Size distribution of organic components in aerosol in downtown Rome

It is definitively demonstrated that the main fraction of organic components of aerosols are belonging to the fine fraction of particles, i.e. those comprised between 0.01 and 2.5 pm of diameter (Ventakaraman et a1.,1994,). This is especially true for toxic species, and also consistent with the finding that the most of organic particulates are released by combustion processes, which usually emit fine and ultrafine black carbon on which organic are easily adsorbed. Fine particles are the most interacting between all with bronchioli and alveoli of lungs, therefore a synergism is developped of both physical and chemical mechanisms affecting human health. Till nowadays, the most of investigations about the size distribution of particulate organics were focussed on polynuclear aromatic hydrocarbons and n-alkanes. The results of a more extensive field experiment performed in downtown Rome are here presented. In particular, nitrated-PAH and n carboxylic acids were also evaluated and both fine (below 2.5 urn), coarse (up to 10.2 pm), particles were investigated.