Monitoring of sequential gasoline-ethanol releases using high frequency ground penetrating radar

Our hydrogeophysical field experiment evaluated the ability of high frequency (450 & 900 MHz) ground penetrating radar (GPR) to monitor sequential releases of gasoline followed by ethanol. The initial GPR images of the gasoline release zone reveal the development of shallow (i.e., above 10 ns) high reflectivity events and a significant velocity pull-up of an underlying stratigraphic reflection. Temporal evolution of the impacted zone reflectivity and the velocity pull-up indicate a progressive redistribution of gasoline in the impacted zone. GPR profiles obtained during frozen soil conditions clearly show that the presence of gasoline affects the freezing process. Preliminary analysis of the sequential ethanol release GPR data indicates an significant expansion of the impacted zone following this release.