Air pollution at an urban traffic tunnel in Lisbon, Portugal—an INAA study M. Almeida-Silva, N. Canha, M.C. Freitas n , H.M Dung, I. Dionı ´sio Instituto Tecnolo ´gico e Nuclear, URSN, E.N. 10, 2686-953 Sacave´m, Portugal article info Available online 15 January 2011 Keywords: Air pollution Urban Traffic Tunnel Chemical elements INAA Enrichment factors abstract In this study, the results of chemical concentrations inside and outside of a Lisbon (Portugal) traffic tunnel were compared, during one week. They were obtained by Instrumental Neutron Activation Analysis (INAA). The tunnel values largely exceed the Air Ambient legislated values and the Pearson Correlations Coefficients point out to soil re-suspension/dispersed road dust (As, Ce, Eu, Hf, Fe, Mo, Sc, Zn), traffic-markers (Ba, Cr), tire wear (Cr, Zn), break wear (Fe, Zn, Ba, Cu, Sb), exhaust and motor oil (Zn) and sea-spray (Br, Na). On all days these elements inside the tunnel were more enriched than outside; significant statistical differences were found for Co (p ¼0.005), Br (p ¼0.008), Zn (p ¼0.01) and Sb (p ¼0.005), while enrichment factors of As and Sc are statistically identical. The highest values were found for As, Br, Zn and Sb, for both inside and outside the tunnel. & 2011 Elsevier Ltd. All rights reserved. 1. Introduction In the past 30 years, outdoor levels of some pollutants are decreasing in many cities of Europe and US, due to emission controls on vehicles, heating, power generation and industry. However in developing countries the outdoor air pollution is worsening due to the increasing number of vehicles and indus- tries. The major outdoor air pollutants are particulates, O 3 , CO, SO x ,H 2 S, acid gases (HF, HCl), NO x , Pb and other metals, volatile organics, solvents, pesticides, methane, bioaerosols and radio- nuclides (Freitas, 2009; Freitas et al., 2009). Tunnels have been built, in developing cities, to facilitate mobility of people within the cities. An efficient tunnel construction has the potential to reduce traffic congestion. On the other hand, since ventilation outlets collect vehicle exhausts and release it all in one or two locations, road tunnels in urban areas give rise to problems including localized air pollution (Ma et al., 2004). So, under- standing emissions from traffic includes identification of the sources, which is also crucial for designing control measures (Sternbeck et al., 2002). In this study, the results of chemical concentrations inside and outside of a Lisbon (Portugal) traffic tunnel were compared. They were determined by Instrumental Neutron Activation Analysis (INAA) (Freitas et al., 2008; Dung et al., 2008) and their sources were assessed. 2. Experimental 2.1. Sampling site and equipment From 9 to 21 October 2008, at rush traffic hours and weekend, different fractions of air particulate matter were collected inside a traffic tunnel in Lisbon, using quartz filters in different selectors. Particles were collected within the periods 08:00 and 10:00 and 17:00 and 19:00 from Monday to Saturday except on Tuesday, which was within 08:45–09:45 and 17:45 and 18:45. The col- lected fractions were PM 10 2.5 , PM 2.5 1 , PM 10.5 and PM 0.5 , which correspond, respectively, to particles with aerodynamic diameter between 2.5 and 10 mm, 1 and 2.5 mm, 0.5 and 1 mm and below 0.5 mm. Daily collection time varied between 0.46 and 3.95 h (it depended on the size collected fraction, less for the coarser particles, more for the finer ones) and the collected air volumes varied between 31.19 and 267.81 m 3 . Low and high volume air samplers were used. 2.2. Sample analysis The collected filters and blank filters, turned available by Aveiro University, Portugal, were irradiated at the Portuguese Research Reactor (RPI-ITN; nominal power: 1 MW) for analyses by k 0 -INAA (De Corte, 1987). Irradiation time was 5 h at a neutron flux density of 8  10 12 cm 2 s 1 , at an irradiation position with 103.4 71.3 thermal-to-epithermal neutron flux ratio and an 1/E 1+ a epithermal neutron flux distribution shape factor of  0.0351 70.0004. Each sample was rolled up and put into an aluminum foil for irradiation, removed from the foil after irradiation and put in a polyethylene container for measurement. Samples were measured 7 h after 3–5 days and after 3–4 weeks, with an ORTECs automatic sample Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/apradiso Applied Radiation and Isotopes 0969-8043/$ - see front matter & 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.apradiso.2011.01.014 n Corresponding author. Tel.: +351 219946130; fax: +351 219941039. E-mail address: cfreitas@itn.pt (M.C. Freitas). Applied Radiation and Isotopes 69 (2011) 1586–1591