AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Constraining the Range of Product Chemical Formulas, Volatilities, and Reaction Mechanisms of SOA-forming Reactions
JESSE KROLL, Kelly Daumit, James Hunter, Sean Kessler, MIT
Abstract Number: 195 Working Group: Aerosol Chemistry
Abstract The formation and evolution of secondary organic aerosol (SOA) is characterized by reactions that can change both the carbon oxidation state (OS$_C) of and the number of carbon atoms (n$_C) in a molecule, resulting in dramatic changes to the volatility and other key properties of the molecule. However such changes can be hard to predict due to the very large number of chemical transformations and reaction products that are possible. Here the full range of possible products from a given SOA precursor are described, using a simple three-dimensional chemical space (defined by O/C, H/C and n$_C), combined with fundamental rules governing atmospheric oxidation. This range of products is pathway-independent, and thus holds for any possible formation mechanism: gas-phase oxidation, particle-phase chemistry, oxidation in liquid water, etc. One benefit of this chemical space, which is closely related to other recently-proposed (and mostly two-dimensional) spaces, is that few assumptions about the distribution of functional groups are necessary in order to determine the volatility (c*) of a given organic species. Thus the predominant phase of the species is determined directly from its location in this three-dimensional space. We use this approach to constrain the underlying mechanisms of a number of different oxidation systems recently studied in our laboratory, including the gas-phase oxidation of volatile precursors, the heterogeneous oxidation of low-volatility species, and the oxidation of water-soluble species within liquid-water aerosol particles.