AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Secondary Organic Aerosol Formation from Aromatic Compounds: Relationship between SOA Yield and Chemical Structure
PING TANG, Shunsuke Nakao, Chia-Li Chen, David R. Cocker III, University of California, Riverside
Abstract Number: 545 Working Group: Aerosol Chemistry
Abstract Formation of secondary Organic Aerosol (SOA) from benzene, toluene, ethylbenzene, xylene isomers, ethyltoluene isomers, thrimethylbenzene isomers, propylbenzene, isopropylbenzene, tetramethylbenzene, pentamethylbenzene and hexamethylbenzene was investigated in a series of smog chamber experiments. Experiments were performed in dry air under no NO$_x and low NO$_x conditions. It is observed that under low-NO$_x conditions aerosol formed from aromatic hydrocarbon with more carbon atoms has a lower yield, which is consistent with Odum’s definition of high-yield and low-yield aromatics (Odum, 1996). While under no-NO$_x conditions no such trend was observed. This might relate to the hydroxyl radical (OH radical) level available in these systems. Under no-NOx conditions, H$_2O$_2 photolysis can provide a stable OH source. Mz43(C$_2H$_3O$^+)/mz44 (CO$^(2+)) ratio determined by ToF-HR-AMS increased with increasing number of alkyl substituent on aromatic ring, which indicates more ketone/ aldehyde was formed. Ketones are harder to oxidize than aldehydes and therefore go through lesser oxidation thus result in a lower aerosol yield. In addition, aerosol volatility measured by VTDMA was compared. It is found that aerosol formed from aromatic with more carbon number has a higher volatility.