128 research outputs found

    Ecophysiology and phytoremediation potential of heavy metal(Loid) accumulating plants

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    Soil contamination with heavy metal(loid)s is a major environmental problem that requires effective and affordable remediation technologies. The utilisation of plants to remediate heavy metal(loid)s contaminated soils has attracted considerable interest as a low cost green remediation technology. The process is referred to as phytoremediation, and this versatile technology utilises plants to phytostabilise and/or phytoextract heavy metal(loid)s from contaminated soils, thereby effectively minimising their threat to ecosystem, human and animal health. Plants that can accumulate exceptionally high concentrations of heavy metal(loid)s into above-ground biomass are referred to as hyperaccumulators, and may be exploited in phytoremediation, geobotanical prospecting and/or phytomining of low-grade ore bodies. Despite the apparent tangible benefits of utilising phytoremediation techniques, a greater understanding is required to comprehend the ecophysiological aspects of species suitable for phytoremediation purposes. A screening study was instigated to assess phytoremediation potential of several fern species for soils contaminated with cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb) and zinc (Zn). Hyperaccumulation was not observed in any of the studied species, and in general, species excluded heavy metal uptake by restricting their translocation into aboveground biomass. Nephrolepis cordifolia and Hypolepis muelleri were identified as possible candidates in phytostabilisation of Cu-, Pb-, Ni- or Zn-contaminated soils and Dennstaedtia davallioides appeared favourable for use in phytostabilisation of Cu- and Zn-contaminated soils. Conversely, Blechnum nudum, B. cartilagineum, Doodia aspera and Calochlaena dubia were least tolerant to most heavy metals and were classified as being least suitable for phytoremediation purposes Ensuing studies addressed the physiology of arsenic (As) hyperaccumulation in a lesser known hyperaccumulator, Pityrogramma calomelanos var. austroamericana. The phytoremediation potential of this species was compared with that of the well known As hyperaccumulator Pteris vittata. Arsenic concentration of 3,008 mg kg–1 dry weight (DW) occurred in P. calomelanos var. austroamericana fronds when exposed to 50 mg kg–1 As without visual symptoms of phytotoxicities. Conversely, P. vittata was able to hyperaccumulate 10,753 mg As kg–1 DW when exposed to 100 mg kg–1 As without the onset of phytotoxicities. In P. calomelanos var. austroamericana, As was readily translocated to fronds with concentrations 75 times greater in fronds than in roots. This species has the potential for use in phytoremediation of soils with As levels up to 50 mg kg–1. Localisation and spatial distribution of As in P. calomelanos var. austroamericana pinnule and stipe tissues was investigated using micro-proton induced X-ray emission spectrometry (µ-PIXE). Freeze-drying and freeze-substitution protocols (using tetrahydrofuran [THF] as a freeze-substitution medium) were compared to ascertain their usefulness in tissue preservation. Micro-PIXE results indicated that pinnule sections prepared by freeze-drying adequately preserved the spatial elemental distribution and tissue structure of pinnule samples. In pinnules, µ-PIXE results indicated higher As concentration than in stipe tissues, with concentrations of 3,700 and 1,600 mg As kg–1 DW, respectively. In pinnules, a clear pattern of cellular localisation was not resolved whereas vascular bundles in stipe tissues contained the highest As concentration (2,000 mg As kg–1 DW). Building on these µ-PIXE results, the chemical speciation of As in P. calomelanos var. austroamericana was determined using micro-focused X-ray fluorescence (µ-XRF) spectroscopy in conjunction with micro-focused X-ray absorption near edge structure (µ-XANES) spectroscopy. The results suggested that arsenate (AsV) absorbed by roots was reduced to arsenite (AsIII) in roots prior to transport through vascular tissues as AsV and AsIII. In pinnules, AsIII was the predominant species, presumably as aqueous-oxygen coordinated compounds. Linear least-squares combination fits of µ-XANES spectra showed AsIII as the predominant component in all tissues sampled. The results also revealed that sulphur containing thiolates may, in part sequester accumulated As. The final aspect of this thesis examined several ecophysiological strategies of Ni hyperaccumulation in Hybanthus floribundus subsp. floribundus, a native Australian perennial shrub species and promising candidate in phytoremediation of Ni-contaminated soils. Micro-PIXE analysis revealed that cellular structure in leaf tissues prepared by freeze-drying was adequately preserved as compared to THF freeze-substituted tissues. Elemental distribution maps of leaves showed that Ni was preferentially localised in the adaxial epidermal tissues and leaf margin, with concentration of 10,000 kg–1 DW in both regions. Nickel concentrations in stem tissues obtained by µ-PIXE analysis were lower than in the leaf tissues (1,800 mg kg–1 vs. 7,800 mg kg–1 DW, respectively), and there was no clear pattern of compartmentalisation across different anatomical regions. It is possible that storage of accumulated Ni in epidermal tissues may provide Ni tolerance to this species, and may further act as a deterrent against herbivory and pathogenic attack. In H. floribundus subsp. floribundus seeds, µ-PIXE analysis did not resolve a clear pattern of Ni compartmentalisation and suggests that Ni was able to move apoplastically within the seed tissues. The role of organic acids and free amino acids (low molecular weight ligands [LMW]) in Ni detoxification in H. floribundus subsp. floribundus were quantified using high performance liquid chromatography (HPLC) and ultra performance liquid chromatography (UPLC). Nickel accumulation stimulated a significant increase in citric acid concentration in leaf extracts, and based on the molar ratios of Ni to citric acid (1.3:1–1.7:1), citric acid was sufficient to account for approximately 50% of the accumulated Ni. Glutamine, alanine and aspartic acid concentrations were also stimulated in response to Ni hyperaccumulation and accounted for up to 75% of the total free amino acid concentration in leaf extracts. Together, these LMW ligands may complex with accumulated Ni and contribute to its detoxification and storage in this hyperaccumulator species. Lastly, the hypothesis that hyperaccumulation of Ni in certain plants may act as an osmoticum under water stress (drought) was tested in context of H. floribundus subsp. floribundus. A 38% decline in water potential and a 68% decline in osmotic potential occurred between water stressed and unstressed plants, however, this was not matched by an increase in accumulated Ni. The results suggested that Ni was unlikely to play a role in osmotic adjustment in this species. Drought stressed plants exhibited a low water use efficiency which might be a conservative ecophysiological strategy enabling survival of this species in competitive water-limited environments

    Closing the loop: A systems thinking led sustainable sanitation project in Australia

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    This paper will explain a research project being carried out in Sydney, Australia at the University of Technology Sydney (UTS) highlighting the systems thinking principles and action research methodology being adopted in this project. UTS is set to participate in an Australia-first research project, led by the Institute of Sustainable Futures (ISF), exploring the use of innovative urine diverting toilets in an institutional setting. A UTS Challenge Grant (an internal grant scheme to promote innovative collaborative research) has been awarded to the project which will enable safe nutrient capture and reuse from urine diverting toilets installed on campus for a trial period. The Challenge Grant has some enthusiastic industry partners including the local water utility Sydney Water; the sanitaryware manufacturer CaromaDorf; the Nursery and Garden Industry Association; government partners (NSW Department of Health, and City of Sydney) and the UTS Facilities Management Unit. Researchers from the University of Western Sydney and University of New South Wales in Australia as well as Linkoping University in Sweden are collaborators in this research

    Tracing potential soil contamination in the historical Solvay soda ash plant area, Jaworzno, Southern Poland

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    This study of soil conditions was carried out on 30 meadow soil (podzol) samples from the vicinity of the soda ash heap in Jaworzno, supplemented by analyses of 18 samples of waste deposited on the heap. In all samples, the total content of macroelements (Ca and Na) and heavy metals (Cd, Cr, Ni, Pb and Zn) as well as pH were analysed. The element concentrations were measured using inductively coupled plasma optical emission spectrometry (ICP-OES). The materials examined were neutral to ultra-alkaline. Total accumulations (mg kg(−1)) of chemical elements in the soil vary from 130.24 to 14076.67 for Ca, 41.40–926.23 for Na, 0.03–3.34 for Cd, 0.94–103.62 for Cr, 0.94–35.89 for Ni, 3.51–76.47 for Pb and 12.05–279.13 for Zn, whereas quantities of the same elements in the waste samples vary from 171705.13 to 360487.94 for Ca, 517.64–3152.82 for Na, 0.2–9.89 for Cd, 1.16–20.40 for Cr, 1.08–9.79 for Ni, 0.1–146.05 for Pb and 10.26–552.35 for Zn. The vertical distribution of the metals was determined in each soil profile. Despite enrichment of heavy metals in the uppermost horizon on the top of the heap, the results lead to the conclusion that the relation of historical production of soda ash in Jaworzno to current contamination of the local soil environment is insignificant

    Elemental and chemically specific x-ray fluorescence imaging of biological systems

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    Российский консенсус по профилактике, диагностике и лечению рака желудка

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    The Russian consensus on prevention, diagnostic and treatment of gastric cancer was prepared on the initiative of the Moscow clinical scientific center named after A. S. Loginov according to the Delphi method. Its aim was to clarify and consolidate the opinions of specialists on the most relevant issues of prevention, diagnosis and treatment of gastric cancer. An interdisciplinary approach was provided by the participation of leading gastroenterologists, oncologists and surgeons.Российский консенсус по профилактике, диагностике и лечению рака желудка подготовлен по инициативе Московского клинического научного центра им А. С. Логинова ДЗМ по Дельфийской системе. Его целью явилась консолидация мнений отечественных специалистов по наиболее актуальным вопросам профилактики, скрининга, диагностики и лечения рака желудка. Междисциплинарный подход обеспечен участием ведущих гастроэнтерологов, онкологов и хирургов.Цель статьи: представить положения Российского консенсуса по профилактике, диагностике и лечению рака желудка

    Strawberry fields forever? Urban agriculture in developed countries: a review

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