Chemical and mineralogical analysis of individual mineral dust particles

Individual mineral dust particles collected in a dust storm over Israel were analyzed by a scanning electron microscopy and energy-dispersed system (SEM-EDS). The analysis shows that the particles were mostly aggregates of varying mineralogical composition rather than pure minerals. It is also shown that sulfur (not associated with gypsum) and, to a lesser extent, iron tended to reside on the particles' surface, while Ca, Mg, K, Al, and Si were all an integral part of the particles. The lack of NaCl and sulfuric acid aerosols in the sample indicates that the air mass did not interact with marine air or with clouds. This conclusion is further supported by back trajectory calculations. These findings suggest that the sulfur in the aerosols did not result from atmospheric processes but rather originated from processes in the source region. Black residue, surrounding some of the particles, suggests the possible existence of organic matter in the sample, probably originating from biological activity in the soil at the source of the particles. The method of individual particle analysis provides important information about the composition and morphology of the particles, information that otherwise cannot be obtained by bulk analysis methods.