Abstract
Abstract. Submicron aerosol chemical composition was studied during a year-long period (26 July 2016–31 July 2017) and two wintertime intensive campaigns (18 December 2013–21 February 2014 and 23 December 2015–17 February 2016), at a central site in Athens, Greece, using an Aerosol Chemical Speciation Monitor (ACSM). Concurrent measurements included a particle-into-liquid sampler (PILS-IC), a scanning mobility particle sizer (SMPS), an AE-33 Aethalometer, and ion chromatography analysis on 24 or 12 h filter samples. The aim of the study was to characterize the seasonal variability of the main submicron aerosol constituents and decipher the sources of organic aerosol (OA). Organics were found to contribute almost half of the submicron mass, with 30 min resolution concentrations during wintertime reaching up to 200 µg m−3. During winter (all three campaigns combined), primary sources contributed about 33 % of the organic fraction, and comprised biomass burning (10 %), fossil fuel combustion (13 %), and cooking (10 %), while the remaining 67 % was attributed to secondary aerosol. The semi-volatile component of the oxidized organic aerosol (SV-OOA; 22 %) was found to be clearly linked to combustion sources, in particular biomass burning; part of the very oxidized, low-volatility component (LV-OOA; 44 %) could also be attributed to the oxidation of emissions from these primary combustion sources. These results, based on the combined contribution of biomass burning organic aerosol (BBOA) and SV-OOA, indicate the importance of increased biomass burning in the urban environment of Athens as a result of the economic recession. During summer, when concentrations of fine aerosols are considerably lower, more than 80 % of the organic fraction is attributed to secondary aerosol (SV-OOA 31 % and LV-OOA 53 %). In contrast to winter, SV-OOA appears to result from a well-mixed type of aerosol that is linked to fast photochemical processes and the oxidation of primary traffic and biogenic emissions. Finally, LV-OOA presents a more regional character in summer, owing to the oxidation of OA over the period of a few days.
Highlights
Exposure to fine particulate matter is recognized as a leading cause of premature mortality in Europe
In this study we present, for the first time, long-term results regarding the sources of submicron organic aerosol (OA) in Athens from high temporal-resolution measurements during a year-long period, complemented by two intensive winter campaigns
The Aerosol Chemical Speciation Monitor (ACSM) operates following a similar principle to the aerosol mass spectrometer (AMS) (Jayne et al, 2000) where ambient air is drawn through a critical orifice to a particle focusing aerodynamic lens; the resulting particle beam is flash-vaporized at 600 ◦C, ionized via electron impact ionization, and guided through a quadrupole mass spectrometer
Summary
Exposure to fine particulate matter is recognized as a leading cause of premature mortality in Europe. Organic carbon (OC) is among the key PM components that record the strongest associations with short-term mortality (Ito et al, 2011; Klemm et al, 2011). Stavroulas et al.: Submicron organic aerosol composition in an urban Mediterranean environment (Athens). In view of the health significance of fine aerosols, the characterization of their chemical properties and short-term variability is critical, especially at the urban background level which is more relevant for average population exposure. While the majority of transformations related to particulate sulfate and nitrate have been well described, there is much progress to be made regarding the understanding of mechanisms that govern secondary organic aerosol (SOA) formation from precursors
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