Thesis (MScAgric)--University of Stellenbosch, 2007. / Bibliography. Also available via the Internet.

Thesis (Ph. D.)--Jyväskylä Yliopisto, 1980. / Includes bibliographical references (p. 46-57).

Thesis--Auburn University, 2009. / Abstract. Includes bibliographical references (p. 61-63).

Thesis (Ph. D.)--Jyväskylä Yliopisto, 1980. / Bibliography: p. 46-57.

Thesis (M.S.)--University of Wisconsin--Madison, 1968. / Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

The investigation and remediation of land contaminated with metals (copper, nickel, lead and zinc) was investigated. Calcium, iron and manganesele vels within the soils studied were also investigated. Several soils were used to assessth e three-stageB CR sequential extraction procedure and recent recommended modifications to this procedure. In general the modifications to the procedure were found to increase levels of copper, lead and iron extracted by the reductant used in the procedure. The modified BCR sequential extraction procedure was then used to assess the success of remediation strategies. Column leaching experiments, with EDTA, were set up to simulate soil-flushing technologies. Soil was extracted using the BCR procedure both before and after treatment. The experiments highlighted the need to consider the soil characteristics when determining a remediation strategy. The technique was shown to be successful for the leaching of the more mobile forms of copper, lead and zinc from the soils studied. Phytoremediation and chelate assisted phytoremediation were also investigated using the BCR sequential extraction procedure. Taraxacum officianale (dandelion) was grown in soil contaminated with zinc. The experiment was designed to study the ability of the plant to accumulate metals and also to study the effect of the addition of the chelator EDTA and the effect of the addition of a fertiliser. These methods were shown to remove significant proportions of zinc, copper and lead from the soil studied, however the time frame for remediation based on such techniques may be considerably longer than that for conventional methods.

Chromium contamination of groundwater and soils continues to pose a major environmental concern. Soils may have become contaminated with chromium through former industrial activities geochemical enrichment. The nature of the industrial activity will determine the form and concentration of the chromium as well as the presence of co-contaminants and the pH and redox of the soil. Chemical reductants have been widely used for the transformation of hexavalent chromium in the environment. Over recent decades attention focused on the chemical reductant calcium polysulphide which has performed effectively in the treatment of groundwater and soil samples contaminated with Cr(VI). Yet a detailed understanding of calcium polysulphide (CaSx) performance has not yet been established. Hexavalent chromium concentrations in aqueous and groundwater samples were significantly reduced by calcium polysulphide and CaSx:chromate molar ratio of 1.5 was sufficient to prevent partitioning of Cr(VI) into solution and to precipitate the solution phase. Calcium polysulphide was used for the remediation of solid chromite ore processing residue (COPR) samples. Prior to the application of calcium polysulphide to COPR, each of the key steps were optimized. A range-finding experiment was conducted to understand the dosage and treatment regime at which Cr(VI) immobilization within COPR was optimal. The results indicated that unsaturated deployment of CaSx into the medium outperformed that in saturated systems. A higher polysulphide amendment dose of 5% w/v concentration enhanced the final treatment of Cr(VI) within COPR. The toxicity and carcinogenicity of Cr(VI) over Cr(III) requires a technique capable of discriminating between valencies. The EPA Method 7196A specifically quantifies the concentrations of Cr(VI) in environmental samples and was used for all analysis to differentiate between Cr(VI) and Cr(III). Cr(III) was calculated as the difference between the Cr(VI) and Cr-total concentrations. In addition to the EPA 7196A, a novel ion exchange resin (IER) procedure was developed to differentiate the two species of chromium. After optimisation, Amberlite resins IRA 400 and IR-120 were used for the specific sorption and subsequent analysis of aqueous Cr(VI) and Cr(III) solutions. For the selective removal of chromate from groundwater, waste water and soil samples, Amberlite IRA 400 achieved a consistent performance of >97% removal in a range of trials. The IERs in this work were applied as analytical tools however they could be applied as remediation tools. While aqueous treatment of chromium contaminated media using CaSx was very successful, COPR treatment proved to be difficult due to the complex nature of the system. An understanding of stoichiometric responses to CaSX has been established, but the nuances of soil physicochemical interactions require more thorough investigation.

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