A platform for research: civil engineering, architecture and urbanism
A platform for research: civil engineering, architecture and urbanism
Inferring deposition velocities from changes in aerosol size distributions downwind of a roadway
Abstract Deposition velocities for particulate matter (PM) from road traffic in the Lake Tahoe basin were estimated with a mass-balance model and measurements using four size-specific PM profilers and meteorological instruments located at 15 m upwind and 5, 30 and 100 m downwind of major highway in the Lake Tahoe basin. Coarse PM (2.5–10 μm) concentration decreased exponentially with downwind distance from the highway. With tall aspen trees barrier, at 30 m and 100 m downwind, the PM10 mass concentrations decreased respectively to 51% and 11% from the observed concentrations at 5 m. Particles with diameters between 0.3 and 0.5 μm show almost a homogeneous distribution across the road indicating the smallest particles are unrelated to a road source. Calculated deposition velocities generally increased with particle size and ranged from <0.1 cm s−1 for particles of 1–2.5 μm diameter to 1.6 cm s−1 for particles >15 μm diameter, which is consistent with the Stokes settling velocities, implying the Stokes settling velocities may represent a reliable lower bound on the deposition rate. The wind speed and direction play important roles in determining the deposition velocities of road traffic induced particles. Higher PM concentrations were observed when strong onshore winds dominated during the daytime coupled with high traffic counts. Between late afternoon and early morning, offshore winds blew traffic induced PM towards the Lake, where they could deposit and impact the water clarity.
Research highlights ► Novel deposition velocity measurements were consistent with Stokes settling Vs. ► Coarse PM concentration decreased faster than fine PM with distance from road. ► Night offshore winds blew suspended road dust to Lake Tahoe, impact water clarity.
Inferring deposition velocities from changes in aerosol size distributions downwind of a roadway
Abstract Deposition velocities for particulate matter (PM) from road traffic in the Lake Tahoe basin were estimated with a mass-balance model and measurements using four size-specific PM profilers and meteorological instruments located at 15 m upwind and 5, 30 and 100 m downwind of major highway in the Lake Tahoe basin. Coarse PM (2.5–10 μm) concentration decreased exponentially with downwind distance from the highway. With tall aspen trees barrier, at 30 m and 100 m downwind, the PM10 mass concentrations decreased respectively to 51% and 11% from the observed concentrations at 5 m. Particles with diameters between 0.3 and 0.5 μm show almost a homogeneous distribution across the road indicating the smallest particles are unrelated to a road source. Calculated deposition velocities generally increased with particle size and ranged from <0.1 cm s−1 for particles of 1–2.5 μm diameter to 1.6 cm s−1 for particles >15 μm diameter, which is consistent with the Stokes settling velocities, implying the Stokes settling velocities may represent a reliable lower bound on the deposition rate. The wind speed and direction play important roles in determining the deposition velocities of road traffic induced particles. Higher PM concentrations were observed when strong onshore winds dominated during the daytime coupled with high traffic counts. Between late afternoon and early morning, offshore winds blew traffic induced PM towards the Lake, where they could deposit and impact the water clarity.
Research highlights ► Novel deposition velocity measurements were consistent with Stokes settling Vs. ► Coarse PM concentration decreased faster than fine PM with distance from road. ► Night offshore winds blew suspended road dust to Lake Tahoe, impact water clarity.
Inferring deposition velocities from changes in aerosol size distributions downwind of a roadway
Zhu, Dongzi (author) / Kuhns, Hampden D. (author) / Gillies, John A. (author) / Etyemezian, Vicken (author) / Gertler, Alan W. (author) / Brown, Scott (author)
Atmospheric Environment ; 45 ; 957-966
2010-11-03
10 pages
Article (Journal)
Electronic Resource
English
Computer modelling of downwind sails
| Online Contents | 1996
Size distributions and settling velocities of suspended particles from road and highway
| Springer Verlag | 2010