5-Arsenic Contamination of Ground Water in West Bengal (India) - Build-Up in Soil Crop Systems.

Abstract

The widespread arsenic (As) contamination in groundwater in parts of West Bengal (India) and Bangladesh is well documented In West Bengal alone, 75 blocks, located primarily in 5 districts on the eastern bank of the river Bhagirathi, are affected, with 5-6 million population reportedly drinking groundwater laden to various degrees with As contamination. A large number ofp eople have actually shown the symptoms of As poisoning culminating into several deaths. A large part of the Bengal delta basin bound by the rivers Bhagirathi and Padma is affected. Since a greater part of this delta has fallen in Bangladesh, the districts of Bangladesh contiguous to the contaminated zones of West Bengal are more widely affected by arsenic contamination of groundwater. The source of such contamination is believed to be of geogenic origin. The exact sequence of geochemical reactions that lead to the release of As in groundwater from the aquifer sediments, however, is still debated. This indeed calls for an immediate attention since what remains essentially a point and fixed source of As contamination as for drinking water (e.g., a tubewell discharging contaminated water) may very well become a diffuse and uncertain source of contamination when As finds its way into the food web accompanied by possible biomagnification up in the food chain. Indeed different crop plants raised in a crop cafeteria experiment exhibited varying tendencies to accumulate As. Such accumulation in different plant parts also tended to fall off in the following sequence: root> stem>leaf> economic produce. Moreover, inclusion of pulses/other legumes/green manure crops in the cropping sequences, coupled with organic manure addition, was found helpful in moderating As build-up in soil and plant parts. Notwithstanding what is stated above, much more and sustained research work remains to be done to characterize the entire gamut of intricacies of As contamination spectrum in soil-plant-animal system, as well as evolve effective remedial measures to contain the toxin in the said system.