The stable isotopic composition of molecular hydrogen in the tropopause region probed by the CARIBIC aircraft
The stable isotopic composition of molecular hydrogen in the tropopause region probed by the CARIBIC aircraft
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CARIBIC飞机探测对流层顶区域氢分子的稳定同位素组成
DOI：
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发表时间：
2012
期刊：
影响因子：
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通讯作者：
T. Röckmann
中科院分区：
文献类型：
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作者：
A. Batenburg;T. Schuck;A. Baker;A. Zahn;C. Brenninkmeijer;T. Röckmann
抽象的。利用CARIBIC飞机在对流层上部-平流层下部（UTLS）采集了450多个大气样品，分析了H2分子混合比（χ（H2））和H2同位素组成（氘含量，δ D）。超过120个分析样本含有来自最低平流层（LMS）的空气。结果表明，χ（H2）随热对流层顶（TP）以上O3源高度的变化不大，而δ D随高度的增加而增加。同位素富集是由H2的产生和破坏过程引起的，这些过程使平流层H2库中的氘（D）富集;剖面的确切形状主要由平流层与对流层空气的混合决定。δ D与甲烷（χ（CH 4））和一氧化二氮（χ（N2 O））的混合比呈负相关，这是由于甲烷和一氧化二氮的寿命相对较长.相关系数分别为δ D [‰]=−0.35 · χ（CH 4）[ppb]+768和δ D [‰]=−1.90· χ（N2 O）[ppb]+745。这些相关性类似于以前发表的结果，可能在全球范围内适用于LMS。在印度次大陆40° N范围内，夏季风季节前后的χ（H2）没有明显的季节变化，但δ D在7、8、9月的季风季节中降低了12.3‰。这种δ D的降低与这些样品中χ（CH 4）的增加相关。与χ（CH 4）的显著相关性以及伴随δ D降低的可察觉的χ（H2）增加的缺失表明，在潮湿季节中非常D-耗尽的H2的微生物产生可能有助于这种现象。有些样品具有很高的χ（H2）和很低的δ D值，这表明污染效应。飞机发动机排气羽流是一个可疑的原因，因为这种影响主要发生在机场附近收集的样本中，但在其他化学示踪剂中没有发现类似的信号来支持这一点。H2污染的同位素来源特征似乎处于化石燃料燃烧特征的低端。
Abstract. More than 450 air samples that were collected in the upper troposphere – lower stratosphere (UTLS) region by the CARIBIC aircraft (Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container) have been analyzed for molecular hydrogen (H 2 ) mixing ratios (χ(H 2 )) and H 2 isotopic composition (deuterium content, δ D ). More than 120 of the analyzed samples contained air from the lowermost stratosphere (LMS). These show that χ(H 2 ) does not vary appreciably with O 3 -derived height above the thermal tropopause (TP), whereas δ D does increase with height. The isotope enrichment is caused by H 2 production and destruction processes that enrich the stratospheric H 2 reservoir in deuterium (D); the exact shapes of the profiles are mainly determined by mixing of stratospheric with tropospheric air. Tight negative correlations are found between δ D and the mixing ratios of methane (χ(CH 4 )) and nitrous oxide (χ(N 2 O)), as a result of the relatively long lifetimes of these three species. The correlations are described by δ D [‰]=−0.35 · χ(CH 4 )[ppb]+768 and δ D [‰]=−1.90· χ(N 2 O)[ppb]+745. These correlations are similar to previously published results and likely hold globally for the LMS. Samples that were collected from the Indian subcontinent up to 40° N before, during and after the summer monsoon season show no significant seasonal change in χ(H 2 ), but δ D is up to 12.3‰ lower in the July, August and September monsoon samples. This δ D decrease is correlated with the χ(CH 4 ) increase in these samples. The significant correlation with χ(CH 4 ) and the absence of a perceptible χ(H 2 ) increase that accompanies the δ D decrease indicates that microbial production of very D-depleted H 2 in the wet season may contribute to this phenomenon. Some of the samples have very high χ(H 2 ) and very low δ D values, which indicates a pollution effect. Aircraft engine exhaust plumes are a suspected cause, since the effect mostly occurs in samples collected close to airports, but no similar signals are found in other chemical tracers to support this. The isotopic source signature of the H 2 pollution seems to be on the low end of the signature for fossil fuel burning.