Abstract
Abstract. To identify the relative contribution of local versus regional sources of particulate matter (PM) in the Greater Athens Area (GAA), simultaneous 24-h mass and chemical composition measurements of size segregated particulate matter (PM1, PM2.5 and PM10) were carried out from September 2005 to August 2006 at three locations: one urban (Goudi, Central Athens, "GOU"), one suburban (Lykovrissi, Athens, "LYK") in the GAA and one at a regional background site (Finokalia, Crete, "FKL"). The two stations in the GAA exceeded the EU-legislated PM10 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. High levels of PM2.5 and PM1 were also found at both 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 the same PM fractions at both GAA sites indicating important spatial homogeneity within GAA. During the warm season (April to September), the PM1 ratio between GAA and FKL ranged from 1.1 to 1.3. On the other hand this ratio was significantly higher (1.6–1.7) during the cold season (October to March) highlighting the role of long-range transport and local sources during the warm and cold seasons respectively. Regarding the coarse fraction no seasonal trend was observed for both GAA sites with their ratio (GAA site/FKL) being higher than 2 indicating significant contribution from local sources such as soil and/or road dust. Chemical speciation data showed that on a yearly basis, ionic and crustal mass represent up to 67–70% of the gravimetrically determined mass for PM10 samples in the GAA and 67% for PM1 samples in LYK. The unidentified mass might be attributed to organic matter (OM) and elemental carbon (EC), in agreement with the results reported by earlier studies in central Athens. At all sites, similar seasonal patterns were observed for nss-SO42−, a secondary compound, indicating significant contribution from regional sources in agreement with PM1 observations. 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. Particulate Organic Matter (POM) and EC, seemed to be the main contributor of the local PM mass within the GAA (up to 62% in PM1. Dust from local sources contributed also significantly to the local PM10 mass (up to 33%).
Highlights
The interest on aerosols has widely increased the last years due to their impact on air quality, human health and climate change
The unidentified mass might be attributed to organic matter (OM) and elemental carbon (EC), in agreement with the results reported by earlier studies in central Athens
They are calculated from back trajectory analysis every 12 h, with the Hysplit Dispersion Model (Hybrid Single – Particle Lagrangian Integrated Trajectory; Draxler and Hess, 1998) using the location of air parcels 24 h before arrival at each site during the whole sampling period 2005–2006
Summary
The interest on aerosols has widely increased the last years due to their impact on air quality, human health and climate change. The 2008/50/EC directive enacted a yearly limit value for PM10 of 40 μg m−3 and a maximum authorized 24-h mean value of 50 μg m−3 that cannot be exceeded more than 35 days in a calendar year To propose such a strategy precise knowledge of PM sources is a prerequisite. Natural sources for the assessment of PM-related air quality, since EU recognizes the weakness of individual countries in reducing PM levels that are maintained by long range transport To address these critical issues for the GAA, mass and chemical composition of size segregated aerosols simultaneously collected at 3 locations, were analyzed: two sites in Athens, representing the urban and suburban environment (GOU; LYK) and a remote background site (FKL) for which previous studies (Mihalopoulos et al, 1997; Gerasopoulos et al, 2007; Koulouri et al, 2008b) documented its ability to represent the Eastern Mediterranean regional background. FKL is situated 70 km northeast of Heraklion, the site characteristics and the prevailing meteorology
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