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.
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 18% to NMVOCs;
  • The Decree-Law 84/2018, which transposes the new Ceilings Directive, (Diretive (EU) 2016/2284) establishes 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, are valid until 31 December 2019.
  • The 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, 2019

The value of the Tropospheric Ozone Formation Potential (TOFP), which is given by the aggregate emissions of NOx and NMVOCs, has decreased by approximately 38% since 1990, with 337 kt of NMVOC equivalent in 2017. Regarding the ceilings established in the Gothenburg Protocol (CLRTAP) and the first 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 2017 is already at about 6% below the threshold for 2020 (358kt of NMVOC). With respect to the reduction commitments for 2030, TOFP in 2016 is about 42% above the threshold for 2030 (236kt of NMVOC).

Emissions of tropospheric ozone precursors by pollutant

Source: APA, 2019

By analysing emissions per pollutant, both NMVOC and NOx emissions increased slightly from 2016 to 2017, respectively with TOFP values of 160kt NMVOC and 177kt NMVOC equivalent. Compared with 1990 levels, there is a 36% reduction for NMVOCs and a 40% reduction for NOx.

 

Aggregate emissions of tropospheric ozone precursors by activity sector

Source: APA, 2019

By examining emissions of these pollutants by sector of economic activity, the most significant improvements in relation to 1990 were achieved in the energy and transport sectors, with a reduction of about 76% and 50%, respectively. The industrial sector, which contributed the most to ozone formation in the troposphere in 2017, showed a 3% increase in emissions of these pollutants compared to 1990.

Comparison of emissions in Portugal in 2017 with European and international emission ceilings

Source: APA, 2019

Comparing 2017 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 145kt of NOx and 160kt of NMVOCs. Portugal is thus complying with the goals established at international and EU levels.

With regard to the new reduction commitments to be fulfilled from 2020 onwards, emissions of these substances by 2017 are already slightly below the new thresholds: a reduction of 36% for NOx compared to the year 2005 (159 kt) and a reduction of 18% compared to the year of 2005 for NMVOCs (165kt).

Reduction commitments for 2030 will require efforts for a reduction of 63% for NOx compared to the year 2005 (92kt) and 38% compared to the year 2005 for NMVOCs (125kt).

 

Last update: 
Thursday, 23 May, 2019
More information at: 

Portuguese Environment Agency – www.apambiente.pt