2009年8月底长江口海水中甲烷的分布与释放通量

Distribution and fluxes of methane at Changjiang(Yangtze River)Estuary at the end of August 2009

于2009年8月27日至9月2日对长江口海域进行了大面调查,采集了表层和底层海水样品,对溶解甲烷(CH4)浓度进行了测定。结果表明,夏季长江口海域表、底层溶解甲烷的浓度分布特征基本一致,即从近岸向远海逐渐降低,底层浓度约为表层的2倍。利用Liss and Merlivat(1986)公式、Wanninkhof(1992)公式、Raymod and Cole(2001)公式和平均瞬时风速估算出夏季长江口海域CH4的海-气交换通量分别为(22.1±38.4)μmol/(m2.d)、(34.3±59.6)μmol/(m2.d)和(48.6±84.5)μmol/(m2.d)。夏季长江口海域表层海水中CH4均呈过饱和状态,是大气中CH4的净源。

A survey was carried out at the Changjiang （Yangtze River） estuary from August 27 to September 2, 2009. Dissolved CH4 was measured in both surface and bottom seawaters. The horizontal distribution of dissolved CH4 decreased from the river mouth to the open sea. Dissolved CH4 in the bottom waters was twice of that in the surface. Sea to air CH4 fluxes were 22.1 μmol/（m2·d）±38.4 μmol/（m2·d）, 34.3 μmol/（m2·d）±59.6 μmol/（m2·d）,and 48.6 μmol/（m2·d）±84.5 μmol/（m2·d）, respectively, calculated with Liss and Merlivat （LM86）, Wanninkhof （W92）, and Raymond and Cole （RC01） relationships and average in situ wind speed. Methane in the surface waters of Changjiang estuary was supersaturated in summer, making Changjiang estuary a net source of atmospheric methane.