Distribution, chemical fractionation, and potential environmental risks of Hg, Cr, Cd, Pb, and As in wastes from ultra-low emission coal-fired industrial boilers in China

This study conducted a comprehensive investigation of the distribution, chemical fractionation, and potential environmental risks of Hg, Cd, Cr, Pb, and As in waste based on new data from five ultra-low emission (ULE) coal-fired industrial boilers (CFIBs). The results showed that fly ash was enriched with Cd, Pb, As, and Hg, while its Cr contents were not invariably higher than those of slag. Fly ash was the predominant output flow for Hg, Cd, Cr, Pb, and As in the tested ULE boilers, with higher proportions of HTEs in the fly ash and lower proportions of HTEs in the flue gas than in the non-ULE boilers. The average proportions of residual Hg, Cd, Cr, Pb, and As in wastes revealed the following order: slag > fly ash > flue gas desulfurization (FGD) by-products. The potential environmental risks of Hg, Cd, Cr, Pb, and As in the fly ash, slag, and FGD by-products of CFIBs at the county level in the Beijing-Tianjin-Hebei Air Pollution Transmission Channel Cities (“2 +26 cities”) region showed spatial heterogeneity. It is predicted that the potential release of Pb, Cr, and Cd in the fly ash would increase and that of the FGD by-products would decrease after the implementation of the ULE retrofitting of all CFIBs. [Display omitted] •De-PM devices led to the higher distribution of HTEs in waste of ULE boiler.•Hg in slag demonstrates a weaker environmental stability.•HTEs in wastes undergo chemical transformation with the flow of flue gas.•Potential environmental risks of HTEs in wastes showed spatial heterogeneity.•Potentially releasable HTEs in FGD by-products were predicted to be reduced.