Theme 3-8-Arsenic in groundwater and redox conditions in the Bengal delta – Possible in situ remediation

Abstract

Widespread arsenic contamination in groundwater in the Bengal Delta seems to be largely natural depending on reducing conditions in the aquifers. Reduction of ferric hydroxides with adsorbed arsenic species occurs at intermediate depth. In situ remediation might be achieved by artificial recharge stabilising the ferric hydroxides. It might however be problematic to keep the aquifer oxic. Sulphate levels are generally low and sulphur deficiency for crops common. The low sulphate levels favour methane fermentation over sulphate reduction. Application of gypsum to the surface soils might favour immobilisation of the arsenic in the form of sulphides.