Post-monsoon groundwater hydrogeochemical characterization and quality assessment using geospatial and multivariate analysis in Chhotanagpur Plateau, India.

A hydrogeochemical study of groundwater in Chhotanagpur Plateau, India, was accomplished to evaluate general hydrochemistry, hydrogeochemical processes and quality for irrigation purposes. Samples were collected and analysed for physico-chemical parameters including pH, conductivity and major ions. The analytical results indicate that groundwater is acidic to slightly alkaline. The overall ionic concentration in the area follows the order: Ca²⁺ > Mg²⁺> Na⁺ > K⁺ > NH₄⁺ > Li⁺ and HCO₃⁻ > Cl⁻ > SO₄²⁻ > NO₃- > F⁻ > PO₄⁻. Rock weathering, in particular carbonate and silicate weathering, determines groundwater hydrochemistry. The bivariate plot of (Ca + Mg) versus (HCO₃ + SO₄) reveals that the reverse ion exchange process has contributed to the hydrochemistry of the region. Piper diagram reveals that most of the groundwater samples are Ca–HCO₃ and mixed Ca–Mg–SO₄ type while some samples are Ca–Cl type. The results of the principal component analysis highlight that geological factors determine the characteristics of groundwater. However, anthropogenic activities like urban sewage discharge, chemical and pesticide discharge, and mining activities have a detrimental impact on groundwater quality. Spatial variation in the composite groundwater quality index for irrigation calculated by inverse distance weighted method reveals that the groundwater quality ranges from good to excellent in 16.5% and 83.5% of the samples, respectively. In a few samples, higher concentrations of magnesium, sodium and sulphate make the groundwater unsuitable for irrigation. The study recommends that anthropogenic activities should be carried out properly to ensure the long-term sustainability of groundwater in the area. The findings will be helpful to government officials and policy planners for proper groundwater management. [ABSTRACT FROM AUTHOR]