A MYSTERIOUS SPOT ON THE OUTDOOR CONCENTRATION OF RADON ISOTOPES

Temporal and spatial distribution of Rn-222 and Rn-220 and their proge ny concentrations in the open atmosphere, Rn-222 and Rn-220 exhalation rates, radioactivities in soil and underground water, including some meteorological factors, were measured at a spot of high Rn-222 and Rn- 220 concentrations to investigate the source and occurrence mechanism, Hourly mean concentrations of Rn-222 and Rn-220 during August 1993 we re about 230 Bq m(-3) and 130 Bq m(-3) at 1 m above ground surface, Di urnal variations were high at daytime and low at nighttime, which give s an inverse variation compared with the typical variation in the norm al environment, Rn-222 concentrations varied quickly in a few minutes and reached a maximum of about 14 kBq m(-3). The maximum daily mean Rn -222 concentration at 5 cm above ground surface was 11 kBq m(-3). Conc entrations of Po-218, Pb-214, Bi-214, and Rn-220 progeny were 8 simila r to 61 Bqm(-3), 1 similar to 7 Bqm(-3), 0.5 similar to 5 Bq m(-3), an d 0.02 similar to 0.14 Bq m(-3), respectively, The equilibrium factor for Rn-222 was estimated to be 0.01 similar to 0.2. The main source of the mysterious spot of high Rn-222 and Rn-220 concentrations was a sm all but deep channel between the basement of the building and the surr ounding soil, and the extremely localized weather condition. Copyright (C) 1996 Elsevier Science Ltd.