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| Titel |
Oxalate metal complexes in aerosol particles: implications for the hygroscopicity of oxalate-containing particles |
| VerfasserIn |
T. Furukawa, Y. Takahashi |
| 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. 9 ; Nr. 11, no. 9 (2011-05-10), S.4289-4301 |
| Datensatznummer |
250009704
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| Publikation (Nr.) |
 copernicus.org/acp-11-4289-2011.pdf |
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| Zusammenfassung |
| Atmospheric aerosols have both a direct and an indirect cooling effect that
influences the radiative balance at the Earth's surface. It has been
estimated that the degree of cooling is large enough to weaken the warming
effect of carbon dioxide. Among the cooling factors, secondary organic
aerosols (SOA) play an important role in the solar radiation balance in the
troposphere as SOA can act as cloud condensation nuclei (CCN) and extend the
lifespan of clouds because of their high hygroscopic and water soluble
nature. Oxalic acid is an important component of SOA, and is produced via
several formation pathways in the atmosphere. However, it is not certain
whether oxalic acid exists as free oxalic acid or as metal oxalate complexes
in aerosols, although there is a marked difference in their solubility in
water and their hygroscopicity. We employed X-ray absorption fine structure
spectroscopy to characterize the calcium (Ca) and zinc (Zn) in aerosols
collected at Tsukuba in Japan. Size-fractionated aerosol samples were
collected for this purpose using an impactor aerosol sampler. It was shown
that 10–60% and 20–100% of the total Ca and Zn in the finer
particles (<2.1 μm) were present as Ca and Zn oxalate complexes,
respectively. Oxalic acid is hygroscopic and can thus increase the CCN
activity of aerosol particles, while complexes with various polyvalent metal
ions such as Ca and Zn are not hygroscopic, which cannot contribute to the
increase of the CCN activity of aerosols. Based on the concentrations of
noncomplexed and metal-complexed oxalate species, we found that most of the
oxalic acid is present as metal oxalate complexes in the aerosols,
suggesting that oxalic acid does not always increase the hygroscopicity of
aerosols in the atmosphere. Similar results are expected for other
dicarboxylic acids, such as malonic and succinic acids. Thus, it is advisable
that the cooling effect of organic aerosols should be estimated by including
the information on metal oxalate complexes and metal complexes with other
dicarboxylic acids in aerosols. |
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