Annual distribution and atmospheric deposition of Po and Pb in aerosols from Busan, the largest port city in Korea

Abstract

The annual distributions of radionuclides, Po and Pb, were investigated in Busan in South Korea where the largely affected by port infrastructure. Aerosol samples were collected from April 2019 to February 2020 using a high volume air sampler. The average activities of Po and Pb ranged 0.01 to 0.4 mBq m (average 0.13±0.2 (1σ) mBq m , n=90) and 0.1 to 1.7 mBq m (average 0.65±0.9 (1 σ) mBq m , n=91), respectively. Contrast to Pb activities (relatively consistent in entire sampling period), Po activities especially varied upto 3 factors, those are remarkably higher in fall and winter relative to those in summer season. The substantially higher Po in fall and winter seems to be attribute to input of anthropogenic Po from broad port area surrounded by maritime infrastructure (e.g., shipyard, trade warehouse, factories, ship anchorage, and etc.), together with the changes in seasonal wind direction. In our study area, both Po level and related dry depositional fluxes were comparable or slightly higher (approximately 1-2 times) than those in other regions worldwide. We also attempted to quantify the aerosol residence time based on Po- Pb tracer. The aerosol residence time using Po- Pb pair in our study area estimated to be 41 to 48 days. These results imply that aerosols occurred in harbor city could cause a crucial impact in individuals and surrounding society, and the impact is likely to last for more than weeks to months.