The Production and Evolution o...

The Production and Evolution of Secondary Organic Aerosol During Smog Chamber Photochemical Reaction Studies of PAH with the OH Radical and the Subsequent Detection of These Products in Smog Samples from Seoul, South Korea and Los Angeles, California

It has long been known that Polycyclic Aromatic Hydrocarbons (PAH) react with atmospheric oxidants such as ozone and the OH radical.  Our experiments have uniquely centered on the reactions of PAH with the OH radical in a 10m3 smog chamber.  PAH such as naphthalene, acenaphthene and phenanthrene have been studied, primarily because they can easily be put into the vapor phase for gas-phase reactions.  The OH radical is generated through the photochemical reaction of isopropylnitrite in the presence of NO and light to generate the OH radical while, at the same time eliminating ozone from the reaction.  Thus, the products are formed from the unique reaction of the PAH with the OH radical.  Ultra-violet fluorescent lamps surrounding the chamber are turned on for a measured amount of time then turned off.  While the lights are on, OH is produced.  When the lights are turned off, the OH radical production ceases immediately, thus freezing the reaction so that air samples may be withdrawn from the chamber for product analysis.  The lights are then turned back on and the process is repeated numerous times until the isopropyl nitrite and/or NO are depleted and ozone begins to appear.  The products are withdrawn from the chamber either through an annular diffusion denuder and filterpack for gas/particle partitioned analysis of the products or through a thermal desorption tube containing XAD resin for total product analysis by thermal desorption-multidimensional gas chromatography-time of flight mass spectrometry (TDS-GCxGC-TOFMS).  The denuder samples are solvent extracted and run as solutions by GCxGC-TOFMS.

This paper will describe our experimental system and will demonstrate how the gas to particle partitioning of products evolves during the course of the reactions and the production of  secondary organic aerosols (SOA).   Numerous products detected in the smog chamber, will be shown to be present in smog samples from Seoul, South Korea.  Additionally, we will show the monthly variation of the concentrations of products such as 2-formylcinnamaldehyde and dibenzopyranone over the course of a year.

Presentation Type: 
Invited Presentation
Author 1: 
Douglas A. Lane
Author 2: 
JiYi Lee
Author 3: 
Antonio H. Miguel
Additional Authors: 
no more authors
Author Roles
Corresponding Author: 
Douglas A. Lane
Presenting Author: 
Antonio H. Miguel