Abstract

The troposphere is governed by photochemical and radical-mediated processes that control atmospheric oxidation capacity, secondary pollutant formation, and the chemical lifetime of gases. Quantitative understanding of these processes requires both robust observational frameworks capable of resolving complex precursor–product relationships and instrumentation with sufficient sensitivity and selectivity to detect reactive and low-concentration species. This dissertation advances atmospheric chemistry through the parallel development of quantitative observational methodologies and refined spectroscopic measurement techniques. The first component of this work evaluates atmospheric oxidation systems using long-term monitoring data and empirical diagnostics. Multi-year analyses of ozone and particulate matter trends were conducted to characterize variability across diverse meteorological regimes in Utah and along the Northern Wasatch Front. Empirical ozone isopleths were constructed from observational datasets to assess precursor sensitivity and nonlinear photochemical behavior in Salt Lake Valley. Deviations from the Leighton Photostationary relationship were evaluated under real atmospheric conditions to quantify the influence of peroxy radicals and reservoir species such as peroxyacetyl nitrate on air quality. These studies provide a quantitative framework for interpreting oxidation regimes, precursor interactions, and photochemical balance across spatial and temporal scales. The second component centers on development, refinement, and application of spectroscopic instrumentation for detection of atmospherically relevant trace gases. A custom-built radiometer was designed and deployed for characterization of photon flux relevant to photochemical rate calculations. Broadband Cavity-Enhanced Absorption Spectroscopy configurations were implemented and enhanced for detection of trace species including glyoxal and hydroxyl radical. Instrument intercomparisons and interferometric approaches were evaluated to extend sensitivity while preserving spectral resolution. In addition, the absorption cross-section of molecular bromine was refined using ultraviolet-visible and cavity-enhanced techniques. The resulting cross-section definition demonstrates measurable impacts on calculated photolysis rates and modeled oxidation capacity. Integration of observational analysis and spectroscopic development illustrates the interdependence of chemical interpretation and measurement capability. Empirical ozone diagnostics rely on accurate photolysis characterization, while cross-section refinement directly influences atmospheric modeling outcomes. Collectively, this dissertation strengthens both the analytical frameworks used to interrogate atmospheric oxidation chemistry and the measurement foundations upon which those frameworks depend.

Degree

PhD

College and Department

Computational, Mathematical, and Physical Sciences; Chemistry and Biochemistry

Rights

https://lib.byu.edu/about/copyright/

Date Submitted

2026-03-31

Document Type

Dissertation

Keywords

atmospheric oxidation chemistry, ozone, ozone isopleth, nitrogen oxides, volatile organic compounds, peroxyacetyl nitrate, hydroxyl radical, molecular bromine, Broadband Cavity-Enhanced Absorption Spectroscopy (BBCEAS), radiometer

Language

english

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