Studies on temporal change in depth profiles of the Rn concentrations in natural water columns

Abstract

Although radon loss should be taken into account when determining the amount of radon in a water sample, only a few papers have exclusively investigated the factors connected to radon loss. To clarify radon loss behavior, this study examines the temporal changes in depth profiles using a large volume of natural water in a simple system where the effects of external factors (pressure, stirring, air convection, etc.) are suppressed. Analyzing the results using a box model indicates that at low temperature, the depth profile of the residual radon at the surface remarkably decreases, but at high temperature the depth profile is uniform. The exponential decrease of the total residual radon in water depends on the elapsed time and temperature. In addition, the box model analysis provides the activation energies of transfer from water to air and in water. The water depth profiles are formed by the supply balance of radon from deep water to the surface and the discharge of radon from the surface to the air.