Heavy metals in sediments of two nearby streams from Southeastern Black Sea coast: Contamination and ecological risk assessment

Heavy metal pollution in the sediments of calislar and Akcaova Streams may expose hazardous risk to environment and public health through food chain in Ordu province of southeastern Black Sea region of Turkey. The enrichment and distributions of the heavy metals in the sediments of these two streams demonstrated a decreasing trend in the mean heavy metal toxic levels in mg kg(-1) as follows Fe (8135.27) > Mn (272.56) > Zn (25.68) > Cu (13.03) > Co (5.13) > Pb (3.74) > Ni (3.62) > Cr (3.52) > Cd (0.005) in calislar Stream and Fe (9939.12) > Mn (286.97) > Zn (24.24) > Cu (19.31) > Ni (10.95) > Co (6.2) > Cr (4.90) > Pb (3.97) > Cd (0.09) > Ag (0.07) in Akcaova Stream, respectively. The sum of the toxic units of Fe, Mn, Zn, and Cu in both streams were significantly higher. The assessment of sediment pollution was carried out using multivariate statistical approaches and indices such as enrichment factor (EF), contamination factor (CF), geoaccumulation index (I-geo), and potential ecological risk factor (E-r(i)). The results of the cluster analysis in both streams showed that Co, Pb, and Cr were mainly associated with natural sources. EF values indicated that the average concentration of all metals from both streams were lower than potential effect levels with the exception of Cu, and Ag in Akcaova Stream. Relatively low levels of pollution indicators in calislar Stream pointed out no environmental contamination and suggested that metal contamination sourced most likely from the naturally present minerals in the area. Akcaova Stream sediments were moderately contaminated with Cu (EF > 2), and significantly contaminated with Ag (EF = 5 - 20) according to the average EF values attributable to anthropogenic activities.