Graduate Thesis Or Dissertation

 

Use of Targeted and Non-Targeted Analysis to Study Complex PAH Environmental Mixtures Public Deposited

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  • Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous contaminants formed from the incomplete combustion of organic material. These contaminants are of concern because of their widespread presence in the environment and toxic properties. In addition, PAHs encompass a class of diverse compounds with varying physicochemical properties and exist in the environment as complex mixtures. Research has primarily focused on parent (or unsubstituted) PAHs, mainly the 16 U.S. Environmental Protection Agency priority PAHs. However, many other PAH derivatives, such as oxygen containing PAHs, co-occur in these complex mixtures and may be equally, if not more, toxic than parent PAHs. This dissertation investigates PAHs in complex soil and house dust environmental mixtures. Previous studies have suggested that the partial degradation of PAHs during bioremediation may result in increased toxicity postbioremediation. However, there is limited information on these transformation products in soil. An effects-directed analysis approach, incorporating targeted gas chromatography mass spectrometry (GC/MS), the DT40 genotoxicity and zebrafish developmental toxicity assays demonstrated increased toxicity postbioremediation in four soil extract fractions (C, D, E and F). Non-targeted analysis, combing comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC×GC/TOF-MS) and liquid chromatography quadrupole time-of-flight mass spectrometry (LC/QTOF-MS), was subsequently used to characterize the toxic soil extract fractions postbioremediation. Several of the tentatively identified compounds contained an oxygen and/or nitrogen in their elemental compositions, suggesting they would be relatively polar. Additionally, targeted GC/MS analysis of high molecular weight 302 PAHs (MW302-PAHs, PAHs with molecular weight ≥ 302 a.m.u), which are highly mutagenic, showed no degradation postbioremediation. The data suggest that monitoring the disappearance of a subset of parent PAH compounds may potentially overestimate the efficiency of bioremediation. In the second part of the dissertation, a targeted approach, using GC×GC/TOF-MS, was used to investigate the long-term associations between parent PAHs, methylated PAHs, selected oxygenated PAHs, and thirdhand smoke (THS) in house dust. THS contains a complex mixture of toxic chemicals, and was recently shown to be a significant contributor of PAHs in settled house dust in smoker and non-smoker homes. However, less is known about how PAHs, more specifically other PAH derivatives, may associate with THS. In a pilot study, five homes were evaluated for the different PAH classes, tobacco-specific nitrosamines (TSNAs) and nicotine, up to six months after smoking had ended. Individual PAHs, 2+1 methylphenanthrene (2+1MPHE), 2-methylanthracene (2MANT), retene (RET), dibenz[a,h]anthracene (DBahA), 9,10-anthraquinone (9,10AQ), 2-methylanthraquinone (2MAQ), benzanthrone (BZ), benzo[cd]pyrenone (BcdP), 5,12-naphthacenequinone (5,12NQ) and 9-fluorenone (9FLO) dust loadings were significantly correlated with nicotine and TSNA dust loadings over time (R²: 0.47-0.72, p < 0.05). This suggests that these compounds may strongly associate with THS and should potentially be considered when assessing the long-term risks associated with THS exposure. This dissertation demonstrates that PAHs exist in complex mixtures, and uses various tools (i.e. targeted and/or non-targeted methods, toxicity testing, complementary instrumental techniques) to investigate PAH compounds beyond those routinely monitored. Many of these compounds, such as transformation products, may be of ecological and toxicological significance.
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  • 2017-08-22 to 2018-06-07

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