Modeling Study of the Atmospheric Transport of Radioactivity Released into the Air as a Result of Forest Fires in the Exclusion Zone in April 2020

Abstract

In April 2020, the largest forest fire occurred in the Chornobyl Exclusion zone in its history. The results of modeling the atmospheric transport of radioactive aerosols raised into the atmosphere as a result of fires in forest and grass areas in the Exclusion zone, as well as in radioactively contaminated forests outside it in Kyiv and Zhytomyr regions are presented in the paper. To assess the consequences of forest fires, a set of models of lifting, atmospheric transport and deposition of radionuclides on the underlying surface LEDI, developed at the Institute for Safety Problems of Nuclear Power Plants of the National Academy of Sciences of Ukraine, was used. Calculations of the dynamics of the 137Cs activity concentration field in the surface air on a regional scale (in Ukraine) and on a local scale (within the Exclusion zone) were performed. According to the simulation results, the maximum values of the 137Cs activity in the surface air of Kyiv in some periods during April 4−20 could reach 2−4 mBq/m3, and the integral value of 137Cs activity in the air of Kyiv for the whole period was about 450 mBq⋅s/m3. The obtained results are generally consistent with the data of measurements of radioactive contamination of the nearground air in Kyiv and areas of the nuclear power plants in Ukraine. The analysis of the consistency of the simulation results with the data of measurements of the 137Cs activity concentration in the air in the Exclusion zone was performed. The main ways to improve the methodology for assessing the consequences of forest fires by modeling the atmospheric transport of radionuclides are identified.

A tuning-free wildfire detection algorithm reveals the impact of both Chornobyl wildfires and the Russian invasion of Ukraine in 2022

“…1). As Protsak et al [30][31] mentioned, the amount of radionuclides from the surface biomass resuspended into the atmosphere was considered to be limited, because the total burned area in March 2022 was smaller than that of the 2020 wild res, resulting in little or no additional radiation exposure to the public [3][4][5] .…”

“…To assess the hazards of air pollution after a large wild re and to relate re severity to changes in land cover, it is important to be able to detect the burned area accurately and rapidly. The amount of radionuclides released into the atmosphere by wild res in the area around Chornobyl can vary greatly depending on the extent to which the res spread 3,4,6,7 , because the radionuclides derived from the Chornobyl accident in the environment are known to be extremely heterogeneous 8-10 . For instance, Igarashi et al 11 found that the inventories of 137 Cs and 90 Sr at two sites located only 5 km apart differ signi cantly, by as much as 13 times and two times, respectively.…”

“…For instance, thermal anomalies detected by satellites indicated that in 2020 wild res in the Chornobyl Exclusion Zone (ChEZ) spread over an extensive area, and satellite images helped to produce an initial estimate that the burned area covered nearly 30% of the ChEZ 1,2 . Such information was used to assess the redistribution of radionuclides 3,4 and the potential risk of radiation exposure due to the re and smoke 5 . Satellite images are the only information available for estimating the burned area in case of large wild res.…”

Application of a tuning-free burned area detection algorithm to the Chornobyl wildfires in 2022

“…For instance, thermal anomalies detected by satellites indicated that in 2020 wildfires in the Chornobyl Exclusion Zone (ChEZ) spread over an extensive area, and satellite images helped to produce an initial estimate that the burned area covered nearly 30% of the ChEZ 1 , 2 . Such information was used to assess the redistribution of radionuclides 3 , 4 and the potential risk of radiation exposure due to the fire and smoke 5 . Satellite images are the only information available for estimating the burned area in case of large wildfires.…”

“…To assess the hazards of air pollution after a large wildfire and to relate fire severity to changes in land cover, it is important to be able to detect the burned area accurately and rapidly. The amount of radionuclides released into the atmosphere by wildfires in the area around Chornobyl can vary greatly depending on the extent to which the fires spread 3 , 4 , 6 , 7 , because the radionuclides derived from the Chornobyl accident in the environment are known to be extremely heterogeneous 8 – 10 . For instance, Igarashi et al .…”