Effects of biochar underwent different aging processes on soil properties and Cd passivation

This study aims to determine the efficacy of biochar underwent different aging process including freeze-thaw cycling aging (FB), acidified aging (AB), and microbial aging (MB) on soil physicochemical properties and Cd passivation. The Cd-contaminated soil (3 mg·kg^-1) amended with the three kinds of aging biochar (at 4% w:w) were subjected to 56-day incubation. The application of FB and MB in soil increased the soil pH (0.82-1.04, 0.27-9.36), CEC (1.06-2.53 cmol·kg^-1, 1.66-2.59 cmol·kg^-1), and organic matter content (2.28-4.67 g·kg^-1, 3.70-5.48 g·kg^-1). FB performed best in stabilizing Cd (17.06-23.65%). On the contrary, AB decreased the soil pH and CEC by 0.82-1.04 and 1.32-2.40 cmol·kg^-1 and activated Cd by 11.6-19.24%. In conclusion, the efficacy of biochar on soil remediation and Cd passivation varied with aging method and cycle, and freeze-thaw treatment is an effective approach to improve the performance of biochar.