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| Titel |
Towards closing the gap between hygroscopic growth and CCN activation for secondary organic aerosols – Part 3: Influence of the chemical composition on the hygroscopic properties and volatile fractions of aerosols |
| VerfasserIn |
L. Poulain, Z. Wu, M. D. Petters, H. Wex, E. Hallbauer, B. Wehner, A. Maßling, S. M. Kreidenweis, F. Stratmann |
| 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 ; 10, no. 8 ; Nr. 10, no. 8 (2010-04-23), S.3775-3785 |
| Datensatznummer |
250008371
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| Publikation (Nr.) |
 copernicus.org/acp-10-3775-2010.pdf |
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| Zusammenfassung |
| The influence of varying levels of water mixing ratio, r, during the
formation of secondary organic aerosol (SOA) from the ozonolysis of α-pinene
on the SOA hygroscopicity and volatility was investigated. The
reaction proceeded and aerosols were generated in a mixing chamber and the
hygroscopic characteristics of the SOA were determined with the Leipzig
Aerosol Cloud Interaction Simulator (LACIS) and a Cloud Condensation Nuclei
counter (CCNc). In parallel, a High-Resolution Time-of-Flight Aerodyne
Aerosol Mass Spectrometer (HR-ToF-AMS) located downstream of a thermodenuder
(TD) sampling from the mixing chamber, to collect mass spectra of particles
from the volatile and less-volatile fractions of the SOA. Results showed
that both hygroscopic growth and the volatile fraction of the SOA increased
with increases in r inside the mixing chamber during SOA generation. An
effective density of 1.40 g cm−3 was observed for the generated SOA
when the reaction proceeded with r>1 g kg−1. Changes in the
concentrations of the fragment CO2+ and the sum of
CxHyOz+ (short name CHO) and CxHy+ (short
name CH) fragments as measured by the HR-ToF-AMS were used to estimate
changes in the oxidation level of the SOA with reaction conditions, using
the ratios CO2+ to CH and CHO to CH. Under humid conditions, both
ratios increased, corresponding to the presence of more oxygenated
functional groups (i.e., multifunctional carboxylic acids). This result is
consistent with the α-pinene ozonolysis mechanisms which suggest
that water interacts with the stabilized Criegee intermediate. The
volatility and the hygroscopicity results show that SOA generation via
ozonolysis of α-pinene in the presence of water vapour (r<16.9 g kg−1)
leads to the formation of more highly oxygenated compounds that
are more hygroscopic and more volatile than compounds formed under dry
conditions. |
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