Physical and Mathematical Modeling of Diesel Fuel Liquid and Vapor Movement in Porous Media

Abstract

Two‐dimensional physical modeling of diesel fuel leaks was conducted in sand tanks to determine liquid and vapor migration characteristics. Mathematical modeling provided estimation of vapor concentrations at discrete times and distances from the vapor source and was compared to the physical experiment. The mathematical gaseous diffusion model was analogous to the Theis equation for ground‐water flow, accounted for sorptive effects of the media, and was calibrated using measured concentrations from the sand tank. Mathematically different positions of the vapor source were tested to better relate observed liquid flow rates and media configuration to gaseous concentrations. The calculated diffusion parameters were then used to estimate theoretical, three‐dimensional vapor transport from a hypothetical liquid leak of 2.0 1/hr for 30 days. The associated three‐dimensional vapor plume, which would be reasonably detectable by commercially available vadose zone monitors, was estimated to have a diameter of 8 m with a vapor concentration of 50 ppm at the outside edge of the vapor plume. A careful application of the method and values can be used to give a first approximation to the number of vapor monitors required at a field site as well as the optimal locations for the monitors.

Modeling and experimental validation of volatile organic contaminant diffusion through an unsaturated soil

“…The corresponding experimental system was designed to eliminate moisture, temperature, and pressure gradients across the soil bed. Density-driven advection is negligible when the specific gravity of the contaminant-laden air relative to clean air is less than 1.2 [Johnson and Kreamer, 1994]. This condition was met for both the toluene and TCE experiments in this work.…”

Effect of Density‐Driven Advection on Trichloroethylene Vapor Diffusion in a Porous Medium

“…Th ey showed that density-driven advection is not negligible in the case of an air-compound mixture that has a density 1.15 times higher than that of uncontaminated soil air. Johnson and Kreamer (1994) emphasized that the density limit for notable density-driven advection Verti cal mass transfer of trichloroethylene (TCE) in a low water-saturated porous medium was studied in laboratory columns. A numerical transport model was used to interpret the measured vapor breakthrough curves, to determine apparent TCE diff usion coeffi cients, and to analyze the steady-state conditi ons of verti cal vapor mass transport.…”

“…They showed that density‐driven advection is not negligible in the case of an air–compound mixture that has a density 1.15 times higher than that of uncontaminated soil air. Johnson and Kreamer (1994) emphasized that the density limit for notable density‐driven advection is about 1.2. This ratio is 1.27 at 20°C for saturated TCE vapor and thus density‐driven advective mass transport might be significant for this compound.…”

Hazardous wastes: Assessment, management, minimization

“…Dharmavaram et al (1994) evaluated the fate and transport processes in an ammonia spill from a barge. Johnson and Kreamer (1994) used sand tanks for physical modeling of diesel fuel leaks; liquid and vapor phase data were compared to mathematical models. Based on their results, monitor placement for underground diesel fuel storage systems can be improved.…”