Estimation of 222Rn flux from ground surface based on the variation analysis of 222Rn concentration in a closed chamber

A method for quantification of the Rn-222 flux from the ground surface into the atmosphere is described. A chamber made of polymethylmethacrylate (PMMA) was embedded in the soil and Rn-222 concentration and various affecting environmental factors were measured every hour. How environmental factors affect the Rn-222 concentration was considered and it was found that there were clear relationships between the variations of Rn-222 concentration and various environmental factors, especially air pressure. A simple lumped-parameter model approach was developed to obtain the undisturbed Rn-222 flux, which is the hypothetical situation without the chamber. The values of the parameter were found by fitting the model to the measured data for air pressure and Rn-222 concentration in the chamber. The effective diffusion coefficient obtained by the analysis agreed well with that obtained by the relation reported by Rogers and Nielson. The undisturbed Rn-222 AUX from the ground surface into the atmosphere was estimated by using the parameter values obtained.