膨润土对镉污染土壤团聚体结构特征及有机碳含量的影响

通过4年田间原位钝化修复定位试验,研究施用膨润土钝化修复重金属镉污染菜地过程中,膨润土对土壤团聚体结构、稳定性以及有机碳含量变化特征。结果表明,与对照相比,施加膨润土后2～5 mm和5～8 mm粒径土壤团聚体数量增加,而2 mm的粒径团聚体数量则有所降低。投加膨润土提高了土壤团聚体稳定性,其几何平均直径(Geometric mean diameter, GMD)和平均质量直径(Mean weight diameter, MWD)分别增加9.57%～33.48%和4.74%～31.39%。与对照相比,全土和各粒径团聚体中有机碳含量随膨润土投加量增加而增加,而颗粒有机碳的含量则相反,最大降低了11.64%。投加膨润土提高了2～5 mm粒级团聚体对土壤有机碳含量的贡献率,0.5 mm粒级团聚体对土壤有机碳含量贡献率降低。投加膨润土后土壤烯烃类、烷烃类和酚类官能团含量有所增加,与对照相比,增加幅度分别为1.52%～4.55%、2.60%～36.28%和2.06%～10.98%。

Effects of bentonite on the characteristics of aggregate structure and organic carbon content in Cd-contaminated soils

Field experiments were conducted to investigate the effects of bentonite on the composition and stability of soil aggregates and organic carbon content during the processes of in situ immobilization remediation of Cd-contaminated vegetable field. The results showed that the amounts of 2~5 mm and 5~8 mm particle aggregates after applying bentonite increased, and the amounts of particle aggregates (<2 mm) decreased, compared to those of the control. The values of geometric mean diameter (GMD) and mean weight diameter (MWD) increased from 9.57% to 33.48% and from 4.74% to 33.39%, respectively, indicating the stability of aggregates improved. In contrast to the CK, the bentonite treatments enhanced the organic carbon in the whole soil and all aggregate particle sizes, but the contents of particle organic carbon in the whole soil and all aggregate particle sizes were inhibited, with a maximum reduction of 11.64%. The contribution rate of the soil organic carbon content in the 2~5 mm aggregates increased under the addition of bentonite, whereas <0.5 mm aggregates showed an opposite trend. The contents of functional groups of alkenes, alkanes, and phenols increased from 1.52% to 4.55%, from 2.60% to 36.28%, and from 2.06% to 10.98%, respectively, from those of the control groups.