Influence of Saharan Dust Transport Events on PM₂.₅ Concentrations and Composition over Athens

Remoundaki, E.; Papayannis, A.; Kassomenos, P.; Matuzevičius, Eugenijus; Kokkalis, P.; Tsezos, M.

Influence of Saharan Dust Transport Events on PM₂.₅ Concentrations and Composition over Athens

2013

The evaluation of the contribution of natural sources to PM₁₀ and PM₂.₅ concentrations is a priority especially for the countries of European south strongly influenced by Saharan dust transport events. Daily PM₂.₅ concentrations and composition were monitored at an urban site at 14 m above ground level, at the National Technical University of Athens campus from February to December 2010. The typical dust constituents Si, Al, Fe, K, Ca, Mg, and Ti were determined by wavelength dispersive X-ray fluorescence spectrometry (WDXRF). Sulfur, a tracer of anthropogenic origin and major constituent of PM₂.₅, was determined by both WDXRF and ionic chromatography. The contribution of dust and sulfates in PM₂.₅ was calculated from the analytical determinations. An annual mean of 20 μg/m³ was calculated from the mean daily PM₂.₅ concentrations data. Twenty-two per cent of daily concentrations of PM₂.₅ reached or exceeded the EU annual target concentration of 25 μg/m³. The exceedances occurred during 13 short periods of 1–4 days. Back-trajectory analysis was performed for these periods in order to identify the air masses origin. From these periods, ten periods were associated to Saharan dust transport events. The most intense dust transport event occurred between February 17th and 20th and was responsible for the highest recorded PM₂.₅ concentration of 100 μg/m³ where the dust contribution in PM₂.₅ reached 96 %. The other dust transport events were less intense and corresponded to less pronounced enhancements of PM₂.₅ concentrations, and their contribution ranged from 15 to 39 % in PM₂.₅ concentrations. Air masses originated from northwest Africa while the influence of central Sahara was quite smaller.

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