Risk Assessment of Groundwater Contamination by Heavy Metals in the Gangetic Plain: A Multivariate Statistical and Index-Based Study

Groundwater in the Gangetic Plain of India is increasingly vulnerable to heavy metal contamination, raising serious public health concerns. This study analyzed 12 heavy metals (As, Cr, Ni, Mn, Fe, Zn, Pb, Cu, Se, Mo, Cd, and Co) in 30 groundwater samples using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Statistical evaluations included Shapiro-Wilk normalization, Pearson correlation (SPSS v25), and Principal Component Analysis (OriginLab v10.15). Heavy Metal Pollution Index (HPI), non-carcinogenic Health Risk Assessment (HI), and carcinogenic risk (CR) analyses were performed. The results showed that 70% of the samples from Ballia exceeded the HPI threshold (>100), with the highest value being 328.77. Lead (Pb) and Arsenic (As) were the dominant contributors to non-carcinogenic risk, with HI values peaked at 28,334.8. The carcinogenic risk values for As and Ni exceeded the acceptable limits in all districts, with Prayagraj and Ballia showing total CR values of 2.17 and 3.00, respectively. Strong correlations among metals (e.g., Cd–Mn, r = 0.80) suggest anthropogenic origins, particularly from industrial and agricultural sources. These findings highlight the urgent need for routine monitoring, point-source control, and localized treatment to ensure groundwater safety.