SEASONAL-VARIATION IN RADIOCESIUM CONCENTRATION IN WILLOW PTARMIGAN AND ROCK PTARMIGAN IN CENTRAL NORWAY AFTER THE CHERNOBYL FALLOUT

Radioactive caesium (20-60 kBq m(-2)) was deposited after the Chernoby l accident in the mountains of central Norway. Two sympatric ptarmigan species, willow ptarmigan Lagopus lagopus and rock ptarmigan L. mutus , inhabit this alpine ecosystem and are important game species. In 198 7 and 1988, a study was carried out to try to identify factors affecti ng radioactive caesium concentration in these birds. Juvenile willow p tarmigan contained more radiocaesium than adults, but the two sexes di d not differ in radiocaesium concentration. The radiocaesium concentra tion of food plants correlated with radiocaesium concentration of rock ptarmigan, and a seasonal variation in radiocaesium concentration of both ptarmigan species was seen. Rock ptarmigan contained more radioca esium than willow ptarmigan during winter, but not in summer. This dif ference was related to differences in diet. The bioconcentration facto r was 0.4-0.6. The aggregated transfer coefficient was 0.003-0.009 m(2 ) kg(-1) for both species. In spite of the high deposition, the radioc aesium concentration in muscle rarely exceeded the limit recommended f or human food consumption (600 Bq kg(-1)). (C) 1998 Elsevier Science L td. All rights reserved.