RADIOCESIUM IN SWEDISH REINDEER AFTER THE CHERNOBYL FALLOUT - SEASONAL-VARIATIONS AND LONG-TERM DECLINE

Data about Cs-137 activity concentrations in reindeer muscle were collected from different parts of Sweden during 1986-1992. The data were used to evaluate seasonal and geographical variations and long-term decline of Cs-137 in reindeer. The seasonal variation is shown in an example from one of the most contaminated areas, the Saami community Vilhelmina Norra, where Cs-137 activity concentrations in reindeer during winter exceed those found during summer by about 20 times. Activity concentrations of Cs-137 in reindeer were fairly well correlated to ground deposition. The ratio between Cs-137 in reindeer (kBq kg(-1) wet weight) and ground deposition (kBq m(-2)) was calculated to be 0.76 m(2) kg(-1) for the winter period, January-April, in 1987. Activity concentrations of Cs-137 i, reindeer decreased significantly during the years 1986-1992. The decline was generally more rapid during September, November, and December [corresponding to an effective ecological half-life (T-Eff) Of 3.2 y] than during January-April when T-Eff was calculated to 4.2 y. There was a general trend toward a slower decrease during the last of the observed years.