IV.5 BENZENE (C₆H₆)

IV.5.1 Air pollution caused by C₆H₆ in the year 2013

In 2013 benzene concentrations were measured in total in 29 localities. The level of the limit value (5 µg.m^-3) was not exceeded in any locality in 2013 (Fig. IV.5.1). The highest concentrations were reached at the stations in the agglomeration of Ostrava/Karviná/Frýdek-Místek and Ostrava-Přívoz and Ostrava-Fifejdy were the most loaded localities in the recent years (Table XIII.10). In 2013, for the first time from the beginning of the measurements in 1999, the result benzene concentration in the locality Ostrava-Přívoz (3.95 µg.m^-3) did not reach the limit value; the concentration in the locality Ostrava-Fifejdy decreased from 4.1 µg.m^-3 in the year 2012 to 3.5 µg.m^-3. Higher concentrations depicted by the field of the annual average benzene concentration (Fig. IV.5.1) are connected primarily with industrial activities, and namely with coke production and processing of chemical products (CHMI 2013d).

In comparison with the year 2012, approximately 31 % of localities (4 localities) recorded the decrease of annual average concentration, 69 % of localities (9 localities) recorded a slight increase of these concentrations (of the total number of 13 stations which measured benzene concentrations both in 2012 and 2013). In the summer period benzene concentrations are usually lower than those in the winter period (Fig. IV.5.2). This annual course is probably the result of worse dispersion conditions in winter periods (Schnitzhofer et al. 2008).

IV.5.2 The development of C₆H₆ concentrations

The annual average concentration of benzene in the CR within the period 2005–2013 reached its maximum levels in the year 2006. Since then the concentration has been gradually decreasing with one positive deviation in the year 2010. The years 2006 and 2010 were characterized by deteriorated dispersion conditions in the CR which could result in the increased accumulation of benzene in the air (Fig. IV.5.4).

Higher annual average concentrations are measured in the localities situated in the cities; the highest benzene concentrations are usually reached at the stations classified as urban industrial and urban traffic (Fig. IV.5.4). The localities situated in rural areas reach the lowest levels. The same results were reached also by Karakitsios et al. (2007). This is caused by higher concentration of industrial production and road transport in the cities.

Although benzene reaches the highest annual average concentrations in the agglomeration of Ostrava/ Karviná/Frýdek-Místek (Fig. V.1, Fig. IV.5.3), the results of the long-term automated measurements in this area show that the average annual concentrations of benzene have had a downward trend there since 2012. The exceedances of the annual limit value at the station Ostrava-Přívoz before the year 2013 occurred due to the fact that this locality recorded 1-hour concentrations higher than 50 µg.m^-3, i.e. such concentrations that at other stations in Ostrava occurred in much smaller numbers, and outside Ostrava they did not occurred at all. Benzene concentrations in Ostrava were temporarily influenced also by the removal of old ecological loads in Ostrava-Mariánské Hory in 2011¹. The annual concentrations decreased after the shutdown of the coke plant Koksovny Jan Šverma (shut down on 31. 12. 2010) and after the implementation of a number or measures aimed at the reduction of emissions from the sources of the companies BorsodChem MCHZ, s. r. o. and the coke plant OKK koksovny, a. s. (CHMI 2013d). The second highest average concentration of benzene is usually measured in the agglomeration of Brno. However, this agglomeration is represented by only one traffic locality, Brnostřed, which as the only one from this area had the continuous and sufficiently long time series of measurements necessary for the assessment of the trend. Therefore it is necessary to point out that the values measured in this locality are not representative for the whole agglomeration of Brno.

IV.5.3 Emissions of C₆H₆

The balance of benzene emissions is based for the great part on the calculation from the reported VOC emissions. The reported emissions can be found only in the sources with the obligation, set by the legislation, to ascertain air pollution levels, mainly for the verification of the compliance with the emission limit values. There are certain exceptions, and namely the sources such as coke plants and connected branches of chemical production for which the operator is obliged to ascertain benzene emissions pursuant to the integrated permit and specific procedures are used to ascertain the release. The Ostrava area where such technologies are used is one of the few localities with frequent exceedances of the set limit values in the long term.

Emission balances were produced only exceptionally in the recent years, as a rule they were presented within the respective project results. The last of them presents the data for the year 2010 and the greatest share of the total amount of benzene (approx. 1,250 t.year^-1) is represented by the use of paints (Resler, Jareš 2014). The shares of benzene in VOC emissions result partly from composition of the used products (e.g. solvents, paints, finishes and adhesives), or fuels, or they are determined from the assumed composition of specific organic substances formed during the combustion of various types of fuels. The greatest amount of benzene emissions for the year 2013 (as well as for the previous one) was reported by the chemical production company DEZA, a. s. – Chemické výroby, Valašské Meziříčí (5.356 t.year^-1), further emissions items are about one order lower.

 

Tab. XIII.10 Stations with the highest values of annual average concentrations of benzene

 

Fig. IV.5.1 Field of annual average concentration of benzene in the ambient air in 2013
 

Fig. IV.5.2 24-hour concentrations at the stations with the highest annual benzene concentrations in 2013
 

Fig. IV.5.3 Annual average concentrations of benzene in 2003–2013 at selected stations
 

Fig. IV.5.4 Trends of benzene annual characteristics in the Czech Republic, 2005–2013
 

Fig. IV.5.5 Five-year average of annual average concentrations of benzene, 2009–2013

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¹Removal of old ecological loads in Ostrava-Mariánské Hory was carried out in 2011 by remediation of waste lagoons formed by waste disposal from refinery production launched at the end of 19th century (starting from 1965 also waste from regeneration of exploited lubricating oils was deposited there from the state enterprise OSTRAMO Ostrava, since 1992 OSTRAMOVlček and co., s. r. o.). The shutdown occurred in 1996.