EAPSI: Day vs night greenhouse gas emissions from the draw-down zone of China's Three Gorges Reservoir

水电站会排放二氧化碳(CO2)和甲烷(CH4)等吸热气体，就像它们原本要取代的燃煤发电厂一样。河流携带的碳进入缓慢流动的水库水域时，会在沉积物中沉淀下来。当沉积物暴露在含氧水中时，微生物会将碳转化为二氧化碳。在没有氧气的情况下，微生物也会产生甲烷。因此，产生的气体的比例取决于水中氧的存在，氧的存在在白天和晚上都有变化。以前对水库二氧化碳和甲烷排放的研究几乎都是在白天进行的。这项研究将与中国科学院的陈淮博士合作，测量世界上最大的水库之一--中国的三峡--的二氧化碳和甲烷排放量。这些在白天和夜间进行的测量将有助于更准确地了解水电在整个发展中国家扩张时产生的二氧化碳和甲烷排放量。水库中二氧化碳和甲烷的排放量在空间上和时间上都不同。随着三峡水库水位的年年涨跌，三峡库区周边20%的库区被淹没和降水。在这个下降区的衰老植物是微生物氧化的丰富和规则的底物。这项研究将以溶解和气泡的形式测量下降区的Diel CO2和CH4通量。尽管其他水库的研究在白天也进行了类似的测量，但在1)光合作用(消耗二氧化碳并产生氧气)、2)呼吸(消耗氧气)和3)大气压力(可能控制气泡释放)方面的差异可能意味着，目前对水库中二氧化碳和甲烷通量的估计是不准确的。该NSF EAPSI奖是与中国科技部合作资助的。

Hydropower reservoirs emit heat-trapping gases such as carbon dioxide (CO2) and methane (CH4) like the coal-fired power plants they were designed to replace. Carbon carried by river waters settles in sediments when it enters slow-moving reservoir waters. When sediments are exposed to oxygenated water, microbes convert carbon to CO2. Without oxygen, microbes also produce CH4. Therefore, the proportions of gases produced depend on the presence of oxygen in water, which varies between day and night. Previous studies of CO2 and CH4 emissions from reservoirs have been almost exclusively conducted during the day. In collaboration with Dr. Huai Chen of the Chinese Academy of Sciences, this study will measure CO2 and CH4 emissions from one of the world's largest reservoirs, China's Three Gorges. These measurements, conducted during day and night, will contribute to a more accurate understanding of CO2 and CH4 emissions from hydropower as it expands throughout the developing world.Production of CO2 and CH4 in reservoirs varies spatially, as well as temporally. As water levels in the Three Gorges Reservoir rise and fall annually, 20% of the reservoir area around its margins is flooded and dewatered. Senesced plants in this draw-down zone are a rich and regular substrate for microbial oxidation. This study will measure diel CO2 and CH4 fluxes from the draw-down zone in dissolved and bubble form. Though studies in other reservoirs have taken similar measurements during the day, diel differences in 1) photosynthesis, which consumes CO2 and produces oxygen, 2) respiration, which consumes oxygen, and 3) atmospheric pressure, which may govern bubble release, could mean that current estimates of CO2 and CH4 fluxes in reservoirs are inaccurate. This NSF EAPSI award is funded in collaboration with the Chinese Ministry of Science and Technology.