Characteristics of traffic-induced fugitive dust from unpaved roads

The characteristics of fugitive dust emitted from vehicles traveling on unpaved dirt roads were measured using a suite of instruments including a real-time fugitive dust sampler. The fugitive dust sampler is formed from a combination of a large particle inlet and an optical particle spectrometer that reports particle sizes from 6 to 75 mu m. The large particle inlet permits the sampling of particles up to 75 mu m with only a moderate dependence of sampling efficiency on wind-speed. Measurements made with the sampler showed that particles as large as similar to 50 mu m were suspended from vehicular movement on the dirt roads, with the mode of the fugitive dust particle number size distribution similar to 2 mu m, while the mass distribution mode was similar to 7 mu m. A comparison of the fugitive dust sampler measurements with those made using standard PM instruments showed that the conventional instruments have a wind-direction bias that can result in under-sampling of large particles. The current measurements suggest that particles suspended from dirt roadways are of importance for local air quality within the near-road environment.