10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Chemistry of New Particle Growth During Spring Time in the Seoul Metropolitan Area, Korea
HWAJIN KIM, Qi Zhang, Korea Institue of Science and Technology
Abstract Number: 418 Working Group: Aerosol Chemistry
Abstract New particle formation and growth events (NPEs) were frequently observed (24 out of 60 days) during April 14 to June 15, 2016 in the Seoul metropolitan area (SMA). In this study, we investigated the chemical mechanisms of new particle growth based on measurements conducted using an aerodyne high resolution time-of-flight aerosol mass spectrometer (HR-AMS) and a scanning mobility particle sizer (SMPS). Both instruments were deployed as part of the KORUS-AQ campaign (Korea-US Air Quality study). NPEs usually started in the afternoon between ~12:00 and 13:00 with the appearance of an ultrafine mode at < 20 nm (in mobility diameter, Dm, measured by a SMPS operating in the range 18-947 nm) followed by the growth of this modal diameter to ~45-80 nm during the next ~6-12 h. The growth rate was on average 4.48 ± 1.39 nm/h. Comparing to the non-NPE days, our results indicate that NPEs in SMA occurred when the concentration of preexisting particles was lower (15 vs 23 µg/m3), higher ozone (48 vs 27 ppb), stronger solar radiation (2.13 vs1.04 MJ/m2), and drier conditions (36 vs 65%). The evolution of the size-resolved chemical composition of new particles was investigated based on the HR-AMS size distribution measurements. The results showed that the concentration of LV-OOA (low volatile oxidized organic aerosol) and/or sulfate increased when NPEs occurred and that the concentrations of those species increased continuously as particles grew. Nitrate concentration also increased at the later stage of the particle growth. These results indicate that the frequently occurring NPEs in Seoul during spring were mainly driven by intensive formation of secondary species by photochemical reactions. Details on the mechanisms of NPEs in SMA will be discussed.