Jorma Keskinen Tampere University of Technology (TUT) Occurrence and fate of traffic generated nanoparticles in (urban) atmosphere

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 DTDR 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 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 H 2 SO 4 -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 NaCl Si NH 4 NO 3 (NH 4 ) 2 SO 4 Traffic source Liquid particles

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