Groundwater quality, fluoride health risk and geochemical modelling for drinking and irrigation water suitability assessment in Tundla block, Uttar Pradesh, India

Groundwater quality assessment is crucial for determining the suitability of water resources required for human consumption and agriculture. To investigate the quality of groundwater in Tundla block, Uttar Pradesh, India, 50 samples were harvested from boreholes and hydrochemistry analysis was carried out. Entropy water quality index (EWQI) and irrigation water quality index (IWQI) were computed employing different suitability pa-rameters to assess its suitability for drinking and irrigation purposes. Geochemical modelling using PHREEQC served to simulate the solubility equilibria of mineral combinations by determining the saturation index (SI). Based on EWQI values the groundwater samples fall under two classes, these being medium (70%) and poor (30%) quality. The USSL plot indicated high salinization of the groundwater sample. Piper plot reveals the presence of two hydrogeochemical facies, viz. mixed type (72% samples) and Cl--Na+ type (28% samples). Geochemical modelling based on thermodynamic laws confirms the presence of high-solubility evaporitic minerals such as anhydrite, fluorite, and gypsum, and more stable precipitated mineral types like calcite, aragonite, and dolomite. A fraction of samples showed over-saturation of some minerals, namely dolomite (38%), calcite (32%), and aragonite (20%). Around 28% of the samples exhibited a large amount of F- in groundwater at concentrations higher than BIS-prescribed safe limits (> 1.5 mg L-1). Conducting health risk assessment shows that children and infants in the region are at a non-cancer risk (HQ > 1) due to sustained F -intake through drinking water. The spatial distribution of EWQI revealed medium-quality groundwater for drinking purposes in the south-central sub-area of Tundla. With reference to irrigation, groundwater sources are of better quality in the south sub-area.