Department of Crop and Soil Sciences, §The Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University , Pullman, Washington 99164, United States.
Environ Sci Technol. 2014 Jul 1;48(13):7272-9. doi: 10.1021/es501797y. Epub 2014 Jun 17.
Capillary fringe fluctuations due to changing water tables lead to displacement of air-water interfaces in soils and sediments. These moving air-water interfaces can mobilize colloids. We visualized colloids interacting with moving air-water interfaces during capillary fringe fluctuations by confocal microscopy. We simulated capillary fringe fluctuations in a glass-bead-filled column. We studied four specific conditions: (1) colloids suspended in the aqueous phase, (2) colloids attached to the glass beads in an initially wet porous medium, (3) colloids attached to the glass beads in an initially dry porous medium, and (4) colloids suspended in the aqueous phase with the presence of a static air bubble. Confocal images confirmed that the capillary fringe fluctuations affect colloid transport behavior. Hydrophilic negatively charged colloids initially suspended in the aqueous phase were deposited at the solid-water interface after a drainage passage, but then were removed by subsequent capillary fringe fluctuations. The colloids that were initially attached to the wet or dry glass bead surface were detached by moving air-water interfaces in the capillary fringe. Hydrophilic negatively charged colloids did not attach to static air-bubbles, but hydrophobic negatively charged and hydrophilic positively charged colloids did. Our results demonstrate that capillary fringe fluctuations are an effective means for colloid mobilization.
由于地下水位变化导致的毛管 fringe 波动会导致土壤和沉积物中空气-水界面的移动。这些移动的空气-水界面可以使胶体颗粒移动。我们通过共焦显微镜可视化胶体在毛管 fringe 波动期间与移动的空气-水界面相互作用。我们在填充有玻璃珠的柱状物中模拟了毛管 fringe 波动。我们研究了四种特定条件：（1）胶体悬浮在水相中，（2）胶体最初附着在湿润多孔介质中的玻璃珠上，（3）胶体最初附着在干燥多孔介质中的玻璃珠上，以及（4）胶体悬浮在水相中同时存在静态气泡。共焦图像证实，毛管 fringe 波动会影响胶体的输运行为。最初悬浮在水相中的亲水性带负电荷的胶体在排水通道后沉积在固-水界面上，但随后被随后的毛管 fringe 波动去除。最初附着在湿或干玻璃珠表面上的胶体被毛管 fringe 中的移动空气-水界面所脱离。亲水性带负电荷的胶体不会附着在静态气泡上，但是疏水性带负电荷和亲水性带正电荷的胶体则会。我们的结果表明，毛管 fringe 波动是胶体迁移的有效手段。
