ABSTRACT
Zinc (Zn) is ubiquitous in the environment, occurring on the Earth’s crust at an average concentration of about 70 mg/kg (Lindsay and Norvell 1978, Lindsay 1979). Zinc metal is very rarely found in nature, requiring extreme reducing conditions to exist. Rather, Zn typically occurs in the +2 oxidation state, primarily as various geogenic minerals such as sphalerite (zinc sulfi de), smithsonite (zinc carbonate), zincite (zinc oxide), hemimorphite (zinc silicate), and willemeite (zinc silicate) (Lindsay 1979, Van Damme 2010, Jacquat 2011). Sorption is the dominant reaction mechanism governing fate and transport of zinc in soil and sediment environments at or just below
circumneutral pH (Puls and Bohn 1988, Hesterberg et al. 1997a, Elzinga et al. 1999, Smolders et al. 2004, Grafe and Sparks 2005). In higher pH environments, zinc can partition as solid-phase precipitates, independently or on the surfaces of minerals, and is less soluble than sorption complexes (Roberts et al. 2003, Nachtegaal et al. 2005, Panfi li et al. 2005). Remediation efforts to Zn contaminated soils have demonstrated that in situ amendments and pH adjustments can alter the chemistry of zinc to less extractable and bioavailable forms (Agbenin 1998, Mench et al. 2000, Basta et al. 2001, Zwonitzer et al. 2003, Brown et al. 2004, Nachtegaal et al. 2005, Williams et al. 2011).
