Integrated Multivariate and Spatial Assessment of Heavy Metal Contamination and Associated Health Risks in Indo-Gangetic Alluvial Aquifer: A Case Study from the Gorakhpur District, India

Groundwater quality assessment is critical for sustaining safe drinking water supplies, particularly in vulnerable alluvial aquifers such as those of the Indo-Gangetic Basin. This study evaluates the concentration and distribution of eight heavy metals — Zinc (Zn), Chromium (Cr), Iron (Fe), Copper (Cu), Manganese (Mn), Arsenic (As), Lead (Pb), and Uranium (U) — alongside pH and Electrical Conductivity (EC) in groundwater samples collected from 32 locations across Gorakhpur District, Uttar Pradesh. Groundwater samples were collected and analysed following standard protocols. Samples were collected and analysed following APHA and WHO protocols. Descriptive statistics indicated that 68.8% of the samples exceeded WHO limits for iron, while manganese and arsenic exceeded safe levels in 6 and 1 samples, respectively. Spearman’s rank correlation analysis supported strong positive associations among Fe, Mn, and EC, suggesting a shared mobilization mechanism. Multivariate analysis through Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA) identified geogenic reductive processes as dominant contributors to Fe and Mn enrichment. while GIS-based spatial mapping highlighted distinct contamination hotspots in the central and northern parts of the district. Human health risk assessment showed Hazard Index (HI) >1 in 9 locations for adults, primarily due to iron and manganese exposure. Carcinogenic Risk (CR) assessment flagged elevated lifetime cancer risks (>10⁻⁴) at 16 locations due to arsenic, lead and uranium. These findings highlight localized but significant non-carcinogenic and carcinogenic risks, emphasizing the need for targeted mitigation, periodic monitoring, and community health surveillance. This integrative framework combining hydro-chemical assessment, multivariate statistics, spatial analysis, and health risk assessment provides a robust basis for sustainable groundwater management in vulnerable alluvial settings.