A THEORETICAL TREATMENT OF ADSORPTION OF RADON GAS ON CHARCOAL

The use of an activated charcoal sampler for radon monitoring has beco me popular in recent years because of its passiveness and low price. D ynamics of adsorption on a passive sampler have been described with th eoretical models. However, extrapolation of the measured results of ra don on charcoal to the diurnal fluctuations of the ambient radon conce ntration is often difficult and even misleading because of the oversim plification of these models. A more generalized approach is undertaken by treating the diurnal variations in radon concentrations as poly-ex ponential functions and by solving for explicit particular solutions o f Fick's equation. The application of these solutions to various pract ical situations is explored. This includes their use for charcoal samp ler calibration. Estimated values of the adsorption coefficients, k, a nd diffusion constant D, appear to be agreeable with corresponding rep orted values. A triple-sampler protocol is also proposed for radon sur vey in areas of high diurnal fluctuations.