Transport of colloids and colloid-facilitated transport of contaminants in soil and groundwater aquifers have been widely acknowledged in the literature. Mineral-grain attachment, air-water interface and contact line retention are the major mechanisms determining the extent of colloidal transport in unsaturated porous media. Although unsaturated colloidal transport has been extensively studied in past years, its complete understanding is pending. The present study investigates the parameters that affect the behavior of colloids on air-water interface and contact line. The principal elements of the employed experimental system include a glass channel micromodel and laser scanning confocal microscope, which allows the visualization of colloidal systems at the pore scale. The study includes both dynamic (flow) and static experiments. The flow experiments showed strong influence of hydrodynamic conditions both on air-water interface and contact line retention whereas the static experiments reflected the effect of solution chemistry. Applying to natural dynamic systems, the combined effect of chemical and hydrodynamic conditions on colloidal retention in soil is expected.
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