| 1. |
- Kaasalainen, Hanna, et al.
(författare)
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Chemical analysis of sulfur species in geothermal waters
- 2011
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Ingår i: Talanta. - : Elsevier BV. - 0039-9140 .- 1873-3573. ; 85:4, s. 1897-1903
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Tidskriftsartikel (refereegranskat)abstract
- Analytical methods have been developed to determine sulfur species concentrations in natural geothermal waters using Reagent-Free™ Ion Chromatography (RF™-IC), titrations and spectrophotometry. The sulfur species include SO 4 2-, S 2O 3 2-, and ∑S 2- with additional determination of SO 3 2- and S xO 6 2- that remains somewhat semiquantitative. The observed workable limits of detections were ≤0.5 μM depending on sample matrix and the analytical detection limits were 0.1 μM. Due to changes in sulfur species concentrations upon storage, on-site analyses of natural water samples were preferred. Alternatively, the samples may be stabilized on resin for later elution and analysis in the laboratory. The analytical method further allowed simultaneous determination of other anions including F -, Cl -, dissolved inorganic carbon (DIC) and NO 3 - without sample preservation or stabilization. The power of the newly developed methods relies in routine analysis of sulfur speciation of importance in natural waters using techniques and facilities available in most laboratories doing water sample analysis. The new methods were successfully applied for the determination of sulfur species concentrations in samples of natural and synthetic waters. © 2011 Elsevier B.V. All rights reserved.
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| 2. |
- Kaasalainen, Hanna, et al.
(författare)
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Geochemistry and speciation of Fe(II) and Fe(III) in natural geothermal water, Iceland
- 2017
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Ingår i: Applied Geochemistry. - : Elsevier. - 0883-2927 .- 1872-9134. ; 87, s. 146-157
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Tidskriftsartikel (refereegranskat)abstract
- The geochemistry of Fe(II) and Fe(III) was studied in natural geothermal waters in Iceland. Samples of surface and spring water and sub-boiling geothermal well water were collected and analyzed for Fe(II), Fe(III) and Fetotal concentrations. The samples had discharge temperatures in the range 27–99 °C, pH between 2.46 and 9.77 and total dissolved solids 155–1090 mg/L. The concentrations of Fe(II) and Fe(III) were determined in the <0.2 μm filtered and acidified fraction using a field-deployed ion chromatography spectrophotometry (IC-Vis) method within minutes to a few hours of sampling in order to prevent post-sampling changes. The concentrations of Fe(II) and Fe(III) were <0.1–130 μmoL/L and <0.2–42 μmoL/L, respectively. In-situ dialysis coupled with Fe(II) and Fe(III) determinations suggest that in some cases a significant fraction of Fe passing the standard <0.2 μm filtration method may be present in colloidal/particulate form. Therefore, such filter size may not truly represent the dissolved fraction of Fe but also nano-sized particles. The Fe(II) and Fe(III) speciation and Fetotal concentrations are largely influenced by the water pH, which in turn reflects the water type formed through various processes. In water having pH of ∼7–9, the total Fe concentrations were <2 μmoL/L with Fe(III) predominating. With decreasing pH, the total Fe concentrations increased with Fe(II) becoming increasingly important and predominating at pH < 3. In particular in waters having pH ∼6 and above, iron redox equilibrium may be approached with Fe(II) and Fe(III) possibly being controlled by equilibrium with respect to Fe minerals. In many acid waters, the Fe(II) and Fe(III) distribution may not have reached equilibrium and be controlled by the source(s), reaction kinetics or microbial reactions
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| 3. |
- Kaasalainen, Hanna, et al.
(författare)
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Impact of declining oxygen conditions on metal(loid) release from partially oxidized waste rock
- 2019
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Ingår i: Environmental Science and Pollution Research. - : Springer. - 0944-1344 .- 1614-7499. ; 26:20, s. 20712-20730
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Tidskriftsartikel (refereegranskat)abstract
- The best available technology for preventing the formation of acid drainage water from the sulfidic waste rock at mine closure aims to limit the oxygen access to the waste. There is, however, a concern that contaminants associated with secondary minerals become remobilized due to changing environmental conditions. Metal(loid) mobility from partially oxidized sulfidic waste rock under declining and limited oxygen conditions was studied in unsaturated column experiments. The concentrations of sulfate and metal(loid)s peaked coincidently with declining oxygen conditions from 100 to < 5 sat-% and to a lesser extent following a further decrease in the oxygen level during the experiment. However, the peak concentrations only lasted for a short time and were lower or in the similar concentration range as in the leachate from a reference column leached under atmospheric conditions. Despite the acid pH (~ 3), the overall quality of the leachate formed under limited oxygen conditions clearly improved compared with atmospheric conditions. In particular, the release of As was two orders of magnitude lower, while cationic metals such as Fe, Cu, Mn, and Zn also decreased, although to a lesser extent. Decreased sulfide oxidation is considered the primary reason for the improved water quality under limited oxygen conditions. Another reason may be the immobility of Fe with the incorporation of metal(loid)s in Fe(III) minerals, in contrast to the expected mobilization of Fe. The peaking metal(loid) concentrations are probably due to remobilization from solid Fe(III)-sulfate phases, while the relatively high concentrations of Al, Mn, and Zn under limited oxygen conditions were due to release from the adsorbed/exchangeable fraction. Despite the peaking metal(loid) concentrations during declining oxygen conditions, it is clear that the primary remediation goal is to prevent further sulfide oxidation.
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| 4. |
- Kaasalainen, Hanna, et al.
(författare)
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Sulfur speciation in natural hydrothermal waters, Iceland
- 2011
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Ingår i: Geochimica et Cosmochimica Acta. - : Elsevier BV. - 0016-7037 .- 1872-9533. ; 75:10, s. 2777-2791
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Tidskriftsartikel (refereegranskat)abstract
- The speciation of aqueous dissolved sulfur was determined in hydrothermal waters in Iceland. The waters sampled included hot springs, acid-sulfate pools and mud pots, sub-boiling well discharges and two-phase wells. The water temperatures ranged from 4 to 210°C, the pHT was between 2.20 and 9.30 at the discharge temperature and the SO4 and Cl concentrations were 0.020-52.7 and <0.01-10.0mmolkg-1, respectively. The analyses were carried out on-site within ~10min of sampling using ion chromatography (IC) for sulfate (SO42-), thiosulfate (S2O32-) and polythionates (SxO62-) and titration and/or colorimetry for total dissolved sulfide (S2-). Sulfite (SO32-) could also be determined in a few cases using IC. Alternatively, for few samples in remote locations the sulfur oxyanions were stabilized on a resin on site following elution and analysis by IC in the laboratory. Dissolved sulfate and with few exceptions also S2- were detected in all samples with concentrations of 0.02-52.7mmolkg-1 and <1-4100μmolkg-1, respectively. Thiosulfate was detected in 49 samples of the 73 analyzed with concentrations in the range of <1-394μmolkg-1 (S-equivalents). Sulfite was detected in few samples with concentrations in the range of <1-3μmolkg-1. Thiosulfate and SO32- were not detected in <100°C well waters and S2O32- was observed only at low concentrations (<1-8μmolkg-1) in ~200°C well waters. In alkaline and neutral pH hot springs, S2O32- was present in significant concentrations sometimes corresponding to up to 23% of total dissolved sulfur (STOT). In steam-heated acid-sulfate waters, S2O32- was not a significant sulfur species. The results demonstrate that S2O32- and SO32- do not occur in the deeper parts of <150°C hydrothermal systems and only in trace concentrations in ~200-300°C systems. Upon ascent to the surface and mixing with oxygenated ground and surface waters and/or dissolution of atmospheric O2, S2- is degassed and oxidized to SO32- and S2O32- and eventually to SO42- at pH >8. In near-neutral hydrothermal waters the oxidation of S2- and the interaction of S2- and S0 resulting in the formation of Sx2- are considered important. At lower pH values the reactions seemed to proceed relatively rapidly to SO42- and the sulfur chemistry of acid-sulfate pools was dominated by SO42-, which corresponded to >99% of STOT. The results suggest that the aqueous speciation of sulfur in natural hydrothermal waters is dynamic and both kinetically and source-controlled and cannot be estimated from thermodynamic speciation calculations. © 2011 Elsevier Ltd.
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| 5. |
- Kaasalainen, Hanna, et al.
(författare)
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The chemistry of trace elements in surface geothermal waters and steam, Iceland
- 2012
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Ingår i: Chemical Geology. - : Elsevier BV. - 0009-2541 .- 1872-6836. ; 330-331, s. 60-85
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Tidskriftsartikel (refereegranskat)abstract
- The geochemistry of trace elements in surface geothermal fluids in Iceland was studied. The sampled fluids included hot springs, mud pots, steam vents and soil solutions with temperatures ranging from 4 to 100. °C, pH between 2.01 and 9.10 and total dissolved solids between 86 and 4375. ppm. The surface geothermal waters may be categorized into three groups based on their chemical composition, namely NaCl waters, steam-heated acid-sulfate waters and mixed waters. NaCl waters with pH >. 8 are considered to represent aquifer geothermal fluids that have undergone boiling in the upflow. They contained only low concentrations of most metals,
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| 6. |
- Kaasalainen, Hanna, et al.
(författare)
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The geochemistry of trace elements in geothermal fluids, Iceland
- 2015
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Ingår i: Applied Geochemistry. - : Elsevier BV. - 0883-2927 .- 1872-9134. ; 62, s. 207-223
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Tidskriftsartikel (refereegranskat)abstract
- Trace element geochemistry was studied in geothermal fluids in Iceland. The major and trace element compositions of hot springs, sub-boiling, and two-phase (liquid and vapor) wells from 10 geothermal areas were used to reconstruct the fluid composition in the aquifers at depth. Aquifer fluid temperatures ranged from 4 to 300 °C, pH values between 4.5 and 9.3, and fluids typically contained total dissolved solids
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| 7. |
- Nyström, Elsa, et al.
(författare)
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Prevention of sulfide oxidation in waste rock by the addition of lime kiln dust
- 2019
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Ingår i: Environmental Science and Pollution Research. - : Springer. - 0944-1344 .- 1614-7499. ; 26:25, s. 25945-25957
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Tidskriftsartikel (refereegranskat)abstract
- During the operation of a mine, waste rock is often deposited in heaps and usually left under ambient conditions allowing sulfides to oxidize. To focus on waste rock management for preventing acid rock drainage (ARD) formation rather than ARD treatment could avoid its generation and reduce lime consumption, costs, and sludge treatment. Leachates from 10 L laboratory test cells containing sulfide-rich (> 60% pyrite) waste rock with and without the addition of lime kiln dust (LKD) (5 wt.%) were compared to each other to evaluate the LKD’s ability to maintain near neutral pH and reduce the sulfide oxidation. Leaching of solely waste rock generated an acidic leachate (pH < 1.3) with high concentrations of As (21 mg/L), Cu (20 mg/L), Fe (18 g/L), Mn (45 mg/L), Pb (856 μg/L), Sb (967 μg/L), S (17 g/L), and Zn (23 mg/L). Conversely, the addition of 5 wt.% LKD generated and maintained a near neutral pH along with decreasing of metal and metalloid concentrations by more than 99.9%. Decreased concentrations were most pronounced for As, Cu, Pb, and Zn while S was relatively high (100 mg/L) but decreasing throughout the time of leaching. The results from sequential extraction combined with element release, geochemical calculations, and Raman analysis suggest that S concentrations decreased due to decreasing sulfide oxidation rate, which led to gypsum dissolution. The result from this study shows that a limited amount of LKD, corresponding to 4% of the net neutralizing potential of the waste rock, can prevent the acceleration of sulfide oxidation and subsequent release of sulfate, metals, and metalloids but the quantity and long-term stability of secondary minerals formed needs to be evaluated and understood before this method can be applied at a larger scale.
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| 8. |
- Nyström, Elsa, 1987-, et al.
(författare)
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Prevention of Sulfide Oxidation in Waste Rock using By-products and Industrial Remnants : a Suitability Study
- 2017
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Ingår i: Mine Water & Circular Economy. ; , s. 1170-1178
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Konferensbidrag (refereegranskat)abstract
- Prevention and mitigation of acid rock drainage from mining are decisive for limiting environmental impact. Five by-products and industrial remnants (lime kiln dust, blast furnace slag, granulated blast furnace slag, cement kiln dust and fly ash) were investigated for their suitability to prevent acidity and metal(loid)s during leaching from highly sulfidic (50wt%, sulfide) waste rock in small scale laboratory test cells. Variations in pH and electrical conductivity in leachate allowed differentiation between the different materials. Lime kiln dust (5wt%) and fly ash (1 and 2.5wt%) were observed to be the most suitable materials to prevent acidity and metal(loid)s leaching.
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| 9. |
- Nyström, Elsa
(författare)
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Suitability of industrial residues for preventing acid rock drainage generation from waste rock
- 2018
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- One of the main and most challenging environmental problems related to mining is the generation of acid rock drainage (ARD), a leachate characterized by low pH and elevated concentrations of sulfate, metals, and metalloids formed when sulfide-bearing minerals are subjected to oxygen and water. During the operation of a mine, waste rock is often deposited in heaps and usually left under ambient conditions, enabling sulfides to oxidize. Generated ARD is commonly treated actively with alkaline material in an attempt to raise the pH and precipitate metals, with subsequent formation of sludge, which requires additional treatment. To focus on the treatment of waste rock rather than the ARD could prevent the generation of ARD; reduce the lime consumption, costs, and sludge treatment. This thesis aims to identify and evaluate the potential of different industrial residues to maintain circumneutral pH in a sulfide oxidation environment, allowing secondary minerals to form on the reactive sulfide surface to prevent sulfide oxidation and generation of ARD.Five different industrial residues (blast furnace slag, granulated blast furnace slag, cement kiln dust, bark ash, and lime kiln dust) were selected in a feasibility study performed prior to this study. The selection was based primarily on their alkaline properties, availability, and early yield. The waste rock was selected due to its high content of sulfides (>50%) and potential to generate ARD. Initial characterization of the industrial residues included combining mineralogical and chemical composition with batch testing (L/S 10). Sulfide oxidation in the leaching of the waste rock accelerated after week 29 resulting in high concentrations of major elements such as Al, Fe and S but also extremely high concentrations of e.g. As, Cu, Mn, Pb, Sb and Zn despite their relatively low content in the waste rock. Leaching was conducted during 14-153 weeks. The initial characterization implied that all of the studied industrial residues has the potential to prevent ARD generation. However, the enrichment and leachability of Pb in the cement kiln dust, as well as Cr and Zn in the bark ash, suggested the presence of elements of potential concern that could limit the use of the materials. When the industrial residues were added to the waste rock surface in small-scale laboratory test cells, blast furnace slag, granulated blast furnace slag, and cement kiln dust self-cemented and failed to maintain circumneutral pH, whereas bark ash (1wt.%) prevented acidity, metal and metalloid leaching. However, the use of bark ash may prove problematic due to the release of Cl, K, and Na likely related to salt dissolution. Lime kiln dust (5wt.%), the most promising of the industrial residues, maintained a circumneutral pH throughout the time of leaching, with an overall decrease of metal and metalloid concentrations by more than 99.9%. Results from investigations of secondary minerals formed combined with element release during the leaching period suggest that the addition of LKD to the waste rock led to decreasing concentrations of S in the leachate due to decreased sulfide oxidation, which subsequently led to gypsum dissolution. Moreover, the addition of LKD to the waste rock generated a lower amount of secondary minerals compared to when no addition was made.The results from these studies increase the understanding of advantages and limitations of using selected industrial residues in the treatment of mine waste. Moreover, it shows that a rather small amount of alkaline material, corresponding to 4% of the net neutralizing potential of waste rock, can prevent the acceleration of sulfide oxidation and subsequent release of sulfate, metals, and metalloids. However, the quantity and long-term stability of the formed secondary minerals need to be evaluated and understood before this method can be applied at larger scale.
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| 10. |
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