Pathways and risk analysis of arsenic and heavy metal pollution in riverine water: Application of multivariate statistics and USEPA-recommended risk assessment models

This study analyzed surface water from the River Swat, Pakistan, using inductively coupled plasma mass spectrometry, multivariate statistical techniques, and US-EPA risk assessment models to evaluate the concentrations, distribution, pathways, and potential risks of arsenic (As) and heavy metals, including chromium (Cr), manganese (Mn), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), cadmium (Cd), mercury (Hg), and lead (Pb). The results revealed significant correlations (p ≤ 0.01) among metals that indicated common pollution sources, likely influenced by anthropogenic point and non-point activities. Along the monitored sites (S1-S10), the mass flow of ∑metals showed a dynamic pattern: progressively increasing downstream, decreasing at S6-S7, rising again at S7-S8, and then steadily declining toward S10, with Ni being the most abundant metal, followed by Cr > As> Cu > Mn > Co > Zn > Hg > Cd > Pb. The As and Heavy Metal Pollution Index (HPI), As and Heavy Metal Evaluation Index (HEI), and Pollution Index (PI) revealed variations in pollution levels, ranking the metals in the orders of Co > As> Cr > Cd > Mn > Hg > Ni > Pb > Cu > Zn, As> Cr > Ni > Hg > Cd > Co > Mn > Cu > Zn > Pb, and Hg > Ni > As> Co > Cu > Cd > Mn > Zn > Pb, respectively. However, according to the risk assessment, overall individual metal contamination in the River Swat water was below the ecological risk threshold (ERI 〈110). Where, the Chronic Daily Intakes (CDIs), Hazard Quotients (HQs), Hazard Indices (HIs), Cancer Risks (CRs), and Total Cancer Risks (TCRs) of Cr, Mn, Co, Ni, Cu, Zn, As, Cd, Hg, and Pb associated with daily river water intake and dermal contact indicate that long-term exposure to untreated river water may pose both carcinogenic and non-carcinogenic health risks to residents.