A review of the work of the Atmospheric Dispersion Modelling Working Group

An outline review is presented of the Group's first four reports. The first was confined to the dispersion of short and continuous releases in the range from 100 metres to a few tens of kilometres downwind for activity which does not deposit on to the ground. The second describes procedures for including dry and wet deposition processes in the models given in the first report. The third and fourth describe models for calculating activity concentrations in air and deposition rates at long range (about one hundred to a few thousand kilometres from the source) from either a continuous or a short release. As future work the Group is considering methods of selecting appropriate values for deposition velocity and washout coefficient, models for the entrainment of effluent around buildings from sources close to a building, and dispersion at a coastal site. Models for plume rise from both an isolated source and a source in a building wake, dispersion in complex terrain, and dispersion of material which fails under gravity are being considered at a lower priority. (U.K.)