AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Photochemical Generation of OH Radicals in Secondary Organic Aerosols
RACHEL HEMS, Jenny Wong, Shouming Zhou, Jonathan Abbatt, University of Toronto, Canada
Abstract Number: 358 Working Group: Aerosol Chemistry
Abstract Aerosol aging processes have been shown to lead to oxidation of the organic components of aerosol. Oxidation can increase aerosol hygroscopicity leading to an increase in the loss of aerosol particles through wet deposition. Heterogeneous oxidation of organic aerosols is often assumed to be the dominant chemical aging process. However, in viscous aerosol particles, heterogeneous oxidation is limited by diffusion and so restricted to the surface. In this regime, condensed phase oxidation processes may be significant. Secondary organic aerosol (SOA) formation under low NOx conditions is known to generate significant amounts of organic peroxides in the condensed phase. When exposed to sunlight, peroxides can photodissociate to produce hydroxyl and alkoxyl radicals which can initiate oxidation of organics. The relevance of this condensed phase source of radicals within the larger context of oxidative aging processes is largely unknown and is the focus of this work. In particular, it is not known if OH radicals are formed, and, if formed, whether they participate in chemical modification of the particles. Particle phase photochemical OH radical generation is investigated within SOA formed by terpene ozonolysis in an environmental chamber. The oxidation of levoglucosan, a reactive bicyclic sugar that is often associated with biomass burning aerosol particles, is used as a tracer for condensed phase OH radical formation, where the levoglucosan is mixed with the SOA material. Preliminary results will be presented.