Environmental Geoscience
Honours Projects
Potential Projects
The honours projects below are available for students beginning in 2008, or mid-year in 2007. Contact Dr
John Webb for more information.
Effect of airborne particulates emitted by power stations on reducing rainfall in downwind areas
It is well established that the very fine airborne particulates emitted by chimneys at industrial plants and power stations prevent the nucleation of rain droplets, and therefore reduce the rainfall in downwind areas. This project will look at whether the power stations of the La Trobe valley have had any effect on rainfall in the region. The power stations have very efficient scrubbers on their smokestacks, and it might be expected that the effect would now be small, but could have been much greater in the past. The project will involve looking at the rainfall records from weather stations both downwind and upwind of the power stations, and statistically comparing the rainfall for different time periods to see if there is any significant difference. MODIS satellite images of the area will also be studied to determine the amount of particulates emitted now and at different times in the past.
Possible contamination of the underground stream in Moon's Cave, Buchan, eastern Victoria
The underground stream in Moon's Cave has recently been precipitating large amounts of iron hydroxide, turning the stream bed orange; this has been accompanied by a strong sulphurous smell. In the past the stream was contaminated by sewerage from a toilet block in the campground at Buchan, but some years ago this was diverted to a treatment plant, and the treated water is discharged into the Buchan River. It is possible that the iron/sulphur contamination is natural and is derived from the cave sediments, which are organic rich and therefore can dissolve these species. Small areas of iron precipitation are known from nearby surface streams. To establish the origin of the contamination, the underground stream water and precipitate will be sampled and analysed, as will the surface stream at precipitation sites. Samples will also be collected for bacterial analysis. The results will be very important for management of the site. The project will be supported by the Buchan Caves Management Authority and the Victorian Speleological Association, who will help with sample collection.
Assessment of climate change at the Last Glacial Maximum in central Victoria
At the Last Glacial Maximum (LGM) ~20,000 years ago the glaciers were at their maximum extent and sea level was ~120m lower than at present; in Victoria the climate was colder, drier and perhaps also more windy. In southern Victoria sand dunes were active at this time and there was a lot of wind blown dust, implying that the vegetation cover was much less than at present. Many of the gullies in the highlands around central Victoria are partly filled with sediment that is now being eroded, and it has been suggested that this sediment was stripped from the hills during the LGM because of the reduced vegetation on the hills. The project will test this hypothesis by sampling the sediment in a number of different gullies and extracting plant material and charcoal for carbon dating, to see if the material was in fact deposited ~20,000 years ago.
Airborne radiometric images of the highland areas in central Victoria show that there are alluvial fans scattered along the highland margin; these appear to have been deposited relatively recently but are not active at present. A second project will look at one or two of these fans, describing the surface sediment, sampling it in a number of places and extracting plant material and charcoal for carbon dating, to see if the material was in fact deposited ~20,000 years ago.
Hydrology and hydrogeology of Lakes Gnotuk and Bullen Meri, western Victoria
Lakes Gnotuk and Bullen Meri lie within adjacent maars (volcanic craters) in western Victoria. Despite their closeness, their salinity and water composition are quite different. The lake sediments have been extensively studied as a detailed palaeoclimatic record, but the water chemistry has received less attention. At present there is a proposal for a housing development on the crater rim, and concerns have been raised that this will impact on the water quality of the lakes. The project will involve studying the hydrochemistry of the lakes, relating this to the regional groundwater and determining the dominant processes influencing the water composition. In addition, the variations in lake level and salinity will be modelled, starting with the existing model by Roger Jones and adding modifications that have been developed at La Trobe University. The project will be supported by Corangamite Shire.
Salinity stratification within bores
It has long been known that groundwater in some bores is stratified, with a layer of fresher water over more saline water at depth; the boundary between the two is sharp, and may coincide with the top of the screened interval. Not all bores are stratified, and the amount and depth of stratification vary greatly. The causes are not known; suggestions include drilling water left in the bore, leakage of rainwater into the bore, failure of the bore (fresher water comes from a different aquifer to the screened interval through a crack in the bore casing), older water from the aquifer, and/or evaporation/condensation within the bore. A preliminary study has shown that none of these ideas can be readily applied, and a more detailed study is required. Previous work throughout western and central Victoria has assembled an extensive database of stratified bores; in most of these the stratification has been removed by pumping. This project will involve visiting as many of these bores as possible to determine if stratification has re-established, and if it has, sampling the fresh and saline layers to determine what the chemical and isotopic differences are between them. In addition, unpumped stratified bores will also be sampled. The results will be combined with the characteristics of the stratified bores like depth, location, diameter etc, to establish the cause(s) of stratification, and to determine if and when stratification will re-establish after a bore has been pumped. This will greatly help with bore sampling procedures, in particular whether bores need to be pumped every time before sampling, and may also provide insights into the aquifer hydrogeology.
Salinisation of Mosquito Creek, western Victoria
Mosquito Creek runs south of Edenhope in the Wimmera region of western Victoria, into Bears Lagoon, which is a RAMSAR-listed site for protection of migratory birds. There are problems of waterlogging and salinisation along the creek, and there is concern that the lagoon will be adversely affected. Primary Industries Research Bendigo is installing a series of 4 nested piezometers in a transect across the site, along with a gauging station on the creek to record EC and flow. The project will use the monitoring data, together with water chemistry and hydrogeology from these and other bores in the area, to develop a hydrogeological model to explain the waterlogging and salinisation, and assess the most appropriate management options. The project will be co-supervised by Jon Fawcett (Primary Industries Research Bendigo) and supported by Department of Primary Industries and Wimmera Catchment Management Authority.
Quantifying and Managing Acid Drainage from the Overburden Dump at the Loy Yang Coal Mine
The Loy Yang Coal Mine is the biggest power producer in Victoria. This brown coal resource in the Latrobe Valley is mined and burnt almost solely for the production of electricity. Coal-poor interseam horizons containing pyritic material are disposed to an overburden dump. The pyrite oxidises to form sulphuric acid which causes a range of on-site problems. This project involves assessment of the scale of the acid drainage discharge issue from the overburden dump and identification of management / mitigation strategies. The project will be supported by Loy Yang Power and co-supervised by Dr Jeff Taylor of Earth Systems.
Covers for Tailings and Waste Rock Dumps, Woodlawn Mine, NSW
This lead-zinc mine has ceased production and the main open-cut is being used for disposal of domestic waste from Sydney. There are a number of tailings and waste rock dumps around the mine site, with the potential to release acidic water due to sulphide oxidation. This project will characterise the dumps in terms of their sulphide and acid-generating potential, analyse any leachate seeping from the dumps, and investigate the best covers for the dumps, to reduce infiltration of water and oxygen. This may involve both field and laboratory trials of different types of covers. The project will be supported by Collex and co-supervised by Dr Jeff Taylor of Earth Systems.
Treatment of Wastewater Generated by Processing of Sewerage Sludge
Sewerage sludge contains moderately high levels of many heavy metals, including Cd, Cu, Cr, Ni, Pb and Zn. Before it can be used as fertilizer, the concentrations must be reduced to levels specified by the EPA (1, 400, 100, 300, 60 and 200 mg/kg respectively). This is accomplished by acid leaching; the leachate contains substantial concentrations of the heavy metals present, and these metals must then be precipitated. The project will look in detail at the precipitation process, in order to determine the most effective methods of precipitation, and if it is possible to precipitate the metals separately. The project will be co-supervised by Bob Heller of Australian Organic Resources.
Remediation of acid mine drainage to produce acid-resistant sludge
Acid mine drainage is typically neutralised using an alkaline material like calcium hydroxide. This reaction precipitates a sludge composed of poorly crystalline ferrihydrite that can contain large amounts of adsorbed heavy metals. The sludge is readily susceptible to acid attack, e.g. if the sludge is disposed of where it can come into contact with acid drainage, and the metals are released back into solution. Research at La Trobe University has shown that if the sludge is composed of magnetite rather than ferrihydrite, it incorporates many heavy metals in a form that is much more resistant to acidity.
This project involves an experimental study of the best way to neutralise acid drainage in such a way as to maximise magnetite precipitation. Initial studies have shown that if dissolved iron is all present as ferrous iron, it will precipitate as ferrous hydroxide (green rust), and this can then be oxidised to form magnetite. However, most acid drainage consists of a mixture of dissolved ferric and ferrous iron; a reducing agent is required to reduce the ferric to ferrous iron. The project will investigate different reducing agents, e.g. calcium polysulphide, sodium metabisulphite, to see which is most effective and has the least side effects (e.g. release of hydrogen bisulphide).
Assessment of the "Coral reef hypothesis" - the impact of calcite precipitation by corals on atmospheric CO2
The "Coral reef hypothesis" states that calcite precipitation, e.g. by corals, forms carbonic acid that will exsolve as CO2:
Ca2+ + 2HCO3- = CaCO3 + H2CO3
H2CO3 = CO2 + H2O
Therefore periods of high biological activity in the oceans by calcite-precipitating organisms (forams, coccoliths, corals, algae etc) should be associated with times of high atmospheric CO2. However, the increased carbonic acid levels could also be removed by dissociation to bicarbonate, driven by the removal of this species by calcite precipitation:
H2CO3 = HCO3- + H+
There has been speculation that the current rise in the CO2 content of the atmosphere due to anthropogenic causes will be removed by calcite precipitation in the oceans, but the coral reef hypothesis argues that the opposite would occur. The project will involve a series of laboratory experiments to test the effect of calcite precipitation on carbonic acid levels, by inducing calcite precipitation in a beaker and measuring the effect on pH and bicarbonate concentrations, under a range of conditions designed to simulate likely natural oceanic scenarios. In addition, the changes in the concentrations of the various species will be modelled using PHREEQC.
|
