Sediment fluxes rather than oxic methanogenesis explain diffusive CH4 emissions from lakes and reservoirs
Sediment fluxes rather than oxic methanogenesis explain diffusive CH4 emissions from lakes and reservoirs
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DOI：
10.1038/s41598-018-36530-w
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发表时间：
2019-01
影响因子：
4.6
通讯作者：
F. Peeters;Jorge Encinas Fernández;H. Hofmann
中科院分区：
文献类型：
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作者：
F. Peeters;Jorge Encinas Fernández;H. Hofmann
湖泊和水库的甲烷排放是全球大气甲烷预算中的主要自然来源。这些排放的很大一部分是由于甲烷从地表水扩散到大气中造成的。最近有人建议，需要在含氧地表水中生产甲烷来补偿湖泊的甲烷扩散排放。相比之下，我们在这里证明来自浅水区沉积物的典型扩散 CH4 通量 Fsed,S 足以解释 CH4 向大气的排放。我们的分析基于表面 CH4 浓度的特殊数据集与 CH4 质量平衡模型的结合，该模型专注于表面混合层，并考虑来自沉积物的 CH4 通量、横向传输、与大气的气体交换，并包括沉积物通量和气体交换的温度依赖性。Fsed,S 不仅解释了观测到的表面 CH4 浓度，还解释了浅水区和开放水域之间的浓度差异，以及 排放量的季节性变化和横向浓度分布。因此，我们的结果支持这样的假设：来自浅层沉积物的扩散通量而不是含氧产甲烷作用是地表水中CH4以及湖泊和水库排放CH4的主要来源。
Methane emissions from lakes and reservoirs are a major natural source in the global budget of atmospheric CH4. A large fraction of these emissions are due to diffusive transport of CH4from surface waters to the atmosphere. It was suggested recently that CH4production in the oxic surface waters is required to compensate for diffusive CH4emissions from lakes. In contrast, we demonstrate here that typical diffusive CH4-fluxes from sediments in shallow water zones,Fsed,S, suffice to explain CH4emissions to the atmosphere. Our analysis is based on the combination of an exceptional data set on surface concentrations of CH4with a mass balance model of CH4that is focused on the surface mixed layer and considers CH4-fluxes from sediments, lateral transport, gas exchange with the atmosphere, and includes temperature dependencies of sediment fluxes and gas exchange.Fsed,Snot only explains observed surface CH4concentrations but also concentration differences between shallow and open water zones, and the seasonal variability of emissions and lateral concentration distributions. Hence, our results support the hypothesis that diffusive fluxes from shallow sediments and not oxic methanogenesis are the main source of the CH4in the surface waters and the CH4emitted from lakes and reservoirs.