Deposition of sulphur and nitrogen in Europe 1900–2050. Model calculations and comparison to historical observations

Abstract

As a contribution to an EU project which dealt with the effects of climate change, air pollution impacts and ecosystems, two different atmospheric chemical transport models were used to simulate the depositions of acidifying and eutrophying pollutants over Europe for the period 1900-2050. Given the unavoidable uncertainties in the historical inputs to these simulations (emissions, meteorology), we generated a new and unique data-set for the purposes of model evaluation; comprising data from the European Air Chemistry Network (EACN) in operation from 1955 to early 1980s and more recent data from the EMEP monitoring network. The two models showed similar and reasonable skills in reproducing both the EACN and EMEP observational data although the MATCH model consistently simulates higher concentrations and depositions than the EMEP model. To further assess the models' ability to reproduce the long-term trend in sulphur and nitrogen deposition we compared modelled concentrations of major ions in precipitation with data extracted from a glacier in the European Alps. While, the shape and timing of the nss-sulphate data agrees reasonably, the ice core data indicate persistently high nitrogen concentrations of oxidised and reduced nitrogen after the 1980s which does not correspond to the model simulations or data from Western Europe in the EMEP monitoring network. This study concludes that nss-sulphate deposition to Europe was already clearly elevated in the year 1900, but has now (mid-2010s) decreased to about 70% of what it was at the beginning of the last century. The deposition of oxidised nitrogen to Europe peaked during the 1980s but has since decreased to half of its maximum value; still it is 3-4 times higher than in the year 1900. The annual deposition of reduced nitrogen to Europe is currently more than two times as high as the conditions in the year 1900.

Large but decreasing effect of ozone on the European carbon sink

“…This set-up (EMEP + RCA3) is also used by Langner et al (2012a), Simpson et al (2014a), Tuovinen et al (2013), Franz et al (2017) and Engardt et al (2017), in which further details and model evaluation can be found. Unfortunately, the threedimensional RCA3 data needed by the EMEP model were not available prior to 1960, but as in Engardt et al (2017) the meteorology of 1900-1959 had to be approximated by assigning random years from 1960 to 1969. This procedure introduces some uncertainty of course, although Langner et al (2012b) show that for the period from 1990 to 2100 it is emissions change, rather than meteorological change, that drives modelled O 3 concentrations.…”

Reanalysis of and attribution to near-surface ozone concentrations in Sweden during 1990–2013

“…As in Andersson et al (2007), boundary values representative of the average concentrations at the lateral and top boundaries of relevant species are interpolated spatially with a monthly temporal resolution. Boundary concentrations of O 3 , oxidized nitrogen and methane are furthermore scaled to mimic observed changes in the hemispheric background during the period 1990 through 2013 following the work of Engardt et al (2017);see Fig. 2a.…”

“…Elevated O 3 concentrations are formed in the troposphere by the oxidation of volatile organic compounds (VOCs) and carbon monoxide (CO), driven by solar radiation in a polluted air mixture that includes nitrogen oxides (NO x , sum of nitric oxide and nitrogen dioxide: NO + NO 2 ). Close to combustion sources, the background O 3 concentrations are reduced through reactions with directly emitted NO (see for example Finlayson-Pitts and Pitts, 2000). However, further away from the source and with sufficient availability of VOCs and under favorable weather conditions these NO x emissions can lead to rises in the O 3 concentration.…”

Assessing the impact of acid rain and forest harvest intensity with the HD-MINTEQ model – Soil chemistry of three Swedish conifer sites from 1880 to 2080

“…During the 20 th century, sulfur (S) deposition, which peaked in the 1980s, was the primary source of acidification in the acidic forest soils of the northern hemisphere (van Breemen et al, 10 1984). However, now that S deposition has dropped to around the 1930s level throughout Western Europe (Bertills et al, 2007;Engardt et al, 2017), focus has shifted towards understanding forest soil dynamics in response to forest biomass production and different harvesting scenarios (Akselsson et al, 2007;Iwald et al, 2013;de Jong et al, 2017).…”