Mapping uranium concentration in soil: Belgian experience towards a European map

Area of Science:

• Environmental Science
• Radiological Science
• Geochemistry

Background:

• Uranium (²³⁸U) mapping is vital due to its decay product, radon (²²²Rn), a major source of public exposure to natural ionizing radiation.
• The European Atlas of Natural Radiation aims to map natural radiation, with uranium concentration in soil being a key focus.
• Belgium offers a suitable case study for developing uranium mapping methodologies due to available diverse datasets.

Purpose of the Study:

• To develop and test methodologies for creating a European-scale map of uranium concentration in soil.
• To harmonize existing radiological and geochemical soil data with airborne survey data for improved accuracy.
• To assess the effectiveness of different spatial interpolation and data smoothing techniques for uranium mapping.

Main Methods:

• Construction of a harmonized uranium soil database by integrating radiological (non-airborne) and geochemical data.
• Calibration of airborne uranium survey data using the harmonized soil database.
• Application of spatial interpolation and data smoothing techniques, including moving average methods constrained by soil class and geological unit.

Main Results:

• A reasonable agreement was observed between maps generated from airborne uranium data and the harmonized soil uranium data at a 1 km x 1 km grid resolution across all tested methods.
• Map agreement improved significantly when data was aggregated to a 10 km x 10 km grid resolution.
• The 10 km x 10 km grid resolution is deemed suitable for the European map of uranium concentration in soil.

Conclusions:

• Harmonizing diverse datasets is effective for calibrating airborne uranium data and improving soil uranium mapping.
• Spatial interpolation and smoothing methods, particularly at coarser resolutions, can yield reliable uranium concentration maps.
• The developed methodology provides a foundation for creating a European-scale map of soil uranium concentration for the European Atlas of Natural Radiation.