In 1986 a more detailed study of the marine bottom water and sediment off the
Danube mouths was initiated. Submerged marine sediment and sea water samples,
up to 20 m depth were collected off the pre-danubian coast, on Sulina, Sf.Gheorghe,
Portita and Buhaz profiles, in 1986, and Sulina and Sf.Gheorghe profiles, in 1987,
and the results were reported in (Osvath et al. 1988).
Environmental sediment/water distribution coefficients and biota concentration
factors have been calculated for the caesium isotopes. Concentration factors of
137
Cs in Black Sea biota are presented in (Osvath et al. 1990a, b) for 14 species of fish,
molluscs and seaweed.
In order to determine the extent of removal of
7 Be and
234 Th from the water
column to the seabed a special sampling procedure was developed. Superficial
sediment layers were collected by a diver from Eforie Sud station (24 m water
depth) in 1994. A custom-designed device with 38 cm
2 surface area, collecting top
sediment was used. Four identical samples were collected within an area of about
400 m
2 . The gamma spectrometric measurements of the samples were performed
immediately (4 days after sampling). Concentrations of
7 Be and
234 Th were determined with less than 5% uncertainty in each sample. Based on a simple steady state
model and a constant deposition rate, the
7 Be equilibrium inventory in water can be
estimated, if the
7 Be mean monthly deposition rate is known.
Using deposition rates measured in samples collected nearshore on land at the
nearby NERSN Constanta monitoring station and a simple steady state model, a
7 Be
equilibrium inventory of 90 Bq/m
2 was estimated. Based on measured concentrations in superficial sediments a
7 Be mean equilibrium inventory in superficial
sediment of 104 Æ 11 Bq/m
2 , which agrees very well with the value estimated
from deposition. Furthermore, a mean residence time of
7 Be in the Black Sea
coastal waters was estimated to be less than 38 days.
The estimated
234
Th flux from the sea water column to the sediment based on
measurements of unsupported
234 Th in top sediments was 4.3 Bq/m
2
/day.
1
10
100
1000
1980
1985
1990
1995
Bq/m^3
Year
Fig. 12.4
137
Cs in coastal
N-W Black Sea surface
water
216
C. Dovlete et al.
Danube mouths was initiated. Submerged marine sediment and sea water samples,
up to 20 m depth were collected off the pre-danubian coast, on Sulina, Sf.Gheorghe,
Portita and Buhaz profiles, in 1986, and Sulina and Sf.Gheorghe profiles, in 1987,
and the results were reported in (Osvath et al. 1988).
Environmental sediment/water distribution coefficients and biota concentration
factors have been calculated for the caesium isotopes. Concentration factors of
137
Cs in Black Sea biota are presented in (Osvath et al. 1990a, b) for 14 species of fish,
molluscs and seaweed.
In order to determine the extent of removal of
7 Be and
234 Th from the water
column to the seabed a special sampling procedure was developed. Superficial
sediment layers were collected by a diver from Eforie Sud station (24 m water
depth) in 1994. A custom-designed device with 38 cm
2 surface area, collecting top
sediment was used. Four identical samples were collected within an area of about
400 m
2 . The gamma spectrometric measurements of the samples were performed
immediately (4 days after sampling). Concentrations of
7 Be and
234 Th were determined with less than 5% uncertainty in each sample. Based on a simple steady state
model and a constant deposition rate, the
7 Be equilibrium inventory in water can be
estimated, if the
7 Be mean monthly deposition rate is known.
Using deposition rates measured in samples collected nearshore on land at the
nearby NERSN Constanta monitoring station and a simple steady state model, a
7 Be
equilibrium inventory of 90 Bq/m
2 was estimated. Based on measured concentrations in superficial sediments a
7 Be mean equilibrium inventory in superficial
sediment of 104 Æ 11 Bq/m
2 , which agrees very well with the value estimated
from deposition. Furthermore, a mean residence time of
7 Be in the Black Sea
coastal waters was estimated to be less than 38 days.
The estimated
234
Th flux from the sea water column to the sediment based on
measurements of unsupported
234 Th in top sediments was 4.3 Bq/m
2
/day.
1
10
100
1000
1980
1985
1990
1995
Bq/m^3
Year
Fig. 12.4
137
Cs in coastal
N-W Black Sea surface
water
216
C. Dovlete et al.