A long-term investigation of the atmospheric radon concentration in Beijing, China

To investigate the levels and behaviour of the atmospheric radon concentration in Beijing, a continuous measurement was carried out and recorded hourly over a five-year period from January 2003 to December 2007. Levels and variations were studied on the basis of 36,731 data points, and the trends of diurnal and yearly variations were also analysed. The range of average concentration of atmospheric radon each year was from 11.2 to 13.0 Bq m(-3), while the average concentration over the five years was 12.1 +/- 4.9 Bq m(-3). The average diurnal pattern of radon concentration showed that the daily maximum appears between 6:00 and 8:00 in the early morning, and the daily minimum appears between 16:00 and 18:00 in the late afternoon. The frequencies of both the maximum and minimum during this period were 30% overall. The yearly pattern features a maximum around October and November and a minimum around April and May.