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 exceedances are connected with significant traffic loads ensuing from the fact that the main routes lead directly through the city centre.

In 2009 the PM₁₀ particles concentrations were monitored in Prague in 15 CHMI localities and in 7 ZÚ localities. The exceedances of 24-hour PM₁₀ limit value (50 μg.m^-3) were recorded in the following localities: Prague 5-Smíchov (48x), Prague 2-Legerova (45x) and Prague 5-Řeporyje (41x). The tolerated number of exceedances is 35. In the first two cases these are the localities with very heavy traffic loads. Of the total number of 21 localities with valid annual average (with sufficient number of measurements with regard to the requirement of minimum data collection) 3 stations recorded 24-hour PM₁₀ limit value exceedances. The annual PM₁₀ limit value (40 μg.m^-3) was not exceeded in any locality, the station Prague 5-Svornosti reached the level of the limit value.

The PM_2.5 particles concentrations were measured in 5 CHMI localities and in 1 ZÚ locality in 2009. In spite of the fact that the valid air pollution limit value for PM_2.5 has not been set in the Czech legislation so far, the comparison of the measured concentrations with the limit value for annual average concentration set by the Directive of the European Parliament 2008/50/EC (25 μg.m^-3) is very interesting. The highest average annual concentrations in Prague localities were as follows: Prague 5-Smíchov 22 μg.m^-3, Prague 5-Mlynářka 21 μg.m^-3 and Prague 4-Libuš 19 μg.m^-3. It is quite evident that the limit value for PM_2.5 fraction set by the Directive 2008/50/EC was not exceeded at any Prague station.

The graphs in Fig. II.4.1.1, II.4.1.2 and II.4.1.3 show the annual course of monthly PM₁₀ and PM_2.5 concentrations, numbers of exceedances of 24-hour PM₁₀ limit value and monthly PM_2.5/PM₁₀ ratios in 2009.

The highest number of exceedances of the 24-hour limit value of PM₁₀ (50 μg.m^-3) was recorded in January in the locality Prague 5-Smíchov. The highest average monthly PM₁₀ concentration was recorded in January in the locality Prague 5-Smíchov (64 μg.m^-3) and the highest average monthly PM_2.5 concentration also in January in the locality Prague 5-Mlynářka (46 μg.m^-3).

The PM_2.5/PM₁₀ ratio at 5 stations in Prague (where PM_2.5 and PM₁₀ are measured simultaneously) ranged from 0.3 (November: Prague 8-Karlín) to 0.9 (February: Prague 5-Smíchov).

NO₂ concentrations were measured in all 22 localities in Prague in 2009. The AMS station Prague 2-Legerova (hot spot) which is located in the immediate vicinity of a communication with heavy traffic, exceeded the hourly NO₂ limit value plus the margin of tolerance (200+10 μg.m^-3). The value of 200 μg.m^-3 was exceeded 98x, the value of 210 μg.m^-3 was exceeded 67x. .The tolerated number of exceedances is 18. The highest 19th hourly concentration at this AMS reached 242μg.m^-3. As concerns other localities, there were also three exceedance of the hourly NO₂ concentration 200 μg.m^-3 in 2009, and namely at the station Prague10-Průmyslová, which is also significantly influenced by traffic.

The annual air pollution limit value plus the margin of tolerance for NO₂ (40+2 μg.m^-3) was exceeded in the following localities: Prague 2-Legerova (68 μg.m^-3), Prague 5-Svornosti (55 μg.m^-3) and Prague 8-Sokolovská (43 μg.m^-3).

It can be expected that the exceedance of air pollution limit values can occur also in other localities exposed to traffic, where there are no measurements.

Fig. II.4.1.6 shows the graphs of annual courses of monthly NO₂ concentrations at selected localities in Prague in 2009. There is a separate AMS 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-Svornosti that is also situated in the immediate vicinity of the communication. It is followed by the third group of localities also markedly influenced by traffic, with similar courses of the levels ranging around the limit value (Prague 8-Sokolovská, Prague 5-Smíchov, Prague 9-Vysočanyand Prague 8-Karlín), and finally there are two localities (Prague 2-Riegrovy sady and Prague 4-Libuš) representing the urban background where the influence of traffic is not as high and the measured concentrations are below the limit value.

Another problem is caused by above-the-limit benzo(a)pyrene concentrations which exceeded the target value in one of three localities which measured it in Prague, and namely Prague 10-Šrobárova. Nevertheless in all three localities there was recorded a slight decrease of the annual average concentrations as compared with the year 2008.

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 station Prague 5-Řeporyje, where the target value for arsenic was exceeded in the recent two years, the average concentration of arsenic (3,5 μg.m^-3) decreased below the target value in 2009.

In 2009 the target value for the ground-level ozone was exceeded relatively closely in the locality Prague 6-Suchdol. The 26^th highest maximum daily 8-hour running average reached 122.3 μg.m^-3. Further highest values, however closely below the limit value, were measured in the following localities: Prague 4-Libuš (119.2 μg.m^-3) and Prague 5-Stodůlky (119.0 μg.m^-3).

Fig. II.4.1.1 Annual course of monthly PM₁₀ concentrations and number of 24-hour PM₁₀ limit exceedances, Prague agglomeration, 2009

Fig. II.4.1.2 Annual course of monthly PM_2.5 concentrations, Prague agglomeration, 2009

Fig. II.4.1.3 Monthly PM_2.5/PM₁₀ ratio, Prague agglomeration, 2009

Fig. II.4.1.4 Annual course of monthly benzo(a)pyrene concentrations, Prague agglomeration, 2009

Fig. II.4.1.5 Annual course of monthly O₃ concentrations, Prague agglomeration, 2009

Fig. II.4.1.6 Annual course of monthly NO₂ concentration at selected stations, Prague agglomeration, 2009

Fig. II.4.1.7 Field of the annual concentration of NO₂, Prague agglomeration, 2009

Fig. II.4.1.8 Field of the annual concentration of benzo(a)pyrene, Prague agglomeration, 2009

II.4.1.2 Brno

Air pollution monitoring network
In 2009 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 Municiple Council of the city of Brno and the Health Institute in Brno. In comparison with the year 2008 one more station was included: CHMI shifted some measurements (mainly due to PAH) from the locality Brno-Kroftova to the new locality Brno-Líšeň characterized as the urban background locality. The PAH are measured here together with heavy metals, PM₁₀ and nitrogen dioxide. The measurement of PM₁₀ was also expanded to the locality Brno-Soběšice, where only total SPM was measured in the past.

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 2009 the limit value for the average annual concentration was exceeded only in the traffic locality Brno-Svatoplukova. The limit value for 24-hour concentration was exceeded again in traffic localities Brno-Svatoplukova, Brno-Zvonařka, Brno-Výstaviště, Brno-střed and Brno-Masná.

On the contrary, at the background station Brno-Tuřany the 24-hour limit value was not exceeded in two recent subsequent years. The highest concentrations of the 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 2009, the exceedance would occur in the traffic localities Brno-Svatoplukova and Brno-Zvonařka. The remaining localities Brno-Lány and Brno-Tuřany with the average annual PM_2.5 concentrations 22.4 μg.m^-3 and 21 μg.m^-3 respectively, would not exceed the mentioned limit value. 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 number of exceedances of the annual average NO₂ concentration has also increased. The limit value exceedances occurred at traffic stations, whose number has increased thanks to the stations of the Municipal Council of the city of Brno and the station Brno-Úvoz (hot spot). It can be therefore expected that the limit value could be exceeded in these localities also in the previous years. The increased concentrations are contributed by the increased intensity of traffic and also by meteorological conditions. In 2009 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 2009.

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, range below the lower assessment threshold. Thus the number of selected measurements was limited in the Brno agglomeration, particularly in case of SO₂.

In the territory of the Brno agglomeration also the target values for tropospheric ozone and benzo(a)pyrene are exceeded. Tropospheric ozone exceeds the target value 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 concentration 1.2 μg.m^-3, and thus the target value was exceeded. On the contrary, the locality Brno-Líšeň measured the average annual BaP concentration only 0.5 μg.m^-3 in 2009. This confirms that even in the Brno agglomeration the target value may be without exceedance in an urban background only minimally influenced by traffic and partly by small sources. 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 large Brno ring road 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 2009
The pollutants exceeding the limit values 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 were averaged and compared with the regional background station Mikulov-Sedlec. Fig. II.4.1.9 shows clearly that there is relatively good correlation between the trends of concentrations from background stations and the regional background station, especially in the 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 at the background localities.

The average monthly PM₁₀ concentrations in individual stations in the Brno agglomeration in 2009 are depicted in Fig. II.4.1.10. In addition to the measured concentrations the figure shows also the sums of monthly precipitation documenting the high concentrations of April 2009.

In early April the monitoring network recorded the increased concentrations of particles in ambient air throughout the whole Czech Republic, transported from the Mt. Redoubt volcano in Alaska. The volcanic particles were also found in the samples measured by the Geological Institute of the Academy of Sciences of the Czech Republic. Moreover, in addition to high PM₁₀ (and SO₂) concentrations caused by the volcanic activity, the month of April was very poor in precipitation – the professional station Brno-Tuřany recorded only 3.4 mm for the whole April. The combination of these factors influenced the situation at the territory of the Brno agglomeration (but also at the regional background station Mikulov-Sedlec), and namely by increasing the average monthly PM₁₀ and SO₂ concentrations to the level of January or February values (Figs. II.4.1.10 and II.4.1.11), in spite of the fact that air temperatures were similar as in May and their average was about 15 �C. The lack of precipitation that wash out the dust from the ambient air, prevent re-suspension and react with SO₂ to form sulphurous acid, was probably the main reason of unusually high concentrations of the above mentioned pollutants in April 2009.

The fine fraction PM_2.5 was measured at 4 station in the Brno agglomeration in 2009 – 2 traffic and 2 background. Both traffic stations would exceed the limit value for the average annual PM_2.5 concentration 25 μg.m^-3. On the contrary, the background localities Brno-Tuřany and Brno-Lány would not exceed this limit. The average monthly shares of PM_2.5 in PM₁₀ in the locality Brno-Tuřany in 2009 are depicted in Fig. II.4.1.12. It is apparent that the share of PM_2.5 in PM₁₀ has a slightly convex character. In the locality Brno-Tuřany the interval of PM_2.5 in PM₁₀ ranges from 66 % (July) to 83 % (January); the 2009 average of PM_2.5 in PM₁₀ was 73 %. This locality, as the only one, uses radiometry (accredited according to ČSN EN ISO/IEC 17025:2005), and moreover, two separate instruments.

The average annual concentrations of NO₂ (Fig. II.4.1.13) 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.4.1.13). 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.

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 urban 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.4.1.14. 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 Corporation Brno. On the contrary, during the heating season the concentrations are increasing, the highest values are recorded in January and December, i.e. 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 most territory of the Czech Republic. In the Brno agglomeration the coverage is in fact 100 %; 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.4.1.15 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. Unlike the previous pollutants the highest 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. In connection with the optimization of the network the traffic locality operated by CHMI (Brno-střed) ended the ozone measurement in 2009.

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 value for PM₁₀, NO₂ and target value for benzo(a)pyrene. The draft and the implementation of the measures aimed at the transport 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 (Brno-Tuřany).

Fig. II.4.1.9 The average annual PM₁₀ concentrations at background and traffic stations, Brno agglomeration, 2002–2009

Fig. II.4.1.10 The influence of precipitation amounts to average monthly PM₁₀ concentrations, Brno agglomeration, 2009

Fig. II.4.1.11 The influence of precipitation amounts to average monthly SO₂ concentrations, Brno agglomeration, 2009

Fig. II.4.1.12 The average monthly concentrations of PM_2.5 and PM₁₀, Brno-Tuřany, 2009

Fig. II.4.1.13 The average annual NO₂ concentrations at background and traffic stations, Brno agglomeration, 2002–2009

Fig. II.4.1.14 The average monthly PAH concentrations, Brno-Líšeň, 2009

Fig. II.4.1.15 26^th highest 8-hour running average of O₃, Brno agglomeration, 2002–2009

Fig. II.4.1.16 Field of the annual concentration of NO₂, Brno agglomeration, 2009

Fig. II.4.1.17 Field of the annual concentration of benzo(a)pyrene, Brno agglomeration, 2009

II.4.1.3 The Moravian-Silesian Region

Suspended particles
The concentrations of suspended particles of PM₁₀ fraction in the Ostrava and Karviná area are the highest within the Czech Republic. Similarly as in the previous years the annual limit value of PM₁₀ concentrations was exceeded at most stations in the Ostrava and Karviná area in 2009. After the decrease in the years 2007–2008 there was recorded a slight increase of annual concentrations in 2009. The annual concentration is influenced substantially by the level of air pollution in the cold parts of the calendar year; it is determined by the prevailing character of dispersion conditions. Fig. 4.1.18 shows the assessment of the winter periods 2004/2005–2009/2010 with regard to meteorological dispersions conditions. The figure depicts the temperature (TV), temperature pseudogradient between meteorological stations in various altitudes (TGr) and the average wind velocity (RV). The increase of pollutants� concentrations occurs mainly at low temperatures and wind velocities and in stable or inversion character of the stratification of the boundary layer of the atmosphere. In 2009 there was a marked influence of deteriorated dispersion conditions in January and December; there occurred some several-day episodes with multiple exceedance of the daily limit value (50 μg.m^-3). The measured 24-hour average concentrations reached even 300 μg.m^-3 at some stations. The daily limit value was exceeded at all stations more frequently than is the allowable number (35 days/year). In the most polluted localities in the Ostrava and Karviná area the number of exceedances was over 100 days in the year. Fig. II.4.1.19 shows the development of the average and maximum PM₁₀ concentrations and the share of the concentrations with double and triple exceedances of the daily limit value in the three winter months in 2004–2010. It is apparent that the character of dispersion conditions influences the result concentrations. The winters with above-the-average temperatures, 2006/2007 and 2007/2008, contributed to lower concentrations in the years 2007 and 2008. This trend, however, was changed in the winter period 2008/2009. The PM₁₀ concentrations for the winter period 2009/2010 reflected the extreme values of January 2010. Their influence will be evaluated in the next year.

The target value of the annual average concentration 25 μg.m^-3 of suspended particles, fraction PM_2.5, introduced by the Directive 2008/50/EC of the European Parliament and of the Council of 21 May 2008 on ambient air quality and cleaner air for Europe, which should be achieved by 1.1.2010 and will be implemented into the Czech legislation, was exceeded in all localities monitoring PM_2.5 in the Moravian-Silesian Region in 2009.

Other pollutants
The NO₂ concentrations in 2009 exceeded the annual limit value 40 μg.m^-3 (including the margin of tolerance for the year 2009 42 μg.m^-3) at the raffic station Ostrava-Českobratrská (hot spot). It can be estimated that similar values are recorded in other localities with traffic loads within the region.
There are constant multiple exceedances of the limit value of benzo(a)pyrene (1 ng.m^-3) in most of the territory of the Moravian-Silesian Region in most localities. The highest exceedance of the annual limit value (9x) was recorded again in the locality Ostrava-Bartovice.

The annual average concentration of benzene remained, similarly as in the previous years, above the limit value in the industrial locality Ostrava-Přívoz despite the fact that one industrial emission source was closed in 2009. However, when taking into account the margin of tolerance, the limit for the protection of health (6 μg.m^-3) was met.

The above-the-limit annual value of arsenic was measured in the locality Ostrava-Mariánské Hory.
The exceedance of the limit value of maximum 8-hour average concentration 120 μg.m^-3 occurs repeatedly at all monitoring stations in the Moravian-Silesian Region; the long-term objective for the protection of health was not met. The localities with higher altitudes exceeded the allowable number of 25 days with above-the-limit maximum daily 8-hour average concentration.

With regard to the valid limit values the situation with SO₂ in the Moravian-Silesian Region is favourable. The CO concentrations are also below the limit value.

Fig. II.4.1.18 Comparison of basic characteristics of meteorological dispersion conditions in winter periods (December–February)

Fig. II.4.1.19 Comparison of the levels of air pollution caused by the PM₁₀ fraction of suspended particles in winter periods (December–February) in the Ostrava-Karviná area

Fig. II.4.1.20 Field of the annual concentration of NO₂, Moravian-Silesian agglomeration, 2009

Fig. II.4.1.21 Field of the annual concentration of benzo(a)pyrene, Moravian-Silesian agglomeration, 2009

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 2009, data on pollutants� concentrations were submitted to the ISKO database from the measurements in 40 localities in the Ústí nad Labem Region (20 CHMI, 9 ČEZ, 10 ZÚ, 1 SŠZE Žatec). Only several localities measured all pollutants.
PM₁₀ concentrations were measured in 27 localities. The exceedances of the 24-hour limit value for PM₁₀ were measured in 7 localities: Lom (the LV 50 μg.m^-3 exceeded 63x), Děčín (54x), Lovosice-MÚ (47x), Ústí n.L.-město (47x), Most (46x), Ústí nad Labem-Všebořická hot spot (44x) and Litoměřice (36x). As compared with the year 2008, when the limit value exceedances occurred in 6 localities, the situation slightly deteriorated. In 2009 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 station Lom (35.6 μg.m^-3), Děčín (33.4 μg.m^-3), Lovosice-MÚ (32.6 μg.m^-3), Ústí n.L.-Všebořická (31.8 μg.m^-3) and Ústí n. L.-město (31.7 μg.m^-3).
PM_2.5 particles were measured in 6 localities in the Ústí nad Labem Region. The highest annual average PM_2.5 concentration was recorded in the locality Doksany; it reached the value of 19 μg.m^-3. This value is below the limit value for the annual average concentration pursuant to the Directive 2008/50/EC.
In 2009 NO₂ concentrations were measured in 35 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 plus the margin of tolerance (58.8 μg.m^-3, in 2008 – 43.9 μg.m^-3).

In 2009 the limit value for 24-hour SO₂ concentration was exceeded only in the Ústí nad Labem Region, and namely in the locality Teplice-ZÚ. The limit value (125 μg.m^-3) was exceeded there 12x (the admissible number of exceedances is 3x).

The 1-hour limit value of SO₂ was not exceeded, the highest 1-hour value (994 μg.m^-3) was measured at the station Měděnec.

Benzo(a)pyrene concentrations were measured in 5 localities, in one of them the target value for the annual average concentration was exceeded (Ústí nad Labem-ZÚ Pasteurova –1.7 ng.m^-3, in 2008 it was 1.34 ng.m^-3, in 2007 1.34).

In the 3-year period 2007–2009 the target value for ground-level ozone was exceeded only in 2 localities of the total number of 11 which measured ozone concentrations in 2009. 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 2009, at selected stations of the Ústí nad Labem Region is depicted in the graphs in Figs. II.4.1.22–II.4.1.29. The graph in Fig. II.4.1.25 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 2009 pollutants� concentrations in the Ústí nad Labem Region were comparable with the previous year, only ozone concentration 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 value120 μg.m^-3 in the average for 3 years.

Fig. II.4.1.22 Annual course of monthly PM₁₀ concentrations and number of 24-hour PM₁₀ limit value exceedances, Ústí nad Labem Region, 2009

Fig.II.4.1.23 36^th highest 24-hour PM₁₀ concentration, Ústí nad Labem Region, 2009

Fig. II.4.1.24 Annual course of monthly PM_2.5 concentrations, Ústí nad Labem Region, 2009

Fig. II.4.1.25 PM_2.5/PM₁₀ proportions, annual average PM₁₀ and PM_2.5 concentrations, Ústí nad Labem Region, 2009

Fig. II.4.1.26 Annual course of monthly benzo(a)pyrene concentrations, Ústí nad Labem Region, 2009

Fig. II.4.1.27 Annual course of monthly PM₁₀ and benzo(a)pyrene concentrations, Ústí nad Labem Region, 2009

Fig. II.4.1.28 Annual course of monthly O₃ concentrations, Ústí nad Labem Region, 2009

Fig. II.4.1.29 Annual course of monthly NO₂ concentrations, Ústí nad Labem Region, 2009

4.1.5 Trends of annual air pollution characteristics of SO₂, PM₁₀ and NO₂ for the period 1996–2008

Fig II.4.1.30 shows the trends of SO₂, PM₁₀, NO₂ and CO annual air pollution characteristics in 1996–2009 and PM_2.5 for the period 2004–2009 for the following agglomerations: Prague, Brno and Moravian-Silesian Region and for the zone Ústí nad Labem Region.

Up to 1999 there was a significant decreasing trend in SO₂ and PM₁₀ concentrations in the agglomerations, the NO₂ concentrations decreased only slightly. In 2001 the decreasing trend was interrupted and, on the contrary, the SO₂ and NO₂ concentrations slightly increased; PM₁₀ concentrations increased significantly, mainly in the Ostrava agglomeration. In 2004, on the contrary, concentrations of all pollutants monitored in the agglomerations decreased, and SO₂ concentrations slightly increased in the Ústí nad Labem Region. Starting from 2005 all agglomerations recorded the increasing trend in NO₂, which was confirmed in 2006. As concerns PM₁₀ and PM_2.5, there has been a similar characteristic increasing trend since 2005, with the steepest progress in the Moravian-Silesian Region. In 2006, however, this trend continued only in PM₁₀ in the Prague and Brno agglomerations, in PM_2.5 in the Ústí nad Labem Region and in Brno. The increase of the pollutants� concentrations, and mainly of PM₁₀ (PM _2.5) in the years 2005 and 2006 is given mainly by deteriorated dispersion conditions. In 2006 these unfavourable meteorological conditions occurred on the whole territory of the Czech Republic. In the Ústí nad Labem Region and in the Moravian-Silesian Region, on the contrary, a very slight decrease of 24-hour PM₁₀ concentrations and stagnation of annual PM₁₀ concentrations was recorded. CO concentrations have remained at similar level since 1999. 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 (measured in fewer localities than PM₁₀) mostly stagnated.

In 2009 the PM₁₀ and PM_2.5 concentrations in agglomerations increased. The most prominent decrease was recorded in the Moravian-Silesian Region. The increase of NO₂ concentrations was recorded in Brno, in other agglomerations the concentrations rather stagnated. The CO concentrations were similar as in the previous years; the slight increase was recorded in Brno and the Ústí nad Labem Region. 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.

Fig. II.4.1.30 Trends of SO₂, PM₁₀, PM_2.5, NO₂ and CO annual characteristics in agglomerations, 1996-2009