Geochemical and environmental assessment of river sediments in the East of Gilan province (case study: Otaghvarrud, Shalmanrud, and Polrud rivers), Northern Iran

Abstract In this study, the pollution of heavy metals in the sediments of the Otaghvarrud, Shalmanrud, and Polrud rivers was assessed to determine the geochemical and environmental contamination. Samples were collected from 19 stations along these rivers. The investigation focused on six heavy metals: arsenic (As), lead (Pb), chromium (Cr), nickel (Ni), copper (Cu), vanadium (V), and zinc (Zn), using ICP-OES analysis. Various statistical parameters, including the Pearson coefficient, dendrogram, and principal component analysis (PCA), were evaluated. The results indicated a high correlation among Cu, Ni, V, Zn, and Cr, suggesting a geogenic origin. As exhibited characteristics of a combination of anthropogenic, geogenic, and metal origins, while Pb showed an anthropogenic origin likely from agriculture and industry. Additional parameters, such as the mean of geoaccumulation index (Igeo), enrichment factor (EF), contamination factor (CF), pollution load index (PLI), Nemerow integrated pollution index (NIPI), ecological risk (ER), and environmental risk index (RI), were assessed to determine the pollution levels of the heavy metals. The findings revealed low to medium pollution for the analyzed metals. Notably, Otaghvarrud exhibited higher pollution levels compared to the other rivers due to the presence of basalts, pillow lavas, and splits along its route. These geological features contributed to the transport and deposition of these metals in the river. Based on the research findings, it was concluded that the sediments in the studied rivers are on the verge of heavy metal pollution. Furthermore, an examination of the health risk assessment indicators, including the HI (hazard index) and CRI (carcinogenic risk index), indicated a higher potential risk of carcinogenic and non-carcinogenic diseases in children compared to adults.