Remediation effect of modified biochar on Cd-contaminated soil in post-mining land on the Loess Plateau, China

Le résumé fourni par la source

Biochar (BC) has been widely used in remediating soil Cd contamination, and the efficiency of remediation can be improved by modification. However, Cd immobilization mechanism of modified biochar and its influence factor in coal mine soil receive little attention. In this study, characterizations of four modified biochars (H 2 O 2 -BC, HNO 3 -BC, KMnO 4 -BC and CaCl 2 -BC) and their remediation effects on soil Cd contamination at different addition ratio (1%, 2% and 3%) were investigated. Modified biochar addition significantly affected soil pH and CEC. The acidic functional group and carboxyl group of CaCl 2 -BC and HNO 3 -BC were higher ( p <0.05) than those of BC and other modified biochars. There were significant differences in soil Cd fractions under different modified biochar treatments. The exchangeable fraction with high bioavailability and Fe-Mn oxides bound fraction with potential ecotoxicity of soil Cd decreased under HNO 3 -BC and CaCl 2 -BC treatments at a 2% addition ratio, respectively. The diethylene triamine pentaacetic acid -extractable Cd (DTPA-Cd) in soil, ready to be absorbed by plants, decreased under modified biochar treatments, and the largest reduction occurred in HNO 3 -BC addition at 2% ratio. RDA analysis indicated that soil pH and carboxyl group significantly ( p < 0.05) affected Cd fractions in coal mining soil. Our study suggests that HNO 3 -BC increased main functional groups, leading to high adsorption and complexation capacity, which promoted the removal of soil Cd with high mobility and activity. Therefore, HNO 3 -BC could serve as an effective measure for Cd pollution remediation in degraded ecosystems, especially in the alkaline soil in northern China.

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