Placing and Capping Fine-Grained Dredged Material

Dredging '02 ◽  
2003 ◽  
Author(s):  
Mark T. Otten ◽  
Gregory L. Hartman
Keyword(s):  
Dredged Material ◽  
Fine Grained

Emissions of porewater compounds and gases from the subaquatic sediment disposal site “rodewischhafen”, hamburg harbour

1998 ◽  
Vol 37 (6-7) ◽  
pp. 87-93 ◽  
Author(s):  
M. Kussmaul ◽  
A. Groengroeft ◽  
H. Koethe
Keyword(s):  
Water Surface ◽  
Disposal Site ◽  
Dredged Material ◽  
Water Fluxes ◽  
Gas Emissions ◽  
Fine Grained ◽  
Deposit Surface ◽  
Groundwater Samples ◽  
High Concentrations ◽  
Mud Deposit

In the year 1993 a confined and unused harbour basin was used to store 290,000 m3 of fine-grained dredged material from Hamburg harbour. About 70% of the deposit surface was water covered. The edge areas were above the water table and covered with reed. Emissions of dissolved compounds into the groundwater, as well as surface gas emissions were measured from 1994 to 1996. As indicators for water fluxes from the deposit we used NH4+ and HCO3− because of their high concentrations in mud porewater in comparison to groundwater. The average concentrations of NH4+ and HCO3− in the porewater increased during 2 years from 85 to 250 mg NH4+ 1−1 and from 2.0 to 3.1 g HCO3− 1−1, while the groundwater samples showed constant values of 8 mg NH4+ 1−1 and 0.7 g HCO3− 1−1. Furthermore, the average gas emissions over the water surface were 3.2 g CH4 m−2 d−1 and 0.8 g CO2 m−2 d−1. In contrast, no methane and 3.0 g CO2 m−2 d−1 were emitted from land areas. The results indicated, that there were no significant emissions of mud porewater compounds into the groundwater but high CH4-emissions over the water covered surface of the mud deposit.

Macrofaunal recolonisation following the intertidal placement of fine-grained dredged material

2009 ◽  
Vol 168 (1-4) ◽  
pp. 499-510 ◽  
Author(s):  
Stefan George Bolam ◽  
Jon Barry ◽  
Michaela Schratzberger ◽  
Paul Whomersley ◽  
Mike Dearnaley
Keyword(s):  
Dredged Material ◽  
Fine Grained

scholarly journals HYDRODYNAMIC ANALYSIS OF SLUDGE DUMPED IN COASTAL WATERS

1972 ◽  
Vol 1 (13) ◽  
pp. 121
Author(s):  
Billy L. Edge
Keyword(s):  
Dredged Material ◽  
Transport Mechanisms ◽  
Environmental Pressures ◽  
Hydrodynamic Analysis ◽  
Fine Grained ◽  
Land Disposal ◽  
Physical Forces ◽  
Maintenance Dredging ◽  
Disposal Problem ◽  
Wastewater Sludges

Due to increased environmental pressures, there is a rapidly growing tendency to shift from traditional land disposal of dredged material to offshore or ocean disposal. The quantities of such materials are quite large, resulting in a very serious disposal problem. For example, maintenance dredging alone produces approximately six million cubic yards of material annually in Charleston Harbor. Existing techniques are reasonably adequate to describe the transport and settling characteristics of coarse, sandy dredge materials discharged from barges or hopper dredges at sea. However, such approaches need to be modified to describe the transport of fine-grained clay and silt materials. This material constitutes a significant portion of the dredged material resulting from both new harbor and channel construction and maintenance dredging along the coast of the Carolinas and Georgia. These fine-grained materials are subject to many additional physical forces as well as chemical phenomena, e.g., flocculation, salinity and temperature variations, etc. A hydrodynamic model for fine-grained dredged material has been developed which considers many of these forces. It is also applicable for describing the transport mechanisms associated with barge disposal of wastewater sludges from municipal and industrial sources. The results of the model indicate what discharge strategies are necessary for placing the sludge at a desired location or depth with a predetermined concentration.

scholarly journals The Fate of Nitrogen in Dredged Material Used for Tidal Marsh Restoration

2021 ◽  
Vol 9 (8) ◽  
pp. 849
Author(s):  
Lorie W. Staver ◽  
Jeffrey C. Cornwell ◽  
Nicholas J. Nidzieko ◽  
Kenneth W. Staver ◽  
J. Court Stevenson ◽  
...  
Keyword(s):  
Organic Matter ◽  
Chesapeake Bay ◽  
Tidal Marsh ◽  
Aquatic Vegetation ◽  
Dredged Material ◽  
Submersed Aquatic Vegetation ◽  
Labile Organic Matter ◽  
Marsh Restoration ◽  
Fine Grained ◽  
Tidal Marsh Restoration

Tidal marsh restoration using dredged material is being undertaken in many coastal areas to replace lost habitat and ecosystem services due to tidal marsh loss. The fate of high levels of nitrogen (N) in fine-grained dredged material used as a substrate for marsh restoration is uncertain, but if exported tidally may cause subtidal habitat degradation. In this study, a mass balance was developed to characterize N fluxes in a two-year-old restored tidal marsh constructed with fine-grained dredged material at Poplar Island, MD, in Chesapeake Bay, and to evaluate the potential impact on the adjacent submersed aquatic vegetation (SAV) habitat. Denitrification and N accumulation in Spartina organic matter were identified as the major sinks (21.31 and 28.5 mg N m−2 d−1, respectively), while tidal export of TN was more modest (9.4 mg N m−2 d−1) and inorganic N export was low (1.59 mg N m−2 d−1). Internal cycling helped retain N within the marsh. Mineralization of N associated with labile organic matter in the dredged material was likely a large, but unquantified, source of N supporting robust plant growth and N exports. Exceedances of SAV water quality habitat requirements in the subtidal region adjacent to the marsh were driven by elevated Chesapeake Bay concentrations rather than enrichment by the marsh.

Application of an image management system in microscopy

1992 ◽  
Vol 50 (2) ◽  
pp. 1052-1053
Author(s):  
Richard S. Chemock
Keyword(s):  
Data Storage ◽  
Cost Savings ◽  
Image Data ◽  
Analytical Techniques ◽  
Operational Mode ◽  
Fine Grained ◽  
Image Recording ◽  
Primary Output ◽  
Capacity Data ◽  
Image Management System

One of the most common tasks in a typical analysis lab is the recording of images. Many analytical techniques (TEM, SEM, and metallography for example) produce images as their primary output. Until recently, the most common method of recording images was by using film. Current PS/2R systems offer very large capacity data storage devices and high resolution displays, making it practical to work with analytical images on PS/2s, thereby sidestepping the traditional film and darkroom steps. This change in operational mode offers many benefits: cost savings, throughput, archiving and searching capabilities as well as direct incorporation of the image data into reports.The conventional way to record images involves film, either sheet film (with its associated wet chemistry) for TEM or PolaroidR film for SEM and light microscopy. Although film is inconvenient, it does have the highest quality of all available image recording techniques. The fine grained film used for TEM has a resolution that would exceed a 4096x4096x16 bit digital image.

Use of fractals to describe microstructures of porous thick-film platinum electrodes

1992 ◽  
Vol 50 (1) ◽  
pp. 314-315
Author(s):  
Steven D. Toteda
Keyword(s):  
Fractal Dimension ◽  
Power Plants ◽  
Electrical Response ◽  
Cubic Phase ◽  
Platinum Electrodes ◽  
Fine Grained ◽  
Impedance Response ◽  
Platinum Particles ◽  
Energy Surfaces ◽  
Highly Porous

Zirconia oxygen sensors, in such applications as power plants and automobiles, generally utilize platinum electrodes for the catalytic reaction of dissociating O2 at the surface. The microstructure of the platinum electrode defines the resulting electrical response. The electrode must be porous enough to allow the oxygen to reach the zirconia surface while still remaining electrically continuous. At low sintering temperatures, the platinum is highly porous and fine grained. The platinum particles sinter together as the firing temperatures are increased. As the sintering temperatures are raised even further, the surface of the platinum begins to facet with lower energy surfaces. These microstructural changes can be seen in Figures 1 and 2, but the goal of the work is to characterize the microstructure by its fractal dimension and then relate the fractal dimension to the electrical response. The sensors were fabricated from zirconia powder stabilized in the cubic phase with 8 mol% percent yttria. Each substrate was sintered for 14 hours at 1200°C. The resulting zirconia pellets, 13mm in diameter and 2mm in thickness, were roughly 97 to 98 percent of theoretical density. The Engelhard #6082 platinum paste was applied to the zirconia disks after they were mechanically polished ( diamond). The electrodes were then sintered at temperatures ranging from 600°C to 1000°C. Each sensor was tested to determine the impedance response from 1Hz to 5,000Hz. These frequencies correspond to the electrode at the test temperature of 600°C.

Amorphous silica coating on α-alumina particles

1995 ◽  
Vol 53 ◽  
pp. 210-211
Author(s):  
J. W. Mellowes ◽  
C. M. Chun ◽  
I. A. Aksay
Keyword(s):  
Amorphous Silica ◽  
Heterogeneous Nucleation ◽  
Homogeneous Nucleation ◽  
Silica Coating ◽  
Full Density ◽  
Optimal Conditions ◽  
Fine Grained ◽  
Alumina Particles ◽  
Complete Mullitization ◽  
Powder Compacts

Mullite (3Al2O32SiO2) can be fabricated by transient viscous sintering using composite particles which consist of inner cores of a-alumina and outer coatings of amorphous silica. Powder compacts prepared with these particles are sintered to almost full density at relatively low temperatures (~1300°C) and converted to dense, fine-grained mullite at higher temperatures (>1500°C) by reaction between the alumina core and the silica coating. In order to achieve complete mullitization, optimal conditions for coating alumina particles with amorphous silica must be achieved. Formation of amorphous silica can occur in solution (homogeneous nucleation) or on the surface of alumina (heterogeneous nucleation) depending on the degree of supersaturation of the solvent in which the particles are immersed. Successful coating of silica on alumina occurs when heterogeneous nucleation is promoted and homogeneous nucleation is suppressed. Therefore, one key to successful coating is an understanding of the factors such as pH and concentration that control silica nucleation in aqueous solutions. In the current work, we use TEM to determine the optimal conditions of this processing.

Interfacial structures of dissimilar materials joined by capacitor-discharge welding

1994 ◽  
Vol 52 ◽  
pp. 534-535
Author(s):  
C. P. Doğan ◽  
R. D. Wilson ◽  
J. A. Hawk
Keyword(s):  
Rapid Solidification ◽  
Fusion Zone ◽  
Dissimilar Materials ◽  
Solidification Process ◽  
Weld Interface ◽  
Capacitor Discharge ◽  
Fine Grained ◽  
Iron Aluminum ◽  
Conductive Ceramics ◽  
Capacitor Discharge Welding

Capacitor Discharge Welding is a rapid solidification technique for joining conductive materials that results in a narrow fusion zone and almost no heat affected zone. As a result, the microstructures and properties of the bulk materials are essentially continuous across the weld interface. During the joining process, one of the materials to be joined acts as the anode and the other acts as the cathode. The anode and cathode are brought together with a concomitant discharge of a capacitor bank, creating an arc which melts the materials at the joining surfaces and welds them together (Fig. 1). As the electrodes impact, the arc is extinguished, and the molten interface cools at rates that can exceed 106 K/s. This process results in reduced porosity in the fusion zone, a fine-grained weldment, and a reduced tendency for hot cracking.At the U.S. Bureau of Mines, we are currently examining the possibilities of using capacitor discharge welding to join dissimilar metals, metals to intermetallics, and metals to conductive ceramics. In this particular study, we will examine the microstructural characteristics of iron-aluminum welds in detail, focussing our attention primarily on interfaces produced during the rapid solidification process.

TEM/AEM characterization of fine-grained clay minerals in very-low-grade rocks: Evaluation of contamination by empa involving celadonite family minerals

1996 ◽  
Vol 54 ◽  
pp. 694-695
Author(s):  
Gejing Li ◽  
D. R. Peacor ◽  
D. S. Coombs ◽  
Y. Kawachi
Keyword(s):  
Electron Microscopy ◽  
Volcanic Rocks ◽  
Analytical Electron Microscopy ◽  
Metamorphic Rocks ◽  
New Mineral ◽  
Chemical Compositions ◽  
Low Grade ◽  
Fine Grained ◽  
Depth Analysis ◽  
Mineral Aggregates

Recent advances in transmission electron microscopy (TEM) and analytical electron microscopy (AEM) have led to many new insights into the structural and chemical characteristics of very finegrained, optically homogeneous mineral aggregates in sedimentary and very low-grade metamorphic rocks. Chemical compositions obtained by electron microprobe analysis (EMPA) on such materials have been shown by TEM/AEM to result from beam overlap on contaminant phases on a scale below resolution of EMPA, which in turn can lead to errors in interpretation and determination of formation conditions. Here we present an in-depth analysis of the relation between AEM and EMPA data, which leads also to the definition of new mineral phases, and demonstrate the resolution power of AEM relative to EMPA in investigations of very fine-grained mineral aggregates in sedimentary and very low-grade metamorphic rocks.Celadonite, having end-member composition KMgFe3+Si4O10(OH)2, and with minor substitution of Fe2+ for Mg and Al for Fe3+ on octahedral sites, is a fine-grained mica widespread in volcanic rocks and volcaniclastic sediments which have undergone low-temperature alteration in the oceanic crust and in burial metamorphic sequences.

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