巢湖不同富营养化区域甲烷排放通量与途径

为了更好的认识不同富营养化区域甲烷（CH₄）排放通量及途径的时空异质性，本文以我国典型富营养化浅水湖泊-巢湖为研究对象，设置西北湖湾、西湖心和中湖心3个研究点位，采用漂浮通量箱和经验模型分析等方法对其水-气界面CH₄排放通量与途径进行季节性研究.结果表明水体与沉积物中CH₄溶存浓度、水-气界面CH₄排放通量同水体营养盐水平及叶绿素a含量的空间变化相一致，且均表现为西北湖湾最高，其水体CH₄溶存浓度为（0.178 ±0.002）~（1.123 ±0.026）μmol/L、表层沉积物中CH₄含量为（70.5 ±30.7）~（189 ±97.0）μmol/L、CH₄总排放通量为（50.1 ±2.93）~（1232 ±28.6）μmol/（m²·h）；3个点位的CH₄扩散通量占总排放量的7.3%~42.9%，冒泡通量占57.1%~92.7%，富营养化程度最高的西北湖湾冒泡通量占比最高；CH₄排放通量大小与途径同时受季节变化影响，夏季CH₄冒泡与总排放通量均最高，其中冒泡对总通量的贡献高达98.1%.

Emission fluxes and pathways of methane in different eutrophic areas of Lake Chaohu

In order to better understand the spatiotemporal heterogeneity of methane emission fluxes and pathways in eutrophic lakes. Emission fluxes and pathways of CH₄ were studied in areas of different trophic levels in Lake Chaohu, a large and shallow eutrophic lake in Eastern China. A total of three study sites were deployed in the northwestern bay, the center of the west lake, and the center of the middle lake, respectively. Seasonal CH₄ emission fluxes and pathways at the water-air interface were examined by using floating flux chambers and an empirical diffusion model. The spatial variations of CH₄ concentrations and emission fluxes shared similar patterns with nutrient levels and chlorophyll-a contents in the waters and the sediments. The highest CH₄ were found in the northwestern bay, in which dissolved CH₄ in water was (0.178 ±0.002)~(1.123 ±0.026) μmol/L, CH₄ in surface sediments was (70.5 ±30.7)~(189 ±97.0) μmol/L, and the total emission flux of CH₄ was (50.1 ±2.93) ~ (1232 ±28.6)μmol/(m²·h). Diffusive fluxes of CH₄ in the three areas accounted for 7.3% ~ 42.9% of the total emission, and the fluxes of ebullition accounted for 57.1% ~ 92.7% of the total emission. The northwestern bay which was also more eutrophic than the other two areas shared the highest proportion of the ebullition. CH₄ emission pathways in Lake Chaohu were influenced by seasonal changes. There were the highest total CH₄ emission fluxes and ebullition fluxes in the summer, in which the contribution of ebullition to the total emission fluxes was as high as 98.1%.