Groundwater inflows control patterns and sources of greenhouse gas emissions from streams
Groundwater inflows control patterns and sources of greenhouse gas emissions from streams
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地下水流入控制河流中温室气体排放的模式和来源
DOI：
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发表时间：
2019
影响因子：
4.5
通讯作者：
R. Sponseller
中科院分区：
文献类型：
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作者：
A. Lupon;B. Denfeld;H. Laudon;J. Leach;J. Karlsson;R. Sponseller
源头溪流可能是大气中二氧化碳（CO2）和甲烷（CH4）的重要来源。然而，地下水流连通性对碳(C)气体逃逸模式和来源的影响仍然知之甚少。我们通过详细研究一条1.4公里长的湖泊出水口河流，探索了北方景观中的这些联系，该河流由多个地形驱动的地下水输入区提供水文。在无冰期间，我们每隔两周测量一次50米的河流和地下水溶解有机碳（DOC）、二氧化碳和甲烷浓度，并通过质量平衡模型和水生代谢的独立估算估算河流中的碳气体产量。C气体浓度的空间分布具有一致性，CH4和CO2浓度峰值均出现在各地下水输入带之后。此外，来自河岸土壤的侧向C气体输入是河流中CO2和CH4的主要来源。河流内DOC矿化和CH4氧化占河流CO2排放的17-51%，且在流量相对较大时贡献最大。总的来说，我们的研究结果说明了地下水流道的性质和安排如何通过作为气体的直接来源和提供促进水生代谢的有机基质来组织溪流C浓度、转化和排放的模式。因此，精确评估集水区结构如何影响地下水流连接的时间和大小，对于从机制上理解和衡量水源的碳逃逸率至关重要。
Headwater streams can be important sources of carbon dioxide (CO2) and methane (CH4) to the atmosphere. However, the influence of groundwater–stream connectivity on the patterns and sources of carbon (C) gas evasion is still poorly understood. We explored these connections in the boreal landscape through a detailed study of a 1.4 km lake outlet stream that is hydrologically fed by multiple topographically driven groundwater input zones. We measured stream and groundwater dissolved organic C (DOC), CO2, and CH4 concentrations every 50 m biweekly during the ice‐free period and estimated in‐stream C gas production through a mass balance model and independent estimates of aquatic metabolism. The spatial pattern of C gas concentrations was consistent over time, with peaks of both CH4 and CO2 concentrations occurring after each groundwater input zone. Moreover, lateral C gas inputs from riparian soils were the major source of CO2 and CH4 to the stream. DOC mineralization and CH4 oxidation within the stream accounted for 17–51% of stream CO2 emissions, and this contribution was the greatest during relatively higher flows. Overall, our results illustrate how the nature and arrangement of groundwater flowpaths can organize patterns of stream C concentrations, transformations, and emissions by acting as a direct source of gases and by supplying organic substrates that fuel aquatic metabolism. Hence, refined assessments of how catchment structure influences the timing and magnitude of groundwater–stream connections are crucial for mechanistically understanding and scaling C evasion rates from headwaters.