组配钝化剂对镉铅复合污染土壤修复效果研究

Effects of combined passivating agents on remediation of Cd and Pb compound–contaminated soil

为研究组配钝化剂(纳米羟基磷灰石∶巯基化膨润土∶生物质炭=1∶2∶2)对镉铅复合污染土壤修复效果,以南京近郊某蔬菜基地镉(Cd)、铅(Pb)含量超标(Cd:0.89～1.37 mg·kg-1, Pb:441.9～707.8 mg·kg-1)的两块菜地土壤为研究对象,采用盆栽试验方法,研究不同钝化剂添加量(0、0.5%、1%、2.5%和5%)对菜地土壤理化性质和土壤Cd、Pb有效态含量的变化以及小白菜富集转运Cd、Pb的影响。结果表明:组配钝化剂能够有效提高土壤pH和CEC,使两种土壤有效态Cd和有效态Pb含量显著降低,同时降低了小白菜可食部位和根部对Cd、Pb的富集。与对照相比,两种土壤有效态Cd和有效态Pb最大降幅分别为60.34%～63.83%和81.84%～85.19%,小白菜可食部位降幅最大值分别为64.44%～81.48%和80.07%～82.98%。小白菜对Cd的富集和转运能力高于Pb,且2.5%～5%的钝化剂用量可同时显著降低小白菜对Cd、Pb的富集转运。添加钝化剂可以显著降低土壤中重金属Cd、Pb有效性,进而降低小白菜可食部位对Cd、Pb的积累和转运。从食品安全角度考虑,中度污染土壤(土壤A)推荐钝化剂用量为5%,轻度污染土壤(土壤B)推荐钝化剂用量为2.5%。

To understand the influence of combined passivating agents(nano-hydroxyapatite∶mercaptobentonite∶biochar=1∶2∶2)on the remediation of Cd and Pb compound–contaminated soil(Cd:0.89~1.37mg·kg-1,Pb:441.9~707.8mg·kg-1),using Cd-Pb contaminated soils collected from vegetable bases in Nanjing,a pot experiment was carried out to investigate the effects of different amounts of the com?bined passivating agents(0,0.5%,1%,2.5%,and5%)on the soil physical and chemical properties,contents of available Cd and Pb in the tested soils,and accumulation and translocation of Cd and Pb in pakchoi(Brassica chinensis L.).The results indicated that the application of combined passivating agents can effectively increase the soil pH and cation exchange capacity,and significantly decrease the contents of available Cd and Pb in the tested soils.Furthermore,the concentrations of Cd and Pb in the edible parts and roots of pakchoi decreased ob?viously.Compared with those in the control treatment,the maximum degrees of reduction for the Cd and Pb contents were60.34%~63.83%and81.84%~85.19%,respectively.The contents of Cd and Pb in the edible parts of pakchoi decreased by64.44%~81.48%and80.07%~82.98%,respectively.It was found that the bioaccumulation capacity of pakchoi was greater for Cd than that for Pb.The accumulation and translocation of Cd and Pb in pakchoi decreased significantly when the amount of passivating agent was2.5%~5%.The application of com?bined passivating agents can significantly decrease the effectiveness of Cd and Pb in the tested soil,and thus decrease the accumulation of Cd and Pb in the edible parts of pakchoi.From the perspective of food safety,the recommended application rate for soil A was5%,and that for soil B was2.5%.