沼渣协同硫酸亚铁修复Cr(Ⅵ)污染土壤

通过稳定化实验、连续提取实验及植物毒性实验,研究了沼渣对硫酸亚铁稳定化Cr （Ⅵ）污染土壤的促进效果与机制.结果表明,沼渣协同硫酸亚铁对土壤中Cr （VI）有良好的稳定化效果.最佳的修复条件为：n（Fe）/n（Cr）=3∶1,含水率为35%,沼渣投加量为4.5%,反应时间为12 d,此时Cr （VI）稳定化效率为99.85%,残余六价铬含量为1.49 mg·kg^-1,满足《土壤环境质量建设用地土壤污染风险管控标准》（GB 36600—2018）第二类用地筛选值5.7 mg·kg^-1的限值要求.由连续提取实验结果可知,沼渣+硫酸亚铁稳定化处理后酸溶态铬含量显著降低,而可还原态、可氧化态和残渣态铬含量明显增加.风险分析进一步表明,沼渣+硫酸亚铁稳定化处理后铬的风险等级由非常高风险降至低风险.植物毒性分析可知,沼渣+硫酸亚铁稳定化处理植物毒性显著降低.微生物多样性和群落结构分析可知,沼渣+硫酸亚铁稳定化处理后土壤中细菌群落的丰度和多样性均明显增加.

Remediation of Cr(VI) from contaminated soil with the combination of biogas residue and ferrous sulfate

This study investigated the promotion effect and mechanism of biogas residue on the immobilization Cr(VI) in contaminated soil by using ferrous sulfate through stabilization experiment, sequential extraction experiment and plant toxicity tests. The experimental results showed that the combination of biogas residue and ferrous sulfate has a good effect on Cr(VI) stabilization in soil. The optimal remediation conditions are:Fe/Cr molar ratio of 3:1, water content of 35%, biogas residue dosage of 4.5%, and reaction time of 12 d. At these conditions, the efficiency of Cr(VI) stabilization is 99.85%, and residual Cr(VI) concentration is 1.49 mg·kg^-1, which meets the limit value of 5.7 mg·kg^-1 of the second type of land screening value in "soil environmental quality management and control standard for soil pollution risk of construction land" (GB 36600-2018). The results of sequential extraction showed that the acid-soluble Cr content was significantly decreased after the biogas residue + ferrous sulfate stabilization treatment, while the reducible, oxidizable and residual Cr content is significantly increased. Risk analysis further suggested that the risk level of Cr decreased from very high risk to low risk. Phytotoxicity analysis showed that the phytotoxicity of soil samples were significantly reduced after biogas residue+ferrous sulfate stabilized treatment. In addition, microbial diversity and community structure analysis showed the abundance and diversity of bacterial communities in the soil increased significantly after the biogas residue+ferrous sulfate stabilization treatment.