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

Abstract

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 SO ₂ 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 SO ₂ 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 SO ₂ in the overground air layer would be in the ranges 25–450 μg/m³ depending on emission intensity and wind parameters. The annual mean concentrations are below 25 μg/m³ on the main territory, but may be up to 50–75 μg/m³ near the power plants. In Kohtla-Järve town the annual mean values of 15.8–19.1 μg/m³ and MC values of 271–442 μg/m³ 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/m² 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.