海南东部沿岸河流和潟湖中溶存甲烷的分布及通量

甲烷(CH4)作为大气中重要的温室气体,直接或间接地影响全球气候变化。于2009年3月27日至4月15日对海南东部河流(文昌河、文教河、万泉河)、潟湖(八门湾、博鳌、小海和老爷海)等进行了调查,采集了表层和部分底层水样,对溶解CH4浓度进行了测定并初步估算了其水-气交换通量。结果表明,文昌河、文教河受人为活动影响较大,表层CH4饱和度较高,分别为(60664±25118)%、(38582±26339)%,污水输入、红树林输入和现场产生是其CH4的主要来源。万泉河表层CH4饱和度为(9472±5594)%,现场产生是其水体溶存CH4的主要源。八门湾、博鳌、小海和老爷海潟湖表层水体溶存CH4均处于过饱和状态,但其饱和度远小于入湖河流,分别为(2471±2937)%、(5692±3435)%、(546±251)%和(6878±4635)%,其中河流输入、地下水和红树林间隙水输入、现场产生是潟湖中CH4的主要来源,水体中CH4的氧化和水-气交换是潟湖中CH4的主要汇。初步估算出文昌河和万泉河CH4的水-气交换通量分别为5967.0±5142.1和496.2±335.9μmol·m 2·d 1,八门湾、博鳌、小海和老爷海潟湖的水-气交换通量分别为528.7±625.0、441.7±473.3、26.6±21.6和1287.8±1453.3μmol·m 2·d 1。海南东部河流、潟湖是近岸水体及大气CH4的净源。

Distribution and fluxes of methane in tropical rivers and lagoons of eastern Hainan

Methane(CH4) is an important greenhouse gas,which can influence the Earth’s climate change both directly and indirectly.Distributions and fluxes of CH4 in rivers and lagoons of eastern Hainan were obtained during the survey from March 27th to April 15th in 2009.Surface waters of the three rivers(Wenchang,Wenjiao and Wanquan rivers) were over-saturated in CH4 with respect to atmospheric equilibrium (60664±25118)%,(38582±26339)% and(9472±5594)%,respectively].Surface waters of the lagoons were also over-saturated in CH4,but at much lower levels than those in the rivers.The dissolved CH4 in the lagoons mainly come from riverine input,inputs from groundwater and fringing mangrove forest,and in-situ production;the main sinks of methane in the lagoons were oxidation and outgassing.The estimated air–water CH4 fluxes using the RC01 formula of Wenchang and Wanquan rivers were 5967.0±5142.1 and 496.2±335.9μmol.m 2.d 1,respectively.Air–water CH4 fluxes of the logoons were 528.7±625.0,441.7±473.3,26.6±21.6,and 1287.8±1453.3μmol.m 2.d 1 for Bamen bay,Bo’ao,Xiaohai,and Laoyehai,respectively.Estuaries and lagoons in eastern Hainan are persistently supersaturated in CH4,which indicates that they are net sources of atmospheric CH4.