SOX + PPM
8 Modelling of acidification and eutrophication .1 The earlier RAINS approach
8.3 Atmospheric modelling of acid deposition
The recent review of the new EMEP Eulerian model concluded that
• “There was high confidence in the EMEP model’s ability to represent the broad spatial patterns in the deposition of sulphur and oxidized nitrogen compounds across Europe;
• While a spatial resolution of 50 km x 50 km represents a major improvement compared with the EMEP Lagrangian model, considerable sub-grid scale variations can still be expected and so some additional statistical treatment will be required to account for in-square variations;
• There was every confidence in the model’s ability to reproduce the observed trends in sulphur and oxidized nitrogen deposition;
• There was limited confidence in the model’s ability to represent the spatial pattern and trends in reduced nitrogen deposition because of the lack of understanding of the fate and behaviour of ammonia and the difficulties associated with the model representation of ammonia emissions and deposition.”
To explore the response of the recent version of the EMEP Eulerian model towards changes in precursor emissions, the same 87 model experiments with the EMEP Eulerian model as described in the PM chapter have been performed and the responses of various deposition metrics have been investigated. Of particular interest was the detection of potential non-linearities that would preclude the use of simple linear source-receptor matrices for the calculations in RAINS. While the new EMEP model provides dry deposition estimates for a range of different land-use classes, lack of the underlying land-use information did not allow this first analysis to explore deposition other than grid average. Once this information will be obtained from EMEP, the analysis presented below will be repeated for deposition to deciduous and coniferous forests.
The following graphs compare changes of calculated annual deposition of the various acidifying compounds for the UK grid cells (red crosses) and other European receptors (black crosses) resulting from changes in UK emissions.
Figure 8.3 (left panel) shows the ratio between changes in SO2 emissions and resulting changes in sulphur deposition for (1) change from CLE to MFR, (2) change from CLE to UFR. There is an almost perfect linear relationship, both for receptors close to the sources and remote sites. As demonstrated in the right panel, the response is almost independent of the overall pollution level.
Although not shown here, there is a very small impact on sulphur deposition if NOx emissions are reduced, and a more noticeable effect when NH3 is reduced, which warrants further investigation.
When emissions of all pollutants are modified simultaneously, the sulphur deposition response appears to be independent of the overall pollution level (Figure 8.4). On this basis, the use of linear source-receptor relationships seems appropriate to reproduce the response in sulphur deposition calculated with the full EMEP Eulerian model.
For the deposition of oxidised nitrogen compounds, similar findings emerge. There is rather good linearity for changes in NOx emissions (Figure 8.5). These are virtually independent of changes in SO2 emissions, but show a noticeable dependency towards isolated changes in NH3 (Figure 8.6).
Again, if the various pollutants are reduced in an ensemble, a linear description seems to perform very well (Figure 8.7).
The response of deposition of reduced nitrogen towards changes in NH3 emissions is extremely linear (Figure 8.8). Single-pollutant changes of NOx emissions exert a very small disturbance, which is however below 0.5 percent and disappears if emissions are reduced in an ensemble (Figure 8.9).
From this preliminary analysis a representation of the source-receptor relationships for acid deposition resulting from the full Eulerian EMEP model through linear functions would seem to be an acceptable approach for integrated assessment. The caveat applies that this finding needs to be confirmed for forest-specific deposition.
The Mapping Manual of the ICP on Modelling & Mapping" also requests that calculations on the excess of critical loads need to be based on multi-year meteorology, in order to exclude the influence of inter-annual variability. For the earlier policy application of RAINS, source-receptor relationships were computed for 10 meteorological years, and the average relationships were used for calculations in RAINS. This inter-annual variability is indeed an important factor and needs to be considered in an integrated assessment. Thus, it is the plan to use calculations for as many meteorological years as possible for the analysis. The practical availability of EMEP model results will determine what can be done for RAINS.
−350 −300 −250 −200 −150 −100 −50 0
−700
−600
−500
−400
−300
−200
−100 0
∆ total dep. SOx CLE−>MFR
∆ total dep. SOx CLE−>UFR
non−UK grids UK grids
∆ S emis ratio
0 100 200 300 400 500 600 700
0 100 200 300 400 500 600 700
− ∆ total dep. SOx CLE−>UFR
∆ total dep. SOx UFR−>CLE
non−UK grids UK grids
∆ emis ratio
Figure 8.3: Left panel: Change of total sulphur deposition (dry + wet) due to changes in the UK SO2
emissions from CLE to MFR versus the deposition changes resulting from a reduction of UK SO2
emissions from CLE to UFR. Right panel: Differences in total sulphur deposition (dry + wet) due to changes in the UK SO2 emissions from UFR to CLE with all other European emissions at UFR, versus a change of the UK SO2 emissions from CLE to UFR with all other European emissions at CLE.
0 100 200 300 400 500 600 700
∆ total dep. SOx UFR−>CLE
non−UK grids UK grids
∆ emis ratio
Figure 8.4: Differences in total sulphur deposition (dry + wet) due to changes in the UK SO2, NOx and NH3 emissions from UFR to CLE with all other European emissions at UFR, versus a change of the UK emissions from CLE to UFR with all other European emissions at CLE.
−100 −80 −60 −40 −20 0
∆ total dep. oxid. N CLE−>MFR
∆ total dep. oxid. N CLE−>UFR
non−UK grids
− ∆ total dep. oxid. N CLE−>UFR
∆ total dep. oxid. N UFR−>CLE
non−UK grids UK grids
∆ emis ratio
Figure 8.5: Left panel: Change of deposition of oxidised nitrogen (dry + wet) due to changes in the UK NOx emissions from CLE to MFR versus the deposition changes resulting from a reduction of UK NOx emissions from CLE to UFR. Right panel: Differences in total deposition of oxidised nitrogen (dry + wet) due to changes in the UK NOx emissions from UFR to CLE with all other European emissions at UFR, versus a change of the UK NOx emissions from CLE to UFR with all other European emissions at CLE.
0 5 10 15 0
5 10 15 20 25 30
∆ total dep. oxid. N CLE−>MFR
∆ total dep. oxid. N CLE−>UFR
non−UK grids UK grids
∆ A emis ratio
Figure 8.6: Change of deposition of oxidised nitrogen (dry + wet) due to changes in the UK NH3
emissions from CLE to MFR versus the deposition changes resulting from a reduction of UK NH3
emissions from CLE to UFR
0 20 40 60 80 100 120 140 160 180 200
0 20 40 60 80 100 120 140 160 180 200
− ∆ total dep. oxid. N CLE−>UFR
∆ total dep. oxid. N UFR−>CLE
non−UK grids UK grids
∆ emis ratio
Figure 8.7: Differences in deposition of oxidised nitrogen (dry + wet) due to changes in the UK SO2, NOx and NH3 emissions from UFR to CLE with all other European emissions at UFR, versus a change of the UK emissions from CLE to UFR with all other European emissions at CLE.
−500 −400 −300 −200 −100 0
∆ total dep. red. N CLE−>MFR
∆ total dep. red. N CLE−>UFR
non−UK grids
∆ total dep. red. N UFR−>CLE
non−UK grids UK grids
∆ emis ratio
Figure 8.8: Left panel: Change of deposition of reduced nitrogen (dry + wet) due to changes in the UK NH3 emissions from CLE to MFR versus the deposition changes resulting from a reduction of UK NH3 emissions from CLE to UFR. Right panel: Differences in total deposition of reduced nitrogen (dry + wet) due to changes in the UK NH3 emissions from UFR to CLE with all other European emissions at UFR, versus a change of the UK NH3 emissions from CLE to UFR with all other European emissions at CLE.
0 100 200 300 400 500 600 700 800 900 1000
∆ total dep. red. N UFR−>CLE
non−UK grids UK grids
∆ emis ratio
Figure 8.9: Differences in deposition of reduced nitrogen (dry + wet) due to changes in the UK SO2, NOx and NH3 emissions from UFR to CLE with all other European emissions at UFR, versus a change of the UK emissions from CLE to UFR with all other European emissions at CLE.
8.4 References
Amann, M., Bertok, I., Cofala, J., Gyarfas, F., Heyes, C., Klimont, Z., Makowski, M., Schöpp, W. and Syri, S. (1999) Cost-effective Control of Acidification and Ground-level Ozone. International Institute for Applied Systems Analysis (IIASA), Laxenburg, Austria.
European Parliament (1998) Resolution on the Communication to the Council and the European Parliament on a Community Strategy to Combat Acidification (COM(97)0088 - C4-0436/97).
A4-0162/1998, European Parliament, Brussels.
Hettelingh J-P, Posch M, De Smet PAM (2001) Multi-effect critical loads used in multi-pollutant reduction agreements in Europe. Water, Air and Soil Pollution 130: 1133-1138.
Joint expert group on dynamic modelling (2003) Summary report on the fourth meeting prepared by the organizers. Centre for Ecology and Hydrology, United Kingdom.
Posch M, De Smet PAM, Hettelingh J-P, Downing RJ (eds) (1999) Calculation and mapping of critical thresholds in Europe. Status Report 1999, Coordination Center for Effects, RIVM Report 259101009, Bilthoven, Netherlands, iv+165 pp. www.rivm.nl/cce
Posch M, Hettelingh J-P, De Smet PAM (2001) Characterization of critical load exceedances in Europe. Water, Air and Soil Pollution 130: 1139-1144.
Posch M, Hettelingh J-P, Slootweg J (eds) (2003) Manual for dynamic modelling of soil response to atmospheric deposition. Coordination Center for Effects, RIVM Report 259101012, Bilthoven, Netherlands, 71 pp. www.rivm.nl/cce
Schöpp, W., Posch., M., Mylona, S. and Johanssson, M. (2003) Long-term development of acid deposition (1880-2030) in sensitive freshwater regions in Europe. Hydrology and Earth System Sciences, 7(4): 436-446.
Suutari, R., Amann, M., Cofala, J., Klimont, Z., Posch, M. and Schöpp, W. (2001) From Economic Activities to Ecosystem Protection in Europe. An Uncertainty Analysis of Two Scenarios of the RAINS Integrated Assessment Model. EMEP CIAM/CCE Report 1/2001, International Institute for Applied Systems Analysis, Laxenburg, Austria.
TFMM (2003) Review of the Unified EMEP model. Summary report and conclusions of the workshop of the EMEP Task Force on Monitoring and Modelling. United Nations Economic Commission for Europe, Geneva.
Tuinstra, W., Hordijk, L. and Amann, M. (1999) Using computer models in international negotiations. The case of acidification in Europe. Environment 41(9): 33-42.