Screening of short-lived climate pollutants in a street canyon in a mid-sized city in Brazil

Özet

Black carbon (BC) and tropospheric ozone (O3) are two main short-lived climate pollutants also linked tohealth effects. They are ubiquitous in street canyons, since this environment is a hotspot for trafficrelatedpollutants due to their particular airflow characteristics, location within the cities and the highdensity of vehicles and population.We report on BC and O3 concentrations measured in a Brazilian city in November 2014. Measurementsof BC at 880 nm wavelength were conducted in a street canyon on the north and south façades and atrooftop level (7 wavelengths, including 880 nm) whereas O3 was recorded only on the south façade.Concurrent meteorological data were gathered at a suburban and a rooftop sites.Clear diurnal patterns were found for BC related to traffic emissions and atmospheric mixing conditions.Ozone peaked in the afternoon in response to maximum photochemical production and at nightmost likely linked to vertical and/or horizontal transport. By using conditional bivariate probabilityfunctions, we identified on-road traffic as the main local source for BC during daytime, and at night anintermittent signal was associated with local waste and biomass burned on the city's outskirts. Acomplementary air backward trajectory analysis helped conclude that locally produced O3 was enhancedby regional transport from large cities and/or biomass smoke.Mitigation strategies for BC and O3 depletion should target the vehicle fleet, particularly diesel buses,reduction of biomass and waste burning at local level, and decrease of open biomass burning in largeareas in Brazil and neighbor countries