Risk assessment and pollution loads of potentially toxic elements in water of four rivers flowing into the Mediterranean Sea

One of the main sources of metal accumulation in the marine environment is transport by rivers. Using data from 2014 to 2017 for various stations, this study analysed the distribution of potential toxic element (PTE) concentrations in surface waters, the pollution loads and the water quality index of the large rivers flowing into the Mediterranean Sea (Manavgat, Goksu, Seyhan and Ceyhan). 13 different elements (As, Cd, Cr, Co, Cu, Fe,Pb, Li, Mn, Ni, Se, Zn, Al) were determined within the scope of the study. While the estimation of risk assessments for both adults and children via dermal and ingestion pathways using the United States Environmental Agency (USEPA) formulas. Pollution indexes such as Chronic daily intake (CDI), hazard quotient (HQ), hazard index (HI) and carcinogenic risk (CR) were calculated. Additionally, water quality index (WQI), pollution load index (PLI) and contamination factors (CF) were also determined. Since it is a detailed monitoring study of three years, all findings are evaluated using average values for each river. The highest mean PTE concentrations across all rivers were found at stations S4 (Seyhan), S1 and M1 (Manavgat) with Ni (0.1895) > Se (0.0618) > Al (0.0598), respectively. The values of PLI were found to be generally high (3-6) and very high (>6) in all studied rivers. Additionally, these rivers are subject to significant contamination with Pb, as CF>5, indicating very high levels of contamination, was found as a minimum of 166 for Pb in all rivers. Considering all risk assessments, it is concluded that children are more sensitive to ingestion and dermal exposure pathways than adults, and their carcinogenic risk is 4.5 times greater than adults. Besides, according to the statistical analysis, the strong and weak correlation of Al with other elements indicates that the source of the pollution is natural and anthropogenic processes, respectively.