Modelling the transport of reacting chemical contaminants in natural streams

Abstract

A physicochemical model for simulating the transport and speciation of chemical reactants in streams is discussed, in which the reactants are considered conservative with respect to the flowing waters. The computer program for the model, whose theoretical basis has been described previously. uses a convolution integral technique to solve a modified form of the one-dimensional convective-diffusion equation to provide values of analytical concentrations of the reactants at any point along the river at any time. From these concentrations, the chemical submodel; which uses the program MINEQL, calculates the equilibrium distribution of chemical components amongst the various possible species. The model is applied here to a creek, contaminated with acid mine drainage, into which injections of the weak bases sodium acetate and potassium bicarbonate are intentionally made, and has been shown to give a reasonable description of the transport of soluble and colloid forms of heavy metals for experiments of this scale and under conditions where sedimentation effects and adsorption on to stationary reactive surfaces are not important.