Possible relationships between groundwater arsenic concentration and alluvial sediment characteristics in a similar to 19 km(2) area in West Bengal have been investigated using a combination of hydrogeochemical, lithogeochemical and geophysical techniques. Arsenic hotspots, typically associated with elevated groundwater Fe and Mn, were found to be correlated to some extent with old river channels (abandoned meanders, oxbow lakes), where sandy aquifers included intercalated fine-grained overbank deposits rich in As, Fe, Mn and C-org. Otherwise no demonstrably significant overall differences in any of lithology, grain-size distribution, mineral composition or Fe, Mn and organic C content of the sediments were found between two representative sites with contrastingly low (<50 mu g l(-1)) and high (>200 mu g l(-1)) As groundwater contents.Our results are consistent with microbially mediated redox reactions controlled by the presence of natural organic matter within the aquifer and the occurrence of As-bearing redox traps, primarily formed by Fe and Mn oxides/hydroxides, being the most important factors which control the release of As into shallow groundwaters at the study site.
Nath, B., Berner, Z., Mallik, S. B., Chatterjee, D., Charlet, L., & Stueben, D. (2005). Characterization of aquifers conducting groundwaters with low and high arsenic concentrations: A comparative case study from West Bengal, India. Mineralogical Magazine, 69(5), 841-854. https://doi.org/10.1180/0026461056950292