Preliminary studies on the spatial distribution of artificial 137Cs and natural gamma radionuclides in the region of the Ojców National Park, Poland

The aim of the research is to obtain preliminary information about the spatial distribution of gamma radionuclides in the soils taken from the Ojcow National Park with emphasis on the behaviour of artificial radionuclides, with Cs-137 as a representative. The natural radionuclides K-40, Ra-226 (uranium series), and Th-228 (thorium series), which are considered as background radiation, were also determined. In total, 18 soil samples were collected during the summer periods in 2015-2017, while the sampling points were selected with respect to differences in rainfall and local topography gradient. The method was based on gamma-ray spectrometry performed on high-purity germanium (HPGe) gamma detector (relative efficiency 34%). Cs-1(37) was mostly deposited in the top soil layers, with activity in the range of 27.9 divided by 586.6 Bq.kg(-1). We found strong positive correlation of the Cs-1(37) activity with the soil organic matter content, and at the same time, its dependence on the rainfall amount. Consequently, the soil types and local climate can control the spatial distribution of Cs-1(37) on a small spatial scale. The quantity of natural radionuclides was highly similar in all samples with the following mean values: 38.0 Bq.kg(-1) for Th-228, 33.1 Bq.kg(-1) for Ra-226 and 479.9 Bq.kg(-1) for K-40.