crinita, Padina pavonica, Phyllophora crispa, Ulva rigida C. Ulva linza and
Zostera marina. Alpha-radionuclides of
239,240 Pu were analyzed in water, bottom
sediments and the following hydrobionts: macroalgae – C. crinita, U. rigida,
Ph. crispa;bivalves – Mytilus galloprovincialis and fish – Trachurus mediterraneus
ponticus, Sprattus sprattus phalericus, Merlangius merlangus.
Research was done for Pu content and it showed that the 1963 stratospheric
fallout deposition maximum is present at a depth of 18–20 cm. Several lines of
evidence support the 1963 interpretation of this maximum: (i) the Pu ratios in this
depth range agrees with the isotopic composition of stratospheric fallout; (ii) a
238
Pu activity peak is also observed at this depth; (iii) the
238 Pu/
239+240
Pu activity
ratios in this portion of the sediment core are close to the Northern Hemisphere
stratospheric fallout activity ratio of 0.04; and (iv) the
239 +
240 Pu activity peaks also
coincide with a
137 Cs activity maximum found in earlier studies. The seven ICPMSanalyzed intervals between 14–16 cm and 26–28 cm, inclusive, have
240 Pu/
239
Pu ¼ 0.187 Æ 0.005 (1 SD), which coincides with the range of 0.180 Æ 0.014. In
the same depth range of the core, the ten intervals between 14–15 and 24–25 cm
analyzed by alpha spectrometry have
238 Pu/
239 +
240 Pu ¼ 0.038 Æ 0.005 (1 SD).
The upper portion of the sediment core, commencing at about 12 cm, clearly
shows systematic changes stemming from an additional input of non-stratospheric
fallout Pu. The vertical profiles of
238 Pu and
239+240 Pu both show double peaks
above 12 cm. Associated with these peaks are
238 Pu/
239+240 Pu activity ratios and
240
Pu/
239 Pu atom ratios that are significantly higher than stratospheric fallout; the
highest
240 Pu/
39 Pu ratio of 0.307 Æ 0.014 was found in the 4–6 cm depth interval. It
follows that the near-surface double peaks stem from fluvial transport of
Chernobyl-associated radionuclides via the Danube River, as these peaks exhibit
238 Pu/
239+240 Pu and
240 Pu/
239
Pu signatures consistent with mixing of Chernobyl
debris with stratospheric fallout. As a result of the Chernobyl accident, both volatile
fission products (e.g.
137 Cs) and nonvolatile actinides (U, Pu) were distributed over
a widespread area of Eurasia. The non-volatile actinides, along with nonvolatile
fission products are contained in individual “hot” fuel particles of 1–10 pm aerodynamic diameter; these particles have been previously identified in Poland and in
Finland. The transport of “hot” fuel particles over distances of up to ~1000 km is
evident in these previous studies. Deposition of non-volatile Chernobyl particles
into the Danube watershed occurred during the course of the accident; over
subsequent years, material has been eroding from the catchment basin, entering
the Danube River, and is thereafter transported towards the Black Sea.
An initial study of the Chernobyl disaster and its environmental effects was
conducted in 1988 by the United Nations Scientific Committee on the Effects of
Atomic Radiation (UNSCEAR). The USCEAR report depicts the behavior of the
plumes released during the course of the accident.
It was demonstrated using
240 Pu/
239 Pu atom ratios measured by SF-ICPMS, that
Chernobyl-derived Pu is present in the Black Sea’s Danube Delta sediments. The
40
Pu/
239 Pu ratios in the upper portions of a core collected in 1997 indicate mixing
between stratospheric fallout (
240
Pu/
239 Pu ¼ 0.180) and Chernobyl debris (
240 Pu/
239 Pu ¼ 0.403). The elevated
240
Pu/
239 Pu ratios are observed in two early 1990s
306
A. Strezov
Zostera marina. Alpha-radionuclides of
239,240 Pu were analyzed in water, bottom
sediments and the following hydrobionts: macroalgae – C. crinita, U. rigida,
Ph. crispa;bivalves – Mytilus galloprovincialis and fish – Trachurus mediterraneus
ponticus, Sprattus sprattus phalericus, Merlangius merlangus.
Research was done for Pu content and it showed that the 1963 stratospheric
fallout deposition maximum is present at a depth of 18–20 cm. Several lines of
evidence support the 1963 interpretation of this maximum: (i) the Pu ratios in this
depth range agrees with the isotopic composition of stratospheric fallout; (ii) a
238
Pu activity peak is also observed at this depth; (iii) the
238 Pu/
239+240
Pu activity
ratios in this portion of the sediment core are close to the Northern Hemisphere
stratospheric fallout activity ratio of 0.04; and (iv) the
239 +
240 Pu activity peaks also
coincide with a
137 Cs activity maximum found in earlier studies. The seven ICPMSanalyzed intervals between 14–16 cm and 26–28 cm, inclusive, have
240 Pu/
239
Pu ¼ 0.187 Æ 0.005 (1 SD), which coincides with the range of 0.180 Æ 0.014. In
the same depth range of the core, the ten intervals between 14–15 and 24–25 cm
analyzed by alpha spectrometry have
238 Pu/
239 +
240 Pu ¼ 0.038 Æ 0.005 (1 SD).
The upper portion of the sediment core, commencing at about 12 cm, clearly
shows systematic changes stemming from an additional input of non-stratospheric
fallout Pu. The vertical profiles of
238 Pu and
239+240 Pu both show double peaks
above 12 cm. Associated with these peaks are
238 Pu/
239+240 Pu activity ratios and
240
Pu/
239 Pu atom ratios that are significantly higher than stratospheric fallout; the
highest
240 Pu/
39 Pu ratio of 0.307 Æ 0.014 was found in the 4–6 cm depth interval. It
follows that the near-surface double peaks stem from fluvial transport of
Chernobyl-associated radionuclides via the Danube River, as these peaks exhibit
238 Pu/
239+240 Pu and
240 Pu/
239
Pu signatures consistent with mixing of Chernobyl
debris with stratospheric fallout. As a result of the Chernobyl accident, both volatile
fission products (e.g.
137 Cs) and nonvolatile actinides (U, Pu) were distributed over
a widespread area of Eurasia. The non-volatile actinides, along with nonvolatile
fission products are contained in individual “hot” fuel particles of 1–10 pm aerodynamic diameter; these particles have been previously identified in Poland and in
Finland. The transport of “hot” fuel particles over distances of up to ~1000 km is
evident in these previous studies. Deposition of non-volatile Chernobyl particles
into the Danube watershed occurred during the course of the accident; over
subsequent years, material has been eroding from the catchment basin, entering
the Danube River, and is thereafter transported towards the Black Sea.
An initial study of the Chernobyl disaster and its environmental effects was
conducted in 1988 by the United Nations Scientific Committee on the Effects of
Atomic Radiation (UNSCEAR). The USCEAR report depicts the behavior of the
plumes released during the course of the accident.
It was demonstrated using
240 Pu/
239 Pu atom ratios measured by SF-ICPMS, that
Chernobyl-derived Pu is present in the Black Sea’s Danube Delta sediments. The
40
Pu/
239 Pu ratios in the upper portions of a core collected in 1997 indicate mixing
between stratospheric fallout (
240
Pu/
239 Pu ¼ 0.180) and Chernobyl debris (
240 Pu/
239 Pu ¼ 0.403). The elevated
240
Pu/
239 Pu ratios are observed in two early 1990s
306
A. Strezov