Atmos. Chem. Phys. Discuss., 10, 26641-26676, 2010
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Characterization of individual aerosol particles collected during a haze episode in Incheon, Korea using the quantitative ED-EPMA technique
H. Geng1,2, J. Ryu1, S. Maskey1, H.-J. Jung1, and C.-U. Ro1
1Department of Chemistry, Inha University, Incheon, 402-751, Korea
2Research Center of Environmental Science and Engineering, Shanxi University, Taiyuan, 030006, China

Abstract. Haze is an atmospheric phenomenon that leads to low visibility, and is mostly due to elevated levels of fine particulate matter. It can have effects on cloud formation, public health, agriculture, and even the global climate. Although urban haze has been increasing in occurrence over the past several years over the Seoul-Incheon metropolis, Korea, studies of the morphology and chemical composition of ambient aerosol particles by single-particle analysis during haze episodes have rarely been conducted. Herein, a quantitative energy-dispersive electron probe microanalysis (ED-EPMA), called low-Z particle EPMA, was used to analyze individual aerosol particles collected in Incheon, Korea on 13–18 October 2008 (a typical haze episode occurred from 15 to 18 October). Overall, 3600 particles in 12 aerosol samples collected on haze and non-haze days were measured by low-Z particle EPMA. Based on quantitative X-ray analysis, together with secondary electron images of individual particles, we successfully identified the aerosol particle types as follows: elemental carbon (EC), organic carbon (OC), (NH4)2SO4/NH4HSO4-containing, genuine (fresh) and reacted (aged) sea-salt, mineral dust (such as aluminosilicate, SiO2, CaCO3/CaMg(CO3)2, etc.), and K-containing, Fe-rich, and fly ash particles. By analyzing the relative abundances of different particle types, it was concluded that (a) on non-haze days, reacted sea-salts and reacted mineral dust particles were abundant in both the PM2.5–10 and PM1.0–2.5 fractions (with relative abundances of 65.0% and 57.7%, respectively); whereas on haze days, the relative abundances of OC and (NH4)2SO4/NH4HSO4-containing particles were significantly elevated, indicating that organic matter and secondary aerosols were abundant in the atmosphere when haze occurred. (b) in PM2.5–10 fractions, sea-salt and mineral dust particles reacted with NOx/HNO3 significantly outnumbered those reacted with SO2/H2SO4, no matter whether they were collected on haze or non-haze days; but in PM1.0–2.5 fractions on non-haze days, the nitrate-containing reacted particles significantly outnumbered the sulfate-containing ones, whereas it was the reverse on haze days, implying that on haze days there were special sources or formation mechanisms for the reacted fine aerosol particles (aerodynamic diameter<2.5 μm). It is hypothesized that motor vehicles, biomass burning from the areas surrounding Incheon, and haze transported from Eastern China are the major contributors to urban haze formation in Incheon under stagnant meteorological conditions such as low wind speed, high relative humidity, etc.

Citation: Geng, H., Ryu, J., Maskey, S., Jung, H.-J., and Ro, C.-U.: Characterization of individual aerosol particles collected during a haze episode in Incheon, Korea using the quantitative ED-EPMA technique, Atmos. Chem. Phys. Discuss., 10, 26641-26676, doi:10.5194/acpd-10-26641-2010, 2010.
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