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Use of Long-lived Radionuclides for Dating Very Old Groundwaters
Closed for proposals
Project Type
Project Code
F33023CRP
2159Approved Date
Status
Start Date
Expected End Date
Completed Date
26 May 2023Participating Countries
Description
This CRP addresses the use of new tools for the estimation of very old groundwater ages (> 50000 years), which is one of the most elusive hydrological parameter to assess in the case of groundwater resources. With an increasing population and potential impact of climate change, groundwater extracted from deeper horizons is becoming the most important fresh water resource in many areas. Despite significance of age information for water resources, waste management, subsurface reactive transport, and paleoclimate, this parameter is always very difficult to assess. Additionally, ?comprehensive dating tools are not often available to many Member States.The main focus of this new CRP will be the implementation of several isotope hydrology assessments of deep/large aquifer systems using long-lived radionuclides, isotope age tracers and noble gases (carbon-14, krypton-81, chlorine-36, helium-4, etc…). These techniques are either hard to access or to implement in many member states. ? ? ? Following the recent increase in the analytical capacity of the IAEA’s noble gas facility, this CRP will provide the possibility to improve Member States’ capabilities in the assessment of deep groundwater systems by offering the combined use of the paleo-temperature estimates from isotopes of neon, argon, krypton and xenon and the age dating by helium-4 cross calibrated with other isotope techniques. Other noble gas isotopes, such as krypton-81, will also be analysed in selected samples. The case studies to be conducted as part of this CRP will provide a unique data set and excellent information for expanding the use of these age dating tracers to TC projects aiming at assessing deep aquifer systems in Member States.
Objectives
The overall objective of the CRP is to investigate the use of long-lived radionuclides, particularly 4He and 81Kr, to assess their reliability as age tracers of ‘old’ groundwaters. The estimated groundwater age produced from these long-lived radionuclides tracers will be compared with traditional isotopic and hydrochemical tracers in a variety of hydrogeological and climatic environments. Large, well-studied aquifers will be preferentially targeted by this CRP. ?The results obtained from this CRP will be used to produce a global database of long-lived radionuclides age estimations of groundwater. Once this database is compiled, the CRP will explore how groundwater residence times can be used to validate regional-scale groundwater flow models. The second important application is to use the calculated groundwater residence times to estimate the sustainable groundwater resource available into the future.
Specific objectives
Evaluate the performance of different sampling techniques and analytical methodologies for long-lived radionuclides.
Evaluate the usefulness of long-lived radionuclides in deep groundwater system for estimating groundwater ages. This will be completed through a structured program targeting different hydrogeological settings.
Explore the relationship between long-lived radionuclides and traditional hydrochemical tracers to understand their physical and chemical behavior in the different hydrogeological settings.
To understand the processes controlling the 4He accumulation rates in aquifers from different hydrogeological settings to reliably estimate the groundwater residence time (i.e. 4He vs. 81Kr).
Impact
The CRP has significantly advanced the use of long-lived radionuclides, such as 4He and 81Kr, as reliable tracers for groundwater age estimation, enabling better understanding of aquifer dynamics over extended timescales. Its contributions include the development of innovative sampling and analytical methodologies, which have been documented in a comprehensive TECDOC and disseminated through numerous peer-reviewed publications. The project also facilitated international collaboration, creating a global database of groundwater residence times and fostering partnerships among member states. Through targeted training programs, the CRP strengthened the technical capacity of participating teams, empowering them to apply isotope hydrology techniques in research and resource management. The outcomes of the CRP have already influenced sustainable groundwater management, policy development, and regional planning while setting the stage for future research initiatives, including a follow-up CRP focused on groundwater modelling integration.
Relevance
The CRP addressed a critical need for accurate tools to study old groundwater systems, filling gaps left by traditional tracers like 14C. Its focus on applying radionuclides to diverse hydrogeological settings ensured wide applicability, making its outputs relevant to regions with varying geological and climatic characteristics. By targeting sustainable water resource management and extending applications to paleoclimate studies, radioactive waste disposal, and hydrocarbon exploration, the CRP aligned with global priorities in environmental and resource management. Additionally, the CRP directly supported IAEA member states by building capacity through training and knowledge transfer, equipping participants with practical methodologies to address local and regional groundwater challenges. This combination of scientific innovation and practical utility underlines the CRP's essential role in addressing present and future hydrological needs.