EXAMINATION OF EARLY-STAGE CHEMISTRY OF SECONDARY ORGANIC AEROSOL FORMATION USING A FLOW CELL
Alicia J. Kalafut-Pettibone, William Sean McGivern
A laminar flow cell for the study of reactions of volatile organic compounds (VOC) that lead to secondary organic aerosol (SOA) formation has been constructed. In the cell, reactions of VOCs with oxygen are initiated by the ultraviolet photolysis of alkyl halides or addition of photolytically-generated ozone across a double bond to form radical species typical of those produced from atmospheric hydrogen abstraction. Under these experimental conditions, early-stage formation processes dominate, and subsequent oxidative aging is not considered. We propose a mechanism that indexes reaction products by the number of oxygenated substituents, irrespective of structural isomers. Such a treatment shows an increasing net isomerization rate with increasing hydrocarbon length due to the increasing number of available permutation reactions. Presently, we demonstrate growth of particles with both increasing precursor concentrations and increasing exposure to oxidized hydrocarbon. Future experiments will focus on chemical characterization of these products with increasing aerosol mass yield.