Vehicle-based road dust emission measurement -: Part II:: Effect of precipitation, wintertime road sanding, and street sweepers on inferred PM10 emission potentials from paved and unpaved roads

Testing Re-Entrained Kinetic Emissions from Roads (TRAKER) is a new technique to infer paved and unpaved road dust PM10 emission potentials based on particulate matter (PM) measurements made onboard a moving vehicle. Light scattering instruments mounted in front and behind the vehicle's tires measure the differential particle concentration of dust suspended by the vehicle's tire in contact with the road surface. Through empirical regressions relating the differential concentration (i.e. TRAKER signal) with the vehicle speed and the downwind flux of PM10 particles from the road, an equation is derived to infer the speed independent road dust emission potential from the measured TRAKER signal. Measurements from TRAKER offer a new perspective on the processes that affect road dust emissions. The system was used to investigate temporal changes in emission potentials from paved roads in both the winter and summer in the Treasure Valley in Southwest Idaho. During the 3-week wintertime sampling period, the residential road dust PM10 emission potential decreased by similar to50%. Summertime PM10 emission potentials were similar to those observed at the end of the winter sampling and showed no upward or downward trends. Wintertime unpaved road emissions increased consistently with the number of days since the last rainfall. Measurement of road dust emission potentials after road sanding on dry roads indicated a 75% increase in PM10 emissions after 2.5 h. This effect was short lived and emission potentials returned to their pre-sanding levels within 8 h of the sand application. Street sweeping with mechanical and vacuum sweepers was found to offer no measurable reduction in PM10 emission potentials. On several roads, the PM10 emission potentials actually increased immediately after vacuum sweeping. Long term effects of street sweeping on road dust emissions were not evaluated as part of this study and may offer some overall reduction in PM emissions from paved roads. (C) 2003 Elsevier Ltd. All rights reserved.