Methyl ten-butyl ether(MTBE)has been the focus of much attention because it is used in large amounts and was reportedly relatively recalcitrant to bioreme-diation or natural attenuation.Beginning with a few papers a decade ago,evidence has been presented that,in fact,under suitable conditions it is amenable to bioremediation.Many species from widely disparate microbialgenera are able to consume it either as a sole carbon source or as a cometabolite.Optimal conditions differ from site to site.Both aerobic and anaerobic conditions may permit MTBE degradation,with a range of electron acceptors,from oxygen through Fe(III),Mn(IV),sulfate,nitrate,and methanagenesis.MTBE metabolism in the vadose zone can be highly active.The published literature suggests that natural populations are adapting to MTBE,and reported rates of biodegradation appear to be larger in the more recent literature.Plants may serve as efficient conduits to withdraw MTBE from the wet subsurface,releasing it to the atmosphere or the vadose zone,where it may be metabolized or diffuse into the atmosphere where it is quickly photodegraded.The major remaining issues are the time required to attain specified criteria of cleanup or whether augmentation is necessary for effective remediation.
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