The Characteristics And Controlling Factors Of⁷Be And²¹⁰Pb Deposition In Shanghai

7Be and210Pb are widely used in the studies of atmospheric mass transmission. Rainwater samples were collected from August2009to October2010in East China Normal University (North Zhongshan Road campus) of Shanghai to study the variation of specific concentrations and integrated activity of7Be and210Pb for individual rain events and the monthly variations of both the particles. Meanwhile, the controlling factors of the concentration variations are analyzed by using correlation analysis, principal component analysis and air mass back trajectory model.Through the above study, conclusions were drawn as follows:1. The specific concentration range of7Be for51individual rain events is0.21-5.99Bq/L, and the specific concentration range of210Pb is0.01-0.90Bq/L. Meanwhile, the monthly average concentrations of7Be and210Pb have similar seasonal variation:higher concentrations in winter and lower concentrations in summer for7Be, higher concentrations in autumn and winter, while lower concentrations in summer for210Pb. The higher ratio value of7Be/210Pb is in spring and autumn.2. The concentrations of7Be and210Pb for individual rain events are not well related to the precipitations due to the dilution effect of large precipitation. The correlation of integrated concentrations between7Be and210Pb is relatively high due to the same transmission path of7Be and210Pb.3. The concentrations of major soluble ions were in order of SO42-> Ca2+> NH4+> NO3-> Mg2+> Cl-> K+> Na+> F-> Br-. They have higher concentrations in winter and lower concentrations in summer. The concentrations of metal soluble ions were in order of Al> Zn> Fe> Sr> Cu> Ni and the concentrations of spring and winter are higher than that of summer and autumn. 4. The average monthly neutron intensity has a similar variation pattern of the7Be specific concentrations. A statistically significant correlation between the solar spot number and7Be specific concentration has not been found. This can be explained by the fact the study period in this paper is not a complete solar cycle (11years).5. The back-trajectory method was also employed with an attempt to indentify the source of7Be coming to Shanghai. In general, the air mass is from high latitude in winter, while it is from lower latitude in summer.