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| Titel |
Seasonal changes in Fe species and soluble Fe concentration in the atmosphere in the Northwest Pacific region based on the analysis of aerosols collected in Tsukuba, Japan |
| VerfasserIn |
Y. Takahashi, T. Furukawa, Y. Kanai, M. Uematsu, G. Zheng, M. A. Marcus |
| 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 ; 13, no. 15 ; Nr. 13, no. 15 (2013-08-09), S.7695-7710 |
| Datensatznummer |
250085618
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| Publikation (Nr.) |
 copernicus.org/acp-13-7695-2013.pdf |
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| Zusammenfassung |
Atmospheric iron (Fe) can be a significant source of nutrition for
phytoplankton inhabiting remote oceans, which in turn has a large influence
on the Earth's climate. The bioavailability of Fe in aerosols depends mainly
on the fraction of soluble Fe (= [FeSol]/[FeTotal], where
[FeSol] and [FeTotal] are the atmospheric concentrations of
soluble and total Fe, respectively). However, the numerous factors affecting
the soluble Fe fraction have not been fully understood. In this study, the
Fe species, chemical composition, and soluble Fe concentrations in aerosols
collected in Tsukuba, Japan were investigated over a year (nine samples from
December 2002 to October 2003) to identify the factors affecting the amount
of soluble Fe supplied into the ocean. The soluble Fe concentration in
aerosols is correlated with those of sulfate and oxalate originated from
anthropogenic sources, suggesting that soluble Fe is mainly derived from
anthropogenic sources. Moreover, the soluble Fe concentration is also
correlated with the enrichment factors of vanadium and nickel emitted by
fossil fuel combustion. These results suggest that the degree of Fe
dissolution is influenced by the magnitude of anthropogenic activity, such
as fossil fuel combustion.
X-ray absorption fine structure (XAFS) spectroscopy was performed in order
to identify the Fe species in aerosols. Fitting of XAFS spectra coupled with
micro X-ray fluorescence analysis (μ-XRF) showed the main Fe species
in aerosols in Tsukuba to be illite, ferrihydrite, hornblende, and Fe(III)
sulfate. Moreover, the soluble Fe fraction in each sample measured by
leaching experiments is closely correlated with the Fe(III) sulfate fraction
determined by the XAFS spectrum fitting, suggesting that Fe(III) sulfate is
the main soluble Fe in the ocean. Another possible factor that can control
the amount of soluble Fe supplied into the ocean is the total Fe(III)
concentration in the atmosphere, which was high in spring due to the high
mineral dust concentrations during spring in East Asia. However, this factor
does not contribute to the amount of soluble Fe to a larger degree than the
effect of Fe speciation, or more strictly speaking the presence of Fe(III)
sulfate. Therefore, based on these results, the most significant factor
influencing the amount of soluble Fe in the North Pacific region is the
concentration of anthropogenic Fe species such as Fe(III) sulfate that can
be emitted from megacities in Eastern Asia. |
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