Origin and Partitioning of Heavy Metals in Sediments of the Anzali Wetland

Anzali, one of the most important international wetlands, is located on the southern coast of the Caspian Sea in Iran. This wetland receives discharges of domestic, agricultural and industrial wastewater, which affect the distribution of elements. In this study, ten sediment samples from the Anzali wetland were collected and analyzed for total concentration of metals (As, Cd, Cr, Cu, Ni, Pb, Zn and Fe). The results showed relatively higher concentrations of most elements in comparison to that of crust. The chemical partitioning of metals in each sample was determined in four fractions (Loosely bonded, Sulphide bonded, Organo-metallic bonded, Resistant bonded). Based on the chemical partitioning of metals, As and Cd were the most abundant in the loosely bonded, so these elements were major hazard for the aquatic environment and were a major pollutant in this area. Cd is the metal that showed the highest percentages in the Organo-metallic bonded. As, Fe and Cr are displayed in the greatest percentages in the resistant bonded; this imply that these metals are strongly linked to the sediments.