The obtained results (Fig. 18.8) show that Cs content is rather low (compared to
the shelf), while natural nuclide concentrations increase with the depth.
226
Ra
nuclide concentration is higher in the middle depths (55–90 Bq/kg) than other
natural nuclides while at the bottom 2000 m U content is the highest (90–135 Bq/
kg). The character of deep sediment samples is slime except at 2000 m where the
matrix is very hard in structure and black in color.
Radionuclide content in Black Sea sediments
Gamma Spectroscopy
Bq/kg
Cs - 137
Th - 234
Th - 232
Ra - 226
Maslen nos
Sozopol
Balchik
Golden Sands
Ahtopol
Rezovo
Kaliakra
Kavarna
Chernomoretz
Tzarevo
Tuzlata
Bjala
0
10
20
30
40
50
60
Fig. 18.5 Mean nuclide content in silt and slime sediments along the Bulgarian coast
Cs-137 [Bq/kg] - mean value
1991
1992
1993
1994
1995
1996
1998
1999
1991
1992
1993
1994
1995
1996
1998
1991
1992
1993
1994
1995
1996
1998
1999
0
10
20
30
40
50
60
70
sand
silt
slime
Fig. 18.6 Mean
137
Cs content in sediments during the period 1991–1999
18 Radioecology of the Black Sea
315