Abstract View
Molecular Composition Changes in α-Pinene SOA Due to the presence of PAHs
SIMEON SCHUM, Lynn Mazzoleni, Kaitlyn Suski, Alla Zelenyuk, Michigan Technological University
Abstract Number: 507
Working Group: Aerosol Chemistry
Abstract
Terpene emissions, such as α-pinene, contribute to the formation of a large proportion of biogenic secondary organic aerosol (SOA) in the atmosphere. When emitted near anthropogenic emission sources (cars, power plants, industrial processes, etc.) these compounds will interact, which may lead to compositional changes in the organic aerosol and changes in how the aerosol interacts with the environment (light absorptivity, volatility, viscosity, etc.). Recently, α-pinene ozonolysis SOA was formed in the in the presence of various gas-phase PAHs. The data indicate that the presence of PAHs results in significant changes in the aerosol evaporation rates, viscosity, and yields of formation. Low resolution mass spectrometry results also indicated significant changes in the composition of the resulting aerosol, though the extent of the changes in aerosol molecular-composition was difficult to determine. Here we report the analysis of these samples using multiple ionization types (ESI and APPI) and modes (negative/positive) with ultrahigh resolution mass spectrometry (Orbitrap Elite) for a more detailed look at the molecular composition of these samples. We found that the most obvious change in composition occurred for the mixture of α-pinene and pyrene, showing a cluster of oligomers containing a single oxidized pyrene and one or more α-pinene molecules. Additionally, the use of APPI allowed the observation of low-oxygen oligomers of α-pinene that have not been reported previously in experiments with non-acidic seed aerosol. These low-oxygen oligomers seemed enhanced by the presence of benzo[a]anthracene, but were also present in “normal” α-pinene SOA. The presence of these compounds raises questions about the potential for an additional pathway for SOA formation outside the typical oxygen-increasing reaction described in most SOA studies. Here we will present the results of the mass spectrometric analysis of these samples and discuss their potential implications for the understanding of SOA formation and the interaction between biogenic and anthropogenic aerosol sources.