⁷Be and ²¹⁰Pb are the main radionuclides for monitoring the quality of the radiation environment of atmospheric aerosols, and the internal irradiation caused by their adsorption into aerosols and entry into the human body will be harmful to the human body, so it is of great significance to explore the characteristics and mechanisms of their spatial and temporal distribution and dose contribution.

This study aims to investigate the differences in the spatial and temporal distributions of atmospheric ⁷Be and ²¹⁰Pb and the mechanisms of these differences.

In this paper, 75 aerosol samples were collected from Nanning city, from January 2015 to December 2017 and from January 2019 to May 2022 using an ultra-high-flow air aerosol sampler, and the activity concentrations of ⁷Be and ²¹⁰Pb in the aerosol were measured and analyzed using a high-purity germanium (HPGe) γ-spectrometer. The activity concentration data of ⁷Be and ²¹⁰Pb were systematically collected in 17 areas of our country, as well as PM_2.5, PM₁₀ and O₃ air concentration data from January 2014 to November 2023 in Nanning city. Finally, the Lagrangian inverse trajectory analysis technique based on the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model, combined with the clustering analysis method based on MeteoInfo software, was employed to analyze the seasonal characteristic control mechanism of ⁷Be and ²¹⁰Pb.

The activity concentrations of ⁷Be in 41 aerosol samples from January 2019 to May 2022 ranges from 0.27 mBq·m^-3 to 11.95 mBq·m^-3, with a mean value of (3.68±0.51) mBq·m^-3; the activity concentrations of ²¹⁰Pb in 60 aerosol samples from January 2015 to December 2017 and from January 2019 to February 2021 ranges from 0.23 mBq·m^-3 to 4.33 mBq·m^-3, with a mean value of (1.51±0.13) mBq·m^-3. Combining the ⁷Be and ²¹⁰Pb activity concentration data in 17 areas of China, the seasonal distribution of ⁷Be and ²¹⁰Pb activity concentrations in the atmosphere of China is characterized by an overall high in winter and spring, and a low in summer and autumn, but ⁷Be reaches its maximum value in spring while ²¹⁰Pb in winter. The correlation analysis shows that ⁷Be has a significant positive correlation with PM_2.5, PM₁₀, O₃, and has the best correlation with PM₁₀. ²¹⁰Pb has a significant positive correlation with PM_2.5 and PM₁₀ and has the best correlation with PM_2.5, while it is not correlated with O₃. The traceability analysis of air masses in Nanning city of the 2021 shows that the summer air masses mainly come from the oceanic air masses in the south with lower particle concentration, and the winter air masses mainly come from the continental air masses in the north with higher particle concentration. Combining the ⁷Be and ²¹⁰Pb activity concentration data in 17 areas of China, there are effects in the spatial distribution of ⁷Be and ²¹⁰Pb activity concentrations. The latitudinal effects: the mean ²¹⁰Pb activity concentration in the area north of about 40°N (3.20±0.24) mBq·m^-3 is about 2.2 times higher than that in the area south of about 40°N (1.48±0.06) mBq·m^-3; the mean value of ⁷Be activity concentration in the area north of about 35°N (7.44±0.26) mBq·m^-3 is about 1.9 times of that in the area south of about 35°N (3.92±0.19) mBq·m^-3. The altitudinal effect: the ⁷Be activity concentration is greater at high altitude than at low altitude. Based on the average of winter-spring and summer-autumn activity concentrations of ⁷Be and ²¹⁰Pb in 17 regions of the country, it can be estimated that the radiation dose due to ⁷Be and ²¹⁰Pb in winter-spring (42.08 μSv·a^-1) is about 1.4 times higher than that in summer-autumn (31.00 μSv·a^-1). Integration of monitoring data on activity concentrations of ⁷Be and ²¹⁰Pb in 17 regions of the country reveals that the annual effective dose due to ⁷Be and ²¹⁰Pb in the area north of 40°N (65.48 μSv·a^-1) is about 2.0 times higher than that in the area south of 35°N (32.75 μSv·a^-1). The mean annual pending effective doses due to ⁷Be and ²¹⁰Pb are 2.47×10^-3 μSv·a^-1 and 33.57 μSv·a^-1, respectively.

⁷Be and ²¹⁰Pb are adsorbed on the particulate matter and transported in the atmosphere, and the PM_2.5 and PM₁₀ concentrations are low in summer and autumn while high in winter and spring due to the monsoon regulation, so the ⁷Be and ²¹⁰Pb show the seasonal distribution characteristics of low in summer and autumn and high in winter and spring. The highest ⁷Be activity concentration in spring is related to the "spring leakage", while the highest ²¹⁰Pb activity concentration in winter is mainly influenced by the Eurasian land-based air masses in the north. The latitudinal effect of ²¹⁰Pb is probably related to the large amount of particulate matter brought by the northwest land-source winds in winter and the combustion process in winter heating system. The latitudinal effect of ⁷Be may be attributed to the "spring leakage" of ⁷Be that occurs in mid-latitudes in the spring. The altitudinal effect of ⁷Be is controlled by the top-down transport of ⁷Be from the stratosphere to the troposphere.