IV.2.1 Air pollution caused by benzo[a]pyrene in the year 2016
Air pollution by benzo[a]pyrene is one of the main problems associated with ensuring air quality in the Czech Republic. In 2016, the annual average concentration of benzo[a]pyrene exceeded the pollution limit value (1 ng.m-3) at almost 71% of stations (i.e. 31 of a total of 44 stations with sufficient number of measurements for the evaluation). Thus there was an inter-annual increase, as exceeding of the limit was recorded at 62% of stations in 2015 (i.e. at 21 of 34 stations with sufficient number of stations for the evaluation). Compared with 2015, the average annual concentrations in 2016 (evaluated on the basis of a set of stations for which data are available for both 2015 and 2016) decreased at 59% of stations. The average annual concentration (averaged for the same set of stations as those at which measurements were performed in 2015 and 2016) was slightly higher in 2016 (1.78 ng.m-3) compared to 2015 (1.73 ng.m-3).
A number of cities and municipalities, similar to previous years, were evaluated as territories where the pollution limit levels were exceeded (Fig. IV.2.1). In 2016, the pollution limit level was exceeded over 25.9% of the area of the Czech Republic (in 2015 over 20.3% of the area of the Czech Republic), with approx. 55.7% of the population of the Czech Republic (in 2015 with approx. 50.8%).
It must be borne in mind that the estimate of the field of annual average concentrations of benzo[a]pyrene (Fig. IV.2.1) is accompanied by considerably greater uncertainties than for the other mapped substances. The uncertainty of the map is a result of the inadequate number of measuring stations and the absence of more extensive measurements in smaller settlements in the Czech Republic where the fundamental effect of local heating plants would be represented in the air pollution by benzo[a]pyrene. Thus assessment of the inter-annual changes in the affected territory and population by above-limit concentrations of benzo[a]pyrene will also be accompanied by a greater error. The number of locations with measurements of benzo[a]pyrene is limited particularly by the high costs for laboratory analyses. The uncertainties in the maps are described in detail in Annex No. 1.
The highest average annual concentration in 2016, similarly as in previous years, was measured at the industrial location of the Ostrava-Radvanice Health Centre (9.0 ng.m-3, which is nine times the pollution limit level. Above-limit concentrations were also attained at the other four industrial locations and at 63% of urban and suburban background stations. The concentrations of benzo[a]pyrene are measured at six traffic stations, where the pollution limit level was exceeded at five of them (Tab. XIII.6). The exceeding of the pollution limit level for benzo[a]pyrene at most of the stations is a result of the more-or-less even distribution of the main emission sources of this pollutant, i.e. household heating systems. Similar to the other pollutants, the highest concentrations are measured in the O/K/F-M agglomeration as a consequence of the greatest emission burdens in all of the Czech Republic (from various kinds of sources) and the effect of trans-boundary transmission (for more details, see Chap. IV.2.3).
The highest concentrations of benzo[a]pyrene in the Czech Republic are annually measured at the Ostrava- Radvanice Health Centre, Ostrava-Radvanice OZO (waste processing company), Ostrava-Přívoz and Český Těšín stations. The long-term unfavourable conditions in the Ostrava-Karviná area and the year-round effect of emissions in this area are reflected in the fact that, in the summer, when the concentration of benzo[a]pyrene at other stations are frequently around the detection limit (0.04 ng.m-3), daily concentrations at these locations higher than 1 ng.m-3 occur (e.g. Ostrava-Radvanice Health Centre 18.00 ng.m-3 on 30 July 2016 and 8 August 2016, Ostrava-Radvanice OZO 11.00 ng.m-3 on 8 August 2016, Ostrava-Přívoz 2.02 ng.m-3 on 26 August 2016 and Český Těšín 1.45 ng.m--3 on 8 June 2016).
Above-limit benzo[a]pyrene levels probably also occur in municipalities in which its concentration is not routinely monitored. This fact has been repeatedly confirmed by measurements at new locations, e.g. Budišov nad Budišovkou and Mosty u Jablunkova in 2015, Sudice and Osoblaha in 2016 and Valašské Meziříčí, in operation since 2013. The Sudice (3.0 ng.m-3) and Osoblaha (1.8 ng.m-3) locations, where measurements were subsidised from the budget of the Moravian-Silesian region1, are close to the Polish border and are thus exposed to the effect of local heating facilities and other sources of emissions from both the Czech and Polish sides of the border. In contrast, the station at Valašské Meziříčí, located on the property of a school in a residential district, is indirectly affected by emissions of benzo[a]pyrene from individual heating facilities. Nonetheless, the average annual concen- tration of 2.2 ng.m-3 (2.9 ng.m-3 in 2015) classifies this location as highly polluted.
In 2016 in the context of the second year of the campaign for measurement in the Southern Moravian region, measurements were performed in the heating season at two small municipalities (Babice u Rosic and Jinačovice). The measurements were performed at the end of October and beginning of November at a time when outdoor temperatures gradually decreased and the heating season began. The measured daily concentrations of benzo[a]pyrene attained several-fold higher values than those measured at the Brno-Líšeň location, which is in the same region, but residences in the vicinity are connected to a central heating source. The greatest difference in concentrations was measured at the beginning of November, when the average daily temperature decreased below 0 °C and the values of daily concentrations of benzo[a]pyrene at Jinačovice were ten-times higher than those measured at Brno-Líšeň. As, according to the valid legislation, the number of concentration values obtained in the campaign measurements is not sufficient for calculation of the average annual concentrations, the above-mentioned evaluation is based only on comparison of the average daily concentrations (Fig. IV.2.5).
The concentrations of benzo[a]pyrene exhibit a marked annual progression (Fig. IV.2.6) with maxima in the winter and minima in the summer. The elevated concentrations in the atmosphere in the winter are related to the elevated emissions of polycyclic aromatic hydrocarbons (PAH) from seasonal anthropogenic sources – local heating facilities (i.e. the most important sources of benzo[a]pyrene emissions – Fig. IV.2.8). Traffic is also a significant source of PAH and this is exacerbated in the winter by elevated PAH emissions as a consequence of cold engine starts. Elevated concentrations are also caused by deteriorated dispersion conditions in the winter, easier gas-particulate conversion at low temperatures and lower photochemical decomposition of PAH. On the other hand, in the summer, the concentration of PAH decreases because of better dispersion conditions, elevated photochemical decomposition of PAH with greater intensity of solar radiation and higher temperatures and, of course, because of lower emissions from anthropogenic sources (Li et al. 2009; Ludykar et al. 1999; Teixeira et al. 2012).
IV.2.2 Development of benzo[a]pyrene concentrations
Trends in the average annual concentrations of benzo[a]pyrene are depicted from 2006. On a country- wide scale, the level of this pollutant has long been approx. twice the limit value (Fig. IV.2.4). The highest benzo[a]pyrene concentrations were measured in 2006 (more than three times the pollution limit level) as a result of worsened meteorological and dispersion conditions. Since 2007, the concentration of benzo[a]pyrene has fluctuated and has not exhibited any clear trend; inter-annual comparison for 2015/2016 indicates a slight increase in the concentrations at all types of locations with the exception of traffic stations. The highest concentrations are attained at industrial locations; however, above-limit concentrations also occur at traffic, urban and suburban stations (Fig. IV.2.4). As was already mentioned, the inadequate number of measurements at rural locations does not permit better estimation of the concentrations of benzo[a]pyrene in smaller settlements; nonetheless, on the basis of the composition of sources of emissions and, e.g., the study by Krejčí (2012), it can be assumed that the concentrations are above the limit here too. The relationship between the concentrations of benzo[a]pyrene and PM10 particulates in the winter months of 2012–2016 is depicted in Fig. IV.2.7.
IV.2.3 Emissions of benzo[a]pyrene
PAH, of which especially benzo[a]pyrene is monitored in respect of air protection, are produced almost exclusively by combustion processes during which the organic combustible substances present are not sufficiently oxidised. Benzo[a]pyrene is a product of incomplete combustion at temperatures of 300 to 600 °C. Thus, one of its most important sources is the combustion of solid fuels in lowcapacity furnaces, especially household heating systems, and transportation.
Sector 1A4bi – In 2015, Residential: Stationary contributed 97.3% to national benzo[a]pyrene (Fig. IV.2.8) emissions. The combustion of solid fuels, especially coal, in older types of boilers (under-fire boilers, over-fire boilers), especially in older types, is the main reason for such a large percentage. According to expert estimates, in 2010 up to 85% of all the equipment in the Czech Republic for burning solid fuel in households consisted in under-fire boilers and over-fire boilers (Bufka 2011). The impact of Sectors 1A3biii – Road transport: Heavy duty vehicles and buses, 1A3bi – Road transport: Passenger cars and 1A4cii – Agriculture, forestry and fishing: The contribution of off-road vehicles and other machinery is estimated at 1.8%. Other important sources of benzo[a]pyrene emissions are in Sectors 1A4ai – Commercial, institutional: Stationary and 1B1b – Fugitive emissions from solid fuels: Solid fuel transformation (leaks in coke-oven batteries).
In the individual regions of the Czech Republic, the
contributions of the individual emission sources
differ depending to the composition of sources in the
given area. In relation to the predominant contribution
of sector 1A4bi, emissions of benzo[a]pyrene
are distributed over the territory of residential
buildings throughout the Czech Republic and their amounts in the 2007–2015 period depended primarily
on the temperature character of the heating
season (Fig. IV.2.9). The impact of transportation
was felt mainly along motorways, roadways with
high traffic levels and in the territories of larger
urban units. The greatest emissions of benzo[a]pyrene
are produced in the O/K/F-M agglomeration
because of the presence of enterprises manufacturing
iron and steel and the related plants
specialising in coke production (Fig. IV.2.10).