施用典型有机固废生物炭对土壤重金属生物有效性的影响

将有机固废经热解转化为生物炭，具有改良土壤、促进碳固定、钝化重金属等优点，但有机固废生物炭中被钝化重金属进入土壤后生物有效性尚不明确。采用盆栽方法评估了施用市政污泥、中药渣等典型有机固废生物炭对受纳土壤中重金属有效性及植物吸收、传输重金属的影响。结果表明，施用污泥炭、中药渣炭显著增加了土壤中As、Zn的化学提取有效态含量，从而降低了Cr、Pb有效态含量(P < 0.05)，对Cd、Cu、Ni有效态含量也有不同程度的降低趋势；同时，抑制了除Zn以外As、Cd、Cr、Cu、Ni、Pb等6种重金属从土壤向植物的传输、累积，降幅最高达30%。中药渣炭联合污泥炭施用可进一步抑制7种重金属在植物地上部分以及除As、Cr外其他重金属在根中的吸收、累积。本研究结果可为评估有机固废生物炭土地利用的环境风险提供参考。

Effects of application of typical organic solid wastes-derived biochar on bioavailability of heavy metals in soil

Converting organic solid wastes (OSW) into biochar through pyrolysis has been receiving increasing attention due to the merits including ameliorating soil properties, facilitating carbon sequestration, and immobilizing heavy metals. However, the bioavailability of the immobilized heavy metals in soil remains unclear. The effects of two typical OSW- (i.e., municipal sludge- and medicinal herb residue-) derived biochars on the availability of heavy metals in the receiving soil and the uptake and transport of the heavy metals by plants were investigated using pot experiments. The results indicated that the two biochars significantly increased the chemical availability of As and Zn whereas decreased the available contents of Cr and Pb (P < 0.05) in the soil. The available contents of Cd, Cu, and Ni were also decreased to a certain extent by the biochar introduction. Meanwhile, these two biochars significantly decreased, with a maximum decreasing rate of 30%, the uptake of six heavy metals (i.e., As, Cd, Cr, Cu, Ni, and Pb) except for Zn in both the aerial and root parts of maize. The combined application of medicinal herb residue-derived biochar with municipal sludge-derived biochar further decreased the uptake of heavy metals in the plant from soil except for the increased uptake of As and Cr in the root compared to application of municipal sludge-derived biochar alone. This study provides vital basis for assessing the environmental risks of OSW-derived biochar when applied to land.