Chemical Modification of Dust Particles during Different Dust Storm Episodes

Abstract

Two dust episodes (D1: February 13 and D2: March 28-29, 2004) of long-range transport from desert and loess sources, and one dust episode (D3: March 30) mainly from local area, were investigated in spring 2004 in Beijing, China. Dust samples were collected in different dust episodes and scanning electron microscopy with X-ray energy dispersive detector (SEM/EDS) was applied to study the morphology, elemental composition, and chemical modification on the surfaces of dust particles with radius from 0.1 to 6.4 μm. The morphological features of the particles reveal that the three dust plumes carried both dust particles (90-98% by number) and anthropogenic pollutants (e.g., fly ash and soot, 2-10%). Particle compositions show that the amount of S-containing dust particles was higher in D1 and D2 than in D3. Sulfates were introduced into the dust particles through heterogeneous uptake of SO 2 during their transport. In all three dust episodes, fine dust particles (radius < 1 μm) showed a higher degree of chemical modification by SO 2 compared to the coarse particles (radius ≥ 1 μm). Furthermore, long-range transport dust particles were more deeply modified by SO 2 than particles from local areas. The composition of the dust particles indicates that alkaline mineral components determined the level of chemical modification of individual particles. Heterogeneous uptake of SO 2 on a large number of dust particles would increase mass of the internally mixed sulfates on their surfaces. The results suggest that the optical properties of dust particles during dust storm episodes are gradually altered based on how far they are transported.

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

“…2f and Table 2). Sizes of mineral particles are dominant at coarse mode (diameter > 2 mm) (Li and Shao, 2012). Clay, quartz, and feldspar, with certain amounts of calcite, dolomite, and other oxides, together constitute mineral dust (Iwasaka et al, 2003;Jeong and Nousiainen, 2014;Jung et al, 2010;Li and Shao, 2009b;Lu et al, 2006;Okada et al, 2005b;Shao et al, 2008;Shi et al, 2005).…”

“…The fresh (NaCl) and aged halite (Na 2 SO 4 and NaNO 3 ) particles in continental atmosphere are sourced from dry salt-lake during dust storm events (Li and Shao, 2012). In wintertime of North China, the NaCl particles can be emitted by coal-combustion from cooking and horse-hold heating and snow removing agent (Li and Shao, 2013).…”

Investigation of aged aerosols in size-resolved Asian dust storm particles transported from Beijing, China, to Incheon, Korea, using low-&lt;i&gt;Z&lt;/i&gt; particle EPMA

“…Reactive gases (e.g., SO 2 , NO 2 , etc.) were likely adsorbed on some of the dust particles and then oxidized to their acidic forms (e.g., HNO 3 and H 2 SO 4 ), which would be neutralized fully or partially by the alkaline species (e.g., CaCO 3 or Ca/Mg-containing aluminosilicates) or by ambient NH 3 Li and Shao, 2012); sometimes, ammonium salts or secondary aerosols (e.g., NH 4 NO 3 and (NH 4 ) 2 SO 4 ) would be adsorbed directly on dust particles (Manktelow et al, 2010;Formenti et al, 2011). When dust particles from the ADS event left the continent and entered the marine region atmosphere, they likely would have experienced significant modification by the surface uptake of gaseous species and mixing with fresh or aged (reacted) SSAs, rapidly becoming a mixture of mineral, SSA, sulfate, and/or nitrate in the marine atmosphere (Fan et al, 1996).…”

Rapid, 3D Chemical Profiling of Individual Atmospheric Aerosols with Stimulated Raman Scattering Microscopy

“…Previous studies have proposed various possible mechanisms and pathways of heterogeneous reactions of NO x and SO 2 on mineral dust particles using aerosol flow tube methods, aerosol chamber methods, SEM/EDS, and Knudsen cell‐mass spectrometer . Recently, MRS showed promise in obtaining microscopic morphology of particles to understand the reaction mechanisms .…”