The Dynamics of the Dose of External g-Radiation in Pine Stands in the Belarusian Sector of the 30-Kilometer Zone Around the Chernobyl Nuclear Power Plant

The external g-radiation in an area contaminated by accidental radioactive fallout changes due to the radioactive decay of radionuclides and their migration in the vertical profile of the soil. The purpose of the research was to evaluate the quantitative parameters of the dynamics of the dose rate of external g-radiation in the pine plantations of the Belarusian sector of the 30-kilometer zone around the Chernobyl nuclear power plant. Dose rate measurements were carried out at experimental objects from 1987 to 2023. It was shown that at the most polluted experimental facility in the Kr, it decreased from 47 in 1987 to 4.5 mGy/h in the early 20s, and at the Ms facility from 35 to 1.8 mGy/h, respectively. The dynamics of dose rate was approximated by a two-exponential relationship. The first term of the dependence determined the “rapid” changes in the dose index from 1987 to the mid-90s with a half-decrease period of 0.8-1.6 years and is associated with the radioactive decay of medium-lived radionuclides. The second term determined the “slow” dose rate changes since the mid-90s with a half-decrease period of 10-16 years and is due to the radioactive decay of Cs and its redistribution in the surface soil layers. The contribution of “rapid” changes to the dose rate reduction over the entire study period ranged from 55 to 77% and was directly dependent on the partial contribution to the total radioactive contamination of medium-lived radionuclides (Ce and Ru). The estimated accumulated dose of external radiation in the air-plant environment of the experimental facilities of the Kr and Ms can currently reach 2 and 4 Gy. For this reason, it is necessary to conduct further studies to assess the effects of the habitat of a radiosensitive reference organism, pine trees, under conditions of prolonged radiation exposure.