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RADON RISK MAPPING IN SOUTHERN BELGIUM: AN APPLICATION OF GEOSTATISTICAL AND GIS TECHNIQUES

H.C. Zhu * , J.M. Charlet* and A.Poffijn**
* Faculte Polytechnique de Mons, Rue de Houdain 9, 7000 Mons, Belgium
Huichao.Zhu@hydro.fpms.ac.be, Jean-Marie.Charlet@hydro.fpms.ac.be
** Ministry of Public Health, Radiation Protection Unit, Brussels
Andre.Poffijn@Health.fgov.be

A data set of long-term radon measurements in about 2200 houses in southern Belgium has been collected
in an on-going national Rn survey. The spatial variation of indoor Rn concentrations is modelled by
variograms. A radon distribution map is produced using the lognormal kriging technique. A GIS is used
to digitise, process and integrate a variety of data, including geological maps, Rn concentrations
associated with house locations and an administrative map etc. It also allows to evaluate the relationships
between various spatial data sets with the goal of producing radon risk maps. Based on geostatistical
mapping and spatial analysis, we define three categories of risk areas: high risk, medium risk and low risk
area. The correlation between radon concentrations and geological features is proved in this study. High
and medium Rn risk zones are dominantly situated in bedrock from the Cambrian to Lower Devonian,
although a few medium risk zones are within the Jurassic. It is evident that high risk zones are related to
strongly folded and fractured context.
Keywords: Geostatistics; variogram; Lognormal kriging; Geographical information system (GIS); Spatial
analysis; Radon, indoor; Geology; Risk mapping