Using Computational Chemistry and Experimental Approaches to Characterize Light-Absorbing Properties, Chemical Reactivity and Toxicity of Organic Aerosols and Atmospheric Traces Gases
Air pollution is a key environmental factor that contributes to the global burden of disease and climate change. Light-absorbing properties and toxicity mechanisms of atmospheric aerosols and trace gases have not been fully studied in part due to complex chemical compositions and a lack of authentic chemical standards. Even though computational chemistry approaches are quick and useful to predict chemical reactivity and optical absorption of atmospheric pollutants, but experimental data are required to validate theoretical results. Therefore, a combination of computational and experimental approaches is necessary to characterize light-absorbing properties, chemical reactivity and toxicity atmospheric pollutants in both gas and aerosol phases.
This dissertation investigates the climate effects of brown carbon (a class of light-absorbing organic aerosols), and health impacts of carbonyl compounds by using a combination of computational chemistry and experimental approaches. First, by using time-dependent density functional theory and experimental UV-Vis measurements, this dissertation identifies effects of functional groups, pH, and solvation environments on the light-absorbing properties of brown carbon aerosols. Second, the density functional theory methods and dithiothreitol reactivity assays were used to characterize electrophilicity of atmospheric carbonyls and their pathways to modify nucleophiles. Subsequently, to extend the findings to a multipollutant system, carbonyl chemical composition in electron cigarette vaping emissions is characterized using an impinger setup. Global and local site reactivities are computed to help predict the toxicity of carbonyls.
Using a combination of computational chemistry and experimental approaches help to assess light-absorbing properties of brown carbon and health effects of carbonyls. Overall, results from this dissertation contributes to an improved molecular understanding of reactivity, toxicity and light-absorbing properties of important atmospheric pollutants that are associated with public health and climate change.