HR: 17:00h
AN: H54C-04    [Abstracts]
TI: Modeling the Coupled Effects of Pore Space Geometry and Velocity on Colloid and Nanoparticle Transport and Retention
AU: * Bradford, S A
EM: sbradford@ussl.ars.usda.gov
AF: USDA, ARS, US Salinity Laboratory, 450 W. Big Springs Road, Riverside, CA 92507, United States
AU: Torkzaban, S
EM: saeedt@ucr.edu
AF: University of California, Department of Environmental Sciences, Riverside, CA 92521,
AU: Leij, F
EM: f.leij@sbcglobal.net
AF: University of California, Department of Environmental Sciences, Riverside, CA 92521,
AU: Toride, N
EM: ntoride@bio.mie-u.ac.jp
AF: Mie University, 1577 Kurimamachiya-cho, Tsu City, 514-8507, Japan
AU: Simunek, J
EM: jiri.simunek@ucr.edu
AF: University of California, Department of Environmental Sciences, Riverside, CA 92521,
AB: Colloid and nanoparticle retention in porous media has traditionally been assumed to be controlled by chemical interactions between the particles and the solid interface. The influence of system hydrodynamics in classical retention models is only considered for the rate with which particles strike solid surfaces. Recent experimental and theoretical work, however, has demonstrated that hydrodynamics also plays an important role in particle retention under unfavorable attachment conditions. In this case, a balance of adhesive and hydrodynamic forces and torques acting on particles near solid surfaces indicates that particle retention will occur only in low velocity regions that are controlled by the pore space geometry and primarily occur in the smallest regions of the pore space. Computer models that consider the average pore-water velocity in the porous medium and a single attachment rate coefficient are therefore not always adequate to describe retention processes, which frequently produce depth-dependent particle retention profiles (non-exponential). In this work, we highlight various computer models that can be used to account for particle retention in the smallest regions of the pore space. The models may be based on: (i) physical and chemical nonequilibrium; (ii) dual permeability; and (iii) stochastic stream tubes. Applications, implications, and limitations of the various models to characterize particle transport and retention will be demonstrated and discussed.
DE: 1831 Groundwater quality
DE: 1832 Groundwater transport
DE: 1847 Modeling
DE: 1875 Vadose zone
SC: Hydrology [H]
MN: 2007 Fall Meeting