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Explore the occurrence and fate of traffic-generated nanoparticles in urban air, including formation, measurements, and atmospheric distribution. Understand the impact on urban mass distribution and potential health effects.
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Occurrence and fate of traffic generated nanoparticles in (urban) atmosphere Jorma Keskinen Tampere University of Technology (TUT)
Nucleation mode in vehicle exhaust • Nucleation mode in numerous studies, e.g. • Abdul-Khalek and Kittelson, 1999 • Particulates- project • … • Formed after tailpipe during dilution • Highly dependent on dilution conditions • Other affecting parameters:engine type, load, fuel sulphur, condensation sink, after-treatment, lubricating oil • Reproducible measurement? • Link to atmospheric distribution?
Exhaust measurement protocol: Particulates WP300 DT DR But: also tailpipe temperature effect
Totat number count of nanoparticles Particulates WP300
Mass (volume) of nanoparticles Particulates WP300
Ultrafine mode in atmosphere: • Bukowiecki et al., 2002: loading dock, roadway chase • Charron & Harrison, 2003: roadside • Hughes et al., 1998: urban background • Harrison et al.,1999; Shi et al., 1999: urban roadside • Kittelson et al., 2000; 2001: roadway chase • Longlay et al., 2003: road canyon • Morawska et al., 1999: roadway • Sturm 2003, Particulates D7: road tunnel, urban roadside • Vogt et al. 2003 EST: roadway chase • Weingartner et al, 1997: road tunnel • Woo et al., 2001: urban; nanoparticle events, not necessarily traffic • TUT, FMI & Stadia 2003, LIPIKA (urban roadside)
Roadside, winter (0 °C): ultrafine particles dominate LIPIKA study, Finland (TUT, FMI, Stadia; preliminary data): total number nucleation mode number
Occurrence and formation of nanoparticles • Solid evidence of nucleation mode in traffic-influenced locations • High variation in concentration • Dominates number concentration when present • Resemblance to emission measurements • Similar nucleation process takes place • Theoretical understanding only qualitative • Not H2SO4-water(-ammonia)? Pohjola et al., 2003
Fate of nanoparticles in atmosphere • Ultrafine mode can be included in atmospheric models • nucleation events also in atmosphere (Mäkelä et al., 1997) through secondary process • Ultrafine particle mode survives short range transport • Vignati et al., 1999; Pohjola et al., 2003 • dilution rapid enough to make coagulation marginal • quasi-equilibrium within 25 seconds
Overall picture of urban mass distribution (Hillamo, FMI) PM2.5 Liquid particles Traffic source Si NH4NO3 (NH4)2SO4 NaCl
Summary • Trafic generated (liquid) nanoparticles present in traffic influenced urban atmosphere • Nanoparticles survive time-scales relevant to urban mixing and short range transport • Atmospheric measurement convention is to include liquid particles • Should they be controlled? • Health effects? • Practical problems