In Situ Dynamics of Aromatic Hydrocarbons and Bacteria Capable of AH Metabolism in a Coal Tar Waste-Contaminated Field Site

Abstract

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.

Horizontal Transfer of phnAc Dioxygenase Genes within One of Two Phenotypically and Genotypically Distinctive Naphthalene-Degrading Guilds from Adjacent Soil Environments

“…This possibility seems unlikely given the widespread distribution of both alleles in pristine as well as contaminated soils (33,34) and the likelihood of cotransport of PAHs and PAH-degrading bacteria (36). It would not be surprising if additional sampling produced some nahAc alleles in hillside isolates or phnAc alleles in seep isolates.…”

“…To determine the amount of naphthalene in sediment and soil samples, 4 g (wet weight) of soil or 5 g (wet weight) of sediment was mixed with 3 ml of a 9:1 mixture of hexane-butanol and shaken for 5 days in Teflonsealed glass vials as previously described (36). After the mixtures settled, 0.9 l of the organic phase was analyzed as outlined below.…”

The effect of protozoan grazers on the cycling of polychlorinated biphenyls (PCBs) in marine systems

“…These sites have high nutrient concentrations which support dense bacterial populations. The presence of protozoa in many of these sites has been used to explain increased degradation and remineralization of organic matter (Sinclair et al, 1993;Madsen et al, 1996). Protozoa themselves have not been implicated in the remineralization of organic matter.…”

Naphthalene and Donor Cell Density Influence Field Conjugation of Naphthalene Catabolism Plasmids

“…Characteristics and details of this site have been previously published (24)(25)(26)(27)42). Naphthalene-degrading strains isolated from contaminated sediment from our study site (designated Cg) have been previously described (19).…”

“…For the in situ sediment experiments, open-ended glass cylinders (3-cm diameter, 3-cm height, able to contain approximately 15 g of wet sediment) were inserted into contaminated sediments where contaminated water seeps to the surface at the base of a hill (26). Recipient strains, prepared as described above, were added separately to the desired density of cells per gram of wet sediment.…”