Isotopic and Geologic Studies to Identify the Sources of Sulfate in Groundwater Containing High Barium Concentrations

摘要

Dissolved barium in excess of the USEPA drinking water standard occurs in groundwater of a region of the Cambrian-Ordovician aquifer system in northeastern Illinois that is anomalously depleted in dissolved sulfate. The concentration of dissolved sulfate is an important control on the dissolved barium concentration because of the low solubility of the mineral barite (barium sulfate). The depletion of dissolved sulfate is believed to be due to bacterially mediated sulfate reduction occurring in zones of anaerobic conditions. The depletion of O2 in groundwater in confined regions of the flow system is interpreted as evidence of the importance of glacial processes to recharge of the groundwater.