Investigation of natural radioisotope activities in forest soil horizons

Activities of radioisotopes were measured in samples of forest soil. The samples were collected in forests situated along the roads from Złoty Stok (Poland) to Hradec Králové (Czech Republic). Each soil profile was separated into individual horizons and subhorizons. Activities of radioisotopes were measured in the sample of each soil horizon. Activities of the following radioisotopes were determined by gamma-ray spectrometry: 214Pb, 214Bi, 231Th, 235U, 212Pb, 212Bi and 228Ac. Distributions of the data concerning radioactivities were positively skewed. The lowest activity was found for 235U (median value was 2.25 Bg/kg) and the highest one for 228Ac (16.26 Bg/kg in median). In organic horizons activities of radionuclides were lower than in organic ones. Interrelation between activities was examined using ordinary and robust regression methods. It was found that activities of the radioisotopes were well correlated.