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| Titel |
Molecular distributions of dicarboxylic acids, ketocarboxylic acids and α-dicarbonyls in biomass burning aerosols: implications for photochemical production and degradation in smoke layers |
| VerfasserIn |
S. Kundu, K. Kawamura, T. W. Andreae, A. Hoffer, M. O. Andreae |
| 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 ; 10, no. 5 ; Nr. 10, no. 5 (2010-03-02), S.2209-2225 |
| Datensatznummer |
250008165
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| Publikation (Nr.) |
 copernicus.org/acp-10-2209-2010.pdf |
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| Zusammenfassung |
| Aerosols in the size class <2.5 μm (6 daytime and
9 nighttime samples) were collected at a pasture site in Rondônia,
Brazil, during the intensive biomass burning period of 16–26 September 2002
as part of the Large-Scale Biosphere-Atmosphere Experiment in Amazonia –
Smoke, Aerosols, Clouds, Rainfall and Climate (LBA-SMOCC). Homologous
series of dicarboxylic acids (C2–C11) and related compounds
(ketocarboxylic acids and α-dicarbonyls) were identified using gas
chromatography (GC) and GC/mass spectrometry (GC/MS). Among the species
detected, oxalic acid was found to be the most abundant, followed by
succinic, malonic and glyoxylic acids. Average concentrations of total
dicarboxylic acids, ketocarboxylic acids and α-dicarbonyls in the
aerosol samples were 2180, 167 and 56 ng m−3, respectively. These are
2–8, 3–11 and 2–16 times higher, respectively, than those reported in urban
aerosols, such as in 14 Chinese megacities. Higher ratios of dicarboxylic
acids and related compounds to biomass burning tracers (levoglucosan and
K+) were found in the daytime than in the nighttime, suggesting the
importance of photochemical production. On the other hand, higher ratios of
oxalic acid to other dicarboxylic acids and related compounds normalized to
biomass burning tracers (levoglucosan and K+) in the daytime provide
evidence for the possible degradation of dicarboxylic acids (≥C3)
in this smoke-polluted environment. Assuming that these and related
compounds are photo-chemically oxidized to oxalic acid in the daytime, and
given their linear relationship, they could account for, on average, 77%
of the formation of oxalic acid. The remaining portion of oxalic acid may
have been directly emitted from biomass burning as suggested by a good
correlation with the biomass burning tracers (K+, CO and ECa) and
organic carbon (OC). However, photochemical production from other precursors
could not be excluded. |
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