Influences of meteorology on emission sources and physicochemical properties of particulate matter in Seoul, Korea during the heating period

Abstract

Chemical properties of particulate matter (PM), organic aerosol (OA) properties, sources and the volatility distribution were investigated during autumn in Seoul, Korea using aerodyne high resolution time of flight aerosol mass spectrometer (HR-ToF-AMS) with a thermodenuder (TD) combined system (TD-AMS). Overall, the average PM1 + black carbon (BC) concentration was 21.49 μg/m3, ranging from 7.85 μg/m3 to 48.36 μg/m3, and the largest proportion of PM1 components was organic (54%), followed by NO3− (17%), SO42− (12%), NH4+ (9%) and BC (6%). During this period, the O/C and H/C ratios were similar to those in other studies (0.45 and 1.70, respectively), but the N/C ratio was slightly higher than that in other studies. Five organic aerosol (OA) sources were identified through positive matrix factorization (PMF) analysis, where four POAs (HOA, COA, SFOA1 and SFOA2) and one SOA (LVOOA) were identified. A distinct feature during this study was that two different combustion-related sources, SFOA1 and SFOA2 were observed. Two different SFOAs showed time-dependent features and different chemical compositions. SFOA2, which was dominant during the higher-temperature period (16.3 °C (5.1–26.6)) showed less O/C (0.41 vs 0.57) and N/C (0.033 vs 0.059) and more volatile feature than the one of SFOA1 during colder period (10.1 °C (−1.8-19.4)). It might be due to different heating activities and more intensive gas to particle parting and oxidizing processing under colder condition. Haze is also influenced by heating activities. When stagnant conditions occur with high heating activities, enhanced emission sources (SFOA1), enhanced gas-to-particle partitioning (nitrate) and the accumulation of primary OA result in severe haze conditions in urban air. This result suggests that controlling emission sources during heating seasons is still required for haze control in urban environments.