On the use of one-particle models in the calculation of two-particle statistics of turbulent diffusion

Two-particle statistics of turbulent diffusion, such as mean separation between particles, variance of concentration fluctuations, are important in predicting peak concentrations and short-term exposures. However, two-particle models are less developed than one-particle models, it is therefore very useful from the viewpoint of pratical applications to calculate two-particle statistics with the help of one-particle models. This short paper examines some previous works and offers an alternative of using one-particle models in the attempt of estimating two-particle statistics.