Geospatial, index-based and statistical analysis of potentially toxic elements in groundwater of Kumaun Sub-Himalayan plain, India

The deterioration of groundwater quality is a serious concern across the globe, especially where it serves as a primary source of drinking water. This study aimed to investigate the presence and associated health risks of seven potentially toxic elements (PTEs), namely arsenic (As), cadmium (Cd), chromium (Cr), mercury (Hg), molybdenum (Mo), nickel (Ni) and lead (Pb) in groundwater from Kumaun Sub-Himalayan Plain, India. For this purpose, an integrated framework was applied that combines geospatial mapping to identify spatial distribution patterns, pollution index analysis and risk assessment to evaluate contamination status and correlation analysis to apportion pollution sources. Quantification of PTEs was performed using Inductively Coupled Plasma Mass Spectrometry (ICPMS). The concentrations (µg L -1 ) of As, Cd, Cr, Hg, Mo, Ni and Pb were observed to fluctuate from 0.07 to 3.65, Below Detection Limit (BDL) to 2.43, 0.21 to 117.82, BDL to 0.13, 0.1 to 6.46, 0.26 to 7.36 and 0.02 to 8.71, respectively. The overall pollution indices indicate generally low contamination by PTEs across the study area. However, the localized Cr concentrations in 37.5% of the samples was observed to exceed the Bureau of Indian Standards (BIS) and WHO permissible limits. Moreover, the average carcinogenic risk from ingested Cr, As and Cd exceeded the recommended safety threshold, while the dermal exposure risk from Cr surpassed acceptable limits. It is important to note that pollution index-based classification reflects water quality at a single point in time relative to regulatory standards, whereas carcinogenic risk assessment considers long-term exposure. Consequently, even low concentrations of PTEs may pose carcinogenic risks over prolonged periods. The localized exceedances warrant continuous monitoring, targeted mitigation measures and site-specific groundwater management. The study emphasizes the importance of groundwater monitoring to ensure safety of drinking water and address possible health risks in the area. The baseline data from Kumaun Sub-Himalayan Plain of India provide valuable insights to guide targeted remediation strategies and promote sustainable groundwater management.