Characterization of urban aerosols using SEM-microscopy, X-ray analysis and Lidar measurements

We present the results of an extensive study on urban aerosols performed in the summer of 1996 in Lyon. Non-volatile urban particles have been sampled using filters. Size distribution and composition, determined by scanning electronic microscopy (SEM) and X-Ray microanalysis, reveal two main modes at 0.1 and 0.9 μm, the composition of which is soot for the first and 60% in number soot — 40% silica for the second. Mie calculations have been performed using the actual size distribution and composition to determine the optical backscattering and extinction coefficients. The optical characteristics were then used for Lidar measurements. The combined SEM and Lidar techniques allowed to obtain the first quantitative 3D-profiles of urban aerosols concentrations. Potential and limitations of the method are critically discussed.