Time resolved measurements of the size distribution of submicron urban aerosol - preliminary results

The determination of the particle size distributions by diffusion batteries requires several different batteries or stages that are normally connected to a single particle counter step by step. In order to determine the particle size distribution from this sequence of data the aerosol has to be stable within this time interval with respect to both: the concentration and the size distribution. To by-pass this drawback a DB condensation nucleus counter system with seven condensation nucleus counters (CNC) in parallel is used. By technical reasons the diffusion batteries have big differences in their residence time distributions (RTD). Broad RTD will cause smoothing of the concentration fluctuations. For that reason the Fast Fourier Transform (FFT) with finite time windows for the decomposition of the time convolved data is employed before size distributions are evaluated. The CNC-array diffusion battery combination together with the deconvolution allows to measure the complete size distr ibution between 0.015 and 1 mym with time resolution of 23 seconds.