Revegetation strategies for bauxite refinery residue: A case study of Alcan Gove in Northern Territory, Australia

Alumina extraction from bauxite ore with strong alkali produces waste bauxite refinery residue consisting of residue sand and red mud. The amount and composition of refinery residue depend on the purity of the bauxite ore and extraction conditions, and differs between refineries. The refinery residue is usually stored in engineered disposal areas that eventually have to be revegetated. This is challenging because of the alkaline and sodic nature of the residue. At Alcan Gove's bauxite refinery in Gove, Northern Territory, Australia, research into revegetation of bauxite residue has been conducted since the mid-1970s. In this review, we discuss approaches taken by Alcan Gove to achieve revegetation outcomes (soil capping of refinery residue) on wet-slurry disposal areas. Problems encountered in the past include poor drainage and water logging during the wet season, and salt scalding and capillary rise during the dry season. The amount of available water in the soil capping is the most important determinant of vegetation survival in the seasonally dry climate. Vegetation cover was found to prevent deterioration of the soil cover by minimising capillary rise of alkalinity from the refinery residue. The sodicity and alkalinity of the residue in old impoundments has diminished slightly over the 25 years since it was deposited. However, development of a blocky structure in red mud, presumably due to desiccation, allows root penetration, thereby supplying additional water to salt and alkali-tolerant plant species. This has led to the establishment of an ecosystem that approaches a native woodland.

Hearing sensitivity and bone mineral density in older adults: the Health, Aging and Body Composition Study

Bone mineral density (BMD) may be associated with hearing loss in older adults. Demineralization of the cochlear capsule has been associated with hearing loss in those with Paget's disease of the bone and otosclerosis. Osteoporosis may also result in cochlear capsule demineralization. We hypothesized that lower hip BMD and lower heel ultrasound measurements would be associated with hearing loss in a population-based sample of 2,089 older black and white men and women. Bone parameters and hearing function were measured at the fourth clinical follow-up visit. Audiometric threshold testing was used to measure air- and bone-conduction hearing sensitivity. BMD of the hip and its subregions was measured using dual-energy X-ray absorptiometry. Calcaneal bone measurements [broadband ultrasound attenuation (BUA), speed of sound (SOS) and the quantitative ultrasound index (QUI)] were obtained using heel ultrasound. After adjusting for known hearing loss risk factors, no association was found between hearing and any of the bone measurements in whites and black women. In black men, however, lower hip BMD was associated with higher odds of hearing loss; for each standard deviation decrease in total hip BMD, the odds of hearing loss were 1.41 (95% confidence interval 1.08, 1.83), 1.39 (95% CI 1.07, 1.82) for femoral neck BMD and 1.65 (95% CI 1.26, 2.16) for trochanter BMD. Conductive hearing loss was associated with lower heel ultrasound measurements, though only among white men. The results of this study are mixed and inconclusive. Lower BMD of the hip and its subregions was associated with hearing loss among black men, but not among whites or black women. Lower measurements on heel ultrasound were associated with conductive hearing loss, though only among white men. These results suggest that axial and appendicular bone parameters may be modestly associated with hearing loss in older men, but not in women.

Developmental vitamin D (DVD) deficiency in the rat alters adult behaviour independently of HPA function

Developmental vitamin D deficiency (DVD) has been shown to alter the orderly pattern of brain development. Even though the period of vitamin D deficiency is restricted to gestation this is sufficient to induce behavioural abnormalities in the adult offspring consistent with those seen in many animal models of schizophrenia. Given that some of these behavioural alterations could also be an indirect result of either impaired maternal hypothalamic pituitary axis (HPA) function (which in turn could influence maternal care) or the result of a permanent alteration in HPA function in the adult offspring we have examined HPA status in both maternal animals and adult offspring. In this study we have established that HPA function is normal in the maternally vitamin D deficient rat. We replicate the behavioural phenotype of hyperlocomotion whilst establishing that HPA function is also unchanged in the adult mate offspring. We conclude that the behavioural alterations induced by DVD deficiency are due to some adverse event in brain development rather than via an alteration in stress response. (c) 2006 Elsevier Ltd. All rights reserved.

An MRI investigation into the function of the transversus abdominis muscle during "drawing-in" of the abdominal wall

Study Design. An operator blinded dual modality trial of measurement of the abdominal muscles during drawing-in of the abdominal wall. Objectives. 1) To investigate, using magnetic resonance imaging (MRI), the function of the transversus abdominis muscle bilaterally during a drawing-in of the abdominal wall. 2) To validate the use of real-time ultrasound imaging as a measure of the deep abdominal muscle during a drawing-in of the abdominal wall. Summary of Background Data. Previous research has implicated the deep abdominal muscle, transversus abdominis, in the support and protection of the spine and provided evidence that training this muscle is important in the rehabilitation of low back pain. One of the most important actions of the transversus abdominis is to draw-in the abdominal wall, and this action has been shown to stiffen the sacroiliac joints. It is hypothesized that in response to a draw in, the transversus abdominis muscle forms a deep musculofascial corset and that MRI could be used to view this corset and verify its mechanism of action on the lumbopelvic region. Methods. Thirteen healthy asymptomatic male elite cricket players aged 21.3 +/- 2.1 years were imaged using MRI and ultrasound imaging as they drew in their abdominal walls. Measurements of the thickness of the transversus abdominis and internal oblique muscles and the slide of the anterior abdominal fascia were measured using both MRI and ultrasound. Measurement of the whole abdominal cross-sectional area (CSA) was conducted using MRI. Results. Results of the MRI demonstrated that, as a result of draw-in, there was a significant increase in thickness of the transversus abdominis (P < 0.001) and the internal oblique muscles (P < 0.001). There was a significant decrease in the CSA of the trunk (P < 0.001). The mean slide ( +/- SD) of the anterior abdominal fascia was 1.54 +/- 0.38 cm for the left side and 1.48 +/- 0.35 cm for the right side. Ultrasound measurements of muscle thickness of both transversus abdominis and the internal oblique, as well as fascial slide, correlated with measures obtained using MRI (interclass correlations from 0.78 to 0.95). Conclusions. The MRI results demonstrated that during a drawing-in action, the transversus abdominis contracts bilaterally to form a musculofascial band that appears to tighten (like a corset) and most likely improves the stabilization of the lumbopelvic region. Real-time ultrasound imaging can also be used to measure changes in the transversus abdominis during the draw-in maneuver.

Postnatal developmental expression of the PDZ scaffolds Na+-H+ exchanger regulatory factors 1 and 2 in the rat cochlea

Sensory transduction in the mammalian cochlea requires the maintenance of specialized fluid compartments with distinct ionic compositions. This is achieved by the concerted action of diverse ion channels and transporters, some of which can interact with the PDZ scaffolds, Na+-H+ exchanger regulatory factors 1 and 2 (NHERF-1, NHERF-2). Here, we report that NHERF-1 and NHERF-2 are widely expressed in the rat cochlea, and that their expression is developmentally regulated. Reverse transcription/polymerase chain reaction (RT-PCR) and Western blotting initially confirmed the RNA and protein expression of NHERFs. We then performed immunohistochemistry on cochlea during various stages of postnatal development. Prior to the onset of hearing (P8), NHERF-1 immunolabeling was prominently polarized to the apical membrane of cells lining the endolymphatic compartment, including the stereocilia and cuticular plates of the inner and outer hair cells, marginal cells of the stria vascularis, Reissner's epithelia, and tectorial membrane. With maturation (P21, P70), NHERF-1 immunolabeling was reduced in the above structures, whereas labeling increased in the apical membrane of the interdental cells of the spiral limbus and the inner and outer sulcus cells, Hensen's cells, the inner and outer pillar cells, Deiters cells, the inner border cells, spiral ligament fibrocytes, and spiral ganglion neurons (particularly type II). NHERF-1 expression in strial basal and intermediate cells was persistent. NHERF-2 immunolabeling was similar to that for NHERF-1 during postnatal development, with the exception of expression in the synaptic regions beneath the outer hair cells. NHERF-1 and NHERF-2 co-localized with glial fibrillary acidic protein and vimentin in glia. The cochlear localization of NHERF scaffolds suggests that they play important roles in the developmental regulation of ion transport, homeostasis, and auditory neurotransmission.

Modelling pre-clearing vegetation distribution using GIS-integrated statistical, ecological and data models: A case study from the wet tropics of Northeastern Australia

Traditional vegetation mapping methods use high cost, labour-intensive aerial photography interpretation. This approach can be subjective and is limited by factors such as the extent of remnant vegetation, and the differing scale and quality of aerial photography over time. An alternative approach is proposed which integrates a data model, a statistical model and an ecological model using sophisticated Geographic Information Systems (GIS) techniques and rule-based systems to support fine-scale vegetation community modelling. This approach is based on a more realistic representation of vegetation patterns with transitional gradients from one vegetation community to another. Arbitrary, though often unrealistic, sharp boundaries can be imposed on the model by the application of statistical methods. This GIS-integrated multivariate approach is applied to the problem of vegetation mapping in the complex vegetation communities of the Innisfail Lowlands in the Wet Tropics bioregion of Northeastern Australia. The paper presents the full cycle of this vegetation modelling approach including sampling sites, variable selection, model selection, model implementation, internal model assessment, model prediction assessments, models integration of discrete vegetation community models to generate a composite pre-clearing vegetation map, independent data set model validation and model prediction's scale assessments. An accurate pre-clearing vegetation map of the Innisfail Lowlands was generated (0.83r(2)) through GIS integration of 28 separate statistical models. This modelling approach has good potential for wider application, including provision of. vital information for conservation planning and management; a scientific basis for rehabilitation of disturbed and cleared areas; a viable method for the production of adequate vegetation maps for conservation and forestry planning of poorly-studied areas. (c) 2006 Elsevier B.V. All rights reserved.

The effects of temperature and salinity on Acacia harpophylla (brigalow) (Mimosaceae) germination

Acacia harpophylla F. Muell. (brigalow) used to naturally occur over a range of about 50 000 km(2) in Queensland and New South Wales, Australia. Large scale clearing for agriculture has reduced the area to less than 20 000 km(2) and it is estimated that 20-25% of vertebrate fauna living in brigalow communities will become locally extinct as a result of the current clearing induced loss of habitat. Some coal mining companies in central Queensland have become interested in providing habitat for the endangered bridle nail-tailed wallaby that lives in brigalow vegetation. However, there is little known about establishment techniques for brigalow on mine sites and other disturbed ground; an understanding of brigalow biology and ecology is required to assist in the conservation of this threatened vegetation community and for re-creation of bridled nail-tail wallaby habitat in the post mining landscape. Brigalow is an unusual species of Acacia because it is not hard-seeded and germinates readily without the need to break seed-coat imposed dormancy. Germination trials were undertaken to test the ability of brigalow seed to germinate with a range of temperatures and salinity levels similar to those experienced in coal mine spoil. Optimum germination was found to occur at temperatures from 15 to 38 degrees C and no germination was recorded at 45 degrees C. Brigalow was very tolerant of high salt levels and germinated at percentages greater than 50% up to the highest salinity tested, 30 dS/m. Germination of greater than 90% occurred up to an electrical conductivity of 20 dS/m. The results indicate brigalow seed can be sown in summer when rains are most likely to occur, however, shading of the seed with extra soil or mulch may ensure the ground surface does not become too hot for germination. Because of its ability to germinate at high salinity levels, brigalow may be suitable for use in saline mine wastes which are common on sites to be rehabilitated after mining.

The effect of organic mulch amendments on the physical and chemical properties and revegetation success of a saline-sodic minespoil from central Queensland, Australia

Saline-sodic clay minespoil materials excavated during open-cut coal mining in central Queensland, Australia, pose significant challenges for revegetation, particularly where suitable topsoil capping is not available. We examined the ability of sawdust or straw mulch amendments to ameliorate the adverse properties of these minespoils and improve the success of revegetation efforts. In laboratory studies, mulch application improved infiltration, increased soil moisture retention and reduced surface crust strength. In the field, mulches incorporated to a depth of 0.15 m at application rates of at least 20 t/ha straw or 80 t/ha sawdust were needed to mitigate against capillary rise of salts during drying cycles and support satisfactory vegetation cover. Further research is needed to determine whether improvements are maintained beyond the 4-year trial period reported here.

Responses of four Australian tree species to toxic concentrations of copper in solution culture

In Australia, metal-contaminated sites, including those with elevated levels of copper (Cu), are frequently revegetated with endemic plants. Little is known about the responses of Australian plants to excess Cu. Acacia holosericea, Eucalyptus crebra, Eucalyptus camaldulensis, and Melaleuca leucadendra were grown in solution culture with six Cu treatments (0.1 to 40 mu M). While A. holosericea was the most tolerant to excess Cu, all of the species tested were sensitive to excess Cu when compared with exotic tree and agricultural species. The critical external concentrations for toxicity were < 0.7 mu M for all species tested. There was little differentiation between shoot-tissue Cu concentrations in normal versus treated plants, thus, the derivation of critical shoot concentrations was possible only for the most tolerant species, A. holosericea. Critical root Cu concentrations were approximately 210 mu g g(-1) (A. holosericea), 150 mu g g(-1) (E. crebra), 25 mu g g(-1) (E. camaldulensis), and 165 mu g g(-1) (M. leucadendra). These results provide the first comprehensive combination of growth responses, critical concentrations, and toxicity symptoms for three important Australian genera for use in the management of Cu-contaminated sites.

Effect of NaCl on emergence and growth of a range of provenances of Eucalyptus citriodora, Eucalyptus populnea, Eucalyptus camaldulensis and Acacia salicina

High salt levels in mine spoils have been identified as one of the major chemical limitations to plant establishment after coal mining in central Queensland. Soil solution extracts from spoils indicated that EC levels of up to 26 dS/m could be encountered. Glasshouse trials examined the emergence and growth of Eucalyptus citriodora, Eucalyptus camaldulensis and Eucalyptus populnea provenances and Acacia salicina subjected to such EC levels. Relatively low levels of salt (100 mM NaCl, or 11 dS/m) with respect to the levels encountered on mine spoils, were enough to substantially reduce the rate and percentage emergence of all eucalypt provenances. A. salicina was found to be superior to the eucalypts in its ability to emerge and survive under saline conditions. It was the only species to have seedlings emerge and survive at 200 mM NaCl (20 dS/m), and the effect of salt on decreasing seedling dry weight was less pronounced for A. salicina than for any of the eucalypts. Established plants survived the range of salt treatments far better than emerging seedlings, with survival of established plants being reduced only at 300 and 400 mM NaCl (28 and 36 dS/m, respectively). A. salicina performed significantly better at 300 and 400 mM NaCl than most of the eucalypts studied. (c) 2006 Elsevier B.V. All rights reserved.

Frequency band selection of radars for buried object detection

Choice of the operational frequency is one of the most responsible parts of any radar design process. Parameters of radars for buried object detection (BOD) are very sensitive to both carrier frequency and ranging signal bandwidth. Such radars have a specific propagation environment with a strong frequency-dependent attenuation and, as a result, short operational range. This fact dictates some features of the radar's parameters: wideband signal-to provide a high range resolution (fractions of a meter) and a low carrier frequency (tens or hundreds megahertz) for deeper penetration. The requirement to have a wideband ranging signal and low carrier frequency are partly in contradiction. As a result, low-frequency (LF) ultrawide-band (UWB) signals are used. The major goal of this paper is to examine the influence of the frequency band choice on the radar performance and develop relevant methodologies for BOD radar design and optimization. In this article, high-efficient continuous wave (CW) signals with most advanced stepped frequency (SF) modulation are considered; however, the main conclusions can be applied to any kind of ranging signals.

Structure repair of a compacted vertisol with wet-dry cycles and crops

We hypothesized that the four rotation crops: wheat (Triticum aestivum L.), sorghum [Sorghum bicolor (L.) Merr.], lablab [Lablab purpureus (L.) Sweet] and mung bean [ Vigna radiata (L.) R. Wilczek] differ in their ability to repair soil structure. The study was conducted on a Typic Haplustert, Queensland, Australia, locally termed a Black Earth and considered a prime cropping soil. Large (0.5-m depth by 0.3-m diam.) soil cores, collected from compacted wheel furrows in an irrigated cotton (Gossypium hirsutum L.) field, were subjected to three, six, or nine wet-dry cycles that simulated local flood irrigation practices. After each cycle, soil profiles were sampled for clod bulk density, image analysis of soil structure, and evapotranspiration. Generally, all crops improved soil structure over the initial field condition but lablab and mung bean gave improvements to greater depths and more rapidly than wheat and sorghum. Mung bean and lablab caused up to a threefold increase in clod porosity in the 0.1- to 0.4-m soil layer after only three wet-dry cycles, whereas sorghum required nine wet-dry cycles to increase clod porosity in only the 0.2- to 0.3-m layer, and wheat gave no improvement even after nine wet-dry cycles. Image analysis of soil structure showed that lablab and mung bean rapidly (by three wet-dry cycles) produced smaller peds with more interconnected pore space than wheat and sorghum. By nine wet-dry cycles, sorghum achieved deep cracking of the soil but the material between the cracks remained large and dense. Evapotranspiration was double under lablab and mung bean compared with wheat and sorghum. Our results indicate greater cycles of wetting and drying under lablab and mung bean than wheat and sorghum that have led to rapid repair of soil compaction.