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Colorado Water Science Center

EFFECT OF FUEL OXIDANTS ON THE DEGRADATION OF GASOLINE COMPONENTS IN SEDIMENTS OF THE SOUTH PLATTE RIVER ALLUVIAL AQUIFER

National Water-Quality Assessment (NAWQA) Program
South Platte River Basin Study

by Peter B. McMahon, Rick Crowfoot 1, and Duane Wydoski 2

ABSTRACT

The Clean Air Act requires did beginning in 1995 selected major cities blend gasoline with fuel oxidants so that it burns more completely. Ethanol and methyl tert-butyl ether (MTBE) are the fuel oxidants most commonly used to produce cleaner burning gasoline. The debate over which oxidant should be used has focused on economic issues, however, certain environmental questions are of concern as well. For instance, MTBE is not easily degraded and tends to persist in the environment. A survey of the quality of groundwater collected from 30 randomly distributed wells in Denver determined that more than 80 percent of the wells had measurable concentrations of MTBE. Ethanol is more easily degraded than MTBE but there are few data on ethanol concentrations in natural waters. Perhaps more important than the persistence of fuel oxidants in the environment is what effect they have on the degradation of gasoline components in the environment. For example, benzene is carcinogenic and commonly found in waters contaminated with gasoline. Readily degraded organic compounds such as ethanol are known to enhance the biological degradation of other organic compounds through cometabolic processes. However, it is not known what effect relatively nondegradable compounds such as MTBE have on degradation processes. The effects of MTBE and ethanol on the degradation of gasoline components in sediments of the South Platte River alluvial aquifer will be presented. Results from this study will provide policy makers with information that could be used in evaluating which fuel oxidant is more effective in producing a cleaner environment.

1 U.S. Geological Survey, Box 25046, MS 415, Denver Federal Center, Lakewood, CO 80225
2 U.S. Geological Survey, 5293 Ward Rd., MS407, National Water-Quality Laboratory, Arvada, CO 80002

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