ABSTRACT
Arsenic contamination of groundwater in these areas has mainly occurred due to natural reasons (Bose & Sharma 2002, Ahmed et al. 2004). According to the most accepted and most plausible theory, in the Late Pleistocene/ Holocene period, iron and arsenic-bearing minerals in upstream of the Ganges river belt may have undergone oxidation due to exposure to atmosphere during erosion, resulting in subsequent mobilization of arsenic and iron downstream. The mobilized iron got precipitated as iron oxy-hydroxide and arsenic got either adsorbed onto or co-precipitated with iron oxy-hydroxide. These arsenic containing precipitates then got deposited in the Gangetic delta region in the form of iron oxy-hydroxide coating on aquifer sediments. In the present day situation, reducing conditions prevailing in the sub-surface environment is causing dissolution of this coating and mobilization of adsorbed/co-precipitated arsenic (Bhattacharya et al. 1997, Nickson et al. 1998, 2000, McArthur et al. 2001.
