Natural attenuation mechanisms of inorganic pollutants: sorption/desorption kinetics on soil mineral surfaces

摘要

Recent advances in soil metal remediation have incorporated corrosive soil leaches, vitrification technologies, and grout curtains to lberate or immobilize inorganic contaminates from soils. Natural attenuation, an alternate in-situ approch, may prove to be more cost-effective and provide greater environmental protection in the long run these current technologies. Kinetics of sorption/desorption reactions on soil mineral surfaces, provides information on inorganic ion sorption reaction rates and mechanmisms and determines how con-stituents, such as dissolved organic carbon (DOC), affect reaction rates and mechanisms. This is information that can be used to assess natural attenuation of inorganic pollutants. Adsorption/desorption reactions of inorganic ions on oxide surfaces are characterized by very rapid reaction rates. Relaxiation techniques. uch as pressure-jump, allow one to measure reaction rates on millisecond time scales. P-jump studies indicated that metal ions such as Cu~(2+), Pb~(2+), and Ni~(2+), and the oxyanions, arsenate and phosphate, formed inner-sphere surface complexes with goethite. The desorption step was the slower process and could be considered the rate-limiting step, which indicates that the inorganic ion-goethite surface bond created by thewe ions is more difficult to break than to form. Batch studies reveal that DOC can inhibit the precipitation and adsorption of phosphate onto soil mineral surfaces. This process may also affect the sorption of other inorganic ions onto soil surfaces. Inhibition of sorption results in more inorganic pollutants present in the soil solution, which enhances their mobility toward ground water.