Contributions of natural and anthropogenic sources to atmospheric methane variations over western Siberia estimated from its carbon and hydrogen isotopes
Contributions of natural and anthropogenic sources to atmospheric methane variations over western Siberia estimated from its carbon and hydrogen isotopes
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DOI：
10.1029/2011gb004232
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发表时间：
2012-12
影响因子：
5.2
通讯作者：
T. Umezawa;T. Machida;S. Aoki;T. Nakazawa
中科院分区：
文献类型：
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作者：
T. Umezawa;T. Machida;S. Aoki;T. Nakazawa
2006-2009年，在西伯利亚西部1 km和2 km高度进行了大气CH 4（δ 13 CH 4和δ D-CH 4）碳、氢同位素比值（精度分别为0.08‰和2.2‰）以及CH 4浓度的飞机测量。δ 13 CH 4和δ D-CH 4在低海拔地区几乎总是较低，而CH 4浓度较高，这意味着地面上有较强的来源，同位素值较低。δ 13 CH 4在夏末表现出明显的季节性最小值，而CH 4和δ D-CH 4的季节性变化由于局地扰动而不明确。通过考察CH 4浓度与同位素的关系，我们发现冬季（12 - 4月）的δ 13 CH 4和δ D-CH 4的同位素来源特征分别为−41.2 ± 1.8和−187 ± 18‰，夏季（6 - 10月）的相应值分别为−65.0 ± 2.5和−282 ± 25‰。这些数值表明，冬季化石燃料设施和夏季湿地的CH 4排放量占主导地位。研究还发现，短期CH 4变化更受化石CH 4比湿地的影响。这一发现大概反映了这样一个事实，即前者是从有限的地区释放出来的，如化石燃料设施的泄漏，而后者是从广阔的湿地释放出来的。通过采用大气化学传输模型中使用的CH 4排放数据集，我们计算了西伯利亚西部CH 4源的季节性同位素变化，并将其与本研究中获得的估计值进行了比较。结果表明，甲烷排放数据集的季节变化是合理的，至少就化石排放与生物排放的比例而言是合理的。
Aircraft measurements of carbon and hydrogen isotopic ratios of atmospheric CH4 (δ13CH4 and δD‐CH4), with the respective precisions of 0.08‰ and 2.2‰, as well as CH4 concentration were made at 1 and 2 km altitudes over western Siberia during 2006–2009. δ13CH4 and δD‐CH4 were almost always lower at lower altitudes, while the CH4 concentration was higher, implying strong sources on the ground with low isotopic values. δ13CH4 showed a clear seasonal minimum in the late summer, while seasonality of CH4 and δD‐CH4 was ambiguous due to the local disturbances. By inspecting the relationships between the CH4 concentration and isotopes, we found that isotopic source signatures in the winter (December–April) are −41.2 ± 1.8 and −187 ± 18‰ for δ13CH4 and δD‐CH4, respectively, and the corresponding values in the summer (June–October) are −65.0 ± 2.5 and −282 ± 25‰. These values indicate predominant CH4emissions from fossil fuel facilities in the winter and wetlands in the summer. It was also found that the shorter‐term CH4 variations are more influenced by fossil CH4 than that from wetlands. The finding presumably reflects the fact that the former is released from limited areas such as leakage from fossil fuel facilities, while the latter is released from a vast expanse of wetland. By employing a CH4 emission data set used in an atmospheric chemistry transport model, we calculated seasonal isotopic changes of CH4 sources in western Siberia and compared them to the estimates obtained in this study. The results indicated that the seasonal change in the CH4 emission data set is reasonable, at least in terms of a ratio of fossil to biogenic emissions.