有机质对红壤和黑土中外源铅镉稳定化过程的影响

采用室内培养方法研究了中国典型红壤和黑土中外源铅（Pb）、镉（Cd）在单一和复合污染下的稳定化过程,探讨了土壤有机质含量对Pb、Cd稳定化过程的影响。结果表明,加入500mg·kg-1Pb、1.0mg·kg-1Cd或1.0mg·kg-1Cd＋500mg·kg-1Pb条件下,各种土壤有效态Pb、Cd含量在培养前期迅速下降,随后变化减缓,培养30d后基本达到平衡。利用二级动力学方程对Pb、Cd稳定化过程进行拟合,在红壤和黑土上,有机质含量高的土样有效态Cd的平衡浓度比有机质含量低的土样中降低12.7%～37.3%;有效态Pb的平衡浓度比有机质含量低的土样中降低78.3%～96.2%,相关分析表明,土壤有机质含量的增加显著抑制了外源Pb、Cd的有效性（P〈0.05）。在铅镉复合污染中,Pb的存在提高了土壤中Cd的有效性,而Cd对Pb的影响较小。与黑土相比,红壤上外源Pb、Cd稳定化速率较小,达到平衡所需的时间较长,且有效态Pb、Cd的平衡浓度较高。因此,在农业生产实践中,通过提高红壤和黑土上有机质的含量能够显著降低外源重金属Pb、Cd的有效性,减少环境污染风险。

Effects of Organic Matter on the Stabilization Process of Added Cadmium and Lead in Red Soil and Black Soil

The stabilization processes of cadmium（Cd） and lead（Pb） in single and combined metal-contaminated red soil and black soil of China were studied.Effects of content of soil organic matter on the stabilization process of added cadmium and lead were also studied.After 500 mg·kg-1 Pb,1.0 mg·kg-1 Cd or 500 mg·kg-1 Pb＋1.0 mg·kg-1 Cd were added in soil,soil available Pb or Cd were decreased rapidly during the first 15 days,then decreased slowly,and stabilized after 30 day＇s incubation.In the combined metal-contaminated soils,existing of Pb increased the concentration of soil available Cd whereas the Cd had no significant effect on the available Pb.The red soil needed more time to reach equilibrium,but had higher equilibrium concentrations of Pb and Cd than the black soil.The second-order equation was used to simulate the stabilization process of Cd or Pb.The equilibrium concentrations of Cd in red soil and black soil were 12.7%~37.3% lower in the soil samples with high organic matter relative to the soil samples with low organic matter,whereas the equilibrium concentrations of Pb in red soil and black soil were 78.3%~96.2% lower.Statistic analysis suggested that high content of soil organic matter retarded the availability of Cd and Pb significantly（P0.05）.Thus,increasing of organic matter in red soil or black soil was an effective way to decrease the availability of Cd and Pb and reduce the risk of environmental pollution in agricultural production.