| 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...
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