RD&D-Programme 2004 - SKB

In connection with the Safe project, the sedimentation environment in northern Uppland
was modelled from approximately 10,000 years ago to 5,000 years in the future /20-76/. The
controlling parameters were the openness of the sea, which determines the force of wave
erosion, and the land uplift process, which determines depth and the creation of protective
islands and archipelagos. The study showed good agreement with the Quaternary geology
map of the area. Most recent Quaternary geology investigations have further confirmed the
model predictions by dating of erosive phases /20-46/. Lake infilling has also been simulated
/20-43/. The study also shows that the minerogenic sedimentation in a lake can for the most
part be explained by biological production. It is above all the silicon skeletons of diatoms
and stoneworts that contribute to this. The site investigations have yielded large quantities of
sediment data, both from the approximately 140 boreholes in the Forsmark area /20-77/ and
from the Quaternary geology investigations /20-78/.
The results of an older study of sediment cores on Äspö have been reported /20-79/, along with
the results of an interesting study at Kallrigafjärden in Forsmark, carried out in conjunction
with a methodology course at Stockholm University /20-80/. In the latter study, the seabed and
surrounding lands were mapped by means of different methods and a map was drawn of what
Kallrigafjärden will look like when it has become dry land.
A study of the distribution of various substances in sediment profiles from lakes has been started
to permit calculations of the mobility of stable analogues of radionuclides in sediments /20-44/.
The site investigations in the two areas have involved extensive investigations in the aquatic
environments, which besides descriptive data will also yield important information on processes
and process rates.
Programme
The projects described above will continue.
The site investigations are expected to furnish necessary data on the distribution of sediments
and accumulation rates. The work will also be done in cooperation with the hydrological,
geochemical and geological programmes and coordinated with research on mireland and
transport processes. Some important areas where studies will be conducted are:
• Modelling of migration processes beneath and through sediments (under way).
• Modelling of reworking and accumulation of sediments, supplemented with field data.
• Modelling of nuclide transport through sediments, or through the shore zone.
• Development of a systems ecology model for the lakes on the sites.
• Development of a general model for radionuclide transport in sea bays.
• Development of a model that describes sorption processes in small streams.
20.8 Long-term variations in climate, land uplift and salinity
Conditions in the biosphere are largely controlled by the climate and the distribution between
land and water. The salinity influences which ecosystems will dominate in the Baltic Sea and
the speciation of the radionuclides. These factors are also important boundary conditions for the
transport models in the geosphere. Shoreline displacement influences which biotope is dominant
in an area. Water flux, groundwater formation and surface runoff are important physical factors
that influence the dose. These factors are highly variable. The range of variation can be studied
with models of present-day conditions and a reconstruction of the conditions since the most
recent ice age.
284 RD&D-Programme 2004