PM mapping in Scotland, 2007 Andrew Kent

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

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

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 PM 10 and PM 2.5 1x1 km background map Modelled concentrations for major road links Checked calibration performance Assessed outputs against objectives relevant to Scottish Government

Scottish monitoring Scottish Government funded expansion of monitoring campaign in 2007 Used Partisol analysers for daily gravimetric concentration PM sites PM sites Used to calibrate model

Modelling process Generalised description presented here Full details in annual report on UK AQ Archive: 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

Point sources Big pointsSmall points

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

Area source calibration PM 10 calibrationPM 2.5 calibration Slope of about 6! VCM corrected TEOM data

Area type kernels 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

Additional contributions 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)

The background map 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

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

Roadside model and calibration PM 10 calibrationPM 2.5 calibration

Calibration checking – background maps PM 2.5 backgroundPM 10 background

Calibration checking – road links PM 2.5 roadsidePM 10 roadside

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

Exceedences PM 10 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

Exceedences PM 2.5 No background exceedences Roadside exceedences Scotland 2010 objective – exceeds at 2 zones Scotland 2020 target value – no exceedences

Scotland daily mean objective

UK daily objective… for comparison

Maps - background PM 10 PM 2.5

Maps - roadside PM 10 PM 2.5

Background maps - difference PM 10 PM 2.5

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 PM 10 than UK model but are higher PM 2.5. 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) Conclusions

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 Future work

? Questions…