PHYSICAL AND CHEMICAL CHARACTERISTICS OF URBAN SNOW RESIDUALS GENERATED FROM TRAFFIC ACTIVITIES

摘要

Urban transportation activities generate a wide gradation of anthropogenic solids with varying physical and chemical properties. These solids accumulate in urban highway snow and remain as residual deposition material after the melting and recession of the snow from the pavement shoulder. This study analyzed the physical characteristics of these residuals and the associated heavy metals for 10 urban highway sites located throughout metropolitan Cincinnati. Results from the residuals analyses indicate that for all sites particle gradations ranged from greater than 5000-μm to less than 25-μm with a mean d_(50) of 1225-μm. Specific gravity (ρ_(sg)) of residual solids ranged from 2.5 to 3.2 as evaluated for intervals across the gradations, with the lower specific gravity associated with particles less than 100-μm. For each gradation, specific surface area (SSA) generally increased with decreasing particle size while the predominance of total surface area (SA) was associated with the coarser size fractions. Cumulative analysis for Pb, Cu, Cd and Zn associated with snow residuals indicated that more than 50% of the heavy metal mass was associated with particles greater than 250-μm and more than 80% was associated with particles greater than 50-μm. Results provide guidance for management of urban snow residuals and design of treatment strategies focused on these residuals.