<b>Untargeted Physiochemical Characterization of Complex Environmental Mixtures</b>

<p dir="ltr">As our awareness of environmental concerns grows, understanding the composition of various environmental mixtures has become vital for assessing the prospects of renewable energy and developing effective pollution mitigation strategies. This dissertation focuses on assessing the composition of three complex environmental mixtures and improving methods of evaluating their properties with high-resolution mass spectrometry. Firstly, renewable biofuels are a possible carbon-neutral alternative to fossil fuels, which have a poorly understood chemical composition. Here (<i>Chapter 3</i>), we employ a non-heating fractionization method to dissect biofuel components without compromising internal integrity. Employing high-resolution mass spectrometry, molecular-level analysis of these fractions provided a thorough characterization of the biofuel components, their fuel viability, and chemical structures. These comprehensive insights inform the need for upgrading processes, ultimately improving the technology of biofuel production. The second material analyzed is polymers and waste plastic feedstocks. Despite the growing demand for plastic, only ~10% of it is recycled globally. Given plastics’ extended lifespan and resistance to degradation, understanding the properties and impacts of plastic pollution, as well as efficient recycling processes, is vital to mitigate their environmental impact. We adopted the Temperature-Programmed Desorption−Direct Analysis in Real Time−High Resolution Mass Spectrometry (TPD-DART-HRMS) as a practical and efficient methodology to provide a wealth of information for characterizing plastic burning pollution and plastic waste feedstocks. We employ a practical parameterization method to describe the gas-partitioning and viscosity of mixed emission plastic sources from complex wildfires (<i>Chapter 4</i>) Additionally, to describe recycling feedstocks, we develop a novel characterization methodology incorporating Kendrick mass defect analysis, assisted with a robust statistical algorithm, which allows evaluation of unknown plastic types and the determination of the presence of compounds of special concern (e.g. halogens) in waste plastic feedstocks (<i>Chapter 5</i>). Lastly, we aimed to assess chemical components of plausible toxicity concern in household dust, aiming to discern their potential impact on infant development (<i>Chapter 6</i>). Employing a multi-modal chemical characterization approach, we evaluate heavy metal content and environmentally persistent free radical concentration, employing electron paramagnetic resonance spectroscopy (EPR), x-ray fluorescence spectroscopy (XRF), and inductively coupled plasma mass spectrometry (ICP-MS), This multi-modal study facilitates a holistic understanding of the potential health risks associated with dust ingestion.</p>