11 
4 Project plan of the Sediment Baseline Study 
In 2001 at its sixth meeting, the Project Group 
MORS identified the need for a Sediment 
Baseline Study as a future activity of the Group to 
provide a more detailed description of the spatial 
distribution of radionuclides in the Baltic Sea 
sediments. The Group noted that especially the 
western part of the Baltic Proper had not been 
covered in an adequate way in the preceding 
studies. Other areas for additional sampling were 
also considered. 
The Chernobyl fallout is very unevenly distributed 
in the Baltic Sea area. During the 20 years since 
the accident, the MORS Group has made several 
efforts to evaluate the total inventories of the most 
important fallout nuclides (especially Cs-137) 
bound in the Baltic Sea sediments. With reference 
to the existing data, there were huge “white areas” 
lacking data especially on the Swedish side of 
the Baltic Proper, in the southeastern parts of the 
Baltic Proper, and in the Gulf of Riga. 
One of the main objectives of the study was 
to obtain more information about the amounts 
of radionuclides in the sediments of the “white 
areas”. In addition to Cs-137, more information 
about Sr-90, Tc-99, 1-129, Np-237, and other 
transuranic elements was needed. The study 
aimed to be arranged cooperatively with the 
planned sediment monitoring programme under 
HELCOM COMBINE and several national sedi 
ment monitoring programmes being planned, e.g., 
in Sweden. 
The study was planned to cover all the sam 
pling stations listed in the regular monitoring 
programme of MORS, with additional stations 
as appropriate. The western and southeastern 
parts of the Baltic Proper would be the main 
target areas in planning for additional samples. 
Furthermore, special attention was to be directed 
to coastal areas, to areas with hard bottoms, 
and to anoxic sediments. The resources among 
the Contracting Parties to increase sampling at 
additional stations were recognized to be limited. 
However, many Contracting Parties announced 
that they were prepared to consider their possibili 
ties to provide additional data. 
A more detailed Project Plan for the study was 
made in 2002 at the seventh meeting of the 
MORS-PRO Group. At that time, the project 
period was planned to span three years (2002- 
2004) and the general objectives of the project 
were defined as follows: 
- to provide additional data on radionuclides in 
Baltic Sea sediments; 
- the sampling and analysis activities should 
mainly be based on the permanent HELCOM/ 
MORS Monitoring Programme. Additional 
samples would be taken with the aim of pro 
viding new data from so-called “white areas”, 
coastal areas, areas with hard bottoms, and 
anoxic sediments; 
- special attention should be directed to Sr-90, 
Tc-99, 1-129, and Np-237 analyses; 
- the sampling and analysis activities would 
be coordinated by Finland so that the whole 
Baltic Sea area would be covered (as fully as 
possible) by new data on Cs-137, Sr-90, Tc-99, 
1-129, Np-237, and Pu and Am isotopes. 
A preliminary plan of national contributions to the 
project was also defined in the MORS-PRO 7 
meeting. 
Due to the delay in sampling and other problems 
that arose in many countries, the eighth meeting 
of the Group decided to prolong the duration of 
the Study by one year. At the same meeting, a 
detailed list of national contributions was updated. 
The Ris0 National Laboratory promised to 
contribute to the project by analysing about 100 
sediment samples taken by the other participants 
for Np-237, Tc-99, and transuranics. The ninth 
meeting prolonged the timetable of the project 
further until 2006. 
Long-lived radionuclides in the seabed of the Baltic Sea