School of Earth Sciences - Theses
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ItemLeachate chemistry of two modern municipal waste landfills in Melbourne, Victoria( 1999-11)This study investigates the occurrence and chemical composition of leachate at Clayton South and Brooklyn Municipal waste landfills in Melbourne, Victoria. Both are ‘modern’ municipal waste landfills, being engineered and managed consistent with current regulatory requirements. These landfills accept only putrescible and solid inert waste, but not soluble chemical, hazardous, liquid or prescribed industrial waste. (For complete abstract open document) Analyses of an extensive range of chemical parameters reveals a complex mixture of inorganic and organic compounds, similar to those of international authors researching leachate chemistry. Dominant ions in these leachates are NH4+, Na+, HC03- and Cl-. Except for Fe, heavy metals are not present in significant concentrations (mostly
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ItemDetection of uranium(VI) in groundwater using a field electroanalytical technique( 1999)In this thesis electroanalytical methods are investigated and a new method developed to determine uranium(VI) in groundwater samples. Differential pulse polarography, differential pulse voltammetry and adsorptive stripping voltammetry methods, with appropriate mercury drop electrodes, were optimised using the adsorptive chelate 2,5-dichloro-3,6-dihydroxy-l,4-benzoquinone (chloranilic acid). An alternative adsorptive stripping voltammetry method, with a hanging mercury drop electrode, was optimised using the chelate 8-hydroxyquinoline (oxine). The liquid mercury requirements of these techniques limit their use in the field. Therefore, mercury film electrode methods that are potentially better suited to field conditions are investigated. Chloranilic acid was found to be a suitable chelating agent for uranium determination in combination with a hanging mercury drop electrode, but the reduction of chloranilic acid was a concern. A new mercury film electrode determination method using chloranilic acid was developed but was found to result in the deterioration of the MFE to the extent of rendering the method unsuitable for uranium determination. An adsorptive stripping voltammetry, MFE method with oxine was investigated. The inability to remove the uranyl-oxine reaction products from the MFE created a memory effect that contributed to a lack of accuracy and precision when performing standard addition determinations. This interference was a significant factor in the inability to reliably measure a uranium response using an adsorptive stripping potentiometry method with oxine. The technique of square wave adsorptive stripping voltammetry with oxine in combination with a hanging mercury drop electrode was found to be the most appropriate method for uranium determination. The method was fast, sensitive, precise and accurate when analysing standard solutions. A low detection limit of 2.7 µg/L was achieved. Groundwater and surface water samples were analysed by the AdSV, HMDE method with oxine. The mineral spring water samples from Daylesford, Victoria, were high in ionic content and contained interfering ions. The unacidified samples contained high concentrations of dissolved C02 that needed to be removed prior to sample analysis to prevent pH changes during analysis. Of six unacidified samples uranium was found in only one sample, the Tipperary Spring sample at 4.9 µg/L U(VI). Interference prevented confirmation of this concentration in the acidified Tipperary Spring sample. The construction of a linear standard addition plot with a positive x-intercept was a common outcome for both the unacidified and the acidified spring samples. The uranium concentration was determined in three surface water samples collected from the Ranger Uranium Mine in the Northern Territory. Matrix interference in these surface water samples resulted in non-linearity for two standard addition determinations. A third sample was successfully analysed to give a concentration of 23 µg/L U(VI), which is in good agreement with an independent determination. The unselective nature of oxine was found to result in significant interference when analysing environmental samples by the AdSV, HMDE method with oxine. This method was found to be inappropriate for field analysis of environmental samples. However, in a laboratory environment the AdSV, HMDE method with oxine was the best performing method when determining uranium in standard solutions.
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ItemOccurrence of nitrate in soil and groundwater in the Corangamite area, Western Victoria( 1996)Soil and groundwater samples taken from two areas of different land use in the Corangamite Region, 200 km west of Melbourne, were analysed for nitrate and ammonium, and in some cases chloride. Both sites are located on the Later Newer Volcanics 'stone rises', and groundwater was sampled from nested bores which intersect the shallow unconfined aquifer and deeper semi-confined aquifer at both sites. The Carpendeit site is an area of native Eucalypt forest, and the Purrumbete North site is a pasture for grazing dairy cows. Low concentrations of nitrate (< 1 mgN/L) in groundwater at Carpendeit correspond to low soil nitrate concentrations (< 3 µgN/cm3 ). Higher groundwater nitrate concentrations occurred in the shallow unconfined aquifer at Purrumbete North, (up to 3 mgN/L), but not in the lower semi-confined aquifer, and corresponds to higher nitrate concentrations in soil (1 to 60 µgN/cm3 ). Elevated nitrate concentrations also occurred in groundwater discharge at McVeans Springs, in the range 2.61 to 4.72 mgN/L, and at Ettrick Springs in the range 8.08 to 16.07 mgN/L, greater than the limit of 10 mgN/L for drinking water specified in ANZECC water quality guidelines. Nitrate in soil under the pasture is probably derived primarily from the activity of nitrogen fixing bacteria associated with subterranean clover introduced to the pasture. Soil nitrate distributions suggest intense return of nitrogen in dung and urea occurs at 'camps' locations on the pasture, where cows tend to gather for shelter. Transport of nitrogen to shallow groundwater is stimulated by cracks and channels in the basalt clay soils. Local groundwater flow includes interaction with the many lakes and temporary ponds 'which form in surface depressions at times of high rainfall. The ponds probably serve as an effective nitrate supply in recharge to the shallow aquifer.