Development and application of a simple apparatus to concentrate 222Rn for the measurement of 222Rn concentration in surface water
Description
Radon-222 (222Rn) concentration in surface water is a good indicator for identifying where groundwater appears at the surface. However, it is necessary to concentrate 222Rn in order to measure it. This operation is painstaking and requires special equipment. In this study, we developed a simple method in which 222Rn is extracted from the sample water by passing air through the sample and then through toluene cooled with dry ice submerged in ethanol.
Since the origin of 222Rn is radium-226 (226Ra) underground, 222Rn concentration in groundwater is much higher than that in surface water. When groundwater appears on the surface, the 222Rn concentration in surface water increases markedly. We propose an apparatus for concentrating 222Rn in toluene cooled in ethanol/dry ice based on the characteristic of 222Rn that it dissolves very readily in cooled toluene (Fig. 1). The air is circulated for 60 min. After concentrating, the toluene is poured into a 20-mL glass vial and the radioactive rays from 222Rn and its progeny are counted using a liquid scintillation counter.
The relationship between 222Rn concentration and counting rate of the liquid scintillation counter was approximately linear, with the line passing through the origin of the coordinate axes, confirming the practicability of the method (Fig. 2).
Application of the method to a study site around Khon Kaen revealed that groundwater leaks into rivers and lakes in areas with elevations below 180 m, a result that agrees with the results from a simulation of groundwater flow (Fig. 3, Table 1).
Figure, table
- Affiliation
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Japan International Research Center for Agricultural Sciences Crop Production and Environment Division
- Classification
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Technical A
- Term of research
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FY2004(FY2002~2004)
- Responsible researcher
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HAMADA Hiromasa ( Crop Production and Environment Division )
- ほか
- Publication, etc.
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Hamada H. & Putiso M.(2005): Development of a simple method to concentrate the radon-222 content of water samples for the measurement of the radon-222 concentration in surface water. J. Japan Soc. Hydrol. & Water Resour., 18, 177-184.
Hamada H., et al. (2004): Measurement of 222Rn concentration in surface water in Northeast Thailand. Abstract of Annual Meeting of the Agricultural Engineering Society, Japan 2004, p.960-907.
- Japanese PDF
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2004_09_A3_ja.pdf691.75 KB