20 
northern Baltic Proper, the Gulf of Bothnia, and 
the Gulf of Finland, the total amounts were slightly 
higher (1.6-6.7 Bq nr 2 ) than generally in the 
southern Baltic Proper, as the activity concentra 
tions ranged from 10 mBq kg -1 to 480 mBq kg -1 
dry weight. 
5.9 Pu-239,240 
Plutonium is created from uranium in nuclear 
reactors. During the 1950s and 1960s, plutonium 
was dispersed worldwide from atmospheric test 
ing of nuclear weapons. The fallout from these 
tests left low concentrations of plutonium in soils 
and sediments around the world. The fallout from 
Figure 8. the Chernobyl accident brought a small addition of 
Vertical distribution of plutonium to the aquatic environment of the Baltic 
Pu-239,240 (Bq kg’ 1 
d.w.) at the station Teili 1 
(northern Baltic Proper) 
in 2002. 
Teili 1 
Bq/kg d.w. 
Concentration peaks of 
Chernobyl-derived Cs-137 
and weapons-tests-origin 
Pu-239,240 at the station 
K15 in the Gulf of Finland 
(Mattila et al., 2006). 
W) 
M 
cr 1 
PQ 
o 
■"T 
<N 
On 
rO 
<N 
S 
Qh 
Sea, but its contribution was minor compared to 
that of the weapons test fallout. 
Data on Pu-239,240 were reported from 51 sedi 
ment cores taken from all sub-regions of the Baltic 
Sea, although most were from the southern Baltic 
Proper. The plutonium peak caused by the weap 
ons test fallout provides an excellent time marker 
(1963), in addition to that of Cs-137 resulting from 
the Chernobyl accident, for the estimation of 
recent sediment accumulation rates in the Baltic 
Sea (Figures 8 and 9). 
The total amounts of Pu-239,240 at different 
sampling stations in the Baltic Sea are shown 
in Figure 10. The inventories of Pu-239,240 in 
the sediments of different sub-regions are given 
in Table 3, as well as the maximum values and 
the median values (Bq nr 2 ) used in the inven 
tory calculations. The ratio 1:10 was used in the 
estimation of Pu-239,240 values for hard bottoms 
versus soft bottoms, analogously with the earlier 
calculations published by Salo et al. (1986) from 
the beginning of the 1980s. 
The total inventory of Pu-239,240 in the seabed 
of the Baltic Sea was estimated at 15.3 TBq. The 
portion for the Bothnian Sea was 45% of the total 
inventory and that for the Baltic Proper was 32%. 
If the ratios 1:20 or 1:5 were to be used for the 
total amounts of Pu-239,240 on hard bottoms 
compared to those on soft bottoms, the result 
would be 14.6 TBq or 16.8 TBq, respectively. 
The estimate is equal to that of Salo et al. (1986) 
from the beginning of the 1980s. This may be 
realistic taking into account the fact that the input 
of plutonium from Chernobyl into the Baltic Sea 
was relatively small, and on the other hand, the 
present estimation was based on a clearly more 
extensive study material. 
5.10 Am-241 
Americium is a man-made radionuclide produced 
in nuclear reactors and nuclear weapons detona 
tions. Most americium-241 in the environment 
originates from the atmospheric testing of nuclear 
weapons during the 1950s and 1960s. Results 
on Am-241 were reported from three stations in 
the southern Baltic Proper and the Belt Sea and 
three stations in the Bothnian Bay and the Gulf 
of Finland. The activity concentrations in the 
samples ranged from 0.08 Bq kg -1 to 3.5 Bq kg -1 
dry weight.