The behaviour of traffic produced nanoparticles in a car cabin and resulting exposure rates

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• 作者：Pouyan Joodatnia^a ; Prashant Kumar^a ; ^b ; ^{P.Kumar@surrey.ac.uk} ; ^{Prashant.Kumar@cantab.net} ; Alan Robins^b
• 关键词：Car cabin exposure ; Nanoparticles dispersion ; Number and size distribution ; Ultrafine particles ; Vehicle emissions
• 刊名：Atmospheric Environment
• 出版年：2013
• 出版时间：February, 2013
• 年：2013
• 卷：65
• 期：Complete
• 页码：40-51
• 全文大小：1605 K

文摘

The aim of this study is to assess particle number concentrations (PNCs) and distributions (PNDs) in a car cabin while driving. Further objectives include the determination of the influence of particle transformation processes on PNCs, PNDs and estimation of PNC related exposure. On-board measurements of PNCs and PNDs were made in the 5-560?nm size range using a fast response differential mobility spectrometer (DMS50), which has a response time of 500?ms. Video records of the traffic ahead of the experimental car were also used to correlate emission events with measured PNCs and PNDs. A total of 30 return trips was made on a 2.7?km route during morning and evening rush hours, with journey times of 7?¡À?2 and 10?¡À?3?min, respectively. The average PNC for the set of morning journeys, 5.79?¡À?3.52?¡Á?10⁴?cm^?3, was found to be nearly identical to the average recorded during the afternoon, 5.95?¡À?4.67?¡Á?10⁴?cm^?3. Average PNCs for individual trips varied from 2.42?¡Á?10⁴?cm^?3 to 2.18?¡Á?10⁵?cm^?3, mainly due to changes in the emissions affecting the experimental car (e.g. when the experimental car was following another vehicle). The largest one second averaged PNC during a specific event, 1.85?¡Á?10⁶?cm^?3, was found to be over 30-times greater than the overall average of 5.87?¡À?4.06?¡Á?10⁴?cm^?3. Correlation of video records and concentration data indicated that close proximity to a preceding vehicle led to a clear increase in PNCs of freshly emitted nucleation mode particles. The evolution of normalised PNDs demonstrated that dilution was the dominant transformation process in the car cabin. The deposition of inhaled particles in the lung was estimated on the basis of either the size-resolved distribution or the total PNC. In general, the two methods yielded similar results but differences up to 30 % were noted in some cases, with the latter method giving the lower values. Overall, the results reflect the importance of size-resolved measurements for deriving accurate evaluations of exposure rates, as well as identifying emissions from nearby traffic as the cause of short-term elevations of PNCs and hence dose rates.