GEOC 45 |
| Markus Flury1, James Harsh2, and Szabolcs Czigany2. (1) Washington State University, Pullman, WA 99164, (2) Department of Crop & Soil Sciences, Washington State University, Johnson Hall, Pullman, WA 99164-6420 |
| We experimentally determined colloid stability of natural colloids extracted from vadose zone sediments from the US DOE Hanford Reservation. We used reference clay minerals, kaolinite and montmorillonite, for comparative purposes. Colloid stability was assessed with three different methods: the batch turbidity method, column mobilization experiments, and dynamic light scattering. Critical coagulation concentrations (CCC) were determined for pure Na and pure Ca electrolyte solutions, as well for mimicked Hanford vadose zone pore waters with varying sodium adsorption ratio (SAR). Critical coagulation concentrations obtained from the batch turbidity method were sensitive to initial colloid mass concentrations, settling time, and CCC criteria. The lower the initial colloid concentration and the longer the settling time, the larger was the CCC. The CCC values determined from dynamic light scattering were lower than those determined from the batch turbidity method. The CCC was strongly affected by the SAR and the absolute electrolyte concentrations. For conditions at the Hanford site, colloids may or may not from stable suspensions, depending on the Na concentrations in the pore water. |
|
Colloid-Facilitated Transport of Contaminants in the Subsurface: The Life and Death of a Colloid
1:00 PM-5:20 PM, Monday, March 29, 2004 Marriott -- Marquis NW, Oral
Division of Geochemistry |