Estimation of Physicochemical Parameters and Vertical Migration of Atmospheric Radionuclides in a Raised Peat Bog in the Arctic Zone of Russia

Abstract

The article presents the results of a study of activity levels and features of the vertical distribution of 210Pb, 137Cs, 234U, 238U and their relationship with the physicochemical parameters of peat deposits. Analysis of the data showed that the vertical distribution of 137Cs and 210Pb was related to the content of water-soluble salts, the water saturation of the deposit, and the values of Eh (oxidation–reduction potential) and rH (relative humidity), which indicates a complex geochemical barrier at a depth of 20 cm in the peat core. The 210Pb dating of the peat core, carried out according to the CF model using the Monte Carlo method (to improve the dating accuracy), showed that the above horizon corresponded to 1963, which is consistent with the data of the 137Cs reference horizon and in terms of several physicochemical parameters (in particular, ash content) also corresponds to the age of 1963, which confirms the correctness and adequacy of the chosen peat core dating model. The peak of anthropogenic radionuclides in peat deposits correlates with a particular major event in the history of radioactive fallout, the Partial Nuclear Test Ban Treaty of 1963, providing a benchmark for geochronological research. The obtained results of the linear accumulation rate, the mass accumulation rate of the peat deposit, and the value of the atmospheric flux of 210Pb are congruent with the data on the peatlands of Northern Europe and the data obtained by earlier analysts of the Subarctic region of European Russia.

Comparison of 210Pb Age Models of Peat Cores Derived from the Arkhangelsk Region

“…The bulk density of turf was obtained using the gravity method for air-dried samples with a fraction size of 0.5-2 mm. The estimate was determined by counting the volume of the samples with a measuring cylinder and determining their weight on technical balances in 5 parallel duplicates for every layer [15,17].…”

Assessment of the Impact of Anthropogenic Drainage of Raised Peat-Bog on Changing the Physicochemical Parameters and Migration of Atmospheric Fallout Radioisotopes in Russia’s Subarctic Zone (Subarctic Zone of Russia)

“…The natural moisture content was determined by the gravimeters method based on sample weight loss while drying at 105 • C in a desiccator [29].…”

“…The bulk density of the peat samples was evaluated using the gravimeter method for the dried samples with a fraction size between 0.5 and 2 mm. An assessment of the bulk density was performed by a measurement of the samples volume with a calibrated cylinder followed by weight measurements in five parallel determinations [29].…”

“…The active and exchange acidity of peat samples were assessed by direct potentiometry in aqueous and chloralkali peat suspension, respectively. In the obtained aqueous suspension, we additionally evaluated the content of water-soluble salts by the conductometric method, as explained by Yakovlev et al [29].…”

“…To address this gap, we conducted research on the example of a small area of the Ilassky peat massif (Arkhangelsk oblast), which was drained with ditches in the later part of the 1960s and the first part of the 1970s to reduce watering of the area during the construction of the highway. As an object for comparison, we used a site with a natural hydrological regime within the same Ilassky massif, the initial (background) physicochemical and radiation parameters of which we studied earlier [29]. Given the single genetic type and the insignificant remoteness of the natural and drained sites from each other, we can assume that the initial concentrations of atmospheric radionuclides arriving at the marsh surface were the same, while differences in the hydrology significantly affected the further redistribution of isotopes.…”