Long-term evolution and synoptic meteorological modulation of PM_2.5 and PM₁₀ in Seoul

Addressing particulate matter (PM) pollution in megacities like Seoul is crucial for public health and environmental sustainability, necessitating a comprehensive understanding of its long-term evolution and meteorological drivers. This study investigated the key factors affecting long-term PM concentrations in Seoul, South Korea, from 2000 to 2021, with a focus on the winter (DJF) and spring (MAM) seasons. To address the gap in PM research caused by the shorter observation period of PM_2.5 compared with PM₁₀, we used an extended PM_2.5 dataset. This enabled a detailed analysis of PM_2.5 and its relationship with PM₁₀, which, despite some differences, generally displayed similar variability. Both PM_2.5 and PM₁₀ exhibited decreasing trends in winter as well as spring, although the rate of decline slowed in the last decade (2011–2020) compared with the earlier decade (2000–2010). Both seasons exhibited a strengthened interannual correlation between PM_2.5 and PM₁₀ in the last decade. Daily PM_2.5 and PM₁₀ levels generally fluctuated in a similar pattern in both seasons, which can be attributed to synoptic-scale meteorological systems, particularly migratory systems from Northwest China, which can remain stationary over Korea for several days, particularly in winter. This pattern continues into spring, albeit with a lower intensity. These findings provide valuable insights into PM_2.5 variability and its correlation with PM₁₀ over time, which may inform future PM_2.5 mitigation strategies.