Characterization of the origin of fine particulate matter in a medium size urban area in the Mediterranean

A multi-stage methodology for investigating particulate pollution is developed and implemented for the case study area of Patras, Greece. Initially a low cost particulate matter mass monitor was used to assess aerosol mass concentrations indicating that the city, despite its small size (population around 200,000) and lack of heavy industry, violates both the daily and annual European Union PM standards. Increased PM10 concentrations were observed during the winter but local vehicular traffic was estimated to account for only 12 ± 4% of the PM10 concentration on an annual basis. In the second stage, PM2.5 chemical composition was measured at the urban center and biomass burning was identified as a major PM source during the colder months. In the third stage, PM2.5 concentration and chemical composition was also followed at a mostly upwind rural site around 40 km from the city. The transported pollution was found to account for 50% of the PM2.5 during winter and for more than 70% during the rest of the year. Almost all of the sulfates and 40–90%, depending on the season, of the organic aerosol are transported to the city from other areas. In the last stage, an intensive campaign took place during winter in order to quantify PM sources during the most polluted period. Nighttime sharp increases of the aerosol levels were observed with organic aerosol levels exceeding 80 μg m−3. Local biomass combustion and fossil fuel emissions for domestic heating were responsible for these levels.