1-48 flow rates, in combination with the associated suspended solids load, lead to the advection of both dissolved and sorbed chemicals along with the water. The effect may differ from one location to another. For example, the analysis performed by Suszkowski indicates that, in the case of the <strong>Passaic</strong> <strong>River</strong>, there is a net movement (i.e., the difference between upstream and downstream transport) of suspended solids in the downstream direction towards <strong>Newark</strong> <strong>Bay</strong>. (Note that it does not necessarily follow that the net movement of chemicals will be in the same direction as the net movement of solids, as the dissolved and sorbed chemical concentrations in the surface and bottom layers also need to be considered.) Should this finding be confirmed by future data and modeling analyses, it can be expected to have important implications to the evaluation of the rates of chemical exchange between the <strong>Passaic</strong> <strong>River</strong> and <strong>Newark</strong> <strong>Bay</strong>. In contrast to the <strong>Passaic</strong> <strong>River</strong> there is a net flux of solids from <strong>Newark</strong> <strong>Bay</strong> into the Hackensack <strong>River</strong> (Suszkowski, 1978; Pence, 2004). This finding also has important implications to the net movement of chemicals between these two regions and should be confirmed in subsequent analyses. Another important aspect of solids transport in <strong>Newark</strong> <strong>Bay</strong> that was quantified by Suszkowski was the high rates of sediment accumulation in a number of localized areas, including Port <strong>Newark</strong> and in the channel north of Shooters Island. He attributed the deposition of solids in these regions to factors that were largely site-specific in nature. It will be important for the model to properly simulate the accumulation of solids in these localized areas, in part because these are areas where maintenance dredging takes place. While not a natural process, maintenance dredging will serve as a sink of both solids and chemicals in <strong>Newark</strong> <strong>Bay</strong>, as it leads to removal of mass from the system. It is expected that a relatively high-resolution model grid will be required to properly simulate the observed high rates of deposition in these localized areas. Use of a high-resolution grid will improve the level of detail that can be represented by both the hydrodynamic and sediment transport models, and as such, should enhance their predictive abilities. This is important since the chemical fate model will use these results to quantify the associated chemical transfers. The significance of removal of dredged material as a sink of chemicals in these areas remains to be evaluated. Sediment transport also has an important bearing on chemical fate via the manner in which the process of burial is represented (Berner, 1980; Boudreau, 1997; Boudreau and Jorgensen, 2001). Sediments typically have a surficial layer where particle mixing occurs as a result of reworking by benthic organisms (bioturbation) and by physical mixing processes related to settling and resuspension. A number of approaches may be used to evaluate the depth over which mixing occurs, including but not necessarily limited to biological surveys of the benthic community, sediment profile imaging, and consideration of radionuclide data. Mixing alone results in the transfer of chemicals along a concentration gradient, from areas of high to low concentration. It is for this reason that historically contaminated sediments, even if buried by the accumulation of clean solids long after the chemical source has been eliminated, may continue to exhibit residual
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