Science of The Total Environment：蚯蚓对生物炭固定重金属作用的影响

南京农业大学生命科学学院陈亚华教授团队采用4周土壤盆栽试验，探讨了蚯蚓对生物炭固定重金属的影响。研究成果发表于Science of The Total Environment（IF=5.589）。

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Highlights

·Sludge biochar and rice husk immobilized Cd, Pb, and Zn in a contaminated soil.

·Earthworm activities increased the bioavailable concentrations of Cd, Pb, and Zn in contaminated soil.

·Earthworm activities significantly reduced soil pH by 0.1–0.19 units.

·Earthworms may weaken the immobilized effect of biochar by lowering soil pH.

Abstract

The effect of earthworms on the immobilization of heavy metals by biochar was investigated using 4-week soil pot experiments. Our results showed that both sludge and rice husk biochars applied to Cd, Pb and Zn contaminated soils significantly reduced the bioavailability of those heavy metals in soils, and their concentrations in soil pore water. The Cd and Pb concentrations in pakchoi shoots were decreased by 10.8%–11.7% and 21.5%–26.5%, respectively, in biochar treatments alone. Biochar and earthworm treatments, alone or in combination, can significantly increase pakchoi growth. However, compared with biochar-treated alone, applying earthworms into pots with biochar treatments significantly reduced soil pH by 0.1–0.19 units, increased the Cd, Pb and Zn concentrations in soil pore water, their bioavailability and total uptake in shoots. Additionally, earthworms weaken the immobilization effect of biochar on heavy metals. The results of principal component analysis and correlation analysis showed that earthworm treatment was the main cause of soil pH reduction, and soil pH was significantly negatively correlated with the bioavailable Cd, Pb and Zn concentrations in the soil. Furthermore, the effect of the earthworm digestive system (casts) on bioavailable Cd, Pb and Zn concentrations could not explain their changes in the soil. In addition, the application of biochar had no significant effect on the survival and heavy metal enrichment of earthworm. Therefore, the effect of earthworms must be considered in the process of Cd, Pb and Zn contaminated farmland soil remediation using biochar.

研究采用4周土壤盆栽试验，探讨了蚯蚓对生物炭固定重金属的影响。结果表明，施用于Cd、Pb、Zn污染土壤的污泥和稻壳生物炭均显著降低了土壤中重金属的生物有效性及其在土壤孔隙水中的浓度。单独施用生物炭处理后，小白菜幼苗的Cd和Pb浓度分别下降了10.8%~11.7%和21.5%~26.5%。单独或联合施用生物炭和蚯蚓均可显著提升小白菜的生长。然而，与单独施用生物炭相比，蚯蚓与生物炭联合施用显著降低了土壤pH值0.1~0.19 个单位，且增加了Cd、Pb和Zn在土壤孔隙水中的浓度、生物有效性及小白菜对其的总吸收量。此外，蚯蚓还削弱了生物炭对重金属的固定作用。主成分分析和相关性分析结果表明，蚯蚓处理是引起土壤pH值下降的主要原因，而土壤pH值与土壤中生物可利用的Cd、Pb、Zn浓度呈显著负相关。然而，蚯蚓的消化系统对土壤中生物可利用Cd、Pb和Zn浓度的影响也不能解释其在土壤中引起的变化。此外，生物炭的施用对蚯蚓的存活和重金属在其体内的富集没有显著影响。综上所述，在利用生物炭对Cd、Pb、Zn污染农田土壤进行修复时，必须考虑蚯蚓的影响。