[PR08]
Transport emissions of air pollutants
Assessments published: [ 2009 2014 2013 2012 2008 ]

The indicator shows the transport emissions of acidifying substances, ozone precursors and particulates. The structure of emissions is indicated by individual substances.

An ozone precursor is a substance contributing to the formation of ground-level (tropospheric) ozone. The ozone precursors include: nitrogen oxides (NOx), carbon monoxide (CO), methane (CH4) and non-methane volatile organic compounds (NMVOC).

Acidifying substances include: sulphur dioxide (SO2), nitrogen oxides (NOx) and ammonia (NH3).

Particulate emissions can be subdivided into primary particulates PM10 (particulates with a diameter of 10 μm or less, which are directly emitted to air) and secondary particulates PM10 or particulate precursors (part of emissions of NOx, SO2 and NH3, which are as a result of photochemical reactions transformed into particulates with a diameter of 10 μm or less).

Image PR8-1: Transport emissions of air pollutants (acidifying substances, ozone precursors and particulates)

Source: Environmental Agency of the Republic of Slovenia; Jožef Stefan Institute.


Image PR8-2: The structure of air pollutant emissions from transport in 2007

Source: Environmental Agency of the Republic of Slovenia; Jožef Stefan Institute.


Reduction of national emissions of nitrogen oxides to 45 thousand tonnes, sulphur dioxide to 27 thousand tonnes, non-methane volatile hydrocarbons to 40 thousand tonnes and ammonia to 20 thousand tonnes by 2010.

Transport is one of the main sources of emissions of acidifying substances, ozone precursors and particulates. These emissions have been reducing in Slovenia and in other European countries; therefore, the environmental objectives for 2010 were already achieved in 2007. In the period 1990-2007, the emissions of acidifying substances reduced by 42 % and ozone precursors by 52 %. In comparison to the year 2000, emissions of particulates reduced by 10 %. In the period 1990-2006 in the EEA-32 countries, transport emissions of acidifying substances decreased by 34 %, ozone precursors by 47 % and particulates by 31 %. This is primarily a result of smaller emissions by passenger cars due to the increased use of catalytic converters, reduced sulphur concentrations in fuels and fleet renewal. It is expected that in the following years the share of the transport sector will become even stronger due to the higher level of reduction of emissions in other sectors (EEA, 2006).

The acidification of soils and waters is caused by emissions of sulphur oxides, nitrogen oxides and ammonia into the atmosphere, and their subsequent chemical reactions and deposition as well as causing damage to ecosystems, buildings and materials (corrosion). The largest share among gases causing acidification belongs to NOx (90 %), although its transport emissions in Slovenia in the period 1990–2007 reduced by 29 %. NOx and NH3 also cause an exceeding accumulation of nitrogen in soil and water bodies (eutrophication).

Tropospheric ozone is a result of photochemical reactions; its precursors, primarily NMVOC, NOx, CO and CH4 contribute the most to its formation. Ozone concentrations depend mainly on the weather during the spring and summer months; therefore, they have highly seasonal fluctuations. Furthermore, the transfer of ozone concentrations across borders is also important. For Slovenia, especially Primorska region, the river Po lowland, where larger amounts of ozone are produced, presents a significant source of ozone. In Slovenia, the largest source of ozone precursors is transport, contributing 41 %. NOx occupies the largest share among particulates (63 %). Ground-level (tropospheric) ozone has adverse effects on human health and ecosystems. High concentrations of ground-level ozone influence the breathing system (especially lungs) of people, while also influencing the reduction of crops in ecosystems, and causing damage to leaves as well as reducing resistance to diseases. Ozone also causes damage to plastic and rubber.

Particulates present a big problem in the urban environment not only in Slovenia, but also in Europe. The inhalation of particulates can cause frequent and heavier respiratory diseases, which increases the possibility of premature death. Smaller particulates are especially dangerous, since they can penetrate deeper into the lungs. The emissions of primary and secondary precursors of PM10 particulates are decreasing, primarily due to SO2 as the secondary PM10precursor, the transport emissions of which reduced by 97 % in the period 1990–2007.

The objectives of improving air quality are stipulated by European legislation (Directive 2001/81/EC on national emission ceilings for certain atmospheric pollutants (Directive NEC)) and Protocol to the 1979 Convention on Long-Range Transboundary Air Pollution to Abate Acidification, Eutrophication and Ground-Level Ozone. The control and reduction of emissions into the air is also the objective of the National Environmental Action Plan (ReNPVO, 2006), which includes several operational programmes with this objective. Its purpose is to ensure better air quality with a gradual reduction in SO2, NOx, NH3 and other emissions. Reduced emissions would consequently lead to less ground-level ozone, acidification and eutrophication. The programme also emphasizes the objectives in the area of transport; namely, an increase in the share of diesel fuel and decrease in gasoline consumption. This would lead to a positive reduction of emissions of volatile organic compounds and greenhouse gases as well as to a negative increase in emissions of particulates and nitrogen oxides.

Data for Slovenia:

Objectives summarised by: Protocol to the 1979 Convention on Long-Range Transboundary Air Pollution to Abate Acidification, Eutrophication and Ground-Level Ozone and Directive 2001/81/EC on national emission ceilings for certain atmospheric pollutants. Control and reduction of emissions into the air is also the objective of the National Environmental Action Plan 2005-2012.
Source database or source: For the calculation of the indicator, the following official data was used:
- emissions of air pollutants, which can be found at the Central Data Repository (CDR), summarised from the National Emissions Inventory,
- greenhouse gases, deposited at the Central Data Repository (CDR), summarised from the GHG Archive.
Date of acquisition for this indicator: 23 December 2009 – data on emissions of air pollutants; 15 January 2010 – data on greenhouse gases.
Data administrator: Environmental Agency of the Republic of Slovenia (ARSO), Environment Office, Air Quality Division – contact persons: Bojan Rode, Tajda Mekinda-Majaron.
Methodology and frequency of data collection for the indicator: The data was prepared on an annual basis from the data on activities (fuel consumption, number of animals, amount of waste, industrial manufacturing, etc), calorific values of fuels and emission factors. The recommended methodology for air pollutants was prepared by a group for emissions inventory and projections of UNECE/EMEP, and for GHG by the Intergovernmental Panel on Climate Change (IPCC). For the preparation of new records, data for the past is also frequently corrected.
Data processing methodology: Total emissions are calculated as the weighted sum of emissions of individual substances. The same weighting factors were used as implemented by the European Environment Agency for its calculations.
Weighting for ground-level ozone was calculated on the basis of the potential of individual substances to form ground-level ozone (»TOFP – Tropospheric Ozone Forming Potential«). Weightings were determined in the study (de Leeuw, 2002) and amount to: NOx – 1.22; NMVOC – 1.0; CO – 0.11; CH4 – 0.014. The unit is a kt equivalent of NMVOC.
The total emissions of acidifying substances were calculated by weightings, calculated on the basis of the assessment of the acidification potential of an individual substance (»Acid equivalent«). Weightings were determined in the research study (de Leeuw, 2002) and amount to: SO2 – 2/64; NOx – 1/46; NH3 – 1/17. The unit is a kt equivalent of acidifying substances.
The total emissions of particulates were calculated by using weightings, determined on the basis of assessments on the deposition and reactions of particulate precursors (de Leeuw, 2002) – Aerosol formation factors and amount to: SO2 – 0.54; NOx – 0.88; NH3 – 0.64; PM10 – 1.00. The unit is a kt equivalent of PM10 emissions.
The average annual growths of emissions were calculated as [(last year/base year)(1 /number of years) –1] x 100.
Information concerning data quality:
- Advantages and disadvantages (at data level): The officially reported data, calculated on the basis of internationally verified methodologies, were used for the calculation of the indicator.
- Relevance, accuracy, robustness, uncertainty (at data level):
Reliability of the indicator (archive data): The reliability of data for the GHG emissions (CH4) was estimated for 1986, 2002 and 2003. For absolute data, it amounts to 16 %, 13.1 % and 12 %, and for trends for the years 2002 and 2003 to 4 % or 3 % respectively. The reliability of emission factors and data on activities was estimated on the basis of an expert assessment. The reliability of data of emissions of external air pollutants differs strongly between substances. The highest data reliability exists for SO2 emissions, since these emissions are directly connected to the concentration of sulphur in fuel, and dependant on the efficiency of purification plants when cleaning flue gases. Data on NOx emissions is much less reliable, since there are more sources for the formation of emissions. Emissions are dependent on the concentration of nitrogen in fuel, the ratio of air and fuel as well as on the combustion temperature, which is a characteristic of combustion plants – that is why emissions factors are different for each plant. The reliability of data for NH3 emissions is high, since they were almost the same when using two different methodologies.
Uncertainty of the indicator (scenarios/projections): Projections have not been prepared.
- Overall assessment (1 = no major comments, 3 = data to be considered with reservation):
Relevance: 1
Accuracy: 2
Completeness over time: 2
Completeness over space: 1

Other sources and literature:
- Second report on the Implementation of the Operational Programme for Limiting Greenhouse Gas Emissions until 2012 for 2008. 2009. Ljubljana, Ministry of the Environment and Spatial Planning.
- Operational Programme for Limiting Greenhouse Gas Emissions until 2012 (OP TGP-01). 2009. Ljubljana, Ministry of the Environment and Spatial Planning.
- Resolution on National Environmental Action Plan 2005–2012. OG RS, no. 2/2006.
- Slovenia’s National Inventory Report 2009. 2009. Ljubljana, Environmental Agency of the Republic of Slovenia.
- Communication from the Commission to the European Council and the European Parliament - An Energy Policy for Europe {SEC(2007) 12}. 2007. Brussels, Commission of the European Communities.
- TERM 2006 03 EEA32 – Transport emissions of air pollutants (CO, NH3, NOx, NMVOCs, PM10, SOx) by mode. Indicator fact sheet. European Environment Agency.
- Act Ratifying the Kyoto Protocol to the United Nations Framework Convention on Climate Change (MKPOKSP). OG RS, no. 60/2002.

Last update of indicator: 21th December 2008.
Matjaž Česen, Jožef Stefan Institute