PROBLEM
How does residential development of formerly
mined lands influence the amount of ionizing
radiation in the resulting residential community?
HYPOTHESIS
If ionizing radiation is measured in the soils of
residential and undeveloped land previously
mined for phosphate, then the residential soils
will show significantly lower levels of radiation
because of the effect of legal liability and soil
stability on where the developer sites the
residential community.
MATERIALS
Materials Used in Soil Sampling:
Radex RD1212 - Geiger Counter
Plastic Freezer Bags
Post Hole Digger
Measuring Scoops
Tape Measure
Computer
Safety Glasses
Triple Beam Balance
Closed-Toe Shoes
Protective Gloves
Materials Used in Lab Preparation and Analysis:
High Purity Germanium Detector
Face Shield
Apron
Aluminum Cans (400g soil)
Electric Can Sealer
Hammer
Electronic scale
Black Permanent Marker
PROCEDURES
1. Using historical images, locate at least three sampling sites on previously mined lands that
currently contain both undeveloped land and land developed into residential property.
2. Research levels of cosmic radiation and general background radiation in Central Florida
and radiation levels of previously mined land in Polk County (to compare to scientist’s
levels).
3. At each sampling site, begin measuring ionizing radiation with a hand-held Geiger counter
at 1 meter above the surface until sampling at site is complete. Measure readings for five
minutes in installments of one measure a minute.
4. Use the post-hole digger (operated by designated supervisor) to obtain a soil sample of at
least 400 grams at a depth of half a meter below the surface and place sample in plastic
freezer bag that is marked for location.
5. Record radiation readings from Geiger counter and coded location of site sample.
6. Take samples to lab at Bureau of Radiation Control in Orlando.
7. Prepare samples for testing by homogenizing soil by grinding and mixing, and measure
out 400 grams using an electronic scale.
8. Label soil bags and aluminum cans and seal cans using an electric can sealer. Let
samples rest for a minimum of 14 days to allow stabilization of elements in can.
9. Place soil samples in high purity germanium detector and test for the amount of
radioactive activity in the sample, esp. Radium 226, Lead 214, Bismuth 214 (lab personnel).
10. Dispose of tested soil samples in designated receptacle.
11. Record results from both lab and in-field testing. Analyze results.
PHOTOS
Soil Sampling
Photos taken by James Lovely
PHOTOS
Lab Preparation & Analysis
Photos taken by James Lovely
SITE MEASUREMENTS
The data supports my hypothesis as average gamma readings from formerly mined lands that have been
developed (in shaded columns) are lower than those of formerly mined lands that remain undeveloped.
Charts by Elizabeth & James Lovely
EPA REDBOOK DATA
Data presented from 672
outdoor gamma exposure
measurements taken by the
EPA on reclaimed mining land
in Polk County.
The average gamma
measurement for the 672 sites
was 0.11 µS / hour.
The average gamma
measurement for the 3
residential sites in this
experiment was 0.117 µS /
hour, near the EPA average for
reclaimed mining land.
The average gamma
measurement for the 3
undeveloped sites in this
experiment was 0.193 µS /
hour, or within the top 10% of
EPA readings for reclaimed
mining land.
Source: Indoor Radiation Exposure Due to Radium - 226 in Florida Phosphate Lands, U.S. Environmental Protection Agency, Office of
Radiation Programs, EPA 520/4-78-013, Feb. 1979, Table 4, Page 27 (units in original table converted from µR / hour to µS / hour ).
Charts by Elizabeth & James Lovely
RADIOACTIVITY
In order to confirm that the gamma
radiation measurements taken at the
six (6) formerly mined sites were
related to the actual presence of
radioactivity in the soil at those sites, I
took soil samples at a depth of ½
meter at each site.
Ionizing Radiation & Radioactivity
μSv/h
Bq/g
Ra 226
S1R1
0.124
0.080
S1U1
0.164
0.185
S2R2
0.112
0.092
S2U2
0.188
0.242
S3R3
0.112
0.025
S3U3
0.226
0.281
Working with the State of Florida’s
Bureau of Radiation Control, I was
able to prepare those soil samples for
testing in a high purity germanium
detector.
The tests revealed a very high (~ 93%)
correlation between the average
gamma radiation reading obtained at
each sample site and the amount of
radioactivity from the related soil
sample attributable to Radium 226,
Lead 214 and Bismuth 214, which are
isotopes in the decay chain for
Radium 226.
Note: Special thanks to the State of Florida’s Bureau of Radiation Control – Orlando Office.
RADIOACTIVITY
Ionizing Radiation & Radioactivity
μSv/h
Bq/g
Pb 214
S1R1
0.124
0.064
S1U1
0.164
0.127
S2R2
0.112
0.071
S2U2
0.188
0.149
S3R3
0.112
0.009
S3U3
0.226
0.271
Ionizing Radiation & Radioactivity
μSv/h
Bq/g
Bi 214
S1R1
0.124
0.060
S1U1
0.164
0.119
S2R2
0.112
0.065
S2U2
0.188
0.145
S3R3
0.112
0.011
S3U3
0.226
0.265
Charts by Elizabeth & James Lovely
CONCLUSION
Ionizing radiation was measured in the soils of residential and undeveloped land previously mined
for phosphate, and the residential soils showed significantly lower levels of radiation. The average levels
of ionizing radiation at the residential sites were as follows: 0.124; 0.112; and 0.116 micro-Sieverts/hr.
The undeveloped sites had average radiation levels of: 0.164; 0.188; and 0.226 micro-Sieverts/hr. The
still undeveloped areas had radiation levels that were from 132% to 195% higher than those of current
residential areas. Through analysis of radioactivity in the soil, it was determined that there was a 93%
correlation between the radioactivity of each soil sample and the radiation reading taken at the related
sample site. The average levels of radioactivity at the residential sites were as follows: 0.045 (Bi 214);
0.048 (Pb 214); and 0.066 (Ra 226) Becquerels/gram. The average levels of radioactivity at the
undeveloped sites were as follows: 0.176 (Bi 214); 0.182 (Pb 214); and 0.236 (Ra 226) Becquerels/gram.
These results prove the scientist’s hypothesis that residential soils on formerly mined lands have
significantly lower levels of both ionizing radiation and radioactivity than undeveloped soils.
Experimentation based on these findings could include further testing of radiation and radioactivity
1) in different types of soils (e.g., sands or clays) in previously mined areas, 2) in a larger number of
samples, 3) focusing on the historical use of the sample site within the mining process. This experiment
was especially strong in testing across multiple mine sites, taking samples from a considerable depth,
testing for ionizing radiation at the location, and evaluating radioactivity at a regulated research institution
with very sensitive gamma radiation detectors.
The results and findings of this experiment could be used by real estate developers looking to build
on formerly mined land and citizens when evaluating the history and safety of the communities in which
they live. The results and findings of this experiment will also help to encourage government bodies that
authorize development of formerly mined land to fulfill their ongoing responsibility to ensure that such
land is reclaimed properly.