中国における Passive 法による屋内外ラドン濃度調査

概要

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Measurements of 222Rn in outdoor air and indoor air have been carried out every 2 months during about one year from Nov. 1988 using passive electrostatic integrating 222Rn monitor developed by Iida et al. The annual mean outdoor 222Rn concentrations at Beijing, Xi'an, Nanjing, Shanghai, Fuzhou and Guiyang were 8.0, 11.2, 6.4, 4.8, 9.5 and 12.2Bq·m-3, respectively. The high outdoor 222Rn levels at Beijing and Xi'an, situated in inland area, may be attributed to high frequency of the occurrence of inversions in winter. The low 222Rn levels at Nanjing and Shanghai and the high 222Rn levels at Fuzhou and Guiyang correspond to their geological conditions and the 226Ra concentrations in soil. The annual mean indoor 222Rn concentrations were about 2-3 fold of outdoor concentrations at every city. The average indoor 222Rn concentration in China was 29.2Bq·m-3. The annual effective dose equivalent resulting from outdoor and indoor 222Rn concentrations amounts to about 0.72mSv·y-1.