Abstract
Particulate air pollution is a health concern. This study determines the microscopic make-up of different varieties of sand particles collected at a sand dune site in Badr, Saudi Arabia in 2012. Three categories of sand were studied: black sand, white sand, and volcanic sand. The study used multiple high resolution electron microscopies to study the morphologies, emission source types, size, and elemental composition of the particles, and to evaluate the presence of surface “coatings or contaminants” deposited or transported by the black sand particles. White sand was comprised of natural coarse particles linked to wind-blown releases from crustal surfaces, weathering of igneous/metamorphic rock sources, and volcanic activities. Black sand particles exhibited different morphologies and microstructures (surface roughness) compared with the white sand and volcanic sand. Morphological Scanning Electron Microscopy (SEM) and Laser Scanning Microscopy (LSM) analyses revealed that the black sand contained fine and ultrafine particles (50 to 500 nm ranges) and was strongly magnetic, indicating the mineral magnetite or elemental iron. Aqueous extracts of black sands were acidic (pH = 5.0). Fe, C, O, Ti, Si, V, and S dominated the composition of black sand. Results suggest that carbon and other contaminant fine particles were produced by fossil-fuel combustion and industrial emissions in heavily industrialized areas of Haifa and Yanbu, and transported as cloud condensation nuclei to Douf Mountain. The suite of techniques used in this study has yielded an in-depth characterization of sand particles. Such information will be needed in future environmental, toxicological, epidemiological, and source apportionment studies.
Highlights
Particulate air pollution significantly impacts public health in both developed and developing countries
Conservation (NYS DEC) microscopy laboratory in Rensselaer NY, using an Olympus SZX12 optical stereo microscope (OSM), Scanning Electron Microscopy (SEM)/energy dispersive X-ray spectrometer (EDS), and an Olympus LEXT laser scanning microscope (LSM, model OLS 3100 Laser Scanning Microscopy (LSM))
White sand appears as a clean crystalline structure, whereas the volcanic sand and the magnetic black sand both have reddish tints indicative of iron oxide
Summary
Particulate air pollution significantly impacts public health in both developed and developing countries. Exposure to PM has been associated with numerous effects on human health, including increased morbidity and mortality, respiratory problems, cardiovascular diseases, lung cancer, renal and brain damage, and human metal poisonings [3,4,5,6] Both fine and coarse particles are readily inhaled into the human respiratory tract. Deposition of black sand particles has recently become common on Douf Mountain (Figure 1), located to the west of Badr. Knowledge of the morphology and chemical characterization of sand particles can aid in control strategies and help to interpret and predict chemical interactions in the atmosphere, downwind fallout rates, potential damage to vegetation, deterioration of materials and structures, and, in particular, impact on human health. The microscopic make-up of different varieties of sand particles collected from a dune near Badr is presented
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