Physico-chemical characteristics of particulate matter in the Eastern Mediterranean

Particulate matter (PM10, PM2.5) measurements were performed during the period 2003–2009 at the Akrotiri monitoring station (suburban/rural) on the island of Crete, Greece. Concurrent measurements of PM10 size distribution/chemical composition were also performed at selected time intervals to determine the PM sources in the region and the factors controlling their levels. Using a beta radiation attenuation monitor, the mean PM10 concentration during the measuring period (15.04.2003–31.12.2009) was equal to 36.1 ± 9.5 μg/m3, whereas the PM2.5 concentration was equal to 23.6 ± 5.8 μg/m3. Back trajectories showed that the dominant air mass origin was from North and Northwest Europe but the intrusion of southern air masses lead to elevated PM concentrations due to Saharan dust events. The 24-h EU limit value of 50 μg/m3 (PM10) was exceeded approximately 13.5% during the measured period. Furthermore, the PM10 mass size distribution of metals, ions and organic carbon/elemental carbon (OC/EC) was characterized using a 9-stage Andersen non-viable impactor and a gravimetric sequential PM10 sampler during two selected periods. The mean PM10 concentration during the first sampling period was equal to 28.3 ± 12.4 μg/m3 (10.08.2007–28.08.2007), whereas during the second sampling period (09.07.2008–19.07.2008) was 41.6 ± 14.0 μg/m3. The measurements showed a bimodal size distribution for the aerosol mass concentration. PM2.1 accounted for 41.0% and 37.2% for PM10 during the two periods respectively. Over the measurement campaigns ions dominated the PM10 mass (50–80%) with the organic mass and metals comprising the major part of the rest. The OC concentration was equal to 2.3 ± 1.2 μg/m3, whereas the EC concentration was equal to 0.8 ± 0.2 μg/m3. Finally, black carbon concentrations were measured in August 2007 with an aethalometer. The mean daily value of black carbon was 0.69 ± 0.22 μg/m3. The measurements showed that the PM values measured at the station correspond to a background/rural station in the region and are in agreement with other measurements in the Eastern Mediterranean region.