Large Seasonal and Habitat Differences in Methane Ebullition on the Amazon Floodplain
Large Seasonal and Habitat Differences in Methane Ebullition on the Amazon Floodplain
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DOI：
10.1029/2020jg005911
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发表时间：
2021-07-01
影响因子：
3.7
通讯作者：
Forsberg, Bruce R.
中科院分区：
文献类型：
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作者：
Barbosa, Pedro M.;Melack, John M.;Forsberg, Bruce R.
热带洪泛区是大气中甲烷 (CH4) 的重要来源，并且沸腾通量可能很重要。我们报告了两年来基于允许检测气泡的浮动室和水下气泡捕集器对亚马逊洪泛区常见栖息地的甲烷沸腾的直接测量。沸腾在空间和时间上变化很大。在 840 次浮室测量中（相当于 10 分钟部署中的 8,690 分钟），22% 捕获了气泡。使用总共部署约 230 天的气泡捕集器测量的沸腾 CH4 通量范围为 0 至 109 mmol CH4 m(-2) d(-1)，平均值为 4.4 mmol CH4 m(-2) d(-1)。在落水过程中，水声测深仪在 34 公里长的 70 米段中的 24% 中检测到气泡。在落水期间，随着水位下降得更快，沸腾通量增加。在被淹没的森林中，最高的沸腾通量出现在落水期间，而在开放水域和草本植物栖息地中，在低水期期间测量到较高的沸腾通量。基于气泡捕集器，以沸腾为代表的扩散加沸腾 CH4 通量的贡献从 1%（湖泊开阔水域中的高水位和上升水位）到 93%（被淹没的森林中的下降水位）不等。将栖息地之间的沸腾通量和扩散通量与水生栖息地的水深和面积覆盖范围的变化相结合，为改进整个漫滩范围内的 CH4 逃逸估计提供了基础。
Tropical floodplains are an important source of methane (CH4) to the atmosphere, and ebullitive fluxes are likely to be important. We report direct measurements of CH4 ebullition in common habitats on the Amazon floodplain over two years based on floating chambers that allowed detection of bubbles, and submerged bubble traps. Ebullition was highly variable in space and time. Of the 840 floating chamber measurements (equivalent to 8,690 min of 10-min deployments), 22% captured bubbles. Ebullitive CH4 fluxes, measured using bubble traps deployed for a total of approximately 230 days, ranged from 0 to 109 mmol CH4 m(-2) d(-1), with a mean of 4.4 mmol CH4 m(-2) d(-1). During falling water, a hydroacoustic echosounder detected bubbles in 24% of the 70-m segments over 34 km. Ebullitive flux increased as the water level fell faster during falling water periods. In flooded forests, highest ebullitive fluxes occurred during falling water, while in open water and herbaceous plant habitats, higher ebullitive fluxes were measured during low water periods. The contribution of diffusive plus ebullitive CH4 flux represented by ebullition varied from 1% (high and rising water in open water of the lake) to 93% (falling water in flooded forests) based on bubble traps. Combining ebullitive and diffusive fluxes among habitats in relation to variations in water depth and areal coverage of aquatic habitats provides the basis for improved floodplain-wide estimates of CH4 evasion.