A new procedure to validate and optimize 210Po measurements in atmospheric aerosols

The exposure to air fine aerosols can cause health effects due to inhalations of alpha emitters such as 222 Rn daughters. Lead-210 and 210 Po are mainly associated to aerosols with median aerodynamic diameter lower than 1 μm. The 210 Po is characterized by having a high radiotoxicity. The precise measurement of 210 Po in surface air aerosols is usually quite complex due to the significant contribution of the 210 Pb on their concentrations. Additionally, there is no possible means to manufacture a certified material to validate the measurements of 210 Pb and 210 Po concentrations in surface air aerosols. For these reasons, this study aims to develop a novel and comprehensive methodology to validate 210 Po measurements in surface air aerosols by preparing in our laboratory “standard samples” with known activities of both 210 Pb and 210 Po. A detailed sensitivity analysis on the precision of 210 Po concentration measurements has been carried out as a function of the involved variables such as sampling time, time elapsed between the sampling start and 210 Po self-deposition and the 210 Po/ 210 Pb activity ratio in surface air aerosols. This study is necessary to find the optimum conditions for a precise measurement of 210 Po in surface air aerosols. In addition, this methodology has been applied for the determination of 210 Po concentrations in 30 samplings campaigns of atmospheric aerosols carried out at the El Carmen campus (Huelva province) from March 25th to July 15th, 2022. The results obtained for 210 Pb and 210 Po concentrations and atmospheric aerosol residence times (via 210 Po/ 210 Pb activity ratio) were consistent with other previous works. • A novel and comprehensive methodology to validate 210 Po measurements in surface air aerosols was developed. • The developed methodology addressed external and internal validations by using a liquid CRM, and varying Δ t d and 210 Po/ 210 Pb activity ratio. • The time elapsed between the sampling start and 210 Po self-deposition, Δ t d , was found to be ≤ 18 days to achieve a relative uncertainty of 210 Po concentration in air about 10%. • The methodology for the 210 Pb and 210 Po measurement was applied to 30 atmospheric aerosols filters obtaining averages of 0.36 ± 0.04 mBq m −3 and 0.014 ± 0.002 mBq m −3 . • For the previous samplings, the atmospheric aerosol residence times were also obtained, with an average of 15 ± 2 d, which agreed well with other previous works.