Background. Soil contamination by hexavalent chromium is becoming a main environmental concern in China. This study\ndeveloped a sewage sludge biochar modified by FeSO4 (CHBC) as a new reductant for Cr(VI)-contaminated soil. The effectiveness\nof CHBC-stabilized Cr(VI)-contaminated soil was investigated. Methods. Typical industrial Cr(VI)-contaminated soil in China\nwas chosen as the medium. The total and Cr(VI) contents of the contaminated soil were 1014.6 and 973.5 mg/kg, respectively. The\neffectiveness of the Cr(VI)-contaminated soil stabilized by CHBC was investigated by the leaching test (US EPA method 1312), the\nsimplified bioaccessibility extraction test (US EPA 2007 protocol and British Geological Survey), alkaline digestion (US EPA\nmethod 3060A), sequential extraction (BCR sequential extraction procedure), X-ray diffraction, and the risk assessment code test.\nResults. Results show that CHBC substantially reduced the leachability and Cr(VI) content of the contaminated soil. The\nleachability and content of Cr(VI) were lower than the thresholds of the Environmental Quality Standards of Soil in China for civil\nreuse and the China Environmental Quality Standards of surface water for civil use when the soil was stabilized with 10%dosage of\nCHBC. Conclusion. CHBC is highly efficient in stabilizing Cr(VI) and can effectively reduce the leachability and bioavailability of\nCr in contaminated soil and thus feasible for stabilizing Cr(VI)-contaminated soil and shows potential for application in the field.
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