Appraisal of contamination levels, pollution sources and health risks of trace metals in the groundwater of Southern Pothohar, Pakistan

Abstract

The contamination of groundwater by trace metals is a significant concern on global scale as it presents direct and indirect hazards to the ecosystem and human health. However, only limited studies have focused on the risks of trace metals’ contamination in major agronomical areas of Pakistan. The present investigation was designed to evaluate the concentrations of selected metals (Mg, K, Ca, Na, Sr, Ag, Li, Zn, Mn, Fe, Co, Cu, Cd, Cr, Pb and Ni) and physicochemical characteristics (EC, pH, TDS, TH, TA, and Cl−) in the groundwater of Southern Pothohar region of Pakistan. Significant seasonal variations in the metal concentrations were detected; average levels of Ni (0.206 mg/L), Cr (0.085 mg/L), Cu (0.038 mg/L), Mn (0.029 mg/L), Ag (0.026 mg/L), and Cd (0.017 mg/L) were comparatively higher in summer, whereas mean values of Ca (9.210 mg/L), Sr (2.181 mg/L), Co (0.195 mg/L), Li (0.033 mg/L), and Zn (0.025 mg/L) showed relatively elevated concentrations in winter. Average contents of Co, Cr, Cd, Pb and Ni were observed to surpass the permissible limits in 37–99% of the samples established by national and international standards. Multivariate statistical analyses revealed that groundwater contamination was predominantly influenced by anthropogenic sources (mostly originating from agricultural waste, domestic waste, combustion processes, industrial effluents and automobile emissions). The Irrigation Water Quality Index (IWQI) value demonstrated that the groundwater is highly suitable for irrigation. Health risk estimation revealed that noncancer risk for Cd, Cr Ni, and Li surpassed the safe limit (HQing > 1) for adults while Pb and Co exceeded the safe limit (1.0) for children and adults in both seasons. Overall, the study indicated more susceptibility of children than adults to noncarcinogenic risks. Additionally, the carcinogenic health risks for nickel, chromium, lead, and cadmium notably exceeded the acceptable threshold of 1.0 × 10− 06, indicating significant lifetime cancer risk linked to these metals in groundwater. The health concerns warrant urgent attention, and immediate actions are necessary to safeguard and improve the groundwater quality in the studied region.