鄱阳湖秋季水-气界面CH_4排放通量的区域差异及影响因素

Spatial heterogeneity and controlling factors of autumn CH_4 flux at water-air interface in Poyang Lake of Jiangxi Province, China

有限的观测点以及空间的异质性已经成为准确估算湖泊水-气界面CH4通量的挑战。鄱阳湖是我国最大的淡水湖,为了解秋季湖区水-气界面的CH4排放通量,2010年10月利用密闭静态箱-气象色谱法对星子、都昌、南矶山和吴城4个湖区水-气界面CH4排放通量及气象、底泥、水体等因素进行了测定。研究表明,都昌湖区CH4排放通量平均值为0.26mg·m-2·h-1,显著高于星子(0.15mg·m-2·h-1)、吴城(0.13mg·m-2·h-1)和南矶山(0.10mg·m-2·h-1)湖区。鄱阳湖水-气界面秋季CH4排放通量平均为0.17mg·m-2·h-1,变异系数为58.6%。相关分析表明,风速显著影响CH4排放通量(P<0.01)。在排除风速>5m·s-1的数据后,底泥有机碳以及水体铵态氮含量与CH4排放通量显著相关,而水体DOC含量与CH4排放通量呈显著负相关(P<0.05)。对鄱阳湖CH4排放量的精确估算,依赖于较广区域和较长时间的观测。

Limited observation stations and high spatial heterogeneity of CH4 flux are the challenges for the accurate estimation of CH4 flux at water-air interface. Poyang Lake is the largest freshwater lake in China. In order to understand the autumn CH4 flux at the water-air interface in the Lake, closed static chambers and gas chromatography were adopted to measure the CH4 fluxes at the water-air interfaces in 4 inner lakes of the Lake in October 2010. The environmental factors including meteorological variables and sediment- and water properties were also measured. The mean CH4 flux in the Duchang inner lake was 0.26 mg·m-2·h-1, which was obviously higher than that in the inner lakes Xingzi （0.15 mg·m-2·h-1）, Wucheng （0.13 mg·m-2·h-1）, and Nanjishan （0.10 mg·m-2·h-1）. The Lake had a mean CH4 flux of 0.17 mg·m-2·h-1, with the coefficient of variation being 58.6%. The CH4 flux was positively correlated with wind speed （P〈0.01）. After excluding the wind speed exceeding 5 m·s-1, the contents of sediment organic carbon and water body ammonium were significantly positively correlated with the CH4 flux. The dissolved organic carbon （DOC） content in water body was negatively correlated with the CH4 flux （P〈0.05）. The accurate estimation of the CH4 flux in the Lake would depend on more frequent measurements in larger areas.