Hydrogeologic and geochemical studies of selected natural radioisotopes and barium in groundwater in Illinois. Research report No. 180 (final)

Dissolved concentration of the natural radioisotopes 222Rn, 226Ra, 228Ra, 230Th, 232Th, 234U, and 238U and the element Ba (2+) were investigated in a study of high concentrations of 226Ra, 228Ra, and Ba (2+) in groundwater from the Cambrian and Ordovician bedrock of northern Illinois. The high radium and barium concentrations are present in the major aquifers - the sandstone bedrock. Therefore, remedial well construction measures will not lower the concentrations. The combined concentrations of 226Ra and 228Ra range from 2.3 to 50.2 pCi/L; the majority of analyses exceed the drinking water reulations of 50.0 pCi/L. The high Ba (2+) concentrations occur in groundwater that is depleted in dissolved SO42- by anaerobic microbial reactions. A map presents the distribution of Ba 2+ in groundwater from the Cambrian and Ordovician bedrock in northeastern Illinois