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

Abstract

Dating young peatlands using the 210Pb dating procedure is a challenging task. The traditional 210Pb age models assume an exponential decline in radioactivity in line with depth in the peat profile. Lead exhibits considerable migratory capacity in Arctic peatlands; hence, to perform precise peat dating, existing models should be enhanced to remove the effects of migration. Independent isotope chronometers, such as 137Cs, can verify this. The Monte Carlo method and IP-CRS were utilised, together with several CA, CF/CS, PF, and CF models, to analyse the peat core samples acquired in the Arkhangelsk region. Data analysis revealed that the height partitioning of 137Cs and 210Pb is associated with physical characteristics, like the peat ash and the bulk density of the bog. Comparison between the natural activity of 210Pb in the peat and the radioactivity of 137Cs measured at depths of 19–21 cm in relation to the global fallout in 1963 indicated that the CF/CS, CF, and IP-CRS models (1965, 1962 and 1964, respectively) gave the closest age to the reference point given. IP-CRS was found to be the preferred model of these three options, as it gave a rather closer correlation with the 137Cs activity specific to the reference layer, allowing the error. The core dating of 210Pb showed an age of 1963 for a depth of 17–19 cm, which was in agreement with the reference horizon 137Cs and ash content, thus validating the accuracy and sufficiency of the selected model turf profile chronology. The maximum content of man-made radioisotopes in the peatlands corresponded to the formulation of the Partial Test Ban Treaty of 1963. The rates of accumulation of peat and atmospheric flux of 210Pb are in good agreement with the values available for the bogs of Northern Europe and those previously estimated by the authors in the subarctic region of European Russia. Although the problems of the complex migration-related distribution of 210Pb in the peat layer were considered, the dating methods used were effective in our study and can be adapted in following studies to perform the age determination of different peat deposits.