Characterization of Water-Soluble Inorganic Ions and Carbonaceous Aerosols in the Urban Atmosphere in Amman, Jordan

The Eastern Mediterranean is a unique region for air pollution because it is the crossroads between three continents exchanging air pollution transported between Africa, Asia, and Europe. Here, we investigated urban particulate matter (PM) carbonaceous and water-soluble ions for eleven months in Amman, Jordan. The PM_2.5 total carbon (TC) annual mean was 7.6±3.6 µg/m³ (organic carbon (OC) 5.9±2.8 µg/m³ and elemental carbon (EC) 1.7±1.1 µg/m³), which was about 16.3% of the PM_2.5. The PM₁₀ TC annual mean was 8.4±3.9 µg/m³ (OC 6.5 ± 3.1 µg/m³ and elemental carbon (EC) 11.9±1.1µg/m³), about 13.3% of the PM₁₀. The PM_2.5 total water-soluble ions (TI) annual mean was 7.9±1.9 µg/m³(about 16.9%), and that of the PM₁₀ was 10.1±2.8 µg/m³ (about 16.0%). The minor ions (F^-, NO₂^-, Br^-, and PO₄^3-) constituted less than 1% in the PM fractions. The significant fraction was for SO₄^2- (PM_2.5 4.7±1.6 µg/m³ (10.0%) and PM₁₀ 5.3±1.9 µg/m³ (8.3%)). The NH₄⁺ had higher amounts of PM_2.5 (1.3±0.6 µg/m3; 2.7%) than that PM₁₀ (0.9±0.4 µg/m³; 1.4%). During sand and dust storm (SDS) events, TC, Cl^-, and NO₃^- were doubled in both PM_2.5 and PM₁₀, SO₄^2- did not increase significantly, and NH₄⁺ slightly decreased. Regression analysis revealed: (1) carbonaceous aerosols in Amman come equally from primary and secondary sources, (2) about 50% of the OC came from non-combustion sources, (3) traffic emissions dominate the PM, (4) agricultural sources have a negligible effect, (5)  SO₄^2- is completely neutralized by NH₄⁺ in the PM_2.5 but there could be additional reactions involved in the PM₁₀, and (6) (NH₄)₂SO₄, was the major species formed by SO₄^2-and NH₄⁺ instead of NH₄HSO₄.