KINETICALLY INFLUENCED TERMS FOR SOLUTE TRANSPORT AFFECTED BY HETEROGENEOUS AND HOMOGENEOUS CLASSICAL REACTIONS

Simulation of transport affected by heterogeneous or homogeneous reversible reactions requires a choice between local equilibrium‐based and kinetics‐based models. The error associated with the use of equilibrium‐based models is equivalent to the error of neglecting certain mathematical terms in the governing kinetics‐based transport equations. Identification and evaluation of these kinetically influenced terms can therefore aid in the development of criteria for applicability of local equilibrium‐ based transport models. This paper extends a four‐step derivation procedure, previously presented for cases of transport affected by surface reactions, to transport problems involving homogeneous reactions (solution phase complex formation or oxidation‐reduction) and/or precipitation‐dissolution reactions. Derivations for these classes of reactions are used to illustrate the manner in which mathematical differences between reaction classes are reflected in the mathematical derivation procedures required to identify kinetically influenced terms. Simulation results for a case of transport affected by a single solution phase complexation reaction and for a case of transport affected by a precipitation‐dissolution reaction are used to demonstrate the nature of departures from equilibrium‐controlled transport as well as the use of kinetically influenced terms in determining criteria for the applicability of the local equilibrium assumption. A final derivation for a multireaction problem demonstrates the application of the generalized procedure to a case of transport affected by reactions of several classes. This paper is not subject to U.S. copyright. Published in 1990 by the American Geophysical Union.