Characterization of Road Dust Emissions in Milan: Impact of Vehicle Fleet Speed

Abstract

Road dust suspension is an increasing concern in terms of being a source of atmospheric particulate matter (PM) in cities, due to its toxicity and the lack of knowledge on emission estimates, impact and mostly with respect to measures to control or mitigate it. Both technological and policy measures have been proposed, but their application is limited by the gap of knowledge on their effectiveness in the real world. This study analyses the real-world emission factors of road dust at ten sites in the city of Milan (Italy), with an emphasis on the impact of different fleet speeds at one particular road. PM 10 emission factors were estimated by means of both the EPA method (based on silt loadings) and the vertical profile of dust deposition. Road dust silt loadings varied within 0.006-0.066 g m -2 , with the highest loadings found at sites affected by construction works. Typical urban roads were found to have fleet-averaged emission factors within 13-32 mg vehicle -1 km -1 , which is in the central range of the literature values in Europe. The emission factors estimated by means of the vertical profile approach were within 19-26 mg VKT -1 , which agree quite well with the EPA method if corrected for speed. In fact, a power-law relation was found between fleet speed and emission factor estimates, with an exponent close to 1.5 for speeds within 36-57 km h -1 . These results suggest that the limitation of the maximum traffic speed can be effective for mitigating road dust emissions in cities.

Geochemical, Mineralogical and Morphological Characterisation of Road Dust and Associated Health Risks

“…Moreover, the joints between granite cubes filled with soil may have constituted an additional source of resuspendable dust. Following the USEPA methodology, PM 10 emission factors for typical urban roads in Milan within 13-32 mg veh −1 km −1 were recently reported, which were found to be in the central range of the literature values in Europe [28]. Based on micro-scale vertical profiles of the deposited mass, PM 10 emission factors from 5.4 to 9.0 mg veh −1 km −1 were obtained at inner-roads of Paris, whilst a higher value was estimated for the ring road (17 mg −1 veh −1 km −1 ) [16].…”

A Review of Road Traffic-Derived Non-Exhaust Particles: Emissions, Physicochemical Characteristics, Health Risks, and Mitigation Measures

“…PM 10 resuspension was between 13 and 32 mg·km –1 ·veh –1 for 10 sites in Milan, Italy. 117 A CO 2 dilution approach determined average vehicle fleet resuspension EFs for dry (4–11 mg·km –1 ·veh –1 ) and moist/wet road surface conditions (2–7 mg·km –1 ·veh –1 ) on a congested London road, UK. 26 The high variability is a result of geographical differences and possibly sampling, measuring and emission factor estimation methods.…”

Tailpipe and Nontailpipe Emission Factors and Source Contributions of PM10 on Major Freeways in the Los Angeles Basin

“…Similarly, the vehicle-specific emission factors for resuspended dust showed high variability in the literature, spanning from LDV and HDV values of 1.1 ± 0.6 mg km −1 veh −1 and 172 ± 7 mg km −1 veh −1 , respectively, 81 to 47 ± 39 mg km −1 veh −1 for LDVs and 260 ± 220 mg km −1 veh −1 for HDV. 45 This observation is the result of environmental and roadway-related factors affecting the resuspended dust source, including the vehicle weight, 82 traffic speed, 83 roadway conditions, 26 street cleaning frequency, 84 wind speed, and wind direction. 30 Overall, the average resuspension emission factor (30.15 mg km −1 veh −1 ) derived from the previously mentioned studies agrees with our average freeway emission factor (31.20 ± 7.22 mg km −1 veh −1 ).…”