Intrinsic capacities of soil microflorae for gasoline degradation

A methodology to determine the intrinsic capacities of a microflora to degr ade gasoline was developed, in particular for assessing the potential of au tochtonous populations of polluted and non polluted soils for natural atten uation and engineered bioremediation. A model mixture (GM23) constituted of the 23 most representative hydrocarbons of a commercial gasoline was used. The capacities of the microflorae (kinetics and extent of biodegradation) were assessed by chromatographic analysis of hydrocarbon consumption and of CO2 production. The degradation of the components of GM23 was assayed in s eparate incubations of each component and in the complete mixture. For the microflora of an unpolluted spruce forest soil, all hydrocarbons of GM23 ex cept cyclohexane, 2,2,4- and 2,3,4-trimethylpentane isomers were degraded t o below detection limit in 28 days. This microflora was reinforced with two mixed microbial communities selected from gasoline-polluted sites and show n to degrade cyclohexane and 2,2,4-trimethylpentane. With the reinforced mi croflora, complete degradation of GM23 was observed. The degradation patter ns of individual components of GM23 were similar when the compounds were pr esent individually or in the GM23 mixture, as long as the concentrations of 2-ethyltoluene and trimethylbenzene isomers were kept sufficiently low (le ss than or equal to 35 mg.l(-1)) to remain below their inhibitory level.