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United States Department of Agriculture

Agricultural Research Service

Title: Straining of Colloids at Textural Interfaces

Authors
item Bradford, Scott
item Simunek, Jirka - U.C. RIVERSIDE, CA
item Van Genuchten, Martinus
item Bettahar, Mehdi - PARSONS ENG, PASADENA,CA

Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: September 1, 2004
Publication Date: October 20, 2004
Citation: Bradford, S.A., Simunek, J., Van Genuchten, M.T., Bettahar, M. 2004. Straining of colloids at textural interfaces. ASA-CSSA-SSSA Annual Meeting Abstracts. CD-ROM, Seattle, WA.

Technical Abstract: Saturated soil column studies were undertaken to characterize the straining behavior of colloids (1.1 micron latex)at soil (variously sized quartz sands) textural interfaces. Mechanisms of colloid transport and retention were deduced from measured effluent concentration curves, final spatial distributions, mass balance information and numerical modeling. Transport and deposition of colloids were found to be highly dependent upon the soil textural interface. Deposition of colloids in a given sand was always most pronounced at the soil surface. Here colloids enter a new pore network and are more likely to encounter smaller pores or dead-end regions of the pore space that contribute to straining. Less deposition occurred at textural interfaces than at the soil surface because transport processes such as advection, dispersion and size exclusion tend to confine colloids to the larger pore networks, and thus limit accessibility to straining sites. Increasing the textural contrast at an interface produced greater deposition when water flowed from coarser to finer textured sands. Conversely, when water flowed from finer to coarser textured sands little deposition occurred. Numerical modeling results indicate the need to account for blocking (filling) and accessibility of straining sites in layered systems. A previously developed straining model was modified to account for this behavior.

Last Modified: 9/23/2014
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