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 are not harmful 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: 
Air quality monitoring database (DMKZ), Slovenian Environment Agency (2018)
Chart note: 

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

Urban background

Ljubljana Bežigrad

Celje

Nova Gorica

Koper

Suburban background

Trbovlje

Urban-traffic type

- Ljubljana center

- Maribor center

Rural/Agricultural type

Murska Sobota - Rakican

permitted exceedance

1992

5

0

5

0

0

0

0

15

15

0

0

0

18

1993

9

0

9

0

0

0

0

21

21

3

0

0

18

1994

14

0

14

0

0

0

0

2

0

2

0

0

18

1995

6

0

6

0

0

0

0

0

0

0

0

0

18

1996

1

0

1

0

0

0

0

0

0

0

0

0

18

1997

0

0

0

0

0

0

0

0

0

0

0

0

18

1998

0

0

0

0

0

0

0

3

3

0

0

0

18

1999

0

0

0

0

0

0

0

2

2

0

0

0

18

2000

0

0

0

0

0

0

0

7

0

7

0

0

18

2001

0

0

0

0

0

0

0

0

0

0

0

0

18

2002

0

0

0

0

0

0

0

0

0

0

0

0

18

2003

0

0

0

0

0

0

0

0

0

0

0

0

18

2004

0

0

0

0

0

0

0

0

0

0

0

0

18

2005

0

0

0

0

0

0

0

0

0

0

0

0

18

2006

0

0

0

0

0

0

0

1

0

1

0

0

18

2007

0

0

0

0

0

0

0

2

0

2

0

0

18

2008

0

0

0

0

0

0

0

0

0

0

0

0

18

2009

0

0

0

0

0

0

0

0

0

0

0

0

18

2010

0

0

0

0

0

0

0

7

7

0

0

0

18

2011

0

0

0

0

0

0

0

0

0

0

0

0

18

2012

0

0

0

0

0

0

0

1

0

1

0

0

18

2013

0

0

0

0

0

0

0

0

0

0

0

0

18

2014

0

0

0

0

0

0

0

0

0

0

0

0

18

2015

0

0

0

0

0

0

0

0

0

0

0

0

18

2016

0

0

0

0

0

0

0

0

0

0

0

0

18

Figure ZR06-2: Average annual concentration of NO2 (annual limit value is 40 μg/m3) 
Sources: 
Air quality monitoring database (DMKZ), Slovenian Environment Agency (2018)
; Air quality monitoring database of Thermal power plant Šoštanj, Trbovlje and TE-TO Ljubljana, Insitute Milan Vidmar (2018)
Chart note: 

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

Urban background

Ljubljana Bežigrad

Celje

Nova Gorica

Koper

Suburban background

Trbovlje

- Škale

Urban-traffic type

Ljubljana center

Maribor center

Rural/Agricultural type

Murska Sobota - Rakican

Rural/Industrial type

- Zavodnje

- Kovk

- Vnajnarje

annual limit value

1992

32

0

32

0

0

0

0

0

49.50

49

50

0

0

6.50

3

10

0

40

1993

37

0

37

0

0

0

0

0

50

47

53

0

0

6.50

5

8

0

40

1994

37

0

37

0

0

0

0

0

43

41

45

0

0

9.50

11

8

0

40

1995

35

0

35

0

0

0

0

0

38.50

38

39

0

0

10

9

11

0

40

1996

33

0

33

0

0

0

0

0

39

39

39

0

0

3.50

5

2

0

40

1997

0

0

0

0

0

29

29

0

37

36

38

0

0

5

7

4

4

40

1998

29

0

29

0

0

18.50

29

8

40.50

42

39

0

0

6

7

7

3

40

1999

28

0

28

0

0

17

26

8

44

49

39

0

0

7

6

9

5

40

2000

30

0

30

0

0

18

28

8

41

38

44

0

0

6

7

7

4

40

2001

26

0

26

0

0

6

0

6

37

36

38

0

0

6

6

6

5

40

2002

27

29

24

27

0

28

28

0

36

0

36

14

14

6

0

6

6

40

2003

29

32

27

27

0

20

32

8

37

0

37

15

15

5

6

3

5

40

2004

26

29

24

25

0

18

27

9

31

0

31

11

11

8

5

13

5

40

2005

26

27

26

24

0

14.50

24

5

33

0

33

14

14

6

3

10

4

40

2006

27

29

28

24

0

16

23

9

39

0

39

15

15

7

4

12

5

40

2007

25

28

23

25

0

15

22

8

37

0

37

17

17

7

3

12

5

40

2008

25

29

21

30

21

15.50

23

8

34

0

34

16

16

7

3

12

5

40

2009

25

31

22

28

19

13

17

9

32

0

32

14

14

6

4

9

4

40

2010

27.75

35

26

29

21

14

20

8

48.50

63

34

0

0

6

5

9

4

40

2011

26.50

31

25

28

22

12.50

17

8

44.50

55

34

16

16

9

9

11

7

40

2012

23.25

22

27

26

18

12

17

7

42.50

52

33

19

19

8

8

6

10

40

2013

25.25

29

26

25

21

12.50

16

9

37.50

43

32

16

16

10

8

13

9

40

2014

22.50

26

28

19

17

12

17

7

35

40

30

12

12

7.33

7

8

7

40

2015

24.50

30

29

22

17

13

18

8

33.50

36

31

12

13

8

7

8

9

40

2016

22.50

29

22

24

15

13.50

18

9

29.50

32

27

12

12

6.67

5

6

9

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: 
Air quality monitoring database (DMKZ), Slovenian Environment Agency (2018)
; Air quality monitoring database of Thermal power plant Šoštanj, Trbovlje and TE-TO Ljubljana, Insitute Milan Vidmar (2018)
Chart note: 

Note to Figure ZR6-3: 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

Urban background

Ljubljana Bežigrad

Celje

Nova Gorica

Koper

Suburban background

Trbovlje

- Škale

Urban-traffic type

Ljubljana center

Maribor center

Rural/Agricultural type

Murska Sobota - Rakican

Rural/Industrial type

- Zavodnje

- Kovk

- Vnajnarje

annual limit value for protection of vegetation

1997

0

0

0

0

0

0

0

0

0

0

0

0

0

7

9

6

5

30

1998

0

0

0

0

0

0

0

0

0

0

0

0

0

6

8

7

3

30

1999

0

0

0

0

0

9

0

9

0

0

0

0

0

8

7

11

6

30

2000

0

0

0

0

0

29.50

50

9

0

0

0

0

0

9

9

9

0

30

2001

44

0

44

0

0

8

0

8

68

64

72

0

0

7

8

7

5

30

2002

42

48

37

41

0

35

52

18

61

0

61

19

19

6.50

0

7

6

30

2003

45

49

44

43

0

32.50

54

11

61

0

61

20

20

6

7

5

6

30

2004

43

46

41

43

0

28.50

47

10

54

0

54

17

17

10

7

17

5

30

2005

43

43

45

41

0

23.50

41

6

60

0

60

20

20

7

5

12

5

30

2006

45

45

46

43

0

24.50

39

10

71

0

71

23

23

8

5

14

5

30

2007

43

45

40

44

0

25.50

38

13

70

0

70

24

24

10

11

14

5

30

2008

42.50

52

40

50

28

25

40

10

63

0

63

22

22

7

6

10

5

30

2009

45

57

47

53

24

23

37

9

61

0

61

20

20

6

5

8

6

30

2010

50.25

64

53

56

28

24.50

40

9

95

122

68

0

0

7.33

7

11

4

30

2011

47

56

47

57

28

21.50

33

10

87.50

105

70

0

0

10.67

11

13

8

30

2012

43.75

47

50

50

28

20.50

32

9

80.50

96

65

28

28

9.33

10

7

11

30

2013

40.50

45

51

45

21

22

34

10

74.50

84

65

21

21

11.33

10

15

9

30

2014

38.50

41

57

35

21

19

29

9

70.50

75

66

17

17

8.67

10

9

7

30

2015

47

56

67

43

22

21.50

33

10

70.50

72

69

17

19

8.67

8

9

9

30

2016

42.25

58

44

45

22

24

37

11

60

58

62

17

20

7.67

6

7

10

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.