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| Titel |
An automated gas exchange tank for determining gas transfer velocities in natural seawater samples |
| VerfasserIn |
K. Schneider-Zapp, M. E. Salter, R. C. Upstill-Goddard |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1812-0784
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| Digitales Dokument |
URL |
| Erschienen |
In: Ocean Science ; 10, no. 4 ; Nr. 10, no. 4 (2014-07-03), S.587-600 |
| Datensatznummer |
250117033
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| Publikation (Nr.) |
 copernicus.org/os-10-587-2014.pdf |
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| Zusammenfassung |
| In order to advance understanding of the role of seawater
surfactants in the air–sea exchange of climatically active trace
gases via suppression of the gas transfer velocity (kw),
we constructed a fully automated, closed air–water gas exchange tank
and coupled analytical system. The system allows water-side
turbulence in the tank to be precisely controlled with an
electronically operated baffle. Two coupled gas chromatographs and
an integral equilibrator, connected to the tank in a continuous
gas-tight system, allow temporal changes in the partial pressures of
SF6, CH4 and N2O to be measured
simultaneously in the tank water and headspace at multiple turbulence
settings, during a typical experimental run of 3.25 h. PC software
developed by the authors controls all operations and data
acquisition, enabling the optimisation of experimental conditions
with high reproducibility. The use of three gases allows three
independent estimates of kw for each turbulence setting;
these values are subsequently normalised to a constant Schmidt
number for direct comparison. The normalised kw estimates
show close agreement. Repeated experiments with Milli-Q water
demonstrate a typical measurement accuracy of 4% for
kw. Experiments with natural seawater show that the system
clearly resolves the effects on kw of spatial and temporal
trends in natural surfactant activity. The system is an effective
tool with which to probe the relationships between kw,
surfactant activity and biogeochemical indices of primary
productivity, and should assist in providing valuable new insights
into the air–sea gas exchange process. |
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