Abstract: 

Current chemical theory is incomplete to accurately predict product formation and structure under non-ideal conditions such as complex, multi-component environmental matrices. Radical reactions occur ubiquitously in the atmosphere and drive the complex, heterogeneous chemistry of VOC oxidation to secondary organic aerosol (SOA). SOA is a significant constituent of fine particulate matter (PM2.5) that is known to cause adverse health outcomes. Oxidation pathways for SOA formation are studied extensively; however, a complete understanding of the mechanistic steps in the evolution of volatile organic compounds (VOCs) to particle mass remains elusive. Techniques to characterize SOA formation often involve mass spectra deconvolution, as atmospheric samples  predominantly contain unidentified peaks. Other uncertainties in SOA formation include the partitioning of gas-phase water-soluble organic carbon (WSOC). Studies of environmental aquatic chemistry such as this require accurate measurement of total organic carbon (TOC). TOC analyzers that operate via wet chemical oxidation (WCO) methods are subject to interference in the presence of salts, which are abundant in nearly all ambient aquatic samples. Beyond these issues with organic compound analyses,  inorganic PM2.5 mass also exhibits measurement uncertainties. PM2.5 as measured by the federal reference method/federal equivalence method (FRM/FEM) uses Teflon filters prone to negative sampling artifacts  through loss of volatile species such as ammonium nitrate, especially in hot and dry areas. While reported PM2.5 mass is substantially reduced over recent decades, in the United States, certain areas may be left behind. This dissertation uses elementary step chemical reactions, kinetic modeling and thermodynamic calculations to elucidate key uncertainties in atmospheric measurements of PM2.5 and TOC.