AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
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Organic Nitrate and Secondary Organic Aerosol Formation from the Reaction of Alpha-Pinene and Nitrate Radical under Simulated Ambient Conditions
GUY BURKE, Yichen Li, Tran Nguyen, UC Davis
Abstract Number: 653 Working Group: Aerosol Chemistry
Abstract The atmospheric chemistry of the nitrate radical (NO3) with monoterpenes is important in understanding ozone and secondary organic aerosol (SOA) formation in the Southeast United States and other regions of mixed biogenic and anthropogenic influence. This chemistry produces NOx reservoir species like organic nitrates (ON) and may be an important source of SOA. However, our knowledge of the NO3 reaction with the most abundant monoterpene, alpha-pinene, has significant uncertainty. Previous studies reported a large range in the SOA and ON yields from the alpha-pinene + NO3 oxidation and did not capture some of the key chemical species observed in the field. This is likely due to the different experimental conditions and the challenge of capturing ambient nighttime and night-to-day transitional chemistry in chamber studies. We studied the alpha-pinene + NO3 reaction in an atmospheric chamber, with particular focus on the RO2+HO2 channel, which resulted in the formation of the nitrooxy hydroperoxides and other ON species that are observed at the SOAS 2013 Campaign, and reduction in the RO2-RO2 and RO2 + NO3 reactions that are not expected to be important in the ambient environment. The yields of gas phase products are measured with CF3O- chemical ionization mass spectrometry (CIMS) and the SOA composition is analyzed with liquid chromatography high-resolution mass spectrometry (LC-HRMS). We will discuss the dependence of ON and SOA yields with respect to reaction conditions such as the estimated concentrations of NO3 and HO2.