National Water-Quality Assessment (NAWQA) Program
Szabo, Zoltan, Fischer, J.M., and Hancock, T.C., 2012, Principal aquifers can contribute radium to sources of drinking water under certain geochemical conditions: U.S. Geological Survey Fact Sheet 2010-3113, 6 p.
Figure 2. Oxygen-poor groundwater contains elevated concentrations of combined radium (radium 226 plus radium 228) compared to groundwater with higher dissolved oxygen concentrations. Low-oxygen conditions decrease the likelihood of adsorption of radium to aquifer materials enhancing the mobility of radium into groundwater. In this study low-oxygen conditions were generally found in parts of the Appalachian Piedmont Mesozoic Basins, New England-New York crystalline rock, Mid-Continent and Ozark Plateau Cambro-Ordovician , and parts of the Glacial aquifer systems in the eastern United States. Oxygen concentrations less than 1 milligram per liter increase the likelihood that combined radium will exceed the combined radium drinking water standard.