Publication Summary

Fate and transport mechanisms were evaluated for copper, PCBs, and PBDEs in order to understand the linkages between their initial release in the environment and their presence in environmental media. Evaluation of copper focused on releases from roofs and dust from brake pads and tires along the surface water pathway. Examination of case studies emphasized that understanding releases, partitioning, and transport of copper in urban streams is basin-specific and requires data more specific than land use/land cover. For PCBs and PBDEs, attenuation processes will become clearer when more ambient concentration measurements are made in urban waters.

Appendix A tables, A1 through A14, are linked in the data supplement above.

Environmental releases of contaminants of concern were categorized according to similar pathways taken to Puget Sound, attenuation processes occurring along the pathway and management strategies that would control releases. Releases were first grouped into two major categories according to the extent to which the releases were initially constrained by physical infrastructures, and then by initial modes of release.

The primary contributions of the U.S. Geological Survey to the Puget Sound Toxics Loading Analyses are to: (1) propose a methodology for evaluating fate and transport mechanisms of transport for copper, polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs), and (2) conduct case studies of these three chemicals using proposed methodology. The case study on copper focused on releases from roofs and dust from brake pads and tires along the surface water pathway. The review of the literature suggests that the degree of attenuation of copper in urban basins is highly site specific and depends on such factors as how rainwater is routed from the gutters of buildings, the nature of roads (road gutters and shoulder types), the type and efficiency of stormwater infrastructures and the nature of stream riparian and hyporheic zones.

The estimated releases of total copper within the Mill and Thornton Creek basins were compared to the copper loadings discharging from the basins during 35 storm events. About 3% of the copper estimated to have been released in the Mill Creek basin was discharged by Mill Creek. Up to 7% of the copper estimated to have been released in the Thornton Creek basin was discharged by Thornton Creek. The difference in attenuation between these two basins is a result of differing geographies, riparian zones and stormwater infrastructures. These copper case studies emphasize that understanding the releases, partitioning and transport of copper in urban streams is basin specific and requires data more specific than land use/land cover.

PCBs and PBDEs in urban waters only recently have been analyzed at ambient concentrations of ng/L and pg/L levels, respectively. The partitioning between dissolved and particulate phases have been determined in a few research projects. A better understanding of attenuation processes will occur when concentrations are measured at ambient levels in urban waters as part of longitudinal studies.