## 3 Results and Discussion  
### Spatial Distribution of Anthropogenic Radionuclides  
Figures 3 and 4 illustrate the variation in pollution density of Cs-137 and Sr-90 along the peat sampling profile. Pollution density is shown for the 0-20 cm layer. Figure 3: Cs-137 pollution density. Cs-137 pollution density ranges from 9.22 \(\times\) 10\({}^{-3}\) (3.41 \(\times\) 10\({}^{2}\)) Ci\(\cdot\)km\({}^{-2}\) (Bq\(\times\)m\({}^{-2}\)) to 1.31 \(\times\) 10\({}^{-1}\) (4.85 \(\times\) 10\({}^{3}\)) Ci\(\times\)km\({}^{-2}\) (Bq\(\times\)m\({}^{-2}\)) with a mean of 4.43 \(\times\) 10\({}^{-2}\) (1.64 \(\times\) 10\({}^{3}\)) Ci\(\times\)km\({}^{-2}\) (Bq\(\times\)m\({}^{-2}\)). Sr-90 pollution density ranges from 2.29 \(\times\) 10\({}^{-3}\) (8.26 \(\times\) 10\({}^{1}\)) Ci\(\times\)km\({}^{-2}\) (Bq\(\times\)m\({}^{-2}\)) to 5.07 \(\times\) 10\({}^{-2}\) (1.88 \(\times\) 10\({}^{3}\)) Ci\(\times\)km\({}^{-2}\) (Bq\(\times\)m\({}^{-2}\)) with a mean of 1.74 \(\times\) 10\({}^{-2}\) (6.44 \(\times\) 10\({}^{2}\)) Ci\(\times\)km\({}^{-2}\) (Bq\(\times\)m\({}^{-2}\)). The distribution patterns of Cs-137 and Sr-90 activity in the samples are similar in many respects (Figures 3 and 4). However, marked differences can be seen between the density of Cs-137 and Sr-90 pollution on the slope, in the plakor zone, and within the tundra lowlands. The highest density of Cs-137 and Sr-90 contamination was found in the tundra lowland zone. We assume that anthropogenic radionuclides in this zone are mainly subject to downward migration. The zones of the plakor, slope, and hilly part of the profile are characterized by decreased pollution density, which is caused by more intensive lateral migration and planar washout (surface runoff). When comparing these findings with previous scarce data on Cs-137 activity levels in the Nenets Autonomous Okrug, a decrease in radiocaesium activity can be observed. According to [43], in the period from 1994 to 2000, Cs-137 levels up to 2000 Bq\(\times\)kg\({}^{-1}\) were observed in some samples from the southern part of the Kanin Peninsula. The author accounted this abnormality to nuclear testing carried out in the Novaya Zemlya archipelago; however, they failed to substantiate this claim. Table S1 of this study illustrates that Cs-137 activity within the peat can reach 191.5 \(\pm\) 17.2 Bq\(\times\)kg\({}^{-1}\). Due to methodological (instrumental) difficulties, information on Sr-90 pollution densities in general on the territory of the Russian Federation is not known. Consequently, the recently obtained data on Sr-90 content in peaks from the western region of the Nenets Autonomous Okrug are new and allow us to estimate the stock of this radionuclide in the tundra area. When comparing Sr-90 results in the Kanin tundra to data obtained in other Arctic regions of Russia and worldwide, an excess of two to three times is evident. Peat profiles in the southern region of Svalbard, for instance, exhibit Sr-90 activity of up to 17.36 Bq\(\times\)kg\({}^{-1}\)\(\pm\) 0.70 Bq\(\times\)kg\({}^{-1}\)[44]. In the peat bogs of Northwest Russia's Murmansk region, Sr-90 activity remains within the range of 7.7 Bq\(\times\)kg\({}^{-1}\)\(\pm\) 3.4 Bq\(\times\)kg\({}^{-1}\), as stated by [45]. Table S1 of this study illustrates that Sr-90 activity within the peat can reach 42.8 \(\pm\) 10.0 Bq\(\times\)kg\({}^{-1}\). Figure 4: Sr-90 pollution density. The initial studies of anthropogenic radioactivity on the territory of the Nenets Autonomous Okrug were carried out in 1990-1992 in the form of a radiometric airborne gamma survey to identify ecologically unfavorable areas [46]. Several small areas were found to have a clear anthropogenic impact, with pollution levels surpassing 0.15 Ci\(\times\)km\({}^{-2}\) (as of 1992). However, the Nes River basin does not appear to be an area of elevated Cs-137 content, with a pollution density of around 0.1 Ci\(\times\)km\({}^{-2}\) (Figure 5).