IV.9.1 Volatile organic compounds (VOC)

Volatile organic compounds (VOC) play an important role in the chemistry of the atmosphere and, consequently, in the oxidation capacity of the atmosphere, which has its influence on the ambient air quality and its state. Along with nitrogen oxides VOC participate significantly in the process of formation of ground-level ozone and other photooxidative pollutants. Transformation and degradation of VOC are usually started by the reaction with the hydroxyl radical (Víden 2005). Pursuant to the Air Protection Act, the volatile organic compound means any organic compound or mixture of organic compounds, with the exception of methane, which has a vapour pressure of 0.01 kPa or higher at a temperature of 20 °C or has corresponding volatility under the specific conditions of its use. With regard to the range of different reactivity lengths in individual VOC and their amount, no limit value has been set for these pollutants.

The monitoring of VOC was integrated into the EMEP programme on the basis of the decision of the EMEP Workshop on Measurements of Hydrocarbons/VOC in Lindau 1989 (EMEP, 1990). The measurements carried out by CHMI in the Observatory Košetice (OBK) were launched during the year 1992, and three years later identical measuring programme was implemented at the station Prague-Libuš. Within EMEP monitoring was carried out first at five stations but during 20 years the number of stations and the range of the measured hydrocarbons changed several times. OBK succeeded in maintaining the homogenous series of measurements up to the present time. Since 2011 the OBK has participated in the project ACTRIS, realized within the EU 7th Framework Programme INFRA-2010-1-1.1.16: Research Infrastructures for Atmospheric Research. The problems connected with VOC are solved in the group WP4 (Trace gases networking: Volatile organic carbon and nitrogen oxides) aimed at the improvement and harmonization of VOC measurements in Europe. Standard operation procedures are developed within the project tasks and the best measuring instruments for quality assurance are tested. CHMI laboratory participated in the round robin test, and the results of VOC analysis carried out in CHMI confirm that the laboratory meets the recommended parameters of GC-system and complies with the required uncertainties both in the standards and samples in most pollutants.

The average annual concentrations of most VOC at the stations in OBK and Prague-Libuš have shown a statistically significant downward trend over the recent 20 years, which reflects the decrease of VOC emissions both in the CR and throughout central Europe (Table IV.9.1.1). The trend of ethane concentrations is more marked at the suburban station than at the background station (Fig. IV.9.1.1). There is only one exception, and namely isoprene (natural origin, produced by deciduous trees). At the OBK station there was not recorded any trend of the average annual concentrations of isoprene and at the station Prague-Libuš even a slight increase of concentrations was recorded. The annual course of most VOC reflects the emission levels, i.e. the maximum values in winter and the minimum values in summer; in isoprene, however, the opposite is true. Generally, it can be stated that concentrations of the main VOC in the 90s of the last century were by approx. 150–200 % higher at the suburban level than at the background station. In the recent decade the differences between both stations have had a significantly decreasing trend.

The latest report on VOC measurements within EMEP (NILU 2013) concludes that the evaluation of the long-term trends uses, in addition to the data from OBK also data from further 9 stations (5 in Germany, 2 in France, one in Finland and one in Switzerland). The level of concentrations recorded in OBK is comparable with the German and French stations. As concerns ethane, the Czech station is characterized by lower annual averages in the long term. The values of most VOC measured in winter are usually very similar to those measured at the German stations, while the summer values from the OBK are markedly lower.

The Geneva Protocol concerning the control of emissions of VOC or their transboundary fluxes was adopted in November 1991 entered into force in September 1997 (UN-ECE 1991). The Protocol specified three options for emission reduction targets:

  1. 30% reduction in emissions of VOC by 1999 using a year between 1984 and 1990 as a basis;
  2. The same reduction as for (1) and ensuring that by 1999 total national emissions do not exceed 1988 levels;
  3. Where emissions in 1988 do not exceed the specified levels, parties may opt as emission ceiling the level of 1999 emissions.

In 1999 the Göthenburg Protocol to abate acidification, eutrophication and ground-level ozone was adopted and it came into force on 17 May 2005 (UN-ECE 1999). The protocol sets the emission ceilings for 2010 for four pollutants incl. VOC. The protocol sets that Europe’s emissions of VOC should be cut by at least 40 % compared to 1990. The CR, similarly as most of central European countries (with the exception of Poland), has met this limit; VOC emissions in the CR for the period 1990–2010 decreased by 51 % (EEA 2013d).

The most significant sources of VOC emissions in the CR are found in the sector of organic solvent use and application (NFR 3A-D); its share in air pollution caused by these substances in 2012 amounted to 52.6 % (Fig. IV.9.1.2). This sector includes the activities connected with coating applications (22.9 %), decreasing and dry cleaning (6.2 %), production and processing of chemical products (9.0 %), solvent use in the printing industry, households etc. (14.5 %). The release of VOC emissions is partly regulated, but most of these pollutants are released in the form of fugitive emissions, and their reduction is difficult. VOC emissions are also produced by insufficient combustion of fossil fuels. The largest amount of VOC emissions from combustion processes is produced in the sector of local household heating (20.5 %), passenger car transport (4.4 %), road freight transport over 3.5 t (5.4 %) and in the sector public electricity and heat production (3.8 %). In connection with transport, VOC emissions are released into air also as vapour from fuel tanks (4.5 %).
In the period 2007–2012 the total VOC emissions had a downward trend (Fig. IV.9.1.3) caused by the application of products with lower content of VOC, e.g. of water-based paints or powder coating. As concerns paints packed for the retailers there is applied the legislative regulation limiting the maximum content of solvents in the products supplied to the market. Owing to the constant renewal of the car fleet traffic emissions of VOC have a decreasing trend.


Tab. IV.9.1.1 Stations with average annual concentrations of VOC in the ambient air


Fig. IV.9.1.1 Annual average concentrations of ethane and isoprene in the ambient air at selected stations, 1997–2013

Fig. IV.9.1.2 Emissions of VOC sorted out by NFR sectors, 2012

Fig. IV.9.1.3 The development of VOC emissions, 2007–2012


IV.9.2 Elemental and organic carbon

Elemental carbon (EC) and organic carbon (OC) are important components of atmospheric aerosols. EC gets into the atmosphere mainly due to incomplete combustion of fossil fuels during traffic, heating, energy production, wood and biomass burning and also agricultural activities. Emissions of OC originate, in addition to incomplete combustion, also from resuspension of biological objects (fungi, spores) or from the abrasion of tyres or plastic materials (Kuhlbusch et al. 2009).

The main reasons for the monitoring and research of EC and OC behaviour in the atmosphere are the impacts on human health and global climate. The negative impact of EC and OC on human health was confirmed in various toxicological and epidemiological studies (Highwood et al., 2006; Adar, Kaufman 2007). As a consequence, the requirement for the measuring of EC and OC in PM at regional stations was set by the European Commission Directive (EC 2008).

Recently the scientists have aimed their attention also to the role of carbonaceous aerosols in the process of global climate change (e.g. Ramanathan, Carmichael 2008). EC is one of a few aerosols with a strong ability to absorb solar radiation, while OC, similarly as further aerosols, contributes mainly to its scattering.

The EC-OC have been measured regularly within the EUSAAR project and later the ACTRIS project in the Observatory Košetice since February 2009. The sampling is carried out every sixth day in PM2.5 fraction. Within the EUSAAR project the standardized protocol for sampling and analysis of measurements was developed and is further elaborated within the ACTRIS network. This protocol should form the basis for the development of the European or worldwide reference method and should be implemented in national and international monitoring networks (such as EMEP) to ensure the consistent measurement within Europe.

The average concentration of total carbon (TC) in PM2.5 in the Observatory Košetice in the period 2009–2013 reached 4.01 µg.m-3, and the respective value for EC was 0.51 µg.m-3, which represents the average share of 12.5 % in TC. Within the ACTRIS network the data from the Observatory Košetice characterize, together with the German station (Melpitz) and the Italian station (Ispra), the continental part of Europe. Data obtained in the Observatory Košetice are highly similar to the results measured at the German station, while the Italian station has recorded the highest concentrations both of TC (about 8 µg.m-3) and EC (closely below 2 µg.m-3) in the long term within the whole ACTRIS network. The concentration levels measured at Scandinavian and mountainous stations are significantly lower (approx. one third of the central European level. Table IV.9.2.1 does not show any marked year-toyear variability. The annual course of concentrations corresponds with the annual course of their emissions, i.e. the maximum levels are recorded in winter and the minimum levels in summer (Fig. IV.9.2.1). The share of EC in TC has continuously decreased during the monitored period from 14.5 % in the year 2009 to 10.4 % in the year 2013 (Fig. IV.9.2.2). TC contributed to total concentrations of PM2.5 fraction in average by 20 %, out of which EC by 3.3 %. Fig. IV.9.2.3 shows the apparently higher share of EC in the cold part of the year. The share of total carbon in PM in the ACTRIS network corresponds with the results achieved in the Observatory Košetice and it ranges around 20 %. There is the only exception, and namely the Ispra station with the share amounting to almost 40 %.


Tab. IV.9.2.1 Average annual characteristics of carbonaceous atmospheric aerosols in the Observatory Košetice, 2009–2013

Tab. IV.9.2.2 Stations measuring elementary carbon (EC) and organic carbon (OC) in PM2.5 in the ambient air with annual average and maximum concentrations


Fig. IV.9.2.1 Average monthly concentrations of elemental carbon and organic carbon in the
Observatory Košetice, 2009–2013

Fig. IV.9.2.2 Average monthly shares of elemental carbon in total carbon in the Observatory Košetice, 2009–2013

Fig. IV.9.2.3 Average monthly shares of elemental carbon in PM2.5 concentrations in the Observatory Košetice, 2009–2013


IV.9.3 Ammonia (NH3)

Concentrations of NH3 in the year 2013

The measurement of NH3 concentrations in 2013 was carried out only in two localities. This low number or localities was caused by the fact that no limit value is set for NH3 and the obligation to monitor its concentrations is not set by legislation. The legislation is focused mainly at the reduction of NH3 emissions (i.e. the maintenance of good agricultural practice and the prevention of serious accidents). In the CR NH3 is measured at the stations Most and Pardubice-Dukla in connection with emissions from industrial sources. In both cases these are the stations classified as urban background.

The highest annual average concentration was measured similarly as in 2012 at the station Pardubice-Dukla (Table IV.9.3.1). In comparison with the previous year (2012) this level decreased to 4.2 µg.m-3 (from 5.1 µg.m-3). The concentration measured in the locality Most remained at similar level as in 2012 (i.e. 2 µg.m-3). Most and Pardubice were chosen for monitoring NH3 concentrations in connection with emissions from chemical industry located in the respective areas.

The average annual concentrations measured in the CR are comparable with the concentrations measured abroad. In Ontario, Canada, the annual average concentrations of NH3 range from 0.1 to 3.0 µg.m-3 (Zbieranowsky, Aherne, 2012), in the areas with intensive agricultural activity this concentration amounts to 3.6 µg.m-3 (Zbieranowsky, Aherne, 2013). In southern Scotland there were measured the average annual concentrations of NH3 in the range 0.40–22.9 µg.m-3, depending on the sampling site (Vogt et al., 2013). The highest values were reached in the locality 70 meters up the wind from the poultry farm. It is thus evident that NH3 concentrations show a marked spatial and time variability (with regard to the main air pollution source).

The spatial variability is influenced by the distance from the source of emissions. The time variability of NH3 concentrations in agricultural areas is caused by the seasonal character of the application of fertilizers within the respective year. Consequently, higher concentrations are reached mainly in spring and autumn (Zbieranowski, Aherne, 2013).

NH3 concentrations are also significantly influenced by higher temperature which, due to increased volatility, results in higher emissions of NH3 from the sources.

Emissions of NH3

Ammonia emissions are produced by decomposition of urea from animal biological waste or during some chemical-technological processes.

Farm animal breeding is the main source of NH3; its share in total emissions of NH3 in 2012 amounted to 69.6 % (Fig. IV.9.3.1). Further significant sources result from the sector of application of mineral nitrogen-containing fertilizers with the share of 26.5 % of total NH3 emissions. The remaining 3.9 % of NH3 emissions are produced by mobile sources equipped with catalytic converters where NH3 is formed by the reduction of nitrogen oxides, and further technological sources. Ammonia is emitted to the atmosphere during the chemical production of fertilizers, during the production of mineral fibres with the use or organic binding agents, in the production of nitric acid etc.

The downward trend in the development of total emissions is connected with the decrease of the number of farm animals, mainly pigs, and in 2012 also poultry, as a consequence of agricultural policy and market economy (Fig. IV.9.3.2). Further reason for emission reduction is the legislation connected with the issuing of integrated permits, within which there were approved and consequently implemented the so called good agricultural practice plans in the largest livestock groups.

Tab. IV.9.3.1 Stations measuring ammonia in the ambient air with the values of annual average and maximum 24-hour concentrations


Fig. IV.9.3.1 Emissions of NH3 sorted out by NFR sectors, 2012

Fig. IV.9.3.2 The development of NH3 emissions, 2007–2012