EVALUATION OF AIRBORNE HEAVY-METAL POLLUTION FROM EUROPEAN SOURCES

An improved MSG-East model for the evaluation of the atmospheric conce ntration and deposition of heavy metals in Europe and adjoining region s 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 nort hern hemisphere to the north of 20 degrees N. Each cell of 150 x 150 k m is simultaneously an emitter and receiver. Input data contain meteoi nformation 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 Euleri an model with total splitting of all processes is used. Its main featu re is variable Eulerian time and spatial steps. The steps are chosen s o that artificial viscosity is equal to zero and advection velocity is kept constant. An approximation with three reference points is used f or the vertical concentration distribution. It is assumed that the pos ition of the boundary layer, the vertical diffusion rate and the dry d eposition rate depend on the temperature and the underlying surface st ate. Exchange with the troposphere and removal from the calculation ar ea are taken into account, so that the balance between emission and de position 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 p resented, as are evaluation data on the pollution of the Arctic and As ia from European sources.