Analyses of Migration Behavior of Heavy Metal Ions in Soil Sphere

从标准土壤样品中提取了黄腐酸（FA）和腐植酸（HA）。此外，还制备了与二氧化硅化学键合的腐植酸（CBHA）。根据pH滴定法对FA、HA和CBHA样品的聚电解质性质和非均质性进行了评估。结果表明：1)HA和CBHA样品中主要含有具有pKa bb0 4的羧酸，而FA的羧酸大多具有pKa<2的特征；2)HA和CBHA平衡所需的时间远长于FA，这可能是由于在水溶液中形成聚集所致。HA主链的疏水性可能是其聚集形成的主要原因，值得进一步研究。基于Gibbs-Donnan模型分析了FA样品和CBHA样品的络合平衡。在FA和/或HA存在的情况下，监测了阳离子交换柱上重金属离子的洗脱行为。柱实验得到的洗脱剖面反映了重金属离子在天然水/土壤系统中的迁移剖面。

Fulvic acid(FA) and Humic acid(HA) have been extracted from standard soil samples. In addition, chemically bonded humic acid(CBHA) with silica was prepared. Both polyelectrolytic nature and heterogeneity nature of the FA, HA, and CBHA samples have been evaluated according to pH titration procedure. It has been clarified that 1) HA and CBHA samples mainly contain carboxylic acids with pKa > 4, whereas most of the carboxylic acids of FA show pKa<2, and 2) the time required for equilibration of HA and CBHA is much longer than FA, probably due to aggregation formation in aqueous solution. The hydrophobic nature of HA backbone is expected to be the main reason for the aggregation formation, which seems worth further study. Complexation equilibria of FA samples as well as CBHA samples have been analyzed based on Gibbs-Donnan model. Elution behavior of heavy metal ions on a cation-exchanger column has been monitored in the presence of FA and/or HA. The elution profile obtained by the column experiment reflects the migration profile of heavy metal ions in natural water/soil systems.