Study On The Variation Of Radon Concentration In Soil On The Air-Ground Interface

Over the past few decades, there has been a large scientific interest in the studyof radon and its progenies for its associated health hazard. Many countries andregions carried out studies on radon in soil considering the soil as the major sourceof environmental radon. Compared with other countries, the long-term measurementand the summary of variation law of radon concentration in soil in naturaloccurrence have not been well studied in our country. As the indoor radon level isralated to the soil radon concentration, so the research about the soil radon variationis very important.This paper is a part of the project of "The study of Radon Radiation Field andEnvironmental Effect on the Air-Ground Interface", financed by the National NaturalScience Foundation of China (No:40374051). Through long-term observation ofchanges of the soil radon concentration, the temperature, humidity and pressure, theanalysis and study on it were carried out. In this paper, some conclusions weredrawn below:(1) In the vertical distribution, the concentration of radon in soil rises with thedepth increasing, the influences of meteorological factors are more obvious when itapproaches the ground. In general cases, the upward migration rate is much higherthan the horizontal migration, this is because the environmental radon level is lowerthan that in soil(approximately 1,000 times), through the diffusion and convection,the radon concentration in depth soil is higher than that in surface soil, therefore, thesampling depth must be rigorous for measurement in wild fields.(2) It is found that the radon seasonal variation is different: The radonconcentration in winter is higher than in spring and summer. The radon concentrationmeasurement in subgrade soil should be carried out within a month.(3) The radon concentration in depth soil increases during rainfall, the reason isthat with the soil moisture increasing, the surface porosity is blocked, whichenhances the radon concentration in deep soil. As a result, the measurement aboutradon in soil should be avoided when the ground humidity is great. (4) In the normal weather, the diurnal variation of the radon concentration showsthat the highest value appears in early morning, while the values in noon andafternoon are lower relatively, While during rainfall, the diurnal variation is different,but the change rule is not obvious.(5) There is some correlation between the soil radon content and themeteorological factors including the temperature, humidity and pressure, the resultindicates that radon concentration in soil is generally correlated negatively with thepressure, and positively with temperature.(6) Established the equation between the radon concentration and themeteorological factors. In different seasons, the main influencing meteorologicalfactors are different.