Assessment of 210Po,210Bi and 210Pb in aerosols and their deposition fluxes in the nearshore region of the East China Sea
The deposition fluxes of 210Po,210Bi and 210Pb in atmosphere are the basis for the application of radionuc-lide tracing in the ocean.In order to reveal the spatio-temporal variation of the activity of 210Po,210Bi and 210Pb in nearshore areas and estimate their deposition fluxes into the sea,in this paper,sampling observation and analysis of two typical areas near the East China Sea in Shanghai and Xiamen in different periods are carried out.A time series study was conducted on the the aerosol activities of 210Po,210Pb and 210Bi in Shanghai and Xiamen from September 2016 to February 2017 and from September to November 2021,respectively.The residence time of aerosol particle was calculated based on 210Po/210Pb and 210Bi/210Pb.Deposition fluxes of three nuclides were also estimated.This pa-per reported the activity of 210Po,210Bi and 210Pb in Shanghai in autumn and winter of 2016.The activity ranges of 210Po,210Pb and210Bi were 0.11-1.27 mBq/m3,0.45-1.83 mBq/m3 and 1.12-6.10 mBq/m3,respectively.In the fall of 2021,the activity ranges of 210Po,210Bi and 210Pb in Xiamen were 0.05-0.85 mBq/m3,0.83-2.52 mBq/m3 and 0.17-1.32 mBq/m3,respectively.The aerosol activity of each nuclide in Shanghai was higher than that in Xiamen.The estimated residence time based on 210Po-210Pb and 210Bi-210Pb methods are significantly different,for example,in Shanghai area,the averaged aerosol residence time based on 210Po-210Pb method was calculated to be(94±54)d,which is much higher than the result from 210Bi-210Pb method.The main reason for this difference is most likely due to the difference in the properties of the tracing isotopes we used.In this paper,based on a one-dimensional simple aerosol deposition rate model,the atmospheric deposition fluxes of 210Pb,210Bi and210Po over Shanghai area into the East China Sea are estimated,and their variation ranges are 0.1-26.35 Bq/(m2·d),0.04-7.91 Bq/(m2·d)and 0.01-5.49 Bq/(m2·d),respectively.The deposition fluxes of 210Po,210Bi and 210Pb estimated based on the model are close to the actual observed values in the study area during the same period in winter within a certain range.The feasibil-ity of estimating the deposition flux of nuclide into the sea with a simple one dimensional aerosol deposition rate model is verified.
nearshore region of the East China Sea210Po210Bi210Pbresidence timedeposition flux
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