Decoupling of carbon dioxide and dissolved organic carbon in boreal headwater streams
Decoupling of carbon dioxide and dissolved organic carbon in boreal headwater streams
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DOI：
10.1002/2016jg003420
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发表时间：
2016-10
期刊：
影响因子：
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通讯作者：
Mattias Winterdahl;M. Wallin;R. H. Karlsen;H. Laudon;M. Öquist;S. Lyon
中科院分区：
文献类型：
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作者：
Mattias Winterdahl;M. Wallin;R. H. Karlsen;H. Laudon;M. Öquist;S. Lyon
溪流和河流向大气排放大量二氧化碳 (CO2)。这种二氧化碳的来源是有机碳 (OC) 的河内矿化和通过地下水流入输入的二氧化碳，但它们的相对重要性很大程度上未知。在这项研究中，我们量化了河内 OC 矿化作为许多嵌套的北方水源河流中 CO2 来源的作用。结果表明，在与估计的水在溪流中的传播时间（<24 小时）相当的时间尺度上，OC 溪流的矿化贡献了 3% 的 CO2 过饱和度。质量平衡显示，在低阶流中，下游 OC 损失≤3%，而在最大（四阶）流中，OC 损失高达 16%。相比之下，85% 的二氧化碳沿着河流网络流失（最长的河流总长度 = 17 公里）。假设河流内 OC 矿化是流 CO2 的主要来源，则需要比文献报道的 OC 矿化率（OC 的 6%）更高的 OC 矿化率（≤ OC 的 0.7%）才能维持观察到的 CO2 过饱和度。此外，模型结果表明地下水流入足以维持观测到的河流二氧化碳浓度。因此，我们得出结论，河道内 OC 矿化是这些北方水源系统中 CO2 的次要来源，而河道 CO2 的主要来源是流入的地下水，输送源自土壤呼吸的 CO2。
Streams and rivers emit large quantities of carbon dioxide (CO2) to the atmosphere. The sources of this CO2 are in‐stream mineralization of organic carbon (OC) and CO2 input via groundwater inflow, but their relative importance is largely unknown. In this study, we quantified the role of in‐stream OC mineralization as a source of CO2 in a number of nested boreal headwater streams. The results showed that mineralization of stream OC contributed 3% of CO2 supersaturation at time scales comparable to the estimated water travel times in the streams (<24 h). Mass balances showed that downstream losses of OC were ≤3% in low‐order streams, whereas up to 16% of the OC was lost in the largest (fourth order) streams. In contrast, 85% of the CO2 was lost along the stream network (longest total stream length = 17 km). Under the assumption that in‐stream OC mineralization was the main source of stream CO2, higher rates of OC mineralization (6% of OC) than those reported across the literature (≤0.7% of OC) would be required to sustain observed CO2 supersaturation. Further, model results indicated that groundwater inflows were sufficient to sustain observed stream CO2 concentrations. We hence conclude that in‐stream OC mineralization was a minor source of CO2 in these boreal headwater systems and that the main source of stream CO2 was inflowing groundwater transporting CO2 originating from soil respiration.