Light-Transmission Visualization of Colloid Transport at the Meso Scale under Heterogeneous Conditions

SELKER 0610076胶体是营养物质和污染物在地下传输的普遍媒介。除了两相模型所预测的以外，移动胶体已被证明有助于污染物的传输，这些污染物对其表面具有很高的亲和力。此外，负责污染物降解的微生物的迁移也是一个胶体迁移过程。因此，了解胶体迁移过程对于预测土壤污染物的迁移和分解以及设计和实施生物修复系统至关重要。环境中的非均质性是普遍存在的，发生在质地转变处、毛细边缘以及湿润和排出前沿，并且对胶体的传输有深远的影响。本研究的目的是观察中观非均质性对变饱和多孔介质中胶体运动的影响。胶体传输的实验室实验主要是在柱子中进行的，数据收集仅限于流出物突破和实验后破坏性采样，无法观察空间和时间变异性对胶体传输过程的影响。将在这项工作中使用并进一步发展的光传输系统为阐明由介观非均匀引起的传输动力学提供了很大的希望。这种可视化技术非常适合于观察饱和转变和物理不均匀对胶体输运的影响。研究的非均质性将包括在毛细管边缘发现的水分变化，垂直于流动路径的不同介质等级的分层的结构变化，以及模拟降雨驱动的渗透事件的流动状况的变化。将在每个区域内探索颗粒大小和胶体浓度的影响。

Selker 0610076Colloids are ubiquitous agents of nutrient and contaminant transport in the subsurface. Beyond what is predicted by two-phase models, mobile colloids have been shown to facilitate the transport of contaminants having a high affinity for their surfaces. Additionally, the migration of microorganisms responsible for contaminant degradation is also a colloidal transport process. Understanding colloid transport processes is therefore essential for predicting the migration and breakdown of soil-borne contaminants, and for the design and implementation of bioremediation systems. Heterogeneity in the environment is ubiquitous, occurring at textural transitions, the capillary fringe, and at wetting and draining fronts, and has profound impact on colloidal transport. The objective of this study is to observe the effects of meso-scale heterogeneity on the movement of colloids in variably-saturated porous media. Laboratory experiments on colloid transport have been conducted largely in columns where data collection has been limited to effluent break through and post-experimental destructive sampling, which has not allowed observation of the effects of spatial and temporal variability upon colloidal transport processes. The light-transmission system which will be used and further advanced in this work holds great promise for elucidation of transport dynamics resulting from meso-scale heterogeneity. This visualization technique is well-suited to observing the effects of saturation transitions and physical heterogeneities on colloidal transport. Heterogeneities explored will include the water content variation found at the capillary fringe, textural variation as layering of different media grades perpendicular to flow paths, and variation of the flow regime to mimic precipitation-driven infiltration events. The impact of particle size and colloid concentration will be explored within each regime.