Civil Engineering Research Seminar: Concentrations, size distribution and transformation of nanoparticles in and outside a car cabin

When?

Thursday 9 August 2012, 13:00 to 14:00

Where?

40 AA 03

Open to:

Students, Staff

Speaker:

Pouyan Joodatnia

Admission price:

No charge

Abstract:

The total number of on-road fossil fuel driven vehicles in operation worldwide was recorded as more than 1 billion in 2010(Sousanis, 2011). A significant proportion of these vehicles are driven in major urban areas, releasing substantial amounts of nanoparticles (i.e. particles <300 nm in size). Exposure to road vehicle induced nanoparticles contributes towards a number of adverse health effects. This study aim to estimate the PNCs at multiple points (representing the driver and passenger positions) in the car cabin, as well as outside the cabin, during journeys in Guildford town. Other objectives include the study of particle transformation processes (i.e. coagulation, dry deposition, etc.) and their possible affect on PNCs and particle number distributions (PNDs) in the car cabin.

A fast response differential mobility spectrometer (Cambustion DMS50) has been deployed for measuring PNCs and PNDs in the 5–560 nm range at multiple points in and outside a car cabin. A total of 150 trips were made during morning (10-12 am) and afternoon (16-18 pm) hours, with corresponding average journey times of 7±2 and 10±3 minutes, respectively.  

Large variations of averaged PNCs at driver seat were observed, with the minimum and maximum being 2.37±1.22×104 cm–3 and 1.99±2.99×105 cm–3 for a morning and an afternoon journey, respectively. Four–point measurements in the cabin indicated slightly greater PNCs at the front seats (3.96×104  and 3.85×104 cm–3) compared to those measured at the rear seats (3.82×104 and 4.00×104 cm–3). The modest difference (~0.1%) between PNCs at the four locations indicates relatively well mixed distribution of nanoparticles in the car cabin. Average PNCs in the car cabin during winter period (5.87±4.06×104 cm–3) were 1.5 times larger than those measured in summer (3.85±3.07×104 cm-3). “In-Out” measurements indicate that average PNCs in the car cabin (2.72±1.03×104 cm–3) is 72% of those measured outside the cabin (3.75±1.62×104 cm‑3). Analyses of normalised mean PNDs at the four positions reveal negligible changes in the overall shape of the curves, suggesting the significant role of dilution process in the car cabin. Time scale analysis of particle transformation processes indicates that dilution process is the fastest process in the car cabin, suggesting the transformation processes (e.g. nucleation, coagulation, condensation) have minimal or no effect on particles in the car cabin, and therefore, the variation of PNCs in the car cabin is mainly due to dilution effects.

Bio: Pouyan started his PhD in august 2010 under supervision of Dr. Prashant Kumar and Prof. Alan Robins, after obtaining a BEng (Aerospace Engineering) from the University of Surrey. His research focuses on nanoparticle dispersion modelling both computationally and experimentally in transport microenvironments.