Artificial Sediment Research Articles

Importance of Prey and Predator Feeding Behaviors for Trophic Transfer and Secondary Poisoning

Hydrophobic contaminants accumulate within aquatic sediments, hence pelagic predators may have limited direct contact with such compounds, but can be exposed via their benthic prey (i.e., via dietary exposure). Here we examine the importance of feeding behaviors of both prey (sediment ingesters or noningesters) and predators (piercers or engulfers) in determining the extent of dietary exposure and toxic effects. A freshwater macroinvertebrate system was used, consisting of two predator species, a piercer (Notonecta glauca) and an engulfer (Ischnura elegans), and three prey species, a sediment noningester (Cloëon dipterum) and two sediment ingesters (Asellus aquaticus, Chironomus riparius). Predators were fed prey previously exposed to artificial sediment dosed with 30 microg/g of 14C benzophenone. The piercer predator accumulated more benzophenone from sediment ingester compared to sediment noningester prey, whereas the engulfer predator accumulated a similar concentration for all three prey species. Toxic effects, in terms of reduced feeding rate, were only observed with the engulfer feeding on sediment noningesters, probably due to the interaction between the narcotic mode of action of benzophenone and predator hunting strategy. The importance of dietary exposure in risk assessments may therefore depend on exposure pathways of prey, feeding behaviors of predators, and the contaminant's toxic mode of action.

Influence of Sediment Grain Size on Elutriate Toxicity of Inorganic Nanomaterials

Abstract Knowledge concerning the ecotoxic effects of nanomaterials, chemical structures with novel properties owing to their small sizes (1 to 100 nm), is wanting and deserves to be documented more fully. In this study we conducted testing with the MARA (microbial array for risk assessment) assay-an 11 microbial species 96-well microplate toxicity test measuring growth inhibition-to determine the toxic potential of four metallic nanopowders (MNPs): copper zinc iron oxide, samarium (III) oxide, erbium (III) oxide, and holmium (III) oxide. MTC (microbial toxicity concentration) endpoint values showed a range of toxicity responses generated by individual strains that was MNP-specific. Cluster analysis undertaken with the (n = 11) MTC values of the four MNPs, reflecting a toxic fingerprint proper to each nanochemical, indicated that their modes of action may be different. Experiments were also conducted with an artificial sediment, composed of varying concentrations of silica sand and kaolin (fine particles < 0.004 mm), spiked with each MNP to assess the contribution of fine particles on the resulting elutriate toxicity. The latter was shown to increase as fines contents decreased, except for CuZnFeO where no particular trends were observed. Toxicity testing was then undertaken with each MNP spiked into natural Saint Lawrence River freshwater sediments displaying low, medium, and high fines contents. Once again, analogous results to those obtained with the artificial sediment experiments were observed for MNP elutriate toxicity. Overall, MARA bioassay data indicate that MNP toxicity can be modulated by sediment grain size and that resulting adverse effects on aquatic biota will in part depend on such sediment characteristics.

Oxygen release compound as a chemical treatment for nutrient rich estuary sediments and water

The objectives of this work were: (i) to evaluate the efficacy of Oxygen Release Compound (ORC®), oxygen providing agent that enhance the oxidation of organic matter in fresh water, marine water, and sediment; and (ii) to explore the potential aquatic toxicity that might be generated due to its use. A bench scale laboratory experiments were conducted using five different water sources (2 freshwater, 2 marine water and a deionised water). During the assay, flasks of 1 L capacity were dosed with artificial sediment and ORC® and kept at room temperature for 10 days. Temperature, pH, DO, UV254, TOC and Mg were periodically measured. The potential aquatic toxicity that might be generated as a by-product of ORC® use was performed. The experimental results reveal that ORC® is indeed effective in releasing oxygen over a long period of time and it is also effective for the remediation of natural waters enriched with organic matter. The toxicity test shows that ORC® treatment did not create any biological toxicity in freshwater samples (IC50 < 1 Toxicity Unit – TU). However, marine water samples reveal a high toxicity and had IC50 > 1 TU. The study proves that ORC® was an appropriate technology that can safely be used to treat natural waters enriched with nutrient and natural organic matter.

High‐frequency acoustic properties of water‐saturated sediments: Laboratory study.

This study was performed in controlled laboratory conditions using several broadband transducers to cover a wide frequency range from 200 kHz to 3MHz. Various types of sediments were used: natural medium and coarse sand, and glass beads with corresponding mean sizes. Sound speed and attenuation were measured and compared with predictions of Biot theory. The theory failed to predict both high attenuation and negative dispersion of sound speed observed at very high frequencies (above 500 kHz for medium sands), which can be assumed an effect of strong grain scattering. All the measurements were performed at different times to ensure the repeatability of the results. A comparison of results obtained for natural sands with those for artificial sediment (glass beads) of the same mean size, allowed observing the influence of the grain shape on the reflected and backscattered signals. Also, the influence of the transducer directivity diagram on the sediment reflectivity was observed. This effect is discussed and shown to be essential in the case of strong incoherent scattering observed for coarse sediments. Finally, the time‐frequency contents of the reflected signal were analyzed. It was found to be very sensitive to the granular structure of the sediment. [Work supported by CNRS and ONR.]

About this title - Sediment-Hosted Gas Hydrates: New Insights on Natural and Synthetic Systems

There is much interest in gas hydrates in relation to their potential role as an important driver for climate change and as a major new energy source; however, many questions remain, not least the size of the global hydrate budget. Much of the current uncertainty centres on how hydrates are physically stored in sediments at a range of scales. This volume details advances in our understanding of sediment-hosted hydrates, and contains papers covering a range of studies of real and artificial sediments containing both methane hydrates and CO 2 hydrates. The papers include an examination of the techniques used to locate, sample and characterize hydrates from natural, methane-rich systems, so as to understand them better. Other contributions consider the nature and stability of synthetic hydrates formed in the laboratory, which in turn improve our ability to make accurate predictive models.

Measurements of sound speed, attenuation, and normal-incidence reflection coefficient in water-saturated glass beads as a function of porosity.

Sound propagation in water‐saturated granular sediments is known to depend on the sediment porosity, but few data in the literature address both its frequency and porosity dependency. To address this deficiency, a method to control porosity [Argo et al. J. Acoust. Soc. Am. 124, 2469 (2008)] was used to prepare artificial sediments composed of water‐saturated glass spheres (130, 265, and 530 μm diameters) with porosities ranging from 0.37 to 0.43. Through‐transmission measurements were performed for frequencies from 250 to 800 kHz to determine the sound speed and attenuation. Pulse‐echo measurements for frequencies from 0.25 to 7.5 MHz were performed to determine the normal‐incidence reflection coefficient. For both classes of measurements, the Fourier phase technique was used to analyze the data. Measurement results will be presented and compared to existing models. A Biot‐based model was found to qualitatively describe the porosity dependence of the sound speed and attenuation, but a transition to a scattering‐dominated regime was observed. [Work supported by NSF, ONR, and the Welch Foundation.]

Short- and Long-Term Response of Deteriorating Brackish Marshes and Open-Water Ponds to Sediment Enhancement by Thin-Layer Dredge Disposal

Artificial sediment enhancement using a thin layer of dredged material has been suggested as a means to increase elevation and create soil conditions conducive to increased marsh structure and function in deteriorating marshes. Using a chronosequence approach, we examined the effects of sediment enhancement in deteriorating marsh and open-water pond habitats located in six brackish marshes. Sediment enhancement of both marsh and interior pond sites had significant, immediate, and long-lasting effects on physical soil properties and nutrient status with increased bulk density and inorganic nitrogen. Vegetative cover and productivity response were minimal for deteriorating vegetated marshes with the short-term response data showing no significant impact of sediment enhancement and long-term trends indicating decreasing productivity over time. In contrast, trajectory models of vegetative cover and productivity in interior pond sites showed increases over time indicating that, for restoration of interior ponds, sediment enhancement may prove valuable. The use of trajectory models emphasizes the need for long-term monitoring to determine restoration success of projects.

The role of sorption and bacteria in mercury partitioning and bioavailability in artificial sediments

This study compared the relative importance of three types of sorption (organic matter–particle, mercury–organic matter and mercury–particle) in controlling the overall mercury partitioning and bioavailability in sediments. We found that all three types of sorption were important for both inorganic mercury (Hg) and methylated mercury (MeHg). Mercury–particle sorption was more important than mercury–fulvic acid (FA) sorption in increasing the mercury concentrations with increasing aging. Bioavailability (quantified by gut juice extraction from sipunculans) was mainly controlled by mercury–particle sorption, while FA–particle and mercury–FA sorption were not as important, especially for MeHg. Bacterial activity also increased the partitioning of Hg or MeHg in the sediments and was further facilitated by the presence of organic matter. The bioavailability of Hg or MeHg from sediments was only slightly influenced by bacterial activity. This study highlights the importance of sorption from various sources (especially mercury–particle sorption) as well as bacteria in controlling the partitioning and bioavailability of Hg or MeHg in sediments.

Effect of solid to solution ratio on biogenic silica determination in coastal sediments

The method of DeMaster (1981) for measuring biogenic silica (BSi) in marine sediments was modified. We found a considerable effect of the solid to solution (S/S) ratio on BSi determination in coastal sediments. The BSi contents determined by DeMaster’s method were overestimated due to the contribution of clay mineral-derived extractable Si at a low S/S ratio ( 2 g l−1). For BSi analysis of coastal sediment samples, the BSi content of representative samples must be measured using various S/S ratios to determine the appropriate S/S ratio in order to minimize the contribution of extractable Si derived from clay minerals and to obtain sufficiently efficient extraction with 1% Na2CO3 before actual sample measurement. One way to determine the appropriate S/S ratio is to use artificial sediment which has a theoretical Si and clay mineral content similar to the sediment sample composition. Using artificial sediment, the S/S ratio of 2 g l−1 seems appropriate for measuring the BSi content of the coastal sediments investigated in this study, because 99.6% recovery can be achieved.

Laboratory measurements of sound speed and attenuation in water‐saturated artificial sediments as a function of porosity.

Several models have been proposed to describe the sound speed and attenuation of acoustic waves in water‐saturated granular sediments. The difference between the predictions of competing models can be only a few percent, and it is difficult to obtain both sufficient knowledge of the sediment physical parameters and sufficiently small measurement uncertainty to adequately verify competing models. Furthermore, the inhomogeneity of natural sediments causes additional measurement and interpretation uncertainty. Therefore, well‐controlled laboratory measurements are useful for model validation and also facilitate exploration of the effects of sediment physical parameter variation. A method for controlling the porosity of an ensemble of water‐saturated granular particles [Schroter et al., Phys. Rev. E 71, 030301(R) (2005)] was used to prepare columns of artificial sediments, composed of monodisperse 280‐μm‐diameter glass spheres and distilled water of varying porosity. Acoustic time‐of‐flight measurements were ...

Effects of aging and sediment composition on hexachlorobenzene desorption resistance compared to oral bioavailability in rats

Studies were conducted to assess the effects of black carbon, clay type and aging (1–1.5 yr) on desorption and bioavailability of hexachlorobenzene (HCB) in spiked artificial sediments. Tenax (a super sorbent)-mediated desorption was used to examine the effects of these parameters on the physicochemical availability of HCB. The Tenax-mediated desorption of HCB from the four aged artificial sediments exhibited biphasic kinetics. The fast desorbing fractions ranged from 64.8% to 22.3%, showing reductions of 4.0–18.9% compared with freshly-spiked sediments. Statistical analysis on the fast desorbing fractions showed that all three treatment effects (i.e., montmorillonite clay, black carbon content, and aging) were significant. Two sediments with higher black carbon content exhibited much greater aging effects (i.e., greater reduction in fast desorbing fraction) than the other two sediments without the addition of black carbon. For both freshly-spiked and aged sediments, the desorption resistant sediment-bound HCB (i.e., slow desorbing fraction) correlated reasonably well to previously reported rat fecal elimination of HCB, which is a measure of the non-bioavailable fraction of sediment-bound HCB. A similar correlation was also observed between fast desorbing fraction and previously reported accumulation of HCB in the rat body (carcass + skin). These observations suggest that physicochemical availability, as defined by the desorption of HCB from sediments, provides a reasonable prediction of the oral bioavailability of sediment-bound HCB to rats. These results showed that montmorillonite clay, black carbon and aging reduced physicochemical availability and ultimately bioavailability of sediment-bound HCB.

Deltamethrin toxicity to the midge Chironomus riparius Meigen—Effects of exposure scenario and sediment quality

We investigated how exposure scenario and sediment characteristics affected deltamethrin bioavailability and toxicity to Chironomus riparius. We designed whole-sediment experiments, including separate spiked-water and spiked-sediment experiments and using both a peat-based artificial and a natural sediment. Deltamethrin was highly toxic to larvae in artificial sediments, with LC 50-values (28 d) of 11 μg/kg for sediment-exposures and 16 pg/L for water-exposures. In contrast, deltamethrin-induced mortality was absent in experiments with natural sediment, both in spiked water and in spiked sediment. This was attributed to the higher organic matter content of the natural sediment, 12.5±0.05%, compared with that in the artificial sediments, 4.1–4.8%, resulting in an efficient and fast sorption and lower bioavailability. Deltamethrin degradation was absent in artificial sediment, while in natural sediment, 50% degraded during 10 days of test-vessel acclimation. Despite a faster degradation, the highest measured concentration in spiked-natural sediment was more than seven times higher than the LC 50-value obtained in tests with spiked-artificial sediment, indicating that low bioavailability, and not compound degradation, was the main reason for the observed lack of deltamethrin toxicity.

Methylmercury extraction from artificial sediments by the gut juice of the sipunculan, Sipunculus nudus

Artificially prepared sediments were used to investigate their binding with methylmercury (MeHg). The bioavailability of sediment-bound MeHg then was quantified by measuring the extraction by gut juice of the sipunculan Sipunculus nudus, as well as by different free amino acids and bovine serum albumin (BSA). Methylmercury distribution in different molecular weight- size fractions of gut juice also was determined using an ultrafiltration methodology. Organic and clay content were the two most important sediment components in MeHg partitioning, but most of the sediment-bound MeHg was complexed by organic matter (fulvic acid > humic acid) in sediments. Treatment with humic or fulvic acid generally increased the amount of bioavailable MeHg. Cysteine was more important than other amino acids in MeHg extraction. Proteins (especially >100 kDa fraction) in gut juice rather than free amino acids were the main agents in gut juice that extracted MeHg from sediments. Most extracted MeHg from artificial sediments was associated with the >100 kDa fraction (probably proteins) of gut juice but not with organic matter from sediments (humic acid and fulvic acid). Our results suggested that competition among different agents in gut juice (especially the large molecular-weight proteins) and the organic content of the sediments controlled the bioavailability of sediment-bound MeHg.

Influence of the biomass content in sediment on the sediment nutrient flux for a pulsed organic load

A laboratory study was carried out to investigate the influence of the biomass content in the sediment on the rate of diagenesis of particulate organic materials (POM) and the consequent sediment oxygen demand (SOD) and nutrient fluxes. Fish food pellets were loaded into the sediment to simulate a sudden POM input. Three types of sediments with different biomass contents were tested, including a raw marine sediment, the marine sediment after one month of cultivation and an artificial sediment of sand and clay without any biomass. There was little difference in organic flux from the three different sediments. However, compared to the artificial sediment, the marine sediments had much higher SOD and ammonia flux. A mathematical model also has been developed for the SOD dynamics and nutrient fluxes. Both the experimental and simulation results indicate the important role of the biomass in the sediment in POM diagenesis, SOD and nutrient fluxes.

円盤状堆積層試料を用いた圧密・浸透連成試験によるメタンハイドレート堆積層における絶対浸透率の定式化―メタンハイドレート貯留層の浸透率評価に関する研究（第５報）―

Methane hydrate (MH) is one of the potential natural gas resources in near future, because it exists in marine sediments or in permafrost regions worldwide. To evaluate the productivity of methane gas from MH reservoirs, it is necessary to develop a gas production simulator for doing case studies.In this study, for the purpose of numerical simulation on MH dissociation process, we carried out an experimental study for estimating permeability of a MH reservoir with compaction of the sediments due to decrease of effective stress in pore space. In actual hydrate fields, it is supposed that vertical consolidation of sediments occurs whereas gas and water flow in a horizontal direction. To reproduce such a situation, we attempted to measure the permeability of artificial MH sediment under the horizontal radial flow condition by using a specially designed apparatus.First, we investigated the relationship between absolute permeability and MH saturation in this radial flow system. When MH saturation increased from 0 to 0.30, permeability decreased from 12.0μm2 to 1.19μm2 that was one 12th of the value of sand matrix without any MH formation. The same tendency of permeability changes was obtained in liner flow system as previously reported, so the measuring technique of permeability by using radial flow system has been established.Second, by using the similar apparatus, compaction-permeability tests were conducted to formulate absolute permeability as a function of porosity and MH saturation. From experimental results, it was found that permeability decrease due to consolidation was remarkable in the cases of small sand grain diameter and large initial porosity. We determined the parameters of permeability reduction factor for porosity through a numerical analysis, and derived the final form of absolute permeability equation for MH reservoirs.

CHARACTERISTICS OF SEDIMENT DISCHARGE AND SEDIMENT TRANSPORT ON BARS

Sediment control along river is very important for river management. These days, countermeasures to deal with rotational degradation, e. g. placing sand at the downstream of the dam, have been taken in some rivers in order to restore the continuity of sand interrupted by dam. To indicate significance of artificial sediment supply in river, we need know where supplied sediment deposit, how sediment supply let river morphology change, and so on. Therefore, we focus on the sediment transport on the bars which is typical landscape of river. We took the experiments to estimate sediment discharge on the bar and to indicate differences between sediment transport on the bars and on the flat bed. As results, characteristics of sediment discharge and sediment transport on the bars are shown.

Erosion Generated by Wave-Induced Currents in the Vicinity of a Jetty: Case Study of the Relationship between the Adour River Mouth and Anglet Beach, France

Abstract Anglet beach, located in the south of the French Atlantic coast, has been experiencing severe erosion for several decades, whereas recurrent dredging has been necessary to fight against the shoaling of the mouth of the Adour River. The channel entrance is protected from the very energetic wave climate by a main jetty, the effect of which on the system appears to be crucial. In this paper, we study the relationship between the two systems in terms of sedimentary exchanges. First, we determine the time history of volume of subtidal beach sand with a bathymetry dataset spanning 24 years. This analysis highlights continuous and large erosion affecting the subtidal part of Anglet beach. This phenomenon had been masked until 1990 thanks to dredged sand releases. However, after that date, the drastic reduction of artificial sediment intakes led to a drop in the sand volume. Numerical modeling is used to study the flow pattern around the mouth of the river. Different wave scenarios are simulated with the...

Exposure of Chironomus riparius larvae to uranium: Effects on survival, development time, growth, and mouthpart deformities

Among non-biologically essential metals, data concerning uranium effects on freshwater benthic macroinvertebrates are scarce. The effects of uranium on survival, development time, growth and mouthpart deformities of midge Chironomus riparius were investigated. A 10-day static laboratory bioassay was performed exposing first instar larvae to artificial sediment spiked with four concentrations of uranium (2.97; 6.07; 11.44; 23.84 μg U g −1 dry wt). As uranium was released from the sediment to the overlying water during this bioassay, both the sediment and the water column act as contamination pathways in giving rise to the observed effects. Significant negative effects on survival, development time, and growth were detected at 6.07, 6.07 and 2.97 μg U g −1 dry wt, respectively. An LC20 of 2.49 μg U g −1 dry wt (95% CI = 1.48–4.27), and an LC50 of 5.30 μg U g −1 dry wt (95% CI = 3.94–7.25) were estimated. With respect to effects of uranium on larvae mouthpart deformities, we found that the lower the concentrations, the higher the deformity rates. These results highlight the potential impact of uranium at population level in environmentally realistic concentrations.

Effects of black carbon and montmorillonite clay on multiphasic hexachlorobenzene desorption from sediments

The desorption kinetics of hexachlorobenzene (HCB) in four freshly spiked artificial sediments were determined using a polymeric adsorbent Tenax-mediated desorption. The sediments included a standard sediment (SS) prepared as per Organisation for Economic Cooperation and Development 218 guidelines and three derived artificial sediments prepared by supplementing the SS sediment with various levels of black carbon (lamp black soot) and/or montmorillonite clay. The desorption kinetics exhibited biphasic behavior, i.e., a fast desorbing fraction followed by a slow desorbing fraction. The addition of either lamp black soot or montmorillonite clay resulted in the reduction of the fast desorbing fraction ( F fast) of HCB in three derived sediments compared with SS sediment. Both black carbon and montmorillonite clay treatment effects on the fast desorbing fraction were statistically significant for the four artificial sediments. The black carbon treatment (i.e., addition of 0.5% wt/wt lamp black soot) effect was an average reduction of F fast by approximately 11%, whereas the montmorillonite treatment (i.e., addition of 15% wt/wt montmorillonite clay) effect was an average reduction of F fast by approximately 17%. The presence of soot black carbon particles reduced the desorption rate of HCB in sediments since black carbon exhibits very high sorption capacity and extremely slow diffusion rate compared with those of the natural organic matter in sediment.

Experimental effects of surfactants on the production of stromatactis-shaped cavities in artificial carbonate sediments

Experimental effects of surfactants on the production of stromatactis-shaped cavities in artificial carbonate sediments