Assessment of Toxicity, Health Risks, and Environmental Impact of Trace Metals in River Sediments of the Middle Black Sea Region (Samsun, Turkey): Bioaccumulation Potential in the Freshwater Amphipod Hyallella azteca

The present work studied the sources, concentrations, distributions, and possible ecotoxicological risks of trace metals (TMs) in surface sediments of the Kızılırmak and Yeşilırmak Rivers, the largest rivers in the Black Sea Region of Türkiye, and the Mert and Engiz Rivers located between these rivers, to evaluate the region’s health risks and pollution status. Average TM concentrations were measured in mg/kg and ordered from smallest to largest as Cd (4.1) < Co (19.9) < Ni (31.6) < Cu (34.9) < Pb (37.8) < Cr (197.6) < Zn (213.9) < Al (24408.8) < Fe (35920). Seasonal changes were observed, especially during the dry season, and Pb, Zn, and Co concentrations were found to increase. Environmental risk assessment indices (EF, CF, I _geo , and PLI) indicated medium and high contamination levels and potential ecological impacts. Likewise, while TRI and ATI among toxicity assessment indices showed medium and high toxic levels, the highest individual growth rate (IGR) results of Hyallella azteca used in bioavailable TM assessment were observed in the control sediment (6.8). However, whereas the survival rate was 100% in the control sediment, it did not fall below 70% at the other sampling points. Bioaccumulation factor (BAF) results showed that Cu, Cd, Co, and Ni metals accumulated in H. azteca tissues. Health risk results indicated no health risk for adults while demonstrating a slight health risk for children. Statistical analyses (PCC and PCA) showed the presence of anthropogenic, lithogenic TM sources and slight effects of industrial and agrogenic sources.