Master of Science (M.Sc.)
Rachel E. O'Brien
John C. Poutsma
Lisa M. Landino
Complex organic mixtures in the environment can contain hundreds to thousands of different organic molecules, and their composition and reactivity can have important environmental implications. In addition to gases, the atmosphere is made of a variety of small liquids and solids called aerosols. These aerosols have large impacts on human health, climate, and atmospheric chemical reactions. Here, secondary organic aerosol (SOA) from the ozonolysis of α-pinene is characterized. The atmospheric lifetime of SOA is very uncertain, but recent laboratory and modeling studies have demonstrated that photolysis is potentially an important process for organic mass loss from aerosol particles.1-5 Photolysis modifies the molecular composition and properties of aerosols through photolytic cleaving and repartitioning of volatile products. Characterization of dry, irradiated SOA can provide insights into photolysis driven changes in absorption properties and chemical composition. These results illuminate aging mechanisms and chemical and physical properties of organic aerosols in order to improve atmospheric modeling and the understanding of atmospheric chemical reactions. However, the high chemical complexity and low atmospheric abundance presents a difficult analytical challenge. Milligrams, or more, of material may be needed for speciated spectroscopic analysis.6 This study used a suite of advanced analytical techniques, including a novel combination of action spectroscopy and mass spectrometry that provides more structural information on organic mixtures than mass spectrometry alone. This study also used tunable light from a free electron laser, infrared and UV/Vis absorption, and computational chemistry to characterize molecules in α-pinene SOA. In addition, complex organic mixtures are also found in particulate matter that has deposited onto Earth’s surface. The preliminary results of dew analysis, including a foundation method of analysis for future study, gives the first look at organic material deposited into dew water on natural surfaces. This offers insight into atmospheric organic deposition to better understand chemical transport, air quality, and carbon cycling in the atmosphere.
© The Author
Walhout, Emma Quinn, "Complex Mixtures: Identifying and Characterizing Secondary Organic Aerosols" (2019). Dissertations, Theses, and Masters Projects. Paper 1563898940.
Available for download on Monday, June 07, 2021