J3.5 MODELLING SMOKE EFFECTS ON LISBON AIR QUALITY A.I. Miranda*, H. Martins, A. Carvalho and C. Borrego Universidade de Aveiro, Aveiro, Portugal 1. INTRODUCTION Each summer season wildland forest fires burn a considerable area of south European landscape. Summer 2003 was one of the most severe fire seasons experienced during the last decades in Southern Europe and, due to persistent extreme fire conditions, Portugal suffered the worst forest fire season that the country has faced in the last 23 years, with a total burnt area of almost 5 times the average (EC, 2004). Smoke has to be considered as one of the several disturbing effects of forest fires. Its impacts on air quality and human health can be significant since large amounts of pollutants, like particulate matter (PM 10 ), carbon monoxide (CO), volatile organic compounds (VOC) and nitrogen oxides (NO x ), are emitted to the atmosphere. The effects of these emissions are felt at different levels: from the contribution to global climate change to the occurrence of local atmospheric pollution episodes (Miranda, 2004). Therefore, the smoke released from forest fires is currently considered an important public health issue (Schwela et al., 1999), particularly near or inside urban areas due to the highest risk of human exposure. During summer 2003 there were reports of more than one thousand people (mainly civilian) needing medical assistance due to smoke intoxications, burns and wounds from forest fires in Portugal (EC, 2004). Satellite images, like the one shown in Figure 1 (URL1), and air pollutants concentration values measured on the Portuguese air quality monitoring network highlighted the impact of forest fire atmospheric emissions. Forest fires spreading north of Lisbon city at September 2003 impacted the urban air quality. The Lisbon air shed, with a population of 3.5 million inhabitants, is the most important urban center in Portugal. Because of its urban/wildland characteristics, high population density, and hence higher risk of human exposure to smoke, and the high levels of pollutants registered, this is a very interesting case for the study of the influence of forest fires emissions on air quality. Figure 1. Portuguese territory satellite image, 4 th August 2003 (URL1). A first analysis of measured values of CO and PM 10 during September was carried out aiming to identify one period where Lisbon was clearly affected by smoke from forest fires. It was possible to identify the 13 th of September as one of the most critical days regarding CO and PM 10 concentration values in Lisbon urban area. In this day, 32 forest fires were registered in the Lisbon Metropolitan Area (LMA), burning an area of about 400 ha of forest stands and shrubs. Table I presents some information concerning the main fires characteristics, like beginning and ending hours, burnt area and type of consumed vegetation. The city suffered particularly the effects of smoke from forest fires spreading north of the urban area at yhe municipalities of Mafra and Loures. In Figure 2 the location of the main September 13 th fires, as well as the LMA air quality monitoring network is presented. The urban area has an air quality monitoring network, which includes several stations, with different typology (urban background or urban traffic), according to location and environmental criteria. * Corresponding author address: Ana I. Miranda, Universidade de Aveiro, Departamento de Ambiente e Ordenamento, 3810-193 Aveiro, Portugal; e-mail: aicm@dao.ua.pt