Size-Fractionated Number and Mass Concentrations in the Urban Background Atmosphere during Spring 2014 in Amman – Jordan

mber size distribution of urban aerosols was never measured in Amman, Jordan. In this study, we aim at investigating the mean number size distribution (optical diameter 0.3–10 µm) and size-fractionated particle number and mass concentrations during spring 2014 in the urban background atmosphere of Amman, Jordan. The overall mean particle number concentration of coarse particles (PN₁₀₋₁) was 1.8±2.9 cm⁻³ and the corresponding mass concentration PM₁₀₋₁ was 22.1±44.3 µg/m³. The overall mean submicron particle number concentration (PN₁₋₀.₀₁) was 26800±12800 cm⁻³ and the corresponding mass concentration PM₁₋₀.₀₁ was 4.7±1.9 µg/m³. The calculated 24-hour PM₁₀ concentrations were 3.7–126.4 µg/m³. According to the Jordanian 24-hour PM₁₀ concentrations limit value (120 µg/m³), there was only one exceedance that observed on April 16ᵗʰ. The mean particle number size distribution during that period was characterized by three main lognormal modes: ultrafine, accumulation and coarse modes. The geometric mean diameters (Dpg) were 0.05 µm, 0.125 µm and 1.7 µm, respectively for the ultrafine mode, accumulation mode and coarse mode. The corresponding mode number concentrations were 12000 cm⁻³, 300 cm⁻³ and 2.6 cm⁻³.