Influence of geology on enhanced indoor radon concentrations in dwellings situated on low radon index bedrock

 

Ivan Barnet, Petra Pacherová, Ivana Fojtíková

Geoscience Research Reports 41, 2008 (GRR for 2007), pages 137–142

Full text (PDF, 1.18 MB)

 

Abstract

Indoor radon concentration in 8.5 % of dwellings situated on the low risk rock types exceeds the action level of 400 Bq.m-3. These dwellings are situated (1) in the contact rim of the Central Bohemian plutonic complex in hornfelses and in the island zone of the plutonic complex in paleoandesites, (2) in Neogene sediments overlying durbachite-syenite basement near Vodnany, (3) in Cretaceous sediments of Eastern Bohemia underlaid by granitoids, and (4) on tectonically influenced Carpathian flysch sediments (SE Moravia). All four areas fit to courses of deep seated faults in the Bohemian Massif and of minor local tectonics in the front of Outer Carpathian nappes. Three possible causes of higher indoor radon concentrations are discussed for particular areas: P-T metamorphic influence of granitoid intrusions, presence of granitoids in geological basement under the low risk sediments and presence of fault zones. The spatial distribution of above mentioned dweelings indicates the possibility of convective radon transport by carrier media (water and gas) through the tectonically weakened zones of regional scale. The low radon risk from bedrock was succesfully predieted for 92.5 % of dwellings.