90Sr and 137Cs in the Black Sea after the Chernobyl NPP accident: inventories, balance and tracer applications

The paper summarizes studies of the distributions of 90Sr and 137Cs in the water and sediments of the Black Sea carried out during a 10-year period following the 1986 accident at the Chernobyl Nuclear Power Plant. Its goal is to assess the temporal evolution of radionuclide inventories and balances and to evaluate the mixing of water masses and the sedimentation processes using man-made radionuclides as tracers. Using mathematical models and field data, mixing time-scales of 5, 16 and 24 years have been estimated, respectively, for the water layers of depths 0–50, 0–100 and 0–200 m. For the Central Basin the ventilation time of the lower pycnocline is estimated at 15–25 years. 137Cs has been used to date shelf and deep-basin sediments, providing the history of chemical and radioactive pollution and of eutrophication during the past 50 years.