부산대학교 도서관

To understand the formation mechanism and controlling factors of O3 in Seoul megacity, the MAPS-Seoul Campaign was conducted at the campus of the Korea Institute of Science and Technology(KIST) in Seoul during May~June 2015. The KIST site is surrounded by freeways and the forest was located at the east side .Along with O3, CO, and NOx, photochemical indicator species including PAN (peroxy acetylnitrate) and hydrogen peroxide(H2O2) were determined by GC-luminol system and HPLC-postcolumn enzyme fluorescence system, respectively from May 18 to June 12. VOCs were sampled with a canister twice a day (09:30and15:00) and analyzed by GC-FID.High ozone concentrations were encountered from the end of May to the early of June and the maximum concentration was 155 ppbv on Jun 10. In the present study, it is noteworthy that meteorological conditions and chemical regimes of air masses were clearly distinguished in May and June. While the fresh urban plumes were regularly pumped into the site, resulting in high NOx concentrations in May, the level of NOx was much reduced unders stagnant condition in June. As a result, O3 concentration was slightly higher in June. H2O2 showed a typical diurnal variation in May, but it was not clear in June with lower concentrations. In general, PAN was well correlation with O3. PAN concentration was raised up to 4.4ppbv in June, during which PAN showed the second peak in accordance with the highest O3 concentration around 6PM. The calculated OH reactivity of VOCS suggests that isoprene played a major role in the enhancement of O3 in the late afternoon, particularly in June when air was stagnated.