Publications—Scientific Investigations Report 2007-5037
By Joseph D. Ayotte, Sarah M. Flanagan, and William S. Morrow
U.S. Geological Survey Scientific Investigations Report 2007-5037
Report Revised October 17, 2007
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Cover 1 (18.7 MB)
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Water-quality data collected from 1,426 wells during 1993–2003 as part of the U.S. Geological Survey National Water-Quality Assessment (NAWQA) program were evaluated to characterize the water quality in glacial and bedrock aquifers of the northern United States. One of the goals of the NAWQA program is to synthesize data from individual studies across the United States to gain regional- and national-scale information about the behavior of contaminants. This study focused on the regional occurrence and distribution of uranium and 222Radon in ground water in the glacial aquifer system of the United States as well as in the Cambrian-Ordovician and the New York and New England crystalline aquifer systems that underlie the glacial aquifer system. The occurrence of uranium and 222Radon in ground water has long been a concern throughout the United States. In the glacial aquifers, as well as the Cambrian-Ordovician and the New York and New England crystalline aquifer systems of the United States, concentrations of uranium and 222Radon were highly variable. High concentrations of uranium and 222Radon affect ground water used for drinking water and for agriculture.
A combination of information or data on (1) national-scale ground-water regions, (2) regional-scale glacial depositional models, (3) regional-scale geology, and (4) national-scale terrestrial gamma-ray emissions were used to confirm and(or) refine the regions used in the analysis of the water-chemistry data. Significant differences in the occurrence of uranium and 222Radon, based primarily on geologic information were observed and used in this report. In general, uranium was highest in the Columbia Plateau glacial, West-Central glacial, and the New York and New England crystalline aquifer groups (75th percentile concentrations of 22.3, 7.7, and 2.9 micrograms per liter (μg/L), respectively). In the Columbia Plateau glacial and the West-Central glacial aquifer groups, about 10 percent of wells sampled had concentrations of uranium that exceeded the U.S. Environmental Protection Agency (USEPA) Maximum Contaminant Level of 30 μg/L; in the New York and New England crystalline aquifer group, 4 percent exceeded 30 μg/L.
Ground-water samples with high concentrations of uranium were commonly linked to geologic sources rich in uranium. In seven of nine aquifer groups defined for this study, concentrations of uranium correlated significantly with concentrations of sulfate in ground water (Spearman’s rho = 0.20 to 0.56; p < 0.05). In the Columbia Plateau, glacial aquifers were derived in part from basaltic lava flows, some felsic volcanic rocks, and some paleo-lake bed materials that may be rich in uranium. In the Columbia Plateau and West-Central glacial aquifer groups, uranium correlated with total dissolved solids, bicarbonate, boron, lithium, selenium, and strontium. In the West-Central glacial aquifer group, rocks such as Cretaceous marine shales, which are abundant in uranium, probably contribute to the high concentrations in ground water; in the southern part of this group, which extends into Nebraska, the glacial or glacial-related sediment may be interbedded with uranium-rich materials that originated to the north and west and in the Rocky Mountains. In New England, crystalline bedrock that is granitic, such as two-mica granites, as well as other high-grade metamorphic rocks, has abundant uranium that is soluble in the predominantly oxic to sub-oxic geochemical conditions. This appears to contribute to high uranium concentrations in ground water.
The highest 222Radon concentrations were present in samples from wells completed in the New York and New England crystalline aquifer group; the median value (2,122 picocuries per liter (pCi/L)) was about 10 times the median value of the glacial and Cambrian-Ordovician aquifer groups. More than 25 percent of the samples from the New York and New England crystalline aquifer group wells had 222Radon concentrations that exceeded the proposed USEPA Alternative Maximum Contaminant Level (AMCL) of 4,000 pCi/L. 222Radon concentrations in samples from the New York and New England crystalline aquifer group were similar to those found in other countries with similar geologic histories and(or) similar bedrock geology. In the New York and New England crystalline aquifer group, concentrations of 222Radon were correlated with uranium (Spearman’s rho = 0.60; p < 0.0001) and with gross alpha particle activity (Spearman’s rho = 0.72; p < 0.0001). Also, in some parts of the New York and New England crystalline aquifer group, 222Radon correlated with lead (Spearman’s rho = 0.52; p = 0.004) and some of the lead concentrations (greater than 2 μg/L) were associated with high 222Radon concentrations (greater than 10,000 pCi/L).
Abstract
Introduction
Purpose and Scope
Heath Effects of Uranium and 222Radon
Previous Investigations
Radionuclides in the Northeast
Radionuclides in the Midwest
Radionuclides in the West
Process Studies and Other Data Related to Radionuclides in Ground Water
Study Design and Methods
Water-Quality Data Sources and Well Selection
Sampling and Analysis
Analysis of Ancillary Data and Explanatory Variables
Statistical Analyses
Evaluations of Quality-Assurance and Quality-Control Data
Uranium and 222Radon in Glacial and Bedrock Aquifers
Uranium by Aquifer Group
222Radon by Aquifer Group
Comparison of Uranium and 222Radon in Drinking-Water Supply and Monitoring Wells
Relation of Uranium and 222Radon in Ground Water to Terrestrial Gamma-Ray Emissions
Correlations of Uranium and 222Radon with Ancillary Data
Anomalously High Uranium and 222Radon Concentrations and Related Factors
New York and New England Crystalline Aquifer Group
West-Central Glacial Aquifer Group
Columbia Plateau Glacial Aquifer Group
Summary and Conclusions
References Cited
Appendix 1. Abbreviations and descriptions of National Water-Quality Assessment (NAWQA) program well networks used to study water quality in glacial, Cambrian-Ordovician, and New York and New England crystalline aquifer systems in the northern United States, 1993–2003.
Appendix 2. Statistical summary of uranium and 222radon concentrations in ground water in the NAWQA well networks used to study water quality in glacial, Cambrian- Ordovician, and New York and New England crystalline aquifer systems in the northern United States, 1993–2003.
Appendix 3. Selected rho and probability values from Spearman correlations of selected trace elements, major ions, and physical properties in ground water, National Uranium Resource Evaluation program streambed sediment, terrestrial gamma-ray emissions, and ancillary data with uranium concentrations in ground water, by aquifer group, in the northern United States, 1993–2003.
Appendix 4. Selected rho and probability values from Spearman correlations of selected trace elements, major ions, and physical properties in ground water, National Uranium Resource Evaluation program streambed sediment, terrestrial gamma-ray emissions, and ancillary data with 222radon concentrations in ground water, by aquifer group, in the northern United States, 1993–2003.
Apppendix 5. Significant rho and probability values from Spearman correlations of selected trace elements, major ions, and physical properties in ground water, National Uranium Resource Evaluation program streambed sediment, terrestrial gamma-ray emissions, and ancillary data with uranium concentrations in selected NAWQA well networks in the Columbia Plateau glacial, West-Central glacial, and the New York and New England crystalline aquifer groups in the northern United States, 1993–2003.
Appendix 6. Significant rho and probability values from Spearman correlations of selected trace elements, major ions, and physical properties in ground water, National Uranium Resource Evaluation program streambed sediment, terrestrial gamma-ray emissions, and ancillary data with 222radon concentrations in NAWQA well networks in the New York and New England crystalline aquifer group in the northern United States, 1993–2003.
1–2. Maps showing—
1. Locations of National Water-Quality Assessment (NAWQA) regional assessments in principal aquifers.
2. Locations of National Water-Quality Assessment (NAWQA) program study units in the northern United States.
3. Diagram showing uranium-238 radioactive decay series.
4–9. Maps showing—
4. Generalized glacial geologic map of the upper Midwestern United States and names of major glacial lobes that were used to modify the glacial aquifer framework.
5. Distributions of (A) equivalent 232thorium and (B) equivalent 238uranium concentrations of near-surface sediments from aerometric gamma-ray surveys in the upper Midwestern United States used to modify the glacial aquifer framework.
6. Locations of generalized aquifer groups in the northern United States.
7. Distribution of (A) uranium and (B) 222radon concentrations in sampled wells in the glacial aquifer groups in the northern United States, 1993–2003.
8. Distribution of (A) uranium and (B) 222radon concentrations in sampled wells in the New York and New England crystalline aquifer group in the northern United States, 1993–2003.
9. Distribution of (A) uranium and (B) 222radon concentrations in sampled wells in the Cambrian-Ordovician aquifer group in the northern United States, 1993–2003.
10–13. Graphs showing—
10. Relation of the 75th percentile of concentrations of uranium in ground water to the 75th percentile concentrations of terrestrial (A) equivalent 238uranium and (B) equivalent 232thorium; and 75th percentile of concentrations of 222radon in ground water to 75th percentile concentrations of terrestrial (C) equivalent 238uranium and (D) equivalent 232thorium in ground-water samples from wells in glacial, Cambrian-Ordovician, and New York and New England crystalline aquifer groups in the northern United States.
11. Relation of concentrations of (A) uranium and (B) 222radon to gross alpha particle activity; and concentrations of 222radon to (C) uranium and (D) lead in ground-water samples from wells in the New York and New England crystalline aquifer group in the northern United States, 1993–2003.
12. Relation of concentrations of uranium to concentrations of (A) calcium, (B) selenium, (C) strontium, (D) lithium, (E) boron, and (F) sodium in ground- water samples from the West-Central glacial aquifer group in the northern United States, 1993–2003.
13. Relation of concentrations of uranium to concentrations of (A) bicarbonate, (B) total dissolved solids, and (C) pH, and (D) relation of concentrations of nitrate to concentrations of total dissolved solids in ground-water samples from wells in the Columbia Plateau glacial aquifer group in the northern United States, 1993–2003.
Ayotte, J.D., Flanagan, S.M., and Morrow, W.S., 2007, Occurrence of Uranium and 222Radon in Glacial and Bedrock Aquifers in the Northern United States, 1993–2003: U.S. Geological Survey Scientific Investigations Report 2007–5037, 84 p.
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