Thesis (PhD)--Macquarie University, Graduate School of the Environment, 2001. / Bibliography: p. 10-1 to 10-23.

Thesis (M.Sc.)(Microbiology))--University of Pretoria, 2009. / Summary in English. Includes bibliographical references.

Thesis (M.S. in chemical engineering)--Washington State University, December 2009. / Title from PDF title page (viewed on Jan. 20, 2010). "Department of Chemical Engineering and Bioengineering." Includes bibliographical references (p. 63-65).

Thesis (M.S. in environmental science)--Washington State University, December 2009. / Title from PDF title page (viewed on Jan. 26, 2010). "School of Earth and Environmental Sciences." Includes bibliographical references (p. 48-51).

Thesis (Ph. D.) in Food and Nutrition Sciences--University of Maine, 2002. / Includes vita. Includes bibliographical references (leaves 93-98).

No description available.

Chlorinated aliphatic hydrocarbons (CAH’s) are a diverse group of industrial chemicals that play a significant role as pollutants of soil and groundwater. They are recalcitrant and resist degradation in most waste treatment systems. Furthermore, physical removal techniques used for CAHs are often very expensive, labour intensive and time consuming. Microbial communities native to contaminated areas are known to participate in biodegradation of these CAHs to an extent. The main focus of this study was therefore to investigate the bioremediation of soil contaminated with a mixture of CAHs, namely carbon tetrachloride (CCl4), dichloromethane (DCM) and 1, 2 dichloroethane (1, 2-DCA). Two different laboratory-scale microcosm types, a stationary microcosm (Type S) and microcosms that received a continuous circulation of groundwater (Type C) were used to determine the effects of 3 different bioremediation approaches, viz, biostimulation, bioaugmentation and a combination of biostimulation and bioaugmentation on the degradation process. For both microcosm types, gas chromatography analysis revealed that the greatest decreases in CAH concentrations occurred in soil that was biostimulated. 1, 2-DCA was rapidly biodegraded in Type C microcosms that contained glucose, with a 57% net degradation in 15 days. Consortia comprising of aerobic Bacillus and Alcaligenes sp. were used for bioaugmenting contaminated soil. However, this approach did not promote biodegradation as significantly as biostimulation experiments. A combination of biostimulation and bioaugmentation revealed that the addition of nutrients was still unable to induce the degradative ability of the introduced microorganisms to produce degradation values comparable to those of biostimulated soil microcosms. Common intermediates of CAH metabolism viz., chloroform, dichloromethane and carbon dioxide were detected by gas chromatography/mass spectrometry. The detection of chloroform and dichloromethane is sufficient evidence to assume that anaerobic conditions had developed, and that biodegradation was occurring under oxygen-limiting or oxygen-free conditions. An aerobic environment was initially created, but soil microbial respiration had probably led to the rapid development of anaerobic conditions and in all likelihood, enhanced degradation. The prevalence of anaerobic conditions can also account for the lack of appreciable degradation by the bacterial consortium used during bioaugmentation. Phospholipid phosphate analysis was conducted and used as an indicator of microbial biomass. It was noted that phospholipid phosphates did not always correlate with the degradation of CAHs in some microcosms. In this regard, different patterns were noted for Type S and Type C microcosms. Microbial biomass patterns for Type C biostimulated and bioaugmented soil microcosms increased within the first 5 days of sampling. This could have been as a result of the larger volume of groundwater required for the circulating microcosm possibly concealing actual CAH concentrations. In contrast, in Type S microcosms, for most treatments, a sharp decline in biomass within the first week was observed. This study clearly demonstrates that the bioremediation of certain chlorinated solvents can be a function of their water solubility. It must also be emphasized that the biodegradation of some CAHs in a mixture can affect the concentrations of others present in the mixture as well, warranting further study with mixtures of CAHs. Furthermore, the development and use of bioreactors, similar to the Type C microcosm can provide novel, simple ways to hasten remediation of chlorinated solvents like 1, 2-DCA. / Thesis (M.Sc.) - University of KwaZulu-Natal, Durban, 2008.

No description available.

The adsorption of sulphate has been studied using alpine and sub-alpine podzolic soils from the Allt a'Mharcaidh catchment, Cairngorms, Scotland, U.K. A detailed investigation of sulphur pools and mechanisms of sulphur retention has revealed that incoming sulphate ion, both marine and anthropogenic, is being retained by a range of adsorption mechanisms. Analysis of the soils has indicated that the sulphur content of the soils is dominated by organic forms of sulphur. Selective chemical fractionation techniques have identified an accumulation of sesquioxides, dominated by amorphous aluminium, in the basal horizons of all the soil profiles. Adsorption of sulphate has been shown to be mainly governed by the quantity and variable charge character of this sesquioxide phase. Fractionation has also suggested that the sesquioxides in the basal horizons of the soils are dominated by a combination of gibbsitic and imogolitic materials, the latter being present as a result of podzolization processes. The generation of sulphate adsorption isotherms has revealed that the organic horizons of the catchment soils show little or no sulphate adsorption capacity, due to a small sesquioxide content. In contrast, the mineral horizons are all capable of adsorbing sulphate, and in most cases this adsorption can be modelled to the Langmuir adsorption equation. The adsorption capacity of particle size fractions of the soils has revealed that even soil particles > 1 mm show an ability to retain sulphate, possibly by physical entrapment of soil solution in mineral pores or amorphous silica gel coatings. The accompanying hydroxyl release that is generally assumed to accompany adsorption of sulphate in the mineral soils was not evident, and unless a ligand exchange reaction was masked by other chemical reactions involving total proton balance, sulphate adsorption in the catchment soils is not due to a specific or 'low affinity' specific mechanism.

It was illustrated that Zn and Cu at or above 1000 and 800 mg kg^-1 respectively were highly toxic to the earthworm studied. Cu was found to be more toxic to the earthworm than Zn in respect to mortality, growth and reproduction parameters in all three different types of soils. The body burdens of earthworms exposed to metal amended soils increased corresponding to the increased concentrations of amended metals irrespective of soils used. It was found that the BCFs in earthworms decreased with the increased concentrations of metals in soils. The higher BCFs is the indication of uptake of higher proportion metals from soil by earthworms. The highest BCFs was found for Ni followed by Zn and Cu indicated their bioavailability to earthworms. The growth (weight) of the earthworms was most affected by Cu. The combined toxicity of Zn:Ni, Zn:Cu and Cu:Ni to reproduction (cocoon production) of earthworms was mainly antagonistic and to some extent additive in both the Insch and Boyndie soils. Zn was more toxic than Cu to the nematodes as the number of nematodes decreased with the increase of metal amendments to soil. It was also found that the number of nematodes increased at the exposure to some lower doses of Cu and Ni. The joint toxicity of Zn:Ni, Zn:Cu and Cu:Ni on the number of nematodes was mainly antagonistic in both the Insch and Boyndie soils. In some cases the combined toxicity of metals to nematodes was not possible to assess because the threshold level was not reached and also due to irregular and inconsistent data. Cruden Bay soil was more vulnerable than Insch and Boyndie soils in evaluating the toxicity of metals to nematodes. Zn was found to be toxic for the <i>lux</i>-marked bacterial biosensor <i>Escherichia coil</i> HB101 pUCD607 and <i>Pseudomonas fluorescens </i>10586r pUCD607 in different soils.