Reconstructing initial VOC concentrations to reveal their role in ozone formation

초록

This study examines the role of volatile organic compounds (VOCs) in ozone (O3) formation in a medium-sized residential city in South Korea. Using continuous measurements of 53 VOC species and photochemically adjusted initial concentrations (PICs), we assessed VOC transformations and their impact on O3 production. Results show that alkenes, particularly isoprene, cis-2-butene, and propene, are dominant contributors to O3 formation, with their influence intensifying under high O3 conditions. PIC of total VOCs (36.1 ppb) were significantly higher than measured concentrations (8.3 ppb), highlighting the extent of photochemical degradation. Ozone formation potential (OFP) analysis showed that metrics based on consumed VOCs better captured O3 variability than those based on measured concentrations, underscoring the importance of accounting for photochemical processing. Positive Matrix Factorization (PMF) identified distinct VOC sources: while LPG/natural gas usage (23.3 %) and coal combustion (22.4 %) dominated measured VOCs, solvent usage (16.2 %) and biogenic emissions (25.7 %) contributed more substantially when PICs were considered. Regional transport also played a key role, suggesting that aged and photochemically processed air masses significantly influence downwind O3 levels. These findings demonstrate the need to prioritize the control of anthropogenic alkenes and aromatic compounds, while also considering the influence of biogenic emissions. Policy measures should incorporate photochemical transformations into source attribution frameworks to support more effective and targeted O3 mitigation strategies.

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