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| Titel |
Distributions of low molecular weight dicarboxylic acids, ketoacids and α-dicarbonyls in the marine aerosols collected over the Arctic Ocean during late summer |
| VerfasserIn |
K. Kawamura, K. Ono, E. Tachibana, B. Charrière, R. Sempéré |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 9, no. 11 ; Nr. 9, no. 11 (2012-11-22), S.4725-4737 |
| Datensatznummer |
250007407
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| Publikation (Nr.) |
 copernicus.org/bg-9-4725-2012.pdf |
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| Zusammenfassung |
| Oxalic and other small dicarboxylic acids have been reported as important
water-soluble organic constituents of atmospheric aerosols from different
environments. Their molecular distributions are generally characterized by
the predominance of oxalic acid (C2) followed by malonic (C3)
and/or succinic (C4) acids. In this study, we collected marine aerosols
from the Arctic Ocean during late summer in 2009 when sea ice was
retreating. The marine aerosols were analyzed for the molecular
distributions of dicarboxylic acids as well as ketocarboxylic acids and
α-dicarbonyls to better understand the source of water-soluble
organics and their photochemical processes in the high Arctic marine
atmosphere. We found that diacids are more abundant than ketoacids and
α-dicarbonyls, but their concentrations are generally low (< 30 ng m−3), except for one sample (up to 70 ng m−3) that was
collected near the mouth of Mackenzie River during clear sky condition.
Although the molecular compositions of diacids are in general characterized
by the predominance of oxalic acid, a depletion of C2 was found in two
samples in which C4 became the most abundant. Similar depletion of
oxalic acid has previously been reported in the Arctic aerosols collected at
Alert after polar sunrise and in the summer aerosols from the coast of
Antarctica. Because the marine aerosols that showed a depletion of C2
were collected under the overcast and/or foggy conditions, we suggest that a
photochemical decomposition of oxalic acid may have occurred in aqueous
phase of aerosols over the Arctic Ocean via the photo dissociation of
oxalate-Fe (III) complex. We also determined stable carbon isotopic
compositions (δ13C) of bulk aerosol carbon and individual
diacids. The δ13C of bulk aerosols showed
−26.5‰ (range: −29.7 to −24.7‰,
suggesting that marine aerosol carbon is derived from both terrestrial and
marine organic materials. In contrast, oxalic acid showed much larger
δ13C values (average: −20.9‰, range:
−24.7‰ to −17.0‰) than those of
bulk aerosol carbon. Interestingly, δ13C values of oxalic acid
were higher than C3 (av. −26.6‰) and C4
(−25.8‰) diacids, suggesting that oxalic acid is
enriched with 13C due to its photochemical processing (aging) in the
marine atmosphere. |
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