Lookup NU author(s): Dr Klaus Schneider-Zapp,
Dr Matthew Salter,
Professor Robert Upstill-Goddard
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
Abstract. 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 normalisedkw estimates show close agreement. Repeated experiments with MilliQ 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.
Author(s): Schneider-Zapp K, Salter ME, Upstill-Goddard RC
Publication type: Article
Publication status: Published
Journal: Ocean Science
Print publication date: 03/07/2014
Online publication date: 03/07/2014
Acceptance date: 24/05/2014
ISSN (print): 1812-0784
ISSN (electronic): 1812-0792
Publisher: Copernicus Publications
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