Institute of Hydrochemistry, Technische Universitt Mnchen, Marchioninistr. 17, D-81377 Munich, Germany.
Water Res. 2010 Feb;44(4):1246-54. doi: 10.1016/j.watres.2009.11.035. Epub 2009 Nov 26.
Dispersion describes the spreading of a tracer or contaminant in an aquifer. Detailed knowledge of dispersion is the key to successful risk assessment in case of groundwater pollution or groundwater protection. The dispersion of colloids on the pore scale is controlled by flow velocity, ionic strength, colloid size, colloid concentration, and colloid-matrix interactions. The objective of this study was to provide quantitative data and to assess the scale dependency of colloid dispersion on the pore scale. The positions of carboxylated polystyrene microspheres (1 microm, 0.5 microm) were recorded during transport experiments in silicon micromodels with three pore topologies. The positions were combined into particle trajectories revealing the flow path of individual colloids. More than thousand trajectories were evaluated for each experiment to obtain the dispersivity of the colloids for flow distances between 10 and 1000 microm. All experiments were run at high Peclet numbers. The pore scale dispersivity was on the order of 8-30% of the flow distance with pure water, dependent on the heterogeneity of the pore topology. The dispersivity was positively correlated with the ionic strength and inversely correlated with the colloid size and the flow velocity. A coating of the micromodel surface with humic acid also increased dispersivity. The quantitative data set presented here supports the theoretical framework for colloid transport and allows to parametrize colloid transport on the pore scale.
弥散描述示踪剂或污染物在含水层中的扩散。详细了解弥散是地下水污染或地下水保护风险评估成功的关键。胶体在孔隙尺度上的弥散受流速、离子强度、胶体大小、胶体浓度和胶体-基质相互作用的控制。本研究的目的是提供定量数据，并评估胶体弥散在孔隙尺度上的尺度依赖性。在具有三种孔隙拓扑结构的硅微模型中进行的运输实验中记录了羧基化聚苯乙烯微球（1 微米、0.5 微米）的位置。将位置组合成颗粒轨迹，揭示了单个胶体的流动路径。为了获得胶体在 10 至 1000 微米的流动距离上的弥散度，对每个实验都进行了超过一千次轨迹评估。所有实验均在高 Peclet 数下进行。在纯水中，孔隙尺度的弥散度约为流动距离的 8-30%，取决于孔隙拓扑的非均质性。弥散度与离子强度呈正相关，与胶体大小和流速呈负相关。在微模型表面涂覆腐殖酸也会增加弥散度。这里提供的定量数据集支持胶体输运的理论框架，并允许在孔隙尺度上参数化胶体输运。
