Abstract

The atmosphere is composed of gases and particles, some of which are recognized as air pollutants owing to their detrimental impact on human health. Beyond their health effects, air pollutants also influence atmospheric reactivity and global radiative forcing. Chemicals such as volatile organic compounds (VOCs) play an important role in the formation and evolution of air pollutants in both particulate and gaseous phases. The characterization of atmospheric particles and gases necessitates sophisticated analytical techniques capable of resolving complex mixtures across wide concentration ranges. Mass spectrometry (MS) is among the most widely used and informative methods and has revolutionized the field of atmospheric chemistry by providing detailed, high-resolution, molecular-level information. This dissertation focuses on the characterization and implications of atmospheric particles and gases as well as the methodological development based on mass spectrometry techniques. Specifically, this work examines brown carbon (BrC) and VOCs as the targets in the particulate phase and gaseous phase, in Chapter 2 and Chapter 3, respectively, and develops an offline aerosol mass spectrometry (AMS) technique in Chapter 4. Atmospheric brown carbon (BrC) from wildfires is a key component of light-absorbing carbon that significantly contributes to global radiative forcing, but its atmospheric evolution and lifetime remain poorly understood. In Chapter 2, the evolution of BrC is investigated by synthesizing data from one laboratory campaign and three aircraft campaigns spanning diverse spatial scales across North America. A method to parameterize the emission ratios of BrC and other species using inert tracers such as acetonitrile (CH3CN) and hydrogen cyanide (HCN) commonly measured by chemical ionization mass spectrometry (CIMS) across campaigns has been developed to estimate the initial conditions for evaluating plume evolution. The BrC evolution is then characterized as a function of hydroxyl radical (OH) exposure. VOCs are key contributors to air pollution and human exposure to toxic chemicals. Their spatial and temporal variability, diverse sources, and chemical complexity present significant challenges for exposure assessment and air quality management. Chapter 3 presents the deployment and application of the Multichannel Organics In-situ enviRonmental Analyzer (MOIRA)a mobile, high-resolution gas chromatography-mass spectrometry (GC-MS) system developed for dynamic, speciated VOC measurements. MOIRA was deployed during the Neighborhood-Scale Assessment of Volatile Organic Compounds in Air (NAVOCA) campaign across a range of indoor and outdoor environments in Louisville, Kentucky. Key findings demonstrate MOIRA’s ability to capture VOC data in multiple different environments. The study underscores the importance of microenvironmental context in VOC exposure and supports the development of routine indoor-outdoor monitoring strategies. Together, these studies demonstrate the value of MS technology in advancing atmospheric chemistry and air quality research. The methodologies and findings presented contribute to improved climate modeling, instrumentation, exposure assessment, and the design of effective environmental health interventions. The High-Resolution Time-of-Flight Aerosol Mass Spectrometry (HR-TOF-AMS) instrument is a widely utilized instrument that enables the quantitative analysis of non-refractory inorganic and organic aerosol species. Chapter 4 presents the development, evaluation, and optimization of an offline AMS technique aimed at chemically characterizing aerosol samples collected on filters by leveraging the capability of HR-TOF-AMS. This technique addresses logistical and financial barriers to widespread AMS deployment, thereby extending the temporal and spatial coverage of aerosol chemical analysis, particularly in underrepresented regions and during non-summer seasons. The study also highlights the potential of the offline AMS technique to be integrated into the Surface Particulate Matter Network (SPARTAN), a global aerosol monitoring initiative. The findings underscore the technique’s value in enhancing long-term, multi-site aerosol studies and support its broader application in atmospheric chemistry, air quality assessment, public health, and climate research.

Committee Chair

Lu Xu

Committee Members

Jay Turner; Brent Williams; Jian Wang; Max Berkelhammer; Randall Martin

Degree

Doctor of Philosophy (PhD)

Author's Department

Energy, Environmental & Chemical Engineering

Author's School

McKelvey School of Engineering

Document Type

Dissertation

Date of Award

8-18-2025

Language

English (en)

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Available for download on Wednesday, August 14, 2030

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