Pollution sources and spreading of sulphur dioxide in the North-Eastern Estonia

The greatest sources of atmospheric emissions of SO2 in Estonia are caused by power plants (TP) which use oil shale. Since 1990 the amount of SO2 discharges has continuously decreased due to fall in production of electric energy, and it was from TP as follows: in 1990-1991 about 180-200 thousand tons, in 1992 about 140 and in 1993-1994 about 100 thousand tons. In 1990 the annual mean emission intensity of SO2 from all North-East (NE) Estonian pollution sources was fixed to be about 6 kg/s, with a maximum of 9.5-11 kg/s in winter period. In 1992-1993 the corresponding values were 3.5-4.6 and 5.1-6.8 kg/s. The single maximum concentrations (MC, per 30 min) of SO2 in the overground air layer would be in the ranges 25-450 mu g/m(3) depending on emission intensity and wind parameters. The annual mean concentrations are below 25 mu g/m(3) on the main territory, but may be up to 50-75 mu g/m(3) near the power plants. In Kohtla-Jarve town the annual mean values of 15.8-19.1 mu g/m(3) and MC values of 271-442 mu g/m(3) were fixed during 1991-1994 by automatic air monitoring system. Many arable lands, forest areas and wild-life preserves are subjected to relatively high sulphur precipitation loads, exceeding 0.5 g S/m(2) per year, of which the role of emissions from local sources is about 60-95% On the basis of air pollution concentration maps, the landscape of NE Estonia is classified into zones of high, moderate and low pollution level.