1. Attaining urban air quality objectives- links to transboundary air pollution Helen ApSimon, Tim Oxley and Marios Valiantis UK Centre for Integrated Assessment Modelling Imperial College London

2. SOURCES EMISSION EXPOSURE EFFECTS/RECEPTORS Energy Agriculture Industry Traffic Sulphur dioxide Ammonia Nitrogen oxides VOCs Sulphur deposition Nitrogen deposition SO 2,SO 4 air concns NO 2,NO 3 air concns Ozone Acidification Eutrophication Human health Materials Yield losses Surface waters Terrestial ecosystems Marine ecosystems Crops Forests Domestic Particles PM 10/2.5 NH 4 concn CO 2 N2O CH4 C L I M A T E AIR QUALITY NO 2

3. Particulate matter PM 10 : Limit values (max. conc at hot-spots) Annual mean conc. 40  g.m- 3 24 hr conc 50  g.m -3 < 35 days per year Targets proposed for PM 2.5 Limit values 25  g.m -3 and “exposure reduction”: 20% at urban background sites BENEFITS e.g. in UK 2005 baseline-> £9 to £21 bn/y for life years lost (DEFRA: Air Quality Strategy for England, Scotland, Wales and N Ireland- consultation document April 2006)

4. NITROGEN DIOXIDE Limit values: Annual mean conc. 40  g.m -3 (21 ppb) I hr mean 200  g.m -3 (105 ppb) <18 times /yr Wide-spread exceedence in European cities, especially at road-side sites. Adds to importance of reducing NOx, but emphasizes urban sources, particularly traffic Illustrate other links to CLRTAP

5. ASAM- European scale (50km) UKIAM- UK scale (5km) BRUTAL- Background Road & Urban Transport modelling of Air quality Limit Values-> Superimpose road-side on background Road network + traffic data-> traffic emissions individual roads and gridded Pop. Data -> urban areas/roads (canyons etc)

6. Modelled background concentrations:- First model NOx using same model, PPM, used for primary PM. Then convert to NO2 using relationship between NO2 and NOx NB Good agreement with measurements, but requires added rural background

7. Background NOx inferred from rural diffusion tube network ->10  g.m -3 most of England Preliminary calculations suggest that imported NOx contributes to this background including shipping- so some transboundary component. Applies to other countries too?

8. EMEP source apportionment: relative importance of transboundary and own country: NOx/ NO 2 conc. not given by EMEP, but probably more like reduced N deposition and PM coarse ?

9. SCENARIO ANALYSIS Superimpose roads: Traffic emissions: traffic flows and vehicle mix combined with speed-dependent emission factors (individual roads and summed over grid square) Scenarios: Tech. measures e.g. EGR, early introduction Euro V,VI ; hybrids/LEVs Local measures/ reduced traffic volumes: congestion zones; :LEZs etc.

10. PRELIMINARY RESULTS Projections of NO2 for 2010 at road-side sites: contributions from roads superimposed in each 1x 1 km grid square on top of background-> mapping of peak concns at hot-spots BAU LEZ Max. tech. reduction case + factors ~CLRTAP -> section across London

11. BRUTAL (15.5.06): Scenario transects across London for peak NO2 at road-side sites in each grid-cell

12. NO 2 secondary- NO 2 primary fraction- evidence depends on O 3 of increase - PMtraps Example: 50 ppb NOx -> 25 ppb NO2 (limit value 21 ppb) Reduce to 35 ppb NOx-> 20 ppb NO2 (OK). BUT! 5 to 20% prim. frac-> 22 ppb NO2; plus more O3 -> 23ppbNO2 (not OK) NO 2 ppb

13. Similar analysis PM 10 e.g. benefits of PM traps NB importance of non-exhaust emissions- brakes/tyres

14. Summary: links UAQ and CLRTAP 1.Local control of urban air quality puts extra emphasis on traffic emissions  detailed modelling of scenarios 2. High economic benefits(PM) 3. Some direct transboundary contribution to NOx/NO 2 ? 4. NO2-NOx ratios dependent on ozone NB background ozone increasing 5. Interaction other pollutants- PM trap-> increased primary NO 2.