Ecotoxicological Assessment of Potentially Toxic Elements in Sediments from Some Southern Rivers of the Caspian Sea using Single and Integrated Pollution Indices

Due to high toxicity, durability in natural conditions, and bioaccumulation in the food chain, potentially toxic elements are considered serious pollutants.

toxic elements (Al, As, Cr, Cd, Co, Cu, Ni, Pb, Zn, V, and Mn) in sediment samples from some coastal rivers flowing into the southern Caspian Sea (Tajan, Babolroud, and Shirood) were assessed. Single (Cf , EF, Igeo, Hq, PLI, and QoC) and integrated contamination indices (m-PEC-q, m-PEL-q, MERMQ, NPI, and CSI) were used to assess the ecotoxicological risk of the metals.

At all sites, the level of Cd was less than the detection limit (<5 mg.kg-1), indicating no significant source of pollution containing Cd. The mean concentration order of the metals in the rivers varied, suggesting that their contaminant sources significantly differed. The metal content of the Tajan River was substantially lower than that of the other rivers. EF values of Cu, Ni, and As showed partial enrichment, probably indicating their anthropogenic origin. According to the single indices of CF, Igeo, PLI, and Hq, the Babolrood and Shirood Rivers, sediment was significantly contaminated by As, Ni, and Zn. Based on NPI values, the Shirood River was extremely polluted by As. Integrated ecotoxicological risk indices of CSI, m-ERM-Q, and m-PEL-q suggest that metals pose medium to low levels of environmental toxicity in the Babolrood and Shirood Rivers.

This research demonstrated the necessity of using management and pollution control strategies such as improving wastewater treatment, promoting sustainable agriculture, and regulating industrial discharges.