Evaluation of PCB dechlorination pathways in anaerobic sediment microcosms using an anaerobic dechlorination model.
A detailed quantitative analysis of anaerobic dechlorination (AD) pathways of polychlorinated biphenyls (PCBs) in sediment microcosms was performed by applying an anaerobic dechlorination model (ADM). The purpose of ADM is to systematically analyze changes in a contaminant profile that result from microbial reductive dechlorination according to empirically determined dechlorination pathways. In contrast to prior studies that utilized modeling tools to predict dechlorination pathways, ADM also provides quantification of individual pathways. As only microbial reductive dechlorination of PCBs occurred in the modeled laboratory microcosms, extensive analysis of AD pathways was possible without the complicating effect of concurrent physico-chemical or other weathering mechanisms. The results from this study showed: (1) ninety three AD pathways are active; (2) tetra- to hepta-chlorobiphenyl (CB) congeners were common intermediates in several AD pathways, penta-CBs being the most frequently observed; (3) the highest rates of dechlorination were for penta-CB homologs during the initial 185 days; (4) the dominant terminal products of AD were PCB 32(26-4), 49(24-25), 51(24-26), 52(25-25), 72(25-35), 73(26-35) and 100(246-24), (5) potential toxicity of the sediment was reduced. ADM serves as a powerful tool not only for a thorough analysis of AD pathways, but also for providing necessary input for numerical fate models (as a degradation term) that investigate dechlorination products or outcome of natural attenuation, or bioremediation/bioaugmentation of PCB-impacted sediments.
Department of Environmental Engineering, Middle East Technical University, Ankara, Turkey.
Hale
H
Demirtepe
A. James Clark School of Engineering, Department of Civil and Environmental Engineering, University of Maryland at College Park, College Park, MD 20742, USA.
Birthe
B
Kjellerup
Institute of Marine and Environmental Technology, Department of Marine Biotechnology, University of Maryland Baltimore County, Baltimore, MD 21202, USA.
Kevin R
KR
Sowers
Department of Environmental Engineering, Middle East Technical University, Ankara, Turkey. Electronic address: ipeki@metu.edu.tr.
Ipek
I
Imamoglu
D000693:Anaerobiosis; D001421:Bacteria, Anaerobic / Q000254:growth & development*; D001673:Biodegradation, Environmental; D019015:Geologic Sediments / Q000737:chemistry / Q000382:microbiology; D054879:Halogenation; D008962:Models, Theoretical; D011078:Polychlorinated Biphenyls / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry*
D014874:Water Pollutants, Chemical; D011078:Polychlorinated Biphenyls
Anaerobic dechlorination model (ADM); Dechlorination pathway; Polychlorinated biphenyls (PCBs); Sediment microcosm