Contribution of the road traffic to air pollution in the Prague city (busy speedway and suburban crossroads)

Two measurement campaigns near busy freeway and suburban crossroad (different traffic intensity) were carried out in Prague city. Both of the two traffic related campaigns were supported with simultaneous measurements at suburban background site to compare measured values with corresponding city background. Extensive set of aerosol instrumentation was used during both campaigns at both measurement sites. Two aerosol spectrometer sets (SMPS and APS) were used to monitor aerosol particle number size distribution. Two BLPI provided information about mass size distribution and chemical composition of collected size resolved aerosol samples. The crossroad campaign was also supported by two EC/OC field analysers providing information about elemental and organic carbon concentrations. Consequent chemical analysis of collected size resolved samples comprised of ion chromatography (water soluble ions), PIXE (elements) and RBS (carbon). Results obtained from spectrometers and BLPIs showed that the main contribution of traffic in ultrafine size range can be attributed to direct exhaust emissions, while the coarse fraction was dominated mainly by regional background aerosol with small traces of brake and tyre abrasion as well as the resuspension of the road dust. Chemical analysis demonstrated that most of the water soluble ions can be found in fine fraction of mass distribution and mostly comes from regional background and long range transport. Most of major elements were found in coarse fraction of mass size distribution and it can be attributed to three different sources: abrasion of different vehicle parts (Fe, Cu, Mn and Zn), resuspension of the road dust (Si, Al, Ca) and long range transport or regional background (Ca and K). Elemental carbon concentration (diesel engine emissions) was found to be proportional to traffic intensity.