Greenhouse Gas Emissions from Reservoirs: Mechanisms and Quantification

内陆水域二氧化碳(CO2)和甲烷(CH4)的排放是全球温室气体(GHG)平衡的重要来源。水库是温室气体排放的特别热点。温室气体排放量在时间和空间上都是高度可变的。目前，人们对温带水库的实际通量知之甚少，涉及的过程也不完全清楚。在这个项目中，我们想要量化德国两个水库的温室气体排放量。中心主题是理解二氧化碳和甲烷排放的规则，特别是理解水位变化、营养状态和气象驱动因素的影响。我们想检验三个主要假设：(1)短期事件对总体平衡的贡献很大。(2)CO2和CH4排放的时间模式取决于水库的营养状态，并复杂地被大气影响所覆盖。(3)CO2和CH4两种气体通量的空间分布取决于内部(如水化学参数和水深)和外部相互作用(如风、气压、辐射和能量平衡)。我们将调查两个不同的水库，哈尔茨山脉的少营养拉普博德水库和卢萨蒂亚的富营养水库鲍岑。二氧化碳和甲烷排放的时间模式将通过微气象和水侧测量相结合的方式进行量化。该项目的核心是一个浮动涡旋协方差(EC)测量系统。将EC通量测量、水体浓度测量和气象基础数据合并，可以确定物理气体传输系数。温室气体排放的空间变异性将通过浮动室测量和沸腾漏斗进行分析。在测量排放率的同时，还分析了沉积物和水化学参数，例如pH值和O2、CO2和CH4的浓度，并连续测量了能量平衡、辐射收支和经典气象变量。将使用适当的建模方法对测量和项目结果进行概括化和区域化。

The emissions of carbon dioxide (CO2) and methane (CH4) from inland waters are an important source in the global greenhouse gas (GHG) balance. Reservoirs are particular hot spots of GHG emissions. The GHG emissions are temporally and spatially highly variable. Currently, not much is known about the actual flux rates from temperate reservoirs, and the processes involved are not completely understood. In this project, we would like to quantify the GHG emissions from two German reservoirs. The central topic is the understanding of the regulation of CO2 and CH4 emissions and, especially, to comprehend effects of altering water levels, trophic state and meteorological drivers. We would like to test three major hypotheses:(1) Short term events contribute significantly to the overall balance.(2) Temporal pattern of CO2 and CH4 emission depend on the trophic state of the reservoir and are complexly overlaid by atmospheric effects.(3) The spatial distribution of the flux rate of the two gasses CO2 and CH4 depends differently on internal (e.g., hydro-chemical parameters and water depth) and external interacting factors (e.g., wind, air pressure, radiation and energy balance).The proposed project is placed in the nexus between limnology, hydrology and boundary layer meteorology. We will investigate two different reservoirs, the oligotrophic Rappbode reservoir in the Harz Mountains and the eutrophic reservoir Bautzen in Lusatia. Temporal patterns of CO2 and CH4 emissions will be quantified by a combination of micrometeorological and water side measurements. Central to the project will be a floating Eddy Covariance (EC) measurement system. The conflation of EC flux measurements, concentration measurements in the water body, and meteorological basic data allows the determination of the physical gas transfer coefficient. The spatial variability of GHG emissions will be analysed by floating chamber measurements and ebullition funnels. The measurements of emission rates are accompanied by the analysis of sediment and hydro-chemical parameters, e.g., pH and concentrations of O2, CO2 and CH4 as well as by continuous measurements of energy balance, radiation budget and classical meteorological variables. Proper modelling approaches will be used for generalisation and regionalisation of measurements and project results.