Short-lived natural radionuclides as tracers in hydrogeological studies - A review.

Fundamental approaches to the study of groundwater rely on investigating the spatial and temporal distribution of stable and radioactive isotopes and other anthropogenic compounds in natural waterbodies. The most often used tracers for estimating groundwater flow paths and residence times, groundwater/surface water interaction as well as tracing chemical (contamination) sources include stable isotopes of water (δ O and δ H), radiocarbon (C; t = 5730 a), tritium (H; t = 12.43 a) as well as unreactive fluorine-containing gases (e.

Global and local meteoric water lines for δO/δO and the spatiotemporal distribution of Δ'O in Earth's precipitation.

Recently, δO and its excess (Δ'O) have become increasingly significant "triple-oxygen-isotope" indicators of distinctive hydrological processes in hydrology and climatology. This situation mirrors the research regarding δO and δH in the 1960s towards a solid theoretical base and a surge in application examples and field studies worldwide. Currently, systematic global measurements for δO in precipitation are still lacking.

Balancing precision and throughput of O and Δ'O analysis of natural waters by Cavity Ringdown Spectroscopy.

O and Δ'O are emerging tracers increasingly used in isotope hydrology, climatology, and biochemistry. Differentiating small relative abundance changes in the rare O isotope from the strong covariance with O imposes ultra-high precision requirements for this isotope analysis. Measurements of O by Cavity Ringdown Spectroscopy (CRDS) are attractive due to the ease of sample preparation, automated throughput, and avoidance of chemical conversions needed for isotope-ratio mass spectrometry.

High spatial resolution prediction of tritium (H) in contemporary global precipitation.

Tritium (H) in Earth's precipitation is vigilantly monitored since historical nuclear bomb tests because of radiological protection considerations and its invaluable role as a tracer of the global water cycle in quantifying surface, groundwater, and oceanic fluxes. For hydrological applications, accurate knowledge of H in contemporary local precipitation is prerequisite for dating of critical zone water and calibrating hydrogeologic transport and groundwater protection models. However, local tritium input in precipitation is hard to constrain due to few H observation sites.

Progress and challenges in dual- and triple-isotope (δ O, δ H, Δ O) analyses of environmental waters: An international assessment of laboratory performance.

Rationale: Stable isotope analyses of environmental waters (δ H, δ O) are an important assay in hydrology and environmental research with rising interest in δ O, which requires ultra-precise assays. We evaluated isotope analyses of six test water samples for 281 laboratory submissions measuring δ H and δ O along with a subset analyzing δ O and Δ O by laser spectrometry and isotope ratio mass spectrometry (IRMS).

Methods: Six test waters were distributed to laboratories spanning a wide δ range of natural waters for δ H, δ O and δ O and Δ O.

Performance of low-cost stainless-steel beverage kegs for long-term storage integrity and easy dispensing of water isotope (δ O, δ H) reference materials.

Rationale: A widespread problem observed in global water isotope (δ O, δ H) proficiency tests is compromised working reference materials due to storage-dispensing evaporation effects. Proper storage requires no evaporation or leakage, which causes isotopic drift and bias. Surveys by the International Atomic Energy Agency (IAEA) show most isotope laboratories use glass or plastic bottles to store working reference materials, with frequent opening and closings that pose evaporation risks.

Comparative evaluation of H- versus H-based enrichment factor determination on the uncertainty and accuracy of low-level tritium analyses of environmental waters.

Analysis of low-level tritium (H) in environmental waters requires pre-concentration using electrolytic enrichment prior to decay counting. Accurate and precise electrolytic enrichment factors (EF) are required to determine the sample's environmental H concentration. Two methods are used to determine EFs: i) the Spike Proxy Method (SPM) and ii) the Deuterium Method (DM) with each having several modalities.

The first IAEA inter-laboratory comparison exercise in Latin America and the Caribbean for stable isotope analyses of water samples.

The use of stable isotopes ( H and O) is widespread in water resources studies. In the Latin America and the Caribbean (LAC) region, the application of isotope techniques has increased in the past decade, but there remains room to gain self-reliance in environmental isotope studies, necessitating easy and fast access to good-quality isotope data. To that end, in 2018 the IAEA carried out the first regional interlaboratory comparison exercise, testing the analytical performance of 25 laboratories using isotope-ratio mass spectrometry and laser absorption spectroscopy.

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 ( 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.

Methods: Seven test waters were distributed by the IAEA to 78 international tritium laboratories.

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

Accurate and precise measurements of low levels of tritium (H) 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.