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| Titel |
Impact of a large wildfire on water-soluble organic aerosol in a major urban area: the 2009 Station Fire in Los Angeles County |
| VerfasserIn |
A. Wonaschütz, S. P. Hersey, A. Sorooshian, J. S. Craven, A. R. Metcalf, R. C. Flagan, 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 ; 11, no. 16 ; Nr. 11, no. 16 (2011-08-15), S.8257-8270 |
| Datensatznummer |
250010002
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| Publikation (Nr.) |
 copernicus.org/acp-11-8257-2011.pdf |
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| Zusammenfassung |
| This study examines the nature of water-soluble organic aerosol measured in
Pasadena, CA, under typical conditions and under the influence of a large
wildfire (the 2009 Station Fire). During non-fire periods, water-soluble
organic carbon (WSOC) variability was driven by photochemical production
processes and sea breeze transport, resulting in an average diurnal cycle
with a maximum at 15:00 local time (up to 4.9 μg C m−3). During
the Station Fire, primary production was a key formation mechanism for WSOC.
High concentrations of WSOC (up to 41 μg C m−3) in smoke plumes
advected to the site in the morning hours were tightly correlated with
nitrate and chloride, numerous aerosol mass spectrometer (AMS) organic mass
spectral markers, and total non-refractory organic mass. Processed residual
smoke was transported to the measurement site by the sea breeze later in the
day, leading to higher afternoon WSOC levels than on non-fire days.
Parameters representing higher degrees of oxidation of organics, including
the ratios of the organic metrics m/z 44:m/z 57 and m/z 44:m/z 43, were elevated in
those air masses. Intercomparisons of relative amounts of WSOC, organics,
m/z 44, and m/z 43 show that the fraction of WSOC comprising acid-oxygenates
increased as a function of photochemical aging owing to the conversion of
aliphatic and non-acid oxygenated organics to more acid-like organics. The
contribution of water-soluble organic species to the organic mass budget
(10th–90th percentile values) ranged between 27 %–72 % and
27 %–68 % during fire and non-fire periods, respectively. The seasonal
incidence of wildfires in the Los Angeles Basin greatly enhances the
importance of water-soluble organics, which has implications for the
radiative and hygroscopic properties of the regional aerosol. |
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