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| Titel |
Heterogeneous oxidation of saturated organic aerosols by hydroxyl radicals: uptake kinetics, condensed-phase products, and particle size change |
| VerfasserIn |
I. J. George, A. Vlasenko, J. G. Slowik, K. Broekhuizen, J. P. D. Abbatt |
| 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 ; 7, no. 16 ; Nr. 7, no. 16 (2007-08-16), S.4187-4201 |
| Datensatznummer |
250005162
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| Publikation (Nr.) |
 copernicus.org/acp-7-4187-2007.pdf |
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| Zusammenfassung |
| The kinetics and reaction mechanism for the heterogeneous oxidation of
saturated organic aerosols by gas-phase OH radicals were investigated under
NOx-free conditions. The reaction of 150 nm diameter Bis(2-ethylhexyl)
sebacate (BES) particles with OH was studied as a proxy for chemical aging
of atmospheric aerosols containing saturated organic matter. An aerosol
reactor flow tube combined with an Aerodyne time-of-flight aerosol mass
spectrometer (ToF-AMS) and scanning mobility particle sizer (SMPS) was used
to study this system. Hydroxyl radicals were produced by 254 nm photolysis
of O3 in the presence of water vapour. The kinetics of the
heterogeneous oxidation of the BES particles was studied by monitoring the
loss of a mass fragment of BES with the ToF-AMS as a function of OH
exposure. We measured an initial OH uptake coefficient of γ0=1.3 (±0.4), confirming that this reaction is highly efficient. The
density of BES particles increased by up to 20% of the original BES
particle density at the highest OH exposure studied, consistent with the
particle becoming more oxidized. Electrospray ionization mass spectrometry
analysis showed that the major particle-phase reaction products are
multifunctional carbonyls and alcohols with higher molecular weights than
the starting material. Volatilization of oxidation products accounted for a
maximum of 17% decrease of the particle volume at the highest OH exposure
studied. Tropospheric organic aerosols will become more oxidized from
heterogeneous photochemical oxidation, which may affect not only their
physical and chemical properties, but also their hygroscopicity and cloud
nucleation activity. |
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