Evaluation of Heavy Metal Contamination and Ecological Risk Assessment in Sediments of Karun using Aquatic Pollution Indices

Background Aims of the Study: The current study was designed to determine the quality of sediments in Karun in Ahvaz, Iran, according to aquatic pollution indices. Materials and Methods: The sediment samples were obtained from six river stations in summer and winter. The sediment samples were air-dried, sifted, homogenized, and stored in plastic bags, and the concentrations of metals were determined in the laboratory. Results: The obtained findings revealed that the mean concentrations of lead, zinc, chrome, and cadmium were 26.27, 72.36, 53.47, and 3.85 mg/kg dw in summer and 13.41, 59.54, 30.28, and 0.42 mg/kg dw in winter, respectively. According to the mean scores of the potential ecological risk index (PERI), in two seasons, the sediment enrichment with metals was observed in the order of Cd Pb Cr Zn; however, according to biological toxicity test (the effects range-median quotient), the sequences of the metals during summer and winter were Cd Cr Zn Pb and Zn Cr Pb Cd, respectively. The comparison of indices between stations showed that in summer, stations 3 and 4 were medium-low priority side according to the mean effects range-median quotient (mERM-Q) and were reported with moderate ecological risk based on the PERI. In winter, stations 2 and 4 had a medium-low priority side and moderate ecological risk according to mERM-Q and PERI, respectively. The results of hazard quotient (HQ) and modified hazard quotient also showed that the HQ values of Pb and Zn (0.1 HQ 1), as well as Cr and Cd (1 HQ 10), were indicative of potential and moderate hazards in these ecosystems, respectively. Conclusion: Based on all the indices, station 4 was the most contaminated site, and Cd was reported with the highest risk. Therefore, entering the wastewater canal and input contaminants, especially cadmium into Karun can be regarded as a major concern.