Mobility of arsenic in the sub-surface environment: An integrated hydrogeochemical study and sorption model of the sandy aquifer materials

International audience; Groundwater and aquifer materials have been characterized geochemically at a field site located in the Chakdaha municipality of West Bengal, India. Sorption experiments were also carried out on a sandy aquifer material to understand the mobility of arsenic (As) in the sub-surface environments. The result shows that the areas associated with high groundwater As (mean: 1.8 μM) is typically associated with low Eh (mean: -129 mV), and high Fe (mean: 0.11 mM), where Fe2+/Fe(OH)3 couple is controlling groundwater redox potential. Analysis of the aquifer material total concentrations showed the dominance of As (range: 8.9-22 mg kg-1), Fe (range: 3.0-9.7% as Fe2O3) and Mn (range: 0.05-0.18% as MnO) in the silt-/clay-rich sediments; whereas fine-/medium-sand rich sediment contains considerably lower amount of As (