Transfer of natural radionuclides ²¹⁰Pb, ²¹⁰Po, ²³⁸U, and ^228,230,232Th in subarctic food chains has been studied in Finland since the 1960s. The unique food chain lichen-reindeer-man related to Sami people in Finnish Lapland and other food chain options, from berries or mushrooms to man, have been explored and the activity concentrations of natural radionuclides in biological samples determined. The results from Finnish radioecological studies are summarized and differences in bioaccumulation between different radionuclides are discussed. It was found out that, although a substantial amount of activity concentration data exist from the research projects executed in Finland during the last 6 decades, more data, especially from U and Th, in biological environment and humans would be useful, e.g., for modeling purposes and for improved assessment of bioaccumulation and adverse effects (both radiological and chemical) of radionuclides.

Summary: ²⁴¹Am and ²⁴⁴Cm were analysed from peat samples collected in Finland immediately after the Chernobyl accident. The separation method included co-precipitation, anion exchange and extraction chromatography. Activities of ²⁴¹Am and ²⁴⁴Cm were measured by alpha spectrometry. The activity of Chernobyl-derived ²⁴¹Am varied between 0.0115 and 9.32 Bq/m² and that of ²⁴⁴Cm from < 0.002 to 1.97 Bq/m² (reference date 1.5.1986). The origin of ²⁴¹Am in Finland is predominantly from atmospheric nuclear tests. However, the geographical distribution of Chernobyl-americium is uneven and depending on a location even 100% of ²⁴¹Am in peat originated from the Chernobyl accident. The deposition pattern of Chernobyl-derived ²⁴¹Am and ²⁴⁴Cm resembles that of other refractory nuclides, such as ⁹⁵Zr, ¹⁴¹Ce and ^239,240Pu.