Integrated EWQI–Monte Carlo framework for assessing groundwater quality and health risk in the Khetri mining region of Jhunjhunu district, Rajasthan, India

In various parts of arid and semi-arid region of India such as Rajasthan people are mainly depended on groundwater for fulfil their daily demands like drinking and watering their crops. However, in the Khetri mining region of Jhunjhunu district, extensive mining and smelting of copper and associated sulfide minerals have led to heavy metal contamination and a deterioration in groundwater quality. Therefore, this study evaluates the overall groundwater quality and the related human health risks in the region severely affected by copper mining and metallurgical activities. We have collected total 59 groundwater samples from both pre- and post-monsoon periods and were examined for physicochemical parameters, cations, anions, and heavy metals (Pb, Cd, Cr, Cu, Fe). Multivariate analysis, including PCA and correlation, revealed that geogenic processes, such as carbonate and silicate weathering, dominate natural groundwater chemistry. Whereas anthropogenic inputs from mining, ore processing, agriculture, and industrial waste significantly elevate toxic metal concentrations. The elevated level of Pb, Cd and Cr were detected across many locations, often exceeding permissible limits. Non-carcinogenic risks (HI) for Cr, Pb and Cd surpassed the safe thresholds in many locations, and carcinogenic risks (CR) for Cr, Cd, and Pb exceeds the permitted limit of 1 × 10⁻⁴ at multiple sites, indicating significant long-term health threats. The integrated EWQI–Monte Carlo framework thus combines the objectivity of entropy-based weighting with the statistical power of probabilistic simulation, enabling a more realistic and comprehensive evaluation of both groundwater quality and the related human health risks. In addition of this, the risk assessment for human health (HRA) revealed that children are at more danger than adults due to their greater exposure per body weight. These findings clearly indicate an urgent need for groundwater quality management through the adoption of remediation actions and the exploration of alternative sources to protect community health from contaminated groundwater.