Sources and variability of inhalable road dust particles in three European cities F. Amato a, * , M. Pandolfi a , T. Moreno a , M. Furger b , J. Pey a , A. Alastuey a , N. Bukowiecki b , A.S.H. Prevot b , U. Baltensperger b , X. Querol a a Institute of Environmental Assessment and Water Research, Spanish Research Council (IDÆA-CSIC), C/Jordi Girona 18e26, 08034 Barcelona, Spain b Laboratory of Atmospheric Chemistry, Paul Scherrer Institut, 5232 Villigen, Switzerland article info Article history: Received 8 March 2011 Received in revised form 25 May 2011 Accepted 1 June 2011 Keywords: PM10 Traffic Non-exhaust Source apportionment PM10 Mineralogy Emissions PMF abstract Despite their importance, current scientific knowledge on non-exhaust emissions by road traffic is scarce, severely hampering a reliable description of these particles in atmospheric dispersion models. Conse- quently, it is still very difficult to convincingly evaluate population exposure to traffic-related compo- nents in large cities, especially given the significant variation in traffic-related air pollution concentrations on a small scale (e.g. within 100e1000 m of a busy road). One factor contributing to this uncertainty is the lack of a reliable emission estimate for vehicular non-exhaust emissions. Emissions vary from location to location due to the impact of climate, road surface characteristics and traffic conditions, but the geographical coverage for which Emission Factors are available and the amount of knowledge regarding the variability within a city environment are very limited. The present study investigates the spatial and chemical properties of the strength of the emission source (road dust particles below 10 mm) in three contrasting European urban environments: two Spanish cities (Barcelona and Girona), and a Swiss city (Zürich). Loadings of road dust <10 mm from the 8 sites sampled in Zürich ranged from 0.2 to 1.3 mg m 2 , the lowest loadings of the study. The minimum loadings in Girona (Spain) were as high as the maximum in Zürich, with a range of 1.3e7.1 mg m 2 . By far the most polluted site in terms of road dust <10 mm mass loading is Barcelona (Spain), where a range of 3.7e23.1 mg m 2 was recorded in the city center samples. Four main sources were found to drive the variability of road dust particles <10 mm: Mineral (road wear and urban dust generated mostly by construction emissions), Motor Exhaust, Brake wear and Tire wear. Road wear/Mineral is the dominating source in Spanish cities (w60%), but represents only 30% of road dust loadings in Zürich where contri- butions are more equally distributed among the four main sources of road dust. Regardless of the city categories loadings of OC, EC, Fe, Cr, Mn, Cu, Zn, Mo, Sn, Sb, Cs, Ba, W, Pb and Bi (mgm 2 ) increase by a factor of 1.2e2.2, from streets with <15 kveh to streets with 15e40 kveh day 1 . At highly trafficked sites (>40 kveh day 1 ) loadings were again increasing by a further factor of 2.6e10.1. Finally, agreement was found between the composition of sampled materials and the composition (available from litera- ture) of PM10 material emitted by vehicles via resuspension (both in Zürich and Barcelona). This permitted to find a relationship, potentially able to calculate emission factors from known amount of deposited pollutants in those cities/environment where no real-world EFs are available from literature. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction As a result of the demographic growth of large European cities, urban air pollution has become increasingly affected by traffic- related emissions in recent years. Emissions of inhalable particu- late matter (PM) from road traffic are responsible for most of the exceedances of the Air Quality Limit Values established by the European legislation for the protection of human health (2008/50/ EC; EEA, 2010). The daily (50 mgm 3 ) and annual (40 mgm 3 ) limit values of PM10 (atmospheric particles with mean aerodynamic diameter <10 mm) concentrations in ambient air are in fact exceeded mostly in the urban areas (EEA, 2010). These standards derive from the epidemiological and toxicological evidence of increased risks of mortality and cardiovascular and respiratory diseases due to an increase of ambient concentrations of PM (Dockery et al., 1993; Dockery and Pope, 1994; Peters et al., 2001; Brunekreef and Holgate, 2002; Brunekreef and Forsberg, 2005; Pope and Dockery, 2006). Although the PM components causing * Corresponding author. E-mail address: fulvio.amato@idaea.csic.es (F. Amato). Contents lists available at SciVerse ScienceDirect Atmospheric Environment journal homepage: www.elsevier.com/locate/atmosenv 1352-2310/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.atmosenv.2011.06.003 Atmospheric Environment 45 (2011) 6777e6787