Academic literature on the topic 'Minesite rehabilitation'

Native grasses have become increasingly important in the post-mining landscape where land rehabilitators try to reconstruct vegetation communities similar to those present before land clearing. So as to include native grasses in these communities, there is a requirement to understand their germination biology, because in the past, many grasses have typically been hard to establish in the final community. The present study found that poor germination of 13 native grass species was due to (1) low percentage of seed fill, (2) low seed viability of filled seeds and/or (3) seed dormancy. Eight species had dormancy treatments investigated. Most were found to exhibit at least one form of dormancy that was either located in the hull structures immediately external to the caryopsis (i.e. the lemma, palea and glumes), within the seed coat (i.e. testa and pericarp, tissues that are found inside the hull, but external to the embryo and endosperm) and/or within the embryo. Seven of the grass species tested were found to have a dormancy mechanism present in two or more locations of their dispersal unit. Germination of the selected native grass species could be improved by (1) processing seeds to enrich the percentage of seeds that are filled, (2) testing viability to ensure a high proportion of the seeds are likely to germinate or (3) using methods to help overcome dormancy and promote germination.

This paper gives a review of available information on natural-series radionuclides in traditional Aboriginal foods of northern Australia. Research on this topic has been carried out primarily for radiological impact assessment purposes in relation to uranium mining activities in the region. Many of the studies have concentrated on providing purely concentration data or concentration ratios, although more detailed uptake studies have been undertaken for freshwater mussels, turtles, and water lilies. The most-studied radionuclides are238U and226Ra. However, dose estimates based on current data highlight the importance of210Po, particularly for the natural (nonmining-related) dose. Data on uptake by terrestrial flora and fauna are scarce in comparison with aquatic organisms, and this knowledge gap will need to be addressed in relation to planning for uranium minesite rehabilitation.

The importance of ectomycorrhizas in Eucalyptus tetrodonta F.Muell. and E. miniata Cunn. ex Schauer dominated forests and woodland communities in the monsoonal tropics of northern Australia was assessed. Ectomycorrhizas colonised between 24 and 54% of final order lateral roots in soil cores collected at 16 native forest sites. Only a minority of the plant species present formed ectomycorrhizas (mainly eucalypts and acacias) but these species contributed more than 75% of the basal area. More than 70 species of putative ectomycorrhizal fungi were collected, with three hypogeous taxa (Nothocastoreum, Hysterangium and an undescribed Boletaceae) most frequently encountered. Glasshouse inoculation experiments confirmed that a diverse range of fungi was capable of forming ectomycorrhizas with E. tetrodonta and E. miniata seedlings, and that the growth of both species could be substantially increased by inoculation with specific fungi. The fungi most effective in increasing seedling growth were generally those which most extensively colonised the seedling roots. A second component of this study investigated the requirements for ectomycorrhizal fungi in native forest rehabilitation following mining. Ectomycorrhizal infectivity was low in disturbed soils and mine spoil materials, with the intensity of disturbance and the presence of regrowth vegetation key determinants of the level of infectivity. Inoculation of seedlings of E. miniata with spores of ectomycorrhizal fungi increased both growth and leaf phosphorus concentrations by between two- and three-fold at 7 months after planting out on a waste rock dump devoid of native ectomycorrhizal propagules. The application of these findings to minesite rehabilitation in the region, and the feasibility of using spores for broad-scale inoculation, are discussed.

Gold and nickel mining are a common land use in the semiarid Eastern Goldfields region of Western Australia,, A frequent outcome of mining activity is highly saline landforms that result from the widespread use of hypersaline (> 50 g L(subscript)-1 NaCl) groundwater for mineral processing and hydraulic tailings reclamation, and from saline horizons in soils, subsoils and mullock. Under State government legislation, all mined land must be rehabilitated to a stable and sustainable landform at the completion of mining activities.There was little land rehabilitation carried out in the mining industry until the mid1980s. At that time, legislation was introduced and, in due course, guidelines were issued on recommended approaches to rehabilitation. Today, rehabilitation of disturbed areas is usually integrated into the mining program and has become the rule rather than the exception. There has, however, been limited innovation in recent years and the established methods are not suitable for every land rehabilitation scenario, especially those where very high salinity is an important factor. The aims of this thesis were to make a contribution towards a better understanding of the ecology of halophytes suitable for use in revegetation and the likely physical requirements for their sustainable establishment on post-mining landforms.In terms of germination, many of the halophytes currently used for rehabilitation of saline substrates are well suited in that they are able to germinate in solutions of up to 20 g L(subscript)-1 NaCl. Furthermore, when higher salinities are encountered, seed dormancy is induced until salinity is reduced to a level at which germination can occur. There were differences observed between germination of annual and perennial chenopods that reflected their successional roles where annual chenopods tend to have a higher salt tolerance and germinate more rapidly. I developed a tolerance index to enable different germination responses to be readily compared. Values for the tolerance index ranged from 5.7 to 25.3 for the halophytic species compared with a value of 0.2 for the glycophytic Secale cereale. Values for saltbushes (Atriplex) and bluebushes (Maireana) ranged from 6.5 to 9.8 while values for samphires (Halosarcia) were higher (10.7-17.4).Germination and early growth of taxa in the succulent genus, Halosarcia, were also studied. Though a member of the Chenopodiaceae, with a number of species occurring commonly throughout the region, Halosarcia spp. are not widely used in rehabilitation. This is in part attributable to the poor level of knowledge of germination and growth characteristics compared with saltbushes and bluebushes, many of which are widely used. Two species studied, H. halocnemoides subsp. halocnemoides and H. pruinosa, are more salt-tolerant for germination than some other chenopods more widely used. Furthermore, in terms of their early growth, each taxon continued to grow in salinities up to 40 g L(subscript)-1 NaCl, although root .Production and mass were reduced at that concentration. Another taxon, H. pergranulata subsp. pergranulata, was found to have a partial physical dormancy attributable to the testa, a phenomenon rare among halophytes. Dormancy was alleviated by scarification but was most effective where this occurred near the micropyle.Field trials were conducted to assess methods of rehabilitating severely salt-affected surfaces (EC(subscript)e > 50 dS m(subscript)-1). In the initial trial, a number of surface treatments, including ripping, rock mulching and mounding, were shown to reduce soil EC, in loam soils over a long period of time (seven years) compared with the control. In a subsequent trial, the use of good quality waste water, in conjunction with ponding banks, strongly promoted the establishment of vegetation by supplementing soil moisture and enhancing soil P although a reduction in soil EC(subscript)e was not observed. The depth and duration of ponding influenced the species that established and the cover achieved. Methods by which a soil cover could be established over hypersaline tailings surfaces were also investigated. The absence of a capillary break layer resulted in severe salinisation (EC(subscript)e > 100 dS m(subscript)-1) of a non-saline clay loam soil cover and likely severe difficulties in establishing and maintaining vegetation on the cover. Two types of capillary break layer, a synthetic membrane and a layer of coarse iron fayalite granules (nickel slag), were both effective at preventing the capillary rise of salts into the soil cover.The physical and biological characteristics of the shores of Lake Lefroy, a large salt lake in the Eastern Goldfields region, were analysed using multivariate techniques.Physical characteristics were strongly influenced by the orientation of the shore relation to the predominant winds, and by depth to the saline groundwater table. Plant species were distributed in zones across the lake shores with small changes in elevation resulting in substantial changes in species distributions. Those plant species occurring at the lowest elevations (Zone I), including Halosarcia spp., exhibited a very high tolerance of saline soil and groundwater through an ability to accumulate Na+ and Cl- and make the necessary osmotic adjustments, and a capacity to tolerance high groundwater levels. Under certain conditions, the lake shore environment could be a useful model for a rehabilitated landform.

Gold and nickel mining are a common land use in the semiarid Eastern Goldfields region of Western Australia,, A frequent outcome of mining activity is highly saline landforms that result from the widespread use of hypersaline (> 50 g L(subscript)-1 NaCl) groundwater for mineral processing and hydraulic tailings reclamation, and from saline horizons in soils, subsoils and mullock. Under State government legislation, all mined land must be rehabilitated to a stable and sustainable landform at the completion of mining activities.There was little land rehabilitation carried out in the mining industry until the mid1980s. At that time, legislation was introduced and, in due course, guidelines were issued on recommended approaches to rehabilitation. Today, rehabilitation of disturbed areas is usually integrated into the mining program and has become the rule rather than the exception. There has, however, been limited innovation in recent years and the established methods are not suitable for every land rehabilitation scenario, especially those where very high salinity is an important factor. The aims of this thesis were to make a contribution towards a better understanding of the ecology of halophytes suitable for use in revegetation and the likely physical requirements for their sustainable establishment on post-mining landforms.In terms of germination, many of the halophytes currently used for rehabilitation of saline substrates are well suited in that they are able to germinate in solutions of up to 20 g L(subscript)-1 NaCl. Furthermore, when higher salinities are encountered, seed dormancy is induced until salinity is reduced to a level at which germination can occur. There were differences observed between germination of annual and perennial chenopods that reflected their successional roles where annual chenopods tend to have a higher salt tolerance and germinate more ++
rapidly. I developed a tolerance index to enable different germination responses to be readily compared. Values for the tolerance index ranged from 5.7 to 25.3 for the halophytic species compared with a value of 0.2 for the glycophytic Secale cereale. Values for saltbushes (Atriplex) and bluebushes (Maireana) ranged from 6.5 to 9.8 while values for samphires (Halosarcia) were higher (10.7-17.4).Germination and early growth of taxa in the succulent genus, Halosarcia, were also studied. Though a member of the Chenopodiaceae, with a number of species occurring commonly throughout the region, Halosarcia spp. are not widely used in rehabilitation. This is in part attributable to the poor level of knowledge of germination and growth characteristics compared with saltbushes and bluebushes, many of which are widely used. Two species studied, H. halocnemoides subsp. halocnemoides and H. pruinosa, are more salt-tolerant for germination than some other chenopods more widely used. Furthermore, in terms of their early growth, each taxon continued to grow in salinities up to 40 g L(subscript)-1 NaCl, although root .Production and mass were reduced at that concentration. Another taxon, H. pergranulata subsp. pergranulata, was found to have a partial physical dormancy attributable to the testa, a phenomenon rare among halophytes. Dormancy was alleviated by scarification but was most effective where this occurred near the micropyle.Field trials were conducted to assess methods of rehabilitating severely salt-affected surfaces (EC(subscript)e > 50 dS m(subscript)-1). In the initial trial, a number of surface treatments, including ripping, rock mulching and mounding, were shown to reduce soil EC, in loam soils over a long period of time (seven years) compared with the control. In a subsequent trial, the use of good quality waste water, in conjunction with ponding banks, strongly ++
promoted the establishment of vegetation by supplementing soil moisture and enhancing soil P although a reduction in soil EC(subscript)e was not observed. The depth and duration of ponding influenced the species that established and the cover achieved. Methods by which a soil cover could be established over hypersaline tailings surfaces were also investigated. The absence of a capillary break layer resulted in severe salinisation (EC(subscript)e > 100 dS m(subscript)-1) of a non-saline clay loam soil cover and likely severe difficulties in establishing and maintaining vegetation on the cover. Two types of capillary break layer, a synthetic membrane and a layer of coarse iron fayalite granules (nickel slag), were both effective at preventing the capillary rise of salts into the soil cover.The physical and biological characteristics of the shores of Lake Lefroy, a large salt lake in the Eastern Goldfields region, were analysed using multivariate techniques.Physical characteristics were strongly influenced by the orientation of the shore relation to the predominant winds, and by depth to the saline groundwater table. Plant species were distributed in zones across the lake shores with small changes in elevation resulting in substantial changes in species distributions. Those plant species occurring at the lowest elevations (Zone I), including Halosarcia spp., exhibited a very high tolerance of saline soil and groundwater through an ability to accumulate Na+ and Cl- and make the necessary osmotic adjustments, and a capacity to tolerance high groundwater levels. Under certain conditions, the lake shore environment could be a useful model for a rehabilitated landform.

Masters Research - Master of Philosophy (MPhil)
Currently, there are approximately 20,000 ha of land that requires rehabilitation in the Hunter Valley, New South Wales. The revegetation of these lands is vital to achieving acceptable environmental outcomes for the affected local communities. Revegetation success is limited, however by the poor quality of soils following disturbance. The soil removal and storage process results in reduced water holding capacity, nutrient retention and physical structure. Organic amendments are commonly used to improve the quality of soils and therefore the outcomes of mine rehabilitation. Biochar is an organic amendment that has not been extensively tested on disturbed soils from the Hunter Valley. Biochar is a relatively recent discovery, with many studies finding its effectiveness to vary based on its production conditions and the existing properties of the receiving soil. Biochar is hypothesised to improve a range of soil physical, chemical and biological properties resulting in improvements to plant growth. The impact of biochar on soils can depend on the biochar properties and receiving soil properties. The varied response of plants and soils to biochars suggests that not all soils will benefit from applications of biochar. The potential for negative responses to biochar and irreversibility of application in a field environment leads to the conclusion that biochars must be adequately tested in a controlled environment before field testing and eventual wide-scale use. With this in mind, a number of experiments were undertaken to determine the impact of plant-derived biochars on disturbed soils from the Bengalla Mine in the Hunter Valley. These experiments included: A baseline soil and biochar characterisation to identify the likely interactions that would take place between the soils and biochars. ; A series of pot plant trials in a glasshouse environment to quantify the interaction between soil and biochar and the plant response to different combinations of soil and biochar. ; Total and matric soil suction tests to determine the impact of biochar on soil water retention. ; Column leaching experiments to elucidate the impact of biochar on soil permeability and water retention. The soil baseline analysis identified Biochar One would have a positive impact on the Bengalla Silty Clay Loam. This was based on the low soil pH and high biochar pH, low soil carbon content and high biochar carbon content, and other properties. Pot Trial One and Pot Trial Two analysed the response of the Bengalla Silty Clay Loam to Biochar One. The results found biochar significantly reduced soil bulk density, improved moisture content, pH, soil carbon, and increased soil nutrient retention from fertiliser. These improvements correlated with a significant increase in seedling germination, plant height and plant yield. The baseline analysis could not determine if Biochar Two would have a positive or negative impact on the Bengalla Light Clay. Pot Trial Three analysed the plant response of the Bengalla Light Clay and Biochar Two. Soil testing found biochar significantly improved some soil properties, but this was not evidenced in the plant growth results. The plant growth increased when biochar was applied at 20 t/ha but trended negatively with increasing biochar application rates. Further testing in the form of total and matric soil suction tests and column leaching experiments were undertaken to elucidate the physical interactions between the two materials. The total and matric soil suction tests found slight reductions in soil suction when applied with biochar, and biochar in isolation (100% biochar) contained significantly less moisture at all suction values. Therefore the negative plant response in the higher biochar application rates in Pot Trial Three can partly be explained by limited water availability. The column leaching experiment was undertaken to assess the impact of biochar on soil permeability. Saturated hydraulic conductivity was higher under the 100 t/ha treatment, which was considered a benefit given the extremely low saturated hydraulic conductivity of the control. The impact of biochar to leachate quality was low, therefore addressing the concern that it may negatively affect downstream water reserves when applied in the field. Overall, the study found biochar significantly improved properties of disturbed soils, however the resulting impact on plant growth was inconsistent. The analysis of soil and biochar characteristics prior to application is highly recommended to determine the likelihood of a positive response and ensure the biochar addresses the limitations of receiving soils. The use of pot trials to further confirm the plant response to soil and biochar combinations is recommended prior to field testing or wide-scale uptake of biochar technology. Careful consideration of reported biochar results is recommended due to the variation in pot trial methodologies. This study identified that the study of biochar and other solid soil amendments lack a formally recognised and standardised pot trial methodology. The pot trial methodologies in this thesis were based on published journal articles and therefore were not deemed to be inappropriate. The development of a standardised methodology would provide a framework for comparing biochars with other biochars and amendments such as composts; and would allow more appropriate application of biochars to different soils.

The aim of this research is to assess various options for the management of topsoil stockpiles on disturbed lands and to evaluate the viability and germinability over time of the seedbanks in these stockpiles for use in rehabilitation. To predict their success, experimental trials were designed and conducted.