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| Titel |
Role of aldehyde chemistry and NOx concentrations in secondary organic aerosol formation |
| VerfasserIn |
A. W. H. Chan, M. N. Chan, J. D. Surratt, P. S. Chhabra, C. L. Loza, J. D. Crounse, L. D. Yee, R. C. Flagan, P. O. Wennberg, J. H. Seinfeld |
| 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. 15 ; Nr. 10, no. 15 (2010-08-04), S.7169-7188 |
| Datensatznummer |
250008678
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| Publikation (Nr.) |
 copernicus.org/acp-10-7169-2010.pdf |
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| Zusammenfassung |
| Aldehydes are an important class of products from atmospheric oxidation of
hydrocarbons. Isoprene (2-methyl-1,3-butadiene), the most abundantly emitted
atmospheric non-methane hydrocarbon, produces a significant amount of
secondary organic aerosol (SOA) via methacrolein (a C4-unsaturated
aldehyde) under urban high-NOx conditions. Previously, we have
identified peroxy methacryloyl nitrate (MPAN) as the important intermediate
to isoprene and methacrolein SOA in this NOx regime. Here we show
that as a result of this chemistry, NO2 enhances SOA formation from
methacrolein and two other α, β-unsaturated aldehydes,
specifically acrolein and crotonaldehyde, a NOx effect on SOA
formation previously unrecognized. Oligoesters of dihydroxycarboxylic acids
and hydroxynitrooxycarboxylic acids are observed to increase with increasing
NO2/NO ratio, and previous characterizations are confirmed by both
online and offline high-resolution mass spectrometry techniques. Molecular
structure also determines the amount of SOA formation, as the SOA mass yields
are the highest for aldehydes that are α, β-unsaturated and
contain an additional methyl group on the α-carbon. Aerosol formation
from 2-methyl-3-buten-2-ol (MBO232) is insignificant, even under
high-NO2 conditions, as PAN (peroxy acyl nitrate, RC(O)OONO2)
formation is structurally unfavorable. At atmospherically relevant
NO2/NO ratios (3–8), the SOA yields from isoprene high-NOx
photooxidation are 3 times greater than previously measured at lower
NO2/NO ratios. At sufficiently high NO2 concentrations, in
systems of α, β-unsaturated aldehydes, SOA formation from
subsequent oxidation of products from acyl peroxyl radicals+NO2 can
exceed that from RO2+HO2 reactions under the same inorganic
seed conditions, making RO2+NO2 an important channel for
SOA formation. |
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