The comparison of selenium and lead accumulation between contaminated muddy and sandy sediments from four estuaries along the Persian Gulf: effect of grain size.

Persian Gulf is one of the most important water sources in the economically developed south part of Iran, and metal pollution is a major concern for the Gulf. The bioavailability and distribution of selenium (Se) and lead (Pb) between muddy and sandy sediments from four estuaries along the Persian Gulf were analyzed. The geoaccumulation index and enrichment factor for metals and correlation between particles size with metals concentration were studied. The average concentration of metals in sediment was ranged 0.08-1.14 µg/g for Se and 0.32-4.37 µg/g for Pb in all estuaries, with the highest concentrations in Musa estuary. The results showed there was positive correlation between particles size of sediment with metals concentration. The highest of metal concentration was absorbed in silt (< 63 μm) sediment, followed by extremely fine sand (63-125 μm), fine sand (125-250 μm), medium sand (250-500 μm) and coarse sand (500-1000 μm), respectively. The organic matter and carbonate in the muddy sediment are higher than sandy sediment, and they had high specific storage capacity for accumulation of heavy metals. The result of Pearson correlation (r) for organic matter and metal was 0.78 for Se and 0.67 for Pb, and for carbonates and metal was 0.54 for Se and 0.61 for Pb. The values of EF in all estuaries show that the enrichment of sediment by heavy metals was by anthropogenic activities such as discharge of petrochemical and oil industrial. Geoaccumulation index indicates that the sediment in the Ahmadi and Ghanam estuaries was unpolluted to moderately polluted, while in the Arvand river is moderately to strongly polluted, and in the Musa estuary is extremely polluted.