Modelling of long-term behaviour of caesium and strontium radionuclides in the Arctic environment and human exposure

In this paper a compartment model of the highly vulnerable Arctic terrestrial food chain “lichen–reindeer–man” is outlined. Based upon an analysis of measured 137Cs and 90Sr contents in lichen and reindeer meat from 1961 up to 2001, site specific model parameters for two regions in north-western Arctic Russia and for Kautokeino municipality in Arctic Norway have been determined. The dynamics of radionuclide activity concentrations in the “lichen–reindeer–man” food chain for all areas was satisfactorily described by a double exponential function with short-term and long-term effective ecological half-lives between 1–2 and 10–12 years, respectively, for both 137Cs and 90Sr. Using parameter values derived from the model, life-time internal effective doses due to consumption of reindeer meat by reindeer-breeders after an assumed single pulse deposit of 1 kBq m−2 of 137Cs were estimated to be 11.4 mSv (Kola Peninsula), 5 mSv (Nenets Autonomous Area), and 2 mSv (Kautokeino, Norway). Differences in vulnerability to radiocaesium deposition were due to differences in transfer between lichen and reindeer and in diet between the three regions.