Potential toxic elements in sediment of some rivers at Giresun, Northeast Turkey: A preliminary assessment for ecotoxicological status and health risk

The concentration of globally alarming potential toxic elements (PTEs) like Aluminum (Al), chrome (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As), cadmium (Cd), lead (Pb), and uranium (U) were measured in surface sediment of seven major rivers residing in Giresun (one of the most important Hazelnut production areas of Turkey). The mean concentrations of PTEs in all river sediments showed the descending order of Al > Fe > Mn > Zn > Cu > Pb > Cr > Ni > Co > As > U > Cd. The level of studied metals in most of the rivers exceeded the threshold effect level (TEL), indicating a potential risk to the environment. Certain indices, including the sediment quality guidelines (SQGs), contamination factor (CF), pollution load index (PLI), enrichment factor (EF), potential ecological risk index (E-r(i)), geoaccumulation index (I-geo), toxic risk index (TRI), modified hazard quotient (mHQ) and ecological contamination index (ECI) were used to assess the ecological risk posed by PTEs in sediment. Contamination factor (CF) and geoaccumulation index (I-geo) demonstrated that most of the sediment samples were moderately to considerably contaminated by Cu, As, Cd and Pb. In view of the potential ecological risk index, sediments from Pazarsuyu Stream (PS), Batlama Stream (BS) and Gelevera Stream (GLS) showed considerable potential ecological risk. The sources of PTEs and the relations between them were determined by using principal component analysis/factor analysis (PCA/FA), Hierarchical clustering analysis (HCA) and Pearson correlation index (PCI). Three factors explaining 83.94% of the total variance was found by PCA/FA. 43.34% of the total variance explained by the first factor (F1) was correlated with Ni, Cr, Pb and Co elements. 28.35% of the total variance explained by the second factor (F2) was correlated with U, Al, the third factor (F3) explains 12.24% of the total variance and correlated with Zn, Cd, Cu and As elements. These factors revealed that the quality of the sediment was mainly influenced by anthropogenic effects. The extent of pollution by heavy metals in the studied streams implies that the condition is much frightening to the biota and inhabitants in the vicinity of these rivers as well.