Methyl tertiary-butyl ether (MTBE) is a fuel additive made by combining methanol and isobutylene. The methanol is typically derived from natural gas; isobutylene can be derived as a byproduct of the petroleum refinery process. Since 1979, MTBE has been used in the United States as an octane-enhancing replacement for lead, primarily in mid and high-grade gasoline at concentrations as high as 8 percent (by volume). Since the middle of the 1980s, it has been widely used through-out the country for this purpose. It is also used as a fuel oxygenate at higher concentrations (11 to 15 percent by volume) as part of the U.S. EPA's programs to reduce ozone and carbon monoxide levels in the most polluted areas of the country.
When MTBE is in the soil as the result of a petroleum release, it may separate from the rest of the petroleum, reaching the groundwater first and dissolving rapidly. Once in the ground-water, MTBE travels at about the same rate as the groundwater whereas benzene and other petroleum constituents tend to biodegrade and adsorb to soil particles.
This classroom exercise will challenge the students to investigate the affects of MTBE spills in the environment by researching the available literature on fuel oxygenates and learning their mode of transport through the soil. Experimentally determined data, both in the physics and chemistry labs, will facilitate building models (using STELLA and Excel) of the contamination process of the groundwater. Mathematics modeling will involve the use of spreadsheet analysis of real-world-data obtained from various web locations.