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INFLUENCE OF UNDERGROUND MINING ON THE GEOGENIC RADON POTENTIAL

R. Klingel 1 , J. Kemski 2
1 Institute of Geology, Bonn University
Nussallee 8, D-53115 Bonn, Germany
tel.: ++49 228 73 2488, fax: ++49 228 73 9037, e-mail: klingel@geo.uni-bonn.de 2 Kemski, Klingel & Veerhoff, Consulting Geologists
Von-Weichs-Strasse 9a, D-53121 Bonn, Germany
tel.: ++49 228 6200910, fax: ++49 228 6200913, e-mail: kemski@kkv-bonn.de

Different aspects of the geogenic radon potential in a coal mining area in south-western Germany are
discussed. Due to the rather low specific radium activities of rocks and soils varying between 10 and
70 Bq/kg a low geogenic radon potential can be expected. Radon concentrations in soil gas in
abandoned mining areas are characterized by a lognormal distribution with a median value of 20
kBq/m 3 . In the neighboring area with deep mining generally younger than two years, radon contents
increase up to a median value of 38 kBq/m 3 . The radon background in mining areas can be
superimposed by an advective, structurally controlled component. Actually, narrow mining induced
fracture zones constant in time and adjacent to the mining area often show radon peaks in soil gas four
to five times higher than the background reaching values of more than 100 kBq/m 3 . A positive
correlation between methane and radon at methane degassing spots is probably caused by a CH4 flow,
which collects radon from the soil and carries it up to the surface. Indoor measurements in about 100
houses over a period of three months were conducted. The radon concentrations on ground floor are
not influenced by the mining activities. In the basement, however, higher radon concentrations were
detected. A time-dependent spatial shift of high indoor values following the direction of underground
coal mining can be explained by the disturbance of the rock system strength in the subsurface leading
to tectonic movements just above the recent mining area.
Key words: deep mining, geogenic radon potential, indoor radon, radon in soil gas