Preprints
https://doi.org/10.5194/acp-2021-342
https://doi.org/10.5194/acp-2021-342

  26 Aug 2021

26 Aug 2021

Review status: this preprint is currently under review for the journal ACP.

Modelling changes in secondary inorganic aerosol formation and nitrogen deposition in Europe from 2005 to 2030

Jan Eiof Jonson1, Hilde Fagerli1, Thomas Scheuschner2, and Svetlana Tsyro1 Jan Eiof Jonson et al.
  • 1Norwegian Meteorological Institute, Oslo, Norway
  • 2Umweltbundesamt, Dessau-Roßlau Germany

Abstract. Secondary inorganic PM2.5 particles are formed from SOx, NOx and ammonia emissions, through the formation of either ammonium sulphate or ammonium nitrate. EU limits and WHO guidelines for PM2.5 levels are frequently exceeded in Europe, in particular in the winter months. In addition the critical loads for eutrophication are exceeded in most of the European continent. Further reductions in ammonia emissions and other PM precursors beyond the 2030 requirements could alleviate some of the health burden from fine particles, and also reduce the deposition of nitrogen to vulnerable ecosystems. Using the regional scale EMEP/MSC-W model, we have studied the effects of year 2030 ammonia emissions on PM2.5 concentrations and depositions of nitrogen in Europe in the light of present (2017) and past (2005) conditions. Our calculations show that in Europe the formation of PM2.5 from ammonia to a large extent is limited by the ratio between the emissions of ammonia on one hand, and SOx plus NOx, on the other hand. As the ratio of ammonia to SOx and NOx is increasing, the potential to further curb PM2.5 levels through reductions in ammonia emissions is decreasing. Here we show that per gram of ammonia emissions mitigated, the resulting reductions in PM2.5 levels simulated using 2030 emissions are about a factor of 2.6 lower than when 2005 emissions are used. However, this ratio is lower in winter, thus further reductions in the ammonia emissions in winter may have similar potentials as SOx and NOx in curbing PM2.5 levels in this season. Following the expected reductions of ammonia emission, depositions of reduced nitrogen should also decrease in Europe. However, as the reductions in NOx emission are larger than for ammonia, the fraction of total nitrogen (reduced plus oxidised nitrogen) deposited as reduced nitrogen is increasing and may exceed 60 % in most of Europe by 2030. Thus the potential for future reductions in the exceedances of critical loads for eutrophication in Europe will mainly rely on the ability to reduce ammonia emissions.

Jan Eiof Jonson et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-342', Anonymous Referee #2, 06 Oct 2021
  • RC2: 'Comment on acp-2021-342', Anonymous Referee #1, 09 Nov 2021

Jan Eiof Jonson et al.

Jan Eiof Jonson et al.

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Short summary
Ammonia emissions are expected to decrease less than SOx and NOx emissions between 2005 and 2030. As the formation of PM2.5 particles from ammonia depends on the ratio between ammonia on one hand, and sulphate (from SOx) and HNO3 (from NOx) on the other hand, the efficiency of particle formation from ammonia is decreasing. Depositions of reduced nitrogen are decreasing much less than oxidized nitrogen. The critical loads for nitrogen deposition will be exceeded in much of Europe also in 2030.
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