Using the gasoline additive MTBE in forensic environmental investigations

A variety of additives are used in gasoline, and they can sometimes be used to help identify the source, timing, or number of gasoline spills at a sit e. The physicochemical characteristics of the additive MTBE, and its histor ical use pattern in the United States since 1979, make it a key compound to study when conducting forensic investigations of gasoline spills. MTBE's l ow octanol:water distribution coefficient and high solubility cause it to d issolve into groundwater more readily than other gasoline components. Thus, the initial appearance of MTBE in the groundwater is often a good indicato r of a recent gasoline spill. MTBE's very low retardation and minimal biode gradation in groundwater can be used with transport rate calculations to es tablish relatively accurate estimates of spill timing. Because MTBE moves f aster in groundwater than BTEX compounds, if a gasoline spill site has a BT EX plume that is longer than the MTBE plume, it is certain that at least tw o distinctly different gasoline releases have occurred. This allows for the identification of new gasoline spills, even when substantial subsurface pe troleum contamination already exists. An example application is reviewed to demonstrate the use of MTBE data in forensic investigations. (C) 2000 AEHS .