Size fractionated aerosol composition at roadside and background environments in the Madrid urban atmosphere Fátima Mirante a, ⁎, Pedro Salvador b , Casimiro Pio a , Célia Alves a , Begoña Artiñano b , Alexandre Caseiro a ,M a . Aranzazu Revuelta b a CESAM, Department of Environment and Planning, University of Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal b CIEMAT, Atmospheric Pollution Unit, Environmental Department, Av. Complutense 22, 28040 Madrid, Spain article info abstract Article history: Received 7 June 2013 Received in revised form 13 October 2013 Accepted 25 November 2013 The chemical composition of size-segregated particulate matter (PM) was studied during summer and winter sampling campaigns, at two different urban sites (roadside and urban background) in the city of Madrid, Spain. PM was sampled with high volume cascade impactors, in 4 size ranges: 10–2.5, 2.5–1, 1–0.5 and b 0.5 μm. The carbonaceous content (OC and EC) was determined by a thermo-optical method, whilst the water soluble ionic species were measured by ion chromatography. The most common synoptic meteorological situations, including those causing the transport of African dusty air masses, were identified in both seasons. Whether the PM 10 mass or the highest concentrations of EC and OC were found predominantly in the ultrafine size fraction at both sites. In contrast with roadside, at the urban background, the particle mass concentrations for the different size ranges were statistically higher in summer than in winter. Observed inter-site differences suggest the existence of other sources and formation processes contributing in the summer period to the levels of PM at the urban background site apart from road traffic emissions. Secondary organic carbon (SOC) showed a clear seasonal pattern, with much higher concentrations in summer than in winter in both places, as well as higher relative contributions at the urban background than at the road traffic site. (NH 4 ) 2 SO 4 levels were at their maximum at both sites in summer in PM 0.5 . Differently, higher values were reached in winter for NH 4 NO 3 in PM 0.5 and for NaCl in PM 2.5–10 . From the ion balances, it was observed that, in summer, the formation of secondary inorganic compounds included an unusual enrichment in Ca 2+ in the submicrometre fraction, either at roadside or at urban background. © 2013 Elsevier B.V. All rights reserved. Keywords: Mass size distribution Chemical speciation Ionic components Minerals Organic carbon Urban aerosols 1. Introduction Particulate matter (PM) is a high priority atmospheric pollutant since it has strong negative impacts on human health, (Schleicher et al., 2011), climate (Das and Jayaraman, 2012), acid rain (Zhang et al., 2012), ecosystems (Katul et al., 2011), visibility (Yuan et al., 2006) and building materials (Costa et al., 2009). A major portion of atmospheric particles is constituted by carbonaceous matter (elemental (EC), organic carbon (OC), carbonated carbon (CC)); at European urban areas, its contribution is known to reach up to 18–32% of PM 10 and 25–31% of PM 2.5 (Putaud et al., 2010). Epidemiological studies have demonstrated that cardiovascular mortality and morbid- ity are associated with exposure to increased levels of urban carbonaceous aerosols (Ito et al., 2011). EC is abundant in the emissions from combustion of fossil fuel (Gillies and Gertler, 2000), and biomass burning (Alves et al., 2010; Vicente et al., 2012). OC sources are poorly characterised, but include direct emission by combustion processes, soil, paved road dust, meat cooking and others, and gas to particle conversion from anthropogenic and biogenic volatile organic com- pounds (VOCs). OC and EC are two of the major components of atmospheric particles emitted by traffic (both diesel and gasoline) (Calvo et al., 2013). There is little information Atmospheric Research 138 (2014) 278–292 ⁎ Corresponding author. Tel.: +351 234 370 958; fax: +351 234 370 309. E-mail address: fmirante@ua.pt (F. Mirante). 0169-8095/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.atmosres.2013.11.024 Contents lists available at ScienceDirect Atmospheric Research journal homepage: www.elsevier.com/locate/atmos