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| Titel |
Ship-based detection of glyoxal over the remote tropical Pacific Ocean |
| VerfasserIn |
R. Sinreich, S. Coburn, B. Dix, R. Volkamer |
| 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. 23 ; Nr. 10, no. 23 (2010-12-01), S.11359-11371 |
| Datensatznummer |
250008926
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| Publikation (Nr.) |
 copernicus.org/acp-10-11359-2010.pdf |
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| Zusammenfassung |
| We present the first detection of glyoxal (CHOCHO) over the remote tropical
Pacific Ocean in the Marine Boundary Layer (MBL). The measurements were
conducted by means of the University of Colorado Ship Multi-Axis
Differential Optical Absorption Spectroscopy (CU SMAX-DOAS) instrument
aboard the research vessel Ronald H. Brown. The research vessel was on a
cruise in the framework of the VAMOS Ocean-Cloud-Atmosphere-Land Study –
Regional Experiment (VOCALS-REx) and the Tropical Atmosphere Ocean (TAO)
projects lasting from October 2008 through January 2009 (74 days at sea).
The CU SMAX-DOAS instrument features a motion compensation system to
characterize the pitch and roll of the ship and to compensate for ship
movements in real time. We found elevated mixing ratios of up to 140 ppt
CHOCHO located inside the MBL up to 3000 km from the continental coast over
biologically active upwelling regions of the tropical Eastern Pacific Ocean.
This is surprising since CHOCHO is very short lived (atmospheric life time
~2 h) and highly water soluble (Henry's Law constant H =
4.2 × 105 M/atm). This CHOCHO cannot be explained by transport of it or its
precursors from continental sources. Rather, the open ocean must be a source
for CHOCHO to the atmosphere. Dissolved Organic Matter (DOM) photochemistry
in surface waters is a source for Volatile Organic Compounds (VOCs) to the
atmosphere, e.g. acetaldehyde. The extension of this mechanism to very
soluble gases, like CHOCHO, is not straightforward since the air-sea flux is
directed from the atmosphere into the ocean. For CHOCHO, the dissolved
concentrations would need to be extremely high in order to explain our
gas-phase observations by this mechanism (40–70 μM CHOCHO, compared to
~0.01 μM acetaldehyde and 60–70 μM DOM). Further, while
there is as yet no direct measurement of VOCs in our study area,
measurements of the CHOCHO precursors isoprene, and/or acetylene over
phytoplankton bloom areas in other parts of the oceans are too low (by a
factor of 10–100) to explain the observed CHOCHO amounts. We conclude that
our CHOCHO data cannot be explained by currently understood processes. Yet,
it supports first global source estimates of 20 Tg/year CHOCHO from the
oceans, which likely is a significant source of secondary organic aerosol
(SOA). This chemistry is currently not considered by atmospheric models. |
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