Evolution of Vehicle Emission Factors in a Megacity Affected by Extensive Biofuel Use: Results of Tunnel Measurements in São Paulo, Brazil

• Published in: Environmental science & technology Vol. 55; no. 10; pp. 6677 - 6687
• Main Authors: Nogueira, Thiago, Kamigauti, Leonardo Yoshiaki, Pereira, Guilherme Martins, Gavidia-Calderón, Mario E, Ibarra-Espinosa, Sergio, Oliveira, Guilherme Librete de, Miranda, Regina Maura de, Vasconcellos, Pérola de Castro, Freitas, Edmilson Dias de, Andrade, Maria de Fatima
• Format: Journal Article
• Language: English
• Published: American Chemical Society 18.05.2021
• Subjects: Anthropogenic Impacts on the Atmosphere; biofuel; light-duty vehicles; vehicle emission factor; heavy-duty vehicles; gasohol
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/acs.est.1c01006

Since 2001, four emission measurement campaigns have been conducted in multiple traffic tunnels in the megacity of São Paulo, Brazil, an area with a fleet of more than 7 million vehicles running on fuels with high biofuel contents: gasoline + ethanol for light-duty vehicles (LDVs) and diesel + biodiesel for heavy-duty vehicles (HDVs). Emission factors for LDVs and HDVs were calculated using a carbon balance method, the pollutants considered including nitrogen oxides (NO x ), carbon monoxide (CO), and sulfur dioxide, as well as carbon dioxide and ethanol. From 2001 to 2018, fleet-average emission factors for LDVs and HDVs, respectively, were found to decrease by 4.9 and 5.1% per year for CO and by 5.5 and 4.2% per year for NO x . These reductions demonstrate that regulations for vehicle emissions adopted in Brazil in the last 30 years improved air quality in the megacity of São Paulo significantly, albeit with a clear delay. These findings, especially those for CO, indicate that official emission inventories underestimate vehicle emissions. Here, we demonstrated that the adoption of emission factors calculated under real-world conditions can dramatically improve air quality modeling in the region.