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Equilibrator-based measurements of dissolved methane in the surface ocean using an integra

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Acta Oceano1.Sin.,2015,Vo1.34,No.6,P.34—41 DOI:10.1007/s13131—015—0685—9 http://www.hyxb.org.ca E—mail:hyxbe@263.net Equilibrator.based measurements of dissolved methane in the surface ocean using an integrated cavity output laser absorption Spectrometer LI Yuhong 一,ZHAN Liyang , ,ZHANG liexia ,2j CHEN Liqi , Key Laboratory ofGlobal Change and Marine—Atmospheric Chemisty,Strate Oceanic Administration,Xiamen 361005,China Third Institute of Oceanography,State Oceanic Administration,Xiamen 361005,China Received 30 May 2014;accepted 14 September 2014  ̄TheChinese SocietyofOceanographyandSpringer-VerlagBerlinHeidelberg2015 Abs仃act A new off-axis integrated cavity output spectroscopy(ICOS)is coupled to Weiss equilibrator for continuous high— resolution dissolved methane measurement in the surface ocean.The time constant for the equilibrator in freshwater at room temperature is determined via dis equilibration and re.equilibration experiments.The constant for methane is about 40 min.The system is calibrated using a standard gas of 3.980x10一.and the precision of the ICOS or fmethane is 0.07%.This system is equipped onboard to measure the spatial distribution in methane concentrations of South Yellow Sea(SYS)along he tcruise track from Shanghai to Qingdao.Result shows that he tmethane concentration varies from 2.79 to 36.36 nmol/L.reveals a signiifcant pattern of methane source in SYS,and a distinct decreasing iend from fsouth to north.The peak value occurs at he coast tarea outside mouth of the Changjiang River,likely to be affected by the Changjiang diluted water mass dissoling a lvarge amount of rich in methane.Moreover,all the surface waters are oversaturated,air-to—sea lfuxes range from 98.59 t0 5 485.35 pmol/(m2.d)(average value(1 169.74+1 398.46)pmol/(m2.d)),indicating a source region orf methane to het atmosphere.Key words:methane,equilibrator,off-axis integrated caitvy output spectroscopy(ICOS),South Yellow Sea Key words:methane,equilibrator,off-axis integrated cavity output spectroscopy(ICOS),South Yellow Sea Citation:Li Yuhong,Zhan Liyang,Zhang Jiexia,Chen Liqi.2015.Equilibrator—based measurements of dissolved methane in the surface ocean using an integrated cavity output laser absorption spectrometer.Acta Oceanologica Sinica,34(6):34-41,doi:10.1007/s13131—015- 0685—9 1 Introduction tracts have been discussed as the possible contributor of meth— Methane(cH4)is the third most important greenhouse gas anogenesis(Tilbrook and Karl,1994).Recently,methanogens has after water vapor and carbon dioxide,which currently accounts been detected in sinking marine particles showing a potential orf about 20%ofthe radiative forcing(Houghton et a1.,2001),in— pathway as a source of methane in the aerobic ocean(Ditchfield luences the clifmate on the earth and plays a signiicantf role in et 1.a,2012).In other studies,a range ofpossible substrates might tropospheric atmospheric chemistry.The ocean plays a modest be utilized by methane.producers,for instance.the degarada methylated compounds such as DMSP yields dimethyl— role in the global CH4 budget as a source to atmospheric(0.4-50 tion of Tg/a,calculated by cH4)(Bates et a1.,1996;IPCC,2007),up to sulifde(DMS)and methylphosphonates tl1 a phosphorus—car- 75%0f that is emitted from estuaries and coastal areas(Bange. bon bond had been highlighted for enhancing the availabiliy tof 2006).In estuary and coastal areas,high productiitvy along with methane production(Damm et a1..2010;Karl et a1..2008;weller high sedimentation rates of organic matter,rapidly consume dis— et a1..2013).DHe to the low.resolution data sets and the seasonal solved oxygen in the overlying water column and release CH4 variabiliy tof air—to—sea emission.high—resulotion and long—time es observations are important to illustrate the CH distribu. from sediments through a serial of microbial mediated(archaea) seripattern in surface seawater and the spatio..temporal variabil.. degradation reactions(Cicerone and Oremland.1988).There is a tion ubiquitous phenomenon that surface mixed layer maximum iy tof air—to—sea lfuxes. where CH concentrations are about 5 nmol/L.supersaturated ith respectw to the atmosphere.Generally production of CHd is strictly limited to anaerobes and reducing environments,the Until the 1960s,the introduciton of gas chromatography(GC), determination of dissolved gas in water was reported.Swinner— ton et a1.(1962)presented a purge&trap pre—processing method to obtain higher detection sensitiity vof hydrocarbons from solu— presence of this methane maximum in vast ocean is known as ons.A further modiicatfion involving an automated gas chro— “the ocean methane paradox”(Reeburgh,2007).Anoxic environ— timents in freshly released fecal pellets and zooplankton digestive matographic system been developed for the measurement of car Foundation item:The Scientiic fResearch Foundation ofThird Institute ofOceangraphy under contract No.2013004;the National Natural Science Foundation of China(NSFC)under contract Nos 40906102 and 41230529;the CHINARE under contract Nos 2012—2013(01—04—02) (0l一02—01)and(03—04—02). Corresponding author,E—mail:zhanliyang@tio.org.cn LI Yuhong et a1.Acta Oceano1.Sin.,2015,Vo1.34,No.6,P.34—41 41 Swinnerton 1 wJ Linnenbom V J,Cheek C H.1962.Determination of dissolved gases in aqueous solutions by gas chromatography. phytoplankton bloom in the southwest Paciic Ocean.Prog tOceanogr,1 16:193-206 Anal Chem,34(4):483—485 Takahashi T,Sutherland S C,Wanninkhof R.et a1.2009.Climatolo一 Wiesenburg D A,Guinasso N L Ir.1979.Equilibrium solubilities of methane,carbon monoxide,and hydrogen in water and sea 昏cal mean and decadal change in surface ocean pCO2,and net sea—air CO。flux over the global oceans.Deep—Sea Res Pt II: water.J Chem Eng Data,24(4):356—360 Zhang Guiling,Zhang ling,Kang Yubao,et a1.2004.Distributions nd aluxes of fmetllane in the East China Sea and he tYellow Sea in Topical Studies in Oceanography,56(8-10):554-577 Tilbrook B D,Karl D M.1994.Dissolved methane distributions. spring.J Geophys Res.109(C7):101—111 ChangJiang(Yangtze River)Estuary and its adjacent marine area:riverine input,sediment release and atmospheric luxes.f sources,and sinks in the western Bransfield Strait.Antarctica., Zhang Guiling,Zhang Jing,Liu Sumei,et 1.2008a.Metahane in the Geophy Res,99(C8):16383—16393 Wanninkhof R.1992.Relationship between wind speed and gas ex. change over the ocean.J Geophy Res:Oceans(1978-2012), Biogeochem,91(1):71—84 97(C5):7373—7382 Weiss R F.1981.Determinations of carbon dioxide and methane by dual catalyst lfame ionization chromatography and nitrous OX. ide by electron capture chromatography.J Chromatogr Sci, l9(12):611-616 Weller D I,Law C S,Marriner A.et 1a.2013.Temporal variation of dis. solved methane in a subtropical mesoscale eddy during a Zhang Guiling,Zhang Jing,Ren Jingling,et a1.2008b.Distributions and sea..to..air lfuxes ofmethane and nitrous Oxide in hte North East China Sea in summer.Mar Chem,110(1-2):42—55 Zhao Yuchuan.201 l_Distributions and fluxes of methane and ni— trous oxide in hte Changjiang(Yangtze River)and its Estuary (in Chinese)【dissertation】.Qingdao:Ocean University of China,1-93 

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