Characterizing Mineral Dust for Surveillance Purposes
The purpose of the U.S. Army Public Health Command (USAPHC) "Enhanced Particulate Matter
Surveillance Program" (EPMSP) was to provide scientifically founded information on the chemical and
physical properties of airborne mineral dusts and other particulates sampled at 15 military bases in the
Middle East. This program clearly identified the need for continuous measurement of aerosol optical
properties, mass density, chemical composition, mineralogy, and particle size distribution of wind-blown
dust and other air pollutants. With regard to battlefield operations, vision and the operation of optical
devices— including range finders, target designators, surveillance cameras, and airborne and satellite
remote sensing—are impacted by elevated levels of ambient aerosols. DoD operations are highly
dependent on atmospheric visibility in particular and the electromagnetic propagation environment in
general. While filter analysis provides elemental and ion concentrations, optical properties of prime
importance in radiative transfer processes and global climate change issues depend on the complex
refractive indices of the mineral components. Optical properties of mineral dust are of importance for the
modeling of visibility impairment and radiative transfer as input for global and regional climate models.
The current DoD research program "Mobile Aerosol Monitoring System for Department of Defense" is an
extension to, and addresses some of the important recommendations from the EPMSP. The Desert
Research Institute (DRI) developed the instrumental capabilities for aerosol sampling as well as
mineralogical and real-time optical characterization of dust aerosols. Mineral dust is re-suspended in a
chamber, passed through PM2.5 size selective impactors, and optical absorption and extinction quantified
on DRIs photoacoustic absorption, and cavity ring down/cavity enhanced detection extinction instrument.
Filter samples are simultaneously collected for mineralogical analysis by X-ray diffraction.
These experimental procedures allow for relating aerosol absorption, extinction, and single-scattering
albedo to mineralogical composition. This paper presents results on mineralogical and optical properties
of re-suspended fine desert dust samples from Africa, China, and the Middle East.