Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA94550, USA.
Rapid Commun Mass Spectrom. 2013 Nov 15;27(21):2472-82. doi: 10.1002/rcm.6704.
Noble gases dissolved in groundwater can reveal paleotemperatures, recharge conditions, and precise travel times. The collection and analysis of noble gas samples are cumbersome, involving noble gas purification, cryogenic separation and static mass spectrometry. A quicker and more efficient sample analysis method is required for introduced tracer studies and laboratory experiments.
A Noble Gas Membrane Inlet Mass Spectrometry (NG-MIMS) system was developed to measure noble gases at natural abundances in gas and water samples. The NG-MIMS system consists of a membrane inlet, a dry-ice water trap, a carbon-dioxide trap, two getters, a gate valve, a turbomolecular pump and a quadrupole mass spectrometer equipped with an electron multiplier. Noble gases isotopes (4)He, (22)Ne, (38)Ar, (84)Kr and (132)Xe are measured every 10 s.
The NG-MIMS system can reproduce measurements made on a traditional noble gas mass spectrometer system with precisions of 2%, 8%, 1%, 1% and 3% for He, Ne, Ar, Kr and Xe, respectively. Noble gas concentrations measured in an artificial recharge pond were used to monitor an introduced xenon tracer and to reconstruct temperature variations to within 2 °C. Additional experiments demonstrated the capability to measure noble gases in gas and in water samples, in real time.
The NG-MIMS system is capable of providing analyses sufficiently accurate and precise for introduced noble gas tracers at managed aquifer recharge facilities, groundwater fingerprinting based on excess air and noble gas recharge temperature, and field and laboratory studies investigating ebullition and diffusive exchange.
溶解在地下水中的稀有气体可以揭示古温度、补给条件和精确的迁移时间。稀有气体样品的采集和分析繁琐，涉及稀有气体的净化、低温分离和静态质谱分析。需要更快、更有效的样品分析方法，以进行引入示踪剂的研究和实验室实验。
开发了一种用于测量气体和水样中天然丰度稀有气体的稀有气体膜进样质谱（NG-MIMS）系统。NG-MIMS 系统由膜进样器、干冰水阱、二氧化碳阱、两个吸气剂、门阀、涡轮分子泵和配备电子倍增器的四极质谱仪组成。每 10 秒测量一次稀有气体同位素（4）He、（22）Ne、（38）Ar、（84）Kr 和（132）Xe。
NG-MIMS 系统可以复制传统稀有气体质谱系统的测量结果，He、Ne、Ar、Kr 和 Xe 的精度分别为 2%、8%、1%、1%和 3%。在人工补给池塘中测量的稀有气体浓度可用于监测引入的氙示踪剂，并将温度变化重建到 2°C 以内。额外的实验证明了实时测量气体和水样中稀有气体的能力。
NG-MIMS 系统能够提供足够准确和精确的分析结果，用于管理含水层补给设施中的引入稀有气体示踪剂、基于过剩空气和稀有气体补给温度的地下水指纹识别，以及研究沸腾和扩散交换的现场和实验室研究。
