Study finds soot particle morphology significantly affected by driving conditions and vehicle age, type
An analysis of the morphological and mixing properties of soot particles collected at six different cloverleaf freeway on-ramps in Southern Michigan by researchers at Michigan Technological University found that driving conditions, vehicle age and vehicle type have significant influence on the morphology of soot particles. The study appears in the ACS journal Environmental Science & Technology
The researchers investigated 5,738 single particles using 2D images from scanning electron microscopy; of those particles, 3,364 were soot. Findings included:
The relative abundance of soot particles shows a positive association with traffic density (number of vehicles per minute).
A classification of the mixing state of freshly emitted soot particles shows that most of them are bare (or thinly coated) (72%) and some are partly coated (22%).
The fractal dimension of soot particles (one of the most relevant morphological descriptors) varies from site to site, and increases with increasing vehicle specific power that represents the driving/engine load conditions, and with increasing percentage of vehicles older than 15 years.
Swarup China, Neila Salvadori, and Claudio Mazzoleni (2014) “Effect of Traffic and Driving Characteristics on Morphology of Atmospheric Soot Particles at Freeway On-Ramps,” Environmental Science & Technology doi: 10.1021/es405178n