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- Backlund, Sandra, et al.
(author)
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Nya finansieringsformer för efterbehandling av förorenad mark : Regeringsuppdrag
- 2016
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Reports (other academic/artistic)abstract
- I Sverige finns ett stort antal förorenade områden för vilka det saknas eller riskerar att saknas finansiering för efterbehandling. Det gör att det finns en risk för att takten i efterbehandlingsarbetet inte går tillräckligt fort för att nå det långsiktiga miljökvalitetsmålet om giftfri miljö.Naturvårdsverket redovisar i den här rapporten ett regeringsuppdrag med två olika förslag som ska förbättra förutsättningarna för att det finns tillgängliga medel. Det ena förslaget handlar om att alla verksamhetsutövare som omfattas av förordning (1998:901) om verksamhetsutövares egenkontroll ska göra en så kallad saneringsplan med tidsbestämd planering för sanering av konstaterade föroreningar.Åtgärderna ska vara kostnadsuppskattade. Det andra förslaget är att alla anmälnings- och tillståndspliktiga verksamhetsutövare betalar in avgifter till en statligt administrerad fond. Fonden kan ge bidrag till efterbehandling när det saknas en ansvarig med betalningsförmåga.
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- Gleisner, Magdalena, et al.
(author)
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Pyrite oxidation by Acidithiobacillus ferrooxidans at various concentrations of dissolved oxygen.
- 2006
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In: Chemical Geology. - : Elsevier BV. - 0009-2541 .- 1872-6836. ; 225:1-2, s. 16-29
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Journal article (peer-reviewed)abstract
- Pyrite oxidation rates were examined at various concentrations of dissolved oxygen (DO) in the presence of the sulfur and iron oxidizer Acidithiobacillus ferrooxidans. Five different batch experiments were performed at room temperature for 75 days under various DO levels (273, 129, 64.8, 13.2, and ≤ 0.006 μM), containing pyrite grains (particle size 63–250 μm) and a modified 9K nutrient medium at pH 3. The reactors were inoculated with A. ferrooxidans. In all experiments, pH decreased with time and sulfur and iron were released to the solution, indicating pyrite oxidation at all DO levels. Pyrite oxidation rates (ca. 5 × 10− 10 mol m− 2 s− 1 at 273 μM DO) from all experiments showed positive correlation with DO, Fe(III), and bacterial concentration. These rates were significantly slower than rates presented in other published studies, but this is probably due to the significantly greater Fe(III) concentration at lower pH in these previous studies. The results obtained in this study suggest that ferric iron reduction at the pyrite surface is the primarily mechanism for microbial pyrite oxidation in the presence of DO. The results from our study support the indirect mechanism of sulfide oxidation, where A. ferrooxidans oxidizes ferrous iron in the presence of DO, which then oxidizes pyrite.
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- Gleisner, Magdalena, 1972-
(author)
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Quantification of mineral weathering rates in sulfidic mine tailings under water-saturated conditions
- 2005
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Doctoral thesis (other academic/artistic)abstract
- Tailings are a fine-grained waste product produced during the metal recovery process. Tailings consist mostly of different silicates but also sulfides (e.g. pyrite), since 100 % metal recovery is not possible. Freshly processed tailings are deposited in large impoundments. If the mine tailings in the impoundments are exposed to water and oxygen, the sulfides will oxidize and release acidity and metals such as Fe, Cu, Zn, and Pb. The sulfide mineral oxidation reactions are catalyzed by sulfur and iron oxidizing bacteria (principally Acidithiobacillus ferrooxidans) that oxidize ferrous iron to ferric iron, which then oxidizes pyrite. When the leachate produced by this process discharges from the impoundment, it is called acid mine drainage, which may lead to the pollution of adjacent streams and lakes.The intention with this thesis is to investigate and quantify mineral weathering processes and element release rates occurring in water-saturated and soil-covered sulfidic mine tailings. The study was performed in different batch and column experiments in room temperature and in the laboratory. The batch experiments were conducted for ca. three months and investigated: a) microbial and abiotic sulfide oxidation in freshly processed tailings under oxic conditions at pH 2-3 and pH 8, b) microbial oxidation of pure pyrite grains at pH 2-3 under different oxygen concentrations ranging from anoxic to oxic conditions. The column experiments, consisting of unoxidized tailings in water-saturated columns, were conducted for up to three years. In these experiments, an oxygen-saturated solution was continually pumped into the column inlet, and investigated: a) differences in oxidation rates between tailings of two different grain sizes, b) factors affecting element discharge rates, acid neutralization, and sulfide oxidation, c) the effect of ions released in a soil cover on release rates in the tailings.Sulfide oxidation processes within the batch experiments were limited by surface kinetics. The microbial oxidation of pure pyrite at atmospheric conditions produced the most rapid rate, while the microbial oxidation of pure pyrite at anoxic conditions was slower by 1.8 orders of magnitude. Microbial and abiotic oxidation of pyrite in freshly-processed tailings resulted in pyrite oxidation rates that were intermediate between these two extremes. The results from the microbial experiments with pure pyrite indicated a positive correlation between the concentration of dissolved oxygen, ferric iron and bacterial cells (at a total cell concentration > 106 cells/mL and a dissolved oxygen concentration ≥ 13.2 µM), which implies an interdependence of these factors. The results from these batch experiments support the indirect mechanism for microbial oxidation by the ferric oxidation pathway. Pyrite oxidation rates estimated from the batch experiments may be comparable with oxidation rates in the unsaturated zone and at the groundwater table in a tailings impoundment.Acid neutralization reactions in the column experiments resulted in the release of base cations to the column leachate. Calcite was the most important neutralizing mineral despite that it was only present in minor amounts in the tailings. It was confirmed that acidity forced the calcite dissolution. Element release rates in the column experiments were controlled by the availability of dissolved oxygen, which was a function of the water flow rate into the column. These column experiments also showed that the results are comparable with results from field studies, justifying the use of column experiments to study processes within tailings impoundments.
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- Herbert, Roger, et al.
(author)
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Variations in pore water geochemistry, density, and magnetic susceptibility in profiles from Impoundment 1, Kristineberg
- 2005
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In: Proceedings, Securing the Future. Skellefteå, Sweden. ; , s. 399-408
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Conference paper (other academic/artistic)abstract
- Impoundment 1 at the Kristineberg mine, northern Sweden, was remediated in 1996 with the installation of a soil cover. Since the installation of the soil cover, oxygen diffusion and water infiltration into the tailings has been greatly reduced, with a resulting decrease in sulfide oxidation in the impoundment. This study investigates the pore water chemistry below the soil cover in order to determine if the pore water composition has been affected by the cover application. In addition, this study assesses vertical variations in tailings composition, in terms of magnetic susceptibility and density, and assesses the impact of these variations on pore water composition. These parameters are studied in tailings cores collected in October 2001.Dissolved oxygen was analyzed in cores from an area of the Impoundment where only a single layer cover exists. Microelectrode analyses in the field showed relatively high dissolved oxygen concentrations (20 – 110 µM) below the cover in cores collected from unsaturated tailings. In saturated tailings, the dissolved oxygen concentrations were generally <2 µM.The results from a tailings core collected in the vicinity of the former dam wall indicate that pore water pH increases from ca. 4.2 to 6.1 over an interval of about 200 cm below the oxidation front, with the lowest pH levels closest to the oxidation front (265 cm depth). The greatest metal and sulfate concentrations are measured in the unoxidized tailings at ca. 300 cm depth, with lower concentrations at the oxidation front and at deeper intervals. Tailings density appears to increase slightly with depth, and magnetic susceptibility greatly varies, reflecting the presence of ferromagnetic mineral phases. Iron redox chemistry in the saturated tailings was investigated with the determination of Fe(II) and Fe(III) in pore water. The measured Fe(III) concentrations are high and exceed ferrihydrite solubility. Ferric iron complexation is discussed as a potential process for maintaining such high Fe(III) levels in solution.
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