Comparison of Emissivity, Transmittance, and Reflectance Infrared Spectra of Polycyclic Aromatic Hydrocarbons with those of Atmospheric Particulates (PM1)

ABSTRACT

Polycyclic Aromatic Hydrocarbons (PAHs) are a group of various complex organic compounds composed of carbon and hydrogen, and two or more condensed benzene rings. They are released into the atmosphere by the incomplete combustion or pyrolysis of organic matter. Some of the major sources of PAHs are burning of coal, wood, oil or gas, vehicle engines exhaust, and open burning. PAHs are of great concern to human health mainly because of their known carcinogenic and mutagenic properties. Consequently, it is very important to study atmospheric PAHs, especially those associated with ultrafine particles. This study aims to identify the spectral features of PAHs in samples of particulate matter < 1 µm (PM₁) using infrared spectrometry. Emissivity and transmittance spectra of PAHs were obtained by infrared spectroscopy. PAHs standards spectra contributed to effectively identify PAHs in PM₁ samples. Emissivity and transmittance spectra in the range of 680–900 cm^–1 exhibited the largest number of bands due to C–C out-of-plane angular deformations and C–H out-of-plane angular deformations. Bands of medium intensity in 2900–3050 cm^–1 region were also observed due to C–H stretching typical of aromatic compounds, although with lower intensity. This study compared the emissivity and transmittance spectra acquired using two different infrared spectrometers in order to identify PAHs in samples of atmospheric particulate matter and analyzed the capability and advantages of each of the infrared spectrometers. In addition, it was confirmed that the PAHs under study can be distinguished by their infrared spectral fingerprints.