Anaerobic biodegradation of natural gas condensate can be stimulated by the addition of gasoline

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Abstract
Biodegradation of a broad range of linear and branched alkanes, parent and alkyl alicyclic hydrocarbons, and benzene and alkyl-substituted benzenes was observed when sediment and groundwater samples collected from a gas condensate-contaminated aquifer were incubated under methanogenic and especially under sulfate-reducing conditions, even though no exogenous nitrogen or phosphorus was added. This finding expands the range of hydrocarbon molecules known to undergo anaerobic decay and confirms that natural attenuation is an important process at this site. The addition of 1 μl of gasoline to the samples (∼10 ppm) had minimal impact on the biodegradation of saturated compounds, but substantially increased the diversity and extent of aromatic compounds undergoing transformation. We attribute this to the promotion or induction of biodegradation pathways in the indigenous microflora following the addition of the gasoline components. The promoting compounds are not precisely known, but may have been present in the initial condensate and reduced in concentration by various mechanisms (dissolution, biodegradation, etc.) such that their concentration in the aquifer fell below necessary levels. A variety of aromatic hydrocarbons would appear to be likely candidates.