Raman Characterization of Ambient Airborne Soot and Associated Mineral Phases

Abstract

Airborne particulate matter samples were collected in an urban and a rural-suburban monitoring stations of the city of Rome, Italy, and the particles were analyzed through the Raman microspectroscopy. A careful examination of the spectral bands, performed with a five-(Voigt) curve deconvolution model previously described by the literature and here adapted to the purpose, lead to the characterization of the graphitic and carbonaceous material plus the identification of the mineral particles associated with it. Statistical analysis of the full-width at half-maximum (FWHM) values of the bands, as well as of their intensity ratio, revealed the presence of two classes of soot particles that can be ascribed to a different degree of crystallinity. The population of soot collected at the urban site, where the vehicular emission component prevails, exhibits mostly crystalline characteristics (with a D1 FWHM of 150-155 cm −1 ), whereas the population collected at the rural-suburban site, particularly the coarse fraction, shows a prevailing amorphous nature (with a D1 FWHM of ∼175 cm −1 ). A similar aspect emerges for the pure black carbon particles, mainly crystalline, and the black carbon particles associated with minerals, generally disordered. These results add useful information and characterization of the soot, a relevant component of the ambient air, and its different features with respect to the urban or rural-suburban areas.

Sublacustrine hydrothermal seeps and silicification of microbial bioherms in the Ediacaran Oued Dar'a caldera, Anti‐Atlas, Morocco

“…Voigt functions have been used for the fitting procedure because this function corresponds to the convolution of the phonon mode (Lorentzian profile) with the resolution of the optical setup (Gaussian profile). The choice was made on the basis of sound foundation, higher accuracy and reproducibility of the fit (see Zanatta & Ferri, 2007;Catelani et al, 2014).…”

Feasibility of the quantification of respirable crystalline silica by mass on aerosol sampling filters using Raman microscopy

“…Raman spectroscopy was also investigated as a potential technique to determine the mineral content of rocks on moons or planets . Only recently has Raman spectroscopy been used to characterise airborne particles of dust from samplers collecting particulate matter <10 μm and particulate matter <2.5 μm from ambient air . Potgieter‐Vermaak and Van Grieken examined the suitability of a number of filter materials for the evaluation of individual aerosol particles using micro‐Raman spectroscopy.…”

authors's response to reviewers' comments

“…The OC / EC thermal-optical analysis of Lab-TBs was performed by a Model-4 Semi-Continuous OC-EC Field Analyzer (Sunset Laboratory Inc., USA). The aerosol samples on quartz filters (∅ 13.06 mm) were analysed following the EUSAAR_2 protocol (Cavalli et al, 2010). The data were corrected for blanks taken from backup quartz filters of same size.…”