Diurnal and seasonal variations in Rn concentration profile in soil

土壌中のラドン濃度分布の日・季節変動

Iskandar, D.*; 山澤 弘実*; 山外 功太郎 ; 太田 雅和*; 小嵐 淳   ; 森泉 純*; Bunawas*; 飯田 孝夫*

Iskandar, D.*; Yamazawa, Hiromi*; Yamasoto, Kotaro; Ota, Masakazu*; Koarashi, Jun; Moriizumi, Jun*; Bunawas*; Iida, Takao*

ラドンはラジウムの壊変によって生成する気体状放射性核種であり、ラドン及びその壊変生成物による被ばく線量は自然放射線による全被ばく線量の約半分を占めている。ラドンの主たる生成源は土壌であるので、土壌中でのラドン濃度の分布やその変動実態を明らかにすることが重要である。本研究では、土壌中のラドン濃度の深さ分布を継続的に測定し、その日周期的変動・季節変動を解析するとともに、環境因子との関連性について検討した。

The Rn concentrations in soil and Rn flux were measured at 6 depths in soil to analyze the seasonal- day-to-day and diurnal variations. The variations of Rn concentrations in soil were larger in shallow depths. It seems that the Rn concentration in soil during night-time was slightly lower than day-time especially at depth of 15 cm. The precipitation may have affected the concentration insoil differently depending on its amounts. The large decrease in air pressure during one day increased the concentration in soil at shallow soil layers. The effect of soil water content on Rn concentration in soil was also observed.