II.4.1 Agglomerations

With regard to the Communication of the Air Quality Protection Division of the Ministry of Environment on delineating zones and agglomerations within the territory of the Czech Republic, air quality assessment in the proposed agglomerations (Prague, Brno and the Moravian-Silesian Region) has been treated with more attention since 2005. In addition to the above agglomerations, special attention is paid in this Yearbook also to the zone Ústí nad Labem Region due to the concentration of industrial plants, higher population density and also due to the recorded above-the-limit concentrations of some pollutants.

II.4.1.1 Prague

The Capital City of Prague is the area in which a lot of people are exposed to ambient air pollution. Most of the limit values and target values exceedances are connected with significant traffic loads ensuing from the fact that the main routes lead directly through the city centre.

In 2010 the concentrations of suspended particles of PM₁₀ fraction were monitored in Prague in 15 CHMI localities and in 7 ZÚ localities. The 24-hour PM₁₀ limit value (the value 50 μg.m^-3 must not be exceeded more than 35x in one year) was exceeded in 10 of 17 localities (in the localities with sufficient number of data for the assessment), i.e. in 59 % of localities; in two localities the number of tolerated exceedances was reached, and in the remaining five localities the number of exceedances of the limit value was lower than 35 (Table II.4.2.4). The majority of localities, in which the limit value was exceeded in 2010, are characterized as traffic. In several cases the limit value was exceeded also in the localities defined as background suburban (e.g. Prague 6-Suchdol, Prague 4-Libuš). In 2010 there were unfavourable dispersion conditions, similarly as in 2005 and 2006, i.e. in the years when the latest exceedance of the limit value was recorded in these localities (Fig. II.4.1.1). The more frequent exceedances of the 24-hour limit value in 2010 in comparison with the years 2007–2009 is documented also by higher share of localities (Fig. II.4.1.2) which exceeded the tolerated number of exceedances¹.

The annual PM₁₀ limit value (40 μg.m^-3) was exceeded in one locality of 21, and namely in the locality Prague 5-Svornosti. Within the long-term evaluation since 2000 the annual PM₁₀ concentration has been decreasing, both in traffic localities and background localities. The 2009/2010 year-to-year comparison, however, shows that there was a slight increase of PM₁₀ concentrations in both types of localities (Fig. II.4.1.3).

The concentrations of pollutants show the marked course during the year, and namely due to various meteorological and dispersion conditions and the seasonal character of some emission sources.

In average for all selected localities, the highest PM₁₀ concentration was reached in February (43 μg.m^-3), the lowest in May (20 μg.m^-3). The highest average monthly concentration of PM₁₀ (58 μg.m^-3) and the highest number of exceedances (16x) of the 24-hour limit value (50 μg.m^-3) were reached in February in the locality Prague 5-Smíchov. The highest average monthly concentration of PM_2.5 (36 μg.m^-3) was recorded in the locality Prague 10-Šrobárova in January. In the average for the selected localities the monthly PM_2.5 concentrations ranged between 30 μg.m^-3 in December and 15 μg.m^-3 in May.
As a rule, the highest concentrations of PM₁₀ and PM 2.5 particles and the highest number of 24-hour limit value of PM₁₀ are reached in the cold period of the year due to the higher emissions caused both by higher intensity of heating and less favourable conditions for the dispersion of pollutants in the ambient air. In 2010 – in addition to the mentioned maxima in February, when especially in the first half of the month there were unfavourable dispersion conditions –the increased concentrations were recorded also in October, due to unfavourable dispersion conditions (Figs. II.4.1.4 and II.4.1.5).

The concentrations of PM_2.5 particles were measured in 5 CHMI localities and in 1 ZÚ locality in 2010. The level of the annual target value for PM_2.5 is 25 μg.m^-3 (the Government Order No. 42/2011 Coll. amending the Government Order No. 597/2006 Coll. on air quality monitoring and assessment). Similarly as in the previous years the valid target value was not exceeded in the territory of the Prague agglomeration (Fig. II.4.1.6). There were two exceptions, and namely the year 2005 when the target value way exceeded at one traffic locality, and the year 2006 when the exceedances occurred at two traffic localities. In 2010 the highest annual average concentration (21.1 μg.m^-3) was recorded in the locality Prague 5-Mlynářka.

NO₂ concentrations were measured in 20 localities in Prague in 2010. The hourly limit value of NO₂ (200 μg.m^-3) was exceeded only in one of 15 localities (the localities with sufficient number of data for the assessment). The value 200 μg.m^-3 was exceeded in the locality Prague 2-Legerova 56x. (Table II.4.2.8).The tolerated number of exceedances is 18. The highest 19^th hourly concentration at this locality reached 231 μg.m^-3. As concerns other localities, no exceedances of the hourly NO₂ concentration were recorded in 2010.

The annual air pollution limit value for NO₂ (40 μg.m^-3) was exceeded in 5 of 20 localities in the Prague agglomeration (Table II.4.2.9), and namely in the localities Prague 2-Legerova (the annual average concentration reached the value of 67 μg.m^-3), Prague 5-Svornosti (59 μg.m^-3), Prague 5-Smíchov (45 μg.m^-3, Prague 9-Vysočany (43 μg.m^-3) and Prague 1-nám. Republiky (41 μg.m^-3).
Generally, it can be stated, that NO₂ concentrations in the territory of the Prague agglomeration increased in most localities. It can be expected that the exceedance of the limit values can occur also in other localities exposed to traffic, where there are no measurements.

The average monthly NO₂ concentrations in selected localities in Prague show similar courses as the concentrations of other pollutants. – i.e. higher concentrations were recorded during the winter period. Moreover, in NO₂ there is an apparent increase of concentrations in February and October. There is a separate locality within the Prague agglomeration, and namely Prague 2-Legerova (hot spot); the NO₂ concentrations in this locality are above the limit value in the whole annual course. Then there is the ZÚ station Prague 5-Smíchov which is also situated in the immediate vicinity of the communication and which shows high loads by suspended particles as well. It is followed by the group of localities classified as traffic (with the exception of Prague 1-nám. Republiky) with similar courses of the levels ranging around the limit value ((Prague 9-Vysočany, Prague 1-nám. Republiky, Prague 8-Karlín, Prague 10-Průmyslová and Prague 8-Sokolovská).

The remaining two localities (Prague 2-Riegrovy sady and Prague 4-Libuš) represent the urban background where the influence of traffic is not as high and the measured concentrations are below the limit value for the most part of the year (Fig. II.4.1.7).

Another problem is caused by benzo(a)pyrene concentrations which in 2010 exceeded the target value in one of two localities in which this pollutant is measured in Prague (Prague 10-Šrobárova). The year-to-year comparison did not changed markedly – the benzo(a)pyrene concentrations decreased in the locality Prague 10-Šrobárova and they increased in the locality Prague 4-Libuš. The long term course of benzo(a)pyrene concentrations in the localities in the Prague agglomeration is depicted in Fig. II.4.1.8. The concentrations of benzo(a)pyrene show, similarly as the above mentioned pollutants, the marked annual courses with the maxima in the winter period (due to the seasonal sources, worse dispersion conditions and easier gas-particles conversion) and with the minima in the summer period (due to the end of heating season and chemical and photochemical disintegration of benzo(a)pyrene. Benzo(a)pyrene concentrations showed also the increased values in October 2010 when in Prague (and other areas of the Czech Republic) there occurred unfavourable dispersion conditions (Fig. II.4.1.9).

The results of the measured concentrations of PM₁₀, NO₂ and benzo(a)pyrene suggest the serious need to find the solution for the traffic situation within the agglomeration.

At the locality Prague 5-Řeporyje, where the target value for arsenic was exceeded in 2007 and 2008, the annual average concentration of arsenic decreased below the target value both in 2009 and 2010.

In 2010 (in the average for 3 years 2008–2010) the target value for the ground-level ozone was exceeded relatively closely in the locality Prague 6-Suchdol where the 26^th highest maximum daily 8-hour running average reached 121 μg.m^-3. Further high values, however closely below the limit value, were recorded in the localities Prague 4-Libuš (117 μg.m^-3) and Prague 5-Stodůlky (119 μg.m^-3). In comparison with other pollutants the ground-level ozone shows the inverse course (Fig. II.4.1.10), i.e. ozone concentrations reach the maximum values in the spring (due to the cumulation of precursors in the ambient air) and in summer (due to favourable conditions for the creations of ozone – high intensity of solar radiation and high temperatures, low air humidity or windless conditions).

Fig. II.4.1.1 The number of exceedances of the 24-hour limit value of PM₁₀ in selected localities (the localities with complete data series for the respective years), Prague agglomeration, 2000–2010

Fig. II.4.1.2 The share of localities (with complete data series for the respective years) in the territory of Prague agglomeration with exceedances of the 24-hour limit value of PM₁₀, 2000–2010

Fig. II.4.1.3 The annual average concentrations of PM₁₀ in selected traffic and background localities (the localities with complete data series for the respective years), Prague agglomeration, 2000–2010

Fig. II.4.1.4 The annual course of monthly concentrations of PM₁₀ and the number of exceedances of the 24-hour limit value of PM₁₀, Prague agglomeration, 2010

Fig. II.4.1.5 The annual course of monthly concentrations of PM_2.5, Prague agglomeration, 2010

Fig. II.4.1.6 The annual average concentrations of PM_2.5 in selected localities, Prague agglomeration, 2004–2010

Fig. II.4.1.7 The annual course of monthly concentrations of NO₂, Prague agglomeration, 2010

Fig. II.4.1.8 The annual average concentrations of benzo(a)pyrene, Prague agglomeration, 2000–2010

Fig. II.4.1.9 The annual course of monthly concentrations of benzo(a)pyrene, Prague agglomeration, 2010

Fig. II.4.1.10 The annual course of monthly concentrations of ozone, Prague agglomeration, 2010

Fig. II.4.1.11 Field of the annual concentration of NO₂, Prague agglomeration, 2010

Fig. II.4.1.12 Field of the 36^th highest 24-hour concentration of PM₁₀, Prague agglomeration, 2010

II.4.1.2 Brno

Air pollution monitoring network

In 2010 the Brno agglomeration carried out air quality measurements at 13 stations of air pollution monitoring operated by 3 institutions: Czech Hydrometeorological Institute (air pollution monitoring incl. sampling accredited according to ČSN EN ISO/IEC 17025:2005), the Municipal Council of the city of Brno and the Health Institute in Brno.

The estimate of the size of polluted areas

The 24-hour limit value for PM₁₀ is constantly exceeded in the territory of the Brno agglomeration. The largest area of the agglomeration affected by the increased concentrations was recorded in 2005, the lowest coverage was measured in 2004. The marked increase of the share of the territory with the exceeded 24-hour limit value for PM₁₀ in 2005 and 2006 was caused mainly by meteorological conditions (long cold winter 2005/2006, frequent occurrence of temperature inversions etc.) and the related anthropogenic activities (longer heating season, the necessity of road spreading, cold starting of the cars etc.). Similar situation occurred also in the year 2002. In addition to the 24-hour limit value also the limit value for the average annual PM₁₀ concentration was exceeded in the above mentioned years. In 2010 the limit value for the average annual concentration was exceeded, similarly as in the previous year, only at the traffic station Brno-Svatoplukova. The limit value for 24-hour concentration was exceeded again in all traffic localities, in 2010, however, the limit value was exceeded also at background stations Brno-Tuřany and Brno-Lány. The background locality Brno-Soběšice has not recorded any exceedances.

After two years of under-the-limit concentrations there was exceeded the 24-hour limit value at the background station Brno-Tuřany. This was caused mainly by meteorological conditions right at the beginning of the year resulting in high PM₁₀ concentrations in the cold part of the year and in high number of exceedances (January – 17, February – 11 and December – 14 of the total number of 50). The highest concentrations of PM_2.5 particles, for which the limit value 25 μg.m^-3 is valid in the European legislation, are also measured mainly in traffic localities. If the limit value was valid already in 2010, the exceedance would occur in the traffic localities Brno-Svatoplukova, Brno-Zvonařka and also in the locality Brno-Lány classified as a background locality. The locality Brno-Lány however, is highly influenced by traffic in highway D1 (at 400 m distance), especially as concerns fine particles and nitrogen oxides. Brno-Tuřany with the average annual PM_2.5 concentrations 23.8 μg.m^-3 is the only locality which does not exceed the limit value 25 μg.m^-3. The above facts suggest that the exceedance of the limit values for PM₁₀ in the Brno agglomeration has its most significant contribution in traffic.

In the recent years the limit value for the annual average concentration of NO₂ has also been exceeded in the Brno agglomeration. The limit value exceedances occur regularly at traffic stations. The increased concentrations are contributed by higher intensity of traffic and also by meteorological conditions. In 2010 the localities Brno-střed, Brno-Svatoplukova and Brno-Úvoz (hot spot) exceeded the LV+MT. As for the hourly limit value, most localities in the Brno agglomeration ranged between the lower and upper assessment thresholds in 2010.

Other limit values for SO₂, CO, Pb and benzene are not exceeded in the Brno agglomeration. On the contrary, the concentrations of individual pollutants, except for benzene, do not reach the lower assessment threshold. Therefore the number of selected measurements was limited in the Brno agglomeration, particularly in case of SO₂.

In the territory of the Brno agglomeration the target values for tropospheric ozone and benzo(a)pyrene are also exceeded. The tropospheric ozone concentrations are recorded at the levels close to the target value in the long term in the whole territory of the agglomeration, but the results are not practically different from those in the remaining part of the Czech Republic.

Benzo(a)pyrene is one of the polycyclic aromatic hydrocarbons (PAH), originating mainly by the combustion of solid and liquid fuels. The increased concentrations of benzo(a)pyrene in the Brno agglomeration can thus be expected mainly in the vicinity of the major line sources. At present benzo(a)pyrene is measured in 2 localities in the Brno agglomeration. The station Brno-Masná (background type), situated, however, in the locality strongly influenced by traffic, reached the same value of concentration as in 2009, i.e. 1.2 μg.m^-3, and thus the target value was exceeded. The average annual B(a)P concentration in the locality Brno-Líšeň reached only 0.8 μg.m^-3 in 2010, which is the worse result than in 2009, nevertheless the target value was not exceeded. The dispersion study elaborated for the Municipal Council shows that the most loaded area as concerns benzo(a)pyrene concentrations is situated in the vicinity of the big city circuit in the locality Zvonařka and near the Brno main railway station.

The remaining pollutants with the set target values (heavy metals arsenic, cadmium and nickel) have been reaching the concentrations only below the lower assessment threshold during several latest years.
 

The trend of concentrations of major pollutants in 2010

The pollutants exceeding the limit value or the target value were selected to show more detailed development of the concentrations, and namely PM₁₀ (and PM_2.5) particles, NO₂, benzo(a)pyrene and tropospheric ozone.

In case of the average annual PM₁₀ concentrations individual types of stations in the Brno agglomeration were averaged and compared with the regional background station Mikulov-Sedlec. Fig. II.4.1.13 shows clearly that there is relatively good correlation between the trends of concentrations from background stations and the regional background station, especially in several recent years the measured concentrations have had similar values. The trend of traffic stations differs in some years from the background stations; in the recent years the averaged concentrations at traffic stations are by about 10 μg.m^-3 higher than the concentrations in background localities.

The average monthly PM₁₀ concentrations at individual stations in the Brno agglomeration in 2010 are depicted in Fig. II.4.1.14. In addition to the measured concentrations the figure shows also the sums of monthly precipitation documenting the high concentrations of particles in October 2010. The precipitation at the professional station Brno-Tuřany amounted only to 8.6 mm for the whole October. The combination of these factors influenced the situation in the territory of the Brno agglomeration (but also at the regional background station Mikulov-Sedlec), and namely by increasing the average monthly PM₁₀ concentrations to the level of February or December values (Fig. II.4.1.14). The lack of precipitation prevented the wash out of the dust from ambient air and simultaneously supported the re-suspension of particles. The dispersion study based on the results of the 15-year measuring of dust and meteorological parameters at the station Brno-Tuřany shows that in the period without precipitation (at least 5 days without precipitation) the PM₁₀ concentrations are in average by 6.1 μg.m^-3 higher than the average PM₁₀ concentrations for the whole period.

The highest number of exceedances of the concentration 50 μg.m^-3, occurred in the cold part of the year, and namely in January, February and December. The graph in Fig. II.4.1.15 shows the numbers of exceedances in individual months of the year 2010 at selected stations carrying out air pollution monitoring.

The fine fraction PM_2.5 was measured at 4 stations in the Brno agglomeration in 2010 – 2 traffic and 2 background stations. Both traffic stations would exceed the limit value for the average annual PM_2.5 concentration 25 μg.m^-3. As concerns background localities, the upcoming limit value was exceeded only in the locality Brno-Lány which is influenced by traffic in highway D1 (at 400 m distance) and thus polluted by fine fraction particles and gases. The only locality, and namely Brno-Tuřany, would not exceed the future limit value. The average monthly shares of PM_2.5 in PM₁₀ in the locality Brno-Tuřany in 2010 are depicted in Fig. II.4.1.16. It is apparent that the share of PM_2.5 in PM₁₀ has a slightly convex character. In the locality Brno-Tuřany the share of PM_2.5 in PM₁₀ ranges from 65 % (August) to 90 % (February); the 2010 average of PM_2.5 in PM₁₀ was 78 % which is by about 5 % more than in 2009. This locality, as the only one, uses radiometry (accredited according to ČSN EN ISO/IEC 17025:2005), and moreover, the measurements are carried out by two separate instruments.

The average annual concentrations of NO₂ (Fig. II.4.1.17) are to a certain extent dependent on the locality disposition – traffic localities are exposed to the highest air pollution loads of NO₂ due to emissions from traffic, which in case of NO_x represent about 80 % in the Brno agglomeration. After the averaging of traffic and background localities, incl. the comparison with the regional background locality in Mikulov-Sedlec, the highest loads were confirmed in traffic localities (Fig. II.4.1.17). The graph shows clearly that the background concentrations in Brno are approx. by 10 μg.m^-3 higher than the regional background, air pollution load in the localities exposed to traffic is by another 15–20 μg.m^-3 higher than the background of the Brno agglomeration.

The influence of traffic on NO_x concentrations is clear from the proportion of NO and NO₂ concentrations. The higher the proportion, the higher the traffic load of the locality. As apparent from Fig. II.4.1.18, the locality with the lowest load is the background station Mikulov-Sedlec, followed by the background locality Brno-Tuřany. The low proportion is reached also in the traffic locality Brno-Arboretum which, however is strongly influenced by the local flora. On the contrary, the proportion in further background locality, Brno-Lány, is close to and occasionally higher than the proportion of the traffic locality Brno-střed. In case of the locality Brno-Lány there is probably the influence of the highway D1 (at 400 m distance). The locality with the highest traffic loads is Brno-Svatoplukova situated in the city quarter Židenice, in the immediate vicinity of the big city circuit, partly enclosed in the corridor of buildings of the Vinohrady quarter. This part of the big city circuit often suffers from tailbacks and poor airing. Therefore this is the most polluted locality within the whole Brno agglomeration as concerns the highest NO_x concentrations as well as the highest levels of dust.

Benzo(a)pyrene is measured only in two localities in the Brno agglomeration. The locality Brno-Masná is exposed mainly to traffic loads, the locality Brno-Líšeň represents the background of the city of Brno with low impact of traffic and is partly influenced by small sources. This results in the increase of concentrations of all PAH during the heating season. The average monthly concentrations in the locality Brno-Líšeň are depicted in Fig. II.4.1.19. The figure shows that during the summer season (May–September, without heating) the concentrations of almost all PAH are zero or very low, in spite of the fact that this locality reaches, according to the dispersion study, the local maxima for these substances produced by the incinerator of the SAKO Brno, a.s. company. On the contrary, during the heating season the concentrations are increasing, the highest values are recorded in January and December, i.e. in the months with the lowest temperatures demanding intensive heating; moreover the dispersion conditions are usually most unfavourable in these months.

Tropospheric ozone exceeds the limit value set by the Government Order No. 597/2006 Coll. in the major part of the territory of the Czech Republic. In the Brno agglomeration the coverage is in fact in background localities where the measured concentrations are close to the target value and in most cases this target value is exceeded. On the contrary, the concentrations in traffic localities do not reach the target value. The exceedances occur mainly in summer as there are most suitable conditions for photochemical creation of tropospheric ozone from NO₂ and VOC. These photochemical reactions are influenced by solar radiation (necessary for the reactions). The graph in Fig. II.4.1.20 presents the 26^th highest 8-hour running average concentrations of tropospheric ozone in individual localities of the Brno agglomeration, the comparison with the regional background station in Mikulov-Sedlec. The concentrations of tropospheric ozone are influenced both by meteorological conditions (solar radiation, temperature) and the characteristics of the locality (traffic, background). In 2010 any of the localities, including the regional background locality Mikulov-Sedlec, did not exceed the target value.

Unlike the previous pollutants the highest ozone concentrations are measured in the locality Mikulov-Sedlec; very similar concentrations are measured also in the background locality of the Brno agglomeration (Brno-Tuřany), and the lowest concentrations are measured in traffic localities (Brno-střed and Brno-Zvonařka). These differences are connected with ozone reactivity, i.e. with the amount of possible reactants in the ambient air. Ozone is a very strong oxidation agent which easily reacts with a lot of compounds in the ambient air, incl. the pollutants (as for instance NO emitted by the traffic), and therefore in the localities with the highest pollutants� concentrations ozone is able to react much more intensively (and thus reduce its concentration in the ambient air). This is the reason why the lowest concentrations of tropospheric ozone are measured in traffic localities, and the highest ones, on the contrary, in the localities not much influenced by the pollutants. The locality Brno-Arboretum is classified as the traffic locality, however, it is located in the Botanical garden, enclosed in the greenery, and thus the recorded O₃ concentrations correspond to those at the background localities.

The above facts show that the Brno agglomeration has its delineated areas with deteriorated air quality, mainly due to high traffic intensity. The traffic localities record the exceedances of the limit values for PM₁₀, NO₂ and the target value for benzo(a)pyrene. The draft and the implementation of the measures aimed at the transport system and the line sources should be the priorities for the solution of the problem of ambient air quality in the Brno agglomeration. The background localities situated outside the city centre with traffic loads (Brno-Tuřany, Brno-Soběšice) are influenced to a significant extent also by small sources (household heating) from neighbouring municipalities. Therefore, during longer winters with low temperatures and unfavourable dispersion conditions (inversion) there may occur exceedances of the 24-hour PM₁₀ limit value also in the localities not influenced by traffic (e.g. Brno-Tuřany).

Fig. II.4.1.13 The average annual PM₁₀ concentrations at background and traffic stations, Brno agglomeration, 2002–2010

Fig. II.4.1.14 The relation between average monthly PM₁₀ concentration and the total precipitation in 2010

Fig. II.4.1.15 The numbers of exceedances of 24-hour limit value of PM₁₀ concentration 50 μg.m^-3 in individual months of the year 2010

Fig. II.4.1.16 The average monthly concentrations of PM_2.5 and PM₁₀, PM_2.5/PM₁₀ proportions, Brno-Tuřany, 2010

Fig. II.4.1.17 The average annual NO₂ concentrations at background and traffic stations, Brno agglomeration, 2002–2010

Fig. II.4.1.18 The influence of traffic on NO_x concentrations – NO/NO₂ proportions, Brno agglomeration, 2002–2010

Fig. II.4.1.19 The average monthly PAH concentrations, Brno-Líšeň, 2010

Fig. II.4.1.20 26^th highest of maximum daily 8-hour running average of O₃, Brno agglomeration, 2002–2010

Fig. II.4.1.21 Field of the annual concentration of NO₂, Brno agglomeration, 2010

Fig. II.4.1.22 Field of the 36th highest 24-hour concentration of PM₁₀, Brno agglomeration, 2010

II.4.1.3 The Moravian-Silesian Region

Air pollution in 2010 – northern Moravia and Silesia

In January 2010 continued the unfavourable air pollution situation from December 2009 and culminated in episodes of smog situations with significantly above-the-limit concentrations of suspended particles of PM₁₀ fraction and the announcement of the regulatory signal for the large sources [35] in the Ostrava-Karviná area on 23–27 January and on 9–12 and 17–20 February. The above-the-limit daily values occurred repeatedly also in March 2010. The worst situation was in the Ostrava-Karviná area, but the January episode affected the entire area of northern and central Moravia and Silesia. On 25 January most stations measured the highest maximum daily concentrations of pollutants over several recent years. The air pollution situation deteriorated again at the end of the year 2010. The first episode of above-the-limit PM₁₀ concentrations in the winter season, along with the announcement of the regulatory signal for the sources in the Ostrava-Karviná area, occurred already on 12–14 October, followed by further episodes on 3–6 and 22–26 December.

Concentrations of PM₁₀ with multiple exceedances of the daily limit value 50 μg.m^-3 influenced also the average annual values. After several years with favourable air pollution situation the average annual concentrations increased (Fig. II.4.1.23). The situation was comparable with the years 2005 and 2006. The number of days with above-the-limit daily concentrations of PM₁₀ particles also increased.

In 2010 increased also the annual average concentrations of other pollutants, e.g. SO₂, NO₂, benzene. Most localities of the Ostrava-Karviná area exceeded the annual limit value for PM_2.5 fraction of suspended particles. The above-the-limit benzene concentrations were measured again in the locality Ostrava-Přívoz.
In comparison with the previous years the number of days with the exceedance of the target value of maximum daily 8-hour concentrations of ground-level ozone 120 μg.m^-3 slightly decreased in 2010 at most stations and did not exceed the tolerated 25 days set by legislation.

Smog situation in the Ostrava-Karviná area from 23 to 27 January 2010²

During the last decade of January 2010 there occurred unfavourable dispersion conditions in the whole area of the Moravian-Silesian and Olomouc regions and in the Silesian Voivodeship, connected with the extensive anticyclone with the centre above northern Russia and with low air temperatures. As a result, there created a markedly unfavourable air pollution situation in the Ostrava-Karviná area and in the adjacent part of Poland, during which the 24-hour average concentrations of PM₁₀ exceeded, for several successive days in multiple levels, not only the daily limit value set by [8], but also the alert threshold set by [35]. Consequently, smog situation formed in the whole area on 23–27 January 2010. During the same period the increased concentrations of PM₁₀ suspended particles were recorded also in other areas of the Czech Republic.

At the beginning of the third decade of January the massive anticyclone with the centre above northern Russia stretched from the northeast to central Europe (Fig. II.4.1.24). Along its southwestern edge cold continental air flowed to the territory of the Czech Republic, mainly at lower levels. The whole central Europe had continuous snow cover and the low clouds gradually dissolved and the wind became weaker. Under these conditions there occurred, mainly at lower altitudes further cooling of the air mass, which resulted in a gradual strengthening of temperature inversion.

During the following days the anticyclone above northeastern Europe slightly weakened and its centre moved slowly towards southwest above the Baltic States. Due to the cloudless character of the weather with only weak ground-level air circulation the air temperature at lower altitudes of the Moravian-Silesian Region was decreasing day by day. On 24 and 25 January it ranged mostly between -17 �C and -23 �C, with no significant change in the mountains with most frequent values around -10 �C.

Only during 27 January 2010 the centre of the anticyclone rapidly moved from the central Europe above the British Islands, and later above the eastern part of the Atlantic Ocean. A significant trough of low pressure moved from northwest to central Europe; it was associated with a frontal system which resulted in significant changes in meteorological conditions for dispersion of pollutants in the atmosphere, mainly the strengthening of ground-level atmospheric circulation, and the exchange of air masses (Fig. II.4.1.25). The warm air broke rapidly into the Czech Republic, which was cleaner as regards the content of pollutants, i.e. oceanic air form northeastern parts of the Atlantic.

Figs. II.4.1.26 and II.4.1.27 show air temperatures and wind velocities measured at meteorological stations operated by CHMI and the Polish Instytut Meteorologii i Gospodarki Wodnej (IMGW).

Fig. II. 4.1.28 shows the wind roses calculated from hourly measurements of wind direction at the stations Lysá hora, Mošnov, Raciborz and Katowice from 01:00 CET on 23. 1. to 12:00 CET on 27. 1. with low wind velocities at lowland stations. While in this period the total frequency of wind directions at Lysá hora was NE+E+SE 78 %, Katowice recorded the most frequent directions NE+E (68 %), in Mošnov N+NE (45 %) and calm 34 % , and at the station Raciborz SE+S (39 %), but also W+NW (35 %). It seems that the station Raciborz, unlike Mošnov, is no longer influenced by windward or leeward effect of the Moravian Gate.

The basic picture of the level of air pollution caused by PM₁₀ on the days with smog situation in the Ostrava-Karviná area is given by the available 24-hour concentrations measured at the assessed stations (Table II.4.1.1). By way of illustration, the table shows also the concentrations measured on 22 and 28 January, i.e. on the days before and after the smog situation. The average value of all concentrations presented in the table for the period from 23 to 27 January is more than 5x higher than the similar values for 22 and 28 January. The minimum concentrations measured from 23 to 27 January at individual stations were 1.6–5.8x higher than the daily limit value 50 μg.m^-3 and the maximum measured concentrations exceeded this value 3.9–11.4x. To illustrate the situation, bold highlighted concentrations in the table exceeded the daily limit value more than 8x. The minimum 24-hour concentrations occurred at all stations in the Ostrava-Karviná area on the last day of the smog situation, i.e. on 27 January, when the short-time (1-hour) concentrations began to decrease in the afternoon hours. The maximum concentration 890 μg.m^-3 was measured at AMS Ostrava-Zábřeh on 25January in the hour 15:00–16:00 CET and the second highest concentration 811 μg.m^-3 was measured at AMS Věřňovice on 27 January in the hour 9:00–10:00 CET. The Polish stations did not recorded such a quick emergence of the smog situation and at the stations Wodzis�aw, Gliwice and Zabrze the maximum daily concentrations fall on the last day of the episode. The area with high PM₁₀ concentrations gradually expanded during the assessed period and apart from the Moravian-Silesian Region also further areas of the Czech Republic were affected. The concentrations higher than the alert threshold 150 μg.m^-3 were recorded on 24–26 January also in other Moravian regions and on 26 January also in the Hradec Králové Region.

Fig. II:4.1.29 presents the maps of air pollution published on CHMI web site (portal.chmi.cz). The maps have only informative character; they are created on the basis of modelling with the use of the measured and non-verified data from automated monitoring stations (AMS). They may contain erroneous data and may be incomplete. The last figure shows also the air pollution map of 28 January 2010 to illustrate the significant impact of the change of meteorological conditions on air pollution situation.

During the smog situation, from 23 to 27 January 2010, the air pollution situation worsened as concerns also SO₂ and NO₂, nevertheless the situation was not as marked as in suspended particles and, in fact, the valid limit values were not exceeded. On one day only the daily limit value 125 μg.m^-3 for SO₂ was exceeded (134 μg.m^-3 at AMS Karviná on 25. 1.).The measured 1-hour concentrations of SO₂ remained far below the short-time limit value 350 μg.m^-3 and the alert threshold; the maximum measured 1-hour concentration of NO₂ 193 μg.m^-3 measured in the hour 15:00–16:00 CET at AMS Ostrava-Zábřeh (i.e. at the same station and on the same day as the maximum short-time concentrations of PM₁₀ and PM_2.5) reached 97 % of the value of the alert threshold for the warning signal. The average of all short-time concentrations in the period 23–27 January is 2.9x higher (for SO₂) and 2.3x higher (for NO₂) than the average for the days 22 and 28 January.

The 8-hour limit value 10,000 μg.m^-3 for CO was not exceeded at any station, even at the traffic station Ostrava-Českobratrská, at which the highest values are usually measured; the highest measured 1-hour value reached 5,837 μg.m^-3 at the station Ostrava-Českobratrská.

All the above information positively confirm the decisive influence of meteorological conditions on the formation, course and termination of the described smog situation. The decisive influence of meteorological conditions for the dispersion of pollutants on current ambient air quality is shown clearly in the already commented figures. In addition, Fig. II.4.1.32 is presented to show for each hour of the assessed period 22–28 January the following:

• average from 1-hour PM₁₀ concentrations from all stations listed in Fig. II.4.1.30;

• average wind velocity and average air temperature for the stations Mošnov a Racibórz;

• vertical pseudogradient of air temperature between meteorological stations Mošnov and Červená
  (in �C per 1000 m).

It is apparent from the figure how the level of air pollution increased with the decrease of wind velocity and temperature gradient, and vice versa, the significant decrease of concentrations occurred after the parallel strengthening of air circulation and the receding of temperature inversion. In the period with the least favourable conditions also the lowest air temperatures were measured. This factor could also have negative impact on air pollution situation because during the heating season, with the decrease of temperatures, the emissions from local sources increase.

Air pollution situation from January 2010 showed again that the long-lasting unfavourable dispersion conditions result in the increase of PM₁₀ suspended particles up to multiple levels of limit values not only in the industrial area Ostrava-Karviná and the adjoining Silesian Voivodeship in Poland. It is also apparent that the situations with multiple exceedances of PM₁₀ limit values will repeat in the future.

The latest similar unfavourable situations with high PM₁₀ concentrations occurred in Ostrava-Karviná area in January 2006 and in February 2005. During those episodes the conditions neither for the announcement of the warning signal nor for the regulatory signal, pursuant to the then valid Decree No. 553/2002 Coll. were fulfilled, i.e. with regard to 1-hour SO₂ and NO₂ concentrations. However, pursuant to the current legislation [35], taking into account the 24-hour PM₁₀ concentrations, the conditions for announcing the warning and regulatory signals would be fulfilled in the Moravian-Silesian Region in both above episodes.

The overall level of air pollution caused by PM₁₀ suspended particles in January 2010 was higher than during the similar situations in February 2005 and January 2006, even though the maximum 24-hour concentration measured in January 2006 exceeded 600 μg.m^-3, and were thus higher than in January 2010. The smog situation of January 2010 also had the longest duration.

Tab. II.4.1.1 Average PM₁₀ 24-hour concentrations

Fig. II.4.1.23 Annual average concentrations of suspended particles of PM₁₀ fraction at the stations in northern Moravia 1996–2010

Fig. II.4.1.24 Synoptic situation on 22.1.2010

Fig. II.4.1.25 Synoptic situation on 28.1.2010

Fig. II.4.1.26 Air temperature in the period 22.1.–29.1.2010

Fig. II.4.1.27 Wind velocity in the period 22.1.–29.1.2010

Fig. II.4.1.28 Wind roses

Fig. II.4.1.29 Maps of 24-hour concentrations of PM₁₀ based on real-time non-verified data, 19.1.–28.1.2010 (source: portal.chmi.cz)

Fig. II.4.1.30 Hourly concentrations of PM₁₀ in the Ostrava-Karviná area, 22.1.–29.1.2010

Fig. II.4.1.31 Hourly concentrations of PM₁₀ in the Silesian Voivodeship, 22.1.–29.1.2010

Fig. II.4.1.32 Hourly concentrations of PM_2.5 in the Ostrava-Karviná area, 22.1.–29.1.2010

Fig. II.4.1.33 Meteorological conditions for dispersion, 22.1.–29.1.2010

Fig. II.4.1.34 Field of the annual concentration of NO₂, Moravian-Silesian agglomeration, 2010

Fig. II.4.1.35 Field of the 36^th highest 24-hour concentration of PM₁₀, Moravian-Silesian agglomeration, 2010

II.4.1.4 Other areas with air pollution loads with higher density of population

The Ústí nad Labem Zone

The Ústí nad Labem Region is defined as a zone. This area has high population density and is highly industrialized, and thus a number of pollutants have above-the-limit concentrations.

In 2010, data on pollutants� concentrations were submitted to the ISKO database from the measurements in 36 localities in the Ústí nad Labem Region (19 CHMI, 10 ČEZ, 5 ZÚ, 1 SŠZE Žatec). Only several localities measured all pollutants.

PM₁₀ concentrations were measured in 28 localities. The exceedances of the 24-hour limit value for PM₁₀ were measured in 16 localities: Děčín (the limit value 50 μg.m^-3 exceeded 73x), Ústí n.L.-Všebořická hot spot (69x), Ústí n.L.-město (63x), Most (60x), Lom (58x), Krupka (49x), Litoměřice (49x), Chomutov (48x), Tušimice (48x), Milá (42x), Doksany (41x), Kostomlaty pod Milešovkou (40x), Teplice (40x), Droužkovice (37x) and Strojetice (37x). As compared with the year 2009, when the limit value exceedances occurred in 7 localities, the situation deteriorated. In 2010 the exceedance of the PM₁₀ annual limit value was not recorded at any station in the Ústí nad Labem Region, the highest annual average concentration of PM₁₀ was measured at the stations Lom (35.7 μg.m^-3), Most (35.5 μg.m^-3), Ústí n.L.-Všebořická (35.4 μg.m^-3), Děčín (34.5 μg.m^-3) and Ústí n. L.-město (33.0 μg.m^-3).

PM_2.5 particles were measured in 7 localities in the Ústí nad Labem Region. The highest annual average PM_2.5 concentration was recorded in the locality Teplice; it reached the value 22.7 μg.m^-3. This value is below the limit value for the annual average concentration pursuant to the Directive 2008/50/EC.

In 2010 NO₂ concentrations were measured in 32 localities in total in the Ústí nad Labem Region (out of which 19 CHMI). The station Ústí n.L.-Všebořická, which is significantly influenced by traffic, exceeded the annual limit value for NO₂ (47.8 μg.m^-3, in 2009 – 58.8 μg.m^-3).

The limit value for 24-hour SO₂ concentration was not exceeded in the Czech Republic in 2010. The highest 24-hour concentration was measured at the station Kostomlaty pod Milešovkou (117 μg.m^-3). The 1-hour limit value of SO₂ was not exceeded, the highest 1-hour concentration (339 μg.m^-3) was measured at the station Nová Víska u Domašína.

Benzo(a)pyrene concentrations were measured in 5 localities, in two of them the target value for the annual average concentration was exceeded (Ústí nad Labem-ZÚ Pasteurova 2010 – 1.6 ng.m^-3, 2009 – 1.7 ng.m^-3, 2008 – 1.45 ng.m^-3, 2007 – 1.34 ng.m^-3 and Teplice 2010 – 1.2 ng.m^-3, 2009 – 1.0 ng.m^-3). In the 3-year period 2008–2010 the target value for ground-level ozone was exceeded only in 1 locality, and namely in Sněžník, of the total number of 11 which measured ozone concentrations in 2010. Similarly as in other parts of the Czech Republic the number of exceedances of the maximum daily 8-hour running average below 120 μg.m^-3decreased. In the Ústí nad Labem Region the decline was recorded in all localities.

Air pollution situation both in individual months as well as for the whole year 2010 at selected stations of the Ústí nad Labem Region is depicted in the graphs in II.4.1.36-43. Fig. II.4.1.36 shows the annual course of monthly concentrations of PM₁₀ and the number of exceedances of the 24-hour PM₁₀ limit value in the Ústí nad Labem Region in 2010. The graph in Fig. II.4.1.39 shows the PM_2.5/PM₁₀ ratio and annual average concentrations of PM₁₀ and PM_2.5 at the stations in the Ústí nad Labem Region measuring both fractions. It is apparent that the highest PM_2.5/PM₁₀ ratio (about 80 %) was achieved at rural background station Doksany.

In general the 2010 pollutants� concentrations in the Ústí nad Labem Region were comparable with the previous year, only PM₁₀ concentration showed the increased number of stations with exceedances of the 24-hour limit value. Ozone concentrations showed, similarly as in the whole Czech Republic, the decrease of both the 26^th highest maximum daily 8-hour running averages and the number of exceedances of the value 120 μg.m^-3 in the average for 3 years (Fig. II.4.1.42).

Fig. II.4.1.36 The annual course of monthly PM₁₀ concentrations and the number of 24-hour PM₁₀ limit value exceedances, Ústí nad Labem Region, 2010

Fig. II.4.1.37 36^th highest 24-hour PM₁₀ concentrations, Ústí nad Labem Region, 2010

Fig. II.4.1.38 The annual course of monthly PM_2.5 concentrations, Ústí nad Labem Region, 2010

Fig. II.4.1.39 The annual average concentrations of PM_2.5 and PM₁₀, PM_2.5/PM₁₀ ratio, Ústí nad Labem Region 2010

Fig. II.4.1.40 The annual course of average monthly benzo(a)pyrene concentrations, Ústí nad Labem Region, 2010

Fig. II.4.1.41 The annual course of average monthly PM₁₀ and benzo(a)pyrene concentrations, Ústí nad Labem Region, 2010

Fig. II.4.1.42 The annual course of average monthly O₃ concentrations, Ústí nad Labem Region, 2010

Fig. II.4.1.43 The annual course of average monthly NO₂ concentrations, Ústí nad Labem Region, 2010

4.1.5 Trends of annual air pollution characteristics of SO₂, PM₁₀ and NO₂ for the period 1996–2010

The trends of SO₂, PM₁₀, NO₂ and CO annual air pollution characteristics for the period 1996–2010 and PM_2.5 for the period 2004–2010 for the agglomerations Prague, Brno and the Moravian-Silesian Region (further on agglomerations) and for the zone Ústí nad Labem Region (further on zone) are depicted in Fig. II.4.1.44.

In the period from 1996 to 1999 there was a significant decreasing trend in SO₂ and PM₁₀ concentrations in the mentioned agglomerations and the zone. The greatest decrease of SO₂ concentrations was recorded in the zone Ústí nad Labem Region and the greatest decrease of PM₁₀ concentrations was recorded in the agglomerations Moravian-Silesian Region and Prague. In comparison with SO₂ and PM₁₀ NO₂ concentrations decreased slightly. In the following years 2000–2001 the decreasing trend of all pollutants except CO was interrupted and, on the contrary, SO₂ concentrations increased in the Moravian-Silesian Region and NO₂ concentrations increased in all agglomerations and the zone. Significant increase of PM₁₀ concentrations in 2000–2001was recorded mainly in the agglomeration Moravian-Silesian Region. CO concentrations have remained at similar level since 1999.

The increasing trend of PM₁₀ and NO₂ concentrations continued in all agglomerations up to 2003 when there were recorded high concentrations of pollutants comparable with the levels measured in 1996. High pollutants� concentrations in 2003 were caused both by unfavourable dispersion conditions in February and December and by subnormal level of precipitation amounts.

In 2004, on the contrary, the ambient air pollution caused by SO₂, PM₁₀ a NO₂ decreased in the agglomerations and the zone. Starting from 2005 all evaluated areas recorded the increasing trend in NO₂, which was confirmed in 2006. As concerns PM₁₀ and PM_2.5, there was a similar characteristic increase in 2005, with the steepest progress in the agglomeration Moravian-Silesian Region. In 2006 the increasing trend of PM₁₀ concentrations continued and as concerns PM_2.5, this increasing trend was recorded in all monitored areas except for Prague. The increase of pollutants� concentrations in the years 2005 and 2006 is given mainly by deteriorated dispersion conditions. In 2006 these unfavourable meteorological conditions occurred in the whole territory of the Czech Republic. In the Ústí nad Labem Region and in the Moravian-Silesian Region, on the contrary, there was recorded a very slight decrease of 24-hour PM₁₀ concentrations and the stagnation of annual PM₁₀ concentrations.

In 2007 there was a marked decrease of air pollution caused by SO₂, PM₁₀, PM_2.5, NO₂ and CO in all agglomerations. The steepest decrease is apparent, after the previous increase, in hourly NO₂ concentrations in Brno. The decrease of pollutants� concentrations in the ambient air was influenced by more favourable meteorological and dispersion conditions in 2007. In 2008 the decrease of SO₂, PM₁₀ and NO₂ concentrations continued, but it was not as steep as in the previous year. PM_2.5 concentrations mostly stagnated.

In 2009 the PM₁₀ and PM_2.5 concentrations in agglomerations increased. The most prominent increase was recorded in the Moravian-Silesian Region. The increase of NO₂ concentrations was recorded in Brno, in other agglomerations the concentrations rather stagnated. The increase of concentrations of pollutants was influenced by less favourable meteorological and dispersion conditions, particularly in January, February and December 2009 as compared with the previous year.

In 2010 the increase of concentrations continued in all pollutants in all agglomerations. The highest year-to year increase of PM₁₀ concentrations was recorded in the Moravian-Silesian Region, where the year-to-year increase of average PM₁₀ concentration increased by 10 μg.m^-3; in the remaining agglomerations the year-to-year increase of PM₁₀ was about 2.5 μg.m^-3. The annual average concentrations of PM_2.5 also increased in all agglomerations; the highest increase was recorded again in the Moravian-Silesian Region (in the year-to-year comparison by 7.5 μg.m^-3), Further marked increase was recorded in NO₂, and namely in the 19^th highest hourly concentration in the Moravian-Silesian Region, the second highest increase of NO₂ was recorded in the Brno agglomeration. The increase of pollutants� concentrations in 2010 was caused by repeated occurrence of unfavourable meteorological and dispersion conditions in the winter period, both at the beginning of the year (January, February) and at the end of the year (Octobern December).

Fig. II.4.1.44 Trends of SO₂, PM₁₀, PM_2.5, NO₂ and CO annual characteristics in agglomerations, 1996–2010