Analysis Of Atmospheric Aerosol Radionuclide Levels

Atmospheric aerosols are closely related to public health.With the improvement of China's urbanization level,various factors have contributed to the accelerated deterioration of air quality.It is significant to study the level of radionuclides in atmospheric aerosols.This thesis combines studies of radionuclides in atmospheric aerosols with time,air quality and meteorological parameter distribution.662 sets of aerosol samples' ground measured gamma spectrum were collected by a station of Beijing from January 2013 to July 2016.At the same time,120 sets of aerosol samples were selected to measure gamma spectrum in China Jin Ping Underground Laboratory.The radionuclide levels of atmospheric aerosol in Beijing area were studied and analyzed comparatively,including the following contents specifically.1.This thesis summarized the theory of gamma spectrometry measurement and analysis.Eight kinds of common radionuclides in atmospheric aerosol were analyzed.They are primary radionuclide 238 U,226Ra,210 Pb,232Th,228 Ra,40K,cosmogenic radionuclide 7Be and artificial radionuclide 137 Cs.The performance parameters of ground and underground Low-Background HPGe spectrometer and sampling and sample preparation device are introduced.Using statistical analysis method,the whole set of operable and low-level theory about quantitative analysis of radionuclide energy spectrum was established.According to the SNIP background elimination algorithm and this quantitative analysis theory,the batch analysis and calculation of gamma spectrum were programmed with the help of Matlab software.2.The nuclide levels of atmospheric aerosol in Beijing area were all in the range of background.Aerosol nuclides' detection rate was low,except 7Be,226 Ra,210Pb and 40 K.Measured results from ground and underground spectrometers did not have distinct differences.The activity concentrations of 8 kinds of radionuclides were as follows: 13.80(0~44.31)?Bq·m-3@238U,21.61(0~116.46)?Bq·m-3@226Ra,5.49(0~150.78)m Bq·m-3@210Pb,17.10(0~130.40)?Bq·m-3@232Th,17.12(0~130.50)?Bq·m-3@228Ra,25.19(0~288.03)?Bq·m-3@40K,2.76(0~6.99)m Bq·m-3@7Be,2.44(0~13.88)?Bq·m-3@137Cs.3.Influenced by Beijing's geographical location,climate environment,particulate emissions and so on,heavy pollution days are mainly concentrated in the winter and spring of stable climate,which is harmful to public health.The study found that the concentration of 8 radionuclides in atmospheric aerosols showed certain variation characteristics with time,season and air quality.For example,7Be with seasonal variation characteristics were obvious.Except 210 Pb,seven other nuclides showed an increasing trend in the past three years.210 Pb,232Th,228 Ra,40K,137 Cs showed an increasing trend with the deterioration of air quality.Except for 210 Pb,the wind direction had obvious influence on the nuclide content.By studying the activities of primary radionuclide of uranium radium and uranium thorium,we know that the concentration of uranium and thorium in atmospheric aerosol is basically stable,but radium has other sources.