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| 2. |
- Alakangas, Lena, et al.
(author)
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Estimation of temporal changes in oxidation rates of sulphides in copper mine tailings at Laver, Northern Sweden
- 2010
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In: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 408:6, s. 1386-1302
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Journal article (peer-reviewed)abstract
- Tailings containing pyrrhotite were deposited in an impoundment at a copper mine at Laver, Northern Sweden, which operated between 1936 and 1946. Since then the oxidation of sulphides has acidified recipient water courses and contaminated them with metals. Measurements from surface water sampled in 1993, 2001 and 2004-05 from a brook into which the tailing impoundment drains indicate that the amounts of sulphide-associated elements such as Cu, S and Zn released into the brook have decreased over time, while pH has increased. The mass transport of S in the brook during 1993 and 2001 corresponded well with the amount of S estimated to be released from the tailings by oxidation. Secondary precipitates such as covellite and gypsum, which can trap sulphur, were shown in earlier studies to be present in only low amounts. The annual release of elements from the tailings was estimated from the volume of tailings assumed to oxidise each year, which depends on movement of the oxidation front with time. The results indicate that the oxidation rate in the tailings has decreased over time, which may be due to the increased distance over which oxygen needs to diffuse to reach unoxidised sulphide grains, or their cores, in the tailings.
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| 4. |
- Alakangas, Lena, et al.
(author)
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Literature review on potential geochemical and geotechnical effects of adopting paste technology under cold climate conditions
- 2013
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Reports (other academic/artistic)abstract
- The purpose of this literature review is to summarize the recent research regarding geochemical and geotechnical stability of paste tailings, identify knowledge gaps and future research needs. The present study has been conducted by the Division of Geosciences and Environmental Engineering together with the Division of Mining and Geotechnical Engineering at Luleå University of Technology on behalf of Boliden Mineral, LKAB and Outotec.A survey conducted by MEND (Mine Environment Neutral Drainage) in 2006 on the environmental effects related to the use of paste tailings summarizes that only a few studies had been performed about long-term effects on the surface and groundwater quality. Instead, the focus had been on the additives and the strength of the paste. It is still uncertain how the paste technology affects the long-term environmental stability from a geochemical point of view. Concerns regarding the stability of paste with high sulphide content are still relevant. Studies performed indicate that sulphide oxidation occurs within cemented paste as well as on the surface of non-cemented paste and cracks formed on the surfaces could induce oxidation. For cemented paste, metals released by sulphide oxidation might be sequestered due to high pH induced by the alkaline additives, but anion such as Se has been shown to be mobilized. The leachate has been shown to be near-neutral initially, but the neutrality decreases with time and probably metals sequestered in the matrix will also be released. Again, it should be noted that no long term study was performed on leaching of paste, cemented or uncemented. The longest leaching study was performed for one year. Arsenic has been proven to be retained in Ca-arsenates in cemented paste, but the long term stability of these precipitates is relatively unknown. Expanded secondary phases e.g. gypsum and ettringite have been observed to form when there is sulphate in the process or drainage of water. These phases could crack the paste, but, on the other hand, can also fill former cracks when deposited in layers. The effects of the formation of these phases are relatively uncertain in a long-term perspective. Presence of different elements such as ammonium, sulphates and metals in the water has been shown to negatively affect the curing process and therefore water is suggested to be treated before use. The presence of carbon dioxide during the paste formation could also affect the curing process, but could sequester metals in carbonate phases.Geotechnical and rheological properties of paste is well defined and documented. Several case studies have been found in literature providing valuable information about the details of the works being carried out. However, a difficulty has been noted during the investigation of the effects of cold climate conditions when current practice is applied in the colder parts of the world. It is not certain how some specific and vital parameters are going to be affected by cold temperatures. Parameters such as deposition slopes and deposition scheme, strength development of the paste are expected to be responsive to cold climate conditions. There are predictions about which properties are going to be affected in what way, but there is also a need to establish a scientific base for discussion. These have been highlighted as research needs and information gaps at the end of the report.
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| 5. |
- Alakangas, Lena, et al.
(author)
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Neutralization/prevention of acid rock drainage using mixtures of alkaline by-products and sulfidic mine wastes
- 2013
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In: Environmental Science and Pollution Research. - : Springer Science and Business Media LLC. - 0944-1344 .- 1614-7499. ; 20:11, s. 7907-7916
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Journal article (peer-reviewed)abstract
- Backfilling of open pit with sulfidic waste rock followed by inundation is a common method for reducing sulfide oxidation after mine closure. This approach can be complemented by mixing the waste rock with alkaline materials from pulp and steel mills to increase the system’s neutralization potential. Leachates from 1 m3 tanks containing sulfide-rich (ca.30 wt %) waste rock formed under dry and water saturated conditions under laboratory conditions were characterized and compared to those formed from mixtures. The waste rock leachate produced an acidic leachate (pH < 2) with high concentrations of As (65 mg/L), Cu (6 mg/L), and Zn (150 mg/L) after 258 days. The leachate from water-saturated waste rock had lower concentrations of As and Cu (<2 μg/L), Pb and Zn (20 μg/L and 5 mg/L), respectively, and its pH was around 6. Crushed (<6 mm) waste rock mixed with different fractions (1–5 wt %) of green liquid dregs, fly ash, mesa lime, and argon oxygen decarburization (AOD) slag was leached on a small scale for 65 day, and showed near-neutral pH values, except for mixtures of waste rock with AOD slag and fly ash (5 % w/w) which were more basic (pH > 9). The decrease of elemental concentration in the leachate was most pronounced for Pb and Zn, while Al and S were relatively high. Overall, the results obtained were promising and suggest that alkaline by-products could be useful additives for minimizing ARD formation
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| 6. |
- Alakangas, Lena, et al.
(author)
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Norrbottens malm- och mineralresurs och dess potentiella betydelse för innovation, samhälle och miljö
- 2014
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Reports (other academic/artistic)abstract
- Gruvindustrins betydelse för samhällsutveckling och infrastruktur i Sverige och inte minst i Norrbottens län är mycket stor. De geologiska förutsättningarna att hitta nya brytvärda förekomster i Norrbotten är goda. Länet är tillsammans med Västerbotten en av Europas viktigaste regioner för utvinning av metaller. Det syns också i den nyligen framtagna regionala mineralstrategin för Norrbotten och Västerbotten. Visionen för den regionala mineralstrategin: ”Genom långsiktigt hållbart nyttjande av Norrbottens och Västerbottens läns mineralresurser har ytterligare tillväxt skapats i regionen och hela Sverige. Vi har utvecklat och stärkt vår ställning som ledande gruv- och mineralnation.”Eftersom framtidspotentialen för gruvnäringen är mycket god men okunnigheten hos både allmänhet och beslutsfattare om näringens betydelse för innovation och samhällsutveckling är stor, kopplat med en utbredd oro för miljöpåverkan, måste dessa viktiga framtidsfrågor belysas. Med finansiering från Länsstyrelsen i Norrbotten bedrevs därför under första hälften av 2014 en förstudie som syftade till att sammanfatta kunskapsläget om framtidens gruvindustri i Norrbotten. Resultaten av förstudien redovisas i den här rapporten. En viktig slutsats är att det under nästa strukturfondsperiod (med start 2015) behövs ett framtidsinriktat forskningsprogram för att belysa de möjligheter som finns. Denna förstudie utgör grund för en kommande ansökan till strukturfonderna. Kompetensen som finns vid Luleå tekniska universitet, Sveriges centrum för gruvrelaterad forskning och utbildning, bör användas för att studera troliga framtidsmöjligheter och hur de ska kunna användas för att få en så positiv utveckling som möjligt för länet. Projektet bör innehålla följande tre huvudinriktningar, som naturligtvis hör ihop:Vilka malm- och mineralresurser finns det potential för i Norrbotten, och vilka kommer sannolikt att exploateras i framtiden?Vad kommer den exploateringen att ha för betydelse för innovation och samhällsutveckling?Vad kommer den exploateringen att få för miljöeffekter och hur ska man göra för att minska miljöbelastningen?En annan slutsats är att nedlagda gruvområden inte måste ses som förstörd natur. Betydande mervärden som gruvturism skulle kunna skapas om vilja, kreativitet och beslutsamhet finns. Detta är ett givet utvecklingsområde där småföretag och entreprenörer kan göra stor insats om de politiska och myndighetsmässiga förutsättningarna finns. Dessa aspekter skulle också kunna belysas i det föreslagna forskningsprogrammet eller i ett eget projekt.
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| 7. |
- Alakangas, Lena, et al.
(author)
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Pilot-scale studies of different covers on unoxidised sulphide-rich tailings, northern Sweden : oxygen diffusion
- 2010
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In: Mine Water and the Environment. - Ostrava : VSB - Technical University Ostrava, Faculty of Mining and Geology, Institute of Environmental Engineering. - 9788024817675 ; , s. 347-350
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Conference paper (peer-reviewed)abstract
- The efficiency of five cover systems to decrease oxygen intrusion into sulphide-rich tailings was studied in pilot-scale test cells (5x5x3 m(3)). The covers consisted of clayey till, sewage sludge, fine-grained apatite concentrate or Trisoplast (a mixture of a polymer, bentonite and tailings sand) as sealing layers and unspecified till as protective cover. In one reference cell, tailings were uncovered. Oxygen concentrations below the entire covers were highest below the Trisoplast and apatite layers, and lowest below the sewage sludge layer. Effective diffusion coefficients (D-eff) and oxygen fluxes were estimated in the covers with non-oxygen-consuming sealing layers (clayey till and apatite). For the protective covers the Deff ranged between E-09 and E-07 m(2)/s, and for the sealing layers between E-10 and E-09 m(2)/s, and for the entire covers between E-10 and E-08 m(2)/s. Seasonal variations in D-eff were larger within the covers than between the different cover systems. Oxygen fluxes through the entire covers with clayey till and apatite ranged between 0.2 and 4 mole m(2)/year, which was a reduction of more than 99% compared to uncovered dry tailings.
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| 8. |
- Alakangas, Lena, et al.
(author)
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Project: ERA-MIN project "Tools for sustainable gold mining in EU"
- 2014
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Other publication (pop. science, debate, etc.)abstract
- This research identifies and evaluates environmental impacts and economical challenges of gold mining in Finland, Sweden, Portugal, Romania, Poland and Ireland. The focus of this project is in gold exploration, mineral processing, water treatment, waste management, environmental monitoring, risk assessment and socio-economic impacts of gold mining. Finasieras av Vinnova
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| 9. |
- Alakangas, Lena
(author)
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Project: Kolarctic ENBI EnviMIne
- 2014
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Other publication (pop. science, debate, etc.)abstract
- The objectives of the project are to develop a methodology for environmentally safe mine closure under specific conditions in the Barents region by cross border cooperation, exchange experiences and scientific knowledge.
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