KAZALCI OKOLJA

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The measured concentrations of nitrogen dioxide and total nitrogen oxides in outdoor air do not exceed the prescribed limit values, so these two pollutants pose no hazard to human health and vegetation.


This indicator shows the frequency of exceeding of the hourly human health limit value for NO2 concentration, mean annual NO2 concentrations that are also important for human health (annual limit value 40 μg/m3) and NOx concentration (plant protection critical value 30 µg/m3) at measuring sites throughout Slovenia in the period 1992–2016. As monitoring of the plant protection critical value is relevant in the natural environment, the Zavodnje, Kovk and Vnajnarje measuring sites are representative for its monitoring.

Nitrogen oxides (the sum of nitrogen monoxide and nitrogen dioxide concentrations) play an important role in the impact of polluted air on the environment, especially through acidification and eutrophication (excessive amount of nutrients in water bodies) as well as formation of photochemical smog. The main sources of nitrogen oxides are traffic, small heating units and thermal power plants using fossil fuels. Nitrogen oxides are formed when nitrogen combines with oxygen at high temperatures. The percentage of nitric oxide (NO) in exhaust gases is over 90%. In the atmosphere, it gradually oxidises into NO2. The rate of transport-related NO oxidation into higher oxides increases with its distance from the emission source. The presence of ozone in outdoor air greatly accelerates the oxidation reaction. Participation of ozone molecules in the oxidation reaction may reduce the concentration of ozone harmful to humans. Therefore, concentrations of ozone are usually lower along busy roads. In addition to traffic, which causes an increase in NO2 concentrations at traffic measuring sites during morning and evening hours and on workdays, meteorological conditions (especially solar radiation, temperatures and seasons of the year) also affect NO2 concentrations.


Charts

Figure ZR06-1: Number of hours with exceeded average 1-hour limit value of NO2 concentration (permitted exceeding is 18 hours) 
Sources: 

Datebase from the national network for monitoring air quality (DMKZ), Slovenian Environemt Agency, 2016.

Note to Figure ZR6-1: The measuring station Ljubljana center, which is operated by the Municipality of Ljubljana, has moved from its location at the intersection of Figovec to Vošnjak and Tivoli streetsat at the end of 2009. The station was renovated in accordance with the requirements of the law. 

np = no data

Show data
1992 1993 1994 1995 1996 1997 1998 1999 2000 2001
Urban background number of hours 5 9 14 6 1 np 0 0 0 0
Ljubljana Bežigrad number of hours np np np np np np np np np np
Celje number of hours 5 9 14 6 1 np 0 0 0 0
Nova Gorica number of hours np np np np np np np np np np
Koper number of hours np np np np np np np np np np
Suburban background number of hours np np np np np 0 0 0 0 0
Trbovlje number of hours np np np np np 0 0 0 0 0
Urban-traffic type number of hours 15 21 2 0 0 0 3 2 7 0
- Ljubljana center number of hours 15 21 0 0 0 0 3 2 0 0
- Maribor center number of hours 0 3 2 0 0 0 0 0 7 0
Rural/Agricultural type number of hours np np np np np np np np np np
Murska Sobota - Rakičan number of hours np np np np np np np np np np
permitted exceedance number of hours 18 18 18 18 18 18 18 18 18 18
2002 2003 2004 2005 2006 2007 2008 2009 2010 2011
Urban background number of hours 0 0 0 0 0 0 0 0 0 0
Ljubljana Bežigrad number of hours np 0 0 0 0 0 0 0 0 0
Celje number of hours 0 0 0 0 0 0 0 0 0 0
Nova Gorica number of hours 0 0 0 0 0 0 0 0 0 0
Koper number of hours np np np np np np 0 0 0 0
Suburban background number of hours 0 0 0 0 0 0 0 0 0 0
Trbovlje number of hours 0 0 0 0 0 0 0 0 0 0
Urban-traffic type number of hours 0 0 0 0 1 2 0 0 7 0
- Ljubljana center number of hours 0 np np np np np np np 7 0
- Maribor center number of hours 0 0 0 0 1 2 0 0 0 0
Rural/Agricultural type number of hours 0 0 0 0 0 0 0 0 np 0
Murska Sobota - Rakičan number of hours 0 0 0 0 0 0 0 0 np 0
permitted exceedance number of hours 18 18 18 18 18 18 18 18 18 18
2012 2013 2014 2015
Urban background number of hours 0 0 0 0
Ljubljana Bežigrad number of hours 0 0 0 0
Celje number of hours 0 0 0 0
Nova Gorica number of hours 0 0 0 0
Koper number of hours 0 0 0 0
Suburban background number of hours 0 0 0 0
Trbovlje number of hours 0 0 0 0
Urban-traffic type number of hours 1 0 0 0
- Ljubljana center number of hours 0 0 0 0
- Maribor center number of hours 1 0 0 0
Rural/Agricultural type number of hours 0 0 0 0
Murska Sobota - Rakičan number of hours 0 0 0 0
permitted exceedance number of hours 18 18 18 18
Figure ZR06-2: Average annual concentration of NO2 (annual limit value is 40 μg/m3) 
Sources: 

Database from the National network for monitoring air quality (DMKZ), Slovenian Environmental Agency; Database of automatic measurement measuring network TPP, TPP Trbovlje the Ljubljana, Milan Vidmar Electric Institute , 2016.

Note to Figure ZR6-2: Measuring Station Ljubljana center, which is operated by the Municipality of Ljubljana, has moved from its location at the intersection of Figovec to Vošnjak and Tivoli streets at the end of 2009. The station was renovated in accordance with the requirements of the law. Data for the new station Ljubljana center will be available from 2010.

np = no data

Show data
1992 1993 1994 1995 1996 1997 1998 1999 2000 2001
Urban background µg/m3 32 37 37 35 33 np 29 28 30 26
Ljubljana Bežigrad µg/m3 np np np np np np np np np np
Celje µg/m3 32 37 37 35 33 np 29 28 30 26
Nova Gorica µg/m3 np np np np np np np np np np
Koper µg/m3 np np np np np np np np np np
Suburban background µg/m3 np np np np np 29 19 17 18 6
Trbovlje µg/m3 np np np np np 29 29 26 28 np
- Škale µg/m3 np np np np np np 8 8 8 6
Urban-traffic type µg/m3 50 50 43 39 39 37 41 44 41 37
Ljubljana center µg/m3 49 47 41 38 39 36 42 49 38 36
Maribor center µg/m3 50 53 45 39 39 38 39 39 44 38
Rural/Agricultural type µg/m3 np np np np np np np np np np
Murska Sobota - Rakičan µg/m3 np np np np np np np np np np
Rural/Industrial type µg/m3 7 7 10 10 4 5 6 7 6 6
- Zavodnje µg/m3 3 5 11 9 5 7 7 6 7 6
- Kovk µg/m3 10 8 8 11 2 4 7 9 7 6
- Vnajnarje µg/m3 np np np np np 4 3 5 4 5
annual limit value µg/m3 40 40 40 40 40 40 40 40 40 40
2002 2003 2004 2005 2006 2007 2008 2009 2010 2011
Urban background µg/m3 27 29 26 26 27 25 25 25 28 27
Ljubljana Bežigrad µg/m3 29 32 29 27 29 28 29 31 35 31
Celje µg/m3 24 27 24 26 28 23 21 22 26 25
Nova Gorica µg/m3 27 27 25 24 24 25 30 28 29 28
Koper µg/m3 np np np np np np 21 19 21 22
Suburban background µg/m3 28 20 18 15 16 15 16 13 14 13
Trbovlje µg/m3 28 32 27 24 23 22 23 17 20 17
- Škale µg/m3 np 8 9 5 9 8 8 9 8 8
Urban-traffic type µg/m3 36 37 31 33 39 37 34 32 49 45
Ljubljana center µg/m3 np np np np np np np np 63 55
Maribor center µg/m3 36 37 31 33 39 37 34 32 34 34
Rural/Agricultural type µg/m3 14 15 11 14 15 17 16 14 np 16
Murska Sobota - Rakičan µg/m3 14 15 11 14 15 17 16 14 np 16
Rural/Industrial type µg/m3 6 5 8 6 7 7 7 6 6 9
- Zavodnje µg/m3 np 6 5 3 4 3 3 4 5 9
- Kovk µg/m3 6 3 13 10 12 12 12 9 9 11
- Vnajnarje µg/m3 6 5 5 4 5 5 5 4 4 7
annual limit value µg/m3 40 40 40 40 40 40 40 40 40 40
2012 2013 2014 2015
Urban background µg/m3 23 25 23 25
Ljubljana Bežigrad µg/m3 22 29 26 30
Celje µg/m3 27 26 28 29
Nova Gorica µg/m3 26 25 19 22
Koper µg/m3 18 21 17 17
Suburban background µg/m3 12 13 12 13
Trbovlje µg/m3 17 16 17 18
- Škale µg/m3 7 9 7 8
Urban-traffic type µg/m3 43 38 35 34
Ljubljana center µg/m3 52 43 40 36
Maribor center µg/m3 33 32 30 31
Rural/Agricultural type µg/m3 19 16 12 12
Murska Sobota - Rakičan µg/m3 19 16 12 13
Rural/Industrial type µg/m3 8 10 7 8
- Zavodnje µg/m3 8 8 7 7
- Kovk µg/m3 6 13 8 8
- Vnajnarje µg/m3 10 9 7 9
annual limit value µg/m3 40 40 40 40
Figure ZR06-3: Critical values ​​for NOx for the protection of plants (annual limited value of  concentration of NOx in the natural environment 30 µg NOx /m3) 
Sources: 

Database from the National network for monitoring air quality (DMKZ), Slovenian Environmental Agency; Database of automatic measurement measuring network TPP, TPP Trbovlje the Ljubljana, Milan Vidmar Electric Institute ,2016.

Note to Figure ZR6-2: Measuring Station Ljubljana center, which is operated by the Municipality of Ljubljana, has moved from its location at the intersection of Figovec to Vošnjak and Tivoli streets at the end of 2009. The station was renovated in accordance with the requirements of the law. Data for the new station Ljubljana center will be available from 2010.

np = no data

Show data
1997 1998 1999 2000 2001 2002 2003 2004 2005 2006
Urban background µg/m3 np np np np 44 42 45 43 43 45
Ljubljana Bežigrad µg/m3 np np np np np 48 49 46 43 45
Celje µg/m3 np np np np 44 37 44 41 45 46
Nova Gorica µg/m3 np np np np np 41 43 43 41 43
Koper µg/m3 np np np np np np np np np np
Suburban background µg/m3 np np 9 30 8 35 33 29 24 25
Trbovlje µg/m3 np np np 50 np 52 54 47 41 39
- Škale µg/m3 9 9 8 18 11 10 6 10
Urban-traffic type µg/m3 np np np np 68 61 61 54 60 71
Ljubljana center µg/m3 np np np np 64 np np np np np
Maribor center µg/m3 np np np np 72 61 61 54 60 71
Rural/Agricultural type µg/m3 np np np np np 19 20 17 20 23
Murska Sobota - Rakičan µg/m3 np np np np np 19 20 17 20 23
Rural/Industrial type µg/m3 7 6 8 9 7 7 6 10 7 8
- Zavodnje µg/m3 9 8 7 9 8 7 7 5 5
- Kovk µg/m3 6 7 11 9 7 7 5 17 12 14
- Vnajnarje µg/m3 5 3 6 5 6 6 5 5 5
annual limit value for protection of vegetation µg/m3 30 30 30 30 30 30 30 30 30 30
2007 2008 2009 2010 2011 2012 2013 2014 2015
Urban background µg/m3 43 43 45 50 47 44 41 39 47
Ljubljana Bežigrad µg/m3 45 52 57 64 56 47 45 41 56
Celje µg/m3 40 40 47 53 47 50 51 57 67
Nova Gorica µg/m3 44 50 53 56 57 50 45 35 43
Koper µg/m3 np 28 24 28 28 28 21 21 22
Suburban background µg/m3 26 25 23 25 22 21 22 19 22
Trbovlje µg/m3 38 40 37 40 33 32 34 29 33
- Škale µg/m3 13 10 9 9 10 9 10 9 10
Urban-traffic type µg/m3 70 63 61 95 88 81 75 71 71
Ljubljana center µg/m3 np np np 122 105 96 84 75 72
Maribor center µg/m3 70 63 61 68 70 65 65 66 69
Rural/Agricultural type µg/m3 24 22 20 np np 28 21 17 17
Murska Sobota - Rakičan µg/m3 24 22 20 np np 28 21 17 19
Rural/Industrial type µg/m3 10 7 6 7 11 9 11 9 9
- Zavodnje µg/m3 11 6 5 7 11 10 10 10 8
- Kovk µg/m3 14 10 8 11 13 7 15 9 9
- Vnajnarje µg/m3 5 5 6 4 8 11 9 7 9
annual limit value for protection of vegetation µg/m3 30 30 30 30 30 30 30 30 30

Goals

Compliance with limit values for nitrogen oxides for human health and vegetation protection:

  • 1-hour NO2 limit value for human health protection: 200 μg/m3 (permitted overage: 18-times within a year);
  • annual NO2 limit value for human health protection (in force since 1 January 2011): 40 μg/m3;
  • critical annual concentration for protection and ecosystems in the natural environment: 30 μg/m3.

    The alert threshold for nitrogen oxide concentrations measured over three consecutive hours at locations representative for air quality in an area of at least 100 km2, an entire area or an agglomerated area may not exceed 400 µg/m3.


High concentrations of nitrogen oxide are mostly limited to a narrow band along busy roads and streets. The highest NO2 concentrations are measured at the central Ljubljana traffic measuring site, where the measured values almost reach or exceed the annual limit value. From the perspective of human health, the Ljubljana centre, Maribor centre, Nova Gorica and Celje measuring sites are the most problematic.

Since 1994, NO2 concentration has not been exceeding the legally prescribed hourly limit value for human health protection. Also the annual limit value of 40 µg/m3 has not been exceeded anywhere in Slovenia since 2014.

The annual limit NOx concentration for the protection of vegetation and allowable in the natural environment has not been exceeded in a long time.

As a rule, NO2 concentrations are higher in wintertime, which is largely a result of unfavourable weather conditions (temperature inversion). They are lower during the summer since NO2 is used for the formation of ozone and because wind conditions are more favourable. Elevated NO2 concentrations are mostly measured along busy roads. The NO2 concentration decreases the further away you get from busy roads. Thanks to the introduction of catalytic converters in cars, NO2 emissions from transport have decreased; however, the decrease was not substantial, due to the permanently increasing volume of traffic. Large thermal power plants that use fossil fuels are another source of nitrogen oxides; however, increased concentrations have not been observed in the vicinity of large thermal power plants in recent years.



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