MODELLING CHEMICAL TRANSFORMATION AND LONG-RANGE TRANSPORT OF POLLUTANTS IN SOUTHERN AFRICA

The paper presents the results of a long-range atmospheric model developed specifically for Southern African conditions. The model utilizes a combined Lagrangian-Eulerian Diffusion (LED) description of the transport and turbulent diffusion of pollutants and incorporates a description of the chemical transformations, dry and wet deposition as well as acidity of precipitation. A unique feature of the model is the use of atmospheric boundary layer dynamics to account for the major role it plays in the turbulent diffusion process. The validation of the modelled results with experimental data from the DEBITS (Deposition of Biogeochemically Important Trace Species) programme confirms its reliability and usefulness in the quantification of ambient gaseous concentrations of SO2 and NO2, as well as dry and wet deposition of S and N over Southern Africa. Country-to-country deposition matrix for the Southern African region is presented for the year 2000 based on results obtained from the LED model. The presented data lays the foundation for the development of integrated regional air quality management plans. The implementation of such a management plan will be obviously beneficial to all countries in the region.