PERSISTENCE OF POLYCYCLIC AROMATIC HYDROCARBON COMPONENTS OF CREOSOTEUNDER ANAEROBIC ENRICHMENT CONDITIONS

Anaerobic biodegradation of an artificial mixture of polycyclic aromat ic hydrocarbons (PAHs), which simulates the PAH component of creosote, was examined under methanogenic, sulfidogenic, and nitrate-reducing c onditions using creosote-contaminated sediment as the source of inocul um. PAH degradation, CH4 formation and ion reduction were monitored fo r up to one year. Despite demonstrating active methanogenic and nitrat e-reducing anaerobic bacterial communities, only limited degradation o f a few PAHs was observed. Under methanogenic conditions limited degra dation of all bicyclic (naphthalene, 1-and 2-methylnaphthalene, biphen yl, and 2,6-dimethylnaphthalene) and one tricyclic PAH, anthraquinone, was detected. 2-Methylanthracene was apparently degraded under nitrat e-reducing conditions. Anthraquinone declined in sulfate enrichments, but this decline was not dependent upon sulfate reduction. None of the 4- or 5-ring PAHs were degraded under any of the enrichment condition s. These data indicate that under the anaerobic conditions tested ther e is only a limited potential to degrade PAHs which must be considered when proposing bioremediation technologies for PAH-contaminated sites , especially if high-molecular-weight PAHs are present.