| 研究実績の概要 |
The sudden and catastrophic or slow and continuous surface release of naturally occurring toxic gases, such as radon or CO2, poses a serious health risk to people living in geologically active regions. Indoor radon activity concentrations, however, vary widely and depend on a variety of factors such as underlying geology, water, weather conditions, and building type. In this project, we seek to understand and estimate radon transport in soil in a region with active faults. The results of this project will 1) help find solutions to mitigate the problem of radon exposure and 2) can be used to apply radon to geohazard studies.
The configuration and validation of the radon and thoron measurement system at the reference point (QST) was completed this year. We developed a new device, called PECAME, for simultaneous measurement of permeability, CO2 and CH4. The PECAME consists of pressure and flow meters, pumps, and sensors to measure CO2 and CH4. Data are collected and stored in memory every one minute using a data logger (GRAPHTEC midi Logger GL220). The PECAME device was tested at a reference site located at the QST campus, and the permeability measurement results were compared with the commercial portable permeability measurement device RADON-JOK. The operating principle of PECAME and RADON-JOK is based on Darcy's law, which describes the flow of fluid through a porous medium.
In addition, subsurface surveys were conducted to identify faults near the active Fugendake volcano (Nagasaki Prefecture) using ground penetrating radar (GRP) and data sets were collected.
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| 今後の研究の推進方策 |
In the second year, a second measurement campaign will be conducted near Fugendake including radon, thoron, permeability, and GRP measurements to collect more data needed to test the transport model.
A process signal will be developed from the radarogram data (GRP) to include the correction for air travel, then a DEWOW filter, the calculation of the loss of energy with depth depending on the medium and the generation of a time-depth model, in order to correct for the subsurface geometry.
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