title: Vehicular Emission Ratios of VOCs in a Megacity Impacted by Extensive Ethanol Use: Results of Ambient Measurements in São Paulo, Brazil.
abstract: The São Paulo Metropolitan Area (SPMA) is a megacity with 20 million people and over 8 million vehicles. Over the past decade a large increase in biofuel usage, more notably ethanol by light-duty vehicles, has made Brazil, and in particular São Paulo, a unique case worldwide. This study presents the first assessment of emission ratios of a selected group of volatile organic compounds (VOCs) relative to carbon monoxide (CO) under ambient conditions. The VOCs studied here include aromatics such as benzene (1.03 pptv/ppbv CO), toluene (3.10 pptv/ppbv CO) and Oxygenated VOCs such as methanol (5.39 pptv/ppbv CO), acetaldehyde (3.93 pptv/ppbv CO), acetone (3.59 pptv/ppbv CO), methyl ethyl ketone (1.42 pptv/ppbv CO), and others. Despite the specificity of the fuel composition, emission ratios were in surprisingly close agreement with other megacities in Europe or in North America. Such results include species whose emission factors have been previously reported to decline (e.g., benzene) or increase (e.g., acetaldehyde) with ethanol usage. Furthermore, diurnal profiles and temperature analysis aid separating the primary anthropogenic, secondary or biogenic components of the species studied here. This study shows that a significant fraction of ethanol in gasoline blends does not result in a well-defined trend in VOC emission profile and certainly motivates further studies.
authors.affiliation: Physics Institute, University of São Paulo , São Paulo, Brazil.
authors.forename: Joel
authors.initials: J
authors.lastname: Brito
authors.affiliation: Physics Institute, University of São Paulo , São Paulo, Brazil.
authors.forename: Florian
authors.initials: F
authors.lastname: Wurm
authors.affiliation: National Institute of Research in Amazonia, Manaus, Amazonia Brazil.|Biogeochemistry Department, Max Planck Institute for Chemistry , Mainz, Germany.
authors.forename: Ana Maria
authors.initials: AM
authors.lastname: Yáñez-Serrano
authors.affiliation: School of Public Health, University of São Paulo , São Paulo, Brazil.
authors.forename: João Vicente
authors.initials: JV
authors.lastname: de Assunção
authors.affiliation: Chemistry Department, Pontifical Catholic University of Rio de Janeiro , Rio de Janeiro, Brazil.
authors.forename: José Marcus
authors.initials: JM
authors.lastname: Godoy
authors.affiliation: Physics Institute, University of São Paulo , São Paulo, Brazil.
authors.forename: Paulo
authors.initials: P
authors.lastname: Artaxo
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D001554:Benzene / Q000032:analysis; D056804:Biofuels; D001938:Brazil; D002248:Carbon Monoxide / Q000032:analysis; D002947:Cities; D004784:Environmental Monitoring / Q000379:methods*; D000431:Ethanol; D005742:Gasoline; D014050:Toluene / Q000032:analysis; D001335:Vehicle Emissions / Q000032:analysis*; D055549:Volatile Organic Compounds / Q000032:analysis*
chemical_list: D000393:Air Pollutants; D056804:Biofuels; D005742:Gasoline; D001335:Vehicle Emissions; D055549:Volatile Organic Compounds; D014050:Toluene; D000431:Ethanol; D002248:Carbon Monoxide; D001554:Benzene