Co-relation of Arsenic contamination with water table fluctuations and groundwater flow dynamics: A case study in a part of Bengal basin

Abstract

ABSTRACT Temporal and seasonal variations of groundwater arsenic concentration are very significant for the exploration of its mobilisation mechanisms and to frame the policies of viable usage of arsenic-contaminated groundwater. Much less is known about the temporal and seasonal pattern of variation of arsenic contamination in shallow groundwater from the present study area (Karimpur blocks, Nadia district, West Bengal, India). So, to extend the understanding, the present study encompasses the steady monitoring of 15 wells of shallow depth from the study area for the period of 2014–2016. It has been observed that geochemical components were varying extensively during the period and the same trends follow for both Fe and As. During the period, the groundwater levels oscillated seasonally which promotes the reductive dissolution of Fe-oxides and/or oxy-hydroxides (As bearing minerals) which is aided by less dispersion of atmospheric oxygen into the shallow aquifers maintaining the reducing environment in the aquifers. The supply of dissolved organic matter into shallow aquifers was also evident by variation of Cl− ion concentration which may help to enhance arsenic mobilisation into shallow groundwater. Moreover, groundwater recharge from both regional rivers and perennial sources influences the evolution of anoxic conditions in the areas with low aquifers permeability consisting mainly of clayey and/or silty intercalations. Likewise, irrigation practices have been augmented to understand its role in arsenic mobilisation.