Radon Exhalation from the Soil

Abstract

Abstract The exhalation of radon from the soil is the main source for high radon concentration in dwellings. A study of the mechanism of exhalation, its dependence on various parameters and the entry points for radon in houses are presented. Electrostatic deposition of the radon daughter products on a surface barrier detector and subsequent analysis of the measured alpha spectra allows one to determine the exhalation rates of 222Rn and 220Rn directly from the soil. For a sampling time of two hours, the lower limit of detection of our equipment was found to be 0.3 x 10-3 Bq.m-2.s-1 for 222Rn. In the south-west part of Germany, the 222Rn exhalation rates from the soil vary approximately between 2 x 10-3 and 100 x 10-3 Bq.m-2.s-1. The water content of the investigated soil, its actual porosity and its radium content determine the radon migration through the pores. For example in regions with volcanic rocks the exhalation rates are up to 10 times higher than in sandstone areas. Some special constructive measures to reduce the entry of radon in buildings are proposed.