Atmospheric helium isotopic ratio from 1910 to 2016 recorded in stainless steel containers
Atmospheric helium isotopic ratio from 1910 to 2016 recorded in stainless steel containers
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不锈钢容器中记录的1910年至2016年大气氦同位素比
DOI：
10.7185/geochemlet.1804
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发表时间：
2018
影响因子：
5.2
通讯作者：
R. Langenfelds
中科院分区：
文献类型：
--
作者：
Christine Boucher;B. Marty;L. Zimmermann;R. Langenfelds
土井：10.7185/geochemlet.1804由于人类活动，大气氦同位素组成（RA = He/Heair = 1.39 × 10 - 6）可能在最近发生了变化。为了验证这种可能性，我们对来自法国（pétanque balls，一种浮动化油器; 1910 - 2016）和塔斯马尼亚州格里姆角（存档空气罐; 1978，1988）的各种不锈钢容器中的空气进行了高精度的氦同位素测量。我们使用了在Centre de Recherches Pétrographiques et Géochimiques（CRPG，Nancy，France）的双收集器质谱仪。我们在法国和格里姆角的空气样本中发现了相似的成分。根据所有样本（包括先前发表的数据）估计的时间变化不显著，106年的趋势为+0.002 ±0.024 ‰/年（2 σ）。我们怀疑，化石燃料开采释放的放射性4He可能至少部分被核试验产生的3He（通过3H衰变）所抵消。这项研究支持大气氦作为实验室间同位素标准的适用性。2017年10月7日收到|2018年1月29日接受|发布时间2018年2月19日1. Centre de Recherches Pétrographiques et Géochimiques，CNRS and University de Lorraine，Vandøuvre-lès-Nancy，France 2.英联邦科学和工业研究组织，海洋和大气，Aspendale，澳大利亚 * 通讯作者（电子邮件：www.example.com; www.example.com）介绍大气氦是一种用作国际标准的痕量气体，其丰度和同位素组成可能受到人类活动的影响（例如，佐野等人，2010年）。因此，检查大气中的3He/4He比率（RAIR）是否随时间保持恒定至关重要。根据奥利弗等人（1984年）的研究，1939年至1981年期间，天然气（NG）的开采可能使全球大气中的氦含量增加了1 ‰至6 ‰。由于NG富含大陆地壳中产生的放射性4He，因此RAIR可能降低≤ 3 ‰/年（Brennwald等人，2013和其中的参考文献;也参见图S-1）。与这种可能性一致，已经报道了高炉冶金炉渣的囊泡中捕获的旧空气的3He过量（相对于当前RAIR值约3 - 4%）（Pierson-Wickman等人，2001;佐野等人，2010）和古代瓷器（Matsuda等人，2010年），这表明工业化前的空气比现在的空气含有更少的4He。然而，这些过量也可能与：（i）宇宙成因/核成因3He从样品基质的释放;（ii）氦提取期间的同位素分馏和（iii）制造期间分馏的RAIR的捕获有关（Pierson-Wickman等人，2001年）。RAIR值的时间变化的发生在几项研究中受到质疑。卢普顿和Evans（2013年）没有检测到来自美国加利福尼亚州拉霍亚的太平洋海洋空气的显著变化（通过直接比较1973年和2013年收集的拉霍亚空气获得的趋势为-0.014 ±0.045 ‰/年）。根据对1978年以来塔斯马尼亚不锈钢瓶中空气采样的分析（Cape Grim Air Archive，CGAA），Mabry等人（2015）得出结论，RAIR值在过去三十年中一直保持稳定（趋势为-0.0095 ± 0.0330 ‰/年）。这些作者认为，在早期研究中，全球生产的NG的平均氦含量被高估了约3倍，因此NG释放的4He可能不会在测量精度范围内影响RAIR值。在这里，我们的目标是限制RAIR的时间变化，这可能与1921年商业氦生产的开始有关（Mohr和Ward，2014）。为此，我们使用了大量的不锈钢材料中的空气，以确保自1910年以来氦气的长期保存。在我们选择的样品中捕获的空气体积（≥ 50 cm3）大于在炉渣/陶瓷的囊泡中捕获的空气体积，允许重复测量，因此更精确。
doi: 10.7185/geochemlet.1804 The atmospheric helium isotope composition (RA= He/Heair = 1.39 × 10-6) could have varied over recent times due to anthropogenic activities. In order to check this possibility, we conducted high-precision helium isotope measurements of air trapped in various stainless steel containers from France (pétanque balls, a float carburettor; 1910–2016) and Cape Grim, Tasmania (archived air tanks; 1978, 1988). We used a double collector mass spectrometer at the Centre de Recherches Pétrographiques et Géochimiques (CRPG, Nancy, France). We found a similar composition between the French and Cape Grim air samples. The temporal variation estimated from all samples including data previously published is not significant, with a trend of +0.002 ± 0.024 ‰/yr over 106 years (2σ). We suspect that the release of radiogenic 4He by fossil fuel exploitation could have been at least partly offset by the production of 3He (via the decay of 3H) from nuclear tests. This study supports the suitability of atmospheric helium as an inter-laboratory isotope standard. Received 7 October 2017 | Accepted 29 January 2018 | Published 19 February 2018 1. Centre de Recherches Pétrographiques et Géochimiques, CNRS and Université de Lorraine, Vandœuvre-lès-Nancy, France 2. Commonwealth Scientific and Industrial Research Organisation, Oceans and Atmosphere, Aspendale, Australia * Corresponding author (email: cboucher@crpg.cnrs-nancy.fr; christibouc@gmail.com) Introduction Atmospheric helium is a trace gas used as an international standard, whose abundance and isotope composition may be impacted by anthropogenic activities (e.g., Sano et al., 2010). It is therefore of the utmost importance to check if the atmospheric 3He/4He ratio (RAIR) has, or has not, been constant over time. According to Oliver et al. (1984), the exploitation of natural gases (NG) could have increased the global atmospheric helium content by 1 to 6 ‰ between 1939 and 1981. Because NG are rich in radiogenic 4He generated in the continental crust, the RAIR could have decreased by ≤3 ‰/yr (Brennwald et al., 2013 and references therein; see also Fig. S-1). In line with this possibility, 3He excesses (~3–4 % relative to the present RAIR value) have been reported for old air trapped in vesicles of blast-furnace metallurgical slags (Pierson-Wickman et al., 2001; Sano et al., 2010) and in ancient porcelains (Matsuda et al., 2010), suggesting that pre-industrial air contained less 4He than the present-day air. However, these excesses might also be related to: (i) the release of cosmogenic/nucleogenic 3He from the sample matrix; (ii) isotope fractionation during helium extraction and (iii) the capture of fractionated RAIR during manufacturing (Pierson-Wickman et al., 2001). The occurrence of temporal variations of the RAIR value has been questioned in several studies. Lupton and Evans (2013) did not detect significant variations in Pacific marine air from La Jolla, California, USA (trend of -0.014 ± 0.045 ‰/ yr obtained by direct comparison of La Jolla air collected in 1973 and 2013). From the analysis of air sampled in stainless steel bottles in Tasmania since 1978 (Cape Grim Air Archive, CGAA), Mabry et al. (2015) concluded that the RAIR value has been stable (trend of -0.0095 ± 0.0330 ‰/yr) over the last three decades. These authors argued that the mean helium content of globally produced NG has been overestimated by ~3 times in early studies, so that 4He released by NG may not have impacted the RAIR value within the precision of measurements. Here, we aim to constrain temporal variation of RAIR that could be related to the beginning of the commercial helium production in 1921 (Mohr and Ward, 2014). To do so, we used large amounts of air trapped in stainless steel materials insuring good preservation of helium over time since 1910. The air volume trapped in our selected samples (≥50 cm3), larger than that trapped in vesicles of slags/porcelains, allows repeated measurements and therefore more precision.