PM mapping in Scotland, 2007

1. PM mapping in Scotland, 2007 Andrew Kent

2. What are we presenting today? 1) Context to the work 2) Modelling process 3) Model results 4) Future work possibilities

3. Background 2004 Modelled concentrations for multiple pollutants for Scotland Scotland met data (RAF Leuchars) and Scotland calibration used Model performance no improvement on UK model Too few sites for robust calibration and verification 2005 Remodelling undertaken in hope that more sites would help Concluded that still more sites desireable 2006 No new modelling undertaken but assessed Scottish monitoring against UK model output Performance good

4. What did we do this year? Modelled PM only Take advantage of new Scottish monitoring campaign – genuine gravimetric PM for direct comparison with legislation Outputs PM10 and PM2.5 1x1 km background map Modelled concentrations for major road links Checked calibration performance Assessed outputs against objectives relevant to Scottish Government

5. Scottish monitoring Scottish Government funded expansion of monitoring campaign in 2007 Used Partisol analysers for daily gravimetric concentration PM10 • 10 sites PM2.5 • 8 sites Used to calibrate model

6. Modelling process Generalised description presented here Full details in annual report on UK AQ Archive: http://www.airquality.co.uk/archive/reports/cat09/0807231621_dd12006mapsrep_v2.pdf Particulate matter Complex pollutant Poorly understood Many components, each with a degree of uncertainty! Contributions to the annual mean model Point sources – big and small point sources Area sources – the largest contribution Long-range transport primary – TRACK model output Sea salt – the only ‘natural’ component in the model SOA – output from HARM model SIA – nitrate, sulphate, ammonium

7. Big points Small points Point sources

8. Dispersed emissions calibrated against monitoring data 1x1km sector specific emission grids Dispersed using a kernel approach Emission footprint - Dispersion model output Invert matrix for dispersion kernel Area sources

9. PM10 calibration PM2.5 calibration Slope of about 6! VCM corrected TEOM data Area source calibration

10. Formerly used 2 dispersion kernels Road traffic kernel Non-road traffic kernel Multiple calibrations for different land cover Large conurbations Elsewhere Now use multiple kernels for different area types single calibration Better describe dispersion over different terrain Less reliance on empirical relationship Area type kernels

11. Long range transport primary TRACK model Lagrangian statistical model 10x10km grid Secondary organic aerosol HARM/ELMO model (Lancaster University) Lagrangian model – changing compositions of air parcels en route to designated receptor sites Secondary inorganic aerosol 28 rural sites measuring sulphate, nitrate and ammonium Interpolating using Krigging on a 5x5km grid Split between fine and coarse fractions Fe and Ca rich dusts Emission not included in NAEI so formerly part of residual in model Distribution based on population and vehicle km travelled Sea salt Same method as SIA, using chloride measurements on a 5x5km grid Split between fine (27%) and coarse (73%) – from Harrison & Yin (2006), APEG (1999) Additional contributions

12. Addition of … Big point sources Small point sources Calibrated area sources Sea salt Long range transport primary SOA Secondary inorganic aerosol Fe and Ca rich dusts The background map

13. Roadside model • Uses scaled emissions from NAEI attributed to each major urban road link in UK • Roadside increment derived from roadside monitoring sites • measured roadside concentration – modelled background concentration • Calibration using roadside increment against traffic-flow adjusted emissions for each road link

14. PM10 calibration PM2.5 calibration Roadside model and calibration

15. PM2.5 background Calibration checking – background maps PM10 background

16. PM2.5 roadside Calibration checking – road links PM10 roadside

17. Exceedences Assessment • Model outputs interrogated to calculate exceedence statistics for • area and population (from background model) • road links and road length (from roadside model) • Assessed model results against appropriate values

18. Exceedences PM10 • No background exceedences • Roadside exceedences • Scotland annual objective – exceeds over 4 zones • Scotland daily mean objective – exceeds over 2 zones • UK daily mean objective – no exceedences

19. Exceedences PM2.5 • No background exceedences • Roadside exceedences • Scotland 2010 objective – exceeds at 2 zones • Scotland 2020 target value – no exceedences

20. Scotland daily mean objective

21. UK daily objective… for comparison

22. PM10 PM2.5 Maps - background

23. PM10 PM2.5 Maps - roadside

24. PM10 PM2.5 Background maps - difference

25. Conclusions • Like pollutants examined in previous years – a Scotland-specific model provides mixed results • Difference between Scotland-specific and UK models is not very large and is attributable to calibration rather than met variation • Scotland-specific model results in generally lower PM10 than UK model but are higher PM2.5.This is due to the calibration factors derived from the monitoring data. • Largest differences between models was across urban areas – probably due to greater urban representation in UK model than in Scotland-specific model (predominantly rural calibration)

26. Future work • Will need discussion with and direction from Scottish Government • No PM mapping possible for 2008 • Recommend: • Comparison of Scottish monitoring against UK model outputs – Scottish verification • Interrogation of UK model outputs for values relevant to Scotland – Scotland AQS values, EU limit values. • These will provide confidence in UK outputs for Scotland • Help identify areas of exceedence for further policy focus and action

27. Questions… • ? andrew.kent@aeat.co.uk