Distribution of radon activity in the atmosphere above Wzgórza Niemczansko-Strzelinskie (South-WestPoland) and its dependence on uranium and thorium content in the underlying rock and indirect ground basement

• Main Author: A. A. Ochmann
• Format: Article
• Language: English
• Published: Istituto Nazionale di Geofisica e Vulcanologia (INGV) 2005-06-01
• Series: Annals of Geophysics
• Subjects: radon; atmosphere; uranium; thorium; rock
• Online Access: http://www.annalsofgeophysics.eu/index.php/annals/article/view/3186
• ISSN: 1593-5213; 2037-416X

Radon activity in the atmosphere and its behavior in the environment have been investigated using LR-115 nuclear
 track detector. The complex geological structure of Wzgórza Niemczansko-Strzelinskie (south-west
 Poland) enabled this problem to be studied in various geological conditions. The eU and eTh content in rocks
 and soil was measured by gamma-spectrometer GR-320. Uranium content of bedrock reached its maximum
 value of 15 ppm in the case of quartz-graphite schist. Thorium reached its maximum value of 35 ppm in the
 case of granodiorite. Radon activity was measured by means of long-term exposure of LR-115. The mean value
 of atmospheric radon activity was 21 Bqm-3 in the air 2 m above the ground surface. The highest radon activities
 were measured in the area of granite and quartz-graphite schist outcrops and in the area of mylonitic
 rocks of the Niemcza Zone. Radon activity in close to ground cup detectors varies from 25 to 300 Bqm-3, these
 values depend on uranium and thorium content in indirect ground basement (soil and weathered rocks). Not
 only uranium and thorium content but also rock disintegration due to tectonic events (shear zones) influenced
 atmospheric radon activity. Seasonal variation is not strong, although higher values were measured in the autumn-
 winter period.