## 3 Results and Discussion
The \({}^{238}\)U histogram pointed to a frequency of the activity concentration class between 170 and 200 Bq/kg followed by those with concentrations slightly above 300 Bq/kg. The elevated \({}^{238}\)U concentration and high variation in the soil reflected the long history of uranium mining practices in the area, such as the exploitation and exploration of uranium ore in the galleries, the dumping of mine tailings and the temporary storage of uranium ore before transport to a processing plant. The activity concentration of \({}^{232}\)Th in all the soil samples from the Lisava area ranged within relatively narrow limits from 7.23 to 48.16 Bq/kg with a mean concentration of 16.21 Bq/kg. The \({}^{232}\)Th analyses displayed an asymmetric distribution, although the variations in the specific activities of \({}^{232}\)Th were relatively low. The statistical parameters calculated for \({}^{232}\)Th showed moderate variation. The box plot and normal Q-Q plot diagrams highlighted outlier values in the soil samples with 2, 5, 6 and 13 IDs. These  
Figure 4: Histogram, boxplot and normal Q-Q plot of \({}^{238}\)U, \({}^{232}\)Th and \({}^{40}\)K in soils from Lisava sector. sampling points were located at the extremities of the study area, where the anthropic influence of uranium mining was decreased and reflected the natural background of thorium content in the soil. The samples with higher \({}^{238}\)U specific activities exhibited low \({}^{232}\)Th specific activities, sometimes being below the average reported for the crustal abundance of 10.5 ppm [9]. The potassium specific activities varied from 497.32 to 615.32 Bq/kg as a result of the lithological features in the investigated perimeter with a mean specific activity of 543.21 Bq/kg. Like \({}^{238}\)U, the descriptive statistics for \({}^{40}\)K (Table 2 and Figure 4) showed wide variations in terms of specific activity and an asymmetric distribution of content values. The average specific activities of \({}^{238}\)U, \({}^{232}\)Th and \({}^{40}\)K found in the analyzed soils are presented in Table 3 alongside the data reported in similar studies. This data showed that thorium and potassium presented lower or comparable averages of specific activity compared with the reference data, while uranium showed a specific activity average that was much higher (197.21 Bq/kg). All the average values of \({}^{238}\)U calculated in the present study were comparable to the values reported for soils around uranium waste deposits from the Crucea ore deposit in Romania (559.7 Bq/kg) and the averages found in the soils around a former uranium mine in Gabrovnica, Serbia (249 Bq/kg) [32; 33]. This comparison showed that the natural radioactivity in the surface soil from the Lisava uranium mining sector was higher as a result of uranium mining. Spatial Distribution of \({}^{238}\)U, \({}^{232}\)Th and \({}^{40}\)K in Soil from Lisava Uranium Mining Sector  
A spatial distribution map of natural radionuclides is useful for identifying areas with high radionuclide concentrations and the possible sources of these elements. The spatial distribution maps for \({}^{238}\)U, \({}^{232}\)Th and \({}^{40}\)K are presented in Figures 5-7. Figure 5: Spatial distribution of \({}^{238}\)U in soils from Lisava uranium mining sector. Figure 6: Spatial distribution of \({}^{232}\)Th in soils from Lisava uranium mining sector. The spatial distribution of \({}^{232}\)Th (Figure 6) in the soils from the Lisava mining sector indicated very low values (green zone on the map) in most of the study area, even/especially where many soils exhibited high uranium concentrations. Here, the specific activities of \({}^{232}\)Th were under the recommended values [28]. Two zones with moderate activity concentrations (up to approximately 48 Bq/kg) were observed in the northeastern and northwestern parts of the perimeter (Figure 6), where the mining footprint was decreased and the relative thorium enrichment was correlated with uranium depletion.