MINERALIZATION OF POLYCYCLIC AND N-HETEROCYCLIC AROMATIC-COMPOUNDS INHYDROCARBON-CONTAMINATED SOILS

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 extra ctable hydrocarbon content of the soil chemical characteristics measur ed. The compounds studied included five polycyclic aromatic hydrocarbo ns (phenanthrene, anthracene, pyrene, and carcinogenic benz[a]anthrace ne and benzo[a]pyrene) and three N-heterocyclic aromatics (9H-carbazol e, and carcinogenic 7H-dibenzo[c,g]carbazole and dibenz[a,j]acridine). Mineralization was measured by serum bottle radiorespirometry. Only p henanthrene, anthracene, pyrene, benz[a]anthracene, and carbazole were mineralized in the soils after 64 d. Two of the soils with eight to 1 5 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 t o 70% for pyrene, background to 40% for benz[a]anthracene, and 25 to 5 0% for carbazole after 64 d. Extents of mineralization by indigenous s oil microbiota appear to be more dependent on the chemical characteris tics of the soil and not soil total biomass and activity. Cultures cap able of degrading phenanthrene, anthracene, and pyrene were obtained f ollowing enrichment techniques. A Mycobacterium sp. capable of degradi ng these three compounds was isolated and reintroduced into two of the soils, resulting in mineralization enhanced above that of the indigen ous soil microbial population. These data indicate that the future suc cess of bioremediation methods relies on the characterization of envir onmental parameters affecting microbial degradation as well as the iso lation of microbial populations that can reduce toxicity in the enviro nment.