Proficiency testing of 78 international laboratories measuring tritium in environmental waters by decay counting and mass spectrometry for age dating and water resources assessment.

RATIONALE: Tritium (3 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 3 H assays for water age dating and monitoring of environmental waters. METHODS: Seven test waters were distributed by the IAEA to 78 international tritium laboratories. Set 1 included a tritium-free groundwater plus three ultra-low 3 H samples (0.5-7 TU) for meeting groundwater dating specifications. Set 2 contained three higher 3 H-content samples (40-500 TU) suitable for testing of environmental monitoring laboratories. RESULTS: Seventy of the laboratories used liquid scintillation counting with or without electrolytic enrichment, seven utilized 3 He accumulation and mass spectrometry, and one used gas-proportional counting. Only ~50% of laboratories demonstrated the ability to generate accurate 3 H data that was precise enough for water age dating purposes. CONCLUSIONS: The proficiency test helped identify recurrent weaknesses and potential solutions. Strategies for performance improvements of 3 H laboratories include: (a) improved quantification of 3 H detection limits and analytical uncertainty, (b) stricter quality control practices in routine operations along with care and recalibration of 3 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 3 H enrichment factors (e.g. >50×).

A laboratory information management system for the analysis of tritium (3H) in environmental waters.

Accurate and precise measurements of low levels of tritium (3H) in environmental waters are difficult to attain due to complex steps of sample preparation, electrolytic enrichment, liquid scintillation decay counting, and extensive data processing. We present a Microsoft Access™ relational database application, TRIMS (Tritium Information Management System) to assist with sample and data processing of tritium analysis by managing the processes from sample registration and analysis to reporting and archiving. A complete uncertainty propagation algorithm ensures tritium results are reported with robust uncertainty metrics. TRIMS will help to increase laboratory productivity and improve the accuracy and precision of 3H assays. The software supports several enrichment protocols and LSC counter types. TRIMS is available for download at no cost from the IAEA at www.iaea.org/water.