Monitoring and analysis of CO<sub>2</sub> and CH<sub>4</sub> fluxes in the Three Gorges Reservoir

Abstract

自成库以来,三峡水库CO₂、CH₄等温室气体通量较蓄水前发生明显改变。如何科学认识和客观评估三峡水库修建及运行对其CO₂、CH₄等温室气体通量的影响备受关注。本文简要回顾了自2009年以来在三峡水库开展CO₂、CH₄等温室气体通量监测与分析工作,综述认为,现阶段三峡水库温室气体排放以水-气界面扩散释放为主要途径。陆源输入的有机碳是主导三峡水库CO₂、CH₄产生的主要碳源,但在局部区段或时段自源性有机碳的贡献亦十分显著。同蓄水前相比,三峡水库碳排放量呈现为净增加,淹没效应约占水库C净增量的20%,库区内点面源污染负荷并未对CO₂排放的净增量产生显著贡献,阻隔效应和生态系统重建效应对三峡水库碳排放的净增量产生显著贡献。近10年来,监测方法比对、监测点位优化等工作在一定程度上完善了三峡水库温室气体通量监测体系。新方法、新技术的引入也为三峡水库温室气体通量监测分析提供了有利支撑和保障,但复杂水文环境下驱动水库碳循环的水文生态机制仍不明晰,这是制约三峡水库碳通量长期趋势预测的难点。未来将通过监测技术持续创新以促进对三峡水库碳通量的精准核算,在深化基础研究的同时,仍亟待提出更科学有效的模型或方法以支撑长期趋势预测,服务水库碳管理。;Since the impoundment in 2003, the flux of CO₂, CH₄ in the Three Gorges Reservoir (TGR) has changed significantly compared with the pre-impoundment status. Accessing the influence of the construction and operation of the TGR on these greenhouse gas fluxes has attracted much attention. In this paper, we reviewed the experience of monitoring and analysis of CO₂, CH₄ fluxes in TGR since 2009. At present, air-water diffusion was the major pathway for carbon emissions in the reservoir. Terrigenous organic carbon input was the main carbon source leading the production of CO₂ and CH₄ in the reservoir. Yet, the contribution of autochthonous organic carbon seemed to be with growing significant. Compared with pre-impoundment status, a net increase of greenhouse gas emissions in TGR is evident. Flooding accounted for about 20% of the net increase of the reservoir formation. Anthropogenic pollution in the reservoir region did not significantly to the net increase of CO₂ emissions. In addition, the dam acting as barriers and reservoir aquatic ecosystem reconstruction were major contributors for the net greenhouse gas emissions. Sampling campaigns and research in the past decade promoted the improvement and optimization of monitoring system of the greenhouse gas emissions in TGR. Application of new monitoring methods and technologies also provided support and reimbursement. However, the hydro-ecological mechanism driving the carbon cycle in the reservoir under complex hydrological environment is still unclear, which is a difficulty in the long-term trend prediction of the reservoir carbon flux. In the future, innovation of monitoring technology will be applied to promote the accurate calculation of the carbon flux of TGR. It is still urgent to put forward more scientific and effective models or methods to support the long-term trend prediction and serve the reservoir carbon management.