On-road emissions of carbonyls from vehicles powered by biofuel blends in traffic tunnels in the Metropolitan Area of Sao Paulo, Brazil

• Formaldehyde (F) and acetaldehyde (A) were the most abundant carbonyl compounds.
• The F/A ratio from Brazilian light-duty vehicles ranged from 0.77 to 1.3, lower than that obtained in other countries.
• Heavy-duty vehicles emit F concentrations close to California's vehicles.

On-road emissions of carbonyls from the current vehicle fleet of Brazil were determined in two experimental campaigns, conducted in traffic tunnels located in the Metropolitan Area of São Paulo (MASP), in southeastern Brazil. Among carbonyl species, formaldehyde and acetaldehyde were the most abundant in all sampling periods. In Brazil, heavy-duty vehicles (HDVs) run on a blend of 95% regular diesel/5% biodiesel from soy, whereas light-duty vehicles (LDVs) run on gasohol (75–80% gasoline/20–25% ethanol) or hydrous ethanol. We found that HDVs showed the highest overall carbonyl emissions, although LDVs were responsible for high emissions of acetaldehyde. In comparison with LDVs in California, which are powered by 90% gasoline/10% ethanol, LDVs in Brazil were found to emit 352% and 263% more formaldehyde and acetaldehyde.

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