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| Titel |
On the roles of sulphuric acid and low-volatility organic vapours in the initial steps of atmospheric new particle formation |
| VerfasserIn |
P. Paasonen, T. Nieminen, E. Asmi, H. E. Manninen, T. Petäjä, C. Plass-Dülmer, H. Flentje, W. Birmili, A. Wiedensohler, U. Hõrrak, A. Metzger, A. Hamed, A. Laaksonen, M. C. Facchini, V.-M. Kerminen, M. Kulmala  |
| 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. 22 ; Nr. 10, no. 22 (2010-11-30), S.11223-11242 |
| Datensatznummer |
250008918
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| Publikation (Nr.) |
 copernicus.org/acp-10-11223-2010.pdf |
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| Zusammenfassung |
| Sulphuric acid and organic vapours have been identified as the key
components in the ubiquitous secondary new particle formation in the
atmosphere. In order to assess their relative contribution and spatial
variability, we analysed altogether 36 new particle formation events
observed at four European measurement sites during EUCAARI campaigns in
2007–2009. We tested models of several different nucleation mechanisms
coupling the formation rate of neutral particles (J) with the concentration
of sulphuric acid ([H2SO4]) or low-volatility organic vapours
([org]) condensing on sub-4 nm particles, or with a combination of both
concentrations. Furthermore, we determined the related nucleation
coefficients connecting the neutral nucleation rate J with the vapour
concentrations in each mechanism. The main goal of the study was to identify
the mechanism of new particle formation and subsequent growth that minimizes
the difference between the modelled and measured nucleation rates. At three
out of four measurement sites – Hyytiälä (Finland), Melpitz
(Germany) and San Pietro Capofiume (Italy) – the nucleation rate was
closely connected to squared sulphuric acid concentration, whereas in
Hohenpeissenberg (Germany) the low-volatility organic vapours were observed
to be dominant. However, the nucleation rate at the sulphuric acid dominant
sites could not be described with sulphuric acid concentration and a single
value of the nucleation coefficient, as K in J=K [H2SO4]2, but
the median coefficients for different sites varied over an order of magnitude. This inter-site variation
was substantially smaller when the heteromolecular homogenous nucleation
between H2SO4 and organic vapours was assumed to take place in
addition to homogenous nucleation of H2SO4 alone, i.e.,
J=KSA1[H2SO4]2+KSA2[H2SO4][org].
By
adding in this equation a term describing homomolecular organic vapour
nucleation, Ks3[org]2, equally good results were achieved. In
general, our results suggest that organic vapours do play a role, not only
in the condensational growth of the particles, but also in the nucleation
process, with a site-specific degree. |
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