Radon activity concentration in the ground and its correlation with the water content of the soil

Radon activity concentration in the ground was measured using Kodak LR-115 cellulose nitrate detectors for approx. 3 yr as part of a survey of exposure to radiation from radon and its decay products. The results show seasonal periodicity with a maximum (summer) to minimum (winter) ratio of the order of 10. The amount of water stored in the soil was deduced from meteorological data on the basis of the water balance of the region. The minima in water content were correlated to maxima in radon concentration resulting in a correlation coefficient of 0.76.