AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
A Chamber Study of the Aging of Reaction Products Formed by Photo-Oxidation of Beta-Pinene
MEHRNAZ SARRAFZADEH, Donald Hastie, York University
Abstract Number: 456 Working Group: Aerosol Chemistry
Abstract The chemical aging processes can influence both the chemical and physical properties of secondary organic aerosols (SOA) and subsequently their effects on climate change and human health. Further oxidation of primary oxidation products with oxidants such as hydroxyl radicals (OH) and ozone (O3) can result in either less volatile products which contribute to particulate mass or form higher volatility products which do not. However, little is known about the effects of aging on SOA.
In this study, beta-Pinene was oxidized by OH in the presence of NO in an indoor smog chamber until no beta-Pinene was measurable. The reaction products mixture was then subjected to high levels of OH and O3; which corresponded to multiple exposure days in the atmosphere. This was done to investigate the aging effects on organic aerosols. Oxidation products were then analyzed online using an atmospheric pressure chemical ionization tandem mass spectrometer (APCI-MS/MS). Both gas and particle phase products were analyzed to distinguish between the aging effects in the two phases. For investigating particle phase products, an on-line counter flow membrane denuder (CFMD) was successfully integrated with the smog chamber and APCI-MS/MS instrument set-up.
The results of this study highlighted the importance of OH induced aging which led to additional particulate mass formation, whereas aging with O3 did not show any visual impact. Also discussed are the changes in the chemical composition of oxidation products during aging with OH which was due to further oxidation of products in the gas phase and there was no evidence for particle phase reactions.