Assessment of heavy metals' bonding with various sedimentary phases in Shefa-Rud river (Guilan Province)

In the present investigation, bulk and chemical partitioning of elements in the Shefa-Rud riverbed sediments are studied. Higher concentrations of elemental concentrations have been observed in estuarine zone when compared with riverine sediments (except for Al, Fe, Pb and Mn). Manganese is mobilized under anoxic conditions prevailing in the Caspian Sea. Lithogenous materials are greatly diluted in the estuarine zone by various pollutants present in the Caspian Sea. Organic metallic bonds are not significantly present in the area of study. Geological units of the area of study have resulted in the lower concentrations of elemental concentrations of riverbed sediments when compared with published values for mean crust and world sediments ones. Though, cluster analysis has clearly shown the importance of alumina-silicates in controlling the distribution of Fe and Mn in riverbed sediments but it could not depict controlling mechanism for other studied elements. Geochemical Index (Igeo) and Enrichment Factor (EF) values are indicative of a clean environment throughout the river course. These values are in a well agreement with results of chemical partitioning data. Quantification of EF values is not logically possible and therefore Igeo values can be used more effectively.