HR: 0800h
AN: H21D-1047    [Abstracts]
TI: Visualization Of Colloids Distribution in Partially Saturated Media
AU: * Zevi, Y
EM: yz59@cornell.edu
AF: Biological \$ Environmental Engineering, Cornell University, Riley Robb Hall, Cornell University, Ithaca, NY 14850
AU: Dathe, A
EM: ad273@cornell.edu
AF: Biological \$ Environmental Engineering, Cornell University, Riley Robb Hall, Cornell University, Ithaca, NY 14850
AU: Richards, B K
EM: bkr2@cornell.edu
AF: Biological \$ Environmental Engineering, Cornell University, Riley Robb Hall, Cornell University, Ithaca, NY 14850
AU: Steenhuis, T S
EM: tss1@cornell.edu
AF: Biological \$ Environmental Engineering, Cornell University, Riley Robb Hall, Cornell University, Ithaca, NY 14850
AB: The distribution of colloid particles onto interfaces in partially saturated media was investigated by using a pore scale visualization technique which consists of a small horizontal chamber and a Leica Confocal Scanning Microscope. Synthetic hydrophilic (carboxylated latex) and hydrophobic (polystyrene latex) microspheres with diameters of 1 $\mu$m were applied using a 1.5 ml/min steady flow rate. Quartz sand of two different sizes (fine and coarse) and glass beads were used as media. For the hydrophilic colloids, we observed retention at the Air/Water meniscus/Solid (AWmS) interface for both sizes of sand grains and glass beads. The colloids were retained at the AWmS interface where the water menisci diminished to a thin water film on the grain surface, and the film thickness approximately equals to the colloid diameter. This mechanism can be explained by additional capillary potentials exerted on colloids, pulling them out from the menisci. Mechanisms for hydrophobic colloids differed slightly. When glass beads were used as media, retention occurred at the AWmS and the solid-water interface. However, with sand grains as media, the retention of hydrophobic colloids mostly occurred at the solid-water interface and only to an insignificant amount at the AWmS interface. The greater retention of hydrophobic colloid at the solid-water interface is due to irregularities in sand grain surfaces (compared to the smoother glass beads). This factor seems to play an insignificant role in the retention of hydrophilic colloids.
UR: http://www.bee.cornell.edu/swlab/colloids/videos2/
DE: 1832 Groundwater transport
DE: 1875 Unsaturated zone
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting