## 3 Results and Discussion
### The Statistical Analysis  
The correlation matrix on measured parameters in the peat profile ISO-1 is displayed in Figure 8. A significant positive correlation (r > 0.50) is observed for the sampling depth, pH of the water extract, organic matter, C and H content, indicating a tendency for these parameters to increase with increasing depth. At the same time, high negative relations (r < \(-\)0.70) are characteristic for the depth and activity of radionuclides \({}^{137}\)Cs, \({}^{210}\)Pb, U, ash, water-soluble salts, Eh and rH, which in turn indicates a decrease in these parameters with depth. The isotope \({}^{137}\)Cs has a very high positive correlation with \({}^{210}\)Pb (r = 0.91), which confirms its single input source. Additionally, \({}^{137}\)Cs is positively correlated at the high correlation level (r > 0.70) with carbonates, ash components, pH of salt extract and water-soluble salt content. \({}^{137}\)Cs has a noticeable positive relationship (r > 0.50) with the parameters Eh and rH. \({}^{137}\)Cs has a high negative bond (r = \(-\)0.72) with organic matter. \({}^{210}\)Pb is characterised by a high  
Figure 8: Correlation matrix of the parameters studied for ISO-1 peat profile. positive correlation with ash components (r = 0.83) and the water-soluble salts concentration (r = 0.79). A noticeable positive relationship (r > 0.50) is observed for the \({}^{210}\)Pb-carbonate and \({}^{210}\)Pb-pH salt-extract pairs. 210 Pb has a high negative bond with organic matter (r = \(-\)0.83). The uranium isotope ratio of \({}^{234}\)U/\({}^{238}\)U is virtually unrelated to the other parameters studied except for the presence of a moderate correlation with N (r = 0.32). Uranium at the level of high positive correlation (r = 0.75) correlates only with ash components, with the correlation of water-soluble salts, O content, oxidation degree, Eh and rH values being noticeable (r from 0.5 to 0.7). For the uranium content, there is an inverse high correlation with organics (r = \(-\)0.75); a marked inverse relationship is observed with the pH of water extract and H content (r = \(-\)0.64 and r = \(-\)0.53, correspondingly). The relationships of other physicochemical parameters and components of the elemental composition are shown in Figure 3. As shown in the correlation matrix, there is a rather complex structure of the connections between the involved parameters, but these general trends indicate that the distribution of \({}^{137}\)Cs, \({}^{210}\)Pb and U is controlled mainly by the content of carbonates, ash, pH of salt extract, water soluble salts, Eh and rH. Those identified relationships are in line with the data of a factor analysis, as shown in Table 2. It should be noted that a couples correlation analysis does not always give clear and correct results for complex natural systems, where the dependent variable is simultaneously determined by the influence of several characteristics. To identify the nature of general relationships between the studied parameters of peat and the accumulation of radioisotopes in the ISO-1 peat core, a factor analysis was carried out. A summary of the factor analysis for the ISO-1 core is shown in Table 2 and Figure 9. Numerically, a data set has been divided by five factors (group) explaining 93.98% of the total dispersion. The first factor with a variance of 42.46% on high loadings isolated the characteristics of the elemental content of organic matter--O, H/C, O/C and the oxidation level (\(\omega\)), and physicochemical parameters--Eh and rH. This is logical and confirms the existing idea that the oxidation-reduction mode of the peatland is one of the key factors affecting the course of chemical and biochemical processes of the biogeotransformation (diagenesis) of organic matter of plant residues in peat [5; 15; 69]. For the second factor with a variance of 27.49% of the general amount by positive loadings radionuclides \({}^{137}\)Cs, \({}^{210}\)P and U, the ash content, water-soluble salts and physicochemical parameters Eh and rH are isolated.