Airborne particle number profiles, particle mass distributions and particle-bound PAH concentrations within the city environment of Basel: an assessment as part of the BRISKA Project

A project aimed at assessing a variety of particulate indicators was carrie d out at three locations in the city of Basel within the score of the Basel Air Quality Risk Assessment Project (BRISKA). Size specific particle numbe r concentrations (0.018-0.421 mu m), particle mass distributions (0.04-49 m u m), and particle-bound polycyclic aromatic hydrocarbon (pPAH) concentrati ons were measured. Locations differed in housing and traffic characteristic s. For particle number and pPAH concentrations, one separate continuous 27- 28-h measurement was performed at each location. Simultaneously, non contin uous measurements assessing the particle mass distribution were performed. Distinct day profiles corresponding to the diurnal traffic profile were obs erved for absolute particle numbers and pPAH concentrations. The number of ultrafine particles as well as pPAH concentrations were more closely correl ated to the number of heavy duty vehicles (r = 0.67-0.86 and 0.85-0.90), re spectively, than to the number of light duty vehicles (r = 0.43-0.59 and 0. 64), respectively. The highest particle number concentrations were found in the ultrafine particle mode (< 0.1 mu m) averaging between 82-87% of the t otal particle numbers < 0.421 mu m while the accumulation mode (0.1-2.8 mu m) made up for most of the particle mass (mean > 82%), For size specific ab solute mass concentrations, the highest concentrations were generally found in the early morning and evening hours. The mass distribution within the a ccumulation mode differed from rush hour episodes, in between rush hour epi sodes and a lawn mowing episode. (C) 2000 Elsevier Science Ltd. All rights reserved.