chapter  4
16 Pages

## Long-Term Fate of Metal Contaminants in Soils and Sediments: Role of Intraparticle Diffusion in Hydrous Metal Oxides

Hydrous oxides of Al, Fe, and Mn are ubiquitous components of soils and sediments, which play an important role in controlling the mobility and bioavailability of metal contaminants released into the environment from various anthropogenic sources (Hesterberg 1998; Jenne 1998; Martinez and McBride 1999). These oxides occur as discrete particles or as coatings on other mineral surfaces; they have large surface areas, microporous structures, and high affinities for metal ions (Jenne 1998; Sparks 1998). The sorption of contaminants to these microporous oxides is recognized as a 2-step process: an initial rapid adsorption that reaches a pseudo equilibrium at the mineral-water interface, followed by a much slower uptake that may continue for a period of days to years (Hodges and Johnson 1987; Brümmer et al. 1988; Fuller et al. 1993; Waychunas et al. 1993; Axe and Anderson 1995, 1997; Papelis et al. 1995a; Raven et al. 1998; Scheidegger et al. 1998; Sparks 1998; Strawn et al. 1998; Scheinost et al. 2001).