高海拔水电水库温室气体的排放特征-以雅鲁藏布江藏木水库为例

Hydroelectric reservoirs are pivotal sources of greenhouse gases (GHGs) to the atmosphere that may influence regional climate change to some extent. However, present emission estimates from reservoirs remain large uncertainties, partly due to data paucity in mountain regions with a large freshwater surface area, and/or the exclusion of emissions from channels up- and downstream of reservoirs. Here, we determined simultaneously CO₂, CH₄ and N₂O concentrations and their diffusive fluxes in the Zangmu reservoir on the Yarlung Tsangpo during high- and low-water periods. Seasonally, GHG concentrations and diffusive fluxes in wet season were greater than those in dry season. Spatially, up- and downstream channels had higher CO₂ and CH₄ concentrations than the reservoir, up- and downstream transects of the reservoir also had more CO₂ and CH₄ concentrations than pelagic zone in midstream transects of the reservoir. Nevertheless, spatiality was minor for N₂O along the flow direction. We also explained the reasons for spatiotemporal patterns of the three GHGs. Compared with other lentic and lotic systems across China, diffusive GHG fluxes were generally low in the Zangmu reservoir and its up- and downstream channels. Given the huge surface area compensates for low fluxes, upscaling these fluxes to the Zangmu reservoir gave a diffusive GHG emission of 106.4 Gg·a^-1, accounting for 31.5% of diffusive GHG emission of the entire Yarlung Tsangpo. Consequently, we recommend the inclusion of high-altitude reservoirs into global reservoir GHG inventories, and also considerating the role of up- and downstream channels that affected by reservoirs in the reservoir-wide systems.