chapter  5
16 Pages

Structural Dynamics of Metal Partitioning to Mineral Surfaces

Partitioning from solution to immobile solid phases in soils and sediments exerts control over the mobility and availability of inorganic contaminants. The extent of contaminant mobility will be influenced by the rates of sorption and desorption reactions. In general, ion exchange and adsorption reactions occur over relatively rapid timescales (milliseconds to days), and one might conclude that these reactions dominate partitioning in soils and sediments. However, efforts to model long-term fate and transport of contaminants are applied over much longer periods of time, more consistent with the timescale of fluid transport in natural systems (days to years). Over this timescale, solid-phase structural transformations that significantly affect the partitioning process, such as mineral nucleation and growth, can occur. The following quote excerpted from Grundl and Sparks (1998) concisely captures the significance of this issue:

When viewed in this context, minerals should not be considered as passive solids, or even as simple sources of a reactive surface but must be considered as

bulk reactants

(emphasis added).