LONG-TERM MODELING OF AIRBORNE POLLUTION WITHIN THE NORTHERN-HEMISPHERE

A long-term modelling (1991-1994) of oxidised sulphur, bound nitrogen and some heavy metals has been carried out by MSC-E/EMEP for the North ern Hemisphere. The transport unit of the model is an Eulerian scheme which could be classified as Pseudo-Lagrangian one. Vertical distribut ion described by means of Gaussian approximation and the exchange with the free troposphere are taken into account Vertical movement is calc ulated proceeding from local mixing conditions, state of the surface, its height (topography) etc. The chemical unit for acid compounds cont ains 25 reactions and 14 compounds including sulphur and nitrogen comp ounds peroxyacetylnitrate, tropospheric ozone, volatile hydrocarbons ( but methane) are considered as a whole via ozone creation potential. T he model time step is I hour, meteorological data (winds, temperature, precipitation etc.) cover 6-hour intervals. The model results show th at very significant part of the Arctic and West Asian acid pollution i s produced by European countries. On the whole the Arctic pollution by SOx NOx and NHx comes from sources of Old World The main source of su lphur pollution is located in Russia and of nitrogen compound - in Cen tral and Northern Europe. About 50% SOx 70% NOx and 40% NHx deposition in Central Asia and Kazakhstan is-imported from external sources. A s imilar situation is observed in European and Asian parts of Russia.