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| Titel |
Modeling the formation and properties of traditional and non-traditional secondary organic aerosol: problem formulation and application to aircraft exhaust |
| VerfasserIn |
S. H. Jathar, M. A. Miracolo, A. A. Presto, N. M. Donahue, P. J. Adams, A. L. Robinson |
| 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. 19 ; Nr. 12, no. 19 (2012-10-04), S.9025-9040 |
| Datensatznummer |
250011492
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| Publikation (Nr.) |
 copernicus.org/acp-12-9025-2012.pdf |
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| Zusammenfassung |
| We present a methodology to model secondary organic aerosol (SOA) formation
from the photo-oxidation of unspeciated low-volatility organics
(semi-volatile and intermediate volatile organic compounds) emitted by
combustion systems. It is formulated using the volatility basis-set
approach. Unspeciated low-volatility organics are classified by volatility
and then allowed to react with the hydroxyl radical. The new methodology
allows for larger reductions in volatility with each oxidation step than
previous volatility basis set models, which is more consistent with the
addition of common functional groups and similar to those used by
traditional SOA models. The methodology is illustrated using data collected
during two field campaigns that characterized the atmospheric evolution of
dilute gas-turbine engine emissions using a smog chamber. In those
experiments, photo-oxidation formed a significant amount of SOA, much of
which could not be explained based on the emissions of traditional speciated
precursors; we refer to the unexplained SOA as non-traditional SOA (NT-SOA).
The NT-SOA can be explained by emissions of unspeciated low-volatility
organics measured using sorbents. We show that the parameterization proposed
by Robinson et al. (2007) is unable to explain the timing of the NT-SOA
formation in the aircraft experiments because it assumes a very modest
reduction in volatility of the precursors with every oxidation reaction. In
contrast the new method better reproduces the NT-SOA formation. The NT-SOA
yields estimated for the unspeciated low-volatility organic emissions in
aircraft exhaust are similar to literature data for large n-alkanes and other
low-volatility organics. The estimated yields vary with fuel composition
(Jet Propellent-8 versus Fischer-Tropsch) and engine load (ground idle
versus non-ground idle). The framework developed here is suitable for
modeling SOA formation from emissions from other combustion systems. |
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