199 



later in the East Greenland Current and two-three years later it has reached Thule in 

 NW-Greenland. It is amazing that pollutants can travel that far and still be detected. 



The studies of global fallout '"Sr and '^^Cs in arctic waters (Aarkrog 1989) have shown 

 that the effective mean residence time of these radionuclides in the surface water of the 

 Arctic Ocean is about 15 years. However, this may be an overestimate if the Arctic 

 Ocean is supplied with significant amounts of run-off from land e.g. from the Siberian 

 rivers. The vertical mixing in the Arctic waters is more rapid than we see it at lower 

 latitudes in the world ocean. This implies a shorter residence time of pollutants in arctic 

 surface water than what is seen in temperate and tropical waters. 



At Thule in NW Greenland an arctic marine ecosystem has been studied with regard to 

 transfer of plutonium since the B-52 accident in 1968. (Aarkrog et al 1984b It appears 

 that the effective halflife of Pu in biota is significantly less than the radiological halflife 

 of 24000 years. It is further more evident that there is a discrimination against Pu when 

 we move to higher trophic levels in the foodchain. 



Conclusion and Summary 



Although the radioecological sensitivity of food products fi-om Arctic regions tend to be 

 higher than we know it from temperate regions, the very low productivity of Nordic 

 regions imply usually low collective doses from these regions. However, high individual 

 doses from radioactive contamination may be seen in the Arctic as we have observed it 

 for e.g. reindeer breeders. 



Radiocaesium is concentrated fi"om lower to higher trophic levels. The marine animals 

 contain orders of magnitude lower ^^Cs levels than terrestrial animals in Nordic regions 

 and the transfer of ^^'Cs is one to two orders of magnitude greater than that of "Sr to 

 meat of animals. (Fig. 5) 



