Mass and chemical composition of size-segregated aerosols (PM1, PM2.5, PM10) over Athens, Greece: local versus regional sources

摘要

To identify the relative contribution of local versus regional sources ofparticulate matter (PM) in the Greater Athens Area (GAA), simultaneous 24-hmass and chemical composition measurements of size segregated particulatematter (PM, PM and PM) were carried out from September2005 to August 2006 at three locations: one urban (Goudi, Central Athens,"GOU"), one suburban (Lykovrissi, Athens, "LYK") in the GAA and one at aregional background site (Finokalia, Crete, "FKL").The two stations in the GAA exceeded the EU-legislated PM limitvalues, both in terms of annual average (59.0 and 53.6 μg m forLykovrissi and Goudi, respectively) and of 24-h value. High levels ofPM and PM were also found at both locations (23.5 and 18.6 forLykovrissi, while 29.4 and 20.2 μg m for Goudi, respectively).Significant correlations were observed between the same PM fractions at bothGAA sites indicating important spatial homogeneity within GAA. During thewarm season (April to September), the PM ratio between GAA and FKLranged from 1.1 to 1.3. On the other hand this ratio was significantlyhigher (1.6–1.7) during the cold season (October to March) highlightingthe role of long-range transport and local sources during the warm and coldseasons respectively. Regarding the coarse fraction no seasonal trend wasobserved for both GAA sites with their ratio (GAA site/FKL) being higherthan 2 indicating significant contribution from local sources such as soiland/or road dust.Chemical speciation data showed that on a yearly basis, ionic and crustalmass represent up to 67–70% of the gravimetrically determined mass forPM samples in the GAA and 67% for PM samples in LYK. Theunidentified mass might be attributed to organic matter (OM) and elementalcarbon (EC), in agreement with the results reported by earlier studies incentral Athens. At all sites, similar seasonal patterns were observed fornss-SO, a secondary compound, indicating significantcontribution from regional sources in agreement with PM observations.The contribution of local sources at both GAA sites was also estimated byconsidering mass and chemical composition measurements at Finokalia asrepresentative of the regional background. Particulate Organic Matter (POM)and EC, seemed to be the main contributor of the local PM mass within theGAA (up to 62% in PM. Dust from local sources contributed alsosignificantly to the local PM mass (up to 33%).