南京市农用地土壤中重金属形态特征分析

Research on the Chemical Speciation of Heavy Metals in Agricultural Soil in Nanjing

以南京市农用地土壤为研究对象,采用顺序提取的方法对Cu、Zn、Pb、Cd做化学形态分析,了解不同元素各形态下空间赋存的含量与占比。结果表明,在农用地土壤中,上述4种金属元素所赋存的化学形态活泼性顺序为Cd>Pb>Cu>Zn,其中Cd主要为醋酸提取态,Pb主要为可还原态,各占总量的40%以上,具有较高的生物有效性和潜在危害性;Cu与Zn主要为残渣态,占总量的60%左右,生物可利用性较低。由因子分析法可知,土壤p H值越大,Zn与Cd就越趋于向稳定的化学形态转化,土壤有机质含量越高,对Cu与Pb的络合能力就越强,可以降低其环境危害性。

Taking the agricultural soil in Nanjing as research object, the chemical speciation of Cu,Zn,Pb and Cd were analyzed by using sequential extraction method. The spatial distribution and the mass ratio of each element were discussed. Results showed that the chemical activity of the 4 elements were in the order of Cd〉Pb〉Cu〉Zn. Acetic acid-extractable Cd and reduced Pb both accounted for over 40% of its total amount, indicating high bio-availability and potential hazard. Residual Cu and Zn accounted for about 60% of its total amount, indication low bio-availability. Through factor analysis,Zn and Cd tended to transform into stable chemical speciation with pH value rising. Cu and Pb had strong complexation ability when organic matter was high in soil, in that case their harm to the environment would be reduced.