Heavy Metal Occurrence, Pathways, and Associated Socio-ecological Risks in Riverine Water: Application of Geographic Information System, Multivariate Statistics, and Risk Assessment Models

Abstract

Heavy metal (HM) pollution is one of the major issues of concern in the world due to its serious health consequences on humans and ecology. In this study, riverine water from the River Kabul in Pakistan was studied using inductively coupled plasma mass spectrometry (ICP-MS) to determine the variation, routes, and possible socio-ecological hazards of chromium (Cr), manganese (Mn), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn) cadmium (Cd), mercury (Hg), and lead (Pb). The results revealed significant HMs variation (p < 0.05) in the sequence of Cr > Zn > Ni > Cu > Cd > Pb > Mn > Co > Hg, indicating prevalent metal contaminations in the river. Multivariate statistics showed significant strong positive correlations (p ≤ 0.01) between the individual HMs contents along the monitoring sites. The strong-moderate levels of Cu, Co, Zn, Mn, Pb, and Cd in riverine systems were observed to be caused by surrounding industrial, agrochemicals, mining, and domestic wastewater discharges along with geogenic sources, the weak levels of Cr and Ni could be induced by erosion of mafic and ultramafic rocks, and mining activities, whereas the low contamination of Hg suggests minimal atmospheric deposition with fewer industrial discharges in the environment. The overall mass flux of the ∑HMs was estimated to be around 164.10 kg/year, with significant HM pollution index (HPI) and pollution index (PI) variations along the river characterizing the potential risk of HMs in decreasing order of Cd > Hg > Cr > Ni > Co > Pb > Mn > Cu > Zn and Cd > Hg > Ni > Pb > Cr > Co > Cu > Mn > Zn, respectively. Individual HM contamination was within the ecological risk threshold (ERI < 110), where, the chronic daily intake (CDIs), hazard quotients (HQs), health indices (HIs), and cancer risks (CRs) of Cd, Ni, Co, Cr, and Pb by daily riverine water ingestion and dermal contact posing considerable human health concerns. To protect the environment and public health, our findings suggest that untreated anthropogenic wastewater discharge into the river system be strictly controlled and regulated through public awareness campaigns and legislation prohibiting the use of herbicides and fertilizers containing high levels of Cr, Ni, Co, Cd, and Pb.