The intrusive and expensive nature of soil cleanup technologies like excavation and incineration created a need to search for alternative remediation technologies. Rhizoremediation and its associated microorganisms has the potential to cleanup contaminated soil in a ‘non invasive’ and cost-effective manner. The literature cites many benefits of the technology if implemented correctly. However, there is still a lack of knowledge concerning the interaction of the plants and microorganisms that are responsible for degrading the organic pollutants. In this study, the potential for degrading Poly aromatic hydrocarbons (PAH’S) by rhizosphere bacteria was investigated. In addition, the hydrocarbon removal efficiencies of different plant rhizospheres were investigated. The metabolic and genetic profiles of soil bacteria in vegetated and non- vegetated soils were determined. The results of the removal efficiencies of different plant rhizospheres showed that the removal of hydrocarbons was more effective in soil vegetated by different plant species. By using co-occurring (different) plant species, hydrocarbons were removed faster than when monoplanted were used. The number of hydrocarbon degrading bacteria in the rhizosphere increased during rhizoremediation of PAH’s contaminated soil. Analysis of the functional and genetic diversity in PAH’s contaminated and non-contaminated rhizosphere and non-rhizosphere soil, using Biolog (physiological community level) and genetic diversity (polymerase chain reaction- denaturant gradient gel electrophoresis) was determined. The biolog did not revealed clear difference on substrate utilization profiles of the microbial communities in the rhizosphere and bulk soil. However, unlike the Biolog DGGE revealed slightly differences in both the metabolic and genetic profiles of the different soil samples. The study on the feasibility of seeding bacteria capable of colonizing and surviving on the rhizosphere showed that Pseudomonas putida successfully colonized the rhizosphere of Eleusine corocana. The number of P putida increased during rhizoremediation of PAH’s. These results suggest that bacteria with the ability to adhere and survive in the root zone can be engineered and seeded for rhizoremediation purposes. However, other factors such as the influence of soil type and organic matter content must be investigated to improve rhizoremediation technology. / Dissertation (MSc)--University of Pretoria, 2009. / Microbiology and Plant Pathology / unrestricted

Dissertation submitted in compliance with the requirements for the Masters Degree in Technology: Civil Engineering, Technikon Natal, 1997. / The strength and durability of any soil structure is dependent on the quality of the compaction of the soil. This quality is measured by employing a standard compaction test, which provides a standard with which density may be compared, called the maximum dry density, and the moisture content of the soil at which this is achieved, called the optimum moisture content. As a matter of routine during quality control, the particle size distribution, plasticity index and liquid limit of the soil are determined at the same time as its maximum dry density and optimum moisture content. / M

Two soil types, the Ladner silty clay loam and the Nicomekl loam, located in the Lower Fraser Valley, representing the modal profile characteristics were selected to study the permeability and the factors affecting it. Undisturbed core samples and fragmented samples were procured for laboratory characterization of the soils. Measurement of the soil permeability in the laboratory confirmed the field observations that the Nicomekl soil was more permeable than the Ladner soil. There was a good correlation in the soil permeability and the soil macroporosity as determined by tension table at 40 cm. water tension. The texture of the two soils, as determined by pipette method, was not sufficiently different to account for the permeability differences. The variations in the organic matter content, as determined by wet combustion method, seemed to have little effect on the permeability behaviour of these soils. The nature of exchangeable cations, as extracted by the ammonium acetate method and quantitatively determined by flame photometry and versenate titration, in the two soils, were found to be very different; the exchangeable cations, Na⁺, K⁺ and Mg⁺⁺, in the Ladner soil seemed responsible for the lower permeability in comparison with the Nicomekl soil which had very low percent base saturation and appeared to have mostly Al⁺⁺⁺ ions present in the exchange complex. The poorer physical conditions of the Ladner were also, perhaps, due to the differences in the exchangeable cations. The X-ray identification of clay minerals, using oriented "aggregate technique", monochromatic copper radiation and surface reflection method, revealed that the Ladner and Nicomekl soils were qualitatively similar in their clay content. Both soils contained montmorillonite, micaceous mineral, chlorite, feldspar and quartz; the presence of kaolinite and vertniculite could not be established. In an intricate mixture of clays as above, quantitative estimation of clay minerals was not performed; hence the effect of clay minerals on the permeability of the two soil types could not be evaluated. Permeability measurements on soil mixtures containing reference clay minerals, using air pressures in a water permeameter, revealed that Na-Bentonite even in small quantities rendered soil highly impermeable. The permeability of soil mixtures containing clays with exchangeable calcium improved with the application of Krilium while the clays with exchangeable sodium did not respond to similar treatment. The effect of Al⁺⁺⁺ ion and weak acids on the flocculation behaviour of Na-Bentonite suggested that the presence of both Al⁺⁺⁺ ions and weak acids promoted soil permeability. X-ray diffraction diagrams using unflitered cobalt radiation indicated that weak acids formed heat stable complexes with bentonite. The bentonite treated with aluminum chloride as well as phosphoric acid plus aluminum gave diffraction patterns indicating that increased c-spacing was due to the complexes formed with bentonite; the deposition of these complexes at the interlayer positions prevented the complete collapse of lattice at elevated temperatures. / Land and Food Systems, Faculty of / Graduate

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