# An Assessment of the Impact of Gypsum Deposit Development on Changes in the Radiation Environment
## 3 Results and Discussions
### Soils, Quaternary Deposits and Gypsum
#### 3.3.3 Radon Flux Density (RFD) from Soil Air  
The studies showed that the RFD varied within the range of 6 \(\pm\) 1 to 181 \(\pm\) 54 mBq (m\({}^{2}\)s)\({}^{-1}\) (Table 6). The maximum values, from 89 \(\pm\) 26 to 181 \(\pm\) 54 mBq (m\({}^{2}\)s)\({}^{-1}\), were observed outside the mining area and were confined to areas with natural occurrence of Quaternary moraine loans with undisturbed soil cover and forest vegetation. The minimum values, from 6 \(\pm\) 1 to  
Figure 6: Areal distribution of ADER values in the gypsum deposit area and adjacent areas (**a**) and distribution of radon flux density from soil air on the North–South profile (see Figure 2b) (**b**).  
\(18\pm 5\) mBq (m\({}^{2}\)s)\({}^{-1}\), were established in the quarry area, in areas where gypsum layers were directly exposed on the surface. Intermediate values, from 20 \(\pm\) 6 to 61 \(\pm\) 18 mBq (m\({}^{2}\)s)\({}^{-1}\), were confined to overburden dumps, represented by clayey deposits with gypsum rock fragments (see Figure 1) (Figure 6b).  
The results indicate that the gypsum layers in the quarry are a virtually impermeable screen preventing radon from exiting from the earth's interior [11]. Outside the quarry, the Quaternary moraine deposits are permeable due to their porosity and humidity. In addition, in sedimentary basins, \({}^{226}\)Ra concentrations in near-surface sediments and soils play a major role in radon production. This is a zone of a specific boundary soil layer with a thickness of 1.5-3.0 m, in which active gas exchange with the atmosphere occurs [72]. According to [31], the average RFD values in watersheds composed of clayey soils were higher than in river valleys dominated by sandy deposits. The average \({}^{226}\)Ra activity concentration in loams was 15-25 Bq kg\({}^{-1}\) and in sands 10-15 Bq kg\({}^{-1}\). We obtained average \({}^{226}\)Ra activity values of 20.7 \(\pm\) 3.0 Bq kg\({}^{-1}\) in loams and 26.8 \(\pm\) 4.0 Bq kg\({}^{-1}\) in soils. In gypsum, \({}^{226}\)Ra activity is minimal, amounting to 3.69 \(\pm\) 1.08 Bq kg\({}^{-1}\) (Table 5).  
Thus, the RFD intensity within the quarry, like the ADER, is directly related to the relative contents of clay, loam, sand and gypsum in the overburden dumps and to the exposure of gypsum layers. The potential radon hazard of the territory is assessed in accordance with the Basic Sanitary Rules for Ensuring Radiation Safety [71], which establish the maximum permissible radon flux density (RFD) from the soil surface at construction sites, amounting to 80 mBq (m\({}^{2}\)s)\({}^{-1}\) for residential and public buildings. Table 6 shows that such areas may occur outside the quarry, and this should be taken into account during their development. In addition, caves are widespread in the study area, usually associated with zones of an increased fracturing of rocks, in which advective transfer is possible--a flow of radon in the volume of the moving gas phase [72]. Such transfer is significantly higher than the diffusion transfer of radon from soils in an undisturbed state and requires separate study.