1. Ian Longley Street canyon aerosol pollutant transport measurements in Manchester I.D. Longley, M.W. Gallagher, J.R. Dorsey, M. Flynn, K. Bower, I. Barlow J.R. Allan, M.R. Alfarra, H. Coe

2. Ian Longley Aerosol in Urban Street Canyons Fine aerosol, linked to adverse health effects (COMEAP, 2001, EPAQS,2000, Colville et al, 2001). Fine aerosol from vehicle emissions. Street canyons act as major emission sites. Large numbers of people exposed. Canyons re-circulate and trap pollutants. Canyon emissions transported across and beyond city – affecting chemical and radiative atmospheric properties and the biosphere.

3. Ian Longley The Air Pollution Chain Emissions Concentrations Exposure Health effect

4. Ian Longley The Air Pollution Chain Emissions Concentrations Exposure Health effect Dispersion

5. Ian Longley Regulatory dispersion models Models are based upon a simple transport mechanism. Poorly understood: a)Fine variation b)Canyon assymetry c)Moving sources d)Dispersive effect of vehicles & other objects e)Behaviour of different aerosol sizes ADMS-Urban, CERC Ltd

6. Ian Longley SCAR – Street Canyon Aerosol Research Numerical modelling – simple canyons. Field studies are rare. Fine scale study. Investigate transport mechanisms. SCAR to apply eddy correlation techniques. Aim: Parameterised size- segregated aerosol emission rates.

7. Ian Longley Experimental site – Princess Street, Manchester

8. Ian Longley SCAR measurements SMPS (TSI 3080 + nano DMA) 2x fine OPC (PMS ASASP-X) Coarse OPC (PMS FSSP) 20 Hz sonic anemometers 18m mast Platform lift for profiling Mobile turbulence system 4 campaigns in 2001: (3 x 1 week, 1 x 2 weeks)

9. Ian Longley Mean aerosol spectra Above: SMPS spectrum from UMIST Land Rover Discovery Tdi Right: in-canyon number and volume (mass) spectra

10. Ian Longley Aerosol Chemistry (from Aerosol Mass Spectrometer, J.R. Allen, M.R. Alfarra, H.Coe) Mode in the mass spectra at around 100-200nm consisting of aliphatic organic chemicals. Organic activity within the Manchester sampling periods correlates well with NO x activity.

11. Ian Longley Temporal variation in fine aerosol spectra (4.6nm<D p <160nm) Total number concentrations generally follow traffic flow Road-side day-time concentrations are generally greater than night-time by a factor of around 4. Day-time and night-time spectra are the same shape. See Movie !

12. Ian Longley Influence of wind speed and direction on fine aerosol number concentrations – 1. PARALLEL FLOW

13. Ian Longley Influence of wind speed and direction on fine aerosol number concentrations – 2. NE PERPENDICULAR Canyon vortex blows emissions away from instruments

14. Ian Longley Influence of wind speed and direction on fine aerosol number concentrations – 3. SW PERPENDICULAR Canyon vortex blows emissions towards instruments Flow at pavement level disconnected from roof-top wind

15. Ian Longley Influence of wind speed and direction on coarse aerosol number concentrations

16. Ian Longley Vertical concentration gradients

17. Ian Longley Vertical concentration gradients

18. Ian Longley Accumulation mode (100nm<D p <1m) aerosol emission fluxes SCAR SASUA: Above Edinburgh* * Dorsey, J.R. et al Atmos. Environ. Vol.36, pp. 791-800.

19. Ian Longley Horizontal fluxes

20. Ian Longley Coarse particle fluxes SASUA All Experiments Aerosol Eddy Flux Measurements d p >1.9  m Mode- CEH instrument Wind driven re-suspension

21. Ian Longley Turbulence Local sources apparent at low wind speed Enhancement during day-time, especially in perpendicular winds

22. Ian Longley Parameterisation for  w Traffic-induced turbulence

23. Ian Longley Parameterisation for  w = 0.16 at a height of 3.5m  wt = 0.0135 T 1/2 T = traffic flow rate (hr -1 )

24. Ian Longley Turbulent variances:  u,v,w /U profiles

25. Ian Longley Turbulent variances:  u,v,w /U profiles

26. Ian Longley Spatial variation in  w /U: 1. Sheltered zone Above: U/U roof Below:  w /U Plan views of canyon

27. Ian Longley Spatial variation in  w /U: 2. Convergence Above: U Below:  w /U

28. Ian Longley Conclusions  The flux of accumulation mode aerosol (100nm<D p <3m) has been measured in a city centre street canyon and found to be related to urban heat emission, traffic activity, wind speed and direction.  Street-level aerosol concentrations have been shown to be influenced by asymmetrical vortex flow within the canyon.  A vertical gradient was found in fine aerosol number concentrations below roof level.  A weak positive vertical gradient was seen in turbulent variances. However, greatly enhanced variances were seen at the bottom of the canyon.  A parameterisation has been derived for  w relating it to local wind speed and direction and traffic flow rate.

29. Ian Longley Forthcoming analysis Flux budget Further describe behaviour of different sizes of aerosol Improved parameterisation for wind-driven and traffic-induced turbulent re-suspension Spectral & quadrant analysis – turbulent scales SCAR-5: suburban street canyon (with Reading University) Improved parameterisation for turbulence, including traffic-layer turbulence

30. Ian Longley Acknowledgements With thanks to CERC Ltd., Cambridge, UK

31. Ian Longley Mean air flow: Channelling

32. Ian Longley Mean air flow: Vertical flow

33. Ian Longley Mean air flow: Vertical flow

34. Ian Longley Mean air flow: Up-canyon

35. Ian Longley Mean air flow: NE perpendicular

36. Ian Longley Mean air flow: SW perpendicular