Heavy Metal(Loid)s Contamination of Groundwater in Khyber District, Pakistan: Spatial Dependence, Source Apportionment, and Human Exposure

Abstract

Heavy metal(loid)s (HM) including Fe, Mn, Cu, Zn, Cd, Cr, Co, Ni, and Pb were analyzed using ICP-MS in the groundwater of the Khyber District. Two indexical approaches were applied for the evaluation of HM contamination and toxicity in groundwater. The study also examined the health risks, sources, and spatial dependence of these HM. The results revealed that Mn, Ni, Cd, and Pb, concentrations violated drinking water guidelines in 44.26%, 52.45%, 1.63%, and 9.83% of the samples, while the rest of the HM were well within the limits. Based on the results it was observed that 18.03%, 6.55%, 6.55%, and 13.1% of the samples were classified as unfit, very poor, poor and marginal, water quality classes, presenting, very severe, excessive, strong, and moderate toxicity to consumers, respectively. Among HM, the Pb, Mn, and Ni required the highest removal rates in comparison to others. Health risk assessment suggested that 8.2% and 16.39% of samples showed non-carcinogenic risks to adults and children, respectively. Hotspots for HM were identified showing enhanced HM-enriched waters in specific regions, indicating areas of concern for future management. Source apportionment suggested that Pb, Cd, Zn, and Cu originated from a mix of geogenic and anthropic sources, while the rest of the HM were attributed to natural occurrences.