Theses and Dissertations at Montana State University (MSU)
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Item An ecological risk assessment for acid mine drainage from copper-nickel mining in the kawishiwi watershed, minnesota(Montana State University, 2021) Tofte, Zaddy Andrea; Chairperson, Graduate Committee: Scott PowellThe mining of heavy metals such as copper and nickel has been identified as a potential source of acid mine drainage (AMD), which is a consequence of the oxidation of sulfide minerals that produces sulfuric acid due to mine wastes being exposed to air and water. Contamination of AMD to surface waters may pose detrimental effects on aquatic organisms. Accidental releases of process or seepage waters are likely to occur by mining ventures. The Kawishiwi watershed lies over a layered mafic intrusion known as the Duluth Complex, a mineral deposit rich in copper and nickel. Twin Metals Minnesota has renewed the mineral leases looking to develop an underground mine operation adjacently to Birch Lake and the South Kawishiwi River. Therefore, an aquatic ecological risk assessment is necessary to access and protect ecosystems that may be exposed to AMD. My study examined four potential contamination scenarios (A-D) in Birch Lake, Kawishiwi Watershed, Minnesota, based on hypothetical spills and metal concentrations. Concentrations reported in seepage waters from mines or from local sources that share the same mineral deposit or rock characteristics, were chosen to represent realistic scenarios. The concentrations varied for copper from 11 to 0.1 ?g/L and for nickel from 1,580 to 9 ?g/L. The scenarios also accounted for a determined size of spill, which varied from 10 to 0.3% of the total volume of the contact water pond 1. This pond is designated in the Twin Metal Minnesota operations plan to collect the waters from direct precipitation or stormwater that comes in contact with ore or tailings. The purpose of my assessment was to estimate the risks of this contamination to fish species living in the lakes. I used these final concentrations from the proposed scenarios to evaluate if exposure would exceed toxicity endpoints. The risk was assessed using the risk quotient (RQ) method, where the RQ is the ratio of exposure to effect. Risk quotient values < 0.5 are consider below regulatory levels of concern. My results suggest that the toxicity endpoint was exceeded for one of the four contamination scenarios by the most sensitive species: embryos of rainbow trout and bluegill. The contamination scenarios representing the two lowest concentrations for copper and nickel did not suggest levels of concern for either of the fish species. Based on my results, the water volume of Birch Lake would provide sufficient dilution in pollution events that are as much or less than ones represented by Scenarios C and D. Conversely, a spill representing Scenario A would pose risks to fish species exceeding levels of concern, especially to the most sensitive species. My assessment may be applicable when considering the risks that aquatic species could face in the event of a leak or spill of AMD of a sulfide mine in the Kawishiwi Watershed.Item Evaluation of selected phosphate sources for the control of acid production from pyritic coal overburden(Montana State University - Bozeman, College of Agriculture, 1990) Spotts, EdwardItem Geochemical characteristics of a waste rock repository at a western gold mine(Montana State University - Bozeman, College of Agriculture, 1997) Outlaw, Jason DwayneItem Hydrology of a waste rock repository capping system at the Zortman Mine(Montana State University - Bozeman, College of Agriculture, 1997) Warnemuende, E. A.Item Hydrologic evaluation of tailings covers at the Golden Sunlight Mine(Montana State University - Bozeman, College of Agriculture, 1994) Strong, Murray RandalItem Metal accumulation in voles from an acid mine drainage impacted wetland(Montana State University - Bozeman, College of Agriculture, 1990) Zavitz, Thomas LindseyItem Geochemical characterization of sulfide mineral weathering for remediation of acid producing mine wastes(Montana State University - Bozeman, College of Agriculture, 1993) Jennings, Stuart Russell; Chairperson, Graduate Committee: Douglas J. DollhopfThe generation of acid mine drainage as a consequence of sulfide mineral oxidation is a widespread source of resource degradation. The objective of this investigation was to evaluate the influence of sulfide mineral weatherability on acid generation processes. In addition to acid generation by pyrite, the weathering characteristics of common sulfide minerals was investigated and correlated to detection by acid-base account (ABA) methodologies. The influence of particle morphology, and not particle size, was found to exert the dominant control on mineral weathering processes. Massive morphology particles generated acid at a significantly greater rate than euhedral morphology samples. Acid generation was a consequence of mineral dissolution which occurred nonuniformly across the surface of minerals during oxidation. Mineral surface weathering occurred at sites of excess energy including grain edges, steps, defects, microcracks and inclusions, resulting in the formation of etch pits. Massive morphology particles exhibited the greatest density of crystalline defect, and had the greatest rate of oxidation. Sulfide minerals found to be acid generating, in addition to pyrite, include marcasite, pyrrhotite, arsenopyrite, chalcopyrite and sphalerite. Minerals containing sulfur in the atomic structure which were not acid producing include barite, anhydrite, gypsum, anglesite, jarosite, chalcocite and galena. Delineation of acid producing and nonacid producing sulfur forms by ABA extraction methods, a standard operating procedure used in the United States, was determined to be ineffective. Effective mineral classification, particle morphology identification and observation of mineral weathering processes were accomplished by scanning electron microscopy. Accurate assessment of sulfur form distribution and sulfide mineral weathering characteristics are required for effective remediation of sites impacted by mining.Item Evaluation of a constructed wetland : sediment characterization and laboratory simulation of wetland chemical processes(Montana State University - Bozeman, College of Agriculture, 1998) Lyons, Dale WellerItem Remediation of acid rock drainage through the use of a constructed passive treatment system which simulates natural processes(Montana State University - Bozeman, College of Agriculture, 1997) Schmidt, T.G.Item Acid mine drainage treatment in an open limestone channel emphasizing aeration & retention(Montana State University - Bozeman, College of Agriculture, 1998) Franti, D. J.