BALTIC SEAENVIRONMENT PROCEEDINGS No. 59 - Helcom

ed by the initial fallout. Figure 2 and 3 display the temporal
evolution of the average surface concentration of Cs-134
and Cs-137, respectively. These figures have been prepared by
the EDC with the monitoring data of seawater available in the
data bank.
Radioactive discharges from nuclear power stations into the
Baltic Sea are of extremely low impact. These releases can
only be detected in the local vicinity of the power plants.
They are of no relevance as far as dose to biota or humans
are concerned. Fig. 4 and 5 show the annual discharges of
Tritium and Cs-137 from most of the nuclear power stations
surrounding the Baltic Sea. These figures have been produced
by the Finnish Centre for Radiation and Nuclear Safety, Helsinki,
on the basis of the data submitted by the Contracting
Parties.
QUALITY ASSURANCE
The group MORS was well aware of the fact that an essential
question of the monitoring programme would be the quality of
the monitoring data. Therefore, the IAEA with its - now named
- Marine Environmental Laboratory (MEL) in Monaco was involved
intensively in the work of quality assurance. The MEL
carried out some intercomparison exercises on seawater and
sediment analyses. It was shown that the quality of the results
reported to the IAEA was partly in excellent agreement
among the laboratories submitting data for the group MORS.
In summer 1992 an experiment was carried out on a Finnish and
a German research vessel to study both the sediment sampling
techniques and the analytical methods on different types of
sediments. This experiment was named MOSSIE (MORS Sediment
Sampling intercalibration Experiment). Almost all MORS laboratories
participated in the cruise with their own devices
for collection of soft sediments on four locations. The
IAEA/Monaco prepared homoginized materials for distribution
within EC MORS laboratories and partly for use of a world
wide intercalibration. The experiment was initiated, because
it has already been shown previously by some of the MORS
laboratories that the sediment coring technique may influence
significantly the final result (3). It is expected that the
report of MOSSIE will be ready by end of the year 1994.
FUTURE PLANS
On its 1993 meeting the group MORS started to prepare a Joint
Evaluation Report on "Radioactivity in the Baltic Sea 1984 -
1991".
This report is expected to contain all aspects of radioactivity
in the Baltic Sea, including the sources of artificial
radioactivity from global fallout, discharges from nuclear
66