生物炭对Cd污染土壤的修复效果与机理

Immobilization and its mechanisms of cadmium contaminated soils by biochar

通过修复培养实验和BCR连续提取实验研究牛粪生物炭(DM)和水稻秸秆生物炭(RS)对2种镉污染土壤的修复效果、影响因素及修复后的Cd的形态分布,探讨可能存在的修复机理。经56 d修复后,与CK相比,5%添加量的牛粪生物炭(DM5%)和水稻秸秆生物炭(RS5%)使TCLP提取态Cd在S1土壤中分别降低了15%和18%,在S2土壤中分别降低了5%和6%。但生物炭添加量为1%时对S2土壤中Cd无显著修复效果。DM5%和RS5%处理使Cd的酸可溶态在S1土壤中降低8.66%和9.25%,在S2土壤中降低7.86%和13.4%,相应的残渣态在S1土壤中升高8.30%和10.54%,在S2土壤中升高8.67%和14.92%。同时,DM5%和RS5%处理使土壤p H提高了7.69%~13.13%,TCLP提取态P增高了0.046~0.39 mg·g^(-1)。结果表明,添加量为5%的牛粪生物炭和秸秆生物炭可有效修复Cd污染土壤。

The main objective of this study was to evaluate the remediation efficiency,impact factors,speciation changes,and immobilization mechanism of Cd in two contaminated soils（ S1 and S2） amended by dairy cattle manure-derived biochar（ DM） and rice straw-derived biochar（ RS） at different ratios through an incubation experiment and a BCR continuous extraction experiment. After 56 days of incubation,the contaminated soils incorporated with DM5% and RS5% could decrease Cd mobility. Compared with CK,the reduction in Cd leachability with DM5% and RS5% treatment in the toxicity characteristic leaching procedure（ TCLP） extract was 15%and 18% in S1 soil,and 5% and 6% in S2 soil,respectively. However,the biochar treatments with the 1% addition did not clearly affect Cd immobilization in S2 soil. Compared with CK,both DM5% and RS5% treatments decreased the acid-soluble Cd,with reductions of 8. 66% and 9. 25% in S1 soil,as well as reductions of7. 86% and 13. 4% in S2 soil,respectively. At the same time,the DM5% and RS5% treatments improved the residual Cd,with an increase to 8. 30% and 10. 54% in S1 soil,respectively,as well as an increase to 8. 67% and 14. 92% in S2 soil,respectively. The p H and P obviously increased by RS5% and DM5% treatments in the TCLP extraction,with an improvement of 7. 69% to 13. 13% for p H and 0. 046 to 0. 39 mg·g^-1 for P. The results indicated that contaminated soils with a 5%（ w/w） biochar addition could clearly immobilize Cd.