This chapter contains maps, graphs and tables that characterise ambient air pollution in the most affected areas of the Czech Republic in respect to sulphur dioxide, suspended particulate matter and nitrogen oxides. In 2000 the following regions were assessed: the Capital City of Prague, Central Bohemian Region, Northwest Region (covering Karlovy Vary Region, Ústí nad Labem Region and Liberec Region) and Moravian-Silesian Region. Lists of all tables and figures are included (see the Table of Contents) while minimum references to tables and figures are made in the text.

The maps and charts depict pollutants� regional distribution in the atmosphere. Maps of annual arithmetic means and 95th percentiles of SO₂, SPM and NO_x concentrations are included for each region and for the whole territory of the Czech Republic – see Chapter 2.3. (For PM₁₀ fraction 90th percentile was used in accordance with EU daily air pollution limit value.)

In 2000 the transport and dispersion model Symos�97 in combination with data measured was used for the purpose of construction of the field of annual arithmetic means of SO_2, to some extent of NO_x and SPM (see Chapter 2.2.1–2.2.4, 2.3). (The model was developed by CHMI in co-operation with EKOAIR company.) This model uses digitally processed terrain DMT 200 developed in VTÚ Dobruška. The SYMOS�97 model is a useful supplement of the SO₂ air pollution assessment, to some extent for NO_x and SPM, in localities with deficient measurement. For the purpose of construction of the fields of SO₂ 95th percentile, model values of annual arithmetic means were used at several sites for re-calculation to 95th percentile values based on statistical methods.

Since 1995, the field of annual arithmetic means of NO_x concentrations has been outlined in a map of the Czech Republic (see Chapter 2.3). This regional evaluation for 2000 has been produced by combining as-measured NO_x values with statistically supported estimates of ambient air pollution levels in localities not covered by adequate measurements, taking into account the categorisation of the country�s territory in terms of emission densities and Symos�97 model. NO_x concentration field is only shown in the outline map of the Czech Republic. For each of the regions, NO_x concentrations are shown using spot symbols method¹ [8]; the stations are distinguished by means of different colours according to the respective classes. Analogously, the relative frequencies of exceeding the daily air pollution limit by the pollutants mentioned are indicated in maps of the Czech Republic in Chapter 2.3 with the exception of PM₁₀ fraction where, in accordance with the respective EU directive, the admissible exceedence is expressed by absolute frequency.

The combined map presentation, using an estimation of the regional distribution of fields of the ambient air pollution characteristics along with an indication of data measured in measuring stations (spot symbols method), was used in 2000 for the presentation of the regional distribution of annual arithmetic means, 95th percentiles of SO₂ and SPM (arithmetical means only) in affected areas (with the exception of Prague). In the maps automated monitoring stations (AMS) are differentiated from manually operated stations. When constructing maps of air pollutants concentrations fields, the main emphasis was laid on AMS stations. In the most cases, values collected from manually operated stations were used solely as complementary information, especially in less affected areas.

In case of the combined map SPM annual mean presentation, AMS stations measuring PM₁₀ fraction were converted to SPM (coefficient 1.2) and identified with other symbol. 95th percentiles of SPM daily concentrations and 90th percentiles of PM₁₀ daily concentrations are presented in maps using spot symbols. In summary maps of the Czech Republic (see Chapter 2.3), two methods were used for the presentation of the regional distribution of annual means and of 95th percentiles of SPM: the concentrations fields and the spot symbols. In case of PM₁₀ fraction both the annual arithmetic mean and 90th percentile are presented in 2000 using spot symbols.

The share taken by the respective concentration category, expressed as a percentage of the area afflicted, is specified for each category on maps showing fields of ambient air pollution characteristics.

The tables and graphs present annual courses of principal pollutants� concentrations and annual profiles of their daily concentrations at selected stations in each of the afflicted regions. Since year 1996, the tables of annual courses have been expanded to include certain annual ambient air pollution characteristics. Annual variations in principal pollutants� daily concentrations are clearly illustrated for selected stations in each region and for the entire Czech Republic. The graphs indicate how the predominant pollutant type differs from one region to another. The tables and graphs of annual courses of principal pollutants� concentrations include, for the first time in this 2000 Yearbook, classification of air pollution monitoring stations (see Explanatory notes to the tables of annual courses and more details in the Tabular Survey, Chapter 1.3.1.3). Presented in this part are also tables that list stations with the highest relative frequency of short-term IH_k exceedence and the highest values of 95th percentiles of half-hour pollutant concentrations. Also tabulated are overviews of the maximum daily concentrations (including date of occurrence), highest annual arithmetical means, highest relative (absolute) frequency of IH_d exceedence, and the highest values of 95th percentiles (90th percentiles) of daily pollutant concentrations. When the frequency of the daily ambient air pollution limit exceedence was markedly higher for only one pollutant in a given region, the table contains, for the purpose of clarity, the values for the other pollutants as well. Chapter 2.3 also contains a table of the highest half-hour pollutant concentrations registered at Czech stations in 2000.

The tables of stations that report the highest annual arithmetic means, the highest relative (absolute) frequency of exceeding IH_d, and the highest values of 95th percentiles (90th percentiles) of daily pollutant concentrations (contained in the annual data set) list only the stations for which the calculated ambient air pollution characteristics have satisfied the conditions of publication (see the Tabular Survey [2]). Expert estimates were also resorted to when constructing maps of pollutant concentration fields to cover sites with insufficient density of measurements (these are almost exclusively sites with low emission densities and low air pollution levels, see also Chapter 2.3).

A certain seasonal variation can be read from tables that show the annual courses of pollutants� concentrations. The most distinct variation can be discerned for sulphur dioxide with its levels in the winter season (months 1 to 3 and 10 to 12) being several times higher than in the summer season (months 4 to 9). These seasonal fluctuations in sulphur dioxide concentrations are due to the seasonal nature of meteorological conditions since frequent air temperature inversions occur in the winter months, with subsequent deterioration in the pollutant dispersion conditions combined with intensive combustion of solid fuels, especially in the regions where gas heating has not been introduced yet. The seasonal variations in nitrogen oxide levels are not as prominent. Concentrations are higher in the winter season, however, these winter-summer differences may equalise in areas with heavy road traffic. The seasonal changes in SPM concentrations are obviously random ones, and no adequate generalisation is at hand.

¹ The method of spot symbols [8] is one of the methods of cartographic presentation using geometrical, pictographic and literal symbols and signs. It is used for depicting the location and quality of discrete objects. In 1999 yearbook this method is used for the presentation of air pollution monitoring stations distribution. The size of the symbols does not express the quantity of the phenomenon; various colours for the respective classes of basic pollutants concentrations are used instead.