Identification of sources and processes affecting particulate pollution in Thessaloniki, Greece

The identification of local and remote particulate pollution sources, as well as the understanding of the factors determining the spatial and temporal variability of the particulate matter in urban areas is an issue of increasing public concern, since the above actions are absolutely essential for the design of effective particulate pollution control strategies. In the present study, the sources and the factors affecting the particulate pollution were studied in Thessaloniki, the second largest Greek city, in order to develop the necessary scientific framework for the subsequent development of integrated mitigation and control strategies and the design and implementation of effective environmental policies. Hourly PM10, PM2.5 and PMc concentrations from two monitoring sites (the Egnatia-Dimarchio and the Eptapyrgio stations) were therefore correlated to gaseous pollutant concentrations (CO, NO, NO2, NOx, SO2 and O3) and meteorological parameters (temperature, wind speed and relative humidity) during the 2-year period between June 2006 and May 2008. The analysis revealed that both sites experienced poor air quality, while a large number of exceedances of the daily and annual EC objectives were observed, especially during the cold season. Positive correlation between particles and NOx in DHM, provided evidence about higher combustion-related emissions during the cold season, whereas increased contribution of secondary particles was suggested during the warm season. In addition, Principal Component Analysis was used to identify the main particulate pollution sources, while the quantification of the combustion and the non-combustion-related fraction of particles was performed through Regression Analysis. Specifically, the non-combustion-related fraction ranged between 25.1 and 72.7%, depending on the site and the season. Finally, concentration roses were constructed in order to gain insight into the distribution of local emission sources around the monitoring sites.

► Both sites experienced poor air quality with a significant number of exceedances.
► Strong correlation between PM and NOx in DHM suggested combustion-related emissions.
► Weak correlation between PM and CO suggested the big number of diesel taxis and buses.
► The non-combustion-related fraction of particles was calculated between 25.1 and 72.7%.
► The synergy among local emissions and sea breezes was detected in both sites.