Current state and trends in the content of ¹³⁷Cs and ⁹⁰Sr in abiotic and biotic components of Arctic ecosystems (Barents and Kara Seas case study)

This publication summarizes long-term data on radioactive contaminants in seawater, bottom sediments, and marine fish and describes current patterns in radionuclide distribution using data collected by the Murmansk Marine Biological Institute during cruises to the Barents and Kara Seas in 2015–2017. During the study period, no short-lived artificial radionuclides were found in the Barents and Kara Seas. ¹³⁷Cs and ⁹⁰Sr isotopes with a longer half-life are still registered in Atlantic waters that are the main source of radioactive contamination in these Arctic seas. Volumetric activity of ¹³⁷Cs and ⁹⁰Sr was compared at different depths. A uniform distribution of ¹³⁷Cs in the vertical column of water and a tendency to increase the volume activity of ⁹⁰Sr from surface to bottom were observed in the Barents Sea. Bottom sediments in the Kara Sea contain on average 2 times more ¹³⁷Cs than the Barents Sea. Atlantic cod is characterized by an extremely low concentration of ¹³⁷Cs in muscular tissue, about an order of magnitude lower than in the period of maximum contamination of Barents Sea waters observed in 1982. Currently there is a decreasing trend in concentrations of anthropogenic radioisotopes in the environment and biota. Processes of ¹³⁷Cs and ⁹⁰Sr removing from biotic and abiotic components are described with exponential functions. Due to natural marine purification processes, the decrease of ¹³⁷Cs and ⁹⁰Sr concentrations in the Barents and Kara Seas occur 2–4 times faster than the physical radioactive decay of these radionuclides. (paper)