Characteristics of ⁷Be and ²¹⁰Pb behavior in the atmosphere over Osaka, Japan, as well as the size distributions of the chemical compositions of aerosols attached by ⁷Be and ²¹⁰Pb.

This article focuses on the simultaneous measurement and analysis of the size distribution and chemical composition of aerosols carrying the radionuclides beryllium-7 (^7Be) and lead-210 (^210Pb) in Daito, Osaka, Japan. The study found that over 80% of ^7Be and ^210Pb were associated with aerosol particles smaller than 2.1 μm, peaking at 0.33–0.55 μm, and identified sulfate ions (SO_4^2−) as their primary carriers during summer 2020, based on strong correlations between radionuclide activity and sulfate concentrations. Seasonal variations showed ^7Be and ^210Pb concentrations peaking in spring and autumn, with deposition velocities highest in summer; wet deposition dominated ^7Be removal, while dry deposition was more significant for ^210Pb. The estimated atmospheric residence times were approximately 5–6 days for both radionuclides. This study represents the first comprehensive simultaneous measurement of the entire particle and ion size distribution of ^7Be and ^210Pb, contributing to improved atmospheric transport modeling and air pollution mitigation strategies.