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MAPPING THE GEOGENIC RADON POTENTIAL IN GERMANY

J. Kemski + , A. Siehl * , R. Stegemann * , M. Valdivia-Manchego *
* Institute of Geology, University of Bonn, Nussallee 8, D-53115 Bonn, Germany
tel.: ++49 228 73-2399, fax: ++49 228 73-9037, e-mail: siehl@uni-bonn.de; stegeman@geo.uni-bonn.
de + Kemski, Klingel & Veerhoff, von-Weichs-Str. 9a, D-53121 Bonn, Germany
tel.: ++49 228 6200910, fax: ++49 228 6200913, e-mail: kemski@kkv-bonn.de

Mapping the geogenic radon potential in Germany is a research project initiated by the German
Federal Ministry for the Environment, Conservation and Reactor Safety. The project was aimed to
develop a standard methodology for the estimation of a geogenic radon potential and to apply this
method to map the region of Germany as an overview for planning purposes. The regionalisation
results from a distance-weighted interpolation of the site-specific values of radon concentration in soil
gas and in-situ gas permeability of soils on a regular grid considering the corresponding geological
units. The map of Germany in a scale of 1: 2 Million is based on the radon concentration in soil gas as
an estimator of the geogenic radon potential assuming the “worst case“ of uniform highest
permeability. The distribution is subdivided into categories of low (< 10 kBq/m 3 ) - medium (10 - 100
kBq/m 3 ) - increased (100 - 500 kBq/m 3 ) and high (> 500 kBq/m 3 ) radon concentration. High values
occur especially in regions with granites and basement rocks of Paleozoic age, and are proven by
measurements in 0,03 % of the total area. Many of these regions are also known for their enhanced
indoor values. The class with increased values takes a portion of 7,86 % and likewise occurs mainly in
regions with outcrops of folded and metamorphic basement, but also of some Meso- and Cenozoic
sediments with increased uranium contents and/or higher emanation coefficients. For 67,3 % of the
country, the radon concentration is classified as “medium“, and an assignment to specific geological
units cannot be made at the map scale considered. Low radon contents, where protective measures
against radon usually have not to be considered, are found in the geologically rather homogeneous part
of northern Germany with unconsolidated Cenozoic sediments, covering about 25 % of the total
country. It is of course not possible to predict the indoor radon concentration of single houses from
these maps, because construction type and structural fabric of houses are essentially governing the
extent to which subsoil radon potential affects the indoor concentration. Besides this, in places with
site-specific geochemical, structural and soil-physical properties, local radon anomalies may occur
which were not recorded in the course of the wide-meshed screening study.
Keywords: Radon mapping, geology, geogenic radon potential, radon activity concentration in soil
gas, gas permeability