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Physicochemical Characterization and Seasonal Variations of PM10 Aerosols in a Harsh Environment

Hamdan, Nasser
Alawadhi, Hussain
Shameer, Mohamed
Published version
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..