| Summary: | Polychlorinated biphenyls (PCBs) and polycylic aromatic hydrocarbons (PAHs) are widespread environmental contaminants, and their presence in the environment is a cause for concern because they are linked to a variety of toxic effects. In this thesis, some aspects of the microbial degradation of PCBs and alkyl PAHs are investigated. Analytical methods for the extraction and analysis (by using gas chromatography coupled to mass spectrometry (GC/MS)) of PCBs were developed and tested. The PCB content of three sediment cores taken from lakes in Cambridge Bay (Nunavut) was analyzed, but no evidence for in-situ microbial dechlorination of PCBs was found. A variety of approaches to the development of microbial enrichment cultures were tested. The most successful were developed by using 4-bromobenzoate, as an amendment to stimulate dehalogenation activity, and sediment collected from Esquimalt Harbour (British Columbia) as an inoculum source. The dechlorination of Aroclor 1260 in soils from Resolution Island (Nunavut) and Saglek (Labrador) by using a variety of enrichment cultures was investigated. Extensive dechlorination of highly-chlorinated PCB congeners was achieved, and the most abundant products from Aroclor 1260 dechlorination were tetrachlorobiphenyls. A method to determine the identity of one major dechlorination product by using MS/MS was developed, and the dechlorination product was found to be 24-24- tetrachlorobipheny 1. Some factors that could affect the extent and rate of PCB dechlorination were investigated. It was found that autoclaving pre-incubated cultures prior to inoculation with PCB-dechlorinating enrichment cultures increased the rate and extent of PCB dechlorination. It was also found that dechlorination of PCBs that had been present in Resolution Island soil for a number of years was not as extensive as dechlorination of PCBs that were freshly added to Resolution Island soil. A variety of incubation temperatures were tested, and the most rapid and extensive PCB dechlorination occurred at 30 °C. The dechlorination of three nona- and four octa-chlorobiphenyl congeners, both singly, and in various combinations, was also investigated. It was established that the dominant dechlorination pathway involved the removal of meta chlorines, although some para and some ortho dechlorination was also observed. The rates and products of PCB dechlorination varied widely, depending on the mixture of congeners present. This is the first time the dechlorination of single octa- and nona-chlorobiphenyl congeners has been reported, and also the first time that the dechlorination of various combinations of these congeners has been investigated. Extensive degradation of penta- and tetra-CBs to biphenyl was also found to occur. A method to detect alkylated polycylic aromatic hydrocarbons (alkyl PAHs) in complex hydrocarbon mixtures was developed, and by using this method, the alkyl PAH content of several hydrocarbon mixtures was determined. Degradation of the alkyl PAH portion of hydrocarbon-contaminated Hall Beach (Nunavut) soil was demonstrated. Science, Faculty of Chemistry, Department of Graduate
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