Abstract
Airborne particulate matter (PM) pollutants were sampled from an urban background site in Sharjah, United Arab Emirates. The fine fraction (PM2.5) (particulates with aerodynamic diameters of less than 2.5 μm) was collected on 47-mm Teflon filters and analyzed using a combined set of non-destructive techniques in order to provide better understanding of the sources of pollutants and their interaction during transport in the atmosphere. These techniques included gravimetric analysis, equivalent black carbon (EBC), X-ray fluorescence, scanning electron microscopy, and X-ray diffraction. Generally, the PM2.5 concentrations are within the limits set by the World Health Organization (WHO) and the United States (US) Environmental Protection Agency. The EBC content is in the range of 10–12% of the total PM concentration (2–4 µg m−3), while S (as ammonium sulfate), Ca (as calcite, gypsum, and calcium carbonate), Si (as quartz), Fe, and Al were the major sources of PM pollution. EBC, ammonium sulfate, Zn, V, and Mn originate from anthropogenic sources such as fossil fuel burning, traffic, and industrial emissions. Natural elements such as Ca, Fe, Al, Si, and Ti are due to natural sources such as crustal materials (enhanced during dust episodes) and sea salts. The average contribution of natural sources in the total PM2.5 mass concentration over the sampling period is about 40%, and the contribution of the secondary inorganic compounds is about 27% (mainly ammonium sulfate in our case). The remaining 22% is assumed to be secondary organic compounds.
Highlights
The United Arab Emirates (UAE) climate is part of the arid East Mediterranean/North African climate, with less than 5 cm of annual rain [1]
It shows that the amounts of airborne PM2.5 collected are below the World Health Organization (WHO) limits for about 30% of sampling days, and below the accepted United States Environmental Protection Agency (US-EPA) limits on more than 60% of the sampling days [30,31]
Gravimetric analysis revealed that the amount of PM2.5 pollution in the city of Sharjah is below international limits except on days that involved dust storms
Summary
The United Arab Emirates (UAE) climate is part of the arid East Mediterranean/North African climate, with less than 5 cm of annual rain [1]. Their study is one of the major works performed in this field in the region, it investigated samples collected from only one site in Qatar, and one in the UAE These two sites were at military bases in the desert far from urban residential areas in both countries. To address some of these issues, preliminary results from a recent study showed that a major constituent of the fine and ultrafine fraction of PM pollutants is ammonium sulfate [19,23,24] Elements such as V, Ni, Cu, Zn, Cr, and Pb, which usually originate from traffic emissions, were observed in the fine and ultrafine fractions of PM. The rest of this paper is organized as follows: the experimental details of gravimetric, XRF, XRD, and microscopy measurements are followed by detailed results, an analysis of each, and conclusions and acknowledgements
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