Air and Noise

Emissions of tropospheric ozone precursors

The "Emissions of tropospheric ozone precursors" fact sheet shows the emissions of nitrogen oxides and non-methane volatile organic compounds, molecules that are at the origin of tropospheric ozone formation.
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Description: 

The potential for tropospheric ozone formation, calculated by adding the total emissions of non-methane volatile organic compounds (NMVOCs) and emissions of nitrogen oxides (NOx) equivalent (multiplied by a conversion factor), enables monitoring of the development of aggregate emissions of tropospheric ozone precursors by activity sector and analysing their contribution.

Tropospheric ozone is a secondary pollutant formed by the reaction of precursor substances in the presence of strong solar radiation. It is a pollutant with a strong oxidising power that accelerates the degradation of materials, promotes the loss of vegetation productivity and increases the morbidity and mortality of the exposed population. As one of the greenhouse gases, it also contributes to the warming of the troposphere.

This fact sheet concerns mainland Portugal and shall be updated on an annual basis.

Objectives and targets: 
  • The Gothenburg Protocol to the Convention on Long-range Transboundary Air Pollution (CLRTAP) of the United Nations Economic Commission for Europe set as targets for air emissions in 2010 NOx = 260 kt and NMVOC = 202 kt (Decree No. 20/2004). The amendments to the Gothenburg Protocol approved by the CLRTAP Decision 2012/2 set emission reduction targets based on the reference year 2005, to be met from 2020 onwards, of 36% to NOx and of 18% to NMVOCs;
  • The Decree-Law No. 84/2018, which transposes the new Ceilings Directive, (Diretive (EU) 2016/2284) establishes new commitments for the reduction of atmospheric emissions by 2020 in line with the CLRTAP Decision 2012/2 and new commitments to be met from 2030 onwards, of 63% and 38% for NOx and NMVOCs respectively, compared to the reference year 2005.
  • The emission ceilings established for 2010 by the previous Directive 2001/81/EC, were in force until 31 December 2019.
  • The national objectives for this area are:
    • To comply with international and European agreements on air emissions;
    • Ensure that the sectoral measures necessary to achieve the objectives of reducing air emissions are implemented;
    • Assess the impact of measures to reduce air emissions, particularly with regard to potential for tropospheric ozone formation.
Progress analysis:

Total emissions of tropospheric ozone precursors

Source: APA, 2021

The value of the Tropospheric Ozone Formation Potential (TOFP), which is given by the aggregate emissions of NOx and NMVOCs, has decreased by approximately 40% since 1990, with 317kt of NMVOC equivalent in 2019. Regarding the ceilings established in the Gothenburg Protocol (CLRTAP) and the previous Ceilings Directive (NEC), the total emissions of these compounds have been below the TOFP value corresponding to those ceilings, since 2006.

Regarding the distance to the new reduction commitments for 2020, the value of TOFP in 2019 is at about 10% below the threshold for 2020 (353kt of NMVOC). With respect to the reduction commitments for 2030, TOFP in 2019 is about 37% above the threshold for 2030 (232kt of NMVOC).

Emissions of tropospheric ozone precursors by pollutant

Source: APA, 2021

Analysing emissions by pollutant, it can be seen that NMVOC emissions registered an increase in emissions of 7kt from 2018 to 2019. As for the NOx pollutant, there was a slight reduction of about 7kt in 2019.

Comparing with 1990 levels, there is a 35% reduction for NMVOCs and a 45% reduction for NOx.

Aggregate emissions of tropospheric ozone precursors by activity sector

Source: APA, 2021

Examining emissions of these pollutants by sector of economic activity, one can observe that the most significant improvements in relation to 1990 were achieved in the energy and transport sectors, with a reduction of about 84% and 54%, respectively. The industrial sector, which contributed the most to ozone formation in the troposphere in 2019, showed a 12% increase in emissions of these pollutants compared to 1990.

The variation when compared to the base year 2005, regarding the new reduction commitments agreed for 2020 and 2030, shows an improvement in all sectors. However, the agricultural and industrial sectors show the lowest variation, with 1% and 11%, respectively, compared to 2005.

Comparison of emissions in Portugal in 2019 with European and international emission ceilings

Source: APA, 2021

Comparing 2019 NOx and NMVOC emissions totals with the ceilings established by the Gothenburg Protocol (CLRTAP) and the thresholds for 2010, both values are lower than the fixed ceilings with 133kt of NOx and 155kt of NMVOCs. Portugal is thus complying, since 2010, with the goals established at international and at EU levels.

Regarding the new reduction commitments to be fulfilled from 2020, one can observe that the emissions of these substances in 2019 are slightly below the new thresholds for the pollutant NOx (36% reduction commitment for NOx compared to 2005, corresponding to 162 kt) and that in 2019 the total NMVOC emissions increased, reaching the limit value for 2020 (commitment to reduce 18% compared to 2005 for NMVOC, corresponding to 155kt).

With regard to the commitments to reduce emissions of these pollutants for 2030 compared to 2005, it will be necessary to make efforts and implement appropriate sectoral measures to reach the reduction commitments of 63% for NOx compared to 2005 (94kt) and 38% compared to 2005 for NMVOC (117kt).

 

Last update: 
Wednesday, 1 September, 2021
More information at: 

Portuguese Environment Agency – www.apambiente.pt