Coupled Solute Migration Through Clay Barrier Materials

9616854可混溶污染物（溶质）在土壤中迁移的传统平流-分散理论实际上代表了更一般的耦合流动理论的一种极限情况，在这种理论中，耦合项（例如由于化学渗透作用而产生的水流）被假定为零。虽然在混相污染物通过相对高渗透性材料迁移的情况下，这一假设通常是可以接受的，但就相对低渗透性、细粒度的典型污染物屏障材料而言，这一假设的准确性尚未得到正式评估。本研究的目的是评估化学渗透和电渗透对混溶污染物通过工程粘土屏障迁移的意义，这些屏障用于废物收容和原位修复。*将在几种不同的测试条件下（应力、压实、溶质浓度和类型）测量粘土的耦合流动参数（例如水力、化学渗透和电渗透电导率、电导率和渗透效率系数）；*预计在低流量条件下主导溶质运输的参数将在相同的土壤，溶质和测试条件下独立测量；*溶质通过实验室土壤柱的测量迁移速率将与使用基于耦合流动和平流扩散建模方法的分析模型的预测速率进行比较；并将开发一个有限差分模型，用于评估体积变化对耦合流动和平流扩散建模方法的溶质质量通量的潜在影响。＊＊＊

9616854 The traditional advection-dispersion theory for miscible contaminant (solute) migration through soil in reality represents a limiting case of the more general coupled-flow theory in which the coupling terms (e.g. water flow due to chemico-osmosis) are assumed to be zero. While this assumption is generally acceptable in the case of miscible contaminant migration through relatively high permeability materials, the accuracy of this assumption in terms of the relatively low-permeability, fine-grained materials typical of pollutant barriers has not been formally evaluated. The goal of this study is to evaluate the significance of chemico-osmosis and electro-osmosis on the migration of miscible contaminants through engineered clay barriers used for waste containment and in situ remediation. The following objectives will be addressed: * coupled flow parameters (e.g. hydraulic, chemico- osmotic, and electro-osmotic conductivity; electrical conductance; and osmotic efficiency coefficient) for clay soils will be measured under several different test conditions (stress, compaction, solute concentration and type); * parameters expected to dominate solute transport under low-flow conditions will be measured independently for the same soils, solutes, and test conditions; * measured migration rates of the solutes through laboratory soil columns will be compared with predicted rates using analytical models based on both the coupled flow and the advective-diffusive modeling approaches; and * a finite difference model will be developed and used to evaluate the potential effect of volume change on solute mass flux for both coupled flow and the advective-diffusive modeling approaches. ***