Annual distribution and atmospheric deposition of 210Po in aerosol in Busan, the largest port city in Korea

Abstract

The annual distributions of radionuclides, Po and Pb, were investigated in Busan, SouthKorea, whose regional atmosphere is largely affected by port infrastructure. Aerosol samples werecollected from Apr. 2019 to Feb. 2020 using a high-volume air sampler. The activities of Po and Pb ranged from 0.01 – 0.40 mBq m (average=0.13±0.2 (1 σ) mBq m , n=90) and 0.10 – 1.7mBq m (average=0.65±0.9 (1 σ) mBq m n=91), respectively. In contrast to Pb activity, whichwas relatively consistent in the entire sampling period, Po activity showed a variation of up to 3factors and was remarkably higher in the autumn and winter (Sep. to Feb.) relative to summeractivity (Jun. to Aug.). The substantially higher Po activity during the autumn and winterseasons was attributable to anthropogenic input from the vast port area surrounded by maritimeinfrastructures (e.g., shipyard, trade warehouse, factories, and ship anchorage), together withseasonal changes in wind directions. In Busan, the levels of Po and its dry depositional fl uxeswere comparable or slightly higher (1 – 2 times) than those in other regions worldwide. We alsoattempted to quantify the aerosol residence time based on a Po-Pb tracer, which suggestedthe mean aerosol residence time in Busan to be 41 to 48 days. These results imply that aerosolsthat exist in harbor cities can interact with and affect individuals and the surrounding society,where the influence is likely to last for weeks to months.