Equilibratorbased measurements of dissolved metha

Authors: Yuhong Li Liyang Zhan Jiexia Zhang Liqi Chen

Publish Date: 2015/06/09

Volume: 34, Issue: 6, Pages: 34-41

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Abstract

A new offaxis integrated cavity output spectroscopy ICOS is coupled to Weiss equilibrator for continuous highresolution dissolved methane measurement in the surface ocean The time constant for the equilibrator in freshwater at room temperature is determined via disequilibration and reequilibration experiments The constant for methane is about 40 min The system is calibrated using a standard gas of 3980×10−6 and the precision of the ICOS for methane is 007 This system is equipped onboard to measure the spatial distribution in methane concentrations of South Yellow Sea SYS along the cruise track from Shanghai to Qingdao Result shows that the methane concentration varies from 279 to 3636 nmol/L reveals a significant pattern of methane source in SYS and a distinct decreasing trend from south to north The peak value occurs at the coast area outside mouth of the Changjiang River likely to be affected by the Changjiang diluted water mass dissolving a large amount of rich in methane Moreover all the surface waters are oversaturated airtosea fluxes range from 9859 to 5 48535 μmol/m2·d average value 1 16974±1 39846 μmol/m2·d indicating a source region for methane to the atmosphereFoundation item The Scientific Research Foundation of Third Institute of Oceangraphy under contract No 2013004 the National Natural Science Foundation of China NSFC under contract Nos 40906102 and 41230529 the CHINARE under contract Nos 20122013 010402 010201 and 030402

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