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| Titel |
Observations of I2 at a remote marine site |
| VerfasserIn |
M. J. Lawler, A. S. Mahajan, A. Saiz-Lopez, E. S. Saltzman |
| 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 ; 14, no. 5 ; Nr. 14, no. 5 (2014-03-14), S.2669-2678 |
| Datensatznummer |
250118484
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| Publikation (Nr.) |
 copernicus.org/acp-14-2669-2014.pdf |
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| Zusammenfassung |
| Inorganic iodine plays a significant role in the photochemistry of the marine
boundary layer, but the sources and cycling of iodine are not well
understood. We report the first I2 observations in marine air that is not
impacted by coastal macroalgal emissions or sea ice chemistry. The data
clearly demonstrate that the very high I2 levels previously reported for
coastal air are not representative of open ocean conditions. In this study,
gas phase I2 was measured at the Cape Verde Atmospheric Observatory, a
semi-remote site in the eastern tropical Atlantic, using atmospheric pressure
chemical ionization tandem mass spectrometry. Atmospheric I2 levels
typically increased beginning at sunset, leveled off after midnight, and then
rapidly decreased at sunrise. There was also a smaller midday maximum in
I2 that was probably caused by a measurement artifact. Ambient I2
mixing ratios ranged from <0.02–0.6 pmol mol−1 in May 2007 and
<0.03–1.67 pmol mol−1 in May 2009. The sea-air flux implied by the
nighttime buildup of I2 is too small to explain the observed daytime IO
levels at this site. Iodocarbon measurements made in this region previously
are also insufficient to explain the observed 1–2 pmol mol−1 of
daytime IO. The observations imply the existence of an unknown daytime source
of gas phase inorganic iodine. Carpenter et al. (2013) recently proposed that
sea surface emissions of HOI are several times larger than the flux of I2.
Such a flux could account for both the nighttime I2 and the daytime IO
observations. |
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