Atmos. Chem. Phys. Discuss., 12, 20135-20180, 2012
© Author(s) 2012. This work is distributed
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Hourly elemental concentrations in PM2.5 aerosols sampled simultaneously at urban background and road site
M. Dall'Osto1, X. Querol1, F. Amato2, A. Karanasiou3, F. Lucarelli4, S. Nava4, G. Calzolai4, and M. Chiari4
1Institute of Environmental Assessment and Water Research, Spanish Research Council (IDAEA-CSIC), c/Jordi Girona 18–26, 08034 Barcelona, Spain
2TNO, Built Environment and Geosciences, Dept. of Air Quality and Climate, Utrecht, The Netherlands
3Centre for Research in Environmental Epidemiology (CREAL), Barcelona, Spain
4National Institute of Nuclear Physics (INFN) and Physics Department, University of Florence, via Sansone 1, 50019 Sesto Fiorentino, Italy

Abstract. Hourly-resolved aerosol chemical speciation data can be a highly powerful tool to determine the source origin of atmospheric pollutants in urban Environments. Aerosol mass concentrations of seventeen elements (Na, Mg, Al, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Sr and Pb) were obtained by time (1 h) and size (PM2.5 particulate matter <2.5 μm) resolved Particle Induced X-ray Emission (PIXE) measurements. In the Marie Curie FP7-EU framework of SAPUSS (Solving Aerosol Problems by Using Synergistic Strategies), the unique approach used is the simultaneous PIXE measurements at two monitoring sites: urban background (UB) and a street canyon traffic road site (RS). Elements related to primary non exhaust traffic emission (Fe, Cu), dust resuspension (Ca) and anthropogenic Cl were found enhanced at the RS, whereas industrial related trace metals (Zn, Pb, Mn) were found at higher concentrations at the more ventilated UB site. When receptor modelling was performed with positive matrix factorization (PMF), nine different aerosol sources were identified at both sites: three types of regional aerosols (secondary sulphate (S) – 27%, biomass burning (K) – 5%, sea salt (Na-Mg) – 17%), three types of dust aerosols (soil dust (Al-Ti) – 17%, urban crustal dust (Ca) – 6%, and primary traffic non exhaust brake dust (Fe-Cu) – 7%), and three types industrial aerosol plumes-like events (shipping oil combustion (V-Ni) – 17%, industrial smelters (Zn-Mn) – 3%, and industrial combustion (Pb-Cl) – 5%). The validity of the PMF solution of the PIXE data is supported by strong correlations with external single particle mass spectrometry measurements. Beside apportioning the aerosol sources, some important air quality related conclusions can be drawn about the PM2.5 fraction simultaneously measured at the UB and RS sites: (1) the regional aerosol sources impact both monitoring sites at similar concentrations regardless their different ventilation conditions; (2) by contrast, local industrial aerosol plumes associated with shipping oil combustion and smelters activities have a higher impact on the more ventilated UB site; (3) a unique source of Pb-Cl (associated with industrial combustion emissions) is found a to be the major (82%) source of Cl in the urban agglomerate; (4) PM2.5 traffic brake dust (Fe-Cu) is mainly primarily emitted and not resuspended, whereas PM2.5 urban crustal dust (Ca) is found mainly resuspended by both traffic vortex and sea breeze; (5) urban dust (Ca) is found the aerosol source most affected by land wetness, reduced by a factor of eight during rainy days and suggesting that wet roads may be a solution for reducing dust concentrations in road sites, far more effective than street sweeping activities.

Citation: Dall'Osto, M., Querol, X., Amato, F., Karanasiou, A., Lucarelli, F., Nava, S., Calzolai, G., and Chiari, M.: Hourly elemental concentrations in PM2.5 aerosols sampled simultaneously at urban background and road site, Atmos. Chem. Phys. Discuss., 12, 20135-20180, doi:10.5194/acpd-12-20135-2012, 2012.
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