Study On Distribution And Model Of Soil Radon In South China

With the improvement of living standard and strengthening of the environmentalprotection awareness, people pay more and more attention to the living environmentalquality. Radon is all around us in the living space.77.7%radon releases from the landsurface and the soil radon concentration is1000times higher than the average radonconcentration on the ground, therefore it is particularly important to study soil radondistribution and the theoretical model within a region. For China has a vast territory,calculating and predicting soil radon level and variation by the theoretical modelshave both great academic significance and practical significance.This thesis introduced the main principles of diffusion and convection andinfluencing factors of radon transmission mechanism firstly, and then focused on thesoil radon distribution law and transport model in south China. On this basis, the fieldsamples were made physical analysis. The theoretical models calculating with theparameters got from the physical analysis were done and compared the theoreticalvalue with field survey data, eventually evaluated the two models; Secondly, for thestudy of different sampling depths, the ratio calculating between two depths withdiffusion model and diffusion-convection model was done and a ratio relationshipformula was given, the result was analyzed and verified according to the field data;Finally, the improvement of two-layer transmission model was analyzed and the newgeneral solution was given.The results show that the level of soil radon concentration is quite high in sometypical granite areas, whereas it’s relatively low in quaternary sediment areas inZhongshan city, Guangdong province, the radon distribution has a lagre range in theentire survey area; Single transport model considered diffusion only could objectivelyreflect the distribution level to a certain extent as well as the diffusion and convectionmodel. For the survey area of granite, there is a smaller relative deviation betweenfield data and theoretical value which calculated by the diffusion-convection model, the diffusion-convection model has a better effect on reflecting the field data level.However, for the survey area of quaternary sediment, the diffusion model reflectsfield data better. In general, these two models both have a certain value to provide abasic prediction for a similar geological background areas of soil radon; For differentdepths of one sampling point, the relative error is less than25%between thetheoretical value calculated with two models and the field data respectively, this resultindicates the soil radon values in depths based on theoretical calculations has a certainreference value and significance; For the improved radon transport model oftwo-layer-media, compared with the former one, the new general solution of equationfor the first layer is the same as of the model before changed, the equation for thesecond layer is different.The general solution of improved model could be a guide forfurther simulation and verification.