Carbonaceous aerosol in urban and rural European atmospheres: estimation of secondary organic carbon concentrations

Aerosol samples from urban, rural and coastal areas in Europe were analysed for carbonaceous content by a thermaloptical transmission method. The fraction of particulate organic carbon with a secondary origin in gas/particle conversion of volatile organic compounds was estimated from the minimum ratio between particulate organic and black carbon, which occurred during periods of reduced photochemical activity. Values calculated by this method ranged from a minimum of 17%, in Birmingham, UK, during winter, to a maximum of 78% at a rural coastal area, in Portugal, with air masses transported directly from the ocean. A clear seasonal dependence was observed at both rural and urban environments, with minimum secondary organic carbon production during winter.