South Dakota Water Science Center
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A Review of the Environmental Behavior and Fate of Fuel OxygenatesPaul J. Squillace
U. S. Geological Survey, 1608 Mt. View Road, Rapid City, South Dakota 57702
Phone (605) 355-4560 ext. 239, Telecopier (605) 355-4523, email@example.com
The ways in which fuel oxygenate compounds behave in water, soil, and air are determined by how they partition among the different media. The behavior of a gasoline oxygenate in water is affected by the oxygenate's (1) solubility in water from gasoline; (2) partitioning between water and soil materials; and (3) paritioning between air and water. Water in equilibrium with oxygenated gasoline can contain high concentrations of the oxygenate. For example, at room temperature water solubility of methyl tert-butyl ether (MTBE) will be about 5,000 mg/L for a gasoline that is 10 percent MTBE by weight. In contrast, the total hydrocarbon solubility in water is typically about 120 mg/L for nonoxygenated gasoline. Fuel oxygenates sorb only weakly to soil and aquifer materials. Therefore, sorption to these materials will not significantly retard their transport by ground water. Fuel oxygenates tend to partition into atmospheric water, including precipitation. For example, washout of gas-phase MTBE by precipitation would not, by itself, greatly alter the gas-phase concentration of the compound in the atmosphere. Nevertheless, the partitioning of MTBE to precipitation is strong enough to allow for submicrograms per liter to 3 ug/L or more inputs of MTBE to ground water and surface water. Occurrence data for MTBE in water and air supports partition theoretical calculations. MTBE and other alkyl ether oxygenates have half lives in the atmosphere that range from about 1 to 14 days. These compounds are generally considered recalcitrant in ground water; whereas ethanol and methanol will readily undergo microbial degradation except where present in concentrations toxic to microorganisms.
Presented and published:
1996, A review of environmental behavior and fate of fuel oxygenates--Society of environmental toxicology and chemistry, in Abstract book, SETAC 17th annual meeting, Nov. 17-21, 1996, Washington, D.C.: Society of Environmental Toxicology and Chemistry, p. 114-115.