II.4.2 Czech Republic

II.4.2.1 Air quality with regard to health protection limit values

II.4.2.1.1 Sulphur dioxide

Sulphur dioxide emitted from anthropogenic sources is created mainly by burning the fossil fuels (mostly coal and heavy fuel oils) and by smelting ores containing sulphur. Volcanos and oceans belong to the main global natural sources of SO₂, nevertheless their share on the territory within EMEP was estimated at only 2 %. In the atmosphere, SO₂ is oxidized to sulphates and H₂SO₄, creating aerosol both in the form of droplets and suspended particles of broad size range. SO₂ and the products originating from it are removed from the atmosphere through wet and dry deposition. SO₂ has irritating effects, high concentrations can cause respiration difficulties.
The 2005 situation of air pollution caused by SO₂ with regard to the limit values set by the legislation is documented by the Tables II.4.1 a II.4.2 and Figs. II.4.10–II.4.13. The table of annual average SO₂ concentrations is also included to illustrate the situation (Table II.4.3).
It is evident from the figures that in 2005 the set air pollution limit value for 24-hour SO₂ concentration 125 μg.m^-3 was not exceeded at any locality (tolerated number of exceedences – 3x). Similarly, no measuring site reported the exceedence of the hourly SO₂ limit value 350 μg.m^-3 (tolerated number of exceedences – 24x, the highest number of exceedences was recorded at the AMS station Ostrava-Zábřeh – 4x).
The map diagrams in Fig. II.4.10 show the evident improvement of air quality resulting from the significant decrease of SO₂ concentrations documented by the marked decline of the 4^th highest 24-hour SO₂ concentration at all stations in the period 1998–2000. In the following years this decreasing trend stopped and has continued again since 2004. In 2005, the slightly decreasing trend was confirmed.
Figs. II.4.12 and II.4.13 document the courses of 24-hour SO₂ concentrations at the stations in 2005. Fig. II.4.13 confirms the increased SO₂ concentrations in winter period of the previous years in the environs of the ZÚ station Úštěk.
Fig. II.4.11, presenting the spatial distribution of the 4^th highest 24-hour SO₂ concentrations, and the Tables II.4.1 and II.4.2 show that in 2005 the air pollution caused by SO₂ did not exceed the limit values for the protection of health at any station. The value of 125 μg.m^-3 was exceeded but within the tolerated number of exceedences. Consequently, the pollution caused by SO₂ is not the reason to list any part of the territory among the areas with deteriorated air quality.

II. 4.2.1.2 Suspended particles, PM₁₀ fraction and PM_2.5 fraction

The particles contained in the ambient air can be divided into primary and secondary particles. The primary particles are emitted directly into the atmosphere, both from natural and anthropogenic sources. Secondary particles are mostly of anthropogenic origin and are created by oxidation and consequent reactions of gaseous compounds in the atmosphere. Similarly as in the whole Europe, most emissions in the Czech Republic are of anthropogenic origin. The main anthropogenic sources include: transport, power stations, combustion sources (industrial and local), fugitive emissions from industry, loading/unloading, mining and building activities. Due to the diversity of emission sources the suspended particles have various chemical composition and various size. The PM₁₀ suspended particles have serious health impacts. More significant impacts on human health, however, are caused by the fine PM_2.5 fraction which was already monitored at a number of stations in the Czech Republic in 2005.
Air pollution caused by PM₁₀, as shown in the Tables II.4.4. and II.4.5, similarly as in Fig. II.4.14, remains one of the main problems of air quality assurance. Fig. II.4.14 shows the increasing trend of PM₁₀ pollution at almost all stations in the Czech Republic from 2001 to 2003. In 2004 this trend stopped but in 2005 the PM₁₀ concentrations increased again at almost all selected stations.
The most affected area of large coverage is, similarly as in the previous years, the Ostrava-Karviná area. In 2005 the air quality in this region was influenced by deteriorated meteorological and dispersion conditions in early February, when the 24-hour PM₁₀ concentration exceeded the value of 400 μg.m^-3 at several stations (see II.4.1 Agglomerations). The limit value of 24-hour PM₁₀ concentration was exceeded in 2005, and namely at the stations in the Moravian-Silesian Region (Český Těšín, Orlová, Ostrava-Přívoz, Bohumín, Havířov, Karviná, Ostrava-Českobratrská (hot-spot), Věřnovice, Frýdek-Místek, Ostrava-Zábřeh and Ostrava-Fifejdy, at the stations in the Central Bohemian Region (Kladno-Švermov and Beroun), in South Moravian Region (Brno-střed) in Ústí nad Labem Region (Most, Ústí n.L.-město and Teplice), in the Zlín Region (Uherské Hradiště and Zlín-Svit), in Olomouc Region (Šumperk and Přerov), in Prague (Legerova in Prague 2 and Karlín in Prague 8). Of the total number of 137 stations at which PM₁₀ measurements were carried out, 93 stations reported exceedences of 24-hour PM₁₀ limit value. The annual PM₁₀ limit value was exceeded at 31 stations. In comparison with the previous year the PM₁₀ concentrations increased also at rural stations.
The number of localities at which both above air pollution characteristics of PM₁₀ fraction exceeded the limit value increased in 2005. Figs. II.4.15 and II.4.16 show that PM₁₀ limit value exceedences are still significant for listing the basic administrative units among the areas with deteriorated air quality. Fig. II.4.15 shows quite evidently that in the towns where the PM₁₀ measurements are carried out the 24-hour average concentrations are above the limit value. However, it can be admitted that also in the towns without PM₁₀ measurements the concentrations of this pollutant can be high or exceed the limit value.
In 2005, in comparison with the previous year, PM₁₀ concentrations increased at the stations classified as background rural. The number of exceedences of 24-hour average concentration 50 μg.m^-3 increased in 26 localities. In 2004 the limit value (without the margin of tolerance) was exceeded in 4 localities, in 2005 in 15 localities. Certain increase in annual averages was also recorded at background rural stations, and namely in 13 localities. On the contrary, in 6 localities the average concentration declined. In 2004 the air pollution limit value was exceeded only in one of the proposed background rural localities, in 2005 in 3 localities.
One of the possible reasons of PM₁₀ increased concentrations at rural stations in 2005, as compared with 2004, can be lower temperatures measured in 2005. Colder winter period probably resulted in more intensive local heating which is the significant emission source of PM₁₀. In 2004, the average temperature for the months of the usual heating period (January–March and November–December) was +0,26 �C, in 2005 only –0,48 �C. Four of these 5 months were colder in 2005 in comparison with the year 2004.
The map of fields of PM₁₀ concentrations (Figs. II.4.15 and II.4.16) were constructed for the first time in 2005 with the use of the empiric model which combines the dispersion model SYMOS, the European model EMEP and the altitude with the measured concentrations at rural background stations according to the methods developed within the ETC/ACC [28]. The application of the SYMOS model as the only one would not be sufficient in the case of PM₁₀ as the model calculations include only the emissions from primary sources. The significant share in PM₁₀ pollution, however, is contributed by secondary¹ particles and re-suspended particles, which are not included in the emissions from the primary sources but considered by the EMEP model.
The areas where PM₁₀ concentrations exceed the respective limit values represent, with regard to the newly constructed map, almost 35 % of the territory of the Czech Republic with more than 67 % of the total population.
The graphs of courses of 24-hour concentrations in 2005 at the stations, where the limit value was exceeded, are shown in Figs. II.4.17 and II.4.18. The selection of 12 stations with the greatest numbers of 24-hour exceedences includes 10 stations from the Moravian-Silesian Region. Fig. II.4.19 presents the number of exceedences of the PM₁₀ 24-hour air pollution limit value.
The complete overview of the air pollution limit value for the PM₁₀ annual average concentration for the recent 5 years is presented in Fig. II.4.20 and Table II.4.6. Fig. II.4.20 shows the annual average PM₁₀ concentrations for the period 2001–2005 at the localities where at least once in this period the annual air pollution limit value was exceeded. Table II.4.6 shows the particular values of the reached average PM₁₀ concentrations. Annual average concentrations exceeding the limit value are printed bold.
In 2005 measurements of the fine fraction of suspended particles (PM_2.5) began. The measurements were carried out in 25 localities and their results show significant contribution of PM_2.5 fraction to air pollution situation in the territory of the Czech Republic. When comparing the results with the proposed annual air pollution limit value, it is evident that in 12 localitites the limit value would be exceeded, mainly at the station in the Ostrava-Karviná area (Věřňovice, Ostrava-Přívoz, Ostrava-Zábřeh, Ostrava-Poruba), which record the highest annual average concentrations, and in the following localities: Beroun, Prague 5-Smíchov, Zlín, Olomouc, Hradec Králové-Brněnská, Teplice, Kladno-střed and Brno-Tuřany. Another 6 localities would rank close below the proposed limit value. The stations with the highest values of annual average concentrations are presented in Table II.4.7. The annual average PM_2.5 concentrations in the localities which measured this fraction in 2005 are presented in Fig. II.4.21.
Fig. II.4.22 shows the seasonal course of the ratio between PM_2.5 and PM₁₀ fractions of suspended particles. The shares of total averages of daily average concentrations from 19 AMS stations and 4 manual stations with valid data for the year 2005 is presented. The measurement results indicate that the ratio between PM_2.5 and PM₁₀ is not constant but shows certain seasonal course. In 2005 the fractions� ratio ranged between 0.69–0.85, with lower values in the summer period.
The seasonal course of PM_2.5/PM₁₀ fraction ratio is connected with the seasonal character of several emission sources. Emissions from combustion sources show higher shares of PM_2.5 fraction than for instance emissions from agriculture and reemissions during dry and windy weather. Consequently, heating in the winter period can cause the higher share of PM_2.5 fraction in comparison with PM₁₀ fraction.

II.4.2.1.3 Nitrogen dioxide

In the field of ambient air monitoring and assessment the term nitrogen oxides NO_x is used for the mixture of NO and NO₂. Air pollution limit value for the protection of human health is set for NO₂, the limit value for the protection of ecosystems and vegetation is set for NO_x.
More than 90 % of the total nitrogen oxides in the ambient air is emitted in the form of NO. NO₂ is formed relatively quickly in the reaction of NO with ground-level ozone or with HO2 or RO2 radicals. A number of chemical reactions part of NO_x is transformed to HNO₃/NO₃^-, which are removed from the atmosphere through deposition (both dry and wet). NO₂ is dealt with due to its negative influence on human health. It plays also the key role in the formation of photochemical oxidants.
In Europe, NO_x emissions result mainly from anthropogenic combustion processes during which NO is formed in reaction between nitrogen and oxygen in the combusted air, and partly also by oxidation of nitrogen from the fuel. Road transport is the main anthropogenic source (significant shares however, have also air transport and water transport), and also combustion processes in stationary sources. Less than 10 % of total NO_x emissions result from combustion directly in the form of NO₂. Natural NO_x emissions result mainly from soil, volcanic activity and creation of bolts of lightning. Globally, they are important, on the European scale, however, they represent less than 10 % of total emissions. Long-term exposure to the increased NO₂ concentrations can cause respiration difficulties.
The exceedence of annual limit values for NO₂ occurred only in limited number of localities exposed to traffic in agglomerations and large cities. Of the total number of 173 localities at which NO₂ was monitored in 2005 the annual limit value, increased by the margin of tolerance 50 μg.m^-3, was exceeded at 4 stations in Prague (Svornosti, Legerova, Sokolovská and Jasmínová) and at 1 station in Děčín. All the measuring sites are markedly influenced by traffic.
The AMS traffic-oriented (hot spot) Prague 2-Legerova station recorded a great number of exceedences (174) of NO₂ hourly concentration 200 μg.m^-3, and the exceedence of the hourly concentration including the margin of tolerance (200+50 μg.m^-3) was recorded 36x, which represents the maximum tolerated number of exceedences per year (see Table II.4.8). The measurement results of this station confirm the big problem of the capital city of Prague with the traffic routes leading through the city centre. The exceedence of the hourly NO₂ concentration 200 μg.m^-3 increased by the margin of tolerance 50 μg.m^-3 was measured 1x at the AMS station Prague 5-Smíchov. In other localities in the Czech Republic (with sufficient number of measurements for the valid annual average) the value of 250 μg.m^-3 was not exceeded.
At most stations presented in Fig. II.4.23 both the annual average concentration and the 19^th highest hourly NO₂ concentration had a moderately declining trend until 2001. In 2002 this trend stopped and in 2003 there was a slight increase of NO₂ pollution at most localities. In 2004 a slight decrease was recorded but in 2005 the increasing trend of NO₂ concentrations continued again, similarly as in case of PM₁₀, at almost all stations.
The field of NO₂ annual average concentration (Fig. II.4.24) gives evidence of air pollution in the cities caused mainly by traffic.
Fig. II.4.25 presents the courses of hourly concentrations in 2005 showing the evident limit value exceedences in several localities. The AMS Prague 2-Legerova (hot spot), monitoring the traffic loads, showed the exceedence of the limit value 200 μg.m^-3 increased by the margin of tolerance in 36 cases in 2005.
When constructing the map in Fig. II.4.25 also traffic census from the year 2005 was regarded. As compared with the previous census in 2000, i.e. during the recent 5 years, the increase of traffic is significant. The higher NO₂ concentrations can occur also in the vicinity of local communications in the villages with intensive traffic and dense local transport network.

II. 4.2.1.4 Carbon monoxide

The insufficient burning of fossil fuels may be an anthropogenic source of air pollution caused by carbon monoxide. These processes occur mainly in transport and in stationary sources, namely household heating.
In 2005 carbon monoxide concentrations were measured at 39 localities. Maximum daily 8-hour running averages of carbon monoxide (Table II.4.10 and Figs. II.4.26 and II.4.27) do not exceed the limit value. At all localities the maximum daily 8-hour running average (as reads the definition for CO limit value), was measured below the lower assessment threshold. The highest concentration was measured at the traffic locality (hot spot) Ostrava-Českobratrská (4476 μg.m^-3). The courses of maximum daily 8-hour running averages for selected localities are presented in Fig. II.4.27.

II.4.2.1.5 Benzene

With the increasing intensity of road transport the monitoring of air pollution caused by aromatic hydrocarbons is becoming relevant. The decisive source of atmospheric emissions of aromatic hydrocarbons – and namely of benzene and its alkyl derivates – are above all exhaust gases of petrol motor vehicles. Another source are loss evaporative emissions produced during petrol handling, storing and distribution. Mobile sources emissions account for approx. 85 % of total aromatic hydrocarbons emissions, while the prevailing share is represented by exhaust emissions. It is estimated that the remaining 15 % of emissions come from stationary sources. Many of these are related to industries producing aromatic hydrocarbons and those industries that use these compounds to produce other chemicals.
The obtained data illustrate that benzene level in petrol is about 1.5 % while diesel fuels contain relatively insignificant levels of benzene. Exhaust benzene is produced primarily by unburned benzene from fuels. Non-benzene aromatics in the fuels can cause 70 to 80 % of the exhaust benzene formed. Some benzene also forms from engine combustion of non-aromatic fuel hydrocarbons. The most significant adverse effects from exposure to benzene are haematotoxicity and carcinogenicity [16].
The situation of the year 2005 is characterized in the Table II.4.11 and Fig. II.4.29. Of the total number of 26 localities monitoring benzene concentrations in 2005 the limit value 5 μg.m^-3 inreased by the margin of tolerance (in 2005 5 μg.m^-3) was exceeded at the ZÚ locality Ostrava-Přívoz (10.4 μg.m^-3). The air pollution limit value (without the margin of tolerance) was exceeded also at the CHMI locality Ostrava-Přívoz (7 μg.m^-3). It was confirmed that higher concentrations are connected with industrial activities (mainly with the production of coke) – locality Ostrava-Přívoz. With the increasing distance the concentrations are lower (Ostrava-Fifejdy 4.1 μg.m^-3) and they decrease much lower in the residential parts of Ostrava (Ostrava-Poruba 2.4 μg.m^-3). The map diagram (Fig. II.4.28) shows the overview of the development of average annual concentrations in 1999–2005. Fig. II.4.30 presents the annual course of 24-hour averages at selected localities.

II.4.2.1.6 Ground-level ozone

Ground-level ozone is formed under the influence of solar radiation during complex photochemical reactions mainly between nitrogen oxides, VOCs (mainly hydrocarbons) and other components of the atmosphere. Ground-level ozone is a secondary pollutant as its primary emitting from anthropogenic air pollution sources is not substantial.
The Government Order No. 350/2002 Coll., as amended, requires to assess the ozone concentrations in relation to human health protection as an average for the latest three years. If the latest three years are not available, the average for the latest two years or one year is taken into account pursuant to the Government Order. In 2005 ozone was measured at 72 localities out of which 50 exceeded the air pollution target value for the three-year period 2003–2005, or shorter (see Table II.4.12). According to this assessment the maximum number of exceedences was recorded, similarly as in 2004, at the locality Krkonoše-Rýchory, where the average number of exceedences of the maximum daily 8-hour running average 120 μg.m^-3 was reached in 75 cases. Relative number of exceedences (69.4 %) was similar as in the previous three-year period 2002–2004. If we go beyond the national legislation requirements and assess the year 2005 separately the target air pollution limit value was exceeded in 41 localities. The average 26^th highest maximum 8-hour running average for the localities measuring in the period 1996–2006 was slightly increased as compared with the year 2005, approximately to the level of 1996–2002.
The ground-level ozone concentrations generally grow with the increasing altitude which is confirmed also by the data measured for the year 2005 when the localities with highest loads (see Table II.4.12) are situated at higher altitudes. The traffic localities in the cities are least loaded as the ozone concentration is reduced mainly by NO emissions. It can be expected that the ozone concentrations are below the target air pollution limit value also in other cities with heavier traffic. However, due to the absence of measurements and the character of the used model, the decrease is not apparent in Fig. II.4.32.
Map diagram in Fig. II.4.31 shows the 26^th highest value of maximum 8-hour running average of ozone concentrations (three-year average) in 1996–2005.
The target air pollution limit value for the protection of health was exceeded in 99 % of the Czech Republic�s territory in the average for the period 2003–2005 (Fig. II.4.32). The average concentration of the 26^th value of the maximum 8-hour running average for the localities which measured continuously in the years 2001–2005 was slightly increased at rural stations in 2003–2005 in comparison with 2002–2004. For the urban stations the situation was comparable. On the contrary, the situation for rural stations is similar as in 2001–2003. At urban stations slight improvement was recorded as compared with the period 2001–2003.
Table II.4.12 presents the stations with the highest values of maximum daily 8-hour running average ozone concentrations in three-year average. Fig. II.4.33 shows the graph of the number of exceedences of the target air pollution limti value for ground-level ozone and Fig. II.4.34 presents the annual courses of maximum daily 8-hour running averages in the localities with the heaviest loads.
Table II.4.13 presents the number of hours of the ozone alert threshold exceedence (180 μg.m^-3) at selected AIM stations in the period of 1992–2005.

II.4.2.1.7 Heavy metals

Lead
Most lead contained in the atmosphere result from anthropogenic emissions caused by high-temperature processes, primarily the burning of fossil fuels, production of iron and steel and metallurgy of non-ferrous metals. Means of transport using leaded petrol represent a very significant source of anthropogenic emissions. In the natural processes lead is released through weathering of rocks and volcanic activity [14].
Airborne lead occurs in the form of fine particles with frequency particle size distribution characterized by the average aerodynamic diameter lower than 1 μm.
The long-term exposure to lead results in harmful impacts on haem biosynthesis, nervous system and blood pressure in humans. The evidence for carcinogenic potential of lead and its compounds in humans is inadequate [14, 15].
Similarly as in the previous years, the lead concentrations at all of the total number of 64 localities which submitted sufficient data for the calculation of valid annual average in 2005 were recorded below the limit value. (Table II.4.14). The highest lead concentrations did not even reach the lower assessment threshold. Maximum annual average was measured in Tanvald 57.1(ng.m^-3), followed by Ostrava-Přívoz (46.1 ng.m^-3) in the PM₁₀ fraction and 40.8 ng.m^-3 in the PM_2.5 fraction.
It is apparent from Fig. II.4.35 that lead levels at the majority of localities do not reach the limit value in the long terms. Courses of short-term average concentrations (24-hour or14-day concentrations, depending on the measurement schedule of the given station) at selected stations are presented Fig. II.4.36.

Cadmium
Globally, the anthropogenic sources of cadmium emission in the ambient air represent about 90 % (mainly iron and steel production, metallurgy of non-ferrous metals, refuse incineration and fossil fuels combustion (brown coal, hard coal and heavy fuel oils) [17]. Emission from transport are less significant. The remaining 10 % represent natural sources (mainly caused by volcanic activity).
Cadmium is bound mainly to the fine particles (aerodynamic diameter up to 2.5 μm), with higher risk of negative effects on human health. Almost all cadmium is bound to particles up to 10 μm, while the minimum amount of cadmium is found in particles with diameter above 10 μm.
The kidney is the critical organ with respect to long-term exposure to cadmium. Its carcinogenic effects are evident in experimental animals and there has been limited evidence in humans so far [15, 17].
In 2005 cadmium was measured at 64 localities which submitted sufficient data for the calculation of the valid annual average.
In the Czech Republic, the heaviest loads of cadmium concentrations are recorded in the Liberec Region (Fig. II.4.38). In 2005 the target air pollution limit value 5 ng.m^-3 as the annual average concentration was exceeded at the locality Tanvald. The annual average cadmium concentration in the PM₁₀ fraction reached 14.1 ng.m^-3 which is high above the target limit value. Cadmium concentrations at this locality reach high levels in the long term. It is supposed that this is caused mainly by high emissions from local glassworks.
The locality Souš where exceedence of the target limit value was recorded in 2004, the concentrations decreased below the target limit value in 2005. The annual average was 4.5 ng.m^-3.
The development of annual average concentrations in the period of 1996–2005 is apparent from Fig. II.4.37.
The courses of short-term (24-hour, or 14-day concentrations, according to the measurement schedule at the respective station) average cadmium concentrations at selected localities in 2005 are presented in Fig. II.4.39.

Arsenic
Arsenic occurs in many forms of inorganic and organic compounds. Anthropogenic sources represent about three quarters of total emissions in the ambient air. Significant amounts are contributed mainly from combustion processes (brown coal, hard coal and heavy fuel oils), iron and steel industry and production of copper and zinc. Main natural sources of arsenic include mainly volcanic activity, wildfires, weathering of minerals and activity of microorganisms (in wetlands, swamps and circumlittoral areas) [17].
Arsenic occurs largely in fine fractions (aerodynamic diameter up to 2.5 μm), which can be transported over long distances and can penetrate deeply into the respiratory system. Almost all arsenic is bound to particles with aerodynamic diameter up to 10 μm [17].
Inorganic arsenic can cause acute, subacute or chronic effects (local or affecting the whole organism). Lung cancer can be considered the critical effect following inhalation exposure [15, 17].
Of the total number of 64 localities which submitted sufficient data for the calculation of the valid annual average for 2005 the target air pollution limit value 6 ng.m^-3 was exceeded in the locality Tanvald (7.2 ng.m^-3). The supposed main reason is, similarly as in the case of cadmium, high emissions from local glassworks. The annual average in the locality Ostrava-Přívoz ZÚ amounted relatively close below the target limit value (5.8 ng.m^-3, see Table II.4.16).
The development of annual average concentrations during the years 1996–2005 is apparent from Fig. II.4.40.
The courses of short-term (24-hour, or 14-day concentrations, according to the measurement schedule at the respective station) average arsenic concentrations (Fig. II.4.42) show the seasonal character of the short-time arsenic concentrations in the ambient air and confirm the significant arsenic contribution from the burning of fossil fuels.

Nickel
Nickel is the fifth most abundant element of the earth core, though in the earth crust its percentage share is lower.
The main anthropogenic sources, which globally represent about three quarters of total emissions, include combustion of heavy fuel oils, mining of nickel-containing ores and nickel refinement, waste incineration and iron and steel production. Main natural sources include continental dust and volcanic activity.
Nickel occurs in the atmospheric aerosol in several chemical compounds which differ by its toxicity for human health and ecosystems.
Nickel is found (up to 30 %)in particles with aerodynamic diameter equal or higher than 10 μm which quickly settle in the vicinity of the source. The size of the remaining nickel particles is lower than10 μm and they can be transported over long distances [17].
The health effects include allergic dermatitis and there is evidence of nickel carcinogenicity for humans [15, 17].
None of the total number of 52 localities from which sufficient data for the calculation of the valid annual average for 2005 were obtained, similarly as in previous years, exceeded the set target air pollution limit value. The highest valid annual average concentration was measured at the locality Příbram OÚNZ with annual average concentration 5 ng.m^-3 which is about one half of the lower assessment threshold.
The annual course of short-term (24-hour, or 14-day) nickel concentrations is apparent from Fig. II.4.44.

II.4.2.1.8 Benzo(a)pyrene

The cause of the presence of benzo(a)pyrene, the main representative of polycyclic aromatic hydrocarbons (PAH) in the ambient air is, similarly as in other PAH, the insufficient burning of fossil fuels both in stationary and mobile sources, and also some technologies, as coke and iron production. Stationary sources are represented mainly by local heating. Mobile sources are represented mainly by diesel motors. The natural background level of benzo(a)pyrene is almost zero with the exception of wildfires [15]. Benzo(a)pyrene as well as several other PAHs are classified as proven human carcinogens [15, 19].
The number of localities monitoring benzo(a)pyrene increased from 16 stations in 2004 to 26 stations in 2005. The air pollution limit value (annual average 1 ng.m^-3) was exceeded at 22 localities. Compared to previous two years, both the absolute and the relative number of localities with exceedences increased. In 2005 the exceedences of the concentration 1 ng.m^-3 was reported from 85 % of localities (in 2004 – 56 %, in 2003 – 66 %). The Government Order No. 350/2002 Coll. was amended by the Government Order No. 429/2005 Coll. The margin of tolerance for benzo(a)pyrene was abrogated and the deadline for fulfilling the target limit value was set, and namely 31.12.2012.
The highest concentration was measured at the station Ostrava-Přívoz ZÚ (9.2 ng.m^-3). Fig. II.4.46 shows that the Ostrava area has the highest benzo(a)pyrene loads in the Czech Republic. Table II.4.18 shows that in almost all localities in the cities, where benzo(a)pyrene measurements were carried out, exceedences of the target air pollution limit value were recorded. Ostrava, Karviná, Prague, Ústí nad Labem and Hradec Králové have recorded long-term exceedences, in 2005, however, due to the extended measurement, exceedences were confirmed also in a number of other cities. Consequently, with regard to the serious benzo(a)pyrene impacts on human health (see above) the situation is rather alarming.
The field of annual average benzo(a)pyrene concentrations (Fig. II.4.46) prepared with the use of combination of emission dispersion models and the measured concentrations illustrate the significant contribution of this component in the delineation of the areas with deteriorated air quality. The areas where the target air pollution limit value for benzo(a)pyrene was exceeded represent 5.2 % of the state�s territory with about 35 % of the population.
However, it is necessary to consider that the estimates of the fields of annual average benzo(a)pyrene concentrations bear the greatest uncertainties which result both from insufficient measurement density and from uncertainties given by dispersion modelling of PAHs emissions; PAHs emission inventories represent the largest source of uncertainties. In 2005 again, benzo(a)pyrene measurements were extended within the National air pollution network and there were more valid annual average concentrations available than in the previous years. Further, it is necessary to note that even in the basic administrative units and cities where there are no measurements and which are not included in the map of air pollution the increased and above-the-limit-value benzo(a)pyrene concentrations may occur due to the local sources.
The development of annual average concentrations in individual localities during 1997–2005 is apparent from Fig. II.4.45. The annual course of short-term concentrations (24-hour once in 3 or 6 days) of benzo(a)pyrene is presented in Fig. II.4.47.

II.4.2.1.9 Other substances

Mercury
Main anthropogenic sources of mercury include combustion of fossil fuels, chlor-alkali production, metallurgy, cement production and refuse incineration. Mercury and its compounds are used in paint industry, battery production, measuring and control instruments (thermometers) [18].
The natural sources (representing about 60 % of total emissions) include mainly mercury evasion from aquatic ecosystems and vegetation, volcanic activity and de-gassing from mercury-rich minerals. It is estimated that in Europe 60 % of mercury is emitted in the form of elemental vapour Hg0, 30 % as divalent mercury (Hg (II)), and only 10 % as particulate phase mercury (H(p)). Most emission from natural sources are in gaseous form Hg0 [18].
Studies of occupationally exposed humans have shown adverse effects on the central nervous system and kidneys at high mercury vapour levels [18]. The increased concentration in the ambient air results in higher atmospheric deposition on top water layers and, consequently, in higher methylmercury concentrations in freshwater fish and its accumulation in food chains. [15, 18].
In 2005 the Government Order No. 350/2002 Coll. was amended by the Government Order No. 429/2005 Coll. which abrogated the valid air pollution limit value 50 ng.m^-3. However, the monitoring of air pollution concentrations continued. In 2005 the CHMI ISKO database received data on mercury concentrations from the CHMI locality Ústí nad Labem-město and from the locality Karviná ZÚ. Only the latter had the sufficient number of measurements for the calculation of the valid annual average. Similarly as in 2004, its value was 1.4 ng.m^-3, i.e. well below the previously valid air pollution limit value.
Ammonia
Major part of ammonia emitted in the ambient air is created by disintegration of nitrogenous organic materials from domestic animals breeding. The remaining amount us emitted through combustion processes or production of fertilizers. It is apparent that ammonia emissions in the ambient air are contributed by vehicles (formation of ammonia in catalytic convertors). Ammonia has irritating effects on eyes, skin and respiratory system. Chronic exposure to increased concentrations can cause headache and vomiting [20]. Quite significant are ammonia odour annoyance impacts on the population.
Similarly as in the case of mercury, the Government Order No. 350/2002 Coll. was amended by the Government Order No. 429/2005 Coll. which abrogated the previously valid limit value. Ammonia monitoring was carried out at 4 localities in 2005. The measured values remained well below the previously valid limit value. The highest daily value was measured at the station Lovosice-MÚ (7.3 μg.m^-3).

II.4.2.1.10 Trends of annual air pollution characteristics of SO₂, PM₁₀, NO₂, NO_x and O₃ for the period 1996–2005

The result concentrations of pollutants in the Czech Republic and agglomerations, related to the respective years, represent average values from the stations which measured for the whole monitored period.
Fig. II.4.48 shows the trends of SO₂, PM₁₀, NO₂, NO_x and O₃ annual air pollution characteristics in the Czech Republic for the period of 1996–2005. Up to the year 2000 air pollution caused by SO₂, PM₁₀, NO₂ and NO_x had a decreasing trend in the whole Czech Republic. In SO₂ and PM₁₀ concentrations the decline was very steep up to the year 1999. In 2001 the decreasing trend was interrupted in the whole Czech Republic and, on the contrary, a slight increase of SO₂, NO₂ and NO_x concentrations and a significant increase of PM₁₀ concentrations occurred. In 2004 this increasing trend of air pollution caused by PM₁₀, NO₂ and NO_x finished and, on the contrary, certain decrease of these pollutants� concentrations occurred, reaching almost the levels of the year 2001. In 2005 the PM₁₀ and NO₂ concentrations returned back to the increasing trend, in PM₁₀ the increase was steeper, beyond the level of the year 2002. Since 2003 a slight decrease of SO₂ concentrations has been observed.
In O₃ there is an apparent decreasing trend up to 1997. In 1998–2002 the O₃ concentrations stagnated. In 2003 there is apparent the increasing trend in concentrations due to long lasting very high temperatures and high levels of solar radiation. In 2004 O₃ concentrations decreased approximately to the level of the year 2001. In 2005 slight increase was recorded again, approximately to the level of the period 1998–2002. The graph of trend shows apparent higher concentrations at rural localities as compared with the concentrations from urban and suburban localities, where ozone is removed mainly by emissions from traffic.

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

In addition to the air pollution 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.

Territories in which the Government Order requires meeting the limit values for the protection of ecosystems and vegetation (EKO code is used in the maps and tables presented in this Yearbook):
a) national parks and protected landscape areas
b) territories with the altitude ≥ 800 meters
c) other selected forested areas published in the Bulletin of the Ministry of the Environment.

II.4.2.2.1 Sulphur dioxide

The results of air pollution monitoring with regard to the limit value for the protection of ecosystems is shown in the Tables II.4.21 and II.4.22 and in Figs. II.4.49–II.4.54. Of the total number of 21 stations classified as rural and measuring in the territory defined for the protection of ecosystems and vegetation, which supplied data valid for the year 2005, any station reported the exceedence of the limit value for annual average concentration. Only one station, Krupka (CHMI), recorded the limit value exceedences for the 2005/2006 winter average concentration (Table II.4.22).
Fig. II.4.49 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. Most rural stations recorded slight increase in SO₂ concentrations in the 2005/2006 winter average, as compared with the previous period, which is probably connected with deteriorated meteorological conditions at the beginning of the year 2006.
The maps in Fig. II.4.51 and II.4.52 show that in 2005 exceedences of the limit value occurred only occasionally and in the areas which are not included within the defined territories for the protection of ecosystems and vegetation, further in very small parts of the Krušné hory Mts. and České středohoří Mts., where the limit value exceedence reaches 0.1 % of the area of the defined territories for the protection of ecosystems and vegetation. The map was constructed from the data of all the stations measuring SO₂. The spot symbols highlight only the rural stations.
For the first time for the year 2005 the Yearbook presents also the graphs of courses of 24-hour SO₂ concentrations at selected stations, related to the air pollution limit value for the winter and annual average (Figs. II.4.53 and II.4.54).

II.4.2.2.2 Nitrogen oxides

Table II.4.23 and Figs. II.4.55–II.4.57 present the situation of ambient air pollution caused by NO_x with regard to ecosystems and vegetation protection. In 2005 the annual NO_x limit (30 μg.m^-3) was not exceeded at any station classified as rural and measuring in the territory defined for the protection of ecosystems and vegetation. 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 2005 slight increase of annual average NO_x concentration occurred at several rural stations (Fig. II.4.55). As it is evident from the map in Fig. II.4.56, in very limited localities of the territory defined by the Government Order on the protection of vegetation, 0.6 % of the area of the defined territory recorded the exceedence of the NO_x concentration air pollution limit value for the protection of ecosystems and vegetation. The occasional exceedences occurred mainly in northern Bohemia, in several small parts of the Krušné hory Mts. and the České středohoří Mts. and in the Central Bohemian Region.
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.
The construction of the map of the field of NO_x concentrations is based on the combination of measurement and modelling results and also traffic census from the year 2005 was regarded. As compared with the previous census in 2000, i.e. during the recent 5 years, 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.
Similarly as in the case of SO₂ the graphs of courses of 24-hour NO_x concentrations at selected stations, related to the limit value for the annual average are presented (Fig. II.4.57).

II.4.2.2.3 Ground-level ozone

For the assessment of vegetation protection against ozone exceedences the national legislation uses, in compliance with the respective EU Directive, the exposure index AOT40². The survey of stations with the highest values of AOT40 is given in Table II.4.24. Of the total number of 29 rural and suburban stations for which the AOT40 calculation is relevant according to the legislation, the air pollution target for the protection of vegetation was exceeded at 20 localities in 2005 (the average for the years 2001–2005). The target limit value for the protection of vegetation was exceeded (in the average for the same period) in 11 of 12 localities operating on the territory defined by the Government Order as the territory on which the limit for the protection of vegetation is not to be exceeded (the stations have the EKO code in the last column of the table). Fig. II.4.58 shows the values of AOT40 exposure index in the 5-year average (min. 3 years) at selected stations in 1996–2005.
The spatial distribution of AOT40 exposure index in 2005 is shown in the map in Fig. II.4.59. It is evident that in the average for the years 2001–2005 exceedences occurred.in 99 % of the territory in which, in compliance with the Government Order the limit value for vegetation protection is not to be exceeded. Since 2004 higher regression coefficient has been used in map construction which results in the increased share of the territory with limit values exceedences. The reason was the observed steeper increase of ozone concentrations with higher altitudes in the period under review.
Fig. II.4.60 presents the AOT40 development in 2001–2005 at selected stations.

Tab. II.4.1 Stations with the highest values of the 25^th and maximum hourly concentrations of SO₂

Tab. II.4.2 Stations with the highest numbers of exceedences of the 24-hour limit value of SO₂

Tab. II.4.3 Stations with the highest values of annual average concentrations of SO₂

Tab. II.4.4 Stations with the highest numbers of exceedences of the 24-hour limit value of PM₁₀

Tab. II.4.5 Stations with the highest values of annual average concentrations of PM₁₀

Tab. II.4.6 Overview of localities with the exceedence of the air pollution limit value for annual average PM₁₀ concentration, 2001–2005

Tab. II.4.7 Stations with the highest values of annual average concentrations of PM_2.5

Tab. II.4.8 Stations with the highest values of the 19th and maximum hourly concentrations of NO₂

Tab. II.4.9 Stations with the highest values of annual average concentrations of NO₂

Tab. II.4.10 Stations with the highest values of maximum 8-hour running average concentrations of CO

Tab. II.4.11 Stations with the highest values of annual average concentrations of benzene

Tab. II.4.12 Stations with the highest values of maximum daily 8-hour running average concentrations of surface ozone

Tab. II.4.13 Number of hours of the surface ozone alert threshold exceedence (180 μg.m^-3) per year at selected AIM stations, 1992–2005

Tab. II.4.14 Stations with the highest values of annual average concentrations of lead in the ambient air

Tab. II.4.15 Stations with the highest values of annual average concentrations of cadmium in the ambient air

Tab. II.4.16 Stations with the highest values of annual average concentrations of arsenic in the ambient air

Tab. II.4.17 Stations with the highest values of annual average concentrations of nickel in the ambient air

Tab. II.4.18 Stations with the highest values of annual average concentrations of benzo(a)pyrene in the ambient air

Tab. II.4.19 Stations with the highest values of average concentrations of mercury in the ambient air

Tab. II.4.20 Stations with the highest values of average concentrations of ammonia in the ambient air

Tab. II.4.21 Stations with the highest values of annual averages of SO₂ concentrations at rural stations

Tab. II.4.22 Stations with the highest values of winter averages of SO₂ concentrations at rural stations, 2005/2005

Tab. II.4.23 Stations with the highest values of annual average of NO_x and NO₂ concentrations at rural stations

Tab. II.4.24 Stations with the highest exposure index AOT40 values of ozone at rural and suburban stations

Fig. II.4.10 4^th highest 24-hour concentrations and maximal hourly concentrations of SO₂ in 1996–2005 at selected stations

Fig. II.4.11 Field of the 4^th highest 24-hour concentration of SO₂ in 2005

Fig. II.4.12 Stations with the highest hourly concentrations of SO₂ in 2005

Fig. II.4.13 Stations with the highest 24-hour concentrations of SO₂ in 2005

Fig. II.4.14 36^th highest 24-hour concentrations and annual average concentrations of PM₁₀ in 1996–2005 at selected stations

Fig. II.4.15 Field of the 36^th highest 24-hour concentration of PM₁₀ in 2005

Fig. II.4.16 Field of annual average concentration of PM₁₀ in 2005

Fig. II.4.17 Stations with the highest exceedence of LV for 24-hour concentrations of PM₁₀ in 2005

Fig. II.4.18 Stations with the highest exceedence of LV for annual concentrations of PM₁₀ in 2005

Fig. II.4.19 Numbers of exceedences of air pollution limit value for the 24-hour concentration of PM₁₀ in 2005

Fig. II.4.20 Annual average PM₁₀ concentrations at the stations with the exceedence of the limit value, 2001–2005

Fig. II.4.21 Annual average concentration of PM_2.5 at stations in 2005

Fig. II.4.22 Average monthly PM_2.5/PM₁₀ proportions in 2005

Fig. II.4.23 19^th highest hourly concentrations and annual average concentrations of NO₂ in 1996–2005 at selected stations

Fig. II.4.24 Field of annual average concentration of NO₂ in 2005

Fig. II.4.25 Stations with the highest hourly concentrations of NO₂ in 2005

Fig. II.4.26 Maximum 8-hour running average concentrations of CO in 1996–2005 at selected stations

Fig. II.4.27 Stations with the highest values of maximum 8-hour running average concentrations of CO in 2005

Fig. II.4.28 Annual average concentrations of benzene in 1999–2005 at selected stations

Fig. II.4.29 Field of annual average concentration of benzene in the ambient air in 2005

Fig. II.4.30 24-hour concentrations at the stations with the highest annual benzene concentrations in 2005

Fig. II.4.31 26th highest values of maximum 8-hour running average of surface ozone concentrations (three-year average) in 1996–2005 at selected stations

Fig. II.4.32 Field of the 26^th highest maximum daily 8-hour running average of surface ozone concentration in three-year average, 2003–2005

Fig. II.4.33 Numbers of exceedences of the target limit value for the maximum daily 8-hour running average of surface ozone concentrations in three-year average, 2003–2005

Fig. II.4.34 Stations with the highest values of maximum daily 8-hour running average concentrations of surface ozone in 2003–2005

Fig. II.4.35 Annual average concentrations of lead in the ambient air in 1996–2005 at selected stations

Fig. II.4.36 1/14-day average concentrations of lead in the ambient air at selected stations in 2005

Fig. II.4.37 Annual average concentrations of cadmium in the ambient air in 1996–2005 at selected stations

Fig. II.4.38 Field of annual average concentration of cadmium in the ambient air in 2005

Fig. II.4.39 1/14-day average concentrations of cadmium in the ambient air at selected stations in 2005

Fig. II.4.40 Annual average concentrations of arsenic in the ambient air in 1996–2005 at selected stations

Fig. II.4.41 Field of annual average concentration of arsenic in the ambient air in 2005

Fig. II.4.42 1/14-day average concentrations of arsenic in the ambient air at selected stations in 2005

Fig. II.4.43 Annual average concentrations of nickel in the ambient air in 1996–2005 at selected stations

Fig. II.4.44 1/14-day average concentrations of nickel in the ambient air at selected stations in 2005

Fig. II.4.45 Annual average concentrations of benzo(a)pyrene in 1997–2005 at selected stations

Fig. II.4.46 Field of annual average concentration of benzo(a)pyrene in the ambient air in 2005

Fig. II.4.47 24-hour concentrations at the stations with the highest annual concentrations of benzo(a)pyrene in 2005

Fig. II.4.48 Trends of SO₂, PM₁₀, NO₂, NO_x and O₃ annual characteristics in the Czech Republic, 1996–2005

Fig. II.4.49 Annual average concentrations of SO₂ in 1996–2005 at selected stations

Fig. II.4.50 Winter average concentrations of SO₂ in 1996/1997–2005/2006 at selected stations

Fig. II.4.51 Field of annual average concentration of SO₂ in 2005

Fig. II.4.52 Field of average concentration of SO₂ in the winter period 2005/2006

Fig. II.4.53 24-hour concentrations at the stations with the highest annual concentrations of SO₂ in 2005

Fig. II.4.54 24-hour concentrations at the stations with the highest winter concentrations of SO₂ in the winter period 2005/2006

Fig. II.4.55 Annual average concentrations of NO_x and NO₂ in 1996–2005 at selected stations

Fig. II.4.56 Field of annual average concentration of NO_x in 2005

Fig. II.4.57 24-hour concentrations at the stations with the highest annual concentrations of NO_x in 2005

Fig. II.4.58 Exposure index AOT40 values of ozone in 1996–2005 at selected stations, average for 5 years

Fig. II.4.59 Field of exposure index AOT40 values, average for 5 years, 2001–2005

Fig. II.4.60 Stations with the highest exposure index AOT40 values in recent 5 years, 2001–2005

¹  Defined in [22] as: Particulate matter originated from atmospheric reactions between sulphur and nitrogen oxides, and ammonia and organic compounds. (see also http://glossary.eea.eu.int/EEAGlossary/S/secondary_particles).

² AOT40: accumulated exposure is calculated as the sum of the difference between hourly ozone concentrations and the threshold level of 80 μg.m^-3 (= 40 ppb) for each hour when this threshold value was exceeded. Pursuant to the requirements of the Government Order No. 350/2002 Coll. AOT40 is calculated for the period of three months (May to July) measured between 8:00 and 20:00 Central European Time (= 7:00 and 19:00 UTC).