title: Mineralization of PAHs in coal-tar impacted aquifer sediments and associated microbial community structure investigated with FISH.
abstract: The microbial community structure and mineralization of polycyclic aromatic hydrocarbons (PAHs) in a coal-tar contaminated aquifer were investigated spatially using fluorescence in situ hybridization (FISH) and in laboratory-scale incubations of the aquifer sediments. DAPI-detected microbial populations in the contaminated sediments were three orders of magnitude greater than nearby uncontaminated sediments, suggesting growth on coal-tar constituents in situ. Actinobacteria, beta- and gamma-Proteobacteria, and Flavobacteria dominated the in situ aerobic (>1 mg l(-1) dissolved oxygen) microbial community, whereas sulfate-reducing bacteria comprised 37% of the microbial community in the sulfidogenic region of the aquifer. Rapid mineralization of naphthalene and phenanthrene were observed in aerobic laboratory microcosms and resulted in significant enrichment of beta- and gamma-Proteobacteria potentially explaining their elevated presence in situ. Firmicutes, Flavobacteria, alpha-Proteobacteria, and Actinobacteria were also enriched in the mineralization assays, but to a lesser degree. Nitrate- and sulfate-limited mineralization of naphthalene in laboratory microcosms occurred to a small degree in aquifer sediments from locations where groundwater chemistry indicated nitrate- and sulfate-reduction, respectively. Some iron-limited mineralization of naphthalene and phenanthrene was also observed in sediments originating near groundwater measurements of elevated ferrous iron. The results of this study suggest that FISH may be a useful tool for providing a much needed link between laboratory microcosms and groundwater measurements made in situ necessary to better demonstrate the potential for natural attenuation at complex PAH contaminated sites.
authors.affiliation: Department of Civil, Construction and Environmental Engineering, Iowa State University, Ames, IA 50011, USA. swrogers@cafoexpert.com
authors.forename: Shane W
authors.initials: SW
authors.lastname: Rogers
authors.forename: Say Kee
authors.initials: SK
authors.lastname: Ong
authors.forename: Thomas B
authors.initials: TB
authors.lastname: Moorman
mesh_terms: D001420:Bacteria, Aerobic / Q000254:growth & development / Q000302:isolation & purification; D001421:Bacteria, Anaerobic / Q000254:growth & development / Q000302:isolation & purification; D001673:Biodegradation, Environmental; D003033:Coal Tar / Q000032:analysis* / Q000737:chemistry; D019015:Geologic Sediments / Q000737:chemistry* / Q000382:microbiology*; D017404:In Situ Hybridization, Fluorescence; D015345:Oligonucleotide Probes; D011084:Polycyclic Aromatic Hydrocarbons / Q000032:analysis* / Q000737:chemistry; D012329:RNA, Bacterial / Q000032:analysis; D012336:RNA, Ribosomal, 16S / Q000032:analysis; D012338:RNA, Ribosomal, 23S / Q000032:analysis; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000737:chemistry
chemical_list: D015345:Oligonucleotide Probes; D011084:Polycyclic Aromatic Hydrocarbons; D012329:RNA, Bacterial; D012336:RNA, Ribosomal, 16S; D012338:RNA, Ribosomal, 23S; D014874:Water Pollutants, Chemical; D003033:Coal Tar