Assessing Heavy Metals Pollution of the Mangrove Sediments along Tidal Flat of the Mehran River Delta, Persian Gulf

The relationship between the concentration of heavy metals and physicochemical factors was studied in the fine-grained sediments of the tidal section of the Mehran delta where mangrove trees have grown. Surface sediments of the tidal zone of the Mehran delta were sampled. The grain size distribution, calcium carbonate, organic matter contents, pH/Eh, and heavy metals concentration were determined in the mud fraction of the sediments. The presence of high calcium carbonate in sediments is an effective factor in the abundance of Mn, Cd, and Pb. Clay and organic matter as adsorptive have contributed to the high concentration of Zn, Cu, while Fe oxy-hydroxides have affected the concentration of Co, Cr, and Ni. According to the index of Enrichment Factor (EF), the average enrichment of the elements in the studied sediments from high to low order is Cr, Ni, Cd, Zn, Mn, Pb, Co, and Cu. According to the Pollution Load Index (PLI), none of the delta sediments including sediments from inside and outside of the mangrove forestare classified as polluted to the heavy metals. According to the Igeo Index, most samples, and only Cd, Cr, and Ni show slight pollution in some samples. Accordingly, there is no current threat of contamination of potentially toxic elements of natural and anthropogenic origins to the mangrove environment and Mehran delta.