Evolution of Secondary Organic Aerosol Composition during Photochemical Ageing
OLGA GARMASH, Ben H. Lee, Maria Zawadowicz, John Shilling, Joel A. Thornton,
University of Washington Abstract Number: 622
Working Group: Aerosol Chemistry
AbstractAerosol particles in the atmosphere affect climate and human health. One of the most abundant constituents of atmospheric particles is secondary organic aerosol (SOA), which forms through oxidation and condensation of organic compounds. In the condensed phase, these compounds undergo additional reactions upon exposure to sunlight and oxidants, otherwise known as ageing. These reactions, in turn, affect the physio-chemical properties of the aerosols, such as hygroscopicity and volatility, and alter their role in the atmosphere.
In the current study, we investigated the ageing of SOA particles produced from the commonly emitted organic compounds from biogenic sources (isoprene, α-pinene and β-caryophyllene) and anthropogenic sources (trimethylbenzene). The experiments were conducted at the Pacific Northwest National Laboratory atmospheric chamber operated in a batch mode. The SOA particles were formed in oxidation by OH-radical and subsequently aged over 15-30 hours under simulated sunlight. SOA composition was routinely sampled using FIGAERO inlet coupled to iodide-ion chemical ionization mass spectrometer. In this presentation, I will discuss the detailed evolution of chemical components undergoing rapid oligomerization and fragmentation as well as the production of lower-volatility species as the ageing progresses. The results of this work will help us to improve our ability to predict the lifetime and cloud-forming potential of organic aerosol particles in the atmosphere.