Abstract: It is very important to measure radon exhalation rate from soil continuously for a better evaluation on the source of radon and its level, environmental radon exposure, and uranium tailings processing. Continuous measurement on radon exhalation rate of soil was studied theoretically and practically. As the result, a device was developed on basis of the flow air method, and a 24 days field continuous measurement was carried out in the northwest of Beijing with the device developed during spring 2012. It was indicated by the experimental results that rainfall has obvious effect on radon exhalation rate from soil. In the process of rainfall, radon exhalation rate increased apparently, and the increment of radon exhalation rate heightened with the rise of precipitation. For days of no rain, the radon exhalation rate from soil presented diurnal variation, and the diurnal periodical change of soil humidity was considered to be the main cause of this phenomenon.

Key words: radon exhalation rate, continuous measurement, precipitation, diurnal variation, soil humidity