## 1 Introduction  
Soil is generally considered to be the environmental component that is the most exposed to the accumulation of pollutants of various origins. Its ability to accumulate metals is related to the type of soil, its physical and chemical properties, and the nature of heavy metals [1]. Whether the soil becomes a threat to humans or not depends on the concentration of radionuclides. Their concentration depends mainly on local geology and climate (geographic location) [2; 3]. There are the so-called High Radiation Background Areas (HBNRAs), where the dose of radiation, due to natural background, is 55-200 times higher than the doses that occur in Normal Background Radiation Areas (NBRAs) [4; 5]. Some of the world's HBNRAs are found in Yangjiang (China), Kerala (India), Gurapari (Brazil), Central Bohemia (Czech Republic), Campania (Italy), Podecettrek (Slovenia), and Tessin (Switzerland) [2; 6]. The presence of uranium \({}^{238}\)U, thorium \({}^{232}\)Th, and radium \({}^{226}\)Ra in soil and rocks results from the natural radiation and includes cosmic radiation and terrestrial radiation from natural radioactive elements. Furthermore, there are artificial radionuclides originating from human activity, most due to their common application in industrial, scientific, and military activities; in medicine; industrial production processes; mining, nuclear power plants; or nuclear weapons [7; 8; 9]. According to reports published by The United Nations Scientific Committee on the Effects of Atomic Radiation [2], the annual average per caput dose from natural sources of radiation is 2.4 mSvy\({}^{-1}\), whereas from anthropogenic sources of radiation,it is 0.6 mSvy\({}^{-1}\)[2; 10; 11]. That makes the radiation of natural radionuclides the source that affects human health the most. As a matter of fact, a large part of the dose comes from gaseous radon \({}^{222}\)Rn and its progenies (from the uranium \({}^{238}\)U series). Soil radiation is mainly caused by the upper layer of the soil [10]. Ionizing radiation is mainly due to gamma-emitting radionuclides, such as uranium \({}^{238}\)U, thorium \({}^{232}\)Th, and their decay products, as well as potassium \({}^{40}\)K and radon \({}^{222}\)Rn, which are usually the largest natural source of radiation [2]. Those radionuclides are of particular interest for radiation protection. There are worldwide studies focusing on the measurements of radionuclides in the soil [7]. Researchers present information about background exposure levels in different countries. The available maps concerning concentrations of radionuclides in soils include GEMAS and FOREGS. Nevertheless, radiological data were not collected with sufficient density to perform local statistics, and the same kind of interpolation has to be performed [12]. In the presented research, radionuclides coming from natural and anthropogenic sources have been studied. The following natural radionuclides are included: potassium \({}^{40}\)K, radium \({}^{226}\)Ra, and actinium \({}^{228}\)Ac. The significant decay product in the uranium \({}^{238}\)U series is radium \({}^{226}\)Ra and in the thorium \({}^{232}\)Th series is actinium \({}^{228}\)Ac. For this reason, the series was given the name radium \({}^{226}\)Ra and actinium \({}^{228}\)Ac decay, respectively. The potassium \({}^{40}\)K isotope is of a naturally radioactive origin. On the other hand, the isotopes of radium \({}^{226}\)Ra and actinium \({}^{228}\)Ac are the main representatives of the radium \({}^{226}\)Ra and actinium \({}^{228}\)Ac series [13]. An artificial radionuclide which concentration was assessed was cesium \({}^{137}\)Cs. In the environment, it occurs as a remnant of nuclear power plant failures, for example, that of the Chernobyl Nuclear Power Plant in 1986 [14; 15]. Its occurrence in environmental components is related to radioactive fallout, which traveled over Poland along with clouds [16; 17]. It is worth mentioning that over the years, radioactive cesium \({}^{137}\)Cs migrated deep into the soil [18; 19].