Particulate matter pollution over a Mediterranean urban area.

The main purpose of this study is to investigate the aerosols' (PM10, PM2.5, and PM1) spatial and temporal distribution in different types of environment in a Mediterranean urban region, the Greater Athens Area based on data from a sampling campaign that took place during the cold and warm period of 2008. The influence of the atmospheric circulation patterns, the possible local transport mechanisms, as well as the differentiation of the PM behaviour from that of the inorganic pollutants (NOx, O3), are analysed and discussed. Furthermore, the Comprehensive Air Quality Model with extensions (CAMx) was applied for selected sampling dates and its results were evaluated against measurements in order to interpret qualitatively the configured picture of the air pollution above the GAA. Analysis of the measurement data show that local sources such as traffic and industry dominate over the prevailing PM loads, especially at the 'hot spot' areas. Moreover, the synoptic circulation patterns associated with calm conditions and southerly flows lead to high particulate pollution levels that also affect the urban background stations. Saharan dust outbreaks appeared to increase the particles' diameter as well as the number of E.U. limit value exceedances within the stations of our network. Without any dependence on the characteristics of the investigated atmosphere, PM1 always constituted the greatest part of the PM2.5 mass while PM10, especially during the Saharan dust episodes, was mainly constituted by the coarse fraction. The numerical modelling approach of the geographical distribution of PM10, PM2.5, NOx and O3 justified the design of the sampling campaign, indicating the need for the systematic and parallel monitoring and modelling of the pollutants' dispersion in order to understand the particulate pollution problem in the GAA and to aid to the formulation of pollution control strategies.