土壤腐殖酸与~(109)Cd、~(65)Zn及其复合存在的络合物稳定性研究

 应用同位素示踪法和离子交换平衡法测定了 Ｃｄ、Ｚｎ为单一离子及复合存在时．土壤胡敏酸（ＨＡ）和富里酸（ＦＡ）与Ｃｄ、Ｚｎ的络合稳定常数及配位数。结果表明、Ｃｄ、Ｚｎ为单一离子时．ＨＡ－１０９Ｃｄ（６５Ｚｎ）络合物的稳定常数与配位数均大于ＦＡ－１０９Ｃｄ（６５Ｚｎ）络合物稳定常数与配位数，而ＨＡ（ＦＡ）－６５Ｚｎ的稳定常数与配位数大于ＨＡ（ＦＡ）－１０９Ｃｄ。１０９Ｃｄ、６５Ｚｎ为复合体系共存与单一存在相比较．ＨＡ（ＦＡ）－６５Ｚｎ络合物稳定常数与配位数有明显的提高，ＨＡ（ＦＡ）－１０９Ｃｄ络合稳定常数与配位数则明显降低。研究结果说明，在重金属污染土壤上施用大分子的腐殖酸较小分子的腐殖酸更能有效地降低重金属元素的植物有效性，Ｚｎ污染土壤上施用腐殖酸较Ｃｄ污染土壤上施用腐殖酸更能有效地降低重金属元素对植物的毒害。而 Ｃｄ、Ｚｎ复合存在时与单一离子存在时相比较，施用腐殖酸将增加 Ｃｄ污染的危害，而减少Ｚｎ污染的危害。

Studies on Stability of~(109)Cd,~(65)Zn Complex with Humus Acids

The radioactive isotope tracer and ion exchange balanced method was used to study the stability of 109Cd,65Zn complexes with humus acids. The stability constants of humic-109Cd(65Zn) complexation was higher than that of fulvic-109Cd(65Zn) complexation. The stability constant of humic (fulvic) -65Zn was higher than that of humic (fulvic) -159Cd. In 109Cd and 65Zn coexisting system, humic (fulvic)-65Zn complex stability constant and co-ordination number obviously increased, but humic (fulvic)-65Zn complex stability constant and co-ordination number obviously decreased. The result showed that the humic matter with higher molecular weight could more effectively reduce plant availability of heavy metals than the humic matter with lower molecular weight in polluted soil, and that humic matter could more effectively reduce plant availability of Zn than that of Cd. Application of humic-acid increased harm of Cd and decreased harm of Zn to plant with Cd-Zn coexistence.