Effect of bubble flow on radon transfer at the water–air interface: experimental studies using optical methods

This study investigates the impact of varying degrees of bubble flow on radon migration at the water–air interface. An apparatus was designed to monitor the change in the activity concentration of radon transferred from water to air at different levels of bubble flow, and high-speed cameras were used to capture the bubble flow. The optical method determined the captured images’ bubble size and average flow velocity. A mathematical model was used to estimate and experimentally measure the activity concentration of radon in air, resulting in the determination of the optimal radon transfer velocity coefficient (K). Based on the experimental and fitted results, empirical equations for the variation of the radon transfer velocity coefficient under different levels of bubble flow were derived. These formulas show that the radon transfer velocity coefficient does not always increase with increasing levels of bubble flow but increases to an upper limit and then stops.