Diurnal and Seasonal Variations of ^<222>Rn Concentration Profile in Soil(Part 3:English)

概要

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The ^<222>Rn concentrations in soil and ^<222Rn flux were measured in the campus of Nagoya University. The measurements were carried out discontinuously between December 1999 and March 2002 at depths of 15, 30, 50, 80, 120, and 200 cm. The ^<222>Rn concentrations in soil were analyzed for seasonal-, day-to-day-, and diurnal variations. The average values of ^<222>Rn concentrations in soil were 1.6, 6.9, 13.6, 24.2, 27.7, and 34.3 kBq・m^<-3> for soil depths of 15, 30, 50, 80, 120, and 200 cm, respectively. The ^<222>Rn flux ranged from 2.5 to 14 mBq・m^<-2>・s^<-1> with the average 7.2 mBq・m^<-2>・s^<-1>. The variations of ^<222>Rn concentrations in soil were larger in shallow depths. It seems that the ^<222>Rn concentration in soil during night-time was slight lower than day-time especially at depth 15 cm. The precipitation may have affected the ^<222>Rn concentration in soil differently depending on its amounts. The large decrease of air pressure during one day increased the ^<222>Rn concentration in soil at the depth 15, 30, and 50 cm. The effect of soil water content on ^<222>Rn concentration in soil was also observed.