土壤性质对水稻土中外源镉与铅生物有效性的影响

Effects of soil properties on the bioavailability of added cadmium and lead in paddy soils

为定量了解土壤理化性质对进入土壤中的外源镉和铅生物有效性的影响,采集了性质相差较大的16个水稻土,通过添加Cd(或Pb)培养和老化处理(Cd的加入量为0、0.2、0.5、1、2和5mg·kg-1;Pb加入量为0、20、50、100、200和500mg·kg-1,培养时间为1年),研究了不同土壤中Cd(或Pb)负荷与土壤中水溶态和交换态Cd(或Pb)的关系。结果表明,随着Cd(或Pb)污染水平的提高,土壤中水溶态和交换态Cd(或Pb)均显著增加,但不同土壤中水溶态和交换态Cd(或Pb)随土壤Cd(或Pb)积累的增加幅度有很大的差异。相关分析表明,水稻土中水溶性Cd(或Pb)主要与土壤Cd(或Pb)污染水平和pH值有关;而交换态Cd(或Pb)主要与土壤Cd(或Pb)污染水平、pH值、CEC及质地等有关。数据显示,pH值较高、质地较黏的土壤可大大减缓因污染引起的Cd和Pb生物有效性的提高。

In order to understand the effect of soil properties on bio-availability of the metals added in soil, 16 paddy soils with diverse properties were collected, and treated with different rates of Cd （0,0.2,0.5,1,2,and 5 mg·kg^-1） or Pb（0,20,50,100,200,and 500 mg·kg^-1）. After one-year incubation, the treated soils were analyzed for water-soluble and exchangeable Cd and Pb. The results show that water-soluble and exchangeable Cd and Pb in the soils increased with increasing loads of Cd and Pb in the soils. However, the increase extent of water-soluble and exchangeable Cd and Pb in the incubated soils varied among the soils. Correlation analysis indicated that soil water-soluble Cd and Pb were mainly correlated with total Cd and Pb, and pH, while soil exchangeable Cd and Pb were mainly correlated with total Cd and Pb, and pH, CEC, and texture of the soils. The soil with high pH and clay content had strong capacity to buffer Cd and Pb pollution. The results suggested that total concentration of Cd and Pb in contaminated soil could not be well used to evaluate the bioavailability of the metals.