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dc.contributor.authorParigi, Roberta
dc.date.accessioned2021-01-13 16:14:03 (GMT)
dc.date.available2022-01-14 05:50:08 (GMT)
dc.date.issued2021-01-13
dc.date.submitted2020-01-11
dc.identifier.urihttp://hdl.handle.net/10012/16641
dc.description.abstractMetal stable isotope analyses have proven to make valuable contributions to the study of the biogeochemical cycling of metals and metalloids in the environment. Processes that control the release, mobility and fate of metals in natural systems often lead to stable isotope fractionation. Before the isotopic signatures of natural samples can be applied as environmental tracers, laboratory-scale studies, focused on the measurement of the magnitude of the isotope fractionation associated with specific processes, are needed. Despite recent studies, Ni stable isotope systematics is still in its infancy, thus further research is required to decipher Ni isotope signatures in complex, natural systems. Nickel, similar to other metals, is a nutritionally essential trace element for several organisms and plants, however the exposure to highly Ni-polluted environments can result in a variety of pathological effects in living organisms. Some of the Ni compounds are also classified as carcinogenic, thus, the investigation of Ni attenuation processes is of great importance to protect living beings and the environment. Laboratory batch experiments were conducted to characterize the isotope fractionation during the precipitation of Ni secondary mineral phases: Ni hydroxide, Ni hydroxycarbonate and Ni sulfide. Data were best represented by Rayleigh-type curves, showing fractionation factors εNi hydroxide = −0.40‰, εNi-hydroxycarbonate = −0.50‰ and, εNi-sulfide = −0.73‰. These values indicate a preferential retention of lighter Ni isotopes by the solid phase in all three systems. Synchrotron-based Powder X-ray diffraction (PXRD), and X-ray absorption spectroscopy (XAS) analyses were performed to characterize the precipitates. The interpretation of isotope results suggests that equilibrium effects are the main mechanisms responsible for the measured Ni isotopic signatures. As bacterial reduction of sulfate under anaerobic conditions has been successfully applied to the treatment of waste streams contaminated by heavy metals, laboratory batch experiments were performed to evaluate isotopic fractionation of Ni during microbially-mediated Ni sulfide precipitation. The final solid product was characterized by Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Synchrotron-based Powder X-ray diffraction (PXRD) and X-ray absorption spectroscopy (XAS). The measured isotope data relative to the fraction of Ni in solution and the fraction of Ni associated with the solid phase followed a linear trend which yielded a Δ60solid-solution = −1.99‰, with lighter Ni isotopes partitioned into the precipitates. Both the results of the solid-phase and isotope analyses suggest a combination of Ni removal mechanisms, including complexation, precipitation, co-precipitation and sorption, thus complicating the interpretation of the isotope data. Previous studies involving calcite interaction with Ni have shown the potential of calcium carbonate in the sequestration of Ni from impacted aquatic and groundwater environments. A flow-through cell experiment was conducted to assess Ni isotopic fractionation during Ni treatment by calcite. Synthetic Ni-contaminated groundwater was pumped through a custom-made flow-through cell containing crushed natural calcite. Measurements oh pH were conducted on the effluent and aqueous samples were collected for determination of the concentrations of anions and cations and Ni isotope analyses. X-ray absorption spectroscopy (XAS) was performed via a Kapton window in the cell to gather information on the speciation of Ni in the system. Confocal X-ray microfluorescence imaging (CMXFI) analysis was also conducted on Ni-bearing calcite particles from the cell to further characterize the mechanisms of Ni removal. Results indicate that there are multiple processes controlling Ni removal by calcite inside the flow-through cell, and that greater enrichment of 60Ni over 58Ni in the effluent compared to the input solution, is associated with higher rates of Ni removal. Nickel isotope analysis was conducted on pore water samples extracted from the Moose Lake tailings impoundment as a supportive tool in the characterization of the processes controlling Ni mobility in the tailings within the ML 25 storage facility which are subject to sulfide mineral oxidation. Samples of the tailings material were analyzed using multiple analytical techniques including transmitted and reflected microscopy, X-ray fluorescence, and synchrotron based X-ray absorption spectroscopy (XAS). The highest Ni concentration (578.9 mg L 1) in pore water was found to coincide with the depth of the front of active sulfide-mineral oxidation, whereas highest Ni concentrations in the tailings solid material (1473 and 5000 mg kg-1) corresponded to the highest peaks in sulfur content. Results show a good correlation between Ni isotopic signatures of the pore water and the weathering zones characteristic of different depths of the tailings impoundment, thus suggesting the potential of Ni stable isotopes as tracers in environmental geochemistry.en
dc.language.isoenen
dc.publisherUniversity of Waterlooen
dc.subjectNi stable isotopesen
dc.subjectNi contamination and remediationen
dc.subjectNi in mine tailingsen
dc.titleNickel Isotope Geochemistry in Mine Waste Systemen
dc.typeDoctoral Thesisen
dc.pendingfalse
uws-etd.degree.departmentEarth and Environmental Sciencesen
uws-etd.degree.disciplineEarth Sciences (Water)en
uws-etd.degree.grantorUniversity of Waterlooen
uws-etd.degreeDoctor of Philosophyen
uws-etd.embargo.terms1 yearen
uws.contributor.advisorBlowes, David
uws.contributor.affiliation1Faculty of Scienceen
uws.published.cityWaterlooen
uws.published.countryCanadaen
uws.published.provinceOntarioen
uws.typeOfResourceTexten
uws.peerReviewStatusUnrevieweden
uws.scholarLevelGraduateen


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