Natural radioactivity in select metamorphic and sedimentary rocks of the Opava Mountains (Poland): A comparison between laboratory and in situ measurements of 232Th, 238U, and 40K activities

rocks from the Opava Mountains region (Eastern Sudetes, Poland) as measured in the laboratory and under in situ field conditions. Activity concentrations for 232Th, 238U, and 40K were obtained using an HPGe gamma-ray spectrometry system. Activities for 232Th ranged from 2 to 39 Bq kg−1 as measured in the laboratory and from 5 to 38 Bq kg−1 measured under in situ field conditions. For 238U, the activity concentrations ranged from 4 to 37 Bq kg−1 in the laboratory and from 7 to 42 Bq kg−1 under in situ field conditions. For 40K, activity concentrations ranged from 12 to 820 Bq kg−1 in the laboratory and from 60 to 826 Bq kg−1 under in situ field conditions. Measured activity concentrations were compared with average activity concentrations of radionuclides in similar types of rocks from different global localities. The in situ field measurement and laboratory measurements did not show significant differences indicating that both methods provide reliable 232Th, 238U, and 40K results for different lithologies.