ranged from 0.01 to 0.04 in the estuarine areas of the Danube and the Dnieper to
1.3–2.2, at the tiefensprung and up to 25–100 in the deep part of the sea. These
evaluations confirmed that the role of sedimentation factor
137 Cs migration in the
Black Sea could be relevant only in the local estuarine areas of rivers.
The scheme of redistribution of the average concentrations of
90 Sr (Bq kg
À1 dw)
in bottom sediments (0–5 cm layer) of the Black Sea in 1986–2015 are presented on
Fig. 17.11. They show that in 1986,
90 Sr concentration in the sediments ranged from
0.4 to 46.4 Bq kg
À1 dry weight.
90 Sr distribution depended both on the depth of the
sediment, and the remoteness of the area from the sources of income of the
radionuclide in the Black Sea – the Dnieper and the Danube Rivers. In the western
deep-water part of the Black Sea at a depth of ~ 2000 m (Fig. 17.11), the
concentration of
90 Sr in 1988 was 0.3 Bq kg
À1 dry weight, which corresponded to
the levels defined in the Black Sea to the ChNPP accident (Barannik 1974;
Database ORChB IMBR 2006).
90
Sr concentration in the sediments of the estuary
of the Chorokh River (south-eastern part of the sea) was also small, and in 2000 was
0.5 Bq kg
À1 dry weight. The most contaminated by 90Sr areas were estuarine zone
of the Dnieper, the Dniester and the Danube, partly area Tarkhankut peninsula,
south-eastern part of Crimea (Feodosia district). The association of elevated concentrations of
90 Sr to these areas not only persisted over time (until 2015), but also
the process of increasing of the concentration of radionuclides in bottom sediments
in studied regions was observed.
17.3.3 Forecast Assessments
The forecast assessments of the time periods to reach to the pre-accident levels of
90
Sr and
137 Cs concentrations in the balance, abiotic and biotic components of the
Black Sea ecosystems are presented in Table 17.5. The periods of time of the
decreasing in twice and total periods of decreasing concentrations of these artificial
radionuclides to pre-accident levels were determined for the balance components,
biotic and abiotic components of the Sevastopol bays of the Black Sea. It was found
that the biogeochemical processes occurring in the Black Sea, in average decrease
in 2–6 times the residence of the post-accident
90 Sr and
137
Cs in comparison with
the physical half-lives, and five periods of decay of investigated radionuclides.
17.4 Conclusion
It was determined, that the main factors of the formation of radioactive pollution in
the Black Sea are: atmospheric fallout on the surface of the sea, entry of the
radionuclides into the oxygen zone with runoff of the rivers, removal of radionuclides through the straits, migration into the deep zone, removal into the thickness
of bottom sediments, radioactive decay.
290
N.Y. Mirzoyeva et al.
1.3–2.2, at the tiefensprung and up to 25–100 in the deep part of the sea. These
evaluations confirmed that the role of sedimentation factor
137 Cs migration in the
Black Sea could be relevant only in the local estuarine areas of rivers.
The scheme of redistribution of the average concentrations of
90 Sr (Bq kg
À1 dw)
in bottom sediments (0–5 cm layer) of the Black Sea in 1986–2015 are presented on
Fig. 17.11. They show that in 1986,
90 Sr concentration in the sediments ranged from
0.4 to 46.4 Bq kg
À1 dry weight.
90 Sr distribution depended both on the depth of the
sediment, and the remoteness of the area from the sources of income of the
radionuclide in the Black Sea – the Dnieper and the Danube Rivers. In the western
deep-water part of the Black Sea at a depth of ~ 2000 m (Fig. 17.11), the
concentration of
90 Sr in 1988 was 0.3 Bq kg
À1 dry weight, which corresponded to
the levels defined in the Black Sea to the ChNPP accident (Barannik 1974;
Database ORChB IMBR 2006).
90
Sr concentration in the sediments of the estuary
of the Chorokh River (south-eastern part of the sea) was also small, and in 2000 was
0.5 Bq kg
À1 dry weight. The most contaminated by 90Sr areas were estuarine zone
of the Dnieper, the Dniester and the Danube, partly area Tarkhankut peninsula,
south-eastern part of Crimea (Feodosia district). The association of elevated concentrations of
90 Sr to these areas not only persisted over time (until 2015), but also
the process of increasing of the concentration of radionuclides in bottom sediments
in studied regions was observed.
17.3.3 Forecast Assessments
The forecast assessments of the time periods to reach to the pre-accident levels of
90
Sr and
137 Cs concentrations in the balance, abiotic and biotic components of the
Black Sea ecosystems are presented in Table 17.5. The periods of time of the
decreasing in twice and total periods of decreasing concentrations of these artificial
radionuclides to pre-accident levels were determined for the balance components,
biotic and abiotic components of the Sevastopol bays of the Black Sea. It was found
that the biogeochemical processes occurring in the Black Sea, in average decrease
in 2–6 times the residence of the post-accident
90 Sr and
137
Cs in comparison with
the physical half-lives, and five periods of decay of investigated radionuclides.
17.4 Conclusion
It was determined, that the main factors of the formation of radioactive pollution in
the Black Sea are: atmospheric fallout on the surface of the sea, entry of the
radionuclides into the oxygen zone with runoff of the rivers, removal of radionuclides through the straits, migration into the deep zone, removal into the thickness
of bottom sediments, radioactive decay.
290
N.Y. Mirzoyeva et al.