AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Products Formed during the Heterogeneous Oxidation of Polycyclic Aromatic Hydrocarbons in an Atmospheric Chamber
KLARA ONDRUSOVA, Richard E. Cochran, Haewoo Jeong, Alena Kubatova, University of North Dakota
Abstract Number: 225 Working Group: Aerosol Chemistry
Abstract Polycyclic aromatic hydrocarbons (PAHs) have long been of great interest due to their known toxicity to human health and indirect impact on our climate. After emitted into the atmosphere through various primary emission sources, PAHs can be oxidized to less volatile derivatives. Such oxidation pathways can occur in both the gas phase and gas-particle (heterogeneous) phase. While significant work has been devoted to determining the mechanisms behind the gas-phase oxidation of PAHs, our current understanding of their oxidation in the heterogeneous phase is limited. In this work PAHs are oxidized in a 10 m3 atmospheric chamber under atmospherically relevant conditions. Focus was given to identifying the wide range of products formed as well as determining the kinetic formation rates of the various products. Initial experiments were performed using model particle substrates, ammonium sulfate and silica particles, to compare kinetic formation rates against those obtained under gas-phase conditions. Experiments were then done using diesel-exhaust PM emitted from an idling diesel engine. PM samples were collected onto quartz filters for off-line analysis by gas chromatography-mass spectrometry (GC-MS). Additionally PM sample were collected onto a newly developed quartz tube sampler for off-line analysis by thermal desorption/pyrolysis-gas chromatography/mass spectrometry (TD/Py-GC/MS). This latter PM sampling method allowed for the investigation of high molecular weight (low volatility) and oligomeric species not easily detected with GC-MS. PM concentrations and size distributions were continuously monitored throughout the experiments using an online scanning mobility particle sizer (SMPS).