197 



seen globally in environmental samples e.g. ^Bi and ""Co (Aarkrog et al, 1984a). 



Technetium-99 is another example of a radionuclide especially observed in Nordic 

 regions, in particular in the marine environment, where it is concentrated in brown algaes 

 (Aarkrog et al 1987a). 



Terrestrial Ecosystems in Nordic regions 



In 1961 a group of Scandinavian scientists with Kurt Lid^n, Jorma Miettinen and Dietrich 

 Merten (IAEA) as keypersons initiated the so-called RIS-symposia (Paakola, 1990). RIS 

 stands for Radioactivity In Scandinavia. These meetings were especially concerned with 

 the critical pathways of radiocaesium in the Nordic regions, in particular with the 

 foodchain: 



lichen - reindeer - man. 



Reindeer-breeders thus became a group of special concern in connection with radioactive 

 fallout in Nordic regions. Beside of Northern Scandinavia, reindeers are found in Alaska, 

 Northern Siberia, Greenland and Iceland. 



The high surface to weight ratio of lichen and the long effective halflife of *^Cs in the 

 lichen carpet is the main reason for the high radioecological sensitivity of lichen to 

 radioactive fallout. Reindeer eat lichen during winter, which results in high levels in meat 

 during this part of the year. (Mattsson, 1972; Hanson, 1973; Miettinen, 1966) Similar 

 seasonal variations are seen in the reindeer breeders. The highest levels reported in man 

 are from Northern Siberia in 1964 where bodyburdens of 0.13 MBq *"Cs were observed. 

 Similar levels were measured in the Murmansk region in the winter 1966-1967. After 

 Chernobyl high levels in reindeer meat ("50 kBq kg') were observed at various localities 

 in Norway and Sweden (Gunnerod et al 1989; Erikson 1990). But although the 

 contamination at such locations were about an order of magnitude higher than in the 

 sixties, the problems were not of a circumpolar nature as after the global fallout period. 



Johanson et al (1990), Bakken et al (1990) and other radioecologists observed after the 



