Study On The Cause And Behavior Of Short-lived Radon Daughters In Rainwater

Atmospheric rainfall is closely related to human life. The short-lived radon daughter in rain originates from the air, and it is present in form of bound or non-bound in the air; it is one of the major factors that cause lung cancer. In addition, the radon daughter in rain also results in significantly high environmental radiation, it cannot be ignored as a factor in the radiation dose evaluation. Therefore, research for natural radioactive rainwater is important and meaningful to the human health and various applications.At present, source of the short-lived radioactive in the rainwater and the study of its laws is still arguable; the derived conclusions and data are mainly taken from the monitoring of the natural rainfall or speculations from theories. Due to the complexity and volatility of the temperature of rainfall, wind speed and other weather conditions especially the extremely unpredictable weather conditions at high-altitude, the study of the radioactive rain under natural conditions is always facing great uncertainty. In order to solve these problems, the following research has been done:1.By monitoring and taking numerous measurements of the short-lived radioactive from the rain in Fuzhou, it is found that the short-lived radioactive in rainwater is related to the rainfall intensity; but this result is obviously different from which that had been concluded in Wuzhou Jiangxi and Maizuru Japan. After comparing and analyzing the different physiognomy weather conditions in the 3 cities of Fuzhou Fujian, Wuzhou Jiangxi and Maizuru Japan, it explains the different influence of the short-lived radioactive in rainwater in the different regions.2.By simulating the process of raindrops scouring the atmosphere and vapour condensation into water, the sources of the short-lived radioactive in rainwater are ascertained. It is found that the short-lived radioactive is not produced in the rainwater in the process of the vapour condensation; but the short-lived radioactive is obviously observed in the rainwater in the process of raindrops scouring from the atmosphere. It is also found by analyzing the ray spectrum data measured from both the processes of the natural rainfall and simulated rainfall that:both spectra characteristic peaks are very close; meanwhile, the Characteristic peak of 214Pb and 214Bi are obviously increased compared to the background water. Therefore, it can be concluded that the short-lived radioactivity in the rainwater is sourced from the captured short-lived radon daughter when the rainfall is washing out the air.3. According to scavenging coefficients for the raindrops to clean radon daughter in the air and decay in succession regularity of radon daughter, the Rain erosion mathematical model is established and the method to determine the model parameters as well the solving process is provided.4. In the process of simulating drips down from a rainfall, water samples obtained from the different rainfall conditions were measured, the feasibility of the rain erosion mathematical model was verified by the measured data, and the values measured from the experimental and calculated from the theoretical deviate from -13.14% to-13.35%.