老化作用对生物炭钝化白云鄂博矿区碱性土壤中Cd2+的影响

生物炭虽然已经广泛用于酸性和中性土壤重金属污染修复，然而当生物炭应用于碱性土壤中经历不同程度的老化后是否会改变其结构和固定重金属的能力却关注较少.因此，以玉米秸秆为原料制备生物炭，采用冻融和干湿这两种人工加速老化培养和一种短期自然老化方法对生物炭进行老化实验.老化后测定土壤的pH和Cd²⁺的有效态含量、总量和形态，并从土壤中分离生物炭进行表征，探讨老化作用对生物炭钝化矿区碱性土壤中Cd²⁺的影响.结果表明，白云鄂博矿区碱性土壤中添加生物炭处理不具有显著的石灰化效应，冻融和干湿加速老化处理中pH整体呈下降趋势.与对照相比，添加生物炭后Cd²⁺有效态含量降低了19.32%~30.67%，总Cd²⁺含量下降了5.02%~7.18%.老化作用未能显著改变Cd²⁺的形态，但降低了酸可提取态与可还原态的比例，说明生物炭即使经历老化，依然能够长期固定Cd²⁺，这与生物炭老化后含氧官能团和孔隙结构的增加有关.研究可为生物炭在矿区环境中的长期应用提供理论依据.

Effect of Aging on Stabilization of Cd2+ Through Biochar Use in Alkaline Soil of Bayan Obo Mining Area

Although biochar has been widely used in the remediation of heavy metal pollution in acidic and neutral soils, less attention has been paid to whether biochar will alter its structural properties and the ability to retain heavy metals after different degrees of aging in alkaline soils. In this study, two artificial accelerated aging methods (freeze-thaw cycle and dry-wet cycle) and a short-term natural aging method were used to simulate the aging process of biochar prepared from corn stalk. We investigated the changes in the soil pH and bioavailability, total content, and transformation of Cd²⁺ before and after aging treatments. Biochar was separated from the soil for characterization to explore the effect of aging on the passivation of Cd²⁺ by biochar in the alkaline soil of the mining area. The results showed that adding biochar to alkaline soil in the Bayan Obo mining area had no significant liming effect, and pH decreased after the freeze-thaw and dry-wet accelerated aging treatments. Compared with that in the control, the CaCl₂-extractable contents of Cd²⁺ decreased by 19.32%-30.67%, and the total contents of Cd²⁺ decreased by 5.02%-7.18%. Aging did not significantly change the transformation of Cd²⁺ but reduced the distribution of acid-soluble and reducible fractions, indicating that biochar could immobilize Cd²⁺ for a long time after aging, which was related to the increase in oxygen-containing functional groups and the pore structure of biochar. These results are important for evaluating its long-term application prospects in the mining environment.