Geochemical Study of Heavy Metal Contamination of Shalmanrud River Sediments

Abstract

Background & Aims: Due to chemical stability, low degradation, and high bioaccumulation power at different levels of the food chain, heavy metals pose many ecological hazards to living organisms. Therefore, the present study investigated the concentrations of heavy metals As, Cr, Cu, Ni, Pb, V, and Zn and evaluated the ecological, carcinogenic, and non-carcinogenic risks of the sediments of the Shalmanrud river. Materials and Methods: Nineteen samples were taken from 15 stations in summer 2021 as control and geochemical background to investigate the heavy metal contamination of the sediments of the Shalmanrud river. After preparation, the samples were chemically degraded using the ICPOES method with the digestion of four acids. Indicators of origin and contamination degree, including geoaccumulation index (Igeo), Enrichment Factor (EF), Pollution Load Index (PLI), Contamination Factor (CF), and Contamination degree (Cd), were calculated to assess the level of sediment contamination. Results: Statistical results showed that the mean concentration of heavy metals increased as As Ni> Cu> V> Zn> Cr>As. The EF index for all studied metals except two samples of Pb metal was less than 1, which indicates the lack of human activity and geogenic concentration of heavy metals in the area due to the geological characteristics of the area. The Contamination Factor (CF) study showed that most samples are in the low to medium contamination class. The results of the Contamination degree (Cd) of most samples of Shalmanrud river showed a moderate contamination trend. Examination of the Pollution Load Index (PLI) showed that most samples were not polluted in the Shalmanrud river. The Ecological Risk (ER) index and Environmental Risk (ER) index of heavy metals indicated a low risk of heavy metals in the sediments of the Shalmanrud river. Conclusion: The results of this study showed that the potential risk for cancer and noncancerous diseases in children was higher than adults and by estimating the non-carcinogenic risk of all pathways (HI), Cr> As> Pb metals in the swallowing pathway and V> Ni> Cr metals were unauthorized in the study area and are hazardous to the health of residents around the Shalmanrud river. The study of contamination indices for Pb, Ni, and Cu metals showed a high level of contamination compared to other heavy metals in the area, which reflects the relatively heterogeneous distribution of these metals due to the geochemical diversity of geological units in the area and anthropogenic activities, such as agriculture, etc.