Intermittent Measurements of 222Rn and 220Rn Progeny in Air for Four Years.

Abstract

To survey the level and behavior of 222Rn and 220Rn progeny in air, measurements were made intermittently (once a day at an identical time) for 4 years at the campus of the authors' college located in the northeastern part of Japan. A filtration method with alpha spectroscopy, using an evacuated chamber, clearly separated 212Po peak from others. Outdoor and indoor air were sampled every morning except holidays. A definite seasonal variation, higher concentrations in autumn and in winter, was observed except indoor 220Rn progeny. 222Rn progeny revealed log-normal distribution, whereas 220Rn progeny revealed Poisson-like distribution. Multiple regression analysis and correlation analysis indicated that most of indoor 222Rn progeny originates from outdoor air. From time series analysis, several-day periods were often observed, which will probably be attributed to the wind speed.