Artificial Sediment Research Articles

Remarked morphological change in a large tidal inlet with low sediment-supply

Sediment transport within small tidal inlets is sensitive to natural processes, whilst large tidal inlets are relatively robust systems because of their large tidal prism. However, remarked morphological changes may be initiated even under the condition of low sediment supply, as illustrated by Jiaozhou Bay, a large coastal embayment on the Shandong Peninsula, eastern China. Jiaozhou Bay is characterized by its relatively slow rate of natural change, and while the embayment has a flood-dominated entrance channel and muddy seabed, the suspended sediment concentration is generally low due to the lack of abundant source material. Observations of sediment dynamics show that net suspended sediment transport is directed towards outside of the bay, with an order of magnitude of 103t during a tidal cycle. The export of sediment associated with this flood-dominated environment implies that the net transport pattern is controlled by tidal exchange processes rather than the strength of the seabed shear stress. Sediment budget calculations show that supply of artificial sediment into the bay can account for up to 72% of the total input, which is in agreement with the 210Pb and 137Cs radioisotope geochronologies, and this leads to accumulation rates of 100–101mmyr−1; without this, the deposition rate would be low under natural conditions. The flood tidal delta area is also influenced by the input of anthropogenic material, and acts as a depocenter with relatively high accumulation rates. Furthermore, although the inlet system has not yet reached its equilibrium state (i.e., the entrance cross-sectional area is still larger than the equilibrium cross-sectional area), land reclamation activities have resulted in a rapid reduction of the embayment area (by 37%) over the last 80 years. Our findings indicate that the rapid changes observed in the tidal basin area and seabed morphology are mainly the result of human activity rather than natural processes.

Development of a reference artificial sediment for chemical testing adapted to the MELA sediment contact assay

Most persistent organic pollutants, due to their hydrophobic properties, accumulate in aquatic sediments and represent a high risk for sediment quality. To assess the toxicity of hydrophobic pollutants, a novel approach was recently proposed as an alternative to replace, refine and reduce animal experimentation: the medaka embryo-larval sediment contact assay (MELAc). This assay is performed with Japanese medaka embryos incubated on a natural sediment spiked with the compound being tested. With the aim of improving this assay, our study developed a reference exposure protocol with an artificial sediment specifically designed to limit natural sediment composition uncertainties and preparation variability. The optimum composition of the new artificial sediment was tested using a model polycyclic aromatic hydrocarbon (PAH), fluoranthene. The sediment was then validated with two other model PAHs, benz[a]anthracene and benzo[a]pyrene. Various developmental end points were recorded, including survival, embryonic heartbeat, hatching delay, hatching success, larval biometry and abnormalities. The final artificial sediment composition was set at 2.5 % dry weight (dw) Sphagnum peat, 5 % dw kaolin clay and 92.5 % dw silica of 0.2- to 0.5-mm grain size. In contrast with natural sediments, the chemical components of this artificial matrix are fully defined and readily identifiable. It is totally safe for fish embryos and presents relatively high sorption capacities for hydrophobic compounds. Studies with other hydrophobic and metallic contaminants and mixtures should be performed to further validate this artificial sediment.

Bioavailability of copper in contaminated sediments assessed by a DGT approach and the uptake of copper by the aquatic plant Myriophyllum aquaticum

The assessment of the potentially harmful effects of metals on biota depends on the speciation and bioavailability of the metals. In the present study, the authors investigated Cu accumulation and toxicity in the aquatic plant Myriophyllum aquaticum after exposure to artificial sediments varying in peat or ferric hydroxide content and spiked with Cu (5-200 mg kg(-1)). Modeling of the kinetic diffusive gradient in thin film (DGT) measurements revealed fast and slow Cu resupply from the solid phase for sediment formulated with and without peat, respectively. Myriophyllum aquaticum proved to be sensitive to Cu, as the Cu accumulation and growth differed depending on the sediment composition and Cu concentration. Comparing the Cu accumulation in M. aquaticum with total dissolved concentration, free concentration, and concentration in solution derived from DGT measurements (CDGT), Cu concentrations revealed that CDGT concentrations were a better predictor of accumulation than the others. However, the relatively weak correlation observed (r(2) = 0.6) and the fact that plant uptake does not increase proportionally to DGT fluxes suggest that Cu uptake in plants was not diffusion limited. Thus, the free Cu concentrations near the root surface were sufficient to meet the plant's demand during the experiment. Furthermore, labile complexes that continuously resupply the Cu(2+) pool may also contribute to the concentrations available for plant uptake. In the range of Cu concentrations investigated in the present study, saturation of uptake processes as well as toxicity are considered responsible for the poor DGT prediction of plant uptake.

Improvement of Fire Hydrant Design to Enhance Water Main Flushing

Flushing is a good practice to avoid problems related to sediment, bio-film growth, and corrosion. Artificial sediment was removed from fire hydrant with pilot scale water distribution main. The sediment removal in fire hydrant and main was carefully compared with different flow rate with velocity ranged from 0.3 to 3.0 m/s and the depth of fire hydrant from 0.5 m to 1.3m. The drain capability of fire hydrant decreased as the flow rate increased. Sediment with higher density was hard to remove from water main. The length effect of upward fire hydrant was relatively minor. Downward drain showed better efficiency for both sand and actual sediment.

Today's sediment budget of the Rhine River channel, focusing on the Upper Rhine Graben and Rhenish Massif

The river bed of the Rhine River is subject to severe erosion and sedimentation. Such high geomorphological process rates are unwanted for economical, ecological, and safety reasons. The objectives of this study were (1) to quantify the geomorphological development of the Rhine River between 1985 and 2006; (2) to investigate the bed erosion process; and (3) to distinguish between tectonic, hydrological, and human controls. We used a unique data set with thousands of bedload and suspended-load measurements and quantified the fluxes of gravel, sand, silt, and clay through the northern Upper Rhine Graben and the Rhenish Massif. Furthermore, we calculated bed level changes and evaluated the sediment budget of the channel. Sediment transport rates were found to change in the downstream direction: silt and clay loads increase because of tributary supply; sand loads increase because of erosion of sand from the bed; and gravel loads decrease because of reduced sediment mobility caused by the base-level control exerted by the uplifting Rhenish Massif. This base-level control shows tectonic setting, in addition to hydrology and human interventions, to represent a major control on morphodynamics in the Rhine. The Rhine bed appears to be in a state of disequilibrium, with an average net bed degradation of 3mm/a. Sand being eroded from the bed is primarily washed away in suspension, indicating a rapid supply of sand to the Rhine delta. The degradation is the result of an increased sediment transport capacity caused by nineteenth and twentieth century's river training works. In order to reduce degradation, huge amounts of sediment are fed into the river by river managers. Bed degradation and artificial sediment feeding represent the major sources of sand and gravel to the study area; only small amounts of sediment are supplied naturally from upstream or by tributaries. Sediment sinks include dredging, abrasion, and the sediment output to the downstream area. Large uncertainties exist about the amounts of sediment deposited on floodplains and in groyne fields. Compared to the natural situation during the middle Holocene, the present-day gravel and sand loads seem to be lower, whereas the silt and clay loads seem to be higher. This is probably caused by the present-day absence of meander migration, the deforestation, and the reduced sediment trapping efficiency of the floodplains. Even under natural conditions no equilibrium bed level existed.

Experimental Study on Low-Power Disturbing Sediment Dredging System

in the River, velocities of surface water flow typically are larger than the near-bottom flow. Combined with background of artificial disturbance sediment, surface water flows is taken to the river bottom to loose and raise sediment, dredge and so as to achieve the purpose of slowing river siltation. Preliminary tests showed that using low-power diversion disturbing sand dredging system, flow velocity of disturbing nozzle is larger than the incipient velocity of sediment, and the purpose of disturbing sediment and sediment transport can be obtained.

Adsorption of tetracyclines on marine sediment during organic matter diagenesis

The effect of decomposition and diagenesis of sediment organic matter (SOM) on the adsorption of emerging pollutants by the sediment has been seldom addressed. In the present experimental study, artificial sediment was incubated to simulate the natural organic diagenesis process and hence investigate the influence of organic diagenesis on the adsorption of tetracyclines (TCs) by marine sediment. During a period of 4 months of incubation, SOM initially added into the sediment underwent biodegradation and diagenesis. The results showed an early decrease in TC adsorption by the sediment, which was likely caused by the competition between the microbial organic products and TC molecules for the adsorption sites. Afterward, TC adsorption by the sediment increased significantly, which was mainly due to the accumulation of condensed SOM. The experimental results indicate the interactions between TCs and the sediment during the dynamic process of SOM diagenesis. Moreover, the remaining SOM is shown to have an increasing affinity with the antibiotics.

Use of artificial sediment to assess toxicity of chromium on Chironomus xanthus, Danio rerio and Poecilia reticulata

AIM: Artificial sediments with simple formulations were used to assess the toxicity of Cr to C. xanthus, D. rerio and P. reticulata. METHODS: The organisms were exposed to two sediment formulations: one without organic matter (S0) and one with 1% organic matter (SIII), both contaminated with Cr at concentrations of 90, 180, 360, 720 and 1440 mg/kg for the assays with C. xanthus, and 375, 750, 1500 and 3000 mg/kg for those with the two fish species. Chromium was obtained from the potassium dichromate (K2Cr2O7). RESULTS: The results of the acute toxicity tests demonstrated a reduction of up to four times in toxicity with the presence of OM, consisting of biodegradable detritus, even at the low concentration used (1%), and that C. xanthus was most sensitive to the metal. The reduction in the chromium toxicity was indicated by the LC50 values, which were higher in SIII (1234.43 mg/kg; 2263.54 m/kg; 2244.48 mg/kg) than in S0 (340.56 mg/kg; 1731.04 mg/kg; 1733.55 mg/kg) for C. xanthus, D. rerio and P. reticulata, respectively. CONCLUSIONS: Because of the repeatability of the results obtained, the artificial sediments with simple formulations were satisfactory to assess toxicity and can thus provide reliable results in ecotoxicological studies

Spatial Distribution of Geobacteraceae and Sulfate‐Reducing Bacteria During In Situ Bioremediation of Uranium‐Contaminated Groundwater

AbstractAnalysis of the physiological status of subsurface microbial communities generally relies on the study of unattached microorganisms in the groundwater. These approaches have been employed in studies on bioremediation of uranium‐contaminated groundwater at a study site in Rifle, Colorado, in which Geobacter species typically account for over 90 percent of the microbial community in the groundwater during active uranium reduction. However, to develop efficient in situ bioremediation strategies it is necessary to know the status of sediment‐associated microorganisms as well. In order to evaluate the distribution of the natural community of Geobacter during bioremediation of uranium, subsurface sediments were packed into either passive flux meters (PFMs) or sediment columns deployed in groundwater monitoring wells prior to acetate injection during in situ biostimulation field trials. The trials were performed at the Department of Energy's (DOE's) Rifle Integrated Field Research Challenge site. Sediment samples were removed either during the peak of Fe(III) reduction or the peak of sulfate reduction over the course of two separate field experiments and preserved for microscopy. Direct cell counts using fluorescence in situ hybridization (FISH) probes targeting Geobacter species indicated that the majority of Geobacter cells were unattached during Fe(III) reduction, which typically tracks with elevated rates of uranium reduction. Similar measurements conducted during the sulfate‐reducing phase revealed the majority of Geobacter to be attached following exhaustion of more readily bioavailable forms of iron minerals. Laboratory sediment column studies confirmed observations made with sediment samples collected during field trials and indicated that during Fe(III) reduction, Geobacter species are primarily unattached (90 percent), whereas the majority of sulfate‐reducing bacteria and Geobacter species are attached to sediment surfaces when sulfate reduction is the predominant form of metabolism (75 percent and 77 percent, respectively). In addition, artificial sediment experiments showed that pure cultures of Geobacter uraniireducens, isolated from the Rifle site, were primarily unattached once Fe(III) became scarce. These results demonstrate that, although Geobacter species must directly contact Fe(III) oxides in order to reduce them, cells do not firmly attach to the sediments, which is likely an adaptive response to sparsely and heterogeneously dispersed Fe(III) minerals in the subsurface. © 2013 Wiley Periodicals, Inc.

Experimental study on the effects of sediment size and porosity on contaminant adsorption/desorption and interfacial diffusion characteristics

The joint effects of the sediment size and porosity on the contaminant adsorption/desorption and interfacial diffusion characteristics were experimentally investigated. The adsorption of Phosphorus (P) on the natural and artificial sediment suspensions was measured with respect to the P adsorption isotherms and kinetics in the experiment. The obtained adsorption isotherms for different grain-sized sediment suspensions fit well with the Langmuir equation, dependent on the initial aqueous concentration and sediment content. The P kinetic adsorption behaviors for cohesive fine-grained and non-cohesive coarse-grained sediment suspensions clearly show the size-dependent feature. On the other hand, the P kinetic release feature of a porous sediment layer is affected by not only the direct desorption of the uppermost sediments, but also the diffusivity in the pore-water within the underlying sediment layer, characterized by the sediment size and porosity, respectively. Furthermore, the temporal contaminant release from the permeable sediment layer into the overlying water column increases with the increasing flow velocity, while this enhancement in mediating the interfacial diffusion flux is somewhat insignificant in an immediate release stage, largely due to the resistance of the diffusive boundary layer on the hydrodynamic disturbance.

Recovery Process on Soft-Bottom Macrobenthic Communities after Artificial Disturbance in Tropical Polluted Estuary (Guanabara Bay, Rio de Janeiro, Brazil)

The regime of disturbance with natural or anthropogenic origin can lead to the destabilization or even to a mass mortality of benthic communities. Due to the heterogeneity of the disturbance there is a formation of patches in different stages of ecological succession. The aim of this study is to follow and describe the resilience in artificial disturbed sediment in a polluted bay in Rio de Janeiro. The sediment was collected, sterilized and placed inside corers (10 cmdiameter ×15 cmheight) in the same place where it was collected. We allocated the samples in two structures, the difference between them was that one was placed closed to the bottom and the other was placed50 cmheight. We found 2352 organisms distributed in 14 taxons. The class Polychaeta and the order Amphipoda showed the highest density in all the survey and treatments. We identified the factors influencing the scenarium: different mechanisms of dispersal, the position of the structures and life history of each group. Disturbance can be the main cause of the patch’s diversity found in estuaries and coastal areas. Because of this, monitoring of selected areas becomes an important tool to understand the regime of disturbance as a key factor structuring benthic communities in soft sediment, also suggesting a metapopulation dynamics.

Electrochemical genotoxicity assay based on a SOS/umu test using hydrodynamic voltammetry in a droplet.

The SOS/umu genotoxicity assay evaluates the primary DNA damage caused by chemicals from the β-galactosidase activity of S. typhimurium. One of the weaknesses of the common umu test system based on spectrophotometric detection is that it is unable to measure samples containing a high concentration of colored dissolved organic matters, sediment, and suspended solids. However, umu tests with electrochemical detection techniques prove to be a better strategy because it causes less interference, enables the analysis of turbid samples and allows detection even in small volumes without loss of sensitivity. Based on this understanding, we aim to develop a new umu test system with hydrodynamic chronoamperometry using a rotating disk electrode (RDE) in a microliter droplet. PAPG when used as a substrate is not electroactive at the potential at which PAP is oxidized to p-quinone imine (PQI), so the current response of chronoamperometry resulting from the oxidation of PAP to PQI is directly proportional to the enzymatic activity of S. typhimurium. This was achieved by performing genotoxicity tests for 2-(2-furyl)-3-(5-nitro-2-furyl)-acrylamide (AF-2) and 2-aminoanthracene (2-AA) as model genotoxic compounds. The results obtained in this study indicated that the signal detection in the genotoxicity assay based on hydrodynamic voltammetry was less influenced by the presence of colored components and sediment particles in the samples when compared to the usual colorimetric signal detection. The influence caused by the presence of humic acids (HAs) and artificial sediment on the genotoxic property of selected model compounds such as 4-nitroquinoline-N-oxide (4-NQO), 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX), 1,8-dinitropyrene (1,8-DNP) and 1-nitropyrene (1-NP) were also investigated. The results showed that the genotoxicity of 1-NP and MX changed in the presence of 10 mg·L−1 HAs. The genotoxicity of tested chemicals with a high hydrophobicity such as 1,8-DNP and 1-NP were decreased substantially with the presence of 1 g·L−1 sediment. This was not observed in the case of genotoxins with a low log Kow value.

Responses of Lumbriculus variegatus to Activated Carbon Amendments in Uncontaminated Sediments

Activated carbon (AC) amendment is a recently developed sediment remediation method. The strong hydrophobic organic contaminant sorption efficiency of AC has been shown in several studies, but effects on benthic organisms require more investigation. The AC induced effects on egestion rate, growth and reproduction of Lumbriculus variegatus were studied by applying bituminous coal based AC in three different particle size fractions, namely <63 μm (90%, AC(p)), 63-200 μm (AC(m)) and 1000 μm (AC(g)), to natural uncontaminated (HS) and artificial sediment (AS). Egestion rate, growth and reproduction decreased with increasing AC concentration and finer AC particle fractions, effects being stronger on HS than on AS sediment. Lipid content in AS was reduced already at the lowest AC doses applied (AC(p) and AC(m) 0.05%, AC(g) 0.25%). In addition, hormesis-like response was observed in growth (AS) and reproduction (AS, HS) indicating that AC may disturb organisms even at very low doses. Potential ecological effects need to be further evaluated in an amendment- and site-specific manner.

Sorption of nalidixic acid onto sediments under batch and dynamic flow conditions

The sorption of nalidixic acid (NA) onto artificial sediments composed of Fe-oxides, Al-oxides, clay and quartz sand was studied under both static batch and dynamic flow conditions. Kinetic and equilibrium sorption experiments showed that the presence of clay increased the sorption capacity of synthetic sediment and that bentonite had the highest sorption coefficient compared to kaolinite. Solute reactive transport experiments showed that the breakthrough point and steepness of the breakthrough curve (BTC) were dependent on both clay type and water velocity. Agreement between batch and column results in terms of sorbed amount and retardation factor was poor regardless of the sediment tested. The presence of even a small amount of clay (3%) can decrease the permeability of the mixed bed and lead to the formation of preferential flow paths in the column system. Different sets of column experiments at various flow rates gave rise to different sorbed amounts at complete breakthrough, leading to chemical nonequilibrium in the flow system. However, this kinetic limitation cannot completely explain the breakthrough behavior of NA in the bentonite column, suggesting that other factors are responsible for this disparity. The presence of immobile water regions was unlikely in the column since more than 90% of the pore water was mobile according to the tracer tests. The inaccessibility of reactive sites and limited physical diffusion in the clay-packed column may play a significant role under flow-through conditions. The reactive transport behavior of NA is therefore strongly dependent on the mineralogy of the clay present in sediments.

Mineral analysis of an artificial pond sediment samples from the Western Cape Province, South Africa

Mineralogical characterization was carried out to determine the major and minor constituent minerals present in sediment samples collected from five different locations at the Western Cape artificial pond sediment, South Africa by Fourier transform infrared (FT-IR) and X-ray diffractometry (XRD) techniques. The minerals were identified with the available literature from the IR absorption band of the locations of different peaks. The FT-IR technique was highly useful in identifying different minerals in sediments. The XRD analysis revealed that the minerals of artificial pond sediments in Western Cape are predominantly composed of quartz while carrolite was present in location one. The presence of pyrite could also suggest anoxia, which in turn will imply differential Fe (Iron) levels in the sediment as a function of the degree of anoxia in the sediment.

Assessing the Oxidative Stress Induced by Paracetamol Spiked in Artificial Sediment on Hyalella azteca

Paracetamol is an antipyretic analgesic widely used globally. It has been recurrently found in water bodies and is known to elicit toxic effects in aquatic species; however, its potential ability to induce oxidative stress in sentinel species remains unknown The objective was to establish a methodology to evaluate the toxicity elicited on the sentinel species Hyalella azteca by paracetamol-enriched sediment using oxidative stress tests. Concentrations used in assays were determined using the previously obtained median lethal concentration (72 h LC50). The following oxidative stress biomarkers were evaluated: lipid peroxidation (LPO), protein carbonyl content (PCC) in order to determine oxidized protein content, and the activity of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPX). LPO and PCC increased significantly while SOD, CAT, and GPX decreased significantly (p < 0.05) with respect to controls. Paracetamol induces oxidative stress on H. azteca, and the set of tests employed is helpful in evaluating the toxicity of this group of pharmaceuticals on aquatic species.

A new tool for visualising multi-dimensional datasets: an example of fish schools around artificial reefs

We demonstrated a tool for visualising multi-dimensional datasets, using an example of fish schools around artificial reefs off the coast of Shimonoseki, Yamaguchi prefecture, Japan. The datasets included acoustic surveys of fish schools, water temperature data, descriptions of the artificial reefs, sediment data, and bathymetry and coastal line data. These datasets were integrated into geographic information system software, which can be used to describe the relationship between water temperature and fish schools; fish schools associated with reefs; and the status of the artificial reefs on the classified seabed. This new tool provides a better understanding of the distribution of fish schools based on their spatial location in context with environmental information around artificial reefs.

The Field Application of Microbial Technology Used in Bioremediation of Urban Polluted River

This paper studies on the field application of microbial technology used in bioremediation of urban polluted river. Xuxi River, a heavily polluted urban river, had been maken the treatment as the research object. In this treatment, Xuxi River was directly added indigenous microorganism agent and microbiological accelerating agent into the river water and sediment in the special inoculation way, without artificial aeration and sediment dredging. After this treatment， the removal rates of COD, TP and NH3-N are up to 43%、56% and 58%, DO increases to 2mg/L, the Nemerow index reduces to 2.2 from 6.4, and a lot of water earthworms and a school of fish reappear. The results indicate that this microbial technology can effectively alleviate the pollution, promote the water quality, and restore the river ecosystem.

排砂による河床への土砂堆積に伴うイワナの局所的な避難空間の減少に関する研究

To evaluate the impacts of sediment flushing on fish, it is necessary to predict the decrease of the local space of the bed at mountain stream which is considered the refuges. First, we flushed sediment from a dam to pick out the local spaces which are the refuges for fish and the impacts of sediment deposition on the local spaces. Second, we conducted a set of experiments using artificial sediment supplies to the pools to investigate the relationships between the volumes of the sediment deposition on the bed and the local spaces. Finally, we constructed a model that could calculate the variations in the volume of the local space based onthe volume of sediment deposited on the bed. We have found that we can roughly predict the variations of the volume of the local space insediment flushing and the impacts on fish based on our model.

Depressurized dissociation of methane-hydrate-bearing natural cores with low permeability

Depressurization is a promising technique for producing natural gas from methane hydrate reservoirs. However, current studies focus mainly on artificial sediments with high permeability. Research on low-permeability conditions such as those of natural cores is scarce; therefore, there is little information on the natural core dissociation characteristics. This report presents the dissociation characteristics of low-permeability methane-hydrate-bearing cores. We used a natural core obtained from the eastern Nankai Trough. From dissociation experiments at the low-permeability core, we clarify differences during the depressurization process: the pressure propagated slowly, and dissociation was driven mainly by sensible heat consumption. The dissociation process was divided into four stages similar to that of the artificial core. We also compared our experimental results with those using two dissociation models for the divided dissociation stage. One of these previously proposed dissociation model were applied to a constant production pressure stage. The other model was a simple sensible heat consuming model, and it described the dissociation during the depressurization process toward constant production pressure. By comparing our experimental results with the theoretical results from the two dissociation models, it was clearly demonstrated that both models can accurately describe the experiment results of the divided dissociation stage.