EVALUATION OF AIRBORNE HEAVY-METAL POLLUTION FROM EUROPEAN SOURCES

An improved MSG-East model for the evaluation of the atmospheric concentration and deposition of heavy metals in Europe and adjoining regions is described. At present, modelling of lead, zinc, arsenic, cadmium and mercury concentrations is carried out within the EMEP grid. At the same time, MSC-East performs model calculations within the whole northern hemisphere to the north of 20 degrees N. Each cell of 150 x 150 km is simultaneously an emitter and receiver. Input data contain meteoinformation and emission data but not measurements. Emissions in a grid cell, with an indication of the country (region) of a specific source, and information on its temporal irregularity are also used. A Eulerian model with total splitting of all processes is used. Its main feature is variable Eulerian time and spatial steps. The steps are chosen so that artificial viscosity is equal to zero and advection velocity is kept constant. An approximation with three reference points is used for the vertical concentration distribution. It is assumed that the position of the boundary layer, the vertical diffusion rate and the dry deposition rate depend on the temperature and the underlying surface state. Exchange with the troposphere and removal from the calculation area are taken into account, so that the balance between emission and deposition is kept. The size distribution of nested particles, chemical transformations and re-emission of mercury are considered. The results of transboundary transport calculations for Europe in 1989-1991 are presented, as are evaluation data on the pollution of the Arctic and Asia from European sources.