International Atomic Energy Agency, Vienna International Centre, Vienna, A-1400, Austria.
Department of Earth Sciences, South Parks Road, University of Oxford, Oxford, OX1 3AN, UK.
Rapid Commun Mass Spectrom. 2020 Sep 15;34(17):e8832. doi: 10.1002/rcm.8832.
Tritium ( H) is an important hydrological tracer that has been commonly used for over 60 years to evaluate water residence times and water dynamics in shallow/recent groundwaters, streams, lakes and the ocean. We tested the analytical performance of 78 international laboratories engaged in low-level H assays for water age dating and monitoring of environmental waters.
Seven test waters were distributed by the IAEA to 78 international tritium laboratories. Set 1 included a tritium-free groundwater plus three ultra-low H samples (0.5-7 TU) for meeting groundwater dating specifications. Set 2 contained three higher H-content samples (40-500 TU) suitable for testing of environmental monitoring laboratories.
Seventy of the laboratories used liquid scintillation counting with or without electrolytic enrichment, seven utilized He accumulation and mass spectrometry, and one used gas-proportional counting. Only ~50% of laboratories demonstrated the ability to generate accurate H data that was precise enough for water age dating purposes.
The proficiency test helped identify recurrent weaknesses and potential solutions. Strategies for performance improvements of H laboratories include: (a) improved quantification of H detection limits and analytical uncertainty, (b) stricter quality control practices in routine operations along with care and recalibration of H standards traceable to primary NIST standards, (c) annual assessment of tritium enrichment factors and instrumental performance, and (d) for water age dating purposes the use of electrolytic enrichment systems having the highest possible H enrichment factors (e.g. >50×).
氚（H）是一种重要的水文示踪剂，已被广泛应用超过 60 年，用于评估浅层/近期地下水、溪流、湖泊和海洋中的水停留时间和水动力。我们测试了 78 个从事低水平 H 分析以进行水龄测定和环境水监测的国际实验室的分析性能。
国际原子能机构（IAEA）向 78 个国际氚实验室分发了 7 种测试水。第 1 组包括一种无氚地下水和三种超低 H 含量的样品（0.5-7 TU），以满足地下水定年的要求。第 2 组包含三种 H 含量较高的样品（40-500 TU），适合用于环境监测实验室的测试。
70 个实验室使用了液体闪烁计数法，或使用或不使用电解富集法，7 个实验室使用了 He 积累和质谱法，1 个实验室使用了气体比例计数法。只有约 50%的实验室能够生成准确的 H 数据，其精度足以满足水龄测定的目的。
该能力验证测试有助于确定常见的弱点和潜在的解决方案。H 实验室的性能改进策略包括：（a）提高 H 检测限和分析不确定度的定量能力，（b）在常规操作中加强质量控制实践，同时对 H 标准进行严格的溯源和重新校准，（c）每年评估氚富集因子和仪器性能，以及（d）对于水龄测定目的，使用具有尽可能高的 H 富集因子（例如>50×）的电解富集系统。
