1,721,144 research outputs found
Evaluation of the Effects of Vegetated Buffer Strips on Fate of Sediment with Mathematical Models
No full textSeveral mathematical models have been developed in recent years to simulate hydrologic and sediment transport processed through vegetated buffer strips. Some of these models are empirically-based equations with limited applicability to conditions other than those under which they have been developed and the input data collected and used. There is a considerable amount of uncertainty in the application of existing process-based models as they consist of empirical sub-models in their structure. The inconsistency between the assumed section of erosion and deposition in and around the grass strip beds in the existing models is also a major limitation. Three independent predictive models are developed and presented in this thesis to fill in the gaps and to improve our predictive capabilities for hydrology and sediment transport across grass strips.
The first model developed in this study is a process-based one capable of simulating surface water profile in the upstream section and within grass strips. The data from the experiments carried out earlier in Griffith University’s GUTSR facilities were used to develop a relationship between the hydraulic roughness and flow characteristics and to develop the model itself. The gradually varied flow equation was used to apply the new relationship and to calculate the flow characteristics in the upstream section and within the grass strip bed.Thesis (PhD Doctorate)Doctor of Philosophy (PhD)Griffith School of EnvironmentScience, Environment, Engineering and TechnologyFull Tex
Evaluation of Sediment Transport Formulas for Queensland Rivers
No full textMeasurement and prediction of sediment transport rates are important for rivers in Queensland, particularly in connection to sediment delivery to near shore lagoons in the Great Barrier Reef. Planning and managing for sustainable sand and gravel extraction also requires accurate and reliable calculation of bed material load in river systems. Using sediment transport formulas can overcome the difficulties and reduce the costs associated with collecting field data. Sediment transport formulas were developed from theories that relate sediment transport to hydraulic and sediment variables, and were calibrated mostly with laboratory experiments. Previous evaluations of these formulas, mostly under the US and European conditions, showed that the suitability of these formulas could vary greatly according to the flow conditions under which they were applied. Evaluating the formulas in Australia is virtuallly nonexistent. In this study, sediment transport formulas are evaluated for Queensland rivers, where a wide range of climatic, hydrological and sediment conditions exist.Thesis (Masters)Master of Philosophy (MPhil)Griffith School of EngineeringScience, Environment, Engineering and TechnologyFull Tex
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Effectiveness of Soil/Spoil Amendments in Minimising Adverse Impacts of Runoff and Erosion at Coal Mine Rehabilitation Sites in the Bowen Basin Region, Central Queensland
No full textEffects of vegetation cover on runoff and soil loss reduction at mine rehabilitation sites are well documented. However, the knowledge of soil amendment applications, namely polyacrylamide (PAM) and gypsum, prior to the establishment of vegetation is still very limited. These soil amendment methods have proven to have the ability to improve soil surface stability in agriculture, however, the application of soil amendments to improve the spoil surface at mine rehabilitation sites is still un–trialled and their effectiveness largely unknown.
This study covers 4 topics namely; (1) to analyse the effectiveness of soil amendments towards improving the hydraulic conductivity of the soil and spoil; (2) to determine the effect of soil amendments application on sediment concentration in the runoff and total soil loss generated from the laboratory based soil erosion experiments; (3) to assess WinSEADS model (Soil Erosion and Deposition Simulation – Windows) to predict sediment concentration and total soil loss under a variety of scenarios; (4) to carry out cost assessment of possible field application of soil amendments under several scenarios.
In the small–scale experiments, the application of soil amendments to the soil and spoil was found to be beneficial in increasing the hydraulic conductivity. The results indicate that gypsum is more effective in maintaining a high hydraulic conductivity when compared with PAM. The percentage increase of hydraulic conductivity was found to depend on the soil amendment application rates; and the physical and chemical characteristics of the soil and spoil.Thesis (PhD Doctorate)Doctor of Philosophy (PhD)Griffith School of EngineeringScience, Environment, Engineering and TechnologyFull Tex
Effects of Land Development on Peak Runoff Rate and its Prediction for Brigalow Catchments in Central Queensland, Australia
No full textThe estimation of runoff volume and peak runoff rate has been the focus of significant
hydrological research worldwide. The results of these studies, usually in the form of empirical relationships or models, are intrinsically linked to the environment in which the study was conducted. This often limits the applicability and accuracy of the method of runoff estimation at alternative and ungauged locations. Within the brigalow belt of central Queensland, Australia, a scarcity of stream gauging stations to measure runoff volume and peak runoff rate has impeded research on the surface water hydrology of the region. Intermittent failure of these stations and consequently, multiple periods of missing data, have added further complexity and challenge to the understanding of catchment hydrology in the region.
Commencing in 1965 and continuing today, the Brigalow Catchment Study in central
Queensland has measured both runoff volume and peak runoff rate from three small
catchments which initially contained native brigalow scrub. The natural hydrology of the three catchments was characterised during a 17-year calibration period from 1965 to 1981. In 1982, two of the three catchments were cleared, with one developed for cropping and one developed for improved pasture, while the third was retained as an uncleared control catchment. Study of the effect of land development on surface hydrology commenced in 1984. Twenty-one years of record was used to quantify the changes in peak runoff rate associated with land development. Results however, were confounded by missing data. To allow for robust analysis, estimates of missing data were generated via three different methods: (1) multiple variable regression analyses; (2) Soil Conservation Service curve number and graphical peak discharge methodologies; and (3) a simple variable infiltration rate model. The suitability of each technique for the estimation of peak runoff rate was assessed using both graphical and numerical evaluation.Thesis (Masters)Master of Philosophy (MPhil)Griffith School of EngineeringScience, Environment, Engineering and TechnologyFull Tex
Effects of land clearing, land use change and land management on soil fertility and runoff water quality in the Brigalow Belt bioregion of central Queensland, Australia
No full textTerrestrial catchments adjacent to the Great Barrier Reef have undergone extensive anthropogenic modification over the last 150 years, including substantial land clearing and land use change. From 1996 to 2006, rates of land clearing in Queensland were among the highest in the world. More than 60% of this clearing occurred within the Brigalow Belt bioregion, which includes 98% of the Fitzroy Basin and 46% of the Burdekin Basin, both of which drain directly into the Great Barrier Reef lagoon. This land clearing and land use change has led to increased pollutant loads of nutrients, sediment and pesticides entering the Great Barrier Reef, which adversely impact the survival of this precious ecosystem. Agricultural land use is currently the largest contributor to pollutant loads.
The effects of land clearing and land use change on runoff in the Brigalow Belt bioregion are well documented. Long-term research has shown clearing of virgin brigalow scrub for cropping or grazed pasture has doubled runoff irrespective of land use. Peak runoff rates doubled when land was cleared for cropping and increased by 50% when cleared for grazed pasture. The short-term effects of land clearing and land use change on land resources such as soil fertility were also documented, but the long-term implications were not.
It was unclear how these changes in hydrology and soil fertility as a result of land clearing and land use change impacted water quality. Contemporary water quality investigations seeking to address this question are confounded by multiple issues. For example, climatic variability in central Queensland is large, so long-term monitoring is essential to develop true systems understanding. Short-term, three-to-five-year monitoring programs often fail to capture extremes in climate, so findings may not translate temporally. Broad-scale land clearing in the Brigalow Belt bioregion of central Queensland commenced in the 1960s and was generally considered to have ceased in 2006. As such, contemporary water quality data sets, while reflective of current catchment condition, likely provide little insight into the magnitude of change in water quality immediately post clearing due to multi-decadal lags between clearing and monitoring. Larger catchment scale water quality studies can be further confounded by mixed land use within a catchment and mixed land management within a single land use. Both scenarios make it difficult to separate land use effects on water quality from land management effects on water quality, with one likely to mask the effects of the other.
When broad-scale land clearing in the Brigalow Belt bioregion of central Queensland commenced in the 1960s, changes in hydrology and soil fertility were anticipated. In order to determine the effects of this land clearing and land use change on hydrology, soil fertility and productivity, the Brigalow Catchment Study was initiated in 1965. The subsequent data collected from this long-term paired, calibrated catchment study provided an opportunity to determine the impacts of land clearing and land use change on water quality. The use of long-term data from paired catchments of a single land use, that have been monitored for hydrological and soil fertility change since prior to clearing, resolves many of the confounding factors common to contemporary water quality studies.
This study of the effects of land clearing and land use change on water quality had four objectives as follows:
1) To determine the impact of changing land use from virgin brigalow scrub into a crop or pasture system on runoff water quality;
2) To evaluate whether clearing of brigalow scrub for cropping or grazing would alter the dynamics of soil organic carbon, nitrogen, phosphorus, sulfur and potassium over time;
3) To determine the impact on water quality of managing grazing land by varying stocking rate; and
4) To determine the impact of managing grazing land with tebuthiuron, a herbicide used for broad-scale woody weed control in grazing systems, on water quality.
All four of these objectives were priority knowledge gaps of the Reef 2050 Water Quality Improvement Plan 2017-2022, the 2017 Scientific Consensus Statement and their predecessors. Long-term water quality modelling indicated that changing land use from virgin brigalow scrub to cropping or grazing increased loads of total suspended solids, total and dissolved inorganic phosphorus, and ammonium nitrogen. The well-managed (unfertilised) pasture system had less nitrogen in runoff compared to runoff from virgin brigalow scrub. In years when runoff occurred from the agricultural catchments, but no runoff occurred from the virgin brigalow scrub, water quality loads were entirely anthropogenic and totally attributable to land use change.
These changes in water quality were modelled by extrapolating data collected at least 17 years after land clearing and land use change. During this 17-year period, significant nutrient fluxes occurred within the surface 0.1 m of the soil profile associated with clearing, burning and subsequent agricultural production. These fluxes, in particular the nine-fold increase in ammonium-nitrogen, the eight-fold increase in nitrate-nitrogen and the two to three-fold increase in bicarbonate- and acid-extractable phosphorus immediately after clearing likely resulted in extremes in water quality loads and pollutant concentrations compared to that observed in later years.
The effect of managing grazing land by varying stocking rate was greater than that of changing land use from virgin brigalow scrub to conservatively grazed pasture. Heavy grazing of improved pasture more than tripled runoff, peak runoff rate and total suspended solids loss compared to conservatively grazed pasture. Loads of total suspended solids, nitrogen and phosphorus in runoff were also greater from heavy than conservative grazing.
The effect of land management on water quality was most easily determined where the input to the system was entirely anthropogenic, such as broad-scale application of herbicide. Unlike nutrients, with no confounding natural input, herbicide loss in runoff was entirely contingent on herbicide use. Tebuthiuron loss in runoff was primarily in the dissolved phase with no correlation to total suspended solids. Concentrations of tebuthiuron in runoff declined exponentially with time, cumulative rainfall and cumulative runoff.
The new knowledge of the effects of land clearing, land use change and land management on soil fertility and runoff water quality generated in addressing the four objectives of this thesis has been extended, both spatially and temporally, by its inclusion in models for Great Barrier Reef catchments. This modelling estimates the effects of land management on water quality from catchments such as the Fitzroy Basin. Specifically, the research presented in this thesis has underpinned the design, calibration and validation of models at both the paddock and catchment scales as part of the Reef 2050 Water Quality Improvement Plan 2017-2022. This new body of knowledge has also been used to guide the development of regulations for protection of the Great Barrier Reef. These regulations were the focus of a 2020 senate inquiry, during which new knowledge from this thesis was presented in both written submissions and given as evidence.Thesis (PhD Doctorate)Doctor of Philosophy (PhD)School of Eng & Built EnvScience, Environment, Engineering and TechnologyFull Tex
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Phytocap soil and vegetation design: laboratory and field trials in Southeast Queensland
No full textPhytocapping is a sustainable landfill cover technology that utilises a vegetated soil cover to create a hydraulic barrier for compacted waste. The vegetation in phytocaps offers various environmental, ecological, and social benefits, including providing habitat for local flora and fauna and contributing to natural green spaces that mitigate air pollution and the urban heat island effect. Additionally, phytocap vegetation employs soil bioengineering to reinforce the soil, enhancing slope stability. Little research has focused on critical phytocapping design parameters, namely soil compaction and vegetation design, which significantly affect hydrological performance, as well as vegetation growth and survival. This thesis aims to inform landfill designers about optimal phytocap design by configuring soil compaction and vegetation design, using coal overburden material. The research comprises five stages that address the objectives. [...]Thesis (PhD Doctorate)Doctor of Philosophy (PhD)School of Eng & Built EnvScience, Environment, Engineering and TechnologyFull Tex
New Methods of Controlling Biological Aerosols
No full textFiltration is the most widely utilised air quality control technique used in a Heating, Ventilating and Air Conditioning (HVAC) duct systems in an indoor environment. Biological particles may be deposited onto, and re-aerosolized from, the filter surface, however, a range of variables such as types of microorganisms, filter characteristics, humidity, temperature and others factors can contribute to re-aerosolization. In this study, new methods are investigated to remove or inactivate the microorganism in the simulated HVAC system and controlled environment by adding various technologies to the current filtration systems. Two new technologies were tested; the first, emitting ions in the testing chamber, and the second, coating tea tree oil (TTO) onto the fibrous filter surface, in order to determine the most efficient and cost effective method for airborne biological particle control. Two commercial low-efficiency HVAC filters were tested in this investigation using a number of monodisperse polystyrene latex (PSL) spheres with diameters 0.5, 0.8, 1.0, and 1.5 [microns]. An influence of air ionization on the filtration process was investigated by running of an ionizer that was placed at a range of distances apart from the filter (5, 15, 25, and 45cm). The results of this investigation show that the current theoretical model underestimates the efficiencies of the particle deposition onto the filter fibres. However, this could be explained by the fact that some incoming particles are repelled from the filter, due to repelling electrostatic forces caused by unipolar ions captured by the filter. This investigation concluded that emitted air ions enhance the filtration efficiency, but found that the efficiency depends upon the filter type and the distance from the ion emitter to the filter surfaces. This investigation has provided strong evidence that ionization enhances the filtration efficiency, and that there are significant enhancements when the ion emitter is operated at 5 cm upstream of the filter. The results of this study illustrate that the continuous emission of negative ions in the vicinity of a low-efficiency HVAC filter significantly enhances its performance of removal airborne biological particles including bacteria, fungal spores and virus in the ambient air environment. Finally, bacteria (B. subtilis, E. coli and P. fluorescens) and fungal spores (Rhizopus stolonifer and A. niger) were examined by coating the filter fibres with biologically active TTO and biologically neutral light mineral oil (MO). It was found experimentally that pre-coating of the filter fibres with TTO and then using this filter for bioaerosols control, resulted in rapid inactivation of captured microorganisms and minimising a number of viable particles possibly blown off from the filter by the air. It was shown that 90 percent of the robust B. subtilis bacterial strain was inactivated during 30 minutes of the technology operation. Furthermore, the inactivation efficiency of some more sensitive bacterial aerosols of E. coli and P. fluorescens were found to be above 99 percent for the same time interval of 30 minutes. Fungal strains were found to be more robust with only 52-54 percent inactivation achieved over 60 minutes experimental run.Thesis (PhD Doctorate)Doctor of Philosophy (PhD)Griffith School of EngineeringScience, Environment, Engineering and TechnologyFull Tex
- …
