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 PM2.5 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 PM2.5. 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 PM2.5 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 PO43-) constituted less than 1% in the PM fractions. The significant fraction was for SO42- (PM2.5 4.7±1.6 µg/m3 (10.0%) and PM10 5.3±1.9 µg/m3 (8.3%)). The NH4+ had higher amounts of PM2.5 (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 PM2.5 and PM10, SO42- 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)  SO42- is completely neutralized by NH4+ in the PM2.5 but there could be additional reactions involved in the PM10, and (6) (NH4)2SO4, was the major species formed by SO42-and NH4+ instead of NH4HSO4.