Integrated assessment of groundwater quality suitability and heavy metal-induced health risks during the post-monsoon season near coal mining areas, Jharkhand, India.

Groundwater is the primary source of freshwater for drinking, agriculture, and industrial activities in mining-intensive regions; however, its quality is increasingly threatened by acid mine drainage (AMD) and heavy metal contamination associated with coal mining. Despite the environmental significance of the Magadh-Amrapali coalfield, integrated post-monsoon investigations on groundwater quality, heavy metals and health risks remains limited. The post-monsoon season was selected because groundwater quality reflects the combined effects of monsoonal recharge, contaminant leaching and dilution. This study, covering 198 km2 surrounding the mining area operated by Central Coalfields Limited, Jharkhand, India, analyzed thirty groundwater samples for 13 physicochemical parameters and six heavy metals (Fe, Cr, Ni, Cu, Zn, and As) using conventional analytical techniques and inductively coupled plasma-optical emission spectrometry( ICP-OES). Entropy-Weighted Water Quality Index (EWQI) and traditional Groundwater Quality Index (GWQI) were comparatively evaluated, with EWQI applying objective entropy-based parameter weighting to reduce subjectivity, while GIS-based Inverse Distance Weighting (IDW) described spatial contamination. Results revealed neutral to slightly alkaline groundwater (pH 7.13-7.70), with iron exceeding the WHO guideline in 63.3% of samples. EWQI demonstrated better performance over GWQI (R2 = 0.87; MAPE = 6.67%). Principal Component Analysis explained 63.27% of the total variance, while Piper analysis identified Ca-Mg-Cl/SO4 as the dominant hydrochemical facies. Health-risk assessment indicated non-carcinogenic risks, expressed as Hazard Quotient and Hazard Index (HI), with HI >1 and elevated carcinogenic risks (CR) from arsenic and hexavalent chromium, particularly among children. The integrated approach provides a robust framework for groundwater management and sustainable water-resource protection in coal-mining regions.