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Aerosol particles re-suspension and emission from road surface on road measurement with a mobile laboratory

Aerosol particles re-suspension and emission from road surface on road measurement with a mobile laboratory. Tareq Hussein 1,2 , Hans Karlsson 1 , Christer Johansson 1 , and Hans-Christen Hansson 1 1 Stockholm University, Department of Applied Environmental Science

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Aerosol particles re-suspension and emission from road surface on road measurement with a mobile laboratory

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  1. Aerosol particles re-suspension and emission from road surfaceon road measurement with a mobile laboratory Tareq Hussein 1,2, Hans Karlsson 1, Christer Johansson 1, and Hans-Christen Hansson 1 1 Stockholm University, Department of Applied Environmental Science SE-10691, Stockholm, Sweden 2 University of Helsinki, Department of Physical Sciences P. O. Box 64, 00014 University of Helsinki, Finland

  2. Background • Many cities in the Nordic countries have severe problems meeting the limit values for PM10 during the late winter and early spring periods (February – May). • The main reason are • Studded tyres that increase the wear of road surfaces. • Traction sanding. • Meteorological parameters and road surface conditions. • For example, in Stockholm, more than 90% of the PM10 emissions during that period are due to non-tailpipe emissions of mechanically generated particles; less than 10% of the PM10 emissions are due to vehicle exhaust particles due to road traffic.

  3. Quantification of the processes In practice, the day-to-day emissions of none-tailpipe emissions are difficult to predict because it depends on meteorological factors as well as factors associated with the road surface and vehicles. • Extensive field measurements in real life situations  EMMA • Laboratory measurements under controlled conditions  VTI • Validated model tools  Omstedt et al. (2005)

  4. EMMA mobile laboratory The EMMA mobile laboratory owned by the ITM consists of • three dust tracks: one installed in front of the van and two are installed behind the front wheels • a GRIMM instrument to measure the size distribution between 0.25–30 mm • a GPS system.

  5. Measurement sites Road network in Stockholm area and we test: • Over different road surfaces with different asphalt types that are commonly used in Stockholm area • Studded versus friction and summer tyres. • We performed several measurement campaigns on selected main roads within Stockholm area. • For the comparison purpose, we performed similar measurements during the summer period when studded tyres are no longer in use. However, the measurements with the EMMA were limited for periods when the road surfaces were dry. Therefore, the measurement campaigns were dependent on weather conditions.

  6. Results, so far, • Dust tracks measurements: • During the early spring: Studded / Friction = 2–4 VTI lab APS [0.523-18.47 mm]: Studded/Friction = 60–100 [30–70 km/h] • During the late summer: Studded / Summer = 5–20 • During the summer time: Summer(left) / Summer(right) = ~1 Particle concentrations behind summer tires were almost similar to the background concentration measured in front of the van.

  7. Studded tyres The particle number size distributions as measured behind the studded tyres were characterized with a distinguished coarse mode (GMD 2–3 mm). The number concentration of this mode was about two order of magnitudes compared to the background condition. Number dM/dlog(Dp) was generated from dN/dlog(Dp) with r = 2.8 g/cm3 Mass

  8. Comparison between real world (EMMA) and the VTI laboratory measurements EMMA: Studded tyres on three road sections, driving speed 60–70 km/h. VTI: Studded tyres, quartzite asphalt, driving speed 30–70 km/h. Mass-size-distributions

  9. Summer tyres We did not observe a clear difference in the particle number size distributions measured behind the summer tyre and the background conditions. Number dM/dlog(Dp) was generated from dN/dlog(Dp) with r = 2.8 g/cm3 Mass

  10. Conclusions • It is evident that studded tyres have a significant contribution to the PM concentration. This effect is a combination between • re-suspension of road dust • direct emissions of aerosol particles due to the road wear • It seems that the summer tires have minor effects on road surface wear. • Friction tyres seem to have enhanced re-suspension of road dust in comparison to the summer tyres.

  11. Acknowledgement This work is financed by the Swedish Road Administration. The post-doctor position for Tareq Hussein at ITM was partly supported by the European Science Foundation (ESF) within the Interdisciplinary Troposphere Research: from the Laboratory to Global Change (INTROP). We also acknowledge funding from the European Network of Excellence ACCENT within the Aerosols exchange program.

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