| 摘要: |
| 甲烷（CH4）对全球温室效应有着较大的贡献。三峡水库自2003年蓄水以来，其CH4排放问题已受到广泛关注。但三峡水库反季节的运行方式，使支流库湾CH4的产生和传输过程受到多方面的影响，进而导致其CH4排放效应尚不十分明确。本文综述了三峡水库支流CH4排放的研究进展，典型支流的CH4排放通量普遍高于干流，位于三峡水库库尾的部分支流CH4排放通量高于三峡水库库首及库中支流。大多数典型支流的CH4通量在夏季均达到全年峰值，而在冬季高水位运行期均处于相对较低的水平。同时本文主要从水环境条件、水动力条件、人类活动及气象条件四个方面阐述了三峡水库支流CH4排放的影响因素。1）水环境条件：支流水华后藻类衰亡分解过程会驱动CH4释放，且藻类的演替过程会加剧CH4的产生；温度可以直接影响CH4的生成速率和消耗速率，也能通过促进藻的生长间接影响CH4排放；支流相对较低的甲烷氧化菌含量是其CH4通量较高的原因之一。2）水动力条件：蓄水期CH4主要以扩散的方式进行释放，支流较低的流速促进了悬浮物的沉积，上游沉积物中的CH4含量高于下游；泄水期CH4主要以冒泡的方式进行释放，下游沉积物中TOC急剧增加，但干流的入侵会削弱支流的温度分层，破坏藻类生长环境，间接影响CH4通量。3）人类活动：农业耕作使支流水体中的营养物浓度增加，甲烷氧化菌的丰富度降低，细菌群落的营养相关代谢增强；建设用地扩大、支流筑坝增加抑制了有机物的传输，增加了水体中的产CH4基质，促进了CH4的产生。4）气象条件：降雨会携带更多营养物质进入支流，同时会增加水体浊度、破坏水体的温度分层，从而对CH4的产生和传输过程造成影响。最后对未来的研究热点进行了展望，以期为三峡水库CH4排放的控制和管理提供参考。 |
| 关键词: 三峡水库 支流 甲烷排放 水环境条件 水动力条件 人类活动 气象条件 |
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| 基金项目:国家自然科学基金(52270196; U20A20326)、重庆市自然科学基金(cstc2020jcyj-msxmX0176)、重庆市教育委员会科学技术项目(KJQN202000745)、水利水运工程教育部重点实验室开放基金 (SLK2021B06)、中国科协青年人才托举工程项目（2022QNRC001） |
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| Research progress on methane emissions from tributaries of the Three Gorges Reservoir |
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Mao yufeng1, He ruixu2, Li hong3, Yang shengfa4, Yu weiwei5, Ye kailai2, Lin tong3, Bai xiaoxia3, He qiang6
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1.National Engineering Research Center for Inland Waterway Regulation, Chongqing Jiaotong University Key Laboratory of Hydraulic and Waterway Engineering of the Ministry of Education, Jiaotong University Key Laboratory of the Three Gorges Reservoir Region’s Eco-Environment, State Ministry of Education, Chongqing University;2.National Engineering Research Center for Inland Waterway Regulation, Chongqing Jiaotong University;3.Key Laboratory of the Three Gorges Reservoir Region’s Eco-Environment, State Ministry of Education, Chongqing University;4.National Engineering Research Center for Inland Waterway Regulation, Chongqing Jiaotong University Key Laboratory of Hydraulic and Waterway Engineering of the Ministry of Education, Jiaotong University;5.Key Laboratory of Hydraulic and Waterway Engineering of the Ministry of Education, Jiaotong University;6.Key Laboratory of Eco-Environment of Three Gorges Region,Ministry of Education,College of Environment and Ecology,Chongqing University
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| Abstract: |
| Methane (CH4) significantly contributes to the global greenhouse effect, and CH4 discharge has received widespread attention from the moment of the impounding of the Three Gorges Reservoir in 2003. However, the processes of CH4 production and transmission in the tributary reservoir bay are affected in many ways by the out-of-season operation mode of the Three Gorges Reservoir, complicating the understanding of the CH4 emission effect. In this paper, we review the research progress of CH4 discharge from tributaries of the Three Gorges Reservoir. The CH4 discharge flux of typical tributaries is generally higher than that of the main stream. Here, the CH4 discharge flux of the tail tributary of the Three Gorges Reservoir is higher than that of the head of the Three Gorges Reservoir and the tributaries in the reservoir. In most typical tributaries, CH4 fluxes peak in the summer and become relatively low during the winter period of high-water operation. At the same time, this paper mainly expounds on the factors that influence the CH4 discharge from the tributaries of the Three Gorges Reservoir from four aspects: water environmental conditions, hydrodynamic conditions, human activities, and meteorological conditions. 1) Water environmental conditions: the decay and decomposition process of algae after tributary bloom drives the release of CH4, and the succession process of algae aggravates the production of CH4; Temperature can directly affect the production and consumption rates of CH4, and it can also indirectly affect CH4 emission by promoting the growth of algae; The relatively low content of methane oxidizing bacteria in the tributaries of the Three Gorges Reservoir is one of the reasons for their high CH4 flux. 2) Hydrodynamic conditions: CH4 is mainly released via diffusion during the water storage period, and the lower flow velocity of the tributaries promotes the deposition of suspended solids, and the CH4 content in the upstream sediment is higher than that in the downstream; CH4 is mainly released in the bubbling mode during the discharge period; the TOC in the downstream sediment sharply increases, but the intrusion of the main stream weakens the temperature stratification of the tributaries, destroys the algae growth environment, and indirectly affects the CH4 flux. 3) Human activities: agricultural farming increases nutrient concentrations in tributary water bodies, reduces the abundance of methane-oxidizing bacteria and enhances the nutrient-related metabolism in bacterial communities; the expansion of construction land and the increase of damming of tributaries inhibit the transport of organic matter, increases the CH4-producing matrix in the water body, and promotes the production of CH4. 4) Meteorological conditions: rainfall carries more nutrients into tributaries while increasing the turbidity and destroying the temperature stratification of the water body, thereby affecting the production and transmission processes of CH4. Finally, future research hotspots are explored to provide a reference for controlling and managing CH4 discharge in the Three Gorges Reservoir. |
| Key words: Three Gorges Reservoir Tributaries Methane emission Water environmental conditions Hydrodynamic conditions meteorological conditions Human activities |
