Speciation, bioaccessibility and human health risk assessment of chromium in solid wastes from an ultra-low emission coal-fired power plant, China

Abstract

Chromium (Cr) in solid wastes from ultra-low emission (ULE) coal-fired power plants (CFPPs) could engender adverse effects on environment and human health. Hence, solid waste samples containing bottom ash, fly ash, gypsum and sludge were collected from a typical ULE CFPP in China to study the distribution, speciation, bioaccessibility and human health risk of Cr. The results showed that Cr was depleted in gypsum, whereas significantly enriched in bottom ash, fly ash and sludge comparing with feed coal. The ratios of Cr(VI) to total Cr in solid wastes were relatively low, but the increase of flow fractions in Cr chemical binding forms implied the deterioration of environmental stability. Based on the in vitro simulated digestion methods of solubility bioavailability research consortium (SBRC) and physiologically based extraction test (PBET), the bioaccessibility of Cr in the gastric and intestinal phases reached the highest values in either gypsum or sludge. After incorporating bioaccessibility in human health risk assessment, the carcinogenic risk (CR) within acceptable limits of Cr in solid wastes to adults and children was concluded, with the non-carcinogenic hazard quotient (HQ) was all within the safety threshold. The Monte Carlo model was applied to evaluate the uncertainty analysis of human health risk assessment at 5% and 95% confidence interval, and the fitting results were consistent with the calculation results of the carcinogenic and non-carcinogenic risk for adults and children. This study is expected to provide insights for the integration of bioaccessibility into the health risk assessment of Cr in solid wastes from ULE CFPPs, thus is conducive to the disposal of solid wastes and human health protection.