Assessment of metal pollution in the Anzali Wetland sediments using chemical partitioning method and pollution indices

Metal pollution in aquatic ecosystems is of immense importance. Under various environment circumstances, the metal contents of sediments can enter into the overlying water body leading to severe toxicity. This study aims to determine metal concentrations in sediments of Anzali International Wetland in Iran. Chemical partitioning method is used to determine the portion of anthropogenic pollution and the mobility potential of each metal. The intensity of metal pollution in sediments of the wetland is assessed using three reliable indices. The results of chemical partitioning reveal that cadmium bear the highest risk of being released into the aquatic environment and high amount of manganese in sulfide bond phase implies the initiation of redox state in aquatic environment of the Anzali Wetland. The results of chemical partitioning studies show that Pb, Cd, Mn and As have the highest anthropogenic portion. Cluster analysis also confirms the results of chemical partitioning and indicates that the mentioned metals can be originated from anthropogenic sources. Sediment pollution indices, including, I (geo), I (POLL), and m-ERM-Q reveal that metals are in the range of low to moderate pollution and also show that the highest metal pollution is in the eastern and central parts of the wetland. This can be ascribed to rivers which are the recipient of industrial, agricultural and municipal wastewaters and flow into these parts of the wetland.