Mohsen Nowrouzi

The concentration and chemical speciation of Pb, Cd and Ni as well as the total organic carbon (TOC) were studied in surface sediments from nine stations in the Hara Biosphere Reserve. The sequential extraction technique was applied to assess the four (exchangeable, acid-reduction, oxidisable-organic and residual) fractions in surface sediment. This investigation was the first study on the basis of the chemical speciation of Pb, Cd and Ni in surface sediments of Hara Biosphere Reserve. The total concentrations of metals were 31.66–42 ?g g?1 for Pb, 3.08–4 ?g g?1 for Cd and 36.81–118.9 ?g g?1 for Ni. The highest percentages of Pb, Cd and Ni were found in the resistant fractions; 51.42%, 60.11%, 91.71%, respectively, indicating that these metals were strongly bound to the sediments. The degree of surface sediments contamination was determined for the individual contamination factors (ICF). The result of ICF values illustrated that all stations (with the exception of stations 3 and 8 for Pb) did not pose a potential risk to fauna and flora of the Hara Biosphere Reserve. The Pearson correlation between the concentration of Pb, Cd, and Ni at the oxidisable-organic fraction with TOC in surface sediment demonstrated that TOC had a positive effect on complexing with metals in the surface sediment. The wastewater from industry was the main source of metal pollution in this region.