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| Titel |
Enhancement of atmospheric H₂SO₄ / H₂O nucleation: organic oxidation products versus amines |
| VerfasserIn |
T. Berndt, M. Sipilä, F. Stratmann, T. Petäjä, J. Vanhanen, J. Mikkilä, J. Patokoski, R. Taipale, R. L. Mauldin III, 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 ; 14, no. 2 ; Nr. 14, no. 2 (2014-01-22), S.751-764 |
| Datensatznummer |
250118303
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| Publikation (Nr.) |
 copernicus.org/acp-14-751-2014.pdf |
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| Zusammenfassung |
| Atmospheric H2SO4 / H2O nucleation influencing effects have
been studied in the flow tube IfT-LFT (Institute for Tropospheric Research –
Laminar Flow Tube) at 293 ± 0.5 K and a pressure of 1 bar using
synthetic air as the carrier gas. The presence of a possible background
amine concentration in the order of 107–108 molecule cm−3
throughout the experiments has to be taken into account. In a first set of
investigations, ozonolysis of olefins (tetramethylethylene,
1-methyl-cyclohexene, α-pinene and limonene) for close to
atmospheric concentrations, served as the source of OH radicals and possibly
other oxidants initiating H2SO4 formation starting from SO2.
The oxidant generation is inevitably associated with the formation of
organic oxidation products arising from the parent olefins. These products
(first generation mainly) showed no clear effect on the number of nucleated
particles within a wide range of experimental conditions for H2SO4
concentrations higher than ~107 molecule cm−3. Also
the early growth process of the nucleated particles was not significantly
influenced by the organic oxidation products in line with the expected
growth by organic products using literature data. An additional,
H2SO4-independent process of particle (nano-CN) formation was
observed in the case of α-pinene and limonene ozonolysis for
H2SO4 concentrations smaller than ~107 molecule cm−3. Furthermore, the findings confirm the appearance of an
additional oxidant for SO2 beside OH radicals, very likely stabilized
Criegee Intermediates (sCI). A second set of experiments has been performed
in the presence of added amines in the concentrations range of a few
107–1010 molecule cm−3 applying photolytic OH radical
generation for H2SO4 production without addition of other
organics. All amines showed significant nucleation enhancement with
increasing efficiency in the order pyridine < aniline < dimethylamine < trimethylamine. This result supports the idea of
H2SO4 cluster stabilization by amines due to strong
H2SO4↔amine interactions. On the other hand, this
study indicates that for organic oxidation products (in presence of the
possible amine background as stated) a distinct H2SO4 / H2O
nucleation enhancement can be due to increased H2SO4 formation
caused by additional organic oxidant production (sCI) rather than by
stabilization of H2SO4 clusters due to
H2SO4↔organics interactions. |
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