Assessing The Contribution Of Regional Sources To Urban Air Pollution By Applying 3d-Pscf Modeling

A three dimensional (3D) variant of the Potential Source Contribution Function (PSCF) model was used in this study, aiming to identify the source areas and altitudinal atmospheric layers associated with PM10 exceedances of the daily EU limit value (> 50 mu g/m(3)) during the different seasons in Athens (Greece). The analysis covers the period 1 May 2015 to 31 December 2018, during which direct Saharan dust intrusions from North Africa and especially Libya and Egypt, occurred mainly within the 0-1000 m a.g.l. layer, and were identified as a significant source of PM10 exceedances during all seasons. The maximum probability of dust events was detected in spring, when the dust transport pathways were also vertically extended. Additionally, an increased probability of PM10 exceedances in winter was linked to northerly airflows within both the 0-1000 m a.g.l. and 1000-2000 m a.g.l. layers, indicating regional transport from the Balkans and Northern Greece. To delineate the emission origin of winter PM10 exceedances, the 3D-PSCF model was also applied on concentrations of Black Carbon (BC), its wood burning related fraction (BCwb) and CO, recognized as markers of incomplete combustion processes. A synoptic analysis showed that the accumulation of local emissions due to stagnant anticyclonic conditions is the primary cause of the PM10, CO, BC and BCwb episodes in Athens during winter, however 3D-PSCF model also clearly demonstrated supplementary contributions from regional combustion sources located in the Balkans and Northern Greece.