冻融作用对黑土和棕壤中Pb、Cd吸附/解吸特征的影响

冻融作用对土壤理化性质具有重要影响，进而影响了土壤中重金属迁移转化过程和环境效应。通过实验模拟研究了冻融作用对黑土和棕壤中Pb、Cd吸附/解吸特征的影响。结果表明：黑土对Pb和Cd的吸附能力大于棕壤；冻融作用降低了土壤对Pb和Cd的吸附能力，这与冻融作用改变了土壤的理化性质有关；随着Pb和Cd吸附量的增大，黑土和棕壤中Pb和Cd的解吸量和解吸率也相应增大；冻融作用促进了黑土和棕壤中Pb和Cd的解吸，并且在同一冻融条件下黑土的解吸能力小于棕壤；冻融作用使得黑土和棕壤对Pb和Cd的解吸量大于未冻融土壤，这与冻融作用使解吸溶液pH的下降幅度增大有关。冻融作用降低了土壤对Pb和Cd的固持能力，增加了土壤中Pb和Cd的生态风险。

Effect of Freeze-Thawing Cycles on Adsorption-Desorption of Lead and Cadmium in Black Soil and Brown Soil

Freeze-thawing has an important effect on physicochemical properties of soil,the migration,transformation and the environmental effects of heavy metal in soils.The effects of freeze-thawing on absorption and desorption characteristics of Pb and Cd in black soil and brown soil were studied by laboratory simulation.The results showed that the absorption ability of Pb and Cd was stronger in black soil than that in brown soil.Freeze-thawing decreased absorption ability of Pb and Cd in the soils,resulting from the change of physicochemical properties of soils under the condition of freeze-thawing.The desorption quantity and rate of Pb and Cd in the soils increased with the increasing adsorption quantity of Pb and Cd.Freeze-thawing enhanced desorption of Pb and Cd in the two soils.However,the desorption ability of Pb and Cd in black soilwere weaker than that in brown soil in the same freeze-thawing condition.The reason is that freeze-thawing made absorption quantity of Pb and Cd in soils increasing was related with the decline of desorption solution pH.Freeze-thawing decreased retention ability of Pb and Cd in soils,consequently increasing ecological risk.