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The oxidation of sulfides present in mine tailings may generate acidic leachate and result in the discharge of contaminants such as metals, derived from mine wastes into the environment. For mine sites in regions with a humid climate such as the Doyon-Westwood mine, Abitibi, Quebec, acid mine drainage (AMD) is often inhibited using the low gas diffusivity of water to control the oxygen flux reaching the tailings. A management technique of increasing importance is a combined approach of water table level control and the judicious use of a monolayer cover to limit oxygen ingress to sulfidic tailings. The objective of this study was to evaluate the effects of design parameters such as the cover material grain size and thickness, the presence of an anti-evaporation layer, and the position of the water table on the performance of the technique, and to evaluate the long-term oxygen consumption by the low-sulfide cover material. Twelve laboratory columns replicating a monolayer cover made of desulfurized tailings placed over reactive tailings were subjected to monthly wetting–drainage cycles and were monitored for over a year before being dismantled. The cover materials and leachates were chemically analysed to characterize and extrapolate the evolution of water quality, and oxygen movement into the system. The results indicated that the level of the water table was the most important factor influencing the effectiveness of the cover. Furthermore, it appears that although residual sulfides from the cover consumed most of the oxygen flux, this advantage is of short duration (up to 4.7 years). Finally, the risks of leachate contaminated with iron and zinc were identified.

Acid mine drainage (AMD) is often treated using active lime treatment, which generates a significant amount of sludge that contains mainly metal hydroxide precipitates, calcium sulfate, and unreacted lime. Previous work showed that sludge may have interesting geotechnical and geochemical properties to be used, in combination with a silty soil, as a part of covers (oxygen barriers) to prevent AMD generation from waste rock and tailings impoundments. The reuse of sludge can reduce the volume of natural soil required for site reclamation. Mixtures of sludge and a natural silty soil were tested in the laboratory (for over 500 days) and in field experiments (4 years) as an oxygen barrier cover placed over acid-generating tailings and waste rock. Data from the testwork include monitoring of leachate geochemical parameters (e.g. pH, conductivity, metal and sulfate content) and hydrogeological parameters (water content, suction, effluent flowrate). Results indicate that soil-sludge mixture is an efficient oxygen barrier.

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.

The possibility of using acid mine drainage (AMD) treatment sludge as a cover component to control AMD generation from mine wastes was investigated through laboratory characterization and kinetic column testing (companion paper). The results showed that mixtures of sludge and waste rock, and sludge and tailings, may be integrated in an AMD prevention and control strategy at Doyon mine site (northwestern Quebec, Canada). In order to further investigate these scenarios in realistic climatic conditions, instrumented field test cells were installed on site to evaluate the performance of the mixtures to control AMD generation from tailings and waste rock under natural field conditions. The main findings from two seasons of monitoring are presented in the paper. The waste rock-sludge mixture placed over waste rock was able to reduce the generation of AMD from the waste rock, therefore confirming lab results, and was able to produce a neutral effluent with low concentrations of dissolved metals. The tailings-sludge mixture placed over tailings, with an evaporation protection layer, maintained a high volumetric water content and reduced sulphide oxidation from the tailings as exhibited by a neutral effluent. Monitoring of the field cells will continue to provide valuable information on the possible sludge valorization options.

In operating mines, acid mine drainage (AMD) is often treated using lime treatment. This process generates a significant amount of sludge that contains metal hydroxide precipitates, gypsum, and unreacted lime. The sludge may have interesting geotechnical and geochemical properties to be used as a part of covers (oxygen barriers) to prevent AMD generation from waste rocks and tailings. The main results of a project aiming to evaluate the use of sludge from the Doyon mine site (Canada) as a material in mine site rehabilitation are presented. The first part of the project involved detailed characterization of sludge, waste rock, and tailings samples. Then, laboratory column leaching tests were performed to evaluate the performance of the mixtures to control AMD produced by tailings and waste rocks. It was found that a sludge–waste rock mixture placed over waste rock reduces the metal loads in the column effluent, which remained acidic, as well as a mixture of sludge and tailings deposited over tailings can reduce metal content in effluents from tailings.

We present a synthesis of diet information for all 78 species of extant African Bovidae (excluding goats and sheep), based on an extensive survey of the literature. We compiled data on food types (percentages of fruits, dicotelydons, and monocotyledons), seasonal and geographic variability, and body mass. Information reported in the literature was evaluated critically to assess its reliability. We performed cluster analyses to identify 6 discrete dietary strategies: frugivores, browsers, generalists, browser-grazer intermediates, variable grazers, and obligate grazers. We identified a positive correlation between an increase in the proportion of monocots in the diet and body mass, and a negative correlation between increases in proportions of dicots and fruits and body mass. We found some degree of correspondence between taxonomic groupings and dietary strategies. Species in the tribes Alcelaphini, Hippotragini, and Reduncini have high proportions of monocots in their diets. Cephalophini, with the exception of Sylvicapra, are frugivores. Tragelaphini and Neotragini, with the exception of Ourebia, have diets that include high proportions of dicots.

Major transformations in the skull and masticatory system characterized the evolution of crown anthropoids. To offer further insight into the phylogenetic and arguably adaptive significance of specific primate mandibular loading and kinematic patterns, allometric analyses of metric parameters linked to masticatory function are performed within and between 47 strepsirhine and 45 recent anthropoid species. When possible, basal anthropoids are considered. These results are subsequently integrated with prior experimental and morphological work on primate skull form. As compared to strepsirhines, crown anthropoids have a vertically longer ascending ramus linked to a glenoid and condyle positioned relatively higher above the occlusal plane. Interestingly, anthropoids and strepsirhines do not exhibit different mean ratios of condylar to glenoid height, which suggests that both clades are similar in their ability to evenly distribute occlusal contacts and perhaps forces along the postcanine teeth. Thus, given the considerable suborder differences in the scaling of both glenoid and condylar height, we argue that much of this variation in jaw-joint height is linked to suborder differences in relative facial height due in turn to increased encephalization, basicranial flexion, and facial kyphosis in anthropoids. Due to a more elongate ascending ramus, anthropoids evince more vertically oriented masseters than like-sized strepsirhines. Having a relatively longer ramus and a more medially displaced lateral pterygoid plate, crown anthropoids exhibit medial pterygoids oriented similar to those of strepsirhines, but with a variably longer lever arm. As anthropoid masseters are less advantageously placed to effect transverse movements/forces, we argue that balancing-side deep-masseter activity underlying a wishboning loading regime serves to increase, or at least maintain, transverse levels of jaw movement and occlusal force at the end of the masticatory power stroke. Crown anthropoids are also more isognathic and isodontic than strepsirhines. A consideration of early anthropoids suggests that the crown anthropoid masticatory pattern, i.e., more vertical masseters due to a high condyle as well as greater isognathy and isodonty, occurred stepwise during stem anthropoid evolution. This appears to correspond to a more transverse, and perhaps progressively larger, power stroke across oligopithecids, parapithecids, and propliopithecids.

The Jebel Qatrani sequence found in the Fayum region of Egypt samples the richest Paleogene mammalian fauna of Africa, including some of the earliest anthropoid primates. The paleoecology of the Fayum has been interpreted as either a woodland bushland or a lowland evergreen tropical forest, although the issue of changing ecological conditions through time has never been investigated. The Fayum fossils can be grouped into four successive and stratigraphically distinct faunal assemblages. Each of these mammalian assemblages is compared with modern mammal communities. Six communities from modern African forest habitats and six communities from woodland bushland habitats are used to produce typical models of ecological diversity. An ecological spectrum for each modern community is generated by assigning mammal species to categories of taxonomic, diet, and body size diversity. Modern forest communities have a higher diversity of rodents and primates, a high diversity of frugivores, low diversity of grazers, and show a steep gradient in body size distribution from a high diversity of small species towards a low diversity of large species. Woodland-bushland communities have a higher diversity of ungulates and carnivores, a low diversity of frugivores but a high diversity of grazers, and a more even body size distribution. Diversity spectra from the four successive Fayum fossil assemblages are compared with the models derived from the modern mammal communities. The Fayum assemblages show similarities to modern forest habitats in patterns of diet diversity and to modern woodland bushland habitats in body size diversity. More detailed analyses of taxonomic diversity suggest that the lowermost assemblages were different in ecological structure from modern habitats, while the uppermost assemblage shows strong resemblances to modern humid tropical forests.