PM10 regional transport pathways in Thessaloniki, Greece

In this study, the most dominant regional transport pathways for the city of Thessaloniki, Greece were identified and linked to air quality issues with respect to particulate matter (PM). Using air mass trajectories, cluster analysis techniques and PM10 measurements of a background-urban station of the greater Thessaloniki area during 2001–2004, it was found that north-eastern and southern flows were the most frequent in appearance with high potential to influence the city of Thessaloniki, especially when coinciding with biomass burning or Saharan dust events correspondingly. These incidents appeared to occur mostly during summer adding to a PM10 monthly mean up to 10 μg m−3. High concentrations of surface PM10 related to north-eastern flows were in most cases accompanied with high aerosol columnar optical depths implying that particulate matter transport from the North-East was multi-layered. South-southwesterly flows originating from N. Africa, though less frequent, seemed to affect decisively Thessalonikiʹs aerosol budget especially during transition seasons. These flows were related with an increase of the monthly PM10 average up to 20–30 μg m−3 for the time period studied. Finally, northerly flows were found to transport rather clean air masses that did not seem to contribute to the air quality deterioration of the city.