Fan Longfeng, Cheng Junxiang, Xie Yangcun, Xu Ligang, Buttler Alexandre, Wu Yuexia, Fan Hongxiang, Wu Yakun
Key Laboratory of Watershed Geographic Sciences, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, PR China; University of Chinese Academy of Sciences, Beijing 100049, PR China.
Key Laboratory of Watershed Geographic Sciences, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, PR China; Jiangxi Research Academy of Ecological Civilization, Nanchang 330036, PR China.
Sci Total Environ. 2024 Mar 25;918:170689. doi: 10.1016/j.scitotenv.2024.170689. Epub 2024 Feb 4.
Gaseous carbon exchange at the water-air interface of rivers and lakes is an essential process for regional and global carbon cycle assessments. Many studies have shown that rivers surrounding urban landscapes can be hotspots for greenhouse gas (GHG) emissions. Here we investigated the variability of diffusive GHG (methane [CH] and carbon dioxide [CO]) emissions from rivers in different landscapes (i.e., urban, agricultural and mixed) and from lakes in Suzhou, a highly urbanized region in eastern China. GHG emissions in the Suzhou metropolitan water network followed a typical seasonal pattern, with the highest fluxes in summer, and were primarily influenced by temperature and dissolved oxygen concentration. Surprisingly, lakes were emission hotspots, with mean CH and CO fluxes of 2.80 and 128.89 mg m h, respectively, translating to a total CO-equivalent flux of 0.21 g CO-eq m d. The global warming potential of urban and mixed rivers (0.19 g CO-eq m d) was comparable to that for lakes, but about twice the value for agricultural rivers (0.10 g CO-eq m d). Factors related to the high GHG emissions in lakes included hypoxic water conditions and an adequate nutrient supply. Riverine CH emissions were primarily associated with the concentrations of total dissolved solids (TDS), ammonia‑nitrogen and chlorophyll a. CO emissions in rivers were mainly closely related to TDS, with suitable conditions allowing rapid organic matter decomposition. Compared with other types of rivers, urban rivers had more available organic matter and therefore higher CO emissions. Overall, this study emphasizes the need for a deeper understanding of the impact of GHG emissions from different water types on global warming in rapidly urbanizing regions. Flexible management measures are urgently needed to mitigate CO and CH emissions more effectively in the context of the shrinking gap between urban and rural areas with growing socio-economic development.
河流和湖泊水 - 气界面的气态碳交换是区域和全球碳循环评估的重要过程。许多研究表明，环绕城市景观的河流可能是温室气体（GHG）排放的热点地区。在此，我们调查了不同景观（即城市、农业和混合景观）河流以及中国东部高度城市化地区苏州湖泊中扩散性温室气体（甲烷[CH₄]和二氧化碳[CO₂]）排放的变异性。苏州城市水网中的温室气体排放呈现典型的季节性模式，夏季通量最高，主要受温度和溶解氧浓度影响。令人惊讶的是，湖泊是排放热点，CH₄和CO₂的平均通量分别为2.80和128.89 mg m⁻² h⁻¹，换算为CO₂当量通量总计为0.21 g CO₂ - eq m⁻² d⁻¹。城市河流和混合河流的全球变暖潜势（0.19 g CO₂ - eq m⁻² d⁻¹）与湖泊相当，但约为农业河流（0.10 g CO₂ - eq m⁻² d⁻¹）的两倍。湖泊中温室气体高排放相关的因素包括缺氧的水体条件和充足的养分供应。河流CH₄排放主要与总溶解固体（TDS）、氨氮和叶绿素a的浓度有关。河流中的CO₂排放主要与TDS密切相关，适宜条件下可使有机物快速分解。与其他类型的河流相比，城市河流有更多可利用的有机物，因此CO₂排放量更高。总体而言，本研究强调需要更深入了解不同水体类型的温室气体排放在快速城市化地区对全球变暖的影响。随着社会经济发展城乡差距缩小，迫切需要灵活的管理措施，以更有效地减少CO₂和CH₄排放。
