IV. AIR QUALITY IN THE CZECH REPUBLIC
IV.1 SUSPENDED PARTICLES
Air pollution caused by PM10 and PM2.5 fraction of suspended particles remains one of the main problems of air quality assurance in the CR. The exceedance of PM10 and PM2.5 limit values is still significant for including the respective settlements among the areas with limit value exceedances.
IV.1.1 Air pollution caused by suspended particles in the year
Suspended particles of PM10 fraction
The limit value for PM10 24-hour concentrations was exceeded in 2013 in 5.7 % of the territory of the CR with approx. 15.9 % of inhabitants, and for PM10 average annual concentration in 0.7 % of the territory with approx. 4.8 % of inhabitants (Figs. IV.1.1 and IV.1.2).
The exceedance of the 24-hour limit value for PM10 was recorded
in 2013 in almost one third of stations (32.6 %, i.e. 42
stations of the total number of 129). In 2012 the daily limit
value was exceeded in 42 % of stations (53 stations of 147;
IV.1.14). In comparison with the year 2012 the 36th highest
concentration of PM10 decreased in almost 60 % of stations. The
average 36th highest concentration of PM10 in 2013 (48.9 µg.m-3) was lower as compared with the year 2012 (51.3 µg.m-3)1.
Consequently, the territory with the exceeded daily limit value
for PM10 decreased from 9.6 % with about one third of the CR
population, to the already mentioned 5.7 % with approx. 15.9 %
The most affected area of large coverage was, similarly as in the previous years (Figs. IV.1.10 and IV.1.11) the agglomeration of O/K/F-M where the daily limit value for PM10 was exceeded in 2013 at most stations. However, the daily limit value for PM10 was exceeded in all zones and agglomerations in at least one locality with the exception of the South-eastern zone (Fig. IV.1.3, Table XIII.4). In the agglomeration of Prague, in the agglomeration of Brno, in the North-eastern zone and in the Southwestern zone the exceedance of the limit value in 2013 was connected primarily with traffic loads; in other zones, however, the exceedances occurred also at the background urban, suburban and rural stations. In 2013 the annual limit value for PM10 was exceeded in 7.4 % of stations, i.e. at 10 stations of the total number of 136 stations in the CR with sufficient amount of data for the evaluation; all exceedances were recorded only at the stations in the agglomeration of O/K/F-M (Table XIII.5, Fig. IV.1.12). In 2012 the exceedances of the annual limit value were recorded in 10.8 % of stations (15 stations of 138; Fig. IV.1.14). The annual average concentration of PM10 decreased in comparison with the year 2012 in 54 % of stations and the average annual concentration in 2013 (26.8 µg.m-3) was slightly lower in comparison with the year 2012 (27.3 µg.m-3)1. The territory with the annual limit value exceedances in 2013 decreased to 0.7 % with approx. 4.8 % inhabitants from 0.9 % of the territory with approx. 5.2 % of inhabitants evaluated in 2012.
The concentrations of PM10 show a clear annual course with the highest concentrations in the cold months of the year (Figs. IV.1.4, IV.1.5, IV.1.6). Higher concentrations of PM10 in the ambient air during the cold part of the year are connected both with higher emissions of particles from seasonal heat sources (e.g. the share of local heating in PM10 and PM2.5 emissions in the CR is 41 % and 59 % respectively – Figs. IV.1.19 and. IV.1.20), and with deteriorated dispersion conditions, more frequent in winter months.
In 2013 the highest concentrations were measured in the months January–March, namely due to frequent unfavourable dispersion conditions. On the contrary, the last three months of the year were, with regard to dispersion conditions, more favourable and recorded the above-the-normal temperatures (see Chapter III). Along with the lower intensity of heating this resulted in lower average monthly concentrations, i.e. in their decrease. The lower intensity of heating and the subsequent decrease of emissions from heating from October to December can be assumed on the basis of degree days comparison in individual months of the heating season (Fig. III.4). Detailed analysis of the reasons for higher concentrations of PM10 in the first months of the year 2013 is presented in Chapter III.
Suspended particles of PM2.5 fraction
The level of air pollution caused by PM2.5 in 2013 did not
changed significantly in comparison with the year 2012. The
annual limit value for PM2.5 was exceeded in 2.4 % of the CR
territory with approx. 9.6 % of inhabitants (Fig. IV.1.7). In
2012 the same part of the territory of the CR with the exceeded
limit value was recorded with approx. 10.2 % of inhabitants. The
exceedances were recorded at six stations in the agglomeration
of O/K/F-M and at one station in the agglomeration of Prague, at
one station in the Moravia-Silesia zone and at one station in
the Central Moravia zone (Table XIII.6,
Fig. IV.1.9) of the
total number of 46 stations (i.e. exceedances in 19.6 % of
stations); in 2012 exceedances were recorded at nine stations of
45 (Fig. IV.1.14). In comparison with the year 2012 the average
annual concentration of PM2.5 increased in almost 60 % of
stations, nevertheless the average annual concentration of PM2.5
in 2013 was only slightly higher as against the year 2012 (20.9
vs. 20.3 µg.m-3); the evaluation was based on the same set of
stations in both years.
Air pollution caused by PM2.5 occurs mainly in the cold part of the year (Fig. IV.1.9); higher concentrations in the cold part of the year are similarly as those in PM10 caused by emissions from heating and deteriorated dispersion conditions.
The ration of PM2.5 and PM10 fractions of suspended particles
The ratio between PM2.5 and PM10 fractions is not constant, it
shows a certain seasonal course, and at the same time it is
dependent on the locality (Fig. IV.1.8). In 2013 the ratio, in
the average from 32 localities in the CR measuring both PM2.5
and PM10 and with sufficient number of values, ranged from 0.68
(August) to 0.82 (January) with lower values in the summer
period. In Prague, where the annual course is influenced by a
large share of traffic localities, this ratio ranged from 0.56 (September)
to 0.75 (March), in Brno from 0.7 (May) to 0.85 (November) and
in the Moravia-Silesia region from 0.69 (May) to 0.85 (January).
When comparing the ratio with regard to the classification of
localities, the ratio in rural localities is from 0.78 (July) to
0.93 (December), in urban localities from 0.7 (August and
September) to 0.81 (February and March), in suburban localities
from 0.67 (May) to 0.84 (December), in traffic localities from
0.61 (September) to 0.75 (January) and in industrial localities
0.63 (July) to 0.91 (January).
The seasonal course of PM2.5/PM10 fraction ratio is connected with the seasonal character of several emission sources. Emissions from combustion sources show higher shares of PM2.5 fraction than for instance emissions from agriculture and reemissions during dry and windy weather. Consequently, heating in the winter period can cause the higher share of PM2.5 fraction in comparison with PM10 fraction. The decrease during the spring and early summer is also explained by the increased amount of larger biogenic particles (e.g. pollen) by some authors (Gehrig, Buchmann 2003). The higher PM2.5/PM10 fraction ratio due to combustion is observed also at industrial stations.
The lowest PM2.5/PM10 ratio is at traffic localities (Fig. IV.1.8). During fuel combustion the emitted particles occur mainly in PM2.5 fraction and thus the ratio should be high in traffic localities. The fact that this is not the case, accents the significance of emissions of larger particles caused by tyre, break lining and road surface abrasion. The share of the coarse fraction at traffic stations increases also due to the re-suspension of particles following winter spreading of roads. The growth of PM10 concentrations can be caused also by the increased abrasion of road surface by spreading and the subsequent re-suspension of the abraded material (EC 2011).
IV.1.2 The development of PM10 and PM2.5 concentrations
The concentrations of PM10 suspended particles, similarly as in other pollutants, decreased significantly in the 90s of the last century. This was caused by marked decrease of emissions of TSP and precursors of suspended particles (SO2, NOx, NH3 and VOC) in the period 1990–2001 due to the legislative changes, restructuring of economy and modernization or closure of the operated sources (more details see Chapter II., Fig. II.1). After the year 2001 the decrease of emissions continued at a slower rate (Fig. II.2), which resulted in the fact that pollutants concentrations were influenced mainly by the prevailing meteorological and dispersion conditions in the given year. In almost all localities in the CR an increasing trend of air pollution caused by PM10 was apparent from 2001 to 2003. In 2003 so far the highest values of PM10 concentrations were measured in the period after the year 2000. High PM10 concentrations in 2003 were caused both by unfavourable dispersion conditions in February and the belowthe-normal precipitation amounts. After a short change in 2004, when routine monitoring of PM2.5, fraction started, high concentrations of suspended particles were recorded again in the years 2005 and 2006, mainly due to the long episodes with unfavourable dispersion conditions. In 2007–2009, on the contrary, there were more favourable dispersion conditions and the concentrations of particles significantly decreased in comparison with the years 2003, 2005 and 2006. In the year 2008 lower concentrations were caused probably also by more marked decrease of emissions of some precursors of particles during the temporary decline in certain sectors due to the economic crisis (more details see Chapter II.). The subsequent increase of concentrations of suspended particles in 2010 was given mainly by the repeated occurrence of unfavourable meteorological and dispersion conditions in the winter period at the beginning and at the end of the year and by the coldest heating season since 1996 (Fig. III.1). During the last three years since 2010 the concentration of suspended particles have been decreasing. The annual average concentration of PM10 has remained below the limit value in the long term, on the contrary, the annual average concentration of PM2.5 and the 36th highest daily concentration of PM10 fluctuates around the limit value (in all cases averaged for all types of localities and the whole CR; Figs. IV.1.15 and IV.1.16).
IV.1.3 Emissions of PM10 and PM2.5
The combustion of fuels and other industrial activities result
in the production of aerosol emissions which can be solid,
liquid or mixed. The Czech legislation defines these emissions
as solid pollutants (TZL), the foreign literature refers to
Total Suspended Particulate Matter (TSP). With regard to the
effects on human health there were defined the size groups
called PMx (Particulate Matter). They contain the particles
smaller than x µm (aerodynamic diameter). Most often emission
inventories define the PM10 and PM2.5 size fractions. Emissions
of TSP have various size and chemical compositions according to
the character of the source and the way of formation. They may
contain heavy metals and they are carriers of VOC.
Emission inventories of PM10 and PM2.5 particles carried out according to valid methods include only the emissions produced by primary sources. In comparison with emissions of other pollutants PM emissions are emitted into the air from a large number of groups of sources. Apart from the sources from which these substances are discharged in a controlled manner, significant amount of PM emissions have their origin in fugitive sources (quarries, landfills of dusty materials, operations with dusty materials etc.). The ambient air quality can be influenced also by emissions of PM produced by re-suspension of dust, not included in emission inventories. The share of individual groups of sources in PM10 and PM2.5 emissions in 2012 is depicted in Figs. IV.1.19 and IV.1.20. The main source of PM emissions is represented by the sector of local household heating; its share in air pollution caused by PM10 amounted to 40.8 % and by PM2.5 to 59.2 %. Other significant sources of PM10 emissions include agricultural activities, where these emissions are produced during tillage, harvest and cleaning of agricultural crops in fields. This sector contributed with 13.1 % of PM10 emissions. With regard to the effects on human health, most significant are the emissions of PM caused by traffic, mainly from fuel combustion in compression ignition engines, producing the particles with the size from units to hundreds of nm (Vojtíšek 2010). Road freight transport over 3.5 t and the share of passenger car transport in PM10 emissions was 6.5 % and in PM2.5 emissions 9.6 %.
The share of households using solid fuels for heating did not changed in the period 2007–2012 significantly, and therefore the trend of PM10 and PM2.5 emissions is influenced especially by the character of heating seasons (Figs. IV.1.21 and IV.1.22). The decrease of emissions is influenced especially by the natural renewal of the car fleet, the decrease of agricultural production and the implementation of emission ceilings of TSP for LCP sources since 2008.
With regard to the fact that the main source of PM10 and PM2.5 emissions is represented by the sector of local household heating, the production of emissions of these pollutants is distributed throughout the whole inhabited territory of the CR (Figs. IV.1.23 and IV.1.24). In the territory of the CR divided into 5x5 km squares there are localities with major energy producers combusting solid fossil fuels (primarily the Moravia-Silesia region and the Ústí nad Labem region). The share of traffic is apparent mainly in big cities.
Fig. IV.1.1 Field of the 36th highest 24-hour concentration of PM10 in 2013
Fig. IV.1.2 Field of annual average concentration of PM10 in 2013
Fig. IV.1.3 Numbers of exceedances of the limit value for 24-hour
concentration of PM10 in 2013
Fig. IV.1.4 Annual course of average monthly concentrations
of PM10 (averages for the given type of station),
Fig. IV.1.5 Stations with the highest exceedance of LV for
24-hour concentrations of PM10 in 2013
Fig. IV.1.6 Stations with the highest exceedance of LV for
annual concentrations of PM10 in 2013
Fig. IV.1.7 Field of annual average concentration of PM2.5
Fig. IV.1.8 Average monthly PM2.5/PM10
ratio in 2013
Fig. IV.1.9 Stations with the highest exceedance of LV for
annual concentrations of PM2.5 in 2013
Fig. IV.1.10 36th highest 24-hour concentrations
and annual average concentrations of PM10 in
2003–2013 at selected stations with UB, SUB, I and T
Fig. IV.1.11 36th highest 24-hour concentrations and annual average concentrations of PM10 in 2003–2013 at selected rural (R) stations
Fig. IV.1.12 Annual average PM10 concentrations at the stations with the exceedance of the limit value, 2009–2013
Fig. IV.1.13 Annual average concentrations of PM2.5 in the ambient air in 2004–2013 at selected stations
Fig. IV.1.14 Share of localities with the exceedance of the
limit value for 24-hour concentrations and annual average
concentrations of PM10 and PM2.5,
Fig. IV.1.15 Trends of PM10 and PM2.5
annual characteristics in the Czech Republic, 1996–2013
Fig. IV.1.16 Trends of selected characteristics of PM10 (index, year 1996 = 100), 1996–2013; (index, year 2000 = 100), 2000–2013 and PM2.5 (index, year 2004 = 100), 2004–2013
Fig. IV.1.17 Five-year average of annual average
concentrations of PM10, 2009–2013
Fig. IV.1.18 Five-year average of annual average concentrations of PM2.5, 2009–2013
Fig. IV.1.19 Emissions of PM10 sorted out by NFR sectors, 2012
Fig. IV.1.20 Emissions of PM2.5 sorted out by NFR sectors, 2012
Fig. IV.1.21 The development of PM10 emissions, 2007–2012
Fig. IV.1.22 The development of PM2.5 emissions,
Fig. IV.1.23 PM10 emission density from 5x5 km
Fig. IV.1.24 PM2.5 emission density from 5x5 km squares, 2012
1Averaged for the same set of stations with measurements both in 2012 and 2013.