Development of analytical methods and measurements of 13C/12C in atmospheric CH4 from the NOAA Climate Monitoring and Diagnostics Laboratory global air sampling network -: art. no. 4178
Development of analytical methods and measurements of 13C/12C in atmospheric CH4 from the NOAA Climate Monitoring and Diagnostics Laboratory global air sampling network -: art. no. 4178
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DOI：
10.1029/2001jd000630
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发表时间：
2002-07-01
影响因子：
4.4
通讯作者：
Tans, PP
中科院分区：
文献类型：
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作者：
Miller, JB;Mack, KA;Tans, PP
[1] 我们描述了自动气相色谱-同位素比质谱 (GC-IRMS) 系统的开发，该系统能够测量大气甲烷 (delta(13)CH(4)) 的碳同位素组成，精度优于 0.1%。该系统需要 200 mL 空气，并在 15 分钟内完成一次分析。小样本量、快速分析时间和高精度的结合使我们能够通过 NOAA 气候监测和诊断实验室合作空气采样网络测量大气 delta(13)CH(4) 的背景变化。然后，我们提供 1998 年 1 月至 1999 年 12 月期间从网络的六个表面站点获得的 delta(13)CH(4) 记录。这些站点是阿拉斯加巴罗 (北纬 71 度)；科罗拉多州尼沃特岭（北纬 40 度）；莫纳罗亚火山，夏威夷（北纬 20 度）；美属萨摩亚 (南纬 14 度)；塔斯马尼亚格里姆角（南纬 41 度）；和南极（南纬 90 度）。 1998年和1999年，全球平均地表δ(13)C值为-47.1千分之1，巴罗与南极之间的平均差为0.6千分之0.6。仅在北半球观察到一致的季节变化，特别是在巴罗，其平均幅度为千分之 0.5。然而，1998 年所有地点都出现了明显的季节变化，但其原因尚不清楚。我们还使用双盒模型来检验年平均 delta(13)C 和 CH4 摩尔分数测量值对大类源排放的限制程度。我们发现，最大的误差来源不是大气 delta(13)C 测量，而是放射性碳衍生化石燃料排放估算、甲烷破坏速率系数和源排放同位素比率。
[1] We describe the development of an automated gas chromatography-isotope ratio mass spectrometry (GC-IRMS) system capable of measuring the carbon isotopic composition of atmospheric methane (delta(13)CH(4)) with a precision of better than 0.1%. The system requires 200 mL of air and completes a single analysis in 15 min. The combination of small sample size, fast analysis time, and high precision has allowed us to measure background variations in atmospheric delta(13)CH(4) through the NOAA Climate Monitoring and Diagnostics Laboratory Cooperative Air Sampling Network. We then present a record of delta(13)CH(4) obtained from six surface sites of the network between January 1998 and December 1999. The sites are Barrow, Alaska (71degreesN); Niwot Ridge, Colorado (40degreesN); Mauna Loa, Hawaii (20degreesN); American Samoa (14degreesS); Cape Grim, Tasmania (41degreesS); and the South Pole (90degreesS). For the years 1998 and 1999, the globally averaged surface delta(13)C value was -47.1parts per thousand, and the average difference between Barrow and the South Pole was 0.6parts per thousand. Consistent seasonal variations were seen only in the Northern Hemisphere, especially at Barrow, where the average amplitude was 0.5parts per thousand. Seasonal variations in 1998, however, were evident at all sites, the cause of which is unknown. We also use a two-box model to examine the extent to which annual average delta(13)C and CH4 mole fraction measurements can constrain broad categories of source emissions. We find that the biggest sources of error are not the atmospheric delta(13)C measurements but instead the radiocarbon-derived fossil fuel emission estimates, rate coefficients for methane destruction, and isotopic ratios of source emissions.