Impact of spatial and vertical distribution of air masses on PM10 chemical components at the Eastern Mediterranean - A seasonal approach

An upgraded three-dimensional (3D) version of the back-trajectory based Concentration Weighted Trajectory (CWT) model, segregating distinct vertical layers of atmospheric transport, was combined with two years of PM10 chemical composition measurements from the Finokalia superstation on the island of Crete, Greece, in the Eastern Mediterranean basin. Three altitudinal transport layers were studied: a) 0 m <= Layer 1 < 1000 m b) 1000 m <= Layer 2 < 2000 m c) 2000 m <= Layer 3, and the analysis was conducted separately for the cold (16 October - 15 April) and the warm (16 April - 15 October) periods. Mediterranean airflows in all layers enriched the concentrations of sea salt water soluble ions (Na+, Cl- , Mg2+ and K+) whilst during the warm period long-range northeastern airflows in layer 2 and layer 3 increased the levels of carbonaceous aerosols (OC and EC) and K+ due to intensive biomass burning in areas around the Black Sea. Peak concentrations of PM10-bound SO42- and NH4+ were associated with continental Northern airflows in layer 2 and layer 3, and were attributed to emissions in Northern Greece, Turkey, Balkan Peninsula and Eastern Europe. In addition, episodes of crustal constituents such as Ca2+, Mn, Al and Fe, were triggered by Saharan dust intrusions occurring mainly during cold period through all altitudinal layers. Moreover, the impact of heavy fuel oil combustion from shipping during warm period was reflected by maritime flows enhancing V concentrations, whilst a Saharan dust source for V was observed in all layers during cold period.