ATR-FTIR Spectral Analysis and Soluble Components of PM₁₀ And PM_2.5 Particulate Matter over the Urban Area of Palermo...

Several epidemiological studies have shown a close relationship between the mass of particulate matter (PM) and its effects on human health. This study reports the identification of inorganic and organic components by attenuated total reflectance-Fourier-transform infrared spectroscopy (ATR-FTIR) analysis in PM₁₀ and PM_2.5 filters collected from three air quality monitoring stations in the city of Palermo (Sicily, Italy) during non-Saharan dust events and Saharan events. It also provides information on the abundance and types of water-soluble species. ATR-FTIR analysis identified sulfate, ammonium, nitrate, and carbonate matter characterized by vibrational frequencies at 603, 615, 670, and 1100 cm^-1 (SO₄^2-); at 1414 cm^-1 (NH₄⁺); at 825 and 1356 cm^-1 (NO₃^-); and at 713, 730, and 877 cm^-1 (CO₃^2-) in PM₁₀ and PM_2.5 filters. Moreover, aliphatic hydrocarbons were identified in the collected spectra. Stretching frequencies at 2950 cm^-1 were assigned to CH₃ aliphatic carbon stretching absorptions, while frequencies at 2924 and 2850 cm^-1 indicated CH₂ bonds. In filters collected during Saharan dust events, the analysis also showed the presence of absorbance peaks typical of clay minerals. The measurement of soluble components confirmed the presence of a geogenic component (marine spray and local rocks) and secondary particles ((NH₄)₂SO₄, NH₄NO₃) in the PM filters. ATR-FTIR characterization of solid surfaces is a powerful analytical technique for identifying inorganic and organic compounds in samples of particulate matter.