II.4 Air quality assessment

The extent of air pollution is objectively determined by monitoring pollutants� concentrations in the ground layer of atmosphere within the network of measuring stations. Within air quality assessment there are compared mainly the recorded air pollution levels with the respective limit values, or with admissible exceedence frequencies of these limits which should not be further exceeded after the date in compliance with the legislation.

The Yearbook presents air quality assessment in the year 2005 with regard to the requirements of the Czech legislation on air quality protection. Pursuant to the Clean Air Act the assessment is aimed mainly at defining the areas with deteriorated air quality, with regard to health protection and the protection of ecosystems and vegetation respectively.

Air quality assessment pursuant to the valid legislation reassumes the results and mainly methods developed within the two research projects solved by CHMI, and namely VaV/740/2/00 �Evaluation of the Czech Republic Readiness to Meet Air Quality Requirements of EU Directives and the LRTAP Convention� [9], and VaV/740/3/02 �Integrated air quality assessment and management with regard to the daughter directives on heavy metals, PAHs, PM₁₀ and benzene� [23]. The complete results of the solution of the projects VaV/740/2/00 and VaV/740/3/02 are available at the CHMI websites.

The EU air quality directives on which the Czech legislation is based require that the member states should divide their territories into zones and agglomerations while the zones are understood as basic units for air quality management. The directives specify namely the requirements for the assessment – the classification of the zones with regard to air quality. The Clean Air Act covers this issue in par. 7 dealing with special air quality protection. Article 1 introduces the term �area of deteriorated air quality� for a specified part of territory, where a value of one or more air quality limit values or ozone target values or value of one or more air quality limit values, enlarged by the relevant margins of tolerance, are exceeded. Special air quality protection is required in agglomerations, i.e. in specified settlement territory, with at least 250 000 inhabitants, or territories with smaller population, where the population density requires special air protection measures and the necessity to assess and manage air quality in the territory.

According to Article 4, par. 7 of Clean Air Act No. 86/2002 Coll. the Ministry of Environment published in its Bulletin of November 2005 the list of zones and agglomerations. The zone, or agglomeration is the territory specified for the monitoring and management of air quality. The areas with deteriorated air quality will be specified according to the Act as the territories within the zones and agglomerations. Three agglomerations were defined: the Capital City of Prague and Brno agglomerations represent the areas where ambient air pollution is connected mainly with high density of population, in the Moravian-Silesian Region agglomeration (covering i.a. the cities of Ostrava, Karviná, Havířov, Český Těšín and Třinec) air pollution is influenced, besides population density, also by high concentration of industrial plants. Due to the delineation of agglomerations air quality assessment in these areas will be determined mainly on the basis of regular measurements of good quality. Other regions of the Czech Republic were defined as zones (including the South-Moravian Region excluding Brno).

In addition to agglomerations, the Yearbook deals in great detail with the zone Ústí nad Labem Region, where, similarly as in the Moravian-Silesian agglomeration, both the population density and industry concentration are higher.

In the areas not included into the category of deteriorated air quality, i. e. in the areas where no limit values are exceeded, it is necessary to ensure the maintenance of good air quality. This corresponds with one of the basic principles of the Directive 96/62/EC, which requires that the once reached complying air quality continues to be maintained in the future.

For the areas with deteriorated air quality the Clean Air Act in its Article 6, par. 7 sets the obligation for the regional and local authorities of municipalities with population above 350,000 to develop programs aimed at the improvement of air quality for those pollutants which show limit values and margins of tolerance exceedences with the aim to reach the limit values in the deadlines set in the implementing regulations.
A new term �hot-spot� is used in the assessment, generally used for localities with high level of ambient air pollution. In our assessment, however, this term refers to the stations oriented exclusively to traffic and to the resulting air pollution loads. These stations meet the criteria for the location of traffic-oriented samplers pursuant to the Government Order No. 350/2002 Coll. (at least 25 m from the edge of large crossroads and max. 5 m from the edge of the road).

The air quality assessment is documented by the tables showing the localities with the highest values of air pollution characteristics assessed pursuant to the Czech legislation. The shades of the background in the tables indicate:

All tables present at least 10 stations with the highest values of the respective air pollution characteristic. The maps depict clearly the development of the respective characteristics mainly in the period 1996–2005. The 2005 exceedence of the limit value enlarged by the margin of tolerance, or the limit values in substance without the margin of tolerance, is marked with red names of the stations.

Further, maps depicting the spatial distribution of air pollution characteristic are presented. These maps show also the measuring stations marked with different symbols and colours according to their type and category of the level of the respective characteristic measured at the presented station. The intervals of the classes in the legend is based on the lower and upper assessment thresholds, air pollution limit value (target air pollution limit value) and on the margin of tolerance for individual substances. The exceedence of the limit value, or the target air pollution limit value is marked with red colour.

For the stations and air pollution characteristics, where the number of exceedences incl. the margin of tolerance was higher than it is allowed, the courses of 24-hour or hourly concentrations in 2005 are presented for the indication of the period of the year during which the limit values were exceeded.
The courses of air pollution caused by individual pollutants at selected stations during the year 2005 are documented by the graphs.

The 2005 evaluation includes the graphs showing the trends of the characteristics of selected pollutants in agglomerations and in the Czech Republic in the period of 1996–2005. The values in the graphs are calculated as total average from average concentrations of those stations in the given territory which measured the monitored pollutant for the whole period 1996–2005.