Abstract
Abstract. The impact of climate and emissions changes on the deposition of reactive nitrogen (Nr) over Europe was studied using four offline regional chemistry transport models (CTMs) driven by the same global projection of future climate over the period 2000–2050. Anthropogenic emissions for the years 2005 and 2050 were used for simulations of both present and future periods in order to isolate the impact of climate change, hemispheric boundary conditions and emissions, and to assess the robustness of the results across the different models. The results from these four CTMs clearly show that the main driver of future N-deposition changes is the specified emission change. Under the specified emission scenario for 2050, emissions of oxidised nitrogen were reduced substantially, whereas emissions of NH3 increase to some extent, and these changes are largely reflected in the modelled concentrations and depositions. The lack of sulfur and oxidised nitrogen in the future atmosphere results in a much larger fraction of NHx being present in the form of gaseous ammonia. Predictions for wet and total deposition were broadly consistent, although the three fine-scale models resolve European emission areas and changes better than the hemispheric-scale model. The biggest difference in the models is for predictions of individual N compounds. One model (EMEP) was used to explore changes in critical loads, also in conjunction with speculative climate-induced increases in NH3 emissions. These calculations suggest that the area of ecosystems that exceeds critical loads is reduced from 64% for year 2005 emissions levels to 50% for currently estimated 2050 levels. A possible climate-induced increase in NH3 emissions could worsen the situation, with areas exceeded increasing again to 57% (for a 30% NH3 emission increase).
Highlights
As noted in Langner et al (2012b), air pollution is still a major problem in Europe, with levels of gases and particles frequently exceeding target values
This study is a follow-up to the ozone study of Langner et al (2012b), and largely follows the same methodology except in three respects: (i) the emission inventories were updated, making use of recent improvements in data sets and finer-scale spatial distributions to provide more accurate model inputs; (ii) we have investigated the effects of emissions changes as well as of climate change; and (iii) 20 yr time windows of simulation were considered instead of 10 yr
The three European-scale chemistry transport models (CTMs) models were driven by the same regional climate model (RCA3) meteorology, and by a common set of boundary conditions given by the fourth CTM, Danish Eulerian Hemispheric Model (DEHM)
Summary
As noted in Langner et al (2012b), air pollution is still a major problem in Europe, with levels of gases and particles frequently exceeding target values. Many sensitive ecosystems are adversely affected by deposition of reactive nitrogen (Nr) from the atmosphere to vegetation and water bodies (Erisman et al, 2013; Sutton et al, 2011). Nr comprises both oxidised and reduced compounds, generally indicated by NOy and NHx respectively. For ammonia and sulfur dioxide, deposition rates depend on humidity levels, temperature and an acidity ratio (defined as the molar ratio of [SO2] / [NH3]) These acidity ratios are a first attempt to account for the observed changes in resistance in areas with different pollution climates (Erisman et al, 2001; Fowler and Erisman, 2003; Fowler et al, 2009).
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
