【作者】 汪青；

【导师】 刘敏； 许世远；

【作者基本信息】 华东师范大学 ， 自然地理学， 2006， 硕士

【摘要】 温室气体排放研究是全球变化研究中的重要方面，也是全球碳氮平衡研究的重要内容。河口滨岸带是重要的温室气体排放源或汇，另一方面，河口具有特殊的复杂环境和强烈的人类活动干扰，温室气体产生、排放机制缺乏深入研究，一些有河口特色的环境因子影响如潮汐的作用等目前仍没有很好的解释。本文以崇明东滩为主要研究区域，对长江口滨岸湿地的三种主要温室气体排放做初步探索，研究了温室气体CH₄、N₂O和CO₂在崇明湿地排放的时间变化、空间分布及其影响因子。研究开展于三种时间尺度，即生长季、昼夜、潮周期，和海陆方向上的四个采样区域，即围垦湿地、高潮滩、中潮滩、低潮滩。 在生长季尺度下，崇明湿地CH₄、N₂O和CO₂表现为排放源，平均通量分别为101.36μg CH₄·m^-2·h^-1、1.74μg N₂O·m^-2·h^-1和547.21mg CO₂·m^-2·h^-1。在昼夜尺度下，CO₂和CH₄通量的日变化表现为夜排放大于昼排放，而N₂O的排放高峰出现在下午时段。CO₂和CH₄的日通量都与15cm地温有密切关系，反映了二者在一定程度上共同受15cm处发生的微生物地球化学反应影响。在潮周期尺度下，温室气体通量依然有明显的时间规律，但与更大的尺度不同，其更多地受水分条件及其造成的氧化一还原转换制约。CH₄和N₂O在潮暴露初期表现为排放，后期变为吸收，CO₂正好相反。低潮滩潮暴露期间排放的N₂O可能主要来自于反硝化过程。 CH₄在高潮滩的排放量最大，围垦湿地和中潮滩排放相对较少，低潮滩则是微量吸收；N₂O只在围垦湿地有明显排放，高、中、低潮滩均是吸收多于排放，且越靠近海端，吸收值越大；CO₂在有植物的围垦湿地、高潮滩和中潮滩出现大量排放，而在低潮滩为微量的吸收。估算结果显示，崇明东滩湿地生态系统CH₄、N₂O和CO₂在生长季排放总量分别为5.1×10⁷g、1.0×10⁵g、1.7×10¹1g。 CH₄排放量与各温度之间存在极显著的高斯相关性，CO₂排放量与各温度之间呈显著及以上线性正相关关系，N₂O排放量与气温呈显著线性正相关关系。半月平均降水量与CH₄排放有较好的线性正相关，降水对N₂O和CO₂排放影响不明显。土壤剖面理化性质如Eh、含水率、有机质、NH₄⁺、SO₄^2-等影响温室气体排放。植物在温室气体传输中有重要作用，割除海三棱蔗草后，CH₄和CO₂更多还原

【Abstract】 The study of greenhouse gases emission is not only an important part of global change research, but also of global carbon and nitrogen balance stduy. Estuarine coastal zones act as source and sink of greenhouse gases in both global and local view. However, gas emission from the estuary and its mechanism have not been studied deeply, impeded by the complicated environment and intensive anthropogenic influence.The temporal and spatial variations as well as effect factors in emissions of greenhouse gases（CO₂, CH4 and N2O） from Chongming Dongtan, the typical and the most important wetland of Yangtze estuary, have been studied in three time scales, i.e. seasonally, diurnally and tidally, and at four sample areas, i.e. reclaimed wetland, high tidal flat, middel tidal flat and low tidal flat.In seasonal scale, the Chongming Dongtan wetland ecosystem is a greenhouse gas emission source of atmosphere. All of the gases emitted significantly from sediment with a value of 547.21 mg·m^-2·h^-1 （mean value, the same below） for CO₂, 10136 μg·m^-2·h^-1 for CH₄, and 1.74μg·m^-2·h^-1 for N₂O.Diurnal fluxes of CO₂ and CH₄ were less than nocturnal ones, while N₂O flux peak was found at afternoon. Both diurnal fluxes of CO₂ and CH₄ were found a close relationship with soil temperature at 15 cm below, which indicated that they were influenced by the biogeochemical processes reacted at depth of 15 cm.In a tidal cycle, CH₄ and N₂O emitted from sediment at the beginning of the exposure after flood and consumed subsequently, but inversely CO₂. N₂O emission from low tidal sediment during exposure produced mainly by denitrification.CH₄ emission from high tidal flat was significantly higher than those from reclaimed wetland and middle tidal flat, and a slight consumption was observed at low tidal flat. N₂O only emitted at reclaimed wetland and consumed at other sampling sites, the farther from coastal line, the larger flux N₂O had. CO₂ had significant更多还原