春季东、黄海溶解甲烷的分布和海气交换通量

Distribution and Air-Sea Fluxes of Methane in the Yellow Sea and the East China Sea in the Spring

于2011年3月17日～4月6日对东、黄海海域进行了大面调查,采集了45个站位不同深度的海水样品,对溶解甲烷(CH4)浓度进行了测定,并估算了其海-气交换通量.结果表明,东、黄海表层海水中溶解甲烷的浓度变化范围是2.39～29.67nmol.L-1,底层海水中甲烷浓度范围是2.63～30.63 nmol.L-1,底层浓度略高于表层,表明底层水体或沉积物中存在甲烷的源.春季东、黄海海域表、底层溶解甲烷的分布特征基本一致,即从近岸向远海逐渐降低,主要受长江冲淡水输入和黑潮水入侵的影响.春季东、黄海海域表层海水中CH4饱和度为93%～1 038%.利用Liss and Merlivat公式(LM86)、Wanninkhof公式(W92)和现场测定的风速估算出春季东、黄海海域CH4的海-气交换通量分别为(2.85±5.11)μmol.(m2.d)-1和(5.18±9.99)μmol.(m2.d)-1,根据本研究结果和文献数据初步估算出东海和黄海年释放甲烷量分别为7.05×10-2～12.0×10-2Tg.a-1和1.17×10-2～2.20×10-2Tg.a-1.春季东、黄海海域表层海水中CH4均呈过饱和状态,是大气中CH4的净源.

A survey was carried out in the Yellow Sea and the East China Sea from March 17 to April 06 of 2011.Dissolved CH4 in various depths were measured and sea-to-air fluxes were estimated. Methane concentrations in surface and bottom waters ranged between 2.39-29.67 nmol·L-1 and 2.63-30.63 nmol·L-1, respectively. Methane concentrations in bottom waters were slightly higher than those in surface waters, suggesting the existence of methane source in bottom waters or sediments. The horizontal distribution of dissolved CH4 showed a decrease from the river mouth to the open sea, and was influenced by the freshwater discharge and the Kuroshio intrusion. Surface methane saturations ranged from 93%-1038%. Sea to air CH4 fluxes were （2.85±5.11） μmol·（m2·d）-1, （5.18±9.99） μmol·（m2·d）-1 respectively, calculated using the Liss and Merlivat （LM86）, the Wanninkhof （W92） relationships and in situ wind speeds, and estimated emission rates of methane from the East China Sea and the Yellow Sea range from 7.05×10-2-12.0×10-2 Tg·a-1 and 1.17×10-2-2.20×10-2 Tg·a-1, respectively. The Yellow Sea and East China Sea are the net sources of atmospheric methane in the spring.