Radon as a natural tracer for underwater cave exploration

Katalin Csondor; Anita Erőss; Ákos Horváth; Dénes Szieberth

doi:10.1016/j.jenvrad.2016.10.020

Radon as a natural tracer for underwater cave exploration

J Environ Radioact. 2017 Jul:173:51-57. doi: 10.1016/j.jenvrad.2016.10.020. Epub 2016 Nov 22.

Authors

Katalin Csondor¹, Anita Erőss², Ákos Horváth³, Dénes Szieberth⁴

Affiliations

¹ Department of Physical and Applied Geology, Institute of Geography and Earth Sciences, Eötvös Loránd University, Pázmány Péter Sétány 1/c, 1117 Budapest, Hungary. Electronic address: kacc91@gmail.com.
² Department of Physical and Applied Geology, Institute of Geography and Earth Sciences, Eötvös Loránd University, Pázmány Péter Sétány 1/c, 1117 Budapest, Hungary. Electronic address: anita.eross@geology.elte.hu.
³ Department of Atomic Physics, Institute of Physics, Eötvös Loránd University, Pázmány Péter Sétány 1/a, 1117 Budapest, Hungary. Electronic address: akos@ludens.elte.hu.
⁴ Department of Inorganic and Analytical Chemistry, Budapest University of Technology and Economics, Műegyetem Rakpart 3, 1111 Budapest, Hungary. Electronic address: denes.szieberth@mail.bme.hu.

PMID: 27887972
DOI: 10.1016/j.jenvrad.2016.10.020

Abstract

The Molnár János cave is one of the largest hypogenic caves of the Buda Thermal Karst (Budapest, Hungary) and mainly characterized by water-filled passages. The major outflow point of the waters of the cave system is the Boltív spring, which feeds the artificial Malom Lake. Previous radon measurements in the cave system and in the spring established the highest radon concentration (71 BqL^-1) in the springwater. According to previous studies, the origin of radon was identified as iron-hydroxide containing biofilms, which form where there is mixing of cold and thermal waters, and these biofilms efficiently adsorb radium from the thermal water component. Since mixing of waters is responsible for the formation of the cave as well, these iron-hydroxide containing biofilms and the consequent high radon concentrations mark the active cave forming zones. Based on previous radon measurements, it is supposed that the active mixing and cave forming zone has to be close to the spring, since the highest radon concentration was measured there. Therefore radon mapping was carried out with the help of divers in order to get a spatial distribution of radon in the cave passages closest to the spring. Based on our measurements, the highest radon activity concentration (84 BqL^-1) was found in the springwater. Based on the distribution of radon activity concentrations, direct connection was established between the spring and the István-room of the cave, which was verified by an artificial tracer. However, the distribution of radon in the cave passages shows lower concentrations (18-46 BqL^-1) compared to the spring, therefore an additional deep inflow from hitherto unknown cave passages is assumed, from which waters with high radon content arrive to the spring. These passages are assumed to be in the active cave formation zone. This study proved that radon activity concentration distribution is a useful tool in underwater cave exploration.

Keywords: Hypogenic; Mixing; Radon; Tracer; Underwater cave.

MeSH terms

Air Pollutants, Radioactive / analysis*
Caves*
Hungary
Radiation Monitoring*
Radon / analysis*

Substances

Air Pollutants, Radioactive
Radon