Date of Award
5-14-2024
Degree Name
Doctor of Philosophy (PhD)
Degree Type
Dissertation
Abstract
Particulate matter (PM) has a significant impact on visibility, hydrological cycles, and climate change through direct and indirect radiative properties. PM is also ubiquitous in both indoor and outdoor air, presenting adverse effects on human health. Organic matter (OM) constitutes 20-50% of these particulate matter, known as organic aerosols (OA). The chemical composition of OA is linked to its sources and processes, making it crucial to understand its characteristics for developing aerosol-related control policies, air quality regulations, and climate models. Semi-volatile organic compounds (SVOCs) compose a substantial portion of OA, existing in both gas and particle phases. The distribution of these compounds between the two phases can change rapidly depending on conditions such as temperature, relative humidity, the chemical composition of particles, and particle concentration, increasing the chemical complexity of OA. Mass spectrometry has been frequently used to analyze the chemical composition of environmental samples, including OA, from bulk scale to the molecular level. Aerosol Mass Spectrometer (AMS) is widely used for analyzing the bulk chemical composition of fine particles. Thermal Desorption Aerosol Gas Chromatography Mass Spectrometry (TAG) enables molecular level of analysis with data acquisition in higher time resolution coupling with an automated particle sampling system. Additionally, the multi-turn Time-Of-Flight mass spectrometry (InfiTOF) has been developed for high-resolution gas analysis of environmental samples. These advancements in mass spectrometry techniques have significantly contributed to our understanding of the fate of OA in indoor and outdoor environments, with ongoing developments aiming for more precise and efficient analysis of complex environmental samples like OA. As mass spectrometry techniques continue to advance, there is a growing demand for advanced tools in data acquisition and analysis to enhance research efficiency. This demand has led to the development of various mass spectrometry tools depending on specific purposes and needs. This dissertation addresses the development of such tools. Chapter 2 presents a mass spectral database and comparison tool for Aerosol Mass Spectrometer (AMS) and Aerosol Chemical Speciation Monitor (ACSM) developed to compare users’ own mass spectral data efficiently and visually with previous studies. Chapter 3 introduces an automated approach, 'AutoPMF,' for quantifying chemical compounds in large GC-MS datasets obtained from TAG using positive matrix factorization (PMF), aimed at saving data-processing time and reducing manual inspection. Furthermore, Chapter 5 presents a guide tool for optimizing resolution in infiTOF mass spectrometer operations to enhance data acquisition efficiency. Each tool is demonstrated for its effectiveness through application with previous data, aligning with its intended purpose. Among the developed tools, AutoPMF was utilized to analyze TAG data, focusing on investigating the influence of particle type on the phase-partitioning of SVOCs in indoor environments described in Chapter 4. Specifically, the study concentrated on gas-to-particle partitioning and the desorption of SVOCs from chamber walls depending on particle type. The results demonstrate that organic particles enhance the phase partitioning of SVOCs, while inorganic particles have no significant impact.
Language
English (en)
Chair
Brent Williams