Identification of refractory zirconia from catalytic converters in dust: An emerging pollutant in urban environments

• Published in: The Science of the total environment Vol. 760; p. 143384
• Main Authors: Meza-Figueroa, Diana, Pedroza-Montero, Martín, Barboza-Flores, Marcelino, Navarro-Espinoza, Sofía, Ruiz-Torres, Rodolfo, Robles-Morúa, Agustín, Romero, Francisco, Schiavo, Benedetto, González-Grijalva, Belem, Acosta-Elias, Mónica, Mendoza-Córdova, Abraham
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 15.03.2021
• Subjects: Catalytic converters; CeO2–ZrO2 washcoat; Inhalable particles; Refractory microcrystals; Vehicle emissions; CeO2–ZrO2 washcoat; Catalytic converters; Refractory microcrystals; Vehicle emissions; Inhalable particles; CeO–ZrO washcoat
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2020.143384

Using catalytic converters is one of the most effective methods to control vehicle emissions. A washcoat of cerium oxide-zirconia (CeO2–ZrO2) has been used to enhance the performance of the catalytic converter device. To date, the prevalence of this material in the environment has not been assessed. In this study, we present evidence of the existence of inhalable zirconia in urban dust. Samples of the washcoat, exhaust pipe, topsoil, and road dust were analyzed by X-ray fluorescence, X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, photoluminescence (PL) spectroscopy, and thermally stimulated luminescence (TSL). The results showed a CeO2–ZrO2 phase separation after sintering. This causes the emission of ZrO2, CeO2, and CeZrOx particles smaller than 1 μm, which can likely reach the alveolar macrophages in the lungs. The Ce-Zr content in road dust exceeds geogenic levels, and a significant correlation of 0.87 (p < 0.05) reflects a common anthropic source. Chronic exposure to such refractory particles may result in the development of non-occupational respiratory diseases. The inhalable crystalline compounds emitted by vehicles are a significant environmental health hazard, revealing the need for further investigation and assessment of zirconia levels generated by automobiles in urban areas worldwide. [Display omitted] •Inhalable zirconia crystals are emitted by aged catalytic converters.•CeO2-ZrO2 phase separation occurs after sintering.•Raman, PL, and TSL allowed the identification of minute zirconia in dust.•Inhalable refractory zirconia is identified as micro to nanocrystals.