A comprehensive assessment of PM emissions from paved roads: Real-world Emission Factors and intense street cleaning trials

Abstract

Compliance with air quality standards requires control of source emissions: fine exhaust particles are already subject to regulation but vehicle fleets increase whilst the non-exhaust emissions are totally uncontrolled. Emission inventories are scarce despite their suitability for researchers and regulating agencies formanaging air quality and PM reductionmeasures. Only few countries in Europe proposed street cleaning as a possible control measure, but its effectiveness is still far to be determined. This study offers first estimates of Real-world Emission Factors for PM10 and brake-wear elements and the effect on PM10 concentrations induced by intense street cleaning trials. A straightforward campaign was carried out in the city of Barcelona with hourly elemental composition of fine and coarse PM to detect any short-term effect of street cleaning on specific tracers of non-exhaust emissions. Samples were analyzed by Particle Induced X-Ray Emission. Real-world Emission Factor for PM10 averaged for the local fleet resulted to be 97 mg veh−1 km−1. When compared to other European studies, our EF resulted higher than what found in UK, Germany, Switzerland and Austria but lower than Scandinavian countries. For brake-related elements, total EFs were estimated, accounting for the sum of direct and resuspension emissions, in 7400, 486, 106 and 86 μg veh−1 km−1, respectively for Fe, Cu, Sn and Sb. In PM2.5Fe and Cu emission factors were respectively 4884 and 306 μg veh−1 km−1. Intense street cleaning trials evidenced a PM10 reduction at kerbside of 3 μg m−3 (mean daily levels of 54 μg m−3), with respect to reference stations. It is important to remark that such benefit could only be detected in small time-integration periods (12:00–18:00) since in daily values this benefit was not noticed. Hourly PM elemental monitoring allowed the identification of mineral and brake-related metallic particles as those responsible of the PM10 reduction.