Ecological risk assessment of Toxic heavy Metal(loid)s in surface sediment of Zarivar International Wetland: an indices analysis approach

Surface sediment is often used to monitor contamination and assess ecological risk. We used multiple indices to assess sediment condition and ecotoxicity caused by heavy metal(loid)s (HMs) in Zarivar International Wetland (Zarivar) of Iran. We sampled the wetland at 12 stations using a Grab sampler, during both rainy and dry seasons. Using an atomic absorption spectroscopy and a mercury analyzer, we measured As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Zn and Hg. HMs temporal and spatial changes and general features of sediment were analyzed. Except Fe and Mn, all metals appear to have anthropogenic sources. We calculated toxic units (TUs) and contamination factors (CF) for all HMs. ∑TU calculations showed As> Cd> Cr and Ni to have the highest contributions in succession. CF indicated Cd, As, Pb and Cr, to have the highest concentrations, respectively. As (38.54 ± 10 mg/kg −1) and Cd (5.75 ± 2.01 mg/kg −1) exceeded their probable effect levels in 100% and 90% of the stations, respectively. Zarivar is classified as "very highly polluted" in rainy season (755.34 ± 289.97) and "considerably polluted" in dry season (489.98 ± 232.62) based on risk index values we calculated.