# An Assessment of the Impact of Gypsum Deposit Development on Changes in the Radiation Environment
## 3 Results and Discussions
### Bottom Sediments
#### 3.2.1 Activity Concentrations of Radionuclides in River Sediments
A significant correlation is observed between the activity concentrations of cesium and uranium isotopes and the contents of organic matter, soluble salts and carbonates in the bottom sediments. \({}^{137}\)Cs, \({}^{238}\)U, \({}^{234}\)U and OM correlate with each other with \(p\) = 0.001-0.002; for \({}^{137}\)Cs and SS, \(p\) = 0.016 was obtained and for \({}^{137}\)Cs and CO\({}_{3}\)\({}^{2-}\)\(p\) = 0.06. As shown in Section 3.1, oxidation-reduction and acid-base conditions do not prevent uranium from being found in the surface waters of the region mainly as part of uranyl-carbonate complexes. UO\({}_{2}\)(CO\({}_{3}\))\({}_{2}\)\({}^{2-}\) accounts for about 55-57% and UO\({}_{2}\)(CO\({}_{3}\))\({}_{3}\)\({}^{4-}\) for 12-27%. Uranium precipitates only in the reducing environment of groundwater circulating relatively deep below the earth's surface [56]. Therefore, the accumulation of isotopes in the bottom sediments apparently occurred through sorption (see Figure 5a,b,e). A significant correlation was also established among \({}^{137}\)Cs, \({}^{238}\)U, \({}^{234}\)U, Ca, Cu, Cr, Pb, Ni, Ti and V. The significance value for isotopes and these chemical elements was \(p\)\(\leq\) 0.01 (see Table 4). For uranium isotopes, there was also a significant correlation with Na, K, Fe, Zn, Mo and Cd. For \({}^{137}\)Cs, it is weaker (on average, \(p\) = 0.15, r = 53). A specific set of elements and the correlation with the contents of organic matter, soluble salts and  
\begin{table}
\begin{tabular}{c c c c c c c c c c c c c c} \hline  & \({}^{238}\)Ra & \({}^{238}\)Th & \({}^{40}\)K & \({}^{238}\)U & \({}^{234}\)U & 100 \({}^{*}\) & 45 \({}^{*}\) & \(<\)45 \({}^{*}\) & CO\({}_{3}\)\({}^{2-}\) & OM \({}^{*}\) & SS \({}^{4}\) & Na & K & Ca \\ \hline \({}^{137}\)Cs & 0.42 & 0.10 & \(-\)0.42 & 0.86\({}^{*}\) & 0.89\({}^{*}\) & \(-\)0.48 & \(-\)0.18 & 0.19 & 0.61 & 0.85\({}^{*}\) & 0.73\({}^{b}\) & 0.56 & 0.62 & 0.77\({}^{*}\) \\ \({}^{228}\)Ra & & 0.27 & \(-\)0.02 & 0.17 & 0.22 & 0.24 & 0.47 & 0.11 & 0.16 & 0.45 & 0.14 & 0.21 & 0.06 & 0.32 \\ \({}^{237}\)Th & & & 0.52 & 0.20 & 0.22 & 0.37 & 0.23 & 0.44 & 0.43 & \(-\)0.04 & 0.26 & 0.34 & 0.48 & 0.18 \\ \({}^{40}\)K & & & & \(-\)0.40 & \(-\)0.32 & 0.50 & \(-\)0.21 & \(-\)0.18 & \(-\)0.13 & \(-\)0.68 & \(-\)0.34 & \(-\)0.16 & \(-\)0.19 & \(-\)0.30 \\ \({}^{238}\)U & & & & & 0.98\({}^{*}\) & \(-\)0.41 & \(-\)0.04 & 0.41 & 0.81\({}^{*}\) & 0.85\({}^{*}\) & 0.98\({}^{*}\) & 0.82\({}^{*}\) & 0.91\({}^{*}\) & 0.88\({}^{*}\) \\ \({}^{234}\)U & & & & & \(-\)0.45 & \(-\)0.06 & 0.28 & 0.84\({}^{*}\) & 0.80\({}^{*}\) & 0.93\({}^{*}\) & 0.81\({}^{*}\) & 0.87\({}^{*}\) & 0.91\({}^{*}\) \\ \hline  & **Mg** & **Sr** & **Fe** & **Mn** & **Zn** & **Cu** & **Cr** & **Pb** & **Ni** & **Mo** & **Cd** & **Co** & **Ti** & **V** \\ \hline \({}^{137}\)Cs & 0.34 & \(-\)0.01 & 0.33 & \(-\)0.43 & 0.55 & 0.92\({}^{*}\) & 0.74\({}^{b}\) & 0.95\({}^{*}\) & 0.72\({}^{b}\) & 0.49 & 0.61 & 0.09 & 0.94\({}^{*}\) & 0.80\({}^{*}\) \\ \({}^{238}\)Ra & 0.24 & 0.19 & 0.05 & 0.24 & 0.17 & 0.36 & 0.19 & 0.54 & 0.21 & \(-\)0.30 & 0.22 & 0.05 & 0.27 & 0.29 \\ \({}^{237}\)Th & 0.42 & 0.21 & 0.5 & 0.24 & 0.38 & 0.18 & 0.37 & 0.15 & 0.43 & 0.08 & 0.43 & 0.58 & 0.19 & 0.42 \\ \({}^{40}\)K & \(-\)0.05 & 0.10 & \(-\)0.06 & 0.51 & \(-\)0.28 & \(-\)0.30 & \(-\)0.32 & \(-\)0.48 & \(-\)0.31 & \(-\)0.54 & \(-\)0.2 carbonates confirm the conclusion about the significant role of the anthropogenic factor in the accumulation of cesium and uranium isotopes in the bottom sediments [8]. The contamination of bottom sediments with \({}^{137}\)Cs is a result of the Chernobyl accident in 1986, when not only soils and bottom sediments but also vegetation were contaminated over large areas of Europe [20,57,58,59,60]. Uranium isotopes are mainly of natural origin, as they are ubiquitous in near-surface sediments, soils, surface and groundwater (see Sections 3.1 and 3.3).