Obsahy přirozených radioaktivních prvků (K, U, Th) v půdách na mapovém listu 24-22 Olomouc – vztah mezi radioaktivitou půdy a matečné horniny

Abstract

The paper deals with natural radioactivity of soils on the map sheet 24-22 Olomouc and compares contents of natural radioactive elements in soils and in their parent rocks (soilforming substrates). Three main types of parent rocks can be distinguished in the studied area: i) siliciclastic flysch sediments of the Moravo-Silesian Palaeozoic, ii) Quaternary sediments of the river Morava floodplain, iii) Quaternary loesses. Contents of potassium, uranium and thorium were measured using a laboratory gamma–ray spectrometer in 1 077 soil samples. It is evident from calculated values of mass activity of 226Ra equivalent (am) that natural radioactivity of the studied soils is low. The average am of soils developed on siliciclastic flysch sediments is 142 Bq.kg-1, 133 Bq.kg-1 on fluvial sediments of the river Morava and 148 Bq.kg-1 on loesses. The average am values calculated for soils developed on siliciclastic flysch sediments and for soils on loesses are almost the same as average am values calculated for their parent rocks. The soils of the river Morava floodplain show higher am values compared to their parent material (sands and pebbles dominate) due to higher uranium and thorium contents.