The Preliminary Survey And Research Of Soil Radon Exhalation Rate In Beijing And Guangdong Area

As a major natural radionuclide irradiation, radon can enter our body through the respiratory tract easily. According to the epidemiological surveys, the total numbers of lung cancer death in 8.2% of people are caused by the inhalation of radon. Radon is listed as one of 19 types of carcinogenic substances by the World Health Organization that draws countries all over the world to pay great attention to air radon. Soil radon is the main source of environmental radon. After producted from the soil particles with the decay of radium, radon enters into the atmosphere from the surface through precipitating. Radon exhalation rate is an important indicator to soil radon assessment. Therefore, it is significant to study soil radon and radon exhalation rate for the environment. Based on the discussion of the two measurement methods for soil radon exhalation rate, preliminary investigation of the radon exhalation rate in Beijing and Guangdong area were completed. This paper analyzed the soil radon and soil radon exhalation rate theory, combining with the soil radon exhalation rate measurements to discuss affecting factors such as soil water content and other factors on the radon exhalation rate. On the basis of the theoretical model of radon exhalation rate the correction was carried out.Through the methods of electrostatic collection of ERS-2 and activated carbon accumulated adsorption, the soil radon exhalation rate was measured in different regions and geological background areas. Among them, the level of radon exhalation rate in Beijing area was about 46.33(14.6~102.3)mBq/m2s, and radium content was about 26.8(23.62~31.30)Bq/kg. The level of radon exhalation rate in Guangdong Province was about 122.62 (27.1~181.6)mBq/m2s, and radium content was about 71.9(44.17~126.1)Bq/kg. Among the affecting factors on radon exhalation rate in soil, the water content was the most obvious. When the soil water content was low (<20%), with the increasing of soil water content, radon exhalation rate also showed an increasing trend. In addition, the soil properties parameters, including soil water content, radium content, dry density, emanation coefficient, porosity, were used in the theoretical model calculation. According to the experimental results of validating the theoretical model. When water saturation was greater than 0.35, the theoretical model was corrected by least squares linear model fitting function. It had relatively lower error after corrected.