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 contaminated field site. Arrays of sorbent materials wrapped in fiberglass mesh fabric were inserted into organic matter-rich freshwater sediments in order to intercept mobile chemicals and bacteria carried by the prevailing hydraulic gradient. Polyurethane foam plugs served as a sorbent for aqueous-phase coal tar components while sterile sand from the site served 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 numbers of aromatic hydrocarbon-degrading bacteria (via viable plate counts). 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 diminishing. Both naphthalene- and phenanthrene-utilizing bacteria were mobile and reached peak titers of 10 4 and 10 3.3, respectively, within 11 days. Thus, comigration of both contaminants and microorganisms occurred at the study site. Furthermore, the in situ abundances of contaminants and microorganisms reflect a dynamic balance between processes causing accrual and elimination.