| 摘要: |
| 城市景观湖泊对温室气体的收支发挥着重要作用。本文以南京市莫愁湖为研究对象，采用静态箱—温室气体分析仪法实时监测湖泊水—气界面CH4通量，分析湖泊主要温室气体CH4在日尺度和季节尺度上因冒泡和扩散排放方式不同对其通量的影响，探究影响湖泊CH4通量的因素。结果表明：（1）在日尺度上，四季24h内CH4均呈排放状态，受白天冒泡影响，四季CH4总通量均存在白天高于夜间的日变化特征。（2）在季节尺度上，莫愁湖CH4排放通量呈现显著的时空异质性，受冒泡通量的影响夏季CH4通量明显高于春、秋、冬三季；B区的CH4总通量（6.04 nmol/(m2s)）显著高于A区（3.82nmol/(m2s)），水体的营养化程度和离岸距离是空间变化的主要影响因素。A、B两区CH4排放夏季以冒泡排放为主，春、秋、冬以扩散排放为主。（3）在日尺度上，CH4通量受气温、水温、辐射和风速等气象要素影响，与水质参数间的关系不显著；在季节尺度上，CH4通量与温度（气温、表层水温）、水体营养盐水平、叶绿素a含量及富营养化程度的时间变化相一致，也随着水体透明度、pH和氧化还原电位的减小而呈增加的趋势。本研究为准确估算城市湖泊CH4总排放量提供重要的数据基础。 |
| 关键词: 城市景观湖泊 莫愁湖 甲烷 日尺度 季节尺度 |
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| 基金项目:国家自然科学基金项目（41877482，41471075）、江苏省碳达峰碳中和科技创新专项资金（BK20220015）和江苏省高校水处理技术与材料协同创新中心项目联合资助. |
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| Characterization of CH4 fluxes in urban landscape lakes at different time scales and analysis of influencing factors——Taking Mochou Lake as an example |
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Ci Zhen,Xie Shutian,Zhang Yiquan,Yin Yifan,Xie Xuan,Lin Hanqi,Chen Xinfang,Feng Muhua
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1.College of water resources and civil engineering, Hunan Agricultural University;2.State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences;3.College of Hydrology and Water Resources, Hohai University;4.School of Applied Meteorology, Nanjing University of Information Science and Technology
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| Abstract: |
| Urban landscape lakes play an important role in the balance of greenhouse gases. In this paper, we took Mochou Lake in Nanjing as the research object, and used the static box-greenhouse gas analyzer method to monitor the CH4 flux at the water-gas interface of the lake in real time, to analyze the influence of CH4, the main greenhouse gas of the lake, on its flux at the daily and seasonal scales due to the different emission modes of bubbling and diffusion, and to explore the factors influencing the fluxes of CH4 in the lake. The results showed that: (1) on the daily scale, CH4 was emitted during 24h in all seasons, and the total CH4 fluxes in all seasons were influenced by bubbling during the daytime, which was higher than that in the nighttime. (2)On the seasonal scale, the CH4 emission fluxes in Mochou Lake showed significant spatial and temporal heterogeneity, and the CH4 fluxes in summer were significantly higher than those in spring, autumn and winter due to the bubbling fluxes; the total CH4 fluxes in area B (6.04 nmol/(m2s)) were significantly higher than those in area A (3.82 nmol/(m2s)), and the nutrient level of the water body and the distance to the shoreline were the main factors for the spatial variations. CH4 emissions in A and B were dominated by bubbling emissions in summer and diffuse emissions in spring, autumn and winter. (3) On the daily scale, CH4 fluxes were influenced by meteorological elements such as air temperature, water temperature, radiation and wind speed, and the relationship with water quality parameters was not significant; on the seasonal scale, CH4 fluxes were consistent with temporal changes in temperature (air temperature, surface water temperature), nutrient levels in the water column, chlorophyll a content and the degree of eutrophication, and also tended to increase with decreases in water clarity, pH, and redox potential . This study provides an important data base for accurate estimation of total CH4 emissions from urban lakes. |
| Key words: urban landscape lake Mochou Lake methane daily scale seasonal scale |
