Research funded by the Swedish FORMAS

1. Particle Number Size Distributions at an Urban Site in southern Sweden: Estimates of the Contribution of Urban Particle Sources Paper 8A1, Session 8, IAC 2006 Erik Swietlicki1, Andreas Massling1, Ingela Dahlberg1, Jakob Löndahl1, Adam Kristensson2, Henric Nilsson3, Susanna Gustafsson3and Matthias Ketzel4 1Division of Nuclear Physics, Lund University, Lund, Sweden 2Department of Chemistry, Copenhagen University, Copenhagen, Denmark 3Environment and Health Protection Board, City of Malmö, Malmö, Sweden 4Department of Atmospheric Environment, National Environmental Research Institute, Roskilde, Denmark Research funded by the Swedish FORMAS

2. Motivation – Human Health • CAFE estimates that fine particles (PM2.5) and ozone combined are responsible for 370,000premature deaths each year in EU25, and the loss of 3.6 millions years of life annually. • (CAFE: Impact Assessment of the Thematic Strategy on Air Pollution and the Directive on “Ambient Air Quality and Cleaner Air for Europe”, SEC(2005)1133, Brussels, 21 Sept. 2005 (http://www.cafe-cba.org/) • WHO estimates that exposure to fine particulate matter in outdoor air leads to about 100 000 deaths (and 725 000 years of life lost) annually in Europe. • (WHO, World Health Report 2002, Geneva) • For Sweden, Forsberg et al. (2005) estimated that the current population exposure to PM10 results in 5000 premature deaths annually. RIP (RIP = Respired Inhalable Particles … and died!)

3. Motivation – Climate • Size-resolved emission data are often close to source (tunnels, tail-pipe, street canyons…). • Regional/global scale models need the size distributions of the urban plume crossing over the city limits. • Are aerosol dynamics (coagulation, condensation…) fast enough to significantly modify the urban plume aerosol size distribution?

4. Malmö Court House Vavihill Malmö Measurements sites – Southern Sweden 55 36' 23'' N, 13 0' 9'' E

5. Malmö SMPS system • Own design, manufacture and calibration • Medium-long DMA • (Vienna-type, own manufacture) • Particle counter: TSI CPC 3760A • 10-551 nm • Closed-loop • (driers and filters in loop) • Scanning mode • (up and downscan, Labview software) • CPC desmearing to improve time resolution • Time resolution: 3 min • RH and T sensors for data QA • Measurements started April 2005

6. Court House, Malmö, Sweden(Urban Roof-top Measurement Site) • Gas phase: NO, NO2, SO2, CO • PM2.5, PM10 • Meteorological data, nearby mast Environment and Health Protection Board, City of Malmö, Sweden

7. The Vavihill site Regional background – Southern Sweden • Twin-DMPS (3-900 nm)

8. Aerosol Size Distributions Urban Roof-top – Malmö, Sweden April 2005 – April 2006 Percentiles Mean 90% 6 980 cm-3 70% Median 30% 10%

9. Aerosol Size Distributions Urban Roof-top – Malmö, Sweden StatisticsApril 2005 – April 2006 Mean PM2.5  10 µg/m3

10. Aerosol Size Distributions Urban Roof-top – Malmö, Sweden April 2005 – April 2006 Average Size Distributions Weekdays 50 nm National holidays have been omitted.

11. Aerosol Size Distributions Urban Roof-top – Malmö, Sweden Harbour Harbour Malmö Malmö city Average size distributions for the various wind sectors.

12. Court House, Malmö(urban roof-top measurement site) • Sources to the urban aerosol (size distribution): • Long-range transported regional background • Urban sources (road traffic, ship traffic, industry,…) • Heating: oil and wood combustion (minor sources in Malmö) • + aerosol dynamics transforming the size distribution within the city limits (condensation, coagulation, deposition, dilution) • Attempt to separate: • Urban contribution to the urban roof-top concentrations • (Urban measurements – Regional Background) • Local traffic contribution (Highest 20% [NO]/[NO2] ratios) • Ship plumes (High [SO2], wind direction from harbour area)

13. Estimated Traffic ContributionMalmö Urban Roof-top Method suggested by Janhäll et al. (2004) Local traffic contribution: Cases with highest 20% [NO]/[NO2] ratios Urban background: Cases with lowest 20% [NOx] subtracted Estimated Traffic Size-dependent emission factors derived from a Swedish tunnel study (Kristensson et al., 2004) are shown for comparison. Tunnel study

14. Derived Traffic Contribution Mode GMDs: 13 nm, 25 nm, 68 nm

15. Rådhuset Ship Traffic Contribution

16. Ship Plumes Nucleation mode particles from homogeneous nucleation of H2SO4 + H20 ? Ship plumes from Malmö City Harbour SO2

17. Urban Roof-top – Regional BackgroundVavihill – Malmö Urban site (Malmö) Backgrund (Vavihill)

18. Malmö City Contribution to the Urban Roof-top Aerosol Mode GMDs: 8 nm, 38-39 nm, 95-100 nm Fresh aerosol (traffic, ships,..) + processed within city limits Weekdays Weekends Malmö City Contr. Malmö City Contribution

19. Malmö City Contribution Traffic Ship? Malmö City Contribution to the Urban Roof-top Aerosol Mode GMDs: 8 nm, 38-39 nm, 95-100 nm Fresh aerosol (traffic, ships,..) + processed within city limits Weekdays July 2005 Malmö City Contribution

20. Harbour Inlet The urban contribution seems to be from road traffic plus ship movements in the harbour. Could the size shift from 25 nm to 40 nm be caused by aerosol dynamics instead?

21. Modelling Urban Aerosol Dynamics Question: Can particles grow from 25 to 40 nm in the urban background? Method Ketzel, M. and Berkowicz, R. (2005): Multi-plume aerosol dynamics and transport model for urban scale particle pollution. Atmospheric Environment39, 3407-3420. AERO3 Model (E. Vignati, JRC) Input Assumptions: The background size distribution at Vavihill (3-modal) The estimated traffic emission size distribution (4-modal) Average wind speed = 4 m/s Emission density for Malmö = 230 (pt/cm3) m/s

22. Emissions Modelling Urban Aerosol Dynamics Regional background, Urban Traffic Emissions and Dilution, No Aerosol Removal process 5 h 3 h 1 h 0 h

23. Modelling Urban Aerosol Dynamics Regional background, Traffic Emissions, Dilution, Coagulation, Deposition with u*=1.33 m/s, No condensation Regional background, Urban Traffic Emissions and Dilution, No Aerosol Removal process 5 h 3 h 1 h 0 h

24. 5 h 3 h 1 h 0 h Modelling Urban Aerosol Dynamics Regional background, Traffic Emissions, Dilution, Coagulation Deposition with u*=1.33 m/s, No condensation Regional background, Traffic Emissions, Dilution, Coagulation, Deposition Condensation, Growth rate=6 nm/h, Condensing vapour conc. = 1.85 x 108 molec cm-3 Regional background, Urban Traffic Emissions and Dilution, No Aerosol Removal process

25. Modelling Urban Aerosol Dynamics Regional background, urban traffic emissions and dilution only Regional background, emissions, dilution, coagulation, deposition, condensation 1 h 1 h 0 h 0 h • Aerosol dynamics alone can not grow the 25 nm traffic mode to 40 nm. This latter mode is probably caused by ship traffic. • Aerosol dynamics is nevertheless likely to affect the urban size distribution even within the city limits of a medium-sized city. • The urban plume contribution to the rural bakground is not simply a linear combination of regional background plus urban emissions and dilution.

26. Particle Number Size Distributions at an Urban Site in southern Sweden: Estimates of the Contribution of Urban Particle Sources Erik Swietlicki, Andreas Massling, Ingela Dahlberg, Jakob Löndahl, Adam Kristensson, Henric Nilsson, Susanna Gustafssonand Matthias Ketzel > Conclusions < • The dominant sources to the urban roof-top aerosol size distribution were determined • and were identified as • Long-range transport • Local road traffic • Ship traffic • Aerosol dynamics play a role

27. Thank you for your attention!