Phytostabilization is an emerging technology for the remediation of mine tailings sites. In arid and semiarid environments, mine tailings disposal sites are a major source of environmental pollution as they are subject to eolian dispersion and water erosion. Mine tailings are acidic to neutral, high in metal content, and nutrient poor. Furthermore, these sites remain unvegetated even after decades of no additional mining activity. In arid and semiarid regions, climatic variables such as high winds, salinity, and drought exacerbate the problem. The Klondyke mine tailings site is a model site for studying plant establishment in mine tailings within semiarid regions. It was a lead and zinc ore- processing operation from 1948 to 1958 and is similar in physicochemical characteristics to other acidic pyritic mine tailings.In a greenhouse study, a native drought tolerant halophyte, Atriplex lentiformis (Torr.) S. Wats., was evaluated for its potential as a phytostabilization candidate in compost-amended tailings from the Klondyke site. Germination, plant growth, and metal uptake of A. lentiformis were examined, and the microbial community was monitored by enumeration of autotrophic iron- and sulfur-oxidizing bacteria as well as heterotrophic bacteria. Results demonstrated that with 10 to 15% compost addition, growth of A. lentiformis was not affected and shoot metal concentrations were generally not a concern for foraging animals. Furthermore, the heterotrophic bacterial community is severely stressed but recovers with compost addition and successful plant growth. Therefore, A. lentiformis is a good candidate for phytostabilization of mine tailings with compost amendments.Poor revegetation of mine tailings has been attributed to the microbial community involved in acidifying tailings; however, no thorough microbial studies have been conducted. The second study characterizes the bacterial community of the Klondyke site and compares it to an offsite control sample. Results demonstrate that the heterotrophic community is indicative of soil health as it has a positive relationship with pH, phylotype richness, and diversity. Also, the mine tailings contain an unexplored diversity of acidophiles that are important in maintaining acidity and thus, metal bioavailability. Therefore, the bacterial community in mine tailings should be monitored in phytostabilization studies to evaluate restoration.

Tailings are the waste produced as a result of the extraction of oil from the tar sands in northern Alberta. Many avenues for the reclamation of tailings are being researched, but one area that has received little attention is phytoremediation. The Alder-Frankia symbiotic relationship in the tailings was investigated for its potential in revegetation and remediation of the tailings. Two species of alders were examined Alnus glutinosa and A. rugosa. The impact of the alders was monitored through the investigation of the differences in the microbial community present in the oil sands tailings and composite tailings (CT) with and without alders. For our investigation we used culture dependent techniques (plate counts and mineralization assays) and culture independent techniques (16S rRNA gene PCR, catabolic PCR and DGGE). The alders lowered the pH of the tailings, increased rates of mineralization, increased the general microbial population in the tailings by one to two orders of magnitude and increased the microbial diversity. / A. rugosa however, had a greater impact on the mineralization of poly aromatic hydrocarbons (PAHs) and, being native to Alberta, was chosen for further experimentation, using only composite tailings. The aim of the experiments was to determine the effect of a Frankia inoculum on the growth of A. rugosa in (CT) and the associated microbial community. The microflora in the bulk soil, rhizosphere and inside the root of inoculated and non-inoculated A. rugosa were compared through microbial enumerations of the community, with general and selective media and mineralization assays. A. rugosa inoculated with Frankia was taller and the roots were more developed and the endophytic community of inoculated A. rugosa had greater rates of naphthalene mineralization. / The results indicate that A. rugosa inoculated with Frankia could be used for the phytoremediation of tailings and for the re-establishment of a forest ecosystem.

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The production and storage of uranium mine mill tailings have the potential to contaminate local groundwater and surface waters with metals and metalloids. As such, an understanding of the solids reservoirs for potential contaminants in uranium ore blends and leach residues (solid wastes generated by the milling of ore) is required to predict long-term controls on these contaminants in tailings porewaters. This study characterized the distribution of the elements of concern (EOCs; As, Mo, Ni, and Se) in uranium ores and waste rock used to blend the mill feeds in the milling process and leach residues from the Key Lake mining operation, Saskatchewan. This study also evaluated the alteration of the clay minerals in these uranium ores, waste rocks and leach residues. X-ray diffraction, electron micro-probe, and mineral liberation analyses showed that the reservoirs for As, Mo, Ni, and Se (in ores and ore blends) were dominated by sulphides including cobaltite, gersdorffite, molybdenite, pyrite, galena and chalcopyrite, secondary Ni-arsenates (annabergite?), Fe-arsenate (scorodite?) and Ni-Co/Ni-sulfates. The secondary arsenates and sulfates present in special waste were identified as major As, Mo, Ni, and Se bearing minerals and most likely the product of oxidation of arsenide-bearing sulphide minerals within the special waste rock. Analyses also showed that sulphides and arsenates occurred in trace amounts in the ores and special waste rock (0.5 to 1.0 wt %). Data showed that 55 to 90% pyrite, 36 to 51% chalcopyrite, 23 to 37% molybdenite, and 52 to 70% galena remained unleached in the leach residues after milling of the ore blends. The percentages of unleached minerals varied between mill feeds and were dependent on the grain-size distribution and the degree of mineral liberation. Cation exchange capacity (CEC) analysis indicated an increase of the CEC values in the leach residues suggesting possible evolution of 2:1 layers into high-charge layers during the milling.

Mining has negative impacts on the environment, and is one of the main contributors to environmental pollution. This holds a potential hazard for ecosystems surrounding mining areas and also for public health in the surrounding communities. There is therefore a need for ecotoxicological research in order to assess these possible risks and find ways to minimize the harmful effects. One way in which to assess soil vitality are soil enzymes which are produced by plants and microorganisms and will therefore be more abundant in healthy soils. Earthworms have been proven to be useful bioindicators for metal contamination of soil, as they are able to accumulate metals from their environment into their body tissue. The aim of this study was to use earthworm bioassays, neutral red retention time analysis (NRRt), enzymatic analysis and RAPD-PCR to determine the effect of mining activity on the environment. This was done by assessing the ecotoxicity of tailings collected from three different mines, viz. gold-, opencast chrome- and coal mines. The metals chosen for analyses included four (Cr, Co, Ni and Pb) of the seven (Cd, Cr, Ni, Pb, Zn, Cu, Co) environmentally important trace elements as described for South African soils. Arsenic was also chosen since it is associated with gold mine tailings. Tailings and soil were collected from three sites at each of the mines which included unrehabilitated (TDF-U) and rehabilitated (TDF-R) substrates from tailings disposal facilities (TDFs) and reference soils (RS) in close proximity to TDFs. The physical and chemical properties of these different substrates were determined in terms of pH, particle size as well as metal contents. In addition to this, they were analysed for microbial community function by means of enzymatic activity, which has been proven to be useful in evaluating contamination of soil. The enzymes analysed in this study included dehydrogenase, ßglucosidase, acid phosphatase, alkaline phosphatase and urease. Earthworms (Eisenia andrei) were exposed to different material for 28 days during which their biomass, reproduction, mortality and lysosomal membrane stability were monitored weekly. Hereafter, they were removed from the material while the cocoons were left behind for a further 56 days. The hatched and unhatched cocoons as well as the juvenile worms were then counted to determine reproduction patterns in the materials. Metal concentrations in the substrates and earthworm body tissues were compared to selected benchmarks. Results indicated that when comparing the different materials from each mine, enzymatic activity proved to be a very sensitive parameter. Enzymatic activity showed significant differences (p < 0.05) between RS, TDF-R and TDF-U materials. Biomass was not a sensitive parameter (p > 0.05) for the worms exposed to the gold and chrome mine tailings, but it was a sensitive parameter (p < 0.05) for the coal mine exposed earthworms, showing early differences between the worms from the different sites (RS, TDF-R and TDF-U). The NRR-t assay was very sensitive (p < 0.05), indicating clear differences between the worms from each investigated site. In terms of reproduction, the production of cocoons showed clear differences (p < 0.05) between the different sites and could therefore be considered a sensitive parameter. Hatching success however, was not a sensitive parameter. The reason being that there were so little cocoons produced that it is not possible to determine the correct percentage of juvenile worms hatching from, for example, only one or two cocoons. Mortality was also not a sensitive endpoint as it was only observed in the coal mine material. RAPD - PCR results indicated genetic differences between earthworms exposed to the control- and the tailings materials, indicating either DNA alterations due to possible genotoxic effects, or genetic variation between individuals of the same species. Since mine waste materials often contain complex mixtures of metals that might be toxic on their own or in combination with other factors, it is difficult to attribute any observed genotoxic effect to any of the specific metals. / Thesis (MSc (Environmental Sciences))--North-West University, Potchefstroom Campus, 2012.

Mining has negative impacts on the environment, and is one of the main contributors to environmental pollution. This holds a potential hazard for ecosystems surrounding mining areas and also for public health in the surrounding communities. There is therefore a need for ecotoxicological research in order to assess these possible risks and find ways to minimize the harmful effects. One way in which to assess soil vitality are soil enzymes which are produced by plants and microorganisms and will therefore be more abundant in healthy soils. Earthworms have been proven to be useful bioindicators for metal contamination of soil, as they are able to accumulate metals from their environment into their body tissue. The aim of this study was to use earthworm bioassays, neutral red retention time analysis (NRRt), enzymatic analysis and RAPD-PCR to determine the effect of mining activity on the environment. This was done by assessing the ecotoxicity of tailings collected from three different mines, viz. gold-, opencast chrome- and coal mines. The metals chosen for analyses included four (Cr, Co, Ni and Pb) of the seven (Cd, Cr, Ni, Pb, Zn, Cu, Co) environmentally important trace elements as described for South African soils. Arsenic was also chosen since it is associated with gold mine tailings. Tailings and soil were collected from three sites at each of the mines which included unrehabilitated (TDF-U) and rehabilitated (TDF-R) substrates from tailings disposal facilities (TDFs) and reference soils (RS) in close proximity to TDFs. The physical and chemical properties of these different substrates were determined in terms of pH, particle size as well as metal contents. In addition to this, they were analysed for microbial community function by means of enzymatic activity, which has been proven to be useful in evaluating contamination of soil. The enzymes analysed in this study included dehydrogenase, ßglucosidase, acid phosphatase, alkaline phosphatase and urease. Earthworms (Eisenia andrei) were exposed to different material for 28 days during which their biomass, reproduction, mortality and lysosomal membrane stability were monitored weekly. Hereafter, they were removed from the material while the cocoons were left behind for a further 56 days. The hatched and unhatched cocoons as well as the juvenile worms were then counted to determine reproduction patterns in the materials. Metal concentrations in the substrates and earthworm body tissues were compared to selected benchmarks. Results indicated that when comparing the different materials from each mine, enzymatic activity proved to be a very sensitive parameter. Enzymatic activity showed significant differences (p < 0.05) between RS, TDF-R and TDF-U materials. Biomass was not a sensitive parameter (p > 0.05) for the worms exposed to the gold and chrome mine tailings, but it was a sensitive parameter (p < 0.05) for the coal mine exposed earthworms, showing early differences between the worms from the different sites (RS, TDF-R and TDF-U). The NRR-t assay was very sensitive (p < 0.05), indicating clear differences between the worms from each investigated site. In terms of reproduction, the production of cocoons showed clear differences (p < 0.05) between the different sites and could therefore be considered a sensitive parameter. Hatching success however, was not a sensitive parameter. The reason being that there were so little cocoons produced that it is not possible to determine the correct percentage of juvenile worms hatching from, for example, only one or two cocoons. Mortality was also not a sensitive endpoint as it was only observed in the coal mine material. RAPD - PCR results indicated genetic differences between earthworms exposed to the control- and the tailings materials, indicating either DNA alterations due to possible genotoxic effects, or genetic variation between individuals of the same species. Since mine waste materials often contain complex mixtures of metals that might be toxic on their own or in combination with other factors, it is difficult to attribute any observed genotoxic effect to any of the specific metals. / Thesis (MSc (Environmental Sciences))--North-West University, Potchefstroom Campus, 2012.

Historical gold mine tailings at several sites in Nova Scotia, Canada are publicly accessible and may pose a threat to human and ecosystem health because of high arsenic (As) concentrations in the tailings (max 25 wt.%) and associated pore waters (up to 100 mg/L). Two of these sites, Montague and Goldenville, are under consideration for remediation. Similar tailings sites have been cleaned up by covering the mine wastes with soil. However, the tailings at Montague and Goldenville have been weathering for at least 70 years, leading to a wide range of As-bearing secondary minerals which may dissolve under a soil cover, releasing As to local waters. The challenge of remediating these heterogeneous tailings lies in the different Eh-pH niches in which iron arsenates (oxidizing, acidic), calcium-iron-arsenates (oxidizing, alkaline), and sulfides (reducing) are stable. The main objectives of this study were to: 1) characterize pre-remediation geochemical controls on As mobility in subsurface tailings; 2) establish hydrogeological influences on As mobility; and 3) identify geochemical changes that result when a low organic soil cover is applied to the tailings. Pore water measurements were combined with bulk chemistry, scanning electron microscopy, and synchrotron micro-X-ray diffraction analyses, which were used to characterize the mineralogical composition of the tailings. Groundwater and surface water flow regimes throughout the tailings were defined through the use of piezometers and hydraulic conductivity measurements. Laboratory leaching experiments were used to assess the effects of a soil cover on the tailings. Variable weathering conditions over time have resulted in a continuum of saturation and redox environments and a range of As hosts in the tailings. In some areas, tailings pore waters are mixing with stream waters leading to As transport beyond the tailings. Applying a low organic soil cover does not induce reducing conditions in the tailings or cause dissolved As concentrations to increase compared to field pore water concentrations. This type of soil cover is effective in slowing sulfide mineral oxidation while maintaining stable conditions for secondary As-phases. The results of this research can be used to inform remediation decisions and guide ongoing environmental management of historical gold mine sites. / Thesis (Ph.D, Geological Sciences & Geological Engineering) -- Queen's University, 2014-06-04 10:22:43.838

Increased demand for rare earth elements (REEs) for applications in modern technologies has led to an increase in REE exploration. Several deposits are expected to begin mining within a decade, but few studies have examined the possible environmental effects created by these mines. Metal toxicity is thought to be greater in aqueous environments when metals occur as free ions rather than complexes, and the speciation can also impact the treatment technologies utilized to reduce metal concentrations. This research investigates the mineralogical source of REEs and the mechanism of REE mobility in low-temperature waters that have interacted with pilot plant tailings from the Nechalacho deposit, Northwest Territories. The Nechalacho deposit is owned by Avalon Rare Metals Inc. and located approximately 100 km east of Yellowknife. The deposit is hosted within a hydrothermally altered layered nepheline-sodalite syenite in the peralkaline Blatchford Lake complex. The main REE ore minerals are zircon, fergusonite, allanite, monazite, bastnäsite, and synchisite-parasite. Characterization of the tailings using mineral liberation analyzer (MLA) show that the ore minerals are fine grained and well liberated. Bastnäsite and synchisite-parasite are the only potentially soluble ore minerals at low temperature and near-neutral pH. Shake flask experiments were designed to simulate the interaction of tailings with three different leach waters to identify soluble phases and mobile elements. Decanted solutions from the shake flasks were filtered to 0.45µm and 0.01µm. Speciation modelling of the 0.01µm filtrate suggests that carbonate ligands will form the dominant complexes with the REEs, and <2% occur as free metal ions. Higher proportions of LREEs (1-6%) occur as free metal ions than HREEs (<1%) and LREEs occur in higher concentrations (2 to 8 times greater) than the HREE. REEs were found in the colloidal fraction ([REEcolloid] = [REE0.45µm] – [REE0.01µm]). Ionic strength is the dominant control on distribution of REEs between colloidal and dissolved fraction. Colloids captured on filters from ultrafiltration analyzed using scanning electron microscopy and synchrotron microanalysis show REEs are hosted in colloidal rare earth minerals (e.g. zircon) and also show colloidal humic acid, Fe-oxides and Mn-oxides. Speciation modeling shows that REE sorption to these phases is probable. / Thesis (Master, Geological Sciences & Geological Engineering) -- Queen's University, 2014-05-28 11:06:41.351