The present paper constitutes a synthesis of the results gotten during the five campaigns of air quality measurement in the years of 2003 and 2004 carried out in the Portuguese city of Viana do Castelo to characterise the reference situation and to accompany the Polis Programme, an urban re-qualification and environmental valorisation plan. The main objective of the monitoring programme consisted of the evaluation of atmospheric pollutants whose levels were susceptible of enhancement in the course of the urbanistic public works. The presented results refer to measurements performed in two distinct places of this city, comprising various consecutive days of acquisition that include, at least, one day of weekend. Viana do Castelo is a small town in the north of Portugal, capi- tal of the Minho district. It is placed in the right margin of the river Lima, close to the mouth, and extends between the sea and the river, in land almost plan, being protected by the luxuriantly green Sta. Luzia hill. The city has 36546 inhabitants in the 5 parishes of the urban area and a total of 87875 inhabitants in 40 parishes of the municipality. The city has a seaport with naval repairing and construction facilities. The Polis Programme for the urban re-qualification and environmental enhancement of middle sized cities - of ministerial responsibility - was meant to play a role in the development of new business in areas involving high levels of competences in urban planning, design and renewal of infrastructures and structure-related equipment, as well as providing animation and profitability for areas of excellence, favouring the forming of private partnerships. The project consists of a series of works to modernise or replace outmoded social infrastructures and restore run-down parts of the central, river frontage and park sections of the city to a condition suitable and appropriate to a modern city. It tries to be environmentally friendly, promoting the extension of pedestrian precincts and areas, and be accompanied by appropriate environmental and educational campaigns. The project is part of a nationwide programme strongly supported by the European Union (EU) and the Portuguese Government to promote urban regeneration and renewal in a range of medium-sized cities in the country. The specific objectives of the Viana do Castelo programme are to restore hitherto under-utilised or degraded areas of the city and to render them useable, accessible and convivial to the citizens and inhabitants of the area. It includes several measures to stop cars from circulating at the historical centre, namely by creating new public transport connections from the outskirt, constructing several parking spaces outside the central zone and creating new green spaces in the city and in the city historical centre. The project is accompanied by a rigorous environmental management programme that includes solid wastes, air, water and noise studies, as well as preventive and remedial instruments. Among the adopted environment measures we can cite the watering of the building sites, especially during the foundations' works, the cleaning of shop-windows and pavements twice a week, the washing of the vehicle wheels, the utilisation of drilling, punching, polishing and sawing machines with jets of water and the covering of construction and excavation materials during transportation. The objective of this work was to investigate the air quality of Viana do Castelo in the scope of the Polis Programme. To this purpose the air pollution levels were measured, with emphasis paid to NO, NO 2 , CO, SO 2 , O 3 , particulate matter (PM 10 and PM 2.5 ) and aromatic volatile organic compounds (benzene, toluene and xylenes - BTX). The occurrence of exceedances of the air quality threshold values was examined, the diurnal profiles were studied and the relationships between each other were explored. The meteorological parameters were also considered in the discussion of the results, as well possible atmospheric pollutant sources, including the construction works within the Polis project. EXPERIMENTAL
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