An Investigation of the Evolution of Distribution and Accumulation of Heavy Metals (Cr, Ni, Cu, Cd, Zn and Pb)in Anzali Wetland's Sediments

To investigate the precipitation of heavy metals in Anzali wetland and evaluate its refining
performance this study was carried out on the wetland . Monthly samples of sediments from 15 stations including inlets, outlets and some internal locations in the wetland were collected and analyzed over a period of six months (July - December 2002). Sediment samples were analyzed for six metals of Cr, Cd, Pb, Zn, Cu and Ni. Wet digestion method was employed for extraction of metals in samples by and through a solution containing HN03 and HCL. Atomic Adsorption Spectrophotometry was employed for measurement of the heavy metals. Statistical methods, including analysis of variance (ANOYA), correlation and Cluster analysis were used for analysis of the data. The results indicated that concentration of heavy metals present in sediments (collected from different stations and at different
times) were significantly different. Among the metals studied, Zn was of the highest concentration Heavy metal concentrations in stations 11, 12 and 13 were lower than in other stations. Sediments in station 5 contained the highest concentrations of heavy metals among all sediments. It can be stated that concentration of heavy metals decreases with an increase in the distance from delta of rivers entering the wetland. This is due to the role and performance of wetland chemical contents in reduction of pollutants, the self-purification action of wetland as well as precipitation of heavy metals at the beginning of the entries into the wetland.