Characterisation of individual aerosol particles collected during a haze episode in Incheon, Korea using the quantitative ED-EPMA technique

Abstract

Abstract. A quantitative energy-dispersive electron probe X-ray microanalysis (ED-EPMA), called low-Z particle EPMA, was used to analyse individual aerosol particles collected in Incheon, Korea on 13-18 October 2008 (a typical haze episode occurred from 15 to 18 October). Overall 3600 individual particles in PM 2.5−10 and PM 1.0−2.5 fractions from 12 aerosol samples collected on haze and non-haze days were analysed. The analysed particles were classified, based on their X-ray spectral data together with their secondary electron images. The major particle types included organic carbon (OC), elemental carbon (EC), sea-salt, mineral dust (such as aluminosilicate, SiO 2 , CaCO 3 /CaMgCO 3 , etc.), (NH 4 ) 2 SO 4 /NH 4 HSO 4 -containing, K-containing, Ferich and fly ash particles. Their relative number abundance results showed that OC particles were significantly increased while sea-salts and mineral dust particles were significantly decreased (especially in PM 1.0−2.5 fraction) when haze occurred. For the other particle types (except Fe-rich particles in PM 2.5−10 fraction), there were no significant differences in their relative abundances between haze and non-haze samples. On non-haze days, the nitrate-containing reacted seasalt and mineral dust particles in PM 1.0−2.5 fraction 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 fine aerosol particles (≤2.5 µm in aerodynamic diameter). The emission of air pollutants from motor vehicles and stagnant meteorological conditions, such as low wind speed and high relative humidity, might be responsible for the elevated level of OC particles on haze days.

Impact of Relative Humidity and Water Soluble Constituents of PM2.5 on Visibility Impairment in Beijing, China

“…In a visibility study in Los Angeles, Farber et al (1994) found that sulfate followed by nitrate and carbon species were the dominant particulate species in hazy weather. Similar results were reported in Seoul through the chemical analysis of PM 2.5 in haze episodes (Kang et al, 2004;Geng et al, 2011). In Shanghai, secondary inorganic pollution, dust, and biomass burning were identified as three typical haze types (Du et al, 2011;Huang et al, 2012).…”

A review of single aerosol particle studies in the atmosphere of East Asia: morphology, mixing state, source, and heterogeneous reactions

“…There are some strongly hygroscopic nitrate particles ((Ca(NO 3 ) 2 and NaNO 3 ) in the coarse fraction produced by heterogeneous reactions between alkaline aerosols and acidic gases (Geng et al, 2011;Laskin et al, 2005Laskin et al, , 2012Li et al, 2011b;Li and Shao, 2009a;Tobo et al, 2010;Zhang and Iwasaka, 2004). These studies show that the nitrates normally occur on the surfaces of individual particles and determine their hygroscopic properties.…”

“…10ced) and completely aged sea salt particles (Fig. 10eef), which contain NaNO 3 , Na 2 SO 4 or Na-containing organic salts through heterogeneous reactions (Geng et al, 2011;Laskin et al, 2012;Li et al, 2011bLi et al, , 2010bZhang and Iwasaka, 2004). Reactions of polluted air with sea salt aerosols from the ocean can lead to high surface ozone levels that adversely affect air quality in densely polluted coastal areas (von Glasow, 2008).…”

“…On the basis of the different elemental, morphological, and mass spectra of single particles in East Asia, nine particle types including mineral dust, K-rich, sea salt, metal, fly ash, sulfate, nitrate, soot, and organic particles have been classified based on the studies from electron microscopy and mass spectroscopy during haze episodes (Bi et al, 2011;Fu et al, 2012b;Geng et al, 2011;Li et al, 2014b;Li and Shao, 2009b;Zhang and Iwasaka, 1999;Zhang et al, 2013Zhang et al, , 2015.…”

Portrait and Classification of Individual Haze Particulates

“…Recently, electron microscopes, such as the Scanning Electron Microscope (SEM) and the Transmission Electron Microscope (TEM), have been used for characterization of individual airborne particulates. These microscopes are powerful tools in determining the sources, formation, and influences of PM2.5 due to their capability of analyzing morphology, chemical composition, and crystal structure (unique in TEM) down to the nanometer scale [18] [19]. In previous studies, various types of airborne particulates have been found to have many different morphologies and chemical compositions [17]- [20], and there is some preliminary research on source apportionment.…”