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Temporal GPR Imaging of an Ethanol Release Within a Laboratory-Scaled Sand Tank
Citation:
Glaser, D., D. Werkema, R. Verstegg, R. Henderson, AND D. Rucker. Temporal GPR Imaging of an Ethanol Release Within a Laboratory-Scaled Sand Tank. JOURNAL OF APPLIED GEOPHYSICS. Elsevier Science Ltd, New York, NY, 86:133-145, (2013).
Impact/Purpose:
Ethanol use has grown in recent years due in large part to its inclusion in fuels as an emissions reducing fuel oxygenate. The additional draw to ethanol has been to replace methyl tertiary butyl ether (MTBE) as a fuel oxygenate in reformulated gasoline (up to 10 percent by volume in gasoline) due to the solubility of MTBE in groundwater and its carcinogenic effects (Wheals et al., 1999). “Flex Fuel” vehicles utilizing E85 (85 percent ethanol, 15 percent gasoline) have also contributed to the use and distribution of ethanol. While ethanol is not considered to be directly harmful to human health, its use has indirect consequences through secondary environmental effects.
Description:
Within the last decade efforts in geophysical detection and monitoring of fossil fuel releases into the subsurface have shown increasing success, including the ability to geophysically detect and delineate enhanced and natural biodegradation and remediation activities. The substitution of biofuels, such as ethanol, for fossil fuels is becoming persistent in the national and international marketplace making it subject to the same types of accidental releases and exposure scenarios currently associated with the transport and storage of fossil fuels. Thus, there is interest from both academics and regulators to investigate the feasibility of applying geophysical methodologies to biofuel releases. In this study, we performed an experimental and numerical investigation of the feasibility of using ground penetrating radar (GPR) to monitor the migration of an ethanol release. A tank scale model of a closed hydrologic system was prepared with Ottawa sand and instrumented with an automated gantry measurement apparatus for time-lapse measurement of zero offset and coincident GPR reflections on multiple horizontal planes. Measurements were acquired in the unsaturated and saturated zones throughout the injection and transport of the ethanol release. The results of the monitoring suggest a measureable contrast within both time and frequency domains of the GPR data coincident with the ethanol release and subsequent migration. We conclude that the monitoring of ethanol in a sand matrix at various levels of saturation is possible with GPR.