As a result of the contemporary forecast estimates it was obtained that a decrease
of the 90Sr concentration in the water of the Dnieper-Bug estuary (northern area of
the north-western part of the Black Sea) to the pre-accident levels will occur up
2018, rather than before 2025, as assumed previously (Mirzoyeva 2008). The
hydrological and biogeochemical processes, occurring in the study area of the
sea, reduce the time of presence of post-accident radionuclides in the marine
environment in the 2–6 times.
To the present time the stationary equilibrium is formed between entrance and
elimination of
90 Sr and
137
Cs in the oxygen zone of the Black Sea, while the content
of radionuclides in the hydrogen-sulphidous zone of the sea has been increasing.
By 2013 the content of
90 Sr and
137 Cs was evaluated in the Black Sea as
1670 TBq and 2843 TBq, respectively, that in 3.6–6.4 and in 1.2–1.6 times was
higher than the content of the radionuclides in the 2000. Herewith 66% and 67%
Fig. 17.11 The maps of contamination of the Black Sea bottom sediments (in a layer 0–5 cm) by
90
Sr for the after accidental period 1986–2015
17 Radionuclides
137
Cs and
90
Sr in Components of the Black Sea Ecosystems. . .
291