Collaborative Research: A Systematic Study of solute Transport Influenced by Preferential Flow Paths at the Decimeter and Smaller Scales

最近在美国密西西比州哥伦布市的宏观分散实验（MADE）站点进行的研究表明，分米和更小尺度上由含水层非均质性引起的优先流动路径似乎对羽状尺度的溶质运移具有主导作用。这项合作研究回应了普遍缺乏的研究，即在MADE站点观察到的dm尺度非均质性对羽状尺度溶质迁移的影响。我们的目的是系统地研究受dm尺度优先流动路径影响的溶质输运特征，并严格检验双域传质方法可以有效表征这种特征的假设。四个具体的要素被纳入拟议的研究。(1)生成三维地质上合理的dm尺度河流沉积通道网络，并模拟这些系统中的详细运输。(2)评估双域质传递模型的能力，以及其他可能的替代模型，以代表溶质传输的关键特征。(3)进行一系列大直径柱实验，测量不同非均质配置和流量下的传质模型参数值。(4)在MADE现场进行示踪试验，利用染料示踪、土壤取心和图像分析，获得传质模型参数值，旨在提供优先流道的直接现场证据。我们将尝试将岩性特征与从示踪剂测试中获得的传质模型参数联系起来。

Zheng0003511Recent studies at the Macrodispersion Experiment (MADE) site in Columbus, Mississippi have indicated that the preferential flow paths resulting from aquifer heterogeneities at decimeter (dm) and smaller scales appear to have a dominant effect on plume-scale solute transport. This collaborative research responds to the general lack of studies on the effect of dm-scale heterogeneities on plume-scale solute transport as observed at the MADE site. Our intent is to systematically study the characteristics of solute transport influenced by dm-scale preferential flow paths, and rigorously test the hypothesis that a dual-domain mass transfer approach can provide an effective representation of such characteristics.Four specific elements are integrated into the proposed research. (1) Generate 3-D geologically plausible networks of dm-scale fluvially deposited channels and simulate detailed transport in such systems. (2) Assess the ability of the dual-domain mass transfer model, and possibly other alternative models, to represent the key characteristics of solute transport. (3) Conduct a series of large-diameter column experiments to measure the mass transfer model parameter values under different heterogeneity configurations and flow rates. (4) Conduct tracer tests at the MADE site to obtain the mass transfer model parameter values, using dye-tracing, soil coring and image analysis aimed at providing direct field evidence of preferential flow paths. We will attempt to relate the lithologic characteristics to the mass transfer model parameters obtained from the tracer tests.