Spatial analysis of the atmospheric helium isotopic composition: Geochemical and environmental implications
Spatial analysis of the atmospheric helium isotopic composition: Geochemical and environmental implications
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大气氦同位素组成的空间分析：地球化学和环境影响
DOI：
10.1016/j.gca.2018.06.010
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发表时间：
2018
影响因子：
5
通讯作者：
B. Marty
中科院分区：
文献类型：
--
作者：
Christine Boucher;T. Lan;T. Lan;J. Mabry;J. Mabry;D. Bekaert;P. Burnard;B. Marty
大气氦同位素组成的空间变化（RA=3He/4Heair= 1.39 × 10−6）可能是由局部和/或区域输入的3He和/或4he引起的。油气开采输入的氦可能导致大气氦/氦的纬向变化。为了测试这种全球变化的可能性，我们对2013年至2015年间在世界各地（79°N-75°S）的500个 cc金属瓶中收集的16个空气样本的氦同位素组成（3He/4He）进行了高精度分析。在大多数情况下，这些空气样本的3he /4He与法国Nancy周围采样的空气样本在≤2‰（95%置信区间）内无法区分。只有在南极C圆顶和日本东京采集的两个空气样品显示出统计上较高的he /4He比率，分别为（2.0 ± 1.4）‰和（1.7 ± 1.5）‰（95%置信区间）。这样的过量表明，空气中潜在的氦同位素变化可能低于4‰，可能是由区域和/或局部现象（例如极光降水、平流层到对流层的交换）暂时产生的。因此，本研究支持使用大气氦同位素比作为实验室间He标准。
Spatial variations in the atmospheric helium isotopic composition (RA=3He/4Heair= 1.39 × 10−6) might be induced by localized and/or regional inputs of3He and/or4He into the air. It has been suggested that inputs of4He from hydrocarbon exploitation may generate latitudinal variations in atmospheric3He/4He. In order to test the possibility of such global variations, we performed high precision analyses of the helium isotopic composition (3He/4He) of sixteen air samples collected in 500 cc metal bottles around the world (79°N–75°S) between 2013 and 2015. In most cases, the3He/4He of these air samples are indistinguishable from that of air sampled around Nancy (France) within ≤2‰ (95% confidence interval). Only two air samples, collected at Dome C (Antarctica) and at Tokyo (Japan), exhibit statistically higher3He/4He ratios interpreted as potential3He excesses of (2.0 ± 1.4)‰ and (1.7 ± 1.5)‰ (95% confidence interval), respectively. Excesses such as these suggest that potential helium isotopic variations in air are likely lower than 4‰ and might be generated temporarily by regional and/or local phenomenon (e.g. auroral precipitation, stratospheric to tropospheric exchanges). Thus, this study supports the use of the atmospheric helium isotopic ratio as an inter-laboratory He standard.