Evaluation of a road dust suspension model for predicting the
concentrations of PM10 in a street canyon in Helsinki
Kauhaniemi M.1*, Kukkonen J.1, Härkönen J.1, Nikmo J.1, Kangas L.1, Omstedt G.2, Ketzel M.3,
Kousa A.4, Haakana M.1, Karppinen A.1
Finnish Meteorological Institute (FMI), Helsinki, Finland
Swedish Meteorological and Hydrological Institute (SMHI), Norrköping, Sweden
3
National Environmental Research Institute (NERI), Aarhus University, Roskilde, Denmark
4
Helsinki Region Environmental Services Authority (HSY), Helsinki, Finland
1
2
*Mari.Kauhaniemi@fmi.fi, Finnish Meteorological Institute, Air Quality Research
A mathematical model for predicting the road dust suspension emissions of PM 10 has been
refined and evaluated. The model, developed by Omstedt et al. (2005), takes into account
particles generated by the wear of road pavement and traction sand, as well as the parameters
that control the suspension of road dust particles into the air, e.g., the street surface moisture.
The model predicts a suspension emission factor that is used together with the direct emission
factor.
The suspension emission model was used in conjunction with the street canyon model OSPM
(Operational Street Pollution Model; Berkowicz, 2000). The predicted PM10 concentrations were
evaluated against results of a measurement campaign conducted in a street canyon, Runeberg
Street, in Helsinki from January to May in 2004. The studied street segment of the Runeberg
Street is approximately north-south oriented (6o - 186o), 24 m wide, and surrounded by 23 m
high buildings on both sides (Kukkonen et al., 2001).
PM10 was measured at 4 m height at a street canyon monitoring station, and at roof level on a
building at an urban background air quality station of Kaisaniemi, about 1.4 km south-east of
Runeberg Street. Meteorological measurements (temperature, humidity, precipitation, global
radiation, and total cloud cover) were made in the Kaisaniemi park, and at the roof top at
Runeberg Street (wind speed and direction). The traffic measurements were conducted in
Runeberg Street next to the air quality monitoring station. The direct PM2.5 exhaust emission
factors based on the nationally conducted laboratory measurements, but emissions for the
wear of vehicle components were not considered as those are not yet available for Finland.
The predicted hourly and daily PM10 concentrations agreed fairly well with the observed data.
The short-term PM10 concentrations were predicted on the average fairly accurately by the
presented modelling system; for instance, the index of agreement (IA) for the hourly
concentrations was 0.83. The main challenges for future studies associated with the
suspension modelling are (i) the cleaning processes of the streets that are currently not
included in the model, (ii) the uncertainties in estimation of the sanding days, and (iii) the
evaluation of the influence of precipitation, especially in case of short-term, spatially limited
and weak rain- or snowfall.
Berkowicz R., 2000. OSPM - A Parameterised Street Pollution Model. Environmental Monitoring
and Assessment Vol. 65, pp. 323-331.
Kukkonen, J., Valkonen, E., Walden, K., Koskentalo, T., Aarnio, P., Karppinen, A., Berkowich,
R., and Kartastenpää, R. , 2001. A measurement campaign in a street canyon in Helsinki and
comparison of results with predictions of the OSPM model, Atmos. Environ., 35, 231-243.
Omstedt, G., Bringfelt, B., Johansson, C., 2005. A model for vehicle-induced non-tailpipe
emissions of particles along Swedish roads. Atmospheric Environment, 39, pp. 6088-6097.