What goes up must come down

Over the last decade the downward trend in emissions has flattened out – some countries are even reporting increasing emissions of ammonia and particulate matter.

Since 1980, total European emissions of sulphur dioxide (SO₂) – the most significant acidifying pollutant and an important precursor to health-damaging secondary fine particles (PM_2.5) – from land-based emission sources have fallen by nearly 90 per cent, from around 53 million tonnes in 1980 to 6 million tonnes in 2016.

Emissions of nitrogen oxides (NOx), non-methane volatile organic compounds (VOCs), and ammonia have also gone down, although to a lesser extent. VOCs have more than halved (-52%) and NOx emissions have come down by 45 per cent since 1980, while ammonia emissions – which emanate primarily from agricultural activities – have dropped by only 25 per cent.

Historic emissions of primary particulate matter (PM_2.5) are not as well documented as those of other air pollutants, and many countries lack emissions data for the 1990s. Between 2000 and 2016 it is estimated that emissions of PM_2.5 from land-based sources have fallen by 24 per cent, from 2.7 to 2 million tonnes.

Although overall emissions continue to fall, the downward trend has flattened out over the last decade. This is especially the case for ammonia and primary particles, which are even reported to be increasing in some countries over the last few years.

Looking specifically at the 28 member states of the EU, between 1980 and 2016 the emissions of SO₂ came down by as much as 94 per cent, while those of NOx and VOCs fell by 57 and 62 per cent respectively. Emissions of ammonia fell by only 25 per cent. Primary PM_2.5 particles were reduced by 28 per cent between 2000 and 2016.

Emissions of SO₂ from international shipping in European waters showed a steady increase up to around 2006, after which emissions have fallen, primarily as a result of ship fuel sulphur regulations introduced by the EU and the International Maritime Organization (IMO). The emission reductions were particularly marked in the northern Sulphur Emission Control Areas (SECA), which cover the Baltic Sea and the North Sea, including the English Channel.

Ship NOx emissions increased steadily for many years, but appeared to stabilise, or even come down somewhat, during the economic crisis of 2008–2009. However, because of the lack of effective international ship NOx regulation, they are likely to increase again as the economy and trade grow.

The data in Table 1 is based on figures reported by countries themselves to the Convention on Long-range Transboundary Air Pollution (LRTAP), and was compiled by the Centre on Emission Inventories and Projections (CEIP) of the European Monitoring and Evaluation Programme (EMEP). The Convention’s EMEP keeps track of the ways in which emissions from one country affect the environment in others. The EMEP report also provides an overview of calculations for source-receptor relationships (including transboundary movements between countries), covering acidifying, eutrophying, photo-oxidant, and particle pollution. This shows that for most European countries the biggest share of depositions of sulphur and nitrogen emanate from outside their own territory.

Table 1: European emissions of sulphur dioxide (SO₂), nitrogen oxides (as NO₂), non-methane volatile organic compounds (NMVOC), ammonia (NH₃), and particulate matter (PM_2.5) (kilotonnes). Data for 2000, 2010 and 2016 is from the 2018 EMEP report, while data for 1990 is from earlier EMEP reports or from the EMEP website. Russia in the table refers only to the western part of the Russian Federation.

Since land-based emissions have been falling much faster than those from international shipping, the proportion of pollutant depositions and concentrations contributed by shipping has been steadily rising. For 2016 it was estimated that ship emissions were responsible for 10 per cent or more of the total depositions of both sulphur and oxidised nitrogen compounds in many countries (see Table 2). In the coastal areas of these countries, shipping’s contribution to the overall pollution load is even higher.

Table 2: The proportion of total air pollutant depositions of sulphur and oxidised nitrogen from shipping, on various countries in 2016.

It should be noted that the contribution of shipping to sulphur deposition in countries around the Baltic Sea and the North Sea decreased markedly after the entry into force of stricter fuel sulphur limits in those sea areas from 2015. Countries that are still particularly exposed to sulphur pollution from shipping include Portugal, Spain, Ireland, Italy and France.

Several more countries are highly impacted by ships’ NOx emissions, especially the Nordic countries, the Netherlands and Portugal, but also many Mediterranean countries as well as Ireland and the United Kingdom.

Christer Ågren

Report: “Transboundary particulate matter, photo-oxidants, acidifying and eutrophying components.” EMEP Status Report 1/2018. www.emep.int