Risk assessment of Cr, As, and Sb to aquatic communities at the water-sediment interface in the lower Yellow River, China, integrated with the Diffusive Gradients in Thin‐films technique

The dynamic concentrations of labile metals/metalloids, measured by the Diffusive Gradients in Thin-films (DGT) technique, can be used for evaluating the toxicity risk of heavy metals to aquatic organisms in sediments. In this study, the different potential risks of the three sediment compartments, overlying water (W), sediment- water interface (SWI) and sediment (S) were independently assessed by studying the concentrations of Cr, As, and Sb in the sediment and water from the lower Yellow River. Total concentrations of these elements and bioavailable concentrations, using DGTs, were explored and probabilistic risk assessment (PRA) based on a Monte Carlo model was performed. The results show that the total heavy metal concentrations in sediment and overlying water were spatially variable due to influences of natural geography and sediment distribution. The trace elements mean concentrations using DGT were 1.68, 1.69 and 0.73 μg·L−1 for Cr, 0.61, 0.51 and 0.39 μg·L−1 for As, and 0.78, 1.16, and 0.41 μg·L−1 for Sb in W, SWI and S, respectively. Among them, the DGT-labile concentration of As displayed a large spatial variability, indicating a close association with anthropogenic activities. The risk quotient (RQ) categories for single heavy metal toxicity demonstrated to be moderate risk for Cr and almost no risk for As and Sb. The combined biotoxicity probability assessment of the three heavy metals showed that they would cause almost no harmful effects to benthic organisms in the whole ecosystem of the Yellow River.