Experiments and Modeling of the Soil-Gas Transport of Volatile Organic Compounds into a Residential Basement.

摘要

This paper presents theoretical and laboratory studies of the advective flow of volatile organics compound (VOC) through soil, and a field investigation of the pressure-driven entry of VOC into a house adjacent to a municipal landfill. The principals of fluid mechanics are used to derive an analytical model of the pressure- driven flow of VOC in soil. The calculation results in the definition of a retardation factor of VOC with respect to the velocity of the bulk soil gas. The retardation equation is then tested in soil-column experiments using sulfur hexafluoride (SF sub 2 ) and hexafluorobenzene (HFB). The measured retardation is in good agreement with the predicted value. These experiments are used to evaluate the potential of SF sub 6 and HFB as tracer gases for use in a field investigation of the advective flow of soil gas into and near the basement of a house near a landfill and to evaluate the potential of the soil-column apparatus for use in screening the advective mobility of VOC important as landfill gas containments. The field study consisted of experiments investigating the influence of basement depressurization on the surrounding soil gas, and quantifying VOC contamination at the site. Soil-gas entry into the house during artificial basement depressurization was measured using SF sub 6 as a tracer, and pressure coupling was measured between the basement and the surrounding soil. Measurements of VOC in ambient air, indoor air, and soil gas indicate that a number of halogenated and oxygenated contaminants present in indoor air had a soil-gas source. Particularly high concentrations of dichlorodifluoromethane, trichlorofluoromethane, and tetrachloroethylene were identified in the soil gas. The pressure field generated in the soil around the basement by basement underpressure was modeled using a modified groundwater model. 39 refs., 26 figs., 9 tabs. (ERA citation 13:052081)