1. NORTRIP- 2010 11 16 1 SMHI road dust emission model Gunnar Omstedt, SMHI model description and results improvements of existing model new parameters Omstedt, G., Bringfelt, B. och Johansson, C., 2005: A model for vehicle-induced non-tailpipe emissions of particles along Swedish roads. Atmospheric Environment, 39, 6088-6097.

2. NORTRIP- 2010 11 16 2 Model description Winter Summer

3. NORTRIP- 2010 11 16 3 l is the dust layer (relative units) g (mm) is the moister amount on the surface Equations 1 and 2 are coupled due to the parameter describing vehicle-induced suspension. If the surface is wet, only a small fraction of l is emitted, then l is increasing. If the surface is dry and l is large, a large fraction of l is emitted, then l is decreasing. (1) (2)

4. NORTRIP- 2010 11 16 4 Referens emissionfactor: the baseline for the model is given by scaling, using NOx as a tracer

5. NORTRIP- 2010 11 16 5 Model description: the fq parameter t denotes present hour and t-1 previous hour g street moister content (mm) rr is the hourly precipitation e h is the hourly reduction factor for g due to evaporation Ep is potential evaporation; k empirical factor found to be k=0.075

6. NORTRIP- 2010 11 16 6 Model description: the fq parameter Rn is net radiation, ra aeodynamic resistance Δe the saturated vapour pressure deficit Input data: (global radiation), cloud cover, windspeed, humidity and temperature f q is the source strength reduction function due to the moisture content of the road

7. NORTRIP- 2010 11 16 7 Model description: the road dust layer - sources Two kinds of particles are put into the model: particles caused by the wear of pavement; particles from traction sand l total dust layer (0,1) l w road wear dust layer (0,1) l s sand dust layer (0,1) α share of road wear particles in the total dust layer β share of sand particles in the total dust layer The road wear dust layer The sand dust layer a st share of studded tyres (%) k st normalising factor, 0.03 f rf hourly decay of road dust layer due to runoff by rain (0,1) f susp hourly decay of road dust layer due to suspension (0,1) N number of sanding days during a winter season

8. NORTRIP- 2010 11 16 8 Model description: the road dust layer - sources The road wear dust layer The sanding dust layer Sanding occasions are calculated based on meteorological data. (Sanding is assumed to occur during slippery conditions).

9. NORTRIP- 2010 11 16 9 Model description: the road dust layer - sinks f susp is the relative hourly decay of the dust depot due to suspension k decay is an empirical parameter (0.001,decresing the dust layer to half of its value within about one dry month) a) suspension b) run-off RF is the hourly water run-off and is used to calculate the hourly decay of road dust layer due to runoff by rain (0,1), f rf RF max is maximum hourly water run-off (10 mm)

10. NORTRIP- 2010 11 16 10 Model description: road dust layer and final results Results using also a dispersion model

11. NORTRIP- 2010 11 16 11 Examples of results

12. NORTRIP- 2010 11 16 12 Hornsgatan 2004

13. NORTRIP- 2010 11 16 13 The model can also be used for PM2.5 by changing the reference emission factor Other results- PM2.5

14. NORTRIP- 2010 11 16 14 PM10 Jagtvej year 2003 Comparison of measured (+) and modelled (solid line) daily mean concentrations of PM10 (µg/m3) at Jagtvej / Copenhagen for the year 2003.(b) The same results as (a) but sorted according to size. Model results are based on measured NOx concentrations. Other results- no studded tyres Ketzel, M., Omstedt, G., Johansson, C., During, I., Pohjola, M., Dieterman,O., Gidhagen, L., Wåhlin,P., Lohmeyer, A., Haakana, M. and Berkowicz, R., 2007: Estimation and validation of PM2.5/PM10 exhaused and non-exhaused emission factors for practical street pollution modelling. Atmospheric Environment 41, 9370-9385.

15. NORTRIP- 2010 11 16 15 Type of stations  19 streets and close to roads stations  21 urban background stations Andersson, S. och Omstedt, G., 2009: Validering av SIMAIR mot mätningar av PM10, NO2 och bensen. Utvärdering för svenska tätorter och trafikmiljöer avseende år 2004 och 2005. SMHI Meteorologi, Nr. 137. Model validation of SIMAIRroad

16. NORTRIP- 2010 11 16 16 Results- streets and roads The uncertainty of modelling estimation is defined as the maximum deviation between the measured and calculated concentration levels for 90 % of individual monitoring points, without taking into account the timing of the events. The average annual modelling uncertainty for PM10 is defined as ±50% Comparison with EU Air Quality Directive targets MRPE annual mean=0.38 ; MRDE annual mean=0.24 MRPE 90-percentile =0.42 Fairmode http://fairmode.ew.eea.europa.eu/

17. NORTRIP- 2010 11 16 17 Improvements  Improve input data; study tyres, wintersanding / salting, street sweeping The computation of the sanding days is currently based on the meteorological parameters. This treatment could be improved by using the predictions of so-called road weather models. The cleaning of road surfaces is not considered in the present version of the model, although it can potentially have a major impact on the suspension emissions. The modelling of the influence of precipitation involves also challenges, especially in case of short-term, spatially limited and weak rain-and snowfall. Mari Kauthaniemi et al., 2010  Include snow in the model; experimental data from northern Sweden (Umeå) and Finland can help us here

18. NORTRIP- 2010 11 16 18 New parameters a) Studded tyres b) Vehicle speed c) CMA d) Street sweeping

19. NORTRIP- 2010 11 16 19 new parameters a) studded tyres Suggestion: include a new function g, where g is a normalised function for the road wear, use a linear relationship based on Norman and Johansson (2006) for dry conditions Typical values: 49 mg/ veh km g with 75% studded tyres1 g with 30% studded tyres0.54 g with 0 % studded tyres0.23

20. NORTRIP- 2010 11 16 20 http://simair.smhi.se/luftkvalitet/documents/meteorologi_134.pdf

21. NORTRIP- 2010 11 16 21 new parameters b) vehicle speed include a new function f, where V is vehicle speed and V ref is the reference vehicle speed What do we know about f ? Measurements in lab. (Gustafsson et al,2005): an increase by a factor of 4 for an increase in vehicle speed from 40 to 80 km/h for studded tyres. Omstedt et al. (2005) similar emission factors for a Swedish highway (110 km/h) as those for Hornsgatan( 40 km/h) Johansson et al.(2008): an increase in emission factors of about 20% from 40 km/h (streets inside Stockholm) to 80 km/h( Essingeleden) Similar results from other studies, emission factors for motorways are not extremely high compare to emission factors for city streets

22. NORTRIP- 2010 11 16 22 new parameters c) CMA What do we know about CMA? timescale,.. keep the surface wet for same days or include a new parameter similar to fq do some sensitivity analyses to find reasonable time scales

23. NORTRIP- 2010 11 16 23 new parameters d) street sweeping decrease the dust layer at selected time (probably rather different results due to selected time) check the timescale for the increase of the dust layer due to studded tyres do some sensitivity analyses

24. NORTRIP- 2010 11 16 24 Databases and models used by the SIMAIR system Gidhagen, L., Johansson, H. and Omstedt, G., 2009: SIMAIR - Evaluation tool for meeting the EU directive on air pollution limits. Atmospheric Environment, 43, 1029-1036. Omstedt,G., Andersson,S., Gidhagen, L. and Robertson, L., 2010. New model tools for meeting the targets of the EU Air Quality Directive: description, validation and evaluation of local air quality improvement due to reduction of studded tyre use on Swedish roads. Accepted ( Int. J.Environment and Pollution)