Transformation of Radioactive Contamination of the Bottom Sediments in the Kaliningrad (Vistula) Lagoon Between 2011 and 2023

The article presents the data of radioecological research of the bottom sediments in the Russian zone of the Vistula Lagoon in 2011–2023. According to research, the specific activity of 137Cs in the bottom sediments of the Lagoon was in the range of 3,9–165 Bq/m3. 137Cs is the main technogenic radionuclides that makes the greatest contribution to the pollution of the Lagoon. Contamination of the bottom sediments with 137Cs is determined by the redistribution of mainly post-Chernobyl fallout. The 137Cs accumulation was recorded in the northern deep-water part of the Primorskaya Bay. According to observations, the effective half-life of 137Cs activity in the sediments of the Lagoon is 10,4–42 years. The content of natural radionuclides is: 226Ra – from 9,0 to 35,3; 232Th – from 3,8 to 43,2; 40K from 227 to 715 Bq/kg. The NRN specific activity in the sediments of the Lagoon did not exceed 153 Bq/kg, which was significantly lower than the established safe level (370 Bq/kg), allowing their handling without restrictions. The correlations between the content of 40K, 226Ra, 232Th in the bottom sediments of the Lagoon were established with the type of sediment