Mineral Particles Of Sizes Research Articles

Responses of root architecture and the rhizosphere microbiome assembly of maize (Zea mays L.) to a soil texture gradient

Responses of root architecture and the rhizosphere microbiome assembly of maize (Zea mays L.) to a soil texture gradient

The Mechanism of Microbial-Ferromanganese Nodule Interaction and the Contribution of Biomineralization to the Formation of Oceanic Ferromanganese Nodules.

Ferromanganese nodules are an important mineral resource in the seafloor; however, the genetic mechanism is still unknown. The biomineralization of microorganisms appears to promote ferromanganese nodule formation. To investigate the possible mechanism of microbial–ferromanganese nodule interaction, to test the possibility of marine microorganisms as deposition template for ferromanganese nodules minerals, the interactions between Jeotgalibacillus campisalis strain CW126-A03 and ferromanganese nodules were studied. The results showed that strain CW126-A03 increased ion concentrations of Fe, Mn, and other metal elements in solutions at first. Then, metal ions were accumulated on the cells’ surface and formed ultra-micro sized mineral particles, even crystalline minerals. Strain CW126-A03 appeared to release major elements in ferromanganese nodules, and the cell surface may be a nucleation site for mineral precipitation. This finding highlights the potentially important role of biologically induced mineralization (BIM) in ferromanganese nodule formation. This BIM hypothesis provides another perspective for understanding ferromanganese nodules’ genetic mechanism, indicating the potential of microorganisms in nodule formation.

Structure and Mineralogy of Hydrophilic and Biwettable Sub-2 µm Clay Aggregates in Oil Sands Bitumen Froth

A primary concern of commercial mined oil sands operations is the extent to which one can minimize the content of water and solids contaminants in the solvent-diluted bitumen products resulting from the bitumen production processes. During bitumen production, particles of about 2 µm or less may be responsible for the stabilization of water-in-bitumen emulsions that form during aqueous extraction of bitumen and purification of bitumen froth subsequently during the froth treatment processes, thus leading to the presence of those contaminants in solvent-diluted bitumen products. In this study, we separate and analyze sub-2 µm clay solids isolated from typical bitumen froth fed to a froth treatment plant at a commercial mined oil sands operation. Analytical transmission electron microscopy (TEM) with spatially-resolved energy-dispersive X-ray spectroscopy (EDX) and electron energy-loss spectroscopy (EELS) demonstrate key differences in morphology and composition between sub-2 µm clay aggregates with two distinct wettability characteristics: hydrophilic vs. biwettable particle surfaces. In particular, clay platelets with <200 nm lateral dimensions and thicknesses of a few atomic layers, which are intermixed within coarser sub-2 µm clay aggregates, are found to confer clear differences in morphological characteristics and wettability behaviors to the sub-2 µm clay aggregates. The <200 nm clay platelets found within sub-2 µm biwettable clays tend to arrange themselves with random orientations, whereas <200 nm clay platelets within sub-2 µm hydrophilic clays typically form well-ordered face-to-face stacks. Moreover, in biwettable sub-2 µm clay aggregates, <200 nm clay platelets often cover the surfaces of ~1–2 µm sized mineral particles, whereas similarly sized mineral particles in hydrophilic sub-2 µm clay aggregates, in contrast, generally have exposed surfaces without clay platelet coverage. These biwettable vs. hydrophilic behaviors are attributed to a difference in the surface characteristics of the <200 nm clay platelets caused by toluene-unextractable organic carbon coatings. Nanometer-scale carbon mapping reveals an inhomogeneous toluene-unextractable organic carbon coating on the surfaces of <200 nm platelets in biwettable clays. In contrast, hydrophilic clays have a significantly lower amount of toluene-unextractable organic carbon, which tends to be concentrated at steps or near metal oxide nanoparticles on clay particle surfaces. Mixing surface-active organic species, such as asphaltene, resin, or carboxylic organic acids of various types with inorganic solids can lead to a dramatically enhanced emulsion stability. Consequently, understanding the origin and characteristics of sub-2 µm clay solids in bitumen froth is important to (i) clarify their potential role in the formation of stable water-in-oil emulsions during bitumen production and (ii) improve froth treatment process performance to further reduce contaminant solids in solvent-diluted bitumen products. We discuss the implications of our results from these two perspectives.

The effective viscosity of slurries laden with vegetative ash

Abstract After a forest fire, ash can blanket the soil surface to depths of tens of centimeters. It has been proposed that the incorporation of vegetative ash into hillslope runoff can, by increasing the flow's effective viscosity, reduce the settling velocity of entrained particles and lead to the development of runoff-generated debris flows. To investigate how the addition of this material might affect the rheology of runoff in burned areas, we measured and compared the effective viscosity of slurries composed of varying concentrations of ash and similarly sized mineral particles (i.e., silt). All the slurries were pseudoplastic (i.e., shear-thinning) and, at low weight concentrations (≤ 0.3 g g− 1), the rheologies of ash and silt slurries were nearly identical. At higher concentrations, however, their rheologies diverged significantly. For example, whereas the viscosity of the silt slurries increased monotonically with concentration, the viscosity of the ash slurries decreased. Ash incorporated into silt slurries induced this same complex behavior, indicating that ash alters the rheological properties of runoff in ways that would not be predicted simply based on its size. In addition, we found that, at high concentrations, the intensity of shear-thinning in the ash slurries was greater than in the silt slurries. Finally, we compared the settling velocities of small particles in clear water and ash slurries and conclude that the rheological characteristics of ashy runoff could promote runoff-generated debris flows in burned landscapes.

Froth Treatment in Athabasca Oil Sands Bitumen Recovery Process: A Review

Bitumen froth treatment is an integrated process step in the Athabasca oil sands bitumen recovery operations. Its objective is to separate mineral solids and water from the bitumen froth. The bitumen froth is diluted with naphthenic or paraffinic solvents to lower its viscosity to facilitate the separation; therefore, bitumen froth treatment is the removal of inorganics (mineral particles and water droplets) from a bitumen organic solvent solution. The micrometer sized mineral particles (mainly clays) and water-in-oil emulsion droplets are the most difficult to remove from the bitumen froth. Research has been carried out that has led to an understanding of the formation, stabilization and properties of the water-in-oil emulsions in the bitumen organic solvent solution. It is known that the water-in-oil emulsions are formed by water entrained into the bitumen froth during the water-based extraction process and stabilized by natural surfactants in bitumen (especially asphaltene) and fine mineral particles. ...

5. Processing

The purpose of the aggregate processing plant is to prepare the rock or mineral in a form suitable for its use as aggregate, commonly defined in terms of particle size and size distribution, particle shape and mechanical properties, e.g. compressive strength. As a result, the process plant usually contains only the unit processes of crushing and grinding (comminution) and sizing together with materials handling and transportation equipment such as conveyors and feeders. The use of water and wet processing techniques facilitates the sizing of fine particles (classification) and the dispersal and subsequent rejection of finely sized mineral particles, e.g. clays. Consequently, the process plant may frequently also contain pumping and slurry handling equipment and unit processes of solid-liquid separation for final dewatering of the aggregate products and even waste products. Mineral separation processes are occasionally employed to reject material of undesirable physical or chemical properties. In this respect the process of sizing is commonly used adventitiously or deliberately to separate a particular mineral fraction of the aggregate as will be discussed below. Comminution is an energy intensive and relatively expensive process whose use must be minimized and the agglomeration of fine particles to create larger sizes is rarely if ever economically justified. Therefore, as discussed in Chapter 3, in the case of sand and gravel deposits it is important to determine the relative proportions of the ‘sand’ and ‘gravel’ sizes.

Fracture-filling minerals as uranium sinks and sources, a natural analogue study at Palmottu, Finland

The nucleation of a mineral crystal and its growth in groundwater carrying fractures 300 m above the Palmottu uranium deposit provide an impressive example of geochemical selectivity of uranium. Fracture-filling material was collected from a 3 mm thick fracture at depth 74.8 - 75 m (drillcore R348). SEM and EDS analyses on a thin section of the original fracture-filling show that the fracture filling is heterogeneous, composing mineral crystal particles and very porous clay-rich aggregates. The results of INAA on millimetre-sized single mineral crystals and aggregates selected from grinded fracture-filling show that porous aggregates (composed of clays and micrometer sized mineral particles) contain up to 1000 ppm U, which is higher than the average of the whole fracture-filling (400 ppm) and host rock related millimetre sized mineral particles (18 - 100 ppm). 233U/238U isotope exchange proves that a large fraction of the uranium in the fracture-filling is not easily exchanged with uranium in the solution. The amount of 238U released in the isotope exchange experiment is too high to be explained by reversible U(VI) sorption. Oxidation state analyses show that 30% of the uranium exists as U(IV). Laboratory batch experiment at anoxic conditions proved that pyrite can immobilise U(VI).

Investigation of bone and cartilage by synchrotron scanning-SAXS and -WAXD with micrometer spatial resolution

Biological materials such as bone or wood are hierarchically structured to optimize mechanical and other properties. Several methods and experimental techniques are usually needed to study these materials on different length scales. We developed a device for small angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD), optimized for position resolved investigations of bone sections using synchrotron radiation. Thin samples can be scanned with 20 µm steps, acquiring two-dimensional SAXS or WAXD patterns at every point. The system was tested by performing one-dimensional scans across bone cartilage interfaces, revealing information about size, shape and orientation of nanometer sized mineral particles as well as about crystal type and texture of these particles.

Precipitation kinetics of calcite in the system CaCO 3H2OC02: The conversion to CO 2 by the slow process H ++HCO 3− → CO 2+H 2O as a rate limiting step

Abstract Precipitation rates of CaCO3 from supersaturated solutions in the H2OCO2CaCO3 system are controlled by three rate-determining processes: the kinetics of precipitation at the mineral surface, mass transport of the reaction species involved to and from the mineral surface, and the slow kinetics of the overall reaction HCO3−+H+ → CO2+H2O. A theoretical model by Buhmann and Dreybrodt (1985a,b) taking these processes into account predicts that, due to the slow kinetics of this reaction, precipitation rates to the surface of CaC03 minerals depend critically on the ratio V/A of the volume V of the solution to the surface area A of the mineral in contact with it, for both laminar and turbulent flow. We have performed measurements of precipitation rates in a porous medium of sized particles of marble, limestone, and synthetic calcite, with V/A ratios ranging from 3·10−4 to 1.2·10−2 cm at 10°C. Calcite was precipitated from supersaturated solutions with [Ca2+] ≈ 4 mmol/L and an initial PCO2 of 5·10−3 or 1·10−3 atm, respectively, using experimental conditions which prevented exchange of CO2 with the atmosphere, i.e., closed system. The results are in qualitative agreement with the theoretical predictions. Agreement with the observed data, however, is obtained by modifying the rate law of Plummer et al. (1978) to take into account surface-controlled inhibition effects. Experiments with supersaturated solutions containing carbonic anhydrase, an enzyme which enhances the conversion of HCO3− into CO2, yield rates increased by a factor of up to 15. This provides for the first time unambiguous experimental evidence that this reaction is rate limiting. We have also measured precipitation rates in batch experiments, stirring sized mineral particles in a solution with V/A ranging from 0.03 to 0.75 cm. These experiments also give clear evidence on the importance of the conversion of HCO3− into CO2 as rate limiting step. Taken together our experiments provide evidence that the theoretical model of Buhmann and Dreybrodt (1985a,b) can be used to predict reliable rates from the composition of Ca++HCO3− solutions with low ionic strength in many geologically relevant situations.

The characteristics of composite suspended sediment particles transported during storm events in the river Exe, Devon, U.K

Abstract Particle size is one of the most important factors controlling the behaviour of fluvial suspended sediment and its role in different environmental and geomorphological processes. Primary mineral particles are frequently transported as composite particles or aggregates, which consist of different sized mineral particles combined with organic matter and biogenic material. The formation and behaviour of such aggregates are controlled by physical, chemical and biological factors which act independently and also in combination at different spatial and temporal scales. This paper examines the nature and behaviour of the composite suspended sediment particles transported by the River Exe, Devon, U.K. during several storm events. Effective size (undispersed) fractions were separated in situ using a field-portable water elutriation apparatus. The absolute (chemically dispersed) grain size composition of each effective size class was examined, in order to provide information on the proportion of the sediment transported as aggregates. In addition, the influence of a number of factors in controlling the occurrence and behaviour of aggregates during storm events has been examined. More detailed information concerning the character and structure of the composite particles has been obtained using Scanning Electron Microscope observation and Energy Dispersive X-Ray analysis (SEM/EDAX).

Siltation of stone-surface periphyton in rivers by clay-sized particles from low concentrations in suspention

The observation that deposits of fine sediment are found on stream beds only in areas of slower water velocity promotes a common misunderstanding of the depositional behaviour of fine suspensoids in flowing water and a disregard for the potential for siltation effects on the biota on the surface of stones in fast flowing water. A model for deposition from turbulent water, whereby particles are lost from suspension where water currents are slowed by boundary friction, provides an explanation for silt infiltration into epilithic periphyton. Theoretically calculated deposition rates of clay sized mineral particles at low suspended concentrations (2 to 5 g m−3) were found to account for observed rates of silt accumulation in epilithic periphyton in a braided river in the South Island of New Zealand. At concentrations between 1 and 10 g m−3 of suspended mineral silt during normal flow, silt accumulation in epilithic periphyton accounted for about 50% of its dry weight. This caused a reduction in the mean organic content of the periphyton to 22% of the dry weight compared to 52% in a reference stream where the concentration of suspended mineral particles was less than 1.0 g m−3 during non-freshet flow. This reduction in proportional organic content is discussed in terms of diminished food value of the periphyton and potential interactions between periphyton and invertebrate consumers.

A micromorphological examination of two alpine soil chronosequences, Southern Norway

The micromorphological characteristics of young alpine soils (< 230 years old) from two chronosequences in Norway are examined. Lenticular and alveolar microstructures, together with matrix granules, suggest that cryic processes are operative in subsurface (Ae, B, C) horizons. Organic matter accumulation, decomposition and incorporation are evident in surface (L, F, Ah) horizons, whereas hydration of biotite, and translocation of silt and fine-sand sized mineral particles, organic material and sesquioxides seem major processes in subsurface (Ae, B) horizons. Consideration of depth-related differences of quantitative micromorphological data has allowed assessment of the intensity of these pedogenic processes. Chronofunctions are constructed for each soil horizon from the quantitative data. This approach allows soil development at the two sites to be assessed in a temporal context. Steady-state conditions do not appear to be attained within the 230 years available for soil development at these sites.

Soil protozoa and soil bacteria

In a paper recently published by Mr. Goodey it is definitely asserted that ciliates, amœbæ and flagellates cannot function as a factor limiting the numbers of bacteria in soils. It does not appear to me that this conclusion is justified by the experimental data given in this paper, and in view of the importance of the subject it seems desirable to bring together the main facts so far ascertained and to summarise the present position of the problem. Soil consists of irregular mineral particles of sizes varying from about 1 mm. diameter downwards, together with a smaller proportion of organic substances of varying degrees of complexity, nutrient and other salts, and the oxides of iron, aluminium, and silicon in a form easily soluble in acids or alkalis. The action of the natural processes tends on the whole to effect intermingling of these constituents, at any rate throughout the top 6 inches.