• Mineralization;
  • Biodegradation;
  • Polycyclic aromatic hydrocarbons;
  • N-Heterocyclic aromatics;
  • Mycobacterium


The comparative mineralization of eight polycyclic aromatic compounds in five soils collected from an abandoned coal tar refinery in eastern Ohio was determined. The soils showed differences only in total extractable hydrocarbon content of the soil chemical characteristics measured. The compounds studied included five polycyclic aromatic hydrocarbons (phenanthrene, anthracene, pyrene, and carcinogenic benz[a]anthracene and benzo[a]pyrene) and three N-heterocyclic aromatics (9H-carbazole, and carcinogenic 7H-dibenzo[c,g]carbazole and dibenz[a,j]acridine). Mineralization was measured by serum bottle radiorespirometry. Only phenanthrene, anthracene, pyrene, benz[a]anthracene, and carbazole were mineralized in the soils after 64 d. Two of the soils with eight to 15 times the hexane-extractable hydrocarbon content consistently showed more rapid initial rates and higher overall extents of mineralization compared to the other three soils. Overall extents of mineralization ranged from 38 to 55% for phenanthrene, 10 to 60% for anthracene, 25 to 70% for pyrene, background to 40% for benz[a]anthracene, and 25 to 50% for carbazole after 64 d. Extents of mineralization by indigenous soil microbiota appear to be more dependent on the chemical characteristics of the soil and not soil total biomass and activity. Cultures capable of degrading phenanthrene, anthracene, and pyrene were obtained following enrichment techniques. A Mycobacterium sp. capable of degrading these three compounds was isolated and reintroduced into two of the soils, resulting in mineralization enhanced above that of the indigenous soil microbial population. These data indicate that the future success of bioremediation methods relies on the characterization of environmental parameters affecting microbial degradation as well as the isolation of microbial populations that can reduce toxicity in the environment.