| Popis: |
Located in southwest Ohio, the Mason and also the Lebanon Correctional Institute drinking water distribution systems obtain their water from the Shaker Creek “buried valley” Aquifer. The Pleistocene valley contains glacial outwash material and some lake clays incised into the limestone-shale bedrock. Analyses were done in water, aquifer material and bedrock samples. The results of arsenic in water ranged from 4-18 µg/L, and show that many of these samples are above the USEPA MCL. Thus, both systems have concerning arsenic levels. Arsenic analyses in the bedrock and glacial outwash material ranged from 4-40 ppm. Therefore, arsenic in the groundwater could be sourced from the glacial aquifer material and/or from the surrounding bedrock. The bedrock geology of the area of study consists of Upper Ordovician-Lower Silurian limestones and shales of southern Ohio and northern Kentucky. The bedrock formation studied and that partly influence the water chemistry in the Shaker Creek buried aquifer is the Kope Formation. Stable isotope analysis of sulfur was used for this study. Many of the geochemical characteristics of arsenic are analogous to those of sulfur. Biogenic reduction is the dominant form of sulfur fractionation in nature and is mainly a product of sulfur reducing bacteria. The present thesis is focused in two main parts. First part covers the study of arsenic in solids and sulfur isotopes were used to calculate sedimentation rates in the Kope Formation. Second part includes the study of arsenic in groundwater and its source in the Shaker Creek Aquifer. This study presents a model of the possible sources and mechanisms of arsenic in groundwater. Sulfur isotopes were used to provide a chemical assessment and a comparison of sulfur isotopes in the bedrock with dissolved sulfur in the aquifer as a test for arsenic release by pyrite dissolution. |
