IV.7 SULPHUR DIOXIDE
 

IV.7.1 Air pollution caused by sulphur dioxide in the year 2016
 

Air pollution by sulphur dioxide in 2016 in relation to the pollution limit value for protection of human health

In 2016, neither the hourly nor the 24-hour pollution limit value for sulphur dioxide (SO₂) was exceeded at any measuring station (Tab. XIII.18 and XIII.19). Only one hourly and 24-hour SO2 concentration exceeding the limit value of 350 μg.m^-3 or 125 μg.m^-3, resp., was exceeded at the Lom station in the Ústí region. However, the permitted number of 24 or 3 values, respectively, greater than the limit value was not exceeded. Substantial impact from important energy-production and industrial sources located in the mining area under the Krušné Mts. can be expected.

The highest SO₂ concentrations were measured at the Lom (371 μg.m^-3), Nová Víska u Domašína (340 μg.m^-3) and Sokolov (293 μg.m^-3) stations. The limit value was exceeded in a single case at the Lom station on 21 May 2016. The hourly concentration of SO₂ gradually attained values of 217, 371 and 148 μg.m^-3 at 8, 9 and 10 o'clock CEST. This episode was probably the result of the penetration of SO₂ down to the ground after disturbance of the morning inversion and the start of turbulence. Only a light wind was blowing from the south-east, but the effect of industrial sources at Záluží cannot be excluded.

The highest 24-hour concentrations of SO₂ were recorded at the Lom (143 μg.m^-3), Ostrava-Radvanice ZÚ (101 μg.m^-3) and Teplice (90 μg.m^-3) stations. The 24-hour pollution limit value was exceeded at the Lom station on 31 December 2016. On that day, the hourly SO₂ concentration reached its highest value of 180–218 μg.m^-3 at 16–21 hours, while elevated concentrations were measured in the morning of 1 January 2017. Only a light wind was blowing from the eastern sector, from which the effect of industrial sources can be anticipated.

The 25^th highest SO₂ concentration attained the highest values at the following stations: Dolní Rychnov (138 μg.m^-3), Ostrava-Radvanice ZÚ (133 μg.m^-3) and Lom (120 μg.m^-3). The fourth highest 24-hour concentration of SO₂ attained the highest values at the Ostrava-Radvanice ZÚ (82 μg.m^-3), Bohumín (52 μg.m^-3) and Nová Víska u Domašína (38 μg.m^-3) stations.

Over 99.9% of the area of the Czech Republic, the 24-hour concentrations of SO₂ were under the lower assessment threshold (LAT). LAT was attained over only less than 0.1% of the territory. These values were recorded primarily in the Ústí region in the area under the Krušné Mts. mining area, especially in the Most district (Fig. IV.7.1).

In relation to the decrease in the concentrations in 2015 and 2016 compared to previous years, the SO₂ concentrations did not exceed the 24-hour concentrations recommended by WHO for protection of human health over most of the territory of the Czech Republic (63.5%); i.e. in this territory, a 24-hour average concentration of 20 μg.m^-3 was not exceeded in 2016.

 
Air pollution by sulphur dioxide in 2016 in relation to the pollution limit value for protection of ecosystems and vegetation

In 2016, neither the annual nor winter average concentrations exceeded the pollution limit value at rural locations (Tab. XIII.21 and XIII.22). The highest winter average concentrations were recorded at the Věřňovice (12.5 μg.m^-3), Lom (11.8 μg.m^-3) and Krupka (11.3 μg.m^-3) locations. The annual average concentrations attained maximum values at the Krupka (8.7 μg.m^-3), Lom (8.6 μg.m^-3) and Věřňovice (6.8 μg.m^-3) locations.

The upper assessment threshold (UAT) for the annual average SO₂ concentration was exceeded in 2016 over only small areas in the Ústí nad Labem, Karlovy Vary and Moravian-Silesian regions (Fig. IV.7.5). The average concentration in the winter of 2015/2016 exceeded UAT in the same regions and also in the Central Bohemian, Hradec Králové, Pardubice and Zlín regions (Fig. IV.7.6).

All the background stations measuring SO₂, taking into account their classification, were used to construct the two maps (Fig. IV.7.5 and IV.7.6). On the maps, point markers designate only rural stations because only at these locations are the average winter and annual average SO₂ concentrations measured in relation to the pollution limit values for protection of ecosystems and vegetation.

IV.7.2 Trends in sulphur dioxide concentrations

A substantial reduction in SO₂ concentrations occurred after 1998 in connection with coming into effect of Act No. 309/1991 Coll. and compliance with some of the prescribed emission limits. Since then, the annual average concentrations of this substance at rural locations have not exceeded the set pollution limit value of 20 μg.m^-3. A further reduction in SO₂ concentrations occurred over all of the Czech Republic in 2008. On the other hand, there was a slight increase in pollution by SO₂ in 2009 and 2010; however a further decreasing trend is apparent between 2011 and 2016. A decrease in most characteristics compared to the previous year was apparent in 2016 (Fig. IV.7.3).

There was an overall decrease in SO₂ concentrations in 2000–2016 (by approx. 40–50% in dependence on the pollution characteristics – Fig. IV.7.4).

The trend in SO₂ concentrations was caused by a reduction in emissions, sulphur removal in coalfired power plants and a change in the fuel employed (see the emission trends in Chap. II). The different meteorological and dispersion conditions in the individual years also had an impact on the inter-annual variations in the concentrations of this substance in the individual years.

Trends in the sulphur dioxide concentrations in relation to the pollution limit values for protection of health

Since 2005, a decreasing trend has been apparent in the 4^th highest 24-hour and 25^th highest hourly SO₂ concentrations at selected locations (Fig. IV.7.2). Compared to 2015, there was a decrease in these values in 2016 at most locations, e.g. at the Krupka, Měděnec, Sněžník and Nová Víska u Domašína stations. On the other hand, the SO₂ concentrations increased at the Sokolov, Milá and Věřňovice stations.

Trends in sulphur dioxide concentrations in relation to the pollution limit values for protection of ecosystems and vegetation

A slow decreasing trend is apparent in the annual and winter average SO₂ concentrations (Fig. IV.7.7 and IV.7.8). Compared to the previous year, the annual SO₂ concentrations decreased in 2016 at almost all the rural locations, e.g. Krupka, Lom and Věřňovice. On the other hand, a slight increase in winter SO₂ concentrations is apparent at most stations, e.g. Věřňovice, Lom and Tušimice. An increase was recorded at the turn of 2016/2017, especially in January and February 2017, in connection with the less favourable meteorological and dispersion conditions.

IV.7.3 Sulphur dioxide emissions

Sulphur dioxide emissions are derived mainly from the combustion of solid fossil fuels containing sulphur. In 2015, on a national scale, 61.2% of SO₂ emissions were derived from sector 1A1a – Public electricity and heat production, while 13.7% were derived from sector 1A4bi – Residential: Stationary (Fig. IV.7.9). SO₂ emissions decreased between 2007 and 2008 in sector 1A1a as a result of the obligation to comply with emission ceilings for LCP sources (Fig. IV.7.10). Another substantial reduction in SO₂ emissions took place after 2012 as a result of preparation of sources for even stricter emissions limits. In relation to the predominant effect of the sector of public energy and heat production, SO₂ emissions are concentrated in the Ústí nad Labem, Moravian-Silesian and Central Bohemian regions, in which the largest production units are located (Fig. IV.7.11).

Tab. XIII.18 Stations with the highest values of the 25^th and maximum hourly concentrations of SO₂

Tab. XIII.19 Stations with the highest numbers of exceedances of the 24-hour limit value of SO₂

Tab. XIII.20 Stations with the highest values of annual average concentrations of SO₂

Tab. XIII.21 Stations with the highest values of annual averages of SO₂ concentrations at rural stations

Tab. XIII.22 Stations with the highest values of winter averages of SO₂ concentrations at rural stations, 2016/2017

 

Fig. IV.7.1 Field of the 4^th highest 24-hour concentration of SO₂, 2016

Fig. IV.7.2 4^th highest 24-hour concentrations and 25^th highest hourly concentrations of SO₂ at selected stations, 2006-2016

Fig. IV.7.3 Trends of SO₂ annual characteristics in the Czech Republic, 2000–2016

Fig. IV.7.4 Trends of selected characteristics of SO₂ (index, year 2000 = 100), 2000–2016

Fig. IV.7.5 Field of annual average concentration of SO₂, 2016

Fig. IV.7.6 Field of average concentration of SO₂ in the winter period 2016/2017

Fig. IV.7.7 Annual average concentrations of SO₂ at selected rural stations, 2006-2016

Fig. IV.7.8 Winter average concentrations of SO₂ at selected rural stations, 2006/2007–2016/2017

Fig. IV.7.9 Total emissions of SO₂ sorted out by NFR sectors, 2015

Fig. IV.7.10 The development of SO₂ total emissions, 2007–2015

Fig. IV.7.11 Sulphur dioxide emission density from 5x5 km squares, 2015