10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Optical Properties and Chemical Constituents of Ambient Fine Particles in an Urban Environment of Korea
JONGBAE HEO, Seungpyo Cheong, Hwajin Kim, Seoul National University
Abstract Number: 1207 Working Group: Aerosol Physics
Abstract Aerosol optical properties, chemical constituents, and sources of ambient fine particles were measured in Seoul, Korea, from May to November 2016. Light scattering (σscat) and absorption (σabs) coefficients were measured with a photoacustic extinctiometer (PAX) and a multiangle absorption photometer (MAAP), respectively. Chemical components of ambient fine particles were observed using a HR-ToF-AMS and their sources were identified using a positive matrix factorization model. During the study period, average mass concentration of fine particles, organic matter (OM), black carbon (BC), SO42-, NO3-, NH4+, and Cl- were 27.4 (±16.9) μg m-3, 13.0 (±8.3) μg m-3, 1.7 (±1.0) μg m-3, 5.0 (±3.6) μg m-3, 4.7 (±4.9) μg m-3, 2.9 (±2.3) μg m-3, and 0.3 (±0.5) μg m-3, respectively, and OM was a major component of fine particles. The observed σscat and σabs were 131.0 (±94.0) M m-1 and 13.6 (±8.2) M m-1, respectively. Both of the scattering and absorption coefficients showed unique diunal patterns with high peaks during the morning and evening rush hours due to the peak emissions of vehicles and the unfavorable meteorological conditions for dispersion of the vehicle emissions. The average of single scattering albedo calculated was 0.9 (±0.1), representing that fine particles in the study area contain relatively high fraction of scattering chemical components. The average mass scattering efficiency of fine particles was 4.70 m2 g-1 and exhibited higher values in spring and lower values in fall, showing a similar trend to mass of fine particles. This seasonal trend is influenced by the variations on chemical constituents of fine particles. Multiple linear regressions were performed to investigate associations of chemical components of fine particles with extinction coefficient (bext). Results showed that OM contributed the most to bext, accounting for 51.3%, followed by (NH4)2SO4, NH4NO3, and BC, 20.4%, 17.7%, and 9.7%, respectively. The PMF model identified four factors contributing to the OM, including low-volatile oxidized organic aerosol (LV-OOA), semi-volatile oxidized organic aerosol (SV-OOA), cooking influced organic aerosol (COA), and hydrocarbon like organic aerosol (HOA). Among the identified four factors, secondary organic aerosol factors (i.e. LV-OOA, SV-OOA) were the dominant contributors to bext. Therefore, reducing emissions of gaseous precursors corresponding to secondary aerosol formation may be important to improve both of air quality and visibility in Seoul.