29 
global fallout, but small amounts of 238 Pu and 
241 Pu in the fallout of the Chernobyl accident 
could be noticed in the activity ratios of 
238 Pu/ 239 ' 240 Pu and 241 Pu/ 239 ' 240 Pu, and in the 
excess amounts of 241 Pu (Ikaheimonen 2003). 
In the years 1999-2006, the reported 241 Am 
concentrations ranged from 0.08 to 4.80 Bq 
kg -1 d.w.. 
The activities of 90 Sr mostly originate from 
global fallout. It has been estimated that the 
input to the Baltic Sea of "Sr activity from the 
Chernobyl fallout only accounts for 13% of 
the total "Sr activity in the Baltic Sea (Luning 
and llus 2003). Because of the small share in 
the Chernobyl fallout and the costly analytical 
methods, the focus on "Sr has been reduced, 
and relatively little sediment data is available. 
Over the period 1999-2006, reported "Sr 
concentrations ranged from 0.1 to 73.8 Bq kg- 
1 d.w.. A rough estimate for the total amount 
of "Sr in the sediments of the Baltic Sea was 
about 26 TBq (llus et al. 2007). 
3B.5 Recommendations and future work 
It will continue to be essential to monitor 
radioactive substances in sediments in the 
Baltic Sea in the future. The continuous 
monitoring work and the compiling of time 
trends for radioactive substances provide 
a basis for understanding the state of the 
Baltic Sea environment and the radioactivity 
it contains. However, there are still several 
significant gaps in our knowledge (llus et al. 
2003, llus et al. 2007). In the near future, we 
should attempt to fill these gaps and increase 
our knowledge of the activities of e.g. "Sr, 
241 Am and natural radionuclides such as 210 Pb, 
in sediments in the Baltic Sea. Plans for the 
future should also include assessments of 
the impacts of ionising radiation on the Baltic 
marine environment. 
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