Publisher Summary

Methyl tertiary (tert)-butyl ether (MTBE), an octane enhancer and a fuel oxygenate in reformulated gasoline, has received increasing public attention. MTBE was first used in gasoline as an octane enhancer, and later to reduce emissions of carbon monoxide and formation of ozone as mandated by the Clean Air Act Amendments of 1990. Because of its low cost, ease of production, and favorable transfer and blending characteristics, MTBE became the most commonly used fuel oxygenates. As MTBE use increased in the mid-1990s, the frequency and extent of contamination were quickly visible across the United States. The widespread use of MTBE to reduce air pollution has instead resulted in major contamination of water resources. Once fuel oxygenates are released to the environment, their behavior is largely determined by how they partition in gasoline, air, water, and onto subsurface solids. The physical and chemical properties of MTBE make environmental contamination a challenging problem. Relative to other gasoline components, such as benzene, toluene, and other aromatic hydrocarbons, MTBE has a higher vapor pressure, and will volatilize easily from the nonaqueous phase.