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| Titel |
α-pinene photooxidation under controlled chemical conditions – Part 2: SOA yield and composition in low- and high-NOx environments |
| VerfasserIn |
N. C. Eddingsaas, C. L. Loza, L. D. Yee, M. Chan, K. A. Schilling, P. S. Chhabra, J. H. Seinfeld, P. O. Wennberg |
| 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. 16 ; Nr. 12, no. 16 (2012-08-16), S.7413-7427 |
| Datensatznummer |
250011393
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| Publikation (Nr.) |
 copernicus.org/acp-12-7413-2012.pdf |
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| Zusammenfassung |
| The gas-phase oxidation of α-pinene produces a large amount of
secondary organic aerosol (SOA) in the atmosphere. A number of carboxylic
acids, organosulfates and nitrooxy organosulfates associated with
α-pinene have been found in field samples and some are used as tracers
of α-pinene oxidation. α-pinene reacts readily with OH and
O3 in the atmosphere followed by reactions with both HO2 and
NO. Due to the large number of potential reaction pathways, it can be
difficult to determine what conditions lead to SOA. To better understand the
SOA yield and chemical composition from low- and high-NOx OH
oxidation of α-pinene, studies were conducted in the Caltech
atmospheric chamber under controlled chemical conditions. Experiments used
low O3 concentrations to ensure that OH was the main oxidant and low
α-pinene concentrations such that the peroxy radical (RO2)
reacted primarily with either HO2 under low-NOx conditions or
NO under high-NOx conditions. SOA yield was suppressed under
conditions of high-NOx. SOA yield under high-NOx conditions was greater when
ammonium sulfate/sulfuric acid seed particles (highly acidic) were present
prior to the onset of growth than when ammonium sulfate seed particles
(mildly acidic) were present; this dependence was not observed under
low-NOx conditions. When aerosol seed particles were introduced after
OH oxidation, allowing for later generation species to be exposed to fresh
inorganic seed particles, a number of low-NOx products partitioned to
the highly acidic aerosol. This indicates that the effect of seed acidity and
SOA yield might be under-estimated in traditional experiments where aerosol
seed particles are introduced prior to oxidation. We also identify the
presence of a number of carboxylic acids that are used as tracer compounds of
α-pinene oxidation in the field as well as the formation of
organosulfates and nitrooxy organosulfates. A number of the carboxylic acids
were observed under all conditions, however, pinic and pinonic acid were only
observed under low-NOx conditions. Evidence is provided for
particle-phase sulfate esterification of multi-functional alcohols. |
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