HR: 14:40h
AN: A53E-05    [Abstracts]
TI: Field and Laboratory Experiments Examining the Stability of Organic Molecular Markers Used for Source Apportionment
AU: * Robinson, A L
EM: alr@andrew.cmu.edu
AF: Carnegie Mellon University, 5000 Forbes Ave, Pittsburgh, PA 15208 United States
AU: Donahue, N M
EM: nmd@andrew.cmu.edu
AF: Carnegie Mellon University, 5000 Forbes Ave, Pittsburgh, PA 15208 United States
AU: Sage, A M
EM: asage@andrew.cmu.edu
AF: Carnegie Mellon University, 5000 Forbes Ave, Pittsburgh, PA 15208 United States
AU: Huff Hartz, K E
EM: karah@andrew.cmu.edu
AF: Carnegie Mellon University, 5000 Forbes Ave, Pittsburgh, PA 15208 United States
AU: Weitkamp, E
EM: eweitkam@andrew.cmu.edu
AF: Carnegie Mellon University, 5000 Forbes Ave, Pittsburgh, PA 15208 United States
AB: Individual organic compounds such as levoglucosan and hopanes are often used as tracers for different sources of primary organic aerosol. An important question is the stability of these reduced organic compounds, particularly in the eastern US and other areas where long-range transport is an important contributor to ambient aerosol concentrations. This paper presents evidence of photochemical aging of molecular markers using both in situ observations and laboratory experiments. First, a large in situ dataset of speciated condensed phase compounds is examined for evidence of aging of important tracers including cholesterol and hopanes. The challenge is to separate mixing and aging effects; we apply a dual-ratio chemical coordinate analysis technique used in the past to constrain photochemical age based on gas-phase hydrocarbon data to the condensed-phase organics data. The ambient data are consistent with significant aging, but a `smoking gun' is difficult to obtain due to the convolved mixing and aging effects, coupled with incomplete or inadequate source profile data. Second, smog chamber experiments have been performed to measure the oxidation of different condensed phase species in complex aerosol mixtures. The speciated smog chamber data are interpreted using a variant of the gas-phase relative kinetics technique. This approach allows us to determine relative oxidation rates for a large number of condensed-phase organic compounds in both model systems and real emissions. Experiments performed with model meat smoke mixtures varying in complexity from simple three component systems to actual meat smoke indicate rapid oxidation of oleic acid and much slower oxidation of cholesterol. We shall draw parallels between ongoing laboratory studies of model and real systems and the corresponding in situ measurements.
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0317 Chemical kinetic and photochemical properties
DE: 0345 Pollution--urban and regional (0305)
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting