Anthropogenic plutonium radioisotopes in the ecosystem components of Sevastopol Bay (the Black Sea)

Modern levels (2010-2020) of ^239+240Pu activity concentration in Sevastopol Bay (Black Sea) surface waters, 0-5 cm layer of bottom sediments and hydrobionts were determined by multistage radiochemical technique. The ^239+240Pu activity concentrations in Sevastopol Bay surface water were on relatively low level: 1.08±0.09 - 1.54±0.17 mBqnr³. The maximum value of ^239+240Pu activity concentration in the bottom sediments surface layer was observed in Sevastopol Bay mouth (993±90 mBqkg¹) and it decreased with distance from the bay entrance to its tail end down to the minimum value - 276±53 mBqkg¹. Based on these results as well as on published data the ²³⁹+²⁴⁰Pu deposition density distribution in the bay boxes and their inventory in 0-5 cm layer of bottom sediments were estimated in every boxes. Total ^239+240Pu inventory in the bottom sediments surface layer was estimated at 121 MBq, with the highest deposition density value determined in the mouth part of the bay. Among studied hydrobiont species the highest ^239+240Pu content was determined for mollusks (for their shells) Mytilus galloprovincialis (Lamarck, 1819) while the lowest - for fish Scorpaena poreus (Linnaeus, 1758). Accumulation ability of studied ecosystem components of Sevastopol Bay against ^239+240Pu was characterized by evaluating concentration factors (C_f). It was shown that the bottom sediments of the bay were the main depot for plutonium anthropogenic radionucludes (C_f (^239+240Pu) = n-10⁵). The C_f (^239+240Pu) were from two to three orders of magnitude lower for the hydrobionts of the bay: n-10³ for brown algae and mollusks and n-10² for green algae and fish.