ABSTRACT
The spatial distribution of groundwater arsenic is focused on the western part of the Bhagirathi River in Bengal Delta. About 21.26% of tubewells in Purbasthali Block contain arsenic above 10 µg/L (WHO guideline) and 41.73% of tubewells have iron above 1 mg/L (Bureau of Indian Standards guidelines is 0.3 mg/L). Maximum concentrations of arsenic and iron in tubewell samples are 374 µg/L and 17.6 mg/L, respectively. Mean value of arsenic and iron concentrations are 48 µg/L and 4.16 mg/L, respectively. It may be noted that 34.64% of tubewlls are located in the depth of 21 to 40 m. Most of the arsenic-contaminated tubewells are located within the depth of 21 to 40 m in the Holocene Newer Alluvium aquifers. Arsenic pollution in the Holocene aquifers is mostly confined in Katwa Formation. Sijua Formation is almost arsenic-safe in groundwater, which is in upper Pleistocene to lower Holocene in age. Most of the contaminated tubewells are located in Holocene Newer Alluvium and spatially associated with meander cut-offs, paleo-meander scars, abandoned channels and back swamp areas.
