IN-SITU DYNAMICS OF AROMATIC-HYDROCARBONS AND BACTERIA CAPABLE OF AH METABOLISM IN A COAL-TAR WASTE-CONTAMINATED FIELD SITE

Field experiments utilizing randomized block designs were implemented to assess the mobility of both coal tar-derived aromatic hydrocarbons and bacteria capable of metabolizing these substances at a contaminate d field site. Arrays of sorbent materials wrapped in fiberglass mesh f abric were inserted into organic matter-rich freshwater sediments in o rder to intercept mobile chemicals and bacteria carried by the prevail ing hydraulic gradient. Polyurethane foam plugs served as a sorbent fo r aqueous-phase coal tar components while sterile sand from the site s erved as a substrate for colonization by bacteria. Replicate sorbents were removed from the sediments at varying intervals and assessed for organic compounds (via gas chromatography/mass spectrometry) and for n umbers of aromatic hydrocarbon-degrading bacteria (via viable plate co unts). Organic contaminants including naphthalene, methyl naphthalene, indenes, and substituted benzenes were detected in the foam sorbents. Contaminant concentrations reached a maximum after 15 days before dim inishing. Both naphthalene- and phenanthrene-utilizing bacteria were m obile and reached peak titers of 10(4) and 10(3.3), respectively, with in 11 days. Thus, comigration of both contaminants and microorganisms occurred at the study site. Furthermore, the in situ abundances of con taminants and microorganisms reflect a dynamic balance between process es causing accrual and elimination.