Web Release Date: November 12,
Particle Phase Acidity and Oligomer Formation in Secondary Organic Aerosol
and
Departments of Environmental Science and Engineering & Chemical Engineering, California Institute of Technology, MC 210-41, Pasadena, California 91125, Schools of Earth and Atmospheric Sciences & Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0340, Department of Mathematics, University of Houston, Houston, Texas 77204-3476, and Department of Chemistry, California Institute of Technology, Pasadena, California 91125
Received for review June 10, 2004
Revised manuscript received September 22, 2004
Accepted September 24, 2004
Abstract:
A series of controlled laboratory experiments are carried
out in dual Teflon chambers to examine the presence of
oligomers in secondary organic aerosols (SOA) from
hydrocarbon ozonolysis as well as to explore the effect of
particle phase acidity on SOA formation. In all seven
hydrocarbon systems studied (i.e., 
-pinene, cyclohexene,
1-methyl cyclopentene, cycloheptene, 1-methyl cyclohexene,
cyclooctene, and terpinolene), oligomers with MW from 250
to 1600 are present in the SOA formed, both in the
absence and presence of seed particles and regardless
of the seed particle acidity. These oligomers are comparable
to, and in some cases, exceed the low molecular weight
species (MW < 250) in ion intensities in the ion trap mass
spectra, suggesting they may comprise a substantial
fraction of the total aerosol mass. It is possible that oligomers
are widely present in atmospheric organic aerosols,
formed through acid- or base-catalyzed heterogeneous
reactions. In addition, as the seed particle acidity increases,
larger oligomers are formed more abundantly in the
SOA; consequently, the overall SOA yield also increases.
This explicit effect of particle phase acidity on the composition
and yield of SOA may have important climatic consequences
and need to be considered in relevant models.
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