Annual distribution and deposition of atmospheric 210Pb in Busan, the largest port city in Korea.

This study examined the annual and seasonal variations of ²¹⁰Pb in aerosols collected in Busan, a major port city in South Korea. Aerosol samples were obtained during two sampling campaigns: (i) total suspended particles (TSP) from April 2019 to February 2020, and (ii) particulate matter with diameters ≤10 μm (PM₁₀) and ≤2.5 μm (PM_2.5) from March 2020 to February 2021. The activity concentrations of ²¹⁰Pb ranged from 0.10 to 1.98 mBq m^-3 (TSP), 0.09-1.97 mBq m^-3 (PM₁₀), and 0.02-2.07 mBq m^-3 (PM_2.5), showing clear seasonal trends. Activities peaked in autumn and winter (October-February) and were lowest in summer (July-September), with up to two-fold seasonal variation. These patterns were mainly attributed to meteorological variability and increased anthropogenic emissions during colder months due to seasonal wind shifts. No significant differences in ²¹⁰Pb activity appeared among size-fractionated samples (TSP, PM₁₀, and PM_2.5), indicating a preferential association of ²¹⁰Pb with fine aerosols. Dry deposition fluxes of ²¹⁰Pb in Busan were comparable to those reported in other global cities, despite only including the dry component. ²¹⁰Pb activities in TSP correlated with ⁴⁰K in fallout dust, likely from resuspended soil, while ²¹⁰Pb in PM_2.5 paralleled ⁷Be variations in air. Moreover, ²¹⁰Pb/Pb ratios showed seasonal changes, notably in PM_2.5 during the dry season. The results suggest that aerosol behavior in Busan is notably influenced by anthropogenic sources during dry months, especially in fine dust (e.g., PM_2.5). Overall, ²¹⁰Pb proves useful as a radioactive tracer for understanding aerosol dynamics.