Abstract
Aerosol samples were collected by filtration at a number of urban and rural sites in Europe over the period 1993 96, and particulate black carbon and organic C concentrations were determined. Results showed that the carbonaceous matter concentrations were highest in the urban areas and lowest at the remote site at Mace Head, Ireland. An increased formation of secondary organic C was observed in summer in the different environments. The increase in the minimum organic C/black C ratio from 1.1 in the large urban areas to 1.5 in the rural areas was attributed to the consistent presence of long-range-transported aerosol containing some secondary organic C in non-urban areas. The amounts of secondary organic C were significantly higher during periods with meteorological conditions favorable to the occurrence of photochemical activity.