Analysis of variations in activity concentrations of 7Be,137Cs and 210Pb in the air in Beijing
Objective To discusses the variations of 7 Be,137Cs and 210Pb activity concentrations in the air in Beijing from March 16,2021 to March 31,2023,and their correlation with temperature,precipitation,relative humidity,barometric pressure,PM10(only limited to 137Cs)and other meteorological parameters.Methods A total of 60 aerosol samples were collected using the HRHA01-SFS1000/A ultra-large flowair sampler in the automatic radiation monitoring station.The activity concentrations of 7Be,137Cs and 210Pb in the aerosol samples were measured by GMX-60 low background anti-Compton high purity germanium gamma spectrometer.Pearson correlation coefficient was used to show the correlation of the relevant parameters.Results The seasonal mean values of7 Be activity concentration were spring 4.31 mBq/m3,summer 3.53 mBq/m3,autumn 3.09 mBq/m3 and winter 2.45 mBq/m3,respectively,ranging from 1.17 to 7.79 mBq/m3,with the overall mean of(3.36±1.33)mBq/m3.The activity concentration of 137 Cs ranged from 0.39 to 8.49 μBq/m3,with an average of(0.59±1.47)μBq/m3.The average activity concentrations of 210Pb were spring 0.53 mBq/m3,summer 0.44 mBq/m3,autumn 0.72 mBq/m3 and winter 0.75 mBq/m3,respectively,ranging from 0.21 to 1.36 mBq/m3,with an average of(0.56±0.26)mBq/m3.The activity concentration of 7 Be was correlated with temperature and pressure(r=0.38,-0.40),the activity concentration of 137 Cs was correlated with precipitation(r=-0.41),and the activity concentration of 210Pb was correlated with temperature and pressure(r=-0.31,0.37).The variation of 137Cs activity concentration in the air showed an obvious seasonal pattern,and the peak value generally appears in spring of each year(March to May),which was related to the frequent spring dust in Beijing.The activity concentration of 210Pb in the air was affected by coal combustion heating in winter,and has a peak value during November to March.Conclusions The activity concentrations of 7Be,137Cs and 210Pb in the air in Beijing are within the normal range,showing a seasonal trend.
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