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AIR POLLUTION IN THE CZECH REPUBLIC IN 2011 Czech Hydrometeorological Institute - Air Quality Protection Division |
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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 (SO2) emitted from anthropogenic sources is created mainly by burning the fossil fuels (coal and heavy fuel oils) and by smelting ores containing sulphur. 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 substances originating from it are removed from the atmosphere through wet and dry deposition. SO2 has irritating effects, high concentrations can cause lung function impairment and the change of lung capacity [15]. The 2011 situation of air pollution caused by SO2 with regard to the limit values set by the legislation is documented by the Tables II.4.2.1 and II.4.2.2 and Figs. II.4.2.1–II.4.2.4. The table of annual average SO2 concentrations is also included to illustrate the situation (Table II.4.2.3). In 2011 neither the limit value for the hourly SO2 concentration nor for the 24-hour SO2 concentration were exceeded in the Czech Republic at any measuring station. At the stations in Ostrava the tolerated number of exceedances (less than or equal to three) of the level for the 24-hour limit value (125 μg.m-3). The highest number of exceedances was recorded in the localities Ostrava-Přívoz (3x), Ostrava-Fifejdy (2x) and Ostrava-Mariánské Hory (1x). Similarly, in case of hourly concentrations the limit value (350 μg.m-3) was exceeded in the tolerated number (less than or equal to 24); the highest number of exceedances was recorded again in the localities in Ostrava and further in the Ústí nad Labem Region (Ostrava-Přívoz 19x, Ostrava-Fifejdy 19x and Ostrava-Mariánské Hory 5x, Komáří Vížka 5x). Less than three exceedances were recorded in the localities in Karviná, Sokolov, Chomutov, Teplice, Most and Pardubice. Fig. II.4.2.1 shows the development of the 4th highest 24-hour and 25th highest hourly SO2 concentration in selected localities. In 2011, in comparison with the year 2010, SO2 concentrations decreased in most localities. 69 % of localities recorded the decrease of the 25th highest 1-hour concentration, 78 % of localities recorded the decrease of the 4th highest 24-hour concentration. Higher concentrations in 2010 were given mainly by the occurrence of unfavourable meteorological and dispersion conditions in the winter period (mainly in January and February) and due to coldest heating season for the recent 10 years. Spatial distribution of the 4th highest 24-hour SO2 concentration is presented in Fig. II.4.2.2. It is apparent that only in approx. 1.3 % of the territory of the Czech Republic SO2 concentrations exceeded the lower assessment threshold. Figs. II.4.2.3 and II.4.2.4 document the courses of 1-hour and 24-hour SO2 concentrations at selected stations in 2011. Tab. II.4.2.1 Stations with the highest values of the 25th and maximum hourly concentrations of SO2 Tab. II.4.2.2 Stations with the highest numbers of exceedances of the 24-hour limit value of SO2 Tab. II.4.2.3 Stations with the highest values of annual average concentrations of SO2
Fig. II.4.2.1 4th highest 24-hour concentrations and 25th highest hourly concentrations of SO2 in 2001–2011 at selected stations
Fig. II.4.2.2 Field of the 4th highest 24-hour concentration of SO2 in 2011
Fig. II.4.2.3 Stations with the highest hourly concentrations of SO2 in 2011
Fig. II.4.2.4 Stations with the highest 24-hour concentrations of SO2 in 2011
II. 4.2.1.2 Suspended particles, PM10 fraction and PM2.5 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, from the natural sources (e.g. volcanic activity, pollen dust or sea spray aerosols) or anthropogenic sources (e.g. combustion of fossil fuels in stationary and mobile sources, tyre wear particulate matter, brake lining dust, road dust). Secondary particles are mostly of anthropogenic origin and are created in the atmosphere from their gaseous precursors SO2, NOx and NH3 through the process called gas-particles conversion. Their share in total emissions of particles in the Czech Republic is about 90 %. The main sources of total emissions, i.e. primary particles and precursors of secondary particles (SO2, NOx, NH3) in the Czech Republic include power engineering (production of electric and heat energy), transport and manufacturing processes. 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 appearing already at low concentrations without a clear lower safe concentrations threshold. Health impacts of particles are influenced by their concentration, size, shape and chemical composition. The acute impact of particles may cause the irritation of mucous membranes of the respiratory system, the increased production of mucus etc. These changes may cause hypo-immunity and increase predispositions to respiratory diseases. The recurrent diseases may result in chronic bronchitis and cardiovascular disorders. The acute impact of particles may accentuate the symptoms in asthmatics and increase the total morbidity and mortality of population. The long-term exposure to particles may result in chronic bronchitis or lower life expectancy. Recently it has been proved that the most serious health impacts (incl. increased mortality) are recorded in fine PM2.5 or PM1 fractions which enter the lower parts of the respiratory system when inhaled. The level of health implications is influenced by a number of factors, such as the current health condition of the individual, allergic predisposition or smoking. Children, the elderly and people who have problems with lung or heart disease are the sensitive groups [36]. Air pollution caused by PM10 remains one of the main problems of air quality assurance. In almost all localities in the Czech Republic there is an apparent increasing trend in air pollution caused by PM10 from 2001 to 2003. In 2004 this trend stopped but in 2005 the PM10 concentrations increased again at almost all localities. In 2006 this trend continued at most localities in annual averages. In 2007, on the contrary, the decrease of PM10 concentrations was recorded. In 2008 the decreasing trend continued at most stations, mainly in daily concentrations. In 2009 there prevailed a slight increase, more marked in the agglomeration Moravian-Silesian Region. In 2010 the PM10 concentrations increased, both in daily and annual characteristics (Figs. II.4.2.5 and II.4.2.6). The greatest increase was recorded again in the zone Moravian-Silesian Region. The growth of concentrations of the suspended particles in 2010 was caused mainly by repeated occurrence of unfavourable meteorological and dispersion conditions in the winter period (January and February) and at the end of the year (October, December). The increase of PM10 concentrations in 2010 was caused probably also by the coldest heating season for the recent 10 years. In 2011 the slight decrease of the 36th highest PM10 concentration was recorded (in average for all types of stations). Nevertheless, the increase of concentrations at urban traffic stations was recorded, and namely by approx. 8 % (4 μg.m-3) as compared with the year 2010. The average concentration at most rural stations decreased below the level of the daily limit value, the concentrations in other types of localities remain above the limit value (Figs. II.4.2.5 and II.4.2.6). It is clear from the data from the localities where the annual limit value was exceeded at least once in the recent 5 years (2007–2011) that the most loaded areas are: the Ostrava-Karviná area, the agglomerations Prague and Brno and the Kladno area. Further, the data show that the highest PM10 loads were recorded in the year 2010, as concerns the assessment of the recent 5 years (Fig. II.4.2.12 and Table II.4.2.6). The exceedance of the daily limit value for PM10 in 2011 at least in one locality was recorded in all zones and agglomerations (Fig. II.4.2.11). In comparison with the year 2010 the highest 36th average 24-hour concentration decreased at 51 % of stations, at 4 % of the stations there was no change and it increased at the remaining stations (the same file of stations with measurements both in 2010 and 2011 has been assessed). In 2011 the most affected area of large coverage was, similarly as in the previous years, the Ostrava-Karviná area. The limit value of 24-hour PM10 concentration was exceeded in 2010 in all localities in the agglomeration the Moravian-Silesian Region and in more than half to most of localities in the zones Ústí nad Labem, Central Bohemian, Olomouc and Zlín regions and in the agglomerations Prague and Brno. The limit value exceedance was recorded in 1 to 3 localities in the remaining zones (Table II.4.2.4). Of the total number of 157 localities in which PM10 measurements were carried out in 2011, 89 localities reported exceedances of 24-hour PM10 limit value (in 2010 83 of 158); (Fig. II.4.2.15). Limit value exceedances are still significant for listing the basic administrative units among the areas with deteriorated air quality. Especially 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 exceeding the limit value. The spatial projections of PM10 concentrations show, that in 2011 the limit values for PM10 24-hour average concentration were exceeded in 21.8 % of the territory of the Czech Republic (Fig. II.4.2.7) with approx. 50.8 % of inhabitants (in 2010 the exceedance was recorded in 21.2 % of the territory with ca 48 % of inhabitants). The graphs of courses of 24-hour concentrations of PM10 in 2011 in the localities, where the limit values for annual average and for 24-hour average were exceeded, are shown in Figs. II.4.2.9 and II.4.2.10. The concentrations of PM10 show a clear course with the highest concentrations in the cold months of the year. Higher concentrations of PM10 in the ambient air during the cold part of the year may be influenced both by higher emissions of particles from seasonal sources (e.g. the share of local heating as concerns PM10 emissions is more than 30 %), and by deteriorated dispersion conditions. In 2011 this applied mainly to the periods January–March and October–December. The maximum concentrations in February and November correspond with bad dispersion conditions in these months. Moreover, these months were subnormal as concerns both temperatures and precipitation, November is characterized even as extremely dry [47]. Consequently, the washing of pollutants from the atmosphere was not sufficient; subnormal February and November temperatures could contribute also to higher intensity of heating. In February and November there were recorded concentrations close to the limit value even in rural localities (Fig. II.4.2.50). The annual PM10 limit value was exceeded in 18 of 169 localities in 2011 (in 2010 in 25 of 170 – Fig. II.4.2.15), the highest annual averages were recorded in the locality Stehelčeves (55.1 μg.m-3), Bohumín (52.7 μg.m-3) and Věřňovice (51.6 μg.m-3). The limit value was exceeded in 2011 mainly in the localities in the Ostrava-Karviná area (in 14 localities), in the Kladno area (in 3 localities) and in one locality in the zone Zlín Region(Table II.4.2.5). The average annual concentrations of PM10 decreased at 65 % of stations (again, the same file of stations for the years 2010 and 2011 has been assessed); the limit value was exceeded in 0.7 % of the territory of the Czech Republic (in 2010 in 1.85 % of the territory). Since 2004 the fine fraction of suspended particles (PM2.5) has been measured in the Czech Republic. In 2011 the measurements were carried out in 49 localities. The measurement results show significant contribution of PM2.5 fraction to air pollution situation, and particularly in the part of the agglomeration Moravian-Silesian Region. When comparing the results with the annual target value (25 μg.m-3) pursuant to the Government Order No. 597/2006 Coll., on air quality monitoring and assessment, as amended, it is evident that in 13 localities the limit value was exceeded (in 2010 the limit value was exceeded in 12 localities of 38; Fig. II.4.2.15). The exceedances occurred namely in the localities in the Ostrava-Karviná area (Věřňovice, Bohumín, Ostrava-Radvanice ZÚ, Ostrava-Přívoz, Ostrava-Zábřeh, Třinec-Kosmos, Studénka and Ostrava-Poruba/ČHMÚ), in the agglomeration Brno (Brno-Svatoplukova, Brno-Zvonařka and Brno-Lány), in the locality Přerov in the zone Olomouc Region and in the locality Plzeň-Lochotín in the zone Plzeň Region (Table II.4.2.7). The annual average PM2.5 concentrations at individual localities in the period 2004–2011 are presented in Fig. II.4.2.13. The year-to-year comparison (again, the same file of stations with measurements both in 2010 and 2011 has been assessed) shows that there was the decrease of the average annual concentration at 79 % of stations. For the first time also the map of the field of average annual concentrations of PM2.5 suspended particles was created for the 2011 assessment. The estimated part of the territory of the Czech Republic with the exceedances of the limit value is 2.6 % (Fig. II.4.2.14). The share of inhabitants exposed to the above-the-limit PM2.5 concentrations is estimated to 13.5 %. Nevertheless, it is necessary to point out, that the mapping methods will be constantly developed, mainly according to the number of measuring stations and their characteristic. According to the annual course of PM2.5 concentrations with regard to the exceedance of the annual target value (Fig. II.4.2.17) it can be stated that the pollution caused by this pollutant occurs mainly during the cold part of the year (the months of January, February, November, December) Higher concentrations of this pollutant in the cold part of the year are caused by emissions from heating and by deteriorated dispersion conditions. The measurement results indicate that the ratio between PM2.5 and PM10 is not constant but shows certain seasonal course and it is also dependent on the locality position (Fig. II.4.2.16). In 2011 the ratio, in the average from 33 localities in the Czech Republic simultaneously measuring PM2.5 and PM10 and with sufficient number of values, ranged from 0.65 (August) to 0.81 (January) with lower values in the summer period. In Prague, where the annual course is influenced by a large share of traffic localities, this ratio ranged from 0.48 (June) to 0.74 (February), in Brno from 0.65 (July) to 0.78 (February) and in the Moravian-Silesian Region from 0.70 (August–September) to 0.86 (January). When comparing the ratio with regard to the classification of localities, the ratio in urban localities is from 0.68 (June) to 0.82 (November), in suburban localities from 0.64 (September) to 0.80 (February), and in traffic localities from 0.60 (September) to 0.72 (January). The seasonal course of PM2.5/PM10 fraction ratio is connected with the seasonal character of several emission sources. Emissions from combustion sources show higher shares of PM2.5 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 PM2.5 fraction in comparison with PM10 fraction. The decrease during the spring and early summer is also explained by the increased amount of larger biogenic particles (e.g. pollen) by some authors [29]. The lowest PM2.5/PM10 ratio is at traffic localities (Fig. II.4.2.16). During fuel combustion the emitted particles occur mainly in PM2.5 fraction and thus the ratio should be high in traffic localities. The fact that this is not the case, accents the significance of emissions of larger particles caused by tire, break lining and road surface abrasion. The share of the coarse fraction at traffic stations increases also due to the re-suspension of particles following winter spreading of roads. The growth of PM10 concentrations can be caused also by the increased abrasion of road surface by spreading and the subsequent re-suspension of the abraded material [48]. Higher PM2.5/PM10 ratio in the localities of the Moravian-Silesian Region is connected with a great share of industrial sources in the Ostrava-Karviná area.
Tab. II.4.2.4 Stations with the highest numbers of exceedances of the 24-hour limit value of PM10 Tab. II.4.2.5 Stations with the highest values of annual average concentrations of PM10 Tab. II.4.2.7 Stations with the highest values of annual average concentrations of PM2.5
Fig. II.4.2.5 36th highest 24-hour concentrations and annual average concentrations of PM10 in 2001–2011 at selected stations with UB, SUB, I and T classification
Fig. II.4.2.6 36th highest 24-hour concentrations and annual average concentrations of PM10 in 2001–2011 at selected rural (R) stations
Fig. II.4.2.7 Field of the 36th highest 24-hour concentration of PM10 in 2011
Fig. II.4.2.8 Field of annual average concentration of PM10 in 2011
Fig. II.4.2.9 Stations with the highest exceedance of LV for 24-hour concentrations of PM10 in 2011
Fig. II.4.2.10 Stations with the highest exceedance of LV for annual concentrations of PM10 in 2011
Fig. II.4.2.11 Numbers of exceedances of the limit value for 24-hour concentration of PM10 in 2011
Fig. II.4.2.12 Annual average PM10 concentrations at the stations with the exceedance of the limit value, 2007–2011
Fig. II.4.2.13 Annual average concentrations of PM2.5 in the ambient air in 2004–2011 at selected stations
Fig. II.4.2.14 Field of annual average concentration of PM2.5 in 2011
Fig. II.4.2.15 Share of localities with the exceedance of the limit value for 24-hour concentrations and annual average concentrations of PM10 and target value for the annual average concentration of PM2.5, 2000–2011
Fig. II.4.2.16 Average monthly PM2.5/PM10 ratio in 2011
Fig. II.4.2.17 Stations with the highest exceedance of LV for annual concentrations of PM2.5 in 2011
II.4.2.1.3 Nitrogen dioxide In the field of ambient air monitoring and assessment the term nitrogen oxides (NOx) 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 NOx. More than 90 % of the total nitrogen oxides in the ambient air are 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. In a number of chemical reactions part of NOx is transformed to HNO3/NO3-, which are removed from the atmosphere through dry and wet deposition. 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, NOx 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 NOx emissions result from combustion directly in the form of NO2. Natural NOx 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 [38]. Exposure to the increased NO2 concentrations affects lung function and can cause lower immunity [15]. The exceedances of annual limit values for NO2 occur only in limited number of stations, and namely in the localities in agglomerations and large cities exposed to traffic. Of the total number of 155 localities in which NO2 was monitored in 2011 the annual limit value was exceeded at 8 stations (Table II.4.2.9). Seven of them are classified as traffic urban, one station as background urban. It can be expected that the exceedances of the limit values can occur also at other sites exposed to traffic, where there is no measurement. The station Prague 2-Legerova (hot spot), aimed at ambient air pollution monitoring caused by traffic, recorded, similarly as in the previous years, the exceedance of the limit value for the hourly concentration. The measurements results at this station confirm the big problem of the capital city of Prague with the traffic running through the city centre. The level of 200 μg.m-3 was exceeded 51x in 2011, while the tolerated number of exceedances is 18; three further localities recorded the exceedance of the limit value (200 μg.m-3), but only once within the year, and thus the limit value was not exceeded. Fig. II.4.2.18 presents the development of the 19th highest hourly concentration and the annual average concentration of NO2 in the period 2001–2011 in selected localities. In 2002, in comparison with the previous years, this decreasing trend of NO2 concentrations 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 appeared again, and continued in 2006. In 2007 a marked decrease of NO2 concentrations was recorded due to more favourable meteorological and dispersion conditions, similarly as in 2008; in the following year, 2009, on the contrary, most stations recorded a slight increase of NO2 concentrations. In 2010, in comparison with 2009, there was recorded a slight increase of annual average concentration in more than 70 % of localities. On the contrary, in 2011 in comparison with the year 2010 the NO2 concentrations decreased in most localities. Approximately 80% of localities recorded both the decrease of the 19th highest 1-hour concentration and the annual average. The map of the field of NO2 annual average concentration (Fig. II.4.2.19) gives evidence of air pollution in the cities caused mainly by traffic. Figs. II.4.2.20 and II.4.2.21 show the graphs of the courses of daily and hourly concentrations in 2011 showing the evident limit value exceedances in selected localities. When constructing the map in Fig. II.4.2.19 also the updated data on emissions from mobile sources in the Czech Republic were regarded. The higher NO2 concentrations can occur also in the vicinity of local communications with intensive traffic and dense local transport network.
Tab. II.4.2.8 Stations with the highest values of the 19th and maximum hourly concentrations of NO2
Tab. II.4.2.9 Stations with the highest values of annual average concentrations
of NO2
Fig. II.4.2.18 19th highest hourly concentrations and annual average concentrations of NO2 in 2001–2011 at selected stations
Fig. II.4.2.19 Field of annual average concentration of NO2 in 2011
Fig. II.4.2.20 Stations with the highest hourly concentrations of NO2 in 2011
Fig. II.4.2.21 Stations with the highest exceedance of LV for annual concentrations of NO2 in 2011
The insufficient burning of fossil fuels may be an anthropogenic source of air pollution caused by carbon monoxde (CO). These processes occur mainly in transport and in stationary sources, namely household heating. Increased CO concentrations can cause headache, deteriorated coordination and attention. CO binds to haemoglobin and the increased concentrations of the created carboxyhaemoglobin reduce the capacity of blood for the oxygen transport. In 2011 carbon monoxide concentrations were measured at 33 localities, classified in most cases as traffic localities in which the highest measured concentrations can be expected. The maximum daily 8-hour running averages did not exceed, similarly as in the previous years, the limit value (10 mg.m-3) at any of the stations (Table II.4.2.10). The highest daily 8-hour average concentration was measured, in the same locality as in the previous three years, and namely in the hot spot locality Ostrava-Českobratrská (3 419.3 μg.m-3). The courses of maximum daily 8-hour running averages for selected localities are
presented in Fig. II.4.2.23.
Fig. II.4.2.22 Maximum daily 8-hour running average concentrations of CO in 2001–2011 at selected stations
Fig. II.4.2.23 Stations with the highest values of maximum daily 8-hour running average concentrations of CO in 2011
II.4.2.1.5 Benzene The anthropogenic sources produce more than 90 % of total emissions in the air. The decisive emission sources are combustion processes, mainly mobile sources, representing about 85 % of total anthropogenic emissions of aromatic hydrocarbons. The prevailing share is contributed by exhaust gases 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 the industries that use these compounds to produce other chemicals. Another significant source is represented by loss evaporative emissions produced during petrol handling, storing and distribution. Exhaust benzene is produced primarily by unburned benzene from fuels. Non-benzene aromatics or non-aromatic hydrocarbons in the fuels can contribute to exhaust benzene emissions. The most significant adverse effects from exposure to benzene are haematotoxicity and carcinogenicity [16]. In 2011 benzene concentrations were measured in total in 32 localities with
valid annual average. The limit value is defined as an annual average
concentration 5 μg.m-3. The value of the limit value was exceeded, similarly as
in the previous years, in the locality Ostrava-Přívoz (6.8 μg.m-3). Higher
concentrations in this area are connected with industrial activities (mainly
with coke production). In comparison with the year 2010, approximately three
quarters of localities recorded the decrease of annual average concentration,
one quarter of localities, on the contrary, recorded its increase. The courses
of annual average concentrations in selected localities are shown in Fig.
II.4.2.24. Fig.
II.4.2.26 presents the annual course of 24-hour averages in
selected localities.
Tab. II.4.2.11 Stations with the highest values of annual average concentrations of benzene
Fig. II.4.2.24 Annual average concentrations of benzene in 2001–2011 at selected stations
Fig. II.4.2.25 Field of annual average concentration of benzene in the ambient air in 2011
Fig. II.4.2.26 24-hour concentrations at the stations with the highest annual benzene concentrations in 2011
II.4.2.1.6 Ground-level ozone Ground-level ozone is a secondary pollutant in the ambient air with no significant emission source of its own. It is formed under the influence of solar radiation during complex photochemical reactions mainly between nitrogen oxides (NOx), VOCs and other components of the atmosphere. Ozone is a very powerful oxidizing agent. Ozone impairs mainly the respiratory system and irritates mucous membranes. It causes morphological, biochemical and functional changes and impairs the immune system response. There is evidence for ozone toxicity to vegetation. The Government Order No. 597/2006 Coll., as amended, requires the assessment of 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 2011 ozone was measured at 76 localities out of which 11 (14.5 %) exceeded the target value within the three-year period 2009–2011, or shorter. In comparison with the previous three-year period 2008–2010 the number of exceedances of the target value 120 μg.m-3 decreased in 55 % of localities, 36 % of localities recorded the increase and 9 % of localities did not record any difference. Consequently, the situation had not changed markedly as compared with the previous three-year period 2008–2010, as it is documented in Fig. II.4.2.29. The comparison of the assessed three-year periods is based mainly on meteorological conditions, i.e. the values of solar radiation, temperature and precipitation in the period from April to September when the highest ozone concentrations are usually measured. When comparing the meteorological conditions in the year 2008, which was not included in the three-year assessment period, and in 2011, there were measured slightly higher temperatures in 2011 during the period April–September (in average by 0.6 C). Approximately three quarters of localities monitoring the respective meteorological parameters recorded the increase of maximum temperatures and 81 % of localities recorded the increase of the total values of daily averages of global solar radiation. According to [39] the year-to-year differences in ozone concentrations are, at the current level of the concentrations of ground-level ozone precursors, given primarily by the above mentioned meteorological conditions and the influence of precursors concentrations is not much significant. The comparison of the concentrations of ground-level ozone precursors in 2008 and 2011 shows that in about two thirds of substances included into the VOC group, monitored in detail in Košetice and Libuš, a slight increase of concentrations was recorded. On the contrary, the annual NO2 concentrations slightly decreased (in 58 % of localities) in comparison with the year 2008. With regard to rather complicated atmospheric chemical processes during ozone formation and disintegration, its dependence on absolute amount and relative representation of its precursors in atmosphere, connected also with long-range transboundary air pollution and on meteorological conditions, it is difficult to comment the year-to-year changes in more detail. The localities with the respective numbers of exceedances of the target value (120 μg.m-3) are presented in Table II.4.2.12). The traffic localities in the cities are the least loaded ones as ozone is degraded there through chemical reaction with NO, as it is apparent from Fig. II.4.2.50. It can be expected that the ozone concentrations are below the target value also in other cities with heavier traffic. However, due to the absence of measurements the probable decrease cannot be documented by the use of current methods of map construction. On the contrary, the highest concentrations are measured in rural background localities due to lower concentrations of substances able to degrade ozone (NO). Fig. II.4.2.27 shows the 26th highest value of maximum 8-hour running average of ozone concentrations (three-year average) in 2001–2011. Table II.4.2.12 presents the stations with the highest values of maximum daily 8-hour running average ozone concentrations in three-year average. Fig. II.4.2.30 shows the graph of the number of exceedances of the target value for ground-level ozone and Fig. II.4.2.31 presents the annual courses of maximum daily 8-hour running averages in the localities with the heaviest loads. Table II.4.2.13 presents the number of hours of the ozone alert threshold exceedance (180 μg.m-3) at selected AIM stations for the period of 1995–2011.
Fig. II.4.2.50 characterizing the monthly trends of ozone (max. 8-hour running
average for the given month) shows apparently the increase of concentrations in
spring and summer months due to favourable conditions for ozone formation, such
as high intensity of solar radiation, high temperatures and low air humidity.
Fig. II.4.2.27 26th highest values of maximum daily 8-hour running average of ground-level ozone concentrations (three-year average) in 2001–2011 at selected stations
Fig. II.4.2.28 Field of the 26th highest maximum daily 8-hour running average of ground-level ozone concentrations in three-year average, 2009–2011
Fig. II.4.2.29 Numbers of exceedances of the target value for the maximum daily 8-hour running average of ground-level ozone concentrations in three-year average, 2009–2011
Fig. II.4.2.30 Stations with the highest values of maximum daily 8-hour running average concentrations of ground-level ozone in 2009–2011
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. In the natural processes lead is released through the
weathering of rocks and volcanic activity [14]. The long-term exposure to lead results in harmful impacts on biosynthesis of haem (nonproteinic component of haemoglobin), on nervous system and blood pressure in humans. WHO classifies lead as concerns its carcinogenity in 2B group (i.e. possibly carcinogenic to humans) [14, 15]. None of 62 localities measuring lead concentrations recorded the exceedance of the limit value (500 ng.m-3). The highest annual average was recorded in the locality Příbram I-nemocnice (52.4 ng.m-3), where in 2011 there were recorded for the first time higher concentrations than in the localitites in the Ostrava-Karviná area which reached always the maxima in each of the previous years. Lead concentrations in all localities remain far below the limit value and do not even reach the lower assessment threshold (see Fig. II.4.2.31). As compared with the year 2010 the concentrations in three quarters of localities increased and one quarter of localities, on the contrary, recorded a slight decrease. The courses of short-term (24-hour or14-day concentrations, depending on the measurement schedule of the given station) average concentrations at selected localities are presented in Fig. II.4.2.32. The stations with the highest values of annual average concentrations are
presented in Table II.4.2.14.
Fig. II.4.2.31 Annual average concentrations of lead in the ambient air in 2001–2011 at selected stations
Fig. II.4.2.32 1/14-day average concentrations of lead in the ambient air in 2011 at selected stations
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]. Emissions 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 in humans [15]. In 2011 cadmium concentrations were monitored in 62 localities in total. None of them exceeded the target value (5 ng.m-3). Similarly as in two previous years the highest annual average was measured in the locality Souš (3.5 ng.m-3). As compared with the year 2010 there was recorded a slight decrease of average annual concentration in more than one half (58 %) of localities; 26 % of localities recorded the increase and the remaining localities did not record any change of the annual average concentration. The target value should be met by 31.12.2012. The development of annual average concentrations in the period of 2001–2011 is apparent from Fig. II.4.2.33. The courses of short-term (24-hour or 14-day concentrations, according to the measurement schedule at the respective station) average cadmium concentrations in selected localities in 2011 are presented in Fig. II.4.2.34. The stations with the highest values of annual average concentrations are
presented in Table II.4.2.15.
Fig. II.4.2.33 Annual average concentrations of cadmium in the ambient air in 2001–2011 at selected stations
Fig. II.4.2.34 1/14-day average concentrations of cadmium in the ambient air in 2011 at selected stations
Arsenic Arsenic occurs in many forms of inorganic and organic compounds. Anthropogenic sources produce 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 62 localities which monitored arsenic concentration in 2011 the target value (6 ng.m-3) was exceeded in two of them, and namely in the Kladno area (locality Stehelčeves) and in Prague 5-Řeporyje. While in the Kladno area exceedances were recorded also in the previous year (localities Stehelčeves and Kladno-Švermov), the latest exceedances in Prague were recorded in 2007 and 2008. The target value should be met by 31.12.2012. In comparison with the previous year 2010 approximately two thirds of localities
recorded the decrease of the annual average concentration, and, on the contrary,
one third of localities recorded its slight increase. The courses of short-term (24-hour or 14-day concentrations, according to the
measurement schedule at the respective station) average arsenic concentrations
show the seasonal character and confirm the significant arsenic contribution
from the burning of fossil fuels (Fig. II.4.2.37).
Fig. II.4.2.35 Annual average concentrations of arsenic in the ambient air in 2001–2011 at selected stations
Fig. II.4.2.36 Field of annual average concentration of arsenic in the ambient air in 2011
Fig. II.4.2.37 1/14-day average concentrations of arsenic in the ambient air in
2011 at selected stations 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. About 70 % of particles containing nickel comprise the fraction smaller than 10
μm. These particles can be transported over long distances. About 30 % of
particles containing nickel have aerodynamic diameter equal or higher than 10 μm
and quickly settle in the vicinity of the source [17]. One of 62 localities monitoring nickel concentrations in 2011 exceeded the target value (20 ng.m-3) for the annual average concentrations, and namely the locality Příbram I-nemocnice. This is the first exceedance of this limit value recorded in a locality in the territory of the Czech Republic since 2003 when air quality started to be assessed according to the European directives. The exceedance was caused by high concentrations in the first third of the year connected probably with demolition activities carried out approx. 200 m from the measuring station. The increase of nickel (and also lead) concentrations in the locality Příbram I-nemocnice starting from 2010 is apparent from Fig. II.4.2.39. This locality recorded the high annual average concentration also in 2010 (14.1 ng.m-3) which, however, did not reach the limit value. The slight decrease of concentrations as compared with the previous year was recorded in almost 60 % of localities, approximately 40 % of localities, on the contrary, recorded the increase of concentrations. The stations with the highest values of the annual average concentrations are
presented in Table II.4.2.17.
Fig. II.4.2.38 Annual average concentrations of nickel in the ambient air in 2001–2011 at selected stations
Fig. II.4.2.39 Monthly concentrations PM10 and metals, locality Příbram, 2011
Fig. II.4.2.40 1/14-day average concentrations of nickel in the ambient air in 2011 at selected stations
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 (coal and wood combustion) which produces more than 60 % of total benzo(a)pyrene emissions. Mobile sources are represented mainly by diesel compression ignition engines. Mobile sources are the second most significant source of benzo(a)pyrene emissions (more than 20 %). The natural background level of benzo(a)pyrene is almost zero with the exception of wildfires [15]. Approximately 80–100 % of PAH with five and more aromatic cores (i.e. also benzo(a)pyrene) are bound mainly to the particles smaller than 2.5 μm, i.e. to the so called fine fraction of atmospheric aerosol PM2.5 (sorption on the surface of the particles). These particles remain in the atmosphere for relatively long time (days to weeks) which enables their transport over long distances (hundreds to thousands of kilometres). Benzo(a)pyrene, as well as several other PAH, are classified as proven human carcinogens [15, 19]. In 2011 benzo(a)pyrene concentrations were monitored in 33 localities; 24 of them exceeded the target value of 1 ng.m-3 (annual average concentrations). In 2011 exceedances were recorded in 23 localities of 33. The highest annual average concentration was measured in the industrial locality Ostrava-Radvanice ZÚ (10.1 ng.m-3) with more than tenfold exceedance of the level of the target value. High above-the-limit concentrations, however, are reached also in traffic localities as well as in the background urban and suburban localities. A number of towns and villages were assessed, similarly as in the previous years, as the areas with the exceeded target value. In 2011 the target value was exceeded in 16.8 % of the territory of the Czech Republic (in 2010 in 14.47 % of the territory of the Czech Republic). The percentage of inhabitants exposed to the above-the-limit benzo(a)pyrene concentrations in 2011 is estimated to 60.2 % (in 2010 it was approx. 65 %). It is necessary to consider that the estimate of the fields of annual average benzo(a)pyrene concentrations (Fig. II.4.2.42), in comparison with other mapped pollutants, is loaded with the greatest uncertainties resulting from insufficient density of measurement. The uncertainty of the map is influenced also by the absence of measurements at rural regional stations. However, the uncertainty is contributed also by the absence of measurements in small settlements in the Czech Republic which would represent the fundamental influence of local heating as concerns ambient air quality pollution caused by benzo(a)pyrene. This influence can be at least partly documented by the result map of the field
of the average annual benzo(a)pyrene concentration for the year 2011 when there
were carried out new measurements in small settlements in the territory of the
Moravian-Silesian Region (stations Heřmanovice and Nový Jičín-Kojetín) and
Olomouc Region (Dolní Studénky). After including the results in the map it is
apparent that the territory of the Czech Republic with the exceedances of the
target value for benzo(a)pyrene is larger than the territory interpreted in the
past years when the measurements representing the influence of local heating
were not available. It can be expected that further similar measurements in
other zones and agglomerations of the Czech Republic would lead to more precise
estimate of the field of annual average concentration and probably also to the
increase of the area with exceedances of the target value for benzo(a)pyrene.
The average annual concentrations increased, in comparison with the year 2010, in 30 % of localities (in average by ca 0.3 ng.m-3, after excluding the high increase in the locality Ostrava-Radvanice), the remaining stations, on the contrary, recorded their decrease (in the average by 0.3 ng.m-3). The highest increase of the average annual concentration was recorded at the station Ostrava-Radvanice, and namely almost by 3 ng.m-3 as compared with the year 2010. The development of average annual concentrations in individual localities during the years 2001–2011 is apparent from Fig. II.4.2.41. Benzo(a)pyrene concentrations show the marked annual course with the maxima in the winter period (due to the seasonal sources, worse dispersion conditions and easier gas-particles conversion) and the minima in the summer period (due to the end of the heating season and the chemical and photochemical disintegration of benzo(a)pyrene). The increased concentrations during the winter period (Figs.
II.4.2.43,
II.4.2.44 and
II.4.2.50) confirm the influence of local heating; in 2011 this
applied mainly to the periods January–March and October–December. The maximum
concentrations in February and November correspond with bad dispersion
conditions in these months. Moreover, these months were subnormal as concerns
both temperatures and precipitation, November is characterized even as extremely
dry [47]. Consequently, the washing of pollutants from the atmosphere was not
sufficient; subnormal February and November temperatures could contribute also
to higher intensity of heating. The annual courses of short-term concentrations
(24-hour once in 3 or 6 days) of benzo(a)pyrene in localities with highest
annual averages are apparent from Fig.
II.4.2.44. The fluctuations of monthly
averages of concentrations for different types of stations in 2004–2011 are
shown in Fig. II.4.2.43. Fig.
II.4.2.45 depicts benzo(a)pyrene concentrations in
individual localities in 2007–2011 in relation to PM10 concentrations, resp. to
its fine fraction PM2.5 to which benzo(a)pyrene is mainly bound.
Fig. II.4.2.41 Annual average concentrations of benzo(a)pyrene in the ambient air in 2001–2011 at selected stations
Fig. II.4.2.42 Field of annual average concentration of benzo(a)pyrene in the ambient air in 2011
Fig. II.4.2.43 Monthly average concentrations of benzo(a)pyrene in various types of localities, 2004–2011
Fig. II.4.2.44 24-hour concentrations at the stations with the highest annual concentrations of benzo(a)pyrene in 2011
Fig. II.4.2.45 Concentrations of benzo(a)pyrene and PM10 particles in individual
localities, 2007–2011 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. As for anthropogenic emissions it is estimated that in Europe approximately 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 (Hg(p)). Most emissions 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 concentrations in the ambient air result 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 spite of the fact that the limit value for mercury has not been set yet, the Czech national legislation recommends, pursuant to the European directives, to carry out its monitoring and assessment according to the annual arithmetic mean.
In 2011 the CHMI ISKO database received data on mercury concentrations in PM10
particles in the ambient air from the locality Karviná-ZÚ where the annual
average reached the value 0.166 ng.m-3. 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 is 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 limit value for ammonia is not defined
in the current European and Czech legislation. Ammonia monitoring was carried
out, similarly as in the previous years, at 3 localities. The highest annual
average concentration was measured at the station Pardubice-Dukla (4.4 μg.m-3).
Elemental and organic carbon in the particles of PM2.5 fraction It is a known fact that carbon is an important component of particles of PM2.5 and PM10 fractions [49, 50]. The results [50, 51] show that in Europe the average share of carbon is 20–40 % of PM10 fraction and 25–50 % of PM2.5 fraction. As concerns carbon in aerosol, we distinguish organic carbon (OC) and elemental carbon (EC). Due to their varied physical and chemical properties both EC and OC have significant impact on climate and human health [52, 53]. EC is formed mainly in insufficient combustion of fossil fuels, and primarily in urban traffic. Other sources include biomass burning which, however, is much less significant and its impact is apparent mainly during winter in rural settlements or when fires take place [54]. OC can be emitted also directly in the solid phase, or its formation is secondary through gas-particles transformation in the atmosphere [55]. Primary OC is created also during the combustion of fossil fuels, in biomass burning or the particles are of biological nature (e.g. plant residues). The EC/OC proportion suggests the proportion of emission sources. Carbon in the form of EC and OC has been monitored since 2009 in PM2.5 fraction in the locality Košetice. The results of the 2011 measurements are presented in Table II.4.2.21. The annual average of EC in PM2.5 fraction was 0.5 μg.m-3, the annual average of OC in PM2.5 fraction reached the value 3 μg.m-3 in 2011.
The trends of SO2, PM10, NO2, NOx and O3 annual air pollution characteristics in the Czech Republic for the period of 1996–2011, and further of benzo(a)pyrene and PM2.5 for the period 2004–2011 are shown in Figs. II.4.2.46 and II.4.2.47. Result concentrations of pollutants in the Czech Republic and in agglomerations, related to the respective years, represent average values from the stations which measured for the whole monitored period. In the 90s air pollution caused by SO2, PM10, NO2 and NOx had a decreasing trend in the whole Czech Republic, and mainly due to a marked decrease of pollutants emissions. In 1996–2000 there was apparent a marked decrease of SO2 concentrations (by ca 70–80 % depending on the respective air pollution characteristic) and PM10 concentrations (by ca 50–60 %) – Fig. II.4.2.48.1 The development of the trends of concentrations of individual pollutants is influenced by the decrease of emissions, by the change of the composition of industrial production and transport means and the used fuels, On the other hand, there is a great influence of meteorological and dispersion conditions. Since 2001 the previous decreasing trend stopped and, on the contrary, in comparison with the year 2000, the ambient air pollutants concentrations stagnated or increased (Fig. II.4.2.49). The decrease of emissions after the year 2000 was not as steep as in the 90s of the 20th century (Fig. I.1.1) and it can be expected that ambient air quality is presently influenced mainly by meteorological and dispersion conditions in the course of the year. In 2001–2003 the concentrations of SO2, PM10, NO2 and NOx increased and in 2003 the reach their maximum levels with regard to the assessment of the development over the recent 10 years. High concentrations of pollutants in the year 2003 were caused both by unfavourable dispersion conditions in February and December, and by subnormal amount of precipitation. In 2004 this increasing trend of air pollution caused by PM10, NO2 and NOx 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, and also PM2.5 concentrations were increased. This increasing trend was confirmed in 2006 in NO2 and in annual PM10 concentrations (at urban stations); more significant increase was recorded in case of one-hour NO2 concentrations – it almost reached the level of the year 1997. On the contrary, 24-hour PM10 concentrations recorded a slight decrease. Annual PM2.5 concentrations stagnated. Between 2003 and 2005 a slight decrease of SO2 concentrations was observed. The increase of some air pollution characteristics in 2005 and 2006 was given mainly by deteriorated dispersion conditions. In 2007 the fluctuating trend of the levels of the above pollutants concentrations stopped and there was recorded a marked decrease of air pollution caused by SO2 and PM10 (both in towns and in the country), PM2.5, NO2 and NOx in all monitored air pollution characteristics. The steepest decrease is evident, after the previous increase, in hourly NO2 concentrations. The decrease of pollutants concentrations in 2007 was given by more favourable meteorological conditions, especially in January and February. In 2008 the decreasing trend of ambient air pollution caused by SO2 and PM10 continued, the PM2.5 concentrations more or less stagnated. As concerns NO2, there was recorded a slight decrease in daily concentrations, in NOx there was a slight decrease in annual averages at rural stations. The fluctuation of the trends of individual pollutants is caused on the one hand by the decline of emissions, the change of the structure of industrial production and of the used fuels; on the other hand there is a significant influence of meteorological conditions, particularly dispersion conditions. In 2009, on the contrary, there was a marked increase of air pollution caused by SO2, PM10, NO2 and NOx roughly to the level of the year 2007 in all these pollutants (except for PM2.5). The increase of the above pollutants concentrations in the ambient air was given by less favourable meteorological and dispersion conditions, mainly in January, February and December 2009 as compared with the year 2008. In 2010 there continued the growth of concentrations in all substances and in all air pollution characteristics. The 36th highest 24-hour PM10 concentrations in the average for the urban and all stations reached the above-the-limit levels, similarly as the annual average PM2.5 concentration (for all stations). Higher concentrations in comparison with the year 2009 were recorded also in SO2 and NO2, nevertheless as regards the average for the whole Czech Republic their levels remain well below the respective limit value. The increase of pollutants concentrations in 2010 was given by repeated occurrence of unfavourable meteorological and dispersion conditions in the winter period at the beginning of the year (January and February) and at the end of the year (October–December). In 2011 the levels of almost all air pollution characteristics decreased, with one exception, and namely the 36th highest PM10 concentration which slightly increased at urban stations in the year-by-year comparison. The more detailed analysis shows clearly that the growth at urban stations was caused by the increase of concentrations at urban traffic stations, and namely by approx. 8 % (4 μg.m-3) in comparison with the year 2011. The average concentration at rural stations decreased below the level of the daily limit value, the concentrations in other types of localities remain above the LV. The average annual concentration of PM10 decreased both at urban and rural stations. Similarly, the average annual PM2.5 concentrations decreased in all types of localities and they dropped below the limit value. The concentrations of other pollutants (SO2, NO2, NOx) decreased in all air pollution characteristics and in all types of localities. The averages for the whole Czech Republic remain below the respective limit values. The greatest year-by-year decrease was recorded in the 4th highest 24-hour concentration of SO2 and the 19th highest 1-hour concentration of NO2. In spite of the fact that during the year there occurred several episodes with very unfavourable meteorological and dispersion conditions, in the long-term aspect (since 2000) and with regard to the national results the year 2011 can be ranked among the better years as concerns ambient air quality. Nevertheless, the limit values continue to be exceeded, mainly in the densely populated areas. They are probably exceeded also in the sites without air quality monitoring (small settlements). For the first time also the trends of average annual benzo(a)pyrene concentrations are assessed. The set target value for benzo(a)pyrene concentrations is 1 ng.m-3. The levels of this pollutant in the average for the whole Czech Republic are above the limit in the long term (almost threefold values). The highest concentrations of benzo(a)pyrene were measured in 2006 (more than threefold exceedance of the level of the target value) and in 2009 due to the unfavourable meteorological and dispersion conditions, similarly as in other pollutants. In the year-by-year comparison 2010/2011 the benzo(a)pyrene concentrations increased and thus the year 2011 is ranked among the years with the highest benzo(a)pyrene concentrations (for the assessed period starting from 2004). The ground-level ozone is the pollutant of a different character than the above assessed pollutants. Ozone is the so called secondary pollutant which reaches its highest concentrations in the warm part of the year. As concerns the period 1996–2006, it is not possible to clearly conclude the trend of the concentrations, as air pollution characteristics show marked fluctuations. In 2003 there is apparent the increasing trend in concentrations due to long-time very high temperatures and high levels of solar radiation. In 2004 O3 concentrations slightly decreased below the level from the years 1997–2002, in 2005, on the contrary, they increased slightly above the level from 1997–2002. On the contrary, since 2006 the pollutants concentrations were decreasing continuously up to 2009. In 2006 the concentrations slightly increased. In 2007 the average from the 26th highest maximum 8-hour running averages slightly decreased. On the contrary, there was a slight increase of the 76th values of maximum 8-hour running averages for the previous 3 years, resulting mainly from the fact that the April–September period of the year 2007 was warmer (in the average for the whole Czech Republic by 1.2 C) than the year 2004 which was included in the previous three-year period but not taken into account for the assessment of the 2005–2007 period. In the period 2006–2008 the 76th highest value of maximum 8-hour running averages decreased, probably due to the decrease of the precursors concentrations (both NOx and VOC). This decrease is visible in the graph of the trends in all types of localities; also apparent is the decrease of concentrations in the year 2008 alone. The decline of ozone concentrations continued also in the period 2007–2009, when there was a marked decrease of the number of exceedances of the limit value 120 μg.m-3 in most localities, and, as it is apparent from the graph, the 26th highest value of the maximum 8-hour running average decreased for the year 2009 alone, as well as the average for 3 years. The graphs of trends also show apparently higher concentrations in rural localities as compared with the concentrations from urban and suburban localities, where ozone is removed mainly by emissions from traffic. In 2010 the 26th highest value of maximum 8-hour running average slightly increased, the values of 3-year averages of concentrations decreased again. In 2011 the situation repeated – the 26th highest value of the maximum 8-hour running average for all types of stations increased again; it was caused by the growth of concentrations at rural stations. However, there continues the decreasing trend of the 26th highest value of the maximum 8-hour running average of ozone concentrations at traffic stations and ozone concentrations in the average for three years.
Fig. II.4.2.46 Trends of SO2, NO2, NOx and O3 annual characteristics in the Czech Republic, 1996–2011
Fig. II.4.2.47 Trends of PM10 , PM2.5 and benzo(a)pyrene annual characteristics in the Czech Republic, 1996–2011
Fig. II.4.2.48 Trends of selected characteristics of SO2, PM10, NO2 and O3 (index, year 1996 = 100), 1996–2011
Fig. II.4.2.49 Trends of selected characteristics of SO2, PM10, NO2 and O3 (index, year 2000 = 100) and PM2.5 (index, year 2004=100), 2000–2011
Fig. II.4.2.50 Annual course of average monthly concentrations of PM10, NO2, benzo(a)pyrene and max. 8-hour running average of O3 in the month (averages and individual stations representative for the given type of station), 2011 1The trend of selected air pollution characteristics is expressed in the indexed form, i.e. the level of air pollution caused by the respective pollutant in 1996–2010 is related to the level (concentration) of the pollutant in 1996 (or in 2000).
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