Distribution, chemical speciation, and potential ecological risks of hazardous trace elements in solid wastes: a case study of an ultra-low emission coal-fired power plant in Tongling, Anhui Province.

The application of ultra-low emission (ULE) technology in Chinese coal-fired power plants (CFPPs) had reduced the emissions of particulate matter but increased the kind of solid wastes, which raising public and scientific concerns over potential risks of hazardous trace elements (HTEs) in solid wastes. This study investigated the concentration, chemical speciation, and potential ecological risk of As, Cd, Cr, Hg, and Pb in bottom ash, fly ash, desulfurization gypsum, and wet sludge from a typical ULE-CFPPs. The results showed that the highest concentrations of As, Cr, Hg, and Pb were found in wet sludge, while Cd had the highest concentration in fly ash. As, Cd, and Hg in fly ash, as well as As, Cr, Hg, and Pb in wet sludge, exceeded soil risk screening values. While Cd, Cr, and Pb were predominantly in the residual fraction, As was mainly in the Fe-Mn oxidation state, indicating greater environmental mobility. The modified risk assessment code results show that As, Cr, and Pb in all solid wastes were classified as low-risk level, whereas Cd in fly ash and Hg in desulfurization gypsum were at moderate level, and these two HTEs in wet sludge even arrived very high-risk. The total risk assessment code revealed wet sludge posed very high risk, with fly ash and desulfurization gypsum categorized as moderate risk, and bottom ash exhibiting low risk. This study provides valuable insights into the ecological risk assessment of HTEs in solid wastes from ULE-CFPPs and contributes to the scientific disposal of solid wastes.