FTIR Characterization of SOA from the Ozonolysis of Isoprene and Methacrolein
BRIAN BOUCHARD, Cindy DeForest Hauser
Abstract Number: 798
Working Group: Carbonaceous Aerosols in the Atmosphere
Last modified: July 22, 2011
Isoprene is the most abundant non-methane VOC and several studies have shown that oxidation of isoprene’s two double bonds leads to secondary organic aerosol (SOA) formation. The OH radical, NOx, and ozone comprise the main oxidizing agents that contribute to SOA formation from isoprene. SOA formed from the direct reaction of ozone and isoprene becomes greater concern in regions that demonstrate both high ozone concentrations and large amounts of isoprene-emitting vegetation. Kudzu, a vine native to Asia, has invaded large areas of the SE United States. This plant is both a strong isoprene emitter and allows for symbiotic bacteria to fix more nitrogen into soil than is natively present in invaded regions. Kudzu invasion thus results in increased soil emissions of NO and consequent increased atmospheric ozone concentrations.
To further study the implications of kudzu invasion for air quality and SOA formation, the reaction of ozone and isoprene is studied and the resulting SOA characterized by FTIR and particle density. Spectra are collected with and without an inline denuder to distinguish between gas and particle phase products. In agreement with previous studies and expected reaction pathways, carbonyl and aldehyde features are prevalent in the IR spectra of both gas and particle phase products. Substantial particle counts are observed in all experiments. In a separate experiment, methacrolein, a major volatile first generation product of isoprene ozonolysis, is reacted directly with ozone and the resulting SOA characterized by FTIR and particle density. The data from isoprene SOA and methacrolein SOA are compared.