Sources and atmospheric processing of organic aerosol in the Mediterranean: insights from aerosol mass spectrometer factor analysis

Atmospheric particles were measured in the late winter (25 February-26 March 2009) at a remote coastal site on the island of Crete, Greece during the Finokalia Aerosol Measurement Experiment-2009. A quadrupole aerosol mass spectrometer (Q-AMS) was employed to quantify the size-resolved chemical composition of non-refractory submicron aerosol, and a thermodenuder was used to analyze the organic aerosol (OA) volatility. Complementary measurements included particle size distributions from a scanning mobility particle sizer, inorganic and organic particle composition from filter analysis, air ion concentrations, O-3, NOx and NOy concentrations, and meteorological measurements. Factor analysis was performed on the OA mass spectra, and the variability in OA composition could best be explained with three OA components. The oxygenated organic aerosol (OOA) was similar in composition and volatility to the summertime OA previously measured at this site and may represent an effective endpoint in particle-phase oxidation of organics. The two other OA components, one associated with amines (Amine-OA) and the other probably associated with the burning of olive branches (OB-OA), had very low volatility but were less oxygenated. Hydrocarbon-like organic aerosol (HOA) was not detected. The absence of OB-OA and Amine-OA in the summer data may be due to lower emissions and/or photochemical conversion of these components to OOA.