Source identification, accumulation and dispersion of heavy metals pollution into the surface sediments of urban runoff (case study, channels of Tehran City).

Heavy metals (HMs) pollution presents a significant challenge for both human health and natural ecosystems on a global scale. This study investigates the pollution of surface sediments resulting from urban runoff, identifies potential pollution sources, and examines the correlation between HMs and two factors: total organic carbon (TOC%) and particle size distribution (PSD). A total of 30 surface sediment samples were collected from three urban channels in the Tehran megacity. The concentrations of key elements, including strontium (Sr), lead (Pb), cadmium (Cd), nickel (Ni), and copper (Cu), were determined using Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES). The mean concentrations of Cd, Ni, Cu, Pb, Sr, were 0.46, 39.80, 161.25, 261.75, 388.50 mg/litter, respectively, following the sequence Sr > Pb > Cu > Ni > Cd. To identify the HMs accumulation, factor analysis(FA) was employed. The HMs rank order based on FA was as follows: 37.7% > 24.4% > 24.1%. According to (FA), the possible accumulation source of Pb and Sr is as different as Cu, Ni, and Cd elements. A significant correlation between Sr with TOC% (r = 0.901, sig = 0.000), Pb with both TOC% and particles < 75µm (r = 0.77, r = 0.63, Sig = 0.000 respectively), while Cu, Ni and Cd with particles < 150µm (r = 0.68, r = 0.81, r = 0.87, Sig = 0.000 respectively) were observed). Overall, the concentration of heavy metals (HMs) demonstrated a significant negative correlation with the particle size of surface sediments.