Risk on assessment of 15 REEs and mixtures by DGT in Songhua River system sediments of China's largest old industrial base

Rare earth elements (REEs) are increasingly used in the high-tech sectors in the world and are therefore called burgeoning contaminants. As diffusive gradients in thin films (DGT) can be used to assess the bioavailability of inorganic matters, in this paper, we evaluated, for the first time, the ecotoxicology risks of REEs and their mixtures in river sediments of China's old industrial base by DGT. During our research, taking the Songhua River system (SRS) as an example, we detected its surficial sediments, of which the DGT-labile concentration of REEs (∑REEs) was 2.07–8.76 μg/L. As for the single toxicity, the risk quotient (RQ) values of Y at all sites were significantly greater than 1; while the values of Nd and Pr in some upstream reaches were all significantly greater than the threshold (1), indicating that these adverse effects of single REEs were not neglected. In terms of the combined toxicity of REEs mixtures, we carried out an assessment of the risks of probabilistic ecotoxicology, which showed that the SRS superficial sediments had a low probability of toxicity to aquatic organisms (0.54%).