## Abstract

This paper follows on from the work of two previous papers that presented a new model [exponential and a generalized Pareto distribution (EGPD)] for the probability density function of the concentration of a contaminant dispersing in the atmosphere. The ideas behind the model are first summarized. It is then shown how the number of independent parameters in the original EGPD model can be reduced from four to three, and a simple physical interpretation of the remaining parameters is postulated. The wide applicability of the new EGPD model for continuous and instantaneous releases under different conditions is illustrated. It is shown that it is superior to the standard distributions that have been previously employed. Finally, some ideas for the behavior of the parameters specifying the model are discussed.

*Corresponding author address:* David M. Lewis, Dept. of Mathematics, City University, Northampton Square, London EC1 0HB United Kingdom.