Concentration of Radiocesium in Mushrooms and Substrates in the Sub-Alpine Forest of Mt. Fuji Japan

Abstract

Concentrations of 137Cs, 134Cs and potassium were surveyed in 32 mushrooms and 24 substrates (upon which the mushrooms grow) obtained from fields in Japan. Radiocesium concentrations (137Cs+134Cs) in mushrooms and substrates in the forests of Mt. Fuji varied widely from 17 to 1083Bq/kg in fresh mushroom samples, and in dry substrate samples they were in the range of 66 to 531Bq/kg, whereas levels of potassium remained essentially constant. 134Cs released from the Chernobyl reactor was determined in some mushrooms and some substrates from the sub-alpine forest of Mt. Fuji. Mushroom-to-substrate concentration ratios of 137Cs were much higher than tree leaves-or mosses-to-substrates concentration ratios near the study locations, and were larger by 100-to 1000-fold than the reported transfer factors of 137Cs from soils to leaf vegetables, root crops or potatoes. Significant correlations between ignition loss of substrates and concentration of 137Cs in mushrooms, and between pH value in substrates and concentration of 137Cs in mushrooms or mushroom-to-soil concentration ratio of 137Cs were found, suggesting possible 137Cs uptake mechanisms. The effective dose equivalent received by the general public was calculated to be 57x10-6 Sv based on the annual intake of 3.7kg of mushrooms and the maximum concentration detected in this study, 1083Bq/kg. It is estimated that this value is less than 2.4% of the annual effective dose equivalent received from natural sources, 2.4x10-3 Sv.

Mushrooms: Radioactive Contamination of Widespread Mushrooms in Japan

“…Radioactive contamination of mushrooms should be considered not only from the viewpoint of food but also from the viewpoint of its effects on plants and animals, including crops, domestic animals, and wood products, through its circulation in the forest ecosystem. From 1950s to 1960s, a high uptake of 137 Cs, derived from atmospheric nuclear weapons tests (NWT), by mushrooms was also noticed in Japan (Muramatsu and Yoshida 1997 ;Sugiyama et al 1994 ;Yoshida and Muramatsu 1996 ).…”

“…Radiocesium concentrations exceeding the safety threshold were detected in mushrooms hundreds of kilometers from F1-NPP. The Japanese interim limit for imported foods was 370 Bq/kg fresh weight (FW) of radiocesium after the Chernobyl nuclear accident in 1986 (Sugiyama et al 1994 ). The interim limit after the Fukushima nuclear accident was set to 500 Bq/kg FW.…”

“…Mushrooms have been reported to accumulate radiocesium (Byrne 1988 ;Kammerer et al 1994 ;Mascanzoni 1987 ;Muramatsu et al 1991 ;Sugiyama et al 1990Sugiyama et al , 1994. For example, the transfer factors (TF) for radiocesium in mushrooms were reported to be 2.6-21 in several culture tests (Muramatsu et al 1991 ;Ban-nai et al 1994 ).…”

Evaluation of Cesium-137 (137Cs) and Elements Intake from Daily Diets in Residents of Kanagawa Prefecture, Japan

“…Among others, mushrooms are known to contain high levels of 137 Cs. [18][19][20][21][22][23][24] The contribution of group 6 to the intake of stable elements also seems to be high. During the survey period, 137 Cs was often detected from imported foods, but it was not possible to identify imported foods in the menus.…”

Soil-dependent uptake of 137Cs by mushrooms: experimental study in the Chernobyl accident areas

“…This has been attributed to both the longterm retention of radiocaesium in forest litter and organic soil layer, in a form that is highly mobile and available for fungal mycelium (Sugiyama et al, 1994), and the specific biochemical feature of fungal tissues, and specifically their fruit bodies, to accumulate and concentrate microscopic quantities of caesium (Vinichuk, 2003). Furthermore, for some mushroom species an increase of 137 Cs specific activity in the first 1e2 years after the accident has been observed (Shutov et al, 1996;Bruk et al, 1999).…”