Vertical distribution, pollution pattern, ecological risks, and geochemical fractionation of potentially toxic metals in riverine core sediments

Potentially toxic metals (PTMs) contamination in urban riverine core sediments can reveal pollution trends linked to anthropogenic activities and urbanization. Thus, this study aimed to evaluate the vertical distribution, contamination, and ecological risks ofPTMs (As, Cd, Cr, Cu, Ni, Pb, Sr, V, and Zn) in core sediments from the Ravi River. Core sediments down to 75 cm depth from three locations were analyzed by Inductively Coupled Plasma Mass Spectrometry (ICP-MS), and a sequential extraction method was used to assess the geochemical fractionation of PTMs. The results showed that As, Cr, Cu, Ni, and Pb were higher inmiddle layers, especially for core sediments from densely populated site (Core A). The geo-accumulation index (Igeo) revealed moderate to high Cd contamination in upper layers and moderate Pb contamination in middle layers of Core A and Core B, due to which the overall ecological risk was high. The As, Cu, Pb, and V geochemical fractions were bound to Fe and Mn oxides with higher proportions after respective residual fractions. Risk assessment code (RAC) calculations indicated Cd and Sr were at moderate risks of bioavailability (>50%). Multivariate statistical analyses showed multiple associations among PTMs, suggesting anthropogenic influence predominantly driven by industrial activities.