Atmospheric Dry and Wet Deposition of Microplastics in an Urban Area and a Remote Island: Year-Round Consecutive Monthly Observations

Atmospheric transport and deposition are key processes in the global spread of microplastics (MPs). However, field-based observational data are limited, and the dynamics of MP transport and deposition are still insufficiently understood. This study aimed to identify the effects of long-range transport and urbanization by comparing identical time-series data on atmospheric MP deposition between an urban city (Seoul, SE; ~10 million residents) and a remote region (Baengnyeong Island, BI; located on the Yellow Sea). In 2023, atmospheric MP deposition samples were simultaneously collected from both regions during the same period every month. Each sample was continuously collected using selective air deposition samplers to separate dry (DD) and wet deposition (WD). A total of 48 samples, comprising 12 pairs of DD and WD from each site, were analyzed for MPs (≥20 µm). Both sites exhibited a lower trend in total deposition (TD; sum of DD and WD) flux of MPs during the summer compared to other seasons, suggesting that MP deposition was influenced by atmospheric stability and monsoon scouring effects. Despite similar monthly pattern, TD flux of MPs was 3.5 times higher at SE (271±155 n/m²/day) than at BI (77.1±76.4 n/m²/day), with significant differences between the two regions for all monthly samples (paired t-test; p