Identification and Analysis of Halogenated Contaminants Formed in Thermal Decomposition of Halogenated Materials
Year: 2014
Type: dissertation
Abstract: Fires release a wide array of contaminants that contribute to detrimental environmental and health effects. The thermal decomposition of halogenated materials in fires produces complex mixtures that include unidentified environmentally persistent and toxic halogenated contaminants. Resulting complex mixtures pose an analytical challenge in assessing the hazards of a fire site where burn conditions and contents are unknown. Non-targeted analytical approaches can facilitate identification of novel compounds in complex mixtures to direct further study. This thesis investigates the thermal decomposition mechanisms and products of halogenated materials using non-targeted analytical techniques, and assesses the environmental relevance of these thermal processes. Mass defect filtering of high-resolution mass spectra is an effective approach to visually resolve and interpret complex chemical information. This non-targeted approach was used to characterize the thermal decomposition products of polychlorotrifluoroethylene (PCTFE) and polyvinylidene fluoride (PVDF). High-resolution mass spectra, obtained by Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS), were interpreted using mass defect plots based on unique mass scales. Novel halogenated compounds were identified, including perchlorinated/fluorinated polycyclic aromatic hydrocarbons (X-PAHs, X=Cl,F), and polyfluorinated polycyclic aromatic hydrocarbons (F-PAHs). Congener profiles of thermal decomposition products provided evidence of associated decomposition mechanisms. The potential of non-targeted analyses to characterize complex environmental samples was further exemplified through studies examining the environmental relevance of combustion-derived contaminants. Using mass defect plots as a screening tool, a variety of brominated contaminants, including polybrominated/chlorinated dibenzofurans (PXDFs, X=Br/Cl), were identified in air and particulates collected from simulation fire studies. Mass defect filtering, in combination with comprehensive two-dimensional gas chromatography high-resolution time of flight mass spectrometry (GCxGC-HRToF) and gas chromatography tandem mass spectrometry (GC-MS/MS) was used to identify bioaccumulative contaminants in aquatic species exposed to soil from an industrial fire site. Compounds identified as bioaccumulative included polybrominated/chlorinated, anthracenes/phenanthrenes and pyrenes/fluoranthenes (X-PAHs, X=Br,Cl). The majority of environmental analyses is targeted and thereby only examines a small subset of compounds present in the environment. This work demonstrates the potential of non-targeted techniques to screen complex environmental samples for halogenated contaminants. This is particularly applicable to combustion-derived mixtures, the complexity of which varies with fire conditions and contents.
Source: TSpace (University of Toronto)
Author: Anne L. Myers
Language: English
Subfield: Health, Toxicology and Mutagenesis
Field: Environmental Science
Domain: Physical Sciences
Open Access status: green
Funder: University of Toronto
OpenAlex ID: W2327088385