Hydrochemical Modeling of Metal Fate and Transport in Freshwater Environments

Abstract

Abstract During the last decade there has been growing interest in the development of hydrochemical models (coupled transport-chemistry-biology models) for better understanding and, eventually, for predicting the fate and transport of metals in freshwater environments. While there has been much discussion of such models and their submodels, and detailed examinations of the mechanistic descriptions and mathematics involved in their formulation, there has been relatively little attention focused on how well they perform in describing field data. This paper provides a look at the state-of-the art in hydrochemical modeling of metal fate and transport in groundwater, riverine and lacustrine systems through review of reported model validation attempts. Focus is on those models that have been applied to describe field data; the degree of success achieved and related factors are examined. Key observations drawn from our review of available hydrochemical models and attempted applications to field data are as follows: (1) most existing models consider steady one-dimensional flow only; (2) most existing models consider only one or a few chemical reaction mechanisms, with sorption-desorption being the most common; (3) local equilibrium is assumed in most models, though kinetic formulations for some chemical processes have been incorporated in some models; and (4) interaction of metals with biota have been considered in only a few models and in a very simplified manner. The most advanced hydrochemical models for metal fate and transport appear to be those for groundwater systems, followed in order by those for rivers and lakes. From a larger perspective, however, hydrochemical models for metals are still at an early stage of development for all freshwater environments.