Determination of black carbon, PM2.5, particle number and NOx emission factors from roadside measurements and their implications for emission inventory development

The road transportation sector contributes largely to air pollution in urban areas, why the knowledge of accurate vehicle emission factors (EF) is crucial to prepare reliable emission inventories, which, in turn, are strategic tools for air quality management. Curbside and rooftop concentrations of several traffic-related species were measured within a busy street canyon in Londrina (Brazil). EF for NOx, black carbon (BC), fine particles (PM2.5) and particle number (PN) were calculated based on these measurements and on inverse modeling using the Operational Street Pollution Model (OSPM). We highlight the importance of this work in quantifying BC, PM2.5, NOx and PN emissions from vehicles driven in an urban area under real conditions in a continent-sized country where there is a lack of EF studies. In the case of EFPN, we report the first value in the entire South America. Our EF were consistent with results from other on-road studies, but much higher than laboratory measurements conducted in Brazil and Europe, especially for particles (quantified as mass and number). This finding suggests that the EF derived from laboratory tests should be revised for all vehicle categories, since inaccurate values can have major implications on the compilation of official national inventories for the road transportation sector and on the assessment of their health and climate (in the case of BC) impacts. Incorporating certification procedures that more closely resemble real driving conditions is highly recommended. Limitations of the EF determined in this research for application in other studies are also discussed.