Synthetic Sediment Research Articles

Sonolysis of synthetic sediment particles: particle characteristics affecting particle dissolution and size reduction

The effect of ultrasound on particle shape and surface structure was explored to understand particle characteristics affecting contaminant desorption and destruction from sediment particles. Compared to only hydrodynamic mixing, in the presence of an ultrasonic probe, operating at 20 kHz with a power density of 460 Wl-1, sonication decreased the particle size of alumina and silica particles following a first-order regime. In addition, the dissolution of particles during sonication is 7-20 times higher than that of non-sonicated solutions. However, the decrease of particle size was not totally explained by dissolution. Scanning electron microscopy studies showed that the surface of particles both became smoothed and pitted as a result of sonication. Therefore, it seems that multiple mechanisms are occurring simultaneously; microstreaming acts to smooth particle surfaces and dissolve particles and shockwaves and microjets imploding on the particle surfaces both shear and pit the surface of the particles. The sonication of humic acid laden particles resulted in a similar decreasing trend. However, the existence of humic acid increased the complexity of the system.

Partitioning and bioaccumulation of cadmium in artificial sediment systems: application of a stable isotope tracer technique

The utility of stable isotope tracers for investigating the relationship between cadmium (Cd) partitioning in artificial sediment-water systems and Cd accumulation in a benthic detritivore (Asellus racovitzai, Isopoda) was explored. In the laboratory, Cd isotopes were applied to synthetic sediment and isotope concentrations were measured in sediment, overlying water and exposed asellids over a 10-day period. Isotope ratios measured in sediment and water were compared to ratios measured in asellids to determine whether Cd partitioning could predict metal bioaccumulation. Two different parameters which might affect Cd partitioning between the sediment and overlying water compartments were investigated: the chemical form in which Cd was added to systems, and the organic matter content of the sediment. To test the effect of chemical form on Cd partitioning, three isotopes of cadmium were individually applied to formulated sediment in varying combinations of 113Cd(NO3)2, 112Cd-humic acid (HA) 114CdSO4. The results demonstrated that chemical form did not influence partitioning, as the Cd isotope that was applied to sediment in the nitrate form exhibited similar partitioning between sediment and overlying water as the isotope that was applied in the sulfate or HA form. However, Cd isotope concentrations in overlying water were strongly related to the pattern of isotope accumulation in asellids suggesting that overlying water concentrations determined Cd bioaccumulation. In contrast, when the organic matter content of sediment was increased through the addition of Sphagnum peat moss, total Cd concentrations in overlying water and tissue were low, and there was no relationship between Cd-isotope concentrations in tissue and water. These results indicate that Cd accumulation occurred primarily from water, and factors that increase metal partitioning to sediment, such as increased sediment organic matter content, decrease Cd accumulation in asellids. The stable isotope tracer method described herein appears to be a useful technique for investigating the relationship between metal partitioning and bioaccumulation in simple sediment systems, but could also be extended to more complex systems, and used with different metals that have multiple stable isotopes.

Sonochemical Desorption and Destruction of 4-Chlorobiphenyl from Synthetic Sediments

The application of ultrasound for the treatment of polychlorinated biphenyl (PCB) contaminated sediments was explored in this study with a model system of 4-chlorobiphenyl (4-CB) and synthetic sediments. In the presence of an ultrasonic probe, operating at 20 kHz with a power density of 460 W L(-1), more than 90% of 4-CB in aqueous homogeneous solution was destroyed after 20 min, with an apparent first-order rate constant, k, of 0.120 min(-1). In addition, experiments investigating the destruction of dissolved 4-CB in the presence of bare silica or alumina particles or dissolved humic acid (HA) had lower degradation rates than in aqueous homogeneous solutions. Increasing the bare particle concentration or dissolved HA concentration further lowered the degradation rate. However, in investigating the desorption and destruction of sorbed 4-CB from humic acid laden alumina particles, the effect of particles and released dissolved HA on the degradation rate are simply additive, and desorption of 4-CB does not appear to further complicate the system. A kinetic analysis of the system revealed that desorption of 4-CB from particles was not a limiting factor in this system.

The removal of heavy metals from contaminated soil by a combination of sulfidisation and flotation

The possibility of removing cadmium, copper, lead and zinc from Belgian loamy soil by a combination of sulfidisation pre-treatment and Denver flotation was investigated. The potentially available--sulfide convertible--metal content of the metal polluted soil was estimated by EDTA (0.1 M, pH 4.65) extraction and BCR sequential extraction. EDTA extraction is better at approximating the metal percentage that is expected to be convertible into a metal sulfide phase, in contrast to the sequential extraction procedure of 'Int. J. Environ. Anal. Chem. 51 (1993) pp. 135-151' in which transition metals present as iron oxide co-precipitates are dissolved by hydroxylammoniumchloride in the second extraction step. To compare the surface characteristics of metal sulfides formed by sulfidisation with those of crystalline metal sulfides, two types of synthetic sediments were prepared and extracted with 0.1 M EDTA (pH 4.65) in anoxic conditions. Separate metal sulfides or co-precipitates with iron sulfide were formed by sulfide conditioning. The Denver flotation of both types of synthetic sediments (kerosene as collector at high background electrolyte concentrations) resulted in similar concentrating factors for freshly formed metal sulfides as for fine-grained crystalline metal sulfides. The selective flotation of metal sulfides after sulfide conditioning of a polluted soil, using kerosene or potassium ethyl xanthate as collectors and MIBC as frother, was studied at high background electrolyte concentrations. The sulfidisations were made in ambient air and inside an anoxic glove box. The concentrating factors corrected by the potentially available metal percentage, determined by 0.1 M EDTA extraction, lie between 2 and 3. The selective flotation of these finely dispersed, amorphous, metal sulfides can possibly be improved by optimising the bubble-particle interaction.

Modelling reservoir sedimentation and estimating historical deposition rates using a data-based mechanistic (DBM) approach

The data-based mechanistic (DBM) modelling methodology is applied to the study of reservoir sedimentation. A lumped-parameter, discrete-time model has been developed which directly relates rainfall to suspended sediment load (SSL) at the reservoir outflow from the two years of measured data at Wyresdale Park Reservoir (Lancashire, UK). This nonlinear DBM model comprises two components: a rainfall to SSL model and a second model, relating the SSL at the reservoir inflow to the SSL at the reservoir spillway. Using a daily measured rainfall series as the input, this model is used to reconstruct daily deposition rates between 1911 and 1996. This synthetic sediment accretion sequence is compared with the variations in sand content within sediment cores collected from the reservoir floor. These profiles show good general agreement, reflecting the importance of low reoccurrence, high magnitude events. This preliminary study highlights the potential of this DBM approach, which could be readily applied to other sites.

NMR Imaging Study of Hydrates in Sediments

Abstract: In this study, hydrates were generated in synthetic sediments in a laboratory cell. After hydrate formation took place and the sediment solidified, the samples were investigated both visually and by the use of nuclear magnetic resonance (NMR) imaging. The hydrates in this initial study were formed from model systems at low pressure. The results show hydrates distribution effects. Scans in the NMR apparatus were also made of the unfrozen samples to serve as a basis for comparison. NMR here maps the mobility of hydrogen atoms and their distribution in a sample. The relevant factor is the density of mobile H‐atoms, and this is shown to be about five times smaller for a volume of (for example) tetrahydrofuran (THF, C4H8O) hydrate than for the fluids of water and/or THF. This correlates very well with an observed signal decrease by a factor of six in an NMR‐studied sample after hydrate formation had taken place.

FUNDAMENTAL EXAMINATION ON THE SYNTHETIC SEDIMENT ROUTING MODEL IN A WHOLE RIVER SYSTEM

It is required to develop an appropriate sediment routing model for describing behavior of sedimentation in a whole river system. This research deals with a synthetic sediment routing model based on DEM (Digital Elevation Models). This kind of model has several subjects to be examined from the viewpoints on model construction such as computational time interval, tuning hydraulic parameters, effects of computational mesh scale on the results, pseudo channel network made from DEM and so on. Authors have hitherto been examined some of the subjects mentioned above in the mountainous Hayakawa River basin (509km2). In order to apply the model to larger river basin, the Fujikawa River basin (3, 571km2), a new method of automatical tracing of the channel network is adopted. In this paper, difference of channel networks between the conventional method and the new one is examined, and reasonable way of smoothing river bed as an initial situation is searched. The results of some cases of simulation on sedimentation in the basin is also discussed.

Detecting sub‐wavelength layers and interfaces in synthetic sediments using seismic wave transmission

The interface between two different homogeneous sediment layers, each composed of uniform grain sizes, is a region of heterogeneity comprising a thin layer with a thickness typically much smaller than a seismic wavelength. Seismic waves propagating parallel to the interface experience a reduction in both their amplitude and frequency content but the effect on group velocity is unresolvable. In the case of a single homogeneous layer bounded on both sides by homogeneous halfspaces, the ability to spatially resolve the layer thickness from amplitude or frequency information is limited by diffraction when the layer thickness is smaller than a seismic wavelength. However, the presence of a subwavelength interface or layer is always marked by a decrease in amplitude and in some cases by a decrease in frequency.

STUDY ON DEVELOPMENT OF THE SEDIMENT ROUTING MODEL BASED ON THE DIGITAL ELEVATION MAP

In order to assess the sediment transport in a whole water system, a synthetic sediment routing model based on the river channel networks obtained from the digital elevation map was examined. The sediment routing model was applied to the Haya River basin and the Abe River basin. Through the application using two kinds of scale of channel network element, and the diffelent catchment area, effects of these elements on the simulation of river bed variation were discussed. The results show that the river bed variation in the two kinds of scale, 250m mesh and 500m mesh, shows about the same behavior except upper part of the basin, and themodel has a possibility to be applicable.

Acoustic monitoring of sediment‐pore fluid interaction

Acoustic and chemical measurements were made on water‐saturated synthetic sediments undergoing diagenesis from uncompacted glass beads into a cemented glass bead, sandstone‐like material. The sediment‐water interaction was investigated as a function of time by monitoring the acoustic properties, water electrical conductivity, pH, and ion concentration. A reduction in the transmitted acoustic wave amplitude was correlated with a decrease in the total number of ions in the pore water. The lowest acoustic wave amplitude occurred when the ionic strength in the pore water had reached a minimum value. Calculation of the electrostatic potential showed that the force of repulsion between beads was strongest when the acoustic wave amplitude was at its minimum and the double layer electrostatic interaction potential between the beads was at a maximum value. At longer times the acoustic wave velocity of the transmitted wave increased as the cementation progressed. These results suggest that the chemical interaction between the pore fluid and grain alters the strength or stiffness of grain‐to‐grain contacts, which in turn alters the elastic modulus of the sediment frame. The important implications of this work are the potential use of acoustic or seismic techniques to monitor ion exchange between pore‐fluids and sediments in‐situ.

Multicomponent Analysis of FTIR Spectra: Quantification of Amorphous and Crystallized Mineral Phases in Synthetic and Natural Sediments

Multicomponent Analysis of FTIR Spectra: Quantification of Amorphous and Crystallized Mineral Phases in Synthetic and Natural Sediments

Toxicity and bioaccumulation of a mixture of heavy metals in Chironomus tentans (Diptera: Chironomidae) in synthetic sediment

Abstract This research investigated toxicity and bioaccumulation of a mixture of Cd, Cu, Pb, and Zn in Chironomus tentans in synthetic sediment, and compared predicted to measured steady-state bioaccumulation factors (BAFs). In a toxicity test, C. tentans were exposed to various dilutions of a base concentration (1.0 X) of a mixture of the four metals (5 μg/g Cd, 10 μg/g Cu, 70 μg/g Pb, and 300 μg/g Zn) in synthetic sediment. Mortality ranged from 17 to 100%. To measure bioaccumulation of the metals, C. tentans were exposed to 0.35 × the base concentration for a period of up to 14 d in two uptake tests. Bioaccumulation of all four metals increased over the 14-d uptake phases. Concentrations of metals in chironomids were significantly correlated with exposure time in the uptake phases. Only concentrations of copper approached background levels after 7 d depuration. Uptake rate coefficients and elimination rate constants were determined for each metal. Bioaccumulation factors were highest for Cd and lowest for Pb. With the exception of Pb, steady-state BAFs were within a factor of about two of those calculated using the first-order kinetic model. The high BAFs calculated may indicate greater bioavailability in synthetic sediment. Studies comparing toxicity and bioaccumulation of natural and synthetic sediments are necessary before the use of synthetic sediments is widely adopted.

Identification and interpretation of complexity in sedimentation velocity boundaries

Synthetic sedimentation velocity boundaries were generated using finite-element solutions to the original and modified forms of the Lamm equation. Situations modeled included ideal single- and multicomponent samples, concentration-dependent samples, noninteracting multicomponent samples, and reversibly self-associating samples. Synthetic boundaries subsequently were analyzed using the method of van Holde and Weischet, and results were compared against known input parameters. Results indicate that this analytical method provides rigorous diagnostics for virtually every type of sample complexity encountered experimentally. Accordingly, both the power and utility of sedimentation velocity experiments have been significantly expanded.

Scattering from a bubble in a saturated sediment

The breathing mode for a gas-filled, spherical cavity in a saturated, poroelastic sediment is investigated. The analysis entails the scattering of an incident displacement field that preferentially excites the monopole resonance of the cavity. The main result demonstrates that a gas-filled, spherical cavity in a saturated poroelastic medium exhibits two distinct breathing mode resonances. These resonances arise from the two distinct longitudinal modes of propagation in saturated poroelastic medium as described by Biot’s theory. Preliminary results from laboratory measurements involving a synthetic sediment will be presented. The experiments utilize spherical glass beads (250–300 μm) saturated with an immersion fluid whose optical index of refraction matches the corresponding index for the glass. [Work supported by ONR.]

On Propagation Characteristics of River Bed Variation due to Large Scale Sediment Yield

This study deals with the effects of the sediment yield on topography of stream or river channels. In this paper, the result of study on propagation characteristics of river bed variation due to large scale sediment yield by using a synthetic sediment routine model in a mountainous river system is presented. After validating the model using the field measurement data, the result of some sets of computer simulations of river bed variation in the conditions of idealized severe sediment yields were carried out. The effects of various conditions of the simulations such as treatment of debris flow and location of observation point, and tendencies of river bed variation are discussed.

Microbial Bioassays to Assess the Toxicity of Solid-Associated Contaminants

Due to the effects that sediment or soil matrices have on the bioavailability of compounds, it has been difficult to screen toxicity of solid-associated contaminants. The majority of microbial assays for testing toxicity of soils and sediments have been performed on water or solvent extracts. These procedures lead to a fractionation of the toxicity, which may underestimate or overestimate exposure routes and consequently potential adverse environmental effects. Recently, a solid-phase Microtox assay which eliminates the need for soil extracts and utilizes whole sediments or soils has been developed. This report describes a toxicity testing procedure using the inhibition of dehydrogenase enzyme activity of Bacillus cereus as test parameter. Studies with soil samples and a synthetic sediment spiked with organic contaminants and copper indicate the higher sensitivity of both solid-phase bioassays compared to water extract testing. A comparison of the results demonstrates that the B. cereus contact test is more sensitive for copper than the Photobacterium phosphoreum solid-phase test.

Comment [on “Shallow magnetic inclinations in the Cretaceous Valle Group, Baja California: Remagnetization, compaction, or terrane translation?” by Douglas P. Smith and Cathy J. Busby

TectonicsVolume 14, Issue 1 p. 218-219 Free Access Comment [on “Shallow magnetic inclinations in the Cretaceous Valle Group, Baja California: Remagnetization, compaction, or terrane translation?” by Douglas P. Smith and Cathy J. Busby] Robert F. Butler, Robert F. ButlerSearch for more papers by this authorWilliam R. Dickinson, William R. DickinsonSearch for more papers by this author Robert F. Butler, Robert F. ButlerSearch for more papers by this authorWilliam R. Dickinson, William R. DickinsonSearch for more papers by this author First published: February 1995 https://doi.org/10.1029/94TC02023Citations: 4AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. References Denham, C. R., A. D. Chave, Detrital remanent magnetization: Viscosity theory of the lock-in zone, J. Geophys. Res., 87, 7126– 7130, 1982. Gordon, R. G., Test for bias in paleomagnetically determined paleolatitudes from Pacific plate Deep Sea Drilling Project sediments, J. Geophys. Res., 95, 8397– 8404, 1990. Irving, E., A. Major, Post-depositional detrital remanent magnetization in a synthetic sediment, Sedimentology, 3, 135– 143, 1964. McFadden, P. L., A. B. Reid, Analysis of palaeomagnetic inclination data, Geophys. J. R. Astron. Soc., 69, 307– 319, 1982. Smith, D. P., C. J. Busby, Shallow magnetic inclinations in the Cretaceous Valle Group, Baja California: Remagnetization, compaction, or terrane translation?, Tectonics, 12, 1258– 1266, 1993. Tarduno, J. A., Absolute inclination values from deep-sea sediments: A reexamination of the Cretaceous Pacific record, Geophys. Res. Lett., 17, 101– 104, 1990. Verosub, K. L., Depositional and postdepositional processes in the magnetization of sediments, Rev. Geophys., 15, 129– 143, 1977. Citing Literature Volume14, Issue1February 1995Pages 218-219 ReferencesRelatedInformation

Examination of Direct Counting Methods for Bacteria in Lake Sediment by Epifluorescence Microscopy.

Direct counting of bacteria in lake sediments by epifluorescence microscopy was examined. To evaluate the counting efficiency we prepared synthetic sediment samples of known bacterial density. In the case of acridine orange (AO) staining, it was impossible to estimate bacterial numbers accurately owing to the difficulty of discriminating bacterial cells from abiotic particles in the samples. However, staining with 4' 6-diamidio-2-phenylindole (DAPI) gave satisfactory results, i.e., recovery of the bacterial counts was more than 93% ; the best efficiency was obtained at the final concentration of the dye of 1.0 μg⋅m1-1. Treatment by ultra sonication with pyrophosphate addition (10 mM) was effective to deflocculate and disperse the bacteria attached to sediment particles. The level of dilution of sediment samples used to prepare microscopic slides was shown to be important to obtain accurate counts. Optimal dilution level should be decided to reduce masking by sediment particles and, in turn, to assure a statistically satisfactory number of bacteria in an optical field. However, the optimum level was variable among samples which had different sediment textures (e.g. water content, particle size, detritus forms and volume) and bacterial density.Vertical profiles of bacterial density in Lake Suwa sediment were compared by the direct counting and plate viable counting. Total bacterial counts were 2.94 × 1010 cells⋅g dw-1 and 3.74 × 109 cells⋅g dw-1 at 0-3 cm and 45-50 cm respectively, and these counts were 600 and 1, 500 times higher than those obtained by the plate method. The size distributions of bacteria at 0-3 cm and 45-50 cm, which were measured using an image analysis system, were concentrated in the range of 0.2 to 0.8 μm, whereas the mode of cell length was 0.46 and 0.39 μm at 0-3 cm and 45-50 cm respectively. At 0-3 cm larger cells existed and the distribution at both depths was significantly different. The relationships of bacterial numbers, size distribution and organic carbon contents in sediment are discussed.

Magnetic anisotropy, scanning electron microscopy, and X ray pole figure goniometry study of inclination shallowing in a compacting clay‐rich sediment

Anisotropy of anhysteretic remanence (AAR), scanning electron microscopy (SEM), and X ray pole figure goniometry studies of clay‐rich sediments were conducted to delineate the interactions between magnetite and clay particles which cause inclination shallowing during compaction. These studies used synthetic sediments composed of kaolinite or illite and two grain sizes of magnetite, 0.45 μm and 2–3 μm. Natural marine sediments which contained 40–50% clay were also used. The sediments were compacted by pressures as high as 0.157 MPa. The sediments' porosity decrease suggests that the compaction experiments model burial depths up to 400–500 m. The main result of this study is that inclination shallowing and void ratio versus pressure curves show two points where behavior changes. A rapid decrease in inclination and void ratio occurs up to a pressure of 0.02 MPa. This is accompanied by a magnetic intensity decrease of 20–30%. Compaction at pressures between 0.02 MPa and 0.05 MPa causes a further decrease in these parameters at moderate rates, while compaction at pressures above 0.05 MPa causes very little change. Percent magnetic anisotropy and X ray pole figure intensity ratio versus pressure curves show only one point where behavior changes at 0.05 MPa with a rapid increase at lower pressures and little change at higher pressures. A model to explain this behavior, based on the SEM observations as well as the magnetic anisotropy, pole figure, and inclination data, suggests that compaction up to 0.02 MPa causes a decrease in pore volume with little reorientation of clay particles. Some magnetic particles are firmly attached to clay particles, whereas other loosely attached particles are either randomized or subvertical ones are preferentially disturbed causing inclination shallowing and an intensity decrease. At pressures between 0.02 MPa and 0.05 MPa, magnetite particles have become firmly attached to clay particles and start to follow the reorientation of clay particles as the clay fabric develops. At 0.05 MPa there is a major change in the clay microstructure with a horizontal fabric becoming evident. Compaction at higher pressures causes little further volume loss and clay particle reorientation and hence little additional inclination shallowing. The randomization/disturbance process suggested by this model causes slightly more than half of the inclination shallowing observed in the samples studied, whereas magnetite‐clay attachment causes the remainder of the inclination decrease.

Sediment Deposition in Storage Tanks

The use of storage tanks in sewerage systems has increased in recent years. The primary functions of such tanks are to attenuate flow and to retain pollutants within the sewer system. The size of the required storage volume is dependent on the purpose for which the tank is to be used but the end product of any design analysis is the definition of fixed volume of storage which has to be included as part of the sewerage system. The main problem is to provide storage and effective separation of gross and suspended solids without incurring poor self cleansing and associated high maintenance costs. The work outlined in this paper involved the development of a laboratory computer controlled monitoring system for the purpose of flow visualisation and for the comparative assessment of the sediment deposition and removal performance of different geometric configurations of storage tank. These systems used sophisticated control procedures and the latter had the facility to generate a flow hydrograph of any shape and duration and to superimpose on this hydrograph a pollutograph of synthetic sediment, in this case crushed olive stone wood flour. Particular attention was focused on the optimum length to breadth ratio for a given storage volume, the configuration of the chamber floor - number, shape and gradient of dry weather flow channels and benching (gradient; the type of roof support and the effect of multiple storms on the redistribution of deposited sediment. The results of the work illustrated that very complex flow patterns were established within the storage tanks as the flow hydrograph was discharged through the system and that these flow patterns governed the sediment settlement, re-entrainment and transport processes in the tank. The velocity distribution within each chamber was a function of tank geometry, the shape, volume, and duration of the inflow hydrograph and the throughflow setting. The paper is concluded by a series of recommendations to aid the design of storage tanks.