Dynamics of methane ebullition from a peat monolith revealed from a dynamic flux chamber system
Dynamics of methane ebullition from a peat monolith revealed from a dynamic flux chamber system
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DOI：
10.1002/2014jg002654
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发表时间：
2014-09
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影响因子：
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通讯作者：
Zhongjie Yu;L. Slater;K. Schäfer;A. Reeve;R. Varner
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文献类型：
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作者：
Zhongjie Yu;L. Slater;K. Schäfer;A. Reeve;R. Varner
北部泥炭地甲烷(CH4)的沸腾很难量化，部分原因是其高度的时空变异性。为了了解甲烷沸腾的复杂行为，本研究利用动态通量箱(DFC)系统在实验室尺度上连续测量了近地表泥炭的CH4通量。还在整体内的三个深度获得了一致的透射式探地雷达气体含量测量结果。开发了一种图解方法，从记录的总CH4通量中分离出扩散、稳定沸腾和间歇性沸腾通量，并确定各个沸腾事件的时间和CH4含量。结果表明，DFC的应用对空气-泥炭甲烷交换的干扰很小，估计的沸腾通量对图形模型的不确定性不敏感。稳态沸腾通量和周期性沸腾通量分别占总通量的36±24%和38±24%。幕式CH4沸腾和三层内气体含量之间的耦合支持了调节CH4沸腾的阈值气体含量的存在。然而，泥炭开始活跃沸腾的阈值在不同泥炭层之间是不同的，在深层观察到更大的阈值(0.14m3m−3)，这表明泥炭的物理结构控制着泥炭中的气泡动力学。温度变化(23°C至27°C)很可能只是泥炭层上层的小周期沸腾事件的原因，而深层的大沸腾事件很可能是由大气压力下降引发的。
Methane (CH4) ebullition in northern peatlands is poorly quantified in part due to its high spatiotemporal variability. In this study, a dynamic flux chamber (DFC) system was used to continuously measure CH4 fluxes from a monolith of near‐surface Sphagnum peat at the laboratory scale to understand the complex behavior of CH4 ebullition. Coincident transmission ground penetrating radar measurements of gas content were also acquired at three depths within the monolith. A graphical method was developed to separate diffusion, steady ebullition, and episodic ebullition fluxes from the total CH4 flux recorded and to identify the timing and CH4 content of individual ebullition events. The results show that the application of the DFC had minimal disturbance on air‐peat CH4 exchange and estimated ebullition fluxes were not sensitive to the uncertainties associated with the graphical model. Steady and episodic ebullition fluxes were estimated to be averagely 36 ± 24% and 38 ± 24% of the total fluxes over the study period, respectively. The coupling between episodic CH4 ebullition and gas content within the three layers supports the existence of a threshold gas content regulating CH4 ebullition. However, the threshold at which active ebullition commenced varied between peat layers with a larger threshold (0.14 m3 m−3) observed in the deeper layers, suggesting that the peat physical structure controls gas bubble dynamics in peat. Temperature variation (23°C to 27°C) was likely only responsible for small episodic ebullition events from the upper peat layer, while large ebullition events from the deeper layers were most likely triggered by drops in atmospheric pressure.