Heavy Metals Mobility/Immobility in Environmental Media

Abstract

Chemical elements are mobilized by physical, chemical and biological vectors. Elements move in solution as cations, anions and ionic complexes. They incorporate into solid inorganic phases (e.g., sediment, suspended sediment, particulates from natural or anthropogenic emissions) or are absorbed/adsorbed by them. The same is true for solid, perhaps vital, organic phases (e.g., soft and hard parts of organisms, particulate organic carbon). In these modes the chemical elements are transported to depositional environments on land or in water bodies by water, wind and glacial ice following surface drainage, aquifer flowpaths, and wind driven water and atmospheric currents. Mobilized heavy metals in an element assemblage can be carried to an environment in concentrations significantly higher than natural levels in speciated forms. If these are bioavailable, they will be toxic to life forms if bioaccumulated over a period of time. When this scenario is met, the metals pose a threat to basic links in an ecosystem foodweb as well as to environmental niches and the ecosystem they comprise.