Chemistry PhD Defense
Dissertation Defense: Demetrios Pagonis, Influence of multiphase processes on the chemistry and measurement of organic compounds in indoor and outdoor environments
ANYL student, Ziemann Lab, CU Boulder
"Organic compounds are ubiquitous in indoor and outdoor environments, with organic aerosols and gases impacting air quality, global climate, and human health. The life cycle of volatile organic compounds (VOCs) in the atmosphere includes emission from indoor and outdoor sources, oxidation in the atmosphere to form secondary organic aerosol (SOA), and eventual deposition to a surface. Understanding each of these processes is necessary to predict the impact of organic compounds on indoor and outdoor environments, and this thesis presents the results of a series of studies across the life cycle of VOCs, examining the chemical and physical processes that transform organic compounds in the atmosphere.
First, the chemistry of multifunctional hydroperoxides in SOA is studied by a series of laboratory studies utilizing a model hydroperoxyaldehyde designed to represent the highly oxidized multifunctional compounds that impact SOA growth in pristine environments. Measurements of reaction rates, equilibrium constants, and decomposition mechanisms provide insight into how chemical structure and aerosol properties affect the chemistry of multifunctional hydroperoxides in SOA. Second, emission rates, deposition velocities, reaction rates, and reaction products from a field study in a university art museum are presented. This study quantifies the significant impact of human activities on indoor VOC emissions, as well as the effect of indoor surfaces and indoor oxidants on the fate of those emissions. Lastly, this thesis presents a study aimed to improve researchers’ ability to make time-resolved measurements of gas-phase organic compounds that partition to instrument surfaces and to Teflon tubing commonly used for sampling lines. The simple chromatography model presented here accurately predicts the delay in instrument response caused by gas-surface partitioning across all the tubing lengths, diameters, flow rates, and analytes tested. Together, the studies presented in this thesis advance the understanding of, and the ability to measure, the fate of organic compounds in indoor and outdoor environments."