scholarly journals Oxygen migration through a cover with capillary barrier effects colonized by roots

2020 ◽  
Vol 57 (12) ◽  
pp. 1903-1914 ◽  
Author(s):  
Alex Proteau ◽  
Marie Guittonny ◽  
Bruno Bussière ◽  
Abdelkabir Maqsoud
Keyword(s):  
Oxygen Consumption ◽  
Root Colonization ◽  
Mine Drainage ◽  
Root Length Density ◽  
Mixed Forest ◽  
Capillary Barrier ◽  
Barrier Effects ◽  
Lower Oxygen ◽  
Oxygen Migration ◽  
Reactivity Coefficient

Covers with capillary barrier effects (CCBEs) are multi-layered oxygen barrier covers used in humid climates to reclaim reactive mine tailings and limit the generation of acid mine drainage. Once constructed, CCBEs are colonized by surrounding plants. Roots modify water storage and respire oxygen. The performance of CCBEs could evolve over time due to root colonization. Twenty-five plots with varying vegetation were investigated at a 17-year-old CCBE in the mixed forest of Quebec, Canada. Geotechnical parameters and root colonization of the moisture-retaining layer (MRL) of the CCBE were characterized. The performance of the MRL to control oxygen migration was assessed using oxygen consumption tests and numerical modeling. Despite root colonization at the surface of the MRL, oxygen fluxes generally complied with the CCBE’s design criteria. Root presence created oxygen consumption in the MRL, which could be expressed with a reactivity coefficient (Kr). A positive correlation (R2 = 0.65) was found between root length density and Kr. Oxygen consumption by root respiration helped to lower oxygen fluxes by 0.5 to 76 g/m2/year, with a mean of 13 g/m2/year. These results will help to better understand the influence of roots on CCBEs’ performance to control oxygen migration.

scholarly journals Aboveground and Belowground Colonization of Vegetation on a 17-Year-Old Cover with Capillary Barrier Effect Built on a Boreal Mine Tailings Storage Facility

Minerals ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 704 ◽  
Author(s):  
Alex Proteau ◽  
Marie Guittonny ◽  
Bruno Bussière ◽  
Abdelkabir Maqsoud
Keyword(s):  
Mine Tailings ◽  
Root Colonization ◽  
Mine Drainage ◽  
Numerical Models ◽  
Mixed Forest ◽  
Plant Colonization ◽  
Herbaceous Species ◽  
Barrier Effect ◽  
Capillary Barrier ◽  
Vegetation Parameters

Acid mine drainage is an important environmental risk linked to the surface storage of reactive mine tailings. To manage this problem, a cover with a capillary barrier effect (CCBE) can be used. This oxygen barrier cover relies on maintaining a fine-grained material layer (moisture-retaining layer, MRL) with a high degree of saturation. CCBEs can be colonized by surrounding plants. Plant roots pump water and could impact CCBE’s performance. This performance is predicted with unsaturated water flow numerical models in which vegetation parameters can be included. Vegetation parameters may be specific in a CCBE environment. Therefore, analyzing and quantifying the vegetation that colonizes this type of cover is necessary. Plant colonization was investigated through cover and density surveys on 12 transects on a 17-year-old CCBE in the mixed forest of Quebec, Canada. Then, aboveground vegetation and root colonization intensity at three depths in the MRL were characterized on 25 plots of five dominant vegetation types (Salix, Populus, Alnus, Picea sp., and herbaceous species). The mean root length density under plots dominated by Salix sp. was higher than in the other plots. Root colonization of the MRL was concentrated in the first 10 cm and occurred under all woody and herbaceous species as well. This work quantitatively describes, for the first time, the vegetation colonizing a CCBE both at the above- and belowground levels. These data will be useful to better predict the long-term performance of this engineered reclamation cover.

scholarly journals Influence of freeze–thaw cycles on the performance of covers with capillary barrier effects made of crushed rock–bentonite mixtures to control oxygen migration

2016 ◽  
Vol 53 (5) ◽  
pp. 753-764 ◽  
Author(s):  
Vincent Boulanger-Martel ◽  
Bruno Bussière ◽  
Jean Côté ◽  
Mamert Mbonimpa
Keyword(s):  
Mine Drainage ◽  
Mine Waste ◽  
Effective Diffusion ◽  
Crushed Rock ◽  
Capillary Barrier ◽  
Freeze Thaw ◽  
Fine Grained ◽  
Barrier Effects ◽  
Attractive Option ◽  
Oxygen Migration

In temperate climates, covers with capillary barrier effects (CCBEs) are being used successfully to prevent oxygen fluxes from reaching covered potentially acid mine drainage (AMD) generating mine tailings. In northern climates, the more attractive option for mine site reclamation is insulation covers, which are designed to keep reactive materials frozen. This article suggests that CCBEs can simultaneously control oxygen migration and mine waste temperature to inhibit AMD generation. However, in northern conditions, where natural fine-grained materials needed for the CCBE moisture-retaining layer are not always available, soil–bentonite mixtures could be used instead. This laboratory study assessed — using instrumented columns — the effects of freeze–thaw cycles on the performance of three CCBEs made with crushed rock–bentonite mixtures. An oxygen diffusion test was developed to determine the effective diffusion coefficient of oxygen (De) and its sensitivity to freeze–thaw cycles. The results show good initial performance for the saturated CCBEs. However, the tested CCBEs are significantly affected by freeze–thaw cycles and have limited oxygen-limiting ability.

Preliminary geotechnical assessment of the potential use of mixtures of soil and acid mine drainage neutralization sludge as materials for the moisture retention layer of covers with capillary barrier effects

2016 ◽  
Vol 53 (5) ◽  
pp. 828-838 ◽  
Author(s):  
Mamert Mbonimpa ◽  
Médard Bouda ◽  
Isabelle Demers ◽  
Mostafa Benzaazoua ◽  
Denis Bois ◽  
...  
Keyword(s):  
Acid Mine Drainage ◽  
Mine Drainage ◽  
Capillary Barrier ◽  
Moisture Retention ◽  
Mine Site ◽  
Barrier Effects ◽  
Acid Mine ◽  
Geotechnical Assessment ◽  
Site Rehabilitation ◽  
Water Contents

Lime treatment of acid mine drainage (AMD) generates sludge that is commonly stored in ponds for dewatering. The use of soil-aged sludge-based mixtures for mine site rehabilitation can allow the emptying of existing basins, thus extending their storage capacity, reducing the volume of the borrow soil pit required for mine site rehabilitation, and consequently reducing the mine footprint. The authors investigated the geotechnical properties of silty soil–sludge mixtures (SSMs) as possible components of covers with capillary barrier effects (CCBEs) to prevent AMD generation from mine waste. SSMs with β values of 10%, 15%, 20%, and 25% sludge (β = wet sludge mass / wet soil mass) were studied. Two water contents were considered for each of the mixture components: 175% and 200% for the sludge and 7.5% and 12.5% for the soil. Results indicate that saturated hydraulic conductivity (ksat) values were in the range of 10−5 cm/s for the soil and SSMs at void ratios ranging from 0.28 to 0.53, with values decreasing slightly when β was increased from 0% to 25%. The air-entry value (AEV) increased from 20 kPa for the soil alone to 35 kPa for the SSM with β = 25%. These values of ksat and AEV are comparable to those of materials used in the moisture retention layers of existing efficient CCBEs. However, the volumetric shrinkage increased from about 2% for the soil alone to values ranging between 24% and 32% for the SSM with β = 25%, depending on the initial water contents of the components. Tools are provided to estimate to which extent the use of sludge in SSMs can reduce the volume of borrow natural soil required for a moisture retention layer of a CCBE.

Field experimental cells to evaluate the hydrogeological behaviour of oxygen barriers made of silty materials

2007 ◽  
Vol 44 (3) ◽  
pp. 245-265 ◽  
Author(s):  
Bruno Bussière ◽  
Michel Aubertin ◽  
Mamert Mbonimpa ◽  
John W Molson ◽  
Robert P Chapuis
Keyword(s):  
Acid Mine Drainage ◽  
Unsaturated Flow ◽  
Mine Drainage ◽  
In Situ Monitoring ◽  
Oxygen Flux ◽  
Capillary Barrier ◽  
Barrier Effects ◽  
Acid Mine ◽  
Hydrogeological Behaviour

An in situ study was initiated to evaluate the efficiency of silts as moisture-retaining material in covers with capillary barrier effects (CCBEs) that aim at controlling the production of acid mine drainage (AMD). This investigation included the construction of four experimental cells covered by different layered cover configurations. Each CCBE was instrumented to monitor its hydrogeological behaviour. The degree of saturation (Sr) in the moisture-retaining (silty) materials was usually maintained above 85%, while Sr in the two sand layers placed above and below the silts was generally lower than 30%–50% (typical hydrogeological behaviour of efficient CCBEs). Suction measurements in the different layers of the four CCBEs were consistent with the observed Sr measurements during the four years of monitoring. The suctions measured in the moisture-retaining materials were lower than their respective air-entry values (AEV), while suctions largely exceeded the AEV of the sand in the capillary break layers. The oxygen flux calculations confirm that in each of the four CCBEs the flux through the CCBEs remained low for the entire duration of the experiment, hence limiting the generation of AMD. This study also confirmed the ability of silty materials to act as moisture retaining in a CCBE. Key words: cover with capillary barrier effects, acid mine drainage, experimental cells, in situ monitoring, unsaturated flow, diffusion, oxygen flux.

Diffusion and consumption of oxygen in unsaturated cover materials

2003 ◽  
Vol 40 (5) ◽  
pp. 916-932 ◽  
Author(s):  
M Mbonimpa ◽  
M Aubertin ◽  
M Aachib ◽  
B Bussière
Keyword(s):  
Analytical Solutions ◽  
Unsaturated Soils ◽  
Numerical Solutions ◽  
Mine Drainage ◽  
Effective Diffusion ◽  
Oxygen Flux ◽  
Capillary Barrier ◽  
Gas Exchanges ◽  
Barrier Effects ◽  
Two Parameters

Covers installed over waste disposal sites are used to control water and gas exchanges with the surrounding environment. One example involves covers built to limit oxygen flux to sulphidic mining and milling wastes, which can be the source of acidic leachate. In this paper, the authors present an approach to evaluate oxygen flux and its controlling parameters, the effective diffusion coefficient De and reaction (consumption) rate coefficient Kr. A laboratory experimental procedure to determine these two parameters simultaneously is described, and the proposed interpretation method is presented with a few sample results. New analytical solutions are developed to calculate oxygen flux through covers with capillary barrier effects (CCBE). The proposed solutions are compared with results ensuing from a numerical treatment of Fick's laws. Specific applications of these analytical solutions are presented and discussed.Key words: unsaturated soils, covers, capillary barrier, Fick's laws, oxygen diffusion, acid mine drainage, analytical solutions, numerical solutions.

The behavior of inclined covers used as oxygen barriers

2003 ◽  
Vol 40 (3) ◽  
pp. 512-535 ◽  
Author(s):  
Bruno Bussière ◽  
Michel Aubertin ◽  
Robert P Chapuis
Keyword(s):  
Mine Drainage ◽  
Simple Relationship ◽  
Gas Migration ◽  
Capillary Barrier ◽  
Barrier Effects ◽  
Original Apparatus ◽  
Migration Barriers ◽  
Sloping Surface ◽  
Oxygen Barriers

Covers with capillary barrier effects (CCBE) have been recently proposed as a viable option for gas migration barriers. However, the effect of geometry on CCBE performance has not been clearly demonstrated. In this paper, the results of a laboratory study performed with an original apparatus called the inclined box are presented. The results obtained show that the hydraulic behavior of layered covers is influenced by the inclination of the slope. Generally, the upper part of the slope contains less water than the lower part. This means that the upper part is less efficient than the lower part for limiting gas migration. The authors have also studied an existing site where a CCBE was built on a sloping surface. After validation of the numerical model with in situ measured data, the model was used to perform a parametric study to quantify the influence of the main CCBE parameters on its performance. The results obtained confirm those measured in the lab and clearly show how geometry influences the performance of the CCBE. Based on these results, a simple relationship is proposed for a preliminary estimation of sloping covers performance to limit oxygen migration by diffusion.Key words: cover with capillary barrier effects, acid mine drainage, slope effects, laboratory investigation, in situ measurements, design criteria.

scholarly journals Geochemical Assessment of Desulphurized Tailings as Cover Material in Cold Climates

Minerals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 280
Author(s):  
Asif Qureshi ◽  
Bruno Bussière ◽  
Mostafa Benzaazoua ◽  
Fannie Lessard ◽  
Vincent Boulanger-Martel
Keyword(s):  
Mine Drainage ◽  
Mine Waste ◽  
Degree Of Saturation ◽  
Processing Plant ◽  
Permafrost Region ◽  
Capillary Barrier ◽  
Barrier Effects ◽  
Zinc Release ◽  
Acid Mine Drainage Generation ◽  
Management Approaches

It is essential to develop effective mine waste management approaches and mine site reclamation techniques to curtail the adverse effects of mining processes on the natural environment. This study focuses on the use of partially desulphurized tailings as a moisture-retaining layer in an insulation cover with capillary barrier effects (ICCBE). Tailings were obtained from a nickel ultramafic ore processing plant at a mining company located in a continuous permafrost region of northern Québec, Canada. The geochemical response of tailings at two different sulphur contents (0.4 and 0.8 wt%), with and without ICCBEs, was tested by applying eight freeze-thaw and wetting cycles. Desulphurization of the tailings allowed to reduce the content of sulphide minerals by about 90%, from ~22 wt% to around 1.2–2.2 wt%. Column kinetic geochemical tests showed that Ni leaching was significantly reduced to concentrations ranging between 0.01–0.22 mg L−1 compared to 0.63–1.92 mg L−1 from the raw tailings (thanks to the desulphurization process). Zinc release was maintained around 0.04–1.72 mg L−1 compared to 0.4–3.69 mg L−1 from the raw tailing. Although all the columns produced leachates displaying circumneutral to slightly alkaline pH, the columns with ICCBE are expected to prevent acid mine drainage generation longer than the other columns due to reduced sulphide content and a constantly high degree of saturation maintained by capillary barrier effects.

Sign in / Sign up

Export Citation Format

Share Document