Mathematical formulations for contaminant partitioning in rivers

摘要

This mathematical model for contaminant transport in rivers provides a preliminary assessment of the contaminant mass and concentration using environmental partitioning. First, the model uses the advection-dispersion equation to model the river flow and contaminant transport in the water. Second, the model uses compartment modeling to partition the contaminant mass into water, sediment, bed sediment, air, fish, vegetation and free product environmental compartments. Finally, the model calculates contaminant concentration in each environmental compartment. As long as this approach is applied with an understanding of its assumptions and limitations, it can be very useful as a preliminary assessment model for contaminant transport in rivers. The purpose of developing this approach was to provide a simple mathematical model that accounts for the time-varying partitioning of contaminant concentration at a given location along the river. This approach is intended to be used as part of the Multimedia Environmental Pollutant Assessment System (MEPAS). Currently MEPAS, and other multimedia contaminant environmental transport and exposure risk assessment methodologies, assumes that once the contaminant enters the water, it is instantaneously and completely dissolved. This assumption, that the contaminant is only present in the dissolved phase tends to over predict water contaminant levels. This approach is intended to address the partitioning of contaminants into environmental compartments in addition to the water column.