Rouyn-Noranda, Canada
Rouyn-Noranda, Canada

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Gonzalez-Merchan C.,University of Quebec at Abitibi - Témiscamingue | Genty T.,Technology Center for Industrial Waste | Bussiere B.,University of Quebec at Abitibi - Témiscamingue | Potvin R.,Technology Center for Industrial Waste | And 3 more authors.
Minerals Engineering | Year: 2016

Available technologies for cyanides (CN-) treatment in gold mine effluents marginally degrade the thiocyanates (SCN-). Commonly, they convert the CN- into a less toxic compound, such as cyanates (OCN-), which afterwards are oxidized and generate ammonia nitrogen (NH3-N). Thus, the pretreated effluents require additional steps for complete degradation of SCN- and NH3-N. Recent research shows that ferrates [Fe(VI)] might represent a sustainable option for the efficient treatment of gold mine effluents. In this context, the objective of the present study was to assess the performance of Fe(VI) in SCN- and/or NH3-N treatment, as well as in their by-products degradation. The performance of Fe(VI) was evaluated using three different synthetic effluents (solutions) and two gold mine effluents contaminated by SCN- and/or NH3-N. Results indicated that more than 97% of SCN- were degraded with Fe(VI), while the NH3-N increased up to 50%, after SCN- oxidation of the presence of NH3-N, within one hour of reaction time. Consequently, for effluents that contain SCN- and NH3-N, longer reaction time is required or complementary treatment technologies, such as nitrification - denitrification, should be evaluated for complete degradation of N-compounds. © 2016 Elsevier Ltd. All rights reserved.

Fenton N.J.,445 Boul Of Luniversite | Bergeron Y.,445 Boul Of Luniversite | Pare D.,Natural Resources Canada
Plant and Soil | Year: 2010

The slow decomposition rate of boreal forest floor bryophytes contributes both to maintaining high soil C reserves as well as affecting conditions for tree growth by maintaining excessively high soil water content, cooling the soil and slowing nutrient cycles. In this study, mass loss of three bryophyte species (Pleurozium schreberi, Sphagnum capillifolium, S. fuscum) was measured in unharvested, partial cut and low-retention cut forest blocks. Mesh decomposition bags containing the three species and wood sticks were placed at two depths in colonies of either P. schreberi or S. capillifolium (environment) in the three harvest treatments and retrieved after two growing seasons. Mass loss was primarily related to substrate type (P. schreberi > S. capillifolium > wood sticks > S. fuscum) and secondarily to depth. Harvest treatment and environment (P. schreberi or S. capillifolium) only weakly affected sphagna mass loss. The weak effect of harvest treatment suggests that conditions created by low retention cuts do not to stimulate decomposition in this system and are not important enough to stimulate carbon loss, or to counteract paludification. On the other hand, the strong effect of bryophyte type indicates that conditions affecting bryophyte colonization and succession are of great importance in driving carbon and nutrient cycles. © 2010 Springer Science+Business Media B.V.

Laamrani A.,University of Québec | Valeria O.,University of Québec | Bergeron Y.,University of Québec | Fenton N.,University of Québec | And 2 more authors.
Forest Ecology and Management | Year: 2014

Northern Canadian boreal forest has a considerable ecological and economic importance, with the black spruce forest type occupying a large extent of this ecosystem. Organic layer thickness and its relationship to topography are two key factors affecting tree growth and productivity of black spruce boreal forests of the Canadian Clay Belt region. This study linked multi-scale models of organic layer thickness and topography to improve our understanding of how these variables influence forest productivity and its distribution at different spatial scales within the Clay Belt region, northwestern Quebec. Field data were used to calculate site indices, which were used as estimators of forest productivity. Organic layer thickness was determined from field measurements obtained by manual probing, whereas topographic variables were extracted from multi-scale LiDAR-derived digital terrain models (DTM) at four resolutions, i.e., 5-, 10-, 15- and 20-m. Correlations between individual predictors and site index were found to be weak; however, few were significant, viz., organic layer thickness. Regression tree-based models were fitted using two different sets of explanatory variables at the four scales: organic layer thickness and topography (model 1); and topographic variables only (model 2). Organic layer thickness, aspect, and slope were the most important variables explaining forest productivity (63% and 31% total variance explained for models 1 and 2, respectively). Model 1 was found to be scale-independent, since the total explained variance was similar under the four resolutions, whereas with model 2, effects of topography on productivity were greater for coarser scales (highest R2 at 20-m resolution). Both models indicated higher forest productivity on southwest-facing slopes (i.e., >2.2%) with shallow organic layers (<35cm), so then where organic horizons are the deepest the tree productivity is low. In contrast, lowest site indices (expressing low productivity) were found in areas with very deep organic layers (>85cm). The resulting models could be applied at operational scales to predict site index at locations for which organic layer thickness information and DTM exist. Such information could be used to help forest managers in predicting how forest growth will respond to various harvesting activities. © 2014 Elsevier B.V.

Laamrani A.,University of Québec | Valeria O.,University of Québec | Fenton N.,University of Québec | Bergeron Y.,University of Québec | Cheng L.Z.,445 Boul Of Luniversite
Geoderma | Year: 2014

Mineral soil topography is difficult to describe in boreal regions because of the thick overlying organic layer despite its presumed importance in determining where and at what rate an organic layer will accumulate (paludification). The overall purpose of this study was to examine the relationship between mineral soil topography and OLT at the landscape scale. More specifically, these relationships can be used to map the distribution and spatial variability of paludification across the landscape, thereby exploring the potential to discriminate between the two commonly known paludification types (permanent and reversible). Seven topographic variables (elevation, slope, aspect, mean curvature, plan curvature, profile curvature and topographic wetness index) were generated from a digital elevation model that we developed for the mineral soil surface (MS-DEM). OLT data were collected from field measurements across the landscape by manual probing and values varied from 5 to 150. cm. The MS-DEM was generated by subtracting OLT field values from the corresponding LiDAR-derived elevation values. Most correlations between OLT and individual predictor variables were weak and illustrated that OLT and its landscape-scale distribution cannot be explained by simple bivariate relationships. Consequently, two regression tree-based models were developed using: (1) only the seven mineral soil topographic variables, and (2) all predictor variables (mineral soil topography and surficial deposits). Mineral soil slope was the most important variable for both models and corresponded to the first level of splitting the dataset into homogenous landscape units in terms of organic layer thickness. Surficial deposit, topographic wetness index (TWI) and aspect were also related to OLT and proved to be contributing to the development of the two models.Model 1 explained 0.34 of the OLT variability and offer simple models with few landscape units that are easy to interpret. Model 1 splitting rules allowed the combination of different maps (slope, TWI and aspect) for producing a landscape units map, on which OLT was determined and related to increasing paludification categories. A good overall accuracy of 74% was achieved for this map. Model 2 was the best model in terms of estimate quality (R2 adj=0.52). Both models were successful in discriminating highly paludified landscape units. Except for one landscape unit that was assigned to permanent paludification type, both models were unable to further subdivide more landscape units into reversible and permanent paludification, suggesting that both of these types interact within the same landscape unit. This study demonstrated that the combination of topographic information from remotely sensed LiDAR data and field OLT measurement data has the potential to be useful for defining both promising and vulnerable areas for forest management. © 2014 Elsevier B.V.

Couvidat J.,INSA Lyon | Benzaazoua M.,INSA Lyon | Benzaazoua M.,445 Boul Of Luniversite | Chatain V.,INSA Lyon | Bouzahzah H.,445 Boul Of Luniversite
Environmental Science and Pollution Research | Year: 2016

Purpose: Dredging of sediments, a requirement for harbor maintenance, removes millions of tons of mineral wastes, contaminated at varying degrees with trace metals, from the water. In previous investigations, Cu and Zn have been identified as highly concentrated trace metals associated to sulfides, mineral phases sensitive to oxidation. In order to ensure their sustainable management, the solidification/stabilization (S/S) and/or the valorization of contaminated sediments as secondary raw materials is a way to be promoted. Indeed, their reuse as a substitute of sand in cemented mortar formulation would allow combining both treatment and valorization of such wastes. Methods: In the present study, the environmental assessment of mortars formulated with raw and weathered marine sediments (in particular contaminated with Cu, Pb and Zn), compared to sand reference mortars, was conducted through two kinetic leaching tests: weathering cell tests (WCTs), in which mortars were crushed and leached twice a week, and a tank monolith leaching test (MLT), in which leaching was performed on monolithic mortars with increasing leachate renewal time. Results: In both leaching tests, calcium and sulfur were released continuously from sediment mortars, showing the oxidation-neutralization processes of sulfides and carbonates. In the MLT, Cu was released by sediment mortars through diffusion, particularly by weathered mortars, at low concentrations during 60 days of the test duration. With the more aggressive WCT, Cu concentrations were higher at the beginning but became negligible after 7 days of testing. Pb was released through diffusion mechanisms until depletion in both tests, whereas Zn was particularly well immobilized in the cemented matrices. Conclusions: The S/S process applied using hydraulic binders proved to be efficient in the stabilization of Cu, Pb, and Zn highly presents in studied sediments, and further valorization in civilian engineering applications could be considered. © 2016 Springer-Verlag Berlin Heidelberg

The humidity cell (HC) kinetic method is widely used to assess acid-generating potential and is the only method normalized by the American Society for Testing and Materials (ASTM). HC test results can be influenced by complete drying of the sample or by a long water saturation step during weekly cycles, which significantly reduces sulfide oxidation rates, leading to erroneous interpretations. This paper investigates a protocol modification of the HC, which involves keeping the sample permanently at an optimal degree of saturation, between 40 and 60 %, corresponding to maximal sulfide reactivity, as demonstrated in the literature. For this purpose, two mine tailings with different acid-generating potentials were submitted to both modified and standard ASTM HC protocols. The influence of the thickness and the porosity of the sample into the HC were also investigated. The results obtained clearly show that, for a given sample, the oxidation rate under the modified ASTM protocol was higher than the standard ASTM protocol, which underestimated tailings reactivity due to excessive drying of the sample. On the other hand, when the porosity of the sample decreased, and its thickness increased, the difference between the standard and the modified HC protocol results decreased. These differences were more significant when the sample was more acid-generating. © 2014, Springer-Verlag Berlin Heidelberg.

Theubou T.A.,445 Boul Of Luniversite | Wamkeue R.,445 Boul Of Luniversite | Kamwa I.,Hydro - Quebec
IECON Proceedings (Industrial Electronics Conference) | Year: 2012

This paper presents a small signal analysis and modeling in an isolated Wind-Diesel Power plant. Such systems are increasingly implemented for power generation in isolated areas where large continental power grids are not reachable. The considered system is mainly constituted by a diesel prime mover driving a Synchronous Generator (Diesel genset), a Self-Excited Induction Generator based Fixed-Speed Wind Turbine, a static synchronous reactive power compensator (STATCOM) and all the active power sinks lumped as a single Load. The reactive power expression of each aforementioned subcomponent is carried out and a small signal analysis is used to derive relationships between reactive powers transients and voltage drifts on the main distribution AC bus. The produced dynamic models have been implemented and simulated using Matlab/Simulink software tools and the main results are carried out. The main results show the influence of the steady state prior to the transients, the effect of the compensation and the influence of the wind power variations. The validity of the model is proven by good accuracy with other models developed in the literature. Presented models can be used for system stability analysis, voltage regulation and reactive power compensation purposes. © 2012 IEEE.

Theubou T.A.,445 Boul Of Luniversite | Wamkeue R.,445 Boul Of Luniversite | Kamwa I.,Hydro - Quebec
IECON Proceedings (Industrial Electronics Conference) | Year: 2012

This paper is a step towards the dynamic modelling and control of complete wind/diesel generation system for islanded areas. It mainly focuses on the control strategy of the grid-side inverter usually used in variable speed wind turbines connected in cogeneration schemes. The considered conversion system is equipped with a geared squirrel cage induction generator (SCIG). The developed control strategy is based on the voltage oriented control (VOC) of a 3-phase inverter connected to a weak grid. The controller's PI regulators are designed using the classical direct synthesis approach and cascade control loops technique in the synchronous dq- reference frame. A grid voltage regulation loop, widely used in D-STATCOM systems is designed to add the automatic reactive power management feature to the inverter. Various simulation results using Matlab/Simulink® software for different system's contingencies such as sudden step changes of the wind power are presented. The reactions of the system to step changes in grid voltage, due to the small size of the considered grid, are also presented and extensively discussed. © 2012 IEEE.

St-Denis A.,University of Quebec at Montréal | Kneeshaw D.,University of Quebec at Montréal | Bergeron Y.,University of Quebec at Montréal | Bergeron Y.,445 Boul Of Luniversite
Forest Ecology and Management | Year: 2010

Black spruce forests growing on clay soils in northwestern Quebec change structure from dense even-aged stands to open uneven-aged stands such that almost all forests older than 200 years have an open canopy. These forests become unproductive over time because they are prone to paludification. The main goal of our study was to document the transition between dense and open stands in terms of gap dynamics, with a focus on tree regeneration. Our objective was to determine whether forests remain open due to a lack of regeneration, a lack of growth or both. Nine stands along a 50-250-year-old time since fire gradient were sampled with the line intersect sampling method. Gap fraction increased with stand age and reached a maximum of 77% in the oldest site. In old-growth stands, gaps were interconnected due to the low density of these forests. Most of the gap makers were found with broken stems. Regeneration was dominated by black spruce layers and was relatively abundant (1.71 stems/m2). However, the majority of gap fillers were smaller than 1 m in height in stands of all ages. Instead of a lack of regeneration, the opening of the forests is due to a lack of growth associated with cold and wet organic deposits. Partial harvesting could be implemented on the most productive sites, while management techniques including soil disturbances will be required on low productivity sites to recreate good growth conditions. © 2009 Elsevier B.V. All rights reserved.

Couvidat J.,CNRS Laboratory of Civil and Environmental Engineering | Benzaazoua M.,CNRS Laboratory of Civil and Environmental Engineering | Benzaazoua M.,445 Boul Of Luniversite | Chatain V.,CNRS Laboratory of Civil and Environmental Engineering | And 2 more authors.
Environmental Science and Pollution Research | Year: 2015

Contaminated dredged sediments are often considered hazardous wastes, so they have to be adequately managed to avoid leaching of pollutants. The mobility of inorganic contaminants is a major concern. Metal sulfides (mainly framboïdal pyrite, copper, and zinc sulfides) have been investigated in this study as an important reactive metal-bearing phase sensitive to atmospheric oxygen action. An oxygen consumption test (OC-Test) has been adapted to assess the reactivity of dredged sediments when exposed to atmospheric oxygen. An experimental column set-up has been developed allowing the coupling between leaching and oxygen consumption test to investigate the reactivity of the sediment. This reactivity, which consisted of sulfide oxidation, was found to occur for saturation degree between 60 and 90 % and until the 20th testing week, through significant sulfates releases. These latter were assumed to come from sulfide oxidation in the first step of the test, then probably from gypsum dissolution. Confrontation results of OC-Test and leachate quality shows that Cu was well correlated to sulfates releases, which in turn, leads to Ca and Mg dissolution (buffer effect). Cu, and mostly Zn, was associated to organic matter, phyllosilicates, and other minerals through organo-clay complexes. This research confirmed that the OC-Test, originally developed for mine tailings, could be a useful tool in the dredged sediment field which can allow for intrinsic characterization of reactivity of a material suspected to readily reacting with oxygen and for better understanding of geochemical processes that affect pollutants behavior, conversion, and transfer in the environment. © 2015 Springer-Verlag Berlin Heidelberg

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