Atmos. Chem. Phys. Discuss., 12, 27297-27331, 2012
www.atmos-chem-phys-discuss.net/12/27297/2012/
doi:10.5194/acpd-12-27297-2012
© Author(s) 2012. This work is distributed
under the Creative Commons Attribution 3.0 License.
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Observation of chemical modification of Asian Dust particles during long-range transport by the combined use of quantitative ED-EPMA and ATR-FT-IR imaging
Young-Chul Song, Hyo-Jin Eom, Hae-Jin Jung, Md Abdul Malek, HyeKyeong Kim, and Chul-Un Ro
Department of Chemistry, Inha University, 253, Yonghyun-dong, Nam-gu, Incheon 402-751, Korea

Abstract. In our previous works, it was demonstrated that the combined use of quantitative energy-dispersive electron probe X-ray microanalysis (ED-EPMA), which is also known as low-Z particle EPMA, and attenuated total reflectance FT-IR (ATR-FT-IR) imaging has great potential for a detailed characterization of individual aerosol particles. In this study, individual Asian Dust particles collected during an Asian Dust storm event on 11 November 2011 in Korea were characterized by the combined use of low-Z particle EPMA and ATR-FT-IR imaging. The combined use of the two single-particle analytical techniques on the same individual particles showed that Asian Dust particles had experienced extensive chemical modification during long-range transport. Overall, 109 individual particles were classified into four particle types based on their morphology, elemental concentrations, and molecular species and/or functional groups of individual particles available from the two analytical techniques: Ca-containing (38%); NaNO3-containing (30%); silicate (22%); and miscellaneous particles (10%). Among the 41 Ca-containing particles, 10, 8, and 14 particles contained nitrate, sulfate, and both, respectively, whereas only two particles contained unreacted CaCO3. Airborne amorphous calcium carbonate (ACC) particles were observed in this Asian Dust sample for the first time, where their IR peaks for the insufficient symmetric environment of CO32− ions of ACC were clearly differentiated from those of crystalline CaCO3. This paper also reports the field observations of CaCl2 particles converted from CaCO3 for the Asian Dust sample collected in the planetary boundary layer. Thirty three particles contained NaNO3, which are the reaction products of sea-salt and NOx/HNO3, whereas no genuine sea-salt particles were encountered, indicating that sea-salt particles are more reactive than CaCO3 particles. Some silicate particles were observed to contain nitrate, sulfate, and water. Among 24 silicate particles, 10 particles contained water, the presence of which could facilitate atmospheric heterogeneous reactions of silicate particles including swelling minerals, such as montmorillonite and vermiculite, and non-swelling ones, such as feldspar and quartz. This paper provides detailed information on the physicochemical characteristics of individual Asian Dust particles that experienced extensive chemical modification during long-range transport through the combined use of the two single-particle analytical techniques.

Citation: Song, Young-Chul, Eom, Hyo-Jin, Jung, Hae-Jin, Malek, Md Abdul, Kim, HyeKyeong, and Ro, Chul-Un: Observation of chemical modification of Asian Dust particles during long-range transport by the combined use of quantitative ED-EPMA and ATR-FT-IR imaging, Atmos. Chem. Phys. Discuss., 12, 27297-27331, doi:10.5194/acpd-12-27297-2012, 2012.
 
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