## 3 Results and Discussion
### Statistical Analysis  
To study the features of the accumulation of atmospheric fallout radionuclides in the peat section, factor analysis was performed, which made it possible to reveal the structure of relationships between the studied peat components. The results of the factor analysis for the ISNO-1 peat profile are presented in Table 2 and Figure 7. Quantitatively, the dataset is split into five factors that account for 91.26% of the cumulative variance. In the first factor with a dispersion of 43.35% for high loads, \({}^{137}\)Cs, \({}^{210}\)Pb, the content of water-soluble salts, moisture saturation, Eh, and rH are all prominent. The correlation of \({}^{137}\)Cs with the content of water-soluble salts and moisture saturation is due to the presence of \({}^{137}\)Cs mainly in the ionic form [66]. The correlation of \({}^{210}\)Pb with water-soluble salts is explained by the presence of lead in the solution mainly in the chelate form in the form of complexes with fulvic acids [67]. Therefore, in the considered case, both \({}^{210}\)Pb and \({}^{137}\)Cs are associated with a greater extent with water-soluble salts, and not with the ash content of peat. Separation in the first factor of the Eh (rH) parameter most likely indicates that redox conditions affect  
Figure 6: Linear accumulation rate \(s\) and mass accumulation rate \(r\) along the depth of the peat profile.  
the sorption (mobility) of \({}^{137}\)Cs in peat due to changes in the state of collectors: compounds of iron, manganese, sulphur and organic substances [72].  
In the second factor with a dispersion of 18.50% of the total sample for positive loads, the parameters of the elemental component of the organic matter of peat are isolated, which is generally a natural fact associated with the transformation of organic matter from the peat deposit [73].  
The third factor explains 16.87% of the variance of the total sample with high factor loadings on the contents of U, carbonates, and ash components. The correlation of U with these physicochemical parameters is probably because the main part of uranium enters the peat deposit together with atmospheric dust particles and aerosols [74].  
The fourth factor with a dispersion of 8% for positive loads includes the \({}^{234}\)U/\({}^{238}\)U uranium isotope ratio, the pH of the salt extract, the content of water-soluble salts, and the elemental parameters O (O/C). The separation of these parameters into one factor is probably due to the peculiarities of the influence of these physicochemical parameters on the isotopic fractionation of \({}^{234}\)U and \({}^{238}\)U [75], which requires additional research.  
The fifth factor explains 4.55% of the variance of the total sample with positive loads on \({}^{210}\)Pb and the C/N parameter. This indicates that some part of \({}^{210}\)Pb in peat is in the form of complexes with humic acids, as mentioned above.  
Despite the high role of organic matter in the accumulation of radionuclides noted by some authors [13,76], the factor analysis data indicate that organic matter is not included in any factor and does not control the accumulation of radionuclides in the peat SINO-1 profile. This is because this study evaluated the total organic matter without dividing it into group components that are carriers of radionuclides (bitumen, humic acids, hardly hydrolysable and easily hydrolysable compounds, and lignin) [77].