Pt. Imhoff et Pr. Jaffe, EFFECT OF LIQUID DISTRIBUTION ON GAS-WATER PHASE MASS-TRANSFER IN AN UNSATURATED SAND DURING INFILTRATION, Journal of contaminant hydrology, 16(4), 1994, pp. 359-380
Citations number
36
Categorie Soggetti
Water Resources","Environmental Sciences","Geosciences, Interdisciplinary
Gas-water phase mass transfer was examined in a homogeneous sand with
both the gas and water phase mobile: water was infiltrated from the to
p of the sand column while benzene-laden air flowed upward from the bo
ttom. Mass-transfer limitations for this situation may be important fo
r applications of bioventing, where water and nutrients are added at t
he ground surface simultaneously with induced air movement to carry ox
ygen and volatile organics to microbial populations. Gas- and water-ph
ase samples indicate that gas-water phase mass transfer was sufficient
ly fast that equilibrium between gas and water phases was achieved at
all sampling locations within the porous medium. Lower-bound estimates
for the gas-water mass-transfer rate coefficient show that mass trans
fer was at least 10-40 times larger than predictions made from an empi
rical model developed for gas-water phase mass transfer in an identica
l porous medium. A water-phase tracer test demonstrates that water flo
w was much more uniform in this study than in those earlier experiment
s, which is a likely explanation for the differing rates of gas-water
phase mass transfer. It is hypothesized that the liquid distribution i
n previous laboratory experiments was less uniform because of preferen
tial flow paths due to wetting front instabilities. Gas-water phase ma
ss-transfer rate coefficients reported in this investigation are for a
n ideal situation of uniform water infiltration: mass-transfer rates i
n field soils are expected to be significantly smaller.