中药渣生物有机肥对镉-汞复合污染土壤的钝化效果

Effects of bio-organic fertilizer made from Chinese traditional herb residues on heavy metal passivation in Cd and Hg compound-contaminated soils

为探究中药渣生物有机肥对农田土壤重金属的钝化效果及影响机制,选取不同镉(Cd)污染水平(高、中、低)自然农田土壤为研究对象,通过土培试验,分析中药渣生物有机肥不同施用比例[0(CK)、1.5%、3.0%和6.0%]对土壤有机质、pH、阳离子交换量(cation exchange capacity,CEC)以及Cd和汞(Hg)的形态变化、钝化率(immobilization efficiency,IE)、迁移率指数(mobility index,MI)的影响,并通过土壤理化性质与重金属形态的相关性分析,初步探讨其钝化机制。结果表明:施用中药渣生物有机肥可提高土壤有机质含量、pH和CEC,且随施用比例的增加而显著提高。施用中药渣生物有机肥可降低土壤中的可交换态和碳酸盐结合态Cd、Hg含量,增加有机结合态和残渣态Cd、Hg含量;且可交换态和碳酸盐结合态含量的降幅及有机结合态和残渣态含量的增幅均以6.0%处理最高,3.0%处理次之,1.5%处理最低。施用中药渣生物有机肥可降低土壤Cd、Hg的迁移率,增加Cd、Hg的钝化率;且迁移率的增幅和钝化率的降幅均以6.0%处理最高,3.0%处理次之,1.5%处理最低。相关性分析结果表明,土壤有机质含量、pH和CEC与可交换态Cd、Hg含量均呈显著负相关(P<0.05),与有机结合态Cd含量呈显著或极显著正相关(P<0.05或P<0.01),土壤有机质含量和CEC与有机结合态Hg含量呈显著正相关(P<0.05)。总体上,施用中药渣生物有机肥可有效改善土壤理化性质,降低土壤重金属Cd、Hg的生物有效性,从而达到修复土壤的目的。

This study aimed to understand the passivation effects and mechanisms of bio-organic fertilizer made from Chinese traditional herb residues(BOFCTHR)on heavy metals in farmland soils.The soils with three levels of Cd-contamination were collected from Longli County(high pollution),Wanshan District,Tongren City(medium pollution),and Danzhai County(low pollution)in Guizhou Province.A soil incubation experiment was conducted to study the effect of BOFCTHR on soil organic matter,p H,cation exchange capacity(CEC),the morphological transformation of Cd and Hg,immobilization efficiency(IE)and mobility index(MI)under the addition of 0(CK),1.5%,3.0%and 6.0%BOFCTHR,respectively;and the correlation between the physiochemical properties of soils and the forms of heavy metals was analyzed.The results showed that the application of BOFCTHR increased significantly soil organic matter content,p H,and CEC in a dose-dependent manner.The application of BOFCTHR decreased exchangeable and carbonate-bound form contents of Cd and Hg,increased organic-bound and residual form contents of Cd and Hg;and the reduce amplitude of exchangeable and carbonate-bound form contents of Cd and Hg,and the increment amplitude of organic-bound and residual form contents of Cd and Hg followed the order:6.0%BOFCTHR>3.0%BOFCTHR>1.5%BOFCTHR.The application of BOFCTHR decreased MI of Cd and Hg,and increased IE of Cd and Hg;and the reduce amplitude of MI of Cd and Hg,and the increment amplitude of IE of Cd and Hg followed the order:6.0%BOFCTHR>3.0%BOFCTHR>1.5%BOFCTHR.The correlation analysis showed that soil organic matter content,p H,and CEC were significant negative correlation with exchangeable form content of Cd and Hg(P<0.05),and significant or extremely significant positive correlation with organic-bound form content of Cd(P<0.05 or P<0.01);soil organic matter content and CEC were significant positive correlation with organic-bound form content of Hg(P<0.05).It is concluded that BOFCTHR may affect the passivation effect of heavy metals in the soil by changing the physiochemical properties.