Mass and chemical composition of size-segregated aerosols

Atmospheric Chemistry and Physics Discussions This discussion paper is/has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP if available. Abstract To identify the relative contribution of local versus regional sources of particulate matter (PM) in the Greater Athens Area (GAA), simultaneous mass and chemical composition measurements of size segregated particulate matter (PM: PM 1 , PM 2.5 and PM 10) were carried out from September 2005 to August 2006 at three locations: one urban (Goudi, 5 Central Athens) and one suburban (Lykovrissi, Athens) in GAA and the third in a regional background site (Finokalia, Crete). The two stations in GAA exceeded the EU-legislated PM 10 limit values, both in terms of annual average (59.0 and 53.6 µg m −3 for Lykovrissi and Goudi, respectively) and of 24-h value, while the concentration levels at the remote site of Finokalia indicated an 10 elevated background. High levels of PM 2.5 and PM 1 were also found at all locations (23.5 and 18.6 for Lykovrissi, while 29.4 and 20.2 µg m −3 for Goudi, respectively). Significant correlations were observed between same PM fractions at both GAA sites indicating important spatial homogeneity within GAA. During the warm season, the PM 1 ratio between the GAA and the background site ranged from 1.1 to 1.3. On the 15 other hand this ratio was significantly higher (1.6–1.7) during the cold season highlighting the role of long-range transport and local sources during the warm and cold seasons respectively. Similar seasonal and geographical patterns were observed for nss-SO 2− 4 , a secondary compound characteristic of regional sources, confirming the above hypothesis. 20 Regarding the coarse fraction no such seasonal trend was observed for both GAA sites with their ratio (GAA site/Finokalia) being higher than 2 indicating significant contribution from local sources such as road dust and/or constructions as confirmed by Ca 2+ measurements. Chemical speciation data showed that on a yearly basis, ionic and crustal mass 25 represent up to 78% of the gravimetrically determined mass for PM 10 samples in GAA. The unidentified mass might be attributed to organic carbon (OC) and elemental carbon (EC), in agreement with the results reported by earlier studies in central Athens. The contribution of local sources at both GAA sites was also estimated by considering mass and chemical composition measurements at Finokalia as representative of the regional background. …