Environmental factors affecting radon exhalation from a sandy soil

The 222Rn transport from soil into atmosphere was analyzed to elucidate the behavior of radioactive gas including H-3 and C-14 in surface environment. To investigate the effect of various environmental factors on 222Rn exhalation from a sandy soil, measurements of 222Rn exhalation rate were continuously carried out with a closed chamber method in Tokai site, JAERI. From the correlation analysis between the 222Rn exhalation rate and environmental factors, it was indicated that volumetric water content from soil surface to about 20 cm depth affects dominantly the 222Rn exhalation. The negative correlation relationship between the rate and atmospheric pressure change was also recognized only under drying conditions. The rate increased with increase of temperature difference between atmosphere and soil. Further consideration on transport mechanisms by temperature gradient may be necessary to discuss gas transport at soil-atmosphere interface. The basic information on gas transport in soil and on gas exhalation and deposition behavior at soil-atmosphere interface was provided by this research dealing with radioactive noble gas 222Rn. (author)