Radioactive contaminants can migrate in groundwater over long distances faster than originally thought, according to the results of field tests at Oak Ridge National Laboratory in Tennessee. Approximately 50 percent of all Americans get their drinking water from groundwater sources, according to the U.S. Environmental Protection Agency. The study has broad implications for risk and performance assessments of current and future waste disposal facilities.
The research is reported in the Nov. 11 Web edition of Environmental Science & Technology, a peer-reviewed journal of the American Chemical Society, the world's largest scientific society. The article also will appear in the journal's Dec. 15 print edition.
Using non-radioactive surrogates injected into groundwater as tracers, the scientists found that dissolved humic material, naturally formed in soils during decomposition of plant matter, can bind radionuclides and prevent them from being retained in the soil, thereby speeding the migration of the contaminant. "The tracers moved at almost the same velocity as the groundwater," said the report's lead author John McCarthy, Ph.D., of the Oak Ridge facility, and were observed 10 to 80 meters from the injection site within a week or less. "This information opposed the results of laboratory tests that suggested contaminants strongly bind to the soil and move only centimeters a year."
"The results have significant implications as to the role than even typically low levels of dissolved humics in groundwater can play in contaminant mobility with respect to existing waste facilities and future repositories," said McCarthy.
There are thousands of waste disposal sites in the U.S. that handle hazardous materials, many of them operated by the Department of Energy, the Department of Defense or EPA, according to McCarthy. However, "we don't know how ubiquitous this facilitated transport process is because these sorts of studies have not been conducted elsewhere," he cautions. "I don't want to be an alarmist about this study," he adds.
The testing was carried out in conjunction with researchers from the University of Tennessee and Colorado State University.
A nonprofit organization with a membership of more than 155,000 chemists and chemical engineers, the American Chemical Society publishes scientific journals and databases, convenes major research conferences, and provides educational, science policy and career programs in chemistry. Its main offices are in Washington, D.C., and Columbus, Ohio.
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