外加碳源水淹条件下高硫土壤中铜的迁移转化

采用高硫低有机质酸性重金属污染土壤,通过研究外加碳源水淹条件下各层土壤中酸可挥发性硫化物(AVS)的产生以及各剖面层中Cu的总量分布、Cu在孔隙水中的浓度及存在形态的变化情况,探讨了水淹土壤中的AVS对Cu迁移转化的影响.结果表明,外加碳源水淹条件下,硫酸根被还原,产生的大量AVS可促使水相中游离活性Cu向惰性较高的硫化物结合态和残渣态转化而被固定;不同深度土壤中AVS产生情况不同,其含量由深层向浅层递增,并在顶层大量聚集,由此导致孔隙水中的Cu2+浓度由土壤深层向浅层递减,这种垂直浓度梯度差,趋动活性态Cu由深层向浅层的垂直迁移,在AVS大量富集的表层中形成丰富的铜硫化物沉淀,使土壤表层中惰性态铜及总量累积增加,底层活性铜及总量下降,从而使铜的生态风险和生物风险降低.

Migration and transformation of copper during flooding in acid sulfate Cu polluted soil provided with artificial carbon source

An acid sulfate Cu polluted soil with low-organic matter content was employed for the goal of understanding the effects of AVS on migration and transformation of Cu. Provided with artificial carbon source, the generation of acid-volatile sulfide (AVS) in each column layer, the distribution of total Cu and porewater Cu in vertical profile and the speciation transformation of Cu were investigated under flooding condition. During the flooding period, considerable AVS was generated due to the reduction of sulfate, which could promote transformation of free Cu into inert sulfide phase and residual phase. The generation of AVS in different column layer differed greatly, with the most abundance in the top layer, and decreased sharply with the depth. The difference of AVS content in each layer resulted in a vertical gradient difference of free Cu content in porewater, which would drive the mobile Cu migration from deeper layer to upper layer, and transformed into copper sulfide phase. The inert and total Cu in top layer increased in the processes, combined with the decreased mobile and total Cu in deeper layer, which may greatly lower the potential ecological risk and bioavailability of Cu in acid sulfate soil