ABSTRACTELECTROMAGNETIC MODELING OF SUBSURFACE LIGHT NON-AQUEOUS PHASE-LIQUIDS SPILLSBySandra Soto-CabánHydrocarbon contamination from fuel leaks and spills has been one of the most common ground water pollution problems in the United States for decades. Generally, underground leaks and spills are difficult to detect and locate and can cause serious health problems to people living close to the contaminated areas. The goal of this study is to simulate a contaminated region and determine its physical limits within a tolerable level of certainty given the characteristics of the soil in question without the environmental and financial cost of physical experimentation. The first part of this study is focused in the determination of the dielectric properties of soil and contaminated soil. A coaxial fixture was designed to characterize dry and contaminated soil samples in the frequency range of 100 MHz to 1 GHz. Experimental results for contaminated and uncontaminated soil samples are presented and analyzed. Values of permittivity obtained using the designed coaxial waveguide were used to calculate the scattering electric fields of a simulated contaminated underground system. The information collected from these simulations was used in the reconstruction of the contrast profile of two lossless configurations involving dielectric circular cylinders buried in soil. The image-reconstruction algorithm is based on the Fourier diffraction theorem and multiple frequencies were used to improve resolution.The problem was simulated using a two-dimensional formulation since three-dimensional structures need not be considered in the context of the underground mapping application. This study is not intended to achieve buried material identification of contaminants. However, a wide, full volume scanning of a potentially contaminated area is useful for ecological impact mitigation since it can be coupled with borehole assays to determine the specific contaminant and extent of contamination. With such information, environmental engineers can determine the need and the most suitable method for mitigation. Hence, the proposed radio frequency based survey research is meant to provide a screening tool to be used in concert with other methods.
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