OCCURRENCE AND DISTRIBUTION OF ARSENIC IN THE HYDROGEOLOGIC SYSTEM OF THE SOUTHERN CUMBERLAND PLATEAU OF TENNESSEE: A PRELIMINARY REPORT

The southern Cumberland Plateau in the vicinity of Sewanee, Tennessee is capped by the Pennsylvanian Warren Point Sandstone and Sewanee Conglomerate. Both formations are quartz arenites with volumetrically minor interbedded shales and coals. Liesegang bands are common within the units and are primarily hematite. Sandy loams developed atop these layers contain perched, discontinuous seasonal aquifers that served as an important water source for the region until the mid-20th Century. Six watersheds were analyzed for arsenic in ground water, surface water, soil, and bedrock. Arsenic concentrations in streams were less than 1 ppb, while concentrations in unfiltered ground water from the seasonal aquifers ranged from 20 to 95 ppb. It is therefore likely that past utilization of these aquifers for drinking water resulted in exposure to relatively high levels of arsenic. The immediate source of arsenic in ground water is the soil, which contains arsenic levels ranging from 2 to 6 ppm. Arsenic analysis of the Warren Point Sandstone and Sewanee Conglomerate reveal relatively low concentrations of arsenic (0.7 to 2.5 ppm in quartz-rich sandstone and conglomerate; 2 to 3 ppm in liesegang bands) and imply that the erosion of these layers is not the major source of arsenic in soils of the area. Coals and dark shales within the stratigraphically higher, highly eroded Whitwell Shale were determined to have the highest concentrations of arsenic in the area (11.1 to 35.1 ppm) and are the likely primary source of arsenic in soils in the region.