Experiments have been conducted to assess the potential impact of ethanol on the cosolubility of benzene and other aromatic hydrocarbons in groundwater. In column experiments selected to evaluate the groundwater impact of cosolubilization for gasoline mixtures containing 6% and 14% ethanol, maximum benzene effluent concentrations were enhanced by 6% and 39%, respectively, and m-xylene concentrations were enhanced by 28 and 36%, respectively, relative to those for a gasoline that did not contain ethanol. These results support previous studies that indicate that releases of gasohol will have only a modest impact on downstream concentrations of BTX for most spill scenarios when biodegradation of BTX is not considered. It is likely that for most sites where spills of gasohol occur that any observed enhancement in downstream BTX concentrations will be due primarily from the effect of ethanol on the bioartenuation of BTX. In these experiments significant tailing in the ethanol aqueous concentrations was also observed, and subsequent visualization experiments confirmed that this can be attributed to mass transfer limited dissolution of ethanol. Although the effect on enhancement in BTX concentrations is limited, such mass transfer limitations may result in the longevity of groundwater source concentrations of ethanol at levels great enough to have an impact on the bioattenuation of BTX.
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