| Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous pollutants of environmental concern. Bioremediation, relying on stimulation of natural microbial degradation processes, is a well-established technology to clean up PAH-contaminated soils. However, bioremediation does not necessarily lead to a reduction in soil toxicity. PAH-contaminated sites are affected by extremely complex mixtures, like coal tar or creosote, and biotransformation products or co-occurring compounds can also contribute to the overall toxicological effects of contaminated soil before and after bioremediation. Therefore, the objective of this dissertation was to use non-target analysis workflows to identify the genotoxic transformation products, important co-occurring pollutants, and the unrecognized biotransformation pathways that could contribute to explain the toxicological effects observed beyond parent PAHs.;To identify the source(s) of increased genotoxicity in bioremediated soil, we pursued a non-target analytical approach combining effect-directed analysis (EDA) and metabolite profiling to compare extracts of PAH-contaminated soil before and after bioremediation. A compound with the composition C 15H8O2 and four methylated homologues were shown to accumulate as a result of bioreactor treatment, and the C15H 8O2 compound was determined to be genotoxic. Its structure was established as a heretofore unidentified alpha,beta-unsaturated lactone, 2H-naphtho[2,1,8-def ]chromen-2-one (NCO), which was confirmed by synthesis. It also accumulated in aerobically incubated soil from two additional PAH-contaminated sites and was formed from pyrene by two pyrene-degrading bacterial cultures known to be geographically widespread, underscoring its potential environmental significance.;Azaarenes are nitrogen heterocyclic polyaromatic compounds that co-occur with PAHs but have been poorly studied in environmental systems. High resolution mass spectrometry (HRMS) and mass-defect filtering were applied to four PAH-contaminated samples to analyze the their diversity, abundance, and biodegradation behavior. The diversity, relatively high concentrations, and persistence of high-molecular-weight azaarenes were highlighted, and isomer-selective biodegradation was observed.;To help elucidate PAH biodegradation pathways and endpoints in contaminated soil, HRMS and stable isotope-assisted metabolomics (SIAM) workflows were tested and applied to a PAH-contaminated soil. Uniformly 13C-labeled fluoranthene, pyrene, or benzo[a]anthracene were spiked into the soil and incubated in microcosms. With SIAM, known and unknown metabolites such as ring-cleavage products and conjugates were detected, and the transformation pathways leading to their formation proposed. |
