MINERALOGICAL PROPERTIES AND INTERNAL STRUCTURES OF FINE INDIVIDUAL PARTICLES OF ASIAN DUST

The long range transport of desert dust affects Earth climate and remote ecosystem via physical and chemical interactions with radiation, gas, and pollutants. The information on the mineralogical and structural properties of individual dust particles is essential for assessing environmental roles of desert dust. The mineralogical and structural analyses of fine individual particles of Asian dust (< 5 μm) collected in Korea, March 18, 2014 were carried out using transmission electron microscopy (TEM) of cross-sectional slices prepared by focused ion beam. TEM analyses of the slices showed roughly ellipsoidal particles with irregular surface topography. The dust particles were aggregates of numerous mineral grains of varying chemistry and size. Internal structures of the dust particles were clay-rich aggregates, large mineral grains with clay-rich coatings, and their intergrades. Irregular submicron pores were common through the particles, particularly in the intergrade particles. Iron oxides were commonly submicron grains of goethite and hematite dispersed through the particles with some larger grains coated with clays. Clay minerals were dominated by illite-smectite series clay minerals including nano-thin plates of illite, smectite and their mixed layers. A comparison with previous TEM analyses on the very coarse particles of Asian dust showed that the mineralogy and internal structures of fine Asian dust were not different from those of very coarse dust particles.