Ecological Risk Assessment of Trace Metal(loid)s in Surface Sediment of the Huaihe River, Anhui Province, China

Quantitative probabilistic risk assessment of trace metal(loid)s in sediment is highly important for the protection and management of aquatic ecosystems. In this study, surface sediment from the Huaihe River (Anhui Province, China) was collected. In addition to the total content, the bioaccessible fractions of trace metal(loid)s (Cu, Pb, Zn, Cr, Cd, As, Hg, and Ni) were investigated using the diffusive gradients in thin films (DGT) technique. Multiple-level risk assessments, including the toxicity unit (TU), risk quotient (RQ), and probabilistic risk assessment (PRA), were conducted based on the species sensitivity distribution (SSD) to evaluate the probabilistic risk of trace metal(loid)s to aquatic biota. The results reveal that the Cu, Pb, Zn, Cr, and Ni levels were higher than the corresponding background levels; however, the total levels were lower than those reported in previous studies, which might be attributed to dredging activities in recent years. The ∑TU values suggested that the trace metal(loid)s in the sediment posed a low toxicity risk. The DGT-labile concentration values were low, demonstrating the low bioaccessibility of the trace metal(loid)s. The DGT-SSD coupled with the PRA revealed that the trace metal(loid)s had a 0.01–3.30% probability of adversely affecting the aquatic biota. Furthermore, the combined toxicity, calculated by summing probabilities of individual metal(loid), indicated a 5.58% probability of adverse effects on aquatic biota.