Preparation and Performance of Vanadium Tailings-Reservoir Sediment-Phosphogypsum-Based Foamed Concrete

Foamed concrete (FC) was prepared from raw materials of vanadium tailings (VTs), reservoir sediment (RS), and phosphogypsum (PG). The physicochemical properties of the raw materials were studied by using X-ray diffraction (XRD), X-ray fluorescence (XRF) analysis, and inductively coupled plasma emission spectrometer (ICP-OES). The preparation and properties of FC were investigated by particle size analysis and strength test. The hydration products and microstructure of FC were analyzed by XRD and field emission scanning electron microscopy (FE-SEM). The results show that when the specific surface area (SSA) of VTs is 768 m2·kg−1 and the content is 40%, the products with a compressive strength of 3.56 MPa and density of 619.1 kg·m−3 meet the requirements of JG/T 266-2011 standard on FC of grades A06 and C3.0; the main mineral phases in the products are calcium silicate hydrate (C-S-H) gel, ettringite (AFt), and calcite, as well as the residual mineral phases after the system reaction include quartz, orthoclase, mullite, pyrite, and PG.

Experimental Study to Investigate Dune Sand Improvement by Adding Fine Waste Materials

Dune sands are poorly graded collapsible soils lacking fines. This experimental study explored the possibility of sustainable invigoration of fine waste materials in dune sand to improve the geotechnical properties. The fine wastes used in this study are reservoir sediments and marble waste powder. The fine waste powder was mixed with dune sand at different percentages (5, 10, 25, 50%) to study the gradation, void ratio and, compaction characteristics. A machine has been manufactured to elucidate the maximum void ratio using a developed and manufactured linear-axis 3D clay printer arm. The geotechnical properties of sand-waste mixes delineated in this study reveals the enhancement in compaction and gradation characteristics of dune sand. According to the results, the binary mixture of dune sand with 25% of marble waste and 50% of reservoir sediment gives the highest maximum dry density. Thus, for improving dune sand’s geotechnical characteristics, the addition of fine marble waste and reservoir sediment to the dune sand is an environment-friendly solution.

Reservoir Sediment Management Using Artificial Neural Networks: A Case Study of the Lower Section of the Alpine Saalach River

Reservoir sedimentation is a critical issue worldwide, resulting in reduced storage volumes and, thus, reservoir efficiency. Moreover, sedimentation can also increase the flood risk at related facilities. In some cases, drawdown flushing of the reservoir is an appropriate management tool. However, there are various options as to how and when to perform such flushing, which should be optimized in order to maximize its efficiency and effectiveness. This paper proposes an innovative concept, based on an artificial neural network (ANN), to predict the volume of sediment flushed from the reservoir given distinct input parameters. The results obtained from a real-world study area indicate that there is a close correlation between the inputs—including peak discharge and duration of flushing—and the output (i.e., the volume of sediment). The developed ANN can readily be applied at the real-world study site, as a decision-support system for hydropower operators.

Spatial distribution of water-mobilizable colloids and phosphorus from dam reservoir sediment

<p>The hydrodynamics of dam reservoirs favor the accumulation of phosphorus (P) in bottom sediments since it has a strong affinity for the sedimentary particles. However mechanical disturbance of sediment (resuspension) may release P back to water column. The load of sedimentary P poses a serious ecological problem related to the maintaining of water eutrophication. The aim of this study was to evaluate the potential of sediments, accumulated in Champsanglard reservoir (Central France), to release water-mobilizable colloidal and dissolved P. A sampling campaign was carried out at different locations along the main channel of reservoir from riverine to lacustrine area and characterized by different hydrodynamics. The results showed that colloids are intrinsic component of reservoir sediment and contribute up to 2.3% of sediment mass. Colloidal P attributed up to 6% of total sedimentary P and 80% of water-mobilizable P (fraction < 1 µm). The stock of water-mobilizable colloids and associated P varied according to particle size distribution and was strongly dependent to channel morphology, hydrodynamics and inlet of tributary.</p><p><strong>Keywords: </strong>Dam reservoir, sedimentary colloids, phosphorus form, spatial variability</p>

Spatial dynamics of soil erosion impacts on food, water and energy security in a large Andean river basin, Chile

<p>The Rapel Basin (ca 14,000 km<sup>2</sup>), Chile, provides a wide range of ecosystem services from mining activities and water supply from its Central Andean headwaters to mixed agricultural food production and hydropower generation in the Central Valley. The breadth of ecosystem service provision, range of land use and wider anthropogenic pressures makes the Rapel system an ideal natural laboratory in which to evaluate tools to support soil erosion mitigation in the context of enhancing food, water and energy security.</p><p>Taking a distributed approach to encompass geological variability plus superimposed land management and natural process variability, replicate tributary sediment samples (n = 10± per tributary, total number of sediment samples= 313) were collected from across the system to characterise sediment inputs from the major potential sediment sources : (a) natural sediment production in steep Andean headwaters driven by (i) glacial retreat and (ii) seasonal snow melt, (b) sediment inputs from major copper mining operations in the Andes, (d) soil erosion on agricultural land in the Central valley basin area and (e) soil erosion on agricultural land in the Coastal Mountain Belt bordering the hydropower reservoir, Lake Rapel. Samples of river bed sediment from two main sub-catchments (north: Cachapoal River, South: Tinguiririca River) were collected at the outlet to the upper Andean catchment, below the central valley agricultural zone and downstream of a major tributary confluence above the reservoir. In addition, 12 surficial sediment samples were collected from the main arm of the reservoir. All materials were analysed for major and minor element geochemistry by Wave-length Dispersive X-Ray Fluorescence (44 elements).</p><p>Mixtures were compared in terms of their source material groups in a series of nested MixSIAR mixing model runs after selection of appropriate tracer groups following established procedures. In the northern tributary to the reservoir, mining effluent dominated the sediment supply in upper reaches (78%) with the reminder from natural landscape denudation plus a small proportion of glacial-derived sediments (5%). The influence of the mine was diluted by significant inputs of sediment from agricultural sources (fruit orchards and grain production) in the central basin (agriculture 53%, mining 25%) but given the scale of the system, mining remained a major contributor to the reservoir sediment column, with high Cu concentrations (ca 450 mg kg<sup>-1</sup>) observed in reservoir sediment. In the southern tributary, in the absence of mining, natural erosion upstream was dominated by snow melt processes (70%) compared to glacial melt (30%). In the lower reaches downstream of agricultural land, agricultural inputs dominated (53%) with natural erosion in mountain headwaters still contributing (45% overall). Evaluation of reservoir sediment against main geological, natural and anthropogenic tributary-based classification demonstrated significant inputs of sediment from Coastal Mountain agriculture (41%) where steep hillslopes are being actively converted from natural vegetation to plantations (olives, avocados etc). Moreover, sediment contribution coming from mining activities were still considerable (31%).</p><p>Future land-management decisions require quantification of soil erosion  hotspots for targeted mitigation measures. Natural science results are discussed in the context of parallel participatory approaches to developing stakeholder consensus on future actions.</p>