Master of Science (M.Sc.)
John C Poutsma
Rachel E O'Brien
Organic aerosols are very complex in nature and can contain upwards to thousands of different chemical species. Their structure and reactivity can have effects on the molecule’s atmospheric lifetime, human health, and even climate implications. In the atmosphere, there are several aging processes that organic aerosols can undergo that ultimately change the chemical composition of the aerosol. Depending on the process that ensues, the chemical and optical properties are subject to change. In this study, α-pinene ozonolysis reacted secondary organic aerosol (SOA) molecules were generated, collected, and concentrated on Teflon filters. The SOA were aged in a photolytic chamber for 4 days by being irradiated by a xenon (Xe) arc lamp in varying relative humidity (RH) conditions. The changes in the chemical and optical absorption properties that incurred from aging were monitored via UV/Vis absorption spectroscopy, Attenuated Total Reflectance Fourier-Transform infrared spectroscopy (ATR-FTIR), and Fourier-Transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). UV/Vis analysis of the α-pinene sample irradiated for varying amounts of time determined a λmax of ~280 nm. As photoirradiation time increased, the carbonyl peak decreased, indicating the removal of volatile carbonyl-containing compounds with photolysis. ATR-FT-IR analysis allowed for the change in functional groups to be monitored during different light/RH aging conditions. ATR-FT-IR confirmed the presence of a carbonyl in the samples, likely from carboxylic acids forming. However, inconsistent sample loading prevented quantitative conclusions from being made. FT-ICR-MS analysis monitored chemical changes in the sample, ultimately supporting that oligomerization of the sample occurs during photolysis. The shift in the intensity patterns remained the focus of analysis, for chemical identity characterizations were not performed. The majority of these results remain investigative in nature, and no firm conclusions were made due to unforeseen circumstances. Further targeted research on this project is necessary. In a congruent project, an Eksigent nanoLC 2DTM instrument was repaired and interfaced to a Thermo LTQ XLTM Linear Ion Trap/LTQ OrbitrapTM Mass Spectrometer. A detailed and labeled user guide with specialized troubleshooting solutions is offered here. The LTQ MS was equipped with a PicoView Nanospray (NSI) source. The source requires a packed borosilicate capillary for the analytical column, where the guide for set up is included here. A major flow/pressure issue was fixed by rebuilding the LC pumps, replacing disintegrated seals, and calibrating the flow meters. Additional issues resulted with the NSI source, clogged capillaries, and the autosampler programming.
© The Author
Nicks, Laurel Lee Anne, "Effects Of Ozonolysis And Photolytic Aging On The Chemical And Optical Properties Of Α-Pinene Secondary Organic Aerosols / Interfacing An Eksigent Liquid Chromatograph To An Ltq/Orbitrap Mass Spectrometer" (2023). Dissertations, Theses, and Masters Projects. William & Mary. Paper 1697552719.
Available for download on Monday, August 25, 2025