High-precision helium isotope measurements in air
High-precision helium isotope measurements in air
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DOI：
10.1039/c3ja50155h
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发表时间：
2013-11
影响因子：
3.4
通讯作者：
J. Mabry;T. Lan;P. Burnard;B. Marty
中科院分区：
文献类型：
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作者：
J. Mabry;T. Lan;P. Burnard;B. Marty
氦有两种不同的天然同位素，在大气中的来源和汇都不同（3 He/4 Heair = 1.382 ± 0.005 × 10−6）。大气氦同位素组成的变化可能低于典型的测量精度阈值（0.2至0.5%，2σ）。为了研究这种可能性，有必要能够以高精度（低于0.2%2 σ）持续测量空气中的氦同位素。我们已经创建了一个空气净化和测量系统，提高了氦同位素测量精度。通过在测量周期开始时净化大量空气，我们可以快速进行标准范围内的测量。控制每个测量等分试样中的氦气量可以最大限度地减少压力影响。用这种方法，我们将标准误差提高了2倍，在一个单一的步骤中测量相同数量的气体。单个测量的标准误差为0.2至0.3%（2σ），需要三个重复样品才能达到0.1%或更好的误差。校准样品的长期重现性为0.033%（2σ）。
Helium has two natural isotopes which have contrasted, and variable sources and sinks in the atmosphere (3He/4Heair = 1.382 ± 0.005 × 10−6). Variations in the atmospheric helium isotopic composition may exist below typical measurement precision thresholds (0.2 to 0.5%, 2σ). In order to investigate this possibility, it is necessary to be able to consistently measure helium isotopes in air with high precision (below 0.2% 2σ). We have created an air purification and measurement system that improves the helium isotope measurement precision. By purifying a large quantity of air at the start of a measurement cycle we can make rapid standard-bracketed measurements. Controlling the amount of helium in each measured aliquot minimizes pressure effects. With this method we improve the standard errors by 2× over measuring the same amount of gas in a single step. Individual measurements have standard errors of 0.2 to 0.3% (2σ), with three repeat samples needed to reach 0.1% or better errors. The long-term reproducibility of our calibration sample is 0.033% (2σ).