198 



Chernobyl accident that mushrooms were an important source of radiocaesium to grazing 

 ruminants and some game animals. A strong seasonal variation of ^^Cs in roe deer was 

 e.g. demonstrated in Sweden . This variation was mainly due to consumption of 

 mushrooms in the autumn. Thus the availability of mushrooms becomes important for the 

 observed radiocaesium levels in certain game animals and grazing ruminants (e.g. goat 

 and reindeer). A steady decrease of '^'Cs is thus not always observed in such animals. 



Herbage - sheep - man is another critical pathway for radionuclides in Arctic regions. 

 (Hove et al, 1990) The effective halflife of ^^ Cs in this foodchain is quite long. 



Freshwater Ecosystems in Arctic regions 



Drinking water in the arctic and subarctic is usually derived from surface water including 

 melting of snow and ice. Hence we do not see the same efficient removal of radionuclides 

 from the water as is the case for groundwater derived drinking water. Especially in 

 Greenland where permafrost is common the drinking water levels tend to be relatively 

 high. Furthermore the '"Sr concentration seem closer related to the accumulated fallout 

 than to the fallout rate (Hansen et al, 1990). 



Already in the sixties it was observed that lakes with a low conductivity (oligotrophic 

 lakes) contained fish with a relatively high ^Cs content (Carlsson, 1976, Hasanen et al, 

 1966). It was also observed that the excretion of *"Cs decreased with decreasing 

 temperature (Kolehmainen et al, 1966). After the Chernobyl accident the combination 

 of high fallout and low conductivity resulted in fish levels in the middle part of Sweden 

 greater than 15 kBq "^Cs kg' fish. (Hikanson, 1991). 



Marine Eco systems in Nordic Regions 



Fig. 4 shows the current system in the Arctic. Dotted lines represent warm currents and 

 full lines are the cold ones. The discharges from nuclear reprocessing in Western Europe 

 have been used to measure dilution factors and transport times in this current system 

 (Aarkrog et al 1987). A waterbome pollutant in the North Sea is found about five years 



