Spatial distribution of radon and thoron in the soil around active faults as a contribution to the elevated indoor radon

我们分析了在Fugendake火山（U1）附近进行的第一次测量的数据。氡浓度低于预期值，垂直分布和纬向分布变化不大。因此，我们选择了另一个活动断层，在高山市（T1）附近具有不同的地质结构。采用主动式氡-钍射气浓度测定装置，测定了土壤气中氡（Rn）和钍射气（Tn）浓度，并测定了土壤氡析出率、土壤渗透率和CO2浓度。用HPGe探测器对采集的土壤样品中的Ra和Th进行了测量。测定了土样的容重和孔隙度。采用地球物理方法结合标准土工圆锥测斜仪，对该地区的地质构造和土壤特性进行了识别，并对预测的断层位置和走向进行了定位。所获得的数据准备作为输入的氡扩散对流传输模型。

We analysed the data from the first measurements taken near the Fugendake volcano (U1). The radon concentration was lower than expected with low variation of horizonal nor vertical distribution. We therefore chose another active fault site, with a different geological structure near Takayama city (T1). Radon (Rn) and thoron (Tn) concentrations in soil gas with an active device together with radon exhalation rate, soil permeability and CO2 were measured. Measurements of Ra and Th in the collected soil samples were carried out using HPGe detector. Bulk density and porosity of soil samples were determined. Geophysical methods combined with the standard geotechnical cone penetrometer were used to recognize the geological structure and soil characteristics of the area and locate the predicted faults positions and routes. Obtained data were prepared as an input for the radon diffusion-convection transport model.