Remediation of mine waste by the application of till cover is one of the more common methods used in Sweden to prevent oxidation of sulphide-rich minerals. Although the general conclusion from Swedish state-of-the-art field studies is that dry covers may be effective, they are expensive to construct. Further investigations are also needed to understand the processes occurring in till covered waste deposits. The Kristineberg mining area has been chosen as the main field site for the research program MiMi (Mitigation of the environmental impact of mining waste) funded by the Foundation for Strategic Environmental Research (MISTRA). MiMi focuses on finding new and improved methods to mitigate the environmental problems related to mining operations and disposal of mining waste. An extensive sampling programme was carried out in Kristineberg during 1998 and 1999. The Kristineberg mine is a Boliden mine, located within the Skellefte ore field. It is a Zn-Cu deposit developed in the 1940s and still in production. This thesis consists of three papers outlining the geochemical conditions prevailing in tailings Impoundment 1 at the Kristineberg mine, after remediation by applying till cover. The impoundment investigated was in use until the early 1950s and it was remediated in 1996. Two different remediation methods have been used; in the area with a shallow groundwater table 1.0 m of till was used to raise the groundwater table above the tailings. In other areas, with a deeper groundwater table, a sealing layer consisting of a 0.3 m thick layer of a compacted clayey till underlying a 1.5 m thick protective cover of unspecified till was used. Field studies include sampling of solid tailings, saturated tailings pore water as well as pore water from the vadose zone. Laboratory investigations consist of a five-step sequential extraction on solid tailings samples. Pre-remediation oxidation has resulted in a zonation of the tailings with an upper oxidised zone above unoxidised tailings. Just below the oxidation front, there is a secondary enrichment of especially Cu but also of other elements. Metals released by sulphide oxidation were thus secondarily enriched. Tailings remediated by the combination of a till cover and a raised groundwater table, resulted in a remobilisation of metals around and a few metres below the former oxidation front. Although the concentrations of several elements still are high in the pore water, they are lower than before the remediation. The general conclusion is that the remediation has succeeded in preventing further oxidation in this part of the impoundment. Sequential extractions performed on selected samples from the drilling of the impoundment show that most of the remaining sulphide-associated trace elements in the oxidised zone still belong to the sulphide fraction. At the level of the peaks of metal concentrations in the pore water (and the solid secondary enrichment) substantial concentrations of the trace elements Cd, Co, Cu, Ni, and Zn is present in the adsorbed/exchangeable/carbonate fraction. Other trace elements are retained with other secondary formations such as amorphous or crystalline iron oxyhydroxides e.g., As, Ba, and Pb. Especially the adsorbed/exchangeable/carbonate fraction is easily dissolved and the raised groundwater table remobilise these trace elements into the pore water, as could be seen from the pore water extractions. In Impoundment 1, where the sealing layer was applied, sampling of the infiltrating water was performed by tension lysimeters. Tension lysimeters were installed in the protective till cover, in the oxidised tailings, in the uppermost unoxidised tailings and at an intermediate depth. The groundwater at the same location was also sampled. The tension lysimeters in the till protective cover contained relatively low concentrations of most elements. Elements such as Al, Cd, Co, Cu, Fe, Mn, Ni, S, Si, and Zn had the highest concentrations in the second tension lysimeter in the tailings. Between the second and the third tension lysimeters the concentration of most elements decreased. The increase between the first and the second tension lysimeters can be explained by remobilisation of secondarily retained oxidation products. The decrease between the second and the third tension lysimeters is interpreted as co-precipitation with different iron oxyhydroxides as well as adsorption onto secondarily formed minerals and primary mineral surfaces. Between the deepest tension lysimeter and the groundwater table, the element concentrations decrease further. Most of the pre-remediation oxidation products that are secondarily retained below the oxidation front and are released by the small amount of infiltrating water, is tertiarily retained during continued downward transport. Thus, if the depth to the groundwater table is large enough, the metals released by infiltrating water do not reach it. / Godkänd; 2000; 20070317 (ysko)

<p>Godkänd; 1997; 20070418 (ysko)</p>

Godkänd; 1998; 20070404 (ysko)

The analytical performance of laser ablation (LA) for multielemental determination of geological and biological samples has been investigated. In the present study, LA has been used for sample introduction in inductively coupled plasma sector field mass spectrometry (ICP-SFMS). Although LA can provide semi-quantitative results rapidly and easily, the calibration process still remains the "Achilles heel" of the technique. The major goal of this study has been to investigate the capabilities of LA-ICP-SFMS for qualitative and quantitative analysis of various solid materials. LA was used for analyses of coal were calibration was performed by using coal powder doped with analyte elements. This was done by adding solution standards (including analyte and internal standard elements) to the coal, drying and finally homogenising, followed by pressing tablets. LA results were compared with data obtained by conventional solution nebulisation (SN) after preparation of coal samples using microwave (MW) digestion or fusion. In spite of a relatively poor agreement for elements such as As, Se, Sn, Re, Te, and Tl, accuracy obtained with LA in the present study is otherwise generally superior to previously reported data for LA and slurry nebulisation. For about 50 elements, results obtained with LA fall within 20% of those obtained by SN. The study shows the potential of LA quantification, based on solution-doped powders. However, the necessity of sample grinding and homogenising results in loss of spatial distribution information and makes the approach more vulnerable to sample contamination. The possibilities of sulphide minerals analysis by ICP-SFMS have been investigated. Seven elements (Co, Fe, Cd, Ag, Mn, Cu and S) have been quantitatively determined in sphalerite samples from the Zinkgruvan mine, using Zn as internal standard (IS). A straightforward calibration procedure allows on-line correction for possible Fe impurities at percent levels. Consequently, the use of complimentary techniques for determination of actual Zn content in the samples is avoided. The LA-ICP-SFMS results were compared with data from conventional SN introduction of sample solutions following acid digestion. Good agreement was found between the methods. For homogeneously distributed elements the overall precision for LA was found to be better than 10% RSD. A method for total mineral dissolution of five sulphides (sphalerite, pyrite, galena, pyrrhotite and chalcopyrite) has been developed, followed by multielemental analysis by ICP-SFMS. By performing this mineral characterisation the intention was to determine whether the analysed bulk mineral samples could be used as in-house LA calibration standards. The use of LA was focused towards elucidating whether the observed deviations in results obtained by ICP-SFMS for the two reference material powders used were caused by sample inhomogeneity or by inefficient matrix dissolution. It was found that the reference materials showed lack of accuracy in recommended concentrations for many trace and ultra trace elements, as well as possible inhomogeneity when using 50 mg sample amounts. The sulphide minerals studied appears to be suitable as matrix matched calibration standards for the determination of about 20 trace and ultra trace elements by LA. Laser ablation was also used for analysing element to sulphur ratios in washed human nails. The element ratios were then used to display the effectiveness of the applied washing method applied prior to MW digestion and analysis by ICP-SFMS. Based on the LA analysis, it was found that, even after the applied nail washing procedure, many elements are enriched in the surface of the nail. / Godkänd; 2000; 20070317 (ysko)

Godkänd; 1997; 20070418 (ysko)

Godkänd; 1994; 20080401 (ysko)

No description available.

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 (&gt;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.

No description available.

No description available.