| 三峡库区万州段河流水-气界面CO2通量支干流对比及影响机制初探 |
| 摘要点击 1555 全文点击 539 投稿时间：2021-04-12 修订日期：2021-06-29 |
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| 中文关键词 三峡库区 CO2通量 支干流对比 随机森林算法 影响机制 |
| 英文关键词 Three Gorges Reservoir area CO2 flux comparison of tributary and main stream random forest algorithm influence mechanism |
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| 中文摘要 |
| 以三峡库区万州段干流及典型支流澎溪河为研究对象，监测2019年4~9月水华期间水体中CO2浓度以及12个环境指标，估算水-气界面CO2通量并进行支干流对比.将12个环境指标分为气候因子、水环境因子、碳源因子、营养因子和沉积物因子，探讨5类因子对CO2通量的影响途径和贡献率，进一步为控制水库温室气体排放提供数据积累和理论支持.结果表明，监测期间内高阳、黄石和万州平均CO2通量分别为（1.445±1.739）、（3.118±2.963）和（2.899±1.144）mmol·（m2·h）-1，表现为：澎溪河支流高阳 < 干流万州 < 澎溪河支流黄石.从变化幅度来看，支流水体CO2通量变幅较大，干流水体变化幅度则相对较小，是较稳定的CO2 "源".长江干流作为陆地向海洋的生源物质运输枢纽，相比其支流碳含量和流速更高，这使得通常情况下干流CO2通量大于支流.但水文情势的不同使得同一支流不同点位CO2通量具有明显空间差异，支流高阳点位位于库湾处利于浮游植物生长使CO2通量较低，支流黄石点位位于流速较快的河道，受干流回水顶托和倒灌作用使CO2通量显著大于干流万州点位.各指标对CO2通量的影响在支干流也存在较大差异，水温（T）、溶解氧（DO）、溶解有机碳（DOC）和溶解无机碳（DIC）对支流CO2通量的影响显著，氨氮（NH4+-N）则对干流CO2通量影响显著.营养元素因子和碳源因子对CO2通量的贡献率分别为32.37%和27.25%，总占比过半，之后依次为气候因子、水环境因子和沉积物因子，分别为18.81%、13.49%和8.08%.水库CO2的排放控制可以着重从控制水体富营养化和控制碳源入手，全球变暖和底泥淤积等宏观现象也会对水库CO2排放有一定的影响. |
| 英文摘要 |
| The main stream of the Three Gorges Reservoir area in Wanzhou and its tributary (the Pengxi River) were selected as a survey area to monitor the CO2 concentration. Twelve related indicators were selected during the blooming period from April to September 2019, which were divided into Climate factors, Water environment factors, Carbon source factors, Nutrient factors, and Sediment factors. These factors were considered for further discussion of the impact pathways and contribution to CO2 flux. The average CO2 fluxes of Gaoyang (the Pengxi River), Huangshi (the Pengxi River), and Wanzhou (the main stream) were (1.445±1.739), (3.118±2.963), and (2.899±1.144) mmol·(m2·h)-1, respectively, showing that Gaoyang < Wanzhou < Huangshi. The CO2 flux of tributary showed a large variation, while the main stream had a relatively small variation, which is a stable "source" of CO2. The main stream of the Yangtze River, as a hub for the transportation of biomass from land to sea, has higher carbon concentration and higher flow rate than its tributaries, which makes the CO2 flux of the main stream usually larger than that of the tributary. However, the difference in hydrological conditions result in spatial differences in CO2 flux at different points of the same tributary. Gaoyang is located in the reservoir bay, which is conducive to the growth of phytoplankton and the CO2 flux is lower; Huangshi is located in a river with a faster flow rate. The backwater support and backflow of the main stream make the CO2 flux significantly greater than that at Wanzhou. The effects of various indicators on the CO2 flux are also markedly different in the tributary and main stream. Temperature (T), DO, dissolved organic carbon (DOC), and dissolved inorganic carbon (DIC) have significant effects on CO2 fluxes in the tributary, while NH4+-N has a significant impact on CO2 fluxes in the main stream. Nutrient factors and carbon source factors contribute 32.37% and 27.25%, respectively, to CO2 flux, accounting for more than half of the total, followed by climate factors, water environment factors, and sediment factors, which contribute 18.81%, 13.49%, and 8.08%, respectively. Reservoir CO2 emission control can focus on controlling the eutrophication and carbon sources; phenomena such as global warming and sedimentation will also have a certain impact on the CO2 emission of reservoirs. |
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