## 3 Results and Discussion
### Variations in the Radioisotopes Content in the ISO-1 Peat Profile  
The \({}^{137}\)Cs concentrations in the analysed ISO-1 peat core sampled in the dried section of the Ilassky bog ranges from 2.6 to 142.6 Bq/kg (Figure 4). The maximum activity (142.6 Bq/kg) is concentrated in the upper horizon 0-4 cm. In the underlying horizon of 4-6 cm, the activity of \({}^{137}\)Cs falls sharply and makes 68.8 Bq/kg with the further smooth decrease down the section without expressed peaks. The \({}^{137}\)Cs distribution in the ISO-1 profile corresponds to the typical distribution pattern in upland peatlands, which is explained by the high mobility of radio-cesium in peat waters and its absorption by both sphagnum mosses, which are not demanding for mineral nutrition, and by more demanding vascular plants [22; 47; 57]. However, this distribution is characteristic, as a rule, for natural bogs without anthropogenic impact on peat deposits [24]. At the same time, in addition to the \({}^{137}\)Cs maximum concentration in the upper part of the section, a similar maximum of \({}^{137}\)Cs activity at 19-21 cm was detected in the natural section within the studied bog massif (core ISNO-1). Studies of the physical and chemical characteristics of the natural peat core have revealed the presence of a complicated geochemical hurdle of redox, sulphide and sorption sort in the 19-21 cm horizon, conditions leading to the containment of \({}^{137}\)Cs [29]. This is probably due to a disturbance of the natural hydrological regime of the dried ISO-1 core, in which the formation of a pronounced geochemical barrier does not occur and there are no factors limiting the migration of \({}^{137}\)Cs up through the section. This is especially noticeable in the differences in the \({}^{137}\)Cs activities in the upper horizons of the natural ISNO-1 and dried ISO-1 peat core (45.6 Bq/kg in the ISNO-1 profile and 142.6 Bq/kg in the ISO-1 profile, respectively). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Parameter** & **Factor 1** & **Factor 2** & **Factor 3** & **Factor 4** & **Factor 5** \\ \hline Depth & \(-\)0.55 & \(-\)0.62 & \(-\)0.45 & \(-\)0.29 & \(-\)0.06 \\ \({}^{137}\)Cs & 0.10 & 0.44 & 0.88 & 0.10 & 0.03 \\ \({}^{210}\)Pb & 0.01 & 0.64 & 0.71 & 0.02 & 0.14 \\ \({}^{234}\)U/\({}^{238}\)U & \(-\)0.09 & \(-\)0.03 & 0.11 & 0.11 & 0.94 \\ U & 0.30 & 0.80 & 0.00 & 0.25 & \(-\)0.29 \\ CO\({}_{3}\)\({}^{2-}\) & 0.17 & 0.22 & 0.60 & 0.71 & \(-\)0.01 \\ Ash & 0.03 & 0.90 & 0.34 & 0.23 & 0.04 \\ pHwater & \(-\)0.67 & \(-\)0.43 & 0.43 & \(-\)0.35 & 0.12 \\ pHsalt & \(-\)0.33 & \(-\)0.05 & 0.92 & 0.10 & 0.10 \\ Water soluble salts & 0.38 & 0.50 & 0.68 & 0.29 & \(-\)0.15 \\ Organic matter & \(-\)0.03 & \(-\)0.90 & \(-\)0.34 & \(-\)0.23 & \(-\)0.04 \\ N & \(-\)0.39 & 0.11 & 0.50 & 0.56 & 0.28 \\ C & \(-\)0.96 & \(-\)0.10 & \(-\)0.02 & 0.11 & 0.16 \\ H & \(-\)0.39 & \(-\)0.72 & 0.00 & 0.51 & \(-\)0.09 \\ O &With close total stocks of \({}^{137}\)Cs in both peat deposits, changes in the hydrological regime lead to significant differences in the vertical distribution of \({}^{137}\)Cs. From this, we can conclude that drainage of the peatland in the conditions of the Arkhangelsk oblast leads to the mobilisation of \({}^{137}\)Cs and accelerates its migration up the section. The \({}^{210}\)Pb concentration in the ISO-1 peat column sampled at a site with a disturbed hydrological regime ranges from 6.3 to 567.9 Bq/kg. The maximum activity of \({}^{210}\)Pb (567.9 Bq/kg) falls on a horizon of 4-6 cm. In the uppermost horizon of 0-4 cm, the activity of \({}^{210}\)Pb is 500.8 Bq/kg. The concentration of \({}^{210}\)Pb maximums in the upper horizons is a natural process confirming the entry of \({}^{210}\)Pb into the peatland with atmospheric precipitation [58, 59, 60]. Below the 4-6 cm horizon, \({}^{210}\)Pb activity decreases exponentially to a depth of 20-22 cm (from 567.9 to 23.9 Bq/kg).