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SUMMARY:High Temporal Resolution Measurements of Roadside Particle Size   
 Distributions and Their Implications for Exposure - Dr Alison Tomlin\, Lee
 ds University
DTSTART:20090115T133000Z
DTEND:20090115T143000Z
UID:TALK16133@talks.cam.ac.uk
CONTACT:8442
DESCRIPTION:High time resolution\, size segregated studies of ultrafine pa
 rticle  \nnumber concentrations (PNC) were performed at two UK roadside  \
 nlocations using a DMS500 particle spectrometer including sampling with  \
 nand without a thermodenuder. Intercomparisons between the DMS500\, an  \n
 SMPS and a CPC\, indicate that the SMPS can underestimate PNC due to  \nth
 e transient nature of excursions in concentrations and the longer  \nscan 
 time of the instrument. Short duration transient periods of high  \nnumber
  concentrations made considerable contributions to hourly  \naverage PNC. 
 The transient nature of changes in PNC potentially  \naffects the type of 
 exposure experienced in the roadside environment\,  \nas well as indoor ou
 tdoor exchange. The transient shifts were  \ndominated by Aitken mode part
 icles during high traffic periods\, with  \nthe Aitken mode associated wit
 h soot based diesel emissions. The  \nthermodenuder studies indicated the 
 presence of highly volatile liquid  \ndroplets in the nucleation mode whic
 h were lost on heating. Nucleation  \nmode particle numbers were shown to 
 be highly dependant on atmospheric  \nand traffic conditions as well as pr
 e-existing particle surface area.  \nThe transient nature of the modal con
 centrations and its significance  \nfor human exposure in urban areas will
  be disucssed as well as issues  \nrelated to suitable particle concentrat
 ion metrics.\n
LOCATION:Lecture Room 6\, Engineering Department
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