Japanese Journal of Health Physics
Online ISSN : 1884-7560
Print ISSN : 0367-6110
ISSN-L : 0367-6110
Original Paper
Source of Atmospheric Radon in the Gyokusendo, a Limestone Cave in Okinawa, Japan
Yoshitaka SHIROMAMasato SHIROMASeigou KINAMasahiro HOSODAYumi YASUOKANaofumi AKATAMasahide FURUKAWA
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2016 Volume 51 Issue 4 Pages 218-226

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Abstract

In order to understand the source of atmospheric radon concentration in the Gyokusendo which is the limestone cave on Okinawa Island, the radon concentrations in the drip water from the ceiling were measured using a liquid scintillation counter. The arithmetic mean (± standard deviation) of radon concentration was 8.7 ± 2.0 kBq m-3. This result suggests that the atmospheric radon in the cave was supplied from the drip water. When comparing the monthly precipitations which are considered to exert a profound influence on isotopic compositions of water seeping into a cave, the variation of radon concentration in the drip water was shown the delay of 60-90 days. The radon concentration in the soil water was estimated to be 47.3 kBq m-3. Furthermore, the radon concentrations in the percolation water at the cave over a period of 9 to 10 days were calculated to be 9.3-7.7 kBq m-3. The estimated radon concentration in the percolation water was almost equivalent with the measurement concentration in the drip water. These results suggest that the radon atoms in the drip water were generated from the soil above the cave. In other words, emanated radon from the soil particles might be the source of radon in the Gyokusendo.

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© 2016 Japan Health Physics Society
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