Hydrogeochemical characterization and quality assessment of groundwater in parts of Southern Gangetic Plain

A comprehensive assessment of groundwater is carried out in parts of the Southern Gangetic Plain to identify the hydrogeochemical processes influencing groundwater geochemistry and to ascertain the suitability of groundwater for drinking and irrigational uses. Results of detailed chemical analysis reveal that groundwater of the study area is slightly acidic (pH values from 6.2 to 7.37) during post-monsoon, with dominant concentrations of Na⁺ and Ca²⁺ cations and HCO₃ ⁻ and Cl⁻ anions. Groundwater chemistry is largely controlled by rock-weathering and ion-exchange processes with secondary contribution from anthropogenic sources. In particular, values of EC, total hardness and concentrations of Na⁺ and HCO₃ ⁻ exceed the prescribed limits of Indian and WHO water quality standards. Suitability of groundwater for irrigation purposes are evaluated on the basis of sodium adsorption ratio, sodium percent (%Na⁺), magnesium hazard, residual sodium carbonate and Kelley’s index. In this regard, nearly 40–50 % of the groundwater in the study area is found to be of excellent to good quality. In addition, principal component analysis, performed to identify the dominant geochemical processes, shows that the first three components are together account for 80.84 and 78.85 % of the total variance in the dataset for post-monsoon and pre-monsoon periods, respectively. This analysis also reveals key contributions from hydrogeochemical processes like mineral dissolution, silicate and carbonate weathering alongside anthropogenic activities like leaching of fertilizers from agricultural lands.