根茬连续还田对镉污染农田土壤中镉赋存形态和生物有效性的影响

通过盆栽试验研究不同镉污染土壤上分别连作3茬玉米和菜豆,根茬连续还田后对后茬作物生长、镉吸收及土壤中镉赋存形态的影响.结果表明,两种镉污染土壤上分别连作3茬菜豆和玉米,根茬累计还田量占土壤质量的0.4%～1.1%,通过根茬累计还田的镉占土壤全镉的1.3%～3.5%.玉米和菜豆根茬连续还田对后茬大白菜和冬小麦生长均无显著影响,但在镉污染土壤上根茬连续还田后显著增加了后茬大白菜地上部镉含量.根茬连续还田对后茬小麦吸收镉无影响.根茬连续还田增加了土壤轻组有机质含量和模拟镉污染土壤中轻组有机质中镉占土壤全镉的比例.镉污染土壤连续还田玉米根茬后土壤碳酸盐结合态镉含量显著降低,在模拟镉污染土壤上菜豆根茬连续还田显著降低了土壤交换态镉含量,根茬连续还田增加了土壤中氧化物结合态镉含量.

Phytoavailability and Chemical Speciation of Cadmium in Different Cd-Contaminated Soils with Crop Root Return

Pot experiments were conducted under greenhouse condition to investigate the effects of crop root return on succeeding crops growth, Cd uptake and soil Cd speciation in Cd-contaminated soil and artificial Cd-contaminated soil. The results showed that the amount of root residue returned to soil by corn and kidney bean growth successive for 3 times was 0.4%-1.1%. The Cd returned to soil by root residue was 1.3%-3.5% to the total soil Cd. There was no significant difference in the shoot dry weights of winter wheat and Chinese cabbage grown on the 2 Cd-contaminated soils with and without root return. While Cd concentration of Chinese cabbage increased significantly in the Cd-contaminated soil with corn or kidney bean root return. Light fraction of soil organic matter increased with root return in both of the Cd-contaminated soils. The percentage of Cd in the light fraction of soil organic matter increased with root return in the artificial Cd-contaminated soil. Soil carbonates-bound Cd concentration decreased significantly with corn root return in the Cd-contaminated soil. Soil exchangeable Cd concentration decreased and soil Fe-Mn oxide-bound Cd concentration increased significantly with kidney bean root return in the artificial Cd-contaminated soil.