Year of Award
2025
Document Type
Dissertation
Degree Type
Doctor of Philosophy (PhD)
Degree Name
Chemistry
Department or School/College
Department of Chemistry and Biochemistry
Committee Chair
Lu Hu
Commitee Members
Robert Yokelson, Christopher Palmer, Michael DeGrandpre, Ashley Ballantyne
Keywords
Air qulaity modeling, Biomass burning emissions, Human exposure / health risk assessment, Ozone photochemistry, Volatile organic compounds (VOCs), Wildfire smoke
Abstract
Wildfires are a significant source of volatile organic compounds (VOCs) in the western U.S., emitting hundreds to thousands of species that play key roles in tropospheric oxidation, ozone production, and secondary organic aerosol formation. Many VOCs have only recently been identified and quantified in laboratory burning experiments, leaving uncertainties about their emission estimates from wildfires, their roles in plume OH oxidation chemistry, and their evolution during smoke aging. This dissertation aims to improve our understanding of the emissions, chemistry, and health impacts of VOCs in wildfire smoke using detailed in-situ measurements made during the summer 2018 Western Wildfire Experiment for Cloud Chemistry, Aerosol Absorption, and Nitrogen (WE-CAN) field campaign and the 2019 Fire Influence on Regional to Global Environments and Air Quality (FIREX-AQ).
Using these comprehensive datasets, first, I assess four widely used wildfire emission inventories and find that they underestimate total VOC emissions by more than a factor of six, driven largely by underestimated dry matter burned and incomplete VOC speciation1. Second, I assess an explicit chemical mechanism (MCM) and the computationally constrained reduced mechanism used in state-of-the-art CTMs like GEOS-Chem, showing that MCM generally reproduces early-plume chemistry whereas GEOS-Chem underperforms due to missing reactive VOCs, especially furanoids (Jin et al., in review). Third, I develop a refined emission inventory, formulate a reduced chemical mechanism for furanoids, and incorporate them into the GEOS-Chem, revealing that furanoids contribute up to 20% of global glyoxal abundance and likely serve as a critical source of brown carbon in source regions (Jin et al., in prep). Lastly, I evaluate the impact of wildfire plumes on human exposure, finding that smoke can produce ~100 excess cancer cases per million and elevate the non-cancer hazard index to three, an effect that current chemical transport models fail to reproduce (Jin et al., submitted).
Collectively, this PhD research advances understanding of wildfire VOC emissions and chemistry, highlights the importance of previously overlooked reactive species, and provides a foundation for improving atmospheric models and air quality predictions in wildfire-prone regions.
Recommended Citation
Jin, Lixu, "FROM PLUMES TO PEOPLE: CONSTRAINING THE EMISSIONS, CHEMISTRY, AND HEALTH IMPACTS OF WESTERN U.S. SMOKE" (2025). Graduate Student Theses, Dissertations, & Professional Papers. 12585.
https://scholarworks.umt.edu/etd/12585
© Copyright 2025 Lixu Jin