Mathematical Models Of Toxic Substances In Estuaries With Application to Kepone In The James River
Date
1981-02
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Abstract
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.
Description
Keywords
Mathematical Models, Toxic Substances, Estuaries, James River