Accumulation and fate of contaminants (Zn, Pb, Fe and S) in substrates of wetlands constructed for treating mine wastewater

Substrates of treatment wetlands, which were constructed at an operational lead-zinc mining facility (Tara Mines) in Ireland, were analysed over a 5-year period for metal content. Lead, zinc, iron and sulphate were removed from wastewater passing though the treatment systems and were significantly retained in the substrates. The degree to which these contaminants are bio-available depends on the biogeochemical conditions of the substrates, namely the pH, redox potential, amount of organic carbon present and the contaminant loading. Various sediment fractions (water-soluble, exchangeable, carbonate-bound, organic matter-bound and residual) were also analysed in these treatment wetlands, in order to estimate the fate of metals and sulphur over time. Results showed that the majority of metals and sulphur were retained in immobile residual forms, principally as metal-sulphides. Furthermore, the neutral-alkaline pH and reducing biogeochemistry of the treatment systems suggest that metals are not toxic under these conditions

Biological outcome measurements for behavioral interventions in multiple sclerosis

Behavioral interventions including exercise, stress management, patient education, psychotherapy and multidisciplinary neurorehabilitation in general are receiving increasing recognition in multiple sclerosis (MS) clinical practice and research. Most scientific evaluations of these approaches have focused on psychosocial outcome measures such as quality of life, fatigue or depression. However, it is becoming increasingly clear that neuropsychiatric symptoms of MS are at least partially mediated by biological processes such as inflammation, neuroendocrine dysfunction or regional brain damage. Thus, successful treatment of these symptoms with behavioral approaches could potentially also affect the underlying biology. Rigidly designed scientific studies are needed to explore the potential of such interventions to affect MS pathology and biological pathways linked to psychological and neuropsychiatric symptoms of MS. Such studies need to carefully select outcome measures on the behavioral level that are likely to be influenced by the specific intervention strategy and should include biomarkers with evidence for an association with the outcome parameter in question. In this overview, we illustrate how biological and psychological outcome parameters can be combined to evaluate behavioral interventions. We focus on two areas of interest as potential targets for behavioral interventions: depression and fatigue

Insights into the high-energy γ-ray emission of Markarian 501 from extensive multifrequency observations in the Fermi era

We report on the γ-ray activity of the blazar Mrk 501 during the first 480 days of Fermi operation. We find that the average Large Area Telescope (LAT) γ-ray spectrum of Mrk 501 can be well described by a single power-law function with a photon index of 1.78 ± 0.03. While we observe relatively mild flux variations with the Fermi-LAT (within less than a factor of two), we detect remarkable spectral variability where the hardest observed spectral index within the LAT energy range is 1.52 ± 0.14, and the softest one is 2.51 ± 0.20. These unexpected spectral changes do not correlate with the measured flux variations above 0.3 GeV. In this paper, we also present the first results from the 4.5 month long multifrequency campaign (2009 March 15-August 1) on Mrk 501, which included the Very Long Baseline Array (VLBA), Swift, RXTE, MAGIC, and VERITAS, the F-GAMMA, GASP-WEBT, and other collaborations and instruments which provided excellent temporal and energy coverage of the source throughout the entire campaign. The extensive radio to TeV data set from this campaign provides us with the most detailed spectral energy distribution yet collected for this source during its relatively low activity. The average spectral energy distribution of Mrk 501 is well described by the standard one-zone synchrotron self-Compton (SSC) model. In the framework of this model, we find that the dominant emission region is characterized by a size ≲0.1 pc (comparable within a factor of few to the size of the partially resolved VLBA core at 15-43 GHz), and that the total jet power (≃1044 erg s-1) constitutes only a small fraction (∼10-3) of the Eddington luminosity. The energy distribution of the freshly accelerated radiating electrons required to fit the time-averaged data has a broken power-law form in the energy range 0.3 GeV-10 TeV, with spectral indices 2.2 and 2.7 below and above the break energy of 20 GeV. We argue that such a form is consistent with a scenario in which the bulk of the energy dissipation within the dominant emission zone of Mrk 501 is due to relativistic, proton-mediated shocks. We find that the ultrarelativistic electrons and mildly relativistic protons within the blazar zone, if comparable in number, are in approximate energy equipartition, with their energy dominating the jet magnetic field energy by about two orders of magnitude. © 2011. The American Astronomical Society

Bioremediation of alkaline mine effluent using treatment wetlands

Decommissioning of metal mine effluent traditionally involved costly chemical applications. Development of passive treatment systems, employing both biotic and abiotic components has been recognized as a cost-effective, ecologically favorable approach in the last decade. This paper documents construction of the first (experimental) treatment system in Ireland at a large lead-zinc mine, attempting to promote adoption of this innovative treatment alternative for future applications

Constructed Wetlands for Treating Processed Mine Water - an Irish Case Study

Mine wastewater is characteristically elevated in metals and sulfate and conventionally treated with costly chemical applications. The development of passive treatment systems, employing both biotic and abiotic processes, has been recognized as an economically feasible, ecologically acceptable technology in the last decade. However, to-date most of these passive systems have been applied to abandoned mine waters for the primary purpose of increasing pH and removing metals. Two experimental-scale treatment wetlands were constructed and monitored at an active lead/zinc mine (Tara Mines) in Ireland, to treat alkaline mine seepage with elevated sulfate (and also metal) levels. Each system comprised three 12 m² (2 m depth) in-series surface-flow cells viz., inflow, vegetated and outflow and contained spent mushroom substrate (SMS). Typical aqueous concentrations of 830 mg L⁻¹ sulfate, 0.15 mg L⁻¹ lead and 2.0 mg L⁻¹ zinc entered the treatment wetlands at a flow rate of c. 650 mL min⁻¹. Anaerobic substrates, in which sulfate-reducing bacteria were indigenous, were conducive to biological reduction of sulfate to sulfide. Sulfide subsequently precipitated with metal cations. Monitoring of these wetlands over a 2-year period showed successful (maximum) removal of sulfate (29 g m⁻² day ⁻¹ (69%)), lead (6.6 mg m⁻² day ⁻¹ (64%)), and zinc (70 mg m⁻² day ⁻¹ (98%)). These contaminants were somewhat associated with the vegetation roots but more significantly so with the substrates. The interacting processes within the wetland ecosystems responsible for decontamination of the wastewater are currently being elucidated and quantified using a systems dynamic model. The communities of colonizing macroinvertebrates, macrophytes, algae and microorganisms also contributed to development of diverse ecosystems and a successful alternative treatment process

Constructed wetlands for treatment of mine tailings at Tara Mines, Ireland

Natural and constructed wetlands can filter pollutants from water. Recently this property has been exploited in utilising wetlands for passive water treatment. Using relatively concentrated waste, wetlands have been shown to be effective in retaining in excess of 90% metals (MAY et al. 1993) and over 70% sulphate (WINTER & KICKUTH 1989). This approach to water quality improvement is more favourable than traditional treatment methods requiring intensive chemical and labour inputs. Experimental wetlands have been constructed on site at Tara Mines, County Meath, Ireland to facilitate a research project investi- gating the capacity of filter systems in retaining sulphate and metals from mine tailings water. It is expected that such systems, based on natural processes, will be efficient yet require little maintenance and will, therefore, be economically attractive

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Complex projectsDepartment of ArchitectureArchitecture and The Built Environmen

Wetlands for removal of sulphate and metals from mine tailings water

Natural and artificial vegetated wetlands have the unique ability to retain pollutants from water. Frequently, this ‘filtering’ property is exploited in water quality control, which is a more favourable and cost effective approach to treating wastewater. Wetlands have shown to effectively retain pollutants such as excess nutrients and metals, yet few studies report sulphate retention by wetlands. Some researchers consider this an inert compound. However, sulphate (SO4 2-) is not inert and can be reduced to sulphide (S 2-) under waterlogged conditions, rendering an insoluble sulphide complex. Plant, soil and microbial activity within wetlands can detoxify sulphate-enriched water. This research aims to develop an artificial wetland and estimate the capacity of such systems for treating sulphate-enriched water originating from mine tailings. Experimental wetlands have been constructed at Outokumpu Zinc-Tara Mines Ltd., County Meath, Ireland. It is anticipated that these systems, based on natural processes will be efficient yet require minimum maintenance and will therefore be economically attractive

Ecological development of constructed wetlands built for treating mine tailings water at Tara Mines, Ireland

Mine associated wastewater is characteristically elevated in metals and other contaminants and has been conventionally treated with costly chemical applications. The development of passive treatment systems such as wetlands, which employ both biotic and abiotic processes, has been recognized as an economically feasible, ecologically acceptable treatment technology in the last decade. Not only can constructed wetlands provide an efficient facility for treating wastewater, they can also offer ancillary benefits such as ecological niches and therefore be of educational and often recreational value to society as well. Two experimental-scale treatment wetlands were constructed at an active lead/zinc mine near Navan, Ireland in 1997 to treat water enriched with sulfate and metals. Each system comprised three 12 m2 (2 m depth) in-series surface-flow cells viz., inflow, vegetated and outflow. Sulfate-reducing bacteria were indigenous in the anaerobic spent mushroom substrate used, where biological reduction of sulfate to sulfide occurred. Sulfide subsequently precipitated with metals from the water. The treatment efficiency of the wetlands was promising with concentrations of sulfate (up to 29 g m-2 day -1 (69%)), lead (6.6 mg m-2 day -1 (64%)) and zinc (70 mg m-2 day -1 (98%)) successfully removed from the wastewater. The ecological functioning of these constructed wetlands was also demonstrated with food webs, nesting niches and refuge sites afforded by colonizing communities of macroinvertebrates, macrophytes, microorganisms and other visiting wildlife. By 15 months following construction of the treatment wetlands, 30 species of macroinvertebrates were identified in system 1 and 21 species in system 2, while 3 plant species, 3 algae species and 1 moss had also colonized the ecosystems. Sulfate reducing bacteria genera included Desulfotomaculum, Desulfovibrio, Desulfococcus and Desulfobulbus. Annual dieback of planted species Typha latifolia and Phragmites australis contributed substantial amounts of biomass to the ecosystems, which led to a renewal of the carbon supply that drove the biologically mediated treatment process. It is speculated that the ecological diversity of the wetlands contributed to their treatment success based on inherent ecosystem complexity