Abstract
Water contamination from sulphate is a growing concern in the Neyveli region of South India, where industrial activities have significantly impacted water quality. This study presents a comprehensive assessment of sulphate contamination and associated non-carcinogenic health risks in surface- and groundwater systems within the Neyveli lignite-mining region of Tamil Nadu, India. A stratified pre-monsoon survey of 81 samples in which 30 groundwater samples (bore wells, hand pumps, and open wells), and 51 surface water (ash ponds, drainage canals, ponds) were analysed for pH, EC, TDS, salinity, and sulphate using UV-VIS spectrophotometry, and spatial patterns were visualised via IDW interpolation in ArcGIS 10.8. Sulphate concentrations ranged from ~ 6-2,486.7 mg L⁻¹, exceeding the WHO permissible value of 400 mg L⁻¹; hotspots clustered near mine pits, ash-pond cells, and drainage corridors (SW3, SW36, SW38, SW50, GW10). Correlation analysis indicated negligible to very weak associations with EC/TDS/salinity (r ≈ 0.15-0.17), suggesting localised enrichment mechanisms rather than uniform ionic loading. Age-/gender-specific risk appraisal showed Hazard Quotient (HQ) > 1 at 19 sites for children (23.4%), 18 for teenagers (22.2%), 13 for adult males (16.0%), and 11 for adult females (13.6%). Critical contamination hotspots were identified at SW3, SW36, SW38, SW50, and GW10, where HQ values consistently exceeded acceptable risk thresholds across multiple demographic categories. Analytical QA/QC supported data reliability (recoveries 96.4 ± 2.1%, duplicate RPD 1.8-4.2%). In response to these findings, Neyveli Lignite Corporation India Limited (NLCIL) has undertaken several mitigation initiatives, including Water Treatment Plants and groundwater recharge structures. To enhance water quality management, remediation strategies like RO, gypsum ion exchange, fly ash adsorption, and sulphate-reducing bioreactors are recommended.