Factors Controlling Solute Dilution in Heterogeneous Formations

本研究的目的是量化土壤导电性的异质性、局部分散和其他因素在控制多孔介质中稀释时间行为中的相互作用。虽然异质性对溶解化学品羽状物扩散的影响已经进行了广泛的研究，但异质性对污染物稀释的影响仍有待确定，特别是在与示踪剂试验和补救项目有关的“早期”阶段。稀释是量化的措施，如峰浓度和溶质占用的体积。扩散用浓度分布的空间二阶矩来量化。在评估地下水污染的环境影响时，除了污染的空间范围外，重要的是能够预测峰值浓度。在这项工作中，我们将进行理论分析，详细的数值实验，并与现场数据进行比较。污染物稀释措施将与多孔介质的本构参数有关，主要是与水力导电性的可变性有关。稀释的预测将通过解析近似或“闭包”进行，这将导致确定性方程，并通过变分分析。将对近似的性能进行数值评估，并将结果与现场实验结果进行比较。这项工作的贡献将是更好地理解非均质多孔介质中污染物浓度水平的时间演化，并指导从业者评估地下环境中污染物的稀释。

9522651 Kitanidis The objective of the proposed research is to quantify the interaction of heterogeneity in soil hydraulic conductivity, local dispersion, and other factors in controlling the temporal behavior of dilution in porous media. Although the effect of heterogeneity on the spreading of plumes of dissolved chemicals has been studied extensively, the effect of heterogeneity on dilution of contaminants remains to be determined, especially at "early" times, which are relevant in tracer tests and remediation projects. Dilution is quantified by measures such as the peak concentration and the volume occupied by solute. Spreading is quantified by the spatial second moment of the concentration distribution. In assessing environmental impacts of groundwater contamination, if is important to be able to anticipate peak concentration in addition to the spatial extent of contamination. In this work, we will conduct theoretical analysis, detailed numerical experiments, and comparisons with field data. Contaminant dilution measures will be related to the porous media constitutive parameters and, primarily, the variability of hydraulic conductivity. Predictions of dilution will be made via analytical approximations or "closures" which lead to deterministic equations and through variational analysis. The performance of the approximations will be numerically assessed and the results will be evaluated by comparison with results from field experiments. The contribution of this work will be a better understanding of the time-evolution of contaminant concentration levels in heterogeneous porous media, and guidance to the practitioner to assess dilution of contaminants in the subsurface environment.