Geochemical modeling to infer genetic origin of groundwater and associated health risks in desertic aquifers

Abstract

Lower rainfall coupled with higher evapotranspiration leads to enhanced salinity and inorganic contamination of groundwater in arid and semi-arid regions. In this study, 100 groundwater samples were collected from a part of the Thar Desert of India and analysed for various physico-chemical water quality parameters for quality assurance for potablewater supply. The electrical conductivity of the samples showed an ion-enriched aquifer environment with high alkalinity. The concentration of Na+, SO42−, Cl−, NO3− and F− ions in most of the samples were above the World Health Organization (WHO) guidelines for drinking water, posing a major public health concern. Saturation indices (SI) indicates that the dissolution of calcite bearing minerals and ion-exchange were major processes controlling the groundwater chemistry in the region. Most of the samples are oversaturated with aragonite, calcite, chalcedony, and dolomite while undersaturated with anhydrite, gypsum, halite. The results suggest that weathering of aquifer minerals and salinization due to high evaporation controls the quality and origin of major ions. The Na–Cl and Na–HCO3 water facies indicates the influence of evaporation and thus conducive condition for F− enrichment in groundwater while NO3− is mostly due to anthropogenic activities. The health index (HI) for risk assessment suggests both F− and NO3− contribute to the health risk of the residing population as the HI values were found to be > 1 in 97% and 93% for children and adults, respectively. The treatment technologies should be adopted to remove the multiple contaminants present in the groundwater of this region.