HR: 1330h
AN: H22C-0945    [PDF]
TI: Size Exclusion Effects of Colloid Transport in Saturated Porous Media
AU: * Sirivithayapako, S
EM: sanya@bren.ucsb.edu
AF: Bren School of Environmental Science and Management, 2400 Bren Hall University of California, Santa Barbara, Santa Barbara, CA 93106-5131 United States
AU: Keller, A A
EM: keller@bren.ucsb.edu
AF: Bren School of Environmental Science and Management, 2400 Bren Hall University of California, Santa Barbara, Santa Barbara, CA 93106-5131 United States
AB: We present physical evidence of colloid exclusion from certain pore spaces due to size exclusion, and the connection between our pore scale observations and column scale experiments of colloid transport in saturated porous media. At the pore scale, we observed the influence of the ratio between pore throats and colloids (T/C ratio) at different flow velocities on the size exclusion effect. Preferential paths, a result of size exclusion, become more distinct for larger colloids and for greater pressure gradients, with an important effect on dispersion of the colloids. The measured colloid velocities are 4 to 5.5 times greater than the estimated pore water velocity. In the saturated sand column, early breakthrough of colloids increases with colloid size and water velocity, compared to a conservative solute tracer. For the column experiments, the observed colloid velocities are 1.1 to 1.2 times greater than the tracer velocities. Dispersion of colloids is significantly less relative to the tracer. The dispersion coefficient can be about one order of magnitude smaller, for example comparing 3 mm colloids and the tracer. In contrast with solute transport, dispersivity is not just a function of the medium characteristics, but is also a function of colloid size due to the size exclusion effect, particularly at low Peclet numbers.
DE: 1829 Groundwater hydrology
DE: 1832 Groundwater transport
SC: Hydrology [H]
MN: 2003 Fall Meeting