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- Road tunnel, roadside, and urban background measurements of aliphatic compounds in size-segregated particulate matterPublication . Oliveira, Cesar; Martins, Natercia; Mirante, Fátima; Caseiro, Alexandre; Pio, Casimiro; Matos, Manuel; Silva, Hugo; Oliveira, Cristina; Camões, FilomenaParticulate matter samples were collected in a road tunnel in Lisbon (PM0.5, PM0.5-1, PM1-2.5, and PM2.5-10) and at two urban locations representing roadside and background stations (PM2.5 and PM2.5-10). Samples were analysed for organic and elemental carbon (OC and EC), n-alkanes, n-alkenes, hopanes, some isoprenoid compounds, and steranes. Particulate matter concentrations in the tunnel were 17-31 times higher than at roadside in the vicinity, evidencing an aerosol origin almost exclusively in fresh vehicle emissions. PM0.5 in the tunnel comprised more than 60% and 80% of the total OC and EC mass in PM10, respectively. Concentrations of the different aliphatic groups of compounds in the tunnel were up to 89 times higher than at roadside and 143 times higher than at urban background. Based on the application of hopane-to-OC or hopanes-to-EC ratios obtained in the tunnel, it was found that vehicle emissions are the dominant contributor to carbonaceous particles in the city but do not represent the only source of these triterpenic compounds. Contrary to what has been observed in other studies, the Sigma hopane-to-EC ratios were higher in summer than in winter, suggesting that other factors (e.g. biomass burning, dust resuspension, and different fuels/engine technologies) prevail in relation to the photochemical decay of triterpenoid hydrocarbons from vehicle exhaust
- Size-segregated chemical composition of aerosol emissions in an urban road tunnel in PortugalPublication . Pio, Casimiro; Mirante, Fátima; Oliveira, Cesar; Matos, Manuel; Caseiro, Alexandre; Oliveira, Cristina; Querol, Xavier; Alves, Célia; Martins, Natércia; Cerqueira, Mário; Camões, Filomena; Silva, Hugo; Plana, FelicianoAn atmospheric aerosol study was performed in 2008 inside an urban road tunnel, in Lisbon, Portugal. Using a high volume impactor, the aerosol was collected into four size fractions (PM0.5, PM0.5-1, PM1-2.5 and PM2.5-10) and analysed for particle mass (PM), organic and elemental carbon (OC and EC), polycyclic aromatic hydrocarbons (PAH), soluble inorganic ions and elemental composition. Three main groups of compounds were discriminated in the tunnel aerosol: carbonaceous, soil component and vehicle mechanical wear. Measurements indicate that Cu can be a good tracer for wear emissions of road traffic. Cu levels correlate strongly with Fe, Mn, Sn and Cr, showing a highly linear constant ratio in all size ranges, suggesting a unique origin through sizes. Ratios of Cu with other elements can be used to source apportion the trace elements present in urban atmospheres, mainly on what concerns coarse aerosol particles. (C) 2013 Elsevier Ltd. All rights reserved.