Colloid Retention in Unsaturated Porous Media due to Capillary Forces

毛细管力导致不饱和多孔介质中的胶体保留

• 批准号: 0635954
• 负责人: Tammo Steenhuis
• 金额: $ 19.01万
• 依托单位: Cornell Univ - State: AWDS MADE PRIOR MAY 2010
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-04-01 至 2010-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0635954&HistoricalAwards=false
• 关键词: Colloid; Retention; Unsaturated; Porous; Media

Colloid transport is an important mechanism in the movement of contaminants through the vadose zone to groundwater. However, direct observations of colloid transport in unsaturated soils have typically been limited. As a result, differing and conflicting colloid transport mechanisms have been proposed for the effects that the air phase plays on the retention of colloids, with little predictive ability to date. Proposed are pore-scale visualization studies of colloid movement and retention in unsaturated natural sand. These observations, coupled with breakthrough measurements, will allow greater understanding of the actual mechanisms governing colloidal transport in unsaturated media. Our hypothesis is that capillary forces determine the unique features of colloid retention and release in the thin water films where the air-water and water-solid interfaces closely approach each other in unsaturated porous media. We will investigate how the nature and magnitude of interfacial interaction energies through changes in properties of both the porous media such as surface roughness and the colloid properties will result in observable and predictable changes in capillary force-dependent retention behavior including water meniscus contact angle, extent and location of retention at the air-water-solid interface; 3 D reconstructions of images obtained using bright-field microscopy and confocal scanning laser microscopy will be analyzed digitally and used to quantify the movement and retention, rates of colloids. These experimental results will then be used to test and quantify the mechanisms that governing colloid retention and transport in unsaturated porous media.Recent experience confirms that the role of colloidal transport in groundwater contamination is typically ignored in the environmental regulatory and assessment sphere. The research will improve the knowledge on how micrometer-size colloids move in unsaturated hydrological systems and thereby will help improve models in order to make possible more accurate predictions of conditions under which groundwater contamination can take place.

胶体迁移是污染物通过包气带向地下水迁移的重要机制。然而，胶体在非饱和土壤中的迁移的直接观察通常是有限的。因此，不同的和相互冲突的胶体传输机制已被提出的影响，空气相发挥对胶体的保留，几乎没有预测能力的日期。提出了孔隙尺度的可视化研究胶体运动和保留在非饱和天然砂。这些观察，再加上突破性的测量，将允许更好地理解的实际机制，在不饱和介质中的胶体运输。我们的假设是，毛细作用力决定了胶体的保留和释放的独特功能，在薄水膜的空气-水和水-固体界面紧密接近对方在非饱和多孔介质。我们将研究如何通过多孔介质的性质（如表面粗糙度和胶体性质）的变化来改变界面相互作用能的性质和大小，从而导致毛细力依赖的保留行为（包括水弯月面接触角、空气-水-固体界面处的保留程度和位置）的可观察和可预测的变化;使用明场显微镜和共聚焦扫描激光显微镜获得的图像的3D重建将被数字化分析，并用于量化胶体的移动和保留率。这些实验结果将被用来测试和量化的机制，管理胶体在不饱和多孔media.Recent经验证实，胶体运输地下水污染的作用通常被忽视的环境监管和评估领域。这项研究将增进关于微米级胶体如何在不饱和水文系统中移动的知识，从而有助于改进模型，以便能够更准确地预测地下水污染可能发生的条件。