Falling atmospheric pressure as a trigger for methane ebullition from peatland
Falling atmospheric pressure as a trigger for methane ebullition from peatland
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DOI：
10.1029/2006gb002790
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发表时间：
2007-06
影响因子：
5.2
通讯作者：
T. Tokida;T. Miyazaki;M. Mizoguchi;O. Nagata;F. Takakai;A. Kagemoto;R. Hatano
中科院分区：
文献类型：
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作者：
T. Tokida;T. Miyazaki;M. Mizoguchi;O. Nagata;F. Takakai;A. Kagemoto;R. Hatano
泥炭地被广泛认为是大气中甲烷的重要来源，甲烷是一种强有力的温室气体。目前，关于CH4环境排放的大部分信息来自不频繁的、时间上不连续的地面通量测量。为了利用相关的生物地球化学因素，例如地下水位位置或泥炭温度，通过假设通量在相当长的非采样期间是稳定的，已经做出了巨大的努力来外推测量的排放速率，以建立季节或年度平均值。然而，这一假设还没有得到明确的验证，关于甲烷通量在单个通量测量的时间尺度内的连续变化也知之甚少。在这项研究中，我们显示了甲烷排放速率的突变与大气压力的下降有关。我们发现，甲烷通量可以在几十分钟内发生两个数量级的变化，这是由于大气压力下降引发的自由相甲烷的释放。在测量期间，沸腾对总甲烷通量的贡献是显著的(50-%)。这些结果清楚地表明，野外活动必须被设计成覆盖由沸腾引起的这种快速的时间变化，这在高温天气中可能特别重要。还应修改基于工艺的甲烷排放模型，将大气压力作为控制泥炭地沸腾的甲烷排放的关键因素。
Peatlands are widely regarded as a significant source of atmospheric CH4, a potent greenhouse gas. At present, most of the information on environmental emissions of CH4 comes from infrequent, temporally discontinuous ground‐based flux measurements. Enormous efforts have been made to extrapolate measured emission rates to establish seasonal or annual averages using relevant biogeochemical factors, such as water table positions or peat temperatures, by assuming that the flux was stationary during a substantial nonsampling period. However, this assumption has not been explicitly verified, and little is known about the continuous variation of the CH4 flux in a timescale of individual flux measurement. In this study, we show an abrupt change in the CH4 emission rate associated with falling atmospheric pressure. We found that the CH4 flux can change by 2 orders of magnitude within a matter of tens of minutes owing to the release of free‐phase CH4 triggered by a drop in air pressure. The contribution of the ebullition to the total CH4 flux during the measurements was significant (50–64%). These results clearly indicated that field campaigns must be designed to cover this rapid temporal variability caused by ebullition, which may be especially important in intemperate weather. Process‐based CH4 emission models should also be modified to include air pressure as a key factor for the control of ebullient CH4 release from peatland.