Exposure Frequency Distributions from Multiple Instantaneous Cloud Sources

Abstract

The problem analyzed is the release of polluting material into a turbulent atmosphere from a multitude of known sources dispersed in time and space. Each source produces a cloud instantaneously. Mathematical procedures are derived for the purpose of computing the time development of the frequency distribution of the exposure (dosage, ct product) at a specified point in the field. The scale of the source and point configuration is meant to be comparable to that of the turbulence. Both free-air exposures and exposures behind a barrier are discussed. Individual clouds are assumed to have Gaussian mass distributions and deterministic developments. But cloud center movements are treated by statistical means, and covariances between clouds are taken into account. A homogeneous turbulence field is assumed, and the turbulence frequency distribution is in principle used for cloud travel. Results are presented for some source systems of interest for chemical defence.