Bioavailability and Ecological Risk Assessment of Nickel in Surface Sediments of Persian Gulf, Strait of Hormuz and Sea of Oman

Different studies conducted on the sediments of the Persian Gulf, strait of Hormoz and the Sea of Oman show that the amount of nickel as a toxic metal in these water bodies is more than its threshold effect level. In order to determine the risk of nickel for benthic organisms, the sediment samples of these water areas were subjected to sequential extraction and analysis in order to determine the bioavailability of nickel and subsequently the level of biological risks to benthic organisms.

In this study, the surface sediments of 5 stations in the Persian Gulf, the Strait of Hormuz and the Sea of Oman were analyzed in order to determine the total nickel concentration and determine the bioavailability of nickel during 6 successive extraction stages. Total nickel concentration was measured by Inductively Coupled Plasma Mass Spectrophotometer (ICPMS) and nickel concentration, which was extracted during 6 stages were analyzed by Atomic Absorption analyzing instrument (Furnace).

The results showed that the concentration of nickel in the monitored stations varied between 96 and 113 mg/kg, which is more than the nickel threshold Effect Level (TEL: 15.9 mg/kg). The results of consecutive extraction in 6 stages showed that the concentration of stages 1 and 2 (accessible part of metals for benthic life) was lower than the detection limit of the instrument and their concentration can be neglected.

The amount of nickel in the third stage of extraction (bonding with oxide or hydroxides of iron and manganese) was much lower than the TEL (15.9 mg/Kg) and under environmental changes and redox conditions, the bioavailability of nickel will be lower than the TEL. The results showed that although the nickel pollution in the coastal sediments of the Persian Gulf, the Strait of Hormuz and the Sea of Oman was more than the TEL; but due to the low exchangeable part, the current pollution is not considered a serious risk for the marine life.