National Water-Quality Assessment (NAWQA) Program
Modified from Szabo, Zoltan, dePaul, V.T., Fischer, J.M., Kraemer, T. F., and Jacobsen, Eric, 2012, Occurrence and geochemistry of radium in water from principal drinking-water aquifers of the United States: Applied Geochemistry v. 27, no. 3, p. 729-752.
Figure 3. Acidic groundwater contains elevated concentrations of combined radium (radium 226 plus radium 228) compared to groundwater with higher pH. Low-pH conditions decrease the likelihood of adsorption of radium to aquifer materials enhancing the mobility of radium into groundwater. In this study low-pH conditions were most commonly found in the North Atlantic Coastal Plain, but low-pH conditions were also found in the Southeastern Coastal Plain, and in parts of the Glacial aquifer system in the New England States. A pH less than about 6 increases the likelihood that combined radium will exceed the combined radium drinking water standard.