ACCUMULATION OF RADIOCESIUM IN BASIDIOMYCETES COLLECTED FROM JAPANESEFORESTS

A variety of mushrooms, plants and soils collected in Japanese forests were analyzed for Cs-137, Cs-134 and K-40. The Cs-137 concentrations in forest soils ranged from < 0.6-175 Bq/kg on a dry weight basis. The highest Cs-137 concentrations in the soil profiles were observed most ly in the surface soil layer (0-5 cm). Litter layers contained signifi cantly less Cs-137 than the surface soil layer. Concentrations of Cs-1 37 in plants were in general much lower than those in mushrooms. The l evels of Cs-137 in 81 mushroom species collected in 1989 and 1990 vari ed very widely, ranging from <4 to 16300 Bq/kg (dry wt.), while those of K-40 were relatively constant. The median concentrations of Cs-137 and K-40 were 45 and 1110 Bq/kg (dry wt.), respectively. The Cs-137 co ncentrations in mycorrhizal fungi tended to be higher than those in sa prophytes, although the concentration range of each type varied widely . High concentrations of Cs-137 in several Hebeloma species, ammonia f ungi, were observed. In addition to the species-specific accumulation, the concentrations in many mushrooms reflected the layers in which th eir mycelia were growing.