Measurement and Evaluation of Ecological Risk of Heavy Metals in Surface Sediments of Pars Special Economic Energy Zone

Today, heavy metals pollution in aquatic ecosystems is one of the most important global environmental problems. Because this metals have characteristics such as chemical stability, low degradability and bioaccumulation ability at different levels of the food chain cause the abundant ecological risks for organisms. Therefore, this study investigates the concentration of heavy metals (mercury, cadmium, lead, chromium, copper, nickel, zinc and iron) and ecological risk assessment of them in coastal sediments in the Special Economic Energy Zone - South Pars.
In order to assess the concentration of metals, 16 stations along the coast was selected and three samples were taken at each station. After preparation and digestion of the samples, the concentrations of these metals were determined by using Polarography.
The results showed that the average total concentration of metals in sediment were (Fe > Zn> Cu > Ni> Cr > Pb > Cd > Hg), to amount (56.065 ± 2.04 > 45.91±12.035 > 28.58±1.77 > 18.96 ± 0.84 > 8.59±0.47 > 0.447 ± 0.07 > 0.03 ± 0.016 mg/kg) respectively. In addition, evaluation indicators of the environment such as; Geo accumulation index (Igeo), Contamination factor (CF), Pollution Load Index (PLI) represents less pollution and partly average in the region. Also the investigation ecological risk and environmental risk of heavy metals showed the risk was alike with (Cd >Cu> Pb> Ni> Zn> Cr> Hg) respectively.
According to the results, it can be concluded that pollution in the region for Hg, Zn, Cr, Pb and Ni were low and moderate for Cd and Cu. High concentrations of cadmium in comparison with the corresponding amount in the crust of the Earth, along with high levels of pollution factor, pollution modified for Cd, Cu implies the effects of human activities on pollution and accumulation of these heavy metals in sediments. Based on the calculation of the ecological risk index of metals we can expressed that among the measured elements, sediments in terms of Cadmium are in moderate ecological risk.