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Clayey soils from Boulgou (North Cameroon): geotechnical, mineralogical, chemical characteristics and properties of their fired products
In this study, clayey soils are characterized as backfill and potential fusible raw materials for engineering. Geotechnical tests (particle size distribution, Atterberg limits, densities) and chemico-mineralogical analyses (X-ray fluorescence, X-ray diffraction and Fourier transform infrared) were carried out on samples collected from field in the locality of Boulgou (North Cameroon) followed by the determination of mechanical properties of fired bricks (850–1200 °C). The excavations carried out have revealed a thick layer of clayey soils (~ 2 to 2.5 m) over a sandy layer. This clay formation presents some stratifications with limited influence variation in terms of mineralogy. Mean grain size distribution is dominated by sand (62–80%), clay (12–25%) and silt (6–9%). It corresponds to silty–clayey soils regarding their methylene blue values (3.3–5.6), with low plastic (13–22%) to high plastic (33%) characteristics. They are classified by USCS as clayey sand/silty clay, while one sample is a poorly graded sand (SP). Clay minerals observed are kaolinite (6–12%), montmorillonite (2–6%) and illite (8–10%). Those parameters associated with their fine nature and high compressibility make them suitable engineering applications for backfill material and barriers. From chemical analyses, relatively high contents in alkali and alkaline earth elements (~ 4 to 6%) to be used as potential fusible raw materials for fired bricks or gres ceramics were revealed. Bricks characteristics are varied: linear shrinkage (0.3 to 9%), bulk density (1.8 to 2.3 g/cm
3
), water absorption (19.7 to 1.3%) and flexural strength (0.3 to 17.4 MPa). Overall, the requirement for fired brick (< 20%) is met up by the water absorption values. As from 1050 °C, these soils are made suitable for brick-making with good characteristics (metallic sound, good cohesion and flexural strength).
Journal Article
Lost Antarctica : adventures in a disappearing land
\"Few of us will ever get to Antarctica. The bitter cold and three months a year without sunlight makes the sixth continent virtually uninhabitable for humans. Yet marine biologist James B. McClintock has spent three decades studying the frozen land in order to understand better the world that lies beneath it. In this luminous and closely observed account, one of the world's leading experts on Antarctica introduces the reader to this fascinating world--the extraordinary wildlife that persists despite the harsh conditions and the way each of the pieces fit into the puzzle of the intricate environment: from single-celled organisms to baleen whales, with leopard seals, penguins, 50-foot algae, sea spiders, coral, and multicolored sea stars, in between. Now, as temperatures rise, the fragile ecosystem is under attack. Adelie penguins that have successfully nested on Antarctic islands for several hundred years have been nearly wiped out. King crabs that used to populate the deep seafloor are moving into shallower waters, disturbing the set order of life there. Lost Antarctica is an appeal to understand and appreciate the wondrous place at the bottom of the world that we are on the brink of losing\"-- Provided by publisher.
Book
The quest for seafloor macrolitter: a critical review of background knowledge, current methods and future prospects
The seafloor covers some 70% of the Earth’s surface and has been recognised as a major sink for marine litter. Still, litter on the seafloor is the least investigated fraction of marine litter, which is not surprising as most of it lies in the deep sea, i.e. the least explored ecosystem. Although marine litter is considered a major threat for the oceans, monitoring frameworks are still being set up. This paper reviews current knowledge and methods, identifies existing needs, and points to future developments that are required to address the estimation of seafloor macrolitter. It provides background knowledge and conveys the views and thoughts of scientific experts on seafloor marine litter offering a review of monitoring and ocean modelling techniques. Knowledge gaps that need to be tackled, data needs for modelling, and data comparability and harmonisation are also discussed. In addition, it shows how research on seafloor macrolitter can inform international protection and conservation frameworks to prioritise efforts and measures against marine litter and its deleterious impacts.
Journal Article
Environmental contamination : health risks and ecological restoration
\"Drawn from presentations made during the Croucher Advanced Study Institute workshop held in 2010, this volume covers all the fundamentals necessary for contaminated site assessment and remediation. It discusses historical and emerging contaminants, human health, risk assessment and bioremediation. It contains numerous case studies, many of them from the Asia-Pacific region, that look at the effects of rapid industrialization. It also examines both historical and emerging contaminants such as persistent organic pollutants and electronic waste\"-- Provided by publisher.
Book
Dynamic ice loss from the Greenland Ice Sheet driven by sustained glacier retreat
The Greenland Ice Sheet is losing mass at accelerated rates in the 21st century, making it the largest single contributor to rising sea levels. Faster flow of outlet glaciers has substantially contributed to this loss, with the cause of speedup, and potential for future change, uncertain. Here we combine more than three decades of remotely sensed observational products of outlet glacier velocity, elevation, and front position changes over the full ice sheet. We compare decadal variability in discharge and calving front position and find that increased glacier discharge was due almost entirely to the retreat of glacier fronts, rather than inland ice sheet processes, with a remarkably consistent speedup of 4–5% per km of retreat across the ice sheet. We show that widespread retreat between 2000 and 2005 resulted in a step-increase in discharge and a switch to a new dynamic state of sustained mass loss that would persist even under a decline in surface melt.Glacier retreat is the main process behind Greenland Ice Sheet dynamic mass loss over the past three decades, according to an analysis of discharge variability and calving front positions.
Journal Article
From landfill gas to energy : technologies and challenges
\"A comprehensive description of technologies available for converting old landfills to energy producers, and capturing the green house gases emitting from them. Its key assets are the case studies of successful landfill gas (LFG) recovery for energy projects around the world, and that it highlights why this has not been done in many more landfills around the world. Technical, financial, and social challenges facing the conversion of landfills to energy producers will be detailed, and solutions offered to either remine the landfill for recovering useful land (as is planned in dense urban areas of India) or close them properly while recovering the methane for energy use. Intended as a guide with background information and instructive tools to educate, guide and establish a basis for decision-making, technical feasibility assessment, economic assessment, and market evaluation of all aspects necessary for developing successful LFG management projects. \"-- Provided by publisher.
Book
Evidence for increasing global wheat yield potential
Wheat is the most widely grown food crop, with 761 Mt produced globally in 2020. To meet the expected grain demand by mid-century, wheat breeding strategies must continue to improve upon yield-advancing physiological traits, regardless of climate change impacts. Here, the best performing doubled haploid (DH) crosses with an increased canopy photosynthesis from wheat field experiments in the literature were extrapolated to the global scale with a multi-model ensemble of process-based wheat crop models to estimate global wheat production. The DH field experiments were also used to determine a quantitative relationship between wheat production and solar radiation to estimate genetic yield potential. The multi-model ensemble projected a global annual wheat production of 1050 ± 145 Mt due to the improved canopy photosynthesis, a 37% increase, without expanding cropping area. Achieving this genetic yield potential would meet the lower estimate of the projected grain demand in 2050, albeit with considerable challenges.
Journal Article
Climate mitigation forestry—temporal trade-offs
The 1.5 °C target for global warming calls for evaluating short-term (30–50 years) climate change mitigation with different forests usage. In the current scientific literature and in the public debate, there are contrasting views on how forests should be managed to maximize total climate benefit, including the use of products and changes in carbon pools. Three major factors influence the conclusions in different studies: (a) time horizon, (b) site productivity, (c) substitution calculations. Here we show the dependency among these factors by an analysis of four harvest scenarios: 95%, 60%, 40% and 0% of growth, which are compared to a business as usual scenario (80%). The analyses are made for five counties in Sweden, which covers a wide range in forest productivities, from 2.5 m 3 ha −1 yr −1 (north) to 11.5 m 3 ha −1 yr −1 (south). The results show: (a) Reduced harvest levels provide increased climate benefits on short time scales (at least 50 years). (b) Increased harvesting from current level is counterproductive on both short and long term. (c) The potential effect on the carbon balance of a no-harvest scenario in the five counties, is larger (1.1–16 times) than the expected emissions from all other anthropogenic activities until 2045. (d) Short-term climate benefits of reduced harvesting are largest in highly productive forests. Smaller but more long-lasting benefits can be obtained by aiming at harvest reductions in less productive forests. (e) Strategies focused on short-term benefits need to be adapted to the future development of substitution factors and forest growth. If substitution effects become higher, increased harvest levels will be beneficial after 2050 in high productive forests. However, if future substitution effects decrease, which is a plausible and desired development, low harvest strategies are preferred in both short- and long-term time perspectives. We conclude that even moderate reductions of harvest levels would provide substantial climate benefits.
Journal Article