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| Titel |
Gas phase formation of extremely oxidized pinene reaction products in chamber and ambient air |
| VerfasserIn |
M. Ehn, E. Kleist, H. Junninen, T. Petäjä, G. Lönn, S. Schobesberger, M. Maso, A. Trimborn, M. Kulmala  , D. R. Worsnop, A. Wahner, J. Wildt, Th. F. Mentel |
| 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 ; 12, no. 11 ; Nr. 12, no. 11 (2012-06-11), S.5113-5127 |
| Datensatznummer |
250011231
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| Publikation (Nr.) |
 copernicus.org/acp-12-5113-2012.pdf |
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| Zusammenfassung |
| High molecular weight (300–650 Da) naturally charged negative ions have
previously been observed at a boreal forest site in Hyytiälä,
Finland. The long-term measurements conducted in this work showed that these
ions are observed practically every night between spring and autumn in
Hyytiälä. The ambient mass spectral patterns could be reproduced in
striking detail during additional measurements of α-pinene
(C10H16) oxidation at low-OH conditions in the Jülich Plant
Atmosphere Chamber (JPAC). The ions were identified as clusters of the
nitrate ion (NO3−) and α-pinene oxidation products
reaching oxygen to carbon ratios of 0.7–1.3, while retaining most of the
initial ten carbon atoms. Attributing the ions to clusters instead of single
molecules was based on additional observations of the same extremely
oxidized organics in clusters with HSO4− (Hyytiälä) and
C3F5O2−
(JPAC). The most abundant products in the ion
spectra were identified as C10H14O7,
C10H14O9,
C10H16O9, and
C10H14O11. The mechanism
responsible for forming these molecules is still not clear, but the initial
reaction is most likely ozone attack at the double bond, as the ions are
mainly observed under dark conditions. β-pinene also formed highly
oxidized products under the same conditions, but less efficiently, and
mainly C9 compounds which were not observed in Hyytiälä, where
β-pinene on average is 4–5 times less abundant than α-pinene.
Further, to explain the high O/C together with the relatively high H/C, we
propose that geminal diols and/or hydroperoxide groups may be important. We
estimate that the night-time concentration of the sum of the neutral
extremely oxidized products is on the order of 0.1–1 ppt
(~106–107 molec cm−3). This is in a similar range as the
amount of gaseous H2SO4 in Hyytiälä during day-time. As
these highly oxidized organics are roughly 3 times heavier, likely with
extremely low vapor pressures, their role in the initial steps of new
aerosol particle formation and growth may be important and needs to be
explored in more detail in the future. |
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