In order to know the variability and to understand the sources of carbonaceous aerosol in the Central Mediterranean area, a two month (May and June 2010) field campaign was carried out at Trisaia ENEA Research Centre (Italy). The semi-continuous measurements of organic carbon (OC) and elemental carbon (EC) showed one order of magnitude variation during the campaign, with very low EC concentrations. The diurnal variation of EC was similar to the diurnal variation of NO2 concentration, of number concentration of aerosol particles with diameters between 0.25 and 2.5 mu m and of traffic flow while the diurnal variation of OC was more related to the meteorological conditions. The increase of OC observed early in the morning may be due to an increase of the secondary organic aerosol (SOA) fraction, in low wind conditions, increasing solar radiation and in the presence of air masses rich in volatile organic compounds (VOC) transported from the NW, and due to the presence of primary biological aerosol particles such as bacteria, spores and pollen. (C) 2012 Elsevier Ltd. All rights reserved.