Characterization of Organic Species in PM2.5 and Source Apportionment in Ulsan, Korea

Abstract

Organic compounds, such as polycyclic aromatic hydrocarbons (PAHs) and fatty acids (FAs), are emitted from specific sources and can serve as molecular markers for PM2.5 source apportionment. In this study, the characteristics and sources of PM₂.₅ and 57 associated organic species (OS) were investigated in Ulsan, Korea. The OS exhibited significant correlations with PM₂.₅ and organic carbon, indicating that they can serve as effective tracers of PM₂.₅ high-pollution episodes. FAs and n-alkanes were dominant in spring, reflecting mixed influences from industrial activities and biogenic emissions, whereas levoglucosan concentrations were elevated in fall, highlighting a strong impact of biomass burning. Positive Matrix Factorization (PMF) was applied under two scenarios: one using major PM₂.₅ components and the other incorporating both major components and organic species. The PMF results identified secondary inorganic aerosol as the largest contributor to PM₂.₅, followed by biomass burning, industrial activities, fossil fuel combustion, and natural sources. When 21 organic tracers were included, the PMF analysis further resolved secondary and primary organic aerosol sources and distinguished biomass-burning contributions into local and long-range transported sources. This source separation was further supported by diagnostic ratios of PAHs. Overall, these results demonstrate that integrating organic molecular markers into receptor modeling substantially improves PM2.5 source resolution and provides quantitative evidence for the combined effects of primary emissions, secondary formation, and regional transport in an industrialized coastal city. © 2026, Korean Society for Atmospheric Environment. All rights reserved.