RESUMO
The Laptev Sea is remote from the impact of technogenic radionuclides, which makes it a convenient natural testing ground for determining the natural flux of radionuclides to the marine environment and further to sediments. Analysis of the use of different models for dating recent sediments using 210Pb showed that in conditions of erosion-accumulative (unstable) sedimentation of the shelf, the constant initial concentration (CIC) model is most preferable. This study uses a new age-depth model "RUS2023" to recalculate the excess 210Pb (210Pbex) activity into calendar years, which is a variation of the CIC model. The proposed model differs in that when calculating the age of horizons, corrections for the grain-size composition and sorption capacity of sediments are used. In ten studied sediment cores from the Laptev Sea, using this model, strong variability in 210Pbex flux from the atmosphere was revealed. One of the possible sources of 210Pbex, in addition to global fallout due to the decay of 222Rn, are forest fires, which contribute to its burst emission into the atmosphere as part of aerosols. Taking into account the area of forest fires in Siberia, Yakutia and the Far East, they are able to supply into the atmosphere together about 2.5 × 1014 Bq year-1, which is comparable to emissions from all nuclear power plants in Russia. This model can also be useful in reconstructing sedimentological events that cause disturbances in the chronology of sedimentary sequence, for example, when dating landslides or turbidites.
