| 长江中溶存甲烷的分布与释放 |
| 摘要点击 4634 全文点击 3009 投稿时间：2010-01-04 修订日期：2010-07-30 |
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| 中文关键词 长江 甲烷（CH4） 释放 分布 通量 |
| 英文关键词 Changjiang (Yangtze River) methane (CH4) emission distribution flux |
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| 中文摘要 |
| 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-1， 2008年9月长江下游和河口表层水中甲烷平均浓度为（80.9±58.3）nmol·L-1，各站位底层水体中甲烷浓度与表层基本一致.长江中溶存甲烷均处于过饱和状态，是大气中甲烷的净源.长江向大气释放甲烷的平均通量为（385.1±278.0）μmol·（m2·d）-1.长江徐六泾表层水中甲烷的年平均浓度为（167.5±91.4）nmol·L-1，高值出现在2月和7月，向大气释放甲烷的年平均通量为（690.9±291.6）μmol·（m2·d）-1.长江中溶存甲烷浓度的空间分布呈现自中游向下沿江逐渐增大的趋势，最高值出现在鄱阳湖下游的孤山站，然后向下游呈递减趋势.支流及湖泊富甲烷水的输入对长江干流甲烷的浓度分布有明显的影响.长江口自徐六泾向外海方向，表层水中甲烷浓度迅速减小.本研究初步估算出长江每年向大气释放甲烷量为208 Gg·a-1，向东、黄海输入甲烷的量为112×106 mol·a-1. |
| 英文摘要 |
| 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·L-1 in January 2008 and (80.9±58.3) nmol·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) μmol·（m2·d）-1. Besides, average methane concentration at Xuliujing was (167.5±91.4) nmol·L-1 with an average air-water flux (690.9±291.6) μmol·（m2·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 112×106 mol·a-1 in the estuary. |
