长江中溶存甲烷的分布与释放

2008年1月和9月对长江的中、下游和长江口进行了调查,2007年9月～2008年8月每月在长江徐六泾进行了调查,用吹扫捕集-气相色谱法测定了长江各站位水体中甲烷的浓度并用Wanninkhof公式估算向大气的甲烷释放通量.结果表明,2008年1月长江中、下游表层水中甲烷平均浓度为(330.8±186.9)nmol·L-...

Distribution and Emission of Methane from the Changjiang

Field surveys along the Changjiang were carried out in January 2008 and September 2008, persistently. Monthly survey at Xuliujing of the Changjiang Estuary was carried out from September 2007 to August 2008. Concentrations of methane in the Changjiang were measured by purge and trap-gas chromatography and the atmospheric methane fluxes were calculated according to the equation by Wanninkhof. The mean concentration in surface waters of the Changjiang was (330.8 +/- 186.9) nmol x L(-1) in January 2008 and (80.9 +/- 58.3) nmol x L(-1) in September 2008, persistently. Concentrations in bottom waters were consistent with those in surface waters. Supersaturated in methane with an average air-water flux of (385.1 +/- 278.0) micromol x (m2 x d)(-1). Besides, average methane concentration at Xuliujing was (167.5 +/- 91.4) nmol x L(-1) with an average air-water flux (690.9 +/- 291.6) micromol x (m2 x d)(-1), the high values appeared in February and July. Along the middle reaches of the Yangtze River, methane concentrations were increased, and the lower reaches were reduced. In the estuary, methane concentrations decreased rapidly from Xuliujing to the sea, showed negative correlation with salinity. The input of CH4-rich water form tributaries and lakes impacted the methane concentration trend of the Changjiang. The Changjiang was estimated to contribute 208 Gg CH4 to the atmosphere annually. However, the freshwater CH4 discharge to the East China Sea was 112 x 10(6) mol x a(-1) in the estuary.