| 1. |
- Bäckström, Mattias, 1974-, et al.
(författare)
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Mixing of acid rock drainage with alkaline ash leachates : fate and immobilisation of trace elements
- 2011
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Ingår i: Water, Air and Soil Pollution. - : Springer. - 0049-6979 .- 1573-2932. ; 222:1-4, s. 377-389
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Tidskriftsartikel (refereegranskat)abstract
- Acid rock drainage (ARD) from mine waste dumps often contains ferrous iron, sulphate and high concentrations of trace elements detrimental to the environment. Future costs will be enormous if the problem is not treated today. Simple, low maintenance, cost-effective methods for remediation of historical mine sites are therefore desired. In this study several mine waters were mixed with an alkaline ash leachtes in order to study the fate of the trace elements from both the mine waters (Cd, Cu, Pb, Zn, Ni and Co) and the ash leachates (Cr and Mo). It was found that the addition of ash water will precipitate hydrous ferric oxides (HFO) and hydrous aluminium oxides (HAO) and thereby inducing trace element sorption and co precipitation. It is also clear that the composition of the formed HFO/HAO mix determines the efficiency of the sorption for different trace elements. It is apparent that the amount of precipitating iron will determine the effectiveness of the removal of the trace elements. Sorption occurred much earlier (often one pH unit or more) in the system with high iron concentrations compared to the systems with lower iron concentrations. Removal of cadmium and zinc is difficult below pH 8 if the amount of precipitates is low. Using ash for generation of alkaline water may be a problem with regards to chromium and molybdenum. It is, however, possible to avoid problems with molybdenum by keeping the final pH around 7 and chromium(VI) from the ash water will be reduced into chromium(III) and precipitated as the hydroxide in the presence of iron(II) from the mine waters.The results imply that it is possible to also use fly ashes in alkaline leach beds in order to neutralize ARD followed by precipitation and sorption of trace elements.
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| 2. |
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| 3. |
- Bäckström, Mattias, 1974-, et al.
(författare)
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Use of multivariate statistics in order to understand the flow of acid rock drainage from an abandoned mining site
- 2016
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Ingår i: Journal of Environmental Protection. - : Scientific Research Publishing. - 2152-2197 .- 2152-2219. ; 7:3, s. 358-371
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Tidskriftsartikel (refereegranskat)abstract
- Pathways for acid rock drainage from an abandoned mining site (sulphidic ore) were investigated by analysing ground, seepage and surface waters. It was found that in affected ground and seepage waters pH was lower (average pH 5.0); sulphate higher (average 350 mg/L) and trace element concentrations were significantly increased (4330 μg/L copper and 7700 μg/L zinc) compared to surrounding waters. Multivariate statistics (principal component analysis) were used on the data set. Obtained loading plot showed a clear negative correlation between pH and parameters found at high concentrations, indicating that these parameters are found at the source term (acid rock drainage). Lead was also found in close proximity to iron and turbidity indicating that lead might be associated with particles. The score plot presented almost all samples from high concentrations to low concentrations along the first principal component (explaining 63% of the variation in the data set) indicating that dilution was an important mechanism for the decrease in concentrations as opposed to immobilisation on surfaces along the flowpath. Decrease in fluoride and sulphate along one of the suspected flowpath coincided with an increase in calcium. Through geochemical calculations it was concluded that calcite (CaCO3) dissolved along the flowpath and thus induced precipitation of gypsum (CaSO4) and fluorite (CaF2). Through a combination of PCA and geochemical calculations the most likely flowpaths for contaminated water from the abandoned mining site were presented, making it possible to prevent further negative effects on the surface water.
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| 4. |
- Åhlgren, Kristina, 1976-, et al.
(författare)
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Understanding Groundwater Composition at Kvarntorp, Sweden, from Leaching Tests and Multivariate Statistics
- 2017
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Ingår i: Mine Water & Circular Economy. - Lappeenranta, Finland : Lappeenranta University of Technology. - 9789523350656 - 9789523350663 ; , s. 770-776
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Konferensbidrag (refereegranskat)abstract
- Due to oil production from alum shale, the Kvarntorp area is heavily polluted. A waste deposit consisting mostly of shale ash and fines is of important concern. Groundwater shows that parameters such as pH, U, V, Ni and Mo are different at different localities around the deposit. Leaching tests indicate that burned and unburned shale residues leave different signatures on leachates. Principal component analysis of groundwater and leaching tests suggest that ground-water is affected by the waste deposit and that it is more influenced by shale ash than by fines.
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| 5. |
- Bäckström, Mattias, 1974-, et al.
(författare)
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Fly ash injection into weathered mine waste
- 2013
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Ingår i: Annual International Mine Water Association Conference. - Colorado, USA : IMWA. - 9780615793856 ; , s. 513-519
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Konferensbidrag (refereegranskat)abstract
- By adding alkaline ashes through injection to weathered mine waste pH increased approximately 3 units, trace element was immobilized and flow rate decreased due to formation of hard pans. Reduction in trace element concentrations was around 96.9-99.6 % for copper, 94.7-99.7 % for zinc and 22.9-99.8 % for cadmium. For lead the best reduction was 97.3 % and the worst -393 % (increase). MSWI ashes performed worst with low buffering capacity and increase in vanadium and molybdenum concentrations.
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| 6. |
- Bäckström, Mattias, 1974-, et al.
(författare)
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Permanent under water storing of weathered mine waste after removal of fine fraction and addition of ash
- 2014
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Ingår i: An Interdisciplinary Response to Mine Water Challenges. - Xuzhou : China University of Mining and Technology Press. - 9787564624378 ; , s. 711-714
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Konferensbidrag (refereegranskat)abstract
- Weathered sulphidic mine waste is a major environmental problem. An experiment was performed in order to study water covers for oxidized mine waste. In two experiments oxidized mine waste were covered with water, in one experiment the fine fraction was removed and in one experiment alkaline ash was also added prior to water covering. It was found that removal of the fine fraction decreased pH and increased trace element concentrations. Water covering of the mine waste with and without ash decreased trace element concentrations indicating that co disposing oxidized sulphidic mine waste and ash under water might be a promising remediation method.
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| 7. |
- Bäckström, Mattias, 1974-, et al.
(författare)
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Uranium leaching from a burning black shale deposit : Present conditions and future scenarios
- 2015
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Ingår i: Uranium – Past and Future Challenges. - Cham : Springer Publishing Company. - 9783319110592 - 9783319110585 ; , s. 47-54
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Konferensbidrag (refereegranskat)abstract
- During WW2 oil was produced through pyrolysis of alum shale giving rise to waste that was deposited in the open pits and in a waste deposit. The waste deposit still today has significantly elevated temperatures (above 500 °C). Remaining pyrite in the waste material has also led to ARD with elevated trace metal concentrations. The waste deposit is no great environmental problem today but as soon as the waste pile cools off both the volumes of drainage and concentration of uranium will increase significantly.
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