1. Network for the support of European Policies on Air Pollution The assessment of European control measures and the effects of non-linearities

2. Non-linearities

3. Definition What goes up comes down, the atmospheric mass balance for the emitted reactive pollutants is closed. However, the distance scale for the processes of transport, transformation and deposition are large, and differ between the different pollutants (some emitted nitrogen escapes from the European domain, and surface ozone concentrations over Europe are dominated by the advected flux into Europe from the North Atlantic). In this project, we have identified non-linearities in source- receptor relationships at regional scales in sulphur and nitrogen compounds in air or deposition.

4. Apparent non-linearities………where for example unknown sources contribute to the deposition Real non-linearities occur when the processes regulating the lifetime of pollutants change with time (oxidation, deposition)

5. Three examples 1.Shipping and the sulphur budget 2.Changes in dry deposition with time due to changes in SO 2 / NH 3 3.Oxidized nitrogen budgets

6. Trends in sulphur deposition throughout the UK 1986-2001 Group 1*: nss-SO 4 2- = -3.25 y + 6542 Group 2*: nss-SO 4 2- = -1.06 y + 2159 Group 3 * : nss-SO 4 2- = -0.21 y + 459 Group 4: nss-SO 4 2- = -0.11 y + 237 * Statistically significant, P < 0.01

8. Shipping!

9. Vessel traffic densities for year 2000 based on the sum of reported distributions from AMVER data (AMVER, 2001)

10. Some areas of the UK show large reductions in acid deposition while other areas (eg Wales and Western Scotland), including some very heavily affected areas have changed little. Work continues on the influence of shipping emissions on S and N deposition (Univ Oslo) % reduction from 87-01 in total non- marine Sulphur

11. 2. Has the SO 2 dry deposition velocity changed ? Concentrations are declining faster than expected by models Current LRT models treat deposition velocity as simply coupled to meteorology and vegetation LIFE project provides important clues Is there evidence of regional variations in surface resistance and deposition velocity?

12. The surface reactions are regulated by SO 2 /NH 3 interactions in suface water films

14. EMEP 2003 : Total deposition of oxidized S, 2000 mg S m -2 yr -1

15. 0 20 40 60 80 100 120 140 160 180 200 Speulder ForestMelpitzAuchencorth R c (sm -1 ) 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 NH 4 /SO 4 R c SO 2 R c NH 3 NH 4 /SO 4

16.  Dry deposition rates of SO 2 are regulated by chemical processes in water films on terrestrial surfaces.  NH 3 is the most important of the pollutants which regulate canopy resistance to SO 2 deposition.  Long term rates of SO 2 deposition have increased with time as NH 3 /SO 2 ratios have increased.  Non-linearity is introduced into source-receptor matrices by changes in SO 2 emission in the presence of significant NH 3 concentrations.  Dynamic chemical models are able to reproduce the measured fluxes and resistances of SO 2 and NH 3 but are not currently applied in Long-Range Transport models.

17. EMEP model predicts slower trend in ambient SO 2 than observed

18. Sulphur in the UK 1987-2001

19. Non-linearities in the oxidized nitrogen budgets

20. NO x emissions Most of the change in emission has already taken place (2005: 50% since late 80’s, only <10% in the next 15 years)

22. UK Emission deposition and export of atmospheric N 1900-2000

23. Cause 1 From 1990 to 2010 land-based NO x will decrease from 13.4 to 6.6 Mt While NO x from shipping will increase from 2.8 to 4.6 Mt. So, by 2010, 70% of NO x will originate from shipping (in EU)

25. Cause 2 NO 2 emissions declined ~50% More O 3 at night NO 2  NO 3  HNO 3

26. Ecosystem Type1995-19972010 Acid grassland2719 Heathland5642 Coniferous woodland8879 Deciduous woodland9692 All ecosystems4032 Exceedances of critical loads of ecosystems for eutrophication by nitrogen in the UK (%)

27. Detecting the signal of Nitrogen deposition in semi-natural vegetation 400 1kmx1km survey plots throughout the UK Species composition and cover 1978, 1980, 2000 N deposition (Reduced and Oxidized) 5km Clear signal linking loss of biodiversity to N deposition.

28. Conclusions Non-linearities exist and are a cause of regional variation in response to emission changes Detailed examination of the excellent long term data for air and precipitation composition is a vital step Models are the tools to summarize our knowledge, for integration, assessment and exploration of the interactions…but they lag behind our understanding of processes