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| Titel |
Seasonal differences in oxygenated organic aerosol composition: implications for emissions sources and factor analysis |
| VerfasserIn |
F. Canonaco, J. G. Slowik, U. Baltensperger, A. S. H. Prévôt |
| 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 ; 15, no. 12 ; Nr. 15, no. 12 (2015-06-29), S.6993-7002 |
| Datensatznummer |
250119855
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| Publikation (Nr.) |
 copernicus.org/acp-15-6993-2015.pdf |
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| Zusammenfassung |
Aerosol chemical speciation monitor (ACSM) measurements were performed in
Zurich, Switzerland, for 13 months (February 2011 through February 2012).
Many previous studies using this or related instruments have utilized the
fraction of organic mass measured at m/z 44 (f44), which is typically
dominated by the CO2+ ion and related to oxygenation, as an indicator
of atmospheric aging. The current study demonstrates that during summer
afternoons, when photochemical processes are most vigorous as indicated by
high oxidant – OX (O3 + NO2), f44 for ambient secondary organic
aerosol (SOA) is not higher but is rather similar or lower than on days with
low OX. On the other hand, f43 (less oxidized fragment) tends to
increase. These changes are discussed in the f44 / f43 space
frequently used to interpret ACSM and aerosol mass spectrometer (AMS) data.
This is likely due to the formation of semi-volatile oxygenated aerosol
produced from biogenic precursor gases, whose emissions increase with ambient
temperature.
In addition, source apportionment analyses conducted on winter and summer
data using positive matrix factorization (PMF) yield semi-volatile oxygenated
organic aerosol (SV-OOA) factors that retain source-related chemical
information. Winter SV-OOA is highly influenced by biomass burning, whereas
summer SV-OOA is to a high degree produced from biogenic precursor gases.
These sources contribute to substantial differences between the winter and
summer f44 / f43 data, suggesting that PMF analysis of
multi-season data employing only two OOA factors cannot capture the seasonal
variability of OOA. |
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