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Use of Long-lived Radionuclides for Dating Very Old Groundwaters (F33023)

(Photo: IAEA)

CRP at a Glance

The increasing global water demand for agriculture, domestic and industrial uses, combined with the impact of pollution and climate change on surface waters, is forcing local water authorities to rely more and more on groundwater. Shallow aquifers, containing groundwater recently recharged, are initially used in first instance, often in a conjunctive manner with water supply sources derived from rivers or lakes. However, intense exploitation of these shallow aquifer systems often leads to important lowering of the water tables, water quality deterioration, soil subsidence and other environmental impacts. Exploration and exploitation of deeper aquifer systems, containing older groundwater, probably recharged thousands of years ago or at distant areas, is often the next option used as a source of water. A proper understanding of the origin, history and dynamics of old groundwaters found in deep aquifers is a key pre-requisite for the assessment of the reliability and potential of these resources as a major source of water supply in medium and long-terms.
Recent breakthrough developments in analytical methods (e.g., Atom trap trace analysis) allow the precise determination of dissolved noble gases, such as Helium-4, as well as trace-level noble gas radionuclides, such as Krypton-81, present in very old groundwaters. The long half-life and the lack of geochemical interactions make these isotopes excellent tracers to estimate groundwater ages and dynamics.

Nuclear Component

Measurement and interpretation of stable and radioactive isotopes present in groundwater samples (e.g, 18O, 2H, 14C-13C of DIC, Helium-4, Krypton-81 and other noble gas isotopes) collected in deep aquifers studied by the CRP participants.

CRP Overall Objective

To assess the usefulness of the recently available long-lived radionuclides, isotope age tracers and noble gases (Carbon-14, Krypton-81, Chlorine-36, Helium-4, etc…), coupled with groundwater flow modelling to better understand and assess deep groundwater systems as long-term source of water supply.

Noble gas sampling (Photo:IAEA)

Field equipment for noble gas sampling (Photo: IAEA)

Noble gas analytical system (Photo: IAEA)

Specific research objectives

  1. To assess and improve the use of newly available radioisotopes and related age indicators to investigate groundwater age and dynamics of deep aquifers containing old groundwaters
  2. To improve the interpretation of hydrological processes, pathways and interactions between groundwater bodies in large sediment basins
  3. To explore mechanisms controlling sizes of subsurface 4He flux entering deep aquifer at different hydrogeological settings in order to better calibrate 4He accumulation ages and ultimately to enable on-site estimation by using a fieldable mass spectrometer
  4. To prepare conceptual models and help in the development and calibration of mathematical models to simulate groundwater flow and transport

Expected research outcomes

  1. More experienced counterparts in Member States in the planning and implementation of environmental isotopes studies aiming at the assessment of groundwater dynamics and age of deep aquifer systems
  2. Better understanding and assessment of deep groundwater systems as long-term source of water supply

How to join the CRP?

Please submit your Proposal for Research Contract or Agreement directly to the IAEA’s Research Contracts Administration Section, using the form templates (http://cra.iaea.org/cra/forms.html) on the CRA web site (preferably via email): [email protected]