II.4 Air quality assessment

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

The Yearbook presents air quality assessment in the year 2007 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 the protection of human health.

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, PAH, 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 the area within the zone or agglomeration, where the level of the respective air pollution limit value is exceeded in one or more pollutants.

According to Article 4, par. 7 of Clean Air Act No. 86/2002 Coll., as amended, the Ministry of Environment publishes annually the list of zones and agglomerations in its Bulletin. The zone is a part of the territory delimited by the Ministry for the monitoring and management of air quality, and the agglomeration is a residential area where the population concentration is at least 350,000 inhabitants, delimited by the Ministry for the monitoring and management of air quality. The areas with deteriorated air quality are specified annually as the territories within the zones and agglomerations. Three agglomerations were defined; the Capital City of Prague and the city of 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 without the territory of the city of 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, and consequently, also monitored in the future.

In 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 showed in the previous year the exceedances of air pollution limit values plus the margins of tolerance, or of air pollution limit values in cases if the margin of tolerance is not set. The aim of the programs is to reach the limit values in the deadlines set in the implementing regulations.

The term �hot-spot� is used in the assessment, generally 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 localities meet the criteria for the location of traffic-oriented samplers pursuant to the Government Order No. 597/2006 Coll.

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

All tables for individual pollutants present at least 10 stations with the highest values of the respective air pollution characteristic in the given year. The maps depict clearly the development of the respective characteristics mainly in the period 1996–2007. The 2007 exceedance of the limit value enlarged by the margin of tolerance, or the limit values in substances without the margin of tolerance, is highlighted 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 are based on the lower and upper assessment thresholds, limit value (target value) and on the margin of tolerance for individual substances. The exceedance of the limit value, or the target value is marked with red colour.

For the stations and air pollution characteristics, where the number of exceedances of the limit value plus the margin of tolerance was higher than it is allowed, the courses of 24-hour or hourly concentrations in 2007 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 2007 are documented by the graphs.

The 2007 evaluation includes the graphs showing the trends of the characteristics of selected pollutants in agglomerations and in the Czech Republic in the period of 1996–2007. The values in the graphs are calculated as total average from average concentrations only of those monitoring stations in the given territory which measured the monitored pollutant for the whole period 1996–2007.