Identification of Groundwater Arsenic Contaminated Vulnerability Zones in Alluvial Tract of West Bengal, India

Abstract

Underground water is regarded to be free from all types of pollutants hence it is considered to be safe
for drinking. Consequentially, it is a predominant source of drinking water in several parts of the world
particularly in the developing countries. Regrettably, empirical studies have also been conducted in
other parts of the World and it is found that in twenty countries the subsurface water is contaminated
with arsenic. Serious arsenic contamination is reported along the River Bhagirathi in Ganga–
Brahmaputra delta in the linear tract of 470 km. The occurrence of arsenic in groundwater is mainly
in the shallow and intermediate aquifer, the deeper aquifers are free from contamination. Arsenic
mobilization in water is favoured by desorption of arsenic from iron and other metals oxides. In Bengal
Plains such conditions tend to occur in shallow aquifers in quaternary strata underlying the regions
large alluvial and deltaic plains. The occurrence of arsenic in groundwater is influenced by local
geology, geo-chemistry and hydrology of the alluvial aquifers. The present study envisages studying the
spatial pattern of groundwater contamination in West Bengal and identifies the arsenic contaminated
vulnerability zones. Spatial variation in respect to the depth and proximity to river Bhagirathi is noticed
in the alluvial tract.