Mathematical Models Of Toxic Substances In Estuaries With Application to Kepone In The James River

The primary purpose of this research project is to develop the equations for modeling of toxic substances in estuaries and to demonstrate the application of these equations to present and anticipated problem areas. The present structure of the model is two-dimensional (longitudinal-vertical) interacting with lateral embayments which may operate in a steady-state or time-variable mode. The water column is segmented into two vertical layers to incorporate the typical estuarine circulation interacting with a bed which is also segmented into two layers - an active interfacial region and a deeper stationary bed. Adsorption-desorption kinetics are included which, in the case of the Kepone distribution of the James River, are assumed to be at equilibrium. Both steady-state, as well as time-variable, conditions were analyzed to calibrate the model to reproduce presently observed concentrations of Kepone. Sensitivity analyses and projections were conducted to estimate the time required to reduce the present level of contamination. In order to provide the necessary background for the development of the model, the various factors which affect the kinetic interactions of sorption and which affect the distributions of the suspended and bed solids are discussed in the introductory sections. This is followed by the development of a one-dimensional analysis, similar to the classical estuarine water quality equations in present use. This type of analysis may be used for preliminary assessment of a problem. An example of its application to the James River is included. A procedure of analysis to address the problem of organic chemicals in estuaries has been structured. The procedure involves a series of analytical and computational steps, relating to the fluid transport, the solids distribution and the concentrations of the organic chemical in the water and the bed. Each step involves the determination or assignment of the appropriate transport, transfer and/or reaction coefficients to analyze a particular constituent of the system. Equally important, each step provides the input for the computation of the next element, for which an additional coefficient is required. The analysis proceeds in a sequence of increasing complexity, each element yielding a calibration or validation of an essential constituent. The final output is the temporal or spatial distribution of the organic chemical. Specific recommendations are presented relating to further calibration and validation of these models in other estuaries. Particular attention should be directed to an assessment of the inputs, characterization of bed conditions and evaluation of kinetic interactions. It is planned to incorporate these factors in ongoing research.Grant No. R-80456