Hydrogeochemical Study of Arsenic Affected Areas of West Bengal, India, and Similar Contaminated Sites in Midwestern United States
Kansas State University Department of Geology Manhattan, KS 66506
In eastern India, the aquifer that supplies much of the population with drinking water in Ganges-Brahmaputra-Meghna delta is contaminated with naturally-occurring arsenic. Additionally, traces of anthropogenic arsenic higher than the maximum acceptable amount (10 ppb) recommended by United States Environmental Protection Agency and World Health Organization have been found in areas of Kansas and Missouri rivers. Groundwater and shallow aquifer sediments (2m-40m) have been collected from areas within Murshidabad district, West Bengal, India, to study their hydrochemical and geochemical properties to correlate between groundwater arsenic concentrations and solid-phase arsenic concentrations. One area with very low (<1ppb) arsenic west of the Bhagirathi River and four areas with very high (>4000ppb) arsenic east of the Bhagirathi have been targeted in this study to understand the sediment dynamics within this fluviodeltaic system. The major minerals dominating the aquifer sediments are phyllosilicates, apatite, prismatic Fe-Mg rich minerals, magnetite, and phosphates such as vivianite, along with siderite, and the expected quartz and feldspars. Preliminary analysis of the groundwater shows no correlation between arsenic concentrations and dissolved oxygen or conductivity. Particle size analysis and mineral characterization, Scanning Electron Microscopy, X-ray Diffraction, and sequential extractions studies are being done to better understand the leaching mechanism(s) of arsenic from these reworked sediment grains under changing redox conditions to account for observed varying concentrations of arsenic. Once these analyses are completed, similar field work and laboratory analysis will ensue with surface and aquifer sediments and water samples collected from areas reported in the Midwestern United States.
AAPG Search and Discovery Article #90094 © 2009 AAPG Foundation Grants in Aid