HR: 0800h
AN: H51F-0842    [Abstracts]
TI: Effects of Ethanol on the Behaviour of Gasoline at the Water Table: Numerical Simulation of Laboratory Experiments
AU: * Yu, S
EM: s7yu@sciborg.uwaterloo.ca
AF: Department of Earth and Environmental Sciences, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada
AU: Freitas, J
EM: jgardena@sciborg.uwaterloo.ca
AF: Department of Earth and Environmental Sciences, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada
AU: Unger, A
EM: aunger@uwaterloo.ca
AF: Department of Earth and Environmental Sciences, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada
AU: Barker, J F
EM: jfbarker@sciborg.uwaterloo.ca
AF: Department of Earth and Environmental Sciences, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada
AB: A numerical model has been used to reproduce a series of laboratory experiments designed to examine the effects of ethanol on gasoline movement in the vadose zone, particularly in the capillary fringe. The multi-phase multi-component model, CompFlow Bio was modified to incorporate two significant effects of ethanol dissolved in the aqueous phase on the fate and transport of gasoline in the subsurface: the enhanced dissolution of gasoline in the aqueous phase due to cosolvency effects, and the reduction in surface/interfacial tension (and hence capillary pressure curve) between the total liquid and gas phases as well as the aqueous and non- aqueous phases. To simulate these processes, a log-linear relationship was added to the model to represent the cosolvency effect, while empirical relationships were used to scale the surface/interfacial tensions inherent in the capillary pressure curves. A series of 2D laboratory experiments were performed in a plexiglass box packed with 390 micrometer glass beads to visualize the impact of ethanol on the fate and transport of gasoline both above and below the water table. These experiments consisted of injecting gasoline into the plexiglass box, allowing it redistribute itself above, within, and below the capillary fringe, and then injecting ethanol above the gasoline source zone. The experiments were used to establish a qualitative comparison with the numerical model. Comparison between the numerical model and the experiments indicate that the model is capable of capturing the general behaviour of the system; specifically, the collapse of the capillary fringe followed by the remobilization and subsequent collection of non-aqueous phase gasoline in at the bottom of collapsed capillary fringe region. Surprisingly, the remobilized non-aqueous phase gasoline that collected at the bottom of the collapsed capillary fringe exhibited higher saturations than those observed prior to the injection of ethanol. The empirical relationships added to CompFlow Bio used to simulate cosolvency effects as well as scaling of the capillary pressure curves were essential to capture the general behaviour of the gasoline source zone following the injection of ethanol.
DE: 1846 Model calibration (3333)
DE: 1847 Modeling
DE: 1875 Vadose zone
SC: Hydrology [H]
MN: 2007 Fall Meeting