AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
The Role of Multiphase Aging in the Chemistry of Organic Aerosol
KELLY DAUMIT, Jesse Kroll, MIT
Abstract Number: 573 Working Group: Aerosol Chemistry
Abstract Atmospheric organic aerosol (OA) is known to undergo rapid oxidation ("aging"), involving changes to particle mass and oxidation state, over the timescale of several hours. However, laboratory studies generally cannot reproduce this rate of aging, requiring longer oxidant exposures to achieve the same degree of oxidation as in the atmosphere. As a result, the phases and mechanisms by which rapid aging of ambient OA occurs are poorly understood. The goal of this work is to determine the relative efficiency of aging OA in various phases through an examination of the partitioning and rates of oxidation. Oxidation of OA components can take place in the gas phase, condensed organic phase, or liquid water phase. The rate of oxidation in each case is a function of the rate coefficient, oxidant concentration, and fraction of the reactant present in that phase. This last quantity is controlled by the organic molecule’s saturation vapor pressure, its Henry's law constant, and the mass concentrations of the solvent (organic aerosol loading or liquid water content). This underscores the necessity for realistic partitioning conditions in experiments designed to represent ambient oxidation. In this work the contributions of these quantities to the oxidation rate of model organics are examined, in an effort to better understand the phase in which OA aging occurs. Aqueous-phase oxidation experiments will be conducted under partitioning conditions representative of the atmosphere, in order to gain insight into the kinetics of aging in the aqueous phase relative to that in the gas phase.