Study of size-segregated particle (PM1, PM2,5, PM10) concentrations over Greece

Abstract

This study reports particulate matter levels of various size fractions (PM10, PM2.5, and PM1) and identify their controlling factors, in various locations over Greece. It combines long-term data sets involving particle concentrations as measured in the island of Crete in the Eastern Mediterranean and the Greater Area of Athens. Measurements were carried out in various sites at urban (Central Athens and Heraklion, Crete), suburban (Lykovrissi, Athens) and natural background (Finokalia, Crete) locations, for a time period extending from 2004 to 2006. Size-segregated mass measurements of 3 sizes (PM10, PM2.5 and PM1) are reported. The EU annual limit value of 40 μg m-3 for PM10 was exceeded on a yearly basis at both of measurement sites in Athens, while frequent exceedances of the 24-h limit value of 50 μg m-3 were recorded. Concentration levels of PM2.5 and PM1 were also found elevated, when regarded in perspective to either existing limit values (for PM2.5) or levels reported for other large metropolitan areas (for PM1). In addition even at the background station of Finokalia in Crete, average PM10 concentrations exceeded 30 μg m-3. Moreover, at the same station, average concentrations of PM2.5, notably exceed 15 μg m-3 (a characteristic value, relative to the USEPA PM2.5 air quality standard). At all sites coarse particles have been found to comprise a noteworthy portion of total PM10 particles (with PM2.5/PM10 ratios ranging between 45-60%), while fine particle mass concentrations heavily relied on those of particles in the submicron range (PM1/PM2.5 ratios spanning between 55-75%). The short and long-term temporal variability of each fraction were examined and spatial associations were statistically analyzed, in an attempt to identify possible affinities in particle level profiles, effective over a larger regional scale. It has been observed that at several instances, severe particle episodes recorded in the region of Crete have largely affected the Greek mainland and have triggered a response to the monitoring network in Athens. Special focus has been given to events of dust transport from N. Africa, which is found to be more frequent during spring and fall, and during which the PM10 limit value of 50 μg m-3 is violated and concentrations of even finer particle fractions are affected. Air mass back trajectories were studied, for episode days during dust transport events. Data of particle chemical composition were utilized, contributing to an initial identification and characterization of major natural and anthropogenic source types, which determine particle concentrations.