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| Titel |
Laboratory studies of the chemical composition and cloud condensation nuclei (CCN) activity of secondary organic aerosol (SOA) and oxidized primary organic aerosol (OPOA) |
| VerfasserIn |
A. T. Lambe, T. B. Onasch, P. Massoli, D. R. Croasdale, J. P. Wright, A. T. Ahern, L. R. Williams, D. R. Worsnop, W. H. Brune, P. Davidovits |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 11, no. 17 ; Nr. 11, no. 17 (2011-09-01), S.8913-8928 |
| Datensatznummer |
250010045
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| Publikation (Nr.) |
 copernicus.org/acp-11-8913-2011.pdf |
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| Zusammenfassung |
| Secondary organic aerosol (SOA) and oxidized primary organic aerosol (OPOA)
were produced in laboratory experiments from the oxidation of fourteen
precursors representing atmospherically relevant biogenic and anthropogenic
sources. The SOA and OPOA particles were generated via controlled exposure of
precursors to OH radicals and/or O3 in a Potential Aerosol Mass (PAM) flow
reactor over timescales equivalent to 1–20 days of atmospheric aging.
Aerosol mass spectra of SOA and OPOA were measured with an Aerodyne aerosol
mass spectrometer (AMS). The fraction of AMS signal at m/z = 43
and m/z = 44 (f43, f44), the
hydrogen-to-carbon (H/C) ratio, and the oxygen-to-carbon (O/C) ratio of the
SOA and OPOA were obtained, which are commonly used to characterize the level
of oxidation of oxygenated organic aerosol (OOA). The results show that
PAM-generated SOA and OPOA can reproduce and extend the observed
f44–f43 composition beyond that of ambient OOA as measured by an
AMS. Van Krevelen diagrams showing H/C ratio as a function of O/C ratio
suggest an oxidation mechanism involving formation of carboxylic acids
concurrent with fragmentation of carbon-carbon bonds. Cloud condensation
nuclei (CCN) activity of PAM-generated SOA and OPOA was measured as a
function of OH exposure and characterized as a function of O/C ratio. CCN
activity of the SOA and OPOA, which was characterized in the form of the
hygroscopicity parameter κorg, ranged from
8.4×10−4 to 0.28 over measured O/C ratios ranging from 0.05 to
1.42. This range of κorg and O/C ratio is significantly
wider than has been previously obtained. To first order, the
κorg-to-O/C relationship is well represented by a linear function of the
form κorg = (0.18±0.04) ×O/C + 0.03,
suggesting that a simple, semi-empirical parameterization of OOA
hygroscopicity and oxidation level can be defined for use in chemistry and
climate models. |
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