State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Haidian, Beijing, China; Yale School of the Environment, New Haven, CT, USA; Department of Geography, National University of Singapore, Kent Ridge, Singapore.
School of Water Resources and Hydropower Engineering, Wuhan University, Wuhan, China.
Sci Total Environ. 2021 Mar 15;760:143336. doi: 10.1016/j.scitotenv.2020.143336. Epub 2020 Nov 4.
Groundwater discharge to river networks makes up a major source of riverine CO emission, available evidence however comes mainly from headwater streams which are directly connected to terrestrial ecosystems and spatially limited in terms of system size. Here relying on coupled water and CO mass balances, we quantified the groundwater-mediated CO input to the Yangtze River mainstem on an annual basis, where the mass balance of water provided physical constraints on CO exchange between the river and groundwater. A landscape topographic control of the groundwater-river interaction was proposed where mountain reaches preferentially receive water and CO discharge from the groundwater while plain alluvial reaches predominantly lose water to the aquifers. Groundwater CO inputs were however small in magnitude on all reaches (0.3-14% of the total CO emission and transport by the river) and unable to account for the discrepancy between surface evasion and internal metabolism in the river. Minor direct groundwater discharge to the reaches in comparison to smaller streams (negative to < 3.5% of the surface water flows) was concluded to be the main reason for low groundwater-sourced CO in the large river reaches.
地下水向河网的排泄构成了河流 CO 排放的主要来源，但现有证据主要来自与陆地生态系统直接相连且在系统规模上空间有限的源头溪流。在这里，我们依赖于水和 CO 质量平衡的耦合，每年量化了长江干流的地下水介导的 CO 输入，其中水的质量平衡为河流和地下水之间的 CO 交换提供了物理约束。提出了一种控制地下水-河流相互作用的景观地形控制方法，其中山区河段优先从地下水中接收水和 CO 排放，而平原冲积河段则主要将水输送到含水层。然而，所有河段的地下水 CO 输入量都很小（占河流 CO 排放和运输总量的 0.3-14%），并且无法解释河流表面逸出和内部代谢之间的差异。与较小的溪流相比，这些河段的地下水直接排放量较小（< 地表水流量的 3.5%），这被认为是大河段中地下水来源的 CO 含量较低的主要原因。
