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| Titel |
Seasonal variations of the water soluble organic carbon mass fraction of aerosol in two valleys of the French Alps |
| VerfasserIn |
J.-L. Jaffrezo, G. Aymoz, C. Delaval, J. Cozic |
| 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 ; 5, no. 10 ; Nr. 5, no. 10 (2005-10-27), S.2809-2821 |
| Datensatznummer |
250003111
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| Publikation (Nr.) |
 copernicus.org/acp-5-2809-2005.pdf |
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| Zusammenfassung |
| Concentrations of Water Soluble Organic Carbon (WSOC) and WSOC fraction to
Organic Carbon (OC) were measured at two urban sites in valleys of the
French Alps during a period of two and a half years. Concentrations were as
high as 10–15μg C/m3 in winter, but there is a clear seasonal
cycle of the WSOC fraction, with minima occurring during winter. This
reflects a marked dependency on temperature, with the average WSOC fraction
being stable at 54.8±7.7% and 75.9±6.3% for temperatures
in the ranges −10 to +3°C and 12 to 24°C, respectively. Several
points are noteworthy in this evolution. First, there are limiting factors
that prevent lower mass fractions in the low temperature range and higher
mass fractions in the high temperature range. Second, the mass fraction at
the lower temperature is rather high, in apparent contradiction with OC
being mainly insoluble close to the emission sources. Third, the range of
20% for the change of the WSOC fraction between these extreme conditions
is indeed rather narrow when compared to evaluations of the secondary (and
supposedly water soluble) OC fraction proposed in the literature, with most
of the published values being in the range 40 to 70%. A comparison of the
evolution of WSOC concentrations with that of dicarboxylic acids (DCA)
clearly indicates the influence of two regimes in the formation of WSOC: one
at higher temperatures classically linked with the increase of DCA
concentrations and associated with oxidation processes, and another at lower
temperatures involving a much lower increase of DCA concentrations. We
proposed several hypotheses involving processes that could be responsible
for the large concentrations of WSOC in the particulate phase at our sites
during winter time. |
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