School of Earth Sciences - Theses
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ItemEnvironmental fate and transport of TNT in soil at the former explosives factory Maribyrnong( 2002)Highly toxic explosives compounds can potentially contaminate soil and groundwater and pose extended environmental hazard due to their persistence. Explosives contamination within soils was investigated at the former Explosives Factory at Maribyrnong (EFM), by sampling and spectrophotometric / HPLC analysis. The environmental fate and transport of 2,4,6-trinitrotoluene (TNT) was assessed via batch and microcosm testing to quantify the influence of key subsurface sinks, adsorption, and transformation, and hence evaluate natural attenuation as a remediation option. A five tonne crystalline TNT source zone was delineated within soils at the base of a TNT process waste lagoon. This source was found to be supplying aqueous TNT loading to subsurface soils and groundwater, with the resultant plume localised to the shallow clay sequence due to a combination of natural attenuation processes and hydrogeological constraints. Freundlich described sorptive partitioning was found to be the main TNT sink at EFM (KF= 29 mL/g), while transformation rates were moderate (3.86 x 10-4 hr-1) due to aerobic conditions, and TNT toxicity inhibiting microbial degradation. Slow groundwater migration toward the Maribyrnong River (0.7 m/yr) and upward hydraulic gradients within underlying sand and gravel aquifers serve to increase TNT residence time within the clay aquitard, leading to increased interaction with adsorptive substrates and microbes and/or elements of the soil matrix responsible for aerobic transformation. Remediation of the contaminated lagoon may involve removal and treatment/landfilling of the top 1m of soil, then refilling with an impermeable capping allowing ongoing natural attenuation of residual TNT at depth via anaerobic degradation and sorption.
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ItemVertical structure Of atmospheric trace gases over Southeast Australia( 2000-01)Trace gas (CO2 and its carbon and oxygen isotopes, CH4, CO, H2 and N2O) vertical profile data above Cape Grim, Tasmania for the period April 1992 to February 1997 are investigated. A climatology of the distribution of each trace gas has been compiled from statistical treatment of the raw data. These climatologies are useful for verification of transport model outputs. Here, the CO2 climatology is compared to simulation results from two transport models (Melbourne University Transport Model and TM2Z) using three different sets of CO2 fluxes separately (compiled with different methods by different authors). Large discrepancies are found between simulations and observations, especially in the free troposphere (4-6 km). By considering emission ratios, trajectories, satellite fire counts and simulation with biomass burning fluxes, the influence of tropical biomass burning plumes on the southeastern Australian region in the austral winter/spring is studied and quantified. This identification process requires a multiple-species approach where the large CO anomalies and the unexpected behaviour of H2 are most revealing. The frequent presence of burning plumes in the mid troposphere complicates one of the original motivations for the Cape Grim Overflight Program, which is to estimate the air-sea exchange of CO2 in this region. A suggestion arising from analysis of pre-1992 aircraft sampling in this region was that the regional CO2 air-sea flux south of Australia is exceptionally large.
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ItemThe hydrogeology of the Gippsland Basin, and its role in the genesis and accumulation of petroleum( 2002)The Gippsland Basin of southeastern Australia is the most energy-rich basin of Australia producing petroleum, gas and brown coal. Three-quarters of the Basin lies offshore and the rest onshore. The basin was initiated as a rift valley, caused by the separation of the Australian continent from the Antarctic followed by a number of tectonic events throughout the basin history. Early Cretaceous sedimentary rocks form the basement, which is in turn covered with Late Cretaceous to Recent sediment of sand, clay, limestone, and brown coal seams. The total thickness of the in-filling sediments offshore attains up to 6000 m, but onshore is up to 1200 m. There are three main acquifer systems, the Hydrostratigraphic Units 2, 4, and 7, all of which are confined. The two lower aquifer systems, Units 4 and 7, contain high temperature groundwater. It is generally agreed that the hydrocarbons offshore have been derived from terrestrial matters including brown coal and ligneous clay offshore. In the present study, the author has developed a case that hydrocarbons offshore being derived not only from the offshore source but also from onshore brown coals and coaly matter and in this hydrocarbon forming processes, groundwater has played a significant role. The Central Deep, in particular, provides favourable conditions for hydrocarbon maturation. Throughout the basin history, the Central Deep has experienced the oil window temperatures. In supporting this hypothesis, geochemical studies on groundwater, brown coal, and hydrocarbons as well as hydrodynamics are presented.
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ItemThe geochronology and thermochronology of the Brockman Creek 01, Melita 01 and Melita 02 kimberlites, Western Australia( 2000-10)Due to the difficulties inherent in dating kimberlites, two independent methods are employed to confirm the unusually old ages of approximately 2 Ga for three occurrences in Western Australia. Phlogopite micas from three kimberlites were dated using 40Ar/39Ar and 87Rb/86Sr dating techniques in order to provide an estimate of the intrusion ages. The high reliability of the age estimates is indicated by the similar results produced by the 87Rb/86Sr method. Argon loss is suspected for phlogopite samples, resulting in the apparently reliable 40Ar/39Ar total fusion ages that do not correspond to previously determined emplacement ages. (For complete abstract open document)
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ItemThe potential for natural attenuation of petroleum hydrocarbons in groundwater: Shell Newport Terminal, Victoria( 2000-10)Groundwater in the fractured and jointed Quaternary Newer Volcanics basaltic aquifer system beneath the Shell Newport Terminal has been contaminated by petroleum hydrocarbons. This petroleum hydrocarbon contamination has resulted from a number of different spill incidents over the terminal's long operation. Petroleum hydrocarbon contamination has led to the formation of a light nonaqueous phase liquid (LNAPL) floating on the water table. Associated dissolved and vapour phases have also developed within the basaltic aquifer. The effectiveness of natural attenuation processes to remediate the petroleum hydrocarbon contamination has been evaluated based on the gas chromatography / mass spectroscopy analysis of LNAPL samples and changes in groundwater geochemistry. Three distinct LNAPL plumes were identified within the Shell Newport Terminal jet facility plume (kerosene source); off-site plume along High 8t (mixed source of leaded petrol, kerosene, and diesel); and black oil fuel gantry plume, which is migrating off-site to Digman Reserve (mixed source of leaded petrol, shell sol A, and diesel). LNAPL ratio analysis revealed only that the samples were degraded compared to their estimated source composition. Further interpretation of ratios was difficult due to constraints involved in source compositions, sampling limitations, heterogeneity of the groundwater system, and high transport velocities of the groundwater compared to LNAPL migration. (For complete abstract open document)
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ItemThe fate of cyanide in groundwater at gasworks sites in south-eastern Australia( 2000-09)The fate and transport of cyanide in groundwater was investigated at gasworks sites in southeastern Australia. Two gasworks sites were investigated during this research: one in Tasmania and the other in Adelaide. The research followed three principal methods of investigation: field work, laboratory work and numerical modelling. The field work was aimed at observing the behaviour of cyanide in highly contaminated groundwater environments. Measured field parameters and laboratory analytical results from groundwater sampling were used to describe the hydrodynamics and hydrochemistry of the groundwater environment, providing a framework for groundwater flow and solute transport modelling. Groundwater and soil samples were also collected for use in laboratory experiments. The results from both field sites indicate contrasting hydrogeological environments, however, inorganic (metallic and non-metallic) and organic contaminants were measured in solution at both sites. The maximum concentrations observed at both sites were up to 5,300 mg/L CN(Total) (Adelaide site) and 21 mg/L CN(Total) (Tasmanian site). Results from geochemical modelling of solutes in groundwater at the field sites indicate that cyanide was predominantly in its free form in solution, with metallo- and alkali-cyanides also present.
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ItemHydrogeology of the newer volcanic basalt aquifer at the Shell Terminal Newport Victoria( 2000-10)The Shell Terminal at Newport, Victoria and adjacent areas have been intensively used as terminals for large petroleum companies (BP,Ampol,Caltex, Mobil and Shell) for many years. As a consequence the groundwater is contaminated with light non-aquaeous phase liquids (LNAPLs) and an associated dissolved phase.
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ItemThe tectonic evolution of the Songpan Garzê Fold Belt, Southwest China( 2001)Structural observations suggest that all pervasive deformation of the Songpan Garzê Fold Belt occurred continuously and progressively during the Indosinian Orogeny (c.230-200 Ma), and prior to widespread post-tectonic magmatism c.195-180 Ma. Development of the arcuate structural grains and discrete high-grade metamorphic complexes that characterise the southeast Songpan Garzê Fold Belt can be explained entirely in terms of this progressive Indosinian deformation. Likewise, all greenschist-amphibolite facies Barrovian-style metamorphism within the southeast Songpan Garzê Fold Belt is correlated with Indosinian orogenesis. Thermodynamic modelling of micaceous, garnet- and aluminosilicate-bearing metamorphic assemblages, all of which define Indosinian-aged tectonic fabrics, suggests a continuous textural evolution that occurred under the influence of a simple clockwise P-T-t path. There is no structural or metamorphic evidence to substantiate the pervasive Yenshanian (Jurassic-Cretaceous) or Himalayan (Tertiary-Recent) orogenic overprints that previous studies of the terrane have inferred. The distribution of progressive structure and locally variable timing relationship between progressive deformation and peak metamorphism imply that Indosinian deformation occurred diachronously across the southeast Songpan Garzê Fold Belt. Such deformation was characterised by the westward migration of progressive structural ‘fronts’, towards the interior of the terrane, in response to lateral growth of the transpressive interface between the Songpan Garzê Fold Belt and adjacent Yangtze Craton. In contrast, consistent timing relationships between peak metamorphism, basement anatexis and the diapiric exhumation of high-grade metamorphic rocks suggest that the thermal maturation of the terrane was spatially and temporally uniform across the southeast Songpan Garzê Fold Belt. Post-Indosinian modification of the Songpan Garzê Fold Belt was limited to brittle strike-slip dissection, predominantly focussed into the discrete west-northwest-trending Xianshui He and Kunlun fault zones. Sinistral displacement of these two fault zones, from at least the Miocene onward, transported two large tracts of the terrane towards the southeast, effectively intact. This displacement was absorbed by reactivation of the Longmen Mountains Thrust Nappe Belt and transpressive exhumation of the Min Shan Uplift Zone. Modification of the Songpan Garzê Fold Belt did not accommodate any significant vertical distortion that might have contributed to isostatic rebound of the present-day 4500-metre Tibetan Plateau. Nevertheless, uplift of the greater Songpan Garzê Fold Belt occurred from at least the Neogene onward, accommodated by reactivation of the Songpan Garzê/Yangtze interface and present-day boundary of the northeast Tibetan Plateau. New 40Ar/39Ar and Rb/Sr thermochronology from southeast Songpan Garzê Fold Belt identifies two discrete cooling episodes: 1) late-Triassic-Jurassic cooling from peak-metamorphic conditions of >500° C to temperatures of around 350° C; and 2) rapid Tertiary-Recent cooling to near-surface temperatures. Both cooling episodes are interpreted to record erosional exhumation of the terrane. Whilst Mesozoic cooling is correlated with limited post-Indosinian rebound of the thin-skinned Songpan Garzê accretionary wedge, Tertiary-Recent cooling is thought to reflect an isostatic potential associated with Himalayan Orogenesis in central Asia. Surprisingly, this latter event does not seem to have been coupled to the rapid Neogene uplift of the Tibetan Plateau. Tertiary-Recent exhumation, uplift and structural modification of the Songpan Garzê Fold Belt are inferred to have been bolstered by a pervasively thickened viscous lower crust. This thickening is attributed to penetrative east-directed deformation of deeper lithosphere beneath the detached thin-skinned veneer of the Songpan Garzê Fold Belt. Such an interpretation favours penetrative deformation of the mid-lower crust as the dominant mechanism by which India/Eurasia intracontinental convergence was absorbed - not lateral escape or extrusion of eastern Asia - and highlights the role that the Yangtze Craton has played throughout Mesozoic and Tertiary orogenesis: acting as a rigid backstop to penetrative deformation of the more plastic Songpan Garzê Fold Belt.
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ItemExtreme temperature events in Australia( 2001)A high-quality set of historical daily temperature data has been developed for Australia. This data set includes 103 stations, most of which have data from the period between 1957 and 1996, and some for longer periods. A new technique, involving the matching of frequency distributions, is presented for the adjustment of temperature records for inhomogeneities at the daily timescale, and this technique is used in the development of the data set. A number of additional findings are presented on the impact of changing times of observation and accumulation of observations over periods longer than one day on the Australian temperature record. This data set was used for an extensive study of extreme temperature events in Australia. Widespread changes in the frequency of extreme temperature events in Australia were found over the 1957-1996 period. These changes were found both by an analysis or trends at individual stations and by analysis of spatial averages of indices of extreme temperature. In general, increases were found in the frequency of high maximum and high minimum temperatures, and decreases in the frequency of low maximum and low minimum temperatures. The changes were greatest for low minimum temperatures and least for high maximum temperatures, and were generally greatest in winter. The greatest decreases in the frequency of extreme low minima were found in Queensland. The trends were not universal, with trends opposite to those for Australia as a whole being found in some regions in some seasons. It was found, after examination of several possible models, that the frequency distribution of Australian daily maximum and minimum temperatures was best represented by a composite of two or three Gaussian distributions with different parameters. Using this model, it was found that the observed changes in temperature primarily resulted from changes in the means of the component distributions, indicating that the changes resulted principally from overall warming of the atmosphere rather than changes in circulation or air-mass incidence. The relationship between the frequency of extreme temperatures and the Southern Oscillation Index (SOl) was examined, with strong relationships being found in some seasons in many parts of Australia for most extreme variables, particularly high maximum temperatures. The weakest relationships were found for low minimum temperatures. Many of these relationships, except in winter, were as strong (or stronger) with the value of the SOl one season previously as they were with the SOl of the current season, indicating potential useful skill in the forecasting of seasonal frequencies of extreme temperatures in many cases.
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ItemGeologic and geomorphic applications of Aster satellite imagery, northern Flinders Ranges, South Australia( 2002)Multispectal ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) satellite data has been evaluated for geologic and geomorphic interpretations within the northern Flinders Ranges, South Australia. ASTER is a new remote sensing imaging system on board NASA’s Terra satellite, launched in December, 1999. ASTER measures the reflectance of the Earth’s surface within 14 bandwidths of the visible, near infrared, short wave infrared and thermal infrared sections of the electromagnetic spectrum, with a minimum spatial resolution of 15 m. ASTER has the ability to produce digital elevation models (DEM), important for understanding the dynamics of the landscape by draping false colour images over topography. The northern Flinders Ranges is one of the most diverse geological settings on the Australian continent, making it an ideal ‘test site’ to demonstrate the capabilities of the ASTER instrument. The area contains a range of geology from Precambrian basement to Quaternary desert landforms. The ability of ASTER Level 1B data to discriminate between the large range of lithologies is assessed. Geomorphic interpretations made from exploiting the high resolution ASTER data and DEM has revealed a significant record of post Pliocene landscape development, attributed to a combination of climatic and tectonic factors. Such features as incision morphology and the identification of palaeodrainages have enabled constraints to be placed on the Quaternary degradational and aggradational events. For example, estimates of Quaternary sediment flux rates in some areas of the study area are essentially extracted from ASTER DEM data. ASTER has persisted to be extremely useful in the study of aeolian landform morphology in regions surrounding the northern Flinders Ranges. The short wave infrared has proved useful for identifying areas of high surface moisture, directly relating to the depth to water table. The application of principal component analysis to ASTER short wave infrared data is used to accurately identify specific mineralogical character.