HR: 13:40h
AN: H23H-01 INVITED     [Abstracts]
TI: Colloid Transport under Partially Saturated Transient and Preferential Flow Conditions
AU: * McCarthy, J F
EM: jmccart1@utk.edu
AF: University of Tennessee, Department of Earth and Planetary Sciences, Knoxville, TN 37996-1410 United States
AU: Zhuang, J
EM: jzhuang@utk.edu
AF: University of Tennessee, Department of Earth and Planetary Sciences, Knoxville, TN 37996-1410 United States
AU: Perfect, E
EM: eperfect@utk.edu
AF: University of Tennessee, Department of Earth and Planetary Sciences, Knoxville, TN 37996-1410 United States
AU: Tyner, J S
EM: jtyner@utk.edu
AF: University of Tennessee, Biosystems Engineering and Environmental Science, Knoxville, TN 37996-4531 United States
AU: Steenhuis, T S
EM: tss1@cornell.edu
AF: Cornell University, Biological and Environmental Engineering, Ithaca, NY 14853-5701 United States
AB: This study evaluates the impacts of natural flow regimes on colloid transport. While experiments that impose steady-state flow conditions are critical for developing fundamental understanding of colloid-media interactions, flow in natural subsurface environments is dominated by transient flow involving temporary increases in water content and flow rate during rain events, followed by decreasing water content during drainage. There is a strong relationship between water content and colloid transport efficiency, making it important to evaluate how transient flow conditions affect the rate and extent of colloid transport. In addition, water flow is only distributed uniformly near the surface even such uniform wetting throughout the columns is often assumed in models of water and colloid transport under partial saturation. Rather, infiltrating water and colloids are transported via preferential flow paths under near saturated conditions and with higher velocities than that would occur under uniform wetting conditions. To our knowledge, infiltration, remobilization and percolation of colloids in porous media under such conditions has not been previously documented, but is critical to evaluating the potential for colloid transport in natural subsurface systems. Colloid transport and mobilization in one- and two-dimensional experimental systems are being examined using both model porous media (Accusand) and natural Hanford sediments, and includes the transport of both model colloids (montmorillonite), as well as colloids derived from Hanford sediments. Because Hanford sedimentary deposits exist as sorted layers of coarse and fine sediments, the effects of such layering on the distribution of water flow through these layers and the subsequent impacts on preferential flow and colloid transport are also being evaluated. The upper and lower boundary conditions are a constant flux less than saturated hydraulic conductivity and a constant matric potential, respectively. Transient changes in water content are measured at several locations along the flow paths via gamma-ray attenuation. These results demonstrate the importance of the combined effects of preferential flow and transient water flow on colloid transport.
DE: 1829 Groundwater hydrology
DE: 1832 Groundwater transport
DE: 1875 Unsaturated zone
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting