玉米和小麦秸秆生物炭对土壤重金属污染修复实验研究

Experimental study on remediation effect of maize and wheat biochar on heavy metal contaminated soil

为揭示不同秸秆生物炭对土壤中重金属污染修复的效果和机理,文章取矿山附近农田酸性土壤,以质量比5%分别施加玉米秸秆生物炭(maize biochar,MBC)和小麦秸秆生物炭(wheat biochar,WBC),并在培养10、25、40、55 d后取样分析土壤物理、化学性质和重金属形态变化,比较2种生物炭对Hg、Cd、Pb单一和复合污染土壤的修复效果。结果表明:施加2种生物炭均使土壤pH值、电导率显著提升;WBC对Hg的修复效果更好,MBC对Cd、Pb的修复效果更好,说明对Hg固化的主要作用可能是与官能团的络合反应,对Cd、Pb固化的主要作用可能是沉淀与阳离子交换吸附作用;Hg、Cd在单一污染土壤中修复效果更好,Pb在复合污染土壤中修复效果更好,3种重金属元素复合污染土壤的修复中,竞争吸附对Hg、Cd起抑制作用,对Pb起促进作用。

In order to reveal the effect and mechanism of different straw biochars on repairing the heavy metal contamination in the soil,the acid soil of farmland near the mine was chosen,and maize biochar(MBC)and wheat biochar(WBC)were applied at a rate of 5%,respectively.After 10,25,40 and 55 days,sampling and analysis of soil physicochemical properties and heavy metal fractions changes were made.The remediation effects of the two biochars on the soil with single and combined contamination of Hg,Cd,Pb were compared.It was found that soil pH and conductivity increased significantly after soil incubation with MBC and WBC.Besides,WBC had better remediation effect on Hg,and MBC had better remediation effect on Cd and Pb.It showed that the main immobilization mechanism on Hg might be the complexation reaction with functional groups,and Cd and Pb were mainly immobilized by precipitation and cation exchange absorption.In the soil with single contamination,the repairing effect on Hg and Cd was better,and the repairing effect on Pb was better in the soil with combined contamination.In the remediation of the soil contaminated by three heavy metals,competitive adsorption inhibited Hg and Cd,and promoted Pb.