THE NATURAL DEPURATION RATE OF CS-137 RADIONUCLIDES IN A LICHEN AND MOSS SPECIES

Caesium-137 concentrations in lichen and moss samples have been studie d for calculations of natural depuration rates. The lichen and moss sp ecies were collected from the same trees in western and eastern Black Sea region during the periods of 1987-1992 and 1990-1993, respectively . The natural depuration rates are estimated at biological half-lives. The pattern of depuration results represented by a single component f or each non-vascular plant. The biological half-lives of Cs-137 in a l ichen and moss samples (Xanthoria parietina and Leucodon immersus) are estimated to be 58.6 and 10.9 months, respectively. This work set sup ports the view that radioactivity monitoring in lichens can be a more useful monitor than mosses to determine the lasting effect of radioact ive fallout.