Spatiotemporal Variations of Radon Concentration in the Atmosphere of Zhijindong Cave (China)

Abstract

Ensuring high air quality in the atmosphere of Zhijindong Cave is essential, for it is one of the most scenic in Asia and has received millions of tourists each year. Radon, as the most important radioactive carcinogen, is a priority and has been measured since just after its opening. However, an artificial exit was opened in 2002, and it is still unclear what the influence of that has been on the radon concentration in the cave atmosphere. In this study, we use RAD7 to monitor the spatiotemporal variations of radon concentration in the atmosphere of Zhijindong Cave for a whole year. The results show that radon concentration is generally higher in the hot season and lower in the cold season, and both with a distinct spatial differences. The highest measured radon concentration is 1691 Bq/m³, which is lower compared with the previous study. The reduced radon concentration could be caused by the strengthened cave ventilation due to the artificial exit. The temporal variation of radon concentration is related to the outside temperature change, while the spatial variation is mostly related to the different cave layers. The effective dose is negligible for tourists, but can be as high as 9.7 mSv for tour guides and 22.6 mSv for photographers.