Abstract
We have conducted a comprehensive sampling campaign of PM10 pollutants at a site next to a major highway, using standard protocols. Particulate matter (PM) total mass, elemental and chemical/mineral compositions of the fine and coarse fractions of traffic-related PM pollutants were determined using several complementary techniques, including gravimetric analysis, x-ray fluorescence, scanning electron microscopy, energy dispersive spectroscopy, and x-ray diffraction. The PM mass concentrations show that PM10 is within acceptable international standards except during dust storms within the sampled periods. Desert dust, crustal minerals, and sea salts are the major natural sources of PM10 pollution. Examples of these minerals are quartz [SiO2], calcite [CaCO3], gypsum [CaSO4·2H2O], palygorskite [(Mg,Al)2Si4O10(OH)•4(H2O], chlorite-serpentine [(Mg,Fe)6AlSi3O10(OH)8], halite [NaCl] and nitratine [NaNO3]. Anthropogenic mineral-based pollutants, such as mascagnite [(NH4)2SO4] and koktaite [(NH4)2Ca(SO4)2·H2O], were also observed to contribute to PM10. Trace elements such as Zn, Cu, Fe, Cr and Mn that are markers for traffic sources, Ni and V that are markers for heavy oil combustion, and Pb, which is attributed to industrial emissions, were also identified in PM10. Seasonal variation of the average total mass concentrations and the average mass concentration of elements emitted from natural sources show that the hot season is associated with higher pollution levels compared to the cold season due to increased dust events in the spring and summer. Correlation coefficients between elements have identified elements originating from common sources such as dust storms (e.g., Si, Ca, Al, Fe, Ti, Mn) and sea breeze (Cl and Na), in addition to anthropogenic elements. Enrichment factors calculations have identified elements that mainly have crustal origins, and elements that are partially or highly enriched by humans. Anthropogenic elements were more enriched during the cold season due to reduced human activities in the summer.
Highlights
Air pollution emission has been increasing over the years, especially in the Middle East and North Africa (MENA) region, due to increased fossil fuel burning and other anthropogenic activities
We have recently reported the chemical composition of the fine fraction of PM10 (PM2.5)
We report here a 10-month campaign of sampling PM10 aerosols from a roadside traffic site
Summary
Air pollution emission has been increasing over the years, especially in the Middle East and North Africa (MENA) region, due to increased fossil fuel burning and other anthropogenic activities. Pollution due to natural and anthropogenic sources from these dust storms, sea salt from the Arabian Gulf, traffic, and a large number of mega construction and industrial projects have made it necessary to perform intensive investigation of the chemical composition and sources of these pollutants. It is established that fine particulate matter (PM), with mean aerodynamic diameter of 2.5 μm or smaller, usually referred to as PM2.5, are linked to anthropogenic sources such as traffic and industrial emissions, and upstream and downstream oil and gas operations. Natural sources such as desert dust, construction materials and sea spray contribute to both the fine fraction and the coarse fraction of PM10 (PM with mean aerodynamic diameter of 10 μm or smaller) (Hamdan et al, 2018; Hamdan et al, 2018)
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