Radon Risk Potential Map Method Based On Soil Radon And Soil Air Permeability

Radon is a radioactive inert gas and the half-life is of 3.8d. Natural radiation absorbed by the human body mainly caused by the radiation exposure from radon. Meanwhile, the main source of indoor radon emits from soil and rocks which perhaps increase the potential dangers of radiation for the human being. The risk assessment and definition of radon potential have the great value for the urban construction and scheme.The thesis makes the theoretical analyses to the physical progress from the generation of radon to the indoor. 226 Ra decays into radon which bled from the mineral lattice and form free radon in the pores of soil. The free radon in the soil influences by the diffusion and convection. Because of the concentration and pressure gradation, the radon in the soil emits to the atmosphere or to the indoor according to steady rate. Based on the above results, soil air permeability and soil radon are the key factors for the risk radon potential. The main controlling factors include Ra content, emanation coefficient, water saturation and porosity of soil.The experiment data measured in Guangdong province and Beijing survey area including soil radon concentration, soil air permeability, soil Ra content, indoor concentration, soil saturation and even the environmental parameter such as temperature and moisture. The results show that soil Ra activity and soil radon concentration in Guangdong province where lever is higher than the national average data are higher than Beijing area. Soil radon concentration has good relationship with geological background which can be divided into four categories in this research. For example, the radon concentration in weathering ganite soil is almost twice higher than sedimentary of Quaternary Period. Studied in the two cities, Zhongshan and Zhuhai, the indoor concentration in wreathing ganite is obviously higher than Quaternary sedimentary and is higher than national and global average data. Soil air permeability in weathering ganite is also higher than other sedimentary soil.Radon risk potential map was carried out in Guangdong area. SRP and indoor radon concentration were researched according four geological backgrounds. Random sampling survey show indoor radon data in about 24% houses is higher than 100Bq/m3 in high radon potential area confined by SRP value; 17% in middle radon potential area and no sample in low radon potential area. Above all, Radon potential index method is suitable to risk potential map in China.