Accretion and Partitioning of Heavy Metals Associated with Snow Exposed to Urban Traffic and Winter Storm Maintenance Activities. II

Compared to storm water runoff, urban roadway snow exposed to traffic and winter maintenance practices has a much greater capacity to accumulate and retrain heavy metals and other anthropogenic constituents. Heavy metals once released in the environment are not degraded and partition between the dissolved and particulate-bound fractions. Residence time, solid loadings, alkalinity, hardness, and pH influence partitioning. Accretion and partitioning of Pb, Cu, Cd, Zn, Al, Ca, Na, Mg, and Fe from a series of urban highway sites in Cincinnati, Ohio, are compared to temporal accretion trends at a control site removed from the highway environment. Results from partitioning analysis indicate that Pb, Cu, Cd, Zn, Al, Mg, and Fe were all highly particulate bound, while Na and Ca were mainly dissolved for all highway sites. Partition coefficients for most heavy metals in snowmelt ranged from 103 to 106 L/kg. Concentrations for Pb, Cu, Cd, Zn, and cyanide were orders of magnitude higher than at the control site and exceeded storm water runoff concentrations by one to two orders of magnitude. For residuals analyses, the specific surface area generally increased with decreasing particle size while the predominance of total surface area (SA) was associated with the medium to coarser size fractions. Heavy metal mass trends followed similar general trends to that of the SA. Characterization of accretion and partitioning of these metals is a necessary first step toward development of management and treatment strategies designed to address urban snow pollution.