Leaching efficiency of radon from rock was observed with fresh and weathered granites. Portions of 500 g of samples were brought into contact with a 2l of water, respectively, for the period of 1 month or more. Radon was determined by the liquid scintillation counting The observed radon concentrations ranged from 0.3 to 1.0Bq/l. The leaching efficiencies from the fresh granite were around 2%, while those from the weathered around 6%, indicating that weathering accounts significantly for the enhancement of the leaching efficiency. Microscopic surface areas of the weathered granite were larger than that of the fresh one, and a positive, but not adequate, correlation between the leaching efficiency of radon and the microscopic surface area was observed. Depletion of210Pb in the weathered granite was estimated to be attributed to the escape of radon into the atmosphere and the meteoric water from the outcrop during a long period of time, together with possible leaching of210Pb itself.
An applicability of imaging plate to personal dosimeter was investigated by irradiating bremsstrahlung X rays and60Co and137Cs gamma rays on UR type imaging plate. For imaging plate attached with filters of 0.8 mm Sn, 0.4 mm Pb, and 1.8 mm plastic, the sensitivities were 212 PSL/mm2⋅mSv and 1 150 PSL/mm2⋅mSv for60Co γ-ray and 140 keV X rays respectively. The linearity between 1 cm dose equivalent and PSL density was observed for very wide range of 1μSv to 10 mSv. It was found out that the imaging plate detector is useful as a new type wide range personal dosimeter.
Concentrations of137Cs and stable Cs in wild mushrooms, cultivated mushrooms and those substrates were measured by gamma-ray spectrometry and neutron activation analysis. The average concentration of137Cs in 80 wild mushrooms in Japan was 87.5Bq/kg (wet wt.), and concentration of137Cs in mycorrhizal mushrooms was higher than that of saprophytic mushrooms. High concentrations of137Cs were found in Pleurotus ostreatus (Fr.) Kummer Y-1, saprophytic mushrooms, cultivated in culture substrates containing high137Cs. Clear correlations with 5% level of significance were found between wild mushroom-to-substrate ratios (wet/dry) of137Cs concentration and those of stable Cs. Cultivated P. ostreatus-to-culture substrate ratios (wet/wet) of137Cs concentration were stable in the order of 100when the culture substrate was containing 10000Bq/kg (wet wt.) of137Cs or 1000mg/kg (wet wt.) of stable Cs. The ratios of137Cs concentration in cultivated mushrooms were about equal to those in wild mushrooms. Higher concentration of137Cs in culture substrate after sampling P. ostreatus was observed at the upper layer where mycelium density was high.
Regional cerebral blood flow (γ-CBF) of 10 pregnant women were quantified by133Xe SPECT study with inhalation method before and after artificial abortion. During pregnancy, value of γ-CBF in each region except occipital lobe was significantly higher than that of the post abortion. Arterial blood gas was analyzed after SPECT procedure. PCO2concentration increased significantly after artificial abortion. Although its mechanism is unknown, our preliminary work demonstrates that γ-CBF increased by pregnancy.