Acid rain and air pollution: 50 years of progress in environmental science and policy

Abstract

Because of its serious large-scale effects on ecosystems and its transboundary nature, acid rain received for a few decades at the end of the last century wide scientific and public interest, leading to coordinated policy actions in Europe and North America. Through these actions, in particular those under the UNECE Convention on Long-range Transboundary Air Pollution, air emissions were substantially reduced, and ecosystem impacts decreased. Widespread scientific research, long-term monitoring, and integrated assessment modelling formed the basis for the policy agreements. In this paper, which is based on an international symposium organised to commemorate 50 years of successful integration of air pollution research and policy, we briefly describe the scientific findings that provided the foundation for the policy development. We also discuss important characteristics of the science-policy interactions, such as the critical loads concept and the large-scale ecosystem field studies. Finally, acid rain and air pollution are set in the context of future societal developments and needs, e.g. the UN's Sustainable Development Goals. We also highlight the need to maintain and develop supporting scientific infrastructures.

Keywords: Acid rain; Air pollution; Critical loads; Ecosystems; Integrated assessment modelling; Monitoring; Nitrogen; Policy development; Sulphur.

Fig. 1

European emissions of sulphur dioxide (SO₂—black), nitrogen oxides (NO_x, calculated as NO₂—green) and ammonia (NH₃—blue) 1880–2020 (updated from Fig. 2 in Schöpp et al. 2003)

Fig. 2

The timeline of science and policy interactions in Europe and North America 1967–2018. (updated from Driscoll et al. 2012). Abbreviations not occurring in text. NAAQS: National Ambient Air Quality Standards under the US Clean Air Act; CCAA: Canadian Clean Air Act; RADM: Regional Atmospheric Deposition Model; MAGIC Model of Acidification of Groundwater in Catchments. It should be mentioned that Canada and US are both parties to the Air Convention and they have also signed and ratified most of its protocols

Fig. 3

Svante Odén around 1970 (photo Ellis B. Cowling)

Fig. 4

The outcome of emission control of SO2, NOx, and NH3 between 1990 and 2010 presented as maps on exceedance of critical loads of acidity. Such maps have played an important role for illustrating outcomes of future policies as well as of actions taken (from Maas and Grennfelt 2016)

Fig. 5

Links between sources and effects used as an illustration in the preparation of the Gothenburg Protocol. From Grennfelt et al.

Fig. 6

Atmospheric monitoring stations have been of importance for understanding the long-range transport and chemical conversions of atmospheric pollutants. Pallas air pollution background station in Northern Finland (Photo Martin Forsius)

Fig. 7

Field experiments have played an important role for the overall understanding of the interactions between atmospheric deposition and ecosystem effects. The photo illustrates the covered catchment experiment to study the recovery of ecosystems at reduced emissions in Risdalsheia Norway (Photo NIVA)

Fig. 8

The scientific support to regional air pollution policies consists today of a series of steps. The policy side may often only see the integrated assessment step and not realise that the legitimacy of the use of scientific support builds on an advanced system of underlying research and development