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| Titel |
Changes in organic aerosol composition with aging inferred from aerosol mass spectra |
| VerfasserIn |
N. L. Ng, M. R. Canagaratna, J. L. Jimenez, P. S. Chhabra, J. H. Seinfeld, D. R. Worsnop |
| 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 ; 11, no. 13 ; Nr. 11, no. 13 (2011-07-07), S.6465-6474 |
| Datensatznummer |
250009897
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| Publikation (Nr.) |
 copernicus.org/acp-11-6465-2011.pdf |
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| Zusammenfassung |
| Organic aerosols (OA) can be separated with factor analysis of aerosol mass
spectrometer (AMS) data into hydrocarbon-like OA (HOA) and oxygenated OA
(OOA). We develop a new method to parameterize H:C of OOA in terms of
f43 (ratio of m/z 43, mostly C2H3O+, to total signal in the
component mass spectrum). Such parameterization allows for the
transformation of large database of ambient OOA components from the f44
(mostly CO2+, likely from acid groups) vs. f43 space
("triangle plot") (Ng et al.,
2010) into the Van Krevelen diagram (H:C vs. O:C) (Van Krevelen, 1950).
Heald et al. (2010)
examined the evolution of total OA in the Van Krevelen diagram. In this work
total OA is deconvolved into components that correspond to primary (HOA and
others) and secondary (OOA) organic aerosols. By deconvolving total OA into
different components, we remove physical mixing effects between secondary
and primary aerosols which allows for examination of the evolution of OOA
components alone in the Van Krevelen space. This provides a unique means of
following ambient secondary OA evolution that is analogous to and can be
compared with trends observed in chamber studies of secondary organic aerosol formation. The
triangle plot in Ng et al. (2010) indicates that f44 of OOA components
increases with photochemical age, suggesting the importance of acid
formation in OOA evolution. Once they are transformed with the new
parameterization, the triangle plot of the OOA components from all sites
occupy an area in Van Krevelen space which follows a ΔH:C/ΔO:C
slope of ~ −0.5. This slope suggests that ambient OOA aging
results in net changes in chemical composition that are equivalent to the
addition of both acid and alcohol/peroxide functional groups without
fragmentation (i.e. C-C bond breakage), and/or the addition of acid groups
with fragmentation. These results provide a framework for linking the bulk
aerosol chemical composition evolution to molecular-level studies. |
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