Relevant aspects of air quality in Oporto (Portugal): PM10 and O3.

The air quality Framework Directive (FWD) and the correspondent Daughter Directives defined the new strategy for air quality management in Europe. In general, the new standards are more restrictive than those established by the previous legislation. In Portugal, some difficulties can be previewed to achieve those new standards. Thus, this paper aims at evaluating the impact of application of the FWD to Oporto Metropolitan Area in what concerns to the most critical air pollutants in the area (PM10 and O3). The specific objectives were: (i) to analyse the concentration exceedances between 1999 and 2001; (ii) to identify the main emission sources; (iii) to evaluate the possibility of a new redistribution of the existing monitoring sites; (iv) to contribute to the definition of a new strategy for air quality management. The results showed that; (i) the standard values for PM10 and O3 were largely surpassed, possibly concluding that the FWD application implies a strong impact on the air quality management strategies; (ii) the main emission sources (road traffic and the neighbour stationary sources localised upwind) affect all the Metropolitan area through intra-region pollutant transport; (iii) it is safer maintaining the site localisation to avoid previewing exceedances through mathematical correlations; (iv) the reduction of PM10 and of ozone precursors must be performed considering new technologies for 'cleaner production' and gaseous depuration, a rigorous urban and territory planning, the creation of an efficient public transport network and the definition of strict measures for car maintenance.