CONCENTRATION OF RADIOCESIUM IN MUSHROOMS AND SUBSTRATES IN THE SUB-ALPINE FOREST OF MT FUJI JAPAN

Concentrations of Cs-137, Cs-134 and potassium were surveyed in 32 mus hrooms and 24 substrates (upon which the mushrooms grow) obtained from fields in Japan. Radiocesium concentrations (Cs-137+Cs-134) in mushro oms and substrates in the forests of Mt. Fuji varied widely from 17 to 1083 Bq/kg in fresh mushroom samples, and in dry substrate samples th ey were in the range of 66 to 531 Bq/kg, whereas levels of potassium r emained essentially constant. Cs-134 released from the Chernobyl react or was determined in some mushrooms and some substrates from the sub-a lpine forest of Mt. Fuji. Mushroom-to-substrate concentration ratios o f Cs-137 were much higher than tree leaves- or mosses-to-substrates co ncentration ratios near the study locations, and were larger by 100-to 1000-fold than the reported transfer factors of Cs-137 from soils to leaf vegetables, root crops or potatoes. Significant correlations betw een ignition loss of substrates and concentration of Cs-137 in mushroo ms, and between pH value in substrates and concentration of Cs-137 in mushrooms or mushroom-to-soil concentration ratio of Cs-137 were found , suggesting possible Cs-137 uptake mechanisms. The effective dose equ ivalent received by the general public was calculated to be 57 X 10(-6 ) Sv based on the annual intake of 3.7 kg of mushrooms and the maximum concentration detected in this study, 1083 Bq/kg. It is estimated tha t this value is less than 2.4% of the annual effective dose equivalent received from natural sources, 2.4 X 10(-3) SV.