II.4.2.2 Air quality with regard to the limit values for the protection of ecosystems and vegetation

In addition to the limit values for the protection of health the national legislation introduced, in compliance with EU Directives, also the limit values for the protection of ecosystems and vegetation. The survey of the limits is presented Chapter II.3.

II.4.2.2.1 Sulphur dioxide
The results of SO₂ air pollution monitoring with regard to the limit value for the protection of ecosystems and vegetation are shown in the Tables II.4.2.21 and II.4.2.22 and in Figs. II.4.2.47 and II.4.2.48. None of the total number of 48 stations, classified as rural, reported the exceedance of the limit value for annual average concentration. Due to very mild winter there were no exceedances of the limit value for the 2007/2008 winter average concentration at any of these stations (Table II.4.2.22).

Fig. II.4.2.48 demonstrates the significant improvement of air quality with regard to sulphur dioxide after 1997 in connection with coming into force of the Act No. 309/1991 Coll. and meeting the set emission limit values by the end of 1998. Since then the annual averages of SO₂ have not exceeded the set limit value 20 μg.m^-3 at rural stations. In 2007 there was further significant increase of air pollution caused by SO₂ on the whole territory of the Czech Republic due to favourable meteorological and dispersion conditions. In the winter period 2007/2008, due to favourable dispersion conditions, air pollution caused by SO₂ decreased at most stations as compared with the previous period of 2006/2007. In the localities of the Ústí nad Labem and Moravian-Silesian regions the level of air pollution was roughly comparable (Fig. II.4.2.48).

The maps in Figs. II.4.2.49 and II.4.2.50 also evidently show that rural localities did not exceed the limit value both for the 2007 annual average concentrations and for the winter average concentration in the winter period 2007/2008. The limit value (20 μg.m^-3) was exceeded only in a few small areas in the districts Most and Teplice. The maps were constructed from the data of all the stations measuring SO₂ with the significance (weight) according to their classification; only rural stations are marked with spot symbols.
This chapter is closed by the graphs of courses of 24-hour SO₂ concentrations at selected stations, related to the limit value for the winter and annual averages (Figs. II.4.2.51 and II.4.2.52).

Tab. II.4.2.21 Stations with the highest values of annual average concentrations at rural stations, SO₂

Tab. II.4.2.22 Stations with the highest values of winter averages of SO₂ concentrations at rural stations, 2006/2007

Fig. II.4.2.47 Annual average concentrations of SO₂ in 1996–2007 at selected rural stations


Fig. II.4.2.48 Winter average concentrations of SO₂ in 1996/1997–2007/2008 at selected rural stations


Fig. II.4.2.49 Field of annual average concentration of SO₂ in 2007


Fig. II.4.2.50 Field of average concentration of SO₂ in the winter period 2007/2008


Fig. II.4.2.51 24-hour concentrations at the stations with the highest annual concentrations of SO₂ in 2007


Fig. II.4.2.52 24-hour concentrations at the stations with the highest winter concentrations of SO₂ in the winter period 2007/2008

II.4.2.2.2 Nitrogen oxides
Table II.4.2.23 and Figs. II.4.2.53–II.4.2.54 present the situation of ambient air pollution caused by NO_x with regard to ecosystems and vegetation protection. In 2007 the NO_x air pollution limit value for annual average concentrations (30 μg.m^-3) was not exceeded in any locality classified as rural. Both the table and the map for NO_x include also the rural stations measuring NO₂, as for the rural stations NO_x concentrations correspond approximately to NO₂ concentrations, in other words, the difference between both concentrations is negligible.

In 2007 annual average NO_x concentrations decreased at most rural stations (Fig. II.4.2.53). As it is evident from the map in Fig. II.4.2.54, rural localities did not record the exceedance of the NO_x concentration limit value for the protection of ecosystems and vegetation in 2007.

The construction of the map of the spatial distribution of annual average NO_x concentrations is based on the combination of measurement and modelling results and also national traffic census from the year 2005 was regarded; as compared with the previous census in 2000 the increase of traffic is significant. The higher NO_x concentrations can occur also in the vicinity of local communications in the villages with intensive traffic and dense local transport network, where there is no measurement of concentrations. For the construction of the map of the field of NO_x concentrations all stations measuring NO_x were used, including the rural stations measuring NO₂. The spot symbols highlight only the rural stations.

This chapter is closed by the graphs of courses of 24-hour NO_x concentrations at selected stations, related to the limit value for the annual average (Fig. II.4.2.55).

Tab. II.4.2.23 Stations with the highest values of annual average concentrations at rural stations, NO_x and NO₂

Fig. II.4.2.53 Annual average concentrations of NO_x and NO₂ in 1996–2007 at selected stations


Fig. II.4.2.54 Field of annual average concentration of NO_x in 2007


Fig. II.4.2.55 24-hour concentrations at the stations with the highest annual concentrations of NO_x in 2007

II.4.2.2.3 Ground-level ozone
For the assessment of vegetation protection against ozone exceedances the national legislation uses, in compliance with the respective EU Directive, the exposure index AOT40 . The survey of stations with the highest values of AOT40 is given in Table II.4.2.24.

Of the total number of 36 rural and suburban stations for which the AOT40 calculation is relevant according to the legislation, the target value for ozone for the protection of vegetation was exceeded at 32 localities in 2007 (the average for the years 2003–2007).

As compared with the previous assessment for the period 2002–2006, the situation has not markedly changed. The temperature for the period from which the AOT40 exposure index is calculated (May–July 2007) was by 0.3 �C lower than that in the year 2002, which has been already excluded from the five-year assessment. The most significant decrease of AOT40 values was recorded on the territory of the Hradec Králové and Pardubice Regions (localities Hr. Králové-observatoř and Svratouch), which reached below the target limit value. As for the measured concentrations in the localities, it can be stated that the number of the localities with the increase of the AOT40 exposure index was slightly higher than the number of localities with its decrease.

The spatial distribution of AOT40 exposure index for the 2007 assessment is shown in the map in Fig. II.4.2.57. Fig. II.4.2.58 presents the AOT40 development in 2003–2007 in selected stations.

Tab. II.4.2.24 Stations with the highest AOT40 values of ozone at rural and suburban stations

Fig. II.4.2.56 Exposure index AOT40 values of ozone in 1996–2007 at selected stations, average for 5 years


Fig. II.4.2.57 Field of exposure index AOT40 values, average for 5 years, 2003–2007


Fig. II.4.2.58 Stations with the highest exposure index AOT40 values in recent 5 years, 2003–2007