Volume 14, No. 5, August 2014, Pages 1372-1382 PDF(1.68 MB)
Mobile Particle and NOx Emission Characterization at Helsinki Downtown: Comparison of Different Traffic Flow Areas
Tero Lähde1,7, Jarkko V. Niemi2,3, Anu Kousa2, Topi Rönkkö4, Panu Karjalainen4, Jorma Keskinen4, Anna Frey5, Risto Hillamo5, Liisa Pirjola1,6
1 Department of Technology, Metropolia University of Applied Sciences, PO Box 4021, FI-00180 Helsinki, Finland
2 Helsinki Region Environmental Services Authority HSY, PO Box 100, FI-00066 HSY, Finland
3 Department of Environmental Sciences, University of Helsinki, PO Box 65, FI-00014 Helsinki, Finland
4 Department of Physics, Tampere University of Technology, PO Box 692, FI-33101 Tampere, Finland
5 Finnish Meteorological Institute, PO Box 503, FI-00101 Helsinki, Finland
6 Department of Physics, University of Helsinki, PO Box 64, FI-00014 Helsinki, Finland
7 Finnish Patent and Registration Office, PO Box 1140, FI-00101 Helsinki, Finland
- Mobile monitoring demonstrated large spatial and temporal variation in exhaust emissions.
- At high traffic flow (HTF) areas, exhaust emissions followed daily average heavy duty vehicle counts.
- Particles smaller than 40 nm (Np40) dominated the number size distribution at the HTF areas.
- At low traffic flow (LTF) areas, the proportion of Np40 was only 15% of that at the HTF areas.
- Changes in particle size distributions during dispersion from the HTF areas were observed.
A two weeks measurement campaign by a mobile laboratory van was performed at downtown Helsinki, Finland, in winter 2010. The characteristics of air pollutants such as fine particles in the size ranges of 7–40 nm (Np40) and 40–1000 nm (Np1000), black carbon (BC), fine particle mass (PM2.5), as well as gaseous compounds NO, NO2, NOx, CO and CO2 were studied. The statistical analysis showed that the air pollution conditions strongly depended on the traffic flow area; therefore, the street sections were classified as high traffic flow areas (HTF1-HTF4), low traffic flow areas (LTF1-LTF5), and urban background areas (BG1-BG3). Large variation of particle emissions was observed, and the momentary peak particle concentrations were 8 × 105 cm–3. At the HTF areas exhaust emissions followed clearly daily average heavy duty vehicle counts rather than the average daily vehicle counts. Higher correlation coefficients were found between CO2 and NO than between CO2 and Ntot. The dispersion studies indicated that the air pollution conditions strongly improved from high traffic flow areas to low traffic flow areas. Therefore, proper city planning and locating, for example, cycle tracks, schools and hospitals farther from busy city streets might significantly reduce exposure risk for humans.
Urban aerosols; Mobile samplers; Automotive exhaust; Air pollution.