One- and two-dimensional experiments were conducted to examine differences in the behavior of gasoline and gasohol (10% ethanol by volume) as they infiltrate through the unsaturated zone and spread at the capillary fringe. Ethanol in the spilled gasohol quickly partitions into the residual water in the vadose zone and is retained there as the gasoline continues to infiltrate. Under the conditions tested, over 99% of the ethanol was initially retained in the vadose zone. Depending on the volume of gasoline spilled and the depth to the water table, this causes an increase in the aqueous-phase saturation and relative permeability, thus allowing the ethanol-laden water to drain into the gasoline pool. Under the conditions tested, the presence of ethanol does not have a significant impact on the overall size or shape of the resulting gasoline pool at the capillary fringe. Residual gasoline saturations in the vadose zone were significantly reduced however because of reduced surface and interfacial tensions associated with high ethanol concentrations. The flux of ethanol in the effluent of the column ranged from 1.4 x 10(-4) to 4.5 x 10(-7) g/(cm2 min) with the LNAPL and from 6 x 10(-3) to 3.0 x 10(-4) g/(cm2 min) after water was introduced to simulate rain infiltration. The experimental results presented here illustrate that the dynamic effects of ethanol partitioning into the aqueous phase in the vadose zone create an initial condition that is significantly different than previously understood.

In 1999, approximately 72 m3 of denatured fuel-grade ethanol spilled at a bulk fuel terminal that had existing contamination within the subsurface. An unanticipated increase in the measured depth of the light nonaqueous phase liquid (LNAPL) was observed in nearby monitoring wells following the spill. This paper presents results of a laboratory analysis designed to understand the apparent increase in LNAPL mobility at this site. The two-dimensional stainless steel and glass tank allowed visual assessment of the potential effects that the addition of denatured ethanol may have on a site with pre-existing gasoline contamination. Digital images of gasoline and ethanol spill experiments were analyzed for changes in the characteristics of the existing gasoline pool and residual gasoline saturation in the unsaturated zone. Reductions in the surface and interfacial tensions resulted in significant changes in the size, shape, and saturation of the gasoline pool after the addition of ethanol to the system. The final gasoline pool occupied a smaller area and had a higher saturation. In addition, some smearing of the gasoline into the saturated zone occurred as the capillary fringe was depressed.

Kerosene, an industrial petroleum product characterized by the presence of a large number of petroleum hydrocarbons (C9-C15), was selected as an example of a nonaqueous pollutant liquid (NAPL) mixture for our studies. Three inert materials (fine, medium and coarse sand) were used in the experiments and the initial amount of kerosene applied ranged from residual to saturated retention capacity.Volatilization in the air phase and saturated mass flow of kerosene in the three sands were studied in the laboratory under controlled conditions. The volatilization was the major physico-chemical process affecting the fate of kerosene in the inert porous medium. During volatilization the liquid kerosene changed its composition by gradually losing its light components (C9-C13), and the viscosity of the remaining liquid kerosene increased. The increase in viscosity led to a decrease in the infiltration rate, for example, by about 20% when the viscosity increased from 1.3 x Pa s. The relationship between the composition of the residual kerosene following volatilization and its mass flow in a sand illustrates the behaviour of non-aqueous pollutants in inert porous media.to 2.0 x