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

A. A. Ochmann


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.



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DOI: https://doi.org/10.4401/ag-3186

Published by INGV, Istituto Nazionale di Geofisica e Vulcanologia - ISSN: 2037-416X