The reaction of α-pinene with the nitrate (NO3) radical exerts significant control over the formation of secondary organic aerosol (SOA) and organic nitrates in the Southeast US, and other regions with joint biogenic and anthropogenic influence. Yet, there are large uncertainties in the organic nitrate yield (10-30%), the SOA yield (0-30%), and the chemical mechanism for this reaction in the literature. For example, the nitrooxy hydroperoxide (the nitrate-RO2 + HO2 product) was observed in significant quantities during the 2013 SOAS campaign, but this chemistry so far has not been described in chamber studies. This work employed a novel set of dark reaction conditions and atmospherically-relevant NO3 production rates (PNO3) to reproduce the nitroxy hydroperoxide product that was observed in the ambient, confirming its chemical origin. We also investigated the organic nitrate production, SOA yield, and RO2 fates for this chemistry at different environmental conditions (various PNO3, relative humidity, particle surface area, and other parameters) in order to understand how the α-pinene + NO3 reaction evolves from the chamber to the atmosphere.

Mechanism of the nitrate oxidation of α-pinene under simulated ambient conditions

2019 Fall National Meeting

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