Coupled Solute Migration Through Clay Barrier Materials

9616855现实中可混溶污染物(溶质)在土壤中迁移的传统平流-弥散理论是更一般的耦合流动理论的极限情况，在该理论中，耦合项(例如，化学渗透引起的水流)被假定为零。虽然这一假设在可混溶污染物通过相对高渗透性材料迁移的情况下通常是可以接受的，但就污染物屏障典型的相对低渗透性、细粒材料而言，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可混溶污染物通过用于废物遏制和原位修复的工程粘土屏障的迁移的意义。*将在几种不同的测试条件(应力、压实、溶质浓度和类型)下测量粘土的耦合流动参数(例如水力、化学渗透和电渗；电导和渗透效率系数)；*对于相同的土壤、溶质和测试条件，将独立测量在低流动条件下主导溶质运移的参数；*将使用基于耦合流动和对流-扩散模拟方法的分析模型，将实验室土柱中测量的溶质运移速率与预测的运移速率进行比较；开发了一个有限差分模型，用来评估耦合流动和对流-扩散模拟方法中体积变化对溶质质量通量的潜在影响。***

9616855 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. ***