This article is devoted to the study of the activity of technogenic Cs-137 and Sr-90, as well as natural radionuclides K-40, Th-232 and Ra-226 in bottom sediments of the Kola coast of the Barents Sea, where a significant number of radiation objects are concentrated. In order to characterize and assess the accumulation of radioactivity in the bottom sediments, we studied the particle size distribution and some physicochemical parameters, such as the content of organic matter, carbonates and ash components. The average activities of natural radionuclides Ra-226, Th-232 and K-40 were 325.0, 25.1 and 466.7 Bq.kg(-1), respectively. Levels of natural radionuclides in the coastal zone of the Kola Peninsula are within the range of marine sediments worldwide. Still, they are slightly higher than those observed in the central areas of the Barents Sea, most likely due to the formation of coastal bottom sediments as a result of the destruction of the natural radionuclide-enriched crystalline basement rocks that make up the Kola coast. The average activities of technogenic Sr-90 and Cs-137 in the bottom sediments of the Kola coast of the Barents Sea are 3.5 and 5.5 Bq.kg(-1), respectively. The highest activities of Sr-90 and Cs-137 were found in the bays of the Kola coast, while they remain below detection limits in the open parts of the Barents Sea. Despite the presence of potential sources of radiation pollution in the coastal zone of the Barents Sea, we did not find any short-lived radionuclides in the bottom sediments, which indicates the absence of a significant influence of local sources on the transformation of the technogenic radiation background. The study of particle size distribution and physicochemical parameters showed that the accumulation of natural radionuclides is largely related to the content of organic matter and carbonates, while the accumulation of technogenic isotopes occurs in the composition of organic matter and the smallest fractions of bottom sediments.
