AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Formation and Growth of Secondary Organic Aerosol Particles from the Ozonolysis of α-cedrene: Contributions from High Molecular Weight Products
YUE ZHAO, Lisa M. Wingen, Veronique Perraud, Barbara J. Finlayson-Pitts, University of California, Irvine
Abstract Number: 62 Working Group: Aerosol Chemistry
Abstract Sesquiterpenes are an important class of biogenic volatile organic compounds (BVOCs) and have a high secondary organic aerosol (SOA) forming potential. However, SOA formation from the oxidation of sesuqiterpenes has received less attention compared to other BVOCs such as monoterpenes and the underlying mechanisms remain poorly understood. Recent work has shown that high molecular weight oligomeric compounds contribute a significant fraction of SOA mass from the oxidation of BVOCs, but to date no such data are available for the oxidation of sesquiterpenes. In this work, we present a detailed experimental investigation of ozonolysis of α-cedrene, with an emphasis on the formation mechanisms of oligomers and their role in initial formation and subsequent growth of SOA particles. The ozonolysis experiments were conducted both in a glass flow reactor (30-35 s reaction times) and in a static Teflon chamber (30-60 min reaction times) in the absence and presence of OH or stabilized Criegee intermediates (SCI) scavengers and at different relative humidities. The chemical composition of SOA particles is characterized as a function of size using different mass spectrometric techniques and infrared spectroscopy. The possible structures and formation mechanisms of selected oligomers are elucidated in light of their fragmentation mass spectra, size-dependent SOA composition, and the effects of water vapor, OH and SCI scavengers. In addition, the identity and formation mechanism of some newly observed monomeric oxidation products, as well as the phase state of SOA particles are examined. Insights into the particle formation and growth mechanisms compared to SOA formation from smaller alkenes are presented.