Chemistry of Sub-micron Aerosols and New Particle Formation in Busan based on Aerosol Mass Spectrometry

Abstract

Chemistry of sub-micron aerosols and new particle formation events (NPEs) were observed during 10th Sept to 6th Oct 2020 near the coastal regions of Busan metropolitan city. In this study, chemical compositions and size distributions of non-refractory sub-micron aerosol particles were quantitated using a real-time high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) and a scanning mobility particle sizer (SMPS). The average mass concentration was 8.28 μg·m-3 and was composed of organics (48%), sulfate (28%), nitrate (10%), ammonium (10%), and chloride (1%), black carbon (4%). Three NPE days were observed during the sampling campaign. NPEs usually started around noon time between ~11:00 and 14:00 with the appearance of an ultrafine mode peaking between ~20 and 30 nm followed by the growth of diameter to 50 - 100 nm during 14:00 to 24:00. Comparing to the non-NPE days, NPEs occurred under conditions of lower pre-existing particulate matters (PM2.5 and PM10) concentrations, higher ozone (45 vs 30 ppb), stronger solar radiation (2.5 vs 1.5 MJ/m2), and drier air (45 vs 75%). Commonly used ambient OA oxidation indicator such as f43:f44 showed that most of the OA from westerly winds were semi-volatile oxygenated OA (SV-OOA) while most of the OA from easterly and westerly winds were low-volatile oxygenated OA (LV-OOA). Positive matrix factorization (PMF) of OA showed three factors representing different sources (LV-OOA, HOA, and SV-OOA) attributed to the different wind directions. Results from the PMF model suggested that HOA and SV-OOA sources were contributed not only from land source activities but also from shipping activities along the coastal regions