Wetland-based passive treatment systems for gold ore processing effluents containing residual cyanide, metals and nitrogen species.

Gold extraction operations generate a variety of wastes requiring responsible disposal in compliance with current environmental regulations. During recent decades, increased emphasis has been placed on effluent control and treatment, in order to avoid the threat to the environment posed by toxic constituents. In many modern gold mining and ore processing operations, cyanide species are of most immediate concern. Given that natural degradation processes are known to reduce the toxicity of cyanide over time, trials have been made at laboratory and field scales into the feasibility of using wetland-based passive systems as low-cost and environmentally friendly methods for long-term treatment of leachates from closed gold mine tailing disposal facilities. Laboratory experiments on discrete aerobic and anaerobic treatment units supported the development of design parameters for the construction of a field-scale passive system at a gold mine site in northern Spain. An in situ pilot-scale wetland treatment system was designed, constructed and monitored over a nine-month period. Overall, the results suggest that compost-based constructed wetlands are capable of detoxifying cyanidation effluents, removing about 21.6% of dissolved cyanide and 98% of Cu, as well as nitrite and nitrate. Wetland-based passive systems can therefore be considered as a viable technology for removal of residual concentrations of cyanide from leachates emanating from closed gold mine tailing disposal facilities.

Using wikis as an online health information resource.

Wikis can be a powerful online resource for the provision and sharing of information, with the proviso that information found on them should be independently verified. This article defines wikis and sets them in context with recent developments on the internet. The article discusses the use of Wikipedia and other wikis as potential sources of health information for nurses.

The harmful health effects of recreational ecstasy: a systematic review of observational evidence.

OBJECTIVES: To investigate the harmful health effects of taking ecstasy (3,4-methylenedioxymethamphetamine, MDMA) for recreational purposes. DATA SOURCES: MEDLINE, EMBASE, PsycINFO and Web of Knowledge were searched. Additional information on deaths was collected from the General Mortality Register (GMR) and the Special Mortality Register collated by the National Programme on Substance Abuse Deaths (np-SAD). REVIEW METHODS: Studies were categorised according to design, with systematic research syntheses (Level I evidence) the most valid and least open to bias. Where Level I evidence was not available, controlled observational studies (Level II evidence) were systematically reviewed. If neither Level I nor Level II evidence was available, uncontrolled case series and case reports (Level III evidence) were systematically surveyed. Data were extracted by one reviewer and a sample checked by a second. The heterogeneity of Level II evidence was addressed by undertaking stratified analyses for current and former ecstasy users and comparing them either with control groups using other illegal drugs but not ecstasy (polydrug controls) or with controls naïve to illegal drugs (drug-naïve controls). Statistical heterogeneity was minimised by using a random-effects model throughout and investigated using study-level regression analysis (metaregression). RESULTS: Five Level I syntheses were identified; for each it was difficult to ascertain the exact methods adopted and evidence included. Small but significant deficits for ecstasy users compared to controls were reported in areas relating to attention, memory, psychomotor speed, executive systems functioning, and self-reported depressive symptoms. Data from Level II studies were directly pooled for seven individual outcomes, suggesting that ecstasy users performed worse than controls on common measures of immediate and delayed verbal recall (RAVLT, RBMT, digit span). No difference was seen in IQ (NART). The 915 outcome measures identified in Level II studies were analysed in broad domains: immediate and delayed verbal and visual memory, working memory, two measures of attention, three measures of executive function, perceptual organisation, self-rated depression, memory and anxiety, and impulsivity measured objectively and subjectively. Ecstasy users performed significantly worse than polydrug controls in 13/16 domains and significantly worse than drug-naïve controls in 7/12 domains for which sufficient data were available. The largest, most consistent exposure effects were seen in meta-analyses of memory (especially verbal and working memory, with less marked effects seen in visual memory). Former ecstasy users frequently showed deficits that matched or exceeded those seen amongst current users. At aggregate level, the effects do not appear to be dose-related, but are variably confounded by other drug use, particularly alcohol. Of Level III evidence, in the 10 years to 2006, the np-SAD and the GMR recorded an average of around 50 drug-related deaths per year involving ecstasy; it was the sole drug implicated in around 10 cases per year. Retrospective case series, based on hospital emergency department records, reported a death rate of 0-2% from emergency admissions related to ecstasy. Two major syndromes are most commonly reported as the immediate cause of death in fatal cases: hyperthermia and hyponatraemia. CONCLUSIONS: A broad range of relatively low-quality literature suggests that recreational use of ecstasy is associated with significant deficits in neurocognitive function (particularly immediate and delayed verbal memory) and increased psychopathological symptoms. The clinical significance of the exposure effect in individual cases will be variable but, on average, deficits are likely to be relatively small. Ecstasy is associated with a range of acute harms but appears to be a rare cause of death in isolation.

Evaluation of iron ochre from mine drainage treatment for removal of phosphorus from wastewater.

Treatment of polluting discharges from abandoned coal mines in the UK currently produces ca 30,000 t y(-1) of hydrous iron oxides ("ochre"), for which there is no major end-use, but which has previously been shown to have potential for removing P from wastewater and agricultural runoff. The efficiency of ochre for P removal from wastewater was investigated in experiments at two sites in the UK: Leitholm in Scotland and Windlestone in England. The three-year experiment at Leitholm involved diverting secondary-treated wastewater effluent through a trough which contained granular and pelletized ochre at different times. In the nine-month experiment at Windlestone, beds of ochre pellets in horizontal and vertical flow configurations were tested. The ochre treatment systems at Leitholm reduced influent concentrations of total P (TP) and TP mass by ca 80% and 50%, respectively, during optimal flow conditions, and achieved a removal rate of up to 65+/-48 mg TP kg(-1) ochre d(-1). There was no detectable release of potentially toxic metals from the ochre during the experiments. P removal rates by concentration were inversely related to flow and declined during the different phases of the experiments, probably due to clogging. At Windlestone, higher removal rates up to 195 mg TP kg(-1) ochre d(-1) were achieved for short periods of time following cleaning of the experimental system. Ochre has considerable potential to remove P from wastewater in a multi-stage treatment system and has a lifetime estimated to be 10 times longer than other substrates tested for P removal.

Wetland treatment at extremes of pH: a review.

Constructed wetlands are an established treatment technology for a diverse range of polluted effluents. There is a long history of using wetlands as a unit process in treating acid mine drainage, while recent research has highlighted the potential for wetlands to buffer highly alkaline (pH>12) drainage. This paper reviews recent evidence on this topic, looking at wetlands treating acidic mine drainage, and highly alkaline leachates associated with drainage from lime-rich industrial by-products or where such residues are used as filter media in constructed wetlands for wastewater treatment. The limiting factors to the success of wetlands treating highly acidic waters are discussed with regard to design practice for the emerging application of wetlands to treat highly alkaline industrial discharges. While empirically derived guidelines (with area-adjusted contaminant removal rates typically quoted at 10 g Fe m(2)/day for influent waters pH>5.5; and 3.5-7 g acidity/m(2)/day for pH>4 to <5.5) for informing sizing of mine drainage treatment wetlands have generally been proved robust (probably due to conservatism), such data exhibit large variability within and between sites. Key areas highlighted for future research efforts include: (1) wider collation of mine drainage wetland performance data in regionalised datasets to improve empirically-derived design guidelines and (2) obtaining an improved understanding of nature of the extremophile microbial communities, microbially-mediated pollutant attenuation and rhizospheral processes in wetlands at extremes of pH. An enhanced knowledge of these (through multi-scale laboratory and field studies), will inform engineering design of treatment wetlands and assist in the move from the empirically-derived conservative sizing estimates that currently prevail to process-based optimal design guidance that could reduce costs and enhance the performance and longevity of wetlands for treating acidic and highly alkaline drainage waters.

Effective remediation of grossly polluted acidic, and metal-rich, spoil heap drainage using a novel, low-cost, permeable reactive barrier in Northumberland, UK.

A permeable reactive barrier (PRB) for remediation of coal spoil heap drainage in Northumberland, UK, is described. The drainage has typical chemical characteristics of pH<4, [acidity]>1400 mg/L as CaCO3, [Fe]>300 mg/L, [Mn]>165 mg/L, [Al]>100mg/L and [SO4]>6500 mg/L. During 2 years of operation the PRB has typically removed 50% of the iron and 40% of the sulphate from this subsurface spoil drainage. Bacterial sulphate reduction appears to be a key process of this remediation. Treatment of the effluent from the PRB results in further attenuation; overall reductions in iron and sulphate concentrations are 95% and 67% respectively, and acidity concentration is reduced by an order of magnitude. The mechanisms of attenuation of these, and other, contaminants in the drainage are discussed. Future research and operational objectives for this novel, low-cost, treatment system are also outlined.

The effective use of search engines on the Internet.

This article explains how nurses can get the most out of researching information on the internet using the search engine Google. It also explores some of the other types of search engines that are available. Internet users are shown how to find text, images and reports and search within sites. Copyright issues are also discussed.

The impact of pumped water from a de-watered Magnesian limestone quarry on an adjacent wetland: Thrislington, County Durham, UK.

Although quarrying is often cited as a potential threat to wetland systems, there is a lack of relevant, quantitative case studies in the literature. The impact of pumped groundwater discharged from a quarry into a wetland area was assessed relative to reference conditions in an adjacent fen wetland that receives only natural runoff. Analysis of vegetation patterns at the quarry wetland site, using Detrended Correspondence Analysis and the species indicator values of Ellenberg, revealed a clear disparity between community transitions in the quarry wetland and the reference site. Limited establishment of moisture-sensitive taxa, the preferential proliferation of robust wetland species and an overall shift towards lower species diversity in the quarry wetland were explicable primarily by the physico-chemical environment created by quarry dewatering. This encompassed high pH (up to 12.8), sediment-rich effluent creating a nutrient-poor substrate with poor moisture retention in the quarry wetland, and large fluctuations in water levels.

Reference biospheres for post-closure performance assessment: inter-comparison of SHETRAN simulations and BIOMASS results.

Example Reference Biosphere 2B (ERB2B) is a hypothetical river catchment, described in the IAEA-sponsored BIOMASS study on biosphere aspects of post-closure radiological safety assessments for repositories for solid radioactive wastes. In ERB2B, a radioactively contaminated aquifer interacts with the soils and sediments of the river catchment. A 'semi-distributed', lumped-parameter model (SDLP) was set up for the site as part of the BIOMASS study. In the model, empirically derived transfer functions are used to reduce the complexity of real hydrological transport systems to readily calculable mass-balance accounting routines. In this work, a physically based, spatially distributed modelling system SHETRAN was set up for the site and comparison made with the existing SDLP model. The work has shown that, using standard soil properties in SHETRAN, the soil rapidly saturates and much of the hydrologically effective rainfall (precipitation less evapotranspiration) is lost as saturation-excess surface runoff. This is contrary to the assumptions in the SDLP model. The difficulty arose from the original formulation of catchment characteristics in BIOMASS. Specifically, there was a large water volume entering the soils from precipitation together with an upward flux of groundwater across the lower boundary of a substantial part of the catchment. This water had to be lost from the catchment in some way and the thinness of the soil zone precluded dominance of subsurface, lateral flow over surface runoff. Increasing the saturated conductivity from 1 to 20 m d(-1) reduced the surface flows to similar values to those assumed in the SDLP model (this could also have been achieved by increasing the soil depth). Even with the high saturated conductivity there were still major differences between the two representations. In the woodland on the upper slopes of the valley, the SHETRAN simulation was slightly wetter than the SDLP model, whereas in the shrubland and marshland near the river it was drier than the SDLP model. In the SDLP model, subsurface lateral flows are ignored if there is surface flow, and deep subsurface flows are ignored if there are shallow subsurface flows. In the SDLP model, there is a major assumed change in flow regime between summer and winter. This is not the case in the SHETRAN simulation. Overall, this work illustrates the problems of using 'semi-distributed', lumped-parameter models without prior calibration against a physically based model and the potential for implying unexpected and possibly implausible hydrological characteristics through the specification of flows without considering whether they could occur for realistic soil depths and properties. As there is a need for application of such SDLP models, particularly when undertaking probabilistic calculations, it is suggested that, in future, explicit hydrological modelling should be undertaken first, so that a physically realistic representation can be produced as a basis for assessment studies of the migration of radionuclides or other contaminants.

Effects of external iron concentration upon seedling growth and uptake of Fe and phosphate by the common reed, Phragmites australis (Cav.) Trin ex. Steudel.

The objectives of this study were to determine whether, and to what degree, the aqueous iron concentration in the growing medium affects the growth of, and Fe uptake by, Phragmites australis, and whether the presence of iron in the growing environment affects the uptake of the essential element phosphate. The wetland macrophyte P. australis was grown under laboratory conditions in nutrient solution (0.31 mg L(-1) phosphate) containing a range of iron concentrations (0-50 mg L(-1) Fe). A threshold of iron concentration (1 mg L(-1)) was found, above which growth of P. australis was significantly inhibited. No direct causal relationship between iron content in aerial tissues and growth inhibition was found, which strongly suggests that iron toxicity cannot explain these results. Phosphate concentrations in aerial tissues were consistently sufficient for growth and development (2-3 % d. wt) despite significant variation in concentration of phosphate associated with roots. External Fe concentration had a significant effect on the growth of P. australis and on both Fe and phosphate concentrations associated with roots. However, neither direct toxicity nor phosphate deficiency could explain the reduction in growth above 1 mg L(-1) external Fe concentration

Passive treatment of ferruginous mine waters using high surface area media.

Rapid oxidation and accretion of iron onto high surface area media has been investigated as a potential passive treatment option for ferruginous. net-alkaline minewaters. Two pilot-scale reactors were installed at a site in County Durham, UK. Each 2.0 m high cylinder contained different high surface area plastic trickling filter media. Ferruginous minewater was fed downwards over the media at various flow-rates with the objective of establishing the efficiency of iron removal at different loading rates. Residence time of water within the reactors was between 70 and 360 s depending on the flow-rate (1 and 12 l/min, respectively). Average influent total iron concentration for the duration of these experiments was 1.43 mg/l (range 1.08-1.84 mg/l; n = 16), whilst effluent iron concentrations averaged 0.41 mg/l (range 0.20-1.04 mg/l; n = 15) for Reactor A and 0.38 mg/l (range 0.11-0.93 mg/l; n = 16) for Reactor B. There is a strong correlation between influent iron load and iron removal rate. Even at the highest loading rates (approximately 31.6 g/day) 43% and 49% of the total iron load was removed in Reactors A and B, respectively. At low manganese loading rates (approximately 0.50-0.90 g/day) over 50% of the manganese was removed in Reactor B. Iron removal rate (g/m3/d) increases linearly with loading rate (g/day) up to 14 g/d and the slope of the line indicates that a mean of 85% of the iron is removed. In conclusion. it appears that the oxidation and accretion of ochre on high surface area media may be a promising alternative passive technology to constructed wetlands at certain sites.

A strategy for modeling ground water rebound in abandoned deep mine systems.

Discharges of polluted water from abandoned mines are a major cause of degradation of water resources worldwide. Pollution arises after abandoned workings flood up to surface level, by the process termed ground water rebound. As flow in large, open mine voids is often turbulent, standard techniques for modeling ground water flow (which assume laminar flow) are inappropriate for predicting ground water rebound. More physically realistic models are therefore desirable, yet these are often expensive to apply to all but the smallest of systems. An overall strategy for ground water rebound modeling is proposed, with models of decreasing complexity applied as the temporal and spatial scales of the systems under analysis increase. For relatively modest systems (area < 200 km2), a physically based modeling approach has been developed, in which 3-D pipe networks (representing major mine roadways, etc.) are routed through a variably saturated, 3-D porous medium (representing the country rock). For systems extending more than 100 to 3000 km2, a semidistributed model (GRAM) has been developed, which conceptualizes extensively interconnected volumes of workings as ponds, which are connected to other ponds only at discrete overflow points, such as major inter-mine roadways, through which flow can be efficiently modeled using the Prandtl-Nikuradse pipe-flow formulation. At the very largest scales, simple water-balance calculations are probably as useful as any other approach, and a variety of proprietary codes may be used for the purpose.

Mine water pollution in Scotland: nature, extent and preventative strategies.

Scotland was one of the world's first industrialised countries, and has therefore also been one of the first countries to experience wholesale post-industrial dereliction. Water pollution arising from abandoned mines, particularly abandoned coal mines, is second only to sewage as a source of freshwater pollution nation-wide, and in many coalfield catchments it is the pre-eminent source. Most of the pollution is due to net-alkaline ferruginous waters emerging from deep mines. Scrutiny of records from 80 deep mine discharges reveals that iron concentrations in these waters are only likely to exceed 20 mg/l, and the pH to be below 6.5, where the discharge emerges within 0.5 km of the outcrop of the shallowest mined seam. The bulk of mature near-outcrop mine water discharges in Scotland have < 50 mg/l total Fe, and concentrations > 100 mg/l are only likely where a marine bed lies within 25 m of the worked seam. Where the nearest marine bed is more than 80 m above or below the seam, then the total iron will be less than 4 mg/l, and in most cases less than 1 mg/l. Net-acidic mine waters are far more rare than net-alkaline waters in Scotland, and are most commonly associated with unreclaimed spoil heaps (bings). Both net-alkaline and net-acidic discharges have detrimental effects on the hydrochemistry and biological integrity of receiving waters. Scotland has recently pioneered the use of pre-emptive pump-and-treat solutions to prevent mine water pollution, and has also experienced the successful introduction of passive treatment technology for both abandoned and active workings.

Peripapillary chorioretinal atrophy: Bruch's membrane changes and photoreceptor loss.

PURPOSE: To determine relationships among Bruch's membrane ultrastructure, photoreceptor degeneration, and choriocapillaris atrophy with respect to zones of retinal pigment epithelium (RPE) degeneration and atrophy adjacent to the optic nerve head, as a function of age. DESIGN: Human tissue study using clinicopathologic correlation. TISSUES: Eyes from patients 36 to 93 years of age lacking clinical evidence of glaucoma, optic nerve abnormalities, severe myopia, age-related macular degeneration, or other macular or peripapillary chorioretinal pathologic condition. METHODS: Sections through the retina-choroid complex at the temporal aspect of the optic nerve head were used for light microscopic histopathologic analysis (n = 17), electron microscopy (n = 9), carbonic anhydrase histochemical analysis (n = 7), and lipid histochemical analysis (n = 22). Retinal whole mounts were used for photoreceptor counts (n = 5). MAIN OUTCOME MEASURES: We determined the width of RPE degeneration and atrophy, the number of eyes with abnormalities of inner Bruch's membrane, and the number of rod and cone photoreceptors within 1 mm of the disc margin. We determined whether Bruch's membrane changes, photoreceptor degeneration, and choriocapillaris atrophy were associated with RPE degeneration and atrophy. RESULTS: All eyes had peripapillary RPE atrophy, degeneration, or both. The zone of RPE atrophy widened significantly after age 75. Thickening of inner Bruch's membrane and abnormalities of the RPE basal lamina were associated with degenerating and atrophic RPE in all eyes. The RPE basal lamina was narrow, reduplicated, or thickened as a basal laminar deposit. All eyes exhibited degeneration and loss of rods but not cones at the peripapillary termination of Bruch's membrane. Diminution of choriocapillaris coverage of Bruch's membrane was associated with RPE degeneration. Complete loss of the choriocapillaris was associated with RPE atrophy. CONCLUSIONS: Our results suggest that peripapillary chorioretinal atrophy is an age-related degeneration of the RPE-Bruch's membrane complex that resembles that found in the macula and periphery of normal eyes.

The longevity of minewater pollution: a basis for decision-making.

Pollution from abandoned mines is a serious, widespread and increasingly common cause of surface water degradation in the LOIS study region. Indeed, in some areas of the UK it is now the single greatest cause of freshwater pollution. Remediation of such pollution in the long-term is probably best achieved by passive treatment, which has the advantage of concentrating expenditure in capital costs, with only modest financial commitments for long-term maintenance. To plan such remediation, however, it is important to have an understanding of the physical and chemical processes governing pollutant release over scales of many decades. By analysing water quality records for major abandoned mine discharges in Scotland, Wales and Cornwall, long-term acidity generation is shown to have two components: "vestigial' and "juvenile'. The vestigial component relates to the geochemical trauma which occurs as abandoned mine voids are allowed to fill with water for the first time, taking ferrous and ferric hydroxysulphate salts (intermediate products of pyrite oxidation) into solution. Dissipation of vestigial acidity is primarily controlled by the hydraulic retention time of the flooded mine system, and will generally be accomplished in less than 40 years. Juvenile acidity arises from on-going pyrite oxidation in the zone of water table fluctuation within the mined system, and can be expected to continue for many hundreds of years, until the supply of pyrite is finally exhausted. Rational planning for the remediation of minewater pollution should be based on intensive treatment of discharges while the vestigial acidity is being depleted, followed by long-term passive treatment of the juvenile acidity.

Organization of the T-cell receptor delta locus by deletional analysis of acute lymphoblastic leukemias and leukemic cell lines.

To gain a better understanding of the organization of the complex T-cell antigen receptor alpha/delta (TCR alpha/delta) locus, a deletional analysis using the known six variable (V) regions of the TCR delta was performed in informative leukemic cell lines and fresh leukemias. We and others have previously reported a high incidence of V delta 2-(D)-D delta 3 rearrangements in non-T, non-B-lymphoid precursor acute lymphocytic leukemia (LP-ALL). In contrast V delta 4, V delta 5, V delta 6 rearrangements were rare or absent. V delta-J alpha rearrangements were found in LP-ALL and in T-ALL. Our deletion and rearrangement data combined with that of others suggest the following 5' to 3' organization of the TCR alpha/delta locus: V delta 6-(V delta 4-V alpha 1.2)-V alpha 12.1-V alpha 13.1-V delta 1-V delta 17.1-V delta 5-delta Rec-V delta 2-D/J/C delta-V delta 3-TEA-psi J alpha-J alpha G. The frequency of rearrangements of the various V delta genes suggests preferential use of the V delta most proximal to D/J delta.