Geokemisk undersökning vid Rävlidmyrgruvan, Västerbottens län : provtagning, analys och förslag till åtgärder
The mining industry, in terms of ore excavation and metal production, is and has been important to the Swedish economy. In connection with the ore excavation process, large amounts of partly sulphidic waste are produced. When the metal sulphides are exposed to air and water they are eventually oxi...
| Main Author: | |
|---|---|
| Format: | L3 |
| Language: | Swedish Inglés |
| Published: |
SLU/Dept. of Soil Sciences
2007
|
| Subjects: |
| _version_ | 1855571923543523328 |
|---|---|
| author | Frandsen, Sara |
| author_browse | Frandsen, Sara |
| author_facet | Frandsen, Sara |
| author_sort | Frandsen, Sara |
| collection | Epsilon Archive for Student Projects |
| description | The mining industry, in terms of ore excavation and metal production, is and has been
important to the Swedish economy. In connection with the ore excavation process, large
amounts of partly sulphidic waste are produced. When the metal sulphides are exposed to air and water they are eventually oxidised, which leads to the formation of acidic water with high concentrations of metal cations and sulphate ions, so called Acid Mine Drainage
(AMD). This water may reach the nearest surroundings and cause negative environmental
effects. By covering the waste with soil or water, the oxidation process can be minimised.
At the Rävlidmyran mine in the county of Västerbotten open pit mining took place between
1951 and 1991. When the mining activities ceased the pit was filled with water forming a pit lake. Waste rock dumps, which are partly contaminated with the sulphide mineral pyrite, and covered by till material surround the pit lake. Despite previous remediation measures, there is still a leakage of metal ions to the nearby lake Hornträsket. The lake is presently considered as an oligotrophic lake, which is contaminated with heavy metals.
The main purpose of the present study was to investigate possible remediation measures for
reducing heavy metal leakage, based on the results of chemical analyses. The specific
purposes were: (1) to collect samples within the catchment of the Rävlidmyran mine and to
predict how the metal flows take place and to investigate whether sulphate reduction is
important or not (2) to collect samples in the pit lake to get a picture of its chemical and biological condition and (3) to contribute to an updating of a semiquantitative heavy metal budget for the lake Hornträsket and quantify the contribution of heavy metals from the Rävlidmyran mine.
Water samples collected in the catchment were analysed for pH and electrical conductivity
(EC), the total concentrations of Cu, Zn, Cd and Fe, and the concentrations of Cl-, TOC and SO42-. At several sampling points the water flow was measured with a V-notch. Minerogenic and organic sediment samples were also collected and analysed for total concentrations of Cu, Zn, Cd, Fe och As. In the pit lake, water samples were collected at 0-, 2-, 5-, 8 and 12- meter depths. These samples were analysed for pH and EC as well as the total concentrations of Cu, Zn, Cd and Fe plus the concentrations of H2PO4- and SO42-.
Some leakage points were identified where the water had an exceptionally low pH and high
concentrations of metals and sulphate, probably as a direct cause of pyrite oxidation. This conclusion was partly supported by an analysis of sulphur isotopes. Among the sediment samples the organic sediments had the highest concentrations of Cu, Zn and Cd, while the minerogenic sediments had the highest concentrations of Fe and As. It was concluded that the environment in the pit lake was not optimal for sulphate reducing bacteria (SRB). However, analysis of sulphur isotopes indicated that sulphate reduction might occur in microenvironments of the pit lake.
One suggested measure against high acidity is to inject a slurry of reactive lime stone and sewage sludge into the waste rock dump. This should increase the pH and facilitate reducing conditions, which should keep the heavy metals in precipitated metal sulphides. Addition of sewage sludge to the pit lake should favour an increased production of algae. Decomposition of the algae may create reducing conditions that should favour the formation of precipitated metal sulphides. |
| format | L3 |
| id | RepoSLU11708 |
| institution | Swedish University of Agricultural Sciences |
| language | swe Inglés |
| publishDate | 2007 |
| publishDateSort | 2007 |
| publisher | SLU/Dept. of Soil Sciences |
| publisherStr | SLU/Dept. of Soil Sciences |
| record_format | eprints |
| spelling | RepoSLU117082017-11-23T12:09:40Z Geokemisk undersökning vid Rävlidmyrgruvan, Västerbottens län : provtagning, analys och förslag till åtgärder Frandsen, Sara Acid Mine Drainage (AMD) sulfatreducerande bakterier (SRB) sulfidmineral dagbrottssjö The mining industry, in terms of ore excavation and metal production, is and has been important to the Swedish economy. In connection with the ore excavation process, large amounts of partly sulphidic waste are produced. When the metal sulphides are exposed to air and water they are eventually oxidised, which leads to the formation of acidic water with high concentrations of metal cations and sulphate ions, so called Acid Mine Drainage (AMD). This water may reach the nearest surroundings and cause negative environmental effects. By covering the waste with soil or water, the oxidation process can be minimised. At the Rävlidmyran mine in the county of Västerbotten open pit mining took place between 1951 and 1991. When the mining activities ceased the pit was filled with water forming a pit lake. Waste rock dumps, which are partly contaminated with the sulphide mineral pyrite, and covered by till material surround the pit lake. Despite previous remediation measures, there is still a leakage of metal ions to the nearby lake Hornträsket. The lake is presently considered as an oligotrophic lake, which is contaminated with heavy metals. The main purpose of the present study was to investigate possible remediation measures for reducing heavy metal leakage, based on the results of chemical analyses. The specific purposes were: (1) to collect samples within the catchment of the Rävlidmyran mine and to predict how the metal flows take place and to investigate whether sulphate reduction is important or not (2) to collect samples in the pit lake to get a picture of its chemical and biological condition and (3) to contribute to an updating of a semiquantitative heavy metal budget for the lake Hornträsket and quantify the contribution of heavy metals from the Rävlidmyran mine. Water samples collected in the catchment were analysed for pH and electrical conductivity (EC), the total concentrations of Cu, Zn, Cd and Fe, and the concentrations of Cl-, TOC and SO42-. At several sampling points the water flow was measured with a V-notch. Minerogenic and organic sediment samples were also collected and analysed for total concentrations of Cu, Zn, Cd, Fe och As. In the pit lake, water samples were collected at 0-, 2-, 5-, 8 and 12- meter depths. These samples were analysed for pH and EC as well as the total concentrations of Cu, Zn, Cd and Fe plus the concentrations of H2PO4- and SO42-. Some leakage points were identified where the water had an exceptionally low pH and high concentrations of metals and sulphate, probably as a direct cause of pyrite oxidation. This conclusion was partly supported by an analysis of sulphur isotopes. Among the sediment samples the organic sediments had the highest concentrations of Cu, Zn and Cd, while the minerogenic sediments had the highest concentrations of Fe and As. It was concluded that the environment in the pit lake was not optimal for sulphate reducing bacteria (SRB). However, analysis of sulphur isotopes indicated that sulphate reduction might occur in microenvironments of the pit lake. One suggested measure against high acidity is to inject a slurry of reactive lime stone and sewage sludge into the waste rock dump. This should increase the pH and facilitate reducing conditions, which should keep the heavy metals in precipitated metal sulphides. Addition of sewage sludge to the pit lake should favour an increased production of algae. Decomposition of the algae may create reducing conditions that should favour the formation of precipitated metal sulphides. Gruvnäringen, i form av malmbrytning och metallproduktion, är och har varit viktig för den svenska ekonomin. I samband med brytning av malm produceras stora mängder avfall som till stor del är sulfidhaltigt. I kontakt med syre och vatten sker en oxidation av metallsulfiderna i gruvavfallet. En konsekvens av detta är att surt och metallhaltigt lakvatten, (Eng. ’Acid mine drainage (AMD)’) kan nå omgivande terräng och orsaka negativa miljöeffekter. Genom att täcka avfallet med jord eller vatten kan oxidationen minimeras. Vid Rävlidmyrgruvan i Västerbottens län bedrevs mellan 1951 och 1991 gruvbrytning i dagbrott. Gruvan vattenfylldes därpå och en så kallad dagbrottssjö skapades. Dagbrottssjön omges av vallar av moräntäckt sidoberg, som till viss del är förorenat med sulfidmineralet pyrit. Trots åtgärder i dagbrottssjön läcker gruvan metaller till den närbelägna sjön Hornträsket. Idag betraktas den som en näringsfattig och tungmetallförgiftad sjö. Det övergripande syftet med studien var att med ett förbättrat dataunderlag baserat på provtagningar och kemiska analyser utreda vilka åtgärder som behöver vidtas för att minska metalläckage inom avrinningsområdet. De specifika syftena var att: (1) ta prover inom Rävlidmyrgruvans avrinningsområde för att bedöma var de största metallflödena sker samt om det sker en sulfatreduktion; (2) ta vattenprover i dagbrottssjön för att ge underlag för en bedömning av vilka förhållanden som råder i sjön samt (3) med hjälp av framtagna data uppdatera en metallbudget för sjön Hornträsket samt beräkna metalltransporter inom Rävlidmyrgruvans avrinningsområde. Inom avrinningsområdet togs vattenprov som analyserades med avseende på pH, elektrisk konduktivitet (EC), totalkoncentrationerna av Cu, Zn, Cd och Fe samt halterna av Cl- , TOC och SO4 2-. I vissa av provpunkterna mättes vattenflödet med ett V-överfall. Ett antal minerogena och organiska sedimentprov togs som analyserades med avseende på totalkoncentrationerna av Cu, Zn, Cd, Fe och As. I dagbrottssjön togs vattenprover på 0, 2, 5, 8 och 12 meters djup. Proverna analyserades med avseende på pH och EC, totalkoncentrationerna av Cu, Zn, Cd och Fe samt koncentrationerna av H2PO4- och SO42-. Ett antal läckagepunkter med lågt pH och höga metall- och sulfathalter kunde identifieras, vilket troligen var en direkt följd av en pågående sulfidoxidation. Detta kunde delvis bestyrkas av svavelisotopsammansättningen. De organiska sedimentproven hade höga totalhalter av Cu, Zn och Cd, medan de minerogena sedimenten hade höga Fe- och As-halter. Miljön i dagbrottssjön var inte optimal för sulfatreducerande bakterier (SRB). Svavelisotopsammansättningen indikerade dock att det pågick en sulfatreduktion i skyddade mikromiljöer. En åtgärd som föreslogs var att injicera en blandning av mesakalk och avloppsslam i vallen. Detta höjer pH-värdet och skapar på sikt en reducerande miljö, varvid tungmetaller kan fastläggas i utfällda sulfidmineral. Tillförsel av avloppsslam till dagbrottssjön skulle kunna bidra till en ökad algproduktion. Vid nedbrytningen av dessa alger kan reducerande förhållanden skapas, vilket gynnar sulfatreducerande bakterier och sulfidutfällning. Slutligen föreslogs gödsling av de tallar som växer på vallen. Ökad trädtillväxt minskar avrinningen och jorden stabiliseras, vilket minskar erosionen. SLU/Dept. of Soil Sciences 2007 L3 swe eng https://stud.epsilon.slu.se/11708/ |
| spellingShingle | Acid Mine Drainage (AMD) sulfatreducerande bakterier (SRB) sulfidmineral dagbrottssjö Frandsen, Sara Geokemisk undersökning vid Rävlidmyrgruvan, Västerbottens län : provtagning, analys och förslag till åtgärder |
| title | Geokemisk undersökning vid Rävlidmyrgruvan, Västerbottens län : provtagning, analys och förslag till åtgärder |
| title_full | Geokemisk undersökning vid Rävlidmyrgruvan, Västerbottens län : provtagning, analys och förslag till åtgärder |
| title_fullStr | Geokemisk undersökning vid Rävlidmyrgruvan, Västerbottens län : provtagning, analys och förslag till åtgärder |
| title_full_unstemmed | Geokemisk undersökning vid Rävlidmyrgruvan, Västerbottens län : provtagning, analys och förslag till åtgärder |
| title_short | Geokemisk undersökning vid Rävlidmyrgruvan, Västerbottens län : provtagning, analys och förslag till åtgärder |
| title_sort | geokemisk undersökning vid rävlidmyrgruvan, västerbottens län : provtagning, analys och förslag till åtgärder |
| topic | Acid Mine Drainage (AMD) sulfatreducerande bakterier (SRB) sulfidmineral dagbrottssjö |