3 
Contents 
1 Introduction 5 
2 Sources of long-lived radionuclides 
in the Baltic Sea sediments e 
3 Previous inventories of long-lived radionuclides 
in the Baltic Sea sediments 9 
4 Project plan of the Sediment Baseline Study 11 
5 Results and discussion 12 
5.1 Cs-137 12 
5.2 K-40 16 
5.3 Sr-90 17 
5.4 Tc-99 17 
5.5 Ra-226 18 
5.6 Th-232 18 
5.7 Np-237 19 
5.8 Pu-238 19 
5.9 Pu-239,240 20 
5.10 Am-241 20 
6 Conclusions 22 
7 References 24 
Appendix 25 
An Intercomparison of Radionuclide Analyses in a Baltic Sea 
Sediment Sample 25 
Long-lived radionuclides in the seabed of the Baltic Sea