscopy Method for 224RA | 235
2
2
⎛ 1
1 σ AS, 0 σ AD ,0
⎜
+
+ 2 + 2
σγ = γ ⎜
NS N D
AS,0
AD, 0
⎝
2
2
⎞
⎟.
⎟
⎠
(L.6)
Alternatively, the product of the chemical yield of radium and the detector efficiency, γθ,
could be obtained if the 226Ra activity is known from another method. If the 226Ra activity is A1,
then the count rate induced in the detector is
C1 = γθVA1 .
Since the net count rate, C1, is given by
C1 = N T,1 / Δt S − N B,1 / Δt B ,
Then, γθ is given by
N / Δt S − N B,1 / Δt B
γθ = T,1
.
VA1
And the error σγθ in γθ is given by
⎛ σ A2 σ 2 ⎞
⎛ N T,1 N B,1 ⎞
2⎜
1
⎜⎜ 2 + 2 ⎟⎟ + (γθ )
σ γθ
+ V2 ⎟ .
2
⎜
A
V ⎟
Δt B ⎠
⎝ Δt S
⎠
⎝ 1
Alternatively, the error can be written as
2
1
=
(VA1 ) 2
(L.7)
2
σ C2 σ A1 σ V2
σ γθ2
=
+ 2 + 2 .
(γθ ) 2 C12
A1 V
1
Let the 224Ra activity at the time of sample collection, t = 0, be A2,0 (Bq L−1) Then, after
the sample has been prepared, the activity A2 in the sample at the time t is
A2 = γ A2,0 exp(−λ2 t ) ,
where λ2 is the decay constant of 224Ra and γ is the radium yield, which is assumed to be the
same as the 133Ba yield.
The instantaneous 224Ra count rate induced in the detector is
C 2 = θ γVA2, 0 exp(−λ 2 t ) ,
where V is the sample volume and θ is the detector efficiency. Let the start of the sample count
be at t = t2 and let the count duration be ΔtS. Then the total number of 224Ra counts accumulated
from time t2 to time t2 + ΔtS is given by
N2 = ∫
t 2 + ΔtS
t2
C 2 dt .
Evaluating this integral gives
N2 =
θ γ VA2,0
exp(−λ 2 t 2 )[1 − exp(−λ 2 Δt S )] .
λ2
And solving this equation for A2,0 yields
©2010 Water Research Foundation. ALL RIGHTS RESERVED
236 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
A2,0 =
N 2 λ2
.
γθ V exp(−λ2 t 2 )[1 − exp(−λ 2 Δt S )]
(L.8)
Counts N3 from 222Rn, due to the decay of 226Ra, contribute to the 224Ra peak. Thus, the
total number NT,2 of counts in the 224Ra peak is comprised of N2, N3, and the background counts,
so that
N 2 = N T,2 − N 3 − N B,2
Δt S
,
Δt B
where NB,2 is the number of background counts in the background time interval ΔtB. Substituting
this equation into Equation (L.8) gives
A2,0 =
λ2 [ N T,2 − N 3 − N B,2 (Δt S / Δt B )]
.
γθ V {exp(−λ2 t 2 ) − exp[−λ2 (t 2 + Δt S )]}
(L.9)
When γ and θ are determined separately using 133Ba, the error σA2,0 in A2,0 is given by
σ
2
A2 , 0
=
λ22 [ N T + σ N2 3 + N B (Δt S / Δt B ) 2 ]
[γθ V {exp(−λ2 t 2 ) − exp[−λ2 (t 2 + ΔtS )]}] 2
⎛ σ γ2 σ θ2 σ V2 ⎞
+ A ⎜ 2 + 2 + 2 ⎟.
⎜γ
θ
V ⎟⎠
⎝
(L.10)
2
2, 0
When the product γθ is determined using the 226Ra activity from a separate method, the error σA
2,0 in A2,0 is given by
σ
2
A2 , 0
=
λ22 [ N T + σ N2 3 + N B (Δt S / Δt B ) 2 ]
[γθ V {exp(−λ2 t 2 ) − exp[−λ2 (t 2 + Δt S )]}] 2
⎛ σ γθ2
σ V2 ⎞⎟
2 ⎜
.
+ A2,0
+
⎜ (γθ ) 2 V 2 ⎟
⎠
⎝
(L.11)
Next N3 will be determined.
The number of counts per unit time of 222Rn that grows in from 226Ra is given by
C 3 = μC1{1 − exp[−λ3 (t − t1 )]} ,
(L.12)
222
where μ is the fraction of Rn that remains in the Ba(Ra)SO4. To get N3, the above equation
must be integrated from t2 to t2 + ΔtS:
N3 = μ ∫
t 2 + ΔtS
t2
C 3 dt .
Substituting this equation into Eqn. (L.12) yields
N 3 = μC1{Δt S +
1
λ3
exp[−λ3 (t 2 − t1 )][exp(−λ3 Δt S ) − 1] .
©2010 Water Research Foundation. ALL RIGHTS RESERVED
(L.13)
Appendix L: Alpha Spectroscopy Method for 224RA | 237
And the corresponding error is given by
σ N2 3
σ μ2 σ C2
= 2 + 2 ,
μ
C1
1
(L.14)
N 32
where C1 and σC1 are given by Eqns. (L.3) and (L.4), respectively. The values of μ and σμ were
determined from laboratory spikes, which were spiked with about 20 pCi of 226Ra, and were
found to be 0.80 and 0.20, respectively.
In summary, Eqns. (L.5) and (L.6) are used to calculate the 133Ba chemical yield,γ and its
error, respectively. Then, Eqns. (L.1) and (L.2) are used to calculate the 226Ra activity and the
error in the 226Ra activity, respectively. Next, Eqns. (L.13) and (L.14) are used to calculate N3
and the error in N3, respectively. Finally, Eqns. (L.9) and (L.10), along with N3 and its error, are
used to calculate the 224Ra activity and the error in the 224Ra activity respectively.
©2010 Water Research Foundation. ALL RIGHTS RESERVED
238 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
©2010 Water Research Foundation. ALL RIGHTS RESERVED
APPENDIX M
GROSS ALPHA-PARTICLE ACTIVITY DATA
Table M.1 gives the gross alpha-particle activities (GAA) for the 79 samples in the study.
The first column (Sample no.) gives the sample number. The second column (Prep. no.) indicates
whether the GAA is from the first or second preparation. Each preparation contained a triplicate
of samples. The third column (Rep. no.) indicates the number of the sample in a triplicate. Each
sample was counted on the gas proportional counter three times. The fourth column (Count no.)
indicates whether it is the first, second, or third count. The fifth column (Vol.) gives the volume
of the sample used. The sixth column (Mass) gives the residue mass. The seventh column gives
the time, T1, between sample collection and preparation. The eighth column gives the time, T2,
between sample preparation and analysis. The ninth column (GAA) gives the gross alphaparticle activity of the sample and the tenth column (GAA error) gives the counting error in the
GAA.
Table M.1
Gross alpha-particle activity data for samples
Sample no.
RQ091434
RQ091434
RQ091434
RQ091434
RQ091434
RQ091434
RQ091434
RQ091434
RQ091434
RQ091434
RQ091434
RQ091434
RQ091434
RQ091434
RQ091434
RQ091434
RQ091434
RQ091434
RQ091435
RQ091435
RQ091435
RQ091435
RQ091435
RQ091435
RQ091435
RQ091435
RQ091435
Prep.
no.
Rep.
No.
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
Count
No.
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
Vol.
(mL)
1
1
1
2
2
2
3
3
3
1
1
1
2
2
2
3
3
3
1
1
1
2
2
2
3
3
3
50
50
50
50
50
50
50
50
50
40
40
40
40
40
40
40
40
40
50
50
50
50
50
50
50
50
50
Mass
(mg)
100.4
101.6
102.0
100.4
101.6
102.0
100.4
101.6
102.0
83.5
83.0
82.5
83.5
83.0
82.5
83.5
83.0
82.5
100.5
101.2
98.3
100.5
101.2
98.3
101.1
104.0
93.5
T1
(d)
2.46
2.46
2.46
2.46
2.46
2.46
2.46
2.46
2.46
29.47
29.47
29.47
29.47
29.47
29.47
29.47
29.47
29.47
2.46
2.46
2.46
2.46
2.46
2.46
2.46
2.46
2.46
T2
(d)
0.01
0.01
0.01
3.89
3.89
3.89
33.56
33.56
33.56
1.77
1.77
1.77
5.67
5.67
5.67
38.58
38.58
38.78
0.01
0.01
0.01
3.89
3.89
3.89
496.64
496.64
496.64
GAA
(pCi/L)
167.62
197.65
174.64
191.81
197.69
195.81
168.57
171.47
174.48
81.20
69.63
76.26
105.82
126.37
106.94
139.72
149.00
149.36
92.35
77.74
76.85
79.79
81.14
68.41
79.07
73.66
76.05
GAA error
(pCi/L)
23.32
25.03
24.13
24.48
24.94
24.93
17.51
16.99
17.96
12.72
12.61
14.04
13.32
14.11
13.39
14.55
15.38
15.03
20.34
17.58
19.13
19.39
17.90
18.50
10.42
10.18
9.96
(continued)
239
©2010 Water Research Foundation. ALL RIGHTS RESERVED
240 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
Table M.1 (Continued)
Gross alpha-particle activity data for sample
Sample no.
RQ091435
RQ091435
RQ091435
RQ091435
RQ091435
RQ091435
RQ091435
RQ091435
RQ091435
RQ091436
RQ091436
RQ091436
RQ091436
RQ091436
RQ091436
RQ091436
RQ091436
RQ091436
RQ091436
RQ091436
RQ091436
RQ091436
RQ091436
RQ091436
RQ091436
RQ091436
RQ091436
RQ091437
RQ091437
RQ091437
RQ091437
RQ091437
RQ091437
RQ091437
RQ091437
RQ091437
RQ091437
RQ091437
RQ091437
RQ091437
RQ091437
RQ091437
RQ091437
RQ091437
RQ091437
Prep.
no.
Rep.
No.
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
Count
No.
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
Vol. (mL)
1
40
1
40
1
40
2
40
2
40
2
40
3
40
3
40
3
40
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
Mass
(mg)
82.7
82.1
80.9
82.7
82.1
80.9
82.7
82.1
80.9
82.0
76.4
75.1
82.0
76.4
75.1
93.1
87.7
87.0
80.0
84.2
75.7
80.0
84.2
75.7
80.0
84.2
75.7
65.7
68.4
69.5
65.7
68.4
69.5
80.0
81.0
80.0
68.0
75.7
69.9
68.0
75.7
69.9
68.0
75.7
69.9
T1
(d)
29.47
29.47
29.47
29.47
29.47
29.47
29.47
29.47
29.47
2.63
2.63
2.63
2.63
2.63
2.63
2.63
2.63
2.63
29.64
29.64
29.64
29.64
29.64
29.64
29.64
29.64
29.64
2.60
2.60
2.60
2.60
2.60
2.60
2.60
2.60
2.60
29.61
29.61
29.61
29.61
29.61
29.61
29.61
29.61
29.61
©2010 Water Research Foundation. ALL RIGHTS RESERVED
T2
(d)
1.78
1.78
1.78
5.67
5.67
5.67
38.78
38.78
38.78
0.01
0.01
0.01
3.89
3.89
3.89
496.64
496.64
496.64
1.78
1.78
1.78
5.67
5.67
5.67
38.78
38.78
39.49
0.01
0.01
0.01
3.89
3.89
3.89
496.64
496.64
496.64
1.78
1.78
2.36
5.67
5.67
5.67
39.49
39.49
39.49
GAA
GAA error
(pCi/L)
(pCi/L)
20.56
8.76
26.88
10.31
28.35
8.96
34.32
10.87
32.63
8.94
40.77
10.27
60.69
10.62
45.35
10.11
44.82
11.07
57.37
6.28
50.57
5.68
50.90
5.43
63.64
6.58
60.95
6.16
60.60
5.88
74.84
3.71
80.14
3.81
86.15
3.56
30.48
3.23
35.70
3.44
27.63
2.94
41.80
3.48
36.68
3.32
44.12
3.33
53.75
4.04
47.60
3.78
62.71
4.67
43.93
4.76
46.87
5.11
49.58
5.31
43.32
4.72
46.17
5.07
44.11
5.00
60.40
3.94
54.79
4.01
60.74
4.04
18.34
2.42
22.50
2.81
21.32
3.68
22.48
3.61
26.07
4.15
21.36
3.74
32.09
3.35
30.06
3.44
28.62
3.37
Appendix M: Gross Alpha-Particle Activity Data | 241
Table M.1 (Continued)
Gross alpha-particle activity data for sample
Sample no.
RQ091438
RQ091438
RQ091438
RQ091438
RQ091438
RQ091438
RQ091438
RQ091438
RQ091438
RQ091438
RQ091438
RQ091438
RQ091438
RQ091438
RQ091438
RQ091438
RQ091438
RQ091438
RQ091439
RQ091439
RQ091439
RQ091439
RQ091439
RQ091439
RQ091439
RQ091439
RQ091439
RQ091439
RQ091439
RQ091439
RQ091439
RQ091439
RQ091439
RQ091439
RQ091439
RQ091439
RQ091440
RQ091440
RQ091440
RQ091440
RQ091440
RQ091440
RQ091440
RQ091440
RQ091440
Prep.
no.
Rep.
No.
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
Count
No.
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
Vol. (mL)
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
Mass
(mg)
49.9
53.3
50.3
49.9
53.3
50.3
49.9
53.3
50.3
50.1
49.9
49.5
50.1
49.9
49.5
50.1
49.9
49.5
20.3
20.1
20.3
20.3
20.1
20.3
20.3
20.1
20.3
20.6
20.8
20.8
20.6
20.8
20.8
20.6
20.8
20.8
24.7
25.5
26.8
24.7
25.5
26.8
24.7
25.5
26.8
T1
(d)
2.67
2.67
2.67
2.67
2.67
2.67
2.67
2.67
2.67
29.68
29.68
29.68
29.68
29.68
29.68
29.68
29.68
29.68
2.52
2.52
2.52
2.52
2.52
2.52
2.52
2.52
2.52
29.53
29.53
29.53
29.53
29.53
29.53
29.53
29.53
29.53
2.57
2.57
2.57
2.57
2.57
2.57
2.57
2.57
2.57
©2010 Water Research Foundation. ALL RIGHTS RESERVED
T2
(d)
0.64
0.64
0.64
3.58
3.58
3.58
34.00
34.00
34.00
1.55
1.55
1.55
4.90
4.90
4.90
39.86
39.86
39.86
0.65
0.65
0.65
3.58
3.58
3.58
34.00
34.00
34.00
1.55
1.55
1.55
4.90
4.90
4.90
39.86
39.86
39.86
0.65
0.65
0.64
3.58
3.58
3.58
34.00
34.00
34.00
GAA
GAA error
(pCi/L)
(pCi/L)
92.98
10.60
91.21
10.91
107.52
11.91
69.39
9.27
71.07
9.70
77.29
10.21
42.12
4.31
45.25
4.53
44.38
4.53
20.81
3.13
18.68
3.15
20.62
3.13
28.14
2.84
28.99
2.78
32.19
3.01
45.52
3.56
41.96
3.35
40.85
3.28
2376.32
39.35
2441.40
39.36
2100.06
35.60
2414.80
39.67
2435.90
39.31
2050.13
35.17
2259.78
22.15
2332.44
22.21
2004.41
20.08
2516.32
23.25
2470.85
22.45
2642.36
23.12
2466.66
18.01
2435.03
17.76
2458.44
17.34
2250.23
16.54
2377.99
16.98
2302.20
16.91
4909.59
57.47
4313.45
55.14
4463.47
56.03
4973.89
57.84
4316.10
55.16
4491.60
56.21
4754.36
32.65
4146.98
31.22
4450.03
32.30
242 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
Table M.1 (Continued)
Gross alpha-particle activity data for sample
Sample no.
RQ091440
RQ091440
RQ091440
RQ091440
RQ091440
RQ091440
RQ091440
RQ091440
RQ091440
RQ091441
RQ091441
RQ091441
RQ091441
RQ091441
RQ091441
RQ091441
RQ091441
RQ091441
RQ091441
RQ091441
RQ091441
RQ091441
RQ091441
RQ091441
RQ091441
RQ091441
RQ091441
RQ091442
RQ091442
RQ091442
RQ091442
RQ091442
RQ091442
RQ091442
RQ091442
RQ091442
RQ091442
RQ091442
RQ091442
RQ091442
RQ091442
RQ091442
RQ091442
RQ091442
RQ091442
Prep.
no.
Rep.
No.
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
Count
No.
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
Vol. (mL)
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
Mass
(mg)
24.6
27.3
28.6
24.6
27.3
28.6
24.6
27.3
28.6
97.8
92.9
89.2
97.8
92.9
89.2
97.8
92.9
89.2
94.0
91.5
92.3
94.0
91.5
92.3
94.0
91.5
92.3
64.7
67.1
65.3
64.7
67.1
65.3
64.7
67.1
65.3
63.5
65.2
64.5
63.5
65.2
64.5
63.5
65.2
64.5
T1
(d)
29.58
29.58
29.58
29.58
29.58
29.58
29.58
29.58
29.58
2.71
2.71
2.71
2.71
2.71
2.71
2.71
2.71
2.71
29.66
29.66
29.66
29.66
29.66
29.66
29.66
29.66
29.66
2.76
2.76
2.76
2.76
2.76
2.76
2.76
2.76
2.76
29.70
29.70
29.70
29.70
29.70
29.70
29.70
29.70
29.70
©2010 Water Research Foundation. ALL RIGHTS RESERVED
T2
(d)
1.55
1.55
1.77
4.90
4.90
4.90
39.86
39.86
39.86
0.70
0.70
0.70
3.62
3.62
3.62
37.41
37.41
37.41
0.81
0.81
0.81
4.51
4.51
4.51
39.49
39.49
39.49
0.70
0.70
0.70
3.62
3.62
3.62
37.41
37.41
37.41
0.81
0.81
0.81
6.55
6.55
6.55
39.49
39.49
39.86
GAA
GAA error
(pCi/L)
(pCi/L)
4777.03
33.11
4333.69
32.06
4301.57
22.96
4694.64
25.10
3789.29
23.65
3985.04
24.19
4524.53
24.55
3605.98
23.29
3855.61
24.12
37.47
5.48
45.17
5.80
35.05
5.11
46.94
5.98
42.51
5.64
42.90
5.51
36.44
5.52
33.59
5.09
33.91
5.03
15.81
3.01
16.47
2.94
12.13
2.83
19.96
3.21
18.27
2.99
19.90
3.13
41.94
4.44
29.97
3.65
36.02
3.93
60.24
5.69
67.46
6.06
64.85
6.14
55.91
5.50
59.80
5.73
66.09
6.19
53.01
5.39
65.49
5.99
67.21
6.15
21.79
2.94
24.03
2.91
22.59
2.99
42.08
4.65
47.99
5.08
39.76
4.62
54.16
4.04
60.18
4.30
54.47
4.04
Appendix M: Gross Alpha-Particle Activity Data | 243
Table M.1 (Continued)
Gross alpha-particle activity data for sample
Sample no.
RQ091444
RQ091444
RQ091444
RQ091444
RQ091444
RQ091444
RQ091444
RQ091444
RQ091444
RQ091444
RQ091444
RQ091444
RQ091444
RQ091444
RQ091444
RQ091444
RQ091444
RQ091444
RQ091713
RQ091713
RQ091713
RQ091713
RQ091713
RQ091713
RQ091713
RQ091713
RQ091713
RQ091713
RQ091713
RQ091713
RQ091713
RQ091713
RQ091713
RQ091713
RQ091713
RQ091713
RQ091720
RQ091720
RQ091720
RQ091720
RQ091720
RQ091720
RQ091720
RQ091720
RQ091720
Prep.
no.
Rep.
No.
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
Count
No.
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
Vol. (mL)
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
Mass
(mg)
56.6
54.3
52.0
56.6
54.3
52.0
56.6
54.3
52.0
53.4
53.3
52.9
53.4
53.3
52.9
53.4
53.3
52.9
14.0
15.0
14.5
14.0
15.0
14.5
14.0
15.0
14.5
14.6
14.9
14.6
14.6
14.9
14.6
14.6
14.9
14.6
31.4
35.6
33.0
31.4
35.6
33.0
31.4
35.6
33.0
T1
(d)
2.64
2.64
2.64
2.64
2.64
2.64
2.64
2.64
2.64
29.58
29.58
29.58
29.58
29.58
29.58
29.58
29.58
29.58
2.56
2.56
2.56
2.56
2.56
2.56
2.56
2.56
2.56
32.43
32.43
32.43
32.43
32.43
32.43
32.43
32.43
32.43
2.55
2.55
2.55
2.55
2.55
2.55
2.55
2.55
2.55
©2010 Water Research Foundation. ALL RIGHTS RESERVED
T2
(d)
0.70
0.70
0.79
3.62
3.62
4.20
37.41
37.42
38.47
0.81
0.81
0.81
4.51
4.51
4.51
39.49
39.49
39.49
0.97
0.97
0.97
4.81
4.81
4.81
33.82
33.82
33.82
0.02
0.02
0.02
3.74
3.74
3.86
35.84
35.84
36.78
0.97
0.97
0.97
4.81
4.81
4.81
33.89
33.89
33.89
GAA
GAA error
(pCi/L)
(pCi/L)
28.16
4.63
23.52
4.22
22.96
3.40
27.26
3.70
23.34
3.41
28.37
3.60
31.54
3.88
27.19
3.61
24.87
3.36
18.15
2.27
15.42
2.19
16.31
2.25
21.98
3.29
17.67
3.16
19.28
3.13
25.52
2.70
23.00
2.76
23.25
2.64
19.71
3.30
17.09
3.16
20.52
3.43
17.92
2.58
17.16
2.58
19.64
2.74
17.74
3.10
11.56
2.67
15.42
3.06
6.87
1.50
5.89
1.42
6.79
1.54
9.68
2.46
9.88
2.57
8.94
2.35
11.51
1.53
13.95
1.69
14.99
2.69
54.14
6.92
61.87
7.73
65.27
7.91
51.11
5.50
56.32
6.05
52.46
5.82
36.08
5.41
33.65
5.10
37.07
5.31
244 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
Table M.1 (Continued)
Gross alpha-particle activity data for sample
Sample no.
RQ091720
RQ091720
RQ091720
RQ091720
RQ091720
RQ091720
RQ091720
RQ091720
RQ091720
RQ091721
RQ091721
RQ091721
RQ091721
RQ091721
RQ091721
RQ091721
RQ091721
RQ091721
RQ091721
RQ091721
RQ091721
RQ091721
RQ091721
RQ091721
RQ091721
RQ091721
RQ091721
RQ091722
RQ091722
RQ091722
RQ091722
RQ091722
RQ091722
RQ091722
RQ091722
RQ091722
RQ091722
RQ091722
RQ091722
RQ091722
RQ091722
RQ091722
RQ091722
RQ091722
RQ091722
Prep.
no.
Rep.
No.
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
Count
No.
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
Vol. (mL)
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
Mass
(mg)
29.9
28.0
28.8
29.9
28.0
28.8
29.9
28.0
28.8
34.1
32.9
32.9
34.1
32.9
32.9
34.1
32.9
32.9
33.9
34.0
34.3
33.9
34.0
34.3
33.9
34.0
34.3
7.4
7.4
6.9
7.4
7.4
6.9
7.4
7.4
6.9
7.3
7.2
8.4
7.3
7.2
8.4
7.3
7.2
8.4
T1
(d)
32.41
32.41
32.41
32.41
32.41
32.41
32.41
32.41
32.41
2.40
2.40
2.40
2.40
2.40
2.40
2.40
2.40
2.40
32.26
32.26
32.26
32.26
32.26
32.26
32.26
32.26
32.26
2.45
2.45
2.45
2.45
2.45
2.45
2.45
2.45
2.45
32.32
32.32
32.32
32.32
32.32
32.32
32.32
32.32
32.32
©2010 Water Research Foundation. ALL RIGHTS RESERVED
T2
(d)
0.02
0.02
0.02
3.86
3.86
3.86
36.78
36.78
36.78
0.97
0.97
0.97
4.81
4.81
4.81
33.89
34.00
34.00
0.02
0.02
0.02
3.86
3.86
3.86
36.78
36.78
36.78
0.97
0.97
0.97
4.81
4.81
4.81
34.00
34.00
34.03
0.02
0.02
0.02
3.86
3.86
3.86
36.78
36.90
36.90
GAA
GAA error
(pCi/L)
(pCi/L)
12.55
2.62
13.14
2.45
13.34
2.66
24.48
4.68
24.32
4.64
23.03
4.48
29.62
4.63
33.22
4.75
28.36
4.61
90.18
9.29
82.85
8.70
88.03
8.64
87.99
7.51
80.73
7.02
87.56
7.03
85.89
7.92
92.49
8.52
90.32
7.94
82.84
6.30
74.41
5.92
76.90
5.81
91.61
9.41
79.96
8.76
84.23
8.94
96.11
8.58
88.40
8.43
96.37
8.49
69.79
5.51
80.77
5.96
78.50
5.82
100.53
5.37
109.87
5.66
95.09
5.22
126.92
6.80
132.80
6.91
123.59
6.59
32.37
2.67
33.66
2.75
34.60
2.83
76.50
5.76
74.69
5.67
78.76
5.95
120.93
6.58
124.24
6.63
123.57
6.86
Appendix M: Gross Alpha-Particle Activity Data | 245
Table M.1 (Continued)
Gross alpha-particle activity data for sample
Sample no.
RQ091723
RQ091723
RQ091723
RQ091723
RQ091723
RQ091723
RQ091723
RQ091723
RQ091723
RQ091723
RQ091723
RQ091723
RQ091723
RQ091723
RQ091723
RQ091723
RQ091723
RQ091723
RQ091724
RQ091724
RQ091724
RQ091724
RQ091724
RQ091724
RQ091724
RQ091724
RQ091724
RQ091724
RQ091724
RQ091724
RQ091724
RQ091724
RQ091724
RQ091724
RQ091724
RQ091724
RQ091725
RQ091725
RQ091725
RQ091725
RQ091725
RQ091725
RQ091725
RQ091725
RQ091725
Prep.
no.
Rep.
No.
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
Count
No.
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
Vol. (mL)
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
Mass
(mg)
2.9
2.8
2.8
2.9
2.8
2.8
2.9
2.8
2.8
3.6
3.5
4.0
3.6
3.5
4.0
3.6
3.5
4.0
3.6
3.5
3.4
3.6
3.5
3.4
3.6
3.5
3.4
4.3
4.3
3.7
4.3
4.3
3.7
4.3
4.3
3.7
54.3
52.1
53.4
54.3
52.1
53.4
54.3
52.1
53.4
T1
(d)
2.33
2.33
2.33
2.33
2.33
2.33
2.33
2.33
2.33
32.19
32.19
32.19
32.19
32.19
32.19
32.19
32.19
32.19
2.34
2.34
2.34
2.34
2.34
2.34
2.34
2.34
2.34
32.21
32.21
32.21
32.21
32.21
32.21
32.21
32.21
32.21
2.40
2.40
2.40
2.40
2.40
2.40
2.40
2.40
2.40
©2010 Water Research Foundation. ALL RIGHTS RESERVED
T2
(d)
1.05
1.05
1.05
4.96
4.96
4.96
34.03
34.03
34.03
0.18
0.18
0.18
3.74
3.74
3.74
36.91
36.91
36.91
1.05
1.05
1.05
4.96
4.96
4.47
34.03
34.08
34.08
0.18
0.18
0.18
3.74
3.74
3.74
36.91
36.91
36.91
1.05
1.05
1.05
4.47
4.47
4.47
34.08
34.08
34.14
GAA
GAA error
(pCi/L)
(pCi/L)
17.92
1.59
20.28
1.70
17.56
1.58
11.56
1.30
12.03
1.33
13.23
1.39
7.13
1.84
7.83
1.90
5.88
1.70
2.99
0.60
3.07
0.59
3.41
0.65
4.72
1.39
5.66
1.54
4.36
1.50
5.60
1.55
5.58
1.68
6.80
1.69
17.36
1.63
16.67
1.57
18.03
1.66
10.53
1.33
9.70
1.23
13.33
1.44
6.42
1.76
7.45
1.98
6.03
1.68
2.69
0.66
3.14
0.60
3.35
0.67
3.58
1.26
4.80
1.52
6.18
1.55
7.44
1.80
8.37
1.84
5.94
1.63
24.20
3.34
24.32
3.35
24.83
3.47
28.38
3.57
27.79
3.53
25.98
3.51
29.98
4.58
30.45
4.58
29.15
3.66
246 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
Table M.1 (Continued)
Gross alpha-particle activity data for sample
Sample no.
RQ091725
RQ091725
RQ091725
RQ091725
RQ091725
RQ091725
RQ091725
RQ091725
RQ091725
RQ091726
RQ091726
RQ091726
RQ091726
RQ091726
RQ091726
RQ091726
RQ091726
RQ091726
RQ091726
RQ091726
RQ091726
RQ091726
RQ091726
RQ091726
RQ091726
RQ091726
RQ091726
RQ091751
RQ091751
RQ091751
RQ091751
RQ091751
RQ091751
RQ091751
RQ091751
RQ091751
RQ091751
RQ091751
RQ091751
RQ091751
RQ091751
RQ091751
RQ091751
RQ091751
RQ091751
Prep.
no.
Rep.
No.
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
Count
No.
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
Vol. (mL)
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
140
1
140
1
140
2
140
2
140
2
140
3
140
3
140
3
140
1
140
1
140
1
140
2
140
2
140
2
140
3
140
3
140
3
140
Mass
(mg)
50.7
52.6
55.3
50.7
52.6
55.3
50.7
52.6
55.3
48.1
47.4
46.1
48.1
47.4
46.1
48.1
47.4
46.1
49.9
44.6
46.0
49.9
44.6
46.0
49.9
44.6
46.0
71.0
75.1
70.6
71.0
75.1
70.6
71.0
75.1
70.6
69.8
68.9
69.9
69.8
68.9
69.9
69.8
68.9
69.9
T1
(d)
32.26
32.26
32.26
32.26
32.26
32.26
32.26
32.26
32.26
2.40
2.40
2.40
2.40
2.40
2.40
2.40
2.40
2.40
32.26
32.26
32.26
32.26
32.26
32.26
32.26
32.26
32.26
1.40
1.40
1.40
1.40
1.40
1.40
1.40
1.40
1.40
31.26
31.26
31.26
31.26
31.26
31.26
31.26
31.26
31.26
©2010 Water Research Foundation. ALL RIGHTS RESERVED
T2
(d)
0.18
0.18
0.18
3.14
3.14
3.74
37.14
37.14
37.14
1.50
1.50
1.50
5.86
5.86
5.86
33.81
33.81
33.81
0.86
0.86
0.86
3.14
3.14
3.14
37.15
37.15
37.72
1.50
1.50
1.50
5.86
5.86
5.90
33.81
33.81
33.81
0.86
0.86
0.86
3.14
3.14
3.14
37.80
37.80
37.86
GAA
GAA error
(pCi/L)
(pCi/L)
8.68
1.63
11.08
1.92
9.92
1.96
16.26
2.18
17.10
2.33
21.19
3.24
26.12
3.60
30.59
3.80
38.13
4.42
23.93
2.10
25.21
2.13
22.66
2.03
27.90
4.16
26.81
4.08
26.51
4.03
34.42
3.72
32.82
3.66
30.44
3.53
9.81
2.80
11.70
2.80
8.22
2.62
16.97
2.17
17.17
2.07
19.71
2.27
26.36
3.41
25.23
3.17
30.09
4.26
91.68
5.69
82.73
5.34
75.25
4.97
55.83
4.35
58.24
4.58
53.18
4.49
47.49
6.53
31.70
5.66
34.31
5.42
20.74
2.99
19.14
2.77
20.45
2.82
28.70
4.06
23.40
3.54
24.86
3.60
46.97
4.24
41.04
4.03
44.84
4.19
Appendix M: Gross Alpha-Particle Activity Data | 247
Table M.1 (Continued)
Gross alpha-particle activity data for sample
Sample no.
RQ091992
RQ091992
RQ091992
RQ091992
RQ091992
RQ091992
RQ091992
RQ091992
RQ091992
RQ091992
RQ091992
RQ091992
RQ091992
RQ091992
RQ091992
RQ091992
RQ091992
RQ091992
RQ091993
RQ091993
RQ091993
RQ091993
RQ091993
RQ091993
RQ091993
RQ091993
RQ091993
RQ091993
RQ091993
RQ091993
RQ091993
RQ091993
RQ091993
RQ091993
RQ091993
RQ091993
RQ091994
RQ091994
RQ091994
RQ091994
RQ091994
RQ091994
RQ091994
RQ091994
RQ091994
Prep.
no.
Rep.
No.
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
Count
No.
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
Vol. (mL)
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
180
1
180
1
180
2
180
2
180
2
180
3
180
3
180
3
180
1
180
1
180
1
180
2
180
2
180
2
180
3
180
3
180
3
180
1
180
1
180
1
180
2
180
2
180
2
180
3
180
3
180
3
180
Mass
(mg)
66.1
65.0
66.1
66.1
65.0
66.1
66.1
65.0
66.1
68.0
67.4
65.0
68.0
67.4
65.0
68.0
67.4
65.0
86.4
90.4
90.7
86.4
90.4
90.7
86.4
90.4
90.7
91.1
88.0
90.3
91.1
88.0
90.3
91.1
88.0
90.3
79.2
80.2
81.5
79.2
80.2
81.5
79.2
80.2
81.5
T1
(d)
2.57
2.57
2.57
2.57
2.57
2.57
2.57
2.57
2.57
37.20
37.20
37.20
37.20
37.20
37.20
37.20
37.20
37.20
2.60
2.60
2.60
2.60
2.60
2.60
2.60
2.60
2.60
37.23
37.23
37.23
37.23
37.23
37.23
37.23
37.23
37.23
2.62
2.62
2.62
2.62
2.62
2.62
2.62
2.62
2.62
©2010 Water Research Foundation. ALL RIGHTS RESERVED
T2
(d)
0.87
0.93
0.93
4.47
4.47
4.47
32.35
32.35
32.35
0.02
0.02
0.02
9.25
9.25
10.15
43.29
43.29
43.29
0.87
0.87
0.87
4.63
4.63
4.63
32.35
32.35
32.35
0.02
0.05
0.05
9.20
9.20
9.20
43.29
43.29
43.29
0.87
0.87
0.87
4.63
4.68
4.68
32.35
32.35
32.35
GAA
GAA error
(pCi/L)
(pCi/L)
3.34
1.79
5.54
1.73
4.77
1.63
3.57
2.08
3.53
1.89
3.80
1.98
0.63
2.13
2.79
1.86
2.44
1.99
5.60
2.14
4.90
2.19
5.52
2.29
3.65
1.85
3.15
1.55
4.84
2.47
2.19
2.03
2.18
2.47
2.81
2.00
50.49
4.41
51.54
4.72
48.68
4.48
49.79
4.53
45.63
4.39
44.98
4.57
40.22
4.07
36.81
3.98
35.30
3.59
45.91
4.39
56.12
4.67
37.11
3.96
42.32
3.90
54.29
4.33
35.54
3.63
47.05
4.34
49.72
4.17
32.89
3.59
30.91
4.02
27.15
3.65
21.68
3.37
30.61
3.80
25.97
3.59
20.01
3.08
25.42
3.22
19.23
3.00
19.35
3.13
248 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
Table M.1 (Continued)
Gross alpha-particle activity data for sample
Sample no.
RQ091994
RQ091994
RQ091994
RQ091994
RQ091994
RQ091994
RQ091994
RQ091994
RQ091994
RQ091995
RQ091995
RQ091995
RQ091995
RQ091995
RQ091995
RQ091995
RQ091995
RQ091995
RQ091995
RQ091995
RQ091995
RQ091995
RQ091995
RQ091995
RQ091995
RQ091995
RQ091995
RQ091996
RQ091996
RQ091996
RQ091996
RQ091996
RQ091996
RQ091996
RQ091996
RQ091996
RQ091996
RQ091996
RQ091996
RQ091996
RQ091996
RQ091996
RQ091996
RQ091996
RQ091996
Prep.
no.
Rep.
No.
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
Count
No.
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
Vol. (mL)
1
180
1
180
1
180
2
180
2
180
2
180
3
180
3
180
3
180
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
Mass
(mg)
87.4
84.7
89.8
87.4
84.7
89.8
87.4
84.7
89.8
4.0
3.4
3.4
4.0
3.4
3.4
4.0
3.4
3.4
3.2
3.7
3.6
3.2
3.7
3.6
3.2
3.7
3.6
20.7
20.5
20.7
20.7
20.5
20.7
20.7
20.5
20.7
20.5
21.0
20.9
20.5
21.0
20.9
20.5
21.0
20.9
T1
(d)
36.92
36.92
36.92
36.92
36.92
36.92
36.92
36.92
36.92
2.50
2.50
2.50
2.50
2.50
2.50
2.50
2.50
2.50
36.81
36.81
36.81
36.81
36.81
36.81
36.81
36.81
36.81
2.56
2.56
2.56
2.56
2.56
2.56
2.56
2.56
2.56
36.99
36.99
36.99
36.99
36.99
36.99
36.99
36.99
36.99
©2010 Water Research Foundation. ALL RIGHTS RESERVED
T2
(d)
0.37
0.41
1.09
9.54
9.54
9.54
43.61
43.61
43.61
0.44
0.44
0.44
4.38
4.38
4.38
32.35
32.35
32.35
0.25
0.25
0.25
9.47
9.47
9.47
44.13
44.13
44.13
0.44
0.44
0.44
4.39
4.39
4.39
32.73
32.73
32.73
0.13
0.13
0.13
8.09
8.09
8.17
43.41
43.41
43.41
GAA
GAA error
(pCi/L)
(pCi/L)
23.78
3.28
29.26
3.77
34.71
3.71
27.54
3.22
34.03
3.45
33.13
3.54
24.26
3.22
25.62
3.22
26.50
3.48
19.74
2.89
24.18
3.21
19.68
2.91
18.79
2.86
14.62
2.53
18.18
2.86
10.19
2.16
8.92
2.04
9.94
2.15
4.48
1.72
4.14
1.52
3.81
1.52
7.93
1.92
7.38
1.88
8.30
2.02
7.89
1.96
8.48
2.12
10.51
2.21
31.05
4.65
27.49
4.36
29.69
4.38
32.21
4.71
33.17
4.60
31.86
4.53
41.24
5.12
31.26
4.55
39.49
5.06
12.00
2.93
13.17
3.14
14.05
3.24
30.81
4.69
34.35
4.91
28.35
4.32
36.49
5.11
41.23
5.33
38.82
5.18
Appendix M: Gross Alpha-Particle Activity Data | 249
Table M.1 (Continued)
Gross alpha-particle activity data for sample
Sample no.
RQ091997
RQ091997
RQ091997
RQ091997
RQ091997
RQ091997
RQ091997
RQ091997
RQ091997
RQ091997
RQ091997
RQ091997
RQ091997
RQ091997
RQ091997
RQ091997
RQ091997
RQ091997
RQ091998
RQ091998
RQ091998
RQ091998
RQ091998
RQ091998
RQ091998
RQ091998
RQ091998
RQ091998
RQ091998
RQ091998
RQ091998
RQ091998
RQ091998
RQ091998
RQ091998
RQ091998
RQ091999
RQ091999
RQ091999
RQ091999
RQ091999
RQ091999
RQ091999
RQ091999
RQ091999
Prep.
no.
Rep.
No.
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
Count
No.
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
Vol. (mL)
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
150
1
150
1
150
2
150
2
150
2
150
3
150
3
150
3
150
1
150
1
150
1
150
2
150
2
150
2
150
3
150
3
150
3
150
1
140
1
140
1
140
2
140
2
140
2
140
3
140
3
140
3
140
Mass
(mg)
20.2
21.1
20.7
20.2
21.1
20.7
20.2
21.1
20.7
22.8
21.9
24.2
22.8
21.9
24.2
22.8
21.9
24.2
69.6
66.3
68.2
69.6
66.3
68.2
69.6
66.3
68.2
88.6
79.9
81.7
88.6
79.9
81.7
88.6
79.9
81.7
57.4
64.0
58.0
57.4
64.0
58.0
57.4
64.0
58.0
T1
(d)
2.55
2.55
2.55
2.55
2.55
2.55
2.55
2.55
2.55
36.98
36.98
36.98
36.98
36.98
36.98
36.98
36.98
36.98
2.61
2.61
2.61
2.61
2.61
2.61
2.61
2.61
2.61
37.05
37.05
37.05
37.05
37.05
37.05
37.05
37.05
37.05
2.58
2.58
2.58
2.58
2.58
2.58
2.58
2.58
2.58
©2010 Water Research Foundation. ALL RIGHTS RESERVED
T2
(d)
0.44
0.44
0.44
4.39
4.39
4.46
32.83
32.83
32.83
0.21
0.21
0.21
8.17
8.17
8.17
43.41
43.41
43.41
0.87
0.87
0.87
4.68
4.68
4.68
32.83
32.83
32.83
0.97
0.97
0.97
8.35
8.35
8.35
43.47
43.47
43.47
1.48
1.48
1.48
4.82
4.82
4.89
32.83
33.92
33.92
GAA
GAA error
(pCi/L)
(pCi/L)
19.29
3.54
20.59
3.80
21.48
3.88
25.27
4.11
28.42
4.40
26.24
4.16
38.77
2.99
45.60
3.24
38.98
3.00
13.43
3.45
12.34
3.12
12.49
3.35
32.21
4.79
33.80
4.85
30.24
4.92
31.42
4.67
34.63
4.80
32.90
4.94
27.00
3.59
38.67
4.04
25.51
3.59
28.47
3.35
34.86
3.68
35.43
3.82
31.64
3.47
45.22
4.00
36.45
3.79
14.97
2.39
17.91
2.76
15.65
3.02
29.14
3.24
36.99
3.62
30.41
3.42
23.75
3.19
34.08
3.37
35.90
3.35
55.73
4.95
57.62
4.87
50.58
4.86
54.61
4.70
51.67
4.85
50.27
4.57
50.29
4.16
50.94
4.56
49.97
4.39
250 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
Table M.1 (Continued)
Gross alpha-particle activity data for sample
Sample no.
RQ091999
RQ091999
RQ091999
RQ091999
RQ091999
RQ091999
RQ091999
RQ091999
RQ091999
RQ092000
RQ092000
RQ092000
RQ092000
RQ092000
RQ092000
RQ092000
RQ092000
RQ092000
RQ092000
RQ092000
RQ092000
RQ092000
RQ092000
RQ092000
RQ092000
RQ092000
RQ092000
RQ092001
RQ092001
RQ092001
RQ092001
RQ092001
RQ092001
RQ092001
RQ092001
RQ092001
RQ092001
RQ092001
RQ092001
RQ092001
RQ092001
RQ092001
RQ092001
RQ092001
RQ092001
Prep.
no.
Rep.
No.
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
Count
No.
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
Vol. (mL)
1
140
1
140
1
140
2
140
2
140
2
140
3
140
3
140
3
140
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
Mass
(mg)
66.6
78.1
72.0
66.6
78.1
72.0
66.6
78.1
72.0
53.7
63.7
58.6
53.7
63.7
58.6
53.7
63.7
58.6
79.1
71.7
69.5
79.1
71.7
69.5
79.1
71.7
69.5
76.5
73.7
77.4
76.5
73.7
77.4
76.5
73.7
77.4
77.1
81.5
71.4
77.1
81.5
71.4
77.1
81.5
71.4
T1
(d)
37.02
37.02
37.02
37.02
37.02
37.02
37.02
37.02
37.02
2.66
2.66
2.66
2.66
2.66
2.66
2.66
2.66
2.66
37.10
37.10
37.10
37.10
37.10
37.10
37.10
37.10
37.10
2.72
2.72
2.72
2.72
2.72
2.72
2.72
2.72
2.72
37.35
37.35
37.35
37.35
37.35
37.35
37.35
37.35
37.35
©2010 Water Research Foundation. ALL RIGHTS RESERVED
T2
(d)
0.96
0.96
0.96
11.14
11.14
11.14
44.11
44.12
44.12
1.48
1.48
1.48
4.47
4.47
4.58
33.92
33.92
33.92
0.96
0.96
0.97
11.14
11.14
11.14
44.12
44.12
44.12
1.48
1.48
1.48
4.58
4.99
5.03
33.92
33.92
33.92
0.76
0.76
1.75
10.94
10.94
10.94
43.80
43.92
43.92
GAA
GAA error
(pCi/L)
(pCi/L)
22.32
2.54
27.65
3.10
25.05
2.76
43.46
3.61
49.34
4.19
48.36
4.02
47.25
4.13
50.14
4.15
57.10
4.34
43.32
5.19
48.10
5.04
47.20
5.49
37.32
4.11
40.38
4.62
40.31
4.42
30.65
3.94
29.97
4.13
23.86
3.74
13.40
1.95
13.16
1.61
13.27
1.65
24.35
3.22
29.38
3.48
28.99
3.32
27.87
3.65
30.19
3.80
26.07
3.57
70.34
5.77
84.91
6.56
82.09
5.90
56.77
5.03
83.62
5.50
81.74
6.15
57.19
4.93
59.55
4.98
60.84
5.24
26.63
2.31
27.92
2.48
30.06
3.69
56.53
4.42
55.07
4.50
60.53
4.50
50.38
4.82
53.85
4.48
59.95
4.91
Appendix M: Gross Alpha-Particle Activity Data | 251
Table M.1 (Continued)
Gross alpha-particle activity data for sample
Sample no.
RQ092029
RQ092029
RQ092029
RQ092029
RQ092029
RQ092029
RQ092029
RQ092029
RQ092029
RQ092029
RQ092029
RQ092029
RQ092029
RQ092029
RQ092029
RQ092029
RQ092029
RQ092029
RQ092250
RQ092250
RQ092250
RQ092250
RQ092250
RQ092250
RQ092250
RQ092250
RQ092250
RQ092250
RQ092250
RQ092250
RQ092250
RQ092250
RQ092250
RQ092250
RQ092250
RQ092250
RQ092251
RQ092251
RQ092251
RQ092251
RQ092251
RQ092251
RQ092251
RQ092251
RQ092251
Prep.
no.
Rep.
No.
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
Count
No.
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
Vol. (mL)
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
100
1
100
1
100
2
100
2
100
2
100
3
100
3
100
3
100
1
100
1
100
1
100
2
100
2
100
2
100
3
100
3
100
3
100
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
Mass
(mg)
58.2
58.7
58.7
58.2
58.7
58.7
58.2
58.7
58.7
79.8
90.8
94.7
79.8
90.8
94.7
79.8
90.8
94.7
97.8
99.6
85.6
97.8
99.6
85.6
97.8
99.6
85.6
71.5
67.6
68.7
71.5
67.6
68.7
71.5
67.6
68.7
56.4
55.1
60.4
56.4
55.1
60.4
56.4
55.1
60.4
T1
(d)
1.66
1.66
1.66
1.66
1.66
1.66
1.66
1.66
1.66
35.97
35.97
35.97
35.97
35.97
35.97
35.97
35.97
35.97
4.59
4.59
4.59
4.59
4.59
4.59
4.59
4.59
4.59
50.16
50.04
50.04
50.16
50.04
50.04
50.16
50.04
50.04
4.57
4.57
4.57
4.57
4.57
4.57
4.57
4.57
4.57
©2010 Water Research Foundation. ALL RIGHTS RESERVED
T2
(d)
1.48
1.48
1.49
4.47
4.47
4.47
33.92
34.49
34.49
0.40
0.40
0.40
10.47
10.47
10.47
44.35
44.35
44.35
0.96
0.96
0.96
5.87
5.87
5.87
43.03
43.03
43.03
0.02
0.14
0.14
3.32
3.45
3.45
32.99
33.12
33.12
2.00
2.00
2.00
5.68
6.62
6.62
43.64
43.64
43.64
GAA
GAA error
(pCi/L)
(pCi/L)
9.30
2.53
6.15
2.39
5.23
2.48
5.39
2.77
6.50
2.61
6.80
2.89
4.07
2.10
6.27
2.43
4.76
2.16
4.89
1.83
5.93
2.20
7.56
2.15
5.77
2.02
3.48
1.79
5.30
2.25
3.45
1.84
4.25
1.76
3.98
2.23
33.78
3.13
35.60
3.31
33.05
3.05
32.10
3.55
31.70
3.38
31.86
2.93
27.94
3.05
29.22
3.46
27.77
2.78
20.32
2.96
22.47
2.80
23.80
3.01
20.22
2.83
19.47
2.56
22.24
2.84
20.77
2.94
24.10
2.91
25.16
3.10
14.82
2.19
14.99
2.20
15.29
2.37
19.26
3.58
20.98
3.35
19.76
3.46
25.34
2.53
25.24
2.46
23.64
2.55
252 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
Table M.1 (Continued)
Gross alpha-particle activity data for sample
Sample no.
RQ092251
RQ092251
RQ092251
RQ092251
RQ092251
RQ092251
RQ092251
RQ092251
RQ092251
RQ092252
RQ092252
RQ092252
RQ092252
RQ092252
RQ092252
RQ092252
RQ092252
RQ092252
RQ092252
RQ092252
RQ092252
RQ092252
RQ092252
RQ092252
RQ092252
RQ092252
RQ092252
RQ092253
RQ092253
RQ092253
RQ092253
RQ092253
RQ092253
RQ092253
RQ092253
RQ092253
RQ092253
RQ092253
RQ092253
RQ092253
RQ092253
RQ092253
RQ092253
RQ092253
RQ092253
Prep.
no.
Rep.
No.
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
Count
No.
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
Vol. (mL)
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
100
1
100
1
100
2
100
2
100
2
100
3
100
3
100
3
100
1
100
1
100
1
100
2
100
2
100
2
100
3
100
3
100
3
100
1
125
1
125
1
125
2
125
2
125
2
125
3
125
3
125
3
125
1
125
1
125
1
125
2
125
2
125
2
125
3
125
3
125
3
125
Mass
(mg)
53.4
58.6
59.6
53.4
58.6
59.6
53.4
58.6
59.6
74.0
85.1
72.4
74.0
85.1
72.4
74.0
85.1
72.4
79.4
79.1
76.4
79.4
79.1
76.4
79.4
79.1
76.4
82.5
82.1
84.1
82.5
82.1
84.1
82.5
82.1
84.1
89.5
79.3
87.3
89.5
79.3
87.3
89.5
79.3
87.3
T1
(d)
50.02
50.02
50.02
50.02
50.02
50.02
50.02
50.02
50.02
4.54
4.54
4.54
4.54
4.54
4.54
4.54
4.54
4.54
49.99
49.99
49.99
49.99
49.99
49.99
49.99
49.99
49.99
4.59
4.59
4.59
4.59
4.59
4.59
4.59
4.59
4.59
50.04
50.04
50.04
50.04
50.04
50.04
50.04
50.04
50.04
©2010 Water Research Foundation. ALL RIGHTS RESERVED
T2
(d)
0.14
0.24
0.14
3.45
3.45
3.45
32.45
32.45
32.45
0.96
2.00
2.00
5.87
5.87
5.87
43.03
43.03
43.03
0.14
0.14
0.14
3.45
3.45
3.45
33.12
33.12
33.12
2.00
2.00
2.00
5.95
5.95
5.95
43.03
43.03
43.65
0.14
0.15
0.15
3.45
3.45
3.45
33.12
33.12
33.12
GAA
GAA error
(pCi/L)
(pCi/L)
7.34
2.70
9.80
2.82
8.92
3.02
15.15
3.04
12.87
2.85
13.95
3.17
20.62
3.25
20.99
3.59
17.75
3.09
30.52
3.21
33.36
3.49
34.00
3.54
50.10
3.83
44.45
3.16
48.52
3.46
53.59
3.45
48.77
3.37
59.82
3.32
18.97
2.95
15.85
3.00
15.07
2.65
37.91
3.63
33.91
3.68
29.88
3.16
58.20
4.87
65.37
4.77
59.52
4.70
25.76
3.19
23.98
3.16
26.79
3.25
26.13
2.92
24.08
2.85
25.94
3.11
22.22
2.80
24.49
3.02
29.44
3.52
22.67
2.80
23.23
2.77
23.41
3.07
20.41
2.63
22.49
2.62
22.38
2.94
24.44
3.04
20.89
2.94
21.97
2.72
Appendix M: Gross Alpha-Particle Activity Data | 253
Table M.1 (Continued)
Gross alpha-particle activity data for sample
Sample no.
RQ092254
RQ092254
RQ092254
RQ092254
RQ092254
RQ092254
RQ092254
RQ092254
RQ092254
RQ092254
RQ092254
RQ092254
RQ092254
RQ092254
RQ092254
RQ092254
RQ092254
RQ092254
RQ092255
RQ092255
RQ092255
RQ092255
RQ092255
RQ092255
RQ092255
RQ092255
RQ092255
RQ092255
RQ092255
RQ092255
RQ092255
RQ092255
RQ092255
RQ092255
RQ092255
RQ092255
RQ092256
RQ092256
RQ092256
RQ092256
RQ092256
RQ092256
RQ092256
RQ092256
RQ092256
Prep.
no.
Rep.
No.
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
Count
No.
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
Vol. (mL)
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
Mass
(mg)
97.3
94.3
97.4
97.3
94.3
97.4
97.3
94.3
97.4
93.0
90.0
94.3
93.0
90.0
94.3
93.0
90.0
94.3
27.7
26.8
26.2
27.7
26.8
26.2
27.7
26.8
26.2
26.2
25.4
26.2
26.2
25.4
26.2
26.2
25.4
26.2
33.2
32.3
31.9
33.2
32.3
31.9
33.2
32.3
31.9
T1
(d)
4.53
4.53
4.53
4.53
4.53
4.53
4.53
4.53
4.53
50.03
50.03
50.03
50.03
50.03
50.03
50.03
50.03
50.03
4.59
4.59
4.59
4.59
4.59
4.59
4.59
4.59
4.59
50.09
50.09
50.09
50.09
50.09
50.09
50.09
50.09
50.09
4.62
4.62
4.62
4.62
4.62
4.62
4.62
4.62
4.62
©2010 Water Research Foundation. ALL RIGHTS RESERVED
T2
(d)
0.03
0.60
0.60
5.49
5.50
5.50
41.95
41.95
42.64
0.47
0.47
0.47
4.15
4.15
4.15
33.03
33.03
33.03
0.60
0.60
0.61
5.41
5.41
5.41
42.64
42.64
42.64
1.45
1.45
1.45
5.15
5.15
5.15
32.37
34.95
34.95
0.61
0.61
0.61
5.41
5.41
5.41
42.64
42.64
42.64
GAA
GAA error
(pCi/L)
(pCi/L)
26.63
3.47
20.05
3.03
26.06
3.32
22.71
3.20
18.18
3.05
22.14
3.16
24.17
3.55
15.56
2.68
20.49
3.22
22.23
3.48
18.32
2.99
18.51
3.32
21.58
3.34
18.52
2.87
21.48
3.36
21.61
3.03
18.22
2.74
16.33
3.03
15.18
2.62
15.83
2.77
11.99
2.33
19.14
4.04
20.92
4.21
17.78
4.04
22.14
3.08
17.62
2.86
19.80
2.88
9.66
1.74
9.52
1.65
9.57
1.74
16.14
2.56
12.51
2.33
14.47
2.56
19.03
2.88
16.45
3.65
21.49
4.17
118.62
7.44
108.84
7.06
105.82
6.91
107.42
8.96
115.98
9.42
104.58
8.90
99.52
6.87
116.92
7.30
97.58
6.63
254 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
Table M.1 (Continued)
Gross alpha-particle activity data for sample
Sample no.
RQ092256
RQ092256
RQ092256
RQ092256
RQ092256
RQ092256
RQ092256
RQ092256
RQ092256
RQ092257
RQ092257
RQ092257
RQ092257
RQ092257
RQ092257
RQ092257
RQ092257
RQ092257
RQ092257
RQ092257
RQ092257
RQ092257
RQ092257
RQ092257
RQ092257
RQ092257
RQ092257
RQ092258
RQ092258
RQ092258
RQ092258
RQ092258
RQ092258
RQ092258
RQ092258
RQ092258
RQ092258
RQ092258
RQ092258
RQ092258
RQ092258
RQ092258
RQ092258
RQ092258
RQ092258
Prep.
no.
Rep.
No.
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
Count
No.
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
Vol. (mL)
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
Mass
(mg)
32.7
36.2
35.8
32.7
36.2
35.8
32.7
36.2
35.8
70.5
68.3
72.4
70.5
68.3
72.4
70.5
68.3
72.4
60.6
62.4
62.2
60.6
62.4
62.2
60.6
62.4
62.2
25.2
25.1
25.0
25.2
25.1
25.0
25.2
25.1
25.0
25.0
25.0
25.5
25.0
25.0
25.5
25.0
25.0
25.5
T1
(d)
50.13
50.13
50.13
50.13
50.13
50.13
50.13
50.13
50.13
5.18
5.18
5.18
5.18
5.18
5.18
5.18
5.18
5.18
50.15
50.15
50.15
50.15
50.15
50.15
50.15
50.15
50.15
5.07
5.07
5.07
5.07
5.07
5.07
5.07
5.07
5.07
50.04
50.04
50.04
50.04
50.04
50.04
50.04
50.04
50.04
©2010 Water Research Foundation. ALL RIGHTS RESERVED
T2
(d)
1.45
1.45
1.45
5.41
5.41
5.42
34.95
34.95
34.95
0.07
0.07
0.07
4.96
4.96
4.96
41.44
41.44
41.44
1.45
1.45
1.45
5.42
5.42
5.42
32.20
32.20
32.20
0.39
0.39
0.39
4.88
4.88
4.87
42.11
42.11
42.11
1.92
1.92
1.92
5.42
5.42
5.42
32.20
32.20
32.36
GAA
GAA error
(pCi/L)
(pCi/L)
119.07
5.84
97.75
5.60
110.17
6.06
112.35
6.99
101.50
6.88
106.63
7.13
110.38
9.74
103.69
9.90
110.56
10.26
304.92
11.42
295.05
11.05
303.74
11.65
304.23
10.80
273.85
10.48
287.44
10.51
292.52
8.93
290.28
8.36
301.70
8.88
283.61
9.62
285.47
9.93
288.89
9.85
273.53
11.63
303.63
12.40
278.41
11.74
297.10
12.13
327.44
12.74
325.45
12.09
8.40
1.38
7.90
1.22
9.71
1.36
15.80
3.62
13.75
3.47
20.43
3.96
23.81
3.01
19.07
2.69
25.25
3.14
10.42
3.04
12.32
3.18
10.54
3.11
14.49
1.96
15.73
2.08
13.85
2.03
19.34
3.87
20.56
4.12
19.18
2.75
Appendix M: Gross Alpha-Particle Activity Data | 255
Table M.1 (Continued)
Gross alpha-particle activity data for sample
Sample no.
RQ092847
RQ092847
RQ092847
RQ092847
RQ092847
RQ092847
RQ092847
RQ092847
RQ092847
RQ092847
RQ092847
RQ092847
RQ092847
RQ092847
RQ092847
RQ092847
RQ092847
RQ092847
RQ092848
RQ092848
RQ092848
RQ092848
RQ092848
RQ092848
RQ092848
RQ092848
RQ092848
RQ092848
RQ092848
RQ092848
RQ092848
RQ092848
RQ092848
RQ092848
RQ092848
RQ092848
RQ092849
RQ092849
RQ092849
RQ092849
RQ092849
RQ092849
RQ092849
RQ092849
RQ092849
Prep.
no.
Rep.
No.
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
Count
No.
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
Vol. (mL)
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
Mass
(mg)
14.1
15.6
15.6
14.1
15.6
15.6
14.1
15.6
15.6
18.0
12.7
19.8
18.0
12.7
19.8
18.0
12.7
19.8
15.5
15.4
17.3
15.5
15.4
17.3
15.5
15.4
17.3
19.9
21.4
17.5
19.9
21.4
17.5
19.9
21.4
17.5
21.6
22.2
22.9
21.6
22.2
22.9
21.6
22.2
22.9
T1
(d)
3.51
3.51
3.51
3.51
3.51
3.51
3.51
3.51
3.51
34.17
34.17
34.17
34.17
34.17
34.17
34.17
34.17
34.17
3.45
3.45
3.45
3.45
3.45
3.45
3.45
3.45
3.45
34.10
34.10
34.10
34.10
34.10
34.10
34.10
34.10
34.10
3.62
3.62
3.62
3.62
3.62
3.62
3.62
3.62
3.62
©2010 Water Research Foundation. ALL RIGHTS RESERVED
T2
(d)
0.57
0.57
0.57
4.90
4.90
4.90
42.86
42.86
42.86
0.86
0.86
0.86
3.77
3.77
3.77
39.20
39.20
39.20
0.64
0.64
0.64
4.90
4.90
5.36
42.86
42.86
42.86
0.86
0.86
0.86
3.77
3.77
3.77
39.20
39.20
39.20
0.78
0.78
0.78
5.36
5.36
5.36
42.86
42.86
42.86
GAA
GAA error
(pCi/L)
(pCi/L)
35.23
4.33
36.66
4.49
35.57
4.50
32.78
2.42
35.07
2.58
35.51
2.59
30.82
4.05
33.36
4.38
35.71
4.50
33.80
4.49
25.94
3.71
41.41
5.15
37.12
4.69
27.73
3.84
40.84
5.11
37.09
4.73
31.80
4.17
42.56
5.25
88.95
6.88
85.32
6.73
94.57
7.37
67.95
11.28
77.42
3.88
85.06
6.91
77.42
6.60
70.19
6.40
90.54
7.41
79.74
7.07
82.31
7.43
77.08
6.93
72.23
6.76
78.65
7.26
69.51
6.59
71.83
6.82
82.12
7.56
77.58
6.90
55.53
5.98
49.06
5.78
50.27
5.88
52.56
5.94
54.27
6.05
55.43
6.24
50.33
5.73
47.52
5.62
43.81
5.50
256 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
Table M.1 (Continued)
Gross alpha-particle activity data for sample
Sample no.
RQ092849
RQ092849
RQ092849
RQ092849
RQ092849
RQ092849
RQ092849
RQ092849
RQ092849
RQ092850
RQ092850
RQ092850
RQ092850
RQ092850
RQ092850
RQ092850
RQ092850
RQ092850
RQ092850
RQ092850
RQ092850
RQ092850
RQ092850
RQ092850
RQ092850
RQ092850
RQ092850
RQ092851
RQ092851
RQ092851
RQ092851
RQ092851
RQ092851
RQ092851
RQ092851
RQ092851
RQ092851
RQ092851
RQ092851
RQ092851
RQ092851
RQ092851
RQ092851
RQ092851
RQ092851
Prep.
no.
Rep.
No.
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
Count
No.
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
Vol. (mL)
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
Mass
(mg)
24.1
24.8
24.7
24.1
24.8
24.7
24.1
24.8
24.7
16.7
16.2
16.0
16.7
16.2
16.0
16.7
16.2
16.0
20.4
19.1
21.5
20.4
19.1
21.5
20.4
19.1
21.5
22.4
21.5
25.9
22.4
21.5
25.9
22.4
21.5
25.9
28.5
33.2
27.8
28.5
33.2
27.8
28.5
33.2
27.8
T1
(d)
34.27
34.27
34.27
34.27
34.27
34.27
34.27
34.27
34.27
3.67
3.67
3.67
3.67
3.67
3.67
3.67
3.67
3.67
34.34
34.34
34.34
34.34
34.34
34.34
34.34
34.34
34.34
3.69
3.69
3.69
3.69
3.69
3.69
3.69
3.69
3.69
34.36
34.36
34.36
34.36
34.36
34.36
34.36
34.36
34.36
©2010 Water Research Foundation. ALL RIGHTS RESERVED
T2
(d)
0.86
0.86
0.86
3.77
3.77
3.77
39.20
39.20
39.20
0.79
0.85
0.85
5.84
5.84
5.84
43.54
43.54
43.54
1.01
1.01
1.01
3.85
3.85
3.85
39.77
39.77
39.77
0.85
0.87
1.88
5.84
5.84
5.84
43.54
43.54
43.54
1.01
1.01
1.01
3.85
3.85
3.85
39.77
39.77
39.85
GAA
GAA error
(pCi/L)
(pCi/L)
46.64
5.95
51.01
6.29
45.06
5.68
49.56
6.14
52.88
6.40
47.04
5.79
50.95
6.21
52.02
6.12
52.59
6.11
14.66
3.05
15.00
3.00
19.11
3.40
12.65
1.66
13.39
1.67
15.81
1.81
14.50
3.01
12.53
2.82
15.18
3.09
19.33
3.63
15.04
3.17
16.63
3.52
19.65
3.65
17.67
3.42
17.50
3.59
15.76
3.38
14.25
3.28
17.48
3.64
13.28
3.29
13.60
3.20
12.05
1.98
10.84
1.82
14.61
1.91
10.91
1.93
11.69
3.31
13.16
3.20
9.51
3.15
14.61
3.88
12.58
3.75
12.91
3.68
13.92
3.83
16.09
4.12
18.17
4.20
15.66
3.90
17.37
4.40
12.35
3.45
Appendix M: Gross Alpha-Particle Activity Data | 257
Table M.1 (Continued)
Gross alpha-particle activity data for sample
Sample no.
RQ092852
RQ092852
RQ092852
RQ092852
RQ092852
RQ092852
RQ092852
RQ092852
RQ092852
RQ092852
RQ092852
RQ092852
RQ092852
RQ092852
RQ092852
RQ092852
RQ092852
RQ092852
RQ092853
RQ092853
RQ092853
RQ092853
RQ092853
RQ092853
RQ092853
RQ092853
RQ092853
RQ092853
RQ092853
RQ092853
RQ092853
RQ092853
RQ092853
RQ092853
RQ092853
RQ092853
RQ092854
RQ092854
RQ092854
RQ092854
RQ092854
RQ092854
RQ092854
RQ092854
RQ092854
Prep.
no.
Rep.
No.
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
Count
No.
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
Vol. (mL)
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
Mass
(mg)
23.0
22.8
23.2
23.0
22.8
23.2
23.0
22.8
23.2
31.3
26.9
30.6
31.3
26.9
30.6
31.3
26.9
30.6
26.6
22.2
22.7
26.6
22.2
22.7
26.6
22.2
22.7
23.8
28.2
23.4
23.8
28.2
23.4
23.8
28.2
23.4
33.5
33.0
33.2
33.5
33.0
33.2
33.5
33.0
33.2
T1
(d)
3.41
3.41
3.41
3.41
3.41
3.41
3.41
3.41
3.41
34.07
34.07
34.07
34.07
34.07
34.07
34.07
34.07
34.07
3.43
3.43
3.43
3.43
3.43
3.43
3.43
3.43
3.43
34.11
34.11
34.11
34.11
34.11
34.11
34.11
34.11
34.11
3.77
3.77
3.77
3.77
3.77
3.77
3.77
3.77
3.77
©2010 Water Research Foundation. ALL RIGHTS RESERVED
T2
(d)
1.88
1.88
1.88
5.84
5.84
5.84
43.64
43.64
43.64
1.01
1.01
1.01
3.85
3.85
3.85
39.77
39.77
39.77
1.89
2.59
2.59
4.50
4.50
4.50
42.94
42.94
42.94
0.04
0.04
0.04
3.91
3.91
3.91
39.84
39.84
39.84
2.59
2.59
2.59
4.50
4.50
4.50
42.94
42.94
42.94
GAA
GAA error
(pCi/L)
(pCi/L)
209.05
6.76
222.93
6.93
194.77
6.61
207.17
7.01
221.83
7.17
185.93
6.40
188.55
11.05
223.52
12.29
181.34
11.02
262.42
15.22
236.31
13.57
231.38
13.53
265.01
15.30
222.11
13.16
217.99
13.14
263.30
15.11
206.41
12.25
212.00
12.92
260.56
7.85
265.66
7.47
309.63
8.33
267.79
7.95
263.46
7.63
314.37
8.29
233.97
9.11
261.15
9.31
297.30
9.87
285.86
9.70
286.66
10.53
295.87
9.95
291.79
13.86
293.29
15.07
312.91
14.45
329.47
15.20
304.76
15.76
341.08
15.65
12.08
2.11
13.61
2.34
12.09
2.08
6.47
1.89
9.28
1.88
9.07
2.02
3.32
2.09
3.72
1.76
2.34
1.73
258 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
Table M.1 (Continued)
Gross alpha-particle activity data for sample
Sample no.
RQ092854
RQ092854
RQ092854
RQ092854
RQ092854
RQ092854
RQ092854
RQ092854
RQ092854
RQ092855
RQ092855
RQ092855
RQ092855
RQ092855
RQ092855
RQ092855
RQ092855
RQ092855
RQ092855
RQ092855
RQ092855
RQ092855
RQ092855
RQ092855
RQ092855
RQ092855
RQ092855
RQ092856
RQ092856
RQ092856
RQ092856
RQ092856
RQ092856
RQ092856
RQ092856
RQ092856
RQ092856
RQ092856
RQ092856
RQ092856
RQ092856
RQ092856
RQ092856
RQ092856
RQ092856
Prep.
no.
Rep.
No.
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
Count
No.
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
Vol. (mL)
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
150
1
150
1
150
2
150
2
150
2
150
3
150
3
150
3
150
1
150
1
150
1
150
2
150
2
150
2
150
3
150
3
150
3
150
1
150
1
150
1
150
2
150
2
150
2
150
3
150
3
150
3
150
1
150
1
150
1
150
2
150
2
150
2
150
3
150
3
150
3
150
Mass
(mg)
41.6
30.1
34.9
41.6
30.1
34.9
41.6
30.1
34.9
98.2
81.7
90.6
98.2
81.7
90.6
98.2
81.7
90.6
110.0
118.9
119.6
110.0
118.9
119.6
110.0
118.9
119.6
76.7
90.0
82.6
76.7
90.0
82.6
76.7
90.0
82.6
96.9
117.5
110.7
96.9
117.5
110.7
96.9
117.5
110.7
T1
(d)
34.46
34.46
34.46
34.46
34.46
34.46
34.46
34.46
34.46
3.67
3.67
3.67
3.67
3.67
3.67
3.67
3.67
3.67
34.35
34.35
34.35
34.35
34.35
34.35
34.35
34.35
34.35
3.65
3.65
3.65
3.65
3.65
3.65
3.65
3.65
3.65
34.33
34.33
34.33
34.33
34.33
34.33
34.33
34.33
34.33
©2010 Water Research Foundation. ALL RIGHTS RESERVED
T2
(d)
0.04
0.04
0.04
3.91
3.91
3.91
39.84
39.84
39.84
0.91
0.93
0.93
4.50
4.50
4.50
42.94
42.94
42.94
0.04
0.04
0.04
3.98
3.98
3.98
39.96
39.96
39.96
0.93
0.94
1.89
4.50
4.50
4.50
42.94
42.94
42.94
0.04
0.04
0.04
3.98
3.98
3.98
39.96
40.16
40.16
GAA
GAA error
(pCi/L)
(pCi/L)
4.62
2.39
2.85
1.54
3.13
1.96
7.03
3.77
2.06
2.05
2.57
2.61
5.02
3.21
4.80
2.50
4.74
2.69
89.15
5.34
75.09
4.52
76.29
4.89
85.23
5.46
70.38
4.62
67.95
4.57
70.32
5.05
57.30
4.34
54.72
4.14
102.90
6.36
120.06
7.41
97.57
6.08
103.13
6.39
117.02
7.33
102.43
6.20
95.80
7.19
99.00
7.53
98.48
7.83
51.27
3.87
68.58
4.72
54.66
4.10
45.98
3.53
64.68
4.54
50.00
3.98
40.72
3.40
57.30
4.22
45.26
3.91
90.06
5.36
97.06
6.23
98.14
6.10
84.14
5.21
87.71
5.95
87.71
5.86
78.63
6.38
85.58
7.45
91.18
7.59
Appendix M: Gross Alpha-Particle Activity Data | 259
Table M.1 (Continued)
Gross alpha-particle activity data for sample
Sample no.
RR093078
RR093078
RR093078
RR093078
RR093078
RR093078
RR093078
RR093078
RR093078
RR093078
RR093078
RR093078
RR093078
RR093078
RR093078
RR093078
RR093078
RR093078
RR093079
RR093079
RR093079
RR093079
RR093079
RR093079
RR093079
RR093079
RR093079
RR093079
RR093079
RR093079
RR093079
RR093079
RR093079
RR093079
RR093079
RR093079
RR093080
RR093080
RR093080
RR093080
RR093080
RR093080
RR093080
RR093080
RR093080
Prep.
no.
Rep.
No.
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
Count
No.
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
Vol. (mL)
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
Mass
(mg)
47.0
47.5
47.4
47.0
47.5
47.4
47.0
47.5
47.4
46.5
45.2
47.8
46.5
45.2
47.8
46.5
45.2
47.8
45.2
45.5
45.3
45.2
45.5
45.3
45.2
45.5
45.3
46.0
45.7
45.9
46.0
45.7
45.9
46.0
45.7
45.9
32.4
32.1
30.6
32.4
32.1
30.6
32.4
32.1
30.6
T1
(d)
3.07
3.07
3.07
3.07
3.07
3.07
3.07
3.07
3.07
46.12
46.12
46.12
46.12
46.12
46.12
46.12
46.12
46.12
3.10
3.10
3.10
3.10
3.10
3.10
3.10
3.10
3.10
46.15
46.15
46.15
46.15
46.15
46.15
46.15
46.15
46.15
3.19
3.19
3.19
3.19
3.19
3.19
3.19
3.19
3.19
©2010 Water Research Foundation. ALL RIGHTS RESERVED
T2
(d)
0.36
0.36
0.36
5.48
5.48
5.48
170.10
170.13
170.13
4.12
4.12
4.12
5.96
6.01
6.05
41.20
41.20
41.20
0.48
0.48
0.48
5.48
5.48
5.48
170.13
170.13
170.13
4.12
4.12
4.15
6.05
6.05
6.05
41.21
41.21
41.21
0.12
0.12
0.12
5.95
5.95
5.95
170.01
170.01
170.01
GAA
GAA error
(pCi/L)
(pCi/L)
36.74
5.29
42.57
5.58
40.69
5.68
33.74
3.89
34.91
3.97
38.76
4.10
37.63
4.14
39.97
4.28
36.75
4.16
39.27
5.02
33.08
4.34
36.71
4.66
34.25
4.57
38.46
5.03
37.10
4.84
33.80
3.77
28.57
3.54
37.88
4.14
18.61
3.69
20.54
3.67
20.36
3.84
28.70
3.59
34.30
3.63
35.44
3.68
44.10
4.29
48.44
4.31
50.36
4.36
30.51
4.24
28.70
4.23
30.77
4.38
33.89
4.66
33.47
4.64
31.62
4.30
44.92
4.34
49.58
4.58
40.65
3.93
15.06
3.86
16.50
4.01
9.27
3.40
11.12
3.44
8.49
3.08
8.78
3.16
10.95
3.08
11.79
3.18
11.23
2.93
260 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
Table M.1 (Continued)
Gross alpha-particle activity data for sample
Sample no.
RR093080
RR093080
RR093080
RR093080
RR093080
RR093080
RR093080
RR093080
RR093080
RR093081
RR093081
RR093081
RR093081
RR093081
RR093081
RR093081
RR093081
RR093081
RR093081
RR093081
RR093081
RR093081
RR093081
RR093081
RR093081
RR093081
RR093081
RR093082
RR093082
RR093082
RR093082
RR093082
RR093082
RR093082
RR093082
RR093082
RR093082
RR093082
RR093082
RR093082
RR093082
RR093082
RR093082
RR093082
RR093082
Prep.
no.
Rep.
No.
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
Count
No.
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
Vol. (mL)
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
110
1
110
1
110
2
110
2
110
2
110
3
110
3
110
3
110
1
110
1
110
1
110
2
110
2
110
2
110
3
110
3
110
3
110
Mass
(mg)
34.4
39.4
34.4
34.4
39.4
34.4
34.4
39.4
34.4
34.0
35.1
34.2
34.0
35.1
34.2
34.0
35.1
34.2
35.7
37.0
36.1
35.7
37.0
36.1
35.7
37.0
36.1
91.5
91.8
91.9
91.5
91.8
91.9
91.5
91.8
91.9
92.7
88.8
89.8
92.7
88.8
89.8
92.7
88.8
89.8
T1
(d)
46.24
46.24
46.24
46.24
46.24
46.24
46.24
46.24
46.24
3.22
3.22
3.22
3.22
3.22
3.22
3.22
3.22
3.22
46.27
46.27
46.27
46.27
46.27
46.27
46.27
46.27
46.27
3.13
3.13
3.13
3.13
3.13
3.13
3.13
3.13
3.13
46.18
46.18
46.18
46.18
46.18
46.18
46.18
46.18
46.18
©2010 Water Research Foundation. ALL RIGHTS RESERVED
T2
(d)
4.15
4.15
4.84
5.86
5.95
5.95
41.22
41.22
41.22
0.18
0.18
0.18
5.94
5.94
5.94
170.00
170.00
170.09
4.83
4.83
4.83
5.94
5.94
5.94
41.85
41.85
41.85
1.42
1.42
1.42
5.94
5.94
5.94
170.39
170.39
170.39
3.29
3.29
3.29
6.26
6.27
6.27
41.96
41.96
42.18
GAA
GAA error
(pCi/L)
(pCi/L)
7.90
2.37
7.89
2.51
7.32
2.32
6.31
2.54
7.75
2.53
6.42
2.34
8.41
1.85
9.76
2.03
8.84
2.02
159.01
10.77
164.95
11.30
160.92
11.32
87.02
8.19
93.12
8.75
91.57
8.57
90.28
7.26
88.99
7.36
132.10
8.78
52.71
5.84
42.85
5.57
53.46
6.07
59.05
6.32
56.45
6.26
50.73
5.65
79.81
7.52
77.37
7.60
79.47
7.58
59.65
3.71
63.18
3.72
59.12
3.68
52.27
3.85
54.91
3.86
45.47
3.96
84.95
4.46
60.10
3.75
55.78
3.55
32.49
4.23
26.82
3.75
32.69
4.17
38.40
4.63
35.43
4.73
39.19
4.30
49.57
4.16
48.23
4.18
43.69
3.78
Appendix M: Gross Alpha-Particle Activity Data | 261
Table M.1 (Continued)
Gross alpha-particle activity data for sample
Sample no.
RR093083
RR093083
RR093083
RR093083
RR093083
RR093083
RR093083
RR093083
RR093083
RR093083
RR093083
RR093083
RR093083
RR093083
RR093083
RR093083
RR093083
RR093083
RR093084
RR093084
RR093084
RR093084
RR093084
RR093084
RR093084
RR093084
RR093084
RR093084
RR093084
RR093084
RR093084
RR093084
RR093084
RR093084
RR093084
RR093084
RR093085
RR093085
RR093085
RR093085
RR093085
RR093085
RR093085
RR093085
RR093085
Prep.
no.
Rep.
No.
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
Count
No.
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
Vol. (mL)
1
110
1
110
1
110
2
110
2
110
2
110
3
110
3
110
3
110
1
110
1
110
1
110
2
110
2
110
2
110
3
110
3
110
3
110
1
100
1
100
1
100
2
100
2
100
2
100
3
100
3
100
3
100
1
100
1
100
1
100
2
100
2
100
2
100
3
100
3
100
3
100
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
Mass
(mg)
82.2
82.2
84.7
82.2
82.2
84.7
82.2
82.2
84.7
84.1
84.1
85.5
84.1
84.1
85.5
84.1
84.1
85.5
93.2
94.5
96.1
93.2
94.5
96.1
93.2
94.5
96.1
95.9
95.7
96.2
95.9
95.7
96.2
95.9
95.7
96.2
52.6
53.8
52.8
52.6
53.8
52.8
52.6
53.8
52.8
T1
(d)
3.12
3.12
3.12
3.12
3.12
3.12
3.12
3.12
3.12
46.17
46.17
46.17
46.17
46.17
46.17
46.17
46.17
46.17
3.08
3.08
3.08
3.08
3.08
3.08
3.08
3.08
3.08
46.13
46.13
46.13
46.13
46.13
46.13
46.13
46.13
46.13
3.18
3.18
3.18
3.18
3.18
3.18
3.18
3.18
3.18
©2010 Water Research Foundation. ALL RIGHTS RESERVED
T2
(d)
1.41
1.41
1.41
6.03
6.03
6.03
170.38
170.38
170.38
3.35
3.35
3.35
6.26
6.26
6.26
43.21
43.21
43.21
1.42
1.42
1.42
6.03
6.03
6.03
170.38
170.38
170.38
3.28
3.28
3.28
6.26
6.82
6.82
44.01
44.01
44.01
0.34
0.34
0.34
5.47
5.47
5.47
170.08
170.08
170.08
GAA
GAA error
(pCi/L)
(pCi/L)
56.43
3.43
62.91
3.77
63.58
3.70
53.34
4.00
61.46
4.27
54.91
4.14
58.70
3.61
72.46
4.00
60.21
3.61
31.53
4.07
28.95
3.88
36.20
4.39
41.46
4.33
38.50
4.00
40.25
4.09
51.21
4.46
55.65
4.64
52.97
4.84
71.44
4.43
66.44
4.00
76.94
4.35
58.96
5.19
52.74
4.62
62.15
5.16
57.53
4.09
56.20
4.17
67.98
4.43
25.60
3.96
31.15
4.15
28.90
4.53
36.40
4.44
40.87
4.97
42.37
5.40
51.47
5.64
52.90
5.85
47.35
5.29
16.68
2.89
22.49
3.28
15.38
2.85
17.66
2.96
21.11
3.21
17.13
2.98
20.26
3.47
20.64
3.39
21.28
3.45
262 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
Table M.1 (Continued)
Gross alpha-particle activity data for sample
Sample no.
RR093085
RR093085
RR093085
RR093085
RR093085
RR093085
RR093085
RR093085
RR093085
RR093373
RR093373
RR093373
RR093373
RR093373
RR093373
RR093373
RR093373
RR093373
RR093373
RR093373
RR093373
RR093373
RR093373
RR093373
RR093373
RR093373
RR093373
RR093374
RR093374
RR093374
RR093374
RR093374
RR093374
RR093374
RR093374
RR093374
RR093374
RR093374
RR093374
RR093374
RR093374
RR093374
RR093374
RR093374
RR093374
Prep.
no.
Rep.
No.
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
Count
No.
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
Vol. (mL)
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
150
1
150
1
150
2
150
2
150
2
150
3
150
3
150
3
150
1
150
1
150
1
150
2
150
2
150
2
150
3
150
3
150
3
150
Mass
(mg)
56.2
54.6
55.6
56.2
54.6
55.6
56.2
54.6
55.6
36.5
36.0
35.7
36.5
36.0
35.7
36.5
36.0
35.7
36.0
33.7
35.1
36.0
33.7
35.1
36.0
33.7
35.1
83.8
83.8
87.6
83.8
83.8
87.6
83.8
83.8
87.6
85.1
83.3
88.3
85.1
83.3
88.3
85.1
83.3
88.3
T1
(d)
46.23
46.23
46.23
46.23
46.23
46.23
46.23
46.23
46.23
3.24
3.24
3.24
3.24
3.24
3.24
3.24
3.24
3.24
37.16
37.16
37.16
37.16
37.16
37.16
37.16
37.16
37.16
3.25
3.25
3.25
3.25
3.25
3.25
3.25
3.25
3.25
37.17
37.17
37.17
37.17
37.17
37.17
37.17
37.17
37.17
©2010 Water Research Foundation. ALL RIGHTS RESERVED
T2
(d)
4.10
4.10
4.10
6.04
6.04
6.09
44.01
44.02
44.01
1.08
1.08
1.08
5.87
5.87
5.87
42.02
42.02
42.02
0.18
0.18
0.17
4.38
4.38
4.38
31.20
31.20
31.20
1.79
1.79
1.79
5.90
5.90
5.90
43.34
43.34
43.34
0.89
0.89
0.89
5.02
5.02
5.02
31.20
31.20
31.20
GAA
GAA error
(pCi/L)
(pCi/L)
13.82
3.20
11.62
2.73
16.18
3.05
13.58
2.88
14.13
2.88
15.80
3.21
19.96
3.41
20.67
1.91
22.04
3.30
28.44
4.02
25.44
3.78
27.95
3.91
25.72
4.35
24.63
4.26
27.91
4.26
25.58
4.40
25.33
4.40
27.09
4.50
37.55
5.05
67.14
6.36
53.33
5.81
35.86
3.46
68.31
4.68
55.24
4.19
37.88
4.37
64.31
5.59
51.62
5.00
31.64
3.27
32.04
3.22
34.17
3.52
27.45
3.38
32.42
3.27
29.90
3.44
27.60
3.25
28.97
3.23
26.78
3.04
45.35
3.77
55.36
4.27
51.30
3.96
37.84
3.56
52.59
4.19
46.31
3.83
41.03
3.55
50.40
3.98
50.78
4.18
Appendix M: Gross Alpha-Particle Activity Data | 263
Table M.1 (Continued)
Gross alpha-particle activity data for sample
Sample no.
RR093375
RR093375
RR093375
RR093375
RR093375
RR093375
RR093375
RR093375
RR093375
RR093375
RR093375
RR093375
RR093375
RR093375
RR093375
RR093375
RR093375
RR093375
RR093376
RR093376
RR093376
RR093376
RR093376
RR093376
RR093376
RR093376
RR093376
RR093376
RR093376
RR093376
RR093376
RR093376
RR093376
RR093376
RR093376
RR093376
RR093377
RR093377
RR093377
RR093377
RR093377
RR093377
RR093377
RR093377
RR093377
Prep.
no.
Rep.
No.
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
Count
No.
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
Vol. (mL)
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
160
1
160
1
160
2
160
2
160
2
160
3
160
3
160
3
160
1
160
1
160
1
160
2
160
2
160
2
160
3
160
3
160
3
160
1
90
1
90
1
90
2
90
2
90
2
90
3
90
3
90
3
90
Mass
(mg)
45.9
45.6
48.1
45.9
45.6
48.1
45.9
45.6
48.1
50.3
46.5
43.4
50.3
46.5
43.4
50.3
46.5
43.4
105.6
104.3
106.6
105.6
104.3
106.6
105.6
104.3
106.6
105.4
114.1
113.1
105.4
114.1
113.1
105.4
114.1
113.1
111.2
113.4
113.7
111.2
113.4
113.7
111.2
113.4
113.7
T1
(d)
3.20
3.20
3.20
3.20
3.20
3.20
3.20
3.20
3.20
37.12
37.12
37.12
37.12
37.12
37.12
37.12
37.12
37.12
3.24
3.24
3.24
3.24
3.24
3.24
3.24
3.24
3.24
37.16
37.16
37.16
37.16
37.16
37.16
37.16
37.16
37.16
3.17
3.17
3.17
3.17
3.17
3.17
3.17
3.17
3.17
©2010 Water Research Foundation. ALL RIGHTS RESERVED
T2
(d)
1.79
1.79
1.79
5.87
5.87
5.87
42.02
42.02
42.02
0.18
0.18
0.18
4.38
4.38
4.38
31.20
31.20
31.20
1.79
1.79
1.79
5.89
5.92
6.00
43.34
43.34
43.34
0.89
0.89
0.89
5.02
5.02
5.02
31.37
31.37
31.37
1.89
1.93
1.93
5.97
5.97
5.97
43.34
43.34
44.16
GAA
GAA error
(pCi/L)
(pCi/L)
18.39
3.61
22.38
3.87
16.82
3.59
22.22
3.67
27.14
4.02
26.18
4.16
31.66
4.53
34.59
4.79
32.12
4.41
18.06
3.32
18.18
3.44
22.08
3.47
36.00
4.09
29.70
3.66
28.68
3.28
41.55
4.80
42.05
4.72
40.22
4.29
33.97
3.39
41.58
3.65
44.37
3.84
38.46
3.81
49.24
4.23
48.98
3.96
39.81
3.97
44.75
3.80
46.09
4.06
54.32
4.45
73.76
5.34
78.41
5.26
40.85
4.14
63.17
4.95
69.44
5.17
50.06
4.34
65.40
4.99
73.50
5.08
126.39
8.96
128.66
9.17
130.03
9.09
161.39
9.89
165.23
10.26
102.94
7.71
152.07
9.45
155.88
9.85
105.86
8.57
264 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
Table M.1 (Continued)
Gross alpha-particle activity data for sample
Sample no.
RR093377
RR093377
RR093377
RR093377
RR093377
RR093377
RR093377
RR093377
RR093377
RR093378
RR093378
RR093378
RR093378
RR093378
RR093378
RR093378
RR093378
RR093378
RR093378
RR093378
RR093378
RR093378
RR093378
RR093378
RR093378
RR093378
RR093378
RR093660
RR093660
RR093660
RR093660
RR093660
RR093660
RR093660
RR093660
RR093660
RR093660
RR093660
RR093660
RR093660
RR093660
RR093660
RR093660
RR093660
RR093660
Prep.
no.
Rep.
No.
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
Count
No.
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
Vol. (mL)
1
90
1
90
1
90
2
90
2
90
2
90
3
90
3
90
3
90
1
50
1
50
1
50
2
50
2
50
2
50
3
50
3
50
3
50
1
50
1
50
1
50
2
50
2
50
2
50
3
50
3
50
3
50
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
100
1
100
1
100
2
100
2
100
2
100
3
100
3
100
3
100
Mass
(mg)
116.4
114.7
119.3
116.4
114.7
119.3
116.4
114.7
119.3
85.1
87.4
88.6
85.1
87.4
88.6
85.1
87.4
88.6
86.8
87.1
92.4
86.8
87.1
92.4
86.8
87.1
92.4
51.9
54.5
49.8
51.9
54.5
49.8
51.9
54.5
49.8
22.3
22.6
23.2
22.3
22.6
23.2
22.3
22.6
23.2
T1
(d)
37.09
37.09
37.09
37.09
37.09
37.09
37.09
37.09
37.09
3.24
3.24
3.24
3.24
3.24
3.24
3.24
3.24
3.24
37.16
37.16
37.16
37.16
37.16
37.16
37.16
37.16
37.16
5.31
5.31
5.31
5.31
5.31
5.31
5.31
5.31
5.31
143.13
143.13
143.13
143.13
143.13
143.13
143.13
143.13
143.13
©2010 Water Research Foundation. ALL RIGHTS RESERVED
T2
(d)
0.89
0.89
0.89
5.02
5.02
5.02
31.37
31.37
32.18
1.93
2.96
2.96
6.00
6.77
6.77
44.16
44.16
44.16
0.89
2.39
2.39
5.02
5.12
6.38
32.18
32.18
32.18
0.88
0.88
0.88
4.04
4.04
4.04
31.77
31.77
31.77
0.97
0.97
0.97
5.20
5.20
5.20
104.16
104.16
104.16
GAA
GAA error
(pCi/L)
(pCi/L)
108.88
7.96
75.93
6.82
58.94
6.77
165.96
10.64
118.62
8.23
103.04
7.96
201.10
11.00
158.45
9.68
146.36
9.92
54.57
8.09
51.87
8.39
63.22
9.60
42.03
6.91
47.78
8.04
44.76
8.69
45.56
8.70
42.61
7.93
36.40
8.12
47.90
8.18
29.05
7.34
68.95
10.23
62.75
8.25
27.42
7.24
79.04
9.98
90.51
10.81
48.94
8.32
99.84
10.36
60.84
5.08
71.65
5.85
51.90
4.68
61.48
5.11
68.96
5.74
53.95
4.76
66.79
5.49
63.92
5.62
57.65
5.09
53.10
4.59
54.72
4.56
54.84
4.61
57.34
4.16
64.19
4.47
61.69
4.33
56.63
4.51
62.45
4.82
59.29
4.69
Appendix M: Gross Alpha-Particle Activity Data | 265
Table M.1 (Continued)
Gross alpha-particle activity data for sample
Sample no.
RR093661
RR093661
RR093661
RR093661
RR093661
RR093661
RR093661
RR093661
RR093661
RR093661
RR093661
RR093661
RR093661
RR093661
RR093661
RR093661
RR093661
RR093661
RR093662
RR093662
RR093662
RR093662
RR093662
RR093662
RR093662
RR093662
RR093662
RR093662
RR093662
RR093662
RR093662
RR093662
RR093662
RR093662
RR093662
RR093662
RR093663
RR093663
RR093663
RR093663
RR093663
RR093663
RR093663
RR093663
RR093663
Prep.
no.
Rep.
No.
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
Count
No.
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
Vol. (mL)
1
50
1
50
1
50
2
50
2
50
2
50
3
50
3
50
3
50
1
50
1
50
1
50
2
50
2
50
2
50
3
50
3
50
3
50
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
1
100
1
100
1
100
2
100
2
100
2
100
3
100
3
100
3
100
1
200
1
200
1
200
2
200
2
200
2
200
3
200
3
200
3
200
Mass
(mg)
16.4
17.9
16.1
16.4
17.9
16.1
16.4
17.9
16.1
15.8
16.8
16.5
15.8
16.8
16.5
15.8
16.8
16.5
63.9
64.3
62.7
63.9
64.3
62.7
63.9
64.3
62.7
30.3
31.2
30.6
30.3
31.2
30.6
30.3
31.2
30.6
89.2
92.8
88.7
89.2
92.8
88.7
89.2
92.8
88.7
T1
(d)
5.42
5.42
5.42
5.42
5.42
5.42
5.42
5.42
5.42
143.23
143.23
143.23
143.23
143.23
143.23
143.23
143.23
143.23
5.13
5.13
5.13
5.13
5.13
5.13
5.13
5.13
5.13
142.94
142.94
142.94
142.94
142.94
142.94
142.94
142.94
142.94
5.18
5.18
5.18
5.18
5.18
5.18
5.18
5.18
5.18
©2010 Water Research Foundation. ALL RIGHTS RESERVED
T2
(d)
0.88
0.88
0.88
3.22
3.22
3.22
33.06
33.06
33.06
0.11
0.11
0.11
5.20
5.20
5.20
104.46
104.46
104.46
0.88
0.88
0.88
4.04
4.04
4.04
31.77
31.77
31.77
0.97
0.98
0.98
5.21
5.21
5.21
104.97
104.97
104.97
0.03
0.03
0.03
4.04
4.04
4.04
31.77
33.06
33.06
GAA
GAA error
(pCi/L)
(pCi/L)
0.44
2.13
4.14
2.11
4.26
1.91
4.11
1.95
-1.07
2.08
3.41
1.98
12.18
2.64
4.25
2.12
6.41
2.15
-0.95
1.76
-1.29
1.84
0.31
1.76
4.40
1.87
1.46
1.65
1.00
1.63
1.06
1.56
-0.12
1.65
2.85
1.80
31.20
3.77
33.12
3.62
35.06
3.67
52.31
4.74
52.62
4.77
51.29
4.60
67.08
5.28
68.54
5.14
73.25
5.17
25.72
3.36
22.71
3.21
26.81
3.33
46.27
3.94
47.76
3.88
48.68
3.83
60.12
4.48
62.26
4.79
64.94
4.88
30.55
3.36
34.25
3.78
27.80
3.16
32.33
3.59
31.82
3.35
30.65
3.25
33.22
3.64
36.48
3.82
30.66
3.33
266 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
Table M.1 (Continued)
Gross alpha-particle activity data for sample
Sample no.
RR093663
RR093663
RR093663
RR093663
RR093663
RR093663
RR093663
RR093663
RR093663
RR093664
RR093664
RR093664
RR093664
RR093664
RR093664
RR093664
RR093664
RR093664
RR093664
RR093664
RR093664
RR093664
RR093664
RR093664
RR093664
RR093664
RR093664
RS095390
RS095390
RS095390
RS095390
RS095390
RS095390
RS095390
RS095390
RS095390
RS095390
RS095390
RS095390
RS095390
RS095390
RS095390
RS095390
RS095390
RS095390
Prep.
no.
Rep.
No.
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
Count
No.
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
Vol. (mL)
1
100
1
100
1
100
2
100
2
100
2
100
3
100
3
100
3
100
1
80
1
80
1
80
2
80
2
80
2
80
3
80
3
80
3
80
1
80
1
80
1
80
2
80
2
80
2
80
3
80
3
80
3
80
1
180
1
180
1
180
2
180
2
180
2
180
3
180
3
180
3
180
1
150
1
150
1
150
2
150
2
150
2
150
3
150
3
150
3
150
Mass
(mg)
43.3
43.8
44.7
43.3
43.8
44.7
43.3
43.8
44.7
96.8
86.0
95.1
96.8
86.0
95.1
96.8
86.0
95.1
73.8
72.0
74.1
73.8
72.0
74.1
73.8
72.0
74.1
48.3
48.3
50.0
48.3
48.3
50.0
48.3
48.3
50.0
41.0
47.1
42.3
41.0
47.1
42.3
41.0
47.1
42.3
T1
(d)
143.00
143.00
143.00
143.00
143.00
143.00
143.00
143.00
143.00
5.29
5.29
5.29
5.29
5.29
5.29
5.29
5.29
5.29
143.11
143.11
143.11
143.11
143.11
143.11
143.11
143.11
143.11
3.06
3.06
3.06
3.06
3.06
3.06
3.06
3.06
3.06
76.00
76.00
76.00
76.00
76.00
76.00
76.00
76.00
76.00
©2010 Water Research Foundation. ALL RIGHTS RESERVED
T2
(d)
0.10
0.10
0.10
4.32
4.32
4.32
104.96
104.96
104.96
0.03
0.03
0.03
3.23
3.23
3.23
33.06
33.06
33.06
0.10
0.10
0.10
4.32
4.32
4.32
104.96
104.96
105.03
0.03
0.03
0.03
3.06
3.06
3.06
33.10
33.10
33.10
0.02
0.02
0.02
3.99
3.99
3.99
35.49
35.49
35.49
GAA
GAA error
(pCi/L)
(pCi/L)
19.41
2.76
16.11
2.50
16.53
2.59
24.09
2.80
24.16
2.87
25.50
2.93
37.38
3.54
37.48
3.50
35.25
3.50
29.46
5.53
24.49
4.46
25.61
5.09
39.47
5.98
30.96
4.73
29.36
5.42
53.06
6.29
51.72
5.89
42.71
6.26
14.50
3.63
12.54
3.43
13.06
3.35
29.44
4.44
26.00
4.10
31.38
4.38
35.15
2.76
29.10
2.32
36.51
2.69
29.19
3.61
24.70
3.51
26.83
3.50
27.84
3.55
24.34
3.47
23.60
3.32
26.45
3.48
26.85
3.57
27.34
3.49
8.33
2.41
6.86
2.38
8.47
2.40
17.68
2.92
16.45
3.01
16.54
2.98
25.85
2.97
24.97
3.19
26.37
2.97
Appendix M: Gross Alpha-Particle Activity Data | 267
Table M.1 (Continued)
Gross alpha-particle activity data for sample
Sample no.
RS095391
RS095391
RS095391
RS095391
RS095391
RS095391
RS095391
RS095391
RS095391
RS095391
RS095391
RS095391
RS095391
RS095391
RS095391
RS095391
RS095391
RS095391
RS095392
RS095392
RS095392
RS095392
RS095392
RS095392
RS095392
RS095392
RS095392
RS095392
RS095392
RS095392
RS095392
RS095392
RS095392
RS095392
RS095392
RS095392
RS095393
RS095393
RS095393
RS095393
RS095393
RS095393
RS095393
RS095393
RS095393
Prep.
no.
Rep.
No.
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
Count
No.
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
Vol. (mL)
1
180
1
180
1
180
2
180
2
180
2
180
3
180
3
180
3
180
1
150
1
150
1
150
2
150
2
150
2
150
3
150
3
150
3
150
1
180
1
180
1
180
2
180
2
180
2
180
3
180
3
180
3
180
1
150
1
150
1
150
2
150
2
150
2
150
3
150
3
150
3
150
1
180
1
180
1
180
2
180
2
180
2
180
3
180
3
180
3
180
Mass
(mg)
72.8
74.3
74.2
72.8
74.3
74.2
72.8
74.3
74.2
60.4
63.3
60.0
60.4
63.3
60.0
60.4
63.3
60.0
55.3
53.2
55.5
55.3
53.2
55.5
55.3
53.2
55.5
45.5
46.4
46.0
45.5
46.4
46.0
45.5
46.4
46.0
36.5
35.3
32.3
36.5
35.3
32.3
36.5
35.3
32.3
T1
(d)
3.06
3.06
3.06
3.06
3.06
3.06
3.06
3.06
3.06
76.00
76.00
76.00
76.00
76.00
76.00
76.00
76.00
76.00
3.08
3.08
3.08
3.08
3.08
3.08
3.08
3.08
3.08
76.03
76.03
76.03
76.03
76.03
76.03
76.03
76.03
76.03
3.50
3.50
3.50
3.50
3.50
3.50
3.50
3.50
3.50
©2010 Water Research Foundation. ALL RIGHTS RESERVED
T2
(d)
0.03
0.03
0.03
3.06
3.06
3.06
33.10
33.10
33.10
0.39
0.39
0.39
4.07
4.07
4.07
39.27
39.27
39.27
0.03
0.03
0.03
3.06
3.06
3.06
33.10
33.10
33.10
0.40
0.40
0.44
3.99
3.99
3.99
37.43
37.43
37.43
0.03
0.03
0.03
3.00
3.00
3.00
33.50
33.50
33.50
GAA
GAA error
(pCi/L)
(pCi/L)
52.36
4.11
54.75
4.23
51.07
4.09
52.68
4.11
53.64
4.22
48.29
4.03
63.46
4.41
58.77
4.33
54.16
4.19
23.33
3.05
21.06
2.90
21.25
2.85
35.31
3.41
41.23
3.81
34.36
3.27
57.40
4.19
62.16
4.46
57.48
4.05
39.95
4.15
36.31
3.90
42.01
4.02
41.00
4.25
40.68
4.06
41.21
4.09
49.55
4.64
45.04
4.16
43.60
4.22
15.59
2.84
16.15
3.07
18.98
3.16
27.12
3.52
25.94
3.42
31.19
3.81
40.68
4.14
41.02
4.25
52.25
4.58
5.50
2.07
6.42
2.16
3.02
1.61
4.88
2.02
4.76
2.00
4.37
1.72
3.90
2.10
6.21
2.28
6.25
2.02
268 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
Table M.1 (Continued)
Gross alpha-particle activity data for sample
Sample no.
RS095393
RS095393
RS095393
RS095393
RS095393
RS095393
RS095393
RS095393
RS095393
RS095394
RS095394
RS095394
RS095394
RS095394
RS095394
RS095394
RS095394
RS095394
RS095394
RS095394
RS095394
RS095394
RS095394
RS095394
RS095394
RS095394
RS095394
RS095395
RS095395
RS095395
RS095395
RS095395
RS095395
RS095395
RS095395
RS095395
RS095395
RS095395
RS095395
RS095395
RS095395
RS095395
RS095395
RS095395
RS095395
Prep.
no.
Rep.
No.
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
Count
No.
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
Vol. (mL)
1
150
1
150
1
150
2
150
2
150
2
150
3
150
3
150
3
150
1
180
1
180
1
180
2
180
2
180
2
180
3
180
3
180
3
180
1
150
1
150
1
150
2
150
2
150
2
150
3
150
3
150
3
150
1
150
1
150
1
150
2
150
2
150
2
150
3
150
3
150
3
150
1
150
1
150
1
150
2
150
2
150
2
150
3
150
3
150
3
150
Mass
(mg)
29.1
27.8
26.7
29.1
27.8
26.7
29.1
27.8
26.7
77.2
73.2
67.5
77.2
73.2
67.5
77.2
73.2
67.5
60.1
64.1
64.6
60.1
64.1
64.6
60.1
64.1
64.6
57.3
55.8
56.0
57.3
55.8
56.0
57.3
55.8
56.0
56.4
51.5
50.6
56.4
51.5
50.6
56.4
51.5
50.6
T1
(d)
77.12
77.12
77.12
77.12
77.12
77.12
77.12
77.12
77.12
2.49
2.49
2.49
2.49
2.49
2.49
2.49
2.49
2.49
76.11
76.11
76.11
76.11
76.11
76.11
76.11
76.11
76.11
3.91
3.91
3.91
3.91
3.91
3.91
3.91
3.91
3.91
77.53
77.53
77.53
77.53
77.53
77.53
77.53
77.53
77.53
©2010 Water Research Foundation. ALL RIGHTS RESERVED
T2
(d)
0.03
0.03
0.03
3.91
3.92
3.92
35.91
35.92
36.83
0.03
0.03
0.03
3.50
3.50
3.50
33.50
33.50
33.50
0.88
0.88
0.88
4.09
4.09
4.09
38.19
38.19
38.19
0.03
0.03
0.03
3.00
3.00
3.00
33.50
33.50
33.50
0.19
0.19
0.19
3.22
3.22
3.22
38.19
38.19
38.19
GAA
GAA error
(pCi/L)
(pCi/L)
2.23
2.16
0.33
1.89
1.20
1.88
2.12
2.14
2.78
2.15
1.76
1.76
5.21
2.28
6.21
2.20
4.36
2.12
95.42
5.20
87.60
4.89
83.65
4.65
87.93
5.02
90.26
5.00
87.48
4.90
73.68
4.71
79.46
4.87
71.61
4.53
68.55
4.44
64.71
4.49
69.01
4.70
70.00
4.48
69.60
4.75
63.91
4.39
61.91
4.26
59.01
4.39
58.82
4.45
29.67
3.44
26.12
3.27
21.30
3.07
39.51
3.79
37.25
3.74
37.36
3.68
47.72
4.25
48.52
4.25
46.31
3.99
27.08
3.54
22.14
3.16
23.30
3.15
40.93
4.10
35.09
3.63
37.92
3.85
65.06
4.75
58.58
4.39
63.55
4.29
Appendix M: Gross Alpha-Particle Activity Data | 269
Table M.1 (Continued)
Gross alpha-particle activity data for sample
Sample no.
RS095396
RS095396
RS095396
RS095396
RS095396
RS095396
RS095396
RS095396
RS095396
RS095396
RS095396
RS095396
RS095396
RS095396
RS095396
RS095396
RS095396
RS095396
RS095397
RS095397
RS095397
RS095397
RS095397
RS095397
RS095397
RS095397
RS095397
RS095397
RS095397
RS095397
RS095397
RS095397
RS095397
RS095397
RS095397
RS095397
RS095398
RS095398
RS095398
RS095398
RS095398
RS095398
RS095398
RS095398
RS095398
Prep.
no.
Rep.
No.
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
Count
No.
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
2
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
Vol. (mL)
1
180
1
180
1
180
2
180
2
180
2
180
3
180
3
180
3
180
1
150
1
150
1
150
2
150
2
150
2
150
3
150
3
150
3
150
1
100
1
100
1
100
2
100
2
100
2
100
3
100
3
100
3
100
1
100
1
100
1
100
2
100
2
100
2
100
3
100
3
100
3
100
1
150
1
150
1
150
2
150
2
150
2
150
3
150
3
150
3
150
Mass
(mg)
40.8
39.5
42.9
40.8
39.5
42.9
40.8
39.5
42.9
33.0
30.5
32.3
33.0
30.5
32.3
33.0
30.5
32.3
91.5
90.7
90.7
91.5
90.7
89.6
91.5
90.7
89.6
91.0
92.1
91.0
91.0
92.1
91.0
91.0
92.1
91.0
94.4
90.1
89.1
94.4
90.1
89.1
94.4
90.1
89.1
T1
(d)
2.42
2.42
2.42
2.42
2.42
2.42
2.42
2.42
2.42
76.04
76.04
76.04
76.04
76.04
76.04
76.04
76.04
76.04
4.26
4.26
4.26
4.26
4.26
4.26
4.26
4.26
4.26
76.46
76.46
76.46
76.46
76.46
76.46
76.46
76.46
76.46
4.05
4.05
4.05
4.05
4.05
4.05
4.05
4.05
4.05
©2010 Water Research Foundation. ALL RIGHTS RESERVED
T2
(d)
0.12
0.12
0.12
3.00
3.00
3.00
33.50
33.50
33.50
0.03
0.03
0.03
3.92
3.92
3.92
36.84
36.84
36.84
0.26
0.26
0.26
2.84
2.91
2.91
32.97
32.97
33.01
0.03
0.03
0.04
3.89
3.89
3.89
39.48
39.48
39.48
0.26
0.26
0.26
2.91
3.02
3.02
33.01
33.01
33.70
GAA
GAA error
(pCi/L)
(pCi/L)
76.18
5.63
77.23
5.68
82.27
6.03
69.42
5.18
77.38
5.42
74.89
5.51
70.69
5.28
69.89
5.21
76.74
5.56
67.94
5.74
67.47
5.57
71.56
5.86
68.29
5.75
65.91
5.49
62.40
5.52
76.96
5.64
67.88
5.06
70.81
5.32
32.39
4.00
27.66
3.83
27.66
3.83
32.84
4.87
24.84
4.60
22.59
4.43
29.25
4.47
29.49
4.74
29.86
4.65
25.55
2.99
28.89
3.12
27.94
3.05
22.83
2.48
24.82
2.50
27.57
2.54
26.77
2.49
24.44
2.32
27.12
2.50
22.80
2.70
20.65
2.62
24.53
2.71
19.08
3.23
20.11
3.15
19.84
3.09
20.03
3.20
22.49
2.96
23.76
3.22
270 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
Table M.1 (Continued)
Gross alpha-particle activity data for sample
Sample no.
RS095398
RS095398
RS095398
RS095398
RS095398
RS095398
RS095398
RS095398
RS095398
RS095399
RS095399
RS095399
RS095399
RS095399
RS095399
RS095399
RS095399
RS095399
RS095399
RS095399
RS095399
RS095399
RS095399
RS095399
RS095399
RS095399
RS095399
RS095400
RS095400
RS095400
RS095400
RS095400
RS095400
RS095400
RS095400
RS095400
RS095400
RS095400
RS095400
RS095400
RS095400
RS095400
RS095400
RS095400
RS095400
Prep.
no.
Rep.
No.
Count
No.
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
Vol. (mL)
1
150
1
150
1
150
2
150
2
150
2
150
3
150
3
150
3
150
1
130
1
130
1
130
2
130
2
130
2
130
3
130
3
130
3
130
1
100
1
100
1
100
2
100
2
100
2
100
3
100
3
100
3
100
1
130
1
130
1
130
2
130
2
130
2
130
3
130
3
130
3
130
1
100
1
100
1
100
2
100
2
100
2
100
3
100
3
100
2
3
3
100
Mass
(mg)
104.1
107.9
94.7
104.1
107.9
94.7
104.1
107.9
94.7
77.2
73.1
56.1
77.2
73.1
56.1
77.2
73.1
56.1
62.6
62.9
52.0
62.6
62.9
52.0
62.6
62.9
52.0
71.2
56.7
72.4
71.2
56.7
72.4
71.2
56.7
72.4
55.4
50.4
56.0
55.4
50.4
56.0
55.4
50.4
T1
(d)
76.25
76.25
76.25
76.25
76.25
76.25
76.25
76.25
76.25
5.67
5.67
5.67
5.67
5.67
5.67
5.67
5.67
5.67
72.35
72.35
72.35
72.35
72.35
72.35
72.35
72.35
72.35
5.70
5.70
5.70
5.70
5.70
5.70
5.70
5.70
5.70
72.38
72.38
72.38
72.38
72.38
72.38
72.38
72.38
56.0
72.38
©2010 Water Research Foundation. ALL RIGHTS RESERVED
T2
(d)
0.67
0.67
0.67
3.90
3.90
3.90
39.48
39.48
39.48
0.04
0.04
0.04
4.09
4.09
4.09
40.48
40.48
40.48
0.18
0.18
0.18
2.97
2.97
2.97
35.95
35.95
35.95
0.04
0.04
0.04
5.02
5.02
5.02
40.48
40.48
40.48
0.18
0.18
0.18
2.97
2.97
2.97
35.95
35.95
35.95
GAA
GAA error
(pCi/L)
(pCi/L)
16.84
2.66
14.95
2.44
13.84
2.45
19.42
2.65
15.46
2.78
19.11
2.53
26.49
3.06
20.42
2.74
22.83
2.59
56.09
4.32
56.09
4.32
35.38
2.99
60.92
4.60
64.75
4.42
40.61
3.18
61.15
4.44
59.65
4.37
45.25
3.22
53.62
3.59
52.16
3.64
41.43
2.85
51.64
3.62
55.74
3.54
40.70
2.97
58.23
4.17
62.57
4.32
53.13
3.55
107.54
5.35
98.17
4.76
118.07
5.89
107.87
5.56
90.99
4.44
115.59
5.57
97.49
5.08
86.70
4.43
104.70
5.54
84.11
4.52
84.95
4.39
88.99
4.78
84.03
4.68
79.79
4.19
88.84
4.62
85.62
4.54
93.90
4.61
99.06
5.01
APPENDIX N
GROSS RADIUM ACTIVITY DATA
Table N.1 gives the gross radium activities (GRA) for the 79 samples in the study. The
first column (Sample no.) gives the sample number. The second column (Prep. no.) indicates
whether the GAA is from the first or second preparation. Each sample was counted on the gas
proportional counter three times. The third column (Count no.) indicates whether it is the first,
second, or third count. The fourth column (Mass) gives the residue mass. The fifth column gives
the time, T1, between sample collection and preparation. The sixth column gives the time, T2, between sample preparation and analysis. The seventh column (GRA) gives the gross radium activity of the sample and the eighth column (GRA error) gives the counting error in the GRA.
Table N.1
Gross radium activity data for samples
Sample no.
RQ091434
RQ091434
RQ091434
RQ091434
RQ091434
RQ091434
RQ091435
RQ091435
RQ091435
RQ091435
RQ091435
RQ091435
RQ091436
RQ091436
RQ091436
RQ091436
RQ091436
RQ091436
RQ091437
RQ091437
RQ091437
RQ091437
RQ091437
RQ091437
RQ091438
RQ091438
RQ091438
RQ091438
RQ091438
RQ091438
Prep. No.
Count No.
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
Mass (mg)
19.5
19.5
19.5
17
17
17
16.7
16.7
16.7
15.3
15.3
15.3
20.8
20.8
20.8
19.8
19.8
19.8
23.3
23.3
23.3
22.9
22.9
22.9
23.1
23.1
23.1
23.4
23.4
23.4
T1 (d)
1.08
1.08
1.08
37
37
37
1.08
1.08
1.08
37
37
37
1.25
1.25
1.25
37.17
37.17
37.17
1.23
1.23
1.23
37.15
37.15
37.15
1.29
1.29
1.29
37.21
37.21
37.21
T2 (d)
0.22
3.01
7.84
0.35
6.86
39.05
0.22
3.01
7.84
0.35
6.86
39.05
0.22
3.01
7.84
0.35
6.86
39.05
0.22
3.01
7.84
0.35
6.86
39.05
0.22
3.01
7.84
0.35
6.86
39.05
271
©2010 Water Research Foundation. ALL RIGHTS RESERVED
GRA
(pCi/L)
68.29
34.17
21.09
12.94
15.11
15.97
25.96
12.1
9.72
5.24
4.77
4.84
21.88
2.51
1.93
1.56
1.42
1.46
22.75
11.06
7.49
5.94
5.4
5.97
45.41
18.72
7.28
4.25
3.65
4.72
GRA error
(pCi/L)
4.09
2.03
2.16
1.82
1.19
1.08
2.59
1.24
1.56
1.28
0.7
0.62
2.16
0.23
0.28
0.26
0.15
0.14
2.14
1.05
1.22
1.15
0.63
0.58
3.05
1.37
1.18
0.94
0.51
0.51
272 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
Table N.1 (Continued)
Gross radium activity data for samples
Sample no.
RQ091439
RQ091439
RQ091439
RQ091439
RQ091439
RQ091439
RQ091440
RQ091440
RQ091440
RQ091440
RQ091440
RQ091440
RQ091441
RQ091441
RQ091441
RQ091441
RQ091441
RQ091441
RQ091442
RQ091442
RQ091442
RQ091442
RQ091442
RQ091442
RQ091444
RQ091444
RQ091444
RQ091444
RQ091444
RQ091444
RQ091713
RQ091713
RQ091713
RQ091713
RQ091713
RQ091713
RQ091720
RQ091720
RQ091720
RQ091720
RQ091720
RQ091720
RQ091721
RQ091721
Prep. No.
Count No.
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
Mass (mg)
20
20
20
20.6
20.6
20.6
21.6
21.6
21.6
13.2
13.2
13.2
18.5
18.5
18.5
18.9
18.9
18.9
22.6
22.6
22.6
26.7
26.7
26.7
19
19
19
25.4
25.4
25.4
22.4
22.4
22.4
17
17
17
24.8
24.8
24.8
20.3
20.3
20.3
23.9
23.9
T1 (d)
1.15
1.15
1.15
37.07
37.07
37.07
1.19
1.19
1.19
37.11
37.11
37.11
1.27
1.27
1.27
37.19
37.19
37.19
1.32
1.32
1.32
37.24
37.24
37.24
1.2
1.2
1.2
37.12
37.12
37.12
2.24
2.24
2.24
37.24
37.24
37.24
2.23
2.23
2.23
37.22
37.22
37.22
2.08
2.08
T2 (d)
0.22
3.01
7.84
0.35
6.86
39.05
0.22
3.01
7.84
0.35
6.86
39.05
0.22
3.01
7.84
0.35
6.86
39.05
0.22
3.01
7.84
0.35
6.86
39.05
1.12
3.01
9.03
0.35
6.86
39.05
0.35
6.86
39.05
0.31
6.01
42.14
0.35
6.86
39.05
0.31
6.01
42.14
0.82
7.11
©2010 Water Research Foundation. ALL RIGHTS RESERVED
GRA
(pCi/L)
12.25
6.64
4.38
4.88
2.96
3.3
4.04
2.25
1.6
0.66
0.3
0.17
15.72
7.52
5.36
5.33
4.37
4.12
17.93
10.19
6.07
5.34
4.68
5.75
5.03
3.55
3.91
2.47
2.42
2.7
14.25
5.03
4.12
2.54
3.42
3.55
33.53
10.13
7.14
5.49
6
5.75
7.52
5.17
GRA error
(pCi/L)
1.69
0.87
1.01
1.1
0.5
0.46
0.96
0.5
0.6
0.73
0.28
0.21
1.92
0.94
1.12
1.13
0.6
0.52
1.93
1.01
1.12
1.02
0.56
0.54
1.26
0.74
1
0.76
0.41
0.38
1.65
0.6
0.48
1.04
0.61
0.52
2.47
0.83
0.62
1.14
0.7
0.59
1.11
0.6
Appendix N: Gross Radium Activity Data | 273
Table N.1 (Continued)
Gross radium activity data for samples
Sample no.
RQ091721
RQ091721
RQ091721
RQ091721
RQ091722
RQ091722
RQ091722
RQ091722
RQ091722
RQ091722
RQ091723
RQ091723
RQ091723
RQ091723
RQ091723
RQ091723
RQ091724
RQ091724
RQ091724
RQ091724
RQ091724
RQ091724
RQ091725
RQ091725
RQ091725
RQ091725
RQ091725
RQ091725
RQ091726
RQ091726
RQ091726
RQ091726
RQ091726
RQ091726
RQ091751
RQ091751
RQ091751
RQ091751
RQ091751
RQ091751
RQ091992
RQ091992
RQ091992
RQ091992
Prep. No.
Count No.
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
Mass (mg)
23.9
17.7
17.7
17.7
14.8
14.8
14.8
22.7
22.7
22.7
15.2
15.2
15.2
16.2
16.2
16.2
12.7
12.7
12.7
25.7
25.7
25.7
16.2
16.2
16.2
20.2
20.2
20.2
22.1
22.1
22.1
24.2
24.2
24.2
18.8
18.8
18.8
21.6
21.6
21.6
18.9
18.9
18.9
17.9
T1 (d)
2.08
37.07
37.07
37.07
2.14
2.14
2.14
37.13
37.13
37.13
2.01
2.01
2.01
37
37
37
2.02
2.02
2.02
37.02
37.02
37.02
2.08
2.08
2.08
37.07
37.07
37.07
2.08
2.08
2.08
37.07
37.07
37.07
1.08
1.08
1.08
36.07
36.07
36.07
2.09
2.09
2.09
37.14
T2 (d)
39.35
0.31
6.01
42.14
0.82
7.11
39.35
0.31
6.01
42.14
0.82
7.11
39.35
0.31
6.01
42.14
0.82
7.11
39.35
0.31
6.01
42.14
0.82
7.11
39.35
0.31
6.01
42.14
0.82
7.11
39.35
0.31
6.01
42.14
0.82
7.11
39.35
0.31
6.01
42.14
0.31
6.01
42.14
5.38
©2010 Water Research Foundation. ALL RIGHTS RESERVED
GRA
(pCi/L)
4.54
4.57
4.51
4.87
53.7
34.38
32.27
35.82
34.23
35.46
16.41
4.22
2.26
2.25
1.3
1.7
14.29
2.88
1.57
2.21
1.95
1.46
8.04
4.18
3.47
4.1
3.43
3.72
9.08
5.01
4.61
3.89
4.01
3.96
32.46
7.4
5.39
5.35
4.69
5.18
0.15
0.2
0.16
0.14
GRA error
(pCi/L)
0.5
1.13
0.65
0.58
3.54
1.93
1.69
2.67
1.74
1.59
1.9
0.66
0.44
0.92
0.41
0.38
2
0.65
0.46
0.76
0.4
0.29
1.32
0.63
0.51
0.97
0.53
0.47
1.24
0.61
0.52
0.89
0.53
0.46
2.45
0.77
0.59
1.15
0.63
0.56
0.6
0.25
0.2
0.31
274 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
Table N.1 (Continued)
Gross radium activity data for samples
Sample no.
RQ091992
RQ091992
RQ091993
RQ091993
RQ091993
RQ091993
RQ091993
RQ091993
RQ091994
RQ091994
RQ091994
RQ091994
RQ091994
RQ091994
RQ091995
RQ091995
RQ091995
RQ091995
RQ091995
RQ091995
RQ091996
RQ091996
RQ091996
RQ091996
RQ091996
RQ091996
RQ091997
RQ091997
RQ091997
RQ091997
RQ091997
RQ091997
RQ091998
RQ091998
RQ091998
RQ091998
RQ091998
RQ091998
RQ091999
RQ091999
RQ091999
RQ091999
RQ091999
RQ091999
Prep. No.
Count No.
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
Mass (mg)
17.9
17.9
22.3
22.3
22.3
25.8
25.8
25.8
21.6
21.6
21.6
25.7
25.7
25.7
14.7
14.7
14.7
21
21
21
14.8
14.8
14.8
21.5
21.5
21.5
17.7
17.7
17.7
19.9
19.9
19.9
23.2
23.2
23.2
28.1
28.1
28.1
28.1
28.1
28.1
25.9
25.9
25.9
T1 (d)
37.14
37.14
2.12
2.12
2.12
37.17
37.17
37.17
2.14
2.14
2.14
37.19
37.19
37.19
2.02
2.02
2.02
37.07
37.07
37.07
2.08
2.08
2.08
37.13
37.13
37.13
2.07
2.07
2.07
37.12
37.12
37.12
2.13
2.13
2.13
37.18
37.18
37.18
2.1
2.1
2.1
37.15
37.15
37.15
T2 (d)
14.34
40.04
0.31
6.01
42.14
5.38
14.34
40.04
0.31
6.01
42.14
5.38
14.34
40.04
0.52
6.23
42.35
5.38
14.34
40.04
0.52
6.23
42.35
5.38
14.34
40.04
0.52
6.23
42.35
5.38
14.34
40.04
0.52
6.23
42.35
5.38
14.34
40.04
0.52
6.23
42.35
5.38
14.34
40.04
©2010 Water Research Foundation. ALL RIGHTS RESERVED
GRA
(pCi/L)
0.1
0.19
3.59
0.82
0.54
0.4
0.32
0.24
2.94
0.99
0.31
0.67
0.61
0.35
18.8
5.68
2.38
3.59
3.38
3.41
24.09
12.1
8.91
9.83
9.22
10.1
11.94
10.85
9.21
8.75
8.07
8.84
9.99
5.3
4.47
4.39
4.1
4.59
17.55
9.81
6.53
5.79
5.55
5.94
GRA error
(pCi/L)
0.23
0.23
0.91
0.3
0.21
0.24
0.18
0.19
0.91
0.34
0.2
0.26
0.21
0.19
2.23
0.84
0.48
0.58
0.48
0.47
2.46
1.17
0.84
0.89
0.75
0.78
1.62
1.02
0.79
0.87
0.73
0.75
1.36
0.66
0.51
0.53
0.45
0.47
1.62
0.82
0.56
0.63
0.54
0.56
Appendix N: Gross Radium Activity Data | 275
Table N.1 (Continued)
Gross radium activity data for samples
Sample no.
RQ092000
RQ092000
RQ092000
RQ092000
RQ092000
RQ092000
RQ092001
RQ092001
RQ092001
RQ092001
RQ092001
RQ092001
RQ092029
RQ092029
RQ092029
RQ092029
RQ092029
RQ092029
RQ092250
RQ092250
RQ092250
RQ092250
RQ092250
RQ092250
RQ092251
RQ092251
RQ092251
RQ092251
RQ092251
RQ092251
RQ092252
RQ092252
RQ092252
RQ092252
RQ092252
RQ092252
RQ092253
RQ092253
RQ092253
RQ092253
RQ092253
RQ092253
RQ092254
RQ092254
Prep. No.
Count No.
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
Mass (mg)
17.7
17.7
17.7
25.5
25.5
25.5
25.8
25.8
25.8
21.9
21.9
21.9
26.1
26.1
26.1
14.2
14.2
14.2
24.1
24.1
24.1
23.7
23.7
23.7
21.2
21.2
21.2
13.3
13.3
13.3
23.7
23.7
23.7
26.3
26.3
26.3
24
24
24
24.5
24.5
24.5
24.5
24.5
T1 (d)
2.18
2.18
2.18
37.23
37.23
37.23
2.24
2.24
2.24
37.29
37.29
37.29
1.17
1.17
1.17
36.23
36.23
36.23
2.25
2.25
2.25
37.18
37.18
37.18
2.23
2.23
2.23
37.16
37.16
37.16
2.19
2.19
2.19
37.13
37.13
37.13
2.25
2.25
2.25
37.18
37.18
37.18
2.15
2.15
T2 (d)
0.52
6.23
42.35
5.38
14.34
40.04
0.52
6.23
42.35
5.38
14.34
40.04
0.52
6.23
42.35
5.38
14.34
40.04
5.38
14.34
40.04
0.34
4.38
43.41
6.25
16.08
40.26
0.34
4.38
43.41
6.25
16.08
40.26
0.34
4.38
43.41
6.25
16.08
40.26
0.34
4.38
43.41
6.25
16.08
©2010 Water Research Foundation. ALL RIGHTS RESERVED
GRA
(pCi/L)
21.84
7.09
5.05
4.99
4.57
4.91
30.36
12.24
9.58
9
8.26
8.97
0.33
0.13
0.08
0.56
0.29
0.23
0.56
0.34
0.31
0.67
0.28
0.22
4.11
3.24
3.33
2.2
3.47
2.65
7.67
7.66
7.74
8.78
9.44
9.61
0.41
0.24
0.07
0.87
0.69
0.46
0.32
0.25
GRA error
(pCi/L)
2.19
0.84
0.6
0.61
0.51
0.51
2.22
0.94
0.7
0.85
0.71
0.73
0.41
0.18
0.13
0.37
0.26
0.28
0.29
0.2
0.2
0.78
0.28
0.19
0.58
0.47
0.46
1.3
0.72
0.51
0.73
0.66
0.66
1.5
0.84
0.7
0.24
0.17
0.17
0.8
0.33
0.22
0.25
0.2
276 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
Table N.1 (Continued)
Gross radium activity data for samples
Sample no.
RQ092254
RQ092254
RQ092254
RQ092254
RQ092255
RQ092255
RQ092255
RQ092255
RQ092255
RQ092255
RQ092256
RQ092256
RQ092256
RQ092256
RQ092256
RQ092256
RQ092257
RQ092257
RQ092257
RQ092257
RQ092257
RQ092257
RQ092258
RQ092258
RQ092258
RQ092258
RQ092258
RQ092258
RQ092847
RQ092847
RQ092847
RQ092847
RQ092847
RQ092847
RQ092849
RQ092849
RQ092849
RQ092849
RQ092849
RQ092849
RQ092850
RQ092850
RQ092850
RQ092850
Prep. No.
Count No.
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
Mass (mg)
24.5
24.7
24.7
24.7
25.6
25.6
25.6
19.1
19.1
19.1
14.8
14.8
14.8
12.7
12.7
12.7
16.5
16.5
16.5
14.3
14.3
14.3
—
—
—
12.4
12.4
12.4
16
16
16
15.3
15.3
15.3
15.5
15.5
15.5
13.4
13.4
13.4
14.5
14.5
14.5
24.8
T1 (d)
2.15
37.09
37.09
37.09
2.22
2.22
2.22
37.15
37.15
37.15
2.25
2.25
2.25
37.18
37.18
37.18
2.27
2.27
2.27
37.2
37.2
37.2
—
—
—
37.1
37.1
37.1
2.02
2.02
2.02
37.05
37.05
37.05
2.12
2.12
2.12
37.16
37.16
37.16
2.18
2.18
2.18
37.21
T2 (d)
40.26
0.34
4.38
43.41
6.25
16.08
40.26
0.48
4.39
43.41
6.25
16.08
40.26
0.34
4.39
43.41
6.25
16.08
40.26
0.34
4.39
43.41
—
—
—
0.34
4.39
43.41
0.34
4.39
43.41
0.18
4.14
0.34
4.39
43.41
0.18
4.14
35.86
0.49
4.88
43.93
0.18
©2010 Water Research Foundation. ALL RIGHTS RESERVED
GRA
(pCi/L)
GRA error
(pCi/L)
0.58
-0.01
0.3
0.26
4.22
3.56
3.1
7.51
3.42
3.06
3.06
2.51
2.67
8.86
3.96
2.83
3.18
2.96
3.06
8.75
3.91
2.85
—
—
—
0.23
0.5
0.24
0.16
0.53
0.44
0.41
1.87
0.61
0.46
0.62
0.5
0.5
2.07
0.76
0.52
0.55
0.48
0.5
1.96
0.72
0.75
—
—
—
4.68
5.52
5.81
0.4
0.41
0.19
0.6
0.62
1.84
0.95
0.76
0.88
0.36
0.22
0.93
0.47
9.09
4.1
2.54
3.7
3.31
2.75
0.49
0.46
-0.14
1.35
2.00
0.74
0.47
1.28
0.71
0.51
0.85
0.42
0.22
0.74
Appendix N: Gross Radium Activity Data | 277
Table N.1 (Continued)
Gross radium activity data for samples
Sample no.
RQ092850
RQ092850
RQ092851
RQ092851
RQ092851
RQ092851
RQ092851
RQ092851
RQ092852
RQ092852
RQ092852
RQ092852
RQ092852
RQ092852
RQ092853
RQ092853
RQ092853
RQ092853
RQ092853
RQ092853
RQ092854
RQ092854
RQ092854
RQ092854
RQ092854
RQ092854
RQ092855
RQ092855
RQ092855
RQ092855
RQ092855
RQ092855
RQ092856
RQ092856
RQ092856
RQ092856
RQ092856
RQ092856
RR093078
RR093078
RR093078
RR093078
RR093078
RR093078
Prep. No.
Count No.
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
Mass (mg)
24.8
24.8
15.3
15.3
15.3
25.2
25.2
25.2
17.2
17.2
17.2
25.1
25.1
25.1
14.2
14.2
14.2
17.7
17.7
17.7
26.5
26.5
26.5
21.3
21.3
21.3
25.3
25.3
25.3
25.2
25.2
25.2
22.3
22.3
22.3
23.6
23.6
23.6
15.3
15.3
15.3
19.2
19.2
19.2
T1 (d)
37.21
37.21
2.2
2.2
2.2
37.23
37.23
37.23
1.91
1.91
1.91
36.95
36.95
36.95
1.94
1.94
1.94
36.98
36.98
36.98
2.29
2.29
2.29
37.32
37.32
37.32
2.18
2.18
2.18
37.22
37.22
37.22
2.16
2.16
2.16
37.2
37.2
37.2
2.14
2.14
2.14
44.11
44.11
44.11
T2 (d)
4.14
35.86
0.49
4.88
43.93
0.18
4.14
35.86
0.49
4.88
43.93
0.18
4.14
35.86
0.49
4.88
43.93
0.18
4.14
35.86
0.49
4.88
43.93
0.18
4.14
35.87
0.49
4.88
43.93
0.18
4.14
35.87
0.49
4.88
43.93
0.18
4.14
35.87
0.18
4.14
35.87
0.94
4.85
30.25
©2010 Water Research Foundation. ALL RIGHTS RESERVED
GRA
(pCi/L)
0.53
0.41
0.38
0.3
0.36
0.39
0.41
0.04
2.18
0.72
0.83
1.26
0.59
0.62
28.72
16.55
14.07
17.37
13.22
14.9
12.03
2.36
0.77
1.61
1.07
0.64
0.91
0.78
0.29
0.33
0.32
0.37
1.03
0.35
0.23
1.28
0.14
0.15
1.76
0.8
0.33
0.56
0.55
0.7
GRA error
(pCi/L)
0.27
0.19
0.68
0.33
0.25
0.51
0.25
0.15
0.85
0.35
0.28
0.7
0.3
0.19
2.79
1.42
1.09
2.06
1.18
1.02
1.37
0.42
0.22
0.73
0.36
0.25
0.49
0.3
0.19
0.62
0.28
0.19
0.57
0.23
0.15
0.69
0.24
0.15
0.95
0.45
0.27
0.59
0.35
0.28
278 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
Table N.1 (Continued)
Gross radium activity data for samples
Sample no.
RR093079
RR093079
RR093079
RR093079
RR093079
RR093079
RR093080
RR093080
RR093080
RR093080
RR093080
RR093080
RR093081
RR093081
RR093081
RR093081
RR093081
RR093081
RR093082
RR093082
RR093082
RR093082
RR093082
RR093082
RR093083
RR093083
RR093083
RR093083
RR093083
RR093083
RR093084
RR093084
RR093084
RR093084
RR093084
RR093084
RR093085
RR093085
RR093085
RR093085
RR093085
RR093085
RR093373
RR093373
Prep. No.
Count No.
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
Mass (mg)
17.4
17.4
17.4
14.3
14.3
14.3
17.2
17.2
17.2
17.7
17.7
17.7
17.7
17.7
17.7
17.6
17.6
17.6
24.5
24.5
24.5
20.5
20.5
20.5
21.4
21.4
21.4
25
25
25
21.1
21.1
21.1
24.6
24.6
24.6
14.8
14.8
14.8
26.4
26.4
26.4
15.5
15.5
T1 (d)
2.18
2.18
2.18
44.15
44.15
44.15
2.27
2.27
2.27
44.24
44.24
44.24
2.28
2.28
2.28
44.25
44.25
44.25
2.2
2.2
2.2
44.16
44.16
44.16
2.17
2.17
2.17
44.14
44.14
44.14
2.14
2.14
2.14
44.11
44.11
44.11
2.24
2.24
2.24
44.21
44.21
44.21
2.18
2.18
T2 (d)
0.18
4.35
36.08
0.94
4.85
30.25
0.39
4.35
36.08
0.94
4.85
30.25
0.39
4.35
36.08
0.94
4.85
30.25
0.39
4.35
36.08
0.94
4.85
30.25
0.39
4.35
36.08
0.94
4.86
30.25
0.39
4.35
36.08
0.94
4.86
30.25
0.39
4.35
36.08
0.94
4.86
30.25
0.94
4.86
©2010 Water Research Foundation. ALL RIGHTS RESERVED
GRA
(pCi/L)
10.43
7.16
7.51
8.64
7.02
8.16
7.05
2.69
1.76
1.74
1.75
1.4
83.61
26.45
9.97
12.44
9.83
10.3
24.3
9.23
5.38
4.99
4.27
4.79
26.46
10.17
5.92
5.95
6.16
5.94
27.51
10.06
4.96
5.05
4.87
5.61
8.2
4.08
2.98
2.29
2.7
3.04
0.8
0.29
GRA error
(pCi/L)
1.7
0.89
0.73
1.43
0.92
0.82
1.4
0.57
0.37
0.7
0.46
0.33
4.58
1.7
0.83
1.52
1
0.84
2.07
0.85
0.53
0.97
0.61
0.54
2.29
0.96
0.59
0.91
0.67
0.55
2.33
0.94
0.53
0.87
0.62
0.54
1.58
0.72
0.5
0.66
0.45
0.4
0.67
0.32
Appendix N: Gross Radium Activity Data | 279
Table N.1 (Continued)
Gross radium activity data for samples
Sample no.
RR093373
RR093373
RR093373
RR093373
RR093374
RR093374
RR093374
RR093374
RR093374
RR093374
RR093375
RR093375
RR093375
RR093375
RR093375
RR093375
RR093376
RR093376
RR093376
RR093376
RR093376
RR093376
RR093377
RR093377
RR093377
RR093377
RR093377
RR093377
RR093378
RR093378
RR093378
RR093378
RR093378
RR093378
RR093660
RR093660
RR093660
RR093660
RR093660
RR093660
RR093661
RR093661
RR093661
RR093661
Prep. No.
Count No.
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
Mass (mg)
15.5
16
16
16
19.6
19.6
19.6
20.8
20.8
20.8
17.1
17.1
17.1
19.9
19.9
19.9
20.7
20.7
20.7
19.8
19.8
19.8
18.3
18.3
18.3
17
17
17
20
20
20
16.5
16.5
16.5
24
24
24
17.2
17.2
17.2
26.9
26.9
26.9
22.9
T1 (d)
2.18
38.24
38.24
38.24
2.19
2.19
2.19
38.25
38.25
38.25
2.14
2.14
2.14
38.19
38.19
38.19
2.17
2.17
2.17
38.23
38.23
38.23
2.1
2.1
2.1
38.16
38.16
38.16
2.17
2.17
2.17
38.23
38.23
38.23
3.22
3.22
3.22
268.23
268.23
268.23
3.33
3.33
3.33
268.34
T2 (d)
30.25
0.89
4.88
33.08
0.94
4.86
30.25
0.89
4.88
33.08
0.94
5.07
30.25
0.89
4.88
33.08
1.15
5.07
31.04
0.89
4.88
33.08
1.15
5.07
31.04
0.89
4.88
33.08
1.15
5.07
31.04
0.89
4.88
33.08
0.89
4.88
33.08
0.11
5.98
42.75
0.89
4.88
33.08
0.11
©2010 Water Research Foundation. ALL RIGHTS RESERVED
GRA
(pCi/L)
0.33
1.91
0.91
0.95
0.75
0.22
0.25
1.14
0.8
1.02
5
5.33
4.67
4.77
4.95
4.95
1.22
0.82
0.33
0.57
0.15
0.42
22.17
16.63
13.69
11.93
11.84
12.02
15.84
6.66
4.74
4.57
3.46
4.05
3.54
2.35
1.88
4.48
2.52
1.36
1.61
0.86
0.43
1.34
GRA error
(pCi/L)
0.25
0.85
0.44
0.33
0.53
0.29
0.19
0.58
0.33
0.28
1.08
0.76
0.59
0.95
0.67
0.55
0.61
0.32
0.22
0.59
0.3
0.25
1.94
1.26
0.97
1.53
1.1
0.93
1.58
0.78
0.54
1.08
0.65
0.56
0.74
0.43
0.32
1.3
0.54
0.36
0.6
0.28
0.18
0.71
280 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
Table N.1 (Continued)
Gross radium activity data for samples
Sample no.
RR093661
RR093661
RR093662
RR093662
RR093662
RR093662
RR093662
RR093662
RR093663
RR093663
RR093663
RR093663
RR093663
RR093663
RR093664
RR093664
RR093664
RR093664
RR093664
RR093664
RS095390
RS095390
RS095390
RS095390
RS095390
RS095390
RS095391
RS095391
RS095391
RS095391
RS095391
RS095391
RS095392
RS095392
RS095392
RS095392
RS095392
RS095392
RS095393
RS095393
RS095393
RS095393
RS095393
RS095393
Prep. No.
Count No.
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
Mass (mg)
22.9
22.9
23.2
23.2
23.2
25.9
25.9
25.9
24.1
24.1
24.1
22.7
22.7
22.7
17.7
17.7
17.7
24.1
24.1
24.1
26.8
26.8
26.8
14.2
14.2
14.2
25.3
25.3
25.3
14.3
14.3
14.3
27.1
27.1
27.1
12.6
12.6
12.6
15.7
15.7
15.7
11.7
11.7
11.7
T1 (d)
268.34
268.34
3.03
3.03
3.03
268.05
268.05
268.05
3.09
3.09
3.09
268.1
268.1
268.1
3.2
3.2
3.2
268.21
268.21
268.21
2.18
2.18
2.18
84.07
84.07
84.07
2.18
2.18
2.18
84.08
84.08
84.08
2.21
2.21
2.21
84.1
84.1
84.1
2.22
2.22
2.22
84.11
84.11
84.11
T2 (d)
5.98
42.75
0.89
4.88
33.08
0.11
5.98
42.75
0.89
4.88
33.08
0.11
5.98
42.75
0.89
4.88
33.08
0.33
5.98
42.75
0.33
5.98
42.75
4.16
7.38
34.13
0.33
5.98
42.75
4.16
7.38
34.13
0.33
5.98
42.76
4.16
7.38
34.13
0.11
5.98
42.76
4.16
7.38
34.13
©2010 Water Research Foundation. ALL RIGHTS RESERVED
GRA
(pCi/L)
0.59
0.54
14.11
9.55
8.94
11.12
10.26
10.7
13.99
4.46
3.46
12.6
5.26
4.69
6.88
4.55
4.09
6.14
4.92
4.39
11.41
4.96
3.86
4.77
4.29
6.23
18.71
8.95
7.47
7.43
7.74
6.48
16.79
7.83
6.07
5.84
5.98
5.48
4.53
1.67
1.59
1.49
1.68
1.87
GRA error
(pCi/L)
0.27
0.21
1.65
0.89
0.72
1.46
0.83
0.75
1.59
0.59
0.43
1.68
0.64
0.52
1.31
0.68
0.54
1.14
0.59
0.48
1.39
0.58
0.44
0.65
0.85
1.6
1.8
0.78
0.62
0.78
1.05
1.53
1.69
0.72
0.56
0.74
0.99
1.52
1.27
0.5
0.38
0.47
0.71
1.36
Appendix N: Gross Radium Activity Data | 281
Table N.1 (Continued)
Gross radium activity data for samples
Sample no.
RS095394
RS095394
RS095394
RS095394
RS095394
RS095394
RS095395
RS095395
RS095395
RS095395
RS095395
RS095395
RS095396
RS095396
RS095396
RS095396
RS095396
RS095396
RS095397
RS095397
RS095397
RS095397
RS095397
RS095397
RS095398
RS095398
RS095398
RS095398
RS095398
RS095398
RS095399
RS095399
RS095399
RS095399
RS095399
RS095399
RS095400
RS095400
RS095400
RS095400
RS095400
RS095400
Prep. No.
Count No.
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
Mass (mg)
26.1
26.1
26.1
11.1
11.1
11.1
24.6
24.6
24.6
23.5
23.5
23.5
16.1
16.1
16.1
10.7
10.7
10.7
15.3
15.3
15.3
12.1
12.1
12.1
22.4
22.4
22.4
13.9
13.9
13.9
17.4
17.4
17.4
12.1
12.1
12.1
19.3
19.3
19.3
11.7
11.7
11.7
T1 (d)
1.21
1.21
1.21
83.11
83.11
83.11
2.63
2.63
2.63
84.52
84.52
84.52
1.14
1.14
1.14
83.03
83.03
83.03
3.14
3.14
3.14
84.13
84.13
84.13
2.93
2.93
2.93
83.92
83.92
83.92
4.24
4.24
4.24
81.18
81.18
81.18
4.27
4.27
4.27
81.21
81.21
81.21
T2 (d)
0.11
5.98
42.76
4.16
7.38
34.13
0.11
5.98
42.76
4.16
7.38
34.13
0.11
5.98
43
4.16
7.38
34.13
1.15
5.3
42.09
4.16
7.38
34.13
1.15
5.3
42.09
4.16
7.38
34.13
1.25
3.45
38.04
4.16
7.38
34.13
1.25
3.45
38.04
4.16
7.38
34.13
©2010 Water Research Foundation. ALL RIGHTS RESERVED
GRA
(pCi/L)
2.99
1.25
0.67
0.57
1.55
3.91
8.11
7.32
7.51
7.31
7.36
7.15
3.11
0.35
0.5
0.68
0.56
1.23
1.05
0.72
0.27
0.44
0.74
2.1
5.02
2.17
2.07
1.83
1.79
4.06
2.93
4.65
5.04
4.21
4.66
6.45
7.12
6.26
6.44
6.38
6.36
8
GRA error
(pCi/L)
0.88
0.32
0.21
0.34
0.64
1.45
1.26
0.72
0.63
0.63
0.83
1.27
1.08
0.33
0.28
0.34
0.48
1.03
0.64
0.37
0.26
0.29
0.48
1.13
0.9
0.45
0.35
0.46
0.64
1.43
0.55
0.64
0.6
0.66
0.92
1.7
0.79
0.7
0.65
0.79
1.05
1.84
282 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
©2010 Water Research Foundation. ALL RIGHTS RESERVED
APPENDIX O
RADIOCHEMICAL DATA
URANIUM DATA
234
U,
U
activity
(pCi/L)
0.21
0.23
0.19
0.10
0.08
1342.30
1784.85
0.61
0.11
1.14
0.03
0.04
16.16
0.21
0.09
0.07
0.01
0.07
0.27
0.00
13.21
8.14
0.12
0.15
0.03
0.14
0.32
0.07
0.09
0.01
10.24
0.25
0.12
238
Sample no.
RQ091434
RQ091435
RQ091436
RQ091437
RQ091438
RQ091439
RQ091440
RQ091441
RQ091442
RQ091444
RQ091713
RQ091720
RQ091721
RQ091722
RQ091723
RQ091724
RQ091725
RQ091726
RQ091751
RQ091992
RQ091993
RQ091994
RQ091995
RQ091996
RQ091997
RQ091998
RQ091999
RQ092000
RQ092001
RQ092029
RQ092250
RQ092251
RQ092252
235
Table O.1
U, and U activities of the samples
235
234
U
U
Error
Error
activity
activity
(pCi/L)
(pCi/L)
(pCi/L)
(pCi/L)
0.03
0.03
0.01
3.25
0.03
0.01
0.01
1.92
0.03
0.01
0.01
2.84
0.02
0.01
0.01
1.69
0.02
0.01
0.01
0.66
56.13
55.33
5.84
1556.03
29.45
78.23
5.16
3003.96
0.06
0.03
0.01
0.78
0.02
0.01
0.01
1.65
0.06
0.07
0.01
7.08
0.01
0.01
0.01
0.06
0.01
0.02
0.01
0.03
0.55
0.74
0.07
49.88
0.04
0.02
0.01
0.19
0.03
0.01
0.01
0.13
0.02
0.01
0.01
0.12
0.01
0.00
0.00
0.12
0.02
0.04
0.01
0.35
0.02
0.01
0.01
1.53
0.01
0.00
0.00
0.01
0.32
0.57
0.05
19.21
0.22
0.34
0.04
12.32
0.02
0.01
0.01
0.14
0.03
0.01
0.01
0.58
0.01
0.00
0.00
0.11
0.03
0.02
0.01
1.85
0.04
0.02
0.01
3.19
0.01
0.01
0.01
0.90
0.02
0.01
0.01
1.54
0.01
0.00
0.01
0.02
0.18
0.43
0.03
11.32
0.04
0.01
0.01
1.85
0.02
0.00
0.01
0.54
238
283
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Error
(pCi/L)
0.15
0.11
0.13
0.10
0.07
64.03
42.09
0.07
0.10
0.16
0.02
0.01
1.48
0.04
0.04
0.03
0.02
0.04
0.06
0.01
0.43
0.29
0.02
0.05
0.02
0.11
0.14
0.05
0.06
0.01
0.19
0.10
0.04
284 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
238
238
Sample no.
RQ092253
RQ092254
RQ092255
RQ092256
RQ092257
RQ092258
RQ092847
RQ092848
RQ092849
RQ092850
RQ092851
RQ092852
RQ092853
RQ092854
RQ092855
RQ092856
RR093078
RR093079
RR093080
RR093081
RR093082
RR093083
RR093084
RR093085
RR093373
RR093374
RR093375
RR093376
RR093377
RR093378
RR093660
RR093661
RR093662
RR093663
RR093664
RS095390
RS095391
RS095392
RS095393
U,
U
activity
(pCi/L)
8.84
7.62
0.04
21.86
95.72
0.05
8.97
22.67
3.67
3.89
3.14
115.00
117.91
0.07
13.61
12.05
14.94
0.07
0.09
0.22
0.08
0.03
0.08
0.08
12.97
10.22
2.02
13.00
0.01
0.02
11.05
0.07
0.50
0.05
1.66
0.08
0.20
0.15
0.02
235
Table O.1 (Continued)
U, and 234U activities of the samples
235
234
U
U
Error
Error
activity
activity
(pCi/L)
(pCi/L)
(pCi/L)
(pCi/L)
0.16
0.34
0.03
8.66
0.14
0.32
0.03
7.98
0.01
0.01
0.00
0.25
0.36
0.87
0.06
34.26
1.51
4.05
0.26
139.94
0.02
0.00
0.01
0.07
0.24
0.37
0.04
10.99
0.39
1.01
0.07
27.88
0.16
0.15
0.03
15.48
0.17
0.16
0.03
4.58
0.14
0.13
0.02
4.25
1.97
5.01
0.33
149.38
2.00
5.37
0.34
169.72
0.01
0.00
0.00
0.09
0.22
0.59
0.04
22.50
0.31
0.53
0.05
15.82
0.25
0.61
0.04
20.39
0.03
0.00
0.02
0.17
0.02
0.01
0.01
1.79
0.04
0.03
0.02
3.42
0.02
0.01
0.01
0.29
0.01
0.01
0.01
0.35
0.02
0.01
0.01
0.35
0.02
0.00
0.01
0.76
0.23
0.55
0.04
14.93
0.18
0.49
0.04
15.68
0.07
0.10
0.02
3.15
0.21
0.58
0.04
19.23
0.01
0.00
0.00
0.05
0.01
0.00
0.01
0.03
0.34
0.72
0.08
36.77
0.02
0.03
0.02
0.11
0.04
0.04
0.01
1.24
0.02
0.03
0.01
0.23
0.08
0.08
0.02
2.91
0.03
0.01
0.01
1.05
0.02
0.01
0.00
3.11
0.02
0.01
0.01
2.76
0.01
0.00
0.00
0.04
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Error
(pCi/L)
0.16
0.15
0.03
0.48
1.96
0.02
0.28
0.45
0.47
0.19
0.17
2.37
2.59
0.02
0.31
0.38
0.31
0.06
0.10
0.18
0.03
0.04
0.04
0.05
0.25
0.24
0.09
0.27
0.01
0.02
0.80
0.04
0.06
0.04
0.11
0.10
0.08
0.08
0.01
Appendix O: Radiochemical Data | 285
238
235
U,
238
Sample no.
RS095394
RS095395
RS095396
RS095397
RS095398
RS095399
RS095400
U
activity
(pCi/L)
0.22
6.67
28.18
5.55
0.92
11.81
27.08
Table O.1 (Continued)
U, and 234U activities of the samples
235
234
U
U
Error
Error
activity
activity
(pCi/L)
(pCi/L)
(pCi/L)
(pCi/L)
0.02
0.01
0.01
0.29
0.13
0.29
0.03
6.06
0.46
1.17
0.08
36.94
0.12
0.26
0.02
9.12
0.05
0.06
0.01
3.15
0.26
0.45
0.05
18.12
0.46
1.12
0.08
35.07
Error
(pCi/L)
0.03
0.13
0.56
0.16
0.09
0.33
0.56
RADIUM DATA
224
Ra,
Ra
activity
(pCi/L)
17.13
7.28
6.11
6.07
12.60
2.62
0.19
5.27
9.17
1.66
5.47
9.83
1.30
10.88
7.47
5.92
2.99
2.26
12.21
-0.01
1.04
0.97
6.79
4.99
224
Sample no.
RQ091434
RQ091435
RQ091436
RQ091437
RQ091438
RQ091439
RQ091440
RQ091441
RQ091442
RQ091444
RQ091713
RQ091720
RQ091721
RQ091722
RQ091723
RQ091724
RQ091725
RQ091726
RQ091751
RQ091992
RQ091993
RQ091994
RQ091995
RQ091996
226
Table O.2
Ra, and Ra activities of the samples
224
226
226
228
Ra
Ra
Ra
Ra
error
activity
error
activity
(pCi/L)
(pCi/L)
(pCi/L)
(pCi/L)
2.10
14.53
0.45
12.61
1.33
5.73
0.28
4.16
1.01
6.36
0.29
4.19
0.92
4.73
0.27
3.98
2.00
3.87
0.22
9.61
1.87
1.84
0.16
0.4
0.17
0.09
0.08
0.48
0.99
4.02
0.23
3.24
2.42
5.92
0.27
5.24
1.35
1.79
0.17
0.68
0.97
3.44
0.23
3.27
1.19
4.62
0.25
6.2
0.34
3.61
0.25
1.54
1.23
26.89
0.59
16.09
1.76
1.41
0.17
4.99
1.34
1.3
0.16
6.03
0.48
4.03
0.24
2.57
0.39
3.94
0.23
2.62
1.96
4.5
0.25
12.38
0.08
0.14
0.05
-0.07
0.75
0.31
0.07
0.67
0.72
0.27
0.07
0.47
1.28
1.77
0.15
6
0.68
6.25
0.28
6.07
228
©2010 Water Research Foundation. ALL RIGHTS RESERVED
228
Ra
error
(pCi/L)
0.86
0.55
0.54
0.55
0.77
0.34
0.36
0.54
0.69
0.36
0.64
0.61
0.4
0.89
0.55
0.63
0.44
0.45
0.81
0.35
0.43
0.35
0.65
0.66
286 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
224
Ra,
Ra
activity
(pCi/L)
0.85
2.51
6.88
7.86
9.18
0.08
1.07
1.30
1.75
1.56
4.83
7.04
3.72
4.72
4.31
0.12
0.23
2.57
0.19
0.18
0.40
6.15
4.91
0.65
0.43
0.48
2.34
3.16
32.85
8.01
9.21
10.17
3.48
0.19
0.30
0.86
0.44
9.06
7.72
224
Sample no.
RQ091997
RQ091998
RQ091999
RQ092000
RQ092001
RQ092029
RQ092250
RQ092251
RQ092252
RQ092253
RQ092254
RQ092255
RQ092256
RQ092257
RQ092258
RQ092847
RQ092848
RQ092849
RQ092850
RQ092851
RQ092852
RQ092853
RQ092854
RQ092855
RQ092856
RR093078
RR093079
RR093080
RR093081
RR093082
RR093083
RR093084
RR093085
RR093373
RR093374
RR093375
RR093376
RR093377
RR093378
226
Table O.2 (Continued)
Ra, and 228Ra activities of the samples
224
226
226
228
Ra
Ra
Ra
Ra
error
activity
error
activity
(pCi/L)
(pCi/L)
(pCi/L)
(pCi/L)
0.25
7.2
0.28
0.22
0.85
3.91
0.22
2.32
1.57
6.42
0.29
4.23
1.36
4.23
0.24
6.39
1.44
7.93
0.31
8.12
0.14
0.08
0.07
0.01
0.86
0.2
0.06
0.4
0.29
2.81
0.19
0.18
0.43
7.74
0.31
0.6
1.17
0.12
0.05
0.29
3.83
0.14
0.07
0.21
1.01
2.95
0.2
2.01
3.00
0.74
0.11
0.72
3.47
1.51
0.15
2.22
0.57
4.42
0.23
0.22
0.12
0.08
0.05
0.18
0.19
0.11
0.06
0.63
0.58
2.23
0.18
1.62
0.16
0.11
0.07
0.48
0.16
0.07
0.07
0.01
0.31
0.35
0.07
0.21
0.82
10.65
0.36
2.56
3.72
0.57
0.09
1.86
0.50
0.48
0.11
0.34
0.35
0.23
0.07
-0.09
0.39
0.33
0.09
0.75
1.10
6.29
0.29
1.5
0.89
0.99
0.13
2.14
3.45
7.51
0.32
27.45
1.52
4.39
0.24
7.08
1.73
5.26
0.27
6.35
2.36
4.61
0.25
7.77
0.90
2.71
0.2
2.28
0.16
0.14
0.08
0.19
0.22
0.15
0.06
0.19
0.22
4.11
0.25
0.4
0.32
0.09
0.07
0.1
1.40
13.97
0.45
0.66
1.54
3.76
0.24
7.95
©2010 Water Research Foundation. ALL RIGHTS RESERVED
228
Ra
error
(pCi/L)
0.33
0.45
0.58
0.67
0.76
0.31
0.32
0.32
0.32
0.29
0.29
0.44
0.36
0.45
0.27
0.28
0.34
0.41
0.33
0.26
0.31
0.45
0.41
0.37
0.3
0.32
0.37
0.47
1.22
0.68
0.65
0.7
0.53
0.3
0.32
0.34
0.3
0.36
0.73
Appendix O: Radiochemical Data | 287
224
Ra,
Ra
activity
(pCi/L)
1.14
0.13
2.39
6.73
0.97
4.11
4.53
4.59
0.61
0.18
0.67
0.04
0.13
3.61
2.80
7.78
226
224
Sample no.
RR093660
RR093661
RR093662
RR093663
RR093664
RS095390
RS095391
RS095392
RS095393
RS095394
RS095395
RS095396
RS095397
RS095398
RS095399
RS095400
Table O.2 (Continued)
Ra, and 228Ra activities of the samples
224
226
226
228
Ra
Ra
Ra
Ra
error
activity
error
activity
(pCi/L)
(pCi/L)
(pCi/L)
(pCi/L)
0.45
1.19
0.24
1.17
0.18
0.34
0.12
0.14
0.49
9.52
0.37
2.96
1.20
3.54
0.24
7.17
0.37
4.62
0.27
0.27
0.63
4.05
0.25
5.02
0.74
6.92
0.32
4.11
0.75
5.72
0.3
2.74
0.40
1.09
0.12
1.62
0.17
0.11
0.05
1
0.28
7.07
0.28
0.59
0.08
0.28
0.08
1.11
0.19
0.09
0.07
0.17
0.86
2.97
0.2
1.05
0.72
4.58
0.25
1.79
1.27
6.46
0.29
3.85
228
Ra
error
(pCi/L)
0.55
0.54
0.49
0.7
0.33
0.71
0.61
0.55
0.55
0.44
0.39
0.45
0.31
0.42
0.43
0.53
THORIUM DATA
228
Th,
Th
activity
(pCi/L)
0.00
0.03
0.03
0.04
0.17
0.02
0.05
0.07
0.01
0.04
-0.08
0.03
0.06
-0.16
228
Sample no.
RQ091434
RQ091435
RQ091436
RQ091437
RQ091438
RQ091439
RQ091440
RQ091441
RQ091442
RQ091444
RQ091713
RQ091720
RQ091721
RQ091722
230
Table O.3
Th, and Th activities of the samples
228
230
230
232
Th
Th
Th
Th
error
activity
error
activity
(pCi/L)
(pCi/L)
(pCi/L)
(pCi/L)
0.04
0.02
0.14
0.04
0.03
0.06
0.16
0.03
0.03
0.10
0.14
0.02
0.03
0.04
0.30
0.01
0.05
0.08
0.16
0.03
0.03
0.02
0.14
0.02
0.03
0.01
0.30
0.02
0.03
0.12
0.16
0.02
0.03
-0.03
0.14
0.01
0.02
0.03
0.29
0.02
0.11
-0.19
0.09
0.01
0.11
-0.02
0.10
0.01
0.07
-0.19
0.09
0.00
0.18
-0.19
0.10
0.02
232
©2010 Water Research Foundation. ALL RIGHTS RESERVED
232
Th
error
(pCi/L)
0.02
0.02
0.01
0.01
0.02
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
288 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
228
Th,
Th
activity
(pCi/L)
-0.13
-0.04
0.01
-0.01
-0.14
0.07
0.13
0.22
-0.08
0.29
0.08
0.09
0.05
-0.07
0.15
0.08
0.04
0.03
0.08
0.00
0.03
0.06
1.91
1.18
0.03
0.00
-0.02
0.08
-0.01
0.02
0.04
0.53
0.00
0.01
0.02
0.00
-0.02
0.04
0.02
228
Sample no.
RQ091723
RQ091724
RQ091725
RQ091726
RQ091751
RQ091992
RQ091993
RQ091994
RQ091995
RQ091996
RQ091997
RQ091998
RQ091999
RQ092000
RQ092001
RQ092029
RQ092250
RQ092251
RQ092252
RQ092253
RQ092254
RQ092255
RQ092256
RQ092257
RQ092258
RQ092847
RQ092848
RQ092849
RQ092850
RQ092851
RQ092852
RQ092853
RQ092854
RQ092855
RQ092856
RR093078
RR093079
RR093080
RR093081
230
Table O.3 (Continued)
Th, and 232Th activities of the samples
228
230
230
232
Th
Th
Th
Th
error
activity
error
activity
(pCi/L)
(pCi/L)
(pCi/L)
(pCi/L)
0.10
-0.20
0.10
0.01
0.12
-0.06
0.10
0.03
0.08
-0.12
0.09
0.01
0.08
-0.24
0.09
0.01
0.16
-0.33
0.10
0.01
0.07
0.26
0.23
0.03
0.08
0.56
0.17
0.03
0.09
0.55
0.30
0.02
0.13
-0.04
0.11
0.02
0.19
0.85
0.27
0.02
0.06
0.26
0.16
0.02
0.09
0.46
0.29
0.03
0.12
0.20
0.11
0.01
0.13
-0.07
0.09
0.01
0.17
0.71
0.18
0.03
0.06
0.84
0.31
0.03
0.05
0.18
0.11
0.01
0.04
0.19
0.16
0.04
0.05
0.01
0.29
0.02
0.04
-0.20
0.10
0.01
0.04
-0.16
0.09
0.01
0.08
1.40
0.36
0.05
0.26
0.68
0.59
0.06
0.13
0.55
0.12
0.02
0.05
0.08
0.21
0.04
0.04
0.23
0.16
0.06
0.04
-0.09
0.10
0.02
0.07
-0.39
0.19
0.03
0.04
0.02
0.10
0.04
0.03
-0.26
0.10
0.01
0.04
0.18
0.16
0.03
0.15
0.49
0.33
0.07
0.05
-0.12
0.09
0.02
0.05
-0.15
0.09
0.01
0.04
-0.33
0.09
0.01
0.03
0.10
0.16
0.07
0.08
0.04
0.43
0.05
0.11
0.37
0.41
0.05
0.15
-0.43
0.19
0.03
©2010 Water Research Foundation. ALL RIGHTS RESERVED
232
Th
error
(pCi/L)
0.01
0.01
0.01
0.01
0.01
0.03
0.02
0.01
0.01
0.02
0.01
0.01
0.01
0.01
0.02
0.01
0.01
0.02
0.01
0.01
0.01
0.03
0.03
0.01
0.03
0.02
0.01
0.02
0.01
0.01
0.01
0.03
0.01
0.01
0.01
0.01
0.03
0.03
0.01
Appendix O: Radiochemical Data | 289
228
230
Th,
Th
activity
(pCi/L)
-0.02
0.02
-0.08
-0.01
0.01
0.02
0.03
0.02
0.01
-0.01
0.04
0.00
-0.07
0.02
0.01
0.01
0.09
0.04
-0.01
0.53
0.03
0.00
0.07
0.14
0.06
0.01
228
Sample no.
RR093082
RR093083
RR093084
RR093085
RR093373
RR093374
RR093375
RR093376
RR093377
RR093378
RR093660
RR093661
RR093662
RR093663
RR093664
RS095390
RS095391
RS095392
RS095393
RS095394
RS095395
RS095396
RS095397
RS095398
RS095399
RS095400
210
Table O.3 (Continued)
Th, and 232Th activities of the samples
228
230
230
232
Th
Th
Th
Th
error
activity
error
activity
(pCi/L)
(pCi/L)
(pCi/L)
(pCi/L)
0.12
-0.28
0.20
0.03
0.12
-0.44
0.20
0.03
0.06
0.00
0.09
0.01
0.04
0.18
0.10
0.03
0.02
-0.08
0.10
0.01
0.02
0.08
0.10
0.01
0.10
0.01
0.10
0.03
0.02
0.38
0.11
0.02
0.02
0.12
0.09
0.01
0.05
-0.06
0.09
0.01
0.13
0.84
0.34
0.23
0.12
-0.50
0.20
0.02
0.12
0.55
0.20
0.09
0.19
0.24
0.20
0.08
0.08
0.14
0.32
0.03
0.04
0.09
0.10
0.02
0.04
1.00
0.19
0.29
0.03
0.06
0.10
0.01
0.03
-0.07
0.09
0.01
0.05
0.45
0.11
0.13
0.02
0.41
0.17
0.02
0.02
-0.02
0.10
0.01
0.02
1.10
0.13
0.11
0.03
0.07
0.10
0.10
0.04
0.52
0.33
0.06
0.03
0.09
0.10
0.02
232
Th
error
(pCi/L)
0.02
0.02
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.04
0.01
0.02
0.02
0.01
0.01
0.04
0.01
0.01
0.02
0.01
0.01
0.02
0.02
0.02
0.01
PB AND 210PO DATA
Table O.4
Pb and Po activities of the samples
210
Pb er- 210Po activi210
Pb activity
ror
ty
(pCi/L)
(pCi/L)
(pCi/L)
0.23
0.47
0.03
-0.09
0.47
0.10
0.1
0.56
-0.01
0.41
0.53
0.11
0.23
0.48
0.03
210
Sample no.
RQ091434
RQ091435
RQ091436
RQ091437
RQ091438
210
©2010 Water Research Foundation. ALL RIGHTS RESERVED
210
Poerror
(pCi/L)
0.09
0.07
0.11
0.08
0.07
290 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
Table O.4 (Continued)
Pb and 210Po activities of the samples
210
Pb er- 210Po activi210
Pb activity
ror
ty
(pCi/L)
(pCi/L)
(pCi/L)
2.4
0.69
2.41
0.83
0.64
0.12
0.26
0.39
-0.02
0.07
0.36
0.12
-0.18
0.43
0.14
-0.05
0.36
0.07
0.01
0.38
0.10
2.66
0.48
2.91
0.51
0.42
0.02
-0.18
0.39
0.03
-0.07
0.34
0.11
-0.05
0.34
0.03
0.43
0.35
-0.04
-0.02
0.34
0.29
0.35
0.39
1.91
0.21
0.39
-0.07
-0.21
0.35
0.17
0.11
0.4
-0.01
1.62
0.55
0.46
2.55
0.6
3.17
-0.02
0.32
0.11
0.13
0.34
0.01
0.42
0.4
-0.20
-0.16
0.38
0.12
0.4
0.42
4.11
-0.09
0.31
0.13
0.15
0.33
-0.04
0.29
0.37
-0.20
0
0.33
0.10
0.07
0.35
0.05
0.14
0.35
-0.05
4.6
0.72
27.40
3.4
0.63
5.72
0.48
0.37
-0.18
3.7
0.69
0.89
0.49
0.47
0.70
0.72
0.45
8.03
0.53
0.45
2.66
-0.03
0.42
0.25
210
Sample no.
RQ091439
RQ091440
RQ091441
RQ091442
RQ091444
RQ091713
RQ091720
RQ091721
RQ091722
RQ091723
RQ091724
RQ091725
RQ091726
RQ091751
RQ091992
RQ091993
RQ091994
RQ091995
RQ091996
RQ091997
RQ091998
RQ091999
RQ092000
RQ092001
RQ092029
RQ092250
RQ092251
RQ092252
RQ092253
RQ092254
RQ092255
RQ092256
RQ092257
RQ092258
RQ092847
RQ092848
RQ092849
RQ092850
RQ092851
©2010 Water Research Foundation. ALL RIGHTS RESERVED
210
Poerror
(pCi/L)
0.26
0.13
0.08
0.06
0.09
0.05
0.05
0.25
0.06
0.05
0.05
0.05
0.05
0.06
0.24
0.18
0.18
0.20
0.29
0.41
0.16
0.18
0.20
0.20
0.39
0.25
0.26
0.30
0.27
0.29
0.28
1.92
0.83
0.35
0.98
0.62
0.90
0.70
0.59
Appendix O: Radiochemical Data | 291
Table O.4 (Continued)
Pb and 210Po activities of the samples
210
Pb er- 210Po activi210
Pb activity
ror
ty
(pCi/L)
(pCi/L)
(pCi/L)
0.53
0.44
1.86
14.39
1.45
4.39
0.35
0.41
0.53
0.05
0.36
0.01
-0.1
0.42
0.27
0.29
0.96
-0.22
0.34
0.65
0.35
0.55
0.64
-0.44
0.6
0.6
-0.53
0.35
0.52
-0.27
0.37
0.49
-0.34
0.31
0.43
-0.30
0.3
0.49
-0.27
0.27
0.3
0.17
-0.15
0.3
0.22
0.24
0.33
0.22
0.14
0.32
-0.03
0.29
0.27
-0.03
0.16
0.31
-0.18
1.02
0.38
1.32
-0.23
0.3
0.24
0.54
0.4
0.07
-0.01
0.34
0.08
0.07
0.35
-0.02
0.1
0.39
-0.05
0.18
0.42
-0.06
0.47
0.42
-0.28
0.38
0.52
-0.17
0.32
0.41
55.57
0.87
0.44
-0.50
4.17
0.63
3.14
0.32
0.42
-0.03
0.03
0.45
0.36
0.06
0.4
0.34
0.77
0.4
-0.09
210
Sample no.
RQ092852
RQ092853
RQ092854
RQ092855
RQ092856
RR093078
RR093079
RR093080
RR093081
RR093082
RR093083
RR093084
RR093085
RR093373
RR093374
RR093375
RR093376
RR093377
RR093378
RR093660
RR093661
RR093662
RR093663
RR093664
RS095390
RS095391
RS095392
RS095393
RS095394
RS095395
RS095396
RS095397
RS095398
RS095399
RS095400
©2010 Water Research Foundation. ALL RIGHTS RESERVED
210
Poerror
(pCi/L)
0.65
2.50
0.59
0.51
0.59
0.94
0.56
0.63
0.59
0.51
0.52
0.46
0.52
0.38
0.37
0.41
0.40
0.34
0.39
0.38
0.27
0.37
0.31
0.32
0.39
0.42
0.37
0.52
3.32
0.45
0.69
0.37
0.40
0.36
0.40
292 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
©2010 Water Research Foundation. ALL RIGHTS RESERVED
APPENDIX P
INORGANIC DATA
METAL CONCENTRATIONS OF THE SAMPLES
Sample no.
RQ091434
RQ091435
RQ091436
RQ091437
RQ091438
RQ091439
RQ091440
RQ091441
RQ091442
RQ091444
RQ091713
RQ091720
RQ091721
RQ091722
RQ091723
RQ091724
RQ091725
RQ091726
RQ091751
RQ091992
RQ091993
RQ091994
RQ091995
RQ091996
RQ091997
RQ091998
RQ091999
RQ092000
RQ092001
RQ092029
RQ092250
RQ092251
RQ092252
RQ092253
Na
(mg/L)
582.95
654.92
54.00
44.88
5.30
7.60
13.36
118.49
12.88
11.01
17.20
40.84
13.93
4.87
1.56
3.26
9.07
7.53
41.30
121.32
59.74
61.01
2.91
8.29
8.29
36.57
38.12
37.20
55.20
122.00
115.71
32.72
191.29
52.16
Table P.1
Metal concentrations of the samples
K
Ca
Mg
Ba
(mg/L) (mg/L) (mg/L) (μg/L)
17.54
83.27
36.59
7.67
10.90
35.66
13.23
8.79
14.90
57.55
19.21
27.07
13.57
54.65
15.19
59.83
3.22
70.12
28.35
82.50
0.36
32.10
0.89
-0.12
2.44
27.97
1.34
0.51
5.96
31.60
11.79
36.96
3.90
71.68
24.73
46.02
3.18
90.57
27.14
162.08
1.68
2.89
2.67
76.96
2.70
5.93
5.52
186.59
1.28
46.13
13.34
22.24
0.98
3.07
4.21
107.74
0.66
1.40
1.29
31.53
0.30
0.90
1.28
31.92
2.15
96.40
29.70
302.36
1.77
84.14
27.12
259.87
3.09
123.76
50.16
41.00
4.24
1.15
0.32
20.80
6.12
90.61
16.67
98.35
6.25
78.00
15.12
87.87
0.38
0.62
0.48
16.72
3.17
17.34
3.00
19.27
2.60
19.83
2.73
8.49
4.35
86.00
42.22
40.07
3.97
99.84
32.55
57.15
15.85
58.99
19.93
68.18
15.03
58.09
18.97
41.21
0.62
0.74
0.07
1.07
5.69
143.87
33.45
71.06
4.49
63.64
31.80
86.00
6.21
73.34
26.04
172.51
1.78
152.30
44.21
88.33
293
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Mn
(μg/L)
167.11
17.04
6.02
4.99
23.02
0.88
0.67
49.18
51.55
168.48
16.17
34.73
77.29
6.79
10.06
7.02
19.58
20.33
141.00
28.48
27.49
31.00
19.92
77.68
90.20
10.35
45.30
4.10
5.25
3.42
71.52
2.24
5.83
-0.19
Fe
(mg/L)
1.25
0.57
0.47
0.16
0.19
0.00
0.00
0.35
0.32
0.28
0.20
0.22
0.33
0.00
0.00
0.22
0.43
0.39
1.13
0.47
0.04
0.06
0.00
1.13
0.52
0.05
0.14
0.20
0.19
0.00
0.00
0.02
0.18
0.00
294 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
Sample no.
RQ092254
RQ092255
RQ092256
RQ092257
RQ092258
RQ092847
RQ092848
RQ092849
RQ092850
RQ092851
RQ092852
RQ092853
RQ092854
RQ092855
RQ092856
RR093078
RR093079
RR093080
RR093081
RR093082
RR093083
RR093084
RR093085
RR093373
RR093374
RR093375
RR093376
RR093377
RR093378
RR093660
RR093661
RR093662
RR093663
RR093664
RS095390
RS095391
RS095392
RS095393
RS095394
RS095395
Na
(mg/L)
59.57
6.53
49.39
94.98
11.30
11.77
7.29
10.93
17.63
22.29
17.16
7.01
15.37
96.34
60.15
28.07
9.40
8.28
6.54
74.39
85.51
85.24
15.16
27.27
99.78
37.19
110.55
26.51
516.57
34.62
25.87
64.95
50.45
174.55
25.00
45.60
31.00
26.00
129.00
60.50
Table P.1 (Continued)
Metal concentrations of the samples
K
Ca
Mg
Ba
(mg/L) (mg/L) (mg/L) (μg/L)
7.90
78.37
16.51
41.90
3.09
40.54
16.71
145.56
1.84
6.23
1.51
8.99
1.78
23.38
3.73
1.89
2.40
28.60
3.40
196.00
0.84
8.96
1.34
0.61
1.09
19.83
2.37
1.47
0.46
31.31
0.81
23.60
0.35
4.42
0.18
2.03
1.47
8.73
0.42
2.02
0.88
17.28
0.70
3.17
3.47
22.45
4.18
11.33
3.33
24.92
10.01
45.89
4.76
66.05
16.95
50.32
4.30
84.61
20.87
93.08
6.46
46.63
12.70
58.36
1.28
88.30
26.09
357.25
1.53
47.65
26.43
86.73
1.45
52.44
28.94
103.77
12.56
178.07
43.34
30.17
15.48
163.24
37.15
20.27
17.25
200.36
43.87
19.16
7.16
77.55
23.72
30.32
1.80
32.67
3.74
76.28
10.73
91.91
15.80
93.52
2.19
52.14
7.10
240.08
11.10
108.60
17.76
66.66
10.06
276.56
68.60
35.62
12.51
53.57
10.15
15.80
2.67
36.80
15.39
22.89
1.77
104.40
14.08
17.98
3.73
33.88
10.50
54.93
8.08
78.42
25.06
33.23
22.65
127.97
31.94
68.27
8.90
66.90
26.00
118.00
7.30
66.20
24.00
16.00
6.20
54.40
20.80
23.00
2.40
36.80
3.70
315.00
2.40
ND
ND
10.00
1.10
63.30
9.80
9.00
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Mn
(μg/L)
10.20
35.46
85.35
449.98
50.00
2.23
0.66
166.20
3.18
0.03
0.34
142.16
145.20
1.89
4.29
0.09
25.10
-0.19
1.38
261.49
220.75
166.99
148.28
0.05
9.97
7.91
50.67
2.42
92.77
21.12
0.11
80.90
29.79
0.03
1.00
21.00
18.00
22.00
25.00
6.00
Fe
(mg/L)
0.12
0.07
1.29
0.34
ND
0.18
0.37
0.07
0.01
0.00
0.00
3.11
0.03
0.03
0.11
0.01
1.92
0.01
0.20
2.26
2.00
1.88
0.79
0.00
0.04
0.11
0.01
0.09
0.76
0.01
0.00
0.49
0.93
0.01
0.30
0.30
0.30
0.20
0.40
0.60
Appendix P: Inorganic Data | 295
Sample no.
RS095396
RS095397
RS095398
RS095399
RS095400
Na
(mg/L)
7.10
35.80
60.90
98.40
71.00
Table P.1 (Continued)
Metal concentrations of the samples
K
Ca
Mg
Ba
(mg/L) (mg/L) (mg/L) (μg/L)
0.90
59.40
26.90
3.00
2.40
230.00
51.50
15.00
3.20
102.00
31.90
49.00
3.00
66.60
36.40
45.00
2.50
102.00
28.50
54.00
Mn
(μg/L)
87.00
ND
24.00
55.00
219.00
Fe
(mg/L)
1.00
ND
0.50
ND
0.60
CONCENTRATIONS OF SOME OF THE ANIONS OF THE SAMPLES
In the following table “SE” denotes a sampling error, “ND” denotes a value that was below the detection limit, and “NA” denotes a sample results that was not analyzed by mistake.
Table P.2
Concentrations of the anions of the samples
Nitrate
Chloride Fluoride Sulfide
Sample no.
and Nitrite
(mg/L)
(mg/L) (mg/L)
(mg/L)
RQ091434
18.88
1.94
ND
-0.28
RQ091435
32.69
4.20
ND
-0.27
RQ091436
16.28
1.25
ND
-0.28
RQ091437
13.89
1.24
ND
-0.27
RQ091438
1.59
0.41
ND
-0.27
RQ091439
2.84
0.85
ND
0.79
RQ091440
4.64
1.58
ND
1.51
RQ091441
66.30
1.79
ND
-0.28
RQ091442
6.42
0.51
ND
-0.24
RQ091444
3.06
0.94
SE
SE
RQ091713
19.34
0.01
0.004
2.05
RQ091720
69.15
0.00
ND
4.78
RQ091721
40.95
0.73
ND
0.01
RQ091722
7.82
0.02
ND
7.59
RQ091723
2.18
0.03
ND
2.78
RQ091724
3.61
0.03
ND
2.40
RQ091725
23.43
0.24
ND
-0.17
RQ091726
13.64
0.33
ND
-0.17
RQ091751
1.06
0.33
ND
-0.14
RQ091992
1.07
1.40
ND
-0.16
RQ091993
27.75
0.42
ND
0.36
RQ091994
27.95
0.46
ND
0.34
RQ091995
3.61
0.03
ND
0.37
RQ091996
1.47
0.56
ND
-0.16
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Sulfate
(mg/L)
1152.17
936.88
82.19
41.95
52.23
25.07
21.01
78.68
114.81
94.99
14.18
5.23
15.20
0.13
0.13
0.13
35.55
31.22
141.48
12.20
223.00
193.00
1.99
7.91
296 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
Table P.2 (Continued)
Concentrations of the anions of the samples
Nitrate
Chloride Fluoride Sulfide
Sample no.
and Nitrite
(mg/L)
(mg/L) (mg/L)
(mg/L)
RQ091997
1.21
0.30
ND
-0.17
RQ091998
59.40
0.43
ND
-0.13
RQ091999
98.60
0.44
ND
-0.14
RQ092000
13.16
1.04
SE
-0.16
RQ092001
22.74
1.27
ND
-0.17
RQ092029
5.55
0.78
0.030
-0.16
RQ092250
240.80
0.54
0.005
2.39
RQ092251
9.12
0.73
0.004
-0.05
RQ092252
257.25
0.70
0.003
-0.05
RQ092253
96.10
0.32
ND
5.87
RQ092254
18.81
0.68
0.003
0.20
RQ092255
2.08
0.28
ND
-0.02
RQ092256
16.23
0.61
ND
-0.02
RQ092257
67.95
0.78
0.009
-0.02
RQ092258
3.67
1.15
SE
SE
RQ092847
2.77
3.78
ND
-0.18
RQ092848
15.00
2.07
ND
0.01
RQ092849
0.25
3.40
ND
-0.23
RQ092850
2.02
0.25
ND
-0.21
RQ092851
12.68
0.27
ND
-0.01
RQ092852
1.66
1.29
ND
0.25
RQ092853
1.27
0.12
ND
-0.16
RQ092854
37.11
0.08
ND
0.31
RQ092855
33.59
0.27
ND
5.35
RQ092856
49.65
0.19
ND
3.69
RR093078
30.6
0.06
ND
3.92
RR093079
1.1
0.90
0.01
-0.18
RR093080
4.1
0.26
ND
-0.08
RR093081
3.1
0.22
ND
-0.07
RR093082
22.2
0.99
ND
-0.08
RR093083
33.4
1.67
ND
-0.09
RR093084
36.9
1.64
ND
-0.09
RR093085
2.4
0.70
ND
-0.17
RR093373
13.50
0.54
ND
6.84
RR093374
33.60
0.56
0.01
5.02
RR093375
43.80
0.13
ND
-0.22
RR093376
37.00
0.36
0.01
3.79
RR093377
27.30
2.42
0.02
-0.18
RR093378
71.40
1.18
0.02
-0.17
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Sulfate
(mg/L)
7.27
183.00
124.00
30.60
72.80
2.97
281.00
21.70
41.50
258.00
184.50
26.30
14.00
18.70
25.54
2.56
1.61
4.70
5.24
7.68
1.71
3.72
24.70
127.80
154.00
17.9
ND
31.6
33.6
390
349
530
79.5
16.80
173.00
13.30
160.00
808.00
990.00
Appendix P: Inorganic Data | 297
Table P.2 (Continued)
Concentrations of the anions of the samples
Nitrate
Chloride Fluoride Sulfide
Sample no.
and Nitrite
(mg/L)
(mg/L) (mg/L)
(mg/L)
RR093660
26.70
1.72
ND
0.00
RR093661
SE
SE
SE
SE
RR093662
7.78
2.40
0.003
-0.32
RR093663
10.80
0.66
0.004
-0.30
RR093664
258.00
1.17
ND
-0.19
RS095390
26.50
0.38
ND
ND
RS095391
60.30
2.75
ND
ND
RS095392
30.20
2.81
ND
ND
RS095393
21.70
0.12
0.01
ND
RS095394
19.20
0.88
0.02
ND
RS095395
104.00
0.12
0.01
ND
RS095396
38.20
0.48
0.01
0.59
RS095397
4.20
0.97
ND
2.07
RS095398
15.30
0.49
0.01
ND
RS095399
77.80
0.64
ND
ND
RS095400
55.10
0.53
0.04
ND
Sulfate
(mg/L)
19.50
SE
38.70
178.00
307.00
48.80
140.00
88.50
ND
76.20
ND
34.70
522.00
267.00
168.00
104.00
ALKALINITY, PH, CONDUCTIVITY, TURBIDITY, AND DISSOVLED SILICA (SIO2)
In the following table “SE” denotes a sampling error.
Table P.3
Alkalinity, pH, conductivity, turbidity, and dissolved silica (SiO2) of the samples
Alkalinity Conductivity Turbidity pH
Silica
Sample no.
(mg/L)
(µS/cm)
(NTU)
(SU) (mg/L)
RQ091434
415.86
2841.00
7.70 7.44
9.85
RQ091435
529.12
2887.00
1.53 7.90
10.64
RQ091436
254.25
691.00
0.79 7.73
7.95
RQ091437
253.47
612.00
0.93 7.68
8.14
RQ091438
273.82
603.00
1.11 7.62
7.96
RQ091439
73.44
165.20
0.24 7.68
29.70
RQ091440
72.10
217.30
0.05 7.99
24.42
RQ091441
219.09
774.00
0.55 7.95
13.68
RQ091442
207.57
622.00
1.39 7.76
8.52
RQ091444
SE
SE
SE
SE
SE
RQ091713
6.78
138.10
0.155 5.76
10.87
RQ091720
0.89
318.60
0.191 4.67
12.47
RQ091721
112.78
394.90
0.446 7.30
27.23
©2010 Water Research Foundation. ALL RIGHTS RESERVED
298 | Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
Table P.3 (Continued)
Alkalinity, pH, conductivity, turbidity, and dissolved silica (SiO2) of the samples
Alkalinity Conductivity Turbidity pH
Silica
Sample no.
(mg/L)
(µS/cm)
(NTU)
(SU) (mg/L)
RQ091722
1.64
100.10
0.093 4.93
10.97
RQ091723
1.04
40.70
0.050 4.78
5.52
RQ091724
1.70
42.80
4.45 5.06
5.40
RQ091725
298.84
676.00
3.05 7.76
13.33
RQ091726
273.81
598.00
1.81 7.92
13.48
RQ091751
458.38
1020.00
12.4 7.65
14.71
RQ091992
262.17
526.00
0.75 7.76
37.76
RQ091993
168.64
831.00
0.37 7.53
21.15
RQ091994
159.76
769.00
0.65 7.62
21.29
RQ091995
2.08
34.87
0.25 4.96
5.26
RQ091996
62.59
153.10
8.16 7.37
38.08
RQ091997
68.14
160.90
1.27 7.22
40.84
RQ091998
206.00
908.00
0.67 7.66
20.49
RQ091999
218.89
988.00
1.28 7.64
8.53
RQ092000
268.63
608.00
0.67 7.82
8.67
RQ092001
255.04
693.00
2.01 7.69
8.56
RQ092029
245.69
496.00
0.20 9.03
18.52
RQ092250
273.69
1416.00
0.05 7.64
24.78
RQ092251
312.94
637.00
0.13 7.69
10.05
RQ092252
266.00
1393.00
0.54 7.71
11.20
RQ092253
238.60
1243.00
0.06 7.43
44.20
RQ092254
180.91
766.00
0.64 7.84
24.80
RQ092255
158.65
370.00
0.54 7.92
7.84
RQ092256
90.00
271.00
11.50 7.71
12.55
RQ092257
144.48
567.00
1.42 7.80
11.75
RQ092258
SE
SE
SE
SE
SE
RQ092847
39.40
118.20
0.48 7.81
16.75
RQ092848
50.11
174.50
0.19 7.92
18.00
RQ092849
92.86
217.50
0.63 7.47
24.60
RQ092850
42.54
111.80
0.18 8.76
20.90
RQ092851
49.09
170.70
0.06 8.64
23.70
RQ092852
83.76
184.90
0.05 8.98
30.50
RQ092853
83.93
185.70
7.72 7.58
27.60
RQ092854
70.90
324.10
0.20 6.60
29.80
RQ092855
277.95
915.00
0.10 7.50
47.40
RQ092856
220.11
905.00
0.60 7.42
48.80
RR093078
150.24
460.00
0.39 7.92
65.40
RR093079
324.96
607.00
23.00 7.49
22.80
RR093080
199.36
447.00
0.56 7.89
9.89
RR093081
217.72
477.00
0.40 7.92
9.52
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Appendix P: Inorganic Data | 299
Table P.3 (Continued)
Alkalinity, pH, conductivity, turbidity, and dissolved silica (SiO2) of the samples
Alkalinity Conductivity Turbidity pH
Silica
Sample no.
(mg/L)
(µS/cm)
(NTU)
(SU) (mg/L)
RR093082
342.56
1358.00
3.03 7.61
21.40
RR093083
306.52
1284.00
3.75 7.63
17.50
RR093084
273.75
1491.00
20.70 7.69
16.00
RR093085
240.96
610.00
12.00 7.64
7.64
RR093373
97.71
322.10
0.33 7.81
35.40
RR093374
267.24
952.00
0.12 7.69
49.80
RR093375
157.84
468.00
0.77 7.74
24.00
RR093376
364.31
1078.00
0.22 7.66
52.00
RR093377
113.11
1602.00
0.63 7.06
40.70
RR093378
186.33
2494.00
3.42 7.60
26.30
RR093660
172.07
457.00
3.28 7.99
13.45
RR093661
SE
SE
SE
SE
SE
RR093662
211.49
510.00
17.30 7.86
11.25
RR093663
206.69
760.00
1.13 7.55
13.40
RR093664
175.16
1673.00
0.04 7.59
40.60
RS095390
249.00
636.00
1.70 7.46
1.88
RS095391
149.00
753.00
1.40 7.76
7.11
RS095392
156.00
580.00
1.60 7.76
7.02
RS095393
127.00
327.00
0.80 7.83
23.50
RS095394
183.00
589.00
0.40 9.08
32.90
RS095395
185.00
695.00
0.20 7.35
6.32
RS095396
181.00
533.00
1.00 7.82
3.07
RS095397
262.00
1360.00
0.60 7.70
17.10
RS095398
222.00
936.00
39.00 7.84
13.80
RS095399
244.00
1000.00
0.20 8.03
24.80
RS095400
328.00
957.00
1.50 7.64
29.40
©2010 Water Research Foundation. ALL RIGHTS RESERVED
Evaluation of Gross Alpha and Uranium Measurements for MCL Compliance
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