污染水体重金属形态分布的化学平衡模式

研究了湘江霞湾江段重金属污染区内镉、铅和铜的形态分布化学平衡模式,该模式体系包括12种金属和12种配体,涉及134个络合反应、42个沉淀反应和2个混合固体沉淀、5个氧化-还原反应、3种金属在颗粒物上的吸附反应。模拟研究了重金属沉淀的边界和区域,实验测定了该江段河水与重金属的络合容量和络合物的条件稳定常数作为有机配体的计算参数,考察了该江段悬浮沉积物对重金属吸附的表面络合常数作为吸附反应的输入参数。计算得到了该江段不同站位镉、铅和铜的形态分布,其结果与形态分析实测和水质分析结果基本一致。

A STUDY ON HEAVY METAL SPECIATION IN POLLUTED-RIVER WATER USING A CHEMICAL EQUILIBRIUM MODEL

Speciation of cadmium, lead and copper in polluted river water from-Xiawan section of Xiangjiang River was investigated using a modified REDEQL2 chemical equilibrium program. 12 metals and 12 ligands that form 134 complexes, 42 precipitates, 2 mixed solid precipitates, 5 oxidation-reduction reactions and adsorption of the metals on suspended solids -were considered according to water quality data collected during a period of 1982 to 1985. The precipitation diagrams were simulated and the comple-xation capacities, conditional stability constants and adsorption constants were measured so as to derive the model input parameters. The calculated results, which were quite consistent with measured data, indicated that at pH 7.5-8. 0 the dominant species are precipitates and adsorbed forms and the dissolved species, including free ions and inorganic complexes, account, for less than 10% of metals in the system. As pH decreases, the fractions, of dissolved metals increase sharply.