Accumulation of radiocesium in basidiomycetes collected from Japanese forests

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