HR: 08:20h
AN: A31E-02    [Abstracts]
TI: Evolution of Diesel Exhaust Aerosol in an Urban Environment
AU: * Kroll, J H
EM: kroll@aerodyne.com
AF: Aerodyne Research, Inc., 45 Manning Road, Billerica, MA 01821, United States
AU: Smith, J D
EM: jdsmith@lbl.gov
AF: Lawrence Berkeley National Laboratory, One Cyclotron Road, Berkeley, CA 94720, United States
AU: Wilson, K R
EM: KRWilson@lbl.gov
AF: Lawrence Berkeley National Laboratory, One Cyclotron Road, Berkeley, CA 94720, United States
AU: Canagaratna, M
EM: mrcana@aerodyne.com
AF: Aerodyne Research, Inc., 45 Manning Road, Billerica, MA 01821, United States
AU: Herndon, S C
EM: herndon@aerodyne.com
AF: Aerodyne Research, Inc., 45 Manning Road, Billerica, MA 01821, United States
AU: Onasch, T B
EM: onasch@aerodyne.com
AF: Aerodyne Research, Inc., 45 Manning Road, Billerica, MA 01821, United States
AU: Wood, E C
EM: ezrawood@aerodyne.com
AF: Aerodyne Research, Inc., 45 Manning Road, Billerica, MA 01821, United States
AU: Worsnop, D R
EM: worsnop@aerodyne.com
AF: Aerodyne Research, Inc., 45 Manning Road, Billerica, MA 01821, United States
AU: Ahmed, M
EM: mahmed@lbl.gov
AF: Lawrence Berkeley National Laboratory, One Cyclotron Road, Berkeley, CA 94720, United States
AU: Leone, S R
EM: srleone@lbl.gov
AF: Lawrence Berkeley National Laboratory, One Cyclotron Road, Berkeley, CA 94720, United States
AB: We present laboratory and field measurements of the composition of the largely unoxidized fraction of organic aerosol found in urban areas. Aerosol evolution from the oxidation of the low-volatility fraction of diesel exhaust was studied by reacting emissions from a modern diesel engine with OH in a flow reactor. The exhaust was first passed through a charcoal denuder, which removed all volatile components and left only semivolatile and intermediate-volatility organic compounds (SVOC's and IVOC's) available for reaction. Oxidation leads to a substantial (40%) increase in aerosol mass and volume, indicating the formation of secondary organic aerosol (SOA) from these compounds. Measurement of the aerosol composition using an Aerodyne aerosol mass spectrometer (AMS) indicates a very low level of oxidation, in contrast with most other laboratory-generated SOA. This is likely because large, relatively low-volatility hydrocarbons require only a small degree of oxidation (addition of 1-2 oxygen atoms) to be of sufficiently low vapor pressure to partition efficiently into the aerosol phase. An aerosol component with a very similar mass spectrum is derived from factor analysis of aerosol mass spectra taken in and around Mexico City as part of the MILAGRO 2006 campaign. This component has a mass spectrum that is distinct from that corresponding to primary diesel emissions ("hydrocarbon-like organic aerosol"). The similarities and relationships between this aerosol component and the aerosol generated from the laboratory oxidation of diesel exhaust will be discussed.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0322 Constituent sources and sinks
DE: 0345 Pollution: urban and regional (0305, 0478, 4251)
DE: 0365 Troposphere: composition and chemistry
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting