Detection of spatial correlations among aerosol particles

Most approaches for evaluating rates of fundamental processes in aerosol science depend upon the implicit assumption that aerosol particles are independently and identically distributed in space. The validity of this assumption has not been examined in several decades, despite the fact that the presence of correlations can be shown to alter theoretical expressions significantly for such phenomena as attenuation of electromagnetic radiation and coagulation rate. Here, we provide evidence that the classification of the positions of aerosol particles as a Poisson process-even under stationary conditions-is often in error. In particular, small-scale aerosol clustering is experimentally demonstrated. Some consequences of these findings are discussed.