Radionuclides in
Groundwater
State Hygienic Laboratory
at the University of Iowa
Dustin May
Laboratory Supervisor
• What is radioactivity? And
more importantly, why should
you care?
Radioactivity
• Types of Radioactivity
– Alpha (α)
• Helium nucleus, 2 protons, 2 neutrons, positive charge
– Beta (β-/β+)
• Electrons or Positrons, can have negative or positive charge
– Photons (Gamma/X-Rays)
• Electromagnetic radiation
• Often occur as a result of beta decay or electron capture
(γ/x-rays) or due to material interaction (x-ray,
Bremsstrahlung)
– Neutrons
• Deeply penetrating, usually man-made, often in particle
accelerators
Radioactivity
• Radioactivity Units
– Becquerel (Bq) = disintegrations per second, SI
Unit, named after Henri Becquerel
– Curies (Ci) = 2.22x1012 disintegrations per minute,
named after Marie & Pierre Curie
• Roughly the disintegrations per minute of 1 gram of
radium-226…it’s a long story.
• https://www.orau.org/ptp/articlesstories/thecurie.htm
Radioactivity
• Health Physics
– Radioactive particles cause damage to cells and
DNA
– Usually via either direct action (kinetic) or indirect
action (free-radicals and reactive oxygen species)
– Two main types of effects, stochastic and
deterministic
– Exposure to radiation comes from many sources
– There is no such thing as a “safe” dose of radiation
Radioactivity
• Natural Radioactivity
– Generally the result of
two decay series,
originating from the
primordial nuclides,
Th-232 and U-238
– K-40 is the most
abundant radioactive
nuclide
• Also the only natural
positron emitter
– Cosmic Radiation
• Gamma/X-Rays,
particles generated in
in atmosphere
Figure 1. Autunite ore, Calcium uranyl phosphate
(Parent, 2011)
NORM
• Uranium Series
– Abundant in rock and
soil
– Mixture of long and
short half-lives
– Leads to complex
relationships
– Radium is especially
soluble
• Ra-226 is usually
most concerning in
water
– Radon is a noble gas,
low adsorption, nonreactive
Figure 2. Uranium decay chain. Half-lives and decay information
were obtained from the NuDat 2 Database (NNDC 2013).
Abbreviations: d, days; h, hours; m, minutes; s, seconds; y, years.
NORM
• Thorium Series
– Thorium is more
abundant than U
– Radium especially
soluble
• Ra-228 usually
most concerning in
water, but has a
much shorter t1/2
than Ra-226
– Half-lives are very
different than U
series
Figure 3. Natural thorium decay chain. Half-lives and decay
information were obtained from the NuDat 2 Database (NNDC
2013). Abbreviations: d, days; h, hours; m, minutes; s, seconds; y,
years.
Radioactive Equilibrium
A
A. Figure 4. Secular Equilibrium,
daughter t1/2 <<< parent t1/2
B. Figure 5. Transient Equilibrium,
daughter t1/2 < parent t1/2
C. Figure 6. No Equilibrium,
daughter t1/2 > parent t1/2
B
C
Groundwater and Minerals
Figure 7. Interaction between minerals and groundwater (Porcelli & Swarzenski, 2003)
Iowa Bedrock Aquifers
Figure 8. Iowa bedrock aquifers (Prior et al, 2003).
Risk Based Regulation
• Drinking Water
Regulations
– Community water
supplies
• >15 connections or
25 persons
• Safe Drinking Water
Act (SDWA)
– Combined Radium –
MCL = 5 pCi L-1
• Only Ra-226 and Ra228
Risk Based Regulation
• Drinking Water
Regulations
– Uranium – MCL = 30
μgL-1
• Regulated as mass, not
radioactivity
– Gross Alpha Particles –
MCL = 15 pCiL-1
• Regulated excluding
Uranium
– Gross Beta/Photon
Emitters – MCL = 4
mremyr-1
• No enforcement in Iowa
• Dependent on
susceptibility to manmade nuclides
Risk
• Review of Risk from Public Water Supplies
– Risk calculated based of EPA FGR 13
– Several assumptions made
• 2 Liters consumed/day
• Lifetime of consumption (70 years)
– EPA guidelines for Maximum Contaminant Level (MCL)
• 1:10,000 to 1:1,000,000 mortal cancer incidence (CI)
• Available Data, Public Water Supplies in Iowa 2012-2017
–
–
–
–
–
–
547 Community Water Systems Tested
856 Gross Alpha Analyses
293 Uranium Analyses
1049 Ra-226 Analyses
1055 Ra-228 Analyses
1.62 million Iowans Served
Risk Based Regulation
Figure 9. Risk Estimate for Iowans Consuming Public Drinking Water (May, 2017)
Risk Based Regulation
• Private Drinking
Water
– No regulation
– Installation testing,
few tested for
radionuclides
– Many wells are not
treated
– Water softening
– Radionuclide
impact in private
well water
Figure 18. Well Spudder (Wikipedia, 2016)
Current Research
• Polonium-210
– Alpha emitter
– High specific activity
(166 TBqg-1)3
– Uranium series
– t1/2 = 138 days
– Parent Pb-210
• t1/2 = 22.2 years
Figure 10. Uranium Decay Series (Nelson, unpublished)
Current Research
• Polonium-210 Health
Risk
– ~50% ingested Po-210
retained (ICRP, 1993;
Thomas et al, 2001)
– Accumulates in
reticuloendothelial
system (Moroz &
Parfenov, 1971)
• liver, spleen, kidneys,
and lymph nodes
– Ra-226 and Pb-210
incorporate into bony
tissue
• Potential source of Po210
Figure 11. Death by acute radiation syndrome via Po-210 (Telegraph, 2006)
Current Research
• Iowa Groundwater Monitoring Project
– Fall 2015 Sampling, 59 sites
– Public Wells
– Mostly shallow, alluvial wells
– Generally deemed vulnerable to surface water
contamination
– Found very low concentrations of NORM
Current Research
Figure 12. Sampling sites for FY2016 IGWM (Hruby, 2015)
Current Research
• Private Well Water Study
– Iowa is majority rural; represents a significant
population at risk
– Private wells are entirely unregulated
– Co-funded by CHEEC and SHL
– Will examine 50 confined-aquifer wells across
Iowa
– Broad range of chemical parameters
– Uranium-series radionuclides, including radon
Questions?
• Feel free to contact me:
– [email protected]
Reference List
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Parent, Géry. (2011). Autunite_1(France).jpg [Image file]. Retrieved from:
https://upload.wikimedia.org/wikipedia/commons/3/39/Autunite_1(France).jpg
Focazio MJ, et al. Occurrence of Selected Radionuclides in Ground Water Used for Drinking Water in the United States: A Targeted
Reconnaissance Survey, 1998; U.S. Geological Survey Water-Resources Investigations Report 00-4273. Reston, VA:U.S. Geological Survey, U.S.
Department of the Interior (2001).
ICRP, 1993. Age-dependent Doses to Members of the Public from Intake of Radionuclides - Part 2 Ingestion Dose Coefficients. ICRP Publication
67. Ann. ICRP 23 (3-4).
Thomas PA, Fisenne I, Chorney D, Baweja AS, and Tracy BL. Human Absorption and Retention of Polonium-210 from Caribou Meat. Radiat Prot
Dosimetry (2001) 97 (3): 241-250.
Moroz BB and Parfenov YD. 1971. Effects of Polonium-210 on the Organism. Moscow, Atomizdat. Translation Series Report AEC-tr-7300, Biology
and Medicine (TID 4500), United States Atomic Energy Commission, Technical Information Center, National Technical Information Service, U.S.
Department of Commerce, Springfield, VA. Issued April 1972.
“Polonium-210.” Fact Sheet. May 2010. Health Physics Society. McLean, VA. Web.
Telegraph. (2006). Death by polonium-210 [Image file]. Retrieved from: http://i.telegraph.co.uk/multimedia/archive/00631/news-graphics2006-_631086a.gif
Porcelli, D and Swarzenski, PW. The Behavior of U- and Th-series Nuclides in Groundwater. Reviews in Mineralogy and Geochemistry (2003) 52
(1): 317-361
Wikipedia. (2016). 874px-Well_spudder_8606.jpg [Image file]. Retrieved from:
https://upload.wikimedia.org/wikipedia/en/thumb/5/59/Well_spudder_8606.jpg/874px-Well_spudder_8606.jpg
Frame, PW. (1996). How the Curie Came to Be. Retrieved from: https://www.orau.org/ptp/articlesstories/thecurie.htm
Prior JC, Boekhoff, JL, Howes MR, Libra RD, VanDorpe PE. (2003). Iowa’s Groundwater Basics. Iowa Department of Natural Resources, Iowa.