Uncommon chemical species in PM_2.5 and PM₁₀ and its potential use as industrial and vehicular markers for source...

Chemical characterization of PM_2.5 and PM₁₀ is important to identify potential compounds that induce biological responses that translate into cardio-respiratory health problems. This study shows the reliability of the use of crystalline phases, identified in samples from receptor sites, as source markers, helping researchers to infer the main sources of air pollution, even without the use of receptor models. PM_2.5 and PM₁₀ samples were collected at two sites in an urban industrialized region located at southeast of Brazil and analyzed by Synchrotron X-ray Diffraction to identify crystalline compounds. Results show 5 PM₁₀ and PM_2.5 species not previously reported in the literature. We propose reaction mechanisms for these species and identify specific sources for each crystalline phase found: BaTiO₃ was found in PM₁₀ receptor samples and proved to be a vehicular marker formed during brake action; maghemite (γ-Fe₂O₃), pyracmonite [(NH₄)₃Fe(SO₄)₃], ammonium perchlorate (NH₃OHClO₄) and potassium ferrate (K₂Fe₂O₄) were found in PM_2.5 proved to be markers of industrial activities. The crystalline phases found in PM samples from receptor sites and the mechanisms of reactions showed the reliability of the use of crystalline phases as source markers in the identification of potential sources of air pollution without misinterpretation of the likely source.