Multiple studies in the Bengal basin have shown that elevated As in groundwater coincides with reduced, relatively dark sediments of Himalayan provenance. In West Bengal state (India), As concentrations > 10 μg/L tend to occur east of the River Bhagirathi-Hoogly, the main distributary of the Ganges. Associations among sediment chemistry and mineralogy for four cores from either side of the Bhagirathi-Hoogly (cores 1 and 2 to the east, 3 and 4 to the west) in Murshidabad district were investigated. Ten sediment samples were collected from each boring at various depths to a maximum of 38 to 43 m. Sediment chemistry was investigated using sequential extraction, digestion and analysis of As, Al, Ca, Fe, and Mn on an ICP-OES and GFAAS, and by total carbon analysis on a CNS analyzer. Organic carbon content was measured gravimetrically by HCl digestion. Sediment mineralogy was investigated using thin-section petrography and a microprobe EDS. Pyroxenes and phyllosilicates appear to be the primary sources of arsenic in the study area. Additionally, core 4 sediments are mineralogically similar to cores 1 and 2 despite differences in arsenic concentrations in the groundwater. We conclude that a 65-ft (20-m) silt layer overlying the aquifer sands in core 4 acts as a local aquitard and restricts arsenic mobilization locally.
| Identifer | oai:union.ndltd.org:uky.edu/oai:uknowledge.uky.edu:ees_etds-1002 |
| Date | 01 January 2011 |
| Creators | Eastridge, Emily |
| Publisher | UKnowledge |
| Source Sets | University of Kentucky |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Theses and Dissertations--Earth and Environmental Sciences |
Page generated in 0.0019 seconds