| Abstract
| - A controlled gasoline spill experiment was performedunder outdoor conditions typical for winter in temperateregions to study the fate of methyl tert-butyl ether (MTBE),ethanol, benzene, and selected other petroleum hydrocarbons. Artificial gasoline containing MTBE and ethanol(5% w/w of each) was placed at a defined depth into a 2.3m thick unsaturated zone of alluvial sand overlying agravel aquifer in a lysimeter. During an initial period of 41days without recharge, MTBE and hydrocarbon vaporsmigrated by vapor-phase diffusion to groundwater, whileethanol vapors were naturally attenuated. In a subsequentperiod of 30 days with 5-mm daily recharge, all solublecompounds including ethanol were transported to thegroundwater. Ethanol disappeared concomitantly withbenzene and all other petroleum hydrocarbons exceptisooctane from the aerobic groundwater due to biodegradation. MTBE persisted for longer than 6 months atconcentrations larger than 125 000 μg L-1. No evidencefor MTBE biodegradation was found, whereas >99.6% ofethanol removal from the lysimeter was due to biodegradation.It is concluded that MTBE-free gasoline would be lessharmful for groundwater resources and that ethanol is anacceptable substitute.
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