[Seminar] Prof. Wonbae Jeon

Modeling studies on chemical production/loss of PM2.5 and O3 during their long-range transport

The first study investigates the production/loss of sulfate on the sea surface during its transport from Eastern China to South Korea. Results of the CMAQ simulation show high sulfate (SO42-) concentrations over the sea surface areas between Eastern China and South Korea despite nearly zero emissions. The results from a quantitative analysis using the integrated process rate (IPR) in CMAQ suggest that increasing SO42- concentrations during the transport was mainly attributable to chemical SO42- productions. The chemical production of SO42- over the Yellow Sea can primarily be attributed to the “aerosol process”, which is mainly dependent on weather conditions (e.g., temperature and wind speed) and concentrations of precursors such as SO2 and OH. The results of the analysis of the mechanism of SO42- formation using the Sulfur Tracking Model (STM) show that most chemical SO42- production on the surface of the Yellow Sea is the result of the aqueous-phase chemical reactions following the SO2 oxidation reaction (OH + SO2 → H2SO4 + HO2). The second study presents an analysis of high surface ozone (O3) episodes occurring in a rural area (Chuncheon), which is situated 70 km to the prevailing westerly downwind direction of Seoul Metropolitan Area. Although Chuncheon has much lower emission levels than Seoul, the daily mean and maximum O3 levels were higher in Chuncheon than those in Seoul during the episode days. Results of CMAQ simulation demonstrate that the O3 concentration in the air mass moving from Seoul to Chuncheon was very sensitive to the concentration of nitrogen oxide (NOx) because of abundant biogenic volatile organic compounds (BVOCs). The IPR results also show that the NOx emitted from Seoul strongly affected the high O3 levels over its downwind area, mainly with local BVOC emissions. The produced O3 was gradually accumulated during its transport downwind, leading to an O3 concentration maximum at Chuncheon.