REACTIVE SOLUTE TRANSPORT MODELING IN GROUNDWATER

基于原状土柱实验和模拟结果，研究了不同交换选择系数下溶质的反应性输运。实验结果表明，Ca-Na和Ca-Mg交换的选择性系数可以认为是恒定的，而Ca-K交换的选择性系数随着K在固相中的等效分数的增加而增加。这种关系可以用指数回归方程近似表示，并将其纳入本研究建立的模拟模型中。对固相中等效分数的可变选择系数的使用导致了对液相和固相阳离子浓度分布的可接受的预测。相比之下，使用恒定的选择系数进行Ca-K交换对固相中阳离子浓度的空间分布提供了不太令人满意的预测。因此，可以通过对所考虑的土壤使用可变的选择系数来改善模型的性能。人们提出了各种测定固体中活性溶质命运的数学模型。并与实验结果进行了比较，讨论了模型的可靠性。应该强调的是，这些模型中使用的土壤化学参数在确定控制土壤中溶质运移的机制方面起着重要作用。

The reactive solute transport with a variable exchange selectivity coefficient was investigate based on undisturbed soil column experiments and simulation results. The experimental results indicated that the selectivity coefficients for Ca-Na and Ca-Mg exchange could be considered constant, while the slectivity coefficient for Ca-K exchange increased with the equivalent fraction of K in the solid phase This relationship was approximated by an exponential regression equation, which was incorporated in the simulation model developed in this study. The use of a variable selectivity coefficient for the equivalent fraction in the solid phase resulted in an acceptable prediction of cation concentration distributions for both the liquid and the solid phases. In contrast, the use of a constant selectivity coefficient for Ca-K exchange provided a less satisfactory prediction for the spatial distribution of cation concentrations in the solid phase. Therefore, it is concluded that the model performance can be improved by using a bariable selectivity coefficient for the soil under consideration. A variety of mathematical models for the determination of the fate of reactive solutes in soild has been proposed. The reliability of these models was discussed in comparison with experimental results. It should be emphasized that the soil chemical paramenters used in these models play an important role in identifying which mechanisms control the solute transport in soils.