Arsenic contamination in parts of Yamuna sub-basin, West Bengal.

Abstract

Arsenic rarely occurs in free state and is generally found in combination with Sulphur, Oxygen and Iron. In the environment, Arsenic occurs as a result of several inputs that contain this element in organic and inorganic forms. Arsenic is present in Coal, Lead, Zinc, Gold and Copper ores in the form of several minerals viz. Arsenopyrite (FeAsS), Orpiment (As2S3), Realgar (AsS), Arsenolite (As2O3) and Lollingite (FeAs2). The commonly existing species in groundwater are in two forms viz. Arsenite [As(III)] which is the reduced state of inorganic Arsenic and Arsenate [As(V)], which is the oxidized state of inorganic Arsenic, The As(III) form is more mobile and toxic for living organisms. Recently, the symptoms of chronic arsenic poisoning have been observed in many parts of West Bengal (India) and Bangladesh. In the present study, an integrated evaluation of hydrogeology and hydrochemistry has been carried out by processing the available data of Yamuna sub-basin (Part of Nadia and North 24 Parganas district) of West Bengal in order to understand the possible reason of arsenic pollution in the ground water. Arsenic has generally been observed in higher concentration in shallow aquifer. Northwestern region of the study area has been observed to be the most effected with premonsoon periods exhibiting higher concentration. Transmissivity values have been observed to vary inversely with arsenic concentrations. Arsenic values have not indicated any well defined association with many other constituents. Arsenic buildup could also not be conclusively related to lowering of ground water table of the study area.