Sediment and hydrogeochemical contrasts between low and very high arsenic affected areas west and east of river Bhagirathi, West Bengal, India

Arsenic concentrations in Bengal Delta sediments are comparable to global averages, but its highly heterogeneous spatial distribution (on scales of meters to kilometers) in sediments and ground-waters is poorly understood. This work targets two very high arsenic (As) affected areas east and two low As affected areas west of the river Bhagirathi in the district of Murshidabad. Detailed sediment chemistry along with hydro-geochemistry and reactive transport models, are coupled to understand the release mechanism of As into the groundwaters in this work. On the one hand this work proposes that the perennial ponds are not the source of dissolved organic matter that mobilizes As at shallow depths in this aquifer and on other hand proposes microbially-mediated oxidation-reduction and competitive ion-exchange processes occurring within the sediments of the shallow aquifers that drive As mobilization and sequestration.