| 1. |
- Alakangas, Lena, et al.
(författare)
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Pilot-scale studies of different covers on unoxidised sulphide-rich tailings in northern Sweden : the geochemistry of leachate waters
- 2006
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Ingår i: Mine Water and the Environment. - : Springer Science and Business Media LLC. - 1025-9112 .- 1616-1068. ; 25:3, s. 171-183
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Tidskriftsartikel (refereegranskat)abstract
- Leachate water quality from covered and uncovered unoxidised sulphide-rich tailings in six pilot-scale (5x5x3 m3) test cells was monitored during 2004 and 2005. The covers consisted of a layer of clayey till, sewage sludge, apatite or Trisoplast (a commercial mixture of tailings, bentonite, and a polymer). All layers were protected by an unspecified till except in one reference cell, where the tailings were left open. All leachate waters showed near-neutral pH as a result of neutralization by calcite in the tailings and by Ca(OH)2 added prior to deposition. Average dissolved sulphur concentrations in the leachates were ≈ 600 mg L-1, except in the cell with sewage sludge (300 mg L-1). The source of sulphur was mainly pyrite oxidation, but residual sulphur probably remained from the enrichment process. The near-neutral pH favoured precipitation of metal-(oxy)hydroxides with subsequent removal of trace elements such as Cd, Cu and Pb (< 15 μg L-1) from the solutions. High concentrations of Co, Mn, Ni, and Zn were found in leachates from the apatite, Trisoplast, and uncovered tailings cells. High As concentrations were found in the leachates in the sewage sludge and clayey till cells. The lowest metal concentrations, redox potential, and highest pH were found in the sewage sludge cell. Decreased elemental metal concentrations during 2004 suggest improved performance over time.
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| 2. |
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| 3. |
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| 4. |
- Hällström, Lina P.B.
(författare)
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Mobility of Be, Bi, F, Ga, Ge and W in Surface Water and the Water Quality Impact on Epilithic Diatoms Downstream of the Historical Yxsjoberg Mine Site, Sweden
- 2022
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Ingår i: Mine Water and the Environment. - : Springer Nature. - 1025-9112 .- 1616-1068. ; 41:3, s. 731-747
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Tidskriftsartikel (refereegranskat)abstract
- There is a potential risk that the geochemical cycles of several critical metals will be affected when mining of these metals increases to meet the demand of green technology. The geochemistry of Be, Bi, Ga, Ge, and W, herewith called CM5, is lacking, yet is necessary to ensure responsible mine waste and water management. Beryllium, Bi, and W are all considered immobile, but in previous studies of skarn tailings in Yxsjoberg, Sweden, all three elements were mobilized. The tailings are enriched in CM5, together with pyrrhotite, calcite, and fluorite. The mobility and environmental impact of CM5 and F in surface waters downstream of the Yxsjoberg mine site, Sweden, were studied using monthly water samples from seven locations and analysis of diatoms at five of these locations. Bismuth, Ge, and W were present at low concentrations, transported in the particulate phase, and likely settled in the sediments hundreds of meters from the tailings. Beryllium and F were present at high concentrations and dominantly transported in the dissolved phase. At these pH conditions (5.6), Be should form insoluble hydroxides; however, elevated concentrations of dissolved Be were observed more than 5 km from the mine site. Diatoms downstream of the mine site were negatively affected by the mine drainage. The release of low quality neutral mine drainage will continue for hundreds of years if remediation actions are not undertaken since only a small portion of the tailings have weathered during 50-100 years of storage.
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| 5. |
- Jia, Yu, et al.
(författare)
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Metal Mobilization in Tailings Covered with Alkaline Residue Products : Results from a Leaching Test Using Fly Ash, Green Liquor Dregs, and Lime Mud
- 2015
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Ingår i: Mine Water and the Environment. - : Springer Science and Business Media LLC. - 1025-9112 .- 1616-1068. ; 34:3, s. 270-287
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Tidskriftsartikel (refereegranskat)abstract
- The in situ dynamics of repeated percolation of rainwater through unoxidized mine tailings was simulated using a modified column test to predict long-term weathering characteristics. Fly ash, green liquor dregs, and lime mud waste materials from the paper mill industry were used in the column tests to assess the effect of alkaline paper mill residue on pH buffering and controlling the mobility of metals and semi-metals from the tailings. The experiment was continued for 15 cycles, each comprising reaction, leaching, and idle steps (1 week per step). The cumulative percolated water through the tailings represented a liquid:solid ratio of 1.6. The leached content of inorganic elements decreased with time in both the covered and the uncovered tailings. The presence of the alkaline materials consistently reduced the mobility of most contaminants (e.g. Cd, Co, Cr, Mn, Ni and Zn), but not As. The leachate was modeled using PHREEQC. XRD analysis of the remaining tailings samples after termination of the test showed detectable variations in mineral composition. The alkaline residue products all fulfilled the requirements as a cover material from a geochemical prospective, with the exception of As. The green liquor dregs and lime cover increased the pH of the tailings more rapidly than did the fly ash.
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| 6. |
- Karlsson, Teemu, et al.
(författare)
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A Test of Two Methods for Waste Rock Drainage Quality Prediction: Aqua Regia Extraction and Single-addition Net-acid Generation Test Leachate Analysis : [两种废矿石排水质量预测方法: 王水提取法和单添加净产酸实验 (NAG) 滤出液分析法] [Ein Test von zwei Methoden zur Qualitätsvorhersage von Haldensickerwässern: Königswasseraufschluss und Sickerwasseranalyse über den Nettosäurebildungspotentialtest bei einmaliger Zugabe]
- 2021
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Ingår i: Mine Water and the Environment. - : Springer. - 1025-9112 .- 1616-1068. ; 40:3, s. 736-751
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Tidskriftsartikel (refereegranskat)abstract
- The mobility of contaminants from mine waste can be assessed using different extraction methods. Aqua regia (AR) extraction is the most commonly used method in Finland. Another method is the analysis of leachate from net acid generation (NAG) tests, which is primarily designed for acid production potential assessment. We investigated the performance of single-addition NAG test leachate analysis and AR extraction in drainage quality prediction, using waste rock and drainage water samples from several Finnish waste rock sites. Our objective was to improve interpretation of the AR and single-addition NAG test leachate analysis results in drainage quality prediction. The AR extraction effectively reflected elements that occurred in elevated concentrations in drainage water, though it over-predicted Al, As, Cd, Co, Cu, and Ni in some circumneutral drainages, and Cr in general. The single-addition NAG test leachate analysis also performed well in assessing the mobility of contaminants including Al and Cr at acid mine drainage sites. As the contaminants tend to precipitate in neutral NAG test solution, the usability of the method in neutral mine drainage cases should be further investigated. Furthermore, the conclusions presented in this study are limited to waste rock samples collected from the surface of piles; future work will examine waste rock history, dump cores, drainage quality changes, etc. in more detail.
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| 7. |
- Mäkitalo, Maria, et al.
(författare)
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An Evaluation of Using Various Admixtures of Green Liquor Dregs, a Residual Product, as a Sealing Layer on Reactive Mine Tailings
- 2016
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Ingår i: Mine Water and the Environment. - : Springer Science and Business Media LLC. - 1025-9112 .- 1616-1068. ; 35:3, s. 283-293
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Tidskriftsartikel (refereegranskat)abstract
- Green liquor dregs (GLD), a residual product from sulfate paper mills, was blended with tailings, fly ash, and bark sludge with the aim of improving the material’s physical properties so that it could function as a sealing layer in dry covers on sulfidic mine waste. Geotechnical and geochemical investigations, including weathering cell tests, were carried out on GLD with admixtures to assess their effectiveness. Due to its alkaline character, GLD was shown to have the potential to improve leachate quality by decreasing metal mobility when blended with tailings. The admixtures showed favorable sealing layer properties such as high water retention capacity and low hydraulic conductivity. However, caution must be exercised when the dregs are blended with tailings containing large amounts of As and Mo, since increased leaching of these elements may be expected.
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| 8. |
- Nason, Peter, et al.
(författare)
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Biodegradation of Biosolids Under Aerobic Conditions : Implications for Cover Materials for Sulfide Mine Tailings Remediation
- 2016
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Ingår i: Mine Water and the Environment. - : Springer Science and Business Media LLC. - 1025-9112 .- 1616-1068. ; 35:3, s. 273-282
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Tidskriftsartikel (refereegranskat)abstract
- Sewage sludge residue (biosolids) was investigated for its potential as a long-term tailings cover. Biosolids may prevent oxygen diffusion into underlying sulfide tailings through microbial aerobic biodegradation of organic matter. Biosolids were investigated at laboratory-, pilot-, and field-scale using analysis of total organic matter (TOM) mass reduction and O2, CO2, CH4 concentrations to quantify the biodegradation rate. A 156-day, open microcosm experiment, in which the loss of biosolids mass over time at differing temperatures, mimicking ambient (20–22 °C), mesophilic (34 °C), and thermophilic (50 °C) conditions, indicated that TOM biodegradation was best in the mesophilic temperature range, with 14.8, 27.2, and 26.7 % mass depletion at ambient, mesophilic, and thermophilic conditions, respectively. The data was correlated to field-scale data that evaluated biodegradation rates via decreasing O2 and increasing CO2 concentrations. Field biodegradation rates were less than laboratory rates because lower mean annual temperatures (0.6–0.7 °C) diminished microbial activity. A calibrated model indicates that 20 % of a field application of biosolids will degrade within 2 years. However, the rate declines with time due to exhaustion of the most readily degradable organic fraction. If biodegradation cannot be maintained, the long-term effectiveness of biosolids as a covering material for mine tailings remains a concern.
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| 9. |
- Nason, Peter, et al.
(författare)
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Impact of Sewage Sludge on Groundwater Quality at a Formerly Remediated Tailings Impoundment
- 2014
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Ingår i: Mine Water and the Environment. - : Springer Science and Business Media LLC. - 1025-9112 .- 1616-1068. ; 33:1, s. 66-78
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Tidskriftsartikel (refereegranskat)abstract
- Sewage sludge can be a suitable, organic-rich substrate to promote vegetation ofsulfide-mine tailings, but it may contain contaminants, that, when oxidized, canadversely affect underlying groundwater systems. The geochemical impact of asurface application of 12,000 metric tons of anaerobically-digested sewage sludge on the groundwater quality of a remediated sulfide-tailings impoundment in northern Sweden was evaluated to determine if sludge-borne metals and nitrate were released to the underlying groundwater system. Two years of data from a field-scale groundwater monitoring programme initiated just before the sludge application was compared to groundwater data from 1998-2006. Grass was successfully established within two years. However, until that occurred, elevated concentrations of sludge-borne metals (Cu, Ni, Pb, Zn) were released to the underlying groundwater. In addition, the release of nitrate likely exacerbated metal concentrations by providing an oxidant for pyrite in the underlying tailings. The release was periodic due to the establishment of the grass, which immobilized metals and nitrate in the sludge. Metals bound asorgano-metallic complexes, due to dissolved organic carbon released from the sludge, migrated across the tailings impoundment. Model simulations indicate that the plume will take six years to exit the groundwater environment. Though the impacts are relatively short-term, this type of application should be reconsidered in the future.
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| 10. |
- Nhantumbo, Clemencio, et al.
(författare)
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A Simplified Model to Simulate pH and Alkalinity in the Mixing Zone Downstream of an Acidic Discharge
- 2018
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Ingår i: Mine Water and the Environment. - : Springer Science and Business Media LLC. - 1025-9112 .- 1616-1068. ; 37:3, s. 552-564
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Tidskriftsartikel (refereegranskat)abstract
- A modelling methodology was developed that simulates the resulting pH and alkalinity in the mixing zone when acidic water is discharged into a river. The input to the model are the: pH, alkalinity, flow, and temperature of both the river water and the acidic discharge. Two different scenarios were simulated: (1) a change of pH in the acidic discharge, assuming constant flow; and (2) a change in the flow of the acidic discharge, assuming constant pH. The model incorporates the effect of carbonic acid and the modelled values agree well with the laboratory results. The model setup was subsequently used to predict the anticipated effect of contamination of the Zambezi River in Mozambique. The results indicate that the river will be impacted if the average pH of the water in the tributaries coming from the mining area is below 3. The model could be used by water managers to predict the potential impact of acidic discharges in poorly monitored rivers.
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