RESUMO
Three coastal lagoons on the Sefidrud Delta, Caspian Sea, were investigated to evaluate heavy metal pollution in sediments. Amirkola Lagoon is located in the eastern part of the delta (abandoned delta lobe) and is aged more than 500 years, whereas Kiashahr and Zibakenar lagoons are in the western or active part delta lobe and formed in the last decades. One hundred six sediment samples and three sediment cores were taken from studied lagoons. The samples were analyzed by ICP-OES. Geo-accumulation index (Igeo), contamination factor (CF), degree of contamination (Cdeg), pollution load index (PLI), and Potential ecological risk index (RI) were employed to determine heavy metal pollution for Co, Cr, Cu, Ni, Pb, V and Zn. Nonparametric statistical analysis (Two-step cluster analysis, analysis of variance, and T-test technique) was used to discriminate the pollution sources. Based on contamination indices, the Kiashahr and Zibakenar lagoons show significant to moderate contamination with Co, Cu, Pb, Zn, and V, whereas the Amirkola Lagoon samples show the lowest metal contamination. PLI values demonstrated metal contamination in the Kiashahr and Zibakenar lagoons but no contamination in the Amirkola Lagoon. Although there was a notable rise in RI values from Amirkola to two other lagoons, all indicated low ecological risk. Statistical methods designated the unique interpretation of contaminant sources. Although the same geogenic origin of sediments in the Sefidrud Delta and lagoons deposits, Co, Zn, and Pb show anthropogenic sources in the newly-formed Kiashahr and Zibakenar lagoons.
