Models of Sorptive Toxic Substances in Freshwater Systems. I: Basic Equations

Abstract
Equations that define the steady‐state distribution of solids and sorptive chemicals in freshwater systems are developed. Instantaneous equilibrium between the dissolved and particulate components of the compound is assumed for various partitioning functions. Solutions are developed for both solids‐dependent and solids‐independent partitioning. The exchange of the suspended and bed solids, in conjunction with the transfer and kinetic pathways of the dissolved and particulate components of the chemical, is taken into account. The relationships among these variables are successively reduced to a single differential equation, an analytical solution of which is developed. The exchange coefficients of both the dissolved and particulate components of the chemical between the water column and bed are key factors, for which guidelines are developed. The equations are developed for batch systems, which provide the basis for the subsequent developments in freshwater systems.