scholarly journals PHYSICAL CHANGES IN ESTUARINE SEDIMENTS ACCOMPANYING CHANNEL DREDGING

1974 ◽  
Vol 1 (14) ◽  
pp. 75
Author(s):  
Charles K. Sollitt ◽  
Stephen D. Crane
Keyword(s):  
Bottom Sediments ◽  
Biological Activities ◽  
Physical Characteristics ◽  
Estuarine Sediments ◽  
Low Flow ◽  
Bottom Surface ◽  
Army Corps ◽  
Clay Material ◽  
Partial Recovery ◽  
Core Samples

The physical characteristics of estuarine sediments provide useful information about sediment sources, the nature of bottom surface stresses and sediment transport mechanisms. Changes in sediment composition and state are also useful indicators for estimating the effects of unnatural stresses on dependent chemical and biological activities. In this study, the changes in several sediment properties have been monitored for an isolated estuarine dredging project. The effect of estuarine hopper dredge activities has been evaluated for an Army Corps of Engineers project at Coos Bay, Oregon. The project included suction head dredging at a shoal area within the navigation channel and in bay spoiling at a deep section of channel one mile downstream from the dredge site. Core samples were taken five days before dredging and two, thirteen and seventy days after dredging at the dredge and spoil sites. Subsequent laboratory analysis of the core samples revealed that dredging induced redistribution of bottom sediments produced significant changes in several physical characteristics of the dredged material. Repeated resuspension of bottom sediments during the dredging and spoiling operations caused a net loss of fine grained sediments and light organic constituents. Several symptomatic changes were observed which validate this finding, including: an increase in median grain size and decrease in uniformity of dredge spoils due to loss of fine fractions; a decrease in volatile solids in the dredge spoils due to a net loss of organics; a decrease in porosity at the spoils site due to the ability of the coarse grain sediments to resist resuspension; and a decrease in hygroscopic moisture content due to loss of porous organics and silt-clay material from the spoils. Conditions following dredging were observed for a period of seventy days. Partial recovery of the sediment system was observed after two weeks with no further recovery in two months. The initial recovery came about due to the availability of local sources of resuspended sediment adjacent to the dredge site. This occured under low flow conditions in early fall. Complete recovery of the system was not observed and probably requires the relatively large sources of sediment which accompany heavy winter and spring runoff. Thus, the immediate effects of dredging may persist until the annual cycle of sediment erosion and deposition have occurred.

The Behavior of Arsenic in Selected United Kingdom Estuaries

1983 ◽  
Vol 40 (S2) ◽  
pp. s143-s150 ◽  
Author(s):  
W. J. Langston
Keyword(s):  
United Kingdom ◽  
Bottom Sediments ◽  
Coastal Waters ◽  
Estuarine Sediments ◽  
Tamar Estuary ◽  
Physicochemical Conditions ◽  
Dissolved Species

High As concentrations occur in certain United Kingdom estuaries as a result of mineralization and associated processes including mining and metal refining. Analyses of dissolved and particulate As, carried out in estuaries of differing contamination, indicate that As is readily precipitated with Fe during mixing at the freshwater–seawater interface. This gives rise to significant correlations between the two elements in suspended and bottom sediments. More than 80% of the As entering Restronguet Creek, the most contaminated of the estuaries studied, is retained by estuarine sediments, which consequently act as sinks for riverine inputs and limit transport of dissolved species to coastal waters. However, the behavior of As in different estuaries varies with the physicochemical conditions present and the nature of the source. Most significantly, remobilization of sediments is recognized as a feature affecting the cycling of As in the Tamar Estuary.

scholarly journals TRACING ESTUARINE SEDIMENTS BY NEUTRON ACTIVATION

1976 ◽  
Vol 1 (15) ◽  
pp. 116
Author(s):  
Richard M. Ecker ◽  
John F. Sustar ◽  
William T. Harvey
Keyword(s):  
San Francisco ◽  
Research Laboratory ◽  
Estuarine Sediments ◽  
Disposal Site ◽  
Army Corps ◽  
Army Corps Of Engineers ◽  
Corps Of Engineers ◽  
Stanford Research Institute ◽  
Fine Sediments ◽  
The U.S

Tracing the movement of dredged sediments in north San Francisco Bay was accomplished jointly by the San Francisco District of the U.S. Army Corps of Engineers, Explosive Excavation Research Laboratory (now the Explosive Effects Division of the Weapon Effects Laboratory, U.S. Army Waterways Experiment Station), and the Stanford Research Institute. The study involved developing a technique which would permit the longterm tracing of fine sediments dredged from Mare Island Strait after disposal at the Carquinez Strait disposal site; application of the tracer; disposal of the tagged sediment for the February-March 1974 dredging of Mare Island Strait; sampling bottom sediments throughout the study area for a 10-month period; and, quantitative analysis of the collected samples.

scholarly journals Initial survey of microplastics in bottom sediments from United States waterways

2021 ◽  
Author(s):  
Justin Wilkins ◽  
Andrew McQueen ◽  
Joshua LeMonte ◽  
Burton Suedel
Keyword(s):  
Bottom Sediments ◽  
Polymer Composition ◽  
Army Corps ◽  
Army Corps Of Engineers ◽  
Us Army ◽  
The Us ◽  
Initial Survey ◽  
Study Sites ◽  
Polymer Type ◽  
Number Of Particles

Given the reported extent of microplastics in the aquatic environment, environmentally relevant exposure information for sediments dredged by the US Army Corps of Engineers will lend context to the risks posed by this contaminant during dredging. We measured the occurrence, abundance, and polymer composition of microplastics in sediments collected from nine dredged waterways and two non-dredged reference areas. The number of particles in sediment samples ranged from 162 to 6110 particles/kg dry wt., with a mean of 1636 particles/kg dry wt. Fragments were the most prevalent shape observed among the 11 study sites (100% frequency of occurrence), followed by fibers (81%), spheres (75%), foams (38%) and films (34%). Based on analyses of chemical composition of the particles using Fourier transform infrared spectroscopy, polyethylene:propylene was the most common polymer type observed. Consistent with results presented by other investigators microplastic concentrations and polymer types in bottom sediments in this study were also aligned with the most widely used plastics worldwide.

Structural, physical characteristics and biological activities assessment of scleroglucan from a local strain Athelia rolfsii TEMG

2020 ◽  
Vol 163 ◽  
pp. 1196-1207
Author(s):  
Islam A. Elsehemy ◽  
Azza M. Noor El Deen ◽  
Hassan M. Awad ◽  
Mohamed H. Kalaba ◽  
Saad A. Moghannem ◽  
...  
Keyword(s):  
Biological Activities ◽  
Local Strain ◽  
Physical Characteristics ◽  
Athelia Rolfsii

Abstract 626: Shear Stress Regulates Angiotensin Type One Receptor Expression in Endothelial Cells

Circulation ◽  
2007 ◽  
Vol 116 (suppl_16) ◽  
Author(s):  
Bhama Ramkhelawon ◽  
Jose Vilar ◽  
Alain Tedgui ◽  
Lehoux Stephanie
Keyword(s):  
Endothelial Cells ◽  
Shear Stress ◽  
Protein Expression ◽  
Atherosclerotic Lesion ◽  
Receptor Expression ◽  
Low Flow ◽  
Immunocytochemical Staining ◽  
Cholesterol Depletion ◽  
Partial Recovery ◽  
Angiotensin Type

Several studies have shown that angiotensin II tends to favour atherosclerotic lesion formation and progression, acting mainly through angiotensin type one receptors (AT1R). Conversely, shear stress (SS) confers atheroprotective effects in the vasculature. However, whether SS regulates endothelial AT1R expression remains unknown. Using en face staining of C57BL/6 mouse aortas, we found a pronounced expression of AT1R in the inner regions of the aortic arch and at collateral artery branch points, known to have low flow and to be atheroprone, compared with neighboring high SS regions. Furthermore, staining of vessels from hypercholesterolemic LDLR−/−mice demonstrated a clear expression of AT1R only in endothelium overlying plaques. Using HUVECs exposed to a laminar SS of 15dynes/cm2, we observed a biphasic decrease in AT1R protein expression characterized by a first reduction at 1 hr (31+4% of static control, p<0.001), partial recovery at 3 hr (65+9%), and a second more prolonged decrease at 6, 12 and 24 hrs (48+9%, 36+9%, 33+5% of static control, respectively)(p<0.001). AT2R levels remained unchanged in these conditions. Shear-induced downregulation of AT1R was abolished by treatment with L-NAME (10–7M), suggesting that NO regulates AT1R in sheared endothelial cells. In accordance, stimulating static HUVECs with a NO donor for 1 hour decreased AT1R protein expression. The acute loss of AT1R at 1 hour SS suggested a rapid endocytosis and degradation of the protein. Indeed, immunocytochemical staining demonstrated a clear colocalisation of AT1R with caveolin-1 in HUVECs submitted to 5 mins SS, similar to that observed in angII-stimulated cells. Cholesterol depletion with methyl-beta-cyclodextrin prevented AT1R-caveolin colocalisation. No colocalisation of AT1R with clathrin was observed. In comparison, AT2R did not undergo endocytosis under any conditions tested. Finally, RT-PCR revealed a significant (p<0.001) decrease of AT1R mRNA in HUVECs exposed to SS during 6 (4+1% of static control), 12 (4+1%) and 24 hours (15+4%), suggesting a transcriptional downregulation of AT1R at length. Hence, our results demonstrate that SS may convey some of its atheroprotective effects through degradation and downregulation of AT1R in endothelial cells.

scholarly journals Exploring hydrologically similar catchments in terms of the physical characteristics of upstream regions

2017 ◽  
Vol 49 (5) ◽  
pp. 1467-1483 ◽  
Author(s):  
Yi Jin ◽  
Jintao Liu ◽  
Lu Lin ◽  
Aihua Wang ◽  
Xi Chen
Keyword(s):  
Hydrologic Model ◽  
Physical Characteristics ◽  
High Flow ◽  
Low Flow ◽  
Model Parameters ◽  
Physical Factors ◽  
Ungauged Catchments ◽  
Response Factors ◽  
Average Annual Runoff ◽  
Huai River

Abstract Catchment classification strategies based on easily available physical characteristics are important for extrapolating hydrologic model parameters and improving hydrologic predictions in ungauged catchments. In this study, we conduct an experiment of catchment classification and explore the feasibility of characterizing hydrologically similar catchments using certain physical characteristics in upstream regions of the Huai River Basin. The similarity metrics of hydrologic response factors (high flow, low flow and average annual runoff) and physical factors (topography, shape, soil and vegetation) are fed into the K-means algorithm for catchment classification. All the catchments are classified into two classes regardless of the types of metrics used. By comparing the overlap coefficient (η) and Rand index (RI) between any two classification results, we found that the topography classification displays the highest concordance with the high flow classification (η = 79.2% and RI = 0.66) among all metrics. Including more metrics would not produce consistently better classification results. The optimal combination of metrics, with η = 87.5%, is the high flow metrics (Q10%, SFH and MAX90) with the topography metrics (AS and HI). The results indicate that the physical metrics adopted for hydrologic classification should be determined carefully in terms of specific hydrologic characteristics.

scholarly journals Simulation of Flow in Turbopump Vaneless and Vaned Diffusers with Fluid Injection

2000 ◽  
Vol 6 (1) ◽  
pp. 57-65
Author(s):  
Ali Ogut ◽  
Diego Garcia Pastor
Keyword(s):  
Flow Separation ◽  
Flow Region ◽  
Design Flow ◽  
Low Flow ◽  
Fluid Injection ◽  
Bottom Surface ◽  
Suction Surface ◽  
Vaned Diffuser ◽  
Flow Rates ◽  
Wide Range

In future space missions by NASA there will be a need for “Space Transfer Vehicles” to perform varying orbital transfers and descents. This requires engines capable of producing different levels of thrust. To accomplish this, the turbopumps employed in these engines should efficiently provide a wide range of flow outputs. However, current fuel and oxidizer turbopumps with vaned diffusers do not perform efficiently at off-design (low) flow rates mainly due to flow separation in the vaned diffuser.This paper evaluates the effectiveness of boundary layer control by fluid injection (blowing) for suppressing or eliminating the flow separation in a vaned diffuser. A 3-D flow model including vaneless and vaned diffusers of a liquid hydrogen (LH2) turbopump is studied using the CFD code FIDAP. The paper presents the results of the model at design and offdesign flow conditions.The model results showed that flow separation occurs at the top or suction surface of the vaneless diffuser and at the bottom or pressure surface of the vaned diffuser at off-design flow rates. When fluid injection was applied through the bottom surface of the vaned diffuser, the separated flow region was reduced almost entirely, resulting in an increase in pressure recovery of up to 21% with varying fluid injection rates. Results also showed that there is an optimum injection rate which is most effective in reducing or eliminating the region of flow separation.

scholarly journals Legacy Metal Contaminants and Excess Nutrients in Low Flow Estuarine Embayments Alter Composition and Function of Benthic Bacterial Communities

2021 ◽  
Vol 12 ◽  
Author(s):  
Simone C. Birrer ◽  
Franziska Wemheuer ◽  
Katherine A. Dafforn ◽  
Paul E. Gribben ◽  
Peter D. Steinberg ◽  
...  
Keyword(s):  
Bacterial Communities ◽  
Expression Patterns ◽  
Austral Summer ◽  
16S Rrna Gene Sequencing ◽  
Estuarine Sediments ◽  
Low Flow ◽  
Rrna Gene ◽  
Anthropogenic Stressors ◽  
Storm Drain ◽  
And Function

Coastal systems such as estuaries are threatened by multiple anthropogenic stressors worldwide. However, how these stressors and estuarine hydrology shape benthic bacterial communities and their functions remains poorly known. Here, we surveyed sediment bacterial communities in poorly flushed embayments and well flushed channels in Sydney Harbour, Australia, using 16S rRNA gene sequencing. Sediment samples were collected monthly during the Austral summer-autumn 2014 at increasing distance from a large storm drain in each channel and embayment. Bacterial communities differed significantly between sites that varied in proximity to storm drains, with a gradient of change apparent for sites within embayments. We explored this pattern for embayment sites with analysis of RNA-Seq gene expression patterns and found higher expression of multiple genes involved in bacterial stress response far from storm drains, suggesting that bacterial communities close to storm drains may be more tolerant of localised anthropogenic stressors. Several bacterial groups also differed close to and far from storm drains, suggesting their potential utility as bioindicators to monitor contaminants in estuarine sediments. Overall, our study provides useful insights into changes in the composition and functioning of benthic bacterial communities as a result of multiple anthropogenic stressors in differing hydrological conditions.

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