Spatial distribution of Sr-90 and Cs-137 in soil of terrestrial ecosystems in the vicinity of Beloyarsk NPP

On the basis of the created network of radioecological monitoring, the content of most radiologically significant artificial radionuclides in soil of the terrestrial (anthropogenic, natural and agrarian) ecosystems of the 30-km zone of influence of the Beloyarsk Nuclear Power Plant (NPP) was estimated in 2013 and 2019. In the ArcMap 10.5 module of the ArcGIS package, a GIS project was developed for the spatial distribution of the ambient dose equivalent rate (ADER), as well as the 137Cs и 90Sr contamination density of the soil cover in the area of the nuclear power plant. Areas in the Olkhovsky swamp of the NPP sanitary protection zone were identified with an average of 3-7 times higher ADER levels compared to the regional levels. For many years, the process waters of the Beloyarsk NPP containing artificial radionuclides were discharged into this swamp. The density of soil contamination with 137Cs in the Olkhovsky swamp reaches an average of 2.4 MBq/m2, 90Sr – 23 kBq/m2. According to the degree of decrease in the 137Cs content in the soil cover, the terrestrial ecosystems of the Beloyarsk NPP location area are arranged in a row: Olkhovsky swamp, forests, grasslands, anthropogenic areas, virgin lands, vegetable gardens, arable lands. Local areas with an increased density of 90Sr contamination (2-3 kBq/m2) are noted in the southern direction from the Beloyarsk NPP at a distance of 10-25 km and are caused by both the emissions from the reactors of the first stage of the nuclear power plant and the influence of the East Ural radioactive trace from the accident at the Mayak Production Association. The 137Cs/90Sr ratio in the soils of the area where the Beloyarsk NPP is located is on average 3.3, which is higher than the global radioactive fallout (1.6) and is explained by the impact of the nuclear fuel cycle enterprises of the Ural region in the initial period of their operation.