nuclear plants, with satellites, aircraft and nuclear submarines, in which radioactive
material has been dispersed (or could be dispersed in the future) into the marine
environment. The most important was the Chernobyl accident which caused worldwide distribution of some of the radionuclides released (e.g.
137 Cs). Other nuclear
accidents which have occurred in coastal sea areas (e.g. in Vladivostok Bay) or
inland (e.g. at Chelyabinsk) have had only regional effects on the radionuclide
concentrations of the marine environment.
One of the most widespread is the
137 Cs isotope. Its major sources come from the
atmospheric deposition of debris from atmospheric nuclear explosions that
occurred in the 50 and 60’s and in the northern hemisphere from nuclear accidents
in particular.
18.1.2 Radionuclides in the Black Sea Marine Environment
Since 1945 there has been a continuous release of technogenic radionuclides to the
environment, leading to their accumulation in the seas and oceans, the main source
of contamination being nuclear weapons tests in the atmosphere, on land and in
water. The Danube was the main contributor for nuclides in the Black Sea region
before 1986 mainly
90 Sr and
137 C) Polikarpov (1966), Kulebakina and Zesenko
(1984), Sokolova (1975), while the Dnyepr took second place.
After the Chernobyl accident a considerable increase occurred in nuclides
quantity in the environment (Buesseler et al. 1987; Kulebakina et al. 1988;
Kulebakina and Polikarpov 1989; Baumann et al. 1989; Broberg 1989; Hadderingh
and Kema 1989). The Black Sea being near to the reactor accepted great quantity
direct atmospheric radionuclide fallout. Additionally Chernobyl nuclides entered
and continued to enter the environment carried by the big rivers – Danube, Dnyepr,
Dnester.
A major part of the distribution and migration of long lived nuclide contaminants
(mainly
137 Cs,
90 Sr) are not only the hydrophysical processes but also the
biosedimentation and sorption on bottom sediments and concentration by biota. It
is known that
137 Cs and
90 Sr fallout before 1986 are found in sea water mainly in
soluble forms (Shvedov et al. (1962), and are weakly affected by biological
migration (contrary to other nuclides as
141 Ce,
144 Ce,
103 Ru,
95 Zr etc.). Chernobyl
radionuclides are characterized by a higher content of nonsoluble forms (even “hot”
particles) which are part of the reactor fuel. These peculiarities affect the behavior
of the Chernobyl nuclides in sediments and their accumulation in biota. The
contamination of sea bed sediments by
137 Cs and
90 Sr had a “spot” character
which was due to the way Cs entered the environment at the beginning – mainly
airborne on different particles.
Cesium penetrated rather quickly the water depths – in 1987 Cs was measured up
to 120 m, while in 1988 it reached 200–250 m. The observed phenomenon of “self
decontamination” of Black Sea waters was due to the radioactivity spots dilution
298
A. Strezov
material has been dispersed (or could be dispersed in the future) into the marine
environment. The most important was the Chernobyl accident which caused worldwide distribution of some of the radionuclides released (e.g.
137 Cs). Other nuclear
accidents which have occurred in coastal sea areas (e.g. in Vladivostok Bay) or
inland (e.g. at Chelyabinsk) have had only regional effects on the radionuclide
concentrations of the marine environment.
One of the most widespread is the
137 Cs isotope. Its major sources come from the
atmospheric deposition of debris from atmospheric nuclear explosions that
occurred in the 50 and 60’s and in the northern hemisphere from nuclear accidents
in particular.
18.1.2 Radionuclides in the Black Sea Marine Environment
Since 1945 there has been a continuous release of technogenic radionuclides to the
environment, leading to their accumulation in the seas and oceans, the main source
of contamination being nuclear weapons tests in the atmosphere, on land and in
water. The Danube was the main contributor for nuclides in the Black Sea region
before 1986 mainly
90 Sr and
137 C) Polikarpov (1966), Kulebakina and Zesenko
(1984), Sokolova (1975), while the Dnyepr took second place.
After the Chernobyl accident a considerable increase occurred in nuclides
quantity in the environment (Buesseler et al. 1987; Kulebakina et al. 1988;
Kulebakina and Polikarpov 1989; Baumann et al. 1989; Broberg 1989; Hadderingh
and Kema 1989). The Black Sea being near to the reactor accepted great quantity
direct atmospheric radionuclide fallout. Additionally Chernobyl nuclides entered
and continued to enter the environment carried by the big rivers – Danube, Dnyepr,
Dnester.
A major part of the distribution and migration of long lived nuclide contaminants
(mainly
137 Cs,
90 Sr) are not only the hydrophysical processes but also the
biosedimentation and sorption on bottom sediments and concentration by biota. It
is known that
137 Cs and
90 Sr fallout before 1986 are found in sea water mainly in
soluble forms (Shvedov et al. (1962), and are weakly affected by biological
migration (contrary to other nuclides as
141 Ce,
144 Ce,
103 Ru,
95 Zr etc.). Chernobyl
radionuclides are characterized by a higher content of nonsoluble forms (even “hot”
particles) which are part of the reactor fuel. These peculiarities affect the behavior
of the Chernobyl nuclides in sediments and their accumulation in biota. The
contamination of sea bed sediments by
137 Cs and
90 Sr had a “spot” character
which was due to the way Cs entered the environment at the beginning – mainly
airborne on different particles.
Cesium penetrated rather quickly the water depths – in 1987 Cs was measured up
to 120 m, while in 1988 it reached 200–250 m. The observed phenomenon of “self
decontamination” of Black Sea waters was due to the radioactivity spots dilution
298
A. Strezov