Temporal and Spatial Variation of Radon Concentrations in Environmental Water from Okinawa Island, Southwestern Part of Japan
Open Access
- 23 January 2021
- journal article
- research article
- Published by MDPI AG in International Journal of Environmental Research and Public Health
- Vol. 18 (3), 998
- https://doi.org/10.3390/ijerph18030998
Abstract
In this study, to get a better understanding in characterizing groundwater and ensure its effective management, the radon concentrations in water samples were measured through Ryukyu limestone in southern Okinawa Island, Japan. Water samples were collected from a limestone cave (Gyokusendo cave, dropping water) and two springs (Ukinju and Komesu, spring water), and the radon concentrations were measured by liquid scintillation counters. The radon concentrations in the samples from the Gyokusendo cave, and Ukinju and Komesu springs were 10 ± 1.3 Bq L−1, 3.2 ± 1.0 Bq L−1, and 3.1 ± 1.1 Bq L−1, respectively. The radon concentrations showed a gradually increasing trend from summer to autumn and decreased during winter. The variation of radon concentrations in the dripping water sample from the Gyokusendo cave showed a lagged response to precipitation changes by approximately 2–3 months. The estimated radon concentrations in the dripping water sample were calculated with the measured radon concentrations from the dripping water obtained during the study period. Based on our results, groundwater in the Gyokusendo cave system was estimated to percolate through the Ryukyu limestone in 7–10 days, and the residence time of groundwater in the soil above Gyokusendo cave was estimated to be approximately 50–80 days. This work makes a valuable contribution to the understanding of groundwater processes in limestone aquifers, which is essential for ensuring groundwater sustainability.Keywords
This publication has 23 references indexed in Scilit:
- Radon and CO2 as natural tracers to investigate the recharge dynamics of karst aquifersJournal of Hydrology, 2011
- Introductory perspective on the COREF ProjectIsland Arc, 2006
- Analysis of recharge by paddy field irrigation using 222Rn concentration in groundwater as an indicatorJournal of Hydrology, 1998
- Anomaly in Atmospheric Radon ConcentrationHealth Physics, 1997
- Radon distribution and the ventilation of a limestone cave on Okinawa.GEOCHEMICAL JOURNAL, 1997
- Ground-Water Radon Anomaly Before the Kobe Earthquake in JapanScience, 1995
- Tutorial review. Calculating standard deviations and confidence intervals with a universally applicable spreadsheet techniqueThe Analyst, 1994
- Radon transport from soil to airReviews of Geophysics, 1992
- Using 222Rn to examine groundwater/surface discharge interaction in the Rio Grande de Manati, Puerto RicoJournal of Hydrology, 1990
- Special Applications (2), Measurements of Radon ActivityRADIOISOTOPES, 1975