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The indicator shows the frequencies in the exceeding the target ozone value and the ozone alert threshold per calendar year. The target value for 2010 is set according to the World Health Organisation guidelines for Europe (Fact Sheet No 187, WHO's 1999 Guidelines for Air Pollution Control). It is determined in such a way that the highest average 8-hour running value is calculated from 1-hour concentrations for each day. The highest 8-hour concentration of ozone may not exceed 120 μg/m3 for more than 25 days per year (calculated as a three-year average). The alert threshold is defined as 1-hour concentration higher than 180 μg/m3. This value, as well, is set according to the World Health Organisation guidelines for Europe. It is intended for the protection of human health from short-term exposure to high concentrations of ozone. With such a high level of concentration there is a need to start warning the population of excessive ozone concentrations. The alert value is set at 240 μg/m3; however, during the last decade it has rarely been reached in Slovenia.


Charts

Figure ZR07-1: Number of days with exceeded target value for ozone in Slovenian urban areas with highest average 8-hour floating value > 120 μg/m3 (annual limit value 25 days)
Sources: 

Automatic Air Quality Measurement Database (ANAS), Environmental Agency of the Republic of Slovenia, 2008

Show data
1995 1996 1997 1998 1999 2000 2001 2002 2003 2004
Ljubljana number of days 11 40 30 20 20 49 40 25 81 32
Maribor number of days np np 1 4 0 6 3 4 19 1
Celje number of days np np 16 29 8 28 34 33 78 18
Velenje number of days np np 0 17 11 12 1 57 87 6
Nova Gorica number of days np np np np np np np 36 105 46
Trbovlje number of days np np np 13 6 13 np 9 65 4
Hrastnik number of days np np 11 37 13 32 0 21 63 4
Murska Sobota - Rakičan number of days np np np np np np np np 101 15
Iskrba number of days np np np np np np np np 94 38
Otlica number of days np np np np np np np np np np
2005 2006 2007
Ljubljana number of days 38 47 43
Maribor number of days 0 7 4
Celje number of days 43 39 35
Velenje number of days 10 66 61
Nova Gorica number of days 43 56 51
Trbovlje number of days 14 31 15
Hrastnik number of days 12 45 26
Murska Sobota - Rakičan number of days 31 28 34
Iskrba number of days 60 67 61
Otlica number of days np 90 98
Figure ZR07-2: Number of days with exceeded warning value for ozone in Slovenian urban areas (highest 1-hour value > 180 μg/m3)
Sources: 

Automatic Air Quality Measurement Database (ANAS), Environmental Agency of the Republic of Slovenia, 2008

Show data
1995 1996 1997 1998 1999 2000 2001 2002 2003 2004
Ljubljana number of hours 4 20 7 2 0 3 1 4 18 4
Maribor number of hours np np 0 0 0 0 0 0 0 0
Celje number of hours np np 1 0 0 0 3 0 2 0
Velenje number of hours np np 0 0 1 0 0 1 5 0
Nova Gorica number of hours np np np np np np np 26 102 27
Trbovlje number of hours np np np 0 0 0 np 0 7 0
Hrastnik number of hours np np 0 2 0 2 0 0 1 0
Murska Sobota - Rakičan number of hours np np np np np np np np 6 0
Iskrba number of hours np np np np np np np np 11 1
Otlica number of hours np np np np np np np np np np
2005 2006 2007
Ljubljana number of hours 11 10 8
Maribor number of hours 0 0 0
Celje number of hours 0 3 0
Velenje number of hours 0 6 14
Nova Gorica number of hours 33 34 19
Trbovlje number of hours 0 1 0
Hrastnik number of hours 0 5 0
Murska Sobota - Rakičan number of hours 1 0 0
Iskrba number of hours 0 1 7
Otlica number of hours np 69 44
Figure ZR07-3: Parameter AOT40
Sources: 

Automatic Air Quality Measurement Database (ANAS), Environmental Agency of the Republic of Slovenia, 2008

Show data
2003 2004 2005 2006 2007
Ljubljana (micro g/m3).h 59178 28600 32868 39709 38758
Maribor (micro g/m3).h 23830 6335 6138 11163 12878
Celje (micro g/m3).h 58848 21467 34097 33911 33944
Velenje (micro g/m3).h 56553 17510 19786 51790 49973
Nova Gorica (micro g/m3).h 77134 40977 42893 50736 44426
Trbovlje (micro g/m3).h 41534 9110 21635 29303 26035
Hrastnik (micro g/m3).h 46158 23553 15739 40599 31381
Murska Sobota - Rakičan (micro g/m3).h 66786 25863 29288 32094 36586
Iskrba (micro g/m3).h 67231 36629 41417 50810 47006
Otlica (micro g/m3).h np np np 85554 72083

Goals

In accordance with the Decree on Ozone in Ambient Air (OJ RS, No 8/03) containing the provisions from Directive 2002/3/EC, our objective is that by 2010, no monitoring site will indicate exceedance of both target and alert threshold values. These values are determined with a view to protect human health from long-term exposure to high ozone concentrations.


Being a product of photochemical reactions, tropospheric ozone differs from certain other pollutants. Its precursors, especially nitrogen oxides, are substances forming ozone through the above mentioned photochemical reactions. In Slovenia, transport is regarded to be the greatest source of ozone precursors, accountable for about two thirds of them. Ozone concentrations exhibit an explicit annual curve which is strongly connected with the mode of ozone formation requiring an adequate amount of sunlight. Another crucial contributor to the ozone formation is a long-range (transboundary) transport as the Po Valley in Italy is one of the areas in Europe producing the greatest amounts of ozone.

The data do not display a clear trend. Levels of ozone concentrations are determined by emissions of ozone precursors as well as spring and summer weather conditions, and are subject to change year on year. The year 2003 was extremely hot summer with a lot of solar radiation, which caused strong deviation from other years concerning air pollution with ozone.

Slovenia is divided into areas by different levels of air-pollution threat. With regard to ozone, all areas fall within the lowest quality class, as the ozone concentrations exceed the target values throughout the country, including its rural and mountainous areas. The most polluted area in Slovenia is the Primorska region due to ozone transport from the Po Valley.


With the exception of the monitoring site in Velenje, which is part of information system managed by the TE Šoštanj, all the data are taken from the Automatic air quality measurement database (ANAS) maintained by the Monitoring Office (Environmental Agency of the Republic of Slovenia). The data from individual monitoring sites are not directly comparable due to different types of locations with regard to the influence of pollution sources. The Ljubljana, Celje, Velenje and Nova Gorica monitoring sites are not directly affected by the influence of traffic-related emissions. The Maribor and Trbovlje monitoring sites are placed at roadside locations, where ozone reacts with nitrogen oxides from exhaust gases, thus causing the indices of ozone concentrations to be appreciably lower. The monitoring site in Hrastnik is located at the verge of the urban area; in the event of south-western winds it is exposed to the influence of flue gases from the Trbovlje Thermal Power Plant, which may also have a lowering effect on ozone concentrations.

Although provided by a smaller number of monitoring sites, the data on ozone concentrations have otherwise been available since 1992. The number of monitoring sites increased in 2002.

In order to illustrate the trend, the exceedances of target and alert threshold values are also shown for previous years, according to the current Decree on ozone in ambient air, since the limit values as determined in formerly applicable regulations are not comparable with the present target and alert threshold values.


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