Changes in hydraulic conductivity of smectite-sand mixtures (using four reference smectites) as a function of the concentration (0.01, 0.003, 0.002, 0.001 M Cl- and distilled water) and potassium adsorption ratio (of 2, 4, and 6) of the percolating solution were measured. Swelling and dispersion of the clays were evaluated from the changes in hydraulic conductivity of the mixture and from the clay concentration in the effluent.

The effect of exchangeable potassium percentage (EPP) on the hydraulic conductivity of the smectites depended on the charge density of the clays. The effect of potassium at EPPs <20 on the hydraulic conductivity of smectites having high charge density was negligible. Conversely, the hydraulic conductivity of smectites having low charge density (smectites from Wyoming and Belle Fourche, South Dakota), changed markedly when leached with dilute solutions as the EPP of the clay increased. The dispersive effect of exchangeable potassium on low-charge smectites was similar to that of exchangeable sodium. The low hydration energy of the K+ cations, coupled with the strong electrostatic attraction forces between platelets of smectites with high charge density account for the “inefficiency” of K+ in dispersing these smectites.

Mixtures of kaolinite clay and quartz sand were packed in columns and leached with NaCl-CaCl2 solutions of different concentrations (ranging from 0.5 M to distilled water) having sodium adsorption ratios (SAR) of 5, 10 and 20. Sodium hexametaphosphate (NaHMP) (10 g/m3) was added to each solution. Changes in the hydraulic conductivity (HC) and clay concentration in the effluent were measured, and the dispersion of the clay was evaluated. In the absence of NaHMP, using distilled water instead of 0.01 M solutions caused some reduction in the HC; the reduction became more severe as the SAR increased. At SAR 20 the HC dropped to 73% of that obtained when the 0.5 M salt solution was used. This reduction in HC was related to increases in the pH of the effluent and partial dispersion of the clay. On adding the NaHMP to the leaching solutions, a marked decrease in the HC and severe clay dispersion were observed at all SAR levels, if the kaolinite-sand mixtures were leached with dilute solutions and distilled water. The HC dropped to 40% of that obtained when leaching with 0.5 M salt solution, and dispersed clay in the effluent peaked at about 1% in the SAR 20 treatment following leaching with distilled water. The observed reduction in the HC of the kaolinite-sand mixture when NaHMP was added to the leaching solutions was due to the dispersive effect of NaHMP and sodium on the kaolinite. The polyanion NaHMP reduced the edge-to-face particle interactions, thereby enabling the dimise double-layer repulsion forces to predominate. Following addition of the polyphosphate, the response of kaolinite to sodium and electrolyte concentration was similar to that reported in the literature for smectite.

Changes in hydraulic conductivity and clay dispersivity of clay-sand mixtures (four reference smectites and Fithian illite) as a function of concentration (0.01 M Cl− and distilled water) and sodium adsorption ratio (SAR ≤ 30) of the percolating solution were measured. In addition, the effect of sand percentage, sand particle size, and addition of AlCl3 and FeCl3 on the hydraulic conductivity of the mixtures were measured.

Clay dispersion and migration out of the 3% clay columns was substantial. The clay dispersed only in the distilled water system; dispersion increased with an increase in the percentage of exchangeable Na and was about the same for the Wyoming montmorillonite and Fithian illite. Conversely, the clay swelled in the 0.01 M Cl− solution. The swelling of the montmorillonites increased in the order: Upton, Wyoming = Belle Fourche, South Dakota > Polkville, Mississippi > Otay, California, and was higher than that of the Fithian illite. The swelling and dispersion of the clay accounted for the changes in hydraulic conductivity.

Mixtures treated with FeCl3 and AlCl3 were leached with NaCl-CaCl2 solutions until the pH of the effluent exceeded 6.5. The composition of the exchangeable phase was then determined by the SAR of the leach solutions. At pH > 6.5, the polycations hydrolyzed and were present as the hydroxy-polymer species. The hydraulic conductivity of the mixtures decreased as exchangeable Na increased, but the decrease was less than in untreated mixtures, AlCl3 was more effective in maintaining hydraulic conductivity than FeCl3. In montmorillonite clay with an ESP of 20, less than 5% of a complete Al-interlayer was enough to prevent a reduction in hydraulic conductivity. Packets in the day systems tested explain the high efficiency of the Fe and Al polycations.

Based on erosion coupon tests, a sand erosion model for 17-4PH steel was developed. The developed erosion model was validated against the results of compressor erosion tests from a generic rig and from other researchers. A high-fidelity computational fluid dynamics (CFD) model of the test rig was built, a user-defined function was developed to implement the erosion model into the ANSYS CFD software, and the turbulent, two-phase flow-field in multiple reference frames was solved. The simulation results are consistent with the test results from the compressor rig and with experimental findings from other researchers. Specifically, the sand erosion blunts the leading edge, sharpens the trailing edge and increases pressure-surface roughness. The comparisons between the experimental observations and numerical results as well as a quantitative comparison with three other sand erosion models indicate that the developed sand erosion model is adequate for erosion prediction of engine components made of 17-4PH steel.

Bentonite mixed with varying quantities of sand is currently of widespread interest as engineering liners for water containment and waste disposal. However, the alternative use of pumice, widespread in many volcanic regions, has been less studied and requires further characterization of geotechnical properties and performance prior to its extensive use. The objective of this study was to determine and compare the compaction and swelling characteristics of sandbentonite and pumice-bentonite mixtures using available geo-materials from Turkey. Standard Proctor compaction tests and constant volume swell tests were carried out using mixtures with four different bentonite contents (15, 20, 25, 30%) and three different sand and pumice grain size ranges (2.00–1.00; 1.00–0.50; 0.50–0.25 mm). The results indicate that pumice-bentonite mixtures have lower maximum dry unit weights, higher optimum moisture contents and greater swelling potentials than equivalent sand-bentonite mixtures. Important differences occur in the swelling potentials of the sand and pumice mixtures with respect to grain size whereby sand-bentonite mixtures show increased swelling with coarsening grain size, in contrast to the pumice–bentonite mixtures which showed a decrease. These differences are attributed to the amount of grain-size-dependent connected pore space that can be filled during bentonite expansion and the presence of dissolvable salts in the pumice. It is concluded that locally available pumice material could be used to replace sand in engineering bentonite seals, despite some differences in their geotechnical properties.

Although investigation of the hydraulic conductivity behaviour of zeolite-bentonite mixtures (ZBMs) has been a topic of interest for researchers recently, the influence of compaction water content on the hydraulic conductivity of ZBMs has not been studied so far. This study discusses the hydraulic conductivities of ZBMs and compares the results with those of sand-bentonite mixtures (SBMs). The hydraulic conductivities of SBMs were unaffected by compaction water content and bentonite content, but the hydraulic conductivities of ZBMs were substantially different in mixtures containing 10% and 20% bentonite. The hydraulic conductivity of 10% ZBM (i.e. containing 10% bentonite and 90% wt. zeolite) gradually decreased as the water content increased to optimum water content and then it tended to decrease rapidly when the water content exceeded the optimum. In contrast, the hydraulic conductivity of 20% ZBM sharply decreased at the early stages of compaction water content (i.e. on the dry side of optimum water content) and levelled off when the water content was at the optimum water content. However, there is at least one order of magnitude difference between the hydraulic conductivities of ZBMs and SBMs, supporting the zeolite network model as suggested in previous works.

Deposit formation on turbine hardware in propulsion turbine engines can occur in many arid regions globally. Characterising crystalline deposits on metallic substrates can aid in component resilience and health monitor algorithms during particle ingestion. This study has developed two statistical empirical models for prediction from acquired experimental data for the onset of deposits. The prediction models are for crystalline particulate (Arizona Road Test Dust) deposits on a flat rectangular Hastelloy-X test coupon. Particle impingement angles varied between 20° and 80° in experimental flow temperatures of 1,000–1,100°C. Averaged deposits are methodically quantified through normalised particle deposit tallies per area and percent coverage of the surface using microscopic imaging and image processing programs. Deposit accumulation is a quadratic function of both near-surface coupon temperature and coupon angle.

Adsorption of benefin (N-butyl-N-ethyl-α,α,α-trifluoro-2,6-dinitro-p-toluidine), dinitramine (N4,N4-diethyl-α,α,α-trifluoro-3,5-dinitrotoluene-2,4-diamine), fluchloralin [N-(2-chloroethyl)-2,6-dinitro-N-propyl-4-(trifluoromethyl)aniline], oryzalin (3,5-dinitro-N4,N4-dipropylsulfanilamide), profluralin [N-(cyclopropylmethyl)-α,α,α-tri-fluoro-2,6-dinitro-N-propyl-p-toluidine], and trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) was studied in 10 Wisconsin soils. Ratios of the quantity of each herbicide adsorbed and quantities remaining in the soil solution at equilibrium (Kd value) on a Piano silt loam (Typic Argiudoll fine-silty, mixed, mesic) remained relatively constant over a range of concentrations. Herbicide adsorption by the soils was related more closely to soil organic matter than to the other soil chemical and physical properties. Diffusion of the herbicides in Piano silt loam was affected by soil water. Diffusion of trifluralin, profluralin and benefin decreased as soil water increased. Diffusion of dinitramine and fluchloralin did not change significantly with change in water content. Diffusion of oryzalin increased at the highest soil water content. None of the herbicides moved more than 10 mm in the soil during a 17-day period. In unsaturated Piano silt loam, relative mobility of the herbicides was trifluralin ≥benefin>profluralin>fluchloralin>dinitramine≥oryzalin. Oryzalin reached highest mobility in water-saturated soil.

Grain size analyses of three hilltop, primary eolian loess sequences in the Negev desert, southern Israel, show a bimodal grain-size distribution at 50–60 μm and 3–8 μm. Using analyses of mineralogy and OSL ages we demonstrate that the coarse mode is composed mostly of quartz grains and its relative magnitude increases regionally with time, suggesting an enhancement of a time-transgressive proximal dust source compared to a distal, Saharan fine-grain dust. The only proximal dust source for large amount of coarse silt quartz grains is the sands that advanced into Sinai and the Negev concurrently with the loess accretion during the late Pleistocene as a result of the exposure of the Mediterranean shelf. We therefore propose that the coarse silt quartz grains were formed through eolian abrasion within the margins of an advancing sand sea. This relationship between desert sand seas as a source for proximal coarse dust and desert margin loess deposits can be applicable to other worldwide deserts such as Northern Africa, China and Australia.

Quaternary desert loess and sandstone–loessite relationships in the geological record raise questions regarding causes and mechanisms of silt formation and accretion. In the northern Sinai–Negev desert carbonate terrain, only sand abrasion in active erg could have produced the large quantities of quartzo-feldspathic silts constituting the late Quaternary northwestern Negev loess. In the continuum of source (medium to fine sand of dunes) to sink (silts in loess) the very fine sand is unaccounted for in the record. This weakens the sand abrasion model of silt formation as a global process. Here, we demonstrate that, as predicted by experiments, abrasion by advancing dunes generated large quantities of very fine sand (60–110 μm) deposited within the dune field and in close proximity downwind. This very fine sand was generated 13–11 ka, possibly synchronous with the Younger Dryas under gusty sand/dust storms in the southeastern Mediterranean and specifically in the northern Sinai–Negev erg. These very fine sands were washed down slope and filled small basins blocked by the advancing dunes; outside these sampling basins it is difficult to identify these sands as a distinct product. We conclude that ergs are mega-grinders of sand into very fine sand and silt under windy Quaternary and ancient aeolian desert environments.

We have built a 3D lithological model of the Netherlands, for the purpose of mapping on-land aggregate resources down to 50 m below the surface. The model consists of voxel cells (1000 ⋅ 1000 ⋅ 1 m), with lithological composition and aggregate content estimates as primary attributes. These attributes were derived from ∼350,000 borehole descriptions. Overburdens and intercalations of cohesive or otherwise non-dredgeable materials were taken into account to define geologically exploitable aggregates within the total stock. We arrive at about 520 ⋅ 109 m3 of aggregates occurring in the depth range investigated. Some 50% of this amount is considered geologically exploitable and about 25% would in principle (but largely not in reality) be accessible. Most aggregates resources (∼98%) are coarse sand, which is processed for use in concrete, masonry mortars, drains, filters, etc. The total exploitable stock of coarse sand in the depth range investigated amounts to roughly 7500 times the current annual consumption level, and is virtually indepletable. The gravel stock, estimated at some 12 ⋅ 109 m3, is small by comparison, and impels a dependency on imports.

Exploitable aggregates occur in all but the coastal provinces. In accordance with current policy changes, the future may show a shift from concentrated production along the upstream Dutch Rhine and Meuse rivers towards a more even distribution of small-sized operations over the country. Fairly large aggregate stocks, that have not yet been exploited to significant extent, are available in the northern extent of the aggregates occurrences.

In the Netherlands, mineral extraction by means of dredging or quarrying meets with considerable societal resistance. Land surface lowering prior to large land reconstruction projects may raise fewer objections. We have calculated the potential yields of sand and gravel from land surface lowering embedded in planned building and construction projects, and in nature, farmland and recreation area development. Our primary data sets were a compilation of spatial plans for the period 1995 – 2005 and about 95,000 borehole descriptions. Even if embedded consistently, land surface lowering would contribute modestly (up to 5.4 Mio m3/a) to the filling sand provision (annual demand 45 – 50 Mio m3/a).

Being sessile filter feeders, sponges may be disadvantaged by sediments in many ways, e.g. through clogging and burial. However, in order to correctly recognize negative effects of sediments in the field, natural relationships of sponge taxa adapted to a life with sediments need to be understood. The present publication reviews available literature and provides observations on natural and beneficial interactions of sponges with sediments, distinguishing several strategies: (1) Saving energy through sediment incorporation, reducing or replacing spicule production commonly occurs in keratose, verongimorph, tethyid and poecilosclerid sponges, which often received scientific names referring to sediments. (2) Forming sediment crusts externally or embedded in surface tissues reinforces outer layers, provides shade, and for external crusts camouflage and shelter from spongivory and desiccation. External crusts often occur in the tethyids and axinellids, while surface armour is most common in keratose sponges. (3) Anchoring in soft sediments provides a selective advantage for space colonization. This is mainly achieved in the hexactinellid, polymastiid and spirophorine sponges by using spicules (predominantly in deeper water), commonly in endopsammic sponges by rootlets, basal agglutination and basal incorporation of particles, and in various groups by attachment to buried materials (shallow water). (4) Living at least partially embedded in sediments (psammobiosis) appears to be best developed in Oceanapia spp. and bioeroding sponges, generates shelter from various external conditions and reduces the risk of spongivory. Typical morphological characters of sediment-adapted sponges are thus sediment skeletons and surface crusts (reinforcement), stalks and fistules (elevation above sediments), spicule tufts and root-systems (anchoring).

En 2000, des flux de rayonnement anormalement élevés ont été détectés sur certaines plages du littoral camarguais. Les sables du littoral camarguais ont alors fait l’objet d’une caractérisation radiologique montrant des activités moyennes de quelques dizaines de Bq kg-1 en uranium-238 et thorium-232 d’une part, et l’existence de points chauds à plus de 1000 Bq kg-1 d’autre part ; voire plus sur deux plages : l’une située à l’Est du phare de Beauduc, l’autre située à l’Est du phare de l’Espiguette. Cette radioactivité, d’origine naturelle, est responsable de l’exposition des personnes fréquentant ces deux dernières plages relativement isolées, mais néanmoins accessibles à tout public. L’Institut de radioprotection et de sûreté nucléaire a réalisé une évaluation des doses susceptibles d’être reçues par des personnes fréquentant ces deux dernières plages, en se basant sur des mesures et des prélèvements effectués in situ, en établissant expérimentalement la solubilité des sables dans les fluides gastrique et intestinal, et en formulant des hypothèses sur la fréquentation des lieux (scénarios). La dose annuelle maximale ainsi évaluée est de l’ordre de 0,8 mSv pour des adultes et 0,5 mSv pour les enfants ; valeurs vraisemblablement très prudentes dans lesquelles la dose par exposition externe prédomine largement.

This study attempts to ascertain whether the differing provenance sources and plate tectonic settings of deposition of clastic sediments and rocks can be identified by chemical means, thus opening the increased use of these rocks and their metamorphosed derivatives in plate tectonic modelling. Mineralogically immature feldspathic and mafic sands, muds, sandstones and shales from Mesozoic, Cenozoic and Holocene clastic deposits in California, Oregon, Alaska and Colorado have been both modally and chemically analysed providing a valuable data base (217 samples; 216 samples chemically analysed, many for 28 elements).

There is significant upward chemical variation in the Great Valley sequence of California which mimics previously described petrographic variation and in turn reflects provenance changes with igneous episodes and erosional stripping of the Sierra Nevada in late Mesozoic time. Differing sandstone petrofacies result in varying chemical signatures and while the provenances of monomict sediments are easiest to identify, polymict sources involving granitoid or ophiolitic material can often be identified by potassium feldspar or Cr contents. The distinction of K which is derived from detrital potassium feldspar from K derived from detrital illite, micas or other sheet minerals, is best made by a Niggli al–alk plot against k. Mafic sandstones derived from mafic volcanic or plutonic rocks preserve essentially mafic igneous chemistry and could be possible parent sources of some amphibolites which grade into metasediments. The lithified erosion products of the Sierra Nevada calc-alkaline igneous rocks have higher Niggli al–alk and higher average Niggli si at any given mg value than the fresh igneous rocks enabling meta-arkoses to be distinguished from meta-igneous rocks.

Applying previously published chemical criteria gives the actual plate tectonic setting of deposition of most of the sandstones studied. This suggests that the chemical composition of sandstones can yield much more information about the provenance and plate tectonic setting than hitherto recognised.