The contribution of wood burning and other pollution sources to wintertime organic aerosol levels in two Greek cities

The composition of fine particulate matter (PM) in two major Greek cities (Athens and Patras) was measured during two wintertime campaigns, one conducted in 2013 and the other in 2012. A major goal of this study is to quantify the sources of organic aerosol (OA) and especially residential wood burning, which has dramatically increased due to the Greek financial crisis. A high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) was deployed at both sites. PM with diameter less than 1 mu m (PM1) consisted mainly of organics (60-75 %), black carbon (5-20 %), and inorganic salts (around 20 %) in both Patras and Athens. In Patras, during evening hours, PM1 concentrations were as high as 100 mu g m(-3), of which 85% was OA. In Athens, the maximum hourly value observed during nighttime was 140 mu g m(-3), of which 120 mu g m(-3) was OA. Forty to 60% of the average OA was due to biomass burning for both cities, while the remaining mass originated from traffic (12-17 %), cooking (12-16 %), and long-range transport (18-24 %). The contribution of residential wood burning was even higher (80-90 %) during the nighttime peak concentration periods, and less than 10% during daytime. Cooking OA contributed up to 75% during mealtime hours in Patras, while traffic-related OA was responsible for 60-70% of the OA during the morning rush hour.