MEASUREMENT OF CONCENTRATION OF ~(232)Th IN AIR IN WUHAN AREA

the measurements of concentration of ~(232)Th in air in wuhan area show thatthe daily average value is found to be 29.13×10~(-9)Bq/1 in the period from 1981to 1985 based on the measurements of 7346 samples. The highest daily averagevalue is 36.23×10~(-9) Bq/1 in the year 1983. The seasonal changes of the concen-tration of ~(232)Th in air is very obvious for the year 1984 and 1985, being highestin winter with a value of 41.93×10~(-9) Bq/1 in 1984 and 32.85×10~(-9) Bq/1 in 1985,and lowest in summer with values of 25.40×10~(-9) Bq/1 and 14.33×10~(-9)Bq/1 res-pectively. This obvious change with season is related to the weather condition. The concentration of ~(232)Th in air is highest in Qingshan region for six citiesin wuhan area with a value of 49.34×10~(-9)Bq/1 and lowest in wuchan regionwith a value of 18.35×10~(-9) Bq/1. This is due to the difference in the amount ofdust in the air in these regions.