Investigating bauxite residue flocculation by hydroxamate and polyacrylate flocculants utilising the focussed beam reflectance measurement probe     

Luke J. Kirwan   《International Journal of Mineral Processing》2009,90(1-4):74-80

Polyacrylate and hydroxamate flocculants are commonly used to aid solid–liquid separation of bauxite residue from pregnant liquor in the Bayer process. This study presents the direct examination of the bauxite residue flocculation with polyacrylate and hydroxamate flocculants, using the focussed beam reflectance measurement (FBRM) probe to monitor aggregate dimensions.The key difference between polyacrylate and hydroxamate flocculation was found to be the way the aggregates developed post-shear, with hydroxamate flocculation exhibiting a greater degree of post-shear flocculation. Polyacrylate aggregates were found to be more dense and shear resistant, while the hydroxamate aggregates exhibited greater fines capture and lower solids in the supernatant. The solids remaining in the supernatant after flocculation were found to differ for each flocculant, with the polyacrylate system having relatively more coarse particles within the solid and the hydroxamate system being relatively finer and more iron rich. The observed results are discussed in terms of the different way in which each polymer is considered to adsorb onto the residue material.  相似文献   

Natural and Anthropogenic Geohazards in Greater London Observed from Geological and ERS-1/2 and ENVISAT Persistent Scatterers Ground Motion Data: Results from the EC FP7-SPACE PanGeo Project     

Francesca Cigna  Hannah Jordan  Luke Bateson  Harry McCormack  Claire Roberts 《Pure and Applied Geophysics》2015,172(11):2965-2995

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Ecological Parameters of Dynamited Reefs in the Northern Red Sea and their Relevance to Reef Rehabilitation     

B. Riegl  K. E. Luke 《Marine pollution bulletin》1999,37(8-12):488-498

Dynamite damage was investigated on 60 reefs in the Egyptian Red Sea. 65% of the investigated reefs had signs of dynamite damage, mostly in leeward areas (58%). Significant changes in coral and fish community composition within dynamited sites were observed. Coral cover decreased, the amount of bare substratum and rubble increased, fish communities in dynamited areas suffered a decrease in species richness and abundance. Due to a stable pattern of coral community differentiation on northern Red Sea reefs (windward Acropora, leeward Porites) most damage is on near-climax Porites reef slopes or Porites carpets. Natural regeneration of such communities is likely to be very slow, possibly taking several hundred years. Rehabilitation would be difficult since coral transplants would have to mimic the previously existing community.  相似文献   

Which way do you lean? Using slope aspect variations to understand Critical Zone processes and feedbacks   总被引：1，自引：0，他引：1       下载免费PDF全文

Jon D. Pelletier  Greg A. Barron‐Gafford  Hugo Gutiérrez‐Jurado  Eve‐Lyn S. Hinckley  Erkan Istanbulluoglu  Luke A. McGuire  Guo‐Yue Niu  Michael J. Poulos  Craig Rasmussen  Paul Richardson  Tyson L. Swetnam  Greg E. Tucker 《地球表面变化过程与地形》2018,43(5):1133-1154

Soil‐mantled pole‐facing hillslopes on Earth tend to be steeper, wetter, and have more vegetation cover compared with adjacent equator‐facing hillslopes. These and other slope aspect controls are often the consequence of feedbacks among hydrologic, ecologic, pedogenic, and geomorphic processes triggered by spatial variations in mean annual insolation. In this paper we review the state of knowledge on slope aspect controls of Critical Zone (CZ) processes using the latitudinal and elevational dependence of topographic asymmetry as a motivating observation. At relatively low latitudes and elevations, pole‐facing hillslopes tend to be steeper. At higher latitudes and elevations this pattern reverses. We reproduce this pattern using an empirical model based on parsimonious functions of latitude, an aridity index, mean‐annual temperature, and slope gradient. Using this empirical model and the literature as guides, we present a conceptual model for the slope‐aspect‐driven CZ feedbacks that generate asymmetry in water‐limited and temperature‐limited end‐member cases. In this conceptual model the dominant factor driving slope aspect differences at relatively low latitudes and elevations is the difference in mean‐annual soil moisture. The dominant factor at higher latitudes and elevations is temperature limitation on vegetation growth. In water‐limited cases, we propose that higher mean‐annual soil moisture on pole‐facing hillslopes drives higher soil production rates, higher water storage potential, more vegetation cover, faster dust deposition, and lower erosional efficiency in a positive feedback. At higher latitudes and elevations, pole‐facing hillslopes tend to have less vegetation cover, greater erosional efficiency, and gentler slopes, thus reversing the pattern of asymmetry found at lower latitudes and elevations. Our conceptual model emphasizes the linkages among short‐ and long‐timescale processes and across CZ sub‐disciplines; it also points to opportunities to further understand how CZ processes interact. We also demonstrate the importance of paleoclimatic conditions and non‐climatic factors in influencing slope aspect variations. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

Incorporating spatially heterogeneous infiltration capacity into hydrologic models with applications for simulating post‐wildfire debris flow initiation          下载免费PDF全文

Luke A. McGuire  Francis K. Rengers  Jason W. Kean  Dennis M. Staley  Benjamin B. Mirus 《水文研究》2018,32(9):1173-1187

Soils in post‐wildfire environments are often characterized by a low infiltration capacity with a high degree of spatial heterogeneity relative to unburned areas. Debris flows are frequently initiated by run‐off in recently burned steeplands, making it critical to develop and test methods for incorporating spatial variability in infiltration capacity into hydrologic models. We use Monte Carlo simulations of run‐off generation over a soil with a spatially heterogenous saturated hydraulic conductivity (K_s) to derive an expression for an aerially averaged saturated hydraulic conductivity ( ) that depends on the rainfall rate, the statistical properties of K_s, and the spatial correlation length scale associated with K_s. The proposed method for determining is tested by simulating run‐off on synthetic topography over a wide range of spatial scales. Results provide a simplified expression for an effective saturated hydraulic conductivity that can be used to relate a distribution of small‐scale K_s measurements to infiltration and run‐off generation over larger spatial scales. Finally, we use a hydrologic model based on to simulate run‐off and debris flow initiation at a recently burned catchment in the Santa Ana Mountains, CA, USA, and compare results to those obtained using an infiltration model based on the Soil Conservation Service Curve Number.  相似文献   

Scale-dependent analysis of satellite imagery for characterization of glacier surfaces in the Karakoram Himalaya   总被引：1，自引：0，他引：1  

Michael P. Bishop  John F. Shroder  Jr.  Betty L. Hickman  Luke Copland 《Geomorphology》1998,21(3-4)

Information regarding process-structure relationships and change in the Karakoram Himalaya is of great importance in studying glacier hydrollogy, mass balance, and dynamic environmental change. Such information is not readily available. Detailed spatio-temporal assessment requires field investigation coupled with quantitative remote sensing studies. We conducted an investigation of the large Batura Glacier in Pakistan to determine if spectral variability can be quantified and used to characterize glacier surfaces. Specifically, SPOT Panchromatic satellite data were evaluated for differentiating features of glacier structure resulting from ice movement, ablation, and supraglacial fluvial action. Image semivariogram analysis was conducted. for assessing spectral variability patterns and fractal analysis was used to examine scale-dependent variation in the data. Results indicate that spectral variability from fields of ice seracs can exhibit fractal characteristics, although most surface features on the glacier exhibit a change in the fractal dimension over different ranges in scale. The fractal dimension was found to be useful for differentiating between glacier surfaces such as white ice and debris-covered ice. Characteristics of the debris-load and the scale-dependent nature of calculating the fractal dimension ultimately determined the potential of class separability.  相似文献   

Hazard assessment of rainfall-induced landslides: a case study of San Vicente volcano in central El Salvador   总被引：1，自引：0，他引：1  

Daniel M. Smith  Thomas Oommen  Luke J. Bowman  John S. Gierke  Stanley J. Vitton 《Natural Hazards》2015,75(3):2291-2310

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Convective activity in a Martian magma chamber recorded by P‐zoning in Tissint olivine     

N. Mari  L. J. Hallis  L. Daly  M. R. Lee 《Meteoritics & planetary science》2020,55(5):1057-1072

The Tissint Martian meteorite is an unusual depleted olivine‐phyric shergottite, reportedly sourced from a mantle‐derived melt within a deep magma chamber. Here, we report major and trace element data for Tissint olivine and pyroxene, and use these data to provide new insights into the dynamics of the Tissint magma chamber. The presence of irregularly spaced oscillatory phosphorous (P)‐rich bands in olivine, along with geochemical evidence indicative of a closed magmatic system, implies that the olivine grains were subject to solute trapping caused by vigorous crystal convection within the Tissint magma chamber. Calculated equilibration temperatures for the earliest crystallizing (antecrystic) olivine cores suggest a Tissint magma source temperature of 1680 °C, and a local Martian mantle temperature of 1560 °C during the late Amazonian—the latter being consistent with the ambient mantle temperature of Archean Earth.  相似文献   

Distribution, habitat use and ecology of deepwater Anemones (Actiniaria) in the Gulf of Mexico     

Archie W. Ammons  Marymegan Daly 《Deep Sea Research Part II: Topical Studies in Oceanography》2008,55(24-26):2657

The distribution of deepwater Actiniaria is poorly known. Rarely are these organisms identified to family, as this requires both well-preserved specimens and taxonomic expertise. Ecological information is similarly lacking. From the results of a comprehensive surveying program in the deep Gulf of Mexico, we report the occurrence of nine species of Actiniaria. For the most abundant four of these, we plot distributions and discuss habitat use, morphological variation, and feeding strategies. Actiniaria in the Gulf appear to have broad, basin-wide distributions with little depth preference. Faunal biomass is highest in the NE Gulf within submarine canyons or at the base of slope escarpments. Attachment mode is mostly opportunistic on various types of hard substrata, including trash. Sediment-dwelling forms are very abundant at an organically rich site within a large submarine canyon.  相似文献   

Modelling of stormwater biofilters under random hydrologic variability: a case study of a car park at Monash University,Victoria (Australia)     

E. Daly  A. Deletic  B. E. Hatt  T. D. Fletcher 《水文研究》2012,26(22):3416-3424

Biofiltration systems represent an effective technology for the management of urban stormwater runoff volumes and quality. The performance of these systems, although largely dependent on their physical characteristics, is also strongly affected by the natural variability of runoff occurrence and volumes. This article presents a model that describes the statistical behaviour of the main variables involved in the water balance of a biofiltration system, given its main physical properties (filter media and vegetation types) and accounting for the natural inflow variability in terms of occurrence and water volumes. The model permits the analytical derivation of the long‐term (e.g. annual) probability density function of the soil water content in the filter media and the estimation of the main statistics of water fluxes, that is, outflow, evapotranspiration and overflow. By relating the soil water content in the filter media before inflow events to the outflow total nitrogen concentrations, the model also gives estimates of the statistics of nitrogen removal performance as a function of inflow variability. The model was tested against field data collected at a stormwater biofiltration system in Melbourne, Australia. The model could be used to rapidly assess the hydrologic and nitrogen treatment performance of alternative applications of biofiltration for stormwater management across a range of climates. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献