Hydrogeochemical assessment of shallow aquifer in Chakdah, West Bengal for safe water supply

Abstract

ABSTRACT The shallow aquifer hydrogeochemistry and arsenic exposure from drinking water in rural Bengal have been vividly investigated in the present study. It has been observed that shallow aquifers (<50 m) are often contaminated with arsenic, whereas deeper aquifers (>100 m) are mostly free from arsenic contamination. In some pockets, deeper aquifers are contaminated which is surrounded by safer aquifers. Mostly, shallow aquifers (<50 m) are contaminated with arsenic surrounded by safe and/or deep aquifers (>100 m) with low arsenic concentrations and are scattered throughout the study area with more heterogeneity. Furthermore, sedimentological (color of the sediment and its successions) and/or geomorphological features (land-use pattern and local recharge) are playing a key role to control the arsenic distribution pattern in groundwater from the study area. They control local hydrogeochemical factors thereby mobilizing arsenic into groundwater. It has also been found that yellow sand aquifers are mostly free from arsenic contamination. The deeper aquifers mainly consist of coarse to medium sand (mostly yellow sand) which incorporates the relatively lower concentration of arsenic in groundwater. For the long-term mitigation options, the findings from this investigation are very useful.