## 4 Discussion  
The average values of natural radionuclides concentration obtained in the study are significantly lower than the values obtained for Poland (Table 2). More specifically, they are close to the minimum values obtained for Poland, which are: 4.20 Bqkg\({}^{-1}\) for radium \({}^{226}\)Ra, 370 Bqkg\({}^{-1}\) for thorium \({}^{232}\)Th, and 123 Bqkg\({}^{-1}\) for potassium \({}^{40}\)K [2]. Concentrations of natural radionuclides in the soils in Europe and worldwide average are, respectively from 3 to 5 times and from 3 to 7 times higher than concentrations of radionuclides in the Poleski National Park (Table 4). According to the other research conducted in Bosnia and Herzegovina, Croatia, and Republic of Serbia, natural radionuclides concentrations in the soils were mainly higher than the values obtained for the Poleski National Park and worldwide average. The content of natural radionuclides in the soil similar to the study  
Figure 6: The concentration of metals for individual measurement points in the Poleski National Park (mg/kg). Figure 7: The index of geoaccumulation of metals in soil samples of individual sampling points in the Poleski National Park. was obtained by [PERSON] et al. [44] in Shatsk National Natural Park in Ukraine. Such concentrations of natural radionuclides are influenced by the geochemical structure of the soil. Moreover, isotopes such as potassium \({}^{40}\)K are long-lived and others are in a radioactive equilibrium with the other members of the appropriate radioactive series ([PERSON] et al., 2004 [44]). It should be highlighted that contents of radium \({}^{226}\)Ra/uranium\({}^{238}\)U are mainly similar to actinium \({}^{228}\)Ac/thorium \({}^{232}\)Th. According to some studies, there is a strong correlation between the radionuclides since the decay series occurs together in nature [45; 46]. Among anthropogenic radionuclides prevalent in the environment, cesium \({}^{137}\)Cs and plutonium Pu isotopes are of great concern [52]. Those radionuclides occur in the environment due to the nuclear weapon tests, accidents at nuclear reactors, and discharges of radioactive waste from nuclear installations [51; 53; 54]. In Poland, anthropogenic radionuclides are mainly due to the Chernobyl accident which contributed to the spread of many fission products mainly in the northern hemisphere [55]. The concentration of cesium \({}^{137}\)Cs in Poland depends on several factors. Firstly, it is determined by the pathway of the cloud with radioactive products resulting from the Chernobyl accident. Secondly, it is influenced by the type of the soil. Moreover, the concentration of cesium depends on migration processes that occur in the soil and causes a movement of radionuclides among its layers. The average concentration of cesium \({}^{137}\)Cs in the soil in the study was 10.59 Bqkg\({}^{-1}\) with standard deviation equal to 7.34 Bqkg\({}^{-1}\) (Table 2). The variation is significant. What is more, the southern regions are characterized by lower concentrations of anthropogenic radionuclides than the northern regions. It confirms the influences of pathway, type of the soil, and migration processes on cesium \({}^{137}\)Cs concentration in the soil. In order to assess the radiological risk, the possible impact of natural radiation on a human, besides radionuclide concentration in the soil, among others, the absorbed dose and annual effective dose, can be used [56]. It should be noted that the indicator, which is the most commonly used to assess the potential biological effects associated with exposure to ionizing radiation in humans and in radiation protection, is the effective dose rate [51].