15 
Sub-region 
Number 
of stations 
Sum 
(hard 1:20) (TBq) 
Sum 
(hard 1:5) (TBq) 
Percent 
of total (%) 
Bothnian Bay 
17 
165 
195 
8 
Bothnian Sea 
58 
1530 
1740 
73 
Gulf of Finland 
46 
175 
195 
8 
Baltic Proper + Gulf of Riga 
69 
230 
270 
11 
Total 
190 
2100 
2400 
100 
The results were not decay-corrected in 
this evaluation because very often the total 
amounts of Cs-137 seemed to vary at the 
same station in consecutive years without 
any trend, or remained unchanged during the 
whole study period. The variability seemed to 
be caused by other factors than the half-life of 
Cs-137, for example, differences in the exact 
sampling position, success of sampling, etc. 
Figure 4 shows the variability of results at the 
stations LL3a (Gulf of Finland) and EB1 (Both- 
nian Sea) in 2000-2005. In both cases, the 
total amounts of Cs-137 were relatively stable 
during the whole project period. However, if 
the results were to be decay-corrected to the 
middle of the study period (2002), the total 
inventory would be reduced by about 3%, and 
if they were to be decay-corrected to the end 
of 2005, the total inventory would be reduced 
by about 9%. The physical half-life of Cs-137 
is 30.1 years. 
Station LL3a 
Station EB1 
Table 2. 
Inventories of 
Cs-137 in different 
sub-regions of the 
Baltic Sea based 
on the areas of soft 
and hard bottoms in 
each. 
Figure 4. 
Total amounts of 
Cs-137 (Bq nr 2 ) at 
the stations LL3a 
(Gulf of Finland) and 
EB1 (Bothnian Sea) 
in 2000-2005. 
Long-lived radionuclides in the seabed of the Baltic Sea