Radium Testing of Groundwater in U.S. Shows Central, East Coast Regions are Most Susceptible

New USGS report finds levels of radium detected exceed EPA drinking water standards

Groundwater in aquifers on the East Coast and in the central U.S. has the highest risk of contamination from radium, a naturally occurring radioactive element and known carcinogen, according to a study conducted by the U.S. Geological Survey (USGS).

The study reports radium was detected in concentrations that equaled or exceeded U.S. Environmental Protection Agency (EPA) drinking water standards in more than one in five wells tested in the Mid-Continent and Ozark Plateau Cambro-Ordovician aquifer systems, underlying parts of states such as Arkansas, Illinois, Indiana and Iowa, and the North Atlantic Coastal Plain aquifer system, underlying parts of Delaware, Maryland, New Jersey, New York, North Carolina and Virginia.

Radium is generally present at low levels in soil, water and rocks, including groundwater. However, the study found that if the groundwater has low oxygen or low pH, radium is more likely to dissolve and become present. Low oxygen conditions were prevalent in the Mid-Continent and Ozark Plateau Cambro-Ordovician aquifer systems, and low pH conditions were prevalent in the North Atlantic Coastal Plain aquifer system. Low oxygen or low pH conditions were associated with more frequent detections of radium in other aquifers as well.

"This is the first nationwide study to identify geochemical factors present in many aquifers, such as low dissolved oxygen or low pH, that make groundwater more susceptible to radium contamination," said Jeffrey Fischer, USGS hydrologist and a co-author of the paper. "These simple geochemistry measurements are good indicators of where radium is likely to exceed a standard and can help managers and the EPA anticipate areas where radium may be elevated."

More than 1,000 wells were sampled by the USGS National Water-Quality Assessment Program (NAWQA) from 1990 to 2005 and analyzed for radium-226 and radium-228 for comparison to the EPA drinking water standard. A subset of 645 water samples were analyzed for the short-lived radium radionuclide, radium-224, which had not previously been measured in many parts of the country, but is a concern in drinking water. A specific drinking water standard has not been established for this form of radium. The study examined untreated well water, and the findings represent the quality of water in aquifers before treatment.

The study, titled "Occurrence and Geochemistry of Radium in Water from Principal Drinking-Water Aquifers of the United States" by Zoltan Szabo, Vincent T. dePaul, Jeffrey M. Fischer, Thomas F. Kraemer and Eric Jacobsen, is published in the journal “Applied Geochemistry.”

U.S. Geological Survey

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