VOC Composition and Ozone Formation Potential During an Upwind-Downwind Intensive Observation Campaign in South Korea

초록

Volatile organic compounds (VOCs) are key precursors of ozone and secondary pollutants, yet transport-related changes in their composition between upwind and downwind regions remain insufficiently characterized. Simultaneous high-time-resolution measurements were conducted at an urban site in the Seoul Metropolitan Area (SMA) and a suburban downwind site in Chuncheon, South Korea, from 3 to 18 June 2024. Thirteen VOC species were measured using proton-transfer-reaction time-of-flight mass spectrometry (PTR-ToF-MS) and evaluated using backward trajectory clustering, concentration-weighted trajectory analysis, ozone formation potential (OFP), and a toluene-to-benzene ratio-based photochemical aging proxy. The summed concentration of the 13 measured VOC species was higher in SMA (40.24 +/- 19.41 ppb) than in Chuncheon (18.28 +/- 6.39 ppb), while oxygenated VOCs accounted for approximately 80% at both sites. In Chuncheon, VOC composition and OFP varied descriptively among air-mass clusters, with westerly and southwesterly pathways passing through or near SMA associated with relatively elevated aromatic VOC concentrations and OFP. Equivalent photochemical age overlapped substantially among clusters and was not directly proportional to VOC concentration or OFP. These results indicate that downwind VOC characteristics reflect the combined effects of source composition, transport, dilution, atmospheric mixing, and chemical processing.

키워드