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Temporal variations in heavy metal partitioning and loading in urban highway pavement sheet flow : Implications for in situ treatment design Sansalone, John J ; Glenn, Donald W III

By: Contributor(s): Publication details: Transportation Research Record, 2000Description: nr 1720, s. 100-11Subject(s): Bibl.nr: VTI P8167:1720Location: Abstract: In situ treatment design for pavement storm water runoff continues to pose unique challenges because of the unsteady nature of processes such as rainfall runoff, mobilization, partitioning, and delivery of heavy metals. Storm water from pavements and roadways transports dissolved, colloidal, and suspended solids in a heterogeneous mixture, and along with pH, alkalinity, traffic levels, and residence time, influences the partitioning of heavy metals. For effective in situ treatment design, an understanding of heavy metal partitioning and temporal wash-off during a rainfall runoff event is a prerequisite. This study investigates zinc (Zn), cadmium (Cd), copper (Cu), and lead (Pb) partitioning, cumulative loadings, and wash-off in storm water pavement sheet flow from a heavily traveled urban interstate pavement site. Results are presented for a series of eight rainfall runoff events at the instrumented site. Results from partitioning analysis (heavy metal mass transfer) between the dissolved and particulate-bound fractions indicate that Zn, Cd, and Cu masses are predominately dissolved in pavement sheet flow. Although a relatively insoluble heavy metal, Pb mass was also mostly dissolved. These high dissolved fractions can be attributed to low urban rainfall pH levels, relatively short pavement residence times for the pavement sheet flow, and low pavement runoff alkalinity. Plots of cumulative heavy metal mass as a function of elapsed runoff time clearly demonstrate that during all events the pavement sheet flow dissolved fractions dominated the particulate fractions for Zn, Cd, Cu, and Pb. As far as delivery, results also indicate that the dissolved masses for Zn, Cd, Cu, and Pb generally exhibited a "first flush" compared with their particulate masses. The design of in situ treatment systems or source control best management practices loaded by pavement sheet flow require data on partitioning and loading for effective treatment.
Item type: Reports, conferences, monographs
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In situ treatment design for pavement storm water runoff continues to pose unique challenges because of the unsteady nature of processes such as rainfall runoff, mobilization, partitioning, and delivery of heavy metals. Storm water from pavements and roadways transports dissolved, colloidal, and suspended solids in a heterogeneous mixture, and along with pH, alkalinity, traffic levels, and residence time, influences the partitioning of heavy metals. For effective in situ treatment design, an understanding of heavy metal partitioning and temporal wash-off during a rainfall runoff event is a prerequisite. This study investigates zinc (Zn), cadmium (Cd), copper (Cu), and lead (Pb) partitioning, cumulative loadings, and wash-off in storm water pavement sheet flow from a heavily traveled urban interstate pavement site. Results are presented for a series of eight rainfall runoff events at the instrumented site. Results from partitioning analysis (heavy metal mass transfer) between the dissolved and particulate-bound fractions indicate that Zn, Cd, and Cu masses are predominately dissolved in pavement sheet flow. Although a relatively insoluble heavy metal, Pb mass was also mostly dissolved. These high dissolved fractions can be attributed to low urban rainfall pH levels, relatively short pavement residence times for the pavement sheet flow, and low pavement runoff alkalinity. Plots of cumulative heavy metal mass as a function of elapsed runoff time clearly demonstrate that during all events the pavement sheet flow dissolved fractions dominated the particulate fractions for Zn, Cd, Cu, and Pb. As far as delivery, results also indicate that the dissolved masses for Zn, Cd, Cu, and Pb generally exhibited a "first flush" compared with their particulate masses. The design of in situ treatment systems or source control best management practices loaded by pavement sheet flow require data on partitioning and loading for effective treatment.

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