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通过离子交换平衡法测定了胡敏酸的2 个不同分子量分级组分及富里酸与Cd 、Zn 络合反应的稳定常数及配位数,结果表明:随着腐植酸芳构化程度的提高,其与Cd 、Zn 的络合物的配位数及稳定常数也逐渐提高;当胡敏酸的分子量为48339 时,其对Cd 、Zn 的络合物稳定常数log K 值分别为5-20 和4-81 ,配位数分别为1-26 和1-15 ;而当分子量增加为78180 时,logK 值分别为5-68 和5-37 ,配位数分别为1-32和1-26 。富里酸镉、锌的稳定常数( 分子量为2300) 分别为4-44 和4-42 ,配位数分别为1-29 和1-30 。这些结果表明,就减轻污染土壤中Cd 、Zn 对植物的危害而言,施用厩肥等芳构化程度较高的有机物比芳构化程度低的更为有效。
The stability constants and coordination numbers of two different molecular weight components of fulvic acid and the complexation of fulvic acid with Cd and Zn were determined by ion exchange equilibrium method. The results showed that with the increase of aromatization degree of humic acid, The coordination number and stability constant of complexes with Cd and Zn also increased gradually. When the molecular weight of humic acid was 48339, the log K values of complexes with Cd and Zn were 5-20 and 4-81 with coordination numbers 1-26 and 1-15, respectively. When the molecular weight increased to 78180, the logK values were 5-68 and 5-37, respectively, and the coordination numbers were 1-32 and 1-26, respectively. The stability constants (molecular weight 2300) of fulvic acid-cadmium and zinc are 4-44 and 4-42 respectively, and the coordination numbers are 1-29 and 1-30, respectively. These results indicate that organic matter with a higher degree of aromatization, such as manure, is more effective than aromatics, in terms of alleviating the harmful effects of Cd and Zn on plants in contaminated soils.