ULTRAFINE AEROSOL-PARTICLES IN AIRCRAFT PLUMES - ANALYSIS OF GROWTH MECHANISMS

An analysis of in situ measurements of ultrafine volatile aerosols in the plume near field of the DLR aircraft ATTAS using low (0.02g/kg) an d high (2.7g/kg) fuel sulfur contents (FSCs) is presented. The observe d growth of nanoparticles (diameter 5 - 10 nm) is reproduced in detail by a microphysical simulation with chemi-ion emissions of 2.6 x 10(17 )/kg fuel. Volatile aerosol dynamics is controlled by sulfuric acid (H 2SO4) for high FSC, consistent with a S to H2SO4 conversion of 1.8 %. The very high conversion for low FSC (55 %) prescribed in the model to match the observations contradicts direct in situ measurements of H2S O4 and suggests that species other than H2SO4, likely exhaust hydrocar bons, control particle growth in such cases.