Monday, 7 November 2005
12

Studying Colloid Transport in Porous Media with Geocentrifuges.

Markus Flury1, Szabolcs Czigany2, Prabhakar Sharma1, and Earl Mattson3. (1) Washington State University, Dept. of Crop & Soil Sciences, PO Box 646420 Washington State Univ, Pullman, WA 99164-6420, (2) University of Pecs, TTK, Geographical Institute, Department of Physical Geography, Pecs, 7624, Hungary, (3) Idaho National Laboratory, Mailstop 2107, Idaho Falls, ID 83415

Flow and transport experiments with unsaturated porous media can take prohibitively long time, because hydraulic conductivities decrease exponentially with decreasing water saturation. Experimental time can be shortened by using centrifuges. However, compelling evidence is needed to assure the applicability of centrifuges for studying colloid transport, as colloid filtration is affected by centrifugation. We determined the suitability of centrifuges to study colloid transport in porous media. We used filtration theory to predict the effect of particle density and flow rate on transport of colloids as affected by centrifugal accelerations. From filtration theory, a functional relation between centrifugal acceleration and pore water velocity and colloid density was derived, which allows us to predict at which acceleration colloid filtration will be dominated by sedimentation. For typical pore water velocities in the subsurface, it is expected that the filtration behavior of natural subsurface colloids will be impacted at centrifugal accelerations as low as 3 g.

Handout (.pdf format, 410.0 kb)

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