Belgian NORM Observatory

ALLIANCE contact: Dr. Nathalie Vanhoudt


Site overview

The Belgian NORM site is a calcium difluoride sludge heap from the phosphate industry partly covered with vegetation such as pine trees, birch trees, grasses, shrubs, etc. Radionuclides present at the site, mainly 238U and its progeny, originate from phosphate ore processing. Contamination levels of 226Ra between 2000 and 6000 Bq kg-1 can be found in the soil and sludge together with co-contaminants such as As, Cd, Cr, Pb and Zn. Although remediation measures are ongoing, a small part of this site (approximately 1 ha) is available for the next five years (from 2020) to perform radioecological research in a NORM and chemically contaminated terrestrial ecosystem. Within this area, a monitoring station is already operational with equipment to follow solar irradiation, rainfall, temperature and sap flow in pine trees. Since the site is privately owned, by agreement with the site owner, permission to access and work there has to be obtained via SCK CEN ( and a working agreement needs to be signed.

Why is the Belgian NORM site a radioecological observatory?

The Belgian NORM site has several features making it interesting for radioecological research, including:

  • The site has a historical contamination (from 1930 to 1979) making it ideal to study the behaviour/mobility/transfer and effects (on vegetation) of a number of naturally occurring radionuclides (e.g. 238U, 226Ra, 210Po, 210Pb) in a long term exposure setting.
  • The presence of a mixture of radionuclides and metals makes it an excellent site to study the impact of mixed pollution in a terrestrial ecosystem.
  • The variety in vegetation present at the site makes it possible to study differences in uptake and effect between plant species.
  • The presence of CaF2 sludge as growth substrate, rather than ordinary soil, is a special situation relevant for other NORM waste heaps, leading to useful site-specific data for models.

ALLIANCE partners have further plans for conducting collaborative studies at the site such as:

  • Sampling campaigns will be set up, using research funds of the partners, to further characterise the site in order to gain more in-depth knowledge of processes determining radionuclide mobility and bioavailability in soil and sludge, and to compare radionuclide behaviour at different NORM sites.
  • Site specific data will be used to improve and/or validate radiological models.
  • Gathered data and knowledge will be shared between partners ensuring efficiency, continuity and sustainability in radioecological research.


ALLIANCE activities at the Belgian NORM observatory

The Belgian NORM site was proposed and developed within the EC-funded STAR and COMET projects to ensure joint long-term radiological research activities. ALLIANCE partners collaborated within the TERRITORIES project that was funded under the first call of the European Joint Programme CONCERT. In this project, a pine forest plot on the Belgian NORM site was instrumented with equipment to monitor energy and water cycles and seasonal variations in radionuclide distribution between soil/sludge and pine tree compartments (e.g. roots, bark, wood, branches, needles). The site acted as a case study to define uncertainties related to sampling and monitoring and to provide guidance in reducing these uncertainties (see Deliverable 9.60). The data obtained at the Belgian NORM site supported research towards the understanding and modelling of long-term influence of vegetation on radionuclide dispersion in forest ecosystems. It also allowed researchers to gain more in-depth knowledge on processes determining radionuclide mobility and bioavailability in soil, especially CaF2 sludges. Within the project, available data were compiled in a dedicated database together with data from other sites (See Deliverable 9.59) and they were used to support research aimed at reducing modelling uncertainties (see Deliverable 9.61).


Relevant ALLIANCE publications

Marko Kaasik, Juan C. Mora, Jordi Vives i Batlle, Nathalie Vanhoudt, Alan H. Tkaczyk, in press. Uncertainties in the use of concentration ratios for modelling NORM waste sites. Accepted for publication in Journal of Environmental Radioactivity.

Useful links

Information related to the TERRITORIES project is available on
The TERRITORIES library database is available on 

Photo credits: Prof. Jordi Vives i Batlle (SCK CEN), Dr. Nathalie Vanhoudt (SCK CEN), Axel Van Gompel (SCK CEN).

Page last updated: Apr/May 2020