ANALYSIS AND PROPERTIES OF INDIVIDUAL AIRBORNE MINERAL DUST PARTICLES

Elevated levels of airborne mineral dust and other particulate matter severely impact on health and safety of people and animals. Dust also contributes to the fertilization of the oceans and continents, and to climate. The affects are largely dependent on the individual particle properties, including mineralogical interrelationships, chemistry, particle shape, size, and associated optical properties. To fully understand the potential health effects of airborne mineral dust requires the integration of results from multiple analytical techniques. This presentation is on the analysis and results from mineral dusts collected in the course of several field campaigns, in the Middle East, U.S.A., Africa, and elsewhere. X-ray fluorescence spectrometry (XRF), ion chromatography (IC), atomic absorption spectrometry (AA), automated colorimetry (AC), inductively coupled plasma optical emission spectrometry (ICP-OES), Inductively coupled plasma mass spectrometry (ICP-MS) and thermal optical reflectance (TOR), all provide chemical concentrations and an assessment of mineral composition of dust samples, but more importantly an accurate measure of potentially harmful trace metals. X-ray diffraction provides a (semi-) quantitative measure of the mineralogical composition of dust. SEM based individual particle analysis provides information on particle size and morphology, as well as mineralogy and mineralogical interrelationships, including mineral coatings and mineral intergrowths. In addition, computer controlled scanning electron microscopy (CCSEM) provides chemical and morphological information on a large number (approximately 1,000) of individual particles on a Nuclepore^® filter. Particle size distribution and mineralogy both contribute to emission properties of dust, explaining differences in emission factors amongst sampling sites. Examples showing the relationships between the chemistry, particle size (by aerodynamic particle sizer (APS)), and the optical properties (single scattering albedo) at three wavelengths will also be mentioned.