Radiocesium Concentrations in Wild Mushrooms and Characteristics of Cesium Accumulation by the Edible Mushroom (Pleurotus ostreatus)

Abstract

Mushrooms collected from a sub-alpine forest of Mt. Fuji and some other locations in Japan in 1996 were analyzed for radiocesium. The ¹³⁷Cs concentrations in 37 mushrooms varied widely from 1.6 to 783 Bq kg ^-1 fresh wt. The characteristics of Cs accumulation were analyzed by culturing fruiting bodies of the edible mushroom Pleurotus ostreatus (Fr.) Kummer Y-1 (P. ostreatus Y-1). The ¹³⁷Cs and stable Cs accumulation expressed as the concentration ratio (CR, ¹³⁷Cs or Cs concentration in the dried fruiting body / ¹³⁷Cs or Cs concentration in the fresh medium) were in good agreement, indicating similar migration. The CR of Cs grown on medium containing both 0.1% Cs and 0.1% K, 10.2, showed a decrease of about 30 percent as compared with that containing 0.1% Cs only. These CR values suggested that Cs accumulation by the fruiting bodies of P. ostreatus Y-1 is affected by the presence of K similarly to previous observations in the mycelia. The ¹³³Cs-NMR spectra from the fruiting bodies of P.ostreatus Y-1 showed two resonance signals, whereas those from the media after harvesting of fruiting bodies showed only one signal. Just before growth of the fruiting bodies, bunches consisting of many mycelia were observed by scanning electron microscopy (SEM). No significant differences in the elemental distribution (Cs, K, P and C) were detected in the mycelium surface by SEM equipped with an energy dispersive X-ray microanalyzer.