The U.S. Geological Survey (USGS), in cooperation with the Miami Conservancy District, collected and analyzed samples of the aquifer materials and ground water from multiple depths at two sites in northern Preble County, Ohio. The aquifer materials included glacial deposits and Silurian carbonate bedrock. In the study area, elevated arsenic concentrations have been detected in ground water from both types of aquifers.
The aquifer materials were described in terms of the stratigraphy and the bulk elemental composition of 70 samples. In addition, six water-producing horizons were selected for more detailed study; ground-water quality was analyzed, microanalytical techniques were used to examine thin sections of the aquifer materials, and simplified geochemical modeling was done to identify plausible reactions between the ground water and aquifer materials.
At both study sites, the highest solid-phase arsenic concentrations were from a roughly similar stratigraphic position - a transition zone that extends from just above the Wisconsinan/Illinoian contact to just below the Pleistocene/Silurian contact.
For carbonate bedrock, the solid-phase arsenic concentrations were generally low (
