Hydrogeochemistry of the alluvial aquifers of the central Gangetic Plain in India: constraints on source and mobility of arsenic

Until recently, most estimates of arsenic (As) pollution have focused on the predominance of As poisoning in the groundwater of West Bengal (India) and Bangladesh (Ahmed et al., 2004), which has been thought to be limited to the Ganges Delta (the lower Ganges Plain). Several authors suggested that the reductive dissolution of Fe(Ill)-­ oxyhydroxides in strongly reducing conditions of the young alluvial sediments is the cause for As mobilization (Bhattacharya et al., 1997; Ahmed et al., 2004; McArthur et al., 2001; Nickson el al., 1998; von Bromssen et al., 2007). Holocene alluvial aquifers of Ballia, Ghazipur and Bhagalpur district in the middle Gangetic Plain have high concentra­tions of geogenic As. The As contaminated aquifers are pervasive within lowland organic rich, clayey deltaic sedi­ments in the Bengal Basin and locally within simi­lar facies in narrow, entrenched river valleys within the Ganges Alluvial Plain (Acharyya & Shah, 2004; Mukherjee et al., 2006). This study has been carried out with the following objectives: I) to quantify the As in the groundwater of the Ghazipur District, Uttar Pradesh, India, and 2) to understand the mechanism controlling the mobilization of As and its evolution