Origin and variability of particulate matter (PM10) mass concentrations over the Eastern Mediterranean

Five-year PM10 concentrations (2000–05) at Heraklion (urban), Crete, and concurrent measurements of TSP and PM10 (2001–02 and 2004–05, respectively) at Finokalia (background) have been used to discriminate between the various sources of PM over the area and investigate the factors that control their levels. PM10 concentrations at Heraklion (51±33 μg m−3) and Finokalia (28±30 μg m−3) lie within the range found for urban and background-rural sites in the Eastern Mediterranean, respectively. Special focus has been given to the influence of transported dust from N. Africa, which is found to be more frequent during spring and fall. The additional effect from local sources has been also calculated at Heraklion (about 20 μg m−3). The EU limit of 50 μg m−3 is exceeded at Heraklion, one in 4 days, during winter and spring (50% due to transported dust) and half of the days during summer and fall (pollution). At Finokalia exceedances are observed in winter and spring during one in 5 days, 80–100% of which are associated with dust events. The mass balance estimation for periods with no influence from dust shows that ions dominate the PM10 mass (40–60%) with dust and particulate carbonaceous matter (PCM) comprising the rest. During the identified dust outbreaks, the contribution of dust rises to 60–65%, while the contribution of ions declines to 30% and only 10% is PCM.