Relationship between Black Carbon and heavy traffic in São Paulo, Brazil

Abstract:

Carbonaceous aerosols play an important role in air quality, human health and global climate change. Black Carbon (BC) can be considered the most efficient light absorber in the visible spectrum and is mainly found in the fine fraction of aerosol. Typically is emitted by incomplete combustion of fossil fuels related to traffic, industrial processes and biomass burning. São Paulo Metropolitan Area (SPMA) with more than 19 million inhabitants, 7 million vehicles, as well as the major industrial and technological park of the country, has high concentrations of air pollutants, especially in the winter and vehicles are considered the principal source of particles emitted to the atmosphere. Since November 2014, Black Carbon and PM_2.5 are being monitored using a MAAP (Multi Angle Absorption Photometer) Thermo 5012 and a Dust Trak DRX-8533 TSI in the East Campus of University of São Paulo, close to important highways and also to the largest airport of Brazil (Guarulhos Airport). Average BC concentration was 1.7 μg/m³ with some peaks above 17.0 μg/m³ and for PM_2.5 average was 10.2 μg/m³. Particle concentrations reached values greater than the air quality standard (60 μg/m³) in the winter months. Winds coming from the East direction predominate. Traffic restrictions to heavy duty vehicles in the road-rings next to the sampling site during some hours of the day are the responsible for the daily BC and PM_2.5 behavior (figure below), where high concentrations occur early in the morning and late at night, when heavy diesel vehicles are released for transit. Seasonal variations are different for BC and PM_2.5 due to local sources of BC and meteorological conditions that have more influence on the particles. The weekly variation indicates that concentrations are lower on Sundays and higher from Tuesday to Thursday. Emission factors for BC were calculated based on traffic information.