Oxidation of mine tailings from Rankin Inlet, Nunavut, at subzero temperatures

2001 ◽  
Vol 38 (5) ◽  
pp. 957-966 ◽  
Author(s):  
J L Meldrum ◽  
H E Jamieson ◽  
L D Dyke
Keyword(s):  
Oxygen Consumption ◽  
Pore Water ◽  
Mine Drainage ◽  
Experimental Program ◽  
Unfrozen Water ◽  
Hudson Bay ◽  
Oxidation Reactions ◽  
Subzero Temperatures ◽  
Direct Measurements

Acid-generating sulphidic tailings from a Ni–Cu mine were exposed on the shores of Hudson Bay for 30 years before burial in a drained bedrock basin. To determine if encapsulation in permafrost will maintain the tailings, and their saline pore water, in a chemically inert state, a field and experimental program was employed. Three years after burial, several boreholes were drilled to collect tailings and pore-water samples and to initiate long-term thermal monitoring. Columns charged with pyrrhotite-bearing, unsaturated tailings were studied at temperatures between +30°C and –10°C. Oxygen consumption was measured directly to determine the effect of low temperatures on oxidation rate. Results of the column experiments indicate that significant oxidation of the Rankin Inlet tailings occurs at +30°C, but at lower temperatures this rate is substantially reduced. At –10°C, unfrozen water was still present in the columns, but oxygen consumption was below the detection limit. The highest measured oxygen flux correlates with a temperature increase of 1°C, consistent with exothermic sulphide oxidation reactions. Thermal modeling and direct measurements have shown that the freezing of the tailings in Rankin Inlet is progressing. The tailings are expected to be ice-bonded approximately 15 years after burial.Key words: acid mine drainage, permafrost, tailings, reclamation, sulphides, oxidation

scholarly journals Influence of Hydrate-Forming Gas Pressure on Equilibrium Pore Water Content in Soils

Energies ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 1841
Author(s):  
Daria Sergeeva ◽  
Vladimir Istomin ◽  
Evgeny Chuvilin ◽  
Boris Bukhanov ◽  
Natalia Sokolova
Keyword(s):  
Porous Media ◽  
Natural Gas ◽  
Water Content ◽  
Pore Water ◽  
Gas Hydrate ◽  
Gas Pressure ◽  
Unfrozen Water ◽  
Direct Measurements ◽  
Highly Nonlinear ◽  
Thermodynamic Equations

Natural gas hydrates (primarily methane hydrates) are considered to be an important and promising unconventional source of hydrocarbons. Most natural gas hydrate accumulations exist in pore space and are associated with reservoir rocks. Therefore, gas hydrate studies in porous media are of particular interest, as well as, the phase equilibria of pore hydrates, including the determination of equilibrium pore water content (nonclathrated water). Nonclathrated water is analogous to unfrozen water in permafrost soils and has a significant effect on the properties of hydrate-bearing reservoirs. Nonclathrated water content in hydrate-saturated porous media will depend on many factors: pressure, temperature, gas composition, the mineralization of pore water, etc. In this paper, the study is mostly focused on the effect of hydrate-forming gas pressure on nonclathrated water content in hydrate-bearing soils. To solve this problem, simple thermodynamic equations were proposed which require data on pore water activity (or unfrozen water content). Additionally, it is possible to recalculate the nonclathrated water content data from one hydrate-forming gas to another using the proposed thermodynamic equations. The comparison showed a sufficiently good agreement between the calculated nonclathrated water content and its direct measurements for investigated soils. The discrepancy was ~0.15 wt% and was comparable to the accuracy of direct measurements. It was established that the effect of gas pressure on nonclathrated water content is highly nonlinear. For example, the most pronounced effect of gas pressure on nonclathrated water content is observed in the range from equilibrium pressure to 6.0 MPa. The developed thermodynamic technique can be used for different hydrate-forming gases such as methane, ethane, propane, nitrogen, carbon dioxide, various gas mixtures, and natural gases.

Influence of Alkalinity and Ambient Temperature on Long-Term Properties of GFRP Reinforcement

2018 ◽  
Vol 760 ◽  
pp. 213-218
Author(s):  
František Girgle ◽  
Lenka Bodnárová ◽  
Ondřej Januš ◽  
Vojtěch Kostiha
Keyword(s):  
Tensile Strength ◽  
Ambient Temperature ◽  
Mechanical Characteristics ◽  
Current Problem ◽  
Concrete Structures ◽  
Experimental Program ◽  
Glass Fibres ◽  
Metallic Reinforcement ◽  
Gfrp Reinforcement

The article deals with the current problem of determining long-term reliability of non-metallic reinforcement in concrete structures. The alkaline environment of concrete with a pH higher than 12.0 affects the glass fibres degradative, whereas this degradation presents by reduction of their mechanical characteristics, resulting in a decrease in the tensile strength of the whole composite. The article summarizes the results of the ongoing experimental program so far, which aims to quantify this influence.

scholarly journals Prediction of long-term settlement and evaluation of pore water pressure using particle filter

2019 ◽  
Vol 59 (1) ◽  
pp. 67-83 ◽  
Author(s):  
Toshifumi Shibata ◽  
Takayuki Shuku ◽  
Akira Murakami ◽  
Shin-ichi Nishimura ◽  
Kazunori Fujisawa ◽  
...  
Keyword(s):  
Particle Filter ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure

Long-term performance of a UASB reactor treating acid mine drainage: effects of sulfate loading rate, hydraulic retention time, and COD/SO42− ratio

2018 ◽  
Vol 30 (1) ◽  
pp. 47-58 ◽  
Author(s):  
Mirabelle Perossi Cunha ◽  
Rafael Marçal Ferraz ◽  
Giselle Patrícia Sancinetti ◽  
Renata Piacentini Rodriguez
Keyword(s):  
Acid Mine Drainage ◽  
Retention Time ◽  
Hydraulic Retention Time ◽  
Loading Rate ◽  
Mine Drainage ◽  
Uasb Reactor ◽  
Acid Mine ◽  
Long Term Performance ◽  
Term Performance

scholarly journals Bird trends from long-term observation data at sites in the Hudson Bay Lowlands

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Rodney W. Brook ◽  
Lisa A. Pollock ◽  
Kenneth F. Abraham ◽  
Glen S. Brown
Keyword(s):  
Hudson Bay ◽  
Observation Data ◽  
Hudson Bay Lowlands ◽  
Long Term Observation

Abstract 15016: Peak Oxygen Consumption Achieved at the End of Cardiac Rehabilitation Predicts Survival in Patients With Coronary Heart Disease

Circulation ◽  
2020 ◽  
Vol 142 (Suppl_3) ◽  
Author(s):  
Salvatore Carbone ◽  
Youngdeok Kim ◽  
Sergey Kachur ◽  
Alban De Schutter ◽  
Hayley E Billingsley ◽  
...  
Keyword(s):  
Coronary Heart Disease ◽  
Oxygen Consumption ◽  
Heart Disease ◽  
Cardiac Rehabilitation ◽  
Peak Oxygen Consumption ◽  
Mortality Data ◽  
Term Survival ◽  
Long Term Survival ◽  
Peak Vo2

Introduction: Several patients with coronary heart disease (CHD) present reduced survival despite completing cardiac rehabilitation (CR), suggesting that the level of cardiorespiratory fitness (CRF) achieved might remain suboptimal. The purposes of this study were: 1) to examine the independent association of peak oxygen consumption (VO 2 ), a measure of CRF, at post-CR with long-term survival; and 2) to establish an optimal cut-off for peak VO 2 at post-CR that best predicts mortality risk. Methods: 853 patients with CHD (mean age of 64±10 years old) who were referred to CR between January 1, 2000, and June 30, 2013, at Ochsner Medical Center were analyzed for this study. We measured pre- and post-CR peak VO 2 . Mortality data were collected using National Death Index. Cox proportional hazard regression model was used to examine the risk of all-cause mortality associated with peak VO 2 at post-CR, independent of peak VO 2 at pre-CR and related changes during CR. Contal and O’Quigley’s method were used to determine the optimal cut-off for peak VO 2 at post-CR based on a split-sample approach. Results: Mean peak VO 2 at post-CR was 21.01±6.25 mL/kg/min (75% and 51% predicted peak VO2 using Wasserman and FRIEND Registry equations, respectively). During a mean follow-up of 6.55 years, 106 subjects (12.4%) died. Peak VO 2 at post-CR independently predicted mortality (Hazard Ratio: 0.82 [0.77-0.87], p<0.001). We identified peak VO 2 of ≥17.6 kg/mL/min as optimal cut-off best predicting survival ( Figure 1, Panel A ) and the %predicted peak VO2 at post-CR ≥62.1% using Wasserman ( Figure 1, Panel B ) and ≥41.4% using FRIEND Registry ( Figure 1, Panel C ) as the alternative optimal cut-offs. Conclusions: In patients with CHD undergoing CR, post-CR peak VO 2 independently predicts long-term survival. These results suggest that patients with CHD presenting a peak VO 2 lower than the cut-off identified herein may benefit from additional sessions of CR or higher intensity exercise training.

Uranium Bioleaching from Low Grade Ore

2020 ◽  
Vol 989 ◽  
pp. 559-563
Author(s):  
Ashimkhan T. Kanayev ◽  
Khussain Valiyev ◽  
Aleksandr Bulaev
Keyword(s):  
Sulfuric Acid ◽  
Acid Mine Drainage ◽  
Mine Drainage ◽  
Sulfuric Acid Concentration ◽  
Acid Leaching ◽  
Leach Solution ◽  
Low Grade ◽  
Bacterial Cells ◽  
Acid Mine

The goal of the present work was to perform bioleaching of uranium from low grade ore from Vostok deposit (Republic of Kazakhstan), which was previously subjected to long-term acid leaching. The ore initially contained from 0.15 to 0.20% of uranium in the form of uraninite, but ore samples used in the study contained about 0.05% of uranium, as it was exhausted during acid leaching, and uranium was partially leached. Representative samples of ore were processed in 1 m columns, leach solutions containing 5, 10, 20 g/L of sulfuric acid and bacterial cells (about 104) were percolated through the ore. Leaching was performed at ambient temperature for 70 days. In one of the percolators, the leaching was performed with leaching solution containing 10 g/L of H2SO4, cells of A. ferrooxidans, and 0.5 g/L of formaldehyde. Leaching with the solution containing 5, 10, and 20 g/L of sulfuric acid made it possible to extract 50, 53, and 58% of uranium. Addition of formaldehyde in leach solution led to the decrease in uranium extraction extent down to 37%. Thus, the results of the present work demonstrated that uranium ore exhausted during long-term acid leaching may be successfully subjected to bioleaching, that allows extracting residual quantities of uranium. Leaching rate of uranium from exhausted ore depended on both sulfuric acid concentration and microbial activity of bacteria isolated from acid mine drainage, formed on uranium deposit. In the same time, acid mine drainage may be used as a source of inoculate, to start bioleaching process.

scholarly journals Bedrock incision by bedload: insights from direct numerical simulations

2016 ◽  
Author(s):  
Guilhem Aubert ◽  
Vincent J. Langlois ◽  
Pascal Allemand
Keyword(s):  
Numerical Approach ◽  
Sediment Supply ◽  
Sediment Flux ◽  
Analytical Models ◽  
Water Stream ◽  
Direct Measurements ◽  
Bedload Sediment ◽  
Discrete Element Simulations ◽  
High Sediment

Abstract. Bedload sediment transport is one of the main processes that contribute to bedrock incision in a river and is therefore one of the key control parameters in the evolution of mountainous lanscapes. In recent years, many studies have addressed this issue through experimental setups, direct measurements in the field or various analytical models. In this article, we present a new direct numerical approach: using the classical methods of discrete element simulations applied to granular materials, we compute explicitely the trajectories of a number of pebbles entrained by a turbulent water stream over a rough solid surface. This method allows us to extract quantitatively the amount of energy that successive impacts of pebbles deliver to the bedrock, as a function of both the amount of sediment available and the Shields number. We show that we reproduce qualitatively the behaviour observed experimentally by Sklar and Dietrich (2001) and observe both a "tool-effect" and a "cover- effect". Converting the energy delivered to the bedrock into an average long-term incision rate of the river leads to predictions consistent with observations in the field. Finally, we reformulate the dependency of this incision rate with Shields number and sediment flux, and predict that the cover term should decay linearly at low sediment supply and exponentially at high sediment supply.

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