EXPERIMENTAL-STUDY OF RADON TRANSPORT IN WATER AS TEST FOR A TRANSPORTATION MICROBUBBLE MODEL

The theory of radon transport by geogas microbubbles is briefly outlined. Physical model experiments were carried out to test the theory directly. The transport characteristics of radon were studied in two experiments in a 8.5 m high column filled with pure water or with a porous medium saturated with water (plastic granules), respectively. Simple devices for the continuous underwater monitoring of radon were devised and used for the measurements. A pulse-like bubble stream was injected into the system during the experiments. In pure water, convection induced by thermal gradient and transport by microbubbles are shown to be the main processes for radon transport. In water-filled porous medium the convection phenomenon is eliminated due to the Presence of granules, therefore the microbubble transport shows markedly. As it was expected, the diffusion process did not play a noticeable role in the movement of radon during the experiments. The results have shown that radon could be carried by microbubbles very fast and efficiently, so the observed geogas upflow phenomenon could be a decisive transport process in the natural environment. A mathematical model for the description of the microbubble radon transport process in water is proposed and theoretical curves of the vertical distribution of radon concentration in water are derived.