| 摘要: |
| 澎溪河流域是三峡水库典型支流，对水库区域碳循环及区域化学风化的影响非常重要。2016年5月—2017年2月对澎溪河流域水-气界面CO2与CH4通量特征进行监测与分析，采用顶空平衡法结合模型估算法计算表层水体CO2与CH4的分压以及水-气界面的交换通量，并运用spearman相关分析法分析了二氧化碳和甲烷的分压和排放通量与其他环境变量之间的相关性。研究发现：澎溪河是温室气体排放“源”，表层水体p (CO2)平均值为(1807.635±315.605) μatm（1 µatm=0.101325 Pa，下同），表层水体p (CH4)平均值为(218.7725±127.9425) μatm；CO2扩散通量平均值为(32.53±3.86) mmol∙m−2∙d−1，水-气界面CH4扩散通量平均值为(0.208±0.143) mmol∙m−2∙d−1，通量与分压趋势基本保持一致。通过与世界上典型河流温室气体扩散通量对比，得出澎溪河流域CO2通量释放量为中等水平，而CH4扩散通量较小，且CH4通量与p (CH4)、水温、pH值显著正相关，而水-气界面CO2扩散通量与p (CO2)显著正相关，与DO、pH值、叶绿素a（Chl-a）显著负相关。 |
| 关键词: 澎溪河 CO2 CH4 水-气界面通量 影响因素 |
| DOI：10.7515/JEE182071 |
| CSTR： |
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| 基金项目:国家自然科学基金项目（51679226，51609026）；重庆市教委科学技术研究项目（KJ1500506）；重庆市基础科学与前沿技术研究项目（cstc2017jcyjAX0280） |
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| CO2 and CH4 flux across water-air interface and environmental factors in Pengxi River of the Three Gorges Reservoir |
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QIN Yu, WANG Ziwei, LI Zhe, YANG Boxiao
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1. Key Laboratory of Hydraulic and Waterway Engineering of the Ministry of Education, Chongqing Jiaotong University, Chongqing 400074, China
2. Kay Laboratory of Reservoir Environment, Chongqing Institute of Green and Intelligence Technology, Chinese Academy of Sciences, Chongqing 400714, China
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| Abstract: |
| Background, aim, and scope The reservoir has always been a source of water and electricity providing energy and convenience for human beings. However, due to the huge water storage capacity, complex dam operation and maintenance process, the reservoir has become the main carrier of carbon cycle in the ecological environment, which emits loads of greenhouse gas to atmosphere. As one of the world’s major dams, the Three Gorges Dam transports many carbon compounds to nature. And this phenomenon has arose the worldwide scholars’ attention. However, there is no uniform method to monitor the absorption and emission of greenhouse gas from reservoir till now. As the typical tributary of the Three Gorges Reservoir, Pengxi River plays a significant role in carbon cycle and chemical efflorescence weathering in reservoir region. Consequently, this paper seeks to establish a method for quantifying gas emissions and to analyze how greenhouse gases change over the course of a year. Moreover, it is also requested what is the major attributer for emission of greenhouse gas. This paper supervises and analysis the fluxes of CO2 and methane in water-gas interface in Pengxi River from May 2016 to February 2017. Materials and methods In reference of previous literature, this study adopted the combination of Headspace balance method and model estimation to obtain the partial pressures of carbon dioxide and methane in surface water and exchange fluxes of CO2 and methane. Additionally, this paper also used field measuring instruments to measure the physical and chemical variables so as to analyze the effects of these factors on greenhouse gas release. The correlation between the partial pressures and fluxes of CO2 and methane and environment variables were analysed by means of the spearman correlation index based on SPSS software. Results Through researching, it was achieved that Pengxi River was the source of greenhouse gas emission. The average value of p (CO2) in surface of waters was analysed to be (1807.635±315.605) μatm (1 µatm=0.101325 Pa, the same below) in Pengxi River, while that of p (CH4) was (218.7725±127.9425) μatm; and the average value for CO2 flux in water-gas interface was (32.53±3.86) mmol·m−2·d−1, CH4 flux average value was (0.208±0.143) mmol·m−2·d−1, the trend of the partial pressure and flux almost remained the same. Moreover, in terms of physical and chemical factors, water temperature, dissolved oxygen (DO) and pH are proved to be generally higher in summer. Discussion In comparison with other similar study in literature, it can be concluded that the diffusive of CO2 was higher in mainstream than that in tributary. The CO2 flux in the Pengxi River basin was moderate, higher than the flux in some small reservoir but smaller than that in large lakes and rivers. And the data for CO2 in this paper are much similar with previous study in Pengxi River. With respect to methane, the amount of methane released from tropical waters is greater. The amount of methane released from Pengxi River located in subtropical zone is not only much smaller than that in tropical waters, but also less than that from other rivers in subtropical zone as well as rivers in temperate zone. Moreover, there was a significant positive correlation between CH4 flux, p (CH4), water temperature, and pH, while the CO2 diffusion flux at the water-air interface was significantly positively correlated with p (CO2) and negatively correlated with DO, pH, and Chl-a. Other environmental factors showed vague effects on the fluxes. Conclusions Compared with the diffusive fluxes of greenhouse gases in typical rivers in the world, the study found that the release of CO2 flux in the Pengxi River basin was moderate, while the diffusion flux of CH4 was small. DO, pH, Chl-a and water temperature have apparent impact on the release of greenhouse gas. Furthermore, the emission of greenhouse gas is greater when water carry larger capacity of that gas. Recommendations and perspectives This research methods can be applied to other reservoirs and extensive analysis of the effects of other influencing factors on greenhouse gas emissions such as nitrogen compounds. In addition, the conclusions which have been achieved give evidence for controlling greenhouse gas emissions in future study. |
| Key words: Pengxi River CO2 CH4 diffusion flux environmental factors |
