Sources and processes of groundwater arsenic mobilization in upper Jhelum basin, western Himalayas

Abstract Arsenic (As) concentration in groundwater is one of the worst problems we are facing owing to its carcinogenic effect. The problem should therefore be addressed scientifically. Although groundwater Arsenic (As) enrichment is reported in many basins across the globe, still scientists have long way to go. In the present study we present new As data in groundwater to understand the processes and aquifer environment responsible for the As mobilization in groundwater of upper Jhelum basin, western Himalayas. The groundwater in the unconsolidated aquifers is less mineralized, with low electric conductivity, moderate pH and is mainly of Ca-Mg-HCO3 type. The results suggest that carbonate dissolution, silicate weathering and active cation exchange is controlling the ionic composition of groundwater. Arsenic (As) concentration in groundwater showed a wide range (0.14 µg L−1–192 µg L−1), with 45% of water samples having As >10 μg L−1 (WHO guidelines for drinking water). The shallow groundwater wells were more As enriched than deep groundwater wells. Groundwater As showed significant correlation with redox sensitive parameters including Fe, Mn, pH, NH4-N, HCO3− and poor correlation with NO3− and SO42−. Besides the lower slope (w.r.t. GMWL) and higher isotopic values (δ18O and δ2H), we observed a significant correlation of δ18O with As, EC and Cl− in shallow groundwater. The study suggests that the source of As is from quaternary deposits of unconsolidated aquifers with their provenance from the volcanic, sedimentary and metamorphic rocks of Himalayan orogeny. The As release from these quaternary deposits requires a proper and favorable aquifer environment.