Aeolian sand transport and aeolian deposits on Venus: A review

NASA Astrophysics Data System (ADS)

Kreslavsly, Mikhail A.; Bondarenko, Nataliya V.

2017-06-01

We review the current state of knowledge about aeolian sand transport and aeolian bedforms on planet Venus. This knowledge is limited by lack of observational data. Among the four planetary bodies of the Solar System with sufficient atmospheres in contact with solid surfaces, Venus has the densest atmosphere; the conditions there are transitional between those for terrestrial subaerial and subaqueous transport. The dense atmosphere causes low saltation threshold and short characteristic saltation length, and short scale length of the incipient dunes. A few lines of evidence indicate that the typical wind speeds exceed the saltation threshold; therefore, sand transport would be pervasive, if sand capable of saltation is available. Sand production on Venus is probably much slower than on the Earth; the major terrestrial sand sinks are also absent, however, lithification of sand through sintering is expected to be effective under Venus' conditions. Active transport is not detectable with the data available. Aeolian bedforms (transverse dunes) resolved in the currently available radar images occupy a tiny area on the planet; however, indirect observations suggest that small-scale unresolved aeolian bedforms are ubiquitous. Aeolian transport is probably limited by sand lithification causing shortage of saltation-capable material. Large impact events likely cause regional short-term spikes in aeolian transport by supplying a large amount of sand-size particles, as well as disintegration and activation of older indurated sand deposits. The data available are insufficient to understand whether the global aeolian sand transport occurs or not. More robust knowledge about aeolian transport on Venus is essential for future scientific exploration of the planet, in particular, for implementation and interpretation of geochemical studies of surface materials. High-resolution orbital radar imaging with local to regional coverage and desirable interferometric capabilities is the

Trajectories and energy transfer of saltating particles onto rock surfaces : application to abrasion and ventifact formation on Earth and Mars

NASA Technical Reports Server (NTRS)

Bridges, Nathan T.; Phoreman, James; White, Bruce R.; Greeley, Ronald; Eddlemon, Eric E.; Wilson, Gregory R.; Meyer, Christine J.

2005-01-01

The interaction between saltating sand grains and rock surfaces is assessed to gauge relative abrasion potential as a function of rock shape, wind speed, grain size, and planetary environment. Many kinetic energy height profiles for impacts exhibit a distinctive increase, or kink, a few centimeters above the surface, consistent with previous field, wind tunnel, and theoretical investigations. The height of the kink observed in natural and wind tunnel settings is greater than predictions by a factor of 2 or more, probably because of enhanced bouncing off hard ground surfaces. Rebounded grains increase the effective flux and relative kinetic energy for intermediate slope angles. Whether abrasion occurs, as opposed to simple grain impact with little or no mass lost from the rock, depends on whether the grain kinetic energy (EG) exceeds a critical value (EC), as well as the flux of grains with energies above EC. The magnitude of abrasion and the shape change of the rock over time depends on this flux and the value of EG > EC. Considering the potential range of particle sizes and wind speeds, the predicted kinetic energies of saltating sand hitting rocks overlap on Earth and Mars. However, when limited to the most likely grain sizes and threshold conditions, our results agree with previous work and show that kinetic energies are about an order of magnitude greater on Mars.

Threshold for sand mobility on Mars calibrated from seasonal variations of sand flux.

PubMed

Ayoub, F; Avouac, J-P; Newman, C E; Richardson, M I; Lucas, A; Leprince, S; Bridges, N T

2014-09-30

Coupling between surface winds and saltation is a fundamental factor governing geological activity and climate on Mars. Saltation of sand is crucial for both erosion of the surface and dust lifting into the atmosphere. Wind tunnel experiments along with measurements from surface meteorology stations and modelling of wind speeds suggest that winds should only rarely move sand on Mars. However, evidence for currently active dune migration has recently accumulated. Crucially, the frequency of sand-moving events and the implied threshold wind stresses for saltation have remained unknown. Here we present detailed measurements of Nili Patera dune field based on High Resolution Imaging Science Experiment images, demonstrating that sand motion occurs daily throughout much of the year and that the resulting sand flux is strongly seasonal. Analysis of the seasonal sand flux variation suggests an effective threshold for sand motion for application to large-scale model wind fields (1-100 km scale) of τ(s)=0.01±0.0015 N m(-2).

Higher-than-predicted saltation threshold wind speeds on Titan.

PubMed

Burr, Devon M; Bridges, Nathan T; Marshall, John R; Smith, James K; White, Bruce R; Emery, Joshua P

2015-01-01

Titan, the largest satellite of Saturn, exhibits extensive aeolian, that is, wind-formed, dunes, features previously identified exclusively on Earth, Mars and Venus. Wind tunnel data collected under ambient and planetary-analogue conditions inform our models of aeolian processes on the terrestrial planets. However, the accuracy of these widely used formulations in predicting the threshold wind speeds required to move sand by saltation, or by short bounces, has not been tested under conditions relevant for non-terrestrial planets. Here we derive saltation threshold wind speeds under the thick-atmosphere, low-gravity and low-sediment-density conditions on Titan, using a high-pressure wind tunnel refurbished to simulate the appropriate kinematic viscosity for the near-surface atmosphere of Titan. The experimentally derived saltation threshold wind speeds are higher than those predicted by models based on terrestrial-analogue experiments, indicating the limitations of these models for such extreme conditions. The models can be reconciled with the experimental results by inclusion of the extremely low ratio of particle density to fluid density on Titan. Whereas the density ratio term enables accurate modelling of aeolian entrainment in thick atmospheres, such as those inferred for some extrasolar planets, our results also indicate that for environments with high density ratios, such as in jets on icy satellites or in tenuous atmospheres or exospheres, the correction for low-density-ratio conditions is not required.

An experimental study of the dynamics of saltation within a three-dimensional framework

NASA Astrophysics Data System (ADS)

O'Brien, Patrick; McKenna Neuman, Cheryl

2018-04-01

Our understanding of aeolian sand transport via saltation lacks an experimental determination of the particle borne kinetic energy partitioned into 3 dimensions relative to the mean flow direction. This in turn creates a disconnect between global wind erosion estimates and particle scale processes. The present study seeks to address this deficiency through an extended analysis of data obtained from a series of particle tracking velocimetry experiments conducted in a boundary layer wind tunnel under transport limited conditions. Particle image diameter, as it appeared within each camera frame, was extensively calibrated against that obtained by sieving, and the ballistic trajectories detected were disassembled into discrete particle image pairs whose distribution and dynamics were then examined in vertical profile with sub-millimeter resolution. The vertical profile of the wind aligned particle transport rate was found to follow a power relation within 10 mm of the bed surface. The exponent of this power function changes with increasing spanwise angle (θ) to produce a family of curves representing particle diffusion in 3 dimensions. Particle mass was found to increase with θ, and the distribution of the total particle kinetic energy was found to be very similar to that for the particle concentration. The spanwise component of the kinetic energy of a saltating particle peaks at θ = 45°, with the stream-aligned component an order of magnitude higher in value. Low energy, splashed particles near the bed account for a majority of the kinetic energy distributed throughout the particle cloud, regardless of their orientation.

Estimation of saltation emission in the Kubuqi Desert, North China.

PubMed

Du, Heqiang; Xue, Xian; Wang, Tao

2014-05-01

The Kubuqi Desert suffered more severe wind erosion hazard. Every year, a mass of aeolian sand was blown in the Ten Tributaries that are tributaries of the Yellow River. To estimate the quantity of aeolian sediment blown into the Ten Tributaries from the Kubuqi Desert, it is necessary to simulate the saltation processes of the Kubuqi Desert. A saltation submodel of the IWEMS (Integrated Wind-Erosion Modeling System) and its accompanying RS (Remote Sensing) and GIS (Geographic Information System) methods were used to model saltation emissions in the Kubuqi Desert. To calibrate the saltation submodel, frontal area of vegetation, soil moisture, wind velocity and saltation sediment were observed synchronously on several points in 2011 and 2012. In this study, a model namely BEACH (Bridge Event And Continuous Hydrological) was introduced to simulate the daily soil moisture. Using the surface parameters (frontal area of vegetation and soil moisture) along with the observed wind velocities and saltation sediments for the observed points, the saltation model was calibrated and validated. To reduce the simulate error, a subdaily wind velocity program, WINDGEN was introduced in this model to simulate the hourly wind velocity of the Kubuqi Desert. By incorporating simulated hourly wind velocity, and model variables, the saltation emission of the Kubuqi Desert was modeled. The model results show that the total sediment flow rate was 1-30.99 tons/m over the last 10years (2001-2010). The saltation emission mainly occurs in the north central part of the Kubuqi Desert in winter and spring. Integrating the wind directions, the quantity of the aeolian sediment that deposits in the Ten Tributaries was estimated. Compared with the observed data by the local government and hydrometric stations, our estimation is reasonable. Copyright © 2014 Elsevier B.V. All rights reserved.

Behavior of Windblown Sand on Mars: Results from Single-Particle Experiments

NASA Technical Reports Server (NTRS)

Marshall, J. R.; Borucki, J.; Sagan, C.

1999-01-01

Experiments are investigating the behavior of individual sand grains in the high-energy martian aeolian regime. Energy partitioning during impact of a saltating grain determines grain longevity, but it also influences the way in which the bed becomes mobilized by reptation. When single grains of sand are fired into loose beds, the bed can absorb up to 90% of the impact energy by momentum transfer to other grains; it has been discovered that the impacting grains cause circular craters even at low impact angles. Hundreds of grains can be splashed by a single high-velocity (100 m/s) impact causing more bed disturbance through reptation than previously thought. The research is supported by NASA's PG&G Program. Because the martian aeolian environment in both high energy and of long duration, the most mobile fractions of windblown sand should have eradicated themselves by attrition, unless sand supply has kept pace with destruction. It is therefore important to understand the rate of grain attrition in order to make sense of the existence of vast dune fields on Mars. Attrition, has been addressed in other studies, but precise data for a single saltating grain striking a loose bed of sand have not been acquired -- the quintessential case to be understood for dunes on Mars. To acquire these data, we are employing a compound crossbow which has the bolt-firing mechanism replaced with a pneumatically-automated sabot system. The sabot can launch individual grains of sand of any size between several millimeters and about 50 microns, at velocities up to 100m/s. This is around the maximum velocity expected for saltating grains on Mars. The sabot sled is equipped with photoelectric sensors for measuring shot velocity. Baffling of the grain's exit orifice has enabled projection of single grains without significant aerodynamic effects from the sabot. Grains are fired into loose beds of sand at about 15 degrees from the horizontal (typical saltation trajectory at impact) while being

Behavior of Windblown Sand on Mars: Results from Single-Particle Experiments

NASA Astrophysics Data System (ADS)

Marshall, J. R.; Borucki, J.; Sagan, C.

1999-09-01

Experiments are investigating the behavior of individual sand grains in the high-energy martian aeolian regime. Energy partitioning during impact of a saltating grain determines grain longevity, but it also influences the way in which the bed becomes mobilized by reptation. When single grains of sand are fired into loose beds, the bed can absorb up to 90% of the impact energy by momentum transfer to other grains; it has been discovered that the impacting grains cause circular craters even at low impact angles. Hundreds of grains can be splashed by a single high-velocity (100 m/s) impact causing more bed disturbance through reptation than previously thought. The research is supported by NASA's PG&G Program. Because the martian aeolian environment in both high energy and of long duration, the most mobile fractions of windblown sand should have eradicated themselves by attrition, unless sand supply has kept pace with destruction. It is therefore important to understand the rate of grain attrition in order to make sense of the existence of vast dune fields on Mars. Attrition, has been addressed in other studies, but precise data for a single saltating grain striking a loose bed of sand have not been acquired -- the quintessential case to be understood for dunes on Mars. To acquire these data, we are employing a compound crossbow which has the bolt-firing mechanism replaced with a pneumatically-automated sabot system. The sabot can launch individual grains of sand of any size between several millimeters and about 50 microns, at velocities up to 100m/s. This is around the maximum velocity expected for saltating grains on Mars. The sabot sled is equipped with photoelectric sensors for measuring shot velocity. Baffling of the grain's exit orifice has enabled projection of single grains without significant aerodynamic effects from the sabot. Grains are fired into loose beds of sand at about 15 degrees from the horizontal (typical saltation trajectory at impact) while being

An improved numerical model suggests potential differences of wind-blown sand between on Earth and Mars

NASA Astrophysics Data System (ADS)

Bo, T. L.; Fu, L. T.; Liu, L.; Zheng, X. J.

2017-06-01

The studies on wind-blown sand are crucial for understanding the change of climate and landscape on Mars. However, the disadvantages of the saltation models may result in unreliable predictions. In this paper, the saltation model has been improved from two main aspects, the aerodynamic surface roughness and the lift-off parameters. The aerodynamic surface roughness is expressed as function of particle size, wind strength, air density, and air dynamic viscosity. The lift-off parameters are improved through including the dependence of restitution coefficient on incident parameters and the correlation between saltating speed and angle. The improved model proved to be capable of reproducing the observed data well in both stable stage and evolution process. The modeling of wind-blown sand is promoted by all improved aspects, and the dependence of restitution coefficient on incident parameters could not be ignored. The constant restitution coefficient and uncorrelated lift-off parameter distributions would lead to both the overestimation of the sand transport rate and apparent surface roughness and the delay of evolution process. The distribution of lift-off speed and the evolution of lift-off parameters on Mars are found to be different from those on Earth. This may thus suggest that it is inappropriate to predict the evolution of wind-blown sand by using the lift-off velocity obtained in steady state saltation. And it also may be problematic to predict the wind-blown sand on Mars through applying the lift-off velocity obtained upon terrestrial conditions directly.

Saltation under Martian gravity and its influence on the global dust distribution

NASA Astrophysics Data System (ADS)

Musiolik, Grzegorz; Kruss, Maximilian; Demirci, Tunahan; Schrinski, Björn; Teiser, Jens; Daerden, Frank; Smith, Michael D.; Neary, Lori; Wurm, Gerhard

2018-05-01

Dust and sand motion are a common sight on Mars. Understanding the interaction of atmosphere and Martian soil is fundamental to describe the planet's weather, climate and surface morphology. We set up a wind tunnel to study the lift of a mixture between very fine sand and dust in a Mars simulant soil. The experiments were carried out under Martian gravity in a parabolic flight. The reduced gravity was provided by a centrifuge under external microgravity. The onset of saltation was measured for a fluid threshold shear velocity of 0.82 ± 0.04 m/s. This is considerably lower than found under Earth gravity. In addition to a reduction in weight, this low threshold can be attributed to gravity dependent cohesive forces within the sand bed, which drop by 2/3 under Martian gravity. The new threshold for saltation leads to a simulation of the annual dust cycle with a Mars GCM that is in agreement with observations.

On Release of Microbe-Laden Particles from Mars Landers

NASA Technical Reports Server (NTRS)

Bellan, Josette; Harstad, Kenneth

2006-01-01

A paper presents a study in which rates of release of small particles from Mars lander spacecraft into the Martian atmosphere were estimated from first principles. Because such particles can consist of, or be laden with, terrestrial microbes, the study was undertaken to understand their potential for biological contamination of Mars. The study included taking account of forces and energies involved in adhesion of particles and of three mechanisms of dislodgement of particles from the surface of a Mars lander: wind shear, wind-driven impingement of suspended dust, and impingement of wind-driven local saltating sand particles. Wind shear was determined to be effective in dislodging only particles larger than about 10 microns and would probably be of limited interest because such large particles could be removed by pre-flight cleaning of the spacecraft, and their number on the launched spacecraft would thus be relatively small. Dislodgement by wind-driven dust was found to be characterized by an adhesion half-life of the order of 10,000 years judged to be too long to be of concern. Dislodgement by saltating sand particles, including skirts of dust devils, was found to be of potential importance, depending on the sizes of the spacecraft-attached particles and characteristics of both Mars sand-particle and spacecraft surfaces.

Field sampling of loose erodible material: A new method to consider the full particle-size range

NASA Astrophysics Data System (ADS)

Klose, Martina; Gill, Thomas E.

2017-04-01

The aerodynamic entrainment of sand and dust is determined by the atmospheric forces exerted onto the soil surface and by the soil-surface condition. If aerodynamic forces are strong enough to generate sand and dust lifting, the entrained sediment amount still critically depends on the supply of loose particles readily available for lifting. This loose erodible material (LEM) is sometimes defined as the thin layer of loose particles on top of a crusted surface. Here, we more generally define LEM as loose particles or particle aggregates available for entrainment, which may or may not overlay a soil crust. Field sampling of LEM is difficult and only few attempts have been made. Motivated by saltation as the most efficient process to generate dust emission, methods have focused on capturing LEM in the sand-size range or on determining the potential of a soil surface to be eroded by aerodynamic forces and particle impacts. Here, our focus is to capture the full particle-size distribution of LEM in situ, including the dust and sand-size range, to investigate the potential and likelihood of dust emission mechanisms (aerodynamic entrainment, saltation bombardment, aggregate disintegration) to occur. A new vacuum method is introduced and its capability to sample LEM without significant alteration of the LEM particle-size distribution is investigated.

Behavior of Windblown Sand on Mars: Results From Single-Particle Experiments

NASA Astrophysics Data System (ADS)

Marshall, J. R.; Borucki, J.; Sagan, C.

1996-03-01

Experiments are investigating the behavior of individual sand grains in the high-energy martian aeolian regime. Energy partitioning during impact of a saltating grain determines grain longevity, but it also influences the way in which the bed becomes mobilized by reptation. When single grains of sand are fired into loose beds, the bed can absorb up to 90% of the impact energy by momentum transfer to other grains; it has been discovered that the impacting grains cause circular craters even at low impact angles. Hundreds of grains can be splashed by a single high-velocity (100 m/s) impact causing more bed disturbance through reptation than previously thought. The research is supported by NASA's PG & G Program.

Potential Use of BEST® Sediment Trap in Splash - Saltation Transport Process by Simultaneous Wind and Rain Tests

PubMed Central

Basaran, Mustafa; Uzun, Oguzhan; Cornelis, Wim; Gabriels, Donald; Erpul, Gunay

2016-01-01

The research on wind-driven rain (WDR) transport process of the splash-saltation has increased over the last twenty years as wind tunnel experimental studies provide new insights into the mechanisms of simultaneous wind and rain (WDR) transport. The present study was conducted to investigate the efficiency of the BEST® sediment traps in catching the sand particles transported through the splash-saltation process under WDR conditions. Experiments were conducted in a wind tunnel rainfall simulator facility with water sprayed through sprinkler nozzles and free-flowing wind at different velocities to simulate the WDR conditions. Not only for vertical sediment distribution, but a series of experimental tests for horizontal distribution of sediments was also performed using BEST® collectors to obtain the actual total sediment mass flow by the splash-saltation in the center of the wind tunnel test section. Total mass transport (kg m-2) were estimated by analytically integrating the exponential functional relationship using the measured sediment amounts at the set trap heights for every run. Results revealed the integrated efficiency of the BEST® traps at 6, 9, 12 and 15 m s-1 wind velocities under 55.8, 50.5, 55.0 and 50.5 mm h-1 rain intensities were, respectively, 83, 106, 105, and 102%. Results as well showed that the efficiencies of BEST® did not change much as compared with those under rainless wind condition. PMID:27898716

Potential Use of BEST® Sediment Trap in Splash - Saltation Transport Process by Simultaneous Wind and Rain Tests.

PubMed

Basaran, Mustafa; Uzun, Oguzhan; Cornelis, Wim; Gabriels, Donald; Erpul, Gunay

2016-01-01

The research on wind-driven rain (WDR) transport process of the splash-saltation has increased over the last twenty years as wind tunnel experimental studies provide new insights into the mechanisms of simultaneous wind and rain (WDR) transport. The present study was conducted to investigate the efficiency of the BEST® sediment traps in catching the sand particles transported through the splash-saltation process under WDR conditions. Experiments were conducted in a wind tunnel rainfall simulator facility with water sprayed through sprinkler nozzles and free-flowing wind at different velocities to simulate the WDR conditions. Not only for vertical sediment distribution, but a series of experimental tests for horizontal distribution of sediments was also performed using BEST® collectors to obtain the actual total sediment mass flow by the splash-saltation in the center of the wind tunnel test section. Total mass transport (kg m-2) were estimated by analytically integrating the exponential functional relationship using the measured sediment amounts at the set trap heights for every run. Results revealed the integrated efficiency of the BEST® traps at 6, 9, 12 and 15 m s-1 wind velocities under 55.8, 50.5, 55.0 and 50.5 mm h-1 rain intensities were, respectively, 83, 106, 105, and 102%. Results as well showed that the efficiencies of BEST® did not change much as compared with those under rainless wind condition.

On the frequency response of a Wenglor particle-counting system for aeolian transport measurements

NASA Astrophysics Data System (ADS)

Bauer, Bernard O.; Davidson-Arnott, Robin G. D.; Hilton, Michael J.; Fraser, Douglas

2018-06-01

A commonly deployed particle-counting system for aeolian saltation flux, consisting of a Wenglor fork sensor and an Onset Hobo Pulse Input Adapter linked to an Onset Hobo Energy Logger Pro data logger, was tested for frequency response. The Wenglor fork sensor is an optical gate device that has very fast switching capacity that can accommodate the time of flight of saltating sand particles through the sensing volume with the exception of very fine sand or silt and very quickly moving particles. The Pulse Input Adapter, in contrast, imposes limitations on the frequency response of the system. The manufacturer of the pulse adapter specifies an upper limit of 120 Hz, although bench tests with an electronic pulse generator indicate that the frequency response of the Pulse Input Adapter, in isolation, is excellent up to 3000 Hz, with only small error (less than 1.6%) due to under-counting during data transfer intervals. A mechanical test of the integrated system (fork sensor, pulse input adapter, and data logger) demonstrates excellent performance up to about 700 Hz (less than 2% error), but significant under-counting above 1000 Hz for unknown reasons. This specific particle-counting system therefore has a frequency response that is well suited for investigation of the dynamics of aeolian saltation as typically encountered in most field conditions on coastal beaches with the exception of extreme wind events and very small particle sizes.

Effect of the particle to fluid density ratio on bedform development: An application of PTV

NASA Astrophysics Data System (ADS)

McKenna Neuman, C. L.; Gordon, M. D.

2009-05-01

The particle to fluid density ratio plays a key role in sediment transport and strongly governs the relative importance of the transport mode. In aeolian systems, this ratio is three orders of magnitude larger than for the transport of sedimentary particles in water, such that saltation is the dominant mode for diameters (250 microns) commonly found in ripples and dunes. The partitioning of fluid momentum to saltators, and therefore to the surface upon impact, is extremely important to the entrainment of sediment, the maintenance of transport, and the scaling of aeolian bedforms. This paper demonstrates the use of Particle Tracking Velocimetry in measuring the partitioning of momentum associated with particle collisions on beds of quartz sand (2630 kg m-3) typical of aeolian dunes, and acrylic particles (1210 kg m-3) similar to blowing snow (920 kg m-3). The experiments were carried out in the boundary layer wind tunnel at Trent University on full beds that were 13.8 m in length and 0.71 m in width. In the majority of experiments, the wind speeds were either at or just above the threshold for saltation so that we could distinguish discrete particle trajectories. Surface ripples formed in the majority of experiments and passed through the camera's field of view so that the height, length and rate of migration could be measured in relation to the distributions of particle impact speed and angle, as well as those for the number, speed and angle of the particles ejected. Although similar in height, the ripples comprised of acrylic particles were 2 to 4 times longer, much more asymmetric, and migrated significantly faster than those in sand. The particle impact and ejection speeds were very similar, although the sand particles approached and left the bed at substantially larger angles than observed for the lighter acrylic particles of similar diameter. In a separate experiment, glass beads were flung onto each bed material at 4 ms-1 in still air. It was discovered that

Difference in the wind speeds required for initiation versus continuation of sand transport on mars: implications for dunes and dust storms.

PubMed

Kok, Jasper F

2010-02-19

Much of the surface of Mars is covered by dunes, ripples, and other features formed by the blowing of sand by wind, known as saltation. In addition, saltation loads the atmosphere with dust aerosols, which dominate the Martian climate. We show here that saltation can be maintained on Mars by wind speeds an order of magnitude less than required to initiate it. We further show that this hysteresis effect causes saltation to occur for much lower wind speeds than previously thought. These findings have important implications for the formation of dust storms, sand dunes, and ripples on Mars.

A new turbulence-based model for sand transport

NASA Astrophysics Data System (ADS)

Mayaud, Jerome; Wiggs, Giles; Bailey, Richard

2016-04-01

Knowledge of the changing rate of sediment flux in space and time is essential for quantifying surface erosion and deposition in desert landscapes. While many aeolian studies have relied on time-averaged parameters such as wind velocity (U) and wind shear velocity (u*) to determine sediment flux, there is increasing evidence that high-frequency turbulence is an important driving force behind the entrainment and transport of sand. However, turbulence has yet to be incorporated into a functional sand transport model that can be used for predictive purposes. In this study we present a new transport model (the 'turbulence model') that accounts for high-frequency variations in the horizontal (u) and vertical (w) components of wind flow. The turbulence model is fitted to wind velocity and sediment transport data from a field experiment undertaken in Namibia's Skeleton Coast National Park, and its performance at three temporal resolutions (10 Hz, 1 Hz, 1 min) is compared to two existing models that rely on time-averaged wind velocity data (Radok, 1977; Dong et al., 2003). The validity of the three models is analysed under a variety of saltation conditions, using a 2-hour (1 Hz measurement resolution) dataset from the Skeleton Coast and a 5-hour (1 min measurement resolution) dataset from the southwestern Kalahari Desert. The turbulence model is shown to outperform the Radok and Dong models when predicting total saltation count over the three experimental periods. For all temporal resolutions presented in this study (10 Hz-10 min), the turbulence model predicted total saltation count to within at least 0.34%, whereas the Radok and Dong models over- or underestimated total count by up to 5.50% and 20.53% respectively. The strong performance of the turbulence model can be attributed to a lag in mass flux response built into its formulation, which can be adapted depending on the temporal resolution of investigation. This accounts for the inherent lag within the physical

Aeolian Erosion on Mars - a New Threshold for Saltation

NASA Astrophysics Data System (ADS)

Teiser, J.; Musiolik, G.; Kruss, M.; Demirci, T.; Schrinski, B.; Daerden, F.; Smith, M. D.; Neary, L.; Wurm, G.

2017-12-01

The Martian atmosphere shows a large variety of dust activity, ranging from local dust devils to global dust storms. Also, sand motion has been observed in form of moving dunes. The dust entrainment into the Martian atmosphere is not well understood due to the small atmospheric pressure of only a few mbar. Laboratory experiments on Earth and numerical models were developed to understand these processes leading to dust lifting and saltation. Experiments so far suggested that large wind velocities are needed to reach the threshold shear velocity and to entrain dust into the atmosphere. In global circulation models this threshold shear velocity is typically reduced artificially to reproduce the observed dust activity. Although preceding experiments were designed to simulate Martian conditions, no experiment so far could scale all parameters to Martian conditions, as either the atmospheric or the gravitational conditions were not scaled. In this work, a first experimental study of saltation under Martian conditions is presented. Martian gravity is reached by a centrifuge on a parabolic flight, while pressure (6 mbar) and atmospheric composition (95% CO2, 5% air) are adjusted to Martian levels. A sample of JSC 1A (grain sizes from 10 - 100 µm) was used to simulate Martian regolith. The experiments showed that the reduced gravity (0.38 g) not only affects the weight of the dust particles, but also influences the packing density within the soil and therefore also the cohesive forces. The measured threshold shear velocity of 0.82 m/s is significantly lower than the measured value for 1 g in ground experiments (1.01 m/s). Feeding the measured value into a Global Circulation Model showed that no artificial reduction of the threshold shear velocity might be needed to reproduce the global dust distribution in the Martian atmosphere.

A High Resolution Look at Black Sand Particles from Sand Dunes of Saudi Arabia Using Electron Microscopy

NASA Astrophysics Data System (ADS)

Hussain, M. M.; Aburizaiza, O. S.; Siddique, A.; Hershey, D. L.; Guerrieri, D. A.; Qurashi, J.; Abbass, M.; Blake, D. R.; Khwaja, H. A.

2013-12-01

Particulate air pollution is a problem of health concern. The microscopic make-up of different varieties of sand particles found and collected at a sand dune site in Badr, Saudi Arabia has been determined. Primary emphasis is given to the use of multiple high resolution electron microscopy (viz., Scanning Electron Microscopy with Energy Dispersive X-ray spectrometry (SEM/EDS) and Laser Scanning Microscopy (LSM)) to study the morphologies, emission source types, size, and elemental composition of the particles, and to evaluate the presence of ';coatings or contaminants' adsorbed or carried on by the black sand particles. White sand contains natural coarse particles associated with wind-blown releases from crustal surfaces, weathering of an igneous/metamorphic rock source, and volcanic activities. Silicates (alumino-silicates) and quartz (clear, milky, rose) dominate white sand and rest appears to contain calcite, olivine, feldspar, and magnetite. Black sand particles exhibit very different morphologies and microstructures (surface roughness) compared with white sand and volcanic ash. Morphological analyses have shown that the black sand contain ultrafine particles. Black sand is strongly magnetic, which indicates the mineral magnetite (strongly magnetic) or elemental iron. Iron, C, O, Ti, Si, V, and S particles dominate the black sand. Natural and anthropogenic sources have been implicated for the observed particles. Analysis revealed that the surface of white sand particles is mainly covered with the fine particles. It is known that emissions from combustion contain carbon soot and other contaminants that are easily absorbed by soil particles during a long-range transport.

Diet and gut microbiota of two supralittoral amphipods Orchestia montagui and Talitrus saltator living in different microhabitats

NASA Astrophysics Data System (ADS)

Abdelrhman, Khaled F. A.; Bacci, Giovanni; Nistri, Annamaria; Mengoni, Alessio; Ugolini, Alberto

2017-10-01

Talitrus saltator (Montagu) and Orchestia montagui Audouin live in different microhabitats of the same supralittoral belt. T. saltator can be found in the damp sand of beaches with scarce or absent wracked material near the water line. O. montagui is frequently found in the Posidonia banquettes or under wracked material, often in contact with the substrate. This study investigates the effect of diet on species-specific gut microbiota patterns in these talitrid species. Adults were collected and fed with artificial food (commercial fish food and pieces of blotting paper) for 51 days. Gut microbiota were analyzed at five time intervals (0 h, 24 h, 7, 23 and 51 days) by 16S rRNA gene metagenomic analysis and by estimating the relative abundance of cellulases (glycosyl hydrolase gene family 48, GHF48) gene copies. The gut microbiota of O. montagui was more affected than that of T. saltator by diet shift. Although the taxonomic profile of the gut microbiota varied with time in both species, with an increase of Protobacteria in O. montagui and of Actinobacteria and Bacteroidetes in T. saltator, genes involved in cellulose degradation (GHF48 family) showed a large-scale increase in O. montagui but not in T. saltator. We conclude that the diet variation has different influence on the composition of gut microbiota in the two talitrid species in accordance with their different alimentary habits: the more generalist T. saltator (detritivore, grazer, and scavenger) showed less changes in its gut microbiota composition than the more specialist O. montagui (detritivore and grazer), which strongly modified its gut microbiota composition by the captivity diet.

Exploring Auditory Saltation Using the "Reduced-Rabbit" Paradigm

ERIC Educational Resources Information Center

Getzmann, Stephan

2009-01-01

Sensory saltation is a spatiotemporal illusion in which the judged positions of stimuli are shifted toward subsequent stimuli that follow closely in time. So far, studies on saltation in the auditory domain have usually employed subjective rating techniques, making it difficult to exactly quantify the extent of saltation. In this study, temporal…

Large-scale variability of wind erosion mass flux rates at Owens Lake 1. Vertical profiles of horizontal mass fluxes of wind-eroded particles with diameter greater than 50 μm

USGS Publications Warehouse

Gillette, Dale A.; Fryrear, D.W.; Xiao, Jing Bing; Stockton, Paul; Ono, Duane; Helm, Paula J.; Gill, Thomas E; Ley, Trevor

1997-01-01

A field experiment at Owens (dry) Lake, California, tested whether and how the relative profiles of airborne horizontal mass fluxes for >50-μm wind-eroded particles changed with friction velocity. The horizontal mass flux at almost all measured heights increased proportionally to the cube of friction velocity above an apparent threshold friction velocity for all sediment tested and increased with height except at one coarse-sand site where the relative horizontal mass flux profile did not change with friction velocity. Size distributions for long-time-averaged horizontal mass flux samples showed a saltation layer from the surface to a height between 30 and 50 cm, above which suspended particles dominate. Measurements from a large dust source area on a line parallel to the wind showed that even though the saltation flux reached equilibrium ∼650 m downwind of the starting point of erosion, weakly suspended particles were still input into the atmosphere 1567 m downwind of the starting point; thus the saltating fraction of the total mass flux decreased after 650 m. The scale length difference and ratio of 70/30 suspended mass flux to saltation mass flux at the farthest down wind sampling site confirm that suspended particles are very important for mass budgets in large source areas and that saltation mass flux can be a variable fraction of total horizontal mass flux for soils with a substantial fraction of <100-μm particles.

The physics of wind-blown sand and dust

NASA Astrophysics Data System (ADS)

Kok, Jasper F.; Parteli, Eric J. R.; Michaels, Timothy I.; Karam, Diana Bou

2012-10-01

The transport of sand and dust by wind is a potent erosional force, creates sand dunes and ripples, and loads the atmosphere with suspended dust aerosols. This paper presents an extensive review of the physics of wind-blown sand and dust on Earth and Mars. Specifically, we review the physics of aeolian saltation, the formation and development of sand dunes and ripples, the physics of dust aerosol emission, the weather phenomena that trigger dust storms, and the lifting of dust by dust devils and other small-scale vortices. We also discuss the physics of wind-blown sand and dune formation on Venus and Titan.

The physics of wind-blown sand and dust.

PubMed

Kok, Jasper F; Parteli, Eric J R; Michaels, Timothy I; Karam, Diana Bou

2012-10-01

The transport of sand and dust by wind is a potent erosional force, creates sand dunes and ripples, and loads the atmosphere with suspended dust aerosols. This paper presents an extensive review of the physics of wind-blown sand and dust on Earth and Mars. Specifically, we review the physics of aeolian saltation, the formation and development of sand dunes and ripples, the physics of dust aerosol emission, the weather phenomena that trigger dust storms, and the lifting of dust by dust devils and other small-scale vortices. We also discuss the physics of wind-blown sand and dune formation on Venus and Titan.

Augmenting Sand Simulation Environments through Subdivision and Particle Refinement

NASA Astrophysics Data System (ADS)

Clothier, M.; Bailey, M.

2012-12-01

Recent advances in computer graphics and parallel processing hardware have provided disciplines with new methods to evaluate and visualize data. These advances have proven useful for earth and planetary scientists as many researchers are using this hardware to process large amounts of data for analysis. As such, this has provided opportunities for collaboration between computer graphics and the earth sciences. Through collaboration with the Oregon Space Grant and IGERT Ecosystem Informatics programs, we are investigating techniques for simulating the behavior of sand. We are also collaborating with the Jet Propulsion Laboratory's (JPL) DARTS Lab to exchange ideas and gain feedback on our research. The DARTS Lab specializes in simulation of planetary vehicles, such as the Mars rovers. Their simulations utilize a virtual "sand box" to test how a planetary vehicle responds to different environments. Our research builds upon this idea to create a sand simulation framework so that planetary environments, such as the harsh, sandy regions on Mars, are more fully realized. More specifically, we are focusing our research on the interaction between a planetary vehicle, such as a rover, and the sand beneath it, providing further insight into its performance. Unfortunately, this can be a computationally complex problem, especially if trying to represent the enormous quantities of sand particles interacting with each other. However, through the use of high-performance computing, we have developed a technique to subdivide areas of actively participating sand regions across a large landscape. Similar to a Level of Detail (LOD) technique, we only subdivide regions of a landscape where sand particles are actively participating with another object. While the sand is within this subdivision window and moves closer to the surface of the interacting object, the sand region subdivides into smaller regions until individual sand particles are left at the surface. As an example, let's say

Transport of colloidal silica in unsaturated sand: Effect of charging properties of sand and silica particles.

PubMed

Fujita, Yosuke; Kobayashi, Motoyoshi

2016-07-01

We have studied the transport of colloidal silica in various degrees of a water-saturated Toyoura sand column, because silica particles are widely used as catalyst carriers and abrasive agents, and their toxicity is reported recently. Since water-silica, water-sand, and air-water interfaces have pH-dependent negative charges, the magnitude of surface charge was controlled by changing the solution pH. The results show that, at high pH conditions (pH 7.4), the deposition of colloidal silica to the sand surface is interrupted and the silica concentration at the column outlet immediately reaches the input concentration in saturated conditions. In addition, the relative concentration of silica at the column outlet only slightly decreases to 0.9 with decreasing degrees of water saturation to 38%, because silica particles are trapped in straining regions in the soil pore and air-water interface. On the other hand, at pH 5 conditions (low pH), where sand and colloid have less charge, reduced repulsive forces result in colloidal silica attaching onto the sand in saturated conditions. The deposition amount of silica particles remarkably increases with decreasing degrees of water saturation to 37%, which is explained by more particles being retained in the sand column associated with the air-water interface. In conclusion, at higher pH, the mobility of silica particles is high, and the air-water interface is inactive for the deposition of silica. On the other hand, at low pH, the deposition amount increases with decreasing water saturation, and the particle transport is inhibited. Copyright © 2016 Elsevier Ltd. All rights reserved.

Surprises from the field: Novel aspects of aeolian saltation observed under natural turbulence

NASA Astrophysics Data System (ADS)

Martin, R. L.; Kok, J. F.; Chamecki, M.

2015-12-01

The mass flux of aeolian (wind-blown) sediment transport - critical for understanding earth and planetary geomorphology, dust generation, and soil stability - is difficult to predict. Recent work suggests that competing models for saltation (the characteristic hopping of aeolian sediment) fail because they do not adequately account for wind turbulence. To address this issue, we performed field deployments measuring high-frequency co-variations of aeolian saltation and near-surface winds at multiple sites under a range of conditions. Our observations yield several novel findings not currently captured by saltation models: (1) Saltation flux displays no significant lag relative to horizontal wind velocity; (2) Characteristic height of the saltation layer remains constant with changes in shear velocity; and (3) During saltation, the vertical profile of mean horizontal wind velocity is steeper than expected from the Reynolds stress. We examine how the interactions between saltation and turbulence in field settings could explain some of these surprising observations.

Corrosion Resistance of a Sand Particle-Modified Enamel Coating Applied to Smooth Steel Bars

PubMed Central

Tang, Fujian; Chen, Genda; Brow, Richard K.; Koenigstein, Michael L.

2014-01-01

The protective performance of a sand particle-modified enamel coating on reinforcing steel bars was evaluated in 3.5 wt% NaCl solution by electrochemical impedance spectroscopy (EIS). Seven percentages of sand particles by weight were investigated: 0%, 5%, 10%, 20%, 30%, 50% and 70%. The phase composition of the enamel coating and sand particles were determined with the X-ray diffraction (XRD) technique. The surface and cross-sectional morphologies of the sand particle-modified enamel coating were characterized using scanning electron microscopy (SEM). XRD tests revealed three phases of sand particles: SiO2, CaCO3 and MgCO3. SEM images demonstrated that the enamel coating wetted well with the sand particles. However, a weak enamel coating zone was formed around the sand particles due to concentrated air bubbles, leading to micro-cracks as hydrogen gas pressure builds up and exceeds the tensile strength of the weak zone. As a result, the addition of sand particles into the enamel coating reduced both the coating and corrosion resistances. PMID:28788203

Simulating Sand Behavior through Terrain Subdivision and Particle Refinement

NASA Astrophysics Data System (ADS)

Clothier, M.

2013-12-01

Advances in computer graphics, GPUs, and parallel processing hardware have provided researchers with new methods to visualize scientific data. In fact, these advances have spurred new research opportunities between computer graphics and other disciplines, such as Earth sciences. Through collaboration, Earth and planetary scientists have benefited by using these advances in hardware technology to process large amounts of data for visualization and analysis. At Oregon State University, we are collaborating with the Oregon Space Grant and IGERT Ecosystem Informatics programs to investigate techniques for simulating the behavior of sand. In addition, we have also been collaborating with the Jet Propulsion Laboratory's DARTS Lab to exchange ideas on our research. The DARTS Lab specializes in the simulation of planetary vehicles, such as the Mars rovers. One aspect of their work is testing these vehicles in a virtual "sand box" to test their performance in different environments. Our research builds upon this idea to create a sand simulation framework to allow for more complex and diverse environments. As a basis for our framework, we have focused on planetary environments, such as the harsh, sandy regions on Mars. To evaluate our framework, we have used simulated planetary vehicles, such as a rover, to gain insight into the performance and interaction between the surface sand and the vehicle. Unfortunately, simulating the vast number of individual sand particles and their interaction with each other has been a computationally complex problem in the past. However, through the use of high-performance computing, we have developed a technique to subdivide physically active terrain regions across a large landscape. To achieve this, we only subdivide terrain regions where sand particles are actively participating with another object or force, such as a rover wheel. This is similar to a Level of Detail (LOD) technique, except that the density of subdivisions are determined by

Three-dimensional simulation of the motion of a single particle under a simulated turbulent velocity field

NASA Astrophysics Data System (ADS)

Moreno-Casas, P. A.; Bombardelli, F. A.

2015-12-01

A 3D Lagrangian particle tracking model is coupled to a 3D channel velocity field to simulate the saltation motion of a single sediment particle moving in saltation mode. The turbulent field is a high-resolution three dimensional velocity field that reproduces a by-pass transition to turbulence on a flat plate due to free-stream turbulence passing above de plate. In order to reduce computational costs, a decoupled approached is used, i.e., the turbulent flow is simulated independently from the tracking model, and then used to feed the 3D Lagrangian particle model. The simulations are carried using the point-particle approach. The particle tracking model contains three sub-models, namely, particle free-flight, a post-collision velocity and bed representation sub-models. The free-flight sub-model considers the action of the following forces: submerged weight, non-linear drag, lift, virtual mass, Magnus and Basset forces. The model also includes the effect of particle angular velocity. The post-collision velocities are obtained by applying conservation of angular and linear momentum. The complete model was validated with experimental results from literature within the sand range. Results for particle velocity time series and distribution of particle turbulent intensities are presented.

A new depositional model for sand-rich loess on the Buckley Flats outwash plain, northwestern Lower Michigan

NASA Astrophysics Data System (ADS)

Nyland, Kelsey E.; Schaetzl, Randall J.; Ignatov, Anthony; Miller, Bradley A.

2018-04-01

Loess was first studied in Michigan on the Buckley Flats, where outwash, overlain by ≈70 cm of loamy sediment, was originally interpreted as loess mixed with underlying sands. This paper re-evaluates this landscape through a spatial analysis of data from auger samples and soil pits. To better estimate the loamy sediment's initial textures, we utilized "filtered" laser diffraction data, which remove much of the coarser sand data. Textures of filtered silt data for the loamy sediment are similar to loess. The siltiest soils are found in the low-relief, central part of the Flats. Spatial analyses revealed that many silt fractions are nearly uniformly distributed, suggesting that the loess was not derived from a single source. The previous depositional model for the loamy mantle relied on loessfall followed by pedoturbation, but does not explain (1) the variation in sand contents across the Flats, or (2) the abrupt contact below the loamy mantle. This contact suggests that the outwash was frozen when the sediments above were deposited. Deep gullies at the western margins of the Flats were likely cut as permafrost facilitated runoff. Our new model for the origin of the loamy mantle suggests that the sands on the uplands were generated from eroding gullies and saltated onto the uplands along with loess that fell more widely. Sands saltating to the west of the Flats may have entrained some silts, facilitating loessfall downwind. At most sites, the loamy mantle gets increasingly silty near the surface, suggesting that saltation ended before loess deposition.

Pathological and molecular characterization of systemic isosporosis (atoxoplasmosis) in captive green-winged saltator (Saltator similis).

PubMed

Oliveira, Ayisa Rodrigues de; Souza, Tayse Domingues de; Mol, Juliana P S; Flecher, Mayra Cunha; Hiura, Emy; Santos, Renato Lima

2018-05-15

Systemic isosporosis, also called atoxoplasmosis or visceral coccidiosis, is a disease that affects birds in general. Pathogenesis of systemic isosporosis and its etiologic agent have not been well characterized, but taxonomically Atoxoplasma is currently considered a junior objective synonym of Isospora. The present report aimed to describe pathological and molecular findings of systemic isosporosis in captive green-winged saltators (Saltator similis) from the State of Espírito Santo, Brazil. In a commercial breeding facility eleven birds with two to nine months of age died from 2015 to 2016. These birds developed nonspecific clinical signs, including bristly feathers, hyporexia, loss of weight, and apathy. Two birds were necropsied, and grossly there were hepatomegaly, splenomegaly, necrosis of lymphoid follicles, hepatic necrosis, and severe enteritis. Merozoites were observed in the heart, small intestine, proventriculus, brain, liver, spleen, and kidneys. 23 S RNA PCR amplicons from DNA extracted from the liver and the intestinal contents had 99% identity with Atoxoplasma sp., whereas amplicons of mitochondrial cytochrome c oxidase subunit 1 ha d 97% identity with Isospora greineri. In conclusion, this report indicates that systemic isosporosis in green-winged saltator is a disease that affects the spleen, liver, and small intestine, with high mortality for young birds, resulting in significant loses to commercial breeding facilities. Copyright © 2018 Elsevier B.V. All rights reserved.

Study on sand particles creep model and open pit mine landslide mechanism caused by sand fatigue liquefaction

NASA Astrophysics Data System (ADS)

Du, Dong-Ning; Wang, Lai-Gui; Zhang, Xiang-Dong; Zhang, Shu-Kun

2017-06-01

The sand particles in the sand - rock composite slope of the open pit mine occurs creep deformation and fatigue liquefaction under the action of vehicle load vibration and hydraulic gradient, which causes landslide geological disasters and it destroys the surface environment. To reveal the mechanism, a mechanics model based on the model considering the soil structural change with a new “plastic hinge” element is developed, to improve its constitutive and creep curve equations. Data from sand creep experiments are used to identify the parameters in the model and to validate the model. The results show that the mechanical model can describe the rotation progress between the sand particles, disclose the negative acceleration creep deformation stage during the third phase, and require fewer parameters while maintaining accuracy. It provides a new creep model considering rotation to analyze sand creep mechanism, which provides a theoretical basis for revealing the open pit mine landslide mechanism induced by creep deformation and fatigue liquefaction of sandy soil.

Experimental Study on Clogging of Fine Particles in Sand Sediments

NASA Astrophysics Data System (ADS)

Hirabayashi, S.

2015-12-01

In the methane hydrate development from the sand sediment beneath the seafloor, it is anticipated that the migrating fine particles may block the pore and consequently reduces the permeability near the production well. Although this phenomenon is known as skin formation, its microscopic mechanism is still unknown. As a part of a Japanese National hydrate research program (MH21, funded by METI), we carried out an experiment on the clogging of fine particles in sand sediments. A transparent core holder was newly developed to directly visualize the behavior of fine particles in the pore of frame sands and formation of skin. It was observed that there seems to be an induction time before the clogging starts to occur. Once clogging occurs, the upstream fine particles cannot move downstream anymore and the skin is formed. It was found that the rate of skin formation is related to the total volume of injected fine particles while the flow velocity has something to do with the length of the induction time.

Supply-limited horizontal sand drift at an ephemerally crusted, unvegetated saline playa

USGS Publications Warehouse

Gillette, Dale A.; Niemeyer, T.C.; Helm, P.J.

2001-01-01

A site at Owens Dry Lake was observed for more than 4 years. The site was a vegetation-free saline playa where the surface formed "ephemeral crusts," crusts that form after rainfall. Sometimes these crusts were destroyed and often a layer of particles on the crust would engage in vigorous aeolian activity. Three "phases" of active sand drifting are defined as almost no movement (extreme supply limitation), loose particles on crust with some degree of sand drift (moderate supply limitation), and unlimited source movement corresponding to a destroyed surface crust (unlimited supply). These "phases" occurred 45, 49, and 6% of the time, respectively. The accumulation of loose particles on the crust was mostly the result of in situ formation. Crusted sediments with loose particles on top can exhibit mass flux rates about the same as for noncrusted sediments. Crusted sediments limit or eliminate sand drift in two conditions: for rough crusts that effect a sufficiently high threshold friction velocity (above the wind friction velocity) and for limited amounts of loose particles on the crust where particle supply is less than would be transported in normal saltation for a thick sandy surface. These "supply-limited" cases are similar to wind erosion of limited spilled material on a hard concrete surface. We quantified "supply limitation" by defining a "potential" or "supply unlimited" sand drift function Q = AG where A represents supply limitation that decreases as the particle source is depleted. Here Q is the mass of sand transported through a surface perpendicular to the ground and to the wind and having unit width during time period t, and G = ??? u*(u*2 - u*t2) dt for u* > u*t. G is integrated for the same time period t as for Q, u* is the friction velocity of the wind, and u*t is the threshold friction velocity of the wind. Hard crusts (usually formed in the summer) tended to show almost no change of threshold friction velocity with time and often gave total

Aeolian sand transport over complex intertidal bar-trough beach topography

NASA Astrophysics Data System (ADS)

Anthony, Edward J.; Ruz, Marie-Hélène; Vanhée, Stéphane

2009-04-01

Aeolian sand transport on macrotidal beaches with complex intertidal bar-trough topography (ridge-and-runnel beaches) was assessed from experiments in northern France that involved measurements of wind speed, saltation, surface moisture contents, and rates of sand trapping across surveyed portions of the upper beach profile. Beaches exhibiting intertidal bars and troughs are much more complex, topographically, than simple reflective or dissipative beaches. Furthermore, the intertidal bar-trough morphology commonly exhibits strong cross-shore variations in the moisture contents of the beach surface and in patterns of bedform development. The results of four 30-minute experiments, conducted along topographically surveyed portions of the upper beach-dune toe profile, show that troughs act as extremely efficient sand interceptors, because of their permanently saturated state, which also inhibits sand mobilisation. Troughs, thus, limit or segment the dry fetch during conditions of intermittent saltation. Flow lines, inferred from the wind profiles, suggest that complex interactions at the boundary layer are generated by the bar-trough topography. Troughs systematically appear to be characterised by air expansion, while bar faces generate ramp wind acceleration for onshore winds, and sometimes immediate downwind deceleration for offshore winds. These effects may also contribute to cross-shore variations in the rates of sand trapping. Finally, a simple conceptual model of effective fetch development, integrating the effects of the spring-neap tidal range and of gross bar-trough morphological variability over time, is proposed for bar-trough beaches. The model highlights the key theme of fetch segmentation induced by cross-shore differentiation in the moisture contents of the beach surface hinged on the complex topography of multiple bars and troughs.

Dissociation of Hexavalent Chromium from Sanded Paint Particles into a Simulated Lung Fluid

DTIC Science & Technology

2006-06-01

was simulated with a porcine based mucin . Sanded particles were collected based on particle size into the impactor’s six petri dishes, which...was used to imitate particle deposition onto a layer of lung fluid. The lung fluid was simulated with a porcine based mucin . Sanded particles were...documented as those directly related to corrosion control such as maintenance, repair, treatment , washing, painting, depainting, and sealing. These

A continuously weighing, high frequency sand trap: Wind tunnel and field evaluations

NASA Astrophysics Data System (ADS)

Yang, Fan; Yang, XingHua; Huo, Wen; Ali, Mamtimin; Zheng, XinQian; Zhou, ChengLong; He, Qing

2017-09-01

A new continuously weighing, high frequency sand trap (CWHF) has been designed. Its sampling efficiency is evaluated in a wind tunnel and the potential of the new trap has been demonstrated in field trials. The newly designed sand trap allows fully automated and high frequency measurement of sediment fluxes over extensive periods. We show that it can capture the variations and structures of wind-driven sand transport processes and horizontal sediment flux, and reveal the relationships between sand transport and meteorological parameters. Its maximum sampling frequency can reach 10 Hz. Wind tunnel tests indicated that the sampling efficiency of the CWHF sand trap varies between 39.2 to 64.3%, with an average of 52.5%. It achieved a maximum sampling efficiency of 64.3% at a wind speed of 10 m s- 1. This is largely achieved by the inclusion of a vent hole which leads to a higher sampling efficiency than that of a step-like sand trap at high wind speeds. In field experiments, we show a good agreement between the mass of sediment from the CWHF sand trap, the wind speed at 2 m and the number of saltating particles at 5 cm above the ground surface. According to analysis of the horizontal sediment flux at four heights from the CWHF sand trap (25, 35, 50, and 100 cm), the vertical distribution of the horizontal sediment flux up to a height of 100 cm above the sand surface follows an exponential function. Our field experiments show that the new instrument can capture more detailed information on sediment transport with much reduced labor requirement. Therefore, it has great potential for application in wind-blown sand monitoring and process studies.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pähtz, Thomas, E-mail: 0012136@zju.edu.cn; State Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography, 310012 Hangzhou; Durán, Orencio

Here, we compare two extreme regimes of non-suspended fluid-mediated particle transport, transport in light and heavy fluids (“saltation” and “bedload,” respectively), regarding their particle fluctuation energy balance. From direct numerical simulations, we surprisingly find that the ratio between collisional and fluid drag dissipation of fluctuation energy is significantly larger in saltation than in bedload, even though the contribution of interparticle collisions to transport of momentum and energy is much smaller in saltation due to the low concentration of particles in the transport layer. We conclude that the much higher frequency of high-energy particle-bed impacts (“splash”) in saltation is the causemore » for this counter-intuitive behavior. Moreover, from a comparison of these simulations to particle tracking velocimetry measurements which we performed in a wind tunnel under steady transport of fine and coarse sand, we find that turbulent fluctuations of the flow produce particle fluctuation energy at an unexpectedly high rate in saltation even under conditions for which the effects of turbulence are usually believed to be small.« less

Solid sand particle addition can enhance the production of resting cysts in dinoflagellates

NASA Astrophysics Data System (ADS)

Yang, Aoao; Hu, Zhangxi; Tang, Yingzhong

2018-03-01

Resting cysts are an important part of the life cycle for many harmful algal bloom-forming dinoflagellates, and play vital roles in the recurrence and geographical spread of harmful algal blooms. Numerous factors have been suggested to regulate the formation of resting cysts, although only a few have been proven to be significant. Cyst formation can be induced by adverse environmental conditions such as drastic changes in temperature, light, salinity, and nutrient levels, and by biological interactions. In this study, we evaluated the ability of an artificial factor (fine sand particles) to enhance the formation of resting cysts. Fine sand particles were added to cultures of dinoflagellates that are known to produce cysts. The addition of fine sand particles significantly increased both the production rate and final yield of cysts in cultures of Scrippsiella trochoidea, Biecheleria brevisulcata, and Levanderina fissa (= Gymnodinium fissum, Gyrodinium instriatum, Gyrodinium uncatenum). The largest increase in the final yield (107-fold) of cysts as a result of sand addition was in S. trochoidea. However, addition of fine sand particles did not induce cyst formation, or barely affected cyst formation, in Akashiwo sanguinea, Cochlodinium polykrikoides and Pheopolykrikos hartmannii, which are also known to be cyst-producing species. We speculated that addition of sand significantly increased the chances of cell collision, which triggered cyst formation. However, further research is required to test this idea. Importantly, our findings indicate that the addition of fine sand particles is a useful method to obtain a large quantity of cysts in a short time for laboratory studies or tests; for example, if a cyst viability test is being used to assess the effectiveness of ships' ballast water treatment.

Wind driven saltation: a hitherto overlooked challenge for life on Mars

NASA Astrophysics Data System (ADS)

Bak, Ebbe; Goul, Michael; Rasmussen, Martin; Moeller, Ralf; Nørnberg, Per; Knak Jensen, Svend; Finster, Kai

2017-04-01

The Martian surface is a hostile environment characterized by low water availability, low atmospheric pressure and high UV and ionizing radiation. Furthermore, wind-driven saltation leads to abrasion of silicates with a production of reactive surface sites and, through triboelectric charging, a release of electrical discharges with a concomitant production of reactive oxygen species. While the effects of low water availability, low pressure and radiation have been extensively studied in relation to the habitability of the Martian surface and the preservation of organic biosignatures, the effects of wind-driven saltation have hitherto been ignored. In this study, we have investigated the effect of exposing bacteria to wind-abraded silicates and directly to wind-driven saltation on Mars in controlled laboratory simulation experiments. Wind-driven saltation was simulated by tumbling mineral samples in a Mars-like atmosphere in sealed quartz ampoules. The effects on bacterial survival and structure were evaluated by colony forming unit counts in combination with scanning electron microscopy, quantitative polymerase chain reaction and life/dead-staining with flow cytometry. The viability of vegetative cells of P. putida, B. subtilis and D. radiodurans in aqueous suspensions was reduced by more than 99% by exposure to abraded basalt, while the viability of B. subtilis endospores was unaffected. B. subtilis mutants lacking different spore components were likewise highly resistant to the exposure to abraded basalt, which indicates that the resistance of spores is not associated with any specific spore component. We found a significant but reduced effect of abraded quartz and we suggest that the stress effect of abraded silicates is induced by a production of reactive oxygen species and hydroxyl radicals produced by Fenton-like reactions in the presence of transition metals. Direct exposure to simulated saltation had a dramatic effect on both D. radiodurans cells and B

Computer Modeling of Sand Transport on Mars Using a Compart-Mentalized Fluids Algorithm (CFA)

NASA Technical Reports Server (NTRS)

Marshall, J.; Stratton, D.

1999-01-01

of sand comminution on Mars. A multiple-grain transport model using just the equations of grain motion describing lift and drag is impossible to develop owing to stochastic effects --the very effects we wish to model. Also, unless we were to employ supercomputing techniques and extremely complex computer codes that could deal with millions of grains simultaneously, it would also be difficult to model grain transport if we attempted to consider every grain in motion. No existing computer models were found that satisfactorily used the equations of motion to arrive at transport flux numbers for the different populations of saltation and reptation. Modeling all the grains in a transport system was an intractable problem within our resources, and thus we developed what we believe to be a new modeling approach to simulating grain transport. The CFA deals with grain populations, but considers them to belong to various compartmentalized fluid units in the boundary layer. In this way, the model circumvents the multigrain problem by dealing primarily with the consequences of grain transport --momentum transfer between air and grains, which is the physical essence of a dynamic grain-fluid mixture. We thus chose to model the aeolian transport process as a superposition of fluids. These fluids include the air as well as particle populations of various properties. The prime property distinguishing these fluids is upward and downward grain motion. In a normal saltation trajectory, a grain's downwind velocity increases with time, so a rising grain will have a smaller downwind velocity than a failing grain. Because of this disparity in rising and falling grain proper-ties, it seemed appropriate to track these as two separate grain populations within the same physical space. The air itself can be considered a separate fluid superimposed within and interacting with the various grain-cloud "fluids". Additional informaiton is contained in the original.

Adverse effects of inhaled sand dust particles on the respiratory organs of sheep and goats exposed to severe sand storms in Mongolia.

PubMed

Kobayashi, Yoshimi; Shimada, Akinori; Nemoto, Mai; Morita, Takehito; Adilbish, Altanchimeg; Bayasgalan, Mungun-Ochir

2014-01-01

Sand storms in Mongolia have increased in frequency and scale, resulting in increased exposure of the inhabitants of Asian countries, including Japan and Korea, to Asian sand dust (ASD), which results in adverse effects on the respiratory system. However, there is no information on the health risks of severe sand storms in domestic animals in Mongolia. The aim of the study was to investigate the effects of sand dust particles on the respiratory organs, including the lungs and tracheobronchial lymph nodes, of sheep and goats exposed to severe sand storms in Mongolia. Seven adult sheep and 4 adult goats that had been exposed to sand storms and 3 sheep with no history of exposure were included in this study. Lung tissues and tracheobronchial lymph nodes were subjected to histopathological and immunohistochemical examination. The mineralogical contents of the lungs and lymph nodes were determined using inductively coupled plasma atomic emission spectroscopy. Fibrosis and granulomatous lesions comprising macrophages containing fine sand dust particles were observed exclusively in the lungs of sheep and goats exposed to sand storms. The activity of macrophages was also demonstrated by the presence of IL-6, TNF, and lysozyme. In addition, silicon, which is the major element of ASD (kosa aerosol), was detected exclusively in the lung tissues of the exposed animals. Our findings suggest that exposure to sand dust particles may affect the respiratory systems of domestic animals during their relatively short life span.

Influence of Particle Morphology on 3D Kinematic Behavior and Strain Localization of Sheared Sand

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alshibli, Khalid A.; Jarrar, Maha F.; Druckrey, Andrew M.

The constitutive behavior of sheared sand is highly influenced by particle morphology, gradation, mineralogy, specimen density, loading condition, stress path, and boundary conditions. The current literature lacks a three-dimensional (3D) systematic experimental study that investigates the influence of particle morphology, confining pressure, and specimen density on the failure mode of sheared sand. In this paper, surface texture, roundness, and sphericity of three uniform sands and glass beads with similar grain size were quantified by using 3D images of particles. In situ nondestructive 3D synchrotron microcomputed tomography (SMT) was used to monitor the deformation of medium-dense and very dense dry sandmore » specimens that were tested under axisymmetric triaxial loading condition at 15 and 400 kPa confining pressures. The particles were identified and tracked in 3D as shearing progressed within the specimens, and maps of incremental particle translation and rotation were developed and used to uncover the relationship between particle morphology, specimen density, and confining pressure on the deformation and failure mode of sheared sand. This paper discusses the relationship between the failure mode and particle morphology, specimen density, and confining pressure.« less

[Carbon sequestration in soil particle-sized fractions during reversion of desertification at Mu Us Sand land.

PubMed

Ma, Jian Ye; Tong, Xiao Gang; Li, Zhan Bin; Fu, Guang Jun; Li, Jiao; Hasier

2016-11-18

The aim of this study was to investigate the effects of carbon sequestration in soil particle-sized fractions during reversion of desertification at Mu Us Sand Land, soil samples were collected from quicksand land, semifixed sand and fixed sand lands that were established by the shrub for 20-55 year-old and the arbor for 20-50 year-old at sand control region of Yulin in Northern Shaanxi Province. The dynamics and sequestration rate of soil organic carbon (SOC) associated with sand, silt and clay were measured by physical fractionation method. The results indicated that, compared with quicksand area, the carbon content in total SOC and all soil particle-sized fractions at bothsand-fixing sand forest lands showed a significant increasing trend, and the maximum carbon content was observed in the top layer of soils. From quicksand to fixed sand land with 55-year-old shrub and 50-year-old arbor, the annual sequestration rate of carbon stock in 0-5 cm soil depth was same in silt by 0.05 Mg·hm -2 ·a -1 . The increase rate of carbon sequestration in sand was 0.05 and 0.08 Mg·hm -2 ·a -1 , and in clay was 0.02 and 0.03 Mg·hm -2 ·a -1 at shrubs and arbors land, respectively. The increase rate of carbon sequestration in 0-20 cm soil layer for all the soil particles was averagely 2.1 times as that of 0-5 cm. At the annual increase rate of carbon, the stock of carbon in sand, silt and clay at the two fixed sand lands were increased by 6.7, 18.1 and 4.4 times after 50-55 year-old reversion of quicksand land to fixed sand. In addition, the average percentages that contributed to accumulation of total SOC by different particles in 0-20 cm soil were in the order of silt carbon (39.7%)≈sand carbon (34.6%) > clay carbon (25.6%). Generally, the soil particle-sized fractions had great carbon sequestration potential during reversion of desertification in Mu Us Sand Land, and the slit and sand were the main fractions for carbon sequestration at both fixed sand lands.

Wood dust particle and mass concentrations and filtration efficiency in sanding of wood materials.

PubMed

Welling, Irma; Lehtimäki, Matti; Rautio, Sari; Lähde, Tero; Enbom, Seppo; Hynynen, Pasi; Hämeri, Kaarle

2009-02-01

The importance of fine particles has become apparent as the knowledge of their effects on health has increased. Fine particle concentrations have been published for outside air, plasma arc cutting, welding, and grinding, but little data exists for the woodworking industry. Sanding was evaluated as the producer of the woodworking industry's finest particles, and was selected as the target study. The number of dust particles in different particle size classes and the mass concentrations were measured in the following environments: workplace air during sanding in plywood production and in the inlet and return air; in the dust emission chamber; and in filter testing. The numbers of fine particles were low, less than 10(4) particles/cm(3) (10(7) particles/L). They were much lower than typical number concentrations near 10(6) particles/cm(3) measured in plasma arc cutting, grinding, and welding. Ultrafine particles in the size class less than 100 nm were found during sanding of MDF (medium density fiberboard) sheets. When the cleaned air is returned to the working areas, the dust content in extraction systems must be monitored continuously. One way to monitor the dust content in the return air is to use an after-filter and measure pressure drop across the filter to indicate leaks in the air-cleaning system. The best after-filtration materials provided a clear increase in pressure drop across the filter in the loading of the filter. The best after-filtration materials proved to be quite effective also for fine particles. The best mass removal efficiencies for fine particles around 0.3 mum were over 80% for some filter materials loaded with sanding wood dust.

Self assembly, mobilization, and flotation of crude oil contaminated sand particles as granular shells on gas bubbles in water.

PubMed

Tansel, Berrin; Boglaienko, Daria

2017-01-01

Contaminant fate and transport studies and models include transport mechanisms for colloidal particles and dissolved ions which can be easily moved with water currents. However, mobilization of much larger contaminated granular particles (i.e., sand) in sediments have not been considered as a possible mechanism due to the relatively larger size of sand particles and their high bulk density. We conducted experiments to demonstrate that oil contaminated granular particles (which exhibit hydrophobic characteristics) can attach on gas bubbles to form granular shells and transfer from the sediment phase to the water column. The interactions and conditions necessary for the oil contaminated granular particles to self assemble as tightly packed granular shells on the gas bubbles which transfer from sediment phase to the water column were evaluated both experimentally and theoretically for South Louisiana crude oil and quartz sand particles. Analyses showed that buoyancy forces can be adequate to move the granular shell forming around the air bubbles if the bubble radius is above 0.001mm for the sand particles with 0.28mm diameter. Relatively high magnitude of the Hamaker constant for the oil film between sand and air (5.81×10 -20 J for air-oil-sand) indicates that air bubbles have high affinity to attach on the oil film that is on the sand particles in comparison to attaching to the sand particles without the oil film in water (1.60×10 -20 J for air-water-sand). The mobilization mechanism of the contaminated granular particles with gas bubbles can occur in natural environments resulting in transfer of granular particles from sediments to the water column. Copyright © 2016 Elsevier B.V. All rights reserved.

Adaptation to life in aeolian sand: how the sandfish lizard, Scincus scincus, prevents sand particles from entering its lungs.

PubMed

Stadler, Anna T; Vihar, Boštjan; Günther, Mathias; Huemer, Michaela; Riedl, Martin; Shamiyeh, Stephanie; Mayrhofer, Bernhard; Böhme, Wolfgang; Baumgartner, Werner

2016-11-15

The sandfish lizard, Scincus scincus (Squamata: Scincidae), spends nearly its whole life in aeolian sand and only comes to the surface for foraging, defecating and mating. It is not yet understood how the animal can respire without sand particles entering its respiratory organs when buried under thick layers of sand. In this work, we integrated biological studies, computational calculations and physical experiments to understand this phenomenon. We present a 3D model of the upper respiratory system based on a detailed histological analysis. A 3D-printed version of this model was used in combination with characteristic ventilation patterns for computational calculations and fluid mechanics experiments. By calculating the velocity field, we identified a sharp decrease in velocity in the anterior part of the nasal cavity where mucus and cilia are present. The experiments with the 3D-printed model validate the calculations: particles, if present, were found only in the same area as suggested by the calculations. We postulate that the sandfish has an aerodynamic filtering system; more specifically, that the characteristic morphology of the respiratory channel coupled with specific ventilation patterns prevent particles from entering the lungs. © 2016. Published by The Company of Biologists Ltd.

Generation rate and particle size distribution of wood dust by handheld sanding operation.

PubMed

Ojima, Jun

2016-11-29

The International Agency for Research on Cancer (IARC) and Japan Society for Occupational Health (JSOH) classified wood dust as a human carcinogen. Former studies have suggested that sanding with a portable sander is one of the processes that are liable to cause highest exposure to wood dust. However, the wood dust by sanding operation has not been investigated sufficiently. In this study, the generation rate and the particle size distribution of the wood dust produced by handheld sanding operation were observed by laboratory experiments. Beech and cypress were taken as typical hard and soft wood specimen respectively, and sanded with a portable sander. Three grades of sand paper (coarse, medium, fine) were attached to the sander in turn to be tested. The quantity of the wood dust produced by the sander was measured by weighing the specimen before and after the sanding and then the generation rate of the dust was calculated. Soft wood generated more dust than hard wood due to the difference in abrasion durability. A coarse sand paper produced more dust than a fine sand paper. The particles of less than 1 μm diameter were scarcely observed in the wood dust. When the specimens were sanded with a fine sand paper, the mass median aerodynamic diameters of beech dust and cypress dust were 9.0 μm and 9.8 μm, respectively. Respirable wood dust is able to be controlled by general ventilation with more than 0.7-4.2 m 3 /min ventilation rate.

Generation rate and particle size distribution of wood dust by handheld sanding operation

PubMed Central

Ojima, Jun

2016-01-01

Objectives: The International Agency for Research on Cancer (IARC) and Japan Society for Occupational Health (JSOH) classified wood dust as a human carcinogen. Former studies have suggested that sanding with a portable sander is one of the processes that are liable to cause highest exposure to wood dust. However, the wood dust by sanding operation has not been investigated sufficiently. In this study, the generation rate and the particle size distribution of the wood dust produced by handheld sanding operation were observed by laboratory experiments. Methods: Beech and cypress were taken as typical hard and soft wood specimen respectively, and sanded with a portable sander. Three grades of sand paper (coarse, medium, fine) were attached to the sander in turn to be tested. The quantity of the wood dust produced by the sander was measured by weighing the specimen before and after the sanding and then the generation rate of the dust was calculated. Results: Soft wood generated more dust than hard wood due to the difference in abrasion durability. A coarse sand paper produced more dust than a fine sand paper. The particles of less than 1 μm diameter were scarcely observed in the wood dust. When the specimens were sanded with a fine sand paper, the mass median aerodynamic diameters of beech dust and cypress dust were 9.0 μm and 9.8 μm, respectively. Conclusions: Respirable wood dust is able to be controlled by general ventilation with more than 0.7-4.2 m3/min ventilation rate. PMID:27725491

Spatiotemporal Integration in Somatosensory Perception: Effects of Sensory Saltation on Pointing at Perceived Positions on the Body Surface

PubMed Central

Trojan, Jörg; Stolle, Annette M.; Carl, Antonija Mršić; Kleinböhl, Dieter; Tan, Hong Z.; Hölzl, Rupert

2010-01-01

In the past, sensory saltation phenomena (Geldard and Sherrick, 1972) have been used repeatedly to analyze the spatiotemporal integration capacity of somatosensory and other sensory mechanisms by means of their psychophysical characteristic. The core phenomenon consists in a systematic mislocalization of one tactile stimulus (the attractee) toward another successive tactile stimulus (the attractant) presented at another location, increasing with shorter intervals. In a series of four experiments, sensory saltation characteristics were studied at the forearm and the abdomen. Participants reported the perceived positions of attractees, attractants, and reference stimuli by pointing. In general, saltation characteristics compared well to those reported in previous studies, but we were able to gain several new insights regarding this phenomenon: (a) the attractee–attractant interval did not exclusively affect the perceived attractee position, but also the perceived attractant position; (b) saltation characteristics were very similar at different body sites and orientations, but did show differences suggesting anisotropy (direction-dependency) in the underlying integration processes; (c) sensory saltation could be elicited with stimulation patterns crossing the body midline on the abdomen. In addition to the saltation-specific results, our experiments demonstrate that pointing reports of perceived positions on the body surface generally show pronounced systematic biases compared to veridical positions, moderate intraindividual consistency, and a high degree of inter-individual variability. Finally, we address methodological and terminological controversies concerning the sensory saltation paradigm and discuss its possible neurophysiological basis. PMID:21833262

Stress and Temperature Distributions of Individual Particles in a Shock Wave Propagating through Dry and Wet Sand Mixtures

NASA Astrophysics Data System (ADS)

Schumaker, Merit; Stewart, Sarah T.; Borg, John P.

2015-06-01

Determining stress and temperature distributions of dynamically compacted particles is of interest to the geophysical and astrological research communities. However, these particle interactions during a shock event are not easily observed in planar shock experiments; it is with the utilization of mesoscale simulations that these granular particle interactions can be unraveled. Unlike homogenous materials, the overall averaged hugoniot state for heterogeneous granular materials differs from the individual stress and temperature states of particles during a shock event. From planar shock experiments on dry and wet sand mixtures, simulations were constructed using CTH. A baseline dry sand simulation was also setup to be compared to sand grains that possessed water particles between grains. It is from these simulations that the distributions of stress and temperatures for individual sand and water particles are presented and compared in this document.

Validation of SWEEP for creep, saltation, and suspension in a desert-oasis ecotone

NASA Astrophysics Data System (ADS)

Pi, H.; Sharratt, B.; Feng, G.; Lei, J.; Li, X.; Zheng, Z.

2016-03-01

Wind erosion in the desert-oasis ecotone can accelerate desertification, but little is known about the susceptibility of the ecotone to wind erosion in the Tarim Basin despite being a major source of windblown dust in China. The objective of this study was to test the performance of the Single-event Wind Erosion Evaluation Program (SWEEP) in simulating soil loss as creep, saltation, and suspension in a desert-oasis ecotone. Creep, saltation, and suspension were measured and simulated in a desert-oasis ecotone of the Tarim Basin during discrete periods of high winds in spring 2012 and 2013. The model appeared to adequately simulate total soil loss (ranged from 23 to 2272 g m-2 across sample periods) according to the high index of agreement (d = 0.76). The adequate agreement of the SWEEP in simulating total soil loss was due to the good performance of the model (d = 0.71) in simulating creep plus saltation. The SWEEP model, however, inadequately simulated suspension based upon a low d (⩽0.43). The slope estimates of the regression between simulated and measured suspension and difference of mean suggested that the SWEEP underestimated suspension. The adequate simulation of creep plus saltation thus provides reasonable estimates of total soil loss using SWEEP in a desert-oasis environment.

Field Calibration of the Saltation-Abrasion Model Using Measurements of the Energy Delivered to the Channel Bed

NASA Astrophysics Data System (ADS)

Turowski, J. M.; Wyss, C. R.; Beer, A. R.

2014-12-01

The saltation-abrasion model (SAM) is one of the highest-developed process models for fluvial bedrock erosion, describing bedrock erosion due to the impact of saltating bedload particles. The fundamental assumption in the model is a proportionality of the erosion rate and the energy delivered to the channel bed by these impacts. So far, the SAM has been calibrated on laboratory data, but field tests are rare. Here, we exploit the availability of high-quality field data at the Erlenbach bedload observatory to test and calibrate the SAM. The Erlenbach is a small, steep stream in the Swiss Prealps that hosts a well-instrumented observatory for bedload transport and erosion. Bedload samples can be taken during floods with automatic basket samplers and bedload transport rates are measured continuously with Swiss plate geophones, a surrogate method for bedload monitoring. The geophone plates can also be used to measure the energy transferred to the bed by passingbedload. Thus, we can calibrate the SAM by exploiting independent data on particle impacts, the energy they transfer to the bed, and bedload samples including grain size distributions. We find that the dimensionless pre-factor to the model is dependent on grain size. Predictions of bedrock erosion can be compared to spatial erosion data obtained from successive scans of bedrock slabs installed in the channel bed immediately upstream of the plate geophones.

Turbulent flow structures and aeolian sediment transport over a barchan sand dune

NASA Astrophysics Data System (ADS)

Wiggs, G. F. S.; Weaver, C. M.

2012-03-01

The turbulent structure of airflow over a barchan sand dune is determined using quadrant analysis of wind velocity data derived from sonic anemometers. Results indicate an increased frequency of ejection and sweep events in the toe region of the dune, characteristic of the turbulent bursting process. In contrast, at the crest there was a significant increase in the occurrence of outward interactions. Combined with high frequency saltation data our analyses show that turbulent structures characterised by a positive streamwise fluctuating velocity (+u‧ sweeps at the toe and outward interactions at the crest) have a dominant influence on sand transport on the dune, together accounting for up to 83% and 95% of transporting events at the toe and crest respectively.

3D finite element modelling of force transmission and particle fracture of sand

DOE Office of Scientific and Technical Information (OSTI.GOV)

Imseeh, Wadi H.; Alshibli, Khalid A.

Global compressive loading of granular media causes rearrangements of particles into a denser configuration. Under 1D compression, researchers observed that particles initially translate and rotate which lead to more contacts between particles and the development of force chains to resist applied loads. Particles within force chains resist most of the applied loads while neighbor particles provide lateral support to prevent particles within force chains from buckling. Several experimental and numerical models have been proposed in the literature to characterize force chains within granular materials. This paper presents a 3D finite element (FE) model that simulates 1D compression experiment on F-75more » Ottawa sand. The FE mesh of particles closely matched 3D physical shape of sand particles that were acquired using 3D synchrotron micro-computed tomography (SMT) technique. The paper presents a quantitative assessment of the model, in which evolution of force chains, fracture modes, and stress-strain relationships showed an excellent agreement with experimental measurements reported by Cil et al. Alshibli (2017).« less

Laboratory and field performance of a laser particle counter for measuring aeolian sand transport

NASA Astrophysics Data System (ADS)

Hugenholtz, Chris H.; Barchyn, Thomas E.

2011-03-01

This paper reports the results of laboratory and field tests that evaluate the performance of a new laser particle counter for measuring aeolian sand transport. The Wenglor® model YH03PCT8 ("Wenglor") consists of a laser (655 nm), photo sensor, and switching circuit. When a particle passes through the 0.6 mm diameter, 30 mm long laser beam, the sensor outputs a digital signal. Laboratory tests with medium sand and a vertical gravity flume show that the Wenglor count rate scales approximately linearly with mass flux up to the saturation point of the sensor, after which the count rate decreases despite increasing mass flux. Saturation depends on the diameter and concentration of particles in the airstream and may occur during extreme events in the field. Below saturation sensor performance is relatively consistent; the mean difference between average count rate response was between 50 and 100 counts. Field tests provide a complimentary frame of reference for evaluating the performance of the Wenglor under varying environmental conditions and to gauge its performance with respect to a collocated piezoelectric impact sensor (Sensit H11-B). During 136.5 h of deployment on an active sand dune the relative proportion of time sand transport recorded by two Wenglors was 0.09% and 0.79%, compared to 4.68% by the Sensit H11-B. The weak performance of the Wenglors is attributed to persistent lens contamination from adhesion of sand grains on the sensors after rainfall. However, during dry and windy conditions the Wenglor performance improved substantially; sensors measured a concentration of sand particles in the airstream more than seven times greater than that measured by the Sensit. Between the two Wenglors, the mean absolute count rate difference was 6.16 counts per second, with a standard deviation of 8.53 counts per second. For short-term measurement campaigns in dry conditions, therefore, the Wenglor is relatively consistent and can outperform the Sensit in detecting

Size-Selective Modes of Aeolian Transport on Earth and Mars

NASA Astrophysics Data System (ADS)

Swann, C.; Ewing, R. C.; Sherman, D. J.; McLean, C. J.

2016-12-01

Aeolian sand transport is a dominant driver of surface change and dust emission on Mars. Estimates of aeolian sand transport on Earth and Mars rely on terrestrial transport models that do not differentiate between transport modes (e.g., creep vs. saltation), which limits estimates of the critical threshold for transport and the total sand flux during a transport event. A gap remains in understanding how the different modes contribute to the total sand flux. Experiments conducted at the MARtian Surface WInd Tunnel separated modes of transport for uniform and mixed grain size surfaces at Earth and Martian atmospheric pressures. Crushed walnut shells with a density of 1.0 gm/cm3 were used. Experiments resolved grain size distributions for creeping and saltating grains over 3 uniform surfaces, U1, U2, and U3, with median grain sizes of 308 µm, 721 µm, and 1294 µm, and a mixed grain size surface, M1, with median grain sizes of 519 µm. A mesh trap located 5 cm above the test bed and a surface creep trap were deployed to capture particles moving as saltation and creep. Grains that entered the creep trap at angles ≥ 75° were categorized as moving in creep mode only. Only U1 and M1 surfaces captured enough surface creep at both Earth and Mars pressure for statistically significant grain size analysis. Our experiments show that size selective transport differs between Earth and Mars conditions. The median grain size of particles moving in creep for both uniform and mixed surfaces are larger under Earth conditions. (U1Earth = 385 µm vs. U1Mars = 355 µm; M1Earth = 762 vs. M1Mars = 697 µm ). However, particles moving in saltation were larger under Mars conditions (U1Earth = 282 µm; U1Mars = 309 µm; M1Earth = 347 µm; M1Mars = 454 µm ). Similar to terrestrial experiments, the median size of surface creep is larger than the median grain size of saltation. Median sizes of U1, U2, U3 at Mars conditions for creep was 355 µm, 774 µm and 1574 µm. Saltation at Mars

3D Experimental Measurement of Lattice Strain and Fracture Behavior of Sand Particles Using Synchrotron X-Ray Diffraction and Tomography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cil, Mehmet B.; Alshibli, Khalid A.; Kenesei, Peter

3D synchrotron X-ray diffraction (3DXRD) and synchrotron micro-computed tomography (SMT) techniques were used to measure and monitor the lattice strain evolution and fracture behavior of natural Ottawa sand particles subjected to 1D compression loading. The particle-averaged lattice strain within sand particles was measured using 3DXRD and then was used to calculate the corresponding lattice stress tensor. In addition, the evolution and mode of fracture of sand particles was investigated using high-resolution 3D SMT images. The results of diffraction data analyses revealed that the major principal component of the lattice strain or stress tensor increased in most of the particles asmore » the global applied compressive load increased until the onset of fracture. Particle fracture and subsequent rearrangements caused significant variation and fluctuations in measured lattice strain/stress values from one particle to another and from one load step to the next one. SMT image analysis at the particle-scale showed that cracks in fractured sand particles generally initiate and propagate along the plane that connects the two contact points. Fractured particles initially split into two or three major fragments followed by disintegration into multiple smaller fragments in some cases. In conclusion, microscale analysis of fractured particles showed that particle position, morphology, the number and location of contact points play a major role in the occurrence of particle fracture in confined comminution of the sand assembly.« less

3D Experimental Measurement of Lattice Strain and Fracture Behavior of Sand Particles Using Synchrotron X-Ray Diffraction and Tomography

DOE PAGES

Cil, Mehmet B.; Alshibli, Khalid A.; Kenesei, Peter

2017-05-27

3D synchrotron X-ray diffraction (3DXRD) and synchrotron micro-computed tomography (SMT) techniques were used to measure and monitor the lattice strain evolution and fracture behavior of natural Ottawa sand particles subjected to 1D compression loading. The particle-averaged lattice strain within sand particles was measured using 3DXRD and then was used to calculate the corresponding lattice stress tensor. In addition, the evolution and mode of fracture of sand particles was investigated using high-resolution 3D SMT images. The results of diffraction data analyses revealed that the major principal component of the lattice strain or stress tensor increased in most of the particles asmore » the global applied compressive load increased until the onset of fracture. Particle fracture and subsequent rearrangements caused significant variation and fluctuations in measured lattice strain/stress values from one particle to another and from one load step to the next one. SMT image analysis at the particle-scale showed that cracks in fractured sand particles generally initiate and propagate along the plane that connects the two contact points. Fractured particles initially split into two or three major fragments followed by disintegration into multiple smaller fragments in some cases. In conclusion, microscale analysis of fractured particles showed that particle position, morphology, the number and location of contact points play a major role in the occurrence of particle fracture in confined comminution of the sand assembly.« less

The effect of adsorbed liquid and material density on saltation threshold: Insight from laboratory and wind tunnel experiments

NASA Astrophysics Data System (ADS)

Yu, Xinting; Hörst, Sarah M.; He, Chao; Bridges, Nathan T.; Burr, Devon M.; Sebree, Joshua A.; Smith, James K.

2017-11-01

Saltation threshold, the minimum wind speed for sediment transport, is a fundamental parameter in aeolian processes. Measuring this threshold using boundary layer wind tunnels, in which particles are mobilized by flowing air, for a subset of different planetary conditions can inform our understanding of physical processes of sediment transport. The presence of liquid, such as water on Earth or methane on Titan, may affect the threshold values to a great extent. Sediment density is also crucial for determining threshold values. Here we provide quantitative data on density and water content of common wind tunnel materials (including chromite, basalt, quartz sand, beach sand, glass beads, gas chromatograph packing materials, walnut shells, iced tea powder, activated charcoal, instant coffee, and glass bubbles) that have been used to study conditions on Earth, Titan, Mars, and Venus. The measured density values for low density materials are higher compared to literature values (e.g., ∼30% for walnut shells), whereas for the high density materials, there is no such discrepancy. We also find that low density materials have much higher water content and longer atmospheric equilibration timescales compared to high density sediments. We used thermogravimetric analysis (TGA) to quantify surface and internal water and found that over 80% of the total water content is surface water for low density materials. In the Titan Wind Tunnel (TWT), where Reynolds number conditions similar to those on Titan can be achieved, we performed threshold experiments with the standard walnut shells (125-150 μm, 7.2% water by mass) and dried walnut shells, in which the water content was reduced to 1.7%. The threshold results for the two scenarios are almost the same, which indicates that humidity had a negligible effect on threshold for walnut shells in this experimental regime. When the water content is lower than 11.0%, the interparticle forces are dominated by adsorption forces, whereas at

Identifying, counting, and characterizing superfine activated-carbon particles remaining after coagulation, sedimentation, and sand filtration.

PubMed

Nakazawa, Yoshifumi; Matsui, Yoshihiko; Hanamura, Yusuke; Shinno, Koki; Shirasaki, Nobutaka; Matsushita, Taku

2018-07-01

Superfine powdered activated carbon (SPAC; particle diameter ∼1 μm) has greater adsorptivity for organic molecules than conventionally sized powdered activated carbon (PAC). Although SPAC is currently used in the pretreatment to membrane filtration at drinking water purification plants, it is not used in conventional water treatment consisting of coagulation-flocculation, sedimentation, and rapid sand filtration (CSF), because it is unclear whether CSF can adequately remove SPAC from the water. In this study, we therefore investigated the residual SPAC particles in water after CSF treatment. First, we developed a method to detect and quantify trace concentration of carbon particles in the sand filtrate. This method consisted of 1) sampling particles with a membrane filter and then 2) using image analysis software to manipulate a photomicrograph of the filter so that black spots with a diameter >0.2 μm (considered to be carbon particles) could be visualized. Use of this method revealed that CSF removed a very high percentage of SPAC: approximately 5-log in terms of particle number concentrations and approximately 6-log in terms of particle volume concentrations. When waters containing 7.5-mg/L SPAC and 30-mg/L PAC, concentrations that achieved the same adsorption performance, were treated, the removal rate of SPAC was somewhat superior to that of PAC, and the residual particle number concentrations for SPAC and PAC were at the same low level (100-200 particles/mL). Together, these results suggest that SPAC can be used in place of PAC in CSF treatment without compromising the quality of the filtered water in terms of particulate matter contamination. However, it should be noted that the activated carbon particles after sand filtration were smaller in terms of particle size and were charge-neutralized to a lesser extent than the activated carbon particles before sand filtration. Therefore, the tendency of small particles to escape in the filtrate would appear

Measurements of the Coefficient of Restitution of Quartz Sand on Basalt: Implications for Abrasion Rates on Earth and Mars

NASA Technical Reports Server (NTRS)

Banks, M.; Bridges, N. T.; Benzit, M.

2005-01-01

Knowledge of the rates at which rocks abrade from the impact of saltating sand provides important input into estimating the age and degree of modification of arid surfaces on Earth and Mars. Previous work has relied on measuring mass loss rates in the field and the laboratory. The susceptibility of rocks and other natural materials has been quantified on a relative scale from laboratory studies.

Investigation of Reversing Sand Dunes at the Bruneau Dunes, Idaho, as Analogs for Features on Mars

NASA Astrophysics Data System (ADS)

Zimbelman, J. R.; Scheidt, S. P.

2012-12-01

The Bruneau Dunes in south-central Idaho include several large reversing sand dunes located within a cut-off meander of the Snake River. These dunes include the largest single-structured sand dune present in North America. Wind records from the Remote Automated Weather Station (RAWS) installation at the Mountain Home Air Force Base, which is ~21 km NW of the Bruneau Dunes, have proved to be very helpful in assessing the regional wind patterns at this section of the western Snake River Plains province; a bimodal wind regime is present, with seasonal changes of strong (sand-moving) winds blowing from either the northwest or the southeast. During April of 2011, we obtained ten precision topographic surveys across the southernmost reversing dune using a Differential Global Positioning System (DGPS). The DGPS data document the shape of the dune going from a low, broad sand ridge at the southern distal end of the dune to the symmetrically shaped 112-m-high central portion of the dune, where both flanks of the dune consist of active slopes near the angle of repose. These data will be useful in evaluating the reversing dune hypothesis proposed for enigmatic features on Mars called Transverse Aeolian Ridges (TARs), which could have formed either as large mega-ripples or small sand dunes. The symmetric profiles across TARs with heights greater than 1 m are more consistent with measured profiles of reversing sand dunes than with measured profiles of mega-ripples (whose surfaces are coated by large particles ranging from coarse sand to gravel, moved by saltation-induced creep). Using DGPS to monitor changes in the three-dimensional location of the crests of the reversing dunes at the Bruneau Dunes should provide a means for estimating the likely timescale for changes of TAR crests if the Martian features are indeed formed in the same manner as reversing sand dunes on Earth.

Evidence of repeated and independent saltational evolution in a peculiar genus of sphinx moths (Proserpinus: Sphingidae).

PubMed

Rubinoff, Daniel; Le Roux, Johannes J

2008-01-01

Saltational evolution in which a particular lineage undergoes relatively rapid, significant, and unparalleled change as compared with its closest relatives is rarely invoked as an alternative model to the dominant paradigm of gradualistic evolution. Identifying saltational events is an important first-step in assessing the importance of this discontinuous model in generating evolutionary novelty. We offer evidence for three independent instances of saltational evolution in a charismatic moth genus with only eight species. Maximum parsimony, maximum likelihood and Bayesian search criteria offered congruent, well supported phylogenies based on 1,965 base pairs of DNA sequence using the mitochondrial gene cytochrome oxidase subunit I, and the nuclear genes elongation factor-1 alpha and wingless. Using a comparative methods approach, we examined three taxa exhibiting novelty in the form of Batesian mimicry, host plant shift, and dramatic physiological differences in light of the phylogenetic data. All three traits appear to have evolved relatively rapidly and independently in three different species of Proserpinus. Each saltational species exhibits a markedly different and discrete example of discontinuous trait evolution while remaining canalized for other typical traits shared by the rest of the genus. All three saltational taxa show insignificantly different levels of overall genetic change as compared with their congeners, implying that their divergence is targeted to particular traits and not genome-wide. Such rapid evolution of novel traits in individual species suggests that the pace of evolution can be quick, dramatic, and isolated--even on the species level. These results may be applicable to other groups in which specific taxa have generated pronounced evolutionary novelty. Genetic mechanisms and methods for assessing such relatively rapid changes are postulated.

Evidence of Repeated and Independent Saltational Evolution in a Peculiar Genus of Sphinx Moths (Proserpinus: Sphingidae)

PubMed Central

Rubinoff, Daniel; Le Roux, Johannes J.

2008-01-01

Background Saltational evolution in which a particular lineage undergoes relatively rapid, significant, and unparalleled change as compared with its closest relatives is rarely invoked as an alternative model to the dominant paradigm of gradualistic evolution. Identifying saltational events is an important first-step in assessing the importance of this discontinuous model in generating evolutionary novelty. We offer evidence for three independent instances of saltational evolution in a charismatic moth genus with only eight species. Methodology/Principal Findings Maximum parsimony, maximum likelihood and Bayesian search criteria offered congruent, well supported phylogenies based on 1,965 base pairs of DNA sequence using the mitochondrial gene cytochrome oxidase subunit I, and the nuclear genes elongation factor-1 alpha and wingless. Using a comparative methods approach, we examined three taxa exhibiting novelty in the form of Batesian mimicry, host plant shift, and dramatic physiological differences in light of the phylogenetic data. All three traits appear to have evolved relatively rapidly and independently in three different species of Proserpinus. Each saltational species exhibits a markedly different and discrete example of discontinuous trait evolution while remaining canalized for other typical traits shared by the rest of the genus. All three saltational taxa show insignificantly different levels of overall genetic change as compared with their congeners, implying that their divergence is targeted to particular traits and not genome-wide. Conclusions/Significance Such rapid evolution of novel traits in individual species suggests that the pace of evolution can be quick, dramatic, and isolated—even on the species level. These results may be applicable to other groups in which specific taxa have generated pronounced evolutionary novelty. Genetic mechanisms and methods for assessing such relatively rapid changes are postulated. PMID:19107205

X-ray Computed Tomography Imaging of the Microstructure of Sand Particles Subjected to High Pressure One-Dimensional Compression.

PubMed

Al Mahbub, Asheque; Haque, Asadul

2016-11-03

This paper presents the results of X-ray CT imaging of the microstructure of sand particles subjected to high pressure one-dimensional compression leading to particle crushing. A high resolution X-ray CT machine capable of in situ imaging was employed to capture images of the whole volume of a sand sample subjected to compressive stresses up to 79.3 MPa. Images of the whole sample obtained at different load stages were analysed using a commercial image processing software (Avizo) to reveal various microstructural properties, such as pore and particle volume distributions, spatial distribution of void ratios, relative breakage, and anisotropy of particles.

Dynamic response of sand particles impacted by a rigid spherical object

NASA Astrophysics Data System (ADS)

Youplao, P.; Takita, A.; Nasbey, H.; Yupapin, P. P.; Fujii, Y.

2018-06-01

A method for measuring the dynamic impact responses that acting on a spherical object while dropping and colliding with dried sand, such as the velocity, displacement, acceleration, and resultant force, is presented and discussed. In the experiment, a Michelson-type laser interferometer is employed to obtain the velocity of the spherical stainless steel object. Then the obtained time velocity profile is used to calculate the acceleration, the displacement, and the inertial force acting on the observed sand particles. Furthermore, a high-speed camera is employed to observe the behavior of the sand during the collision. From the experimental results with the sampling interval for frequencies calculation of 1 ms, the combined standard uncertainty in the instantaneous value of the impact force acts on the observed object is obtained and approximated to 0.49 N, which is related to a corresponding 4.07% of the maximum value at 12.05 N of the impact force.

Evidence for discrete solar and lunar orientation mechanisms in the beach amphipod, Talitrus saltator Montagu (Crustacea, Amphipoda)

PubMed Central

Ugolini, Alberto; Hoelters, Laura S.; Ciofini, Alice; Pasquali, Vittorio; Wilcockson, David C.

2016-01-01

Animals that use astronomical cues to orientate must make continuous adjustment to account for temporal changes in azimuth caused by Earth’s rotation. For example, the Monarch butterfly possesses a time-compensated sun compass dependent upon a circadian clock in the antennae. The amphipod Talitrus saltator possesses both a sun compass and a moon compass. We reasoned that the time-compensated compass mechanism that enables solar orientation of T. saltator is located in the antennae, as is the case for Monarch butterflies. We examined activity rhythms and orientation of sandhoppers with antennae surgically removed, or unilaterally occluded with black paint. Removing or painting the antennae did not affect daily activity rhythms or competence to orientate using the sun. However, when tested at night these animals were unable to orientate correctly to the moon. We subsequently measured circadian gene expression in the antennae and brain of T. saltator and show the clock genes period and cryptochrome 2 are rhythmically expressed in both tissues, reminiscent of other arthropods known to possess antennal clocks. Together, our behavioural and molecular data suggest that, T. saltator has anatomically discrete lunar and solar orientation apparatus; a sun compass, likely located in the brain and a moon compass in the antennae. PMID:27759059

Evidence for discrete solar and lunar orientation mechanisms in the beach amphipod, Talitrus saltator Montagu (Crustacea, Amphipoda)

NASA Astrophysics Data System (ADS)

Ugolini, Alberto; Hoelters, Laura S.; Ciofini, Alice; Pasquali, Vittorio; Wilcockson, David C.

2016-10-01

Animals that use astronomical cues to orientate must make continuous adjustment to account for temporal changes in azimuth caused by Earth’s rotation. For example, the Monarch butterfly possesses a time-compensated sun compass dependent upon a circadian clock in the antennae. The amphipod Talitrus saltator possesses both a sun compass and a moon compass. We reasoned that the time-compensated compass mechanism that enables solar orientation of T. saltator is located in the antennae, as is the case for Monarch butterflies. We examined activity rhythms and orientation of sandhoppers with antennae surgically removed, or unilaterally occluded with black paint. Removing or painting the antennae did not affect daily activity rhythms or competence to orientate using the sun. However, when tested at night these animals were unable to orientate correctly to the moon. We subsequently measured circadian gene expression in the antennae and brain of T. saltator and show the clock genes period and cryptochrome 2 are rhythmically expressed in both tissues, reminiscent of other arthropods known to possess antennal clocks. Together, our behavioural and molecular data suggest that, T. saltator has anatomically discrete lunar and solar orientation apparatus; a sun compass, likely located in the brain and a moon compass in the antennae.

Sediment Particle Characterization for Acoustic Applications: Coarse Content, Size and Shape Distributions in a Shelly Sand/Mud Environment

DTIC Science & Technology

2009-03-31

Distributions in a Shelly Sand/Mud Environment Anatoliy N. Ivakin M A Ivakin. Particle size and shape distributions 2 Goff et al . [3] came to a...site, 37.0=P and 65.2=sρ g /cm 3 [19], were used for calculations. The sediment volume for calculations was taken to be 1885 cm 3 for each of the...typical values used for densities of quartz (sand) particles and calcium carbonate (shell) particles were taken to be 2.65 g /cm 3 and 2.75 g /cm 3

X-ray Computed Tomography Imaging of the Microstructure of Sand Particles Subjected to High Pressure One-Dimensional Compression

PubMed Central

al Mahbub, Asheque; Haque, Asadul

2016-01-01

This paper presents the results of X-ray CT imaging of the microstructure of sand particles subjected to high pressure one-dimensional compression leading to particle crushing. A high resolution X-ray CT machine capable of in situ imaging was employed to capture images of the whole volume of a sand sample subjected to compressive stresses up to 79.3 MPa. Images of the whole sample obtained at different load stages were analysed using a commercial image processing software (Avizo) to reveal various microstructural properties, such as pore and particle volume distributions, spatial distribution of void ratios, relative breakage, and anisotropy of particles. PMID:28774011

Enhanced transport of biodegradable polymer-coated nanoiron particles in sand columns

NASA Astrophysics Data System (ADS)

Jung, B.; O'Carroll, D.; Sleep, B.

2009-05-01

The use of nanoscale zerovalent iron has shown promise as a technology for remediation of subsurface contamination by chlorinated solvents. However, the delivery of nanoiron particles to target contaminated subsurface zones is hindered by the aggregation of particles due to magnetic attraction. To overcome the limitations of aggregation and increase nanoiron mobility in porous media, nanoiron particles have been coated with various polymers. Polymer adsorption onto nanoiron particles provides electrosteric stabilization, increases the mobility, and decreases the attachment onto the soil surface. Various polymers were investigated in this study, including carboxylmethyl cellulose (CMC) and guar gum, both of which are biodegradable. In sand column experiments the transport of nanoiron particles was investigated as a function of type of electrolyte, ionic strength, flow velocity, and nanoiron particle concentration. Settling curves showed the enhanced stability of polymer-coated nanoiron particles compared to bare commercial nanoiron particles (bare RNIP-10DS). A newly developed nanoparticle transport numerical model was used to quantify the attachment efficiency, as well as investigate dominant nanoparticle transport and removal mechanisms. Finally the particle-collector interaction energy was predicted using DLVO (Derjaguin-Landau-Verwey-Overbeek) theory.

Does the Auditory Saltation Stimulus Distinguish Dyslexic from Competently Reading Adults?

ERIC Educational Resources Information Center

Kidd, Joanna C.; Hogben, John H.

2007-01-01

Purpose: Where the auditory saltation illusion has been used as a measure of auditory temporal processing (ATP) in dyslexia, conflicting results have been apparent (cf. R. Hari & P. Kiesila, 1996; M. Kronbichler, F. Hutzler, & H. Wimmer, 2002). This study sought to re-examine these findings by investigating whether dyslexia is characterized by…

Intrachromosomal rearrangements in two representatives of the genus Saltator (Thraupidae, Passeriformes) and the occurrence of heteromorphic Z chromosomes.

PubMed

dos Santos, Michelly da Silva; Kretschmer, Rafael; Silva, Fabio Augusto Oliveira; Ledesma, Mario Angel; O'Brien, Patricia C M; Ferguson-Smith, Malcolm A; Del Valle Garnero, Analía; de Oliveira, Edivaldo Herculano Corrêa; Gunski, Ricardo José

2015-10-01

Saltator is a genus within family Thraupidae, the second largest family of Passeriformes, with more than 370 species found exclusively in the New World. Despite this, only a few species have had their karyotypes analyzed, most of them only with conventional staining. The diploid number is close to 80, and chromosome morphology is similar to the usual avian karyotype. Recent studies using cross-species chromosome painting have shown that, although the chromosomal morphology and number are similar to many species of birds, Passeriformes exhibit a complex pattern of paracentric and pericentric inversions in the chromosome homologous to GGA1q in two different suborders, Oscines and Suboscines. Hence, considering the importance and species richness of Thraupidae, this study aims to analyze two species of genus Saltator, the golden-billed saltator (S. aurantiirostris) and the green-winged saltator (S. similis) by means of classical cytogenetics and cross-species chromosome painting using Gallus gallus and Leucopternis albicollis probes, and also 5S and 18S rDNA and telomeric sequences. The results show that the karyotypes of these species are similar to other species of Passeriformes. Interestingly, the Z chromosome appears heteromorphic in S. similis, varying in morphology from acrocentric to metacentric. 5S and 18S probes hybridize to one pair of microchromosomes each, and telomeric sequences produce signals only in the terminal regions of chromosomes. FISH results are very similar to the Passeriformes already analyzed by means of molecular cytogenetics (Turdus species and Elaenia spectabilis). However, the paracentric and pericentric inversions observed in Saltator are different from those detected in these species, an observation that helps to explain the probable sequence of rearrangements. As these rearrangements are found in both suborders of Passeriformes (Oscines and Suboscines), we propose that the fission of GGA1 and inversions in GGA1q have occurred very

Association of Sand Dust Particles with Pulmonary Function and Respiratory Symptoms in Adult Patients with Asthma in Western Japan Using Light Detection and Ranging: A Panel Study

PubMed Central

Watanabe, Masanari; Noma, Hisashi; Kurai, Jun; Shimizu, Atsushi; Sano, Hiroyuki; Kato, Kazuhiro; Mikami, Masaaki; Ueda, Yasuto; Tatsukawa, Toshiyuki; Ohga, Hideki; Yamasaki, Akira; Igishi, Tadashi; Kitano, Hiroya; Shimizu, Eiji

2015-01-01

Light detection and ranging (LIDAR) can estimate daily volumes of sand dust particles from the East Asian desert to Japan. The objective of this study was to investigate the relationship between sand dust particles and pulmonary function, and respiratory symptoms in adult patients with asthma. One hundred thirty-seven patients were included in the study. From March 2013 to May 2013, the patients measured their morning peak expiratory flow (PEF) and kept daily lower respiratory symptom diaries. A linear mixed model was used to estimate the correlation of the median daily levels of sand dust particles, symptoms scores, and PEF. A heavy sand dust day was defined as an hourly concentration of sand dust particles of >0.1 km−1. By this criterion, there were 8 heavy sand dust days during the study period. Elevated sand dust particles levels were significantly associated with the symptom score (0.04; 95% confidence interval (CI); 0.03, 0.05), and this increase persisted for 5 days. There was no significant association between PEF and heavy dust exposure (0.01 L/min; 95% CI, −0.62, 0.11). The present study found that sand dust particles were significantly associated with worsened lower respiratory tract symptoms in adult patients with asthma, but not with pulmonary function. PMID:26501307

Stress and temperature distributions of individual particles in a shock wave propagating through dry and wet sand mixtures

NASA Astrophysics Data System (ADS)

Schumaker, Merit G.; Kennedy, Gregory; Thadhani, Naresh; Hankin, Markos; Stewart, Sarah T.; Borg, John P.

2017-01-01

Determining stress and temperature distributions of dynamically compacted particles is of interest to the geophysical and astrological research communities. However, the researcher cannot easily observe particle interactions during a planar shock experiment. By using mesoscale simulations, we can unravel granular particle interactions. Unlike homogenous materials, the averaged Hugoniot state for heterogeneous granular materials differs from the individual stress and temperature states of particles during a shock event. From planar shock experiments for dry and water-saturated Oklahoma sand, we constructed simulations using Sandia National Laboratory code known as CTH and then compared these simulated results to the experimental results. This document compares and presents stress and temperature distributions from simulations, with a discussion on the difference between Hugoniot measurements and distribution peaks for dry and water-saturated sand.

Strong feedbacks between hillslope sediment production and channel incision by saltation-abrasion

NASA Astrophysics Data System (ADS)

Lundbek Egholm, David; Faurschou Knudsen, Mads; Sandiford, Mike

2013-04-01

While it is well understood that rivers erode mountain ranges by incising the bedrock and by transporting sediments away from the ranges, the basic physical mechanisms that drive long-term bedrock erosion and control the lifespan of mountain ranges remain uncertain. A particularly challenging paradox is reconciling the dichotomy associated with the high incision rates observed in active mountain belts, and the long-term (108 years) preservation of significant topographic reliefs in inactive orogenic belts (e.g. von Blankenburg, 2005). We have performed three-dimensional computational experiments with a landscape evolution model that couples bedrock landslides and sediment flux-dependent river erosion by saltation-abrasion (Sklar & Dietrich, 2004). The coupled model experiments show strong feedbacks between the channel erosion and the hillslope delivery of sediments. The feedbacks point to hillslope sediment production rate as the main control on channel erosion rates where saltation-abrasion dominates over other fluvial erosion processes. Our models results thus highlight the importance of hillslope sediment production controlled by climate and tectonic activity for scaling erosion rates in fluvial systems. Because of variations in landslide frequency, the feedbacks make tectonic activity a primary driver of fluvial erosion and help clarifying the long-standing paradox associated with the persistence of significant relief in old orogenic belts, up to several hundred-million-years after tectonic activity has effectively ceased. References F. von Blankenburg. The control mechanisms of erosion and weathering at basin scale from cosmogenic nuclides in river sediment. Earth Planet. Sci. Lett. 237, 462-479 (2005). L. S. Sklar, W. E. Dietrich. A mechanistic model for river incision into bedrock by saltating bed load. Water Resour. Res. 40, W06301 (2004).

Influence of the coating level on the heterogeneous ozonolysis kinetics and product yields of chlorpyrifos ethyl adsorbed on sand particles.

PubMed

El Masri, Ahmad; Laversin, Hélène; Chakir, Abdelkhaleq; Roth, Estelle

2016-12-01

Heterogeneous oxidation of chlorpyrifos ethyl (CLP) coated sand particles by gaseous ozone was studied. Mono-size sand was coated with CLP at different coating levels between 10 and 100 μg g -1 and exposed to ozone. Results were analyzed thanks to Gas Surface Reaction and Surface Layer Reaction Models. Kinetic parameters derived from these models were analyzed and led to several conclusions. The equilibrium constant of O 3 between the gas phase and the CLP-coated sand was independent on the sand contamination level. Ozone seems to have similar affinity for coated or uncoated sand surface. Meanwhile, the kinetic parameters decreased with an increasing coating level. Chlorpyrifos Oxon, (CLPO) has been identified and quantified as an ozonolysis product. The product yield of CLPO remains constant (53 ± 10%) for the different coating level. The key parameter influencing the CLP reactivity towards ozone was the CLP-coating level. This dependence had a great influence on the lifetime of the CLP coated on sand particles, with respect to ozone, which could reach several years at high contamination level. Copyright © 2016 Elsevier Ltd. All rights reserved.

Association between pulmonary function and daily levels of sand dust particles assessed by light detection and ranging in schoolchildren in western Japan: A panel study.

PubMed

Watanabe, Masanari; Noma, Hisashi; Kurai, Jun; Kato, Kazuhiro; Sano, Hiroyuki; Tatsukawa, Toshiyuki; Nakazaki, Hirofumi; Yamasaki, Akira; Shimizu, Eiji

2016-01-01

An important aspect of sand dust emissions in association with respiratory disorders is the quantity of particulate matter. This is usually expressed as particulate matter less than 10 μm (PM10) and 2.5 μm (PM2.5). However, the composition of PM10 and PM2.5 varies. Light detection and ranging is used to monitor sand dust particles originating in East Asian deserts and distinguish them from air pollution aerosols. The objective of this study was to investigate the association between the daily levels of sand dust particles and pulmonary function in schoolchildren in western Japan. In this panel study, the peak expiratory flow (PEF) of 399 schoolchildren was measured daily from April to May 2012. A linear mixed model was used to estimate the association of PEF with the daily levels of sand dust particles, suspended particulate matter (SPM), and PM2.5. There was no association between the daily level of sand dust particles and air pollution aerosols, while both sand dust particles and air pollution aerosols had a significant association with SPM and PM2.5. An increment of 0.018 km(-1) in sand dust particles was significantly associated with a decrease in PEF (-3.62 L/min; 95% confidence interval, -4.66 to -2.59). An increase of 14.0 μg/m(3) in SPM and 10.7 μg/m(3) in PM2.5 led to a significant decrease of -2.16 L/min (-2.88 to -1.43) and -2.58 L/min (-3.59 to -1.57), respectively, in PEF. These results suggest that exposure to sand dust emission may relate to pulmonary dysfunction in children in East Asia. Copyright © 2015 The Authors. Production and hosting by Elsevier B.V. All rights reserved.

A combined CFD-experimental method for developing an erosion equation for both gas-sand and liquid-sand flows

NASA Astrophysics Data System (ADS)

Mansouri, Amir

The surface degradation of equipment due to consecutive impacts of abrasive particles carried by fluid flow is called solid particle erosion. Solid particle erosion occurs in many industries including oil and gas. In order to prevent abrupt failures and costly repairs, it is essential to predict the erosion rate and identify the locations of the equipment that are mostly at risk. Computational Fluid Dynamics (CFD) is a powerful tool for predicting the erosion rate. Erosion prediction using CFD analysis includes three steps: (1) obtaining flow solution, (2) particle tracking and calculating the particle impact speed and angle, and (3) relating the particle impact information to mass loss of material through an erosion equation. Erosion equations are commonly generated using dry impingement jet tests (sand-air), since the particle impact speed and angle are assumed not to deviate from conditions in the jet. However, in slurry flows, a wide range of particle impact speeds and angles are produced in a single slurry jet test with liquid and sand particles. In this study, a novel and combined CFD/experimental method for developing an erosion equation in slurry flows is presented. In this method, a CFD analysis is used to characterize the particle impact speed, angle, and impact rate at specific locations on the test sample. Then, the particle impact data are related to the measured erosion depth to achieve an erosion equation from submerged testing. Traditionally, it was assumed that the erosion equation developed based on gas testing can be used for both gas-sand and liquid-sand flows. The erosion equations developed in this work were implemented in a CFD code, and CFD predictions were validated for various test conditions. It was shown that the erosion equation developed based on slurry tests can significantly improve the local thickness loss prediction in slurry flows. Finally, a generalized erosion equation is proposed which can be used to predict the erosion rate in

Advanced Techniques for Simulating the Behavior of Sand

NASA Astrophysics Data System (ADS)

Clothier, M.; Bailey, M.

2009-12-01

Computer graphics and visualization techniques continue to provide untapped research opportunities, particularly when working with earth science disciplines. Through collaboration with the Oregon Space Grant and IGERT Ecosystem Informatics programs we are developing new techniques for simulating sand. In addition, through collaboration with the Oregon Space Grant, we’ve been communicating with the Jet Propulsion Laboratory (JPL) to exchange ideas and gain feedback on our work. More specifically, JPL’s DARTS Laboratory specializes in planetary vehicle simulation, such as the Mars rovers. This simulation utilizes a virtual "sand box" to test how planetary rovers respond to different terrains while traversing them. Unfortunately, this simulation is unable to fully mimic the harsh, sandy environments of those found on Mars. Ideally, these simulations should allow a rover to interact with the sand beneath it, particularly for different sand granularities and densities. In particular, there may be situations where a rover may become stuck in sand due to lack of friction between the sand and wheels. In fact, in May 2009, the Spirit rover became stuck in the Martian sand and has provided additional motivation for this research. In order to develop a new sand simulation model, high performance computing will play a very important role in this work. More specifically, graphics processing units (GPUs) are useful due to their ability to run general purpose algorithms and ability to perform massively parallel computations. In prior research, simulating vast quantities of sand has been difficult to compute in real-time due to the computational complexity of many colliding particles. With the use of GPUs however, each particle collision will be parallelized, allowing for a dramatic performance increase. In addition, spatial partitioning will also provide a speed boost as this will help limit the number of particle collision calculations. However, since the goal of this

Identification and temporal expression of putative circadian clock transcripts in the amphipod crustacean Talitrus saltator

PubMed Central

O’Grady, Joseph F.; Hoelters, Laura S.; Swain, Martin T.

2016-01-01

Background Talitrus saltator is an amphipod crustacean that inhabits the supralittoral zone on sandy beaches in the Northeast Atlantic and Mediterranean. T. saltator exhibits endogenous locomotor activity rhythms and time-compensated sun and moon orientation, both of which necessitate at least one chronometric mechanism. Whilst their behaviour is well studied, currently there are no descriptions of the underlying molecular components of a biological clock in this animal, and very few in other crustacean species. Methods We harvested brain tissue from animals expressing robust circadian activity rhythms and used homology cloning and Illumina RNAseq approaches to sequence and identify the core circadian clock and clock-related genes in these samples. We assessed the temporal expression of these genes in time-course samples from rhythmic animals using RNAseq. Results We identified a comprehensive suite of circadian clock gene homologues in T. saltator including the ‘core’ clock genes period (Talper), cryptochrome 2 (Talcry2), timeless (Taltim), clock (Talclk), and bmal1 (Talbmal1). In addition we describe the sequence and putative structures of 23 clock-associated genes including two unusual, extended isoforms of pigment dispersing hormone (Talpdh). We examined time-course RNAseq expression data, derived from tissues harvested from behaviourally rhythmic animals, to reveal rhythmic expression of these genes with approximately circadian period in Talper and Talbmal1. Of the clock-related genes, casein kinase IIβ (TalckIIβ), ebony (Talebony), jetlag (Taljetlag), pigment dispensing hormone (Talpdh), protein phosphatase 1 (Talpp1), shaggy (Talshaggy), sirt1 (Talsirt1), sirt7 (Talsirt7) and supernumerary limbs (Talslimb) show temporal changes in expression. Discussion We report the sequences of principle genes that comprise the circadian clock of T. saltator and highlight the conserved structural and functional domains of their deduced cognate proteins. Our

The effect of dust lifting process on the electrical properties of the atmosphere

NASA Astrophysics Data System (ADS)

Esposito, Francesca; Molinaro, Roberto; Ionut Popa, Ciprian; Molfese, Cesare; Cozzolino, Fabio; Marty, Laurent; Taj-Eddine, Kamal; Di Achille, Gaetano; Silvestro, Simone; Ori, Gian Gabriele

2015-04-01

Airborne dust and aerosol particles affect climate by absorbing and scattering thermal and solar radiation and acting as condensation nuclei for the formation of clouds. So, they strongly influence the atmospheric thermal structure, balance and circulation. On Earth and Mars, this 'climate forcing' is one of the most uncertain processes in climate change predictions. Wind-driven blowing of sand and dust is also responsible for shaping planetary surfaces through the formation of sand dunes and ripples, the erosion of rocks, and the creation and transport of soil particles. These processes are not confined to Earth, but occur also on Mars, Venus and Titan. It is clear that the knowledge of the atmospheric dust properties and the mechanisms of dust settling and raising into the atmosphere are important to understand planetary climate and surface evolution. On Mars the physical processes responsible for dust injection into the atmosphere are still poorly understood, but they likely involve saltation as on Earth. Saltation is a process where large sand grains are forced by the wind to move in ballistic trajectories on the soil surface. During these hops they hit dust particles, that are well bound to the soil due to interparticle cohesive forces, thus transferring to them the momentum necessary to be entrained into the atmosphere. Recently, it has been shown that this process is also responsible to generate strong electric fields in the atmosphere up to 100-150 kV/m. This enhanced electric force acts as a feedback in the dust lifting process, lowering the threshold of the wind friction velocity u* necessary to initiate sand saltation. It is an important aspect of dust lifting process that need to be well characterized and modeled. Even if literature reports several measurements of E-fields in dust devils events, very few reports deal with atmospheric electric properties during dust storms or isolated gusts. We present here preliminary results of an intense field test

The impact of particle shape on the angle of internal friction and the implications for sediment dynamics at a steep, mixed sand-gravel beach

NASA Astrophysics Data System (ADS)

Stark, N.; Hay, A. E.; Cheel, R.; Lake, C. B.

2014-08-01

The impact of particle shape on the angle of internal friction, and the resulting impact on beach sediment dynamics, is still poorly understood. In areas characterized by sediments of specific shape, particularly non-rounded particles, this can lead to large departures from the expected sediment dynamics. The steep slope (1 : 10) of the mixed sand-gravel beach at Advocate Harbour is stable in large-scale morphology over decades, despite a high tidal range of 10 m or more, and intense shore-break action during storms. The Advocate sand (d < 2 mm) was found to have an elliptic, plate-like shape (Corey Shape Index, CSI ≈ 0.2-0.6). High angles of internal friction of this material were determined using direct shear, ranging from φ ≈ 41 to 49°, while the round to angular gravel was characterized as φ = 33°. The addition of 25% of the elliptic plate-like sand-sized material to the gravel led to an immediate increase in friction angle to φ = 38°. Furthermore, re-organization of the particles occurred during shearing, characterized by a short phase of settling and compaction, followed by a pronounced strong dilatory behavior and an accompanying strong increase of resistance to shear and, thus, shear stress. Long-term shearing (24 h) using a ring shear apparatus led to destruction of the particles without re-compaction. Finally, submerged particle mobilization was simulated using a tilted tray submerged in a water-filled tank. Despite a smooth tray surface, particle motion was not initiated until reaching tray tilt angles of 31° and more, being ≥7° steeper than for motion initiation of the gravel mixtures. In conclusion, geotechnical laboratory experiments quantified the important impact of the elliptic, plate-like shape of Advocate Beach sand on the angles of internal friction of both pure sand and sand-gravel mixtures. The resulting effect on initiation of particle motion was confirmed in tilting tray experiments. This makes it a vivid example of how

Granular encapsulation of light hydrophobic liquids (LHL) in LHL-salt water systems: Particle induced densification with quartz sand.

PubMed

Boglaienko, Daria; Tansel, Berrin; Sukop, Michael C

2016-02-01

Addition of granular materials to floating crude oil slicks can be effective in capturing and densifying the floating hydrophobic phase, which settles by gravity. Interaction of light hydrophobic liquids (LHL) with quartz sand was investigated in LHL-salt water systems. The LHLs studied were decane, tetradecane, hexadecane, benzene, toluene, ethylbenzene, m-xylene, and 2-cholorotoluene. Experiments were conducted with fine quartz sand (passing sieve No. 40 with openings 0.425 mm). Each LHL was dyed with few crystals of Sudan IV dye for ease of visual observation. A volume of 0.5 mL of each LHL was added to 100 mL salt water (34 g/L). Addition of one gram of quartz sand to the floating hydrophobic liquid layer resulted in formation of sand-encapsulated globules, which settled due to increased density. All LHLs (except for a few globules of decane) formed globules covered with fine sand particles that were heavy enough to settle by gravity. The encapsulated globules were stable and retained their shape upon settling. Polarity of hydrophobic liquids as the main factor of aggregation with minerals was found to be insufficient to explain LHL aggregation with sand. Contact angle measurements were made by submerging a large quartz crystal with the LHL drop on its surface into salt water. A positive correlation was observed between the wetting angle of LHL and the LHL volume captured (r = 0.75). The dependence of the globule density on globule radius was analyzed in relation to the coverage (%) of globule surface (LHL-salt water interface) by fine quartz particles. Copyright © 2015 Elsevier Ltd. All rights reserved.

Threshold Velocity for Saltation Activity in the Taklimakan Desert

NASA Astrophysics Data System (ADS)

Yang, Xinghua; He, Qing; Matimin, Ali; Yang, Fan; Huo, Wen; Liu, Xinchun; Zhao, Tianliang; Shen, Shuanghe

2017-12-01

The threshold velocity is an indicator of a soil's susceptibility to saltation activity and is also an important parameter in dust emission models. In this study, the saltation activity, atmospheric conditions, and soil conditions were measured from 1 August 2008 to 31 July 2009 in the Taklimakan Desert, China. the threshold velocity was estimated using the Gaussian time fraction equivalence method. At 2 m height, the 1-min averaged threshold velocity varied between 3.5 and 10.9 m/s, with a mean of 5.9 m/s. Threshold velocities varying between 4.5 and 7.5 m/s accounted for about 91.4% of all measurements. The average threshold velocity displayed clear seasonal variations in the following sequence: winter (5.1 m/s) < autumn (5.8 m/s) < spring (6.1 m/s) < summer (6.5 m/s). A regression equation of threshold velocity was established based on the relations between daily mean threshold velocity and air temperature, specific humidity, and soil volumetric moisture content. High or moderate positive correlations were found between threshold velocity and air temperature, specific humidity, and soil volumetric moisture content (air temperature r = 0.75; specific humidity r = 0.59; and soil volumetric moisture content r = 0.55; sample size = 251). In the study area, the observed horizontal dust flux was 4198.0 kg/m during the whole period of observation, while the horizontal dust flux calculated using the threshold velocity from the regression equation was 4675.6 kg/m. The correlation coefficient between the calculated result and the observations was 0.91. These results indicate that atmospheric and soil conditions should not be neglected in parameterization schemes for threshold velocity.

Disturbance of the inclined inserting-type sand fence to wind-sand flow fields and its sand control characteristics

NASA Astrophysics Data System (ADS)

Cheng, Jian-jun; Lei, Jia-qiang; Li, Sheng-yu; Wang, Hai-feng

2016-06-01

The inclined inserting-type sand fence is a novel sand retaining wall adopted along the Lanxin High-Speed Railway II in Xinjiang for controlling and blocking sand movement. To verify the effectiveness of the new fence structure for sand prevention, a wind tunnel test was used for flow field test simulation of the sand fence. The results indicate that the inclined inserting-type sand fence was able to deflect the flow of the sand and was able to easily form an upward slant acceleration zone on the leeward side of the sand fence. As shown by the percentage change in sand collection rates on the windward side and the leeward side of the sand fence, the sand flux per unit area at 4 m height in the slant upward direction increased on the leeward side of the inclined inserting-type sand fence. By comparing the flow fields, this site is an acceleration zone, which also reaffirms the correspondence of wind-sand flow fields with the spatial distribution characteristic of the wind-carried sand motion. The field sand collection data indicates that under the effects of the inclined inserting-type sand fence, the sandy air currents passing in front and behind the sand fence not only changed in quality, but the grain composition and particle size also significantly changed, suggesting that the inclined inserting-type sand fence has a sorting and filtering effect on the sandy air currents that passed through. The fence retained coarse particulates on the windward side and fine particulates within the shade of the wind on the leeward side.

Comparative Emissions of Random Orbital Sanding between Conventional and Self-Generated Vacuum Systems

PubMed Central

Liverseed, David R.

2013-01-01

Conventional abrasive sanding generates high concentrations of particles. Depending on the substrate being abraded and exposure duration, overexposure to the particles can cause negative health effects ranging from respiratory irritation to cancer. The goal of this study was to understand the differences in particle emissions between a conventional random orbital sanding system and a self-generated vacuum random orbital sanding system with attached particle filtration bag. Particle concentrations were sampled for each system in a controlled test chamber for oak wood, chromate painted (hexavalent chromium) steel panels, and gel-coated (titanium dioxide) fiberglass panels using a Gesamtstaub-Probenahmesystem (GSP) sampler at three different locations adjacent to the sanding. Elevated concentrations were reported for all particles in the samples collected during conventional sanding. The geometric mean concentration ratios for the three substrates ranged from 320 to 4640 times greater for the conventional sanding system than the self-generated vacuum sanding system. The differences in the particle concentration generated by the two sanding systems were statistically significant with the two sample t-test (P < 0.0001) for all three substances. The data suggest that workers using conventional sanding systems could utilize the self-generated vacuum sanding system technology to potentially reduce exposure to particles and mitigate negative health effects. PMID:23065674

Comparative emissions of random orbital sanding between conventional and self-generated vacuum systems.

PubMed

Liverseed, David R; Logan, Perry W; Johnson, Carl E; Morey, Sandy Z; Raynor, Peter C

2013-03-01

Conventional abrasive sanding generates high concentrations of particles. Depending on the substrate being abraded and exposure duration, overexposure to the particles can cause negative health effects ranging from respiratory irritation to cancer. The goal of this study was to understand the differences in particle emissions between a conventional random orbital sanding system and a self-generated vacuum random orbital sanding system with attached particle filtration bag. Particle concentrations were sampled for each system in a controlled test chamber for oak wood, chromate painted (hexavalent chromium) steel panels, and gel-coated (titanium dioxide) fiberglass panels using a Gesamtstaub-Probenahmesystem (GSP) sampler at three different locations adjacent to the sanding. Elevated concentrations were reported for all particles in the samples collected during conventional sanding. The geometric mean concentration ratios for the three substrates ranged from 320 to 4640 times greater for the conventional sanding system than the self-generated vacuum sanding system. The differences in the particle concentration generated by the two sanding systems were statistically significant with the two sample t-test (P < 0.0001) for all three substances. The data suggest that workers using conventional sanding systems could utilize the self-generated vacuum sanding system technology to potentially reduce exposure to particles and mitigate negative health effects.

Aeolian transport of biota with dust: A wind tunnel experiment

NASA Astrophysics Data System (ADS)

Rivas, J. A., Jr.; Gill, T. E.; Van Pelt, R. S.; Walsh, E.

2015-12-01

Ephemeral wetlands are ideal sources for dust emission, as well as repositories for dormant stages of aquatic invertebrates. An important component of invertebrate dispersal and colonization to new areas is the ability to be entrained into the atmosphere. Aquatic invertebrate eggs fall within the size of dust and sand grains (30-600μm), are less dense and aerodynamically shaped. We have shown previously that aquatic invertebrates can be dispersed long distances in dust storms but the extent of transport of taxa based on diapausing egg size/morphology has not been investigated. Here, we control the wind erosion process in a wind tunnel to test entrainment of diapausing stages of brine shrimp, clam shrimp, tadpole shrimp, fairy shrimp, Daphnia, and the rotifers Brachionus plicatilis and B. calyciflorus into the air by saltation. Diapausing eggs were mixed with sterilized wind-erodible soil. The soil/egg mixture was moistened with distilled water and air dried to form a crust. Dust was generated in a wind tunnel by releasing sand grains that act as saltator material similar to wind-entrained natural sands. Maximum wind velocity was 10m/s and entrained particles were sampled through an isokinetic horizontal intake opening. Aeolian sediment was collected from three points in the system; transfer section for coarse sediment, the pan subtending a settling chamber for finer saltation-sized sediment, and two paper filters for suspension-sized sediment. Samples were then passed through 250 and 350 μm sieves to remove abrader sand and rehydrated with various sterile media depending on the type of organism. We retrieved viable brine, fairy, and tadpole shrimp, ostracods, Daphnia, and diapausing eggs of the rotifers after hydration. This experiment demonstrates that resting stages of many invertebrates can be wind-eroded due to size and egg morphology and remain viable under controlled conditions mimicking dust emission.

Influence of Humic Acid on Stability and Attachment of nTiO2 Particles to Sand at Different pH

NASA Astrophysics Data System (ADS)

Cheng, T.

2015-12-01

Stability of nano-scale or micro-scale titanium dioxide particles (nTiO2) and their attachment to sediment grains have important implications to the fate and transport of nTiO2 in subsurface environments. nTiO2 may carry either positive or negative charges in natural water, therefore, environmental factors such as pH, humic substances, and Fe oxyhydroxide coatings on sediment grains, which are known to control the stability and transport of negatively charged colloids, may influence nTiO2 in different manners. The objective of this study is to investigate the effects of pH and humic acid (HA) on the stability and attachment of nTiO2 to sand, with special attention to low HA concentration ranges that are relevant to groundwater conditions. Stability and attachment of nTiO2 to quartz sand and Fe oxyhydroxide coated quartz sand were experimentally measured under a range of low HA concentrations at pH 5 and 9. Results showed that HA can either promote or hinder nTiO2 stability, depending on pH and HA concentration. We also found that HA can either enhance or reduce nTiO2 attachment to Fe oxyhydroxide coating at pH 5, depending on HA concentration. Results further showed that at pH 5, Fe oxyhydroxide coating reduced nTiO2 attachment to sand in the absence of HA but increased nTiO2 attachment in the presence of low concentration of HA. Derjaguin-Landau-Verwey-Overbeek (DLVO) theory was invoked to analyze particle-to-particle and particle-to-sand interactions in order to elucidate the roles of pH, HA, quartz, and Fe coating in nTiO2 stability and attachment. Overall, this study showed that changes in zeta potential of nTiO2 and Fe coating due to pH changes and/or HA adsorption are the key factors that influence stability and attachment of nTiO2.

Shelter Index and a simple wind speed parameter to characterize vegetation control of sand transport threshold and Flu

NASA Astrophysics Data System (ADS)

Gillies, J. A.; Nield, J. M.; Nickling, W. G.; Furtak-Cole, E.

2014-12-01

Wind erosion and dust emissions occur in many dryland environments from a range of surfaces with different types and amounts of vegetation. Understanding how vegetation modulates these processes remains a research challenge. Here we present results from a study that examines the relationship between an index of shelter (SI=distance from a point to the nearest upwind vegetation/vegetation height) and particle threshold expressed as the ratio of wind speed measured at 0.45 times the mean plant height divided by the wind speed at 17 m when saltation commences, and saltation flux. The results are used to evaluate SI as a parameter to characterize the influence of vegetation on local winds and sediment transport conditions. Wind speed, wind direction, saltation activity and point saltation flux were measured at 35 locations in defined test areas (~13,000 m2) in two vegetation communities: mature streets of mesquite covered nebkhas and incipient nebkhas dominated by low mesquite plants. Measurement positions represent the most open areas, and hence those places most susceptible to wind erosion among the vegetation elements. Shelter index was calculated for each measurement position for each 10° wind direction bin using digital elevation models for each site acquired using terrestrial laser scanning. SI can show the susceptibility to wind erosion at different time scales, i.e., event, seasonal, or annual, but in a supply-limited system it can fail to define actual flux amounts due to a lack of knowledge of the distribution of sediment across the surface of interest with respect to the patterns of SI.

Temporal and spatial variability of aeolian sand transport: Implications for field measurements

NASA Astrophysics Data System (ADS)

Ellis, Jean T.; Sherman, Douglas J.; Farrell, Eugene J.; Li, Bailiang

2012-01-01

Horizontal variability is often cited as one source of disparity between observed and predicted rates of aeolian mass flux, but few studies have quantified the magnitude of this variability. Two field projects were conducted to evaluate meter-scale spatial and temporal in the saltation field. In Shoalhaven Heads, NSW, Australia a horizontal array of passive-style sand traps were deployed on a beach for 600 or 1200 s across a horizontal span of 0.80 m. In Jericoacoara, Brazil, traps spanning 4 m were deployed for 180 and 240 s. Five saltation sensors (miniphones) spaced 1 m apart were also deployed at Jericoacoara. Spatial variation in aeolian transport rates over small spatial and short temporal scales was substantial. The measured transport rates ( Q) obtained from the passive traps ranged from 0.70 to 32.63 g/m/s. When considering all traps, the coefficient of variation ( CoV) values ranged from 16.6% to 67.8%, and minimum and maximum range of variation coefficient ( RVC) values were 106.1% to 152.5% and 75.1% to 90.8%, respectively. The miniphone Q and CoV averaged 47.1% and 4.1% for the 1260 s data series, which was subsequently sub-sampled at 60-630 s intervals to simulate shorter deployment times. A statistically significant ( p < 0.002), inverselinear relationship was found between sample duration and CoV and between Q and CoV, the latter relationship also considering data from previous studies.

Aeolian Sand Transport in the Planetary Context: Respective Roles of Aerodynamic and Bed-Dilatancy Thresholds

NASA Technical Reports Server (NTRS)

Marshall, J. R.; Borucki, J.; Bratton, C.

1999-01-01

The traditional view of aeolian sand transport generally estimates flux from the perspective of aerodynamic forces creating the airborne grain population, although it has been recognized that "reptation" causes a significant part of the total airborne flux; reptation involves both ballistic injection of grains into the air stream by the impact of saltating grains as well as the "nudging" of surface grains into a creeping motion. Whilst aerodynamic forces may initiate sand motion, it is proposed here that within a fully-matured grain cloud, flux is actually governed by two thresholds: an aerodynamic threshold, and a bed-dilatancy threshold. It is the latter which controls the reptation population, and its significance increases proportionally with transport energy. Because we only have experience with terrestrial sand transport, extrapolations of aeolian theory to Mars and Venus have adjusted only the aerodynamic factor, taking gravitational forces and atmospheric density as the prime variables in the aerodynamic equations, but neglecting reptation. The basis for our perspective on the importance of reptation and bed dilatancy is a set of experiments that were designed to simulate sand transport across the surface of a martian dune. Using a modified sporting crossbow in which a sand-impelling sabot replaced the bolt-firing mechanism, individual grains of sand were fired at loose sand targets with glancing angles typical of saltation impact; grains were projected at about 80 m/s to simulate velocities commensurate with those predicted for extreme martian aeolian conditions. The sabot impelling method permitted study of individual impacts without the masking effect of bed mobilization encountered in wind-tunnel studies. At these martian impact velocities, grains produced small craters formed by the ejection of several hundred grains from the bed. Unexpectedly, the craters were not elongated, despite glancing impact; the craters were very close to circular in planform

Aeolian Sand Transport in the Planetary Context: Respective Roles of Aerodynamic and Bed-Dilatancy Thresholds

NASA Astrophysics Data System (ADS)

Marshall, J. R.; Borucki, J.; Bratton, C.

1999-09-01

The traditional view of aeolian sand transport generally estimates flux from the perspective of aerodynamic forces creating the airborne grain population, although it has been recognized that "reptation" causes a significant part of the total airborne flux; reptation involves both ballistic injection of grains into the air stream by the impact of saltating grains as well as the "nudging" of surface grains into a creeping motion. Whilst aerodynamic forces may initiate sand motion, it is proposed here that within a fully-matured grain cloud, flux is actually governed by two thresholds: an aerodynamic threshold, and a bed-dilatancy threshold. It is the latter which controls the reptation population, and its significance increases proportionally with transport energy. Because we only have experience with terrestrial sand transport, extrapolations of aeolian theory to Mars and Venus have adjusted only the aerodynamic factor, taking gravitational forces and atmospheric density as the prime variables in the aerodynamic equations, but neglecting reptation. The basis for our perspective on the importance of reptation and bed dilatancy is a set of experiments that were designed to simulate sand transport across the surface of a martian dune. Using a modified sporting crossbow in which a sand-impelling sabot replaced the bolt-firing mechanism, individual grains of sand were fired at loose sand targets with glancing angles typical of saltation impact; grains were projected at about 80 m/s to simulate velocities commensurate with those predicted for extreme martian aeolian conditions. The sabot impelling method permitted study of individual impacts without the masking effect of bed mobilization encountered in wind-tunnel studies. At these martian impact velocities, grains produced small craters formed by the ejection of several hundred grains from the bed. Unexpectedly, the craters were not elongated, despite glancing impact; the craters were very close to circular in planform

Influence of clay particles on the transport and retention of titanium dioxide nanoparticles in quartz sand.

PubMed

Cai, Li; Tong, Meiping; Wang, Xueting; Kim, Hyunjung

2014-07-01

This study investigated the influence of two representative suspended clay particles, bentonite and kaolinite, on the transport of titanium dioxide nanoparticles (nTiO2) in saturated quartz sand in both NaCl (1 and 10 mM ionic strength) and CaCl2 solutions (0.1 and 1 mM ionic strength) at pH 7. The breakthrough curves of nTiO2 with bentonite or kaolinite were higher than those without the presence of clay particles in NaCl solutions, indicating that both types of clay particles increased nTiO2 transport in NaCl solutions. Moreover, the enhancement of nTiO2 transport was more significant when bentonite was present in nTiO2 suspensions relative to kaolinite. Similar to NaCl solutions, in CaCl2 solutions, the breakthrough curves of nTiO2 with bentonite were also higher than those without clay particles, while the breakthrough curves of nTiO2 with kaolinite were lower than those without clay particles. Clearly, in CaCl2 solutions, the presence of bentonite in suspensions increased nTiO2 transport, whereas, kaolinite decreased nTiO2 transport in quartz sand. The attachment of nTiO2 onto clay particles (both bentonite and kaolinite) were observed under all experimental conditions. The increased transport of nTiO2 in most experimental conditions (except for kaolinite in CaCl2 solutions) was attributed mainly to the clay-facilitated nTiO2 transport. The straining of larger nTiO2-kaolinite clusters yet contributed to the decreased transport (enhanced retention) of nTiO2 in divalent CaCl2 solutions when kaolinite particles were copresent in suspensions.

Sands at Gusev Crater, Mars

NASA Astrophysics Data System (ADS)

Cabrol, Nathalie A.; Herkenhoff, Kenneth; Knoll, Andrew H.; Farmer, Jack; Arvidson, Raymond; Grin, Edmond; Li, Ronxing; Fenton, Lori; Cohen, Barbara; Bell, James F.; Aileen Yingst, R.

2014-05-01

Processes, environments, and the energy associated with the transport and deposition of sand at Gusev Crater are characterized at the microscopic scale through the comparison of statistical moments for particle size and shape distributions. Bivariate and factor analyses define distinct textural groups at 51 sites along the traverse completed by the Spirit rover as it crossed the plains and went into the Columbia Hills. Fine-to-medium sand is ubiquitous in ripples and wind drifts. Most distributions show excess fine material, consistent with a predominance of wind erosion over the last 3.8 billion years. Negative skewness at West Valley is explained by the removal of fine sand during active erosion, or alternatively, by excess accumulation of coarse sand from a local source. The coarse to very coarse sand particles of ripple armors in the basaltic plains have a unique combination of size and shape. Their distribution display significant changes in their statistical moments within the ~400 m that separate the Columbia Memorial Station from Bonneville Crater. Results are consistent with aeolian and/or impact deposition, while the elongated and rounded shape of the grains forming the ripples, as well as their direction of origin, could point to Ma'adim Vallis as a possible source. For smaller particles on the traverse, our findings confirm that aeolian processes have dominated over impact and other processes to produce sands with the observed size and shape patterns across a spectrum of geologic (e.g., ripples and plains soils) and aerographic settings (e.g., wind shadows).

Sands at Gusev Crater, Mars

USGS Publications Warehouse

Cabrol, Nathalie A.; Herkenhoff, Kenneth E.; Knoll, Andrew H.; Farmer, Jack D.; Arvidson, Raymond E.; Grin, E.A.; Li, Ron; Fenton, Lori; Cohen, B.; Bell, J.F.; Yingst, R. Aileen

2014-01-01

Processes, environments, and the energy associated with the transport and deposition of sand at Gusev Crater are characterized at the microscopic scale through the comparison of statistical moments for particle size and shape distributions. Bivariate and factor analyses define distinct textural groups at 51 sites along the traverse completed by the Spirit rover as it crossed the plains and went into the Columbia Hills. Fine-to-medium sand is ubiquitous in ripples and wind drifts. Most distributions show excess fine material, consistent with a predominance of wind erosion over the last 3.8 billion years. Negative skewness at West Valley is explained by the removal of fine sand during active erosion, or alternatively, by excess accumulation of coarse sand from a local source. The coarse to very coarse sand particles of ripple armors in the basaltic plains have a unique combination of size and shape. Their distribution display significant changes in their statistical moments within the ~400 m that separate the Columbia Memorial Station from Bonneville Crater. Results are consistent with aeolian and/or impact deposition, while the elongated and rounded shape of the grains forming the ripples, as well as their direction of origin, could point to Ma'adim Vallis as a possible source. For smaller particles on the traverse, our findings confirm that aeolian processes have dominated over impact and other processes to produce sands with the observed size and shape patterns across a spectrum of geologic (e.g., ripples and plains soils) and aerographic settings (e.g., wind shadows).

Sources of organic compounds in fine soil and sand particles during winter in the metropolitan area of Riyadh, Saudi Arabia.

PubMed

Rushdi, Ahmed I; Al-Mutlaq, Khalid; Simoneit, Bernd R T

2005-11-01

Major advances have been made in molecular marker analysis to distinguish between natural and anthropogenic organic matter inputs to the atmosphere. Resuspension of soil and sand by wind is one of the major mechanisms that produces particle dusts in the atmosphere. Soil and sand samples from the Riyadh area were collected in winter 2002, sieved to remove coarse particles and extracted with a mixture of dichloromethane and methanol (3:1, v:v). The total extracts were analyzed by gas chromatography-mass spectrometry in order to characterize the contents and identify the potential sources of the organic components. The major organic compounds of these extracts were derived from natural biogenic and anthropogenic sources. Organic compounds from natural sources, mainly vegetation, were major in samples from outside the city of Riyadh and included n-alkanes, n-alkanoic acids, n- alkanols, methyl alkanoates, and sterols. Anthropogenic inputs were significant in the fine particles of soil and sand samples collected from populated areas of the city. They consisted mainly of n-alkanes, hopanes, UCM (from vehicular emissions), and plasticizers (from discarded plastics, e.g., shopping bags). Carbohydrates had high concentrations in all samples and indicate sources from decomposed cellulose fibers and/or the presence of viable microbiota such as bacteria and fungi.

Are They Telltale Ripples?

NASA Technical Reports Server (NTRS)

2004-01-01

This false-color image from the Mars Exploration Rover Spirit's panoramic camera shows peak-like formations on the martian terrain at Gusev Crater. Scientists have been analyzing these formations, which have coarse particles accumulating on their tops, or crests. This characteristic classifies them as ripples instead of dunes, which have a more uniform distribution of particle sizes. Scientists are looking further into such formations, which can give insight to the wind direction and velocity on Mars, as well as the material that is being moved by the wind. This image was taken on the 40th martian day, or sol, of Spirit's mission.

[figure removed for brevity, see original site] Click on image for larger view [Image credit: NASA/JPL/ASU]

This diagram illustrates how windblown sediments travel. There are three basic types of particles that undergo different motions depending on their size. These particles are dust, sand and coarse sand, and their sizes approximate flour, sugar, and ball bearings, respectively. Sand particles move along the 'saltation' path, hitting the surface downwind. When the sand hits the surface, it sends dust into the atmosphere and gives coarse sand a little shove. Mars Exploration Rover scientists are studying the distribution of material on the surface of Mars to better understand how winds shaped the landscape.

Airborne sand and dust soiling of solar collecting mirrors

NASA Astrophysics Data System (ADS)

Sansom, Christopher; Almond, Heather; King, Peter; Endaya, Essam; Bouaichaoui, Sofiane

2017-06-01

The reflectance of solar collecting mirrors can be significantly reduced by sand and dust soiling, particularly in arid environments. Larger airborne sand and dust particles can also cause damage by erosion, again reducing reflectance. This work describes investigations of the airborne particle size, shape, and composition in three arid locations that are considered suitable for CSP plants, namely in Iran, Libya, and Algeria. Sand and dust has been collected at heights between 0.5 to 2.0m by a variety of techniques, but are shown not to be representative of the particle size found either in ground dust and sand, or on the solar collecting mirror facets themselves. The possible reasons for this are proposed, most notably that larger particles may rebound from the mirror surface. The implications for mirror cleaning and collector facet erosion are discussed.

Chemical compositions and sources of organic matter in fine particles of soils and sands from the vicinity of Kuwait city.

PubMed

Rushdi, Ahmed I; Al-Zarban, Sheikha; Simoneit, Bernd R T

2006-09-01

Fine particles in the atmosphere from soil and sand resuspension contain a variety of organic compounds from natural biogenic and anthropogenic matter. Soil and sand samples from various sites near Kuwait city were collected, sieved to retain the fine particles, and extracted with a mixture of dichloromethane and methanol. The extracts were derivatized and analyzed by gas chromatography-mass spectrometry in order to characterize the chemical compositions and sources of the organic components. The major inputs of organic compounds were from both natural biogenic and anthropogenic sources in these samples. Vegetation was the major natural source of organic compounds and included n-alkanols, n-alkanoic acids, n-alkanes, sterols and triterpenoids. Saccharides had high concentrations (31-43%) in the sand dune and seafront samples, indicating sources from decomposed vegation materials and/or the presence of viable microbiota such as bacteria and fungi. Vehicular emission products, leakage of lubricating oils, discarded plastics and emissions from cooking operations were the major anthropogenic inputs in the samples from the urban areas. This input was mainly UCM, n-alkanes, hopanes, plasticizers and cholesterol, respectively.

On the modeling of the bottom particles segregation with non-linear diffusion equations: application to the marine sand ripples

NASA Astrophysics Data System (ADS)

Tiguercha, Djlalli; Bennis, Anne-claire; Ezersky, Alexander

2015-04-01

The elliptical motion in surface waves causes an oscillating motion of the sand grains leading to the formation of ripple patterns on the bottom. Investigation how the grains with different properties are distributed inside the ripples is a difficult task because of the segration of particle. The work of Fernandez et al. (2003) was extended from one-dimensional to two-dimensional case. A new numerical model, based on these non-linear diffusion equations, was developed to simulate the grain distribution inside the marine sand ripples. The one and two-dimensional models are validated on several test cases where segregation appears. Starting from an homogeneous mixture of grains, the two-dimensional simulations demonstrate different segregation patterns: a) formation of zones with high concentration of light and heavy particles, b) formation of «cat's eye» patterns, c) appearance of inverse Brazil nut effect. Comparisons of numerical results with the new set of field data and wave flume experiments show that the two-dimensional non-linear diffusion equations allow us to reproduce qualitatively experimental results on particles segregation.

Cytotoxicity of yellow sand in lung epithelial cells.

PubMed

Kim, Y H; Kim, K S; Kwak, N J; Lee, K H; Kweon, S A; Lim, Y

2003-02-01

The present study was carried out to observe the cytotoxicity of yellow sand in comparison with silica and titanium dioxide in a rat alveolar type II cell line (RLE-6TN). Yellow sand (China Loess) was obtained from the loess layer in the Gunsu Province of China. The mean particle diameter of yellow sand was about 0.003 +/- 0.001 mm. Major elements of yellow sand were Si(27.7 +/- 0.6%), Al(6.01 +/- 0.17%), and Ca(5.83 +/- 0.23%) in that order. Silica and yellow sand significantly decreased cell viability and increased [Ca2+]i. All three particles increased the generation of H2O2. TiO2 did not change Fenton activity, while silica induced a slight increase of Fenton activity. In contrast, yellow sand induced a significant increase of Fenton activity. Silica, yellow sand and TiO2 induced significant nitrite formations in RLE-6TN cells. Silica showed the highest increase in nitrite formation, while yellow sand induced the least formation of nitrite. Silica and yellow sand increased the release of TNF-a. Based on these results, we suggest that yellow sand can induce cytotoxicity in RLE-6TN cells and reactive oxygen species, Fenton activity and reactive nitrogen species might be involved in this toxicity.

Amyloplast sedimentation and organelle saltation in living corn columella cells

NASA Technical Reports Server (NTRS)

Sack, F. D.; Suyemoto, M. M.; Leopold, A. C.

1986-01-01

Amyloplast sedimentation during gravistimulation and organelle movements was studied in living central rootcap cells of Zea mays L. cv. Merit. Cells from sectioned roots were viewed with a horizontally-mounted videomicroscope. The kinetics of gravity-induced amyloplast sedimentation were comparable to those calculated from experiments using fixed material. Individual amyloplasts fell at an average velocity of 5.5 micrometers min-1; the maximal velocity of fall measured was 18.0 micrometers min-1. Amyloplasts often rotated, sometimes rose in the cytoplasm, and occasionally underwent sudden rapid movements as fast as 58 micrometers min-1. Saltations of other organelles were frequently observed. This appears to be the first report of cytoplasmic streaming in the presumptive statocytes of roots.

Compressive behavior of fine sand.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martin, Bradley E.; Kabir, Md. E.; Song, Bo

2010-04-01

The compressive mechanical response of fine sand is experimentally investigated. The strain rate, initial density, stress state, and moisture level are systematically varied. A Kolsky bar was modified to obtain uniaxial and triaxial compressive response at high strain rates. A controlled loading pulse allows the specimen to acquire stress equilibrium and constant strain-rates. The results show that the compressive response of the fine sand is not sensitive to strain rate under the loading conditions in this study, but significantly dependent on the moisture content, initial density and lateral confinement. Partially saturated sand is more compliant than dry sand. Similar trendsmore » were reported in the quasi-static regime for experiments conducted at comparable specimen conditions. The sand becomes stiffer as initial density and/or confinement pressure increases. The sand particle size become smaller after hydrostatic pressure and further smaller after dynamic axial loading.« less

Aeolian processes aboard a space station: Saltation and particle trajectory analysis

NASA Technical Reports Server (NTRS)

White, B. R.; Greeley, R.; Iversen, J. D.; Leach, R. N.

1986-01-01

The Carousel wind tunnel (CWT) proposed to study aeolian processes aboard a space station consists of two concentric rotating drums. The space between the two drums comprises the wind tunnel test section. Differential rates of rotation of the two drums would provide a wind velocity with respect to either drum surface. Preliminary results of measured velocity profiles made in a CWT prototype indicate that the wall bounded boundary layer profiles are suitable to simulate flat plate turbulent boundary layer flow. The two dimensional flat plate Cartesian coordinate equations of motion of a particle moving through the air are explained. In order to assess the suitability of CWT in the analysis of the trajectories of windblown particles, a series of calculations were conducted comparing cases for gravity with those of zero gravity. Results from the calculations demonstrate that a wind tunnel of the carousel design could be fabricted to operate in a space station environment and that experiments could be conducted which would yield significant results contributing to the understanding of the physics of particle dynamics.

Aeolian processes aboard a Space Station: Saltation and particle trajectory analysis

NASA Technical Reports Server (NTRS)

White, Bruce R.; Greeley, Ronald; Iversen, James D.; Leach, R. N.

1987-01-01

The Carousel Wind Tunnel (CWT) proposed to study aeolian processes aboard a Space Station consists of two concentric rotating drums. The space between the two drums comprises the wind tunnel section. Differential rates of rotation of the two drums would provide a wind velocity with respect to either drum surface. Preliminary results of measured velocity profiles made in a CWT prototype indicate that the wall bounded boundary layer profiles are suitable to simuate flat plate turbulent boundary layer flow. The two dimensional flate plate Cartesian coordinate equations of motion of a particle moving through the air are explained. In order to assess the suitability of CWT in the analysis of the trajectories of windblown particles, a series of calculations were conducted comparing cases for gravity with those of zero gravity. Results from the calculations demonstrate that a wind tunnel of the carousel design could be fabricated to operate in a space station environment and that experiments could be conducted which would yield significant results contributing to the understanding of the physics of particle dynamics.

The role of aluminum in slow sand filtration.

PubMed

Weber-Shirk, Monroe L; Chan, Kwok Loon

2007-03-01

Engineering enhancement of slow sand filtration has been an enigma in large part because the mechanisms responsible for particle removal have not been well characterized. The presumed role of biological processes in the filter ripening process nearly precluded the possibility of enhancing filter performance since interventions to enhance biological activity would have required decreasing the quality of the influent water. In previous work, we documented that an acid soluble polymer controls filter performance. The new understanding that particle removal is controlled in large part by physical chemical mechanisms has expanded the possibilities of engineering slow sand filter performance. Herein, we explore the role of naturally occurring aluminum as a ripening agent for slow sand filters and the possibility of using a low dose of alum to improve filter performance or to ripen slow sand filters.

Electrochemical and Dry Sand Impact Erosion Studies on Carbon Steel

PubMed Central

Naz, M. Y.; Ismail, N. I.; Sulaiman, S. A.; Shukrullah, S.

2015-01-01

This study investigated the dry and aqueous erosion of mild steel using electrochemical and dry sand impact techniques. In dry sand impact experiments, mild steel was eroded with 45 μm and 150 μm sand particles. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and micro-hardness techniques were used to elaborate the surface morphology of the eroded samples. The results revealed significant change in morphology of the eroded samples. In-depth analysis showed that although the metal erosion due to larger particles was significantly higher, the fines also notably damaged the metal surface. The surface damages were appreciably reduced with decrease in impact angle of the accelerated particles. The maximum damages were observed at an impact angle of 90°. The hardness of the samples treated with 45 μm and 150 μm sand remained in the range of 88.34 to 102.31 VHN and 87.7 to 97.55 VHN, respectively. In electrochemical experiments, a triple electrode probe was added into the metal treatment process. The linear polarization resistance (LPR) measurements were performed in slurries having 5% (by weight) of sand particles. LPR of the samples treated with 45 μm and 150 μm sand slurries was calculated about 949 Ω.cm2 and 809 Ω.cm2, respectively. PMID:26561231

Electrochemical and Dry Sand Impact Erosion Studies on Carbon Steel.

PubMed

Naz, M Y; Ismail, N I; Sulaiman, S A; Shukrullah, S

2015-11-12

This study investigated the dry and aqueous erosion of mild steel using electrochemical and dry sand impact techniques. In dry sand impact experiments, mild steel was eroded with 45 μm and 150 μm sand particles. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and micro-hardness techniques were used to elaborate the surface morphology of the eroded samples. The results revealed significant change in morphology of the eroded samples. In-depth analysis showed that although the metal erosion due to larger particles was significantly higher, the fines also notably damaged the metal surface. The surface damages were appreciably reduced with decrease in impact angle of the accelerated particles. The maximum damages were observed at an impact angle of 90°. The hardness of the samples treated with 45 μm and 150 μm sand remained in the range of 88.34 to 102.31 VHN and 87.7 to 97.55 VHN, respectively. In electrochemical experiments, a triple electrode probe was added into the metal treatment process. The linear polarization resistance (LPR) measurements were performed in slurries having 5% (by weight) of sand particles. LPR of the samples treated with 45 μm and 150 μm sand slurries was calculated about 949 Ω.cm(2) and 809 Ω.cm(2), respectively.

Seasonal variation in the free-running period in two Talitrus saltator populations from Italian beaches differing in morphodynamics and human disturbance

NASA Astrophysics Data System (ADS)

Nardi, M.; Morgan, E.; Scapini, F.

2003-10-01

The sandhopper Talitrus saltator Montagu (Amphipoda) is a widespread species adapted to different changing environmental conditions and which typically shows a clear circadian rhythm of locomotor activity. The populations from two beaches on the western Italian coast differing in coastline dynamics (eroded versus dynamically stable) and human disturbance (inside a natural park versus freely used and cleaned for leisure) were studied to highlight intrapopulation variation in the endogenous locomotor rhythm. The activity of adult sandhoppers was studied under constant laboratory conditions within individual recording chambers. Variation of the free-running period was analysed at individual level within each population. Greater variability was found than previously reported for the circadian rhythm period of T. saltator, and seasonal variation was shown for the first time. Differences in the level of variation were correlated with coastline dynamics.

Three dimensional fabric evolution of sheared sand

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hasan, Alsidqi; Alshibli, Khalid

2012-10-24

Granular particles undergo translation and rolling when they are sheared. This paper presents a three-dimensional (3D) experimental assessment of fabric evolution of sheared sand at the particle level. F-75 Ottawa sand specimen was tested under an axisymmetric triaxial loading condition. It measured 9.5 mm in diameter and 20 mm in height. The quantitative evaluation was conducted by analyzing 3D high-resolution x-ray synchrotron micro-tomography images of the specimen at eight axial strain levels. The analyses included visualization of particle translation and rotation, and quantification of fabric orientation as shearing continued. Representative individual particles were successfully tracked and visualized to assess themore » mode of interaction between them. This paper discusses fabric evolution and compares the evolution of particles within and outside the shear band as shearing continues. Changes in particle orientation distributions are presented using fabric histograms and fabric tensor.« less

Aeolian snow transport from wind tunnel experiments

NASA Astrophysics Data System (ADS)

Paterna, E.; Crivelli, P.; Lehning, M.

2016-12-01

Aeolian snow transport has a significant impact on snow redistribution in mountains, prairies as well as on glaciers, ice shelves, and sea ice. In all these environments, the local mass balance is highly influenced by Aeolian snow transport. The dynamics of snow saltation has a high impact on the land surface processes shaping these regions. More specifically, the observed high intermittency of saltation fluxes poses a problem for saltation models and needs to be better understood. We therefore aimed at unveiling the mechanisms underlying snow saltation at different saltation strengths and its coupling with the turbulent fluctuations of the wind. We conducted wind tunnel measurements of the momentum and mass-fluxes during snow saltation. For the mass-flux measurements we employed a shadowgraphy system which acquires images of the snow particle's shadows at high spatial and temporal resolution. The size and displacement of the particles are then determined by means of image analysis and Particle Tracking Velocimetry (PTV), allowing to estimate both snow mass-flux and flow velocity. Our controlled wind tunnel experiments revealed the existence of two regimes of saltation. In a turbulence-dependent regime occurring during weak saltation activity, we observed a strong coupling between snow transport and turbulent flow. Conversely during stronger saltation activity a turbulence-independent regime emerges, where the saltation develops its own length scale and it efficiently decouples from the wind fluctuations. We argue that different entrainment mechanisms could explain the existence of the two different saltation regimes as well as the observed high level of mass-flux intermittency.

Numerical simulation of turbulence and sediment transport of medium sand

NASA Astrophysics Data System (ADS)

Schmeeckle, M. W.

2012-12-01

Eleven numerical simulations, ranging from no transport to bedload to vigorous suspension transport, are presented of a combined large eddy simulation (LES) and distinct element model (DEM) of an initially flat bed of medium sand. The fluid and particles are fully coupled in momentum. The friction coefficient, defined here as the squared ratio of the friction velocity to the depth-averaged velocity, is in good agreement with well-known rough bed relations at no transport and increases with the intensity of bedload transport. The friction coefficient nearly doubles in value at the onset of sediment suspension owing to a rapid increase of the depth over which particles and fluid exchange momentum. The friction coefficient decreases with increasing suspension intensity because of increasingly stable stratification. Fluid Reynolds stress and time-averaged velocity profiles in the bedload regime agree well with previous experiments and simulations. Also consistent with previous studies of suspended sediment, there is an increase in slope of the lower portion of the velocity profile that has been modeled in the past using stably stratified eddy viscosity closures or an adjusted von Karman constant. Stokes numbers in the simulations, using an estimated lagrangian integral time scale, are less than unity. As such, particles faithfully follow the fluid, except for particle settling and grain-grain interactions near the bed. Fluid-particle velocity correlation coefficients approach one in portions of the flow where volumetric sediment concentrations are below about ten percent. Bedload entrainment is critically connected to vertical velocity fluctuations. When a fluid packet approaches the bed from the interior of the flow (i.e. a sweep), fluid is forced into the bed, and at the edges of the sweep, fluid is forced out of the bed. Much of the particle entrainment occurs at these sweep edges. Fluid velocity statistics following the particles reveal that moving bedload

Comparing particle-size distributions in modern and ancient sand-bed rivers

NASA Astrophysics Data System (ADS)

Hajek, E. A.; Lynds, R. M.; Huzurbazar, S. V.

2011-12-01

Particle-size distributions yield valuable insight into processes controlling sediment supply, transport, and deposition in sedimentary systems. This is especially true in ancient deposits, where effects of changing boundary conditions and autogenic processes may be detected from deposited sediment. In order to improve interpretations in ancient deposits and constrain uncertainty associated with new methods for paleomorphodynamic reconstructions in ancient fluvial systems, we compare particle-size distributions in three active sand-bed rivers in central Nebraska (USA) to grain-size distributions from ancient sandy fluvial deposits. Within the modern rivers studied, particle-size distributions of active-layer, suspended-load, and slackwater deposits show consistent relationships despite some morphological and sediment-supply differences between the rivers. In particular, there is substantial and consistent overlap between bed-material and suspended-load distributions, and the coarsest material found in slackwater deposits is comparable to the coarse fraction of suspended-sediment samples. Proxy bed-load and slackwater-deposit samples from the Kayenta Formation (Lower Jurassic, Utah/Colorado, USA) show overlap similar to that seen in the modern rivers, suggesting that these deposits may be sampled for paleomorphodynamic reconstructions, including paleoslope estimation. We also compare grain-size distributions of channel, floodplain, and proximal-overbank deposits in the Willwood (Paleocene/Eocene, Bighorn Basin, Wyoming, USA), Wasatch (Paleocene/Eocene, Piceance Creek Basin, Colorado, USA), and Ferris (Cretaceous/Paleocene, Hanna Basin, Wyoming, USA) formations. Grain-size characteristics in these deposits reflect how suspended- and bed-load sediment is distributed across the floodplain during channel avulsion events. In order to constrain uncertainty inherent in such estimates, we evaluate uncertainty associated with sample collection, preparation, analytical

The behavioural ecology of two sympatric talitrid species, Talitrus saltator (Montagu) and Orchestia gammarellus (Pallas) on a Tyrrhenian sandy beach dune system

NASA Astrophysics Data System (ADS)

Colombini, Isabella; Fallaci, Mario; Gagnarli, Elena; Rossano, Claudia; Scapini, Felicita; Chelazzi, Lorenzo

2013-01-01

The behavioural ecology of a sub-population of Talitrus saltator living on the sandy shore of the Maremma Regional Park (Italy) was compared with that of Orchestia gammarellus inhabiting the retrodunal dune slack area. Monthly monitoring over a year determined the mean distribution patterns, their changes and whether these overlapped. Standard pitfall traps were placed along transects across the beach-dune-dune slack area. Experiments analysed the diel activity rhythms during spring and the activity patterns of the different age classes and the two sexes were compared within and between species. Local environmental conditions were registered with a microclimatic station. During May and September, plant hummocks were monitored to see whether surface movements of O. gammarellus could be restricted to certain periods of the year and to estimate densities within the vegetation. The plant biomass and moisture conditions within the hummocks were also recorded and substratum samples were collected at the base of the shrubs for laboratory analysis. To test for visual cues, orientation experiments with and without landscape view were carried out on the beach during morning and afternoon hours and contemporaneously for each species. Experiments to test the diel variation of scototaxis to a black shape were also performed over a 24 h period of time under controlled conditions. There was a spatial partitioning of the two species, with T. saltator moving along a sea-land axis according to diel and seasonal changes and with some individuals reaching the back of the dune in particular environmental conditions. No spatial overlap with the zonation patterns of O. gammarellus was observed, which was restricted to the dune slack area. Nocturnal surface activity was observed for both species with juveniles peaking at dawn and with O. gammarellus being strictly more nocturnal than T. saltator. Orientation experiments showed a higher ability of T. saltator to orient towards the

New Titan Saltation Threshold Experiments: Investigating Current and Past Climates

NASA Astrophysics Data System (ADS)

Bridges, N.; Burr, D. M.; Marshall, J.; Smith, J. K.; Emery, J. P.; Horst, S. M.; Nield, E.; Yu, X.

2015-12-01

Titan exhibits aeolian sand dunes that cover ~20% of its surface, attesting to significant sediment transport by the wind. Recent experiments in the Titan Wind Tunnel (TWT) at NASA Ames Research Center [1,2] found that the threshold friction speed needed to detach Titanian "sand" is about 50% higher than previous estimates based on theory alone [3], a result that might be explained by the low ratio of particle to fluid density on the body [1]. Following the successful completion of the initial Titan threshold tests, we are conducting new experiments that expand the pressure range above and below current Titan values. The basic experimental techniques are described in [1], with minor updates to the instrumentation as described in [2]. To reproduce the kinematic viscosity and particle friction Reynolds number equivalent to that expected for Titan's nitrogen atmosphere at 1.4 bars and 94 K requires that TWT be pressurized to 12.5 bars for air at 293K. In addition to running experiments at this pressure to reproduce previous results [1] and investigate low density (high density ratio) materials, TWT pressures of 3 and 8 bars are in the experimental matrix to understand threshold under past Titan conditions when the atmospheric pressure may have been lower [4]. Higher pressures, at 15 and 20 bars in TWT, are also being run to understand the putative effects of low density ratio conditions. Our experimental matrix for this follow-on work uses some of the same materials as previously used, including walnut shells, basalt, quartz, glass spheres, and various low density materials to better simulate the gravity-equivalent weight of Titan sand. For these experiments, the TWT is now equipped with a new high pressure Tavis transducer with sufficient sensitivity to measure freestream speeds of less than 0.5 m s-1 at 12.5 bars. New techniques include video documentation of the experiments. We are also investigating methods of measuring humidity of the wind tunnel environment and

Morphological characterization of ceramic fillers made from Indonesian natural sand as restorative dental materials

NASA Astrophysics Data System (ADS)

Karlina, E.; Susra, S.; Fatmala, Y.; Hartoyo, H. M.; Takarini, V.; Usri, K.; Febrida, R.; Djustiana, N.; Panatarani, C.; Joni, I. M.

2018-02-01

Dental composite as restorative dental materials can be reinforced using ceramic fillers. Homogeneous distribution of filler particles shall improve its mechanical properties. This paper presents the results of the preliminary study on the ZrO2-Al2O3-SiO2 ceramic fillers made from Indonesian natural sand that can increase the mechanical properties of dental composite. The synthesis was done using zirconium silicate sand (ZrSiO4) and aluminium oxide (Al2O3) precursors, which dissolved together with 70:30 weight ratios. Two types of sand were used: (1) manufactured sand (mesh #80) and (2) natural sand (mesh #400). The samples then heated in the furnace at 1100 °C for 8 hours. The morphological characterization was then evaluated using JEOL Scanning Electron Microscope (SEM) for the surface structure that analyze particles size and distribution. Ceramic fillers made from natural sand is homogenous, well distributed with average particle size of 5-10 µm. Comparably, ceramic filler made from the manufactured sand is heterogeneous, poorly distributed and appear as agglomerates with average particle size are 30-50 µm. The results suggest that ceramic fillers made from natural sand demonstrate better character to represent as a functional restorative dental material.

Coupling Solute and Fine Particle Transport with Sand Bed Morphodynamics within a Field Experiment

NASA Astrophysics Data System (ADS)

Phillips, C. B.; Ortiz, C. P.; Schumer, R.; Jerolmack, D. J.; Packman, A. I.

2017-12-01

Fine suspended particles are typically considered to pass through streams and rivers as wash load without interacting with the bed, however experiments have demonstrated that hyporheic flow causes advective exchange of fine particles with the stream bed, yielding accumulation of fine particle deposits within the bed. Ultimately, understanding river morphodynamics and ecosystem dynamics requires coupling both fine particle and solute transport with bed morphodynamics. To better understand the coupling between these processes we analyze a novel dataset from a controlled field experiment conducted on Clear Run, a 2nd order sand bed stream located within the North Carolina coastal plain. Data include concentrations of continuously injected conservative solutes and fine particulate tracers measured at various depths within the stream bed, overhead time lapse images of bed forms, stream discharge, and geomorphological surveys of the stream. We use image analysis of bed morphodynamics to assess exchange, retention, and remobilization of solutes and fine particles during constant discharge and a short duration experimental flood. From the images, we extract a time series of bedform elevations and scour depths for the duration of the experiment. The high-resolution timeseries of bed elevation enables us to assess coupling of bed morphodynamics with both the solute and fine particle flux during steady state mobile bedforms prior to the flood and to changing bedforms during the flood. These data allow the application of a stochastic modeling framework relating bed elevation fluctuations to fine particle residence times. This combined experimental and modeling approach ultimately informs our ability to predict not only the fate of fine particulate matter but also associated nutrient and carbon dynamics within streams and rivers.

Feature saltation and the evolution of mimicry.

PubMed

Gamberale-Stille, Gabriella; Balogh, Alexandra C V; Tullberg, Birgitta S; Leimar, Olof

2012-03-01

In Batesian mimicry, a harmless prey species imitates the warning coloration of an unpalatable model species. A traditional suggestion is that mimicry evolves in a two-step process, in which a large mutation first achieves approximate similarity to the model, after which smaller changes improve the likeness. However, it is not known which aspects of predator psychology cause the initial mutant to be perceived by predators as being similar to the model, leaving open the question of how the crucial first step of mimicry evolution occurs. Using theoretical evolutionary simulations and reconstruction of examples of mimicry evolution, we show that the evolution of Batesian mimicry can be initiated by a mutation that causes prey to acquire a trait that is used by predators as a feature to categorize potential prey as unsuitable. The theory that species gain entry to mimicry through feature saltation allows us to formulate scenarios of the sequence of events during mimicry evolution and to reconstruct an initial mimetic appearance for important examples of Batesian mimicry. Because feature-based categorization by predators entails a qualitative distinction between nonmimics and passable mimics, the theory can explain the occurrence of imperfect mimicry. © 2011 The Author(s). Evolution© 2011 The Society for the Study of Evolution.

Compositional variations in sands of the Bagnold Dunes, Gale Crater, Mars, from visible-shortwave infrared spectroscopy and comparison with ground truth from the Curiosity Rover

USGS Publications Warehouse

Lapotre, Mathieu G.A.; Ehlmann, B. L.; Minson, Sarah E.; Arvidson, R. E.; Ayoub, F.; Fraeman, A. A.; Ewing, R. C.; Bridges, N. T.

2017-01-01

During its ascent up Mount Sharp, the Mars Science Laboratory Curiosity rover traversed the Bagnold Dune Field. We model sand modal mineralogy and grain size at four locations near the rover traverse, using orbital shortwave infrared single scattering albedo spectra and a Markov-Chain Monte Carlo implementation of Hapke's radiative transfer theory to fully constrain uncertainties and permitted solutions. These predictions, evaluated against in situ measurements at one site from the Curiosity rover, show that XRD-measured mineralogy of the basaltic sands is within the 95% confidence interval of model predictions. However, predictions are relatively insensitive to grain size and are non-unique, especially when modeling the composition of minerals with solid solutions. We find an overall basaltic mineralogy and show subtle spatial variations in composition in and around the Bagnold dunes, consistent with a mafic enrichment of sands with cumulative transport distance by sorting of olivine, pyroxene, and plagioclase grains during aeolian saltation. Furthermore, the large variations in Fe and Mg abundances (~20 wt%) at the Bagnold Dunes suggest that compositional variability induced by wind sorting may be enhanced by local mixing with proximal sand sources. Our estimates demonstrate a method for orbital quantification of composition with rigorous uncertainty determination and provide key constraints for interpreting in situ measurements of compositional variability within martian aeolian sandstones.

Method for filtering solvent and tar sand mixtures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kelterborn, J. C.; Stone, R. A.

1985-09-03

A method for filtering spent tar sands from a bitumen and organic solvent solution comprises separating the solution into two streams wherein the bulk of the coarser spent tar sand is in a first stream and has an average particle size of about 10 to about 100 mesh and the bulk of the finer spent tar sand is in a second stream; producing a filter cake by filtering the coarser spent tar sand from the first stream; and filtering the finer spent tar sand from the second stream with the filter cake. The method is particularly useful for filtering solutionsmore » of bitumen extracted from bitumen containing diatomite, spent diatomite and organic solvent.« less

Wind-blown sand on beaches: an evaluation of models

NASA Astrophysics Data System (ADS)

Sherman, Douglas J.; Jackson, Derek W. T.; Namikas, Steven L.; Wang, Jinkang

1998-03-01

for the effects of slope and moisture content were calculated using the models of Bagnold [Bagnold, R.A., 1973. The nature of saltation and 'bed-load' transport in water. Proc. R. Soc. London, Ser. A, 332, 473-504] and Belly [Belly, P.-Y., 1964. Sand movement by wind. U.S. Army Corps Eng. CERC. Tech. Mem. 1, Washington D.C., 38 pp.], respectively. None of the models was able to produce a strong correspondence between measured and predicted rates of transport. Best results were obtained using the Bagnold and Zingg models, and the Kadib model was the least viable of this group. The influence of sediment moisture content appeared to be the critical factor in degrading model viability. Overall, none of the models is adequate for general applications to coastal-aeolian environments where moisture content complications tend to override the predictive competence of the simple transport formulations.

Geochemical heterogeneity in a sand and gravel aquifer: Effect of sediment mineralogy and particle size on the sorption of chlorobenzenes

USGS Publications Warehouse

Barber, L.B.; Thurman, E.M.; Runnells, D.R.; ,

1992-01-01

The effect of particle size, mineralogy and sediment organic carbon (SOC) on solution of tetrachlorobenzene and pentachlorobenzene was evaluated using batch-isotherm experiments on sediment particle-size and mineralogical fractions from a sand and gravel aquifer, Cape Cod, Massachusetts. Concentration of SOC and sorption of chlorobenzenes increase with decreasing particle size. For a given particle size, the magnetic fraction has a higher SOC content and sorption capacity than the bulk or non-magnetic fractions. Sorption appears to be controlled by the magnetic minerals, which comprise only 5-25% of the bulk sediment. Although SOC content of the bulk sediment is < 0.1%, the observed sorption of chlorobenzenes is consistent with a partition mechanism and is adequately predicted by models relating sorption to the octanol/water partition coefficient of the solute and SOC content. A conceptual model based on preferential association of dissolved organic matter with positively-charged mineral surfaces is proposed to describe micro-scale, intergranular variability in sorption properties of the aquifer sediments.The effect of particle size, mineralogy and sediment organic carbon (SOC) on sorption of tetrachlorobenzene and pentachlorobenzene was evaluated using batch-isotherm experiments on sediment particle-size and mineralogical fractions from a sand and gravel aquifer, Cape Cod, Massachusetts. Concentration of SOC and sorption of chlorobenzenes increase with decreasing particle size. For a given particle size, the magnetic fraction has a higher SOC content and sorption capacity than the bulk or non-magnetic fractions. Sorption appears to be controlled by the magnetic minerals, which comprise only 5-25% of the bulk sediment. Although SOC content of the bulk sediment is <0.1%, the observed sorption of chlorobenzenes is consistent with a partition mechanism and is adequately predicted by models relating sorption to the octanol/water partition coefficient of the solute and

Study on shear properties of coral sand under cyclic simple shear condition

NASA Astrophysics Data System (ADS)

Ji, Wendong; Zhang, Yuting; Jin, Yafei

2018-05-01

In recent years, the ocean development in our country urgently needs to be accelerated. The construction of artificial coral reefs has become an important development direction. In this paper, experimental studies of simple shear and cyclic simple shear of coral sand are carried out, and the shear properties and particle breakage of coral sand are analyzed. The results show that the coral sand samples show an overall shear failure in the simple shear test, which is more accurate and effective for studying the particle breakage. The shear displacement corresponding to the peak shear stress of the simple shear test is significantly larger than that corresponding to the peak shear stress of the direct shear test. The degree of particle breakage caused by the simple shear test is significantly related to the normal stress level. The particle breakage of coral sand after the cyclic simple shear test obviously increases compared with that of the simple shear test, and universal particle breakage occurs within the whole particle size range. The increasing of the cycle-index under cyclic simple shear test results in continuous compacting of the sample, so that the envelope curve of peak shearing force increases with the accumulated shear displacement.

Characterization of Nanoparticle Release from Surface Coatings by the Simulation of a Sanding Process

PubMed Central

Göhler, Daniel; Stintz, Michael; Hillemann, Lars; Vorbau, Manuel

2010-01-01

Nanoparticles are used in industrial and domestic applications to control customized product properties. But there are several uncertainties concerning possible hazard to health safety and environment. Hence, it is necessary to search for methods to analyze the particle release from typical application processes. Based on a survey of commercial sanding machines, the relevant sanding process parameters were employed for the design of a miniature sanding test setup in a particle-free environment for the quantification of the nanoparticle release into air from surface coatings. The released particles were moved by a defined airflow to a fast mobility particle sizer and other aerosol measurement equipment to enable the determination of released particle numbers additionally to the particle size distribution. First, results revealed a strong impact of the coating material on the swarf mass and the number of released particles. PMID:20696941

Ripples or Dunes?

NASA Technical Reports Server (NTRS)

2004-01-01

This approximate true-color image taken by the Mars Exploration Rover Spirit's panoramic camera shows the windblown waves of soil that characterize the rocky surface of Gusev Crater, Mars. Scientists were puzzled about whether these geologic features were 'ripples' or 'dunes.' Ripples are shaped by gentle winds that deposit coarse grains on the tops or crests of the waves. Dunes are carved by faster winds and contain a more uniform distribution of material. Images taken of these features by the rover's microscopic imager on the 41st martian sol, or day, of the rover's mission revealed their identity to be ripples. This information helps scientists better understand the winds that shape the landscape of Mars. This image was taken early in Spirit's mission.

[figure removed for brevity, see original site] Click on image for larger view [Image credit: NASA/JPL/ASU]

This diagram illustrates how windblown sediments travel. There are three basic types of particles that undergo different motions depending on their size. These particles are dust, sand and coarse sand, and their sizes approximate flour, sugar, and ball bearings, respectively. Sand particles move along the 'saltation' path, hitting the surface downwind. When the sand hits the surface, it sends dust into the atmosphere and gives coarse sand a little shove. Mars Exploration Rover scientists are studying the distribution of material on the surface of Mars to better understand how winds shaped the landscape.

Unique Aeolian Transport Mechanisms on Mars: Respective Roles of Percussive and Repercussive Grain Populations in the Sediment Load

NASA Technical Reports Server (NTRS)

Marshall, John R.

1999-01-01

Experiments show that when sand-size grains impact a sediment surface with energy levels commensurate for Mars, small craters are formed by the ejection of several hundred grains from the bed. The experiments were conducted with a modified crossbow in which a sand-impelling sabot replaced the bolt-firing mechanism. Individual grains of sand could be fired at loose sand targets to observe ballistic effects unhindered by aerodynamic mobilization of the bed. Impact trajectories simulated the saltation process on dune surfaces. Impact craters were not elongated despite glancing (15 deg.) bed impact; the craters were very close to being circular. High-speed photography showed them to grow in both diameter and depth after the impactor had ricochetted from the crater site. The delayed response of the bed was "explosive" in nature, and created a miniature ejecta curtain spreading upward and outward for many centimeters for impact of 100-300 micron-diameter grains into similar material. This behavior is explained by deposition of elastic energy in the bed by the "percussive" grain. Impact creates a subsurface stress regime or "quasi-Boussinesq" compression field. Elastic recovery of the bed occurs by dilatancy; shear stresses suddenly convert the grains to open packing and they consequently become forcefully ejected from the site. Random jostling of the grains causes radial homogenization of stress vectors and a resulting circular crater. A stress model based on repercussive bed dilatancy and interparticle adhesive forces (for smaller grains) predicts, to first order, the observed crater volumes for various impact conditions. On earth, only a few grains are mobilized by a percussive saltating grain; some grains are "knudged" along the ground, and some are partly expelled on short trajectories. These motions constitute reptation transport. On Mars, saltation and reptation become indistinct: secondary or "repercussive" trajectories have sufficient vertical impulse to create a

Unique Aeolian Transport Mechanisms on Mars: Respective Roles of Percussive and Repercussive Grain Populations in the Sediment Load

NASA Technical Reports Server (NTRS)

Marshall, John R.

1999-01-01

Experiments show that when sand-size grains impact a sediment surface with energy levels commensurate for Mars, small craters are formed by the ejection of several hundred grains from the bed. The experiments were conducted with a modified crossbow in which a sand-impelling sabot replaced the bolt-firing mechanism. Individual grains of sand could be fired at loose sand targets to observe ballistic effects unhindered by aerodynamic mobilization of the bed. Impact trajectories simulated the saltation process on dune surfaces. Impact craters were not elongated despite glancing (15 deg.) bed impact; the craters were very close to being circular. High-speed photography showed them to grow in both diameter and depth after the impactor had ricochetted from the crater site. The delayed response of the bed was "explosive" in nature, and created a miniature ejecta curtain spreading upward and outward for many centimeters for impact of 100-300 um-diameter grains into similar material. This behavior is explained by deposition of elastic energy in the bed by the "percussive" grain. Impact creates a subsurface stress regime or "quasi-Boussinesq" compression field. Elastic recovery of the bed occurs by dilatancy; shear stresses suddenly convert the grains to open packing and they consequently become forcefully ejected from the site. Random jostling of the grains causes radial homogenization of stress vectors and a resulting circular crater. A stress model based on repercussive bed dilatancy and interparticle adhesive forces (for smaller grains) predicts, to first order, the observed crater volumes for various impact conditions. On earth, only a few grains are mobilized by a percussive saltating grain; some grains are "knudged" along the ground, and some are partly expelled on short trajectories. These motions constitute reptation transport. On Mars, saltation and reptation become indistinct: secondary or "repercussive" trajectories have sufficient vertical impulse to create a

Gravel-Sand-Clay Mixture Model for Predictions of Permeability and Velocity of Unconsolidated Sediments

NASA Astrophysics Data System (ADS)

Konishi, C.

2014-12-01

Gravel-sand-clay mixture model is proposed particularly for unconsolidated sediments to predict permeability and velocity from volume fractions of the three components (i.e. gravel, sand, and clay). A well-known sand-clay mixture model or bimodal mixture model treats clay contents as volume fraction of the small particle and the rest of the volume is considered as that of the large particle. This simple approach has been commonly accepted and has validated by many studies before. However, a collection of laboratory measurements of permeability and grain size distribution for unconsolidated samples show an impact of presence of another large particle; i.e. only a few percent of gravel particles increases the permeability of the sample significantly. This observation cannot be explained by the bimodal mixture model and it suggests the necessity of considering the gravel-sand-clay mixture model. In the proposed model, I consider the three volume fractions of each component instead of using only the clay contents. Sand becomes either larger or smaller particles in the three component mixture model, whereas it is always the large particle in the bimodal mixture model. The total porosity of the two cases, one is the case that the sand is smaller particle and the other is the case that the sand is larger particle, can be modeled independently from sand volume fraction by the same fashion in the bimodal model. However, the two cases can co-exist in one sample; thus, the total porosity of the mixed sample is calculated by weighted average of the two cases by the volume fractions of gravel and clay. The effective porosity is distinguished from the total porosity assuming that the porosity associated with clay is zero effective porosity. In addition, effective grain size can be computed from the volume fractions and representative grain sizes for each component. Using the effective porosity and the effective grain size, the permeability is predicted by Kozeny-Carman equation

Transport of carboxymethyl cellulose-coated zerovalent iron nanoparticles in a sand tank: Effects of sand grain size, nanoparticle concentration and injection velocity.

PubMed

Li, Jing; Rajajayavel, Sai Rajasekar C; Ghoshal, Subhasis

2016-05-01

The transport of nanoscale zerovalent iron (NZVI) particles colloidally stabilized with 70,000 Da carboxymethyl cellulose (CMC), through sands with mean grain diameters of 180, 340 and 1140 μm (referred to as fine, intermediate and coarse-sized sand, respectively) was investigated in a 70-cm long, two-dimensional tank. The effect of NZVI concentrations (1 and 3 g-Fe L(-1)) and CMC concentrations (1 and 2 g L(-1)) and injection velocities (0.96 and 0.40 cm min(-1)) on particle transport were also evaluated with the intermediate sand. The overall NZVI mass fractions eluted from the tank were 36%, 25% and 16% in the coarse, intermediate and fine sands, respectively, when injected with 1 g L(-1) NZVI stabilized in 1 g L(-1) CMC. However, the mass fraction eluted reduced to 2.33% when the injection velocity was reduced from 0.96 to 0.40 cm min(-1) in the intermediate-sized sand. Maximum transport efficiency (38% NZVI mass eluted) in the intermediate-sized sand was achieved with 3 g L(-1) NZVI suspended in 2 g L(-1) CMC at an injection velocity of 0.96 cm min(-1). The transport efficiency was substantially decreased (11% NZVI mass eluted) when 3 g L(-1) NZVI was stabilized with only 1 g L(-1) CMC. The NZVI mean particle diameters in the porewaters remained unchanged at different locations in the tank suggesting that straining or gravity settling did not influence NZVI deposition. After NZVI injection, the hydraulic conductivity in the tank reduced by 80%-96%, depending on the CMC concentration and injection velocity. Copyright © 2016 Elsevier Ltd. All rights reserved.

Asbestos in play sand

DOE Office of Scientific and Technical Information (OSTI.GOV)

Langer, A.M.; Nolan, R.P.

1987-04-02

A letter in the New England Journal of Medicine (Oct. 2 issue) stated that a carbonate sand marketed in New Jersey was contaminated with 2 to 4 percent tremolite asbestos. The authors were called on by one of the federal agencies to repeat the analysis of this sand, specifically for its asbestos content. The sand was pulverized and immersed in oils with known refractive indexes, and the predominant amphibole was characterized by polarized light microscopy. The optical characteristics were noted, and the indexes of refraction were measured and found to be consistent with tremolite. On the basis of optical characterization,more » the authors concluded that all the tremolite visualized with light microscopy consisted of large, single cleavage fragments and was not asbestiform. They used the technique of x-ray diffraction, as did the author of the original report, which showed the presence of an amphibole mineral (probably tremolite) in the carbonate sand. The technique was not used, and cannot be used, to distinguish between the tremolite habits (asbestiform or nonasbestiform). An acid-insoluble residue, recovered from the carbonate sand, was examined by analytic electron microscopy. The tremolite grains were observed to consist of single untwinned, crystalline fragments. Few defects were noted. Selected area electron diffraction nets were indicative of fragments lying near or at the common amphibole cleavage plane. These characteristics are consistent with cleavage fragments and not asbestos. Aspect ratios reflected short particles (less than 5.1). On the basis of their examination of the carbonate play sand, they conclude that it did not contain tremolite asbestos.« less

Numerical simulation of wind-sand movement in the reversed flow region of a sand dune with a bridge built downstream.

PubMed

He, Wei; Huang, Ning; Xu, Bin; Wang, Wenbo

2018-04-23

A bridge built inside the reversed flow region of a sand dune will change the characteristics of wind-sand movement in this region. The Reynolds-averaged Navier-Stokes simulation and discrete particle tracing are used to simulate the wind-sand movement around a sand dune with a bridge built inside the reversed region. Three cases with different bridge positions are studied. The results show that 1) compared with the isolated dune case, a tall bridge built at the leeward toe leads to an increase in the deposition rate on the leeward slope and a longer reversed flow region downstream of the sand dune; meanwhile, the high speed of crosswind on the bridge indicates that some measures should be taken to protect trains from strong crosswind; 2) a low bridge at the leeward toe has little effect on the sand deposition and reversed flow region of the dune; however, low sand transport rate and crosswind speed on the bridge show that anti-crosswind/sand measures should be taken according to the actual situation and 3) a low bridge on the leeward slope has little effect on the length of reversed flow region, however, high crosswind speed and sand flux on the bridge reveal the need of anti-crosswind/sand measures on the bridge. Moreover, the bridges in the reversed flow region increase the sand flux near the leeward crest; as a result, the moving patterns of the sand dune are changed.

Small Particle Impact Damage on Different Glass Substrates

NASA Technical Reports Server (NTRS)

Waxman, R.; Guven, I.; Gray, P.

2017-01-01

Impact experiments using sand particles were performed on four distinct glass substrates. The sand particles were characterized using the X-Ray micro-CT technique; 3-D reconstruction of the particles was followed by further size and shape analyses. High-speed video footage from impact tests was used to calculate the incoming and rebound velocities of the individual sand impact events, as well as particle volume. Further, video analysis was used in conjunction with optical and scanning electron microscopy to relate the incoming velocity and shape of the particles to subsequent fractures, including both radial and lateral cracks. Analysis was performed using peridynamic simulations.

Geochemical heterogeneity in a sand and gravel aquifer: Effect of sediment mineralogy and particle size on the sorption of chlorobenzenes

USGS Publications Warehouse

Barber, Larry B.; Thurman, E. Michael; Runnells, Donald D.

1992-01-01

The effect of particle size, mineralogy and sediment organic carbon (SOC) on sorption of tetrachlorobenzene and pentachlorobenzene was evaluated using batch-isotherm experiments on sediment particle-size and mineralogical fractions from a sand and gravel aquifer, Cape Cod, Massachusetts. Concentration of SOC and sorption of chlorobenzenes increase with decreasing particle size. For a given particle size, the magnetic fraction has a higher SOC content and sorption capacity than the bulk or non-magnetic fractions. Sorption appears to be controlled by the magnetic minerals, which comprise only 5–25% of the bulk sediment. Although SOC content of the bulk sediment is <0.1%, the observed sorption of chlorobenzenes is consistent with a partition mechanism and is adequately predicted by models relating sorption to the octanol/water partition coefficient of the solute and SOC content. A conceptual model based on preferential association of dissolved organic matter with positively-charged mineral surfaces is proposed to describe micro-scale, intergranular variability in sorption properties of the aquifer sediments.

Observations of transport of bacterial-like microspheres through beach sand

NASA Astrophysics Data System (ADS)

Gast, Rebecca J.; Elgar, Steve; Raubenheimer, Britt

2015-04-01

Often, there is an order of magnitude more fecal indicator bacteria (enterococci) in beach sand than in nearby water. Consequently, sand is considered a reservoir for these bacteria, potentially contributing to poor water quality, and raising questions regarding the human health risks associated with sand exposure. An integral aspect of the distribution and persistence of sand-associated enterococci is the transport of bacteria introduced into the beach environment. Here, plastic microspheres are used as a proxy to examine the wave-induced movement of bacterial-like particles through sand on an ocean beach. Laboratory tests suggest microspheres and bacteria move similarly through sand columns, and have qualitatively similar short-term adsorption-to-sand behavior. Microspheres buried ~0.05 m below the sand surface on an ocean beach moved rapidly [O(10-3) m/s] away from their initial location, both vertically into the ground water below the sand and horizontally seaward within the sediment matrix in response to waves running up the beach face and percolating through the sand.

Experimental studies about the impact of traction sand on urban road dust composition.

PubMed

Kupiainen, Kaarle; Tervahattu, Heikki; Räisänen, Mika

2003-06-01

Traffic causes enhanced PM(10) resuspension especially during spring in the US, Japan, Norway, Sweden and Finland, among other countries. The springtime PM(10) consists primarily of mineral matter from tyre-induced paved road surface wear and traction sand. In some countries, the majority of vehicles are equipped with studded tyres to enhance traction, which additionally increases road surface wear. Because the traction sand and the mineral matter from the pavement aggregate can have a similar mineralogical composition, it has been difficult to determine the source of the mineral fraction in the PM(10). In this study, homogenous traction sand and pavement aggregate with different mineralogical compositions were chosen to determine the sources of PM(10) particles by single particle analysis (SEM/EDX). This study was conducted in a test facility, which made it possible to rule out dust contributions from other sources. The ambient PM(10) concentrations were higher when traction sand was used, regardless of whether the tyres were studded or not. Surprisingly, the use of traction sand greatly increased the number of the particles originating from the pavement. It was concluded that sand must contribute to pavement wear. This phenomenon is called the sandpaper effect. An understanding of this is important to reduce harmful effects of springtime road dust in practical winter maintenance of urban roads

Lagrangian and Eulerian description of bed-load particle kinematics

NASA Astrophysics Data System (ADS)

Ballio, Francesco; Sadabadi, Seyed Abbas Hosseini; Pokrajac, Dubravka; Radice, Alessio

2016-04-01

The motion of bed-load sediment particles transported by a flow can be analyzed within a Lagrangian or an Eulerian framework. In the former case, we consider the particles as individual objects in motion and we study their kinematic properties. The latter approach is instead referred to suitably chosen control volumes. Quantities describing sediment motion in the two frameworks are different, and the relationships among the two approaches are not straightforward. In this work, we intend to discuss the kinematic properties of sediment transport: first, a set of quantities is univocally defined; then, relationships among different representations are explored. Proof-of-concept results presented in the study are from a recent experiment involving weak bed-load sediment transport, where the moving particles were released over a fixed rough bed. The bulk flow velocity was 1.4 times the critical value for incipient particle motion, and particles were mostly moving by rolling and sliding, with limited saltation. The particle motion was filmed from the top and the measurements were conducted by image-based methods, obtaining extensive samples of virtually-instantaneous quantities.

Interannual Variability of Martian Global Dust Storms: Simulations with a Low-Order Model of the General Circulation

NASA Technical Reports Server (NTRS)

Pankine, A. A.; Ingersoll, Andrew P.

2002-01-01

We present simulations of the interannual variability of martian global dust storms (GDSs) with a simplified low-order model (LOM) of the general circulation. The simplified model allows one to conduct computationally fast long-term simulations of the martian climate system. The LOM is constructed by Galerkin projection of a 2D (zonally averaged) general circulation model (GCM) onto a truncated set of basis functions. The resulting LOM consists of 12 coupled nonlinear ordinary differential equations describing atmospheric dynamics and dust transport within the Hadley cell. The forcing of the model is described by simplified physics based on Newtonian cooling and Rayleigh friction. The atmosphere and surface are coupled: atmospheric heating depends on the dustiness of the atmosphere, and the surface dust source depends on the strength of the atmospheric winds. Parameters of the model are tuned to fit the output of the NASA AMES GCM and the fit is generally very good. Interannual variability of GDSs is possible in the IBM, but only when stochastic forcing is added to the model. The stochastic forcing could be provided by transient weather systems or some surface process such as redistribution of the sand particles in storm generating zones on the surface. The results are sensitive to the value of the saltation threshold, which hints at a possible feedback between saltation threshold and dust storm activity. According to this hypothesis, erodable material builds up its a result of a local process, whose effect is to lower the saltation threshold until a GDS occurs. The saltation threshold adjusts its value so that dust storms are barely able to occur.

Experimental Study of the Possibility to Make a Mortar with Ternary Sand (Natural and Artificial Fine Aggregates)

NASA Astrophysics Data System (ADS)

Baali, L.; Naceri, A.; Rahmouni, Z.; Mehidi, M. W. Noui

This experimental study investigates the possibility to make a mortar with a ternary sand (natural and artificial fine aggregates). This method is utilized to correct the particle size distribution of various sands used in mortar. For this investigation, three sands have been used: a dune sand (DS), a slag sand (SS), and brick sand (BS) at different proportions in mortar. After crushing, the artificial fine aggregate (blast furnace slag and waste brick fine aggregate) was sifted in order to use it as fine aggregate. The effect of the quality and grain size distribution of natural fine aggregate (i.e., DS) and artificial fine aggregates (i.e., SS and BS) on the physical properties of ternary sand confected (density, porosity, fineness modulus, equivalent sand, particle size distribution, water absorption) and properties of fresh and hardened mortar were analysed. In the same way for this study, the physical properties and chemical compositions of DS, SS, BS and cement were investigated. The results obtained show that the mechanical strength on mortar depends of the nature and particle size distribution of sand studied. The reuse of this recycled material (slag blast furnace and waste brick) in the industry would contribute to the protection of the environment. This study shows the potential of this method to make mortar with ternary sand (natural and artificial fine aggreagates) in order to improve the physical properties of sand. Utilising natural and artificial fine aggregates to produce quality mortar should yield significant environmental benefits.

Characterization and Evaluation of Incorporation the Casting Sand in Mortar

NASA Astrophysics Data System (ADS)

Zanelato, E. B.; Azevedo, A. R. G.; Alexandre, J.; Xavier, C. G.; Monteiro, S. N.; Mendonça, T. A. O.

The process of casting metals and alloys occurs through the fusion of this metal and its subsequent casting into a mold with the dimensions and geometry close to the final piece. Most foundries use sand casting molds for making you. This work aims to characterize and evaluate the foundry sand to allow its use in segments of Civil Engineering, creating a viable destination for a residue is that discarded. The following characterization tests were performer: particle size, chemical analysis, X-ray Diffraction and Density Real grain. For the execution of the test specimens was used to 1:3 cement and sand, and the incorporation of 10% and 20% of the total mass replacing the sand, and the trace reference. The results show that best results in compression and bending tests were obtained by replacing 10 % of common sand for sand casting.

Experimental studies of shock-induced particle jetting

NASA Astrophysics Data System (ADS)

Xue, Kun; Du, Kaiyuan; Shi, Xiaoliang

2018-05-01

The dispersion of particle rings or shells by a radially divergent shock front trailed by the pressurized gases takes the form of hierarchical particle jetting. Through a semi-two-dimensional configuration, we characterize the evolution of the jetting pattern using the boundary tracking technique. In contrast to the refined filamentary jetting spread induced by the dispersal of soft and ductile flour particles, the hard and brittle quartz sand particles are dispersed into a finger-like branched pattern with much fewer jets. The interplay between the primary and secondary jets suffices to reverse the flour jetting pattern, which by contrast is negligible in the quartz sand jetting. The distinct jetting patterns displayed by the flour and quartz sand particles are related with the distinguishable networks of force chains invoked in two particles which dictate the nucleation of jets.

Simple stochastic cellular automaton model for starved beds and implications about formation of sand topographic features in terms of sand flux

NASA Astrophysics Data System (ADS)

Endo, Noritaka

2016-12-01

A simple stochastic cellular automaton model is proposed for simulating bedload transport, especially for cases with a low transport rate and where available sediments are very sparse on substrates in a subaqueous system. Numerical simulations show that the bed type changes from sheet flow through sand patches to ripples as the amount of sand increases; this is consistent with observations in flume experiments and in the field. Without changes in external conditions, the sand flux calculated for a given amount of sand decreases over time as bedforms develop from a flat bed. This appears to be inconsistent with the general understanding that sand flux remains unchanged under the constant-fluid condition, but it is consistent with the previous experimental data. For areas of low sand abundance, the sand flux versus sand amount (flux-density relation) in the simulation shows a single peak with an abrupt decrease, followed by a long tail; this is very similar to the flux-density relation seen in automobile traffic flow. This pattern (the relation between segments of the curve and the corresponding bed states) suggests that sand sheets, sand patches, and sand ripples correspond respectively to the free-flow phase, congested phase, and jam phase of traffic flows. This implies that sand topographic features on starved beds are determined by the degree of interference between sand particles. Although the present study deals with simple cases only, this can provide a simplified but effective modeling of the more complicated sediment transport processes controlled by interference due to contact between grains, such as the pulsatory migration of grain-size bimodal mixtures with repetition of clustering and scattering.

Liquid-Gas-Like Phase Transition in Sand Flow Under Microgravity

NASA Astrophysics Data System (ADS)

Huang, Yu; Zhu, Chongqiang; Xiang, Xiang; Mao, Wuwei

2015-06-01

In previous studies of granular flow, it has been found that gravity plays a compacting role, causing convection and stratification by density. However, there is a lack of research and analysis of the characteristics of different particles' motion under normal gravity contrary to microgravity. In this paper, we conduct model experiments on sand flow using a model test system based on a drop tower under microgravity, within which the characteristics and development processes of granular flow under microgravity are captured by high-speed cameras. The configurations of granular flow are simulated using a modified MPS (moving particle simulation), which is a mesh-free, pure Lagrangian method. Moreover, liquid-gas-like phase transitions in the sand flow under microgravity, including the transitions to "escaped", "jumping", and "scattered" particles are highlighted, and their effects on the weakening of shear resistance, enhancement of fluidization, and changes in particle-wall and particle-particle contact mode are analyzed. This study could help explain the surface geology evolution of small solar bodies and elucidate the nature of granular interaction.

An Investigation into the Use of Manufactured Sand as a 100% Replacement for Fine Aggregate in Concrete.

PubMed

Pilegis, Martins; Gardner, Diane; Lark, Robert

2016-06-02

Manufactured sand differs from natural sea and river dredged sand in its physical and mineralogical properties. These can be both beneficial and detrimental to the fresh and hardened properties of concrete. This paper presents the results of a laboratory study in which manufactured sand produced in an industry sized crushing plant was characterised with respect to its physical and mineralogical properties. The influence of these characteristics on concrete workability and strength, when manufactured sand completely replaced natural sand in concrete, was investigated and modelled using artificial neural networks (ANN). The results show that the manufactured sand concrete made in this study generally requires a higher water/cement (w/c) ratio for workability equal to that of natural sand concrete due to the higher angularity of the manufactured sand particles. Water reducing admixtures can be used to compensate for this if the manufactured sand does not contain clay particles. At the same w/c ratio, the compressive and flexural strength of manufactured sand concrete exceeds that of natural sand concrete. ANN proved a valuable and reliable method of predicting concrete strength and workability based on the properties of the fine aggregate (FA) and the concrete mix composition.

An Investigation into the Use of Manufactured Sand as a 100% Replacement for Fine Aggregate in Concrete

PubMed Central

Pilegis, Martins; Gardner, Diane; Lark, Robert

2016-01-01

Manufactured sand differs from natural sea and river dredged sand in its physical and mineralogical properties. These can be both beneficial and detrimental to the fresh and hardened properties of concrete. This paper presents the results of a laboratory study in which manufactured sand produced in an industry sized crushing plant was characterised with respect to its physical and mineralogical properties. The influence of these characteristics on concrete workability and strength, when manufactured sand completely replaced natural sand in concrete, was investigated and modelled using artificial neural networks (ANN). The results show that the manufactured sand concrete made in this study generally requires a higher water/cement (w/c) ratio for workability equal to that of natural sand concrete due to the higher angularity of the manufactured sand particles. Water reducing admixtures can be used to compensate for this if the manufactured sand does not contain clay particles. At the same w/c ratio, the compressive and flexural strength of manufactured sand concrete exceeds that of natural sand concrete. ANN proved a valuable and reliable method of predicting concrete strength and workability based on the properties of the fine aggregate (FA) and the concrete mix composition. PMID:28773560

Sheet Flows, Avalanches, and Dune Evolution on Earth and Mars

NASA Technical Reports Server (NTRS)

2003-01-01

This investigation is a collaboration between researchers at Cornell University, the University of Florida, and the University of Rennes 1, France. Flow modeling at Cornell University focused on mechanisms for the suspension and transport of wind-blown sand that are important in both terrestrial and Martian environments. These mechanisms include the saltation (or jumping) of grains, collisions between grains, and the interaction of grains with the velocity fluctuations of the turbulent wind. Of particular interest are sheet flows; these are relatively thin, highly concentrated regions of grains flowing near the ground under the influence of a strong turbulent wind. In them, the grains are suspended by interparticle collisions. Sheet flows may be relatively rare events, but they have the capacity to move great amounts of sand. In order to describe sheet flows, a turbulent mixture theory was formulated for particles in a fluid in which fluctuations in the volume fiaction of the particles take place on the scale of the turbulent eddies. Ensemble averaged equations for particle and fluid mass, momentum, and energy and fluid rate of dissipation were expressed in terms of Farve (concentration) averaged velocities and the associated velocity fluctuations. Correlations that describe the turbulent suspension of particles and dissipation of turbulent energy of both phases due to fluid particle interactions were modeled and boundary conditions at the bed and at the upper surface of the collisional flow were formulated. The boundary conditions at the upper surface were tested in a numerical simulation developed at the University of Florida. Steady and unsteady solutions for steady and unsteady fully-developed flows were obtained over a range of wind speeds fiom the lowest for which collisional between particles occurred to at which turbulent suspension is found to dominate collisional suspension. Below the value of the wind speed at which collisions between particles were

Analyzing the Sand-fixing Effect of Feldspathic Sandstone from the Texture Characteristics

NASA Astrophysics Data System (ADS)

Zhang, lu; Ban, Jichang

2018-01-01

The purpose of this research was aimed to study the sand fixing effect of feldspathic sandstone in Mu Us Sandy Land, to provide a scienticic basis for desertification control, soil and water conservation and development of farming there. Methods of mixing feldspathic sandstone and aeolian sandy soil according to 1: 0, 1: 1, 1: 2, 1: 5, and 0: 1 mass ratioes, the graded composition and characteristics were studied with laser particle size analyzer. The result showed that these features of sand-based, loosely structured, easy to wind erosion of aeolian sandy soil were changed before feldspathic sandstone and aeolian sandy soil compounding. The <0.05 mm particle mass increased with feldspathic sandstone mass increasing. The texture presented this kind of change from sand to sandy loam to loam to silt loam. The small particle size distribution, good homogeneity and other features of aeolian sandy soil were improved to a certain degree, and the particle size distribution became broad before feldspathic sandstone and aeolian sandy soil compounding. The particle grading was continuous, and the grading characteristic was good when m(F): m(S) was 1: 5(Cu was 54.71 and Cc was 2.54) or when m(F): m(S) was 1: 2(Cu was 76.21, Cc was 1.12). The conclusion is that feldspathic sandstone has sand-fixing effect in texture characteristics, which heightens with feldspathic sandstone mass increasing, and when the mass ratio of feldspathic sandstone: aeolian sandy soil is 1: 2 or 1: 5 which compound better.

Retempering of Concrete made by using Manufactured Sand

NASA Astrophysics Data System (ADS)

Pethkar, A. R.; Deshmukh, G.

2014-06-01

Retempering is defined as, " Addition of water and remixing of concrete or mortar which has lost enough workability to become unplaceable". Retempering inevitably results in some loss of strength compared with the original concrete [1]. Adding water to a plastic mix to increase slump is an extremely common practice, even though it is not recommended because it increases the porosity of concrete. Concrete often arrives on site more than half an hour after initial mixing. Placement operations can take anywhere from 10 to 60 min, depending on the field conditions and the size of the load. When the slump decreases to an unacceptable level during the operations, water is added to the mix [1]. In this work, an attempt is made to study the strength characteristics of retempered concrete made by using manufactured sand. Usually the retempering process is there with normal and ready mixed concrete; hence an attempt is made to check the compressive and flexural strength of normal retempered concrete with an addition of retarder 0.2, 0.4 and 0.6 % at retempering time from 15 to 90 min. There is scarcity of natural sand due to various factors, which is replaced by the manufactured sand. The concept of manufactured sand is nothing but breaking stone into smaller and smaller particles in such way that the gradation of particle will match with zone-II of I.S.

Influence of phosphate on the transport properties of lead in sand.

PubMed

Butkus, Michael A; Johnson, Marie C

2011-01-15

Temporal moment analysis was used to examine the transport of lead species in sand columns. The influence of sodium phosphate (PO(4(aq))) and hydroxyapatite (HA) on lead transport was also evaluated. Transport properties of lead microparticles (diameter>0.45 μm) were a function of electrophoretic mobility: those particles with electrophoretic mobility less than -1 × 10(-8)m(2)/Vs exhibited significantly lower dimensionless first temporal moment (θ) and second temporal moment (σ(θ)(2)). The forms of lead investigated in this work had a tendency to move in sand over a wide pH range. Although the PO(4(aq)) amendment substantially reduced lead mass recoveries in the sand column effluent, lead microparticles were formed that had a tendency to move rapidly and with minimal dispersion when compared with controls. Treatments with HA provided limited reduction in lead mass recovery and minimal changes in lead transport properties. A colloid stability model was used to predict attachment of lead particles in sand. Published by Elsevier B.V.

Acoustic sand detector for fluid flowstreams

DOEpatents

Beattie, Alan G.; Bohon, W. Mark

1993-01-01

The particle volume and particle mass production rate of particulate solids entrained in fluid flowstreams such as formation sand or fracture proppant entrained in oil and gas production flowstreams is determined by a system having a metal probe interposed in a flow conduit for transmitting acoustic emissions created by particles impacting the probe to a sensor and signal processing circuit which produces discrete signals related to the impact of each of the particles striking the probe. The volume or mass flow rate of particulates is determined from making an initial particle size distribution and particle energy distribution and comparing the initial energy distribution and/or the initial size distribution with values related to the impact energies of a predetermined number of recorded impacts. The comparison is also used to recalibrate the system to compensate for changes in flow velocity.

[Preparation of polyacrylonitrile/natural sand composite materials and analysis of adsorption properties of Pb(II) on it by FAAS].

PubMed

Abduwayit, Medine; Nurulla, Ismayil; Abliz, Shawket

2015-02-01

Surfaces of natural sand particles were modified with (3-chloropropyl) trichlorosilane, so that bridging groups were introduced on the surfaces of natural sand particles; By grafting polyacrylonitrile onto the modified surfaces of the natural sand particles, a novelpolyacrylonitrile/natural sand composite material was prepared from the acrylonitrile, the azobisisobutyronitrile, the divinylbenzene and the modified natural sand particles, which are as functional monomer, initiator, either skeleton monomer or cross-linking agent and carrier respectively; the composite materials were characterized by using infrared spectroscopy and scanning electron microscopy; On the FTIR spectrum, the main characteristic peaks of various functional groups including nitrile, benzene ring, and silicon hydroxyl, which were from functional monomer, cross-linking agent and carrier respectively, were observed. On the SEM, two different cross section morphologies having different density which were from acrylonitrile and modified sand particles were observed; This proved that the polyacrylonitrile was decorated on modified sand particles during our preparation process. After preparing the composite materials, micro-column of separation and preconcentration was prepared using the composite materials as filler; the adsorption of some toxic heavy metal ions onto the composite materials was observed by flame atomic absorption spectrometry (FAAS); The results show that the adsorption of Pb2+ onto the composite materials was more stronger than the absorption of other toxic heavy metal ions, therefore, in this paper, the adsorption of Pb2+ onto the composite materials was mainly studied, at room temperature, when pH and flow rate of solution were 5. 4 and 4 mL x min(-1) respectively, the trace Pb(II) ions could be quantitatively adsorbed onto the composite materials; the maximum adsorption capacity of Pb(II) on the composite materials can reach 62.9 mg x g(-1). The column was eluted by 0.5 mol x L

A practical method for estimating maximum shear modulus of cemented sands using unconfined compressive strength

NASA Astrophysics Data System (ADS)

Choo, Hyunwook; Nam, Hongyeop; Lee, Woojin

2017-12-01

The composition of naturally cemented deposits is very complicated; thus, estimating the maximum shear modulus (Gmax, or shear modulus at very small strains) of cemented sands using the previous empirical formulas is very difficult. The purpose of this experimental investigation is to evaluate the effects of particle size and cement type on the Gmax and unconfined compressive strength (qucs) of cemented sands, with the ultimate goal of estimating Gmax of cemented sands using qucs. Two sands were artificially cemented using Portland cement or gypsum under varying cement contents (2%-9%) and relative densities (30%-80%). Unconfined compression tests and bender element tests were performed, and the results from previous studies of two cemented sands were incorporated in this study. The results of this study demonstrate that the effect of particle size on the qucs and Gmax of four cemented sands is insignificant, and the variation of qucs and Gmax can be captured by the ratio between volume of void and volume of cement. qucs and Gmax of sand cemented with Portland cement are greater than those of sand cemented with gypsum. However, the relationship between qucs and Gmax of the cemented sand is not affected by the void ratio, cement type and cement content, revealing that Gmax of the complex naturally cemented soils with unknown in-situ void ratio, cement type and cement content can be estimated using qucs.

Purification of Tronoh Silica Sand via preliminary process of mechanical milling

NASA Astrophysics Data System (ADS)

H, Nazratulhuda; M, Othman

2016-02-01

The purification of Tronoh silica sand is an important step in expanding technical applications of this silica sand. However no research on purifying of Tronoh silica sand has been reported. This study is focused on ball milling technique as a preliminary technique for Tronoh silica sand purification. The objectives are to study the effect of ball milling to the purification of the silica sand and to analyze its characteristics after the ball milling process. The samples before and after milling process were analyzed by using XRF, XRD, SEM and TEM. Results showed that the purity of SiO2 was increased, the size of the particles has been reduced and the surface area has increased. The crystalline phases for the silica before and after 4 hour milling time were remained constant.

Strength and microstructure characteristics of the recycled rubber tire-sand mixtures as lightweight backfill.

PubMed

Zhang, Tao; Cai, Guojun; Duan, Weihong

2018-02-01

The disposal of scrap rubber tires has induced critical environmental issue worldwide due to the rapid increase in the number of vehicles. Recycled scrap tires as a construction material in civil engineering have significant environmental benefits from a waste management perspective. A systematic study that deals with strength and microstructure characteristics of the rubber-sand mixtures is initiated, and mechanical response of the mixtures is discussed in this investigation. Experiments were conducted to evaluate the effects of rubber fraction on the basic properties including mass density (ρ), stress-strain characteristics, shear strength, and unconfined compression strength (q u ) of the rubber-sand mixtures. Additionally, scanning electron microscopy (SEM) was carried out to reveal the microstructure characteristics of the mixtures with various rubber fractions. A discussion on the micromechanics of the mixtures also was conducted. This study demonstrates that the ρ, friction angle, and q u decrease linearly with an increase in rubber fraction, whereas shear strain at peak increases. The stress-strain characteristics of the rubber-sand mixtures shift from brittle to ductile as the rubber fraction increase. These changes are attributed to remarkably lower stiffness and higher compressibility of the rubber particle compared with those of the conventional mineral aggregates. With an increase in the rubber fraction, the mechanical response of rubber-sand mixtures exhibits two types: sand-like material and rubber-like material. Rubber particle possesses the capacity to prevent the contacted sand particles from sliding at lower rubber fraction, whereas it transmits the applied loadings as the rubber fraction increased. This outcome reinforces the practicability of using recycled rubber tire-sand mixtures as a lightweight backfill in subbase/base applications.

Evaluation of the performance of the cross-flow air classifier in manufactured sand processing via CFD-DEM simulations

NASA Astrophysics Data System (ADS)

Petit, H. A.; Irassar, E. F.; Barbosa, M. R.

2018-01-01

Manufactured sands are particulate materials obtained as by product of rock crushing. Particle sizes in the sand can be as high as 6 mm and as low as a few microns. The concrete industry has been increasingly using these sands as fine aggregates to replace natural sands. The main shortcoming is the excess of particles smaller than <0.075 mm (Dust). This problem has been traditionally solved by a washing process. Air classification is being studied to replace the washing process and avoid the use of water. The complex classification process can only been understood with the aid of CFD-DEM simulations. This paper evaluates the applicability of a cross-flow air classifier to reduce the amount of dust in manufactured sands. Computational fluid dynamics (CFD) and discrete element modelling (DEM) were used for the assessment. Results show that the correct classification set up improves the size distribution of the raw materials. The cross-flow air classification is found to be influenced by the particle size distribution and the turbulence inside the chamber. The classifier can be re-designed to work at low inlet velocities to produce manufactured sand for the concrete industry.

Sand filter clogging by septic tank effluent.

PubMed

Spychała, M; Błazejewski, R

2003-01-01

The aim of this study was to characterise conditions and factors affecting fine sand clogging by septic tank effluent on the basis of physical modelling. The physical model consisted of 12 sand columns dosed with sewage from one household (5 persons), preliminary treated in a septic tank. Hydraulic loadings of the sand filters were equal to 82 mm/d. The mean discharge from sand columns, measured as the effluent volume collected during 10 minutes, decreased significantly over the experiment period from 34 cm3/min in August 2000 to 20 cm3/min in August 2001 at the same temperature of about 20 degrees C. First the columns clogged almost completely after 480 days in December 2001, however six columns had remained unclogged till the end of the experiment (March 2002). The temperature had a significant impact on hydraulic conductivity. A vertical distribution of accumulated mass and biomass was investigated in partly clogged sand. Microscopic survey of the clogging layer showed a presence of live micro-organisms, residuals of dead micro-organisms, particularly pieces of small animal armour and many fibres. These particles accelerated the accumulation of solids in the upper clogging layer. The study indicated that temperature impact on the filter hydraulic conductivity was more significant for biological activity, than for sewage viscosity.

Particle transport patterns of short-distance soil erosion by wind-driven rain, rain and wind

NASA Astrophysics Data System (ADS)

Marzen, Miriam; Iserloh, Thomas; de Lima, João L. M. P.; Ries, Johannes B.

2015-04-01

Short distance erosion of soil surface material is one of the big question marks in soil erosion studies. The exact measurement of short-distance transported soil particles, prior to the occurrence of overland flow, is a challenge to soil erosion science due to the particular requirements of the experimental setup and test procedure. To approach a quantification of amount and distance of each type of transport, we applied an especially developed multiple-gutter system installed inside the Trier Portable Wind and Rainfall Simulator (PWRS). We measured the amount and travel distance of soil particles detached and transported by raindrops (splash), wind-driven rain (splash-saltation and splash-drift) and wind (saltation). The test setup included three different erosion agents (rain/ wind-driven rain/ wind), two substrates (sandy/ loamy), three surface structures (grain roughness/ rills lengthwise/ rills transversal) and three slope angles (0°/+7°/-7°). The results present detailed transport patterns of the three erosion agents under the varying soil and surface conditions up to a distance of 1.6 m. Under the applied rain intensity and wind velocity, wind-driven rain splash generates the highest erosion. The erodibility and travel distance of the two substrates depend on the erosion agent. The total erosion is slightly higher for the slope angle -7° (downslope), but for wind-driven rain splash, the inclination is not a relevant factor. The effect of surface structures (rills) changes with traveling distance. The wind driven rain splash generates a much higher amount of erosion and a further travel distance of the particles due to the combined action of wind and rain. The wind-driven rain factor appears to be much more significant than the other factors. The study highlights the effects of different erosion agents and surface parameters on short-distance particle transport and the powerful impact of wind-driven rain on soil erosion.

Influence of permeability on nanoscale zero-valent iron particle transport in saturated homogeneous and heterogeneous porous media.

PubMed

Strutz, Tessa J; Hornbruch, Götz; Dahmke, Andreas; Köber, Ralf

2016-09-01

Nanoscale zero-valent iron (NZVI) particles can be used for in situ groundwater remediation. The spatial particle distribution plays a very important role in successful and efficient remediation, especially in heterogeneous systems. Initial sand permeability (k 0) influences on spatial particle distributions were investigated and quantified in homogeneous and heterogeneous systems within the presented study. Four homogeneously filled column experiments and a heterogeneously filled tank experiment, using different median sand grain diameters (d 50), were performed to determine if NZVI particles were transported into finer sand where contaminants could be trapped. More NZVI particle retention, less particle transport, and faster decrease in k were observed in the column studies using finer sands than in those using coarser sands, reflecting a function of k 0. In heterogeneous media, NZVI particles were initially transported and deposited in coarse sand areas. Increasing the retained NZVI mass (decreasing k in particle deposition areas) caused NZVI particles to also be transported into finer sand areas, forming an area with a relatively homogeneous particle distribution and converged k values despite the different grain sizes present. The deposited-particle surface area contribution to the increasing of the matrix surface area (θ) was one to two orders of magnitude higher for finer than coarser sand. The dependency of θ on d 50 presumably affects simulated k changes and NZVI distributions in numerical simulations of NZVI injections into heterogeneous aquifers. The results implied that NZVI can in principle also penetrate finer layers.

The Enigmatic Longevity of Granular Materials on Mars: The Case for Geologically Episodic Dune Formation

NASA Technical Reports Server (NTRS)

Marshall, J.

1999-01-01

considerations of material strength versus mechanical work applied to the material, comminution to sub-sand size would be inevitable. Another semi-analytical approach might be taken by considering that the archetypal aeolian sand surface texture is an irregularly pitted ("frosted") surface composed of chipping hollows approximately 10 microns in diameter, 5 microns deep. Their volume = about 250 cubic microns, or about 1/25000 of the volume of a 100 micron diameter dune grain. Because a saltating grain always strikes another grain, then two surfaces are impacted. Thus each grain undergoes two impacts for every one saltation leap, when the impact statistics are considered for a closed dune system (it can be calculated that a grain can never undergo <1 impact, and never >2 per saltation leap). Hence, if we conservatively assume that there is damage to a grain each time it bounces, but with the minimum damage of only 2 microscopic craters per impact, then approximately 12,500 impacts are required to completely eliminate the grain. Of course, it would require only a fraction of this amount to reduce the grain to below sand size. A grain will make only several tens of saltation leaps on the stoss side of a dune before becoming buried on the lee slope. The dune then has to move its full length before the grain is exhumed again for abrasion. Even with this hiatus in transport, it is easy to see that terrestrial dunes need resupplying with sand in order to survive. In recent theoretical work it has been shown that martian aeolian transport may be initiated with high-speed grains, but this converts to a lower energy dynamic transport equilibrium in which a reptation population dominates grain transport (on Earth, at least half of the flux is by reptation and creep). On Mars, therefore, average grain speeds may be lower than those on Earth, or at least comparable. This would permit greater longevity for martian sands, but it would not go far enough to solve the survival problem. It may

Particle motion in atmospheric boundary layers of Mars and Earth

NASA Technical Reports Server (NTRS)

White, B. R.; Iversen, J. D.; Greeley, R.; Pollack, J. B.

1975-01-01

To study the eolian mechanics of saltating particles, both an experimental investigation of the flow field around a model crater in an atmospheric boundary layer wind tunnel and numerical solutions of the two- and three-dimensional equations of motion of a single particle under the influence of a turbulent boundary layer were conducted. Two-dimensional particle motion was calculated for flow near the surfaces of both Earth and Mars. For the case of Earth both a turbulent boundary layer with a viscous sublayer and one without were calculated. For the case of Mars it was only necessary to calculate turbulent boundary layer flow with a laminar sublayer because of the low values of friction Reynolds number; however, it was necessary to include the effects of slip flow on a particle caused by the rarefied Martian atmosphere. In the equations of motion the lift force functions were developed to act on a single particle only in the laminar sublayer or a corresponding small region of high shear near the surface for a fully turbulent boundary layer. The lift force functions were developed from the analytical work by Saffman concerning the lift force acting on a particle in simple shear flow.

The chemistry of Saudi Arabian sand: A deposition problem on helicopter turbine airfoils

NASA Technical Reports Server (NTRS)

Smialek, James L.

1991-01-01

Recent operations in the Persian Gulf have exposed military helicopter turbines to excessive amounts of ingested sand. Fine particles, less than 10 microns, are able to bypass the particle separators and enter the cooling and combustion systems. The initial sand chemistry varies by location, but is made up of a calcium aluminum silicate glass, SiO2 low quartz (Ca,Mg) CO3 dolomite, CaCO3 calcite, and occasionally CaCl rocksalt. The sand reacts in the hot combustion gases and deposits onto the turbine vanes as CaSO4, glass, and various crystalline silicates. Deposits up to 0.25 in. thick have been collected. Although cooling hole plugging is a considerable problem, excessive corrosion is not commonly observed due to the high melting point of GaSO4.

The chemistry of Saudi Arabian sand - A deposition problem on helicopter turbine airfoils

NASA Astrophysics Data System (ADS)

Smialek, James L.; Archer, Frances A.; Garlick, Ralph G.

Operations in the Persian Gulf have exposed military helicopter turbines to excessive amounts of ingested sand. Fine particles, less than 10 microns, are able to bypass the particle separators and enter the cooling and combustion systems. The initial sand chemistry varies by location, but is made up of a calcium aluminum silicate glass, SiO2 low quartz, (Ca,Mg)CO3 dolomite, CaCO3 calcite, and occasionally NaCl rocksalt. The sand reacts in the hot combustion gases and deposits onto the turbine vanes as CaSO4, glass, and various crystalline silicates. Deposits up to 5 mm thick have been collected. Although cooling hole plugging is a considerable problem, excessive corrosion is not commonly observed due to the high melting point of CaSO4.

The Chemistry of Saudi Arabian Sand - A Deposition Problem on Helicopter Turbine Airfoils

NASA Technical Reports Server (NTRS)

Smialek, James L.; Archer, Frances A.; Garlick, Ralph G.

1992-01-01

Operations in the Persian Gulf have exposed military helicopter turbines to excessive amounts of ingested sand. Fine particles, less than 10 microns, are able to bypass the particle separators and enter the cooling and combustion systems. The initial sand chemistry varies by location, but is made up of a calcium aluminum silicate glass, SiO2 low quartz, (Ca,Mg)CO3 dolomite, CaCO3 calcite, and occasionally NaCl rocksalt. The sand reacts in the hot combustion gases and deposits onto the turbine vanes as CaSO4, glass, and various crystalline silicates. Deposits up to 5 mm thick have been collected. Although cooling hole plugging is a considerable problem, excessive corrosion is not commonly observed due to the high melting point of CaSO4.

Spectroscopic signatures of PETN in contact with sand particles

NASA Astrophysics Data System (ADS)

Ballesteros, Luz M.; Herrera, Gloria M.; Castro, Miguel E.; Briano, Julio; Mina, Nairmen; Hernandez-Rivera, Samuel P.

2005-06-01

The detection of explosive materials is not only important as an issue in landmines but also for global security reasons, unexploded ordnance, and Improvised Explosive Devices detection. In such areas, explosives detection has played a central role in ensuring the safety of the lives of citizens in many countries. Raman Spectroscopy is a well established tool for vibrational spectroscopic analysis and can be applied to the field of explosives identification and detection. The analysis of PETN is important because it is used in laminar form or mixed with RDX to manufacture Semtex plastic explosive and in the fabrication of Improvised Explosive Devices (IEDs). Our investigation is focused on the study of spectroscopic signatures of PETN in contact with soil. Ottawa sand mixed in different proportions with PETN together with the study of the influence of pH, temperature, humidity, and UV light on the vibrational signatures of the mixtures constitute the core of the investigation. The results reveal that the characteristic bands of PETN are not significantly shifted but rather appear constant with respect of the ubiquitous band of sand (~463 cm-1). These results will make possible the development of highly sensitive sensors for detection of explosives materials and IDEs.

Transport and retention of bacteria and viruses in biochar-amended sand.

PubMed

Sasidharan, Salini; Torkzaban, Saeed; Bradford, Scott A; Kookana, Rai; Page, Declan; Cook, Peter G

2016-04-01

The transport and retention of Escherichia coli and bacteriophages (PRD1, MS2 and ФX174), as surrogates for human pathogenic bacteria and viruses, respectively, were studied in the sand that was amended with several types of biochar produced from various feedstocks. Batch and column studies were conducted to distinguish between the role of attachment and straining in microbe retention during transport. Batch experiments conducted at various solution chemistries showed negligible attachment of viruses and bacteria to biochar before or after chemical activation. At any given solution ionic strength, the attachment of viruses to sand was significantly higher than that of biochar, whereas bacteria showed no attachment to either sand or biochar. Consistent with batch results, biochar addition (10% w/w) to sand reduced virus retention in the column experiments, suggesting a potential negative impact of biochar application to soil on virus removal. In contrast, the retention of bacteria was enhanced in biochar-amended sand columns. However, elimination of the fine fraction (<60μm) of biochar particles in biochar-amended sand columns significantly reduced bacteria retention. Results from batch and column experiments suggest that land application of biochar may only play a role in microbe retention via straining, by alteration of pore size distribution, and not via attachment. Consequently, the particle size distribution of biochar and sediments is a more important factor than type of biochar in determining whether land application of biochar enhances or diminishes microbial retention. Copyright © 2016 Elsevier B.V. All rights reserved.

Aeolian features and processes at the Mars Pathfinder landing site

USGS Publications Warehouse

Greeley, Ronald; Kraft, Michael; Sullivan, Robert; Wilson, Gregory; Bridges, Nathan; Herkenhoff, Ken; Kuzmin, Ruslan O.; Malin, Michael; Ward, Wes

1999-01-01

The Mars Pathfinder landing site contains abundant features attributed to aeolian, or wind, processes. These include wind tails, drift deposits, duneforms of various types, ripplelike features, and ventifacts (the first clearly seen on Mars). Many of these features are consistant with formation involving sand-size particles. Although some features, such as dunes, could develop from saltating sand-size aggregates of finer grains, the discovery of ventifact flutes cut in rocks strongly suggests that at least some of the grains are crystalline, rather than aggregates. Excluding the ventifacts, the orientations of the wind-related features correlate well with the orientations of bright wind steaks seen on Viking Orbiter images in the general area. They also correlate with wind direction predictions from the NASA-Ames General Circulation Model (GCM) which show that the strongest winds in the area occur in the northern hemisphere winter and are directed toward 209°. Copyright 1999 by the American Geophysical Union.

Porous media grain size distribution and hydrodynamic forces effects on transport and deposition of suspended particles.

PubMed

Ahfir, Nasre-Dine; Hammadi, Ahmed; Alem, Abdellah; Wang, HuaQing; Le Bras, Gilbert; Ouahbi, Tariq

2017-03-01

The effects of porous media grain size distribution on the transport and deposition of polydisperse suspended particles under different flow velocities were investigated. Selected Kaolinite particles (2-30μm) and Fluorescein (dissolved tracer) were injected in the porous media by step input injection technique. Three sands filled columns were used: Fine sand, Coarse sand, and a third sand (Mixture) obtained by mixing the two last sands in equal weight proportion. The porous media performance on the particle removal was evaluated by analysing particles breakthrough curves, hydro-dispersive parameters determined using the analytical solution of convection-dispersion equation with a first order deposition kinetics, particles deposition profiles, and particle-size distribution of the recovered and the deposited particles. The deposition kinetics and the longitudinal hydrodynamic dispersion coefficients are controlled by the porous media grain size distribution. Mixture sand is more dispersive than Fine and Coarse sands. More the uniformity coefficient of the porous medium is large, higher is the filtration efficiency. At low velocities, porous media capture all sizes of suspended particles injected with larger ones mainly captured at the entrance. A high flow velocity carries the particles deeper into the porous media, producing more gradual changes in the deposition profile. The median diameter of the deposited particles at different depth increases with flow velocity. The large grain size distribution leads to build narrow pores enhancing the deposition of the particles by straining. Copyright © 2016. Published by Elsevier B.V.

Effect of erodent particles on the erosion of metal specimens

NASA Astrophysics Data System (ADS)

Razzaque, M. Mahbubur; Alam, M. Khorshed; Khan, M. Ishak

2016-07-01

This paper presents the experimental results of the measurement of erosion rate of carbon steel specimens in sand water slurry system in a slurry pot tester. Sylhet sand has been sieved to get three sizes of erodent particles; namely, less than 250 micron, 250 to 590 micron and 590 to 1190 micron. Experiments are done with three sand concentrations (10%, 15% and 20%). The rate of erosion of the carbon steel specimens is measured as the loss of weight per unit surface area per unit time under the dynamic action of solid particles. The eroded surfaces of the specimens are examined using Scanning Electron Microscopy (SEM) to visualize the impact of the slurry of various conditions. It is seen that irrespective of the particle size the rate of erosion increases with the increase of slurry concentration. This increment of erosion rate at high concentration is high for large particles. High erosion rate is observed in case of large sand particles. In case of small and fine particles erosion rate is small because of low impact energy as well as the wastage of energy to overcome the hindrance of the finer particles before striking on the specimen surface.

Microstructure Based Material-Sand Particulate Interactions and Assessment of Coatings for High Temperature Turbine Blades

NASA Technical Reports Server (NTRS)

Murugan, Muthuvel; Ghoshal, Anindya; Walock, Michael; Nieto, Andy; Bravo, Luis; Barnett, Blake; Pepi, Marc; Swab, Jeffrey; Pegg, Robert Tyler; Rowe, Chris;

Aeolian transport in the field: A comparison of the effects of different surface treatments

NASA Astrophysics Data System (ADS)

Dong, Zhibao; Lv, Ping; Zhang, Zhengcai; Qian, Guangqiang; Luo, Wanyin

2012-05-01

Aeolian transport represents the result of wind-surface interactions, and therefore depends strongly on variations in the characteristics of the sediment surface. We conducted field observations of aeolian transport of typical dune sand in three 80 m × 80 m plots with different surface treatments: gravel-covered sand, enclosed shifting sand, and open (unprotected) shifting sand. The study was performed at the Shapotou Aeolian Experiment Site in the southeastern part of China's Tengger Desert to compare the effects of these different surface treatments on aeolian transport. To do so, we analyzed the flux density profiles and transport rates above each surface. The flux density profiles for all three treatments followed the exponential decay law that was proposed by most previous researchers to describe the saltation flux density profiles. Coefficients of the exponential decay function were defined as a function of the surface and the wind velocity. The enclosed and open plots with shifting sand had similar flux density profiles, but the flux density above gravel-covered plots showed that transport decayed more slowly with increasing height, producing flux density profiles with a higher average saltation height. The transport rate above the three treatment plots tended to increase proportionally with the cube of the mean wind velocity and with the maximum wind velocity during the observation period, but was more strongly correlated with the square of drift potential. Transport rates above the plot with open shifting sand were greater than those above the plots with enclosed shifting sand and the gravel-covered plot.

Terrestrial Analogs to Wind-Related Features at the Viking and Pathfinder Landing Sites on Mars

NASA Technical Reports Server (NTRS)

Greeley, Ronald; Bridges, Nathan T.; Kuzmin, Ruslan O.; Laity, Julie E.

2002-01-01

Features in the Mojave Desert and Iceland provide insight into the characteristics and origin of Martian wind-related landforms seen by the Viking and Pathfinder landers. The terrestrial sites were chosen because they exhibit diverse wind features that are generally well understood. These features have morphologies comparable to those on Mars and include origins by deposition and erosion, with erosional processes modifying both soils and rocks. Duneforms and drifts are the most common depositional features seen at the Martian landing sites and indicate supplies of sand-sized particles blown by generally unidirectional winds. Erosional features include lag deposits, moat-like depressions around some rocks, and exhumed soil horizons. They indicate that wind can deflate at least some sediments and that this process is particularly effective where the wind interacts with rocks. The formation of ripples and wind tails involves a combination of depositional and erosional processes. Rock erosional features, or ventifacts, are recognized by their overall shapes, erosional flutes, and characteristic surface textures resulting from abrasion by windblown particles. The physics of saltation requires that particles in ripples and duneforms are predominantly sand-sized (60-2000 microns). The orientations of duneforms, wind tails, moats, and ventifacts are correlated with surface winds above particle threshold. Such winds are influenced by local topography and are correlated with winds at higher altitudes predicted by atmospheric models.

Petrology of dune sand derived from basalt on the Ka'u Desert, Hawaii

NASA Technical Reports Server (NTRS)

Gooding, J. L.

1982-01-01

Dune sand from the Ka'u Desert, southwest flank of Kilauea volcano, Hawaii, is moderately well-sorted (median = 1.60 Phi, deviation = 0.60, skewness = 0.25, kurtosis = 0.68) and composed mostly of frosted subangular particles of basalt glass ('unfractionated' olivine-normative tholeitte), olivine, lithic fragments (subophitic and intersertal basalts; magnetite-ilmenite-rich basalts), reticular basalt glass, magnetite, ilmenite, and plagioclase, in approximately that order of abundance. Quantitative lithological comparison of the dune sand with sand-sized ash from the Keanakakoi Formation supports suggestions that the dune sand was derived largely from Keanakakoi ash. The dune sand is too well sorted to have been emplaced in its present form by base-surge but could have evolved by post-eruption reworking of the ash.

Rock Abrasion and Ventifact Formation on Mars from Field Analog, Theoretical, and Experimental Studies

NASA Technical Reports Server (NTRS)

Bridges, N. T.; Laity, J. E.

2001-01-01

Rocks observed by the Viking Landers and Pathfinder Lander/Sojourner rover exhibit a suite of perplexing rock textures. Among these are pits, spongy textures, penetrative flutes, lineaments, crusts, and knobs Fluvial, impact, chemical alteration, and aeolian mechanisms have been proposed for many of these. In an effort to better understand the origin and characteristics of Martian rock textures, abraded rocks in the Mojave Desert and other regions have been studied. We find that most Martian rock textures, as opposed to just a few, bear close resemblance to terrestrial aeolian textures and can most easily be explained by wind, not other, processes. Flutes, grooves, and some pits on Mars are consistent with abrasion by saltating particles, as described previously. However, many other rock textures probably also have an aeolian origin. Sills at the base of rocks that generally lie at high elevations, such as Half Dome, are consistent with such features on Earth that are related to moats or soil ramps that shield the basal part of the rock from erosion. Crusts consisting of fluted fabrics, such as those on Stimpy and Chimp, are similar to fluted crusts on Earth that spall off over time. Knobby and lineated rocks are similar to terrestrial examples of heterogeneous rocks that differentially erode. The location of specific rock textures on Mars also gives insight into their origin. Many of the most diagnostic ventifacts found at the Pathfinder site are located on rocks that lie near the crests or the upper slopes of ridges. On Earth, the most active ventifact formation occurs on sloped or elevated topography, where windflow is accelerated and particle kinetic energy and flux are increased. Integrated 0 together, these observations point to significant aeolian 0 modification of rocks on Mars and cast doubt on whether many primary textures resulting from other processes are preserved. Experimental simulations of abrasion in the presence of abundant sand indicate that

Effect of erodent particles on the erosion of metal specimens

DOE Office of Scientific and Technical Information (OSTI.GOV)

Razzaque, M. Mahbubur, E-mail: mmrazzaque@me.buet.ac.bd; Alam, M. Khorshed; Khan, M. Ishak, E-mail: ishak.buet@gmail.com

2016-07-12

This paper presents the experimental results of the measurement of erosion rate of carbon steel specimens in sand water slurry system in a slurry pot tester. Sylhet sand has been sieved to get three sizes of erodent particles; namely, less than 250 micron, 250 to 590 micron and 590 to 1190 micron. Experiments are done with three sand concentrations (10%, 15% and 20%). The rate of erosion of the carbon steel specimens is measured as the loss of weight per unit surface area per unit time under the dynamic action of solid particles. The eroded surfaces of the specimens aremore » examined using Scanning Electron Microscopy (SEM) to visualize the impact of the slurry of various conditions. It is seen that irrespective of the particle size the rate of erosion increases with the increase of slurry concentration. This increment of erosion rate at high concentration is high for large particles. High erosion rate is observed in case of large sand particles. In case of small and fine particles erosion rate is small because of low impact energy as well as the wastage of energy to overcome the hindrance of the finer particles before striking on the specimen surface.« less

Coupled changes in sand grain size and sand transport driven by changes in the upstream supply of sand in the Colorado River: relative importance of changes in bed-sand grain size and bed-sand area

USGS Publications Warehouse

Topping, D.J.; Rubin, D.M.; Melis, T.S.

2007-01-01

Sand transport in the Colorado River in Marble and Grand canyons was naturally limited by the upstream supply of sand. Prior to the 1963 closure of Glen Canyon Dam, the river exhibited the following four effects of sand supply limitation: (1) hysteresis in sediment concentration, (2) hysteresis in sediment grain size coupled to the hysteresis in sediment concentration, (3) production of inversely graded flood deposits, and (4) development or modification of a lag between the time of a flood peak and the time of either maximum or minimum (depending on reach geometry) bed elevation. Construction and operation of the dam has enhanced the degree to which the first two of these four effects are evident, and has not affected the degree to which the last two effects of sand supply limitation are evident in the Colorado River in Marble and Grand canyons. The first three of the effects involve coupled changes in suspended-sand concentration and grain size that are controlled by changes in the upstream supply of sand. During tributary floods, sand on the bed of the Colorado River fines; this causes the suspended sand to fine and the suspended-sand concentration to increase, even when the discharge of water remains constant. Subsequently, the bed is winnowed of finer sand, the suspended sand coarsens, and the suspended-sand concentration decreases independently of discharge. Also associated with these changes in sand supply are changes in the fraction of the bed that is covered by sand. Thus, suspended-sand concentration in the Colorado River is likely regulated by both changes in the bed-sand grain size and changes in the bed-sand area. A physically based flow and suspended-sediment transport model is developed, tested, and applied to data from the Colorado River to evaluate the relative importance of changes in the bed-sand grain size and changes in the bed-sand area in regulating suspended-sand concentration. Although the model was developed using approximations for steady

Microdunes and other aeolian bedforms on Venus - Wind Tunnel simulations

NASA Technical Reports Server (NTRS)

Greeley, R.; Marshall, J. R.; Leach, R. N.

1984-01-01

The development of aeolian bedforms in the simulated Venusian environment has been experimentally studied in the Venus Wind Tunnel. It is found that the development of specific bedforms, including ripples, dunes, and 'waves', as well as their geometry, are controlled by a combination of factors including particle size, wind speed, and atmospheric density. Microdunes are formed which are analogous to full-size terrestrial dunes and are characterized by the development of slip faces, internal cross-bedding, a low ratio of saltation path length to dune length, and a lack of particle-size sorting. They begin to develop at wind speeds just above saltation threshold and evolve into waves at higher velocities. At wind speeds of about 1.5 m/sec and higher, the bed is flat and featureless. This evolution is explained by a model based on the interaction of alternating zones of erosion and deposition and particle saltation distances.

Microdunes and Other Aeolian Bedforms on Venus: Wind Tunnel Simulations

NASA Technical Reports Server (NTRS)

Greeley, R.; Marshall, J. R.; Leach, R. N.

1985-01-01

The development of aeolian bedforms in the simulated Venusian environment has been experimentally studied in the Venus Wind tunnel. It is found that the development of specific bedforms, including ripples, dunes, and waves, as well as their geometry, are controlled by a combination of factors including particle size, wind speed, and atmospheric density. Microdunes are formed which are analogous to full-size terrestrial dunes and are characterized by the development of slip faces, internal cross-bedding, a low ratio of saltation path length to dune length, and a lack of particle-size sorting. They begin to develop at wind speeds just above saltation threshold and evolve into waves at higher velocities. At wind speeds of about 1.5 m/sec and higher, the bed is flat and featureless. This evolution is explained by a model based on the interaction of alternating zones of erosion and deposition and particle saltation distances.

Inhalation exposure during spray application and subsequent sanding of a wood sealant containing zinc oxide nanoparticles.

PubMed

Cooper, Michael R; West, Gavin H; Burrelli, Leonard G; Dresser, Daniel; Griffin, Kelsey N; Segrave, Alan M; Perrenoud, Jon; Lippy, Bruce E

2017-07-01

Nano-enabled construction products have entered into commerce. There are concerns about the safety of manufactured nanomaterials, and exposure assessments are needed for a more complete understanding of risk. This study assessed potential inhalation exposure to ZnO nanoparticles during spray application and power sanding of a commercially available wood sealant and evaluated the effectiveness of local exhaust ventilation in reducing exposure. A tradesperson performed the spraying and sanding inside an environmentally-controlled chamber. Dust control methods during sanding were compared. Filter-based sampling, electron microscopy, and real-time particle counters provided measures of exposure. Airborne nanoparticles above background levels were detected by particle counters for all exposure scenarios. Nanoparticle number concentrations and particle size distributions were similar for sanding of treated versus untreated wood. Very few unbound nanoparticles were detected in aerosol samples via electron microscopy, rather nano-sized ZnO was contained within, or on the surface of larger airborne particles. Whether the presence of nanoscale ZnO in these aerosols affects toxicity merits further investigation. Mass-based exposure measurements were below the NIOSH Recommended Exposure Limit for Zn, although there are no established exposure limits for nanoscale ZnO. Local exhaust ventilation was effective, reducing airborne nanoparticle number concentrations by up to 92% and reducing personal exposure to total dust by at least 80% in terms of mass. Given the discrepancies between the particle count data and electron microscopy observations, the chemical identity of the airborne nanoparticles detected by the particle counters remains uncertain. Prior studies attributed the main source of nanoparticle emissions during sanding to copper nanoparticles generated from electric sander motors. Potentially contrary results are presented suggesting the sander motor may not have been

The role of water content in triboelectric charging of wind-blown sand.

PubMed

Gu, Zhaolin; Wei, Wei; Su, Junwei; Yu, Chuck Wah

2013-01-01

Triboelectric charging is common in desert sandstorms and dust devils on Earth; however, it remains poorly understood. Here we show a charging mechanism of sands with the adsorbed water on micro-porous surface in wind-blown sand based on the fact that water content is universal but usually a minor component in most particle systems. The triboelectric charging could be resulted due to the different mobility of H(+)/OH(-) between the contacting sands with a temperature difference. Computational fluid dynamics (CFD) and discrete element method (DEM) were used to demonstrate the dynamics of the sand charging. The numerically simulated charge-to-mass ratios of sands and electric field strength established in wind tunnel agreed well with the experimental data. The charging mechanism could provide an explanation for the charging process of all identical granular systems with water content, including Martian dust devils, wind-blown snow, even powder electrification in industrial processes.

Reduced transport potential of a palladium-doped zero valent iron nanoparticle in a water saturated loamy sand.

PubMed

Basnet, Mohan; Di Tommaso, Caroline; Ghoshal, Subhasis; Tufenkji, Nathalie

2015-01-01

Direct in situ injection of palladium-doped nanosized zero valent iron (Pd-NZVI) particles can contribute to remediation of various environmental contaminants. A major challenge encountered is rapid aggregation of Pd-NZVI and hence very limited mobility. To reduce aggregation and concurrently improve particle mobility, the surface of bare Pd-NZVI can be modified with stabilizing surface modifiers. Selected surface-modified Pd-NZVI has shown dramatically improved stability and transport. However, little is known regarding the effects of aquifer grain geochemical heterogeneity on the transport and deposition behavior of surface-modified Pd-NZVI. Herein, the mobility of surface stabilized Pd-NZVI in two granular matrices representative of model ground water environments (quartz sand and loamy sand) was assessed over a wide range of environmentally relevant ionic strengths (IS). Carboxymethyl cellulose (CMC), soybean flour and rhamnolipid biosurfactant were used as Pd-NZVI surface modifiers. Our results show that, both in quartz sand and loamy sand, an increase in solution IS results in reduced Pd-NZVI transport. Moreover, at a given water chemistry, Pd-NZVI transport is notably attenuated in loamy sand implying that geochemical heterogeneity associated with loamy sand is a key factor influencing Pd-NZVI transport potential. Experiments conducted at a higher Pd-NZVI particle concentration, to be more representative of field conditions, show that rhamnolipid and CMC are effective stabilizing agents even when 1 g/L Pd-NZVI is injected into quartz sand. Overall, this study emphasizes the extent to which variation in groundwater chemistry, coupled with changes in aquifer geochemistry, could dramatically alter the transport potential of Pd-NZVI in the subsurface environment.

Dynamic characteristics of motor-gear system under load saltations and voltage transients

NASA Astrophysics Data System (ADS)

Bai, Wenyu; Qin, Datong; Wang, Yawen; Lim, Teik C.

2018-02-01

In this paper, a dynamic model of a motor-gear system is proposed. The model combines a nonlinear permeance network model (PNM) of a squirrel-cage induction motor and a coupled lateral-torsional dynamic model of a planetary geared rotor system. The external excitations including voltage transients and load saltations, as well as the internal excitations such as spatial effects, magnetic circuits topology and material nonlinearity in the motor, and time-varying mesh stiffness and damping in the planetary gear system are considered in the proposed model. Then, the simulation results are compared with those predicted by the electromechanical model containing a dynamic motor model with constant inductances. The comparison showed that the electromechanical system model with the PNM motor model yields more reasonable results than the electromechanical system model with the lumped-parameter electric machine. It is observed that electromechanical coupling effect can induce additional and severe gear vibrations. In addition, the external conditions, especially the voltage transients, will dramatically affect the dynamic characteristics of the electromechanical system. Finally, some suggestions are offered based on this analysis for improving the performance and reliability of the electromechanical system.

Evaluation of Durability Parameters of Concrete with Manufacture Sand and River Sand

NASA Astrophysics Data System (ADS)

Sangoju, Bhaskar; Ramesh, G.; Bharatkumar, B. H.; Ramanjaneyulu, K.

2017-09-01

Most of the states in our country have banned sand quarrying from the river beds, causing a scarcity of natural river sand for the construction sector. Manufacture sand (M-sand) is one of the alternate solutions to replace the river sand (R-sand) in concrete. The main aim of the present study is to evaluate the durability parameters of concrete with M-sand when compared to that of concrete with R-sand. Corrosion of reinforcement is one of the main deteriorating mechanisms of reinforced concrete due to the ingress of chloride ions or carbon-di-oxide. For comparative evaluation of durability parameters, accelerated tests such as Rapid Chloride Permeability Test, Rapid Chloride Migration Test and accelerated carbonation test were carried out on specimens of R-sand and M-sand. All tests were carried out after 90 days of casting. Test results reveal that the durability parameters of the concrete with M-sand in chloride induced environment is relatively better than that of concrete with R-sand and hence is recommended to use M-sand as a replacement to R-sand.

Modeling the dust cycle from sand dunes to haboobs

NASA Astrophysics Data System (ADS)

Kallos, George; Patlakas, Platon; Bartsotas, Nikolaos; Spyrou, Christos; Qahtani, Jumaan Al; Alexiou, Ioannis; Bar, Ayman M.

2017-04-01

The dust cycle is a rather complicated mechanism depending on various factors. The most important factors affecting dust production is soil characteristics (soil composi-tion, physical and chemical properties, water content, temperature etc). The most known production mechanism at small scale is the saltation-bombardment. This mechanism is able to accurately predict uptake of dust particles up to about 10 μm. Larger dust particles are heavier and fall relatively fast due to the gravitational influ-ence. The other controlling factors of dust uptake and transport are wind speed (to be above a threshold) and turbulence. Weather conditions affecting dust produc-tion/transport/deposition are of multi-scale ranging from small surface inhomoge-neities to mesoscale and large-scale systems. While the typical dust transport mech-anism is related to wind conditions near the surface, larger scale systems play an important role on dust production. Such systems are associated with mesoscale phenomena typical of the specific regions. Usually they are associated with deep convection and strong downdrafts and are known as haboobs. Density currents are formed in the surface with strong winds and turbulence. Density currents can be considered as dust sources by themselves due to high productivity of dust. In this presentation we will discuss characteristics of the dust production mechanisms at multiscale over the Arabian Peninsula by utilizing the RAMS/ICLAMS multiscale model. A series of simulations at small-scale have been performed and mitigation actions will be explored.

Study on Production of Silicon Nanoparticles from Quartz Sand for Hybrid Solar Cell Applications

NASA Astrophysics Data System (ADS)

Arunmetha, S.; Vinoth, M.; Srither, S. R.; Karthik, A.; Sridharpanday, M.; Suriyaprabha, R.; Manivasakan, P.; Rajendran, V.

2018-01-01

Nano silicon (nano Si) particles were directly prepared from natural mineral quartz sand and thereafter used to fabricate the hybrid silicon solar cells. Here, in this preparation technique, two process stages were involved. In the first stage, the alkaline extraction and acid precipitation processes were applied on quartz sand to fetch silica nanoparticles. In the second stage, magnesiothermic and modified magnesiothermic reduction reactions were applied on nano silica particles to prepare nano Si particles. The effect of two distinct reduction methodologies on nano Si particle preparation was compared. The magnesiothermic and modified magnesiothermic reductions in the silica to silicon conversion process were studied with the help of x-ray diffraction (XRD) with intent to study the phase changes during the reduction reaction as well as its crystalline nature in the pure silicon phase. The particles consist of a combination of fine particles with spherical morphology. In addition to this, the optical study indicated an increase in visible light absorption and also increases the performance of the solar cell. The obtained nano Si particles were used as an active layer to fabricate the hybrid solar cells (HSCs). The obtained results confirmed that the power conversion efficiency (PCE) of the magnesiothermically modified nano Si cells (1.06%) is much higher as compared to the nano Si cells that underwent magnesiothermic reduction (1.02%). Thus, this confirms the increased PCE of the investigated nano Si solar cell up to 1.06%. It also revealed that nano Si behaved as an electron acceptor and transport material. The present study provided valuable insights and direction for the preparation of nano Si particles from quartz sand, including the influence of process methods. The prepared nano Si particles can be utilized for HSCs and an array of portable electronic devices.

The role of water content in triboelectric charging of wind-blown sand

PubMed Central

Gu, Zhaolin; Wei, Wei; Su, Junwei; Yu, Chuck Wah

2013-01-01

Triboelectric charging is common in desert sandstorms and dust devils on Earth; however, it remains poorly understood. Here we show a charging mechanism of sands with the adsorbed water on micro-porous surface in wind-blown sand based on the fact that water content is universal but usually a minor component in most particle systems. The triboelectric charging could be resulted due to the different mobility of H+/OH− between the contacting sands with a temperature difference. Computational fluid dynamics (CFD) and discrete element method (DEM) were used to demonstrate the dynamics of the sand charging. The numerically simulated charge-to-mass ratios of sands and electric field strength established in wind tunnel agreed well with the experimental data. The charging mechanism could provide an explanation for the charging process of all identical granular systems with water content, including Martian dust devils, wind-blown snow, even powder electrification in industrial processes. PMID:23434920

Visual accumulation tube for size analysis of sands

USGS Publications Warehouse

Colby, B.C.; Christensen, R.P.

1956-01-01

The visual-accumulation-tube method was developed primarily for making size analyses of the sand fractions of suspended-sediment and bed-material samples. Because the fundamental property governing the motion of a sediment particle in a fluid is believed to be its fall velocity. the analysis is designed to determine the fall-velocity-frequency distribution of the individual particles of the sample. The analysis is based on a stratified sedimentation system in which the sample is introduced at the top of a transparent settling tube containing distilled water. The procedure involves the direct visual tracing of the height of sediment accumulation in a contracted section at the bottom of the tube. A pen records the height on a moving chart. The method is simple and fast, provides a continuous and permanent record, gives highly reproducible results, and accurately determines the fall-velocity characteristics of the sample. The apparatus, procedure, results, and accuracy of the visual-accumulation-tube method for determining the sedimentation-size distribution of sands are presented in this paper.

Micromechanical investigation of sand migration in gas hydrate-bearing sediments

NASA Astrophysics Data System (ADS)

Uchida, S.; Klar, A.; Cohen, E.

2017-12-01

Past field gas production tests from hydrate bearing sediments have indicated that sand migration is an important phenomenon that needs to be considered for successful long-term gas production. The authors previously developed the continuum based analytical thermo-hydro-mechanical sand migration model that can be applied to predict wellbore responses during gas production. However, the model parameters involved in the model still needs to be calibrated and studied thoroughly and it still remains a challenge to conduct well-defined laboratory experiments of sand migration, especially in hydrate-bearing sediments. Taking the advantage of capability of micromechanical modelling approach through discrete element method (DEM), this work presents a first step towards quantifying one of the model parameters that governs stresses reduction due to grain detachment. Grains represented by DEM particles are randomly removed from an isotropically loaded DEM specimen and statistical analyses reveal that linear proportionality exists between the normalized volume of detached solids and normalized reduced stresses. The DEM specimen with different porosities (different packing densities) are also considered and statistical analyses show that there is a clear transition between loose sand behavior and dense sand behavior, characterized by the relative density.

Investigating the Impacts of Particle Size and Wind Speed on Brownout

DTIC Science & Technology

2015-03-26

mixture of sand, silt, clay , and organic material, classified based on its size and texture. Sand is the largest of the particle materials, with...smallest soil component is clay , with particle sizes less than 0.002 mm. Ultra-fine in texture, clay feels sticky when wet, is extremely cohesive, and does...not allow air to move through it easily. Clay makes a soil dense and is hard as concrete when dry. Loam is a nearly even mixture of sand and silt

Microbes in Beach Sands: Integrating Environment, Ecology and Public Health

PubMed Central

Whitman, Richard; Harwood, Valerie J.; Edge, Thomas A.; Nevers, Meredith; Byappanahalli, Muruleedhara; Vijayavel, Kannappan; Brandão, João; Sadowsky, Michael J.; Alm, Elizabeth Wheeler; Crowe, Allan; Ferguson, Donna; Ge, Zhongfu; Halliday, Elizabeth; Kinzelman, Julie; Kleinheinz, Greg; Przybyla-Kelly, Kasia; Staley, Christopher; Staley, Zachery; Solo-Gabriele, Helena M.

2014-01-01

SUMMARY Beach sand is a habitat that supports many microbes, including viruses, bacteria, fungi and protozoa (micropsammon). The apparently inhospitable conditions of beach sand environments belie the thriving communities found there. Physical factors, such as water availability and protection from insolation; biological factors, such as competition, predation, and biofilm formation; and nutrient availability all contribute to the characteristics of the micropsammon. Sand microbial communities include autochthonous species/phylotypes indigenous to the environment. Allochthonous microbes, including fecal indicator bacteria (FIB) and waterborne pathogens, are deposited via waves, runoff, air, or animals. The fate of these microbes ranges from death, to transient persistence and/or replication, to establishment of thriving populations (naturalization) and integration in the autochthonous community. Transport of the micropsammon within the habitat occurs both horizontally across the beach, and vertically from the sand surface and ground water table, as well as at various scales including interstitial flow within sand pores, sediment transport for particle-associated microbes, and the large-scale processes of wave action and terrestrial runoff. The concept of beach sand as a microbial habitat and reservoir of FIB and pathogens has begun to influence our thinking about human health effects associated with sand exposure and recreational water use. A variety of pathogens have been reported from beach sands, and recent epidemiology studies have found some evidence of health risks associated with sand exposure. Persistent or replicating populations of FIB and enteric pathogens have consequences for watershed/beach management strategies and regulatory standards for safe beaches. This review summarizes our understanding of the community structure, ecology, fate, transport, and public health implications of microbes in beach sand. It concludes with recommendations for future

The effect of wet-dry weathering on the rate of bedrock river channel erosion by saltating gravel

USGS Publications Warehouse

Inoue, Takuya; Yamaguchi, Satomi; Nelson, Jonathan M.

2017-01-01

Previous work has shown that the bedrock erosion rate E because of collisions of saltating bedload can be expressed by E = βqb(1-Pc), where qb is the sediment transport rate, Pc is the extent of alluvial cover, and β is the abrasion coefficient. However, the dependence of the abrasion coefficient on the physical characteristics of the bedrock material is poorly known, and in particular, the effects of wet-dry weathering on the saltation-abrasion bedrock incision has not been specifically characterized. Observation suggests that the typical wet-dry cycling of exposed bedrock in river beds gives rise to cracks and voids that are likely to alter the incision rate of the material when subjected to impacts of moving sediment. In this study, flume experiments are performed to develop an understanding of how wet-dry cycling affects the rock tensile strength and the bedrock erosion rate. To represent the physical effects of weathering, boring cores taken from natural bedrock channel are exposed to artificial wet-dry cycles. The experimental results suggest the following: (1) the abrasion coefficient for fresh bedrock is estimated by β = 1.0 × 10− 4σT− 2(d/ksb)0.5, where σT is the tensile strength, d is the diameter of colliding gravel, and ksb is the hydraulic roughness height of bedrock; (2) the tensile strength of the bedrock decreases exponentially as a result of repeated wet-dry cycles, σT/σT0 = exp (-CTNWa0/σT0), where σT0 is the initial tensile strength, Wa0 is the initial normalized rate of water absorption., N is the number of wet-dry cycles, and CT is a constant; (3) the erosion rate of fresh bedrock depends on the inverse of the square of tensile strength, but the erosion rate of weathered bedrock depends on the − 1.5 power of tensile strength.

[Suffocation death by occlusion of the airways with sand].

PubMed

Maxeiner, H; Schneider, V

1985-01-01

Eleven cases are reported in which death occurred because of suffocation as a result of occlusion of the respiratory tract by sand (without thoracic compression: 3 cases) or being buried alive (8 cases). Two tables demonstrate the findings and circumstances in the events. Three cases are described in detail. A 22-year-old woman was manhandled by blows and kicks to the head and neck. She became unconscious and her head and neck were covered by a layer of sand so that she suffocated. A 42-year-old man was smothered, while unconscious, in a prone position with his face in the sand, after hard blows to the head by two culprits. A 17-year-old girl finally died by chocking. Previously the culprit had pressed her face into the ground, so that she aspirated particles of soil. The question of vital reactions during aspiration of sand was investigated by microscopic examination of the content of the air passage and by destroying parts of the lungs by sulphuric acid. Minimal aspiration of sand occurred in all cases. Although the postmortal remains were left in the ground, there was no postmortem penetration of sand into the air passage. Histological examinations were carried out to support the diagnosis of violent suffocation. In some cases, there were remarkable findings (mobilization of alveolar cells, hepatocelullar hydropic degeneration), but there were no typical or unanimous findings that pertained to all cases.

Separability studies of construction and demolition waste recycled sand.

PubMed

Ulsen, Carina; Kahn, Henrique; Hawlitschek, Gustav; Masini, Eldon A; Angulo, Sérgio C

2013-03-01

The quality of recycled aggregates from construction and demolition waste (CDW) is strictly related to the content of porous and low strength phases, and specifically to the patches of cement that remain attached to the surface of natural aggregates. This phase increases water absorption and compromises the consistency and strength of concrete made from recycled aggregates. Mineral processing has been applied to CDW recycling to remove the patches of adhered cement paste on coarse recycled aggregates. The recycled fine fraction is usually disregarded due to its high content of porous phases despite representing around 50% of the total waste. This paper focus on laboratory mineral separability studies for removing particles with a high content of cement paste from natural fine aggregate particles (quartz/feldspars). The procedure achieved processing of CDW by tertiary impact crushing to produce sand, followed by sieving and density and magnetic separability studies. The attained results confirmed that both methods were effective in reducing cement paste content and producing significant mass recovery (80% for density concentration and 60% for magnetic separation). The production of recycled sand contributes to the sustainability of the construction environment by reducing both the consumption of raw materials and disposal of CDW, particularly in large Brazilian centers with a low quantity of sand and increasing costs of this material due to long transportation distances. Copyright © 2012 Elsevier Ltd. All rights reserved.

Two-dimensional explosion experiments examining the interaction between a blast wave and a sand hill

NASA Astrophysics Data System (ADS)

Sugiyama, Y.; Izumo, M.; Ando, H.; Matsuo, A.

2018-05-01

Two-dimensional explosion experiments were conducted to discuss the interaction between a blast wave and sand and show the mitigation effect of the sand on the blast wave. The explosive used was a detonating cord 1.0 m in length, which was initiated in a sand hill shaped like a triangular prism and whose cross section was an isosceles triangle with base angles of 30°. Sand-hill heights of 30 and 60 mm were used as parameters to discuss the effect of sand mass upon blast-wave strength. The interaction of the blast wave with the sand/air interface causes multiple peaks in the blast wave, which are induced by successive transmissions at the interface. The increase in the sand mass further mitigates the blast parameters of peak overpressure and positive impulse. The results of this experiment can be utilized to validate the numerical method of solving the problem of interaction between a compressible fluid and a particle layer.

Two-dimensional explosion experiments examining the interaction between a blast wave and a sand hill

NASA Astrophysics Data System (ADS)

Sugiyama, Y.; Izumo, M.; Ando, H.; Matsuo, A.

2018-02-01

Two-dimensional explosion experiments were conducted to discuss the interaction between a blast wave and sand and show the mitigation effect of the sand on the blast wave. The explosive used was a detonating cord 1.0 m in length, which was initiated in a sand hill shaped like a triangular prism and whose cross section was an isosceles triangle with base angles of 30°. Sand-hill heights of 30 and 60 mm were used as parameters to discuss the effect of sand mass upon blast-wave strength. The interaction of the blast wave with the sand/air interface causes multiple peaks in the blast wave, which are induced by successive transmissions at the interface. The increase in the sand mass further mitigates the blast parameters of peak overpressure and positive impulse. The results of this experiment can be utilized to validate the numerical method of solving the problem of interaction between a compressible fluid and a particle layer.

Development of an ash particle deposition model considering build-up and removal mechanisms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kjell Strandstroem; Christian Muellera; Mikko Hupa

2007-12-15

Slagging and fouling on heat exchanger surfaces in power boilers fired with fossil fuels and fuel mixtures has a significant influence on boiler efficiency and availability. Mathematical modelling has long been considered a suitable method to assist boiler operators to determine optimized operating conditions for an existing furnace. The ultimate goal in ash deposition prediction is hereby the determination of the total amount of material deposited and hence the determination of the total reduction in efficiency. Depending on the fuels fired the total deposited mass is a combination of ash particle deposition and ash particle erosion due to non-sticky particles.more » The novel ash particle deposition model presented in this work considers deposition of sticky ash particles, cleansing of deposit by non-sticky sand particles and sticking of sand due to contact with sticky ash. The steady-state modelling results for the total amount of ash deposited on the deposition probe of an entrained flow reactor presented in this work agree well with the experimental data. Only at very high fractions of sand added as non-sticky material, a significant influence of the sand on the overall mass deposited was found. Since the model considers sticking of non-sticking sand due to contact with sticky ash, the fraction of sand deposited on the probe was especially studied. Using a correction factor to consider the influence of operating time on the steady-state simulations led to good agreement between simulations and experimental data. 12 refs., 10 figs.« less

Preparation of Fe2O3-TiO2 composite from Sukabumi iron sand through magnetic separation, pyrometallurgy, and hydrometallurgy

NASA Astrophysics Data System (ADS)

Wahyuningsih, S.; Ramelan, A. H.; Pranata, H. P.; Hanif, Q. A.; Ismoyo, Y. A.; Ichsan, K. F.

2016-11-01

Preparation of Fe2O3/TiO2 composite from Sukabumi iron sand by magnetic separation, roasting, leaching and precipitation treatment has been carried out. Magnetic separation can separate magnetic particles and non-magnetic particles of iron sand content, while the non-magnetic particles (wustite (FeO), hematite (α-Fe2O3), maghemite (γ-Fe2O3) and magnetite (Fe3O4)) was washing with oxalic acid 1 M. The result product then was roasted at 800 °C treated by sodium carbonate (Na2CO3) addition of 1:1; 2:1 and 1:2 (w/w) of iron sand to Na2CO3 weight ratio, respectively. The X-Ray Fluorescence (XRF) analysis result shown that Sukabumi iron sand have hematite (Fe2O3) and titanium dioxide (TiO2) content about 72.17% dan 14.42%. XRD analysis of roasted iron sand shown the rutile (TiO2), Hematite (Fe2O3), NaFeO2, FeO, and Na2TiO3. Leaching of roasted iron sand using sulphuric acid (H2SO4) have influenced by concentrations of the H2SO4 solution. The optimum iron sand dissolution occurred in H2SO4 9 M, which condensation product of the leachant have a weight ratio of Fe:Ti = 1:1 (w/w). Meanwhile, the settling back-filtrate result of second condensation was obtained a ratio of Fe2O3: TiO2 of 3: 1 (w/w).

Simulation model of erosion and deposition on a barchan dune

NASA Technical Reports Server (NTRS)

Howard, A. D.; Morton, J. B.; Gal-El-hak, M.; Pierce, D. B.

1977-01-01

Erosion and deposition over a barchan dune near the Salton Sea, California, are modeled by bookkeeping the quantity of sand in saltation following streamlines of transport. Field observations of near surface wind velocity and direction plus supplemental measurements of the velocity distribution over a scale model of the dune are combined as input to Bagnold type sand transport formulas corrected for slope effects. A unidirectional wind is assumed. The resulting patterns of erosion and deposition compare closely with those observed in the field and those predicted by the assumption of equilibrium (downwind translation of the dune without change in size or geometry). Discrepancies between the simulated results and the observed or predicted erosional patterns appear to be largely due to natural fluctuations in the wind direction. The shape of barchan dunes is a function of grain size, velocity, degree of saturation of the oncoming flow, and the variability in the direction of the oncoming wind. The size of the barchans may be controlled by natural atmospheric scales, by the age of the dunes, or by the upwind roughness. The upwind roughness can be controlled by fixed elements or by sand in the saltation. In the latter case, dune scale is determined by grain size and wind velocity.

Effect of bovine manure on fecal coliform attachment to soil and soil particles of different sizes.

PubMed

Guber, Andrey K; Pachepsky, Yakov A; Shelton, Daniel R; Yu, Olivia

2007-05-01

Manure-borne bacteria can be transported in runoff as free cells, cells attached to soil particles, and cells attached to manure particles. The objectives of this work were to compare the attachment of fecal coliforms (FC) to different soils and soil fractions and to assess the effect of bovine manure on FC attachment to soil and soil fractions. Three sand fractions of different sizes, the silt fraction, and the clay fraction of loam and sandy clay loam soils were separated and used along with soil samples in batch attachment experiments with water-FC suspensions and water-manure-FC suspensions. In the absence of manure colloids, bacterial attachment to soil, silt, and clay particles was much higher than the attachment to sand particles having no organic coating. The attachment to the coated sand particles was similar to the attachment to silt and clay. Manure colloids in suspensions decreased bacterial attachment to soils, clay and silt fractions, and coated sand fractions, but did not decrease the attachment to sand fractions without the coating. The low attachment of bacteria to silt and clay particles in the presence of manure colloids may cause predominantly free-cell transport of manure-borne FC in runoff.

Dust Emissions from Undisturbed and Disturbed, Crusted Playa Surfaces: Cattle Trampling Effect

NASA Astrophysics Data System (ADS)

Zobeck, T. M.; Baddock, M. C.; van Pelt, R.; Fredrickson, E. L.

2009-12-01

Dry playa lake beds can be a significant source of fine dust emissions during high wind events in arid and semiarid landscapes. The physical and chemical properties of the playa surface control the amount and properties of the dust emitted. In this study, we use a field wind tunnel to quantify the dust emissions from a bare, fine-textured playa surface located in the Chihuahua Desert at the Jornada Experimental Range, near Las Cruces, New Mexico, USA. We tested natural, undisturbed crusted surfaces and surfaces that had been subjected to two levels of domestic animal disturbance. The animal disturbance was provided by trampling produced from one and ten passes along the length of the wind tunnel by a 630 kg Angus-Hereford cross cow. The trampling broke the durable crust and created loose erodible material. Each treatment (natural crust, one pass, and ten passes) was replicated three times. A push-type wind tunnel with a 6 m long, 0.5 m wide, and 1 m high test section was used to generate dust emissions under controlled conditions. Clean medium sand was dropped onto the playa surface to act as an abrader material. The tunnel wind speed was equivalent to 15 m/s at a height of 2 m over a smooth soil surface. The tunnel was initially run for ten minutes, with no abrader added. A second 30 minute run was subsequently sampled as abrader was added to the wind stream. Dust and saltating material were collected using an isokinetic slot sampler at the end of the tunnel. Total airborne dust was collected on two 25 cm x 20 cm glass fiber filters (GFF) and measured using a GRIMM particle monitor every 6 sec throughout each test run. Disturbance by trampling generated increased saltating material and airborne dust. The amount of saltating material measured during the initial (no abrader added) run was approximately 70% greater and 5.8 times the amount of saltating material measured on the one pass and ten pass plots, respectively, compared with that observed on the undisturbed

PM 2.5 Airborne Particulates Near Frac Sand Operations.

PubMed

Walters, Kristin; Jacobson, Jeron; Kroening, Zachary; Pierce, Crispin

2015-11-01

The rapid growth of hydraulic fracturing for oil and gas extraction in the U.S. has led to 135 active "frac" sand mines, processing plants, and rail transfer stations in Wisconsin. Potential environmental health risks include increased truck traffic, noise, ecosystem loss, and groundwater, light, and air pollution. Emitted air contaminants include fine particulate matter (PM2.5) and respirable crystalline silica. Inhalation of fine dust particles causes increased mortality, cardiovascular disease, lung disease, and lung cancer. In the authors' pilot study, use of a filter-based ambient particulate monitor found PM2.5 levels of 5.82-50.8 µg/m3 in six 24-hour samples around frac sand mines and processing sites. Enforcement of the existing U.S. Environmental Protection Agency annual PM2.5 standard of 12 µg/m3 is likely to protect the public from silica exposure risks as well. PM2.5 monitoring around frac sand sites is needed to ensure regulatory compliance, inform nearby communities, and protect public health.

Comparison of dust release from epoxy and paint nanocomposites and conventional products during sanding and sawing.

PubMed

Gomez, Virginia; Levin, Marcus; Saber, Anne T; Irusta, Silvia; Dal Maso, Miikka; Hanoi, Roberto; Santamaria, Jesus; Jensen, Keld A; Wallin, Håkan; Koponen, Ismo K

2014-10-01

The release of dust generated during sanding or sawing of nanocomposites was compared with conventional products without nanomaterials. Epoxy-based polymers with and without carbon nanotubes, and paints with different amounts of nano-sized titanium dioxide, were machined in a closed aerosol chamber. The temporal evolution of the aerosol concentration and size distribution were measured simultaneously. The morphology of collected dust by scanning electron microscopy was different depending on the type of nanocomposites: particles from carbon nanotubes (CNTs) nanocomposites had protrusions on their surfaces and aggregates and agglomerates are attached to the paint matrix in particles emitted from alkyd paints. We observed no significant differences in the particle size distributions when comparing sanding dust from nanofiller containing products with dust from conventional products. Neither did we observe release of free nanomaterials. Instead, the nanomaterials were enclosed or partly enclosed in the matrix. A source strength term Si (cm(-3) s(-1)) that describes particle emission rates from continuous sources was introduced. Comparison between the Si parameters derived from sanding different materials allows identification of potential effects of addition of engineered nanoparticles to a composite. © The Author 2014. Published by Oxford University Press on behalf of the British Occupational Hygiene Society.

Analysis of Physical Properties and Mineralogical of Pyrolysis Tires Rubber Ash Compared Natural Sand in Concrete material

NASA Astrophysics Data System (ADS)

Syamir Senin, Mohamad; Shahidan, Shahiron; Syazani Leman, Alif; Izzati Raihan Ramzi Hannan, Nurul

2016-11-01

Waste tires pose significant health and environmental concerns if not recycled or discarded properly. At the same time, natural sand is becoming scarcer and costlier due to its non-availability. Waste tires as fine aggregate can be an economical and sustainable alternative to the natural sand. Recent years, the interest on recycling waste tires into civil engineering applications by the researchers has increased. In this research, the chemical and physical properties of the tires rubber ash and the natural sand have been analysed. The densities of the rubber ash are lower than the natural sand. Rubber ash had finer particle size compared to the natural sand. Almost all chemical in the natural sand had in rubber ash with the additional sulphur trioxide and zinc oxide in the rubber ash, made the rubber ash better than natural sand. Rubber ash seems to be a suitable material to use in concrete as sand replacement.

Late Holocene eolian activity in the mineralogically mature Nebraska Sand Hills

USGS Publications Warehouse

Muhs, D.R.; Stafford, Thomas W.; Swinehart, J.B.; Cowherd, S.D.; Mahan, S.A.; Bush, C.A.; Madole, R.F.; Maat, P.B.

1997-01-01

The age of sand dunes in the Nebraska Sand Hills has been controversial, with some investigators suggesting a full-glacial age and others suggesting that they were last active in the late Holocene. New accelerator mass spectrometry radiocarbon ages of unaltered bison bones and organic-rich sediments suggest that eolian sand deposition occurred at least twice in the past 3000 14C yr B.P. in three widely separated localities and as many as three times in the past 800 14C yr at three other localities. These late Holocene episodes of eolian activity are probably the result of droughts more intense than the 1930s "Dust Bowl" period, based on independent Great Plains climate records from lake sediments and tree rings. However, new geochemical data indicate that the Nebraska Sand Hills are mineralogically mature. Eolian sands in Nebraska have lower K-feldspar (and K2O, Rb, and Ba) contents than most possible source sediments and lower K-feldspar contents than dunes of similar age in Colorado. The most likely explanation for mineralogical maturity is reduction of sand-sized K-feldspar to silt-sized particles via ballistic impacts due to strong winds over many cycles of eolian activity. Therefore, dunes of the Nebraska Sand Hills must have had a long history, probably extending over more than one glacial-interglacial cycle, and the potential for reactivation is high, with or without a future greenhouse warming. ?? 1997 University of Washington.

Coupled large eddy simulation and discrete element model of bedload motion

NASA Astrophysics Data System (ADS)

Furbish, D.; Schmeeckle, M. W.

2011-12-01

We combine a three-dimensional large eddy simulation of turbulence to a three-dimensional discrete element model of turbulence. The large eddy simulation of the turbulent fluid is extended into the bed composed of non-moving particles by adding resistance terms to the Navier-Stokes equations in accordance with the Darcy-Forchheimer law. This allows the turbulent velocity and pressure fluctuations to penetrate the bed of discrete particles, and this addition of a porous zone results in turbulence structures above the bed that are similar to previous experimental and numerical results for hydraulically-rough beds. For example, we reproduce low-speed streaks that are less coherent than those over smooth-beds due to the episodic outflow of fluid from the bed. Local resistance terms are also added to the Navier-Stokes equations to account for the drag of individual moving particles. The interaction of the spherical particles utilizes a standard DEM soft-sphere Hertz model. We use only a simple drag model to calculate the fluid forces on the particles. The model reproduces an exponential distribution of bedload particle velocities that we have found experimentally using high-speed video of a flat bed of moving sand in a recirculating water flume. The exponential distribution of velocity results from the motion of many particles that are nearly constantly in contact with other bed particles and come to rest after short distances, in combination with a relatively few particles that are entrained further above the bed and have velocities approaching that of the fluid. Entrainment and motion "hot spots" are evident that are not perfectly correlated with the local, instantaneous fluid velocity. Zones of the bed that have recently experienced motion are more susceptible to motion because of the local configuration of particle contacts. The paradigm of a characteristic saltation hop length in riverine bedload transport has infused many aspects of geomorphic thought, including

Dunes as New Evidence of Recently Active Surface Processes on Pluto

NASA Astrophysics Data System (ADS)

Radebaugh, Jani; Telfer, Matthew; Parteli, Eric; Beyer, Ross A.; Bertrand, Tanguy; Forget, Francois; Nimmo, Francis; Grundy, William M.; Moore, Jeffrey M.; Stern, S. Alan; New Horizons Team

2017-10-01

The surface of Pluto contains hundreds of aligned, regularly spaced features best described as transverse dunes (Telfer et al. in review). They are spaced by 500-700 meters, are several tens of kilometers long, and are subparallel and with a slightly undulatory planform, as seen by the New Horizons LORRI instrument. Their crests are orthogonal to wind streaks seen nearby, and therefore to the assumed regional winds. They sit atop the nitrogen-rich informally named Sputnik Planitia continental glacier at the base of the informally named Al-Idrisi Montes and appear from New Horizons MVIC data to have a composition enriched in methane. Their presence requires there to be particles that can be saltated as well as wind. The particles, or “sands”, are likely composed of relatively hard methane ice, possibly derived from the methane snow seen to blanket the mountain summits. While Pluto’s nitrogen-rich atmosphere fluctuates in density, perhaps dramatically, current modelled conditions allow for winds that are required to saltate the ice sands (<~10 m/s). These features are relatively fresh in appearance, especially in comparison with features farther south that have severe sublimation erosion textures and deformation from glacier flow. Furthermore, they lie atop convection cell margins of Sputnik Planitia, which overturns at rates of ~500 ka. This indicates the dune-like landforms of Pluto are relatively young. This has implications for the surface activity of other large Kuiper Belt Objects and the interaction between limited solar heating and the exotic properties of their surfaces and atmospheres.

Industrial sand and gravel

USGS Publications Warehouse

Dolley, T.P.

2011-01-01

Domestic production of industrial sand and gravel in 2010 was about 26.5 Mt (29.2 million st), a 6-percent increased from 2009. Certain end uses of industrial sand and gravel, such as sand for container glass, golf course sand, recreational sand, specialty glass and water filtration, showed increased demand in 2010.

Experimental investigation on high performance RC column with manufactured sand and silica fume

NASA Astrophysics Data System (ADS)

Shanmuga Priya, T.

2017-11-01

In recent years, the use High Performance Concrete (HPC) has increased in construction industry. The ingredients of HPC depend on the availability and characteristics of suitable alternative materials. Those alternative materials are silica fume and manufactured sand, a by products from ferro silicon and quarry industries respectively. HPC made with silica fume as partial replacement of cement and manufactured sand as replacement of natural sand is considered as sustainable high performance concrete. In this present study the concrete was designed to get target strength of 60 MPa as per guide lines given by ACI 211- 4R (2008). The laboratory study was carried out experimentally to analyse the axial behavior of reinforced cement HPC column of size 100×100×1000mm and square in cross section. 10% of silica fume was preferred over ordinary portland cement. The natural sand was replaced by 0, 20, 40, 60, 80 and 100% with Manufactured Sand (M-Sand). In this investigation, totally 6 column specimens were cast for mixes M1 to M6 and were tested in 1000kN loading frame at 28 days. From this, Load-Mid height deflection curves were drawn and compared. Maximum ultimate load carrying capacity and the least deflection is obtained for the mix prepared by partial replacement of cement with 10% silica fume & natural sand by 100% M-Sand. The fine, amorphous and pozzalonic nature of silica fume and fine mineral particles in M- Sand increased the stiffness of HPC column. The test results revealed that HPC can be produced by using M-Sand with silica fume.

Investigating selective transport and abrasion on an alluvial fan using quantitative grain size and shape analysis

NASA Astrophysics Data System (ADS)

Litwin, K. L.; Jerolmack, D. J.

2011-12-01

Selective sorting and abrasion are the two major fluvial processes that are attributed to the downstream fining of sediments in rivers and alluvial fans. Selective transport is the process by which smaller grains are preferentially transported downstream while larger grains are deposited closer to the source. Abrasion is defined by the production of fine sediments and sand that occurs by saltation of gravel, where particle-to-particle collisions supply the energy required to break apart grains. We hypothesize that abrasion results in the gradual fining of large grains and the production of fine sands and silts, while sorting accounts for the differences in transport of these two grain-size fractions produced from abrasion, thereby creating the abrupt gravel-sand transition observed in many channel systems. In this research, we explore both selective transport and abrasion processes on the Dog Canyon alluvial fan near Alamogordo, New Mexico. We complete an extensive grain size analysis down the main channel of the fan employing an image-based technique that utilizes an autocorrelation process. We also characterize changes in grain shape using standard shape parameters, as well as Fourier analysis, which allows the study of contributions of grain roughness on a variety of length scales. Sorting appears to dominate the upper portion of the fan; the grain-size distribution narrows moving downstream until reaching a point of equal mobility, at which point sorting ceases. Abrasion exerts a subtle but persistent effect on grains during transport down the fan. Shape analysis reveals that particles become more rounded by the removal of small-scale textural features, a process that is expected to only modestly influence grain size of gravel, but should produce significant quantities of sand. This study provides a better understanding of the importance of grain abrasion and sorting on the downstream fining of channel grains in an alluvial fan, as well as an improved knowledge

Fungal alteration of organic coatings on sand grains

NASA Astrophysics Data System (ADS)

Rothhardt, S.; Gleixner, G.; Benzerara, K.; Fischer, C.; Gaupp, R.

2012-04-01

We studied the fungal alteration of organically coated sand particles, sampled in Eocene sediments in the open cast mining Profen, near Leipzig (Germany). These organic coatings were formed on sand grains after their sedimentation owing to mobilization of organic matter from younger coal layers. The organic coatings formed non-continuous layers on quartz grains, measuring few micrometers up to 30 µm in thickness. It has been shown that organic coatings on sand grains retain efficiently dissolved metals by adsorption from groundwaters. They consequently might be used as adsorbent to purify low heavy metal contaminated water. However, their stability has not been assessed yet especially in the oxic environment and, more specifically, in the presence of microorganisms. This is important in order to evaluate whether coated sands could act as a reliable tool in remediation. In order to address this question we characterized the fungal alteration of organic coatings on sand grains using several techniques, including scanning electron microscopy (SEM), scanning transmission X-ray microscopy (STXM) and vertical scanning interferometry (VSI). Sand grains coated with organics were incubated on complex yeast medium with and without Schizophyllum commune to estimate changes in heavy metal retention. Formation of biominerals and etch pits is induced by fungal colonization as shown by SEM. Surface topography analysis was performed using VSI technique. Etch pit depth ranges from 0.5 to 1 µm. Pit formation is limited to the organic coating; dissolution of quartz grains was not detected. Using STXM we measured near-edge X-ray absorption fine structure (NEXAFS) spectra at the C K-edge, N-edge, and O K-edge to characterize the different organic compartments (fungi, genuine organic coatings, altered organic coatings) down to the 25-nm scale. We observed in the spectra measured at the C K-edge on the altered organic coatings a decrease in aromatic and phenolic groups as well as an

Incipient Motion of Sand and Oil Agglomerates

NASA Astrophysics Data System (ADS)

Nelson, T. R.; Dalyander, S.; Jenkins, R. L., III; Penko, A.; Long, J.; Frank, D. P.; Braithwaite, E. F., III; Calantoni, J.

2016-12-01

Weathered oil mixed with sediment in the surf zone in the northern Gulf of Mexico after the 2010 Deepwater Horizon oil spill, forming large mats of sand and oil. Wave action fragmented the mats into sand and oil agglomerates (SOAs) with diameters of about 1 to 10 cm. These SOAs were transported by waves and currents along the Gulf Coast, and have been observed on beaches for years following the spill. SOAs are composed of 70%-95% sand by mass, with an approximate density of 2107 kg/m³. To measure the incipient motion of SOAs, experiments using artificial SOAs were conducted in the Small-Oscillatory Flow Tunnel at the U.S. Naval Research Laboratory under a range of hydrodynamic forcing. Spherical and ellipsoidal SOAs ranging in size from 0.5 to 10 cm were deployed on a fixed flat bed, a fixed rippled bed, and a movable sand bed. In the case of the movable sand bed, SOAs were placed both proud and partially buried. Motion was tracked with high-definition video and with inertial measurement units embedded in some of the SOAs. Shear stress and horizontal pressure gradients, estimated from velocity measurements made with a Nortek Vectrino Profiler, were compared with observed mobility to assess formulations for incipient motion. For SOAs smaller than 1 cm in diameter, incipient motion of spherical and ellipsoidal SOAs was consistent with predicted critical stress values. The measured shear stress at incipient motion of larger, spherical SOAs was lower than predicted, indicating an increased dependence on the horizontal pressure gradient. In contrast, the measured shear stress required to move ellipsoidal SOAs was higher than predicted, even compared to values modified for larger particles in mixed-grain riverine environments. The laboratory observations will be used to improve the prediction of incipient motion, transport, and seafloor interaction of SOAs.

Submarine sand ridges and sand waves in the eastern part of the China Sea

NASA Astrophysics Data System (ADS)

Wu, Ziyin; Li, Shoujun; Shang, Jihong; Zhou, Jieqiong; Zhao, Dineng; Liang, Yuyang

2016-04-01

Integrated with multi-beam and single-beam echo sounding data, as well as historical bathymetric data, submarine bathymetric maps of the eastern part of the China Sea, including the Bohai Sea, Huanghai Sea, and East China Sea, are constructed to systematically study submarine sand ridges and sand waves in the eastern part of the China Sea, combined with high-resolution seismic, sub-bottom profile and borehole data. Submarine sand ridges are extraordinarily developed in the eastern part of the China Sea, and 7 sand ridge areas can be divided from north to south, that is, the Laotieshan Channel sand ridge area in the Bohai Sea, the Korea Bay sand ridge area in the southern Huanghai Sea, the sand ridge area in the eastern Huanghai islands and the Huanghai Troughs, the Jianggang sand ridge area in the western Huanghai Sea, the sand ridge area in the East China Sea shelf, and the sand ridge and sand wave area in the Taiwan Strait and Taiwan Banks. The distribution area of the sand ridges and sand waves covers more than 450,000 km2, wherein ~10,000 km2 in the Bohai Bay, ~200,000 km2 in the Huanghai Sea, ~200,000 km2 in the East China Sea shelf, and ~40,000 km2 in the Taiwan Strait and Taiwan Banks, respectively. The great mass of sand ridges are distributed within water depth of 5-160 m, with a total length of over 160 km and a main width of 5-10 km. The inner structure of the sand ridges presents features of high-angle inclined beddings, with main lithology of sands, sand-mud alternations partly visible, and a small number of mud cores. Dating results indicate that the sand ridges in the eastern part of the China Sea are mainly developed in the Holocene. Sea-level variation dominates the sand ridge evolution in the eastern part of the China Sea since the LGM, and the sand ridges developed in the area of < 60m water depth are appeared in bad activity, meanwhile sand ridges with good activity are still developed in large scale.

The Particle Theory of Matter

ERIC Educational Resources Information Center

Widick, Paul R.

1969-01-01

Described are activities that are designed to help elementary children understand the possibility of the particle theory of matter. Children work with beads, marbles, B-B shot and sand; by mixing these materials and others they are led to see that it is highly possible for the existence of particles which are not visible. (BR)

Fecal indicators in sand, sand contact, and risk of enteric illness among beachgoers

PubMed Central

Heaney, Christopher D.; Sams, Elizabeth; Dufour, Alfred P.; Brenner, Kristen P.; Haugland, Richard A.; Chern, Eunice; Wing, Steve; Marshall, Stephen; Love, David C.; Serre, Marc; Noble, Rachel; Wade, Timothy J.

2011-01-01

Background Beach sand can harbor fecal indicator organisms and pathogens, but enteric illness risk associated with sand contact remains unclear. Methods In 2007, visitors at two recreational marine beaches were asked on the day of their visit about sand contact. Ten to 12 days later, participants answered questions about health symptoms since the visit. F+ coliphage, Enterococcus, Bacteroidales, fecal Bacteroides, and Clostridium spp. in wet sand were measured using culture and molecular methods. Results We analyzed 144 wet sand samples and completed 4,999 interviews. Adjusted odds ratios (aORs) were computed, comparing those in the highest tertile of fecal indicator exposure with those who reported no sand contact. Among those digging in sand compared with those not digging in sand, a molecular measure of Enterococcus spp. (calibrator cell equivalents/g) in sand was positively associated with gastrointestinal (GI) illness (aOR = 2.0 [95% confidence interval (CI) = 1.2–3.2]) and diarrhea (2.4 [1.4–4.2]). Among those buried in sand, point estimates were greater for GI illness (3.3 [1.3–7.9]) and diarrhea (4.9 [1.8–13]). Positive associations were also observed for culture-based Enterococcus (colony-forming units/g) with GI illness (aOR digging = 1.7 [1.1–2.7]) and diarrhea (2.1 [1.3–3.4]). Associations were not found among non-swimmers with sand exposure. Conclusions We observed a positive relationship between sand contact activities and enteric illness as a function of concentrations of fecal microbial pollution in beach sand. PMID:22157306

Mobility of nanosized cerium dioxide and polymeric capsules in quartz and loamy sands saturated with model and natural groundwaters.

PubMed

Petosa, Adamo Riccardo; Ohl, Carolin; Rajput, Faraz; Tufenkji, Nathalie

2013-10-01

The environmental and health risks posed by emerging engineered nanoparticles (ENPs) released into aquatic environments are largely dependent on their aggregation, transport, and deposition behavior. Herein, laboratory-scale columns were used to examine the mobility of polyacrylic acid (PAA)-coated cerium dioxide nanoparticles (nCeO2) and an analogous nanosized polymeric capsule (nCAP) in water saturated quartz sand or loamy sand. The influence of solution ionic strength (IS) and cation type (Na(+), Ca(2+), or Mg(2+)) on the transport potential of these ENPs was examined in both granular matrices and results were also compared to measurements obtained using a natural groundwater. ENP suspensions were characterized using dynamic light scattering and nanoparticle tracking analysis to establish aggregate size, and laser Doppler electrophoresis to determine ENP electrophoretic mobility. Regardless of IS, virtually all nCeO2 particles suspended in NaNO3 eluted from the quartz sand-packed columns. In contrast, heightened nCeO2 and nCAP particle retention and dynamic (time-dependent) transport behavior was observed with increasing concentrations of the divalent salts and in the presence of natural groundwater. Enhanced particle retention was also observed in loamy sand in comparison to the quartz sand, emphasizing the need to consider the nature of the aqueous matrix and granular medium in evaluating contamination risks associated with the release of ENPs in natural and engineered aquatic environments. Copyright © 2013 Elsevier Ltd. All rights reserved.

Microbially-accelerated consolidation of oil sands tailings. Pathway I: changes in porewater chemistry

PubMed Central

Siddique, Tariq; Kuznetsov, Petr; Kuznetsova, Alsu; Arkell, Nicholas; Young, Rozlyn; Li, Carmen; Guigard, Selma; Underwood, Eleisha; Foght, Julia M.

2014-01-01

Dispersed clay particles in mine tailings and soft sediments remain suspended for decades, hindering consolidation and challenging effective management of these aqueous slurries. Current geotechnical engineering models of self-weight consolidation of tailings do not consider microbial contribution to sediment behavior, however, here we show that microorganisms indigenous to oil sands tailings change the porewater chemistry and accelerate consolidation of oil sands tailings. A companion paper describes the role of microbes in alteration of clay chemistry in tailings. Microbial metabolism in mature fine tailings (MFT) amended with an organic substrate (hydrolyzed canola meal) produced methane (CH4) and carbon dioxide (CO2). Dissolution of biogenic CO2 lowered the pH of amended MFT to pH 6.4 vs. unamended MFT (pH 7.7). About 12% more porewater was recovered from amended than unamended MFT during 2 months of active microbial metabolism, concomitant with consolidation of tailings. The lower pH in amended MFT dissolved carbonate minerals, thereby releasing divalent cations including calcium (Ca2+) and magnesium (Mg2+) and increasing bicarbonate (HCO−3) in porewater. The higher concentrations increased the ionic strength of the porewater, in turn reducing the thickness of the diffuse double layer (DDL) of clay particles by reducing the surface charge potential (repulsive forces) of the clay particles. The combination of these processes accelerated consolidation of oil sands tailings. In addition, ebullition of biogenic gases created transient physical channels for release of porewater. In contrast, saturating the MFT with non-biogenic CO2 had little effect on consolidation. These results have significant implications for management and reclamation of oil sands tailings ponds and broad importance in anaerobic environments such as contaminated harbors and estuaries containing soft sediments rich in clays and organics. PMID:24711805

Microbially-accelerated consolidation of oil sands tailings. Pathway I: changes in porewater chemistry.

PubMed

Siddique, Tariq; Kuznetsov, Petr; Kuznetsova, Alsu; Arkell, Nicholas; Young, Rozlyn; Li, Carmen; Guigard, Selma; Underwood, Eleisha; Foght, Julia M

2014-01-01

Dispersed clay particles in mine tailings and soft sediments remain suspended for decades, hindering consolidation and challenging effective management of these aqueous slurries. Current geotechnical engineering models of self-weight consolidation of tailings do not consider microbial contribution to sediment behavior, however, here we show that microorganisms indigenous to oil sands tailings change the porewater chemistry and accelerate consolidation of oil sands tailings. A companion paper describes the role of microbes in alteration of clay chemistry in tailings. Microbial metabolism in mature fine tailings (MFT) amended with an organic substrate (hydrolyzed canola meal) produced methane (CH4) and carbon dioxide (CO2). Dissolution of biogenic CO2 lowered the pH of amended MFT to pH 6.4 vs. unamended MFT (pH 7.7). About 12% more porewater was recovered from amended than unamended MFT during 2 months of active microbial metabolism, concomitant with consolidation of tailings. The lower pH in amended MFT dissolved carbonate minerals, thereby releasing divalent cations including calcium (Ca(2+)) and magnesium (Mg(2+)) and increasing bicarbonate (HCO(-) 3) in porewater. The higher concentrations increased the ionic strength of the porewater, in turn reducing the thickness of the diffuse double layer (DDL) of clay particles by reducing the surface charge potential (repulsive forces) of the clay particles. The combination of these processes accelerated consolidation of oil sands tailings. In addition, ebullition of biogenic gases created transient physical channels for release of porewater. In contrast, saturating the MFT with non-biogenic CO2 had little effect on consolidation. These results have significant implications for management and reclamation of oil sands tailings ponds and broad importance in anaerobic environments such as contaminated harbors and estuaries containing soft sediments rich in clays and organics.

Method and Device for Extraction of Liquids from a Solid Particle Material

NASA Technical Reports Server (NTRS)

deMayo, Benjamin (Inventor)

2017-01-01

A method, system, and device for separating oil from oil sands or oil shale is disclosed. The method includes heating the oil sands, spinning the heated oil sands, confining the sand particles mechanically, and recovering the oil substantially free of the sand. The method can be used without the addition of chemical extraction agents. The system includes a source of centrifugal force, a heat source, a separation device, and a recovery device. The separation device includes a method of confining the sands while allowing the oil to escape, such as through an aperture.

Industrial sand and gravel

USGS Publications Warehouse

Dolley, T.P.

2012-01-01

Domestic production of industrial sand and gravel in 2011 was about 30 Mt (33 million st), increasing slightly compared with 2010. Some important end uses for industrial sand and gravel include abrasives, filtration, foundry, glassmaking, hydraulic fracturing sand (frac sand) and silicon metal applications.

Industrial sand and gravel

USGS Publications Warehouse

Dolley, T.P.

2013-01-01

Domestic production of industrial sand and gravel in 2012 was about 49.5 Mt (55 million st), increasing 13 percent compared with that of 2011. Some important end uses for industrial sand and gravel include abrasives, filtration, foundry, glassmaking, hydraulic fracturing sand (frac sand) and silicon metal applications.

Testosterone sorption and desorption: effects of soil particle size.

PubMed

Qi, Yong; Zhang, Tian C; Ren, Yongzheng

2014-08-30

Soils contain a wide range of particles of different diameters with different mobility during rainfall events. Effects of soil particles on sorption and desorption behaviors of steroid hormones have not been investigated. In this study, wet sieve washing and repeated sedimentation methods were used to fractionate the soils into five ranges. The sorption and desorption properties and related mechanisms of testosterone in batch reactors filled with fractionated soil particles were evaluated. Results of sorption and desorption kinetics indicate that small soil particles have higher sorption and lower desorption rates than that of big ones. Thermodynamic results show the sorption processes are spontaneous and exothermal. The sorption capacity ranks as clay>silt>sand, depending mainly on specific surface area and surface functional groups. The urea control test shows that hydrogen bonding contributes to testosterone sorption onto clay and silt but not on sand. Desorption tests indicate sorption is 36-65% irreversible from clay to sand. Clays have highest desorption hysteresis among these five soil fractions, indicating small particles like clays have less potential for desorption. The results provide indirect evidence on the colloid (clay)-facilitated transport of hormones (micro-pollutants) in soil environments. Copyright © 2014 Elsevier B.V. All rights reserved.

Iron sand - ZnO based materials of natural origin for dye decolorization under sunlight irradiation

NASA Astrophysics Data System (ADS)

Salprima Yudha, S.; Angasa, Eka; Fitriani, Dyah; Falahudin, Aswin

2017-03-01

A mixed iron sand - ZnO materials was prepared by heating a mixture of natural iron sand and ZnO at 900 °C for 5 hours. XRD study of the sample revealed that, in the mixed iron sand - ZnO present some minor peaks that similar with XRD pattern of γ-Fe2O3 and/or Fe3O4. Observation of the sample using SEM, showed a compact morpholgy and almost homogenenous in particles size. In purpose to evaluate the ability of this materials for textile dying wastewater treatment, a study on rhodamine B decolorization was carried out as a reperesentative.

A bright intra-dune feature on Titan and its implications for sand formation and transport

NASA Astrophysics Data System (ADS)

MacKenzie, Shannon; Barnes, Jason W.; Rodriguez, Sebastien; Cornet, Thomas; Brossier, Jeremy; Soderblom, Jason M.; Le Mouélic, Stephane; Sotin, Christophe; Brown, Robert H.; Buratti, Bonnie J.; Clark, Roger Nelson; Nicholson, Philip D.; Baines, Kevin

2017-10-01

Organic sands cover much of Titan’s equatorial belt, gathered into longitudinal dunes about a kilometer wide and hundreds of kilometers long. At the end of the Cassini era, questions of how such a vast volume of saltable material is or was created on Titan remain unanswered. At least two possible mechanisms suggested for forming sand-sized particles involve liquids: (1) evaporite deposition and erosion and (2) flocculation of material within a lake. Transporting sand from the lakes and seas of Titan’s poles to the equatorial belt is not strongly supported by Cassini observations: the equatorial belt sits higher than the poles and no sheets or corridors of travelling sand have been identified. Thus, previous sites of equatorial surface liquids may be of interest for understanding sand formation, such as the suggested paleoseas Tui and Hotei Regio. A newly identified feature in the VIMS data sits within the Fensal dune field but is distinct from the surrounding sand. We investigate this Bright Fensal Feature (BFF) using data from Cassini VIMS and RADAR. Specifically, we find spectral similarities between the BFF and both sand and Hotei Regio. The RADAR cross sectional backscatter is similar to neighboring dark areas, perhaps sand covered interdunes. We use this evidence to constrain the BFF’s formation history and discuss how this intra-dune feature may contribute to the processes of sand transport and supply.

Broadband Scattering from Sand and Sand/Mud Sediments with Extensive Environmental Characterization

DTIC Science & Technology

2015-09-30

1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Broadband Scattering from Sand and Sand/ Mud Sediments...TERM GOALS To model the effects of volume heterogeneities, both discrete and continuous, in scattering from sand and mud sediments. A better...IMP2 has been used extensively during TREX13 and BayEx14 to measure the porosity in both sand and mud sediments. Analysis of this recent data inspired a

Wave-induced ripple development in mixed clay-sand substrates

NASA Astrophysics Data System (ADS)

Wu, Xuxu; Parsons, Daniel; Baas, Jaco H.; Mouazé, Dominique; McLelland, Stuart; Amoudry, Laurent; Eggenhuisen, Jorris; Cartigny, Matthieu; Ruessink, Gerben

2016-04-01

This paper reports on a series of experiments that aim to provide a fuller understanding of ripple development within clay-sand mixture substrates under oscillatory flow conditions. The work was conducted in the Total Environment Simulator at the University of Hull and constituted 6 separate runs, in which 5 runs were conducted under identical sets of regular waves (an additional run was conducted under irregular waves, but is not discussed in present paper). The bed content was systematically varied in its composition ranging from a pure sand bed through to a bed comprising 7.4% clay. A series of state-of-the-art measurements were employed to quantify interactions of near-bed hydrodynamics, sediment transport, and turbulence over rippled beds formed by wave action, during and after, each run. The experimental results demonstrate the significant influence of the amount of cohesive clay materials in the substrate on ripple evolution under waves. Most importantly, addition of clay in the bed dramatically slowed down the rate of ripple development and evolution. The equilibrium time of each run increased exponentially from 30 minutes under the control conditions of a pure sand bed, rising to ~350 minutes for the bed with the highest fraction of clay. The paper discusses the slower ripple growth rates with higher cohesive fractions, via an influence on critical shear, but highlights that the end equilibrium size of ripples is found to be independent of increasing substrate clay fraction. The suspended particles mass (SPM) concentration indicates that clay particles were suspended and winnowed by wave action. Additionally, laser granulometry of the final substrates verified that ripple crests were composed of pure sand layers that were absent at ripple troughs, reflecting a relatively higher winnowing efficiency at wave ripples crest. The winnowing process and its efficiency is inexorably linked to wave ripple development and evolution. The implications of the results

Compressor cascade performance deterioration caused by sand ingestion

NASA Technical Reports Server (NTRS)

Tabakoff, W.; Balan, C.

1982-01-01

Airfoil cascade erosion and performance deterioration was investigated in a gas particle cascade tunnel. The cascade blades were made of 2024 aluminum alloy and the solid particles used were quartz sand. The results of the experimental measurements are presented to show the change in the blade surface erosion, pressure distribution and the total loss coefficient with erosion. The surface quality of the blades exposed to particulate flows are changing the material surfaces. With time, the surface roughness increases and leads to a decrease in engine performance. It was found that the surface roughness values increase asymptotically to a maximum value with increased erosion. The experimental results indicate that the roughness parameters correlate well against the mass of particles impacting unit area of the surface. Such a correlation is useful in aerodynamics and performance computations in turbomachinery.

A study of the effect of solid particle impact and particle shape on the erosion morphology of ductile metals

NASA Technical Reports Server (NTRS)

Rao, P. V.; Young, S. G.; Buckley, D. H.

1984-01-01

Impulsive versus steady jet impingement of spherical glass bead particles on metal surfaces was studied using a gas gun facility and a commercial sand blasting apparatus. Crushed glass particles were also used in the sand blasting apparatus as well as glass beads. Comparisons of the different types of erosion patterns were made. Scanning electron microscopy, surface profilometry and energy dispersive X-ray spectroscopy analysis were used to characterize erosion patterns. The nature of the wear can be divided into cutting and deformation, each with its own characteristic features. Surface chemistry analysis indicates the possiblity of complex chemical and/or mechanical interactions between erodants and target materials.

Nano sand filter with functionalized nanoparticles embedded in anodic aluminum oxide templates

PubMed Central

Phuong, NguyenThi; Andisetiawan, Anugrah; Van Lam, Do; Kim, Jeong Hwan; Choi, Doo-Sun; Whang, Kyung-Hyun; Nham, Jeasun; Lee, Yun Jung; Yoo, Yeong-Eun; Yoon, Jae Sung

2016-01-01

Since the ancient Egyptians had used sand as filter media for water purification, its principle has been inherited through generations and it is still being used now in industries. The sand filter consists of sand literally, and the voids within the sand bed are the pores for filtration. Here we present a filtration principle using nanoparticles, so that the voids between the nanoparticles can be considered as effective pores in nanoscale dimension. Anodic aluminum oxide (AAO) membrane has been used as the working template, and the nanoparticles have been injected and embedded within the pores of the AAO template. Nanoparticles with multiple sizes have been used in order to obtain smaller voids. Moreover, the nanoparticles have been functionalized, or electrically charged, with arginine/phenylalanine (RF) peptide group. In this way, filtration performance for charged particles or molecules, such as methylene blue, has been enhanced. Consequently, this study is expected to provide a new principle for fabrication of nano voids, or nano pores, and for filtration in nanoscale dimension. PMID:27876886

Nano sand filter with functionalized nanoparticles embedded in anodic aluminum oxide templates.

PubMed

Phuong, NguyenThi; Andisetiawan, Anugrah; Van Lam, Do; Kim, Jeong Hwan; Choi, Doo-Sun; Whang, Kyung-Hyun; Nham, Jeasun; Lee, Yun Jung; Yoo, Yeong-Eun; Yoon, Jae Sung

2016-11-23

Since the ancient Egyptians had used sand as filter media for water purification, its principle has been inherited through generations and it is still being used now in industries. The sand filter consists of sand literally, and the voids within the sand bed are the pores for filtration. Here we present a filtration principle using nanoparticles, so that the voids between the nanoparticles can be considered as effective pores in nanoscale dimension. Anodic aluminum oxide (AAO) membrane has been used as the working template, and the nanoparticles have been injected and embedded within the pores of the AAO template. Nanoparticles with multiple sizes have been used in order to obtain smaller voids. Moreover, the nanoparticles have been functionalized, or electrically charged, with arginine/phenylalanine (RF) peptide group. In this way, filtration performance for charged particles or molecules, such as methylene blue, has been enhanced. Consequently, this study is expected to provide a new principle for fabrication of nano voids, or nano pores, and for filtration in nanoscale dimension.

Nano sand filter with functionalized nanoparticles embedded in anodic aluminum oxide templates

NASA Astrophysics Data System (ADS)

Phuong, Nguyenthi; Andisetiawan, Anugrah; van Lam, Do; Kim, Jeong Hwan; Choi, Doo-Sun; Whang, Kyung-Hyun; Nham, Jeasun; Lee, Yun Jung; Yoo, Yeong-Eun; Yoon, Jae Sung

2016-11-01

Since the ancient Egyptians had used sand as filter media for water purification, its principle has been inherited through generations and it is still being used now in industries. The sand filter consists of sand literally, and the voids within the sand bed are the pores for filtration. Here we present a filtration principle using nanoparticles, so that the voids between the nanoparticles can be considered as effective pores in nanoscale dimension. Anodic aluminum oxide (AAO) membrane has been used as the working template, and the nanoparticles have been injected and embedded within the pores of the AAO template. Nanoparticles with multiple sizes have been used in order to obtain smaller voids. Moreover, the nanoparticles have been functionalized, or electrically charged, with arginine/phenylalanine (RF) peptide group. In this way, filtration performance for charged particles or molecules, such as methylene blue, has been enhanced. Consequently, this study is expected to provide a new principle for fabrication of nano voids, or nano pores, and for filtration in nanoscale dimension.

Induction of chromosome aberrations in cultured human lymphocytes treated with sand dust storm fine particles (PM2.5).

PubMed

Wei, Aili; Meng, Ziqiang

2006-09-30

The clastogenic activity of airborne air fine particulate matter (PM2.5, particulates with an aerodynamic diameter < or =2.5 microm) has already been demonstrated. However little is known about the health risks associated with sand dust storm PM2.5 and its extract. In order to investigate the clastogenic activity of sand dust storm PM2.5 (include its organic and inorganic extract) on human lymphocytes, the normal PM2.5 and sand dust storm PM2.5 samples were collected in Wuwei city (Gansu Province) and Baotou city (Inner Mongolia), China. The chromosomal aberration (CA) test was employed and the cells were treated with 0, 33, 100, 300 microg ml(-1) sand dust storm or normal ambient air PM2.5 suspension (physiological saline as solvent control), or inorganic extract (0, 75, 150, 300 microg ml(-1), physiological saline as solvent control) or organic extract (0, 20, 40, 80 microg ml(-1), DMSO as solvent control) at the beginning of the cell culture. The results indicated that sand dust storm PM2.5 and its extract as well as normal samples can induce increase in CA frequency. With the increase of treatment concentrations the CA frequency increased and the mitotic index (MI) values declined in a dose-response manner. In the same concentrates, the CA frequency of normal ambient air PM2.5 and its extract were significant higher than those of sand dust storm PM2.5 (P<0.05 or 0.01) except the treatment of Wuwei sample at higher doses (100, 300 microg ml(-1)), the treatment of inorganic extract of PM2.5 at the highest dose (300 microg ml(-1)) and the treatment of organic extract of PM2.5 at the higher dose (40 and 80 microg ml(-1)) either in Baotou or in Wuwei (P>0.05). The toxicity of sand dust storm PM2.5 and its extract at high dose is very potent. CA frequency of normal PM2.5 (include its organic extract) from Baotou were higher than those of Wuwei especially in low and middle dose (P<0.05), but the treatment results of sand dust storm PM2.5 (include its all extract) was

Sand Filter Technology

DTIC Science & Technology

2016-08-01

Approved for public release: distribution unlimited TDS-NAVFAC-EXWC-PW-1604 Aug 2016 Sand Filter Technology This report summarizes the...findings from a demonstration of sand filter technology to determine whether the technology will save energy with a simple payback within the...EXWC) performed the evaluation at the Naval Air Station Lemoore, CA. The two year evaluation period began with one year of sand filter operation

Numerical and experimental studies of particle flow in a high-pressure boundary-layer wind tunnel

NASA Technical Reports Server (NTRS)

White, B. R.

1984-01-01

The approach was to simulate the surface environment of Venus as closely as practicable and to conduct experiments to determine threshold wind speeds, particle flux, particle velocities, and the characteristics of various aeolian bedforms. The Venus Wind Tunnel (VWT) is described and the experimental procedures that were developed to make the high-pressure wind tunnel measurements are presented. In terrestrial simulations of aeolian activity, it is possible to conduct experiments under pressures and temperatures found in natural environments. Because of the high pressures and temperatures, Venusian simulations are difficult to achieve in this regard. Consequently, extrapolation of results to Venue potentially involves unknown factors. The experimental rationale was developed in the following way: The VWT enables the density of the Venusian atmosphere to be reproduced. Density is the principal atmospheric property for governing saltation threshold, particle flux, and the ballistics of airborne particles (equivalent density maintains dynamic similarity of gas flow). When operated at or near Earth's ambient temperature, VWT achieves Venusian atmospheric density at pressures of about 30 bar, or about one third less than those on Venus, although still maintaining dynamic similarity to Venus.

Impact of ozonation on particle aggregation in mature fine tailings.

PubMed

Liang, Jiaming; Tumpa, Fahmida; Pérez Estrada, Leonidas; Gamal El-Din, Mohamed; Liu, Yang

2014-12-15

The extraction of bitumen from the oil sands in Canada generates tonnes of mature fine tailings (MFT), consisting of a mineral matrix of sand, clay, and water, which without treatment requires thousands of years to fully consolidate. We assessed the performance of a novel ozonation method designed to enhance the settling of MFT and explored the mechanisms involved. The solid content of MFT obtained from oil sands tailings was adjusted to 1, 3, 5 wt % with water before applying 15, 30, and 60 min of ozonation. MFT settled after a short (15 min) ozonation treatment, resulting in a sample with clear released water on the top and condensed sludge at the bottom. The water chemistry characteristics, particles' surface charge and chemical bonding were measured. Ozonation led to the increased organic acids concentrations in MFT suspension through converting of organic matter from high to low molecular weight, and detaching organic coating on MFT particles. The pH and the concentrations of ions in the MFT suspension were changed significantly, an association of metal ions with MFT particles was promoted, and the surface charges of MFT particles were neutralized. Consequently, the MFT suspension was destabilized and MFT particle precipitation was observed. Copyright © 2014 Elsevier Ltd. All rights reserved.

Detection of sand encroachment patterns in desert oases. The case of Erg Chebbi (Morocco).

PubMed

Puy, Arnald; Herzog, Manuel; Escriche, Pedro; Marouche, Amou; Oubana, Yousef; Bubenzer, Olaf

2018-06-11

Desert oases are fragile agrarian areas, very vulnerable to sand encroachment by wind. Ensuring their conservation highly depends on our capacity to identify sand encroachment patterns, e.g. the origin of sand and its spatial distribution in the irrigated plots. Here we show how to tackle this issue using the case study of Erg Chebbi (Morocco), where two oases (Hassilabiad and Merzouga) are surrounded by dunes, Hamada and alluvial sediments from the Wadi Ziz. We combine field interviews with the study of wind dynamics, sediment sampling, Particle Size Distribution (PSD) tests and End-Member Modelling Analysis (EMMA). We observe that the most relevant contributor to sand encroachment is the Wadi Ziz (30%), followed by the Hamada (28%), an undetermined source of dust (25%), and the Erg dunes (16%). These genetically different sediments cluster unevenly in the oases, indicating the existence of areas with contrasting degrees of exposure to sedimentary sources. The results allow to define on solid grounds which sand source areas should be stabilized first in order to obtain the greatest reduction in sand encroachment. Our approach also provides policy-makers with better tools to identify which spots are specially vulnerable to accumulate a specific sediment, thus allowing for a more nuanced management of sand in oasis environments. Copyright © 2018 Elsevier B.V. All rights reserved.

Seawater Ca2+ concentration influences solar orientation in Talitrus saltator (Crustacea, Amphipoda).

PubMed

Ugolini, Alberto; Ungherese, Giuseppe; Mercatelli, Luca; Saer, Doumett; Lepri, Luciano

2009-03-01

The role of salinity in the ecophysiology of many intertidal invertebrates has been extensively investigated. Calcium (Ca(2+)), magnesium (Mg(2+)), potassium (K(+)) and sodium (Na(+)) are the major constituents of seawater and it has been demonstrated that sandhoppers tested under the sun in diluted seawater (3.5 per thousand) head seaward, instead of going landward as expected. Therefore, the variation in seawater salinity (from 35 per thousand to 3.5 per thousand) influences their directional choice. This paper investigates the contribution of different cations to the sea-land directional choice of Talitrus saltator (Crustacea, Amphipoda) by the sun compass orientation mechanism. Results of releases carried out in basic seawater selectively deprived of Ca(2+), Mg(2+) or K(+) and containing the same concentration of Na(+) indicate that only the reduction in Ca(2+) concentration affects the capacity of solar orientation. The pH does not influence the directional choice of sandhoppers and nor do small variations in salinity in the range 32-39 per thousand. Moreover, the clear photopositive tendency registered in experiments of phototaxis in Ca(2+)-deprived seawater indicates that the absence of Ca(2+) does not affect the normal functioning of the visual cells. Therefore, our results show that Ca(2+) seawater concentration is important for the correct functioning of one of the principal mechanisms of orientation in supralittoral amphipods and it could affect their survival in the field.

Global sand trade is paving the way for a tragedy of the sand commons

NASA Astrophysics Data System (ADS)

Torres, A.; Brandt, J.; Lear, K.; Liu, J.

2016-12-01

In the first 40 years of the 21st century, planet Earth is highly likely to experience more urban land expansion than in all of history, an increase in transportation infrastructure by more than a third, and a great variety of land reclamation projects. While scientists are beginning to quantify the deep imprint of human infrastructure on biodiversity at large scales, its off-site impacts and linkages to sand mining and trade have been largely ignored. Sand is the most widely used building material in the world. With an ever-increasing demand for this resource, sand is being extracted at rates that far exceed its replenishment, and is becoming increasingly scarce. This has already led to conflicts around the world and will likely lead to a "tragedy of the sand commons" if sustainable sand mining and trade cannot be achieved. We investigate the environmental and socioeconomic interactions over large distances (telecouplings) of infrastructure development and sand mining and trade across diverse systems through transdisciplinary research and the recently proposed telecoupling framework. Our research is generating a thorough understanding of the telecouplings driven by an increasing demand for sand. In particular, we address three main research questions: 1) Where are the conflicts related to sand mining occurring?; 2) What are the major "sending" and "receiving" systems of sand?; and 3) What are the main components (e.g. causes, effects, agents, etc.) of telecoupled systems involving sand mining and trade? Our results highlight the role of global sand trade as a driver of environmental degradation that threatens the integrity of natural systems and their capacity to deliver key ecosystem services. In addition, infrastructure development and sand mining and trade have important implications for other sustainability challenges such as over-fishing and global warming. This knowledge will help to identify opportunities and tools to better promote a more sustainable use

The composition of Martian aeolian sands: Thermal emissivity from Viking IRTM observations

NASA Technical Reports Server (NTRS)

Edgett, Kenneth S.; Christensen, Philip R.

1992-01-01

Aeolian sands provide excellent surfaces for the remote determination of the mineralogic composition of Martian materials, because such deposits consist of relatively well-sorted, uniform particle sizes and might consist of chemically unaltered, primary mineral grains derived from bedrock. Dark features on the floors of Martian craters are controlled by aeolian processes and many consist largely of unconsolidated, windblown sand. Measurement of the thermal emissivity of geologic materials provides a way to identify mid-infrared absorption bands, the strength and positions of which vary with mineral structure and composition. The Viking Infrared Thermal Mapper (IRTM) had four surface-sensing mid-IR bands, three of which, the 7, 9, and 11 micron channels, correspond to absorption features characteristic of carbonates, sialic, and mafic minerals, respectively. In this study, the highest quality IRTM data were constrained so as to avoid the effects of atmospheric dust, clouds, surface frosts, and particle size variations (the latter using data obtained between 7 and 9 H, and they were selected for dark intracrater features such that only data taken directly from the dark feature were used, so as to avoid thermal contributions from adjacent but unrelated materials. Three-point emissivity spectra of Martian dart intracrater features were compared with laboratory emission spectra of minerals and terrestrial aeolian sands convolved using the IRTM response function to the four IRTM spectral channels.

Biocolloid transport in water saturated columns packed with sand

NASA Astrophysics Data System (ADS)

Syngouna, V. I.; Chrysikopoulos, C.

2010-12-01

Protection of groundwater supplies from microbial contamination necessitates a solid understanding of the factors controlling the migration and retention of pathogenic organisms (biocolloids) in the subsurface. The transport behavior of three waterborne pathogens (Escherichia coli, MS2, and ΦΧ174) was investigated using laboratory-scale columns packed with clean quartz sand. Various grain sizes and pore water velocities were examined. Though coliform bacteria and coliphages are used worldwide to indicate fecal pollution of groundwater, the various parameters controlling the transport of Escherichia coli MS2 and ΦΧ174 in the subsurface are not fully understood. In this study, the attachment behavior of Escherichia coli, MS2, and ΦΧ174 onto ultra-pure quartz sand were evaluated. The mass recoveries of the three biocolloids examined were found to be proportional to the sand size. The observed mass recoveries were in the order: Escherichia coli > ΦΧ174 > MS2. To assess the importance of biocolloid attachment, the single collector removal efficiency, and the collision efficiency were quantified using the classical colloid filtration theory. Our results indicate that the secondary energy minimum plays an important role in biocolloid deposition even for smaller biocolloid particles (e.g. viruses).

Numerical investigation of adhesion effects on solid particles filtration efficiency

NASA Astrophysics Data System (ADS)

Shaffee, Amira; Luckham, Paul; Matar, Omar K.

2017-11-01

Our work investigate the effectiveness of particle filtration process, in particular using a fully-coupled Computational Fluid Dynamics (CFD) and Discrete Element Method (DEM) approach involving poly-dispersed, adhesive solid particles. We found that an increase in particle adhesion reduces solid production through the opening of a wire-wrap type filter. Over time, as particle agglomerates continuously deposit on top of the filter, layer upon layer of particles is built on top of the filter, forming a particle pack. It is observed that with increasing particle adhesion, the pack height build up also increases and hence decreases the average particle volume fraction of the pack. This trend suggests higher porosity and looser packing of solid particles within the pack with increased adhesion. Furthermore, we found that the pressure drop for adhesive case is lower compared to non-adhesive case. Our results suggest agglomerating solid particles has beneficial effects on particle filtration. One important application of these findings is towards designing and optimizing sand control process for a hydrocarbon well with excessive sand production which is major challenge in oil and gas industry. Funding from PETRONAS and RAEng UK for Research Chair (OKM) gratefully acknowledged.

High purity Fe3O4 from Local Iron Sand Extraction

NASA Astrophysics Data System (ADS)

Gunanto, Y. E.; Izaak, M. P.; Jobiliong, E.; Cahyadi, L.; Adi, W. A.

2018-04-01

Indonesia has a long coastline and is rich with iron sand. The iron sand is generally rich in various elements such as iron and titanium. One of the products processing of the iron sand mineral is iron (II) (III) oxide (magnetite Fe3O4). The stages of purification process to extracting magnetite phase and discarding the other phases has been performed. Magnetite phase analysis of ironsand extraction retrieved from Indonesia have been investigated. The result of analysis element of iron sand shows that it consists of majority Fe around 65 wt%. However, there are still 17 impurities such as Ti, Al, Ce, Co, Cr, Eu, La, Mg, Mn, Na, Sc, Sm, Th, V, Yb, and Zn. After extraction process, Fe element content increases up to 94%. The iron sand powder after milling for 10 hours and separating using a magnetic separator, the iron sand powders are dissolved in acid chloride solution to form a solution of iron chloride, and this solution is sprinkled with sodium hydroxide to obtain fine powders of Fe3O4. The fine powders which formed were washed with de-mineralization water. The X-ray diffraction pattern shows that the fine powders have a single phase of Fe3O4. The analysis result shows that the sample has the chemical formula: Fe3O4 with a cubic crystal system, space group: Fd-3m and lattice parameters: a = b = c = 8.3681 (1) Å, α = β = γ = 90°. The microstructure analysis shows that the particle of Fe3O4 homogeneously shaped like spherical. The magnetic properties using vibrating sample magnetometer shows that Fe3O4 obtained have ferromagnetic behavior with soft magnetic characteristics. We concluded that this purification of iron sand had been successfully performed to obtain fine powders of Fe3O4 with high purity.

Sedimentary differentiation of aeolian grains at the White Sands National Monument, New Mexico, USA

NASA Astrophysics Data System (ADS)

Fenton, Lori K.; Bishop, Janice L.; King, Sara; Lafuente, Barbara; Horgan, Briony; Bustos, David; Sarrazin, Philippe

2017-06-01

Gypsum (CaSO4·2H2O) has been identified as a major component of part of Olympia Undae in the northern polar region of Mars, along with the mafic minerals more typical of Martian dune fields. The source and age of the gypsum is disputed, with the proposed explanations having vastly different implications for Mars' geological history. Furthermore, the transport of low density gypsum grains relative to and concurrently with denser grains has yet to be investigated in an aeolian setting. To address this knowledge gap, we performed a field study at White Sands National Monument (WSNM) in New Mexico, USA. Although gypsum dominates the bulk of the dune field, a dolomite-rich [CaMg(CO3)2] transport pathway along the northern border of WSNM provides a suitable analog site to study the transport of gypsum grains relative to the somewhat harder and denser carbonate grains. We collected samples along the stoss slope of a dune and on two coarse-grained ripples at the upwind margin of the dune field where minerals other than gypsum were most common. For comparison, additional samples were taken along the stoss slope of a dune outside the dolomite transport pathway, in the center of the dune field. Visible and near-infrared (VNIR), X-ray powder diffraction (XRD), and Raman analyses of different sample size fractions reveal that dolomite is only prevalent in grains larger than ∼1 mm. Other minerals, most notably calcite, are also present in smaller quantities among the coarse grains. The abundance of these coarse grains, relative to gypsum grains of the same size, drops off sharply at the upwind margin of the dune field. In contrast, gypsum dominated the finer fraction (<∼1 mm) at all sample sites, displaying no spatial variation. Estimates of sediment fluxes indicate that, although mineralogical differentiation of wind-transported grains occurs gradually in creep, the process is much more rapid when winds are strong enough to saltate the ⩾1 mm grains. The observed grain

Supersonic Particle Impact Test Capabilities: Investigative Report

NASA Technical Reports Server (NTRS)

Rosales, Keisa

2007-01-01

NASA Johnson Space Center White Sands Test Facility (WSTF) performed particle impact flow tests to determine the maximum capabilities of the particle impact test systems in different configurations. Additional flow tests were performed to determine the target pressures at given upstream conditions to supplement the WSTF data located in ASTM Manual 36 (2000).

Vanadium Geochemistry of Oil Sands Fluid Petroleum Coke.

PubMed

Nesbitt, Jake A; Lindsay, Matthew B J

2017-03-07

Vanadium has previously been linked to elevated toxicity of leachates derived from oil sands petroleum coke. However, geochemical controls on V mobility within coke deposits remain poorly constrained. Detailed examinations of porewater and solid-phase V geochemistry were therefore performed on oil sands fluid petroleum coke deposits in Alberta, Canada. Sample collection focused on both active and reclaimed deposits, which contained more than 3 × 10 7 m 3 of fluid petroleum coke. Dissolved V concentrations were highest (up to 3.0 mg L -1 ) immediately below the water table but decreased rapidly with increasing depth. This trend corresponded to a transition from mildly acidic (pH 6-7) and oxic conditions to mildly alkaline (pH 7-8.5) and anoxic conditions. Scanning electron microscopy (SEM), electron microprobe analysis (EMPA), and micro-X-ray fluorescence (μXRF) mapping revealed coke particles exhibited an internal structure characterized by successive concentric layers. The outer margins of these layers were characterized by elevated V, Fe, Si, and Al concentrations, indicating the presence of inorganic phases. Micro-X-ray absorption near-edge structure (μXANES) spectroscopy revealed that V speciation was dominated by V(IV) porphyrins except at outer margins of layers, where octahedrally coordinated V(III) was a major component. Minor to trace V(V) was also detected within fluid petroleum coke particles.

Laboratory studies of dune sand for the use of construction industry in Sri Lanka

NASA Astrophysics Data System (ADS)

de Silva Jayawardena, Upali; Wijesuriya, Roshan; Abayaweera, Gayan; Viduranga, Tharaka

2015-04-01

With the increase of the annual sand demand for the construction industry the excessive excavation of river sand is becoming a serious environmental problem in Sri Lanka. Therefore, it is necessary to explore the possibility for an alternative to stop or at least to minimize river sand mining activities. Dune sand is one of the available alternative materials to be considered instead of river sand in the country. Large quantities of sand dunes occur mainly along the NW and SE coastal belt which belong to very low rainfall Dry Zone coasts. The height of dune deposits, vary from 1m to about 30 meters above sea level. The objective of this paper is to indicate some studies and facts on the dune sand deposits of Sri Lanka. Laboratory studies were carried out for visual observations and physical properties at the initial stage and then a number of tests were carried out according to ASTM standards to obtain the compressive strength of concrete cylinders and mortar cubes mixing dune sand and river sand in different percentages keeping a constant water cement ratio. Next the water cement ratio was changed for constant dune sand and river sand proportion. Microscopic analysis shows that the dune sand consist of 95 % of quartz and 5 % of garnet, feldspar, illmenite and other heavy minerals with clay, fine dust, fine shell fragments and organic matters. Grains are sub-rounded to angular and tabular shapes. The grain sizes vary from fine to medium size of sand with silt. The degree of sorting and particle size observed with dune sands are more suited with the requirement of fine aggregates in the construction industry. The test result indicates that dune sand could be effectively used in construction work without sieving and it is ideal for wall plastering due to its'-uniformity. It could also be effectively used in concrete and in mortars mixing with river sand. The best mixing ratio is 75% dune sand and 25% river sand as the fine aggregate of concrete. For mortar the mixing

Erosion

USDA-ARS?s Scientific Manuscript database

Erosion is the detachment of soil particles and transportation to another location. Wind erosion occurs when wind speed exceeds a critical threshold level, and loose soil particles or soil particles removed by abrasion then move in one of three ways: creep, saltation, and suspension. Erosion by wate...

Abrasion by aeolian particles: Earth and Mars

NASA Technical Reports Server (NTRS)

Greeley, R.; Marshall, J. R.; White, B. R.; Pollack, J. B.; Marshall, J.; Krinsley, D.

1984-01-01

Estimation of the rate of aeolian abrasion of rocks on Mars requires knowledge of: (1) particle flux, (2) susceptibilities to abrasion of various rocks, and (3) wind frequencies on Mars. Fluxes and susceptibilities for a wide range of conditions were obtained in the laboratory and combined with wind data from the Viking meteorology experiment. Assuming an abundant supply of sand-sized particles, estimated rates range up to 2.1 x 10 to the minus 2 power cm of abrasion per year in the vicinity of Viking Lander 1. This rate is orders of magnitude too great to be in agreement with the inferred age of the surface based on models of impact crater flux. The discrepancy in the estimated rate of abrasion and the presumed old age of the surface cannot be explained easily by changes in climate or exhumation of ancient surfaces. The primary reason is thought to be related to the agents of abrasion. At least some sand-sized (approx. 100 micrometers) grains appear to be present, as inferred from both lander and orbiter observations. High rates of abrasion occur for all experimental cases involving sands of quartz, basalt, or ash. However, previous studies have shown that sand is quickly comminuted to silt- and clay-sized grains in the martian aeolian regime. Experiments also show that these fine grains are electrostatically charged and bond together as sand-sized aggregates. Laboratory simulations of wind abrasion involving aggregates show that at impact velocities capable of destroying sand, aggregates from a protective veneer on the target surface and can give rise to extremely low abrasion rates.

Mineralogy and morphology of sand: Key parameters in the durability for its use in artificial beach nourishment.

PubMed

López, M; Baeza-Brotons, F; López, I; Tenza-Abril, A J; Aragonés, L

2018-05-19

Sand is the third most consumed material in the world, although it is a very scarce material. An exhaustive knowledge of sand and its behaviour against the waves is important for selecting the most suitable material to avoid shoreline erosion. To this end, a pattern of behaviour against accelerated wear test has been sought for 26 sand samples with different characteristics and origins (natural, dredged and quarried), with a focus on their mineralogy as well as a comparison of beach evolution carried out by other authors. Several techniques have been applied for characterization: granulometry, calcimetry, XRD and SEM. The results show that the different degrees of sand grain wear are not only due to their size and mineralogy, but also to the morphology of the particles. Copyright © 2018 Elsevier B.V. All rights reserved.

Reduction in soil aggregate size distribution due to wind erosion

NASA Astrophysics Data System (ADS)

Swet, Nitzan; Katra, Itzhak

2017-04-01

Soil erosion process by wind causes emission of fine soil particles, and thus alters the topsoil's properties, fertility, and erodibility. Topsoil resistance to erosion depends on its physicochemical properties, especially on the soil aggregation. Although the key role of aggregates in soil erodibility, quantitative information on the relations between soil aggregate size distribution (ASD) and erosion is still lucking. This study focuses on ASD analyses before and after soil erosion by wind. Wind tunnel experiments and soil analyses were conducted on semiarid loess topsoils with different initial conditions of aggregation. The results show that in all initial soil conditions saltation of sand particles caused the breakdown of macro-aggregates > 500 µm, resulting in increase of micro-aggregates (63-250 µm). The micro-aggregate production increases with the wind shear velocity (up to 0.61 m s-1) for soils with available macro-aggregates. The findings highlight dynamics in soil aggregation in response to erosion process, and therefore the significance of ASD in quantifying soil degradation and soil loss potential.

Weathering and erosion of the polar layered deposits on Mars

NASA Technical Reports Server (NTRS)

Herkenhoff, K. E.

1990-01-01

The Martial polar layered deposits are widely believed to be composed of water ice and silicates, but the relative amount of each component is unknown. The conventional wisdom among Mars researchers is that the deposits were formed by periodic variations in the deposition of dust and ice caused by climate changes over the last 10 to 100 million years. It is assumed here that water ice is an important constituent of the layered deposits, that the deposits were formed by eolian processes, and that the origin and evolution of the north and south polar deposits were similar. Weathering of the layered deposits by sublimation of water ice can account for the geologic relationships in the polar regions. The nonvolatile components of the layered deposits appears to consist mainly of bright red dust, with small amounts of dark dust or sand. Dark dust, perhaps similar to the magnetic material found at the Viking Lander sites, may perferentially form filamentary residue particles upon weathering of the deposits. Once eroded, these particles may saltate to form the dark dunes found in both polar regions.

Relict drainages, conical hills, and the eolian veneer in southwest Egypt - Applications to Mars

NASA Technical Reports Server (NTRS)

Breed, C. S.; Mccauley, J. F.; Grolier, M. J.

1982-01-01

The fluvial and mass wasting origin of the particles in the eolian deposits, the segregation of these materials on the basis of grain size, and the migration of those particles capable of saltation to areas of accumulation in lowland basins of the Sahara are suggested as analogs for the formation and accumulation of 'sand' sheets and dunes on the northern plains and in the polar erg on Mars. Outliers of the Martian plateau in the fretted terrain are seen as having been dissected, at least initially, by channels whose upstream portions are incised in the uplands. The Martian 'wadis' possess many geomorphic peculiarities similar to those of the Gilf (Gilf Kebir Plateau, southwest Egypt) wadis, and like the Egyptian features they have been attributed to mass wasting. Even though basal sapping and removal of debris by wind have almost certainly modified the Martian features, their deep incision in the plateau and their inferred northward extensions in the northern plains are thought to require not only initial downcutting by fairly energetic streams but also prolonged and long-distance flow of water.

Stability of nTiO2 particles and their attachment to sand: Effects of humic acid at different pH.

PubMed

Wu, Yang; Cheng, Tao

2016-01-15

The fate and transport of nano-scale or micro-scale titanium dioxide particles (nTiO2) in subsurface environments are strongly influenced by the stability of nTiO2 and their attachment to sediment grains. nTiO2 may carry either positive or negative charges in natural water, therefore, environmental factors such as pH, humic substances, and Fe oxyhydroxide coatings on sediment grains, which are known to control the stability and transport of negatively-charged colloids, may influence nTiO2 in different manners. The objective of this study is to investigate the effects of pH and humic acid (HA) on the stability and attachment of nTiO2 to sand at HA concentrations that are relevant to typical groundwater conditions, so that mechanisms that control nTiO2 immobilization and transport in natural systems can be elucidated. Stability and attachment of nTiO2 to quartz sand and Fe oxyhydroxide coated quartz sand are experimentally measured under a range of HA concentrations at pH5 and 9. Results show that at pH5, negatively-charged HA strongly adsorbs to positively-charged nTiO2 and Fe oxyhydroxide, which, at low HA concentrations, partially neutralizes the positive charges on nTiO2 and Fe oxyhydroxide, and therefore decreases the repulsive electrostatic forces between the surfaces, resulting in nTiO2 aggregation and attachment. At high HA concentrations, adsorbed HA reverses the surface charges of nTiO2 and Fe oxyhydroxide, and makes nTiO2 and Fe oxyhydroxide strongly negatively charged, resulting in stable nTiO2 suspension and low nTiO2 attachment. At pH9, HA, nTiO2, and Fe oxyhydroxide are all negatively charged, and HA adsorption is low and does not have a strong impact on the stability and attachment of nTiO2. Overall, this study shows that changes in surface charges of nTiO2 and Fe oxyhydroxide coating caused by HA adsorption is a key factor that influences the stability and attachment of nTiO2. Copyright © 2015 Elsevier B.V. All rights reserved.

Quantitative detection of mass concentration of sand-dust storms via wind-profiling radar and analysis of Z- M relationship

NASA Astrophysics Data System (ADS)

Wang, Minzhong; Ming, Hu; Ruan, Zheng; Gao, Lianhui; Yang, Di

2018-02-01

With the aim to achieve quantitative monitoring of sand-dust storms in real time, wind-profiling radar is applied to monitor and study the process of four sand-dust storms in the Tazhong area of the Taklimakan Desert. Through evaluation and analysis of the spatial-temporal distribution of reflectivity factor, it is found that reflectivity factor ranges from 2 to 18 dBz under sand-dust storm weather. Using echo power spectrum of radar vertical beams, sand-dust particle spectrum and sand-dust mass concentration at the altitude of 600 ˜ 1500 m are retrieved. This study shows that sand-dust mass concentration reaches 700 μg/m3 under blowing sand weather, 2000 μg/m3 under sand-dust storm weather, and 400 μg/m3 under floating dust weather. The following equations are established to represent the relationship between the reflectivity factor and sand-dust mass concentration: Z = 20713.5 M 0.995 under floating dust weather, Z = 22988.3 M 1.006 under blowing sand weather, and Z = 24584.2 M 1.013 under sand-dust storm weather. The retrieval results from this paper are almost consistent with previous monitoring results achieved by former researchers; thus, it is implied that wind-profiling radar can be used as a new reference device to quantitatively monitor sand-dust storms.

Modeling Sediment Transport Using a Lagrangian Particle Tracking Algorithm Coupled with High-Resolution Large Eddy Simulations: a Critical Analysis of Model Limits and Sensitivity

NASA Astrophysics Data System (ADS)

Garcia, M. H.

2016-12-01

Modeling Sediment Transport Using a Lagrangian Particle Tracking Algorithm Coupled with High-Resolution Large Eddy Simulations: a Critical Analysis of Model Limits and Sensitivity Som Dutta1, Paul Fischer2, Marcelo H. Garcia11Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Urbana, Il, 61801 2Department of Computer Science and Department of MechSE, University of Illinois at Urbana-Champaign, Urbana, Il, 61801 Since the seminal work of Niño and Garcia [1994], one-way coupled Lagrangian particle tracking has been used extensively for modeling sediment transport. Over time, the Lagrangian particle tracking method has been coupled with Eulerian flow simulations, ranging from Reynolds Averaged Navier-Stokes (RANS) based models to Detached Eddy Simulations (DES) [Escauriaza and Sotiropoulos, 2011]. Advent of high performance computing (HPC) platforms and faster algorithms have resulted in the work of Dutta et al. [2016], where Lagrangian particle tracking was coupled with high-resolution Large Eddy Simulations (LES) to model the complex and highly non-linear phenomenon of Bulle-Effect at diversions. Despite all the advancements in using Lagrangian particle tracking, there has not been a study that looks in detail at the limits of the model in the context of sediment transport, and also analyzes the sensitivity of the various force formulation in the force balance equation of the particles. Niño and Garcia [1994] did a similar analysis, but the vertical flow velocity distribution was modeled as the log-law. The current study extends the analysis by modeling the flow using high-resolution LES at a Reynolds number comparable to experiments of Niño et al. [1994]. Dutta et al., (2016), Large Eddy Simulation (LES) of flow and bedload transport at an idealized 90-degree diversion: insight into Bulle-Effect, River Flow 2016 - Constantinescu, Garcia & Hanes (Eds), Taylor & Francis Group, London, 101-109. Escauriaza and Sotiropoulos

DEM Particle Fracture Model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Boning; Herbold, Eric B.; Homel, Michael A.

2015-12-01

An adaptive particle fracture model in poly-ellipsoidal Discrete Element Method is developed. The poly-ellipsoidal particle will break into several sub-poly-ellipsoids by Hoek-Brown fracture criterion based on continuum stress and the maximum tensile stress in contacts. Also Weibull theory is introduced to consider the statistics and size effects on particle strength. Finally, high strain-rate split Hopkinson pressure bar experiment of silica sand is simulated using this newly developed model. Comparisons with experiments show that our particle fracture model can capture the mechanical behavior of this experiment very well, both in stress-strain response and particle size redistribution. The effects of density andmore » packings o the samples are also studied in numerical examples.« less

Experimental investigation of cephapirin adsorption to quartz filter sands and dune sands

NASA Astrophysics Data System (ADS)

Peterson, Jonathan W.; O'Meara, Theresa A.; Seymour, Michael D.

2008-08-01

Batch experiments were performed to investigate cephapirin (a widely used veterinary antibiotic) adsorption on various size sands of low total organic carbon content (0.08-0.36 wt%). In the aqueous concentration range investigated (11-112 μmol/L cephapirin), adsorption to nearly pure quartz filter sands (0.50-3.35 mm diameter) is low. Isotherms are S-shaped and most display a region of minimum adsorption, where decreased adsorption occurs with increasing solution concentration, followed by increased adsorption at higher concentrations. Cephapirin adsorption to quartz-rich, feldspar-bearing dune sands (0.06-0.35 mm diameter), and the smallest quartz filter sand investigated (0.43-0.50 mm), can be described by linear sorption isotherms over the range of concentrations investigated. Distribution coefficients ( K d) range from 0.94 to 3.45 L/kg. No systematic relationship exists between grain size and amount of adsorption for any of the sands investigated. Cephapirin adsorption is positively correlated to the feldspar ratio (K-feldspar/(albite + Ca-plagioclase). Feldspar-ratio normalization of distribution coefficients was more effective than organic carbon normalization at reducing variability of K d values in the dune sands investigated.

Sand pulses and sand patches on the Colorado River in Grand Canyon

USGS Publications Warehouse

Grams, Paul E.; Buscombe, Daniel; Topping, David; Mueller, Erich R.

2017-01-01

Alluvial sandbars occur in lateral recirculation zones (eddies) along the Colorado River in Grand Canyon National Park (Schmidt, 1990). Resource managers periodically release controlled floods from the upstream Glen Canyon Dam to rebuild these bars (Grams et al., 2015), which erode during fluctuating dam releases, and by hillslope runoff and wind deflation (Hazel et al., 2010). Because the dam blocks upstream sediment, episodic floods from tributaries provide the only supply to replace eroded sand; and much of this sand originates from a single tributary (Topping et al., 2000). Here, we present new evidence for the downstream translation of the sand component of these sediment inputs as discontinuous sand pulses. Improved understanding of the behaviour of these sand pulses may be used to adjust the timing, magnitude, and duration of controlled floods to maximize potential for deposition on sandbars in different segments of the 450 km-long Grand Canyon.

Transport of Lactate-modified Nanoscale Iron Particles in Porous Media

NASA Astrophysics Data System (ADS)

Reddy, K. R.

2012-12-01

Nanoscale iron particles (NIP) have recently shown to be effective for dehalogenation of recalcitrant organic contaminants such as pentachlorphenol (PCP) and dinitrotoluene (DNT) in the environment. However, effective transport of NIP into the contaminated subsurface zones is crucial for the success of in-situ remediation. Previous studies showed that the transport of NIP in soils is very limited and surface-modification of NIP is required to achieve adequate transport. This paper investigates the transport of NIP and lactate-modified NIP (LMNIP) through four different porous media (sands with different particle size and distribution). A series of laboratory column experiments was conducted to quantify the transport of NIP and LMNIP at two different slurry concentrations of 1 g/L and 4 g/L under two different flow velcoities. NIP used in this study possessed magentic properties, thus a magnetic susceptibility sensor system was used to monitor the changes in magnetic susceptibility (MS) along the length of the column at different times during the experiments. At the end of testing, the distribution of total Fe in the sand column was measured. Results showed a linear correlation between the Fe concentration and MS and it was used to assess the transient transport of NIP and LMNIP in the sand columns. Results showed that LMNIP transported better than bare NIP and higher concentration of 4 g/L LMNIP exhibited unform and greater transport compared to other tested conditions. Transport of NIP increased in the order from fine Ottawa sand > medium field sand > coarse field sand > coarse Ottawa sand. Filtration theory and advective-dispersion equation with reaction were applied to capture the transport response of NIP and LMNIP in the sand columns.

Diurnal emissivity dynamics in bare versus biocrusted sand dunes.

PubMed

Rozenstein, Offer; Agam, Nurit; Serio, Carmine; Masiello, Guido; Venafra, Sara; Achal, Stephen; Puckrin, Eldon; Karnieli, Arnon

2015-02-15

Land surface emissivity (LSE) in the thermal infrared depends mainly on the ground cover and on changes in soil moisture. The LSE is a critical variable that affects the prediction accuracy of geophysical models requiring land surface temperature as an input, highlighting the need for an accurate derivation of LSE. The primary aim of this study was to test the hypothesis that diurnal changes in emissivity, as detected from space, are larger for areas mostly covered by biocrusts (composed mainly of cyanobacteria) than for bare sand areas. The LSE dynamics were monitored from geostationary orbit by the Spinning Enhanced Visible and Infrared Imager (SEVIRI) over a sand dune field in a coastal desert region extending across both sides of the Israel-Egypt political borderline. Different land-use practices by the two countries have resulted in exposed, active sand dunes on the Egyptian side (Sinai), and dunes stabilized by biocrusts on the Israeli side (Negev). Since biocrusts adsorb more moisture from the atmosphere than bare sand does, and LSE is affected by the soil moisture, diurnal fluctuations in LSE were larger for the crusted dunes in the 8.7 μm channel. This phenomenon is attributed to water vapor adsorption by the sand/biocrust particles. The results indicate that LSE is sensitive to minor changes in soil water content caused by water vapor adsorption and can, therefore, serve as a tool for quantifying this effect, which has a large spatial impact. As biocrusts cover vast regions in deserts worldwide, this discovery has repercussions for LSE estimations in deserts around the globe, and these LSE variations can potentially have considerable effects on geophysical models from local to regional scales. Copyright © 2014 Elsevier B.V. All rights reserved.

Monitoring Sand Sheets and Dunes

NASA Image and Video Library

2017-06-12

NASA's Mars Reconnaissance Orbiter (MRO) captured this crater featuring sand dunes and sand sheets on its floor. What are sand sheets? Snow fall on Earth is a good example of sand sheets: when it snows, the ground gets blanketed with up to a few meters of snow. The snow mantles the ground and "mimics" the underlying topography. Sand sheets likewise mantle the ground as a relatively thin deposit. This kind of environment has been monitored by HiRISE since 2007 to look for movement in the ripples covering the dunes and sheets. This is how scientists who study wind-blown sand can track the amount of sand moving through the area and possibly where the sand came from. Using the present environment is crucial to understanding the past: sand dunes, sheets, and ripples sometimes become preserved as sandstone and contain clues as to how they were deposited The map is projected here at a scale of 25 centimeters (9.8 inches) per pixel. [The original image scale is 25 centimeters (9.8 inches) per pixel (with 1 x 1 binning); objects on the order of 75 centimeters (29.5 inches) across are resolved.] North is up. https://photojournal.jpl.nasa.gov/catalog/PIA21757

Altitude of the top of the Sparta Sand and Memphis Sand in three areas of Arkansas

USGS Publications Warehouse

Pugh, Aaron L.; Westerfield, Paul W.; Gonthier, Gerard; Poynter, David T.

1998-01-01

The Sparta Sand and Memphis Sand form the second most productive aquifer in Arkansas. The Sparta Sand and Memphis Sand range in thick- ness from 0 to 900 feet, consisting of fine- to medium-grained sands interbedded with layers of silt, clay, shale, and minor amounts of lignite. Within the three areas of interest, the top surface of the Sparta Sand and Memphis Sand dips regionally east and southeast towards the axis of the Mississippi Embayment syncline and Desha Basin. Local variations in the top surface may be attributed to a combination of continued development of structural features, differential compaction, localized faulting, and erosion of the surface prior to subsequent inundation and deposition of younger sediments.

Aeolian bedforms, yardangs, and indurated surfaces in the Tharsis Montes as seen by the HiRISE Camera: Evidence for dust aggregates

USGS Publications Warehouse

Bridges, N.T.; Banks, M.E.; Beyer, R.A.; Chuang, F.C.; Noe Dobrea, E.Z.; Herkenhoff, K. E.; Keszthelyi, L.P.; Fishbaugh, K.E.; McEwen, A.S.; Michaels, T.I.; Thomson, B.J.; Wray, J.J.

2010-01-01

HiRISE images of Mars with ground sampling down to 25 cm/pixel show that the dust-rich mantle covering the surfaces of the Tharsis Montes is organized into ridges whose form and distribution are consistent with formation by aeolian saltation. Other dusty areas near the volcanoes and elsewhere on the planet exhibit a similar morphology. The material composing these "reticulate" bedforms is constrained by their remote sensing properties and the threshold curve combined with the saltation/suspension boundary, both of which vary as a function of elevation (atmospheric pressure), particle size, and particle composition. Considering all of these factors, dust aggregates are the most likely material composing these bedforms. We propose that airfall dust on and near the volcanoes aggregates in situ over time, maybe due to electrostatic charging followed by cementation by salts. The aggregates eventually reach a particle size at which saltation is possible. Aggregates on the flanks are transported downslope by katabatic winds and form linear and "accordion" morphologies. Materials within the calderas and other depressions remain trapped and are subjected to multidirectional winds, forming an interlinked "honeycomb" texture. In many places on and near the volcanoes, light-toned, low thermal inertia yardangs and indurated surfaces are present. These may represent "duststone" formed when aggregates reach a particle size below the threshold curve, such that they become stabilized and subsequently undergo cementation. ?? 2009 Elsevier Inc.

Development and testing of a unique carousel wind tunnel to experimentally determine the effect of gravity and the interparticle force on the physics of wind-blown particles

NASA Technical Reports Server (NTRS)

Leach, R. N.; Greeley, Ronald; White, Bruce R.; Iversen, James D.

1987-01-01

In the study of planetary aeolian processes the effect of gravity is not readily modeled. Gravity appears in the equations of particle motion along with the interparticle forces but the two are not separable. A wind tunnel that perimits multiphase flow experiments with wind blown particles at variable gravity was built and experiments were conducted at reduced gravity. The equations of particle motion initiation (saltation threshold) with variable gravity were experimentally verified and the interparticle force was separated. A uniquely design Carousel Wind Tunnel (CWT) allows for the long flow distance in a small sized tunnel since the test section if a continuous loop and develops the required turbulent boundary layer. A prototype model of the tunnel where only the inner drum rotates was built and tested in the KC-135 Weightless Wonder 4 zero-g aircraft. Future work includes further experiments with walnut shell in the KC-135 which sharply graded particles of widely varying median sizes including very small particles to see how interparticle force varies with particle size, and also experiments with other aeolian material.

Particle shape effect on erosion of optical glass substrates due to microparticles

NASA Astrophysics Data System (ADS)

Waxman, Rachel; Gray, Perry; Guven, Ibrahim

2018-03-01

Impact experiments using sand particles and soda lime glass spheres were performed on four distinct glass substrates. Sand particles were characterized using optical and scanning electron microscopy. High-speed video footage from impact tests was used to calculate incoming and rebound velocities of the individual impact events, as well as the particle volume and two-dimensional sphericity. Furthermore, video analysis was used in conjunction with optical and scanning electron microscopy to relate the incoming velocity and particle shape to subsequent fractures, including both radial and lateral cracks. Indentation theory [Marshall et al., J. Am. Ceram. Soc. 65, 561-566 (1982)] was applied and correlated with lateral crack lengths. Multi-variable power law regression was performed, incorporating the particle shape into the model and was shown to have better fit to damage data than the previous indentation model.

Validation Testing of a Peridynamic Impact Damage Model Using NASA's Micro-Particle Gun

NASA Technical Reports Server (NTRS)

Baber, Forrest E.; Zelinski, Brian J.; Guven, Ibrahim; Gray, Perry

2017-01-01

Through a collaborative effort between the Virginia Commonwealth University and Raytheon, a peridynamic model for sand impact damage has been developed1-3. Model development has focused on simulating impacts of sand particles on ZnS traveling at velocities consistent with aircraft take-off and landing speeds. The model reproduces common features of impact damage including pit and radial cracks, and, under some conditions, lateral cracks. This study focuses on a preliminary validation exercise in which simulation results from the peridynamic model are compared to a limited experimental data set generated by NASA's recently developed micro-particle gun (MPG). The MPG facility measures the dimensions and incoming and rebound velocities of the impact particles. It also links each particle to a specific impact site and its associated damage. In this validation exercise parameters of the peridynamic model are adjusted to fit the experimentally observed pit diameter, average length of radial cracks and rebound velocities for 4 impacts of 300 µm glass beads on ZnS. Results indicate that a reasonable fit of these impact characteristics can be obtained by suitable adjustment of the peridynamic input parameters, demonstrating that the MPG can be used effectively as a validation tool for impact modeling and that the peridynamic sand impact model described herein possesses not only a qualitative but also a quantitative ability to simulate sand impact events.

Fecal indicators in sand, sand contact, and risk of enteric illness among beach-goers

EPA Science Inventory

BACKGROUND: Beach sand can harbor fecal indicator organisms and pathogens, but enteric illness risk associated with sand contact remains unclear. METHODS: In 2007, visitors at 2 recreational marine beaches were asked on the day of their visit about sand contact. Ten to 12 days...

All you need is shape: Predicting shear banding in sand with LS-DEM

NASA Astrophysics Data System (ADS)

Kawamoto, Reid; Andò, Edward; Viggiani, Gioacchino; Andrade, José E.

2018-02-01

This paper presents discrete element method (DEM) simulations with experimental comparisons at multiple length scales-underscoring the crucial role of particle shape. The simulations build on technological advances in the DEM furnished by level sets (LS-DEM), which enable the mathematical representation of the surface of arbitrarily-shaped particles such as grains of sand. We show that this ability to model shape enables unprecedented capture of the mechanics of granular materials across scales ranging from macroscopic behavior to local behavior to particle behavior. Specifically, the model is able to predict the onset and evolution of shear banding in sands, replicating the most advanced high-fidelity experiments in triaxial compression equipped with sequential X-ray tomography imaging. We present comparisons of the model and experiment at an unprecedented level of quantitative agreement-building a one-to-one model where every particle in the more than 53,000-particle array has its own avatar or numerical twin. Furthermore, the boundary conditions of the experiment are faithfully captured by modeling the membrane effect as well as the platen displacement and tilting. The results show a computational tool that can give insight into the physics and mechanics of granular materials undergoing shear deformation and failure, with computational times comparable to those of the experiment. One quantitative measure that is extracted from the LS-DEM simulations that is currently not available experimentally is the evolution of three dimensional force chains inside and outside of the shear band. We show that the rotations on the force chains are correlated to the rotations in stress principal directions.

DEM study of fabric features governing undrained post-liquefaction shear deformation of sand

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Rui; Fu, Pengcheng; Zhang, Jian-Min

In an effort to study undrained post-liquefaction shear deformation of sand, the discrete element method (DEM) is adopted to conduct undrained cyclic biaxial compression simulations on granular assemblies consisting of 2D circular particles. The simulations are able to successfully reproduce the generation and eventual saturation of shear strain through the series of liquefaction states that the material experiences during cyclic loading after the initial liquefaction. Also, DEM simulations with different deviatoric stress amplitudes and initial mean effective stresses on samples with different void ratios and loading histories are carried out to investigate the relationship between various mechanics- or fabric-related variablesmore » and post-liquefaction shear strain development. It is found that well-known metrics such as deviatoric stress amplitude, initial mean effective stress, void ratio, contact normal fabric anisotropy intensity, and coordination number, are not adequately correlated to the observed shear strain development and, therefore, could not possibly be used for its prediction. A new fabric entity, namely the Mean Neighboring Particle Distance (MNPD), is introduced to reflect the space arrangement of particles. It is found that the MNPD has an extremely strong and definitive relationship with the post-liquefaction shear strain development, showing MNPD’s potential role as a parameter governing post-liquefaction behavior of sand.« less

DEM study of fabric features governing undrained post-liquefaction shear deformation of sand

DOE PAGES

Wang, Rui; Fu, Pengcheng; Zhang, Jian-Min; ...

2016-10-05

In an effort to study undrained post-liquefaction shear deformation of sand, the discrete element method (DEM) is adopted to conduct undrained cyclic biaxial compression simulations on granular assemblies consisting of 2D circular particles. The simulations are able to successfully reproduce the generation and eventual saturation of shear strain through the series of liquefaction states that the material experiences during cyclic loading after the initial liquefaction. Also, DEM simulations with different deviatoric stress amplitudes and initial mean effective stresses on samples with different void ratios and loading histories are carried out to investigate the relationship between various mechanics- or fabric-related variablesmore » and post-liquefaction shear strain development. It is found that well-known metrics such as deviatoric stress amplitude, initial mean effective stress, void ratio, contact normal fabric anisotropy intensity, and coordination number, are not adequately correlated to the observed shear strain development and, therefore, could not possibly be used for its prediction. A new fabric entity, namely the Mean Neighboring Particle Distance (MNPD), is introduced to reflect the space arrangement of particles. It is found that the MNPD has an extremely strong and definitive relationship with the post-liquefaction shear strain development, showing MNPD’s potential role as a parameter governing post-liquefaction behavior of sand.« less

Spontaneous Emergence of Order in Vibrated Sand*

NASA Astrophysics Data System (ADS)

Swinney, Harry L.

2004-05-01

Granular media such as sand, pharmaceuticals, cereal, cosmetics, and asteroids are involved in many processes, yet granular media remain less well understood than fluids and solids. Vertically oscillating granular layers provide a test bed for theory and modeling of granular dynamics. Experiments on vertically oscillating granular layers have revealed a variety of spatial patterns that emerge spontaneously as a function of the container acceleration amplitude and frequency: stripes, squares, hexagons, spirals, and oscillons (localized structures). Molecular dynamics simulations yield results in quantitative accord with laboratory observations. Since the gradients of density and velocity are large over a particle mean free path, the applicability of continuum theory has been questionable. However, hydrodynamic equations proposed for dissipative particles yield results in surprising qualitative accord with the laboratory observations. *Work in collaboration with C. Bizon, D. Goldman, W.D. McCormick, S.J. Moon, E. Rericha, M. Shattuck, and J. Swift. Supported by DOE.

Martian Dust Devils: Laboratory Simulations of Particle Threshold

NASA Technical Reports Server (NTRS)

Greeley, Ronald; Balme, Matthew R.; Iverson, James D.; Metzger, Stephen; Mickelson, Robert; Phoreman, Jim; White, Bruce

2003-01-01

An apparatus has been fabricated to simulate terrestrial and Martian dust devils. Comparisons of surface pressure profiles through the vortex core generated in the apparatus with both those in natural dust devils on Earth and those inferred for Mars are similar and are consistent with theoretical Rankine vortex models. Experiments to determine particle threshold under Earth ambient atmospheric pressures show that sand (particles > 60 micron in diameter) threshold is analogous to normal boundary-layer shear, in which the rotating winds of the vortex generate surface shear and hence lift. Lower-pressure experiments down to approx. 65 mbar follow this trend for sand-sized particles. However, smaller particles (i.e., dust) and all particles at very low pressures (w 10-60 mbar) appear to be subjected to an additional lift function interpreted to result from the strong decrease in atmospheric pressure centered beneath the vortex core. Initial results suggest that the wind speeds required for the entrainment of grains approx. 2 microns in diameter (i.e., Martian dust sizes) are about half those required for entrainment by boundary layer winds on both Earth and Mars.

Recent Aeolian Dune Change on Mars

NASA Technical Reports Server (NTRS)

Bourke, M. C.; Edgett, K. S.; Cantor, B. A.

2007-01-01

Previous comparisons of Martian aeolian dunes in satellite images have not detected any change in dune form or position. Here, we show dome dunes in the north polar region that shrank and then disappeared over a period of 3.04 Mars years (5.7 Earth years), while larger, neighboring dunes showed no erosion or movement. The removal of sand from these dunes indicates that not only is the threshold wind speed for saltation exceeded under present conditions on Mars, but that any sand that is available for transport is likely to be moved. Dunes that show no evidence of change could be crusted, indurated. or subject to infrequent episodes of movement.

Soils of eagle crater and Meridiani Planum at the opportunity Rover landing site

USGS Publications Warehouse

Soderblom, L.A.; Anderson, R.C.; Arvidson, R. E.; Bell, J.F.; Cabrol, N.A.; Calvin, W.; Christensen, P.R.; Clark, B. C.; Economou, T.; Ehlmann, B.L.; Farrand, W. H.; Fike, D.; Gellert, Ralf; Glotch, T.D.; Golombek, M.P.; Greeley, R.; Grotzinger, J.P.; Herkenhoff, K. E.; Jerolmack, D.J.; Johnson, J. R.; Jolliff, B.; Klingelhofer, C.; Knoll, A.H.; Learner, Z.A.; Li, R.; Malin, M.C.; McLennan, S.M.; McSween, H.Y.; Ming, D. W.; Morris, R.V.; Rice, J. W.; Richter, L.; Rieder, R.; Rodionov, D.; Schroder, C.; Seelos, F.P.; Soderblom, J.M.; Squyres, S. W.; Sullivan, R.; Watters, W.A.; Weitz, C.M.; Wyatt, M.B.; Yen, A.; Zipfel, J.

2004-01-01

The soils at the Opportunity site are fine-grained basaltic sands mixed with dust and sulfate-rich outcrop debris. Hematite is concentrated in spherules eroded from the strata. Ongoing saltation exhumes the spherules and their fragments, concentrating them at the surface. Spherules emerge from soils coated, perhaps from subsurface cementation, by salts. Two types of vesicular clasts may represent basaltic sand sources. Eolian ripples, armored by well-sorted hematite-rich grains, pervade Meridiani Planum. The thickness of the soil on the plain is estimated to be about a meter. The flatness and thin cover suggest that the plain may represent the original sedimentary surface.

Bioprocessing-Based Approach for Bitumen/Water/Fines Separation and Hydrocarbon Recovery from Oil Sands Tailings

DOE PAGES

Brigmon, Robin L.; Berry, Christopher J.; Wade, Arielle; ...

2016-05-04

Oil sands are a major source of oil, but their industrial processing generates tailings ponds that are an environmental hazard. The main concerns are mature fine tailings (MFT) composed of residual hydrocarbons, water, and fine clay. Tailings ponds include toxic contaminants such as heavy metals, and toxic organics including naphthenics. Naphthenic acids and polyaromatic hydrocarbons (PAHs) degrade very slowly and pose a long-term threat to surface and groundwater, as they can be transported in the MFT. Research into improved technologies that would enable densification and settling of the suspended particles is ongoing. In batch tests, BioTiger™, a microbial consortium thatmore » can metabolize PAHs, demonstrated improved oil sands tailings settling from a Canadian tailings pond. Results also showed, depending on the timing of the measurements, lower suspended solids and turbidity. Elevated total organic carbon was observed in the first 48 hours in the BioTiger™-treated columns and then decreased in overlying water. Oil sands tailings mixed with BioTiger™ showed a two-fold reduction in suspended solids within 24 hours as compared to abiotic controls. The tailings treated with BioTiger™ increased in microbial densities three orders of magnitude from 8.5 × 105 CFU/mL to 1.2 × 108 CFU/mL without any other carbon or energy source added, indicating metabolism of hydrocarbons and other available nutrients. Results demonstrated that bioaugmentation of BioTiger™ increased separation of organic carbon from particles in oil sands and enhanced settling with tailings with improved water quality.« less

Industrial sand and gravel

USGS Publications Warehouse

Dolley, T.P.

2006-01-01

In 2005, domestic production of industrial sand and gravel was about 31 Mt, a 5% increase from 2004. This increase was bouyed by robust construction and petroleum sectors of the US economy. Based on estimated world production figures, the United States was the world's leading producer and consumer of industrial sand and gravel. In the short term, local shortages of industrial sand and gravel will continue to increase.

The jammed-to-mobile transition in frozen sand under stress

NASA Astrophysics Data System (ADS)

Durham, W. B.; Pathare, A.; Stern, L. A.; Lenferink, H. J.

2009-12-01

We conducted laboratory deformation experiments on sand-rich mixtures of sand + ice under sufficient confinement to inhibit macroscopic dilation. Dry sand packs constrained not to dilate when they are under a shearing load reach an immobile or “jammed” state, as load-supporting “force chains” of sand particles form after a small amount of strain and cannot be broken without volume expansion. Our research objective here was to find the minimum volume fraction of ice required to overcome the jammed state. The result surprised us: the required volume fraction is not a fixed number, but depends on the packing characteristics of the sand in question. Experiments were carried out in a triaxial gas deformation rig at confining pressures (60 - 200 MPa) always at least twice the level of differential stresses (11 - 50 MPa) in order to suppress dilatancy. Run temperatures were 223 - 243 K. We used two kinds of quartz sand, one well-sorted, with a maximum dry packing density (MDPD) of about 0.68 sand by volume, and the other a mixture of two sizes, having a higher MDPD of 0.75. Ice volume fraction ranged from well below saturation (where unfilled porosity necessarily remained) to slightly greater than the value of porosity at MDPD. We tested these frozen sands in compression under constant applied differential stress (creep). Strain rates were very low at these conditions, and runs took days or weeks to complete. The amount of strain required to reach the jammed state in ice-undersaturated samples was approximately 0.04, and did not show an obvious dependence on ice content. For both sands, the onset of mobility occurred at approximately 5% above the value of pore volume at MDPD. Furthermore, viscosity of mobile frozen sand near the transition point was extremely sensitive to ice fraction, which implies that at geologic strain rates, far slower than we can reach in the lab, the ice fraction at transition may lie closer to that at MDPD. Cryogenic scanning electron

Beneficiation of Kulon Progo iron sand by using tabling and magnetic separation methods

NASA Astrophysics Data System (ADS)

Oediyani, Soesaptri; Ikhlasul Amal, M.; M. Victoriyan, N.; Juniarsih, Andinnie

2018-04-01

There are two types of iron resources such as primary iron ore and iron sand. In general, primary iron ores use as raw materials in iron and steel making because the iron content is high (± 60%) and can reduce directly. On the other and, iron sand is rarely used as a raw material because the iron content is low (20-40%) but the iron sand reserves are very abundant in Indonesia for instance is about 173 million tons in Kulon Progo, Jogyakarta. In addition, the new regulation of Energy and Mineral Resources Ministry required that iron sands must process before are being export. Therefore, the proper beneficiation methods are need to improve the iron content of iron sand. In this research Kulon Progo iron sand was used as a raw materials because not only the reserves very abundant but also the new iron making plant will build here soon. The combine of ore concentration methods such as tabling and magnetic separation used to improve the iron content. Then, the variable process were inclination of the table (2°,3° and 4°), fraction of feed size (-100 mesh, -150 mesh and -200 mesh) and the magnetic intensity (176, 830, 1500 Gauss). The highest recovery was about 96.75% and the concentrate which is contain 59.78 % Fe achieved by using -200 mesh particle size, 4° inclination of table and 1500 Gauss as a magnetic intensity. In conclusion, this concentrate fulfilled raw material requires of iron making (≥ 55%Fe).

Contamination of New Jersey beach sand with magnetite spherules from industrial air pollution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hassinan, W.T.; Puffer, J.H.

1992-01-01

Spherical particles composed of magnetite, typically 120 [mu]m to 2,450 [mu]m in diameter, are accumulating in the beach sands of New Jersey. Most magnetite spherule surfaces are highly polished but some are corroded or abraded. Their interiors are typically vesicular. Magnetite spherules from 213 New Jersey beach sand samples collected during May 1991 are chemically and morphologically the same as those filtered from industrial smokestacks and the air supplied of Newark, New Jersey and Philadelphia. The average concentration of spherules in New Jersey beach sand is 35 per kg throughout the northern 43 km of beach south of Newark (frommore » Sandy Hook to Belmar Beach). They are rare to absent in the central 86 km stretch of beach but average 34 per kg of sand throughout the southern 91 km of beach east of Philadelphia (from Ventnor City to Villas Beach). The distribution of magnetite spherules in New Jersey beach sand is consistent with a transport pathway model that involves: (1) Prevailing wind dispersal from industrial sources, (2) erosion of spherules that have settled out of the air into the surface drainage system that flows toward the New Jersey coast and (3) longshore transport of spherule contaminated sand away from inlets identified as locations where most of the spherules enter the beach system. The spherules, therefore, are useful tracers indicating how industrial airborne fallout is transported to and along shorelines. The distribution pattern is consistent with generally northward longshore currents north of the Manasquan inlet and generally southward longshore currents south of the Abescon inlet.« less

Effect of Carbon Nanotubes Upon Emissions From Cutting and Sanding Carbon Fiber-Epoxy Composites

PubMed Central

Heitbrink, William A.; Lo, Li-Ming

2015-01-01

Carbon nanotubes (CNTs) are being incorporated into structural composites to enhance material strength. During fabrication or repair activities, machining nanocomposites may release CNTs into the workplace air. An experimental study was conducted to evaluate the emissions generated by cutting and sanding on three types of epoxy-composite panels: Panel A containing graphite fibers, Panel B containing graphite fibers and carbon-based mat, and Panel C containing graphite fibers, carbon-based mat, and multi-walled CNTs. Aerosol sampling was conducted with direct-reading instruments, and filter samples were collected for measuring elemental carbon (EC) and fiber concentrations. Our study results showed that cutting Panel C with a band saw did not generate detectable emissions of fibers inspected by transmission electron microscopy but did increase the particle mass, number, and EC emission concentrations by 20% to 80% compared to Panels A and B. Sanding operation performed on two Panel C resulted in fiber emission rates of 1.9×108 and 2.8×106 fibers per second (f/s), while no free aerosol fibers were detected from sanding Panels A and B containing no CNTs. These free CNT fibers may be a health concern. However, the analysis of particle and EC concentrations from these same samples cannot clearly indicate the presence of CNTs, because extraneous aerosol generation from machining the composite epoxy material increased the mass concentrations of the EC. PMID:26478716

[Environmental toxicity of waste foundry sand].

PubMed

Zhang, Hai-Feng; Wang, Yu-Jue; Wang, Jin-Lin; Huang, Tian-You; Xiong, Ying

2013-03-01

The metal leaching characteristics and volatile organic compounds (VOCs) of five different types of waste foundry sands were analyzed with the toxicity characteristic leaching procedure (TCLP) and head space-gas chromatography (HS-GC). Microtox and soil dehydrogenase activity (DHA) tests were then used to evaluate the bio-effects of these waste sands. The results showed that due to the different metals poured and casting materials used to make the sand molds, there was significant difference among the five waste foundry sands in the compositions and concentrations of metal and organic pollutants. The concentrations of Fe in the leachates of iron and steel casting waste foundry sand exceeded the maximal allowable concentrations specified in the National Standard of Drinking Water Quality, whereas the As concentration in the leachate of aluminum casting waste foundry sand exceeded the standard. The five waste foundry sands had quite different compositions and levels of VOCs, which resulted in different levels of inhibition effects on the luminescent bacteria (30% and 95%). Additionally, the soil DHA tests suggested that metal pollutants in waste foundry sands may inhibit the soil microbial activity, whereas organics in the sands may slightly promote the microbial activity. The results of this study indicated that the waste foundry sands may pose considerable threat to the environment when improperly disposed.

Comparisons of Unconsolidated Sediments Analyzed by APXS (MSL-Curiosity) within Gale Crater, Mars: Soils, Sands of the Barchan and Linear Dunes of the Active Bagnold Dune Field, and Ripple-field Sands.

NASA Astrophysics Data System (ADS)

Thompson, L. M.; O'Connell-Cooper, C.; Spray, J. G.; Gellert, R.; Boyd, N. I.; Desouza, E.

2017-12-01

The MSL-APXS has analyzed a variety of unconsolidated sediments within the Gale impact crater, including soils, sands from barchan [High, Namib dunes], and linear dunes [Nathan Bridges, Mount Desert dunes], within the active Bagnold dune field, and sands from two smaller ripple fields ("mega-ripples"). The Gale "soils" (unsorted, unconsolidated sediments, ranging from fine-grained particles (including dust) to coarser "pebbly" material [>2 mm]), are, to a large degree, similar to Martian basaltic soils quantified by APXS, at Gusev crater (MER-A_Spirit) and Meridiani Planum (MER-B_Opportunity). Some local contributions are indicated by, for example, the enriched K levels (relative to a martian average basaltic soil [ABS]) within coarser Gale soil samples, and a Cr, Mn, Fe enrichment within finer-grained samples. Sands (grain size 62 µm to 2 mm) of the Bagnold dunes, generally, exhibit elevated Mg and Ni, indicating enrichment from olivine and pyroxene, but depleted S, Cl and Zn, indicating high activity levels and low dust. Compositional differences, related both to position within a dune (i.e., crest versus off-crest sand), and type of dune (linear versus barchan), are identified. Off-crest sands have Na, Al, Si, K, P contents similar to (or slightly depleted, relative to) the ABS, enrichment in Mg, and low dust content, whilst crest sands contain very high Mg and Ni (relative to the ABS), low felsic elemental concentrations and very low dust content. Cr is significantly enriched (and, to a lesser degree, Mn, Fe, Ti) in the off-crest sands of the linear dunes. In contrast, barchan dunes off-crest sands have Cr, Mn, Fe, and Ti abundances similar to those in the Gale soils. Additionally, Ni concentrations in barchan dunes off-crest sands are enriched relative to the linear dunes. Analyses from a small, isolated "mega-ripple" reveal a composition similar to that of the Gale soils, including a high dust content. The second mega-ripple, within a larger ripple field, is

Effects of highway runoff on streamflow and water quality in the Sevenmile Creek basin, a rural area in the Piedmont Province of North Carolina, July 1981 to July 1982

USGS Publications Warehouse

Harned, Douglas

1988-01-01

cadmium concentrations frequently exceeded the maximum levels recommended by the EPA for drinking water. The highway is a source of contaminants to surrounding areas. Particulate and metal loads in dustfall and chemical-constituent concentrations in soils decrease exponentially with distance from the highway. The highest concentrations of contaminants were found on the downwind side. Increased concentrations of metals (cadmium, chromium, iron, lead, nickel, and zinc) in rainfall were observed in samples collected near the highway and in samples collected approximately one-half mile away. Material loading due to dustfall was greater than loading due to rainfall. Loading due to saltated particles, those heavier particles bounced along the highway surface, was higher than loading due to dustfall. Saltation loads were greatest during the winter months because of highway deicing and sanding, which supplied an estimated two-thirds of the saltated materials. The remaining one-third of the saltated load came primarily from the deposition of particles from vehicles. Some of the greatest constituent concentrations were measured in the soil water sampled from the lysimeters located adjacent to the highway.

Biochar particle size, shape, and porosity act together to influence soil water properties.

PubMed

Liu, Zuolin; Dugan, Brandon; Masiello, Caroline A; Gonnermann, Helge M

2017-01-01

Many studies report that, under some circumstances, amending soil with biochar can improve field capacity and plant-available water. However, little is known about the mechanisms that control these improvements, making it challenging to predict when biochar will improve soil water properties. To develop a conceptual model explaining biochar's effects on soil hydrologic processes, we conducted a series of well constrained laboratory experiments using a sand matrix to test the effects of biochar particle size and porosity on soil water retention curves. We showed that biochar particle size affects soil water storage through changing pore space between particles (interpores) and by adding pores that are part of the biochar (intrapores). We used these experimental results to better understand how biochar intrapores and biochar particle shape control the observed changes in water retention when capillary pressure is the main component of soil water potential. We propose that biochar's intrapores increase water content of biochar-sand mixtures when soils are drier. When biochar-sand mixtures are wetter, biochar particles' elongated shape disrupts the packing of grains in the sandy matrix, increasing the volume between grains (interpores) available for water storage. These results imply that biochars with a high intraporosity and irregular shapes will most effectively increase water storage in coarse soils.

The sedimentology and dynamics of crater-affiliated wind streaks in western Arabia Terra, Mars and Patagonia, Argentina

USGS Publications Warehouse

Rodriguez, J.A.P.; Tanaka, K.L.; Yamamoto, A.; Berman, D.C.; Zimbelman, J.R.; Kargel, J.S.; Sasaki, S.; Jinguo, Y.; Miyamoto, H.

2010-01-01

Wind streaks comprise recent aeolian deposits that have been extensively documented on Venus, Earth and Mars. Martian wind streaks are among the most abundant surface features on the planet and commonly extend from the downwind margins of impact craters. Previous studies of wind streaks emerging from crater interior deposits suggested that the mode of emplacement was primarily related to the deposition of silt-sized particles as these settled from plumes. We have performed geologic investigations of two wind streaks clusters; one situated in western Arabia Terra, a region in the northern hemisphere of Mars, and another in an analogous terrestrial site located in southern Patagonia, Argentina, where occurrences of wind streaks emanate from playas within maar craters. In both these regions we have identified bedforms in sedimentary deposits on crater floors, along wind-facing interior crater margins, and along wind streaks. These observations indicate that these deposits contain sand-sized particles and that sediment migration has occurred via saltation from crater interior deposits to wind streaks. In Arabia Terra and in Patagonia wind streaks initiate from crater floors that contain lithic and evaporitic sedimentary deposits, suggesting that the composition of wind streak source materials has played an important role in development. Spatial and topographic analyses suggest that regional clustering of wind streaks in the studied regions directly correlates to the areal density of craters with interior deposits, the degree of proximity of these deposits, and the craters' rim-to-floor depths. In addition, some (but not all) wind streaks within the studied clusters have propagated at comparable yearly (Earth years) rates. Extensive saltation is inferred to have been involved in its propagation based on the studied terrestrial wind streak that shows ripples and dunes on its surface and the Martian counterpart changes orientation toward the downslope direction where it

Assessment of the transport of polyvinylpyrrolidone-stabilised zero-valent iron nanoparticles in a silica sand medium

NASA Astrophysics Data System (ADS)

Liang, Bin; Xie, Yingying; Fang, Zhanqiang; Tsang, Eric Pokeung

2014-07-01

Nano zero-valent iron has been considered a promising material for in situ remediation, but its strong tendency to form aggregates makes it difficult to transport in porous media. Thus, stabilization techniques are required to overcome this limitation. In this study, we use polyvinylpyrrolidone (PVP) to synthesise to stabilise iron nanoparticles. The effects of various factors such as nZVI influent concentrations, flow velocity, Ca2+, Mg2+ and humic acid on the transport behaviour of the PVP-nZVI particles were considered. A sedimentation test indicated that PVP-nZVI particles with diameters ranging from 50 to 80 nm were more stable than Bare-nZVI particles. Column experiments demonstrated that PVP-nZVI also exhibited better mobility in silica sand than Bare-nZVI. Due to either the straining or blocking effect, the effluent relative concentration ( C/ C 0) plateau increased with increasing particle concentration. Increasing the flow velocity increased the C/ C 0, resulting in the reduction of overall single-collector contact efficiency ( η 0). Humic acid (HA) enhanced the mobility of PVP-nZVI, and the sedimentation test in the presence of HA suggested that decreased attachment of PVP-nZVI to the silica sand surface rather than decreased aggregation was the primary mechanism of this enhanced mobility.

Evaluating unsupervised methods to size and classify suspended particles using digital in-line holography

USGS Publications Warehouse

Davies, Emlyn J.; Buscombe, Daniel D.; Graham, George W.; Nimmo-Smith, W. Alex M.

2015-01-01

Substantial information can be gained from digital in-line holography of marine particles, eliminating depth-of-field and focusing errors associated with standard lens-based imaging methods. However, for the technique to reach its full potential in oceanographic research, fully unsupervised (automated) methods are required for focusing, segmentation, sizing and classification of particles. These computational challenges are the subject of this paper, in which we draw upon data collected using a variety of holographic systems developed at Plymouth University, UK, from a significant range of particle types, sizes and shapes. A new method for noise reduction in reconstructed planes is found to be successful in aiding particle segmentation and sizing. The performance of an automated routine for deriving particle characteristics (and subsequent size distributions) is evaluated against equivalent size metrics obtained by a trained operative measuring grain axes on screen. The unsupervised method is found to be reliable, despite some errors resulting from over-segmentation of particles. A simple unsupervised particle classification system is developed, and is capable of successfully differentiating sand grains, bubbles and diatoms from within the surf-zone. Avoiding miscounting bubbles and biological particles as sand grains enables more accurate estimates of sand concentrations, and is especially important in deployments of particle monitoring instrumentation in aerated water. Perhaps the greatest potential for further development in the computational aspects of particle holography is in the area of unsupervised particle classification. The simple method proposed here provides a foundation upon which further development could lead to reliable identification of more complex particle populations, such as those containing phytoplankton, zooplankton, flocculated cohesive sediments and oil droplets.

Vehicle non-exhaust emissions from the tyre-road interface - effect of stud properties, traction sanding and resuspension

NASA Astrophysics Data System (ADS)

Kupiainen, Kaarle J.; Pirjola, Liisa

2011-08-01

In Northern cities respirable street dust emission levels (PM 10) are especially high during spring. The spring time dust has been observed to cause health effects as well as discomfort among citizens. Major sources of the dust are the abrasion products from the pavement and traction sand aggregates that are formed due to the motion of the tyre. We studied the formation of respirable abrasion particles in the tyre-road interface due to tyre studs and traction sanding by a mobile laboratory vehicle Sniffer. The measurements were preformed on a test track, where the influence of varying stud weight and stud number per tyre on PM 10 emissions was studied. Studded tyres resulted in higher emission levels than studless tyres especially with speeds 50 km h -1 and higher; however, by using light weight studs, which approximately halves the weight of studs, or by reducing the number of studs per tyre to half, the emission levels decreased by approximately half. Additionally measurements were done with and without traction sand coverage on the pavement of a public road. After traction sanding the emission levels were not affected by tyre type but by formation and suspension of traction sand related dust from the road surface. The emissions after traction sanding decreased as a function of time as passing vehicles' motion shifted the sand grains away from the areas with most tyre-road contact.

Windblown Sand in Ganges Chasma

NASA Image and Video Library

2017-04-25

Dark, windblown sand covers intricate sedimentary rock layers in this image captured by NASA's Mars Reconnaissance Orbiter (MRO) from Ganges Chasma, a canyon in the Valles Marineris system. These features are at once familiar and unusual to those familiar with Earth's beaches and deserts. Most sand dunes on Earth are made of silica-rich sand, giving them a light color; these Martian dunes owe their dark color to the iron and magnesium-rich sand found in the region. https://photojournal.jpl.nasa.gov/catalog/PIA21600

Research on the performance of sand-based environmental-friendly water permeable bricks

NASA Astrophysics Data System (ADS)

Cai, Runze; Mandula; Chai, Jinyi

2018-02-01

This paper examines the effects of the amount of admixture, the water cement ratio, the aggregate grading, and the cement aggregate ratio on the mechanical service properties and of porous concrete pavement bricks including strength, water permeability, frost resistance, and wear resistance. The admixture can enhance the performance of water permeable brick, and optimize the design mix. Experiments are conducted to determine the optimal mixing ratios which are given as; (1) the admixture (self-developed) within the content of 5% of the cement quality; (2) water-cement ratio equal to 0.34; (3) cement-aggregate ratio equal to 0.25; (4) fine aggregate of 70% (particle size 0.6-2.36mm); and coarse aggregate of 30% (particle size: 2.36-4.75mm). The experimental results that the sand-based permeable concrete pavement brick has a strength of 35.6MPa and that the water permeability coefficient is equal to 3.5×10-2cm/s. In addition, it was found that the concrete water permeable brick has good frost resistance and surface wear resistance, and that the its production costs are much lower than the similar sand-based water permeable bricks in China.

Measurement of bedload transport in sand-bed rivers: a look at two indirect sampling methods

USGS Publications Warehouse

Holmes, Robert R.; Gray, John R.; Laronne, Jonathan B.; Marr, Jeffrey D.G.

2010-01-01

Sand-bed rivers present unique challenges to accurate measurement of the bedload transport rate using the traditional direct sampling methods of direct traps (for example the Helley-Smith bedload sampler). The two major issues are: 1) over sampling of sand transport caused by “mining” of sand due to the flow disturbance induced by the presence of the sampler and 2) clogging of the mesh bag with sand particles reducing the hydraulic efficiency of the sampler. Indirect measurement methods hold promise in that unlike direct methods, no transport-altering flow disturbance near the bed occurs. The bedform velocimetry method utilizes a measure of the bedform geometry and the speed of bedform translation to estimate the bedload transport through mass balance. The bedform velocimetry method is readily applied for the estimation of bedload transport in large sand-bed rivers so long as prominent bedforms are present and the streamflow discharge is steady for long enough to provide sufficient bedform translation between the successive bathymetric data sets. Bedform velocimetry in small sandbed rivers is often problematic due to rapid variation within the hydrograph. The bottom-track bias feature of the acoustic Doppler current profiler (ADCP) has been utilized to accurately estimate the virtual velocities of sand-bed rivers. Coupling measurement of the virtual velocity with an accurate determination of the active depth of the streambed sediment movement is another method to measure bedload transport, which will be termed the “virtual velocity” method. Much research remains to develop methods and determine accuracy of the virtual velocity method in small sand-bed rivers.

Regional transport of a chemically distinctive dust: Gypsum from White Sands, New Mexico (USA)

NASA Astrophysics Data System (ADS)

White, Warren H.; Hyslop, Nicole P.; Trzepla, Krystyna; Yatkin, Sinan; Rarig, Randy S.; Gill, Thomas E.; Jin, Lixin

2015-03-01

The White Sands complex, a National Monument and adjoining Missile Range in southern New Mexico, occupies the dry bed of an ice-age lake where an active gypsum dunefield abuts erodible playa sediments. Aerosols entrained from White Sands are sometimes visible on satellite images as distinct, light-colored plumes crossing the Sacramento Mountains to the east and northeast. The IMPROVE network (Interagency Monitoring of PROtected Visual Environments) operates long-term aerosol samplers at two sites east of the Sacramento range. In recent years a spring pulse of sulfate aerosol has appeared at these sites, eclipsing the regional summer peak resulting from atmospheric reactions of sulfur dioxide emissions. A significant fraction of this spring sulfate is contributed by gypsum and other salts from White Sands, with much of the sulfur in coarse particles and concentrations of calcium and strontium above regional levels. The increase in these gypsiferous species coincides with a drought following a period of above-average precipitation. White Sands and the IMPROVE samplers together provide a natural laboratory: a climatically sensitive dust source that is both well characterized and chemically distinct from its surroundings, with a signature that remains identifiable at long-term observatories 100-200 km downwind.

Sand Volcano Following Earthquake

NASA Technical Reports Server (NTRS)

1989-01-01

Sand boil or sand volcano measuring 2 m (6.6 ft.) in length erupted in median of Interstate Highway 80 west of the Bay Bridge toll plaza when ground shaking transformed loose water-saturated deposit of subsurface sand into a sand-water slurry (liquefaction) in the October 17, 1989, Loma Prieta earthquake. Vented sand contains marine-shell fragments. Sand and soil grains have faces that can cause friction as they roll and slide against each other, or even cause sticking and form small voids between grains. This complex behavior can cause soil to behave like a liquid under certain conditions such as earthquakes or when powders are handled in industrial processes. Mechanics of Granular Materials (MGM) experiments aboard the Space Shuttle use the microgravity of space to simulate this behavior under conditions that carnot be achieved in laboratory tests on Earth. MGM is shedding light on the behavior of fine-grain materials under low effective stresses. Applications include earthquake engineering, granular flow technologies (such as powder feed systems for pharmaceuticals and fertilizers), and terrestrial and planetary geology. Nine MGM specimens have flown on two Space Shuttle flights. Another three are scheduled to fly on STS-107. The principal investigator is Stein Sture of the University of Colorado at Boulder. (Credit: J.C. Tinsley, U.S. Geological Survey)

Fluvial particle characterization using artificial neural network and spectral image processing

NASA Astrophysics Data System (ADS)

Shrestha, Bim Prasad; Gautam, Bijaya; Nagata, Masateru

2008-03-01

Sand, chemical waste, microbes and other solid materials flowing with the water bodies are of great significance to us as they cause substantial impact to different sectors including drinking water management, hydropower generation, irrigation, aquatic life preservation and various other socio-ecological factors. Such particles can't completely be avoided due to the high cost of construction and maintenance of the waste-treatment methods. A detailed understanding of solid particles in surface water system can have benefit in effective, economic, environmental and social management of water resources. This paper describes an automated system of fluvial particle characterization based on spectral image processing that lead to the development of devices for monitoring flowing particles in river. Previous research in coherent field has shown that it is possible to automatically classify shapes and sizes of solid particles ranging from 300-400 μm using artificial neural networks (ANN) and image processing. Computer facilitated with hyper spectral and multi spectral images using ANN can further classify fluvial materials into organic, inorganic, biodegradable, bio non degradable and microbes. This makes the method attractive for real time monitoring of particles, sand and microorganism in water bodies at strategic locations. Continuous monitoring can be used to determine the effect of socio-economic activities in upstream rivers, or to monitor solid waste disposal from treatment plants and industries or to monitor erosive characteristic of sand and its contribution to degradation of efficiency of hydropower plant or to identify microorganism, calculate their population and study the impact of their presence. Such system can also be used to characterize fluvial particles for planning effective utilization of water resources in micro-mega hydropower plant, irrigation, aquatic life preservation etc.

Industrial sand and gravel

USGS Publications Warehouse

Dolley, T.P.

2010-01-01

Domestic production of industrial sand and gravel in 2009 was about 27 Mt (30 million st), declining by 10 percent compared with 2008. Certain end uses of industrial sand and gravel, such as foundry and glassmaking sand, may have declined by a factor greater than 10 percent in 2009. U.S. apparent consumption was 24.7 Mt (27.2 million st) in 2009, down by 10 percent from the previous year, and imports declined to 83 kt (91,000 st).

Community airborne particulate matter from mining for sand used as hydraulic fracturing proppant.

PubMed

Peters, Thomas M; O'Shaughnessy, Patrick T; Grant, Ryan; Altmaier, Ralph; Swanton, Elizabeth; Falk, Jeffrey; Osterberg, David; Parker, Edith; Wyland, Nancy G; Sousan, Sinan; Stark, Aimee Liz; Thorne, Peter S

2017-12-31

Field and laboratory studies were conducted to evaluate the impact of proppant sand mining and processing activities on community particulate matter (PM) concentrations. In field studies outside 17 homes within 800m of sand mining activities (mining, processing, and transport), respirable (PM 4 ) crystalline silica concentrations were low (<0.4μg/m 3 ) with crystalline silica detected on 7 samples (2% to 4% of mass). In long-term monitoring at 6 homes within 800m of sand mining activities, the highest daily mean PM concentrations observed were 14.5μg/m 3 for PM 2.5 and 37.3μg/m 3 for PM 10 , although infrequent (<3% of time), short-term elevated PM concentrations occurred when wind blew over the facility. In laboratory studies, aerosolized sand was shown to produce respirable-sized particles, containing 6% to 19% crystalline silica. Dispersion modeling of a mine and processing facility indicated that PM 10 can exceed standards short distances (<40m) beyond property lines. Lastly, fence-line PM and crystalline silica concentrations reported to state agencies were substantially below regulatory or guideline values, although several excursions were observed for PM 10 when winds blew over the facility. Taken together, community exposures to airborne particulate matter from proppant sand mining activities at sites similar to these appear to be unlikely to cause chronic adverse health conditions. Copyright © 2017 Elsevier B.V. All rights reserved.

Ventifacts at the Pathfinder landing site

USGS Publications Warehouse

Bridges, N.T.; Greeley, R.; Haldemann, A.F.C.; Herkenhoff, K. E.; Kraft, M.; Parker, T.J.; Ward, A.W.

1999-01-01

About half of the rocks at the Mars Pathfinder Ares Vallis landing site appear to be ventifacts, rocks abraded by windborne particles. Comparable resolution images taken by the Imager for Mars Pathfinder (IMP) camera and the Viking landers show that ventifacts are more abundant at the Pathfinder site. The ventifacts occur in several forms, including rocks with faceted edges, finger-like projections, elongated pits, flutes, grooves, and possible rills. The trends of elongated pits, flutes, grooves, and rills cluster at ???280-330?? clockwise from north and generally dip 10-30?? away from their trend direction. These orientations are indicative of southeast to northwest winds and differ from the trend of wind tails at the landing site, the direction of local wind streaks, and predictions of the Global Circulation Model, all of which indicate northeast to southwest winds. The disparity between these data sets strongly suggests that local circulation patterns have changed since the abrasion of the ventifacted rocks. The greater number of ventifacts at the Pathfinder site compared to either of the Viking sites is most easily explained as being due to a larger supply of abrading particles, composed of either sand-sized grains or indurated dust aggregates, and higher surface roughness, which should increase the momentum of saltating grains. The Pathfinder ventifacts may have formed shortly after the deposition of outflow channel sediments nearly 2 Gry ago, when a large local supply of abrading particles should have been abundant and atmospheric conditions may have been more conducive to rock abrasion from saltating grains. Based on how ventifacts form on Earth, the several ventifact forms seen at the Pathfinder site and their presence on some rocks but not on others are probably due to local airflow conditions, original rock shape, exposure duration, rock movement, and to a lesser extent, rock lithology. The abundance of ventifacts at the Pathfinder site, together with

Use of coir pith particles in composites with Portland cement.

PubMed

Brasileiro, Gisela Azevedo Menezes; Vieira, Jhonatas Augusto Rocha; Barreto, Ledjane Silva

2013-12-15

Brazil is the fourth largest world's producer of coconut (Cocos nucifera L.). Coconut crops generate several wastes, including, coir pith. Coir pith and short fibers are the byproducts of extracting the long fibers and account for approximately 70% of the mature coconut husk. The main use of coir pith is as an agricultural substrate. Due to its shape and small size (0.075-1.2 mm), this material can be considered as a particulate material. The aim of this study was to evaluate the use of coir pith as an aggregate in cementitious composites and to evaluate the effect of the presence of sand in the performance of these composites. Some composites were produced exclusively with coir pith particles and other composites with coir pith partially substituting the natural sand. The cementitious composites developed were tested for their physical and mechanical properties and characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy to evaluate the effect of coir pith particles addition in cement paste and sand-cement-mortar. The statistical significance of the results was evaluated by one-way analysis of variance (ANOVA) test followed by multiple comparisons of the means by Tukey's test that showed that the composites with coir pith particles, with or without natural sand, had similar mechanical results, i.e., means were not statistically different at 5% significance level. There was a reduction in bulk density and an improved post-cracking behavior in the composites with coir pith particles compared to conventional mortar and to cement paste. These composites can be used for the production of lightweight, nonstructural building materials, according to the values of compressive strength (3.97-4.35 MPa) and low bulk density (0.99-1.26 g/cm(3)). Copyright © 2013 Elsevier Ltd. All rights reserved.

Microbial strengthening of loose sand.

PubMed

Banagan, B L; Wertheim, B M; Roth, M J S; Caslake, L F

2010-08-01

To test whether the addition of Flavobacterium johnsoniae could increase the strength of saturated Ottawa 30 sand. A box model was built that simulates groundwater-like flow through a main sand compartment. Strength tests were performed at seven locations and at two depths, 10.8 and 20.3 cm below the top of the tank, using a vane shear device before and after the addition of bacteria. After the addition of Fl. johnsoniae, sand samples were obtained from multiple sampling ports on the vertical sides of the box model. The presence of a bacterial biofilm was confirmed by staining these sand samples with SYTO-9 and Alexa Fluor 633 and viewing with a confocal microscope. The average shear strength increases after the addition of Fl. johnsoniae were 15.2-87.5%, depending on the experimental conditions. Flavobacterium johnsoniae caused a statistically significant increase in the strength of saturated Ottawa 30 sand. Biofilm-forming bacteria can increase the shear strength of saturated sand. The addition of biofilm-forming bacteria to a building site may be an alternate method to mitigate the effects of liquefaction.

A Visual Basic program to classify sediments based on gravel-sand-silt-clay ratios

USGS Publications Warehouse

Poppe, L.J.; Eliason, A.H.; Hastings, M.E.

2003-01-01

Nomenclature describing size distributions is important to geologists because grain size is the most basic attribute of sediments. Traditionally, geologists have divided sediments into four size fractions that include gravel, sand, silt, and clay, and classified these sediments based on ratios of the various proportions of the fractions. Definitions of these fractions have long been standardized to the grade scale described by Wentworth (1922), and two main classification schemes have been adopted to describe the approximate relationship between the size fractions.Specifically, according to the Wentworth grade scale gravel-sized particles have a nominal diameter of ⩾2.0 mm; sand-sized particles have nominal diameters from <2.0 mm to ⩾62.5 μm; silt-sized particles have nominal diameters from <62.5 to ⩾4.0 μm; and clay is <4.0 μm. As for sediment classification, most sedimentologists use one of the systems described either by Shepard (1954) or Folk (1954, 1974). The original scheme devised by Shepard (1954) utilized a single ternary diagram with sand, silt, and clay in the corners to graphically show the relative proportions among these three grades within a sample. This scheme, however, does not allow for sediments with significant amounts of gravel. Therefore, Shepard's classification scheme (Fig. 1) was subsequently modified by the addition of a second ternary diagram to account for the gravel fraction (Schlee, 1973). The system devised by Folk (1954, 1974) is also based on two triangular diagrams (Fig. 2), but it has 23 major categories, and uses the term mud (defined as silt plus clay). The patterns within the triangles of both systems differ, as does the emphasis placed on gravel. For example, in the system described by Shepard, gravelly sediments have more than 10% gravel; in Folk's system, slightly gravelly sediments have as little as 0.01% gravel. Folk's classification scheme stresses gravel because its concentration is a function of

Wind speed and sediment transport recovery in the lee of a vegetated and denuded nebkha within a nebkha dune field

NASA Astrophysics Data System (ADS)

Gillies, John A.; Nield, Joanna M.; Nickling, William G.

2014-03-01

Field observations of scaled wind speed and sand transport recovery in the lee of a nebka within a field of nebkhas and then subsequently for the nebkha denuded of its vegetation cover were collected. The measurements of wind speed at 0.4 times the element height indicate that for both conditions wind speed recovery in the lee is exponential. The porous vegetation cover influences the rate of this recovery being more gradual for the vegetated form. The return to equilibrium wind speed occurs in both cases at approximately eight element heights. For either case the recovery of shear stress and the return to a constant value occurs much closer to the bluff body form than has been described for porous fences. The recovery of sand transport in the lee appears to be more rapid for the un-vegetated condition, which corresponds to the observed faster rate of wind speed increase. The observations did not show a continual increase in saltation flux with increasing downwind distance due to the increasing shear stress downwind and the increase that may be expected due to the fetch effect. The change in saltation flux with downwind distance was controlled by the sediment supply, which diminished with downwind distance. The interaction of a changing shear stress and the zone of influence created by the wind as it interacts with the roughness dimensions, along with the distribution of sediment available for transport bring increased complexity to modeling sand flux for this type of environment over different temporal scales.

Wind ripples in low density atmospheres

NASA Technical Reports Server (NTRS)

Miller, J. S.; Marshall, J. R.; Greeley, R.

1987-01-01

The effect of varying fluid density (rho) on particle transport was examined by conducting tests at atmospheric pressures between 1 and 0.004 bar in the Martian Surface Wind Tunnel (MARSWIT). This study specifically concerns the effect of varying rho on the character of wind ripples, and elicits information concerning generalized ripple models as well as specific geological circumstances for ripple formation such as those prevailing on Mars. Tests were conducted primarily with 95 micron quartz sand, and for each atmospheric pressure chosen, tests were conducted at two freestream wind speeds: 1.1 U*(t) and 1.5 U*(t), where U*(t) is saltation threshold. Preliminary analysis of the data suggests: (1) ballistic ripple wavelength is not at variance with model predictions; (2) an atmospheric pressure of approximately 0.2 bar could represent a discontinuity in ripple behavior; and (4) ripple formation on Mars may not be readily predicted by extrapolation of terrestrial observations.

Loess as a Quaternary paleoenvironmental indicator

USGS Publications Warehouse

Muhs, Daniel R.; Prins, M.A.; Machalett, B.

2014-01-01

Loess is aeolian sediment that is dominated by silt-sized particles. Unlike either coarser dune sand or finer-grained, long-range-transported dust, loess is relatively poorly sorted, reflecting a combination of transport processes, including saltation, low suspension, and high suspension. Loess can be readily identified in the field; deposits range in thickness from a few centimeters to many tens of meters, and are found over large areas of Eurasia, South and North America (Fig. 1), and smaller areas of New Zealand, Australia, Africa and the Middle East. Loess covers approximately 10% of the Earth’s land surface and is therefore one of the most important terrestrial archives of paleoenvironmental change during the Quaternary. In many regions, loess sections consist of deposits of mostly unaltered sediment with intercalated paleosols. Paleosols represent periods of landscape stability when loess deposition ceased altogether, or at least slowed significantly. Loess can be dated directly using luminescence, radiocarbon, and amino acid geochronology methods.

Connecting meteorology to surface transport in aeolian landscapes: Peering into the boundary layer with Doppler lidar

NASA Astrophysics Data System (ADS)

Gunn, A.; Jerolmack, D. J.; Edmonds, D. A.; Ewing, R. C.; Wanker, M.; David, S. R.

2017-12-01

Aolian sand dunes grow to 100s or 1000s of meters in wavelength by sand saltation, which also produces dust plumes that feed cloud formation and may spread around the world. The relations among sediment transport, landscape dynamics and wind are typically observed at the limiting ends of the relevant range: highly resolved and localized ground observations of turbulence and relevant fluxes; or regional and synoptic-scale meteorology and satellite imagery. Between the geostrophic winds aloft and shearing stress on the Earth's surface is the boundary layer, whose stability and structure determines how momentum is transferred and ultimately entrains sediment. Although the literature on atmospheric boundary layer flows is mature, this understanding is rarely applied to aeolian landscape dynamics. Moreover, there are few vertically and time-resolved datasets of atmospheric boundary layer flows in desert sand seas, where buoyancy effects are most pronounced. Here we employ a ground-based upward-looking doppler lidar to examine atmospheric boundary layer flow at the upwind margin of the White Sands (New Mexico) dune field, providing continuous 3D wind velocity data from the surface to 300-m aloft over 70 days of the characteristically windy spring season. Data show highly resolved daily cyles of convective instabilty due to daytime heating and stable stratification due to nightime cooling which act to enhance or depress, respectively, the surface wind stresses for a given free-stream velocity. Our data implicate convective instability in driving strong saltation and dust emission, because enhanced mixing flattens the vertical velocity profile (raising surface wind speed) while upward advection helps to deliver dust to the high atmosphere. We also find evidence for Ekman spiralling, with a magnitude that depends on atmospheric stability. This spiralling gives rise to a deflection in the direction between geostrophic and surface winds, that is significant for the

Aeolian Grain Evolution on Mars: Implications for Regolith Origins

NASA Astrophysics Data System (ADS)

Sullivan, R. J.; Cabrol, N. A.; Golombek, M.; Herkenhoff, K. E.; Landis, G.; Mer Athena Science Team

2010-12-01

Early wind tunnel experiments and the Viking Lander experience led to concepts of grain evolution and regolith development on Mars. Wind tunnel experiments showed that 100-150 μm grains are easiest to entrain on Mars, but at 10 times higher wind speeds than on Earth. Even if trajectory speeds of martian saltating grains achieve smaller fractions of entraining wind speeds than on Earth, kinetic energies of these grains would be much higher, with greater potential for damage to the grains during return collisions with the particle bed. On this basis Sagan et al. [1977] JGR 82, 28, 4430 proposed that aeolian grain evolution on Mars followed a “kamikaze” pattern in which an initially coarse grain, entrained only relatively rarely by the strongest winds, would be abraded by high kinetic energy impacts and migrate through successively smaller size-frequencies at an ever-increasing rate (as entrainment became easier and thus more likely) until the grain was essentially turned to dust. On this basis it was proposed that sand-sized grains might be relatively short-lived and perhaps rare on Mars. MER observations motivate adjustments to these concepts, with implications for origins of martian regolith reworked by wind. Along both MER traverses, on opposite sides of the planet, regolith is volumetrically dominated by very fine sand mixed with unresolved finer grains. Sorting probably is poor, based on weakly cohesive remolding by rover wheel cleats. The size-frequency of this material, even if not precisely known, is consistent with grains that have evolved by attrition to sizes smaller than the most easily-moved 100-150 μm interval, to where entrainment becomes more difficult due to the increasing relative importance of inter-particle surface forces. At these smaller sizes also, kinetic energies have been reduced proportionally by the cube of the particle radius, so grain-to-grain attrition is less effective for further evolution to even smaller grain sizes

The impact of particle shape on friction angle and resulting critical shear stress: an example from a coarse-grained, steep, megatidal beach

NASA Astrophysics Data System (ADS)

Stark, N.; Hay, A. E.; Cheel, R.; Lake, C. B.

2013-12-01

The impact of particle shape on the friction angle, and the resulting critical shear stress on sediment dynamics, is still poorly understood. In areas characterized by sediments of specific shape, particularly non-rounded particles, this can lead to large departures from the expected sediment dynamics. The steep slope (1:10) of the mixed sand-gravel beach at Advocate Harbour was found stable in large-scale morphology over decades, despite a high tidal range of ten meters or more, and strong shorebreak action during storms. The Advocate sand (d < 2 mm) was found to have an elliptic, plate-like shape. Exceptionally high friction angles of the material were determined using direct shear, ranging from φ ≈ 41-46°, while the round to angular gravel was characterized by φ = 33°. The addition of 25% of the elliptic sand to the gravel led to an immediate increase of the friction angle to φ = 38°. Furthermore, re-organization of the particles occurred during shearing, being characterized by a short phase of settling and compaction, followed by a pronounced strong dilatory behavior and an accompanying strong increase of shear stress. Long-term shearing (24 h) using a ring shear apparatus led to destruction of the particles without re-compaction. Finally, submerged particle mobilization was simulated using a tilted tray in a tank. Despite a smooth tray surface, particle motion was not initiated until reaching tray tilt angles of 31° and more, being 7° steeper than the latest gravel motion initiation. In conclusion, geotechnical laboratory experiments quantified the important impact of the elliptic, plate-like shape of Advocate Beach sand on the friction angles of both pure sand and sand-gravel mixtures. The resulting effect on initiation of particle motion was confirmed in tilting tray experiments. This makes it a vivid example of how particle shape can contribute to the stabilization of the beachface.

Martian and Terrestrial Rock Abrasion from Wind Tunnel and Field Studies

NASA Technical Reports Server (NTRS)

Bridges, N. T.; Greeley, R.; Eddlemon, E.; Laity, J. E.; Meyer, C.; Phoreman, J.; White, B. R.

2003-01-01

Earth and Mars exhibit ventifacts, rocks that have been abraded by saltating sand. Previous theoretical and laboratory studies have determined abrasion susceptibilities of rocks as a function of sand type and impact angle and rock material strengths. For the last two years we have been engaged in wind tunnel and field studies to better understand the fundamental factors which control and influence rock abrasion and ventifact formation on Earth and Mars. In particular, we are examining: 1) What types of rocks (composition, texture, and shape) preferentially erode and what are the relative rates of one type vs. another? 2) What are the controlling factors of the aeolian sand cloud (flux, particle speed, surface roughness, etc) which favor rock abrasion?, 3) How do specific ventifact characteristics tie into their mode of formation and rock properties? We find several important factors: 1) Initial rock shape controls the rate of abrasion, with steeper faces abrading faster than shallower ones. The relationship is partly dependent on angle-dependent flux (proportional to sin[theta]) but exhibits additional non-linear effects from momentum transfer efficiency and rebound effects that vary with incidence angle. 2) Irregular targets with pits or grooves abrade at greater rates than targets with smooth surfaces, with indentations generally enlarging with time. Surfaces become rougher with time. 3) Targets also abrade via slope retreat, which is roughly dependent on the slope of the front face. The formation of basal sills is common, as observed on terrestrial and Martian ventifacts.

Sand Waves in Tidal Channels

DTIC Science & Technology

2007-01-01

sincerely thank Steven Borgeld, from Humboldt State University, for providing the grain size data for the Humboldt Entrance Channel. iv SAND...Wave Characteristics at Moriches Inlet... 182 APPENDIX VII – Sediment Data , Humboldt Entrance Channel, CA ........................... 186 References...waves may be limited by wave action, sand supply, and dredging activity. Bathymetric data collected at Humboldt Inlet, California, show sand waves

Evaluation of sand fills.

DOT National Transportation Integrated Search

1973-11-01

A popular construction technique in south Louisiana for many years has been the use of river sand to establish foundations for highways. The abundance of river sand and the need for it in excavation backfill operations across Louisiana's marshlands h...

China Dust and Sand

Atmospheric Science Data Center

2013-04-16

... article title:  Dust and Sand Sweep Over Northeast China     View Larger Image ... these views of the dust and sand that swept over northeast China on March 10, 2004. Information on the height of the dust and an ...

Faecal indicator bacteria enumeration in beach sand: a comparison study of extraction methods in medium to coarse sands.

PubMed

Boehm, A B; Griffith, J; McGee, C; Edge, T A; Solo-Gabriele, H M; Whitman, R; Cao, Y; Getrich, M; Jay, J A; Ferguson, D; Goodwin, K D; Lee, C M; Madison, M; Weisberg, S B

2009-11-01

The absence of standardized methods for quantifying faecal indicator bacteria (FIB) in sand hinders comparison of results across studies. The purpose of the study was to compare methods for extraction of faecal bacteria from sands and recommend a standardized extraction technique. Twenty-two methods of extracting enterococci and Escherichia coli from sand were evaluated, including multiple permutations of hand shaking, mechanical shaking, blending, sonication, number of rinses, settling time, eluant-to-sand ratio, eluant composition, prefiltration and type of decantation. Tests were performed on sands from California, Florida and Lake Michigan. Most extraction parameters did not significantly affect bacterial enumeration. anova revealed significant effects of eluant composition and blending; with both sodium metaphosphate buffer and blending producing reduced counts. The simplest extraction method that produced the highest FIB recoveries consisted of 2 min of hand shaking in phosphate-buffered saline or deionized water, a 30-s settling time, one-rinse step and a 10 : 1 eluant volume to sand weight ratio. This result was consistent across the sand compositions tested in this study but could vary for other sand types. Method standardization will improve the understanding of how sands affect surface water quality.

Chemistry of sands from the modern Indus River and the Archean Witwatersrand basin: Implications for the composition of the Archean atmosphere

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maynard, J.B.; Ritger, S.D.; Sutton, S.J.

1991-03-01

Both the Indus River and the Witwatersrand basin contain sand with grains of detrital uraninite. Because this mineral is easily oxidized, its presence in Archean strata as a detrital particle has been used as evidence for a low-oxygen atmosphere before 2.5 Ga. However, its presence in modern sand from the Indus River system has been used to argue that detrital uraninite does not provide information about the oxygen concentration of Earth's early atmosphere. Petrographic and chemical study of sand from these two sources reveals differences that suggest the modern Indus sand cannot be used as an analog for the Archeanmore » Witwatersrand occurrences. The Witwatersrand quartzites are depleted in Ca, Mg, and Na, indicating that the original sand from which they formed had been subjected to intense weathering. The chemical index of alteration (CIA), a commonly used indicator of degree of weathering, yields an average value of about 0.80 for Witwatersrand quartzites, comparable to modern tropical streams such as the Orinoco that drain deeply weathered terrains under tropical conditions (CIA=0.75). In contrast, the CIA for Indus sand is 0.45, indicating virtually no chemical weathering. The significance of Archean quartz-pebble conglomerates is not just that they contain unstable detrital phases like uraninite and pyrite, but that these particles are associated with rocks whose compositions suggest intense weathering. These conglomerates must have been subjected to intense weathering under tropical conditions, either in their source area or at the site of deposition, and the preservation of minerals like uraninite such conditions is indeed strong evidence for a low-oxygen atmosphere.« less

Indirect determination of particle shape of fine aggregate.

DOT National Transportation Integrated Search

1973-01-01

Three methods developed by various agencies for measuring indirectly the particle shapes of fine aggregates were used along with a visual classification procedure to study aggregates from eight commercial sources along with a reference sand. The meth...

Early Childhood: Discovery through Sand Play.

ERIC Educational Resources Information Center

McIntyre, Margaret

1982-01-01

Suggestions are given for using sand play to teach science related vocabulary and concepts to preschool and primary age children by using dry sand, wet sand, different sizes and shapes of spoons and containers, sieves, and funnels. (DC)

A parallel direct numerical simulation of dust particles in a turbulent flow

NASA Astrophysics Data System (ADS)

Nguyen, H. V.; Yokota, R.; Stenchikov, G.; Kocurek, G.

2012-04-01

Due to their effects on radiation transport, aerosols play an important role in the global climate. Mineral dust aerosol is a predominant natural aerosol in the desert and semi-desert regions of the Middle East and North Africa (MENA). The Arabian Peninsula is one of the three predominant source regions on the planet "exporting" dust to almost the entire world. Mineral dust aerosols make up about 50% of the tropospheric aerosol mass and therefore produces a significant impact on the Earth's climate and the atmospheric environment, especially in the MENA region that is characterized by frequent dust storms and large aerosol generation. Understanding the mechanisms of dust emission, transport and deposition is therefore essential for correctly representing dust in numerical climate prediction. In this study we present results of numerical simulations of dust particles in a turbulent flow to study the interaction between dust and the atmosphere. Homogenous and passive dust particles in the boundary layers are entrained and advected under the influence of a turbulent flow. Currently no interactions between particles are included. Turbulence is resolved through direct numerical simulation using a parallel incompressible Navier-Stokes flow solver. Model output provides information on particle trajectories, turbulent transport of dust and effects of gravity on dust motion, which will be used to compare with the wind tunnel experiments at University of Texas at Austin. Results of testing of parallel efficiency and scalability is provided. Future versions of the model will include air-particle momentum exchanges, varying particle sizes and saltation effect. The results will be used for interpreting wind tunnel and field experiments and for improvement of dust generation parameterizations in meteorological models.

[Fractal features of soil particle size in the process of desertification in desert grassland of Ningxia, China].

PubMed

Yan, Xin; An, Hui

2017-10-01

The variation of soil properties, the fractal dimension of soil particle size, and the relationships between fractal dimension of soil particle size and soil properties in the process of desertification in desert grassland of Ningxia were discussed. The results showed that the fractal dimension (D) at different desertification stages in desert grassland varied greatly, the value of D was between 1.69 and 2.62. Except for the 10-20 cm soil layer, the value of D gradually declined with increa sing desertification of desert grassland at 0-30 cm soil layer. In the process of desertification in de-sert grassland, the grassland had the highest values of D , the volume percentage of clay and silt, and the lowest values of the volume percentage of very fine sand and fine sand. However, the mobile dunes had the lowest value of D , the volume percentage of clay and silt, and the highest value of the volume percentage of very fine sand and fine sand. There was a significant positive correlation between the soil fractal dimension value and the volume percentage of soil particles <50 μm, and a significant negative correlation between the soil fractal dimension value and the volume percentage of soil particles >50 μm. The grain size of 50 μm was the critical value for deciding the relationship between the soil particle fractal dimension and the volume percentage. Soil organic matter (SOM) and total nitrogen (TN) decreased gradually with increasing desertification of desert grassland, but soil bulk density increased gradually. Qualitative change from fixed dunes to semi fixed dunes with the rapid decrease of the volume percentage of clay and silt, SOM, TN and the rapid increase of volume percentage of very fine sand and fine sand, soil bulk density. Fractal dimension was significantly correlated to SOM, TN and soil bulk density. Fractal dimension 2.58 was a critical value of fixed dunes and semi fixed dunes. So, the fractal dimension of 2.58 could be taken as the

Aggregation and transport of rutile titanium dioxide nanoparticles with montmorillonite and diatomite in the presence of phosphate in porous sand.

PubMed

Guo, Peng; Xu, Nan; Li, Duo; Huangfu, Xinxing; Li, Zuling

2018-08-01

Crop soil is inevitably contaminated by the excess of phosphate (P) fertilizers. A large amount of nanoparticle titanium dioxide (nTiO 2 ) entered soils as well due to the wide use of engineered nanomaterials. It is of great urgency and a high priority to investigate the mechanisms of nTiO 2 deposition with the presence of P in crop soils. This study investigated the transport behavior of (1.0 g L -1 ) rutile nTiO 2 with two representative clay particles (montmorillonite or diatomite) in the presence of P through the saturated quartz sand. In 10 mM NaCl electrolyte solution at pH 6.0, the recovery percentage of nTiO 2 was 36.3% from sand column. Nevertheless, it was reduced to 18.6% and 11.1% while montmorillonite and diatomite present in suspensions, respectively. Obviously, the improvement of nTiO 2 retention in sand was more pronounced by diatomite than montmorillonite. The likely mechanism for this result was that large aggregates were formed due to the attachment of nTiO 2 to montmorillonite and diatomite. Moreover, the surface of diatomite with the larger hydrodynamic radius was less negatively charged by comparison with montmorillonite. However, this phenomenon disappeared with the addition of P. P adsorption increases the repulsive force between particles and sand and the fast release of attached nTiO 2 -montmorillonite and diatomite from sand. The two-site kinetic retention model and the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory suggested that the combination of k 1/ k 1d , k 2 and secondary minimum energy can be used to accurately describe the attachment of nTiO 2 -montmorillonite and diatomite to sand in the presence of P. Copyright © 2018 Elsevier Ltd. All rights reserved.

Comparison of buried sand ridges and regressive sand ridges on the outer shelf of the East China Sea

NASA Astrophysics Data System (ADS)

Wu, Ziyin; Jin, Xianglong; Zhou, Jieqiong; Zhao, Dineng; Shang, Jihong; Li, Shoujun; Cao, Zhenyi; Liang, Yuyang

2017-06-01

Based on multi-beam echo soundings and high-resolution single-channel seismic profiles, linear sand ridges in U14 and U2 on the East China Sea (ECS) shelf are identified and compared in detail. Linear sand ridges in U14 are buried sand ridges, which are 90 m below the seafloor. It is presumed that these buried sand ridges belong to the transgressive systems tract (TST) formed 320-200 ka ago and that their top interface is the maximal flooding surface (MFS). Linear sand ridges in U2 are regressive sand ridges. It is presumed that these buried sand ridges belong to the TST of the last glacial maximum (LGM) and that their top interface is the MFS of the LGM. Four sub-stage sand ridges of U2 are discerned from the high-resolution single-channel seismic profile and four strikes of regressive sand ridges are distinguished from the submarine topographic map based on the multi-beam echo soundings. These multi-stage and multi-strike linear sand ridges are the response of, and evidence for, the evolution of submarine topography with respect to sea-level fluctuations since the LGM. Although the difference in the age of formation between U14 and U2 is 200 ka and their sequences are 90 m apart, the general strikes of the sand ridges are similar. This indicates that the basic configuration of tidal waves on the ECS shelf has been stable for the last 200 ka. A basic evolutionary model of the strata of the ECS shelf is proposed, in which sea-level change is the controlling factor. During the sea-level change of about 100 ka, five to six strata are developed and the sand ridges develop in the TST. A similar story of the evolution of paleo-topography on the ECS shelf has been repeated during the last 300 ka.

Biochar particle size, shape, and porosity act together to influence soil water properties

PubMed Central

Dugan, Brandon; Masiello, Caroline A.; Gonnermann, Helge M.

2017-01-01

Many studies report that, under some circumstances, amending soil with biochar can improve field capacity and plant-available water. However, little is known about the mechanisms that control these improvements, making it challenging to predict when biochar will improve soil water properties. To develop a conceptual model explaining biochar’s effects on soil hydrologic processes, we conducted a series of well constrained laboratory experiments using a sand matrix to test the effects of biochar particle size and porosity on soil water retention curves. We showed that biochar particle size affects soil water storage through changing pore space between particles (interpores) and by adding pores that are part of the biochar (intrapores). We used these experimental results to better understand how biochar intrapores and biochar particle shape control the observed changes in water retention when capillary pressure is the main component of soil water potential. We propose that biochar’s intrapores increase water content of biochar-sand mixtures when soils are drier. When biochar-sand mixtures are wetter, biochar particles’ elongated shape disrupts the packing of grains in the sandy matrix, increasing the volume between grains (interpores) available for water storage. These results imply that biochars with a high intraporosity and irregular shapes will most effectively increase water storage in coarse soils. PMID:28598988

The use of Papuan iron sand and river sand for fine aggregate in mortar for nuclear radiation shield application

NASA Astrophysics Data System (ADS)

Dahlan, K.; Haryati, E.; Aninam, Y. S.

2018-03-01

This study explores the effect of fine aggregate on mortar properties and its application as a nuclear shield. This study was based on a hypothesis that the types of aggregate applied as radiation shield determined the level of its effectiveness on preventing nuclear radiation. There are two types and sources of fine aggregate that was used as main ingredients for mortar production in this research, namely iron sand and river sand. Both types of sand were derived from the respective regions of Sarmi and Jayapura, Papua. The results showed that the mortar materials that were produced with the iron sand provided better results in dispelling radiation than that of river sand. The compressive strength of fine aggregate from the iron sand was 21.62 MPa, while the compressive strength of the river sand was 16.8 MPa. Measuring the attenuation coefficient of material, we found that the largest aggregated value of mortar with fine iron sand reached 0.0863 / cm. On the other hand, the smallest HVT (Half Value Thickness) was obtained from the iron sand mortar, at 8.03 cm.

Faecal indicator bacteria enumeration in beach sand: A comparison study of extraction methods in medium to coarse sands

USGS Publications Warehouse

Boehm, A.B.; Griffith, J.; McGee, C.; Edge, T.A.; Solo-Gabriele, H. M.; Whitman, R.; Cao, Y.; Getrich, M.; Jay, J.A.; Ferguson, D.; Goodwin, K.D.; Lee, C.M.; Madison, M.; Weisberg, S.B.

2009-01-01

Aims: The absence of standardized methods for quantifying faecal indicator bacteria (FIB) in sand hinders comparison of results across studies. The purpose of the study was to compare methods for extraction of faecal bacteria from sands and recommend a standardized extraction technique. Methods and Results: Twenty-two methods of extracting enterococci and Escherichia coli from sand were evaluated, including multiple permutations of hand shaking, mechanical shaking, blending, sonication, number of rinses, settling time, eluant-to-sand ratio, eluant composition, prefiltration and type of decantation. Tests were performed on sands from California, Florida and Lake Michigan. Most extraction parameters did not significantly affect bacterial enumeration. anova revealed significant effects of eluant composition and blending; with both sodium metaphosphate buffer and blending producing reduced counts. Conclusions: The simplest extraction method that produced the highest FIB recoveries consisted of 2 min of hand shaking in phosphate-buffered saline or deionized water, a 30-s settling time, one-rinse step and a 10 : 1 eluant volume to sand weight ratio. This result was consistent across the sand compositions tested in this study but could vary for other sand types. Significance and Impact of the Study: Method standardization will improve the understanding of how sands affect surface water quality. ?? 2009 The Society for Applied Microbiology.

Estimating degradation-related settlement in two landfill-reclaimed soils by sand-salt analogues.

PubMed

McDougall, J R; Fleming, I R; Thiel, R; Dewaele, P; Parker, D; Kelly, D

2018-04-25

Landfill reclaimed soil here refers to largely degraded materials excavated from old landfill sites, which after processing can be reinstated as more competent fill, thereby restoring the former landfill space. The success of the process depends on the presence of remaining degradable particles and their influence on settlement. Tests on salt-sand mixtures, from which the salt is removed, have been used to quantify the impact of particle loss on settlement. Where the amount of particle loss is small, say 10% by mass or less, settlements are small and apparently independent of lost particle size. A conceptual model is presented to explain this behaviour in terms of nestling particles and strong force chains. At higher percentages of lost particles, greater rates of settlement together with some sensitivity to particle size were observed. The conceptual model was then applied to two landfill reclaimed soils, the long-term settlements of which were found to be consistent with the conceptual model suggesting that knowledge of particle content and relative size are sufficient to estimate the influence of degradable particles in landfill reclaimed soils. Copyright © 2018 Elsevier Ltd. All rights reserved.

Sand-wave movement on Little Georges Bank

USGS Publications Warehouse

Twichell, David C.

1983-01-01

A 1-x-1.5-km area on Little Georges Bank (centered at 41?08?N., 68?04?W.) was mapped three times during a ten-month period by sidescan sonar and echo-sounding techniques to assess the morphology and mobility of sand waves on Georges Bank. Sand-wave amplitudes in the survey area ranged from 1-11 m although most were 5-7 m. Wavelengths were not constant as the crests were sinuous and in places, even bifurcated. The sand waves are asymmetrical with their steepest sides facing northwest; however, gradients of their steep sides mostly are 4?-10? which is well below the angle of repose for sand in water. Sand waves tended to have greater relief and a sharper asymmetry during the survey in September than during those in June or April. During the survey period the sand waves moved but the direction and rate of motion was variable. Even along an individual sand wave some parts moved as much as 60 m between surveys while other parts apparently remained stationary. The sand waves were asymmetrical, but movement was not consistently in the direction that the steep sides faced. Along the same sand wave, parts moved to the northwest while other parts moved to the southeast. Despite the complex pattern of sand motion, the mean displacement of the sand waves was below the resolution of the survey technique; to resolve it, a longer survey is needed.

Advanced Crew Escape Suits (ACES): Particle Impact Test

NASA Technical Reports Server (NTRS)

Rosales, Keisa R.; Stoltzfus, Joel M.

2009-01-01

NASA Johnson Space Center (JSC) requested NASA JSC White Sands Test Facility to assist in determining the effects of impaired anodization on aluminum parts in advanced crew escape suits (ACES). Initial investigation indicated poor anodization could lead to an increased risk of particle impact ignition, and a lack of data was prevalent for particle impact of bare (unanodized) aluminum; therefore, particle impact tests were performed. A total of 179 subsonic and 60 supersonic tests were performed with no ignition of the aluminum targets. Based on the resulting test data, WSTF found no increased particle impact hazard was present in the ACES equipment.

METHOD OF PROCESSING MONAZITE SAND

DOEpatents

Calkins, G.D.

1957-10-29

A method is given for the pretreatment of monazite sand with sodium hydroxide. When momazite sand is reacted with sodium hydroxide, the thorium, uranium, and rare earths are converted to water-insoluble hydrous oxides; but in the case of uranium, the precipitate compound may at least partly consist of a slightly soluble uranate. According to the patent, monazite sand is treated with an excess of aqueous sodium hydroxide solution, and the insoluble compounds of thorium, uranium, and the rare earths are separated from the aqueous solution. This solution is then concentrated causing sodium phosphate to crystallize out. The crystals are removed from the remaining solution, and the solution is recycled for reaction with a mew supply of momazite sand.

Experimental hypervelocity impact into quartz sand - Distribution and shock metamorphism of ejecta

NASA Technical Reports Server (NTRS)

Stoeffler, D.; Gault, D. E.; Wedekind, J.; Polkowski, G.

1975-01-01

Results are presented for vertical impacts of 0.3-g cylindrical plastic projectiles into noncohesive quartz sand in which vertical and horizontal reference strate were employed by using layers of colored sand. The impacts were performed at velocities of 5.9-6.9 km/sec with a vertical gun ballistic range. The craters, 30-33 cm in diameter, reveal a radial decay of the ejecta mass per unit area with a power of -2.8 to -3.5. Material displaced from the upper 15% of the crater depth d is represented within the whole ejecta blanked, material from deeper than 28% of d is deposited inside 2 crater radii, and no material from deeper than 33% of d was ejected beyond the crater rim. Shock-metamorphosed particles (glassy agglutinates, cataclastic breccias, and comminuted quartz) amount to some 4% of the total displaced mass and indicate progressive zones of decay of shock intensity from a peak pressure of 300 kbar. The shock-metamorphosed particles and the shock-induced change in the grain size distribution of ejected samples have close analogies to the basic characteristics of the lunar regolith. Possible applications to regolith formation and to ejecta formations of large-scale impact craters are discussed.

Nearshore dynamics of artificial sand and oil agglomerates

USGS Publications Warehouse

Dalyander, P. Soupy; Plant, Nathaniel G.; Long, Joseph W.; McLaughlin, Molly R.

2015-01-01

Weathered oil can mix with sediment to form heavier-than-water sand and oil agglomerates (SOAs) that can cause beach re-oiling for years after a spill. Few studies have focused on the physical dynamics of SOAs. In this study, artificial SOAs (aSOAs) were created and deployed in the nearshore, and shear stress-based mobility formulations were assessed to predict SOA response. Prediction sensitivity to uncertainty in hydrodynamic conditions and shear stress parameterizations were explored. Critical stress estimates accounting for large particle exposure in a mixed bed gave the best predictions of mobility under shoaling and breaking waves. In the surf zone, the 10-cm aSOA was immobile and began to bury in the seafloor while smaller size classes dispersed alongshore. aSOAs up to 5 cm in diameter were frequently mobilized in the swash zone. The uncertainty in predicting aSOA dynamics reflects a broader uncertainty in applying mobility and transport formulations to cm-sized particles.

Trends in Gypsiferous Aerosol Downwind of White Sands, New Mexico

NASA Astrophysics Data System (ADS)

White, W. H.; Trzepla, K.; Yatkin, S.; Gill, T. E.; Jin, L.

2013-12-01

White Sands is a known 'hotspot' of dust emissions in southwestern North America where an active gypsum dunefield abuts erodible playa sediments. Aerosols entrained from White Sands are sometimes visible on satellite images as distinct, light-colored plumes crossing the Sacramento Mountains to the northeast. The U.S. Forest Service operates an aerosol sampler at White Mountain in the lee of the Sacramento range as part of the IMPROVE network (Interagency Monitoring of PROtected Visual Environments). In recent years a spring pulse of sulfate aerosol has appeared at White Mountain, eclipsing the regional summer peak attributed to atmospheric reactions of sulfur dioxide emissions. A significant fraction of this spring sulfate is contributed by gypsum and other salts from White Sands, with clearly increased concentrations of calcium, strontium, and chloride. The increase in these species coincides with a drought following a period of above-average precipitation. White Sands and White Mountain thus provide an unusually well-defined natural laboratory: a climatically sensitive dust source that is both well characterized and chemically distinct from its surroundings, with a signature that remains identifiably distinct at a long-term observatory ~100 km downwind. This paper examines the routine PM2.5 (fine-particle, Dp < 2.5 um) composition data available from White Mountain and other regional IMPROVE sites (e.g. Bosque del Apache), supplemented by some elemental analysis of collocated PM10 samples. The ambient data are compared with chemical analyses of surface samples from White Sands, bulk dry dustfall and soil surface composition at White Mountain, satellite observations of dust plumes, and available meteorological records. Together, the observations document significant, episodic aeolian transport of gypsum and other salts across the Sacramento Mountains. Figure 1. Left: Monthly average concentrations of every-third-day 24h samples. Top right: MODIS image, 2

A study of global sand seas

USGS Publications Warehouse

McKee, Edwin D.

1979-01-01

The birth of the idea that led to this publication on "Global Sand Seas" dates back to the late 1920's. At that time I was engaged in a study of the Coconino Sandstone of Arizona's Grand Canyon. Considerable controversy existed then as to whether this sandstone was a subaqueous deposit or was composed of wind-formed dunes. It became apparent that definitive literature was sparse or lacking on types of dunes, global distribution of these types, the mechanics of their development, the precise nature of their internal structure of cross-stratificiation, and the relation of wind systems to these sand forms. Especially lacking were data on criteria that could confidently be used in the recognition of ancient dunes. The common denominator in this publication is eolian sand bodies. Although the book is concerned primarily with desert sand seas, the subject matter is not restricted to deserts; it includes many references to deposits of coastal sand and to sand bodies in humid climates. Nor does the book deal exclusively with dunes, which, according to most definitions, involve mounds or hills. Many references are made to sand sheets, sand stringers, and other types of sand deposits that have no prominent topographic expression. All sand bodies accumulated by the action of wind are discussed. Chapters A-J of this publication are primarily topical. Chapters cover the grain texture, the color, and the structure of modern dunes and other eolian sands. Special treatment is given to the relation of wind data to dune interpretation, the evolution of form in current-deposited sand bodies as determined from experimental studies, and the discriminant analysis technique for differentiating between coastal and inland desert sands. This topical part of the publication also includes an analysis of criteria used in ancient deposits to interpret their eolian genesis and a consideration of economic application of the principles described, including a discussion of potentials and problems

Sand dune tracking from satellite laser altimetry

NASA Astrophysics Data System (ADS)

Dabboor, Mohammed

Substantial problems arise from sand movement in arid and semi-arid countries. Sand poses a threat to infrastructure, agricultural and urban areas. These issues are caused by the encroachment of sand on roads and railway tracks, farmland, towns and villages, and airports, to name a few. Sand movement highly depends on geomorphology including vegetation cover, shape and height of the terrain, and grain size of the sand. However, wind direction and speed are the most important factors that affect efficient sand movement. The direction of the movement depends on the main direction of the wind, but it has been shown that a minimum wind speed is required, e.g. wind gusts, to initiate sand transport. This fact prevents a simple calculation of sand transport from conventional wind data as wind records rarely contain sub-minute intervals masking out any wind gusts. An alternative of predicting sand transport is the direct observation of sand advance by in situ measurements or via satellite. Until recently, satellite imagery was the only means to compare dune shape and position for predicting dune migration over several years. In 2003, the NASA laser altimetry mission ICESat became operational and monitors elevations over all surface types including sand dunes with an accuracy of about 10-20 cm. In this study, ICESat observations from repeat tracks (tracks overlapping eachother within 50 m) are used to derive sand dune advance and direction. The method employs a correlation of the elevation profiles over several dunes and was sucessfully validated with synthetic data. The accuracy of this method is 5 meters of dune advance. One of the most active areas exhibiting sand and dune movement is the area of the Arabian Peninsula. Approximately one-third of the Arabian Peninsula is covered by sand dunes. Different wind regimes (Shamal, Kaus) cause sand dune movement in the selected study area in the eastern part of the Arabian Peninsula between 20-25 degrees North and 45-55 degrees

High Pressure Quick Disconnect Particle Impact Tests

NASA Technical Reports Server (NTRS)

Rosales, Keisa R.; Stoltzfus, Joel M.

2009-01-01

NASA Johnson Space Center White Sands Test Facility (WSTF) performed particle impact testing to determine whether there is a particle impact ignition hazard in the quick disconnects (QDs) in the Environmental Control and Life Support System (ECLSS) on the International Space Station (ISS). Testing included standard supersonic and subsonic particle impact tests on 15-5 PH stainless steel, as well as tests performed on a QD simulator. This paper summarizes the particle impact tests completed at WSTF. Although there was an ignition in Test Series 4, it was determined the ignition was caused by the presence of a machining imperfection. The sum of all the test results indicates that there is no particle impact ignition hazard in the ISS ECLSS QDs. KEYWORDS: quick disconnect, high pressure, particle impact testing, stainless steel

Distribution, diversity and abundance of bacterial laccase-like genes in different particle size fractions of sediments in a subtropical mangrove ecosystem.

PubMed

Luo, Ling; Zhou, Zhi-Chao; Gu, Ji-Dong

2015-10-01

This study investigated the diversity and abundance of bacterial lacasse-like genes in different particle size fractions, namely sand, silt, and clay of sediments in a subtropical mangrove ecosystem. Moreover, the effects of nutrient conditions on bacterial laccase-like communities as well as the correlation between nutrients and, both the abundance and diversity indices of laccase-like bacteria in particle size fractions were also studied. Compared to bulk sediments, Bacteroidetes, Caldithrix, Cyanobacteria and Chloroflexi were dominated in all 3 particle-size fractions of intertidal sediment (IZ), but Actinobacteria and Firmicutes were lost after the fractionation procedures used. The diversity index of IZ fractions decreased in the order of bulk > clay > silt > sand. In fractions of mangrove forest sediment (MG), Verrucomicrobia was found in silt, and both Actinobacteria and Bacteroidetes appeared in clay, but no new species were found in sand. The declining order of diversity index in MG fractions was clay > silt > sand > bulk. Furthermore, the abundance of lacasse-like bacteria varied with different particle-size fractions significantly (p < 0.05), and decreased in the order of sand > clay > silt in both IZ and MG fractions. Additionally, nutrient availability was found to significantly affect the diversity and community structure of laccase-like bacteria (p < 0.05), while the total organic carbon contents were positively related to the abundance of bacterial laccase-like genes in particle size fractions (p < 0.05). Therefore, this study further provides evidence that bacterial laccase plays a vital role in turnover of sediment organic matter and cycling of nutrients.

Application of a combined measurement and modeling method to quantify windblown dust emissions from the exposed playa at Mono Lake, California.

PubMed

Ono, Duane; Kiddoo, Phill; Howard, Christopher; Davis, Guy; Richmond, Kenneth

2011-10-01

Particulate matter < or =10 microm (PM10) emissions due to wind erosion can vary dramatically with changing surface conditions. Crust formation, mechanical disturbance, soil texture, moisture, and chemical content of the soil can affect the amount of dust emitted during a wind event. A refined method of quantifying windblown dust emissions was applied at Mono Lake, CA, to account for changing surface conditions. This method used a combination of real-time sand flux monitoring, ambient PM10 monitoring, and dispersion modeling to estimate dust emissions and their downwind impact. The method identified periods with high emissions and periods when the surface was stable (no sand flux), even though winds may have been high. A network of 25 Cox sand catchers (CSCs) was used to measure the mass of saltating particles to estimate sand flux rates across a 2-km2 area. Two electronic sensors (Sensits) were used to time-resolve the CSC sand mass to estimate hourly sand flux rates, and a perimeter tapered element oscillating microbalance (TEOM) monitor measured hourly PM10 concentrations. Hourly sand flux rates were related by dispersion modeling to hourly PM10 concentrations to back-calculate the ratio of vertical PM10 flux to horizontal sand flux (K-factors). Geometric mean K-factor values (K(f)) were found to change seasonally, ranging from 1.3 x 10(-5) to 5.1 x 10(-5) for sand flux measured at 15 cm above the surface (q15). Hourly PM10 emissions, F, were calculated by applying seasonal K-factors to sand flux measurements (F = K(f) x q15). The maximum hourly PM10 emission rate from the study area was 76 g/m2 x hr (10-m wind speed = 23.5 m/sec). Maximum daily PM10 emissions were estimated at 450 g/m2 x day, and annual emissions at 1095 g/m2 x yr. Hourly PM10 emissions were used by the U.S. Environmental Protection Agency (EPA) guideline AERMOD dispersion model to estimate downwind ambient impacts. Model predictions compared well with monitor concentrations, with hourly PM10

Critical state of sand matrix soils.

PubMed

Marto, Aminaton; Tan, Choy Soon; Makhtar, Ahmad Mahir; Kung Leong, Tiong

2014-01-01

The Critical State Soil Mechanic (CSSM) is a globally recognised framework while the critical states for sand and clay are both well established. Nevertheless, the development of the critical state of sand matrix soils is lacking. This paper discusses the development of critical state lines and corresponding critical state parameters for the investigated material, sand matrix soils using sand-kaolin mixtures. The output of this paper can be used as an interpretation framework for the research on liquefaction susceptibility of sand matrix soils in the future. The strain controlled triaxial test apparatus was used to provide the monotonic loading onto the reconstituted soil specimens. All tested soils were subjected to isotropic consolidation and sheared under undrained condition until critical state was ascertain. Based on the results of 32 test specimens, the critical state lines for eight different sand matrix soils were developed together with the corresponding values of critical state parameters, M, λ, and Γ. The range of the value of M, λ, and Γ is 0.803-0.998, 0.144-0.248, and 1.727-2.279, respectively. These values are comparable to the critical state parameters of river sand and kaolin clay. However, the relationship between fines percentages and these critical state parameters is too scattered to be correlated.

Thermal diffusivity of peat, sand and their mixtures at different water contents

NASA Astrophysics Data System (ADS)

Gvozdkova, Anna; Arkhangelskaya, Tatiana

2014-05-01

Thermal diffusivity of peat, sand and their mixtures at different water contents was studied using the unsteady-state method described in (Parikh et al., 1979). Volume sand content in studied samples was 0 % (pure peat), 5, 10, 15, 20, 30, 40, 50, 55 and 62 % (pure sand). Thermal diffusivity of air-dry samples varied from 0.6×10-7m2s-1 for pure peat to 7.0×10-7m2s-1 for pure sand. Adding 5 and 10 vol. % of sand didn't change the thermal diffusivity of studied mixture as compared with that of the pure air-dry peat. Adding 15 % of sand resulted in significant increase of thermal diffusivity by approximately 1.5 times: from 0.6×10-7m2s-1 to 0.9×10-7m2s-1. It means that small amounts of sand with separate sand particles distributed within the peat don't contribute much to the heat transfer through the studied media. And there is a kind of threshold between the 10 and 15 vol. % of sand, after which the continuous sandy chains are formed within the peat, which can serve as preferential paths of heat transport. Adding 20 and 30 % of sand resulted in further increase of thermal diffusivity to 1.3×10-7m2s-1 and 1.7×10-7m2s-1, which is more than two and three times greater than the initial value for pure peat. Thermal diffusivity vs. moisture content dependencies had different shapes. For sand contents of 0 to 40 vol. % the thermal diffusivity increased with water content in the whole studied range from air-dry samples to the capillary moistened ones. For pure peat the experimental curves were almost linear; the more sand was added the more pronounced became the S-shape of the curves. For sand contents of 50 % and more the curves had a pronounced maximum within the range of water contents between 0.10 and 0.25 m3m-3 and then decreased. The experimental k(θ) curves, where k is soil thermal diffusivity, θ is water content, were parameterized with a 4-parameter approximating function (Arkhangelskaya, 2009, 2014). The suggested approximation has an advantage of clear

Sand Sources Near Athabasca Valles

NASA Image and Video Library

2014-10-29

This image captured by NASA Mars Reconnaissance Orbiter shows a small channel cutting into young volcanic lavas in a region where massive catastrophic flooding took place in the relatively recent past. The Athabasca Valles region includes a vast lava flow, thought to be the youngest on Mars, with even younger outflow channels that were carved by running water. The source of the water is believed to be the Cerberus Fossae valleys to the north, which may have penetrated to an over-pressurized aquifer in the subsurface. Nowadays, erosion by gravity, wind, and frost gradually wears down the rims of the outflow channels. In this scene, we see dark materials along the channel rim that were probably exposed by this erosion. The dark materials are less red than the surrounding surface and so they appear blue in this enhanced color picture. Viewed close up, the dark materials show ripples that suggest they are made up of mobile sand. It is possible that this sand originated elsewhere and simply collected where we see it today, but the fact that sand is not found elsewhere in the scene suggest to us that it is eroding out of the volcanic layers at the retreating rim of the channel. Sand sources are important because mobile sand grains have only a limited lifetime, wearing down and chipping apart each time they impact the surface. Erosion of the volcanic materials in this region may provide sands to replace those that are destroyed. Few such sand sources have so far been identified on Mars. http://photojournal.jpl.nasa.gov/catalog/PIA18889

Earth-like sand fluxes on Mars.

PubMed

Bridges, N T; Ayoub, F; Avouac, J-P; Leprince, S; Lucas, A; Mattson, S

2012-05-09

Strong and sustained winds on Mars have been considered rare, on the basis of surface meteorology measurements and global circulation models, raising the question of whether the abundant dunes and evidence for wind erosion seen on the planet are a current process. Recent studies showed sand activity, but could not determine whether entire dunes were moving--implying large sand fluxes--or whether more localized and surficial changes had occurred. Here we present measurements of the migration rate of sand ripples and dune lee fronts at the Nili Patera dune field. We show that the dunes are near steady state, with their entire volumes composed of mobile sand. The dunes have unexpectedly high sand fluxes, similar, for example, to those in Victoria Valley, Antarctica, implying that rates of landscape modification on Mars and Earth are similar.

Genome-wide and caste-specific DNA methylomes of the ants Camponotus floridanus and Harpegnathos saltator

PubMed Central

Bonasio, Roberto; Li, Qiye; Lian, Jinmin; Mutti, Navdeep S.; Jin, Lijun; Zhao, Hongmei; Zhang, Pei; Wen, Ping; Xiang, Hui; Ding, Yun; Jin, Zonghui; Shen, Steven S.; Wang, Zongji; Wang, Wen; Wang, Jun; Berger, Shelley L.; Liebig, Jürgen; Zhang, Guojie; Reinberg, Danny

2012-01-01

SUMMARY Background Ant societies comprise individuals belonging to different castes characterized by specialized morphologies and behaviors. Because ant embryos can follow different developmental trajectories, epigenetic mechanisms must play a role in caste determination. Ants have a full set of DNA methyltransferase and their genomes contain methylcytosine. To determine the relationship between DNA methylation and phenotypic plasticity in ants, we obtained and compared the genome-wide methylomes of different castes and developmental stages of Camponotus floridanus and Harpegnathos saltator. Results In the ant genomes, methylcytosines are found both in CpG and non-CpG contexts and are strongly enriched at exons of active genes. Changes in exonic DNA methylation correlate with alternative splicing events such as exon skipping and alternative splice site selection. Several genes exhibit caste-specific and developmental changes in DNA methylation that are conserved between the two species, including genes involved in reproduction, telomere maintenance, and noncoding RNA metabolism. Several loci are methylated and expressed monoallelically, and in some cases the choice of methylated allele depends on the caste. Conclusions These first ant methylomes and their intra- and inter-species comparison reveal an exonic methylation pattern that points to a connection between DNA methylation and splicing. The presence of monoallelic DNA methylation and the methylation of non-CpG sites in all samples suggest roles in genome regulation in these social insects, including the intriguing possibility of parental or caste-specific genomic imprinting. PMID:22885060

Petrography, mineralogy, and geochemistry of deep gravelly sands in the Eyreville B core, Chesapeake Bay impact structure

USGS Publications Warehouse

Bartosova, Katerina; Gier, Susanne; Horton, J. Wright; Koeberl, Christian; Mader, Dieter; Dypvik, Henning

2010-01-01

The ICDP–USGS Eyreville drill cores in the Chesapeake Bay impact structure reached a total depth of 1766 m and comprise (from the bottom upwards) basement-derived schists and granites/pegmatites, impact breccias, mostly poorly lithified gravelly sand and crystalline blocks, a granitic slab, sedimentary breccias, and postimpact sediments. The gravelly sand and crystalline block section forms an approximately 26 m thick interval that includes an amphibolite block and boulders of cataclastic gneiss and suevite. Three gravelly sands (basal, middle, and upper) are distinguished within this interval. The gravelly sands are poorly sorted, clast supported, and generally massive, but crude size-sorting and subtle, discontinuous layers occur locally. Quartz and K-feldspar are the main sand-size minerals and smectite and kaolinite are the principal clay minerals. Other mineral grains occur only in accessory amounts and lithic clasts are sparse (only a few vol%). The gravelly sands are silica rich (~80 wt% SiO2). Trends with depth include a slight decrease in SiO2 and slight increase in Fe2O3. The basal gravelly sand (below the cataclasite boulder) has a lower SiO2 content, less K-feldspar, and more mica than the higher sands, and it contains more lithic clasts and melt particles that are probably reworked from the underlying suevite. The middle gravelly sand (below the amphibolite block) is finer-grained, contains more abundant clay minerals, and displays more variable chemical compositions than upper gravelly sand (above the block). Our mineralogical and geochemical results suggest that the gravelly sands are avalanche deposits derived probably from the nonmarine Potomac Formation in the lower part of the target sediment layer, in contrast to polymict diamictons higher in the core that have been interpreted as ocean-resurge debris flows, which is in agreement with previous interpretations. The mineralogy and geochemistry of the gravelly sands are typical for a passive

Modeling surficial sand and gravel deposits

USGS Publications Warehouse

Bliss, J.D.; Page, N.J.

1994-01-01

Mineral-deposit models are an integral part of quantitative mineral-resource assessment. As the focus of mineral-deposit modeling has moved from metals to industrial minerals, procedure has been modified and may be sufficient to model surficial sand and gravel deposits. Sand and gravel models are needed to assess resource-supply analyses for planning future development and renewal of infrastructure. Successful modeling of sand and gravel deposits must address (1) deposit volumes and geometries, (2) sizes of fragments within the deposits, (3) physical characteristics of the material, and (4) chemical composition and chemical reactivity of the material. Several models of sand and gravel volumes and geometries have been prepared and suggest the following: Sand and gravel deposits in alluvial fans have a median volume of 35 million m3. Deposits in all other geologic settings have a median volume of 5.4 million m3, a median area of 120 ha, and a median thickness of 4 m. The area of a sand and gravel deposit can be predicted from volume using a regression model (log [area (ha)] =1.47+0.79 log [volume (million m3)]). In similar fashion, the volume of a sand and gravel deposit can be predicted from area using the regression (log [volume (million m3)]=-1.45+1.07 log [area (ha)]). Classifying deposits by fragment size can be done using models of the percentage of sand, gravel, and silt within deposits. A classification scheme based on fragment size is sufficiently general to be applied anywhere. ?? 1994 Oxford University Press.

Sand/cement ratio evaluation on mortar using neural networks and ultrasonic transmission inspection.

PubMed

Molero, M; Segura, I; Izquierdo, M A G; Fuente, J V; Anaya, J J

2009-02-01

The quality and degradation state of building materials can be determined by nondestructive testing (NDT). These materials are composed of a cementitious matrix and particles or fragments of aggregates. Sand/cement ratio (s/c) provides the final material quality; however, the sand content can mask the matrix properties in a nondestructive measurement. Therefore, s/c ratio estimation is needed in nondestructive characterization of cementitious materials. In this study, a methodology to classify the sand content in mortar is presented. The methodology is based on ultrasonic transmission inspection, data reduction, and features extraction by principal components analysis (PCA), and neural network classification. This evaluation is carried out with several mortar samples, which were made while taking into account different cement types and s/c ratios. The estimated s/c ratio is determined by ultrasonic spectral attenuation with three different broadband transducers (0.5, 1, and 2 MHz). Statistical PCA to reduce the dimension of the captured traces has been applied. Feed-forward neural networks (NNs) are trained using principal components (PCs) and their outputs are used to display the estimated s/c ratios in false color images, showing the s/c ratio distribution of the mortar samples.

Seeding hydrate formation in water-saturated sand with dissolved-phase methane obtained from hydrate dissolution: A progress report

USGS Publications Warehouse

Waite, William F.; Osegovic, J.P.; Winters, William J.; Max, M.D.; Mason, David H.

2008-01-01

An isobaric flow loop added to the Gas Hydrate And Sediment Test Laboratory Instrument (GHASTLI) is being investigated as a means of rapidly forming methane hydrate in watersaturated sand from methane dissolved in water. Water circulates through a relatively warm source chamber, dissolving granular methane hydrate that was pre-made from seed ice, then enters a colder hydrate growth chamber where hydrate can precipitate in a water-saturated sand pack. Hydrate dissolution in the source chamber imparts a known methane concentration to the circulating water, and hydrate particles from the source chamber entrained in the circulating water can become nucleation sites to hasten the onset of hydrate formation in the growth chamber. Initial results suggest hydrate grows rapidly near the growth chamber inlet. Techniques for establishing homogeneous hydrate formation throughout the sand pack are being developed.

Ocean Sand, Bahamas

NASA Image and Video Library

2011-04-20

NASA image acquired January 17, 2001 Though the above image may resemble a new age painting straight out of an art gallery in Venice Beach, California, it is in fact a satellite image of the sands and seaweed in the Bahamas. The image was taken by the Enhanced Thematic Mapper plus (ETM+) instrument aboard the Landsat 7 satellite. Tides and ocean currents in the Bahamas sculpted the sand and seaweed beds into these multicolored, fluted patterns in much the same way that winds sculpted the vast sand dunes in the Sahara Desert. Image courtesy Serge Andrefouet, University of South Florida Instrument: Landsat 7 - ETM+ Credit: NASA/GSFC/Landsat NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Join us on Facebook

Critical State of Sand Matrix Soils

PubMed Central

Marto, Aminaton; Tan, Choy Soon; Makhtar, Ahmad Mahir; Kung Leong, Tiong

2014-01-01

The Critical State Soil Mechanic (CSSM) is a globally recognised framework while the critical states for sand and clay are both well established. Nevertheless, the development of the critical state of sand matrix soils is lacking. This paper discusses the development of critical state lines and corresponding critical state parameters for the investigated material, sand matrix soils using sand-kaolin mixtures. The output of this paper can be used as an interpretation framework for the research on liquefaction susceptibility of sand matrix soils in the future. The strain controlled triaxial test apparatus was used to provide the monotonic loading onto the reconstituted soil specimens. All tested soils were subjected to isotropic consolidation and sheared under undrained condition until critical state was ascertain. Based on the results of 32 test specimens, the critical state lines for eight different sand matrix soils were developed together with the corresponding values of critical state parameters, M, λ, and Γ. The range of the value of M, λ, and Γ is 0.803–0.998, 0.144–0.248, and 1.727–2.279, respectively. These values are comparable to the critical state parameters of river sand and kaolin clay. However, the relationship between fines percentages and these critical state parameters is too scattered to be correlated. PMID:24757417

High temperature thermal energy storage in moving sand

NASA Technical Reports Server (NTRS)

Turner, R. H.; Awaya, H. I.

1978-01-01

Several high-temperature (to 500 C) heat-storage systems using sand as the storage medium are described. The advantages of sand as a storage medium include low cost for sand, widespread availability, non-toxicity, non-degradation characteristics, easy containment, and safety. The systems considered include: stationary sand with closely spaced tubes throughout the volume, the use of a fluidized bed, use of conveyor belt transporter, and the use of a blower rapid transport system. For a stationary sand bed, very close spacing of heat transfer tubes throughout the volume is required, manifesting as high power related system cost. The suggestion of moving sand past or around pipes is intended to reduce the power related costs at the penalty of added system complexity. Preliminary system cost estimates are offered. These rough calculations indicate that mobile sand heat storage systems cost less than the stationary sand approach.

Load capacity, failure mode and design criteria investigation of sand jacks : full scale load testing of sand jacks.

DOT National Transportation Integrated Search

2008-12-01

A sand-jack is a sand filled container used as a component of cast-in-place bridge false-work. The sand filler facilitates the removal of the false-work by allowing slow and controlled lowering of the bracing that has become wedged beneath the new br...

4D Imaging of Salt Precipitation during Evaporation from Saline Porous Media Influenced by the Particle Size Distribution

NASA Astrophysics Data System (ADS)

Norouzi Rad, M.; Shokri, N.

2014-12-01

Understanding the physics of water evaporation from saline porous media is important in many processes such as evaporation from porous media, vegetation, plant growth, biodiversity in soil, and durability of building materials. To investigate the effect of particle size distribution on the dynamics of salt precipitation in saline porous media during evaporation, we applied X-ray micro-tomography technique. Six samples of quartz sand with different grain size distributions were used in the present study enabling us to constrain the effects of particle and pore sizes on salt precipitation patterns and dynamics. The pore size distributions were computed using the pore-scale X-ray images. The packed beds were saturated with NaCl solution of 3 Molal and the X-ray imaging was continued for one day with temporal resolution of 30 min resulting in pore scale information about the evaporation and precipitation dynamics. Our results show more precipitation at the early stage of the evaporation in the case of sand with the larger particle size due to the presence of fewer evaporation sites at the surface. The presence of more preferential evaporation sites at the surface of finer sands significantly modified the patterns and thickness of the salt crust deposited on the surface such that a thinner salt crust was formed in the case of sand with smaller particle size covering larger area at the surface as opposed to the thicker patchy crusts in samples with larger particle sizes. Our results provide new insights regarding the physics of salt precipitation in porous media during evaporation.

High Pressure Quick Disconnect Particle Impact Tests

NASA Technical Reports Server (NTRS)

Peralta, Stephen; Rosales, Keisa; Smith, Sarah R.; Stoltzfus, Joel M.

2007-01-01

To determine whether there is a particle impact ignition hazard in the quick disconnects (QDs) in the Environmental Control and Life Support System (ECLSS) on the International Space Station (ISS), NASA Johnson Space Center requested White Sands Test Facility (WSTF) to perform particle impact testing. Testing was performed from November 2006 through May 2007 and included standard supersonic and subsonic particle impact tests on 15-5 PH stainless steel, as well as tests performed on a QD simulator. This report summarizes the particle impact tests completed at WSTF. Although there was an ignition in Test Series 4, it was determined the ignition was caused by the presence of a machining imperfection. The sum of all the test results indicates that there is no particle impact ignition hazard in the ISS ECLSS QDs.

Influence of a Reclaimed Sand Addition to Moulding Sand with Furan Resin on Its Impact on the Environment.

PubMed

Holtzer, Mariusz; Dańko, Rafał; Kmita, Angelika

Metalcasting involves having a molten metal poured in a hollow mould to produce metal objects. These moulds are generally made of sand and are chemically bonded, clay-bonded, or even unbounded. There are many binder systems used. Binders based on furfuryl resins constitute currently the highest fraction in the binders no-bake group. Moulding sand, after knocking out the cast, is partially reclaimed, and the remaining part, known as waste foundry sand is used or stored outside the foundry. In this case, the environment hazardous organic compounds and metals can be leached from the moulding sand, thus causing pollution of water and soil. Also during the casting moulds with molten metal, they emit pyrolysis gases containing many different compounds, often dangerous from the BTEX and PAH group, which has adverse impacts on the environment and workers. The article presents the results of research on the impact of the regenerate addition to the moulding sand matrix on emitted gases and the degree of threat to the environment due to leaching of hazardous components. Therefore, for the total assessment of the moulding sands harmfulness, it is necessary to perform investigations concerning the dangerous substances elution into the environment during their management and storage, as well as investigations concerning emissions of hazardous substances (especially from the BTEX and PAHs group) during moulds pouring, cooling, and casting knocking out. Both kinds of investigations indicated that reclaimed sand additions to moulding sands have significantly negative influence on the environment and working conditions.

Ratios of total suspended solids to suspended sediment concentrations by particle size

USGS Publications Warehouse

Selbig, W.R.; Bannerman, R.T.

2011-01-01

Wet-sieving sand-sized particles from a whole storm-water sample before splitting the sample into laboratory-prepared containers can reduce bias and improve the precision of suspended-sediment concentrations (SSC). Wet-sieving, however, may alter concentrations of total suspended solids (TSS) because the analytical method used to determine TSS may not have included the sediment retained on the sieves. Measuring TSS is still commonly used by environmental managers as a regulatory metric for solids in storm water. For this reason, a new method of correlating concentrations of TSS and SSC by particle size was used to develop a series of correction factors for SSC as a means to estimate TSS. In general, differences between TSS and SSC increased with greater particle size and higher sand content. Median correction factors to SSC ranged from 0.29 for particles larger than 500m to 0.85 for particles measuring from 32 to 63m. Great variability was observed in each fraction-a result of varying amounts of organic matter in the samples. Wide variability in organic content could reduce the transferability of the correction factors. ?? 2011 American Society of Civil Engineers.

Strengthening mechanism of cemented hydrate-bearing sand at microscales

NASA Astrophysics Data System (ADS)

Yoneda, Jun; Jin, Yusuke; Katagiri, Jun; Tenma, Norio

2016-07-01

On the basis of hypothetical particle-level mechanisms, several constitutive models of hydrate-bearing sediments have been proposed previously for gas production. However, to the best of our knowledge, the microstructural large-strain behaviors of hydrate-bearing sediments have not been reported to date because of the experimental challenges posed by the high-pressure and low-temperature testing conditions. Herein, a novel microtriaxial testing apparatus was developed, and the mechanical large-strain behavior of hydrate-bearing sediments with various hydrate saturation values (Sh = 0%, 39%, and 62%) was analyzed using microfocus X-ray computed tomography. Patchy hydrates were observed in the sediments at Sh = 39%. The obtained stress-strain relationships indicated strengthening with increasing hydrate saturation and a brittle failure mode of the hydrate-bearing sand. Localized deformations were quantified via image processing at the submillimeter and micrometer scale. Shear planes and particle deformation and/or rotation were detected, and the shear band thickness decreased with increasing hydrate saturation.

Northern Sand Sea

NASA Technical Reports Server (NTRS)

2005-01-01

[figure removed for brevity, see original site]

Our topic for the weeks of April 4 and April 11 is dunes on Mars. We will look at the north polar sand sea and at isolated dune fields at lower latitudes. Sand seas on Earth are often called 'ergs,' an Arabic name for dune field. A sand sea differs from a dune field in two ways: 1) a sand sea has a large regional extent, and 2) the individual dunes are large in size and complex in form.

This VIS image was taken at 82 degrees North latitude during Northern spring. The image is completely dominated by dunes. In sand seas, it is very common for a single type of dune to occur, and for a single predominate wind to control the alignment of the dunes.

Image information: VIS instrument. Latitude 82.2, Longitude 152.5 East (207.5 West). 19 meter/pixel resolution.

Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

Ganges Chasma Sand Sheet

NASA Technical Reports Server (NTRS)

2005-01-01

[figure removed for brevity, see original site]

Our topic for the weeks of April 4 and April 11 is dunes on Mars. We will look at the north polar sand sea and at isolated dune fields at lower latitudes. Sand seas on Earth are often called 'ergs,' an Arabic name for dune field. A sand sea differs from a dune field in two ways: 1) a sand sea has a large regional extent, and 2) the individual dunes are large in size and complex in form.

Today's sand sheet is located in the Ganges Chasma portion of Valles Marineris. As with yesterday's image, note that the dune forms are seen only at the margin and that the interior of the sand sheet at this resolution appears to completely lack dune forms.

Image information: VIS instrument. Latitude -6.4, Longitude 310.7 East (49.3 West). 19 meter/pixel resolution.

Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

Mineral resource of the month: industrial sand and gravel

USGS Publications Warehouse

Dolley, Thomas

2007-01-01

With many diverse uses, industrial sand and gravel, also known as silica sand, is one of the most important nonmetallic minerals in the world. Industrial sand and gravel is a mining industry term used for sands that have a very high percentage of silicon dioxide, or greater than 95 percent quartz. Deposits of industrial sand and gravel can be found virtually everywhere on Earth, but are less widespread than deposits of common construction sand and gravel. Industrial sand and gravel is distinctive in grain size, hardness, inertness and resistance to high temperature and chemical action. Beverage containers, fiberglass insulation, fiber-optic cables and light bulbs are just some of today’s many products produced from industrial sand and gravel.

Removal of Waterborne Particles by Electrofiltration: Pilot-Scale Testing

EPA Science Inventory

Theoretical analysis using a trajectory approach indicated that in the presence of an external electric field, charged waterborne particles are subject to an additional migration velocity which increases their deposition on the surface of collectors (e.g. sand filter). In this st...

Full scale load testing of sand-jacks.

DOT National Transportation Integrated Search

2006-06-01

A sand-jack is a sand filled container used as a component of cast-in-place bridge false-work. The sand filler facilitates the removal of the false-work by allowing slow and controlled lowering of the bracing that has become wedged beneath the new br...

Reduction in soil aggregation in response to dust emission processes

NASA Astrophysics Data System (ADS)

Swet, Nitzan; Katra, Itzhak

2016-09-01

Dust emission by aeolian (wind) soil erosion depends on the topsoil properties of the source area, especially on the nature of the aggregates where most dust particles are held. Although the key role of soil aggregates in dust emission, the response of soil aggregation to aeolian processes and its implications for dust emission remain unknown. This study focuses on aggregate size distribution (ASD) analyses before and after in-situ aeolian experiments in semiarid loess soils that are associated with dust emission. Wind tunnel simulations show that particulate matter (PM) emission and saltation rates depend on the initial ASD and shear velocity. Under all initial ASD conditions, the content of saltator-sized aggregates (63-250 μm) increased by 10-34% due to erosion of macro-aggregates (> 500 μm), resulting in a higher size ratio (SR) between the saltators and macro-aggregates following the aeolian erosion. The results revealed that the saltator production increases significantly for soils that are subjected to short-term (anthropogenic) disturbance of the topsoil. The findings highlight a decrease in soil aggregation for all initial ASD's in response to aeolian erosion, and consequently its influence on the dust emission potential. Changes in ASD should be considered as a key parameter in dust emission models of complex surfaces.

Visualization of Air Particle Dynamics in an Engine Inertial Particle Separator

NASA Astrophysics Data System (ADS)

Wolf, Jason; Zhang, Wei

2015-11-01

Unmanned Aerial Vehicles (UAVs) are regularly deployed around the world in support of military, civilian and humanitarian efforts. Due to their unique mission profiles, these advanced UAVs utilize various internal combustion engines, which consume large quantities of air. Operating these UAVs in areas with high concentrations of sand and dust can be hazardous to the engines, especially during takeoff and landing. In such events, engine intake filters quickly become saturated and clogged with dust particles, causing a substantial decrease in the UAVs' engine performance and service life. Development of an Engine Air Particle Separator (EAPS) with high particle separation efficiency is necessary for maintaining satisfactory performance of the UAVs. Inertial Particle Separators (IPS) have been one common effective method but they experience complex internal particle-laden flows that are challenging to understand and model. This research employs an IPS test rig to simulate dust particle separation under different flow conditions. Soda lime glass spheres with a mean diameter of 35-45 microns are used in experiments as a surrogate for airborne particulates encountered during flight. We will present measurements of turbulent flow and particle dynamics using flow visualization techniques to understand the multiphase fluid dynamics in the IPS device. This knowledge can contribute to design better performing IPS systems for UAVs. Cleveland State University, Cleveland, Ohio, 44115.

Use of sand wave habitats by silver hake

USGS Publications Warehouse

Auster, P.J.; Lindholm, J.; Schaub, S.; Funnell, G.; Kaufman, L.S.; Valentine, P.C.

2003-01-01

Silver hake Merluccius bilinearis are common members of fish communities in sand wave habitats on Georges Bank and on Stellwagen Bank in the Gulf of Maine. Observations of fish size v. sand wave period showed that silver hake are not randomly distributed within sand wave landscapes. Regression analyses showed a significant positive relationship between sand wave period and fish length. Correlation coefficients, however, were low, suggesting other interactions with sand wave morphology, the range of current velocities, and available prey may also influence their distribution. Direct contact with sand wave habitats varied over diel periods, with more fish resting on the seafloor during daytime than at night. Social foraging, in the form of polarized groups of fish swimming in linear formations during crepuscular and daytime periods, was also observed. Sand wave habitats may provide shelter from current flows and mediate fish-prey interactions. ?? 2003 The Fisheries Society of the British Isles.

Blending foundry sands with soil: Effect on dehydrogenase activity.

PubMed

Dungan, Robert S; Kukier, Urzsula; Lee, Brad

2006-03-15

Each year U.S. foundries landfill several million tons of sand that can no longer be used to make metalcasting molds and cores. A possible use for these materials is as an ingredient in manufactured soils; however, potentially harmful metals and resin binders (used to make cores) may adversely impact the soil microbial community. In this study, the dehydrogenase activity (DHA) of soil amended with molding sand (clay-coated sand known as "green sand") or core sands at 10%, 30%, and 50% (dry wt.) was determined. The green sands were obtained from iron, aluminum, and brass foundries; the core sands were made with phenol-formaldehyde or furfuryl alcohol based resins. Overall, incremental additions of these sands resulted in a decrease in the DHA which lasted throughout the 12-week experimental period. A brass green sand, which contained high concentrations of Cu, Pb, and Zn, severely impacted the DHA. By week 12 no DHA was detected in the 30% and 50% treatments. In contrast, the DHA in soil amended with an aluminum green sand was 2.1 times higher (all blending ratios), on average, at week 4 and 1.4 times greater (30% and 50% treatments only) than the controls by week 12. In core sand-amended soil, the DHA results were similar to soils amended with aluminum and iron green sands. Increased activity in some treatments may be a result of the soil microorganisms utilizing the core resins as a carbon source. The DHA assay is a sensitive indicator of environmental stress caused by foundry sand constituents and may be useful to assess which foundry sands are suitable for beneficial use in the environment.

Behaviour of Talitrus saltator (Crustacea: Amphipoda) on a rehabilitated sandy beach on the European Atlantic Coast (Portugal)

NASA Astrophysics Data System (ADS)

Bessa, Filipa; Rossano, Claudia; Nourisson, Delphine; Gambineri, Simone; Marques, João Carlos; Scapini, Felicita

2013-01-01

Environmental and human controls are widely accepted as the main structuring forces of the macrofauna communities on sandy beaches. A population of the talitrid amphipod Talitrus saltator (Montagu, 1808) was investigated on an exposed sandy beach on the Atlantic coast of Portugal (Leirosa beach) to estimate orientation capabilities and endogenous rhythms in conditions of recent changes in the landscape (artificial reconstruction of the foredune) and beach morphodynamics (stabilization against erosion from the sea). We tested sun orientation of talitrids on the beach and recorded their locomotor activity rhythms under constant conditions in the laboratory. The orientation data were analysed with circular statistics and multiple regression models adapted to angular distributions, to highlight the main factors and variables influencing the variation of orientation. The talitrids used the sun compass, visual cues (landscape and sun visibility) to orient and the precision of orientation varied according to the tidal regime (rising or ebbing tides). A well-defined free-running rhythm (circadian with in addition a bimodal rhythmicity, likely tidal) was highlighted in this population. This showed a stable behavioural adaptation on a beach that has experienced a process of artificial stabilization of the dune through nourishment actions over a decade. Monitoring the conditions of such dynamic environments and the resilience capacity of the inhabiting macroinfauna is a main challenge for sandy beach ecologists.

Complexity confers stability: Climate variability, vegetation response and sand transport on longitudinal sand dunes in Australia's deserts

NASA Astrophysics Data System (ADS)

Hesse, Paul P.; Telfer, Matt W.; Farebrother, Will

2017-04-01

The relationship between antecedent precipitation, vegetation cover and sand movement on sand dunes in the Simpson and Strzelecki Deserts was investigated by repeated (up to four) surveys of dune crest plots (≈25 × 25 m) over a drought cycle (2002-2012) in both winter (low wind) and spring (high wind). Vegetation varied dramatically between surveys on vegetated and active dune crests. Indices of sand movement had significant correlations with vegetation cover: the depth of loose sand has a strong inverse relationship with crust (cyanobacterial and/or physical) while the area covered by ripples has a strong inverse relationship with the areal cover of vascular plants. However, the relationship between antecedent rainfall and vegetation cover was found to be complex. We tentatively identify two thresholds; (1) >10 mm of rainfall in the preceding 90 days leads to rapid and near total cover of crust and/or small plants <50 cm tall, and (2) >400 mm of rainfall in the preceding three years leads to higher cover of persistent and longer-lived plants >50 cm tall. These thresholds were used to predict days of low vegetation cover on dune crests. The combination of seasonality of predicted bare-crest days, potential sand drift and resultant sand drift direction explains observed patterns of sand drift on these dunes. The complex vegetation and highly variable rainfall regime confer meta-stability on the dunes through the range of responses to different intervals of antecedent rainfall and non-linear growth responses. This suggests that the geomorphic response of dunes to climate variation is complex and non-linear.

Sand wave fields beneath the Loop Current, Gulf of Mexico: Reworking of fan sands

USGS Publications Warehouse

Kenyon, Neil H.; Akhmetzhanov, A.M.; Twichell, D.C.

2002-01-01

Extensive fields of large barchan-like sand waves and longitudinal sand ribbons have been mapped by deep-towed SeaMARC IA sidescan sonar on part of the middle and lower Mississippi Fan that lies in about 3200 m of water. The area is beneath the strongly flowing Loop Current. The bedforms have not been adequately sampled but probably consist of winnowed siliciclastic-foraminiferal sands. The size (about 200 m from wingtip to wingtip) and shape of the large barchans is consistent with a previously observed peak current speed of 30 cm/s, measured 25 m above the seabed. The types of small-scale bedforms and the scoured surfaces of chemical crusts, seen on nearby bottom photographs, indicate that near-bed currents in excess of 30 cm/s may sometimes occur. At the time of the survey the sand transport direction was to the northwest, in the opposite direction to the Loop Current but consistent with there being a deep boundary current along the foot of the Florida Escarpment. Some reworking of the underlying sandy turbidites and debris flow deposits is apparent on the sidescan sonar records. Reworking by deep-sea currents, resulting in erosion and in deposits characterised by coarsening upwards structures and cross-bedding, is a process that has been proposed for sand found in cores in shallower parts of the Gulf of Mexico. This process is more widespread than hitherto supposed. 

Experimental study of optimal self compacting concrete with spent foundry sand as partial replacement for M-sand using Taguchi approach

NASA Astrophysics Data System (ADS)

Nirmala, D. B.; Raviraj, S.

2016-06-01

This paper presents the application of Taguchi approach to obtain optimal mix proportion for Self Compacting Concrete (SCC) containing spent foundry sand and M-sand. Spent foundry sand is used as a partial replacement for M-sand. The SCC mix has seven control factors namely, Coarse aggregate, M-sand with Spent Foundry sand, Cement, Fly ash, Water, Super plasticizer and Viscosity modifying agent. Modified Nan Su method is used to proportion the initial SCC mix. L18 (21×37) Orthogonal Arrays (OA) with the seven control factors having 3 levels is used in Taguchi approach which resulted in 18 SCC mix proportions. All mixtures are extensively tested both in fresh and hardened states to verify whether they meet the practical and technical requirements of SCC. The quality characteristics considering "Nominal the better" situation is applied to the test results to arrive at the optimal SCC mix proportion. Test results indicate that the optimal mix satisfies the requirements of fresh and hardened properties of SCC. The study reveals the feasibility of using spent foundry sand as a partial replacement of M-sand in SCC and also that Taguchi method is a reliable tool to arrive at optimal mix proportion of SCC.

Murzuk Sand Sea, Sahara Desert, Libya, Africa

NASA Image and Video Library

1993-01-19

STS054-152-189 (13-19 Jan. 1993) --- This near-vertical color photograph shows the very diverse landscape that is part of the great Sahara Desert of north Africa. Specifically, the vast expanse of sand dunes, located in the extreme southwestern corner of Libya, is known as the Murzuk Sand Sea. Close inspection of this photograph shows the agricultural village of Murzuk as evidenced by the numerous center pivot irrigation patterns at the edge of the Murzuk Sand Sea. The very rugged, dissected terrain to the west of this sand sea is the eastern tip of the Tassili N'ajjer Mountains and the Tadrart Plateau that are in neighboring Algeria. Several smaller areas of sand dunes are interspersed between the major areas of rock outcrops. The photograph was taken with a Linhof camera.

Invasive plants on disturbed Korean sand dunes

NASA Astrophysics Data System (ADS)

Kim, Kee Dae

2005-01-01

The sand dunes in coastal regions of South Korea are important ecosystems because of their small size, the rare species found in this habitat, and the beautiful landscapes they create. This study investigated the current vegetative status of sand dunes on three representative coasts of the Korean peninsula, and on the coasts of Cheju Island, and assessed the conditions caused by invasive plants. The relationships between the degree of invasion and 14 environmental variables were studied. Plots of sand dunes along line transects perpendicular to the coastal lines were established to estimate vegetative species coverage. TWINSPAN (Two-Way Indicator Species Analysis), CCA (Canonical Correspondence Analysis), and DCCA (Detrended Canonical Correspondence Analysis) were performed to classify communities on sand dunes and assess species composition variation. Carex kobomugi, Elymus mollis, and Vitex rotundifolia were found to be the dominant species plotted on the east, the west, and the peripheral coasts of Cheju Island, respectively. Vegetation on the south coast was totally extinct. The 19 communities, including representative C. kobomugi, C. kobomugi- Ixeris repens, C. kobomugi- Oenothera biennis, E. mollis, Lolium multiflorum- Calystegia soldanella, and V. rotundifolia- C. kobomugi, were all classified according to TWINSPAN. Oenothera biennis and L. multiflorum were exotics observed within these native communities. CCA showed that invasive native and exotic species distribution was segregated significantly, according to disturbance level, exotic species number, gravel, sand and silt contents, as well as vegetation size. It further revealed that human disturbance can strongly favor the settlement of invasive and exotic species. Restoration options to reduce exotic plants in the South Korean sand dune areas were found to be the introduction of native plant species from one sand dune into other sand dune areas, prohibition of building and the introduction of exotic

Characteristics of SCC with Fly Ash and Manufactured Sand

NASA Astrophysics Data System (ADS)

Praveen Kumar, K.; Radhakrishna

2016-09-01

Self compacting concrete (SCC) of M40 grade was designed. The binder in SCC consists of OPC and fly ash in the ratio of 65:35. River sand was replaced by manufactured sand (M-sand) at replacement levels of 20,40,60,80 and 100%. An attempt was made to evaluate the workability and strength characteristics of self compacting concrete with river sand and manufactured sand as fine aggregates. For each replacement level, constant workability was maintained by varying the dosage of superplasticizer. T50 flow time, V Funnel time, V-funnel T5 time as well as compressive, split tensile and flexural strength of SCC were found at each replacement level of M-sand. They were compared to SCC with river sand. Results indicate favourable use of M-sand in preparation of Self Compacting Concrete.

Science Learning in the Sand.

ERIC Educational Resources Information Center

Sexton, Ursula

1997-01-01

Presents activities that allow students to think about the Earth in a contextual manner and become familiar with constructive and destructive processes as they relate to sand - its origins, cyclical processes, and yielding of new products. Explores the bigger idea with a developmentally appropriate study of water, rocks, sand, physical phenomena,…

Documenting the global impacts of beach sand mining

NASA Astrophysics Data System (ADS)

Young, R.; Griffith, A.

2009-04-01

For centuries, beach sand has been mined for use as aggregate in concrete, for heavy minerals, and for construction fill. The global extent and impact of this phenomenon has gone relatively unnoticed by academics, NGOs, and major news sources. Most reports of sand mining activities are found at the very local scale (if the mining is ever documented at all). Yet, sand mining in many localities has resulted in the complete destruction of beach (and related) ecosystems along with severe impacts to coastal protection and tourism. The Program for the Study of Developed Shorelines at Western Carolina University and Beachcare.org have initiated the construction of a global database of beach sand mining activities. The database is being built through a combination of site visits and through the data mining of media resources, peer reviewed papers, and reports from private and governmental entities. Currently, we have documented sand mining in 35 countries on 6 continents representing the removal of millions of cubic meters of sand. Problems extend from Asia where critical infrastructure has been disrupted by sand mining to the Caribbean where policy reform has swiftly followed a highly publicized theft of sand. The Program for the Study of Developed Shorelines recently observed extensive sand mining in Morocco at the regional scale. Tens of kilometers of beach have been stripped of sand and the mining continues southward reducing hope of a thriving tourism-based economy. Problems caused by beach sand mining include: destruction of natural beaches and the ecosystems they protect (e.g. dunes, wetlands), habitat loss for globally important species (e.g. turtles, shorebirds), destruction of nearshore marine ecosystems, increased shoreline erosion rates, reduced protection from storms, tsunamis, and wave events, and economic losses through tourist abandonment and loss of coastal aesthetics. The threats posed by sand mining are made even more critical given the prospect of a

Rotating drum tests of particle suspensions within a fines dispersion

NASA Astrophysics Data System (ADS)

Cabrera, Miguel Angel; Gollin, Devis; Kaitna, Roland; Wu, Wei

2014-05-01

Natural flows like mudflows, debris flow, and hyperconcentrated flows are commonly composed by a matrix of particles suspended in a viscous fluid. The nature of the interactions between particles immersed in a fluid is related to its size. While coarse particles (sand, gravel, and boulders) interact with each other or with the surrounding fluid, a dispersion of fine particles interacts with each other through colloidal forces or Brownian motion effects (Coussot and Piau, 1995, and Ancey and Jorrot, 2001). The predominance of one of the previous interactions defines the rheology of the flow. On this sense, experimental insight is required to validate the limits where the rheology of a dispersion of fines is valid. For this purpose, an experimental program in a rotating drum is performed over samples of sand, loess, and kaolin. The solid concentration and angular velocity of the rotating drum are varied. Height and normal loads are measured during flow. High-speed videos are performed to obtain the flow patterns of the mixtures. The experiments provide new laboratory evidence of granular mixture behaviour within an increased viscous fluid phase and its characterization. The results show an apparent threshold in terms of solid concentration, in which the mixtures started to behave as a shear-dependent material.

Deducing dust emission mechanisms from field measurements

USDA-ARS?s Scientific Manuscript database

Field observations are needed to both develop and test theories on dust emission for use in global modeling systems. The mechanism of dust emission (aerodynamic entrainment, saltation bombardment, aggregate disintegration) and the amount and particle-size distribution of emitted dust may vary under ...

Insights into the sand fly saliva: Blood-feeding and immune interactions between sand flies, hosts, and Leishmania.

PubMed

Lestinova, Tereza; Rohousova, Iva; Sima, Michal; de Oliveira, Camila I; Volf, Petr

2017-07-01

Leishmaniases are parasitic diseases present worldwide that are transmitted to the vertebrate host by the bite of an infected sand fly during a blood feeding. Phlebotomine sand flies inoculate into the mammalian host Leishmania parasites embedded in promastigote secretory gel (PSG) with saliva, which is composed of a diverse group of molecules with pharmacological and immunomodulatory properties. In this review, we focus on 3 main aspects of sand fly salivary molecules: (1) structure and composition of salivary glands, including the properties of salivary molecules related to hemostasis and blood feeding, (2) immunomodulatory properties of salivary molecules and the diverse impacts of these molecules on leishmaniasis, ranging from disease exacerbation to vaccine development, and (3) use of salivary molecules for field applications, including monitoring host exposure to sand flies and the risk of Leishmania transmission. Studies showed interesting differences between salivary proteins of Phlebotomus and Lutzomyia species, however, no data were ever published on salivary proteins of Sergentomyia species. In the last 15 years, numerous studies have characterized sand fly salivary proteins and, in parallel, have addressed the impact of such molecules on the biology of the host-sand fly-parasite interaction. The results obtained shall pave the way for the development of field-application tools that could contribute to the management of leishmaniasis in endemic areas.

Influence of humic acid concentration on nTiO2 attachment to quartz sand and Fe-coated quartz sand

NASA Astrophysics Data System (ADS)

Cheng, T.; Wu, Y.

2016-12-01

The transport of nano-scale or micro-scale titanium dioxide particles (nTiO2) in subsurface environments are strongly influenced by nTiO2 attachment to sediment grains. The objective of this study is to investigate the role of humic acid (HA) in the attachment of nTiO2 to sand at low HA concentrations that are relevant to typical groundwater conditions, so that mechanisms that control nTiO2 immobilization and transport in groundwater can be elucidated. nTiO2 may carry either positive or negative charges in natural water, therefore, environmental factors such as pH, humic substances, and Fe oxyhydroxide coatings on sediment grains, which are known to control the transport of negatively-charged colloids, may influence nTiO2 in different manners. Attachment of nTiO2 to quartz sand and Fe oxyhydroxide coated quartz sand are experimentally measured under a range of HA concentrations at fixed pH. Experimental results show that at pH 5, negatively-charged HA strongly adsorbs to positively-charged nTiO2 and Fe oxyhydroxide, which, at low HA concentrations, partially neutralizes the positive charges on nTiO2 and Fe oxyhydroxide, and therefore decreases the repulsive electrostatic forces between the surfaces, resulting in relatively high nTiO2 attachment. At high HA concentrations, adsorbed HA reverses the surface charges of nTiO2 and Fe oxyhydroxide, and makes nTiO2 and Fe oxyhydroxide strongly negatively charged, resulting in low nTiO2 attachment. At pH 9, HA, nTiO2, and Fe oxyhydroxide are all negatively charged, and HA adsorption is low and does not have a strong impact on the attachment of nTiO2. This study demonstrates that the changes in surface charges of nTiO2 and Fe oxyhydroxide coating caused by HA adsorption could be a key factor that controls the attachment of nTiO2 to sediment grains.

Microbially-accelerated consolidation of oil sands tailings. Pathway II: solid phase biogeochemistry.

PubMed

Siddique, Tariq; Kuznetsov, Petr; Kuznetsova, Alsu; Li, Carmen; Young, Rozlyn; Arocena, Joselito M; Foght, Julia M

2014-01-01

Consolidation of clay particles in aqueous tailings suspensions is a major obstacle to effective management of oil sands tailings ponds in northern Alberta, Canada. We have observed that microorganisms indigenous to the tailings ponds accelerate consolidation of mature fine tailings (MFT) during active metabolism by using two biogeochemical pathways. In Pathway I, microbes alter porewater chemistry to indirectly increase consolidation of MFT. Here, we describe Pathway II comprising significant, direct and complementary biogeochemical reactions with MFT mineral surfaces. An anaerobic microbial community comprising Bacteria (predominantly Clostridiales, Synergistaceae, and Desulfobulbaceae) and Archaea (Methanolinea/Methanoregula and Methanosaeta) transformed Fe(III) minerals in MFT to amorphous Fe(II) minerals during methanogenic metabolism of an added organic substrate. Synchrotron analyses suggested that ferrihydrite (5Fe2O3. 9H2O) and goethite (α-FeOOH) were the dominant Fe(III) minerals in MFT. The formation of amorphous iron sulfide (FeS) and possibly green rust entrapped and masked electronegative clay surfaces in amended MFT. Both Pathways I and II reduced the surface charge potential (repulsive forces) of the clay particles in MFT, which aided aggregation of clays and formation of networks of pores, as visualized using cryo-scanning electron microscopy (SEM). These reactions facilitated the egress of porewater from MFT and increased consolidation of tailings solids. These results have large-scale implications for management and reclamation of oil sands tailings ponds, a burgeoning environmental issue for the public and government regulators.

Microbially-accelerated consolidation of oil sands tailings. Pathway II: solid phase biogeochemistry

PubMed Central

Siddique, Tariq; Kuznetsov, Petr; Kuznetsova, Alsu; Li, Carmen; Young, Rozlyn; Arocena, Joselito M.; Foght, Julia M.

2014-01-01

Consolidation of clay particles in aqueous tailings suspensions is a major obstacle to effective management of oil sands tailings ponds in northern Alberta, Canada. We have observed that microorganisms indigenous to the tailings ponds accelerate consolidation of mature fine tailings (MFT) during active metabolism by using two biogeochemical pathways. In Pathway I, microbes alter porewater chemistry to indirectly increase consolidation of MFT. Here, we describe Pathway II comprising significant, direct and complementary biogeochemical reactions with MFT mineral surfaces. An anaerobic microbial community comprising Bacteria (predominantly Clostridiales, Synergistaceae, and Desulfobulbaceae) and Archaea (Methanolinea/Methanoregula and Methanosaeta) transformed FeIII minerals in MFT to amorphous FeII minerals during methanogenic metabolism of an added organic substrate. Synchrotron analyses suggested that ferrihydrite (5Fe2O3. 9H2O) and goethite (α-FeOOH) were the dominant FeIII minerals in MFT. The formation of amorphous iron sulfide (FeS) and possibly green rust entrapped and masked electronegative clay surfaces in amended MFT. Both Pathways I and II reduced the surface charge potential (repulsive forces) of the clay particles in MFT, which aided aggregation of clays and formation of networks of pores, as visualized using cryo-scanning electron microscopy (SEM). These reactions facilitated the egress of porewater from MFT and increased consolidation of tailings solids. These results have large-scale implications for management and reclamation of oil sands tailings ponds, a burgeoning environmental issue for the public and government regulators. PMID:24711806

Treating tar sands formations with karsted zones

DOEpatents

Vinegar, Harold J.; Karanikas, John Michael

2010-03-09

Methods for treating a tar sands formation are described herein. The tar sands formation may have one or more karsted zones. Methods may include providing heat from one or more heaters to one or more karsted zones of the tar sands formation to mobilize fluids in the formation. At least some of the mobilized fluids may be produced from the formation.

Behavior of plastic sand confinement grids

DOT National Transportation Integrated Search