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Sample records for flat sediment dynamics

  1. Influence of history and environment on the sediment dynamics of intertidal flats

    USGS Publications Warehouse

    Jones, Craig A.; Jaffe, Bruce E.

    2013-01-01

    Morphological trends of three distinct intertidal environments in South San Francisco Bay were investigated using a combination of measurement and modeling tools. Because of the inherent relationship between the physical environment and the sediment properties, the sediment properties provide a good indicator of morphologic trends. A significant finding of this study is that surface sediment erodibility increases as the energy level in the environment increases. Conversely subsurface sediment erodibility shows a strong relationship to the long-term history of the site. The combination of the measured sediment properties, the history of deposition and erosion, and simple modeling of the physical environment illustrate the interaction of these properties such that an understanding of intertidal flat behavior is developed.

  2. Creation Of Constructed Tidal Flats Using Ocean Dredged Sediment

    NASA Astrophysics Data System (ADS)

    Park, S.; Yi, B.; Lee, I.; Sung, K.

    2007-12-01

    The enforcement of London dumping convention (1972) and protocols (1996) which are comprehensive assessment system for ocean dumping wastes needs environmentally sound treatment and/or reuse of dredged sediment. Creation of constructed tidal flats using dredged sediments could be one of the useful alternatives among other dredged sediment treatments. In this study, the pilot-scale constructed tidal flats with 4 different mixing ratio of ocean dredged sediment were constructed in Nakdong river estuary, Korea. The reed was transplanted from the adjacent reed community after construction, and then the survival and growth rate of the planted reed was measured. Also the changes of Chemical Oxygen Demand (COD), Ignition loss (IL), and the heterotrophic microbial numbers were monitored. The survival rate of the planted reed decreased as the mixing ratio of dredged sediment increased. The survival rate of reed in the constructed tidal flat with 100% dredged sediment was 54% while that in the tidal flat with 0% dredged sediment (original soil of Nakdong river estuary) was 90%. There was little difference of length and diameter of the reed shoot among the 4 different constructed tidal flats. 30% of COD and 9% of IL in the tidal flat with 100% dredged sediment decreased after 202 day, however, the consistent tendency in the change of COD and IL in the other tidal flats was not found possibly due to the open system. It was suggested that the construction of tidal flats using ocean dredged sediment can be possible considering the growth rate of transplanted reeds and the contaminated ocean dredged sediment might be biologically remediated considering the results of decrease of organic matter and increased heterotrophic microbial number in the tidal flat with 100% dredged sediment. However, the continuous monitoring on the vegetation and various environmental factors in the constructed tidal flats should be necessary to evaluate the success of creation of constructed flats using

  3. Flat Subduction and Dynamic Topography

    NASA Astrophysics Data System (ADS)

    Lithgow-Bertelloni, C. R.; Dávila, F. M.; Eakin, C. M.; Crameri, F.

    2014-12-01

    Mantle dynamics manifests at the surface via the horizontal motions of plates and the vertical deflections that influence topography and the non-hydrostatic geoid. The pioneering work of Mitrovica et al. (1989) and Gurnis (1990) on this dynamic topography revolutionized our understanding of sedimentary basin formation, sea level changes and continental flooding. The temporal evolution of subduction can explain the migration of basins and even the drainage reversal of the Amazon (Shephard et al., 2012; Eakin et al., 2014). Until recently, flat subduction has been seen as enhancing downward deflection of the overriding plate and increasing flooding. However, this interpretation depends crucially on the details of the morphology and density structure of the slab, which controls the loci and amplitude of the deflection. We tend to ignore morphological details in mantle dynamics because flow can smooth out short wavelength variations. We have shown instead that details matter! Using South America as a natural laboratory because of the large changes in morphology of the Nazca slab along strike, we show that downward deflection of the overriding plate and hence basin formation, do not occur over flat segments but at the leading edge, where slabs plunge back into the mantle. This is true in both Argentina and Peru. The temporal evolution from a 'normally' dipplng slab to a flat slab leads to uplift over flat segments rather than enhanced subsidence. Critical for this result is the use of a detailed morphological model of the present-day Nazca slab with a spatial resolution of 50-100 km and based on relocated seismicity and magnetotelluric results. The density structure of the slab, due to age and the presence of overthickened crust from aseismic ridge subduction is essential. Overthickened crust leads to buoyant slabs. We reproduce formation and deposition of the Acres-Solimoes basin and the evolution of the Amazon drainage basin in Peru as well as the Mar Chiquita

  4. Use of vertical temperature gradients for prediction of tidal flat sediment characteristics

    NASA Astrophysics Data System (ADS)

    Miselis, Jennifer L.; Holland, K. Todd; Reed, Allen H.; Abelev, Andrei

    2012-03-01

    Sediment characteristics largely govern tidal flat morphologic evolution; however, conventional methods of investigating spatial variability in lithology on tidal flats are difficult to employ in these highly dynamic regions. In response, a series of laboratory experiments was designed to investigate the use of temperature diffusion toward sediment characterization. A vertical thermistor array was used to quantify temperature gradients in simulated tidal flat sediments of varying compositions. Thermal conductivity estimates derived from these arrays were similar to measurements from a standard heated needle probe, which substantiates the thermistor methodology. While the thermal diffusivities of dry homogeneous sediments were similar, diffusivities for saturated homogeneous sediments ranged approximately one order of magnitude. The thermal diffusivity of saturated sand was five times the thermal diffusivity of saturated kaolin and more than eight times the thermal diffusivity of saturated bentonite. This suggests that vertical temperature gradients can be used for distinguishing homogeneous saturated sands from homogeneous saturated clays and perhaps even between homogeneous saturated clay types. However, experiments with more realistic tidal flat mixtures were less discriminating. Relationships between thermal diffusivity and percent fines for saturated mixtures varied depending upon clay composition, indicating that clay hydration and/or water content controls thermal gradients. Furthermore, existing models for the bulk conductivity of sediment mixtures were improved only through the use of calibrated estimates of homogeneous end-member conductivity and water content values. Our findings suggest that remotely sensed observations of water content and thermal diffusivity could only be used to qualitatively estimate tidal flat sediment characteristics.

  5. Use of vertical temperature gradients for prediction of tidal flat sediment characteristics

    USGS Publications Warehouse

    Miselis, Jennifer L.; Holland, K. Todd; Reed, Allen H.; Abelev, Andrei

    2012-01-01

    Sediment characteristics largely govern tidal flat morphologic evolution; however, conventional methods of investigating spatial variability in lithology on tidal flats are difficult to employ in these highly dynamic regions. In response, a series of laboratory experiments was designed to investigate the use of temperature diffusion toward sediment characterization. A vertical thermistor array was used to quantify temperature gradients in simulated tidal flat sediments of varying compositions. Thermal conductivity estimates derived from these arrays were similar to measurements from a standard heated needle probe, which substantiates the thermistor methodology. While the thermal diffusivities of dry homogeneous sediments were similar, diffusivities for saturated homogeneous sediments ranged approximately one order of magnitude. The thermal diffusivity of saturated sand was five times the thermal diffusivity of saturated kaolin and more than eight times the thermal diffusivity of saturated bentonite. This suggests that vertical temperature gradients can be used for distinguishing homogeneous saturated sands from homogeneous saturated clays and perhaps even between homogeneous saturated clay types. However, experiments with more realistic tidal flat mixtures were less discriminating. Relationships between thermal diffusivity and percent fines for saturated mixtures varied depending upon clay composition, indicating that clay hydration and/or water content controls thermal gradients. Furthermore, existing models for the bulk conductivity of sediment mixtures were improved only through the use of calibrated estimates of homogeneous end-member conductivity and water content values. Our findings suggest that remotely sensed observations of water content and thermal diffusivity could only be used to qualitatively estimate tidal flat sediment characteristics.

  6. Characterization of sediment trapped by macroalgae on a Hawaiian reef flat

    USGS Publications Warehouse

    Stamski, R.E.; Field, M.E.

    2006-01-01

    Reef researchers studying community shifts in the balance between corals and fleshy macroalgae have noted that algae are often covered with sediment. This study characterizes sediment trapping by macroalgae within a Hawaiian reef habitat and constrains the controls on this process. Sediment-laden macroalgae were sampled and macroalgal cover was assessed on a wide (???1 km) reef flat off south-central Molokai. Macroalgae trapped a mean of 1.26 (??0.91 SD) grams of sediment per gram of dry weight biomass and that sediment was dominantly terrigenous mud (59% by weight). It was determined that biomass, as a proxy for algal size, and morphology were not strict controls on the sediment trapping process. Over 300 metric tons of sediment were estimated to be retained by macroalgae across 5.75 km2 of reef flat (54 g m-2), suggesting that this process is an important component of sediment budgets. In addition, understanding the character of sediment trapped by macroalgae may help constrain suspended sediment flux and has implications for nutrient dynamics in reef flat environments. ?? 2005 Elsevier Ltd. All rights reserved.

  7. Identification and characterization of metagenomic fragments from tidal flat sediment.

    PubMed

    Kim, Byung Kwon; Park, Yoon-Dong; Oh, Hyun-Myung; Chun, Jongsik

    2009-08-01

    Phylogenetic surveys based on cultivation-independent methods have revealed that tidal flat sediments are environments with extensive microbial diversity. Since most of prokaryotes in nature cannot be easily cultivated under general laboratory conditions, our knowledge on prokaryotic dwellers in tidal flat sediment is mainly based on the analysis of metagenomes. Microbial community analysis based on the 16S rRNA gene and other phylogenetic markers has been widely used to provide important information on the role of microorganisms, but it is basically an indirect means, compared with direct sequencing of metagenomic DNAs. In this study, we applied a sequence-based metagenomic approach to characterize uncultivated prokaryotes from tidal flat sediment. Two large-insert genomic libraries based on fosmid were constructed from tidal flat metagenomic DNA. A survey based on end-sequencing of selected fosmid clones resulted in the identification of clones containing 274 bacterial and 16 archaeal homologs in which majority were of proteobacterial origins. Two fosmid clones containing large metagenomic DNAs were completely sequenced using the shotgun method. Both DNA inserts contained more than 20 genes encoding putative proteins which implied their ecological roles in tidal flat sediment. Phylogenetic analyses of evolutionary conserved proteins indicate that these clones are not closely related to known prokaryotes whose genome sequence is known, and genes in tidal flat may be subjected to extensive lateral gene transfer, notably between domains Bacteria and Archaea. This is the first report demonstrating that direct sequencing of metagenomic gene library is useful in underpinning the genetic makeup and functional roles of prokaryotes in tidal flat sediments. PMID:19763413

  8. Dynamics of intertidal flats in the Loire estuary

    NASA Astrophysics Data System (ADS)

    Kervella, Stephane; Sottolichio, Aldo; Bertier, Christine

    2014-05-01

    Tidal flats form at the edges of many tidal estuaries, and are found in broad climatic regions. Their evolution plays a fundamental role in maintaining the morphodynamic equilibrium of an estuary. The Loire estuary is one of the largest macrotidal systems of the french atlantic coast. Since 200 years, its geometry has been drastically modified through channeling, deepening, embanking, infilling of secondary channels, etc. These works altered many intertidal areas. In the recent years, efforts for the rectification of the morphology have been made in order to restore the ecology of the estuary. In this context, it is crucial to better understand the dynamics of intertidal flats, still poorly understood in this estuary. The aim of this work is to analyse a series of original observations conducted for the first time in two intertidal flats of the central Lore estuary between 2008 and 2010. The tidal flats are situated in the northern bank, at 12 and 17 km upstream from the mouth respectively. Six Altus altimeters were deployed at two cross shore transects, measuring continuously and at a high-frequency bed altimetry and water level, providing information on tide and waves. At the semi-diurnal tidal scale, the surficial sediment of intertidal flats is permanently mobilized. Altimetry variations are low, and their amplitude varies as a function of tides and river flow. At the scale of several months, the sedimentation is controlled by the position of the turbidity maximum (and therefore by the river flow) and also by the tidal amplitude. During low river flow periods, altimetry variations are only due to tidal cycles. During decaying tides, suspended sediment settle mainly on the lower part of the tidal flats, forming fluid mud layers of several cm thick, which can consolidate rapidly; under rising tides, the increasing of tidal currents promotes erosion. During periods of high river flow, the turbidity maximum shifts to the lower estuary. The higher suspended sediment

  9. Transformations of sulfur compounds in marsh-flat sediments

    SciTech Connect

    Swider, K.T.; Mackin, J.E. )

    1989-09-01

    Measurements were made in mud-flat sediments from Flax Pond salt marsh to characterize the rates and mechanisms of sulfur cycling in an organic-rich coastal marine environment. Approximately 13 mmoles/m{sup 2} of reduced sulfur are generated annually in the mud flat and the dominant solid-phase product is pyrite. Ion activity products involving dissolved iron and sulfide species indicate approximate saturation with respect to metastable iron sulfide phases, showing that pyrite is not likely to be the first-formed Fe-bearing sulfide. Comparison of {Sigma}H{sub 2}S vs. SO{sup =}{sub 4} relationships in anoxic incubation experiments with those occurring in the undisturbed sediment permits evaluation of possible mechanisms involved in the transformation of metastable iron monosulfides to pyrite. Oxidants (e.g. MnO{sub 2}) that are introduced into the surface sediment, either by animal activity or physical events, are apparently necessary to cause major oxidation of FeS and {Sigma}H{sub 2}S to pyrite and sulfate. Solid-phase sulfur analyses and net {Sigma}H{sub 2}S accumulation in sediment pore waters are consistent with major sulfide oxidation, indicating that approximately 95% of the sulfide generated in the mud flat is reoxidized to sulfate and roughly half of this oxidation involves dissolved sulfide. The major factors limiting reduced sulfur burial are physical and biological disturbances and a low abundance of reactive solid-phase iron (2 wt%).

  10. Numerical study of sediment transport on a tidal flat with a patch of vegetation

    NASA Astrophysics Data System (ADS)

    Ma, Gangfeng; Han, Yun; Niroomandi, Arash; Lou, Sha; Liu, Shuguang

    2015-02-01

    To understand how vegetation canopies affect sediment transport on tidal flats, a numerical study of tidal flow and sediment transport on an idealized tidal flat with a patch of vegetation is conducted. The numerical model is firstly validated by laboratory measurements of flow and sediment deposition in a partially vegetated open channel. The idealized study shows that a finite patch of vegetation may produce circulation on the tidal flat with converging flow during flood and diverging flow during ebb. The vegetation patch can also generate a tidal phase lag between the vegetated and bare flats. Tidal currents in both zones are asymmetric, with stronger flood current in the vegetated zone and stronger ebb current on the bare flat. The duration of ebb is longer than that of flood. Computed sediment concentration on the bare flat is higher during ebb due to stronger ebb current and larger bottom shear stress. This is in contrast to the tidal flat without a vegetation canopy, where suspended sediment concentration is higher during flood. On the tidal flat without a vegetation canopy, landward net sediment transport occurs on the upper flat, while seaward net sediment transport occurs on the lower flat and subtidal region. On the partially vegetated tidal flat, however, net sediment transport on both the upper and lower flats are in seaward direction. It increases with increasing vegetation density. Alongshore net sediment flux converges inside the canopy and diverges on the bare flat. Sediment exchange rate between the vegetated and bare flats increases with decreasing vegetation density and sediment settling velocity.

  11. A one-dimensional biomorphodynamic model of tidal flats: Sediment sorting, marsh distribution, and carbon accumulation under sea level rise

    NASA Astrophysics Data System (ADS)

    Zhou, Zeng; Ye, Qinghua; Coco, Giovanni

    2016-07-01

    We develop a biomorphodynamic model to investigate sediment and vegetation dynamics on a schematic intertidal flat characterized by an initially well-mixed sand-mud mixture. Major interactions between tides, wind waves, salt marshes, sediment transport and sea level rise (SLR) are taken into account. For a bare flat under only tidal action, the model predicts a convex cross-shore profile with the surficial distribution of mud and sand on the upper and lower part of the intertidal flat, respectively. When wind waves are strong, the intertidal flat is highly eroded resulting in a concave profile near the high water mark. This behavior is pronouncedly altered when the intertidal flat is vegetated with the presence of salt marshes. Numerical results suggest that a considerable amount of mud can still remain in the vegetated region even when wave action is strong. A steeper transition zone forms at the boundary between salt marshes and bare flats because of the differential sediment deposition in the two neighboring regions. The inclusion of wind waves is found to considerably enhance the size of the marsh-edge transition zone. For the numerical experiments designed in this study, the profile shape and sediment sorting behavior of tidal flats are not significantly modified by a gradual rising sea level. However, the impacts of SLR on vegetated tidal flats are still manifold: (a) driving the landward migration of intertidal zone and salt marshes; (b) enhancing sediment erosion on intertidal flats; and (c) drowning salt marshes under limited sediment supply with the constrain of seawalls. Finally, model results suggest that organic carbon accumulation on marshlands may be enhanced with an increasing SLR rate provided that salt marshes are not drowned.

  12. Day-night variation of intertidal flat sediment properties in relation to sediment stability

    NASA Astrophysics Data System (ADS)

    Friend, P. L.; Collins, M. B.; Holligan, P. M.

    2003-11-01

    The majority of investigations that have measured sediment properties related to intertidal sediment stability have been undertaken during daylight subaerial exposure periods. As a consequence, models based upon such data represent only partially the intertidal flat surface conditions within any 24 h period. In this contribution, a comparison is made between surface sediment properties related to sediment stability measured during six consecutive (day/night), semi-diurnal subaerial exposure periods, at three stations on an intertidal sand flat in late March 1999. The study site was selected on the basis of its suitability for sampling and data collection at night, with special regard to safety and logistics. Seawater temperatures ranged from 4.1 to 9.6 °C, and salinities from 33.9 to 34.8. Eleven parameters related to intertidal flat sediment stability were measured, or derived. These variables included the critical erosion shear stress ( τc), chlorophyll a, phaeopigment, and colloidal carbohydrate content, mean grain size and settling velocity of the surface (0-1 mm) sediment fraction. Bed elevation was described using an acretion/erosion parameter (AEP) (West and West 1991), whilst additional physical terms included ambient seawater salinity and temperature, as well as tidal range and wind speed, during the preceding immersion periods. One-way ANOVA was used to detect significant differences between day- and night-time emersion periods; similarly, principal components analysis (PCA) was applied to detect continuous variation between properties. The results show a high degree of temporal and spatial variability between day- and night-time intertidal flat variables, the PCA differentiating clearly between day and night conditions. Surface sediments across the intertidal flat exhibited varying degrees of biostabilisation. The maximum biostabilisation coefficient (18) was recorded at night in high microalgal biomass areas; the minimum (5) occurred during both day

  13. Forced Convection and Sedimentation Past a Flat Plate

    NASA Technical Reports Server (NTRS)

    Pelekasis, Nikolaos A.; Acrivos, Andreas

    1995-01-01

    The steady laminar flow of a well-mixed suspension of monodisperse solid spheres, convected steadily past a horizontal flat plate and sedimenting under the action of gravity, is examined. It is shown that, in the limit as Re approaches infinity and epsilon approaches 0, where Re is the bulk Reynolds number and epsilon is the ratio of the particle radius a to the characteristic length scale L, the analysis for determining the particle concentration profile has several aspects in common with that of obtaining the temperature profile in forced-convection heat transfer from a wall to a fluid stream moving at high Reynolds and Prandtl numbers. Specifically, it is found that the particle concentration remains uniform throughout the O(Re(exp -1/2)) thick Blasius boundary layer except for two O(epsilon(exp 2/3)) thin regions on either side of the plate, where the concentration profile becomes non-uniform owing to the presence of shear-induced particle diffusion which balances the particle flux due to convection and sedimentation. The system of equations within this concentration boundary layer admits a similarity solution near the leading edge of the plate, according to which the particle concentration along the top surface of the plate increases from its value in the free stream by an amount proportional to X(exp 5/6), with X measuring the distance along the plate, and decreases in a similar fashion along the underside. But, unlike the case of gravity settling on an inclined plate in the absence of a bulk flow at infinity considered earlier, here the concentration profile remains continuous everywhere. For values of X beyond the region near the leading edge, the particle concentration profile is obtained through the numerical solution of the relevant equations. It is found that, as predicted from the similarity solution, there exists a value of X at which the particle concentration along the top side of the plate attains its maximum value phi(sub m) and that, beyond this

  14. Coastal sediment dynamics in Spitsbergen

    NASA Astrophysics Data System (ADS)

    Deloffre, J.; Lafite, R.; Baltzer, A.; Marlin, C.; Delangle, E.; Dethleff, D.; Petit, F.

    2010-12-01

    In arctic knowledge on coastal sediment dynamics and sedimentary processes is limited. The studied area is located in the microtidal Kongsfjorden glacial fjord on the North-western coast of Spitsbergen in the Artic Ocean (79°N). In this area sediment contributions to the coastal zone is provided by small temporary rivers that flows into the fjord. The objectives of this study are to (i) assess the origin and fate of fine-grained particles (<63µm) from the piedmont glacier to the coastal zone (0-30m depth), (ii) establish the role of this coastal zone in sediment transfer and (iii) identify the impact of sea ice cover on sediment dynamics. The sampling strategy is based on characterization of sediment and SPM (grain-size, X-rays diffraction, SEM images, carbonates and organic matter contents) from the glacier to the coastal zone completed by a bottom-sediment map on the nearshore using side-scan sonar validated with Ekman binge sampling. River inputs (i.e. river plumes) to the coastal zone were punctually followed using CTD (conductivity, temperature, depth and turbidity) profiles. OBS (water level, temperature and turbidity) operating at high-frequency and during at least 1 years (including under sea ice cover) was settled at the mouth of rivers at 10m depth. In the coastal zone the fine-grained sediment deposit is limited to mud patches located at river mouths that originate the piedmont glacier. However a significant amount of sediment originates the coastal glacier located in the eastern part of the fjord via two processes: direct transfer and ice-drop. Results from turbidity measurements show that the sediment dynamics is controlled by river inputs in particular during melting period. During winter sediment resuspension can occurs directly linked to significant wind-events. When the sea ice cover is present (January to April) no sediment dynamics is observed. Sediment processes in the coastal zone of arctic fjords is significant however only a small amount of

  15. Erythrobacter lutimaris sp. nov., isolated from a tidal flat sediment.

    PubMed

    Jung, Yong-Taek; Park, Sooyeon; Lee, Jung-Sook; Yoon, Jung-Hoon

    2014-12-01

    A Gram-stain-negative, non-motile, coccoid- or oval-shaped bacterial strain, designated S-5(T), belonging to the class Alphaproteobacteria, was isolated from a tidal flat sediment of the Yellow Sea, Korea and was subjected to a polyphasic taxonomic study. Strain S-5(T) grew optimally at pH 7.0-8.0, at 30 °C and in the presence of 2-3 % (w/v) NaCl. Neighbour-joining analysis based on 16S rRNA gene sequences showed that strain S-5(T) fell within the clade comprising the species of the genus Erythrobacter, clustering with the type strains of Erythrobacter pelagi, Erythrobacter citreus and Erythrobacter seohaensis with which it exhibited the highest 16S rRNA gene sequence similarity (96.0-96.7 %). The DNA G+C content was 66.0 mol%. Strain S-5(T) contained Q-10 as the predominant ubiquinone and summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c) and C17 : 1ω6c as the major fatty acids. The major polar lipids were sphingoglycolipid, phosphatidylcholine, phosphatidylglycerol, an unidentified glycolipid and two unidentified lipids. Differential phenotypic properties, together with the phylogenetic and genetic distinctiveness, demonstrated that strain S-5(T) is distinguishable from other species of the genus Erythrobacter. On the basis of the data presented, strain S-5(T) is considered to represent a novel species of the genus Erythrobacter, for which the name Erythrobacter lutimaris sp. nov. is proposed. The type strain is S-5(T) ( = KCTC 42109(T) = CECT 8624(T)). PMID:25253070

  16. Algoriphagus lutimaris sp. nov., isolated from a tidal flat sediment.

    PubMed

    Park, Sooyeon; Kang, So-Jung; Oh, Ki-Hoon; Oh, Tae-Kwang; Yoon, Jung-Hoon

    2010-01-01

    A Gram-negative, non-motile, non-spore-forming bacterial strain, S1-3(T), was isolated from a tidal flat sediment on the west coast of Korea and its taxonomic position was investigated. Strain S1-3(T) grew optimally at 30 degrees C and in the presence of 2 % (w/v) NaCl. Strain S1-3(T) contained MK-7 as the predominant menaquinone and C(16 : 1)omega7c and/or iso-C(15 : 0) 2-OH and iso-C(15 : 0) as the major fatty acids. The DNA G+C content was 41.4 mol%. Phylogenetic analyses based on 16S rRNA gene sequences revealed that strain S1-3(T) fell within the clade comprising Algoriphagus species, clustering with Algoriphagus halophilus IMSNU 14013(T), with which it exhibited 99.6 % 16S rRNA gene sequence similarity. The 16S rRNA gene sequence similarity between strain S1-3(T) and the type strains of other Algoriphagus species was 94.0-97.1 %. Differential phenotypic properties and phylogenetic and genetic distinctiveness of strain S1-3(T) demonstrated that this strain is distinguishable from the other Algoriphagus species as well as A. halophilus. On the basis of phenotypic, chemotaxonomic, phylogenetic and genetic data, strain S1-3(T) is considered to represent a novel species of the genus Algoriphagus, for which the name Algoriphagus lutimaris sp. nov. is proposed. The type strain is S1-3(T) (=KCTC 22630(T) =CCUG 57608(T)). PMID:19648320

  17. Predicting long-term and short-term tidal flat morphodynamics using a dynamic equilibrium theory

    NASA Astrophysics Data System (ADS)

    Hu, Zhan; Wang, Zheng Bing; Zitman, Tjerk J.; Stive, Marcel J. F.; Bouma, Tjeerd J.

    2015-09-01

    Dynamic equilibrium theory is a fruitful concept, which we use to systematically explain the tidal flat morphodynamic response to tidal currents, wind waves, sediment supply, and other sedimentological drivers. This theory stems from a simple analytical model that derives the tide- or wave-dominated tidal flat morphology by assuming that morphological equilibrium is associated with uniform bed shear stress distribution. Many studies based on observation and process-based modeling tend to agree with this analytical model. However, a uniform bed shear stress rarely exists on actual or modeled tidal flats, and the analytical model cannot handle the spatially and temporally varying bed shear stress. In the present study, we develop a model based on the dynamic equilibrium theory and its core assumption. Different from the static analytical model, our model explicitly accounts for the spatiotemporal bed shear stress variations for tidal flat dynamic prediction. To test our model and the embedded theory, we apply the model for both long-term and short-term morphological predictions. The long-term modeling is evaluated qualitatively against previous process-based modeling. The short-term modeling is evaluated quantitatively against high-resolution bed-level monitoring data obtained from a tidal flat in Netherlands. The model results show good performances in both qualitative and quantitative tests, indicating the validity of the dynamic equilibrium theory. Thus, this model provides a valuable tool to enhance our understanding of the tidal flat morphodynamics and to apply the dynamic equilibrium theory for realistic morphological predictions.

  18. Paracoccus lutimaris sp. nov., isolated from a tidal flat sediment.

    PubMed

    Jung, Yong-Taek; Park, Sooyeon; Lee, Jung-Sook; Yoon, Jung-Hoon

    2014-08-01

    A Gram-negative, coccoid or oval-shaped and gliding bacterial strain, designated HDM-25(T), belonging to the Alphaproteobacteria, was isolated from a tidal flat sediment of the Yellow Sea, Korea, and was subjected to a polyphasic taxonomic study. Strain HDM-25(T) grew optimally at pH 7.0-8.0, at 30 °C and in the presence of 2-3% (w/v) NaCl. Neighbour-joining, maximum-likelihood and maximum-parsimony phylogenetic trees based on 16S rRNA gene sequences showed that strain HDM-25(T) fell within the clade comprising the species of the genus Paracoccus, clustering with the type strain of Paracoccus aminophilus, with which it exhibited the highest 16S rRNA gene sequence similarity (97.7%). The 16S rRNA gene sequence similarity between strain HDM-25(T) and the type strains of the other species of Paracoccus was 93.6-97.0%. The DNA G+C content was 65.9 mol% and the mean DNA-DNA relatedness between strain HDM-25(T) and the type strain of P. aminophilus was 10.7±2.7% (9.9±4.0%, reciprocal analysis). Strain HDM-25(T) contained Q-10 as the predominant ubiquinone and summed feature 8 (C(18 : 1)ω7c and/or C(18 : 1)ω6c) and C(16 : 0) as the major fatty acids. The major polar lipids were phosphatidylcholine, phosphatidylglycerol, diphosphatidylglycerol, an unidentified aminolipid, an unidentified glycolipid and an unidentified lipid. Differential phenotypic properties, together with the phylogenetic and genetic distinctiveness, demonstrated that strain HDM-25(T) is distinguishable from other species of the genus Paracoccus. On the basis of the data presented, strain HDM-25(T) is considered to represent a novel species of the genus Paracoccus, for which the name Paracoccus lutimaris sp. nov. is proposed. The type strain is HDM-25(T) ( = KCTC 42007(T) = CECT 8525(T)). PMID:24860114

  19. Loktanella sediminilitoris sp. nov., isolated from tidal flat sediment.

    PubMed

    Park, Sooyeon; Jung, Yong-Taek; Yoon, Jung-Hoon

    2013-11-01

    A Gram-stain-negative, non-motile, rod-shaped bacterial strain, designated D1-W3(T), was isolated from tidal flat sediment of the South Sea, South Korea, and subjected to a taxonomic study using a polyphasic approach. Strain D1-W3(T) grew optimally at pH 7.0-8.0, at 25 °C and in the presence of 2 % (w/v) NaCl. Neighbour-joining phylogenetic analyses based on 16S rRNA gene sequences revealed that strain D1-W3(T) fell within the clade comprising species of the genus Loktanella, clustering with the type strains of Loktanella tamlensis, Loktanella rosea and Loktanella maricola, with which it exhibited the highest 16S rRNA gene sequence similarity values (98.1-98.2 %). The 16S rRNA gene sequence similarity values between strain D1-W3(T) and the type strains of other species of the genus Loktanella were in the range 93.5-96.5 %. The DNA G+C content of strain D1-W3(T) was 58.1 mol% and the mean DNA-DNA hybridization values with L. tamlensis KCTC 12722(T), L. rosea LMG 22534(T) and L. maricola DSW-18(T) were 13-25 %. Strain D1-W3(T) contained Q-10 as the predominant ubiquinone and C18 : 1ω7c as the predominant fatty acid. The major polar lipids were phosphatidylcholine, phosphatidylglycerol, phosphatidylethanolamine and one unidentified aminolipid. Differential phenotypic properties, together with the phylogenetic and genetic distinctiveness, showed that strain D1-W3(T) could be differentiated from other species of the genus Loktanella. On the basis of the data presented, strain D1-W3(T) represents a novel species of the genus Loktanella, for which the name Loktanella sediminilitoris sp. nov. is proposed. The type strain is D1-W3(T) ( = KCTC 32383(T) = CECT 8284(T)). PMID:23749279

  20. Heavy metal pollution and assessment in the tidal flat sediments of Haizhou Bay, China.

    PubMed

    Zhang, Rui; Zhou, Li; Zhang, Fan; Ding, Yingjun; Gao, Jinrong; Chen, Jing; Yan, Hongqiang; Shao, Wei

    2013-09-15

    The heavy metal inventory and the ecological risk of the tidal flat sediments in Haizhou Bay were investigated. Results show that the average concentrations of heavy metals in the surface sediments exceeded the environment background values of Jiangsu Province coastal soil, suggesting that the surface sediments were mainly polluted by heavy metals (Cd, Cr, Cu, Mn, Pb and Zn). In addition, the profiles of heavy metals fluxes can reflect the socio-economic development of Lianyungang City, and heavy metals inputs were attributed to anthropogenic activities. Cr, Cu, Pb and Zn were mainly present in the non-bioavailable residual form in surface sediments, whereas Cd and Mn were predominantly in the highly mobile acid soluble and reducible fractions. The ecological risk of the polluted sediments stemmed mainly from Cd and Pb. According to the Sediment quality guidelines (SQGs), however, the adverse biological effects caused by the heavy metals occasionally occurred in tidal flat. PMID:23820195

  1. Site-specific features influence sediment stability of intertidal flats

    NASA Astrophysics Data System (ADS)

    Defew, Emma C.; Tolhurst, Trevor J.; Paterson, David M.

    The factors that influence the sediment stability and the transport of estuarine mudflats are not yet fully understood but knowledge of them is essential in coastal engineering applications and pollution ecology studies. The suggestion that variation in predictive models of sediment stability might be due to site-specific characteristics is investigated using data from four estuarine mudflats (Eden Estuary, Scotland, the Biezelingsche Ham, Zandkreek, and Molenplaat mudflats in The Netherlands). These estuaries differ in their environmental conditions, macrofaunal species composition and local features (e.g. Enteromorpha mats, migratory biofilms). Stable and unstable sediments were compared, and mean chlorophyll-a concentrations and granulometry of the sediments were significantly different between the two groups. Step-wise multiple linear regressions were applied to the sediment stability data of all sites to establish the influences on erosion threshold of microphytobenthic biomass, water content, granulometry, organic carbon content and the abundance of dominant macrofaunal species. The stability of each site was influenced by different factors. Sediment stability of the Eden Estuary was affected by the Enteromorpha bloom; Biezelingsche Ham was influenced by the highly migratory nature of the diatom biofilms and the abundance of Corophium volutator; the polychaete worm Arenicola marina had a net negative effect on sediment stability of the Zandkreek; and the Molenplaat was influenced by microphytobenthic biomass. This research highlights the need for site-specific calibration of models and suggests that a universal proxy parameter for sediment stability is unlikely to be obtained.

  2. Hydrodynamics and sediment suspension in shallow tidal channels intersecting a tidal flat

    NASA Astrophysics Data System (ADS)

    Pieterse, Aline; Puleo, Jack A.; McKenna, Thomas E.

    2016-05-01

    A field study was conducted on a tidal flat intersected by small tidal channels (depth <0.1 m, width <2 m) within a tidal marsh. Data were collected in the channels, and on the adjacent tidal flat that encompasses approximately 1600 m2 in planform area. Hydrodynamic processes and sediment suspension between the channels and adjacent flat were compared. Shear stress and turbulent kinetic energy were computed from high frequency velocity measurements. Maximum water depth at the field site varied from 0.11 m during the lowest neap high tide to 0.58 m during a storm event. In the channel intersecting the tidal flat, the shear stress, turbulence and along-channel velocity were ebb dominant; e.g. 0.33 m/s peak velocity for ebb compared to 0.19 m/s peak velocity for flood. Distinct pulses in velocity occurred when the water level was near the tidal flat level. The velocity pulse during flood tide occurred at a higher water level than during ebb tide. No corresponding velocity pulse on the tidal flat was observed. Sediment concentrations peaked at the beginning and end of each tidal cycle, and often had a secondary peak close to high tide, assumed to be related to sediment advection. The influence of wind waves on bed shear stress and sediment suspension was negligible. Water levels were elevated during a storm event such that the tidal flat remained inundated for 4 tidal cycles. The water did not drain from the tidal flat into the channels during the storm, and no velocity pulses occurred. Along-channel velocities, turbulent kinetic energy, and shear stresses were therefore smaller in the channels during storm conditions than during non-storm conditions.

  3. How vegetation patterning affects sediment dynamics in complex landscapes

    NASA Astrophysics Data System (ADS)

    Baartman, Jantiene; Temme, Arnaud; Saco, Patricia

    2016-04-01

    Semi-arid ecosystems are often spatially self-organized in typical patterns of vegetation bands with high plant cover interspersed with bare soil areas, also known as 'tigerbush'. Tigerbush dynamics have been studied using model simulations on flat synthetic landscapes, although in some cases straight slopes were used. The feedbacks between vegetation and more realistic and complex landscapes have not been studied yet, even though these landscapes are much more prevalent. Hence, our objective was to determine the effect of landform variation on vegetation patterning and sediment dynamics. We linked two existing models that simulate (a) plant growth, death and dispersal of vegetation, and (b) erosion and sedimentation. The model was calibrated on a straight planar hillslope and then applied to (i) a set of synthetic but more complex topographies and (ii) three real-world landscapes. Furthermore, sediment dynamics were evaluated by comparing simulated sediment output with and without vegetation dynamics. Results show banded vegetation patterning on all synthetic topographies, always perpendicular to the slope gradient. For real topographies, banded vegetation was simulated in the relatively flat, rolling landscape and in the dissected landscape when slopes were gentle. In the steep dissected landscape and the alluvial fan, vegetation was simulated to grow in local depressions where moisture is present whereas hilltops were bare. Including vegetation dynamics resulted in significantly less simulated erosion and relatively more deposition compared to simulations with uniformly distributed vegetation.

  4. Experimental research on the impact of Corbicula fluminea on DIN exchange at a tidal flat sediment-water interface

    NASA Astrophysics Data System (ADS)

    Liu, Jie; Chen, Zhenlou; Xu, Shiyuan; Zheng, Xiangmin

    2007-10-01

    Based on a simulative experiment and a comparison analysis, the effect of bivalve Corbicula fluminea activity on sediment-water exchange of dissolved inorganic nitrogen (DIN) is studied. The areas included three intertidal flat sites of the Changjiang (Yangtze) River estuary in China. The interface exchange flux of ammonium, nitrate and nitrite in the short experiment (6 h) was -46.4-40, -74.8-929.1 and 2.5-14.6 µmol/(m2·h), respectively. It was found that the burrowing activities of C. fluminea increased NH{4/+} and NO{3/-} release from sediments to overlying water in the short-term experiment. During long-term incubation, NH{4/+} and NO{3/-} released in turn from the sediments. At the beginning of incubation, bioturbation by C. fluminea could accelerate NH{4/+} release from sediments 2-17 times in different sites, resulting in stronger nitrification and increased NO{3/-} concentrations in the overlying water. Sediment profile analysis post-incubation shows that organic matter mineralization and sediment-water NH{4/+} exchange had been stimulated by C. fluminea bioturbation and bioirrigation during the experiment. Therefore, C. fluminea activities such as excretion, burrowing, irrigation and turbation can effectively alter nitrogen dynamics and accelerate and stimulate nitrogen exchange and cycling at the sediment-water interface.

  5. Wood and Sediment Dynamics in River Corridors

    NASA Astrophysics Data System (ADS)

    Wohl, E.; Scott, D.

    2015-12-01

    Large wood along rivers influences entrainment, transport, and storage of mineral sediment and particulate organic matter. We review how wood alters sediment dynamics and explore patterns among volumes of instream wood, sediment storage, and residual pools for dispersed pieces of wood, logjams, and beaver dams. We hypothesized that: volume of sediment per unit area of channel stored in association with wood is inversely proportional to drainage area; the form of sediment storage changes downstream; sediment storage correlates most strongly with wood load; and volume of sediment stored behind beaver dams correlates with pond area. Lack of data from larger drainage areas limits tests of these hypotheses, but analyses suggest a negative correlation between sediment volume and drainage area and a positive correlation between wood and sediment volume. The form of sediment storage in relation to wood changes downstream, with wedges of sediment upstream from jammed steps most prevalent in small, steep channels and more dispersed sediment storage in lower gradient channels. Use of a published relation between sediment volume, channel width, and gradient predicted about half of the variation in sediment stored upstream from jammed steps. Sediment volume correlates well with beaver pond area. Historically more abundant instream wood and beaver populations likely equated to greater sediment storage within river corridors. This review of the existing literature on wood and sediment dynamics highlights the lack of studies on larger rivers.

  6. Cycling of trace metals (Mn, Fe, Mo, U, V, Cr) in deep pore waters of intertidal flat sediments

    NASA Astrophysics Data System (ADS)

    Beck, Melanie; Dellwig, Olaf; Schnetger, Bernhard; Brumsack, Hans-Jürgen

    2008-06-01

    Trace metals (Mn, Fe, Mo, U, Cr, V) were studied in pore waters of an intertidal flat located in the German Wadden Sea. The study system is an example of a permeable tidal flat system where pore water exchange is affected by tidal driven pressure gradients besides diffusion. Permanently installed in situ samplers were used to extract pore waters down to 5 m depth throughout one year. The samplers were either located close to the tidal flat margin or in central parts of the tidal flat. Despite dynamic sedimentological and hydrological conditions, the general trends with depth in deep tidal flat pore waters are remarkably similar to those observed in deep sea environments. Rates of trace metal cycling must be comparably large in order to maintain the observed pore water profiles. Trace metals further show similar general trends with depth close to the margin and in central parts of the tidal flat. Seasonal sampling revealed that V and Cr vary concurrent with seasonal changes in dissolved organic carbon (DOC) concentration. This effect is most notable close to the tidal flat margin where sulphate, DOC, and nutrients vary with season down to some metres depth. Seasonal variations of Mn, Fe, Mo, and U are by contrast limited to the upper decimetres of the sediment. Their seasonal patterns depend on organic matter supply, redox stratification, and particulate matter deposited on sediment surfaces. Pore water sampling within one tidal cycle provides evidence for pore water advection in margin sediments. During low tide pore water flow towards the creekbank is generated by a hydraulic gradient suggesting that deep pore waters may be seeping out of creekbank sediments. Owing to the enrichment of specific elements like Mn in pore water compared to sea water, seeping pore waters may have an impact on the chemistry of the open water column. Mass balance calculations reveal that the impact of deep pore waters on the Mn budget in the open water column is below 4%. Mn deep pore

  7. Draft Genome Sequence of Zhouia amylolytica AD3, Isolated from Tidal Flat Sediment

    PubMed Central

    Jia, Baolei; Jin, Hyun Mi; Lee, Hyo Jung

    2016-01-01

    Zhouia amylolytica AD3 was isolated from tidal flat sediment at Taean, South Korea. We report here the draft genome sequence of Z. amylolytica AD3, which is the first report of a genome sequence of the genus Zhouia. The genomic information will provide a better understanding of the physiology, adaptation, and evolution of Zhouia species. PMID:27151796

  8. The role of flow asymmetry and mud properties on tidal flat sedimentation

    NASA Astrophysics Data System (ADS)

    van Maren, D. S.; Winterwerp, J. C.

    2013-06-01

    It is well known that landward transport of fine sediments on tidal flats is caused by lag effects, of which the scour lag and the settling lag are the best known. These lag effects result from a combination of sediment properties and hydrodynamic asymmetries. However, it is not well-understood how, in a quantitative way, these lag effects depend on the sediment properties and the hydrodynamic forcing, and what the relative importance of these sediment properties and hydrodynamics is. As a result, it is not known which lag effect is more important under which conditions. We therefore set out to explore the relative importance of hydrodynamics and sediment properties on tidal-flat sedimentation using a schematized 2DV cross-shore profile model with a tidal range of 6m and an intertidal width of ˜5km. The effect of hydrodynamics is parameterized through a varying offshore tidal asymmetry and four different cross-shore profiles (a horizontal, convex, linear and concave profile). The effect of sediment properties is examined by evaluating a range of settling velocities ws and critical bed shear stresses for erosion τcr. The main findings of this work are that (1) conditions of maximum sediment deposition rates exist for ws ˜0.5mm/s and τcr ˜0.1Pa, (2) deposition rates due to slack tide asymmetry are comparable to symmetric tides, while peak flow asymmetry produces the greatest deposition rates, (3) tidal flat deposition rates are greatest for concave profiles and least for convex profiles mainly due to the horizontal velocity gradient, and (4) the type of lag effect dominating landward transport varies spatially.

  9. Dynamically generated flat-band phases in optical kagome lattices

    NASA Astrophysics Data System (ADS)

    Chern, Gia-Wei; Chien, Chih-Chun; Di Ventra, Massimiliano

    2014-07-01

    Motivated by recent advances in the realization of complex two-dimensional optical lattices, we investigate theoretically the quantum transport of ultracold fermions in an optical kagome lattice. In particular, we focus on its extensively degenerate localized states (flat band). By loading fermions in a partial region of the lattice and depleting the mobile atoms at the far boundary of the initially unoccupied region, we find a dynamically generated flat-band insulator, which is also a population-inverted state. We further show that inclusion of weak repulsion leads to a dynamical stripe phase for two-component fermions in a similar setup. Finally, by preparing a topological insulating state in a partially occupied kagome lattice, we find that the topological chiral current decays but exhibits an interesting oscillating dynamics during the nonequilibrium transport. Given the broad variety of lattice geometries supporting localized or topological states, our work suggests new possibilities for using geometrical effects and their dynamics in atomtronic devices.

  10. Tenacibaculum litoreum sp. nov., isolated from tidal flat sediment.

    PubMed

    Choi, Dong Han; Kim, Yoon-Gon; Hwang, Chung Yeon; Yi, Hana; Chun, Jongsik; Cho, Byung Cheol

    2006-03-01

    A rod-shaped bacterium, designated CL-TF13T, was isolated from a tidal flat in Ganghwa, Korea. Analysis of the 16S rRNA gene sequence revealed an affiliation with the genus Tenacibaculum. The sequence similarities between CL-TF13T and type strains of members of the genus Tenacibaculum were from 94.2 to 97.4%. Cells were motile by means of gliding. Strain CL-TF13T grew on solid medium as pale-yellow colonies with an irregular spreading edge. The strain was able to grow in NaCl at a range of 3-5%. They grew within a temperature range of 5-40 degrees C and at pH range of 6-10. The major fatty acids were summed feature 3 (C(16:1)omega7c and/or iso-C(15:0) 2-OH, 19.6%), iso-C(15:0) (18.8%) and iso-C(17:0) 3-OH (13.6%). Fatty acids such as C(18:3)omega6c (6,9,12) (1.5%) and summed feature 4 (iso I- and/or anteiso B-C(17:1), 1.3%) were uniquely found in minor quantities in CL-TF13T among Tenacibaculum species. The DNA G + C content was 30 mol%. According to physiological data, fatty-acid composition and 16S rRNA gene sequence, CL-TF13T could be assigned to the genus Tenacibaculum but distinguished from the recognized species of the genus. Therefore, strain CL-TF13T (= KCCM 42115T = JCM 13039T) represents a novel species, for which the name Tenacibaculum litoreum sp. nov. is proposed. PMID:16514041

  11. Dynamics of flat membranes and flickering in red blood cells

    NASA Astrophysics Data System (ADS)

    Frey, Erwin; Nelson, David R.

    1991-12-01

    A theory of the dynamics of polymerized membranes in the flat phase is presented. The dynamics of dilute membrane solutions is strongly influenced by long-ranged hydrodynamic interactions among the monomers, mediated by the intervening solvent. We discuss the renormalization of the kinetic coefficients for the undulation and phonon modes due to hydrodynamic “backflow” (Zimm behavior). The dynamics is also studied for free draining membranes (Rouse dynamics) corresponding to the Brownian dynamics method used in Monte Carlo simulations. The long time behavior of the dynamic structure factor is given by stretched exponentials with stretching exponents determined by the exponents of the elastic coefficients and the wave vector dependence of the Oseen tensor. We also study the dynamics of the thickness fluctuations in red blood cells (flicker phenomenon) taking into account the underlying polymerized spectrin skeleton. Qualitatively different dynamical behavior is predicted for spectrin skeletons isolated from heir natural lipid environment.

  12. Historical sediment record and distribution of polychlorinated biphenyls (PCBs) in sediments from tidal flats of Haizhou Bay, China.

    PubMed

    Zhang, Rui; Zhang, Fan; Zhang, Tiancheng; Yan, Hongqiang; Shao, Wei; Zhou, Li; Tong, Hebing

    2014-12-15

    The spatial and temporal variations and sources of polychlorinated biphenyls (PCBs) in sediment of tidal flat from Haizhou Bay, China were investigated. PCBs concentrations in surface sediments ranged from 1.33 to 6.27ngg(-1) dry weight. Low-chlorinated PCBs, dominated by the tri-PCB homologs, were identified as the prevalent contaminate of surface sediments. These results were in agreement with the fact that tri-PCB homologs are the dominant contaminants in China. In surface sediment, the highest level appeared in the estuary, and it decreased with distance from the Linhong River estuary. PCBs concentrations started to rise from the mid-1950s, and reached a maximum in 2005. PCBs in sediment might originate from surface runoff and discharges of local source as well as slight atmospheric deposition, based on PCA. Additionally, the PCBs levels in the sediments were considered to rarely pose hazard to the aquatic and human health, based on Sediment Quality Guidelines (SQGs). PMID:25256297

  13. Sediment transport on macrotidal flats in Garolim Bay, west coast of Korea: significance of wind waves and asymmetry of tidal currents

    NASA Astrophysics Data System (ADS)

    Lee, Hee J.; Jo, Hyung R.; Chu, Yong S.; Bahk, Kyung S.

    2004-05-01

    A self-recording instrument, named Tidal Sediment Dynamics Observational System (TISDOS), was built to monitor transport characteristics of nearbed sediments on tidal flats. It was deployed on a tidal flat in the semi-enclosed Garolim Bay, west coast of Korea, over a 15-day period between 5 and 20 January 2002 to examine sediment-transport processes during winter seasons. The measurements involved brief durations of high waves allowing for observation of wave effects upon the sediment transport on the tidal flat. Time series of various hydrodynamic parameters (water depth, current velocities, wave height, suspended sediment concentration, and bed level) from point measurements show characteristic interrelationships between parameters on both temporal and spatial scales. The tidal flat is dominated by flooding currents up to 2 times stronger than ebb currents. The current speeds measured simultaneously at two stations along a cross-shore transect varied in harmony with water depth, reaching the maximum during spring tide that was steadily decreased onshore. The onshore decrease in current speed was compatible with a fining textural trend from sand on the lower flat to mud toward the upper flat. Both the maximum water depth and current speed during individual tidal cycles also show semi-diurnal asymmetry that was highlighted during spring tide. Waves were of critical importance in resuspending bed material and thus yielding higher suspended sediment concentrations. On the middle flat, the suspended sediment concentrations were highest, exceeding 400 mg/l at 0.5 m above the seabed during large waves (relative wave height, 0.33) under weakest neap currents. In this wavy climate, the suspended sediment concentration increased over time during ebb, in strong contrast with a gradual decrease through time after mid-flood peaks under tidal currents without waves. The daily vertical flux of suspended sediments trapped in a plastic bottle also indicates the significance of

  14. Effects of natural oyster reefs (Crassostrea gigas) on the sediment balance of Oosterschelde tidal flats

    NASA Astrophysics Data System (ADS)

    Paiva, João; de Vries, Mindert

    2014-05-01

    The realization of the storm surge barrier and the two secondary dams not only changed the hydrodynamics, but also the geomorphological characteristics of the Oosterschelde estuary (SW Netherlands) creating a disequilibrium between erosion and sedimentation. This has lead in the last 25 years to a sand deficit in the Oosterschelde resulting in the erosion of the tidal flats (Smaal & Nienhuis, 1992; Nienhuis & Smaal 1994). Due to these phenomena the habitat for intertidal soft-bottom benthic fauna is slowly disappearing, and with it food sources for estuarine birds that use these areas as foraging grounds (Mulder & Louters, 1994). Erosion of tidal flats also locally exposes deeper peat layers, potentially resulting in reduced water clarity and primary production (Nienhuis & Smaal 1994). Adding to these problems an increased risk of dike failures and flooding during storm surges is expected, as the dikes gradually become more exposed to wave action. In this research the effect of oysters (Crassostrea gigas) as ecosystem engineers, on the sediment balance in the Oosterschelde was studied. In our analysis we compared long term bathymetry data for transects with and without oyster reefs. Based on height differences, the transects sedimentation/erosion rates were calculated and used to determine if there was a difference between transects without oyster reefs and transects crossing oyster reefs. From the long term analysis, the overall erosional trend of the Oosterschelde tidal flats is clear. The mean observed erosion was - 0,012 m per year. When considering the sections crossing oyster reefs , a mean accumulation of sediment of + 0,007 m per year was observed. The results suggest that these ecosystem engineers, that cover large areas in the Oosterschelde slow down the erosion of the tidal flats in the Oosterschelde, as they act as sediment accumulators and stabilizers. We estimate at least 70000 m3 of sediment per year is accreted on tidal flats due to the effect of

  15. Influence of Peruvian flat-subduction dynamics on the evolution of western Amazonia

    NASA Astrophysics Data System (ADS)

    Eakin, Caroline M.; Lithgow-Bertelloni, Carolina; Dávila, Federico M.

    2014-10-01

    Convection in the Earth's mantle is mainly driven by cold, dense subducting slabs, but relatively little is known about how 3D variations in slab morphology and buoyancy affect mantle flow or how the surface above deforms in response (i.e. dynamic topography). We investigate this problem by studying the dynamics of an active region of flat-slab subduction located in Peru in South America. Here the slab geometry is well known, based on the regional seismicity, and we have observations from the local geological record to validate our models. Of particular interest is the widespread subsidence and deposition of the Solimões Formation across western Amazonia that coincided with the development of the Peruvian flat-slab during the Mid-Late Miocene. This formation covers an extensive area from the foredeep to the Purus Arch located ∼2000 km away from the trench. Close to the Andes the preservation of several kilometers of sedimentary thicknesses can be easily accounted for by flexure. Based on an estimate of the Andean loading we predict 2.8 to 3.6 km of accommodation space that spans 100 km. The spatial and temporal history of the Solimões Formation however, particularly the thick distal foreland accumulations up to 1.2 km deep, can only be matched with the addition of a longer-wavelength dynamic source of topography. Following the transition from normal to flat subduction, we predict over 1 km of dynamic subsidence (∼1500 km wide) that propagates over 1000 km away from the trench, tracking the subduction leading edge. This is followed by a pulse of dynamic uplift over the flat segment behind it. We therefore propose that a combination of uplift, flexure and dynamic topography during slab flattening in Peru is responsible for the sedimentation history and landscape evolution of western Amazonia that eventually led to the configuration of the Amazon Drainage Basin we know today.

  16. The Dynamics of Sediment Oxygenation in Marsh Rhizospheres

    NASA Astrophysics Data System (ADS)

    Koop-Jakobsen, K.

    2014-12-01

    Many marsh grasses are capable of internal oxygen transport from aboveground sources to belowground roots and rhizomes, where oxygen may leak across the rhizodermis and oxygenate the surrounding sediment. In the field, the extent of sediment oxygenation in marshes was assessed in the rhizosphere of the marsh grass; Spartina anglica, inserting 70 optical fiber oxygen sensors into the rhizosphere. Two locations with S. anglica growing in different sediment types were investigated. No oxygen was detected in the rhizospheres indicating that belowground sediment oxygenation in S. anglica has a limited effect on the bulk anoxic sediment and is restricted to sediment in the immediate vicinity of the roots. In the laboratory, the presence of 1.5mm wide and 16mm long oxic root zones was demonstrated around root tips of S. anglica growing in permeable sandy sediment using planar optodes recording 2D-images of the oxygen distribution. Oxic root zones in S. anglica growing in tidal flat deposits were significantly smaller. The size of oxic roots zones was highly dynamic and affected by tidal inundations as well as light availability. Atmospheric air was the primary oxygen source for belowground sediment oxygenation, whereas photosynthetic oxygen production only played a minor role for the size of the oxic root zones during air-exposure of the aboveground biomass. During tidal inundations (1.5 h) completely submerging the aboveground biomass cutting off access to atmospheric oxygen, the size of oxic root zones were reduced significantly in the light and oxic root zones were completely eliminated in darkness. Sediment oxygenation in the rhizospheres of marsh grasses is of significant importance for marshes ability to retain inorganic nitrogen before it reaches the coastal waters. The presence of oxic roots zones promotes coupled nitrification-denitrification at depth in the sediment, which can account for more than 80% of the total denitrification in marshes.

  17. Wave attenuation and sediment transport over an intertidal sand flat on the Fraser River Delta (Invited)

    NASA Astrophysics Data System (ADS)

    Houser, C.; Hill, P. R.

    2010-12-01

    This paper describes the results of two instrument field studies to examine sediment transport processes and wave attenuation across Roberts Bank, a sandy intertidal bank on the Fraser River Delta. The field work was completed as part of a three-year study of the sensitivity of Roberts Bank to sea level rise and changing storminess. It was hypothesized that the response of the mudflats and salt marshes along the landward margin of the delta were dependent on the ability of the fronting sand flat to attenuate wave height and energy. The attenuation of wave height and energy was monitored at four stations along a shore-normal transect between December 23, 2003 and February 10, 2004. The attenuation varied with the relative wave height ratio (Hs h-1) along the seaward margin, with dissipation increasing as water depths decrease and/or incident wave heights increase. Under the most dissipative conditions observed (Hs h-1 ≈ 0.25), the exponential decay coefficient reached 0.00045. This decay coefficient is an order of magnitude smaller than predicted by a simple wave transformation model due to the relatively large wind fetch over the sand flat. Despite the maintenance of wave energy, the range of wave heights remains constrained in the landward direction, with the frequency of waves capable of entraining sediment on the sand flat decreasing from 11% at the outer flat to 2% at the inner stations. In response, bed elevation change and depth of sediment activation are greatest at the seaward margin and decrease exponentially landward. It is argued that the sand flat provides a natural barrier that defines the extent of mudflat development by limiting the potential for sediment resuspension and morphological change on the mudflat. The ability of the sand flat to provide continued protection to the mudflats and salt marshes depends on how it will respond to change in sea level and storminess. A comparison of the dimensionless, current-induced skin friction with the

  18. Dynamics of Flat Bunches with Second Harmonic RF

    SciTech Connect

    Sen, Tanaji; Bhat, Chandra; Kim, Hyung Jin; Ostiguy, Jean-Francois; /Fermilab

    2010-05-01

    We investigate the dynamics of longitudinally flat bunches created with a second harmonic cavity in a high energy collider. We study Landau damping in a second harmonic cavity with analytical and numerical methods. The latter include particle tracking and evolution of the phase space density. The results are interpreted in the context of possible application to the LHC. A possible path to a luminosity upgrade at the LHC is through the creation of longitudinally flat bunches. They can increase the luminosity roughly by 40% when the beam intensities are at the beam-beam limit. Lower momentum spread which can reduce backgrounds and make collimation easier as well lower peak fields which can mitigate electron cloud effects are other advantages. Use of a second harmonic rf system is a frequently studied method to create such flat bunches. Here we consider some aspects of longitudinal dynamics of these bunches in the LHC at top energy. First we consider intensity limits set by the loss of Landau damping against rigid dipole oscillations. Next we describe numerical simulations using both particle tracking and evolution of the phase space density. These simulations address the consequences of driving a bunch at a frequency that corresponds to the maximum of the synchrotron frequency.

  19. Sedimentation dynamics about salt features

    SciTech Connect

    Lowrie, A.; Blake, D.W.

    1985-02-01

    Detailed side-scan sonar and gridded bathymetric surveys on continental margins reveal the existence of numerous submarine canyons. Recently published compilations of current velocities in submarine canyons indicate that alternating and undirectionaly flows often exceed 20-30 cm/sec with peak velocities ranging from 70 to 100 cm/sec. Current meters attached to the ocean floor have been lost at current velocities of 190 cm/sec. Such velocities are ample to transport sand-size sediments. The results of DSDP Leg 96 show the existence of massive sands and gravels on the Louisiana slope, deposited during the last glacial advance. Thus, present physical oceanographic data may be an analog to conditions during glacially induced lowered sea levels. Salt ridges and domes underlie much of the Louisiana slope, determining morphology. Submarine canyons lace the slope. Given a prograding shelf, the net sediment transport routes will be down the submarine canyons. Sediment deposition patterns around the salt ridges and domes include parallel-bedded foredrifts on the upslope side, lee drifts on the downslope side, and moats along the lateral flanks of the salt features. Major differences exist between the sedimentation patterns around a ridge and a dome. The size and shape of the flow pattern will determine whether there can be a flow over the salt feature with a resulting turbulent wave that may influence sedimentation. Sedimentation patterns about salt features on the present slope should be applicable to similar paleoenvironments.

  20. Evaluation of metals and hydrocarbons in sediments from a tropical tidal flat estuary of Southern Brazil.

    PubMed

    Costa, Eduardo S; Grilo, Caroline F; Wolff, George A; Thompson, Anu; Figueira, Rubens Cesar Lopes; Neto, Renato Rodrigues

    2015-03-15

    Although the Passagem Channel estuary, Espírito Santo State, Brazil, is located in an urbanized and industrialized region, it has a large mangrove system. Here we examined natural and anthropogenic inputs that may influence trace metal (Cd, Cr, Cu, Ni, Sc, Pb and Zn) and hydrocarbon (n-alkane and terpane) deposition in three sediment cores collected in the tidal flat zone of the estuary. The cores were also analyzed for carbonate, grain size and stable isotopic composition (δ(13)Corg. and δ(15)Ntotal). Metal enrichment and its association to petroleum hydrocarbons in the surficial sediments of one of the cores, indicate crude oil and derivative inputs, possibly from small vessels and road run-off from local heavy automobile traffic. At the landward sites, the major contributions for metals and hydrocarbons are from natural sources, but in one case, Cu may have been enriched by domestic effluent inputs. PMID:25530014

  1. The sediments and physical environment of the Sagadahoc Bay tidal flat, Georgetown, Maine

    USGS Publications Warehouse

    Bradley, Wilmot H.

    1950-01-01

    This investigation of the sediments of the Sagadohoc Bay tidal flat was undertaken at the suggestion of the State Geologist of Maine, Dr. Joseph Thefethen, in the hope that the results might be helpful to the biologists of the Maine Department of Sear and Shore Fisheries in their studies of clam productivity and the biologists of the U.S. Fish and Wildlife Service who are making a systematic study of the ecology and potential yields of the soft-shelled clam (Mya arenaria) in Sagadohoc and neighboring bays. The field stage of the investigation lasted from early July to the end of August 1949, during which time I was assisted by W. H. Condon of the U.S. Geological Survey. This report and the accompanying map were prepared in Washington, where the laboratory studies of the sediments were made by T. Woodward of the U.S. Geological Survey.

  2. Modeling studies of the far-field effects of tidal flat reclamation on tidal dynamics in the East China Seas

    NASA Astrophysics Data System (ADS)

    Song, Dehai; Wang, Xiao Hua; Zhu, Xueming; Bao, Xianwen

    2013-11-01

    In recent decades, the reclamation of tidal flat carried out by the authorities around the Bohai Sea, Yellow Sea, and East China Sea (BYECS) has reached new heights as a consequence of significant economic expansion in the coastal areas. We are concerned that the tidal flat reclamation may have not only local but also far-field effects on tidal dynamics in the entire BYECS. Numerical study shows different tidal patterns due to tidal energy redistribution when tidal flats around the BYECS are removed, in which the tidal range and phase are changed, and the amphidromic points are displaced. Tidal flats provide storage and dissipation for tidal energy; the former is much more significant than the latter. Loss of these functions caused by tidal flat reclamation will induce a redistribution of the extra tidal energy. Furthermore, we show that far-field effects on tidal dynamics would be observed on the west coast of Korea following significant reclamation on the Chinese Jiangsu coast. In turn, reclamation on the west coast of Korea may generate the far-field effects on the Chinese coast. Reclamation in the BYECS can result in rise of tidal amplitude and onshore sediment transport. The former may enhance the coastal hazards such as storm surge, and the latter may result in severe siltation. Therefore, careful consideration must always be given to any proposed artificial changes to tidal flat, given the effects of these on both the local environment and further afield.

  3. Variation in numbers and behaviour of waders during the tidal cycle: implications for the use of estuarine sediment flats

    NASA Astrophysics Data System (ADS)

    Granadeiro, José P.; Dias, Maria P.; Martins, Ricardo C.; Palmeirim, Jorge M.

    2006-05-01

    Estuarine sediment flats are essential feeding areas for waders, but their exploitation is constrained by the movements of tides. In this cyclic environment the exposure period of sediment flats decreases several fold from upper to lower flats, and the moving tidal waterline briefly creates particular conditions for waders and their prey. This study attempts to determine how the exposure period and the movement of the tide line influence the use of space and food resources by waders across the sediment flats. Wader counts and observations of feeding behaviour were carried out in all phases of the tidal cycle, in plots forming a transect from upper to lower flats, thus representing a gradient of exposure periods. Pecking, prey intake, and success rates varied little along the gradient. Some species actively followed the tide line while foraging, whereas others are evenly spread over the exposed flats. Black-tailed Godwit, Dunlin and Avocet were 'tide followers', whereas Grey Plover, Redshank and Bar-tailed Godwit were 'non-followers'. Densities of 'followers' near the tide line were up to five times higher than elsewhere. Species differed markedly in the way they used space on the flats, but in general the rate of biomass acquisition (in grams of ash-free dry weight per time exposed) was much higher in lower flats. However, this preference was insufficient to counter the much longer exposure of the upper flats, so the total amount of biomass consumed on the latter was greater. Therefore, it was in these upper flats that waders fulfilled most of their energetic needs. Consequently, upper flats are of particular importance for the conservation of wader assemblages, but because they are usually closer to shore they tend to suffer the highest pressure from disturbance and land reclamation.

  4. The behavior of heavy metals in tidal flat sediments during fresh water leaching.

    PubMed

    Li, QuSheng; Liu, YaNan; Du, YeFeng; Cui, ZhiHong; Shi, Lei; Wang, LiLi; Li, HongJie

    2011-02-01

    Many of the coastal tidal flats in China that were polluted with heavy metals are now being reclaimed for arable land. The safety of these soils for agriculture is of great concern. The present study investigated the sediment chemical properties, concentrations, and speciation of heavy metals at different levels of desalination during a controlled leaching experiment. After leaching with fresh water, the average reductions in the heavy metal species examined in 0-65 cm depth sediment were 32.1% for Pb, 26.2% for Cd, 14.0% for Zn, 13.8% for Cu, and 11.0% for Cr, while the Ni concentration in sediment did not change significantly. The amounts of Cd, Pb, Cr, Cu, and Zn bound to the reducible fraction, the amounts of Cd, Pb, and Zn bound to the exchangeable fraction, the amounts of Pb, Cr, Cu, and Zn associated with the carbonate fraction, and the Cu associated with the oxidizable fraction all decreased significantly. Complexation with salt anions, ion exchange between the cations and the metal ions, removal of SO4(2-), dissolution of carbonate, and the redox potential variations all contributed to the decreases in Pb, Cd, Zn, Cu, and Cr. These results suggest that leaching with fresh water can also remove a fraction of the heavy metal contamination when it diminishes sediment salinity. PMID:21131022

  5. Sediment CO2 efflux from cleared and intact temperate mangroves and tidal flats

    NASA Astrophysics Data System (ADS)

    Bulmer, R. H.; Schwendenmann, L.; Lundquist, C. J.

    2015-02-01

    Temperate mangroves in Southern Australia and New Zealand have been increasing in area over the past 50 years, whereas tropical mangroves have declined by 30-50% over a similar time frame. Tropical mangroves are understood to be an important carbon sink and carbon dioxide (CO2) emissions following clearance are estimated to be comparable or greater than CO2 emissions following the clearance of many terrestrial forest systems. Recreational and amenity values or perceived loss of other estuarine habitats due to expanding temperate mangrove forests have resulted in clearing of temperate mangroves. In this study, we investigated the impact of temperate mangrove clearance on CO2 efflux from the sediment to the atmosphere along with a range of other biotic and abiotic factors. Significantly higher CO2 efflux rates were measured in cleared (1.34 ± 0.46 μmol m2 s-1) and intact mangrove sites (2.31 ± 0.72 μmol m2 s-1) than in tidal flats (-0.23 ± 0.27 μmol m2 s-1). Site and sediment characteristics such as sediment carbon and nitrogen concentration, chlorophyll α concentration, grain size, mangrove height, macrofaunal abundance, sediment temperature and moisture were strongly correlated with sediment CO2 efflux. Our results suggest that carbon stored within temperate mangrove sediment is released over a period of years to decades after mangrove clearance. CO2 efflux from intact and cleared temperate mangroves was found to be comparable to rates observed in the tropics. Disturbance of the surface biofilm resulted in elevated CO2 efflux across all habitats, suggesting the important role of surface biofilm communities in mediating CO2 efflux.

  6. Statistical characterization of spatiotemporal sediment dynamics in the Venice lagoon

    NASA Astrophysics Data System (ADS)

    Carniello, Luca; D'Alpaos, Andrea; Botter, Gianluca; Rinaldo, Andrea

    2016-05-01

    Characterizing the dynamics of suspended sediment is crucial when investigating the long-term evolution of tidal landscapes. Here we apply a widely tested mathematical model which describes the dynamics of cohesive and noncohesive sediments, driven by the combined effect of tidal currents and wind waves, using 1 year long time series of observed water levels and wind data from the Venice lagoon. The spatiotemporal evolution of the computed suspended sediment concentration (SSC) is analyzed on the basis of the "peak over threshold" theory. Our analysis suggests that events characterized by high SSC can be modeled as a marked Poisson process over most of the lagoon. The interarrival time between two consecutive over threshold events, the intensity of peak excesses, and the duration are found to be exponentially distributed random variables over most of tidal flats. Our study suggests that intensity and duration of over threshold events are temporally correlated, while almost no correlation exists between interarrival times and both durations and intensities. The benthic vegetation colonizing the central southern part of the Venice lagoon is found to exert a crucial role on sediment dynamics: vegetation locally decreases the frequency of significant resuspension events by affecting spatiotemporal patterns of SSCs also in adjacent areas. Spatial patterns of the mean interarrival of over threshold SSC events are found to be less heterogeneous than the corresponding patterns of mean interarrivals of over threshold bottom shear stress events because of the role of advection/dispersion processes in mixing suspended sediments within the lagoon. Implications for long-term morphodynamic modeling of tidal environments are discussed.

  7. Isolation and Characterization of Metal-Reducing Shewanella Species from Tidal Flat Sediments of Southwest Coast, Korea

    NASA Astrophysics Data System (ADS)

    Roh, Y.; Lee, J.; Lee, S.; Hur, H.

    2005-12-01

    Although microbe-metal interactions play important roles in the metal geochemistry and organic matter mineralization in tidal flat sediments, study of microbial metal reduction by bacteria isolated from tidal flat sediments is beginning to be studied in Korea. The objective of this study was to explore Fe(III) and metal reduction by metal-reducing bacteria isolated from Tidal Flat Sediments of Southwest Coast, Korea. 10 bacteria strains were isolated from tidal flat sediments of Southwest Coast, Korea. The taxonomic characterization of these strains indicated that they belong to the genus Shewanella. These strains were able to reduce ferric iron of several ferric compounds [FeCl3, Fe-citrate, FeOOH] and metals such as As(V) and Se(VI) using short chain fatty acids as the electron donors. These bacteria exhibited diverse mineral formation capabilities including the formation of magnetite (Fe3O4), siderite (FeCO3), vivianite [Fe3(PO4)28H2O], AsS, and Se(0). One (HN-41) of the isolates reduced akaganeite (FeOOH) and formed mono-dispersed (~ 30 nm) magnetite (Fe3O4) nanoparticles . These results indicate that microbial Fe(III) reduction may not only play important roles in iron and carbon biogeochemistry as well as immobilization of metal contaminants in tidal flat sediment.

  8. Mercury dynamics in lake sediments

    NASA Astrophysics Data System (ADS)

    Feyte, Stéphane; Gobeil, Charles; Tessier, André; Cossa, Daniel

    2012-04-01

    Triplicate porewater depth-profiles of pH and concentrations of total Hg (HgT), methylmercury (MeHg), Fe, Mn, sulfate, total sulfide, total zero-valent sulfur, organic C and major ions were determined at two sampling dates in a perennially oxygenated basin and a seasonally anoxic basin from Lake Tantaré, a Canadian Shield lake. The vertical distribution of HgT, MeHg, acid volatile sulfide, total S, Fe, Mn, Al and organic C were also determined in dated sediment cores from the same lake basins and from the deepest site of two other lakes, one also located in the Canadian Shield and the other in the Northeastern part of the Appalachian Mountains. Application of a one-dimensional transport-reaction equation to the dissolved HgT and MeHg profiles constrains the depth intervals (zones) where these species are produced or consumed in the sedimentary column and yields estimates of net reaction rates of HgT or MeHg in each of the zones as well as their fluxes at the sediment-water interface. Dissolved HgT and MeHg diffused from the overlying water into the sediments, except for MeHg at one of the sampling dates in the perennially oxygenated basin. About 97% and 50% of the MeHg flux to the sediments is presently deposited with settling particles in the perennially oxygenated and seasonally anoxic basins, respectively. Removal of porewater HgT and MeHg occurred at all dates and sampling sites. Comparison of the consumption zones of porewater HgT and MeHg with the profiles of ancillary parameters, coupled with thermodynamic calculations, suggest that pure Hg mineral phases do not form in the sediments, that HgT and MeHg adsorption onto authigenic Fe oxyhydroxides occurs in minor proportions, and that the association of HgT and MeHg to Fe sulfide phases or sulfidized organic matter is possible. Assuming that the net consumption of MeHg in the porewaters was essentially due to demethylation, an apparent first-order rate constant for MeHg demethylation of 0.04-0.8 d-1 was

  9. Beach and reef-flat sediments along the south shore of Molokai, Hawaii

    USGS Publications Warehouse

    Calhoun, R.S.; Field, M.E.

    2000-01-01

    As part of the U.S. Geological Survey's multi-disciplinary Coral Reef Project addressing the health and geological variability of coral reef systems, sediment components and their distribution along the fringing reef on the south shore of the Hawaiian island of Molokai are being examined. Particular interest is being paid to the types and origin of sediment found on the reef. The south shore of Molokai is sheltered by one of the largest fringing reefs in the US. At approximately 50 km in length, up to 1.5 km in width, and covered by 90% live coral in many locations, the reef seemingly should be able to provide ample sediment for large carbonate beaches. However, siliciclastic grains supplied by erosion of the basaltic uplands of Molokai are often the most conspicuous individual nearshore sediment type. Coralline algae and coral are the most common carbonate components of the beaches. On the nearshore reef-flat, chemically-altered carbonate grains, particularly coralline algae, are the most abundant component. Molluscs and Halimeda may be common in specific locations, but are usually minor components. Sediment calcium carbonate levels increase to the west from a minimum at Kamalo, and are high along the east shore of Molokai. However, these general island-scale trends may be overridden by local influences, such as protected stream mouths or high carbonate growth rates. Additionally, trends seen on the beach and nearshore environments may not reflect trends a few hundred meters offshore since shore normal trends are more pronounced than shore parallel ones.

  10. Dynamic intensity normalization using eigen flat fields in X-ray imaging.

    PubMed

    Van Nieuwenhove, Vincent; De Beenhouwer, Jan; De Carlo, Francesco; Mancini, Lucia; Marone, Federica; Sijbers, Jan

    2015-10-19

    In X-ray imaging, it is common practice to normalize the acquired projection data with averaged flat fields taken prior to the scan. Unfortunately, due to source instabilities, vibrating beamline components such as the monochromator, time varying detector properties, or other confounding factors, flat fields are often far from stationary, resulting in significant systematic errors in intensity normalization. In this work, a simple and efficient method is proposed to account for dynamically varying flat fields. Through principal component analysis of a set of flat fields, eigen flat fields are computed. A linear combination of the most important eigen flat fields is then used to individually normalize each X-ray projection. Experiments show that the proposed dynamic flat field correction leads to a substantial reduction of systematic errors in projection intensity normalization compared to conventional flat field correction. PMID:26480456

  11. Remediation of muddy tidal flat sediments using hot air-dried crushed oyster shells.

    PubMed

    Yamamoto, Tamiji; Kondo, Shunsuke; Kim, Kyung-Hoi; Asaoka, Satoshi; Yamamoto, Hironori; Tokuoka, Makoto; Hibino, Tadashi

    2012-11-01

    In order to prove that hot air-dried crushed oyster shells (HACOS) are effective in reducing hydrogen sulfide in muddy tidal flat sediments and increasing the biomass, field experiments were carried out. The concentration of hydrogen sulfide in the interstitial water, which was 16 mg SL(-1) before the application of HACOS, decreased sharply and maintained almost zero in the experimental sites (HACOS application sites) for one year, whereas it was remained at ca. 5 mg SL(-1) in the control sites. The number of macrobenthos individuals increased to 2-4.5 times higher than that in the control site. Using a simple numerical model, the effective periods for suppression of hydrogen sulfide were estimated to be 3.2-7.6 and 6.4-15.2 years for the experimental sites with 4 and 8 tons per 10 × 10 × 0.2m area, respectively. From these results, it is concluded that HACOS is an effective material to remediate muddy tidal flats. PMID:23017947

  12. Surface sedimentation and sediment property of 2014~2015 years on the Dongho open-coast intertidal flat, Gochang coast of southwestern Korea

    NASA Astrophysics Data System (ADS)

    Ryang, Woo Hun; Kang, Na Yeong; Kang, Sol Ip

    2016-04-01

    The Dongho intertidal flat, located on the southwestern coast of Korea, is macro-tide, open-coast, linear shoreline, and sand substrates. In the Dongho intertidal flat, this study has focused on characteristics of surface sedimentation and sediment properties during 2014~2015 years. Can cores (30×17×5 cm3) were sampled at 4 sites with 150 m interval from shoreline to lower intertidal area during the 6 seasons from spring (June) in 2014 to summer (Aug.) in 2015. The 24 can cores of the intertidal flat were analyzed for sediment texture, porosity, wet density, grain density, and shear strength at 2, 10, and 25 cm parts from the top. Sediment type is mostly sand (S) facies of the Folk scheme, and mean grain size and skewness of the sediments are 0.93~2.70 ϕ and -0.50~0.41, respectively. Sediment properties show porosity of 9~32%, wet density of 1.88~2.45 g/cm3, grain density of 2.62~3.09 g/cm3, and shear strength of 8~64 kPa. The cancore peels represent planar and inclined stratification and bioturbated faintly stratification with some shell fragments. The stratification weaken from the shoreline to the lower intertidal site. This is indicative of waning influences of sea wave in the Dongho intertidal flat. Keywords: macro-tide, open-coast, can core, intertidal flat, Gochang coast Acknowledgements: This study was supported by the research grant from the Korean Ministry of Oceans and Fisheries (PJT200538). This presentation is an interim result of the coastal research program in the study area.

  13. Random Forest Classification of Sediments on Exposed Intertidal Flats Using ALOS-2 Quad-Polarimetric SAR Data

    NASA Astrophysics Data System (ADS)

    Wang, W.; Yang, X.; Liu, G.; Zhou, H.; Ma, W.; Yu, Y.; Li, Z.

    2016-06-01

    Coastal zones are one of the world's most densely populated areas and it is necessary to propose an accurate, cost effective, frequent, and synoptic method of monitoring these complex ecosystems. However, misclassification of sediments on exposed intertidal flats restricts the development of coastal zones surveillance. With the advent of SAR (Synthetic Aperture Radar) satellites, polarimetric SAR satellite imagery plays an increasingly important role in monitoring changes in coastal wetland. This research investigated the necessity of combining SAR polarimetric features with optical data, and their contribution in accurately sediment classification. Three experimental groups were set to make assessment of the most appropriate descriptors. (i) Several SAR polarimetric descriptors were extracted from scattering matrix using Cloude-Pottier, Freeman-Durden and Yamaguchi methods; (ii) Optical remote sensing (RS) data with R, G and B channels formed the second feature combinations; (iii) The chosen SAR and optical RS indicators were both added into classifier. Classification was carried out using Random Forest (RF) classifiers and a general result mapping of intertidal flats was generated. Experiments were implemented using ALOS-2 L-band satellite imagery and GF-1 optical multi-spectral data acquired in the same period. The weights of descriptors were evaluated by VI (RF Variable Importance). Results suggested that optical data source has few advantages on sediment classification, and even reduce the effect of SAR indicators. Polarimetric SAR feature sets show great potentials in intertidal flats classification and are promising in classifying mud flats, sand flats, bare farmland and tidal water.

  14. Dynamic Nuclear Polarization of Sedimented Solutes

    PubMed Central

    Ravera, Enrico; Corzilius, Björn; Michaelis, Vladimir K.; Rosa, Camilla; Griffin, Robert G.; Luchinat, Claudio; Bertini, Ivano

    2013-01-01

    Using the 480 kDa iron-storage protein complex, apoferritin, as an example, we demonstrate that sizable dynamic nuclear polarization (DNP) enhancements can be obtained on sedimented protein samples. In sedimented solute DNP (SedDNP), the biradical polarizing agent is co-sedimented with the protein, but in the absence of a glass forming agent. We observe DNP enhancement factors ε>40 at a magnetic field of 5 T and temperatures below 90 K, indicating that the protein sediment state is “glassy” and suitable to disperse the biradical polarizing agent upon freezing. In contrast, frozen aqueous solutions of apoferritin yield ε ≈ 2. Results of SedDNP are compared to those obtained from samples prepared using the traditional glass forming agent glycerol. Collectively, these and results from previous investigations suggest that the sedimented state can be functionally described as a “microcrystalline glass” and in addition provides a new approach for preparation of samples for DNP experiments. PMID:23331059

  15. Contaminated sediment dynamics in peatland headwaters

    NASA Astrophysics Data System (ADS)

    Shuttleworth, Emma; Clay, Gareth; Evans, Martin; Hutchinson, Simon; Rothwell, James

    2016-04-01

    Peatlands are an important store of soil carbon, provide multiple ecosystem services, and when located in close proximity to urban and industrial areas, can also act as sinks of atmospherically deposited heavy metals. The near-surface layer of the blanket peats of the Peak District National Park, UK, is severely contaminated with high concentrations of anthropogenically derived, atmospherically deposited lead (Pb). These peats are severely degraded, and there is increasing concern that erosion is releasing considerable quantities of this legacy pollution into surface waters. Despite substantial research into Pb dynamics in peatlands formal description of the possible mechanisms of contaminated sediment mobilisation is limited. However, there is evidence to suggest that a substantial proportion of contaminated surface sediment may be redistributed elsewhere in the catchment. This study uses the Pb contamination stored near the peat's surface as a fingerprint to trace contaminated sediment dynamics and storage in three severely degraded headwater catchments. Erosion is exposing high concentrations of Pb on interfluve surfaces, and substantial amounts of reworked contaminated material are stored on other catchment surfaces (gully walls and floors). We propose a variety of mechanisms as controls of Pb release and storage on the different surfaces, including: (i) wind action on interfluves; (ii) the aspect of gully walls, and (iii) gully depth. Vegetation also plays an important role in retaining contaminated sediment on all surfaces.

  16. Short-term measurements of exposure and inundation of sediment areas in a tide-less wind flat system at the Southern Baltic Sea coast

    NASA Astrophysics Data System (ADS)

    Karsten, U.; Baudler, H.; Himmel, B.; Jaskulke, R.; Ewald, H.; Schumann, R.

    2012-12-01

    Wind flats are typical coastal landscape elements of the tide-less Southern Baltic Sea. These sediment areas exhibit an irregular and unpredictable pattern of emersion and flooding as a function of the prevailing wind direction and speed. Consequently, wind flats represent very specific and unique coastal habitats that, however, are ecologically poorly understood. The irregular and unpredictable water level fluctuations cause strong physico-chemical gradients which favour the development of laminated microbial mats. These micro-ecosystems accumulate organic material, enrich the sediment with nutrients and reduce erosion of sand particles. In the present study we developed a new autonomous measuring device for precise water level changes and recorded for the first time under in-situ conditions the irregular flooding events of the wind flat Bock (Zingst Peninsula, German Baltic Sea coast). The measured water level changes were compared and correlated with the closest gauging station and the prevailing wind conditions (direction, speed) to better understand the effects of hydrology and meteorology on duration and intensity of inundation. From the 12 measuring periods of over 2.5 years we noted that about half of the time the wind flat was fully exposed and dry, and the other half at least wet with < 1 cm water levels. The strongest flooding of up to 20 and 50 cm water height was a relatively rare event, which, however, depended on wind speed and direction, i.e. wind speed above 8 m s- 1 from north to northeast direction. The undertaken measurements on exposure and inundation intervals of this unique sedimentary ecosystem describe well the wind-driven high dynamics and strong gradients in the environmental parameters, and explain well the abundant occurrence of microbial mats in wind flats.

  17. Tenacibaculum aestuarii sp. nov., isolated from a tidal flat sediment in Korea.

    PubMed

    Jung, Seo-Youn; Oh, Tae-Kwang; Yoon, Jung-Hoon

    2006-07-01

    A novel Tenacibaculum-like bacterial strain, SMK-4(T), was isolated from a tidal flat sediment in Korea. Strain SMK-4(T) was Gram-negative, pale yellow-pigmented and rod-shaped. It grew optimally at 30-37 degrees C and in the presence of 2-3 % (w/v) NaCl. It contained MK-6 as the predominant menaquinone and iso-C(15 : 0), iso-C(16 : 0) 3-OH and C(16 : 1)omega7c and/or iso-C(15 : 0) 2-OH as the major fatty acids (>10 % of total fatty acids). The DNA G+C content was 33.6 mol%. Phylogenetic trees based on 16S rRNA gene sequences showed that strain SMK-4(T) fell within the evolutionary radiation encompassed by the genus Tenacibaculum. Strain SMK-4(T) exhibited 16S rRNA gene sequence similarity levels of 95.2-98.6 % with respect to the type strains of recognized Tenacibaculum species. DNA-DNA relatedness levels and differential phenotypic properties made it possible to categorize strain SMK-4(T) as a species that is separate from previously described Tenacibaculum species. On the basis of phenotypic properties and phylogenetic and genetic distinctiveness, strain SMK-4(T) (=KCTC 12569(T)=JCM 13491(T)) should be classified as a novel Tenacibaculum species, for which the name Tenacibaculum aestuarii sp. nov. is proposed. PMID:16825632

  18. Residues of organochlorine pesticides in intertidal flat surface sediments from coastal zone of Jiangsu Province, China

    NASA Astrophysics Data System (ADS)

    Han, Xiumei; Zheng, Rong; Zhao, Jiale; Ma, Chao; Gao, Xiaojiang

    2014-09-01

    Sixteen surface sediment samples were collected and analysed to evaluate the residues of organochlorine pesticides (OCPs) from intertidal flat in Jiangsu Province. Overall, 22 OCPs were detected with total concentrations of OCPs ranging widely from 0.96 to 12.14 ng/g (dry wt). Total hexachlorocyclohexane (HCH) and total dichlorodiphenyltrichloroethane (DDT) levels varied from <0.01 to 0.67 ng/g and from 0.23 to 4.85 ng/g, respectively. DDTs were the predominant compounds. The dominance of β-HCH indicated a history of HCH pollution. According to the ratios of ( p, p'-DDD+ p, p'-DDE)/ p, p'-DDT and o,p'-DDT/ p, p'-DDT, new input of DDTs did not occur in most sites, and the main sources were historical usage of technical DDTs. OCPs such as dieldrin, endrin, p, p'-DDD, and p, p'-DDT exceeded the effects range low, showing adverse biological effects that would occasionally occur at some sites of the study area.

  19. Sediment dynamics of the Mzymta river estuary

    NASA Astrophysics Data System (ADS)

    Krylenko, Marina; Isupova, Maria

    2010-05-01

    observed because of reduction of sediment transport and change of its structure. Regulated of the Mzymta River flow has led to reduction of a drain of deposits of the river. Now the drain of deposits of the river makes about 70 % from the natural. At reduction of sediment transport of the river Mzymta and deficiency beach deposits the excess line of underwater slope on depth is forward to approach on coast. The canyon "Novy" especially quickly runs into a land. So in its limits 10-metre isobatic curve has promoted towards coast to 90 m during last 100years and 5-metre isobatic curve - to 120 m. At list 2 million м3 of sediments has been withdrawn from around the Mzymta mouth beach during last 10 years. As a result of fulfilled research a detailed characteristic of modern sediment dynamics and determining factors was done. Climatic variations and man impact are basic factors that determine a formation of Mzymta seaside and proceeding of dynamical processes at present.

  20. Periodic dynamics of pairs of sedimenting discs

    NASA Astrophysics Data System (ADS)

    Chajwa, Rahul; Menon, Narayanan; Ramaswamy, Sriram

    2015-11-01

    We study the sedimentation in the Stokes regime of pairs of discs released with a variety of orientations relative to each other and to gravity. The orientation of a settling disk is coupled with the translational degree of freedom. Hydrodynamic interactions between settling disks produces richer dynamics than is possible with sedimenting spheres. We demonstrate the classes of dynamics that follow from a variety of initial conditions, but focus on the periodic oscillations in position and orientation that result when two discs are released parallel to each other with their normals coaxial and in the horizontal plane. We report experiments that study the frequency, wavelength, and amplitude of the periodic flutter as a function of initial separation between the discs. We analyze the motions within a model that combines the hydrodynamics of single discs with a simplified model of their interaction that includes low order terms of appropriate symmetry. This allows us to examine the initial conditions that demarcate periodic from non-periodic dynamics. Also at Dept of Physics and Astronomy, Univ of Massachusetts, Amherst MA 01003.

  1. Contamination, distribution, and sources of heavy metals in the sediments of Andong tidal flat, Hangzhou bay, China

    NASA Astrophysics Data System (ADS)

    Pang, Hong-Jiao; Lou, Zhang-Hua; Jin, Ai-Min; Yan, Kang-Kang; Jiang, Yan; Yang, Xian-Hui; Arthur Chen, Chen-Tung; Chen, Xue-Gang

    2015-11-01

    In this study, we collected sediment samples from three transects along Andong tidal flat, Hangzhou Bay, and studied the concentrations and sources of heavy metals. Enrichment factors (EF), contamination factors (CF), and geoaccumulation indexes (Igeo) showed that transect A was a polluted area while transect B and C were relatively unpolluted. The elevated heavy metal concentrations along transect A may be attributed to the human pollutions along the tidal creeks and passageway. Principal component analyses indicated that Cr, Ni, Cd, Hg, Pb, and Cu were originated from the same sources, and most of the heavy metals presented elevated concentrations near shore, suggesting the near shore pollution by anthropogenic activities. Chondrite-normalized REE patterns of sediment samples were similar to that of Upper Continental Crust, Yangtze River, and East China Sea with enrichment of LREEs, fairly flat patterns of HREEs, and significantly negative Eu anomaly and positive Ce anomaly. It is suggested that the main sources of sediments were terrigenous materials but also influenced by the sediments from East China Sea. This work provided essential information on the pollution status of sediments in the Hangzhou Bay and assessed the possible sources of heavy metals, which will be useful for the environmental protection of Hangzhou Bay.

  2. Effects of Emergent Vegetation on Sediment Dynamics within a Retreating Coastal Marshland

    NASA Astrophysics Data System (ADS)

    Stellern, C.; Grossman, E.; Fuller, R.; Wallin, D.; Linneman, S. R.

    2015-12-01

    Coastal emergent vegetation in estuaries physically interrupts flow within the water column, reduces wave energy and increases sediment deposition. Previous workers conclude that wave attenuation rates decrease exponentially with distance from the marsh edge and are dependent on site and species-specific plant characteristics (Yang et al., 2011). Sediment deposition may exhibit similar patterns; however, sediment, geomorphic and habitat models seldom integrate site-specific biophysical plant parameters into change analyses. We paired vegetation and sediment dynamic studies to: (1) characterize vegetation structure, (2) estimate sediment available for deposition, (3) estimate rate, distribution and composition of sediment deposits, (4) determine sediment accumulation on vegetation, (5) compare sediment deposition within dense tidal wetland relative to non-vegetated tidal flat. These studies integrate a variety of monitoring methods, including the use of sediment traps, turbidity sensors, side-on photographs of vegetation and remote sensing image analysis. We compared sedimentation data with vegetation characteristics and spatial distribution data to examine the relative role of vegetation morphologic traits (species, stem density, biomass, distribution, tidal channels, etc.) on sediment dynamics. Our study is focused on Port Susan Bay of Washington State; a protected delta that has experienced up to 1 kilometer of marsh retreat (loss) over the past fifty years. Preliminary results show that the highest winter deposition occurred in the high marsh/mid-marsh boundary, up to 300m inland of the marsh edge, where bulrush species are most dense. These results will inform restoration efforts aimed at reestablishing sediment supply to the retreating marshland. This research is necessary to understand the vulnerability and adaptability of coastal marshlands to climate change related stressors such as, increased water levels (sea-level rise) and wave energy.

  3. Characterization of uranium and plutonium in surface-waters and sediments collected at the Rocky Flats Facility

    SciTech Connect

    Efurd, D.W.; Rokop, D.J.; Aguilar, R.D.; Roensch, F.R.; Perrin, R.E.; Banar, J.C.

    1994-05-01

    This study was initiated to characterize actinides in environmental samples collected at the Rocky Flats Plant (RFP). Thermal Ionization Mass Spectrometry (TIMS) measurement techniques were used to measure the plutonium and uranium content of water and sediment samples collected from the ponds used to control surface-waters on-site at RFP. TIMS was also used to separate the uranium into anthropogenic and naturally occurring components. The results of these studies are presented.

  4. Utilizing an Extraterrestrial Analogue to Predict Sediment Migration on Frenchman Flat due to Convective Vortex (Dust Devil) Activity

    NASA Astrophysics Data System (ADS)

    McGee, B. W.

    2006-12-01

    A synthesis of terrestrial and Martian data suggests that a convective vortex, or "dust devil," is a significant, non-random terrestrial eolian sediment transport phenomenon, which has implications for sediment-based migration of radionuclides on Frenchman Flat playa, a 20 square-mile mountain-bounded dry lake bed approximately centered in Frenchman Flat on the Nevada Test Site (NTS). Planetary scientists are often forced to rely on terrestrial analogues to begin characterizing extraterrestrial processes. However, as the planetary database matures, an increasing number of well-characterized extraterrestrial analogues for terrestrial processes will become available. Such analogues may provide a convenient means to investigate poorly understood or otherwise inaccessible terrestrial phenomena. Historical atmospheric nuclear experiments conducted from 1951 to 1962 deposited radionuclides into surface sediments across parts of Frenchman Flat playa, where dust devils are known to commonly occur, especially during the summer months. Recent information from both terrestrial and Martian studies yields that dust devils can be significant contributors to both the local eolian sediment transport regime and the regional climate system. Additionally, the use of terrestrial desert environments as Martian analogues, as well as the recent, unique discovery of Mars-like dust devil tracks in Africa, has established a working correlation between Earth, Mars, and the dust devil phenomenon. However, while the difficulty in tracking dust devil paths on Earth has hindered the determination of any net sediment transport due to dust devils, the dramatic albedo contrast in disturbed sediment on Mars lends to the formation of persistent, curvilinear dust devil tracks. These tracks illustrate that in zones of preferential formation, dust devils possess non-random orientations over seasonal timescales with respect to prevailing wind. By calibrating these Martian orientations with meteorological

  5. Celeribacter naphthalenivorans sp. nov., a naphthalene-degrading bacterium from tidal flat sediment.

    PubMed

    Taek Oh, Young; Avedoza, Catherine; Lee, Sang-Suk; Jeong, Sang Eun; Jia, Baolei; Jeon, Che Ok

    2015-09-01

    A Gram-stain-negative, aerobic and moderately halophilic bacterium, designated strain EMB201(T), was isolated from tidal flat sediment of the South Sea in Korea. Cells were motile rods with a single polar flagellum and had catalase- and oxidase-positive activities. Growth of strain EMB201(T) was observed at 15-37 °C (optimum, 30 °C), at pH 5.0-9.5 (optimum, pH 7.0-7.5) and in the presence of 1-7% (w/v) NaCl (optimum, 2-3%). Strain EMB201(T) contained ubiquinone-10 as the sole isoprenoid quinone and summed feature 8 (comprising C18 : 1ω7c/ω6c), C18 : 0ω7c 11-methyl and C10 : 0 3-OH as the major fatty acids. Phosphatidylglycerol and an unidentified amino lipid were identified as the major polar lipids and an unidentified phospholipid and three unidentified lipids were detected as minor components. The G+C content of the genomic DNA was approximately 58.4 mol%. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain EMB201(T) formed a phylogenetic lineage with members of the genus Celeribacter. Strain EMB201(T) was related most closely to Celeribacter halophilus ZXM137(T) with a 16S rRNA gene sequence similarity of 98.3%, and the level of DNA-DNA relatedness between the two strains was 17.0 ± 2.0%. The combined chemotaxonomic and molecular properties suggest that strain EMB201(T) represents a novel species of the genus Celeribacter, for which the name Celeribacter naphthalenivorans sp. nov. is proposed. The type strain is EMB201(T) ( = KACC 18393(T) = JCM 30679(T)). PMID:26297231

  6. Boseongicola aestuarii gen. nov., sp. nov., isolated from a tidal flat sediment.

    PubMed

    Park, Sooyeon; Park, Ja-Min; Lee, Keun-Chul; Bae, Kyung Sook; Yoon, Jung-Hoon

    2014-08-01

    A Gram-stain-negative, aerobic, non-motile and pleomorphic (coccoid, ovoid or rod-shaped) bacterial strain, BS-W15(T), isolated from a tidal flat sediment at Boseong in South Korea, was characterized taxonomically. Strain BS-W15(T) grew optimally at 25 °C, at pH 7.0-8.0 and in the presence of approximately 2.0% (w/v) NaCl. Neighbour-joining and maximum-likelihood phylogenetic trees, based on 16S rRNA gene sequences, revealed that strain BS-W15(T) joined the cluster comprising the type strains of Profundibacterium mesophilum, Hwanghaeicola aestuarii, M. pelagius and M. salinus, showing 93.5-96.4% sequence similarities. Strain BS-W15(T) contained Q-10 as the predominant ubiquinone and C(18 : 1)ω7c as the predominant fatty acid. The polar lipid profile of strain BS-W15(T) contained phosphatidylcholine and phosphatidylglycerol as major components, differentiating it from those of the type strains of P. mesophilum, H. aestuarii, M. pelagius and M. salinus. The DNA G+C content of strain BS-W15(T) was 58.7 mol%. The differential phenotypic properties, together with the phylogenetic and chemotaxonomic data, demonstrate that strain BS-W15(T) is distinct from type strains of P. mesophilum, H. aestuarii, M. pelagius and M. salinus. On the basis of the data presented, strain BS-W15(T) is considered to represent a novel genus and species, for which the name Boseongicola aestuarii gen. nov., sp. nov. is proposed. The type strain is BS-W15(T) ( = KCTC 32576(T) = CECT 8489(T)). PMID:24824636

  7. Aestuariivita boseongensis gen. nov., sp. nov., isolated from a tidal flat sediment.

    PubMed

    Park, Sooyeon; Won, Sung-Min; Kim, Hyangmi; Park, Doo-Sang; Yoon, Jung-Hoon

    2014-09-01

    A Gram-stain-negative, aerobic, non-motile and coccoid, ovoid or rod-shaped bacterial strain, BS-B2(T), which was isolated from a tidal flat sediment at Boseong in South Korea, was characterized taxonomically. Strain BS-B2(T) grew optimally at 30 °C, at pH 7.0-8.0 and in the presence of 2.0 % (w/v) NaCl. The novel strain exhibited highest 16S rRNA gene sequence similarity (97.4 %) to Marivita geojedonensis DPG-138(T). Neighbour-joining, maximum-likelihood and maximum-parsimony phylogenetic trees based on 16S rRNA gene sequences revealed that strain BS-B2(T) is closely related to Primorskyibacter sedentarius KMM 9018(T), showing 96.5 % sequence similarity. Strain BS-B2(T) contained Q-10 as the predominant ubiquinone and C18 : 1ω7c as the predominant fatty acid. The polar lipid profile of strain BS-B2(T) comprised phosphatidylcholine, phosphatidylglycerol, one unidentified aminolipid and one unidentified lipid as major components, and differentiated it from the type strains of P. sedentarius and M. geojedonensis. The DNA G+C content of strain BS-B2(T) was 62.2 mol%. Differential phenotypic properties, together with the phylogenetic and chemotaxonomic data, demonstrated that strain BS-B2(T) can be distinguished from phylogenetically related genera as well as P. sedentarius and M. geojedonensis. On the basis of the data presented, strain BS-B2(T) is considered to represent a novel species of a new genus, for which the name Aestuariivita boseongensis gen. nov., sp. nov. is proposed. The type strain of Aestuariivita boseongensis is BS-B2(T) ( = KCTC 42052(T) = CECT 8532(T)). PMID:24899654

  8. Tenacibaculum caenipelagi sp. nov., a member of the family Flavobacteriaceae isolated from tidal flat sediment.

    PubMed

    Park, Sooyeon; Yoon, Jung-Hoon

    2013-08-01

    A Gram-stain-negative, non-spore-forming, aerobic, non-flagellated, gliding and rod-shaped bacterial strain, designated HJ-26M(T), was isolated from a tidal flat sediment in the Korean peninsula. It grew optimally at 25-30 °C, at pH 7.0-8.0 and in the presence of 2 % (w/v) NaCl. A neighbour-joining phylogenetic tree based on 16S rRNA gene sequences revealed that the strain fell within the clade comprising Tenacibaculum species, clustering coherently with the type strains of Tenacibaculum lutimaris and Tenacibaculum aestuarii. Strain HJ-26M(T) exhibited the highest 16S rRNA gene sequence similarity values of 98.4 and 98.2 % to T. lutimaris TF-26(T) and T. aestuarii SMK-4(T), respectively, and of 94.9-97.4 % to the type strains of the other Tenacibaculum species. Strain HJ-26M(T) contained MK-6 as the predominant menaquinone and iso-C15:0 and iso-C17:0 3-OH as the major fatty acids. The DNA G+C content of strain HJ-26M(T) was 34.5 mol% and its mean DNA-DNA relatedness values with the type strains of T. lutimaris and T. aestuarii were 19 and 23 %, respectively. Differential phenotypic properties, together with the phylogenetic and genetic distinctiveness, revealed that strain HJ-26M(T) is separate from other Tenacibaculum species. On the basis of the data presented, strain HJ-26M(T) is considered to represent a novel species of the genus Tenacibaculum, for which the name Tenacibaculum caenipelagi sp. nov. is proposed. The type strain is HJ-26M(T) (= KCTC 32323(T) = CECT 8283(T)). PMID:23733002

  9. Colonization dynamics of ciliate morphotypes modified by shifting sandy sediments.

    PubMed

    Risse-Buhl, Ute; Felsmann, Katja; Mutz, Michael

    2014-08-01

    Sandy stream-bed sediments colonized by a diverse ciliate community are subject to various disturbance regimes. In microcosms, we investigated the effect of sediment shifting on the colonization dynamics of 3 ciliate morphotypes differing in morphology, behavior and feeding strategy. The dynamics of the ciliate morphotypes inhabiting sediment pore water and overlying water were observed at 3 sediment shifting frequencies: (1) stable sediments, (2) periodically shifting sediments such as migrating ripples, and (3) continuously shifting sediments as occurring during scour events of the uppermost sediment. Sediment shifting significantly affected the abundance and growth rate of the ciliate morphotypes. The free-swimming filter feeder Dexiostoma campylum was vulnerable to washout by sediment shifting since significantly higher numbers occurred in the overlying water than in pore water. Abundance of D. campylum only increased in pore water of stable sediments. On the contrary, the vagile grasper feeder Chilodonella uncinata and the sessile filter feeder Vorticella convallaria had positive growth rates and successfully colonized sediments that shifted periodically and continuously. Thus, the spatio-temporal pattern of sediment dynamics acts as an essential factor of impact on the structure, distribution and function of ciliate communities in sand-bed streams. PMID:25129834

  10. Carbon, nutrient and trace metal cycling in sandy sediments: A comparison of high-energy beaches and backbarrier tidal flats

    NASA Astrophysics Data System (ADS)

    Reckhardt, Anja; Beck, Melanie; Seidel, Michael; Riedel, Thomas; Wehrmann, Achim; Bartholomä, Alexander; Schnetger, Bernhard; Dittmar, Thorsten; Brumsack, Hans-Jürgen

    2015-06-01

    In order to evaluate the importance of coastal sandy sediments and their contribution to carbon, nutrient and metal cycling we investigated two beach sites on Spiekeroog Island, southern North Sea, Germany, and a tidal flat margin, located in Spiekeroog's backbarrier area. We also analyzed seawater and fresh groundwater on Spiekeroog Island, to better define endmember concentrations, which influence our study sites. Intertidal sandy flats and beaches are characterized by pore water advection. Seawater enters the sediment during flood and pore water drains out during ebb and at low tide. This pore water circulation leads to continuous supply of fresh organic substrate to the sediments. Remineralization products of microbial degradation processes, i.e. nutrients, and dissolved trace metals from the reduction of particulate metal oxides, are enriched in the pore water compared to open seawater concentrations. The spatial distribution of dissolved organic carbon (DOC), nutrients (PO43-, NO3-, NO2-, NH4+, Si(OH)4 and total alkalinity), trace metals (dissolved Fe and Mn) as well as sulfate suggests that the exposed beach sites are subject to relatively fast pore water advection, which leads to organic matter and oxygen replenishment. Frequent pore water exchange further leads to comparatively low nutrient concentrations. Sulfate reduction does not appear to play a major role during organic matter degradation. High nitrate concentrations indicate that redox conditions are oxic within the duneward freshwater influenced section, while ammonification, denitrification, manganese and iron reduction seem to prevail in the ammonium-dominated seawater circulation zone. In contrast, the sheltered tidal flat margin site exhibits a different sedimentology (coarser beach sands versus finer tidal flat sands) and nutrients, dissolved manganese and DOC accumulate in the pore water. Ammonium is the dominant pore water nitrogen species and intense sulfate reduction leads to the formation

  11. Distribution and source of main contaminants in surface sediments of tidal flats in the Northern Shandong Province

    NASA Astrophysics Data System (ADS)

    Liu, Zhijie; Li, Peiying; Zhang, Xiaolong; Li, Ping; Xu, Yuanqin

    2014-10-01

    Twenty-nine samples of surface sediments from tidal flats in the Northern Shandong Province were collected for grain size, heavy metal (Hg, Cu, Pb, Zn, Cd, and Cr), and oil pollution analyses. The geoaccumulation index ( I geo) and factor analysis were introduced to evaluate sediment quality and source of contaminants. The mean concentrations of Hg, Cu, Pb, Zn, Cd, Cr, and oil in the surface sediments in the study area are 0.033, 17.756, 19.121, 55.700, 0.291, 59.563, and 14.213 μg g-1, respectively. The heavy metal contamination in the old delta lobe is slightly higher than that in the abandoned delta lobe; however, the opposite was observed for oil pollution. The I geo results revealed that the overall quality of the surface sediments in the study area is in good condition. The heavy metal pollution levels show a descending order: Cd> Hg> Cr> Cu> Zn> Pb, Cd being the main pollutant. The contamination level for in the study area is relatively lower than those for China's other tidal flats. Heavy metals are mainly derived from natural sources of rock weathering and erosion, partly influenced by industrial and agricultural discharge. However, oil pollution is mainly from runoff input, motorized fishing boat sewage, and oil exploitation.

  12. Bathymetric and sediment facies maps for China Bend and Marcus Flats, Franklin D. Roosevelt Lake, Washington, 2008 and 2009

    USGS Publications Warehouse

    Weakland, Rhonda J.; Fosness, Ryan L.; Williams, Marshall L.; Barton, Gary J.

    2011-01-01

    The U.S. Geological Survey (USGS) created bathymetric and sediment facies maps for portions of two reaches of Lake Roosevelt in support of an interdisciplinary study of white sturgeon (Acipenser transmontanus) and their habitat areas within Franklin D. Roosevelt Lake, Washington. In October 2008, scientists from the USGS used a boat-mounted multibeam echo sounder (MBES) to describe bathymetric data to characterize surface relief at China Bend and Marcus Flats, between Northport and Kettle Falls, Washington. In March 2009, an underwater video camera was used to view and record sediment facies that were then characterized by sediment type, grain size, and areas of sand deposition. Smelter slag has been identified as having the characteristics of sand-sized black particles; the two non-invasive surveys attempted to identify areas containing black-colored particulate matter that may be elements and minerals, organic material, or slag. The white sturgeon population in Lake Roosevelt is threatened by the failure of natural recruitment, resulting in a native population that consists primarily of aging fish and that is gradually declining as fish die and are not replaced by nonhatchery reared juvenile fish. These fish spawn and rear in the riverine and upper reservoir reaches where smelter slag is present in the sediment of the river lake bed. Effects of slag on the white sturgeon population in Lake Roosevelt are largely unknown. Two recent studies demonstrated that copper and other metals are mobilized from slag in aqueous environments with concentrations of copper and zinc in bed sediments reaching levels of 10,000 and 30,000 mg/kg due to the presence of smelter slag. Copper was found to be highly toxic to 30-day-old white sturgeon with 96-h LC50 concentrations ranging from 3 to 5 (u or mu)g copper per liter. Older juvenile and adult sturgeons commonly ingest substantial amounts of sediment while foraging. Future study efforts in Lake Roosevelt should include sampling of

  13. Specific Bacterial, Archaeal, and Eukaryotic Communities in Tidal-Flat Sediments along a Vertical Profile of Several Meters†

    PubMed Central

    Wilms, Reinhard; Sass, Henrik; Köpke, Beate; Köster, Jürgen; Cypionka, Heribert; Engelen, Bert

    2006-01-01

    The subsurface of a tidal-flat sediment was analyzed down to 360 cm in depth by molecular and geochemical methods. A community structure analysis of all three domains of life was performed using domain-specific PCR followed by denaturing gradient gel electrophoresis analysis and sequencing of characteristic bands. The sediment column comprised horizons easily distinguishable by lithology that were deposited in intertidal and salt marsh environments. The pore water profile was characterized by a subsurface sulfate peak at a depth of about 250 cm. Methane and sulfate profiles were opposed, showing increased methane concentrations in the sulfate-free layers. The availability of organic carbon appeared to have the most pronounced effect on the bacterial community composition in deeper sediment layers. In general, the bacterial community was dominated by fermenters and syntrophic bacteria. The depth distribution of methanogenic archaea correlated with the sulfate profile and could be explained by electron donor competition with sulfate-reducing bacteria. Sequences affiliated with the typically hydrogenotrophic Methanomicrobiales were present in sulfate-free layers. Archaea belonging to the Methanosarcinales that utilize noncompetitive substrates were found along the entire anoxic-sediment column. Primers targeting the eukaryotic 18S rRNA gene revealed the presence of a subset of archaeal sequences in the deeper part of the sediment cores. The phylogenetic distance to other archaeal sequences indicates that these organisms represent a new phylogenetic group, proposed as “tidal-flat cluster 1.” Eukarya were still detectable at 360 cm, even though their diversity decreased with depth. Most of the eukaryotic sequences were distantly related to those of grazers and deposit feeders. PMID:16597980

  14. Dynamics of DNA Chains on Flat and Patterned Surfaces

    NASA Astrophysics Data System (ADS)

    Li, Bingquan; Xiaohua, Fang; Seo, Young-Soo; Samuilov, Vladimir; Rafailovich, Miriam; Sokolov, Jonathan

    2003-03-01

    The electrophoresis of DNA chains on flat silicon and patterned surfaces was studied by Confocal Fluorescence Microscopy and Atomic Force Microscopy. Solutions of lambda DNA of 48,502 bp and Schizosaccharomyces pombe (S. pombe) of 3 6 Mb were deposited on different surfaces. The surfaces were chemically modified to be hydrophilic or SAM-covered and the patterns were produced over length scales from nano to micro size in the form of gratings or square arrays. The interaction with the surface and mobility of DNA chains depended on the surface chemistry, topography and ion concentration of buffer. The motion of individual chains in the electric field was analyzed both in terms of the dimensions and orientation of the pattern structure. Supported by NSF-MRSEC program (DMR-9632525)

  15. Characterizing Seismic Anisotropy across the Peruvian Flat-Slab Subduction Zone: Implications for the Dynamics of Flat-Slabs

    NASA Astrophysics Data System (ADS)

    Eakin, Caroline; Long, Maureen; Beck, Susan; Wagner, Lara; Tavera, Hernando

    2014-05-01

    -slab anisotropy beneath all stations. Splitting is however is weakest and nulls most prevalent above the incoming Nazca Ridge where the slab is at its most shallow. This suggests the main source for the local S anisotropy may be from a thin mantle wedge layer sandwiched between the slab and upper plate. The deepest local S events sample a large volume of dipping slab material and provide increasing evidence for distinct anisotropy within the subducting slab itself that has fast polarizations parallel to the slab strike. Our detailed shear wave splitting study therefore reveals the presence of complex and multi-layered anisotropy across the Peruvian flat-slab region. We are able to characterize different sources of anisotropy in the sub-slab mantle, slab, asthenospheric wedge and the over-riding plate, each with their own implications for the regional subduction dynamics.

  16. Temperature dependent droplet impact dynamics on flat and textured surfaces

    SciTech Connect

    Azar Alizadeh; Vaibhav Bahadur; Sheng Zhong; Wen Shang; Ri Li; James Ruud; Masako Yamada; Liehi Ge; Ali Dhinojwala; Manohar S Sohal

    2012-03-01

    Droplet impact dynamics determines the performance of surfaces used in many applications such as anti-icing, condensation, boiling and heat transfer. We study impact dynamics of water droplets on surfaces with chemistry/texture ranging from hydrophilic to superhydrophobic and across a temperature range spanning below freezing to near boiling conditions. Droplet retraction shows very strong temperature dependence especially for hydrophilic surfaces; it is seen that lower substrate temperatures lead to lesser retraction. Physics-based analyses show that the increased viscosity associated with lower temperatures can explain the decreased retraction. The present findings serve to guide further studies of dynamic fluid-structure interaction at various temperatures.

  17. Dynamical Generation of Floquet Majorana Flat Bands in s-Wave Superconductors

    NASA Astrophysics Data System (ADS)

    Poudel, Amrit; Ortiz, Gerardo; Viola, Lorenza

    2015-03-01

    We present techniques to dynamically engineer flat bands of symmetry-protected Majorana edge modes in s-wave superconductors. Specifically, we show how time-dependent periodic control may be employed for designing time-independent effective Hamiltonians, which support Floquet Majorana flat bands, starting from topologically trivial equilibrium conditions. In the first approach, a suitably chosen modulation of the chemical potential simultaneously induces Majorana flat bands and dynamically ``activates'' a pre-existing chiral symmetry which is responsible for their protection. In the second approach, a desired chiral symmetry is dynamically generated by suppressing a chirality-breaking term in the static Hamiltonian. In the process, we also show how a non-equilibrium topological state of matter may be reached, that has no known equilibrium counterpart.

  18. Diverse metal reduction and nano- mineral formation by metal-reducing bacteria enriched from inter-tidal flat sediments

    NASA Astrophysics Data System (ADS)

    Kim, Y.; Park, B.; Seo, H.; Roh, Y.

    2009-12-01

    Dissimilatory metal-reducing bacteria utilize diverse metal oxides as electron acceptors and couple this microbial metal reduciton to growth. However, the microbe-metal interactions playing important roles in the metal geochemistry and organic matter degradation in the tidal flat sediments have not been uncovered enough to employ in various environmental and industrial applications. The objective of this study was to examine biomineralization and bioremediation by the facultative metal-reducing bacteria isolated from the inter-tidal flat sediments in southwestern of Korea. 16S-rRNA analysis showed bacterial consortium mainly consists of genus of Clostridium sp. The enriched bacteria were capable of reducing diverse metals such as iron oxide, maganese oxide, Cr(VI) and Se(VI) during glucose fermentation process at room temperature. The bacteria reduced highly toxic and reactive elements such as Cr(VI) and Se(VI) to Cr(III) and Se(0). The results showed that microbial processes induced transformation from toxic states of heavy metals to less toxic and mobile states in natural environments. Andthe bacteria also reduced iron oxyhydroxide such as ferrihydrite and akaganeite (β-FeOOH) and formed nanometer-sized magnetite (Fe3O4). This study indicates microbial processes not only can be used for bioremediation of inorganic contaminants existing in the marine environments, but also form the magnetite nanoparticles which are exhibit superparamagnetic properties that can be useful for relevant medical and industrial applications.

  19. Dynamical generation of Floquet Majorana flat bands in s-wave superconductors

    NASA Astrophysics Data System (ADS)

    Poudel, A.; Ortiz, G.; Viola, L.

    2015-04-01

    We present quantum control techniques to engineer flat bands of symmetry-protected Majorana edge modes in s-wave superconductors. Specifically, we show how periodic control may be employed for designing time-independent effective Hamiltonians, which support Floquet Majorana flat bands, starting from equilibrium conditions that are either topologically trivial or only support a Majorana pair per edge. In the first approach, a suitable modulation of the chemical potential simultaneously induces Majorana flat bands and dynamically activates a pre-existing chiral symmetry which is responsible for their protection. In the second approach, the application of effective parity kicks dynamically generates a desired chiral symmetry by suppressing chirality-breaking terms in the static Hamiltonian. Our results demonstrate how the use of time-dependent control enlarges the range of possibilities for realizing gapless topological superconductivity, potentially enabling access to topological states of matter that have no known equilibrium counterpart.

  20. Suspended sediment dynamics in the Mississippi River basin

    NASA Astrophysics Data System (ADS)

    Ali, K.; Cullis, J. D.; Xu, X.; More, M.; Hassan, M. A.; Simon, A.; Donner, S. D.; Sivapalan, M.

    2010-12-01

    This study investigated sediment trends in a heavily managed basin influenced by substantial human impacts. Spatial and temporal patterns of suspended sediment dynamics were examined in the Mississippi River basin by utilizing all available USGS suspended-sediment data with a minimum of 30 matching samples of suspended-sediment concentration and water discharge. These spatial trends were related to the land use change which has occurred over the last century and this includes dams, soil conservation measures and channelization. Sediment sources and sinks along the main stem of the Mississippi River and its main tributaries were identified and mapped. Three main trends were identified. 1) Sediment yields decreasing with increasing drainage area imply systematically increasing sediment storage downstream the landscape. 2) Sediment yields increasing with drainage area indicate net recruitment of sediment along the main valleys from banks and floodplain erosion. 3) Sediment yields showing no relationship with drainage area are attributed to the complexity arising from diverse climate, geology and land use of the basin. Based on the results, regional scale sediment yield maps were prepared and linked to the land use and the history of the basin.

  1. Sediment dynamics in the Adriatic Sea investigated with coupled models

    USGS Publications Warehouse

    Sherwood, Christopher R.; Book, Jeffrey W.; Carniel, Sandro; Cavaleri, Luigi; Chiggiato, Jacopo; Das, Himangshu; Doyle, James D.; Harris, Courtney K.; Niedoroda, Alan W.; Perkins, Henry; Poulain, Pierre-Marie; Pullen, Julie; Reed, Christopher W.; Russo, Aniello; Sclavo, Mauro; Signell, Richard P.; Traykovski, Peter A.; Warner, John C.

    2004-01-01

    Several large research programs focused on the Adriatic Sea in winter 2002-2003, making it an exciting place for sediment dynamics modelers (Figure 1). Investigations of atmospheric forcing and oceanic response (including wave generation and propagation, water-mass formation, stratification, and circulation), suspended material, bottom boundary layer dynamics, bottom sediment, and small-scale stratigraphy were performed by European and North American researchers participating in several projects. The goal of EuroSTRATAFORM researchers is to improve our ability to understand and simulate the physical processes that deliver sediment to the marine environment and generate stratigraphic signatures. Scientists involved in the Po and Apennine Sediment Transport and Accumulation (PASTA) experiment benefited from other major research programs including ACE (Adriatic Circulation Experiment), DOLCE VITA (Dynamics of Localized Currents and Eddy Variability in the Adriatic), EACE (the Croatian East Adriatic Circulation Experiment project), WISE (West Istria Experiment), and ADRICOSM (Italian nowcasting and forecasting) studies.

  2. Sediment dynamics in an overland flow-prone forest catchment

    NASA Astrophysics Data System (ADS)

    Zimmermann, Alexander; Elsenbeer, Helmut

    2010-05-01

    Vegetation controls erosion in many respects, and it is assumed that forest cover is an effective control. Currently, most literature on erosion processes in forest ecosystems support this impression and estimates of sediment export from forested catchments serve as benchmarks to evaluate erosion processes under different land uses. Where soil properties favor near-surface flow paths, however, vegetation may not mitigate surface erosion. In the forested portion of the Panama Canal watershed overland flow is widespread and occurs frequently, and indications of active sediment transport are hard to overlook. In this area we selected a 9.7 ha catchment for a high-resolution study of suspended sediment dynamics. We equipped five nested catchments to elucidate sources, drivers, magnitude and timing of suspended sediment export by continuous monitoring of overland flow and stream flow and by simultaneous, event-based sediment sampling. The support program included monitoring throughfall, splash erosion, overland-flow connectivity and a survey of infiltrability, permeability, and aggregate stability. This dataset allowed a comprehensive view on erosion processes. We found that overland flow controls the suspended-sediment dynamics in channels. Particularly, rainfalls of high intensity at the end of the rainy season have a superior impact on the overall sediment export. During these events, overland flow occurs catchment-wide up to the divide and so does erosion. With our contribution we seek to provide evidence that forest cover and large sediment yields are no contradiction in terms even in the absence of mass movements.

  3. Rock glaciers and the sediment dynamics in arid mountain belts

    NASA Astrophysics Data System (ADS)

    Blöthe, Jan Henrik; Höser, Thorsten; Rosenwinkel, Swenja; Korup, Oliver

    2016-04-01

    Rock glaciers are common periglacial features in highest elevations of semiarid to arid mountain ranges. Rock glaciers predominate in realms where precipitation values fall below thresholds that allow for ice glacier formation, then even outranging ice glaciers in size and number. The influence of ice glaciers on high-mountain's sediment dynamics is manifold: ice-glacier-driven erosion produces large amounts of clastic material; ice glaciers act as a conveyor belt for sediments, delivering material from their source regions to their terminus; ice glaciers entering trunk valleys form efficient dams that interrupt sediment delivery. While these mechanisms have been addressed in numerous earlier studies, the role of rock glaciers for the sediment dynamics of arid mountain belts remains elusive. We address this shortcoming by analysing a rock glacier inventory that we compiled for the Himalaya-Karakoram ranges and the Tien Shan ranges in Central Asia. Our inventory comprises more than 1000 specimen, a large number of which form dams of large trunk rivers and minor tributaries, disconnecting the sediment fluxes from upstream. In certain regions that are nearly devoid of ice-glaciers, like the Gamugah surface of NW Pakistan, rock glaciers of >10^4-m length occupy valley bottoms entirely, constituting the only mode of transport for sediments produced in headwaters. In conclusion, we call for a better understanding of the role that rock glaciers take in the sediment dynamics of arid mountain belts.

  4. The landward and seaward mechanisms of fine-sediment transport across intertidal flats in the shallow-water region—A numerical investigation

    NASA Astrophysics Data System (ADS)

    Hsu, Tian-Jian; Chen, Shih-Nan; Ogston, Andrea S.

    2013-06-01

    This study investigates transport of fine sediment across idealized intertidal flats with emphasis on resolving processes at the tidal edge, which is defined as the very shallow region of the land-water interface. We first utilize a two-dimensional, vertical numerical model solving the non-hydrostatic Reynolds-averaged Navier-Stokes equations with a k-ɛ turbulence closure. The numerical model adopts the Volume of Fluid method to simulate the wetting and drying region of the intertidal flat. The model is demonstrated to be able to reproduce the classic theory of tidal-flat hydrodynamics of Friedrichs and Aubrey (1996) and to predict the turbidity at the tidal edge that is similar, qualitatively, to prior field observations. The Regional Ocean Modeling System (ROMS) is also utilized to simulate the same idealized tidal flat to evaluate its applicability in this environment. We demonstrate that when a small critical depth (hcrit=2cm) in the wetting and drying scheme is adopted, ROMS is able to predict the main features of hydrodynamics and sediment-transport processes similar to those predicted by the RANS-VOF model. When driving the models with a symmetric tidal forcing, both models predict landward transport on the lower and upper flat and seaward transport in the subtidal region. When the very shallow region of the tidal edge is well resolved, both models predict an asymmetry of tidal velocity magnitude between the flood and the ebb that may encourage landward sediment transport on the flat. Further model simulation suggests that the predicted landward transport of sediment on the flat is mainly due to the settling-lag effect while the asymmetry of tidal velocity magnitude may add a lesser but non-negligible amount. When the bed erosion is limited by the availability of soft mud, the predicted transport direction becomes landward in both the subtidal region and on the flat. These results suggest that the tidal flow generally encourages landward transport while

  5. Degradation of cyanobacterial biomass in anoxic tidal-flat sediments: a microcosm study of metabolic processes and community changes

    PubMed Central

    Graue, Jutta; Engelen, Bert; Cypionka, Heribert

    2012-01-01

    To follow the anaerobic degradation of organic matter in tidal-flat sediments, a stimulation experiment with 13C-labeled Spirulina biomass (130 mg per 21 g sediment slurry) was conducted over a period of 24 days. A combination of microcalorimetry to record process kinetics, chemical analyses of fermentation products and RNA-based stable-isotope probing (SIP) to follow community changes was applied. Different degradation phases could be identified by microcalorimetry: Within 2 days, heat output reached its maximum (55 μW), while primary fermentation products were formed (in μmol) as follows: acetate 440, ethanol 195, butyrate 128, propionate 112, H2 127 and smaller amounts of valerate, propanol and butanol. Sulfate was depleted within 7 days. Thereafter, methanogenesis was observed and secondary fermentation proceeded. H2 and alcohols disappeared completely, whereas fatty acids decreased in concentration. Three main degraders were identified by RNA-based SIP and denaturant gradient gel electrophoresis. After 12 h, two phylotypes clearly enriched in 13C: (i) Psychrilyobacter atlanticus, a fermenter known to produce hydrogen and acetate and (ii) bacteria distantly related to Propionigenium. A Cytophaga-related bacterium was highly abundant after day 3. Sulfate reduction appeared to be performed by incompletely oxidizing species, as only sulfate-reducing bacteria related to Desulfovibrio were labeled as long as sulfate was available. PMID:21918576

  6. A buoy for continuous monitoring of Suspended Sediment Dynamics.

    PubMed

    Mueller, Philip; Thoss, Heiko; Kaempf, Lucas; Güntner, Andreas

    2013-01-01

    Knowledge of Suspended Sediments Dynamics (SSD) across spatial scales is relevant for several fields of hydrology, such as eco-hydrological processes, the operation of hydrotechnical facilities and research on varved lake sediments as geoarchives. Understanding the connectivity of sediment flux between source areas in a catchment and sink areas in lakes or reservoirs is of primary importance to these fields. Lacustrine sediments may serve as a valuable expansion of instrumental hydrological records for flood frequencies and magnitudes, but depositional processes and detrital layer formation in lakes are not yet fully understood. This study presents a novel buoy system designed to continuously measure suspended sediment concentration and relevant boundary conditions at a high spatial and temporal resolution in surface water bodies. The buoy sensors continuously record turbidity as an indirect measure of suspended sediment concentrations, water temperature and electrical conductivity at up to nine different water depths. Acoustic Doppler current meters and profilers measure current velocities along a vertical profile from the water surface to the lake bottom. Meteorological sensors capture the atmospheric boundary conditions as main drivers of lake dynamics. It is the high spatial resolution of multi-point turbidity measurements, the dual-sensor velocity measurements and the temporally synchronous recording of all sensors along the water column that sets the system apart from existing buoy systems. Buoy data collected during a 4-month field campaign in Lake Mondsee demonstrate the potential and effectiveness of the system in monitoring suspended sediment dynamics. Observations were related to stratification and mixing processes in the lake and increased turbidity close to a catchment outlet during flood events. The rugged buoy design assures continuous operation in terms of stability, energy management and sensor logging throughout the study period. We conclude that

  7. A Buoy for Continuous Monitoring of Suspended Sediment Dynamics

    PubMed Central

    Mueller, Philip; Thoss, Heiko; Kaempf, Lucas; Güntner, Andreas

    2013-01-01

    Knowledge of Suspended Sediments Dynamics (SSD) across spatial scales is relevant for several fields of hydrology, such as eco-hydrological processes, the operation of hydrotechnical facilities and research on varved lake sediments as geoarchives. Understanding the connectivity of sediment flux between source areas in a catchment and sink areas in lakes or reservoirs is of primary importance to these fields. Lacustrine sediments may serve as a valuable expansion of instrumental hydrological records for flood frequencies and magnitudes, but depositional processes and detrital layer formation in lakes are not yet fully understood. This study presents a novel buoy system designed to continuously measure suspended sediment concentration and relevant boundary conditions at a high spatial and temporal resolution in surface water bodies. The buoy sensors continuously record turbidity as an indirect measure of suspended sediment concentrations, water temperature and electrical conductivity at up to nine different water depths. Acoustic Doppler current meters and profilers measure current velocities along a vertical profile from the water surface to the lake bottom. Meteorological sensors capture the atmospheric boundary conditions as main drivers of lake dynamics. It is the high spatial resolution of multi-point turbidity measurements, the dual-sensor velocity measurements and the temporally synchronous recording of all sensors along the water column that sets the system apart from existing buoy systems. Buoy data collected during a 4-month field campaign in Lake Mondsee demonstrate the potential and effectiveness of the system in monitoring suspended sediment dynamics. Observations were related to stratification and mixing processes in the lake and increased turbidity close to a catchment outlet during flood events. The rugged buoy design assures continuous operation in terms of stability, energy management and sensor logging throughout the study period. We conclude that

  8. Sediment characteristics and transportation dynamics of the Ganga River

    NASA Astrophysics Data System (ADS)

    Singh, Munendra; Singh, Indra Bir; Müller, German

    2007-04-01

    Understanding of river systems that have experienced various forcing mechanisms such as climate, tectonics, sea level fluctuations and their linkages is a major concern for fluvial scientists. The 2525-km-long Ganga River derives its fluvial flux from northern part of the Indian subcontinent and drops in the Ganga-Brahmaputra delta and the Bengal fan regions. This paper presents a study of the Ganga River sediments for their textural properties, grainsize characteristics, and transportation dynamics. A suite of recently deposited sediments (189 bedload samples and 27 suspended load samples) of the river and its tributaries was collected from 63 locations. Dry and wet sieve methods of grainsize analysis were performed and Folk and Ward's parameters were calculated. Transportation dynamics of the sediment load was assessed by means of channel hydrology, flow/sediment rating curves, bedform mechanics, grainsize images, and cumulative curves. Textural properties of the bedload sediments of the Ganga River tributaries originating from the Himalaya orogenic belt, the northern Indian craton and the Ganga alluvial plain regions are characterised by the predominance of fine to very fine sand, medium to fine sand, and very fine sand to clay, respectively. Downstream textural variations in the bedload and suspended load sediments of the Ganga River are, therefore, complex and are strongly influenced by lateral sediment inputs by the tributaries and channel slope. At the base of the Himalaya, a very sharp gravel-sand transition is present in which median grainsize of bedload sediments decreases from over - 0.16 Φ to 2.46 Φ within a distance of 35 km. Downstream decline in mean grainsize of bedload sediments in the upper Ganga River within the alluvial plain can be expressed by an exponential formula as: mean grainsize (in Φ) = 0.0024 × Distance (in kilometres from the Himalayan front) + 1.29. It is a result of selective transport phenomena rather than of abrasion, the

  9. Fabrication and characterization of a dynamically flat high resolution micro-scanner

    NASA Astrophysics Data System (ADS)

    Hsu, S.; Klose, T.; Drabe, C.; Schenk, H.

    2008-04-01

    We present an ultra flat high frequency micro-scanner for high resolution laser projection applications. The scanner is fabricated in silicon-on-insulator wafers with a 30 µm thick device layer. A backside island is constructed behind the mirror plate to improve the rigidity. The backside island is done with a deep reactive ion etching (DRIE)-tetramethylammonium hydroxide (TMAH) combination process to achieve a height of 86 µm with good uniformity (4% within-wafer non-uniformity). The dynamic deformation is measured with a stroboscopic interferometer. The 1 mm diameter mirror plate has a root-mean-square deformation of less than 27 nm if operated at 30.84 kHz and a mechanical scan angle of ± 10°. The dynamic flatness performance of the device exceeds the optical quality requirement of <λ/10 deformation. The modulation transfer function of the scanner is calculated to demonstrate the resolution improvement from a scanner without backside reinforcement. With a diameter-scan angle product of 10 and a good dynamic flatness, the scanner is capable of performing the horizontal scanning (800 pixels) for an SVGA quality laser projection display.

  10. Dynamic Sediment Modeling: A Case Study at Walnut Creek, Iowa

    NASA Astrophysics Data System (ADS)

    Li, Z.; Zhang, Y.

    2006-12-01

    Deep channel bed incision and severe channel bank erosion, which have strong effects on the evolution of channel and watershed morphology, are becoming serious problems in natural rivers and streams in Iowa as a result of wide distribution of loess soil material, agricultural activity, river training and human intervention. Consequent high sediment concentration can also cause low water quality and jeopardize aquatic habitat. Dynamic modeling of sediment transport in rivers and streams provides a useful tool for monitoring, controlling and forecasting the morphology change and water quality in channels and watersheds. In order to gain insight into sediment transport process, a dynamic sediment model is built for a 7-mile segment of Walnut Creek in Jasper County, Iowa. This creek was intensively surveyed by Iowa Geological Survey Bureau (IGSB) as part of the Walnut Creek Nonpoint Source Monitoring Project. Besides channel geometry data from the survey, hydraulic and sediment data were collected at two gauges upstream and downstream operated by USGS. A software GSTARS3 developed by USGS is adopted to model both channel bed incision and bank erosion which are typical phenomena in Iowa. The dynamic sediment model is calibrated using channel bathymetry data from recent survey conducted by IGSB. Finally, based on forecasting of flow and sediment discharge time series at the upstream and stage time series at the downstream, a sediment forecasting model is developed to see if the stream can go back to the clarity and morphology of original creek. The study on this small surveyed and controlled creek will benefit our research in other Iowa rivers and streams.

  11. Flocculation on a muddy intertidal flat in Willapa Bay, Washington, Part I: A regional survey of the grain size of surficial sediments

    NASA Astrophysics Data System (ADS)

    Law, B. A.; Milligan, T. G.; Hill, P. S.; Newgard, J.; Wheatcroft, R. A.; Wiberg, P. L.

    2013-06-01

    Bottom sediments were collected on a muddy tidal flat in Willapa Bay (southwestern Washington State) and analyzed for grain size using a Coulter Multisizer. The disaggregated inorganic grain size (DIGS) distributions obtained from the sediment were then analyzed using conventional methods including median diameter, d50, the largest 25% of the grain size in the population, d75, skewness, and kurtosis. In addition, the inverse model of Curran et al. (2004) was used to provide process-based parameters for description of the size distributions. To examine small-scale spatial differences in grain size, the results of the analysis were plotted against seabed elevation, obtained from USGS LiDAR data. Results reveal a strong inverse correlation between the mass fraction deposited to the seabed as flocs, which is called the "floc fraction", and elevation on the tidal flat but failed to show any correlation with conventional grain-size descriptors. The dependence of floc fraction on elevation arises mainly due to the differences in size distributions between secondary tidal channels and tidal flats. The extent of flocculation in sediments deposited in the channels of the Shoalwater tidal-flat system is seasonal. Greater precipitation in the winter months is associated with periods of increased suspended-sediment concentrations, which favours more extensive flocculation and the formation and maintenance of low-strength, high-water-content muds. During the summer dry season, lower suspended-sediment concentrations lead to reduced floc fractions in the channels, while the size distributions on the flats resemble those in winter.

  12. Sediment CO2 efflux from cleared and intact temperate mangrove and tidal flat habitat

    NASA Astrophysics Data System (ADS)

    Bulmer, Richard; Lundquist, Carolyn; Schwendenmann, Luitgard

    2015-04-01

    Temperate mangroves in Southern Australia and New Zealand have been increasing in extent over the past 50 years, whereas tropical mangroves have declined by 30-50% over a similar time frame to support development of aquaculture, land development and timber production. Tropical mangroves are understood to be an important carbon sink and carbon emissions following clearance are estimated to be significant; comparable or greater than clearance of many terrestrial forest systems. As temperate mangrove clearance is proposed and has already occurred at some locations, it is important to determine potential carbon emissions from temperate mangroves, as well as exploring the factors which may influence emission rates. Here, we investigated the impact of temperate mangrove clearance on CO2 efflux from the sediment to the atmosphere along with a range of other biotic and abiotic factors. Higher CO2 efflux rates were observed within cleared (1.34

  13. Monitoring Large-Scale Sediment Transport Dynamics with Multibeam Sonar

    NASA Astrophysics Data System (ADS)

    Parsons, D. R.; Simmons, S. M.; Best, J. L.; Keevil, G. M.; Oberg, K.; Czuba, J. A.

    2009-05-01

    Multibeam Echo-Sounder systems have developed rapidly over recent decades and are routinely deployed to provide high-resolution bathymetric information in and range of environments. Modern data handling and storage technologies now facilitate the logging of the raw acoustic back-scatter information that was previously discarded by these systems. This paper describes methodologies that exploit this logging capability to quantify both the concentration and dynamics of suspended sediment within the water column. This development provides a multi-purpose tool for the holistic surveying of sediment transport dynamics by imaging suspended sediment concentration, the associated flows and providing concurrent high-resolution bathymetry. Results obtained a RESON 7125 MBES are presented from both well constrained dock-side testing and full field deployment over dune bedforms in the Mississippi. The capacity of the system to image suspended sediment structures is demonstrated and a novel methodology for estimating 2D flow velocities, based on frame cross-correlation methods, is introduced. The results demonstrate the capability of MBES systems to successfully map spatial and temporal variations in suspended sediment concentration throughout a 2D swath and application of the velocity estimation algorithms allow real-time holistic monitoring of turbulent flow processes and suspended sediment fluxes at a scale previously unrealisable. Turbulent flow over a natural dune bedform on the Mississippi is used to highlight the process information provided and the insights that can be gleaned for this technical development.

  14. Dual-exposure technique for extending the dynamic range of x-ray flat panel detectors

    NASA Astrophysics Data System (ADS)

    Sisniega, A.; Abella, M.; Desco, M.; Vaquero, J. J.

    2014-01-01

    This work presents an approach to extend the dynamic range of x-ray flat panel detectors by combining two acquisitions of the same sample taken with two different x-ray photon flux levels and the same beam spectral configuration. In order to combine both datasets, the response of detector pixels was modelled in terms of mean and variance using a linear model. The model was extended to take into account the effect of pixel saturation. We estimated a joint probability density function (j-pdf) of the pixel values by assuming that each dataset follows an independent Gaussian distribution. This j-pdf was used for estimating the final pixel value of the high-dynamic-range dataset using a maximum likelihood method. The suitability of the pixel model for the representation of the detector signal was assessed using experimental data from a small-animal cone-beam micro-CT scanner equipped with a flat panel detector. The potential extension in dynamic range offered by our method was investigated for generic flat panel detectors using analytical expressions and simulations. The performance of the proposed dual-exposure approach in realistic imaging environments was compared with that of a regular single-exposure technique using experimental data from two different phantoms. Image quality was assessed in terms of signal-to-noise ratio, contrast, and analysis of profiles drawn on the images. The dynamic range, measured as the ratio between the exposure for saturation and the exposure equivalent to instrumentation noise, was increased from 76.9 to 166.7 when using our method. Dual-exposure results showed higher contrast-to-noise ratio and contrast resolution than the single-exposure acquisitions for the same x-ray dose. In addition, image artifacts were reduced in the combined dataset. This technique to extend the dynamic range of the detector without increasing the dose is particularly suited to image samples that contain both low and high attenuation regions.

  15. Sediment pollution and dynamic in the Mar Piccolo of Taranto (southern Italy): insights from bottom sediment traps and surficial sediments.

    PubMed

    Bellucci, Luca Giorgio; Cassin, Daniele; Giuliani, Silvia; Botter, Margherita; Zonta, Roberto

    2016-07-01

    Major and trace element, PAH, and PCB concentrations were measured in surface sediments and particles from sediment traps collected in the First and Second Basin of the Mar Piccolo (Gulf of Taranto) in two periods (June-July and August-September, 2013). The aim of the study was to evaluate pollution degree, sediment transport and particle redistribution dynamic within the area. Results confirm the higher contamination of sediments from the First Basin observed by previous researches, particularly for Cu, Hg, Pb, total PAHs, and total PCBs. Advective transport from the First to the Second Basin appears to be the leading transfer mechanism of particles and adsorbed contaminants, as evidenced by measured fluxes and statistical analyses of contaminant concentrations in surficial sediments and particles from sediment traps. Long-range selective transports of PAHs and microbial anaerobic degradation processes for PCBs have been also observed. These results are limited to a restricted time window but are consistent with the presence of transport fluxes at the bottom of the water column. This mechanism deserves further investigation and monitoring activities, potentially being the main responsible of pollutant delivering to the less contaminated sectors of the Mar Piccolo. PMID:27117149

  16. Litoribaculum gwangyangense gen. nov., sp. nov., isolated from a sea-tidal flat sediment.

    PubMed

    Jin, Hyun Mi; Jeon, Che Ok

    2015-02-01

    A Gram-stain-negative, strictly aerobic bacterium, designated strain GY12(T), was isolated from a tidal flat of South Korea. Cells were moderately halotolerant, catalase- and oxidase-positive rods with gliding motility, and were devoid of flagella. Growth of strain GY12(T) was observed at 15-40 °C (optimum 25-30 °C), pH 6.0-8.5 (optimum pH 7.0-7.5) and with 1-5 % (w/v) NaCl (optimum 1-2 %). The major cellular fatty acids were iso-C15 : 1 G, iso-C15 : 0 and iso-C15 : 0 3-OH. The polar lipids consisted almost entirely of phosphatidylethanolamine, two unidentified aminolipids and two unidentified lipids. The G+C content of the genomic DNA was 34.8 mol% and the only respiratory quinone detected was menaquinone-6 (MK-6). Strain GY12(T) was most closely related to the genera Gaetbulibacter, Flaviramulus, Mariniflexile and Tamlana with 16S rRNA gene sequence similarities of 94-97 %, but phylogenetic inferences based on 16S rRNA gene sequences showed that the strain formed phyletic lineages distinct from these genera within the family Flavobacteriaceae. On the basis of phenotypic and molecular features, strain GY12(T) represents a novel species of a new genus in the family Flavobacteriaceae, for which the name Litoribaculum gwangyangense gen. nov., sp. nov. is proposed. The type strain of the type species is GY12(T) ( = KACC 16441(T) = JCM 18325(T)). PMID:25368139

  17. Dynamics of suspended sediment in Lake Ontario

    NASA Technical Reports Server (NTRS)

    Pluhowski, E. J. (Principal Investigator)

    1973-01-01

    The author has identified the following significant results. The suspended sediment plumes generated by the Welland Canal and the Genesee River are identifiable in most band 5 frames received from ERTS-1. In descending order of value for plume detection in Lake Ontario are bands 4, 6, and 7. Little or no information content relative to plume detection is available in band 7. The Oswego River plume was not visible during low flow periods; however, it was identifiable immediately following storms. Increased suspended sediment loading emanating from storm runoff increases turbidity levels to the point where the plume becomes visible in the ERTS-1 imagery. Despite the fact that it is detectable from high altitude (60,000 feet) photography, the Niagara River plume was not visible in any of the ERTS-1 frames. Numerous examples of shoreline erosion were evident in the December 7, 1972, imagery of western Lake Ontario. Near shore lake circulation patterns are usually apparent whenever turbidity plumes are sensed by the satellite.

  18. A distributed analysis of Human impact on global sediment dynamics

    NASA Astrophysics Data System (ADS)

    Cohen, S.; Kettner, A.; Syvitski, J. P.

    2012-12-01

    Understanding riverine sediment dynamics is an important undertaking for both socially-relevant issues such as agriculture, water security and infrastructure management and for scientific analysis of landscapes, river ecology, oceanography and other disciplines. Providing good quantitative and predictive tools in therefore timely particularly in light of predicted climate and landuse changes. Ever increasing human activity during the Anthropocene have affected sediment dynamics in two major ways: (1) an increase is hillslope erosion due to agriculture, deforestation and landscape engineering and (2) trapping of sediment in dams and other man-made reservoirs. The intensity and dynamics between these man-made factors vary widely across the globe and in time and are therefore hard to predict. Using sophisticated numerical models is therefore warranted. Here we use a distributed global riverine sediment flux and water discharge model (WBMsed) to compare a pristine (without human input) and disturbed (with human input) simulations. Using these 50 year simulations we will show and discuss the complex spatial and temporal patterns of human effect on riverine sediment flux and water discharge.

  19. Sediment dynamics on a steep, megatidal, mixed sand-gravel-cobble beach

    NASA Astrophysics Data System (ADS)

    Hay, A. E.; Zedel, L.; Stark, N.

    2014-08-01

    Results are presented from a pilot study of shore-face sediment dynamics on a steep, poorly sorted, coarse-grained, megatidal beach at the head of the Bay of Fundy, Nova Scotia, Canada. The experiment involved the first field deployment of a prototype wideband, pulse-coherent, bistatic acoustic Doppler profiling system. Measurements of the vertical structure of flow and turbulence above a sloping bed, as well as bed material velocity, demonstrate the capabilities of this instrument vis-à-vis studies of nearshore sediment dynamics at the field scale. The second focus of the paper is the unexpected observation that the surficial sediment median diameter, across the lower two-thirds of the intertidal zone, underwent a pronounced decrease when wave forcing was more energetic, compared to values observed during calmer conditions. The explanation for this result appears to involve the formation - in wave-dominated conditions - of metre-scale wavelength, 20 cm high ripples on the rising tide, which are then planed flat by the swash and/or the shore break on the subsequent ebb.

  20. Aceticlastic and NaCl-Requiring Methanogen “Methanosaeta pelagica” sp. nov., Isolated from Marine Tidal Flat Sediment

    PubMed Central

    Iino, Takao; Suzuki, Ken-Ichiro; Yamaguchi, Kaoru; Kamagata, Yoichi

    2012-01-01

    Among methanogens, only 2 genera, Methanosaeta and Methanosarcina, are known to contribute to methanogenesis from acetate, and Methanosaeta is a specialist that uses acetate specifically. However, Methanosaeta strains so far have mainly been isolated from anaerobic digesters, despite the fact that it is widespread, not only in anaerobic methanogenic reactors and freshwater environments, but also in marine environments, based upon extensive 16S rRNA gene-cloning analyses. In this study, we isolated an aceticlastic methanogen, designated strain 03d30qT, from a tidal flat sediment. Phylogenetic analyses based on 16S rRNA and mcrA genes revealed that the isolate belongs to the genus Methanosaeta. Unlike the other known Methanosaeta species, this isolate grows at Na+ concentrations of 0.20 to 0.80 M, with an optimum concentration of 0.28 M. Quantitative estimation using real-time PCR detected the 16S rRNA gene of the genus Methanosaeta in the marine sediment, and relative abundance ranged from 3.9% to 11.8% of the total archaeal 16S rRNA genes. In addition, the number of Methanosaeta organisms increased with increasing depth and was much higher than that of Methanosarcina organisms, suggesting that aceticlastic methanogens contribute to acetate metabolism to a greater extent than previously thought in marine environments, where sulfate-reducing acetate oxidation prevails. This is the first report on marine Methanosaeta species, and based on phylogenetic and characteristic studies, the name “Methanosaeta pelagica” sp. nov. is proposed for this novel species, with type strain 03d30q. PMID:22344667

  1. Polychlorinated biphenyls and organochlorine pesticides in surface sediments from the sand flats of Shuangtaizi Estuary, China: levels, distribution, and possible sources.

    PubMed

    Yuan, Xiutang; Yang, Xiaolong; Na, Guangshui; Zhang, Anguo; Mao, Yuze; Liu, Guize; Wang, Lili; Li, Xiaodong

    2015-09-01

    Levels of polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) in sediments from the sandy flat system of Shuangtaizi Estuary, the highest-latitude estuary in China, were investigated to identify their possible sources and potential ecological risk. The concentrations of 28 PCBs and 18 OCPs ranged from 1.83 to 36.68 ng g(-1) dw (mean 10.53 ng g(-1) dw) and from 0.02 to 14.57 ng g(-1) dw (mean 5.65 ng g(-1) dw), respectively. Generally, these organic pollutants showed an obvious spatial distribution, and relatively high levels were found at the high-tidal zone near river mouths. Compositional analyses indicated that tetra-PCBs were dominant for PCBs, whereas heptachlor was identified to be prevalent for OCPs in surficial sediment in the sand flats of Shuangtaizi Estuary. Overall, Shuangtaizi Estuary had moderate PCB and OCP levels in the sand flat sediments and posed a low ecological hazard to aquatic biota. Our results indicated that the sediment PCBs came from nonpoint deposition, such as atmospheric contribution and river input, for light chlorinated congeners and point source deposition, such as the industrial sources along river flow, for highly chlorinated congeners, whereas OCPs originate mainly from old residuals and new usage of pesticides in agriculture and aquaculture. PMID:25982989

  2. Static and Dynamic Parameters in Patients With Degenerative Flat Back and Change After Corrective Fusion Surgery

    PubMed Central

    2016-01-01

    Objective To evaluate characteristics of static and dynamic parameters in patients with degenerative flat back (DFB) and to compare degree of their improvement between successful and unsuccessful surgical outcome groups Methods Forty-seven patients with DFB were included who took whole spine X-ray and three-dimensional motion analysis before and 6 months after corrective surgery. Forty-four subjects were selected as a control group. As static parameters, thoracic kyphosis (TK), thoracolumbar junction (TLJ), lumbar lordosis (LL), pelvic incidence (PI), sacral slope (SS), and pelvic tilt (PT) were measured. As dynamic parameters, maximal and minimal angle of pelvic tilt, lower limb joints, and thoracic and lumbar vertebrae column (dynamic TK and LL) in sagittal plane were obtained. Results The DFB group showed smaller TK and larger LL, pelvic posterior tilt, hip flexion, knee flexion, and ankle dorsiflexion than the control group. Most of these parameters were significantly corrected by fusion surgery. Dynamic spinal parameters correlated with static spinal parameters. The successful group obtained significant improvement in maximal and minimal dynamic LL than the unsuccessful group. Conclusion The DFB group showed characteristic lower limb and spinal angles in dynamic and static parameters. Correlation between static and dynamic parameters was found in spinal segment. Dynamic LL was good predictor of successful surgical outcomes. PMID:27606275

  3. Entamoeba marina n. sp.; a New Species of Entamoeba Isolated from Tidal Flat Sediment of Iriomote Island, Okinawa, Japan.

    PubMed

    Shiratori, Takashi; Ishida, Ken-Ichiro

    2016-05-01

    The genus Entamoeba includes anaerobic lobose amoebae, most of which are parasites of various vertebrates and invertebrates. We report a new Entamoeba species, E. marina n. sp. that was isolated from a sample of tidal flat sediment collected at Iriomote Island, Okinawa, Japan. Trophozoites of E. marina were 12.8-32.1 μm in length and 6.8-15.9 μm in width, whereas the cysts were 8.9-15.8 μm in diam. and contained four nuclei. The E. marina cells contained a rounded nucleus with a small centric karyosome and uniformly arranged peripheral chromatin. Although E. marina is morphologically indistinguishable from other tetranucleated cyst-forming Entamoeba species, E. marina can be distinguished from them based on the combination of molecular phylogenetic analyses using SSU rDNA gene and the difference of collection sites. Therefore, we propose E. marina as a new species of the genus Entamoeba. PMID:26452446

  4. Can Human-made Saltpans Represent an Alternative Habitat for Shorebirds? Implications for a Predictable Loss of Estuarine Sediment Flats

    NASA Astrophysics Data System (ADS)

    Dias, Maria P.; Lecoq, Miguel; Moniz, Filipe; Rabaça, João E.

    2014-01-01

    Estuarine areas worldwide are under intense pressure due to human activities such as upstream dam building. Shorebirds strongly depend on estuarine intertidal flats during migration and wintering periods and so are particularly vulnerable to such impacts, whose magnitude will depend on the availability of alternative feeding habitats. In this study we analyze if man-made saltpans can represent an alternative habitat for wintering and migrating shorebirds in the Guadiana estuary, a wetland that is already experiencing environmental changes due to the building of the Alqueva reservoir, the largest in Western Europe. We compared the use of mudflats and saltpans as feeding areas by several shorebird species before the construction of the dam. A dataset with 26 years of counts data was also analyzed in order to detect any long-term trend in shorebirds abundance. We concluded that saltpans, in particular the fully mechanized, can be used as an alternative habitat by larger species during winter and southward migration, thus playing a major role in minimizing the possible effects of sediment loss due to dam building. In contrast, smaller species were particularly dependent on mudflats to feed. A significant change in population trends, from positive to negative, was detected for two species. Although we still have no evidence that this is directly linked to dam building, this result and documented changes that limit primary productivity justifies the implementation of a long-term monitoring scheme of shorebird populations in this estuary. We also reinforce the need to manage the saltpans as key habitats for shorebirds.

  5. Alkaline iron(III) reduction by a novel alkaliphilic, halotolerant, Bacillus sp. isolated from salt flat sediments of Soap Lake.

    PubMed

    Pollock, Jarrod; Weber, Karrie A; Lack, Joe; Achenbach, Laurie A; Mormile, Melanie R; Coates, John D

    2007-12-01

    A halotolerant, alkaliphilic dissimilatory Fe(III)-reducing bacterium, strain SFB, was isolated from salt flat sediments collected from Soap Lake, WA. 16S ribosomal ribonucleic acid gene sequence analysis identified strain SFB as a novel Bacillus sp. most similar to Bacillus agaradhaerens (96.7% similarity). Strain SFB, a fermentative, facultative anaerobe, fermented various hexoses including glucose and fructose. The fructose fermentation products were lactate, acetate, and formate. Under fructose-fermenting conditions in a medium amended with Fe(III), Fe(II) accumulated concomitant with a stoichiometric decrease in lactate and an increase in acetate and CO(2). Strain SFB was also capable of respiratory Fe(III) reduction with some unidentified component(s) of Luria broth as an electron donor. In addition to Fe(III), strain SFB could also utilize nitrate, fumarate, or O(2) as alternative electron acceptors. Optimum growth was observed at 30 degrees C and pH 9. Although the optimal salinity for growth was 0%, strain SFB could grow in a medium with up to 15% NaCl by mass. These studies describe a novel alkaliphilic, halotolerant organism capable of dissimilatory Fe(III) reduction under extreme conditions and demonstrate that Bacillus species can contribute to the microbial reduction of Fe(III) in environments at elevated pH and salinity, such as soda lakes. PMID:17943280

  6. The flatness of Lamellipodia explained by the interaction between actin dynamics and membrane deformation.

    PubMed

    Schmeiser, Christian; Winkler, Christoph

    2015-09-01

    The crawling motility of many cell types relies on lamellipodia, flat protrusions spreading on flat substrates but (on cells in suspension) also growing into three-dimensional space. Lamellipodia consist of a plasma membrane wrapped around an oriented actin filament meshwork. It is well known that the actin density is controlled by coordinated polymerization, branching, and capping processes, but the mechanisms producing the small aspect ratios of lamellipodia (hundreds of nm thickness vs. several μm lateral and inward extension) remain unclear. The main hypothesis of this work is a strong influence of the local geometry of the plasma membrane on the actin dynamics. This is motivated by observations of co-localization of proteins with I-BAR domains (like IRSp53) with polymerization and branching agents along the membrane. The I-BAR domains are known to bind to the membrane and to prefer and promote membrane curvature. This hypothesis is translated into a stochastic mathematical model where branching and capping rates, and polymerization speeds depend on the local membrane geometry and branching directions are influenced by the principal curvature directions. This requires the knowledge of the deformation of the membrane, being described in a quasi-stationary approximation by minimization of a modified Helfrich energy, subject to the actin filaments acting as obstacles. Simulations with this model predict pieces of flat lamellipodia without any prescribed geometric restrictions. PMID:26002996

  7. Signal crayfish as zoogeomorphic agents: diel patterns of fine sediment suspension in a crayfish-affected river and the implications for fine sediment fluxes and dynamics

    NASA Astrophysics Data System (ADS)

    Rice, Stephen; Johnson, Matthew; Reeds, Jake; Longstaff, Holly; Extence, Chris

    2013-04-01

    The signal crayfish (Pacifasticus leniusculus) is a formidable invasive species that has had a deleterious impact on native freshwater fauna across Europe. We contend that the impact of this animal extends beyond ecology into geomorphology and hypothesise that crayfish are significant agents of fine sediment recruitment and mobilisation, with potentially profound impacts on water quality, substrate quality and fine sediment fluxes. Building on pioneering work by colleagues at Queen Mary University, London this poster considers the role of crayfish in fine sediment suspension in a lowland, gravel-bed river. The hypothesis that nocturnal increases in crayfish activity are associated with a greater frequency of sediment suspension events and increases in ambient turbidity, is tested. Strong diel fluctuations in water turbidity were recorded at several sites on the Brampton Arm of the River Nene in England, a river heavily populated by signal crayfish, during August and September 2012. With the exception of three summer flood events, stage measurements during the same period were essentially flat, ruling out a hydraulic cause for overnight rises in turbidity. Water samples collected at midnight and at midday at one site confirm this diel pattern for suspended sediment concentration. Higher mean turbidity values overnight are associated with an increase in the magnitude and frequency of isolated turbidity spikes or events and this is consistent with crayfish nocturnalism. In particular, we suspect that turbidity events are caused by the construction and maintenenance of burrows and by interactions between crayfish and the river bed while foraging, fighting and avoiding each other. Tying the diel SSC signal directly to crayfish activity proved difficult, but several lines of argument presented here suggest that crayfish are the most likely cause of the diel pattern. These results provide substantial support for the idea that signal crayfish are important zoogeomorphic

  8. Contribution of hydrodynamic conditions during shallow water stages to the sediment balance on a tidal flat: Mont-Saint-Michel Bay, Normandy, France

    NASA Astrophysics Data System (ADS)

    Desguée, R.; Robin, N.; Gluard, L.; Monfort, O.; Anthony, E. J.; Levoy, F.

    2011-10-01

    Field measurements were conducted in Mont-Saint-Michel Bay, a megatidal embayment (spring tidal range of 15 m), in order to monitor, over the course of a tidal cycle, sediment transport variability due to waves and tides on the upper part of a tidal flat characterised by shallow water depths. Sensors used to measure currents, water depth and turbidity were installed just above the bed (0.04 m). Two experiments were conducted under contrasting hydrodynamic conditions. The results highlight wave activity over the tidal flat even though observed wind waves were largely dissipated due to the very shallow water depths. Very high suspended sediment concentrations (up to 6 kg/m 3) were recorded in the presence of wave activity at the beginning of the local flood, when significant sediment transport occurred, up to 7 times as much as under conditions of no wave activity. This influence may be attributed to the direct action of waves on bed sediments, to wave-induced liquefaction, and to the erosive action of waves on tidal channel banks. The sediment composition, comprising a clay fraction of 2-5%, may also enhance sediment transport by reducing critical shear stress through the sand lubrication effect. The results also show that antecedent meteorological conditions play an important role in suspended sediment transport on the tidal flat. Total sediment flux directions show a net transport towards the inner part of the bay that contributes to deposition over the adjacent salt marshes, and this tendency also prevails during strong wave conditions. Such sediment transport is characterised by significant variability over the course of the tidal cycle. During fair and moderate weather conditions, 83% and 71% of the total flux was observed, respectively, over only 11% and 28% of the duration of the local tidal cycle and with water depths between 0.04 and 0.3 m. These results suggest that in order to improve our understanding of sediment budgets in this type of coastal

  9. Continuous monitoring bed-level dynamics on an intertidal flat: introducing novel stand-alone high-resolution SED-sensors

    NASA Astrophysics Data System (ADS)

    Hu, Zhan; Lenting, Walther; van der Wal, Daphne; Bouma, Tjeerd

    2015-04-01

    Tidal flat morphology is continuously shaped by hydrodynamic force, resulting in highly dynamic bed elevations. The knowledge of short-term bed-level changes is important both for understanding sediment transport processes as well as for assessing critical ecological processes such as e.g. vegetation recruitment chances on tidal flats. Due to the labour involved, manual discontinuous measurements lack the ability to continuously monitor bed-elevation changes. Existing methods for automated continuous monitoring of bed-level changes lack vertical accuracy (e.g., Photo-Electronic Erosion Pin sensor and resistive rod) or limited in spatial application by using expensive technology (e.g., acoustic bed level sensors). A method provides sufficient accuracy with a reasonable cost is needed. In light of this, a high-accuracy sensor (2 mm) for continuously measuring short-term Surface-Elevation Dynamics (SED-sensor) was developed. This SED-sensor makes use of photovoltaic cells and operates stand-alone using internal power supply and data logging system. The unit cost and the labour in deployments is therefore reduced, which facilitates monitoring with a number of units. In this study, the performance of a group of SED-sensors is tested against data obtained with precise manual measurements using traditional Sediment Erosion Bars (SEB). An excellent agreement between the two methods was obtained, indicating the accuracy and precision of the SED-sensors. Furthermore, to demonstrate how the SED-sensors can be used for measuring short-term bed-level dynamics, two SED-sensors were deployed for 1 month at two sites with contrasting wave exposure conditions. Daily bed-level changes were obtained including a severe storm erosion event. The difference in observed bed-level dynamics at both sites was statistically explained by their different hydrodynamic conditions. Thus, the stand-alone SED-sensor can be applied to monitor sediment surface dynamics with high vertical and temporal

  10. Dynamic chest radiography: flat-panel detector (FPD) based functional X-ray imaging.

    PubMed

    Tanaka, Rie

    2016-07-01

    Dynamic chest radiography is a flat-panel detector (FPD)-based functional X-ray imaging, which is performed as an additional examination in chest radiography. The large field of view (FOV) of FPDs permits real-time observation of the entire lungs and simultaneous right-and-left evaluation of diaphragm kinetics. Most importantly, dynamic chest radiography provides pulmonary ventilation and circulation findings as slight changes in pixel value even without the use of contrast media; the interpretation is challenging and crucial for a better understanding of pulmonary function. The basic concept was proposed in the 1980s; however, it was not realized until the 2010s because of technical limitations. Dynamic FPDs and advanced digital image processing played a key role for clinical application of dynamic chest radiography. Pulmonary ventilation and circulation can be quantified and visualized for the diagnosis of pulmonary diseases. Dynamic chest radiography can be deployed as a simple and rapid means of functional imaging in both routine and emergency medicine. Here, we focus on the evaluation of pulmonary ventilation and circulation. This review article describes the basic mechanism of imaging findings according to pulmonary/circulation physiology, followed by imaging procedures, analysis method, and diagnostic performance of dynamic chest radiography. PMID:27294264

  11. Dynamic behaviour of coastal sedimentation in the Lions Gulf. [France

    NASA Technical Reports Server (NTRS)

    Guy, M. (Principal Investigator)

    1974-01-01

    The author has identified the following significant results. A number of ERTS-1 images covering this geographical zone were studied and compared with cartographic maps, air photographs, and thermal-IR images. Old and recent sediments leave traces in the landscape which are decoded by interpreting the shapes of the clear zones forming a network against the black background representing water and humid zones. Current sedimentation and its mechanism were investigated. It had been hoped that a regular sequence of images would make it possible to follow the dynamics of the Rhone and the coastal rivers in relation to meteorological conditions. In any event only a small number of images spread over a wide period of time were obtained, and a complete study was therefore impossible. However, in comparing some of the ERTS-1 images certain thermal-IR images and information on the flow of the Rhone provided some clarification of mechanisms associated with river dynamics.

  12. Micrometer-sized water droplet impingement dynamics and evaporation on a flat dry surface.

    PubMed

    Briones, Alejandro M; Ervin, Jamie S; Putnam, Shawn A; Byrd, Larry W; Gschwender, Lois

    2010-08-17

    A comprehensive numerical and experimental investigation on micrometer-sized water droplet impact dynamics and evaporation on an unheated, flat, dry surface is conducted from the standpoint of spray-cooling technology. The axisymmetric time-dependent governing equations of continuity, momentum, energy, and species are solved. Surface tension, wall adhesion effect, gravitational body force, contact line dynamics, and evaporation are accounted for in the governing equations. The explicit volume of fluid (VOF) model with dynamic meshing and variable-time stepping in serial and parallel processors is used to capture the time-dependent liquid-gas interface motion throughout the computational domain. The numerical model includes temperature- and species-dependent thermodynamic and transport properties. The contact line dynamics and the evaporation rate are predicted using Blake's and Schrage's molecular kinetic models, respectively. An extensive grid independence study was conducted. Droplet impingement and evaporation data are acquired with a standard dispensing/imaging system and high-speed photography. The numerical results are compared with measurements reported in the literature for millimeter-size droplets and with current microdroplet experiments in terms of instantaneous droplet shape and temporal spread (R/D(0) or R/R(E)), flatness ratio (H/D(0)), and height (H/H(E)) profiles, as well as temporal volume (inverted A) profile. The Weber numbers (We) for impinging droplets vary from 1.4 to 35.2 at nearly constant Ohnesorge number (Oh) of approximately 0.025-0.029. Both numerical and experimental results show that there is air bubble entrapment due to impingement. Numerical results indicate that Blake's formulation provides better results than the static (SCA) and dynamic contact angle (DCA) approach in terms of temporal evolution of R/D(0) and H/D(0) (especially at the initial stages of spreading) and equilibrium flatness ratio (H(E)/D(0)). Blake's contact line

  13. Development of patient collation system by kinetic analysis for chest dynamic radiogram with flat panel detector

    NASA Astrophysics Data System (ADS)

    Tsuchiya, Yuichiro; Kodera, Yoshie

    2006-03-01

    In the picture archiving and communication system (PACS) environment, it is important that all images be stored in the correct location. However, if information such as the patient's name or identification number has been entered incorrectly, it is difficult to notice the error. The present study was performed to develop a system of patient collation automatically for dynamic radiogram examination by a kinetic analysis, and to evaluate the performance of the system. Dynamic chest radiographs during respiration were obtained by using a modified flat panel detector system. Our computer algorithm developed in this study was consisted of two main procedures, kinetic map imaging processing, and collation processing. Kinetic map processing is a new algorithm to visualize a movement for dynamic radiography; direction classification of optical flows and intensity-density transformation technique was performed. Collation processing consisted of analysis with an artificial neural network (ANN) and discrimination for Mahalanobis' generalized distance, those procedures were performed to evaluate a similarity of combination for the same person. Finally, we investigated the performance of our system using eight healthy volunteers' radiographs. The performance was shown as a sensitivity and specificity. The sensitivity and specificity for our system were shown 100% and 100%, respectively. This result indicated that our system has excellent performance for recognition of a patient. Our system will be useful in PACS management for dynamic chest radiography.

  14. STAND, A DYNAMIC MODEL FOR SEDIMENT TRANSPORT AND WATER QUALITY. (R825758)

    EPA Science Inventory

    We introduce a new model–STAND (Sediment-Transport-Associated Nutrient Dynamics)–for simulating stream flow, sediment transport, and the interactions of sediment with other attributes of water quality. In contrast to other models, STAND employs a fully dynamic ba...

  15. Dynamics of the Methanogenic Archaea in Tropical Estuarine Sediments

    PubMed Central

    Torres-Alvarado, María del Rocío; Fernández, Francisco José; Ramírez Vives, Florina; Varona-Cordero, Francisco

    2013-01-01

    Methanogenesis may represent a key process in the terminal phases of anaerobic organic matter mineralization in sediments of coastal lagoons. The aim of the present work was to study the temporal and spatial dynamics of methanogenic archaea in sediments of tropical coastal lagoons and their relationship with environmental changes in order to determine how these influence methanogenic community. Sediment samples were collected during the dry (February, May, and early June) and rainy seasons (July, October, and November). Microbiological analysis included the quantification of viable methanogenic archaea (MA) with three substrates and the evaluation of kinetic activity from acetate in the presence and absence of sulfate. The environmental variables assessed were temperature, pH, Eh, salinity, sulfate, solids content, organic carbon, and carbohydrates. MA abundance was significantly higher in the rainy season (106–107 cells/g) compared with the dry season (104–106 cells/g), with methanol as an important substrate. At spatial level, MA were detected in the two layers analyzed, and no important variations were observed either in MA abundance or activity. Salinity, sulfate, solids, organic carbon, and Eh were the environmental variables related to methanogenic community. A conceptual model is proposed to explain the dynamics of the MA. PMID:23401664

  16. Dynamic flat panel detector versus image intensifier in cardiac imaging: dose and image quality

    NASA Astrophysics Data System (ADS)

    Vano, E.; Geiger, B.; Schreiner, A.; Back, C.; Beissel, J.

    2005-12-01

    The practical aspects of the dosimetric and imaging performance of a digital x-ray system for cardiology procedures were evaluated. The system was configured with an image intensifier (II) and later upgraded to a dynamic flat panel detector (FD). Entrance surface air kerma (ESAK) to phantoms of 16, 20, 24 and 28 cm of polymethyl methacrylate (PMMA) and the image quality of a test object were measured. Images were evaluated directly on the monitor and with numerical methods (noise and signal-to-noise ratio). Information contained in the DICOM header for dosimetry audit purposes was also tested. ESAK values per frame (or kerma rate) for the most commonly used cine and fluoroscopy modes for different PMMA thicknesses and for field sizes of 17 and 23 cm for II, and 20 and 25 cm for FD, produced similar results in the evaluated system with both technologies, ranging between 19 and 589 µGy/frame (cine) and 5 and 95 mGy min-1 (fluoroscopy). Image quality for these dose settings was better for the FD version. The 'study dosimetric report' is comprehensive, and its numerical content is sufficiently accurate. There is potential in the future to set those systems with dynamic FD to lower doses than are possible in the current II versions, especially for digital cine runs, or to benefit from improved image quality.

  17. Dynamic chest radiography with a flat-panel detector (FPD): ventilation-perfusion study

    NASA Astrophysics Data System (ADS)

    Tanaka, R.; Sanada, S.; Fujimura, M.; Yasui, M.; Tsuji, S.; Hayashi, N.; Okamoto, H.; Nanbu, Y.; Matsui, O.

    2011-03-01

    Pulmonary ventilation and blood flow are reflected in dynamic chest radiographs as changes in X-ray translucency, i.e., pixel values. This study was performed to investigate the feasibility of ventilation-perfusion (V/Q) study based on the changes in pixel value. Sequential chest radiographs of a patient with ventilation-perfusion mismatch were obtained during respiration using a dynamic flat-panel detector (FPD) system. The lung area was recognized and average pixel value was measured in each area, tracking and deforming the region of interest. Inter-frame differences were then calculated, and the absolute values were summed in each respiratory phase. The results were visualized as ventilation, blood flow, V/Q ratio distribution map and compared to distribution of radioactive counts on ventilation and perfusion scintigrams. In the results, abnormalities were appeared as a reduction of changes in pixel values, and a correlation was observed between the distribution of changes in pixel value and those of radioactivity counts (Ventilation; r=0.78, Perfusion; r=0.77). V/Q mismatch was also indicated as mismatch of changes in pixel value, and a correlation with V/Q calculated by radioactivity counts (r=0.78). These results indicated that the present method is potentially useful for V/Q study as an additional examination in conventional chest radiography.

  18. Earth surface dynamics - dispatches from the flats (Ralph Alger Bagnold Medal Lecture)

    NASA Astrophysics Data System (ADS)

    Hovius, Niels

    2016-04-01

    Earth's surface is shaped by the physical, chemical and biological processes operating on it and the interactions amongst them. No single discipline can lay claim to this surface, nor offer a full explanation of its dynamics. Only interdisciplinary approaches can unlock answers to key questions such as how do erosion and tectonics interact to build mountains, how do landscapes respond to climate change, how can we read processes from the sedimentary record, what is the role of erosion in Earth's carbon cycle, and how can we give reliable early warning of damaging earth surface process events? The wastelands between established academic fields are rich and bountiful and replete with steep learning curves and pitfalls for the naïve. In this lecture, I shall scour the interfaces of geophysics, geochemistry and geomorphology for understanding of the mechanisms, controls and impacts of mass wasting in steep mountain settings, ending up in remarkably flat places to find new insight into the dynamics of Earth's surface.

  19. Efficient dynamical correction of the transition state theory rate estimate for a flat energy barrier.

    PubMed

    Mökkönen, Harri; Ala-Nissila, Tapio; Jónsson, Hannes

    2016-09-01

    The recrossing correction to the transition state theory estimate of a thermal rate can be difficult to calculate when the energy barrier is flat. This problem arises, for example, in polymer escape if the polymer is long enough to stretch between the initial and final state energy wells while the polymer beads undergo diffusive motion back and forth over the barrier. We present an efficient method for evaluating the correction factor by constructing a sequence of hyperplanes starting at the transition state and calculating the probability that the system advances from one hyperplane to another towards the product. This is analogous to what is done in forward flux sampling except that there the hyperplane sequence starts at the initial state. The method is applied to the escape of polymers with up to 64 beads from a potential well. For high temperature, the results are compared with direct Langevin dynamics simulations as well as forward flux sampling and excellent agreement between the three rate estimates is found. The use of a sequence of hyperplanes in the evaluation of the recrossing correction speeds up the calculation by an order of magnitude as compared with the traditional approach. As the temperature is lowered, the direct Langevin dynamics simulations as well as the forward flux simulations become computationally too demanding, while the harmonic transition state theory estimate corrected for recrossings can be calculated without significant increase in the computational effort. PMID:27609008

  20. Analysis of the fine sediment dynamics in the River Thames catchment (UK) using a sediment rating curve approach

    NASA Astrophysics Data System (ADS)

    Bussi, Gianbattista; Dadson, Simon

    2015-04-01

    The effect of natural and anthropogenic disturbances on sediment transport in lowland rivers is a relevant factor in river management, especially in the context of changing climate and environment. Nevertheless, many of the processes that cause alterations in the sediment cycle are poorly understood, often due to lack of accurate data. In this study, we use a low-frequency suspended sediment sampling dataset to assess the spatial and temporal variations of sediment fluxes in the River Thames (UK). Several sediment rating curves (SRCs) were built in order to analyse spatio-temporal variations of catchment erodibility and sediment transport. First, changes in SRC coefficients in nine different sub-catchments were analysed and related to environmental factors including land cover, geology and vegetation. Then, the temporal variability of SRCs was investigated, both on a seasonal and inter-annual basis. Lastly, a simple dynamic SRC model was implemented in order to provide an estimation of the of sediment transport in the River Thames, and its performances were evaluated. The results quantify the spatial variability of sediment transport within the catchment and reveal a seasonal flushing effect, in which sediment loads are typically substantially higher during the first floods after the summer dry period. We estimate that, for the River Thames, the sediment loads of the first floods after summer are around double that of other floods. We also observed a decrease in the flushing effect which began in the late 1990s.

  1. Predicting the dynamic impact behaviour of spray droplets on flat plant surfaces.

    PubMed

    Delele, M A; Nuyttens, D; Duga, A T; Ambaw, A; Lebeau, F; Nicolai, B M; Verboven, P

    2016-09-14

    The dynamic impact behaviour of water droplets on plant surfaces was investigated based on a multiphase computational fluid dynamics (CFD) model. The study was conducted using the Volume Of Fluid (VOF) approach. The static contact angle of water droplets on leaf surfaces of different plants (apple, pear, leek and cabbage) was measured and found to vary between 54.9 and 138.2°. Impact experiments were conducted by monitoring the flow and impact characteristics of water droplets on leaves in still air with a high speed camera. Droplets were generated by an agricultural flat fan spray nozzle moving across the leaf at constant speed. The nozzle produced droplets with diameters ranging from 20.6 up to 550.8 μm, and droplet velocity values near the impact between 0.03 and 13.2 m s(-1). The CFD model was capable of predicting the observed dynamic impact behaviour of droplets on the plant surfaces. The fate of the droplets after the impact process for adhesion, bouncing or splashing was accurately predicted for Weber numbers (We) in the range of 0.007 to 1096 and droplet Reynolds numbers (Re) between 5 to 8000. The process was highly dependent on the surface and droplet flow characteristics during the impact. Combinations of We, Re and Ohnesorge (Oh) numbers defined the droplet maximum spread factor, the number of secondary droplets generated as a result of the splashing process and the transition between the different impact outcomes. These criteria can then be used in field scale spray deposition and drift models to better understand agricultural spray operations. PMID:27501228

  2. Genome-wide transcriptional responses of Alteromonas naphthalenivorans SN2 to contaminated seawater and marine tidal flat sediment.

    PubMed

    Jin, Hyun Mi; Jeong, Hye Im; Kim, Kyung Hyun; Hahn, Yoonsoo; Madsen, Eugene L; Jeon, Che Ok

    2016-01-01

    A genome-wide transcriptional analysis of Alteromonas naphthalenivorans SN2 was performed to investigate its ecophysiological behavior in contaminated tidal flats and seawater. The experimental design mimicked these habitats that either added naphthalene or pyruvate; tidal flat-naphthalene (TF-N), tidal flat-pyruvate (TF-P), seawater-naphthalene (SW-N), and seawater-pyruvate (SW-P). The transcriptional profiles clustered by habitat (TF-N/TF-P and SW-N/SW-P), rather than carbon source, suggesting that the former may exert a greater influence on genome-wide expression in strain SN2 than the latter. Metabolic mapping of cDNA reads from strain SN2 based on KEGG pathway showed that metabolic and regulatory genes associated with energy metabolism, translation, and cell motility were highly expressed in all four test conditions, probably highlighting the copiotrophic properties of strain SN2 as an opportunistic marine r-strategist. Differential gene expression analysis revealed that strain SN2 displayed specific cellular responses to environmental variables (tidal flat, seawater, naphthalene, and pyruvate) and exhibited certain ecological fitness traits -- its notable PAH degradation capability in seasonally cold tidal flat might be reflected in elevated expression of stress response and chaperone proteins, while fast growth in nitrogen-deficient and aerobic seawater probably correlated with high expression of glutamine synthetase, enzymes utilizing nitrite/nitrate, and those involved in the removal of reactive oxygen species. PMID:26887987

  3. Genome-wide transcriptional responses of Alteromonas naphthalenivorans SN2 to contaminated seawater and marine tidal flat sediment

    PubMed Central

    Jin, Hyun Mi; Jeong, Hye Im; Kim, Kyung Hyun; Hahn, Yoonsoo; Madsen, Eugene L.; Jeon, Che Ok

    2016-01-01

    A genome-wide transcriptional analysis of Alteromonas naphthalenivorans SN2 was performed to investigate its ecophysiological behavior in contaminated tidal flats and seawater. The experimental design mimicked these habitats that either added naphthalene or pyruvate; tidal flat-naphthalene (TF-N), tidal flat-pyruvate (TF-P), seawater-naphthalene (SW-N), and seawater-pyruvate (SW-P). The transcriptional profiles clustered by habitat (TF-N/TF-P and SW-N/SW-P), rather than carbon source, suggesting that the former may exert a greater influence on genome-wide expression in strain SN2 than the latter. Metabolic mapping of cDNA reads from strain SN2 based on KEGG pathway showed that metabolic and regulatory genes associated with energy metabolism, translation, and cell motility were highly expressed in all four test conditions, probably highlighting the copiotrophic properties of strain SN2 as an opportunistic marine r-strategist. Differential gene expression analysis revealed that strain SN2 displayed specific cellular responses to environmental variables (tidal flat, seawater, naphthalene, and pyruvate) and exhibited certain ecological fitness traits –– its notable PAH degradation capability in seasonally cold tidal flat might be reflected in elevated expression of stress response and chaperone proteins, while fast growth in nitrogen-deficient and aerobic seawater probably correlated with high expression of glutamine synthetase, enzymes utilizing nitrite/nitrate, and those involved in the removal of reactive oxygen species. PMID:26887987

  4. Identity and abundance of active sulfate-reducing bacteria in deep tidal flat sediments determined by directed cultivation and CARD-FISH analysis.

    PubMed

    Gittel, Antje; Mussmann, Marc; Sass, Henrik; Cypionka, Heribert; Könneke, Martin

    2008-10-01

    The identity and abundance of potentially active sulfate-reducing bacteria (SRB) in several metre deep sediments of a tidal sand flat in the German Wadden Sea were assessed by directed cultivation and cultivation-independent CARD-FISH analysis (catalysed reporter deposition fluorescence in situ hybridization). Presumably abundant SRB from different sediment layers between 0.5 and 4 m depth were selectively enriched in up to million-fold diluted cultures supplemented with lactate, acetate or hydrogen. Partial 16S rRNA gene sequences obtained from highest dilution steps showing sulfide formation indicated growth of deltaproteobacterial SRB belonging to the Desulfobulbaceae and the Desulfobacteraceae as well as of members of the Firmicutes. Subsequent isolation resulted in 10 novel phylotypes of both litho- and organotrophic sulfate-reducing Deltaproteobacteria. Molecular pre-screening identified six isolates as members of the Desulfobulbaceae, sharing highest identities with either candidatus 'Desulfobacterium corrodens' (95-97%) or Desulfobacterium catecholicum (98%), and four isolates as members of Desulfobacteraceae, being related to either Desulfobacter psychrotolerans (98%) or Desulfobacula phenolica (95-97%). Relatives of D. phenolica were exlusively isolated from 50 and 100 cm deep sediments with 10 and 2 mM of pore water sulfate respectively. In contrast, relatives of D. corrodens, D. psychrotolerans and D. catecholicum were also obtained from layers deeper than 100 cm and with less than 2 mM sulfate. The high in situ abundance of members of both families in sediment layers beneath 50 cm could be confirmed via CARD-FISH analysis performed with a set of six SRB-specific oligonucleotide probes. Moreover, SRB represented a numerically significant fraction of the microbial community throughout the sediment (up to 7%) and reached even higher cell numbers in deep, sulfate-poor layers than in the sulfate-rich surface sediment. This relatively large community size of

  5. Effects of sandy vs muddy sediments on the vertical distribution of microphytobenthos in intertidal flats of the Fraser River Estuary, Canada.

    PubMed

    Yin, Kedong; Zetsche, Eva-Maria; Harrison, Paul J

    2016-07-01

    Benthic algae or microphytobenthos (MPB) in intertidal flats play an important role in the sediment and overlying water ecosystems. We hypothesize that there are effects of sediment texture on the vertical distribution of MPB using chlorophyll a (chl a) as a proxy for MPB biomass and present results over a 2.5-year period. Four sites were sampled monthly: two sandy sites (A10 and A12) and two muddy sites (A0 and A14) on the intertidal flats of the Fraser River Estuary. At the two sandy sites, pigments were distributed down to 10 cm. High ratios of depth-integrated chl a to phaeopigments suggest that the chl a had been recently buried. In contrast, at the muddy sites, pigments were limited to the top 4 cm, with MBP in the top 1 cm contributing up to 60 % of the whole sediment core pigments. As a result, the depth-integrated chl a values were on average 2,044 mg m(-2) (160-4,200) at A10 and 882 mg m(-2) (183-2,569) at A12, the two sandy sites, and much higher than at the two muddy sites where averages of 84 mg m(-2) (41-174) and 235 mg m(-2) (77-854) were measured at A0 and A14, respectively. Despite these lower concentrations at the muddy sites than at the sandy sites, particulate organic carbon (POC) and nitrogen (PON) concentrations showed a homogenous vertical distribution at the two sandy sites. Such a homogeneous vertical distribution of chl a, POC, and PON suggests that vertical transport mechanisms were actively transporting organic material into and out of the sediment. These results suggest that MBP on sandy sediments play a very active role in providing food for herbivores and are interacting with the overlying water column in the sediment-water exchange processes during tidal cycles. PMID:27053045

  6. Response of reef corals on a fringing reef flat to elevated suspended-sediment concentrations: Molokaʻi, Hawaiʻi

    PubMed Central

    Jokiel, Paul L.; Storlazzi, Curt D.; Field, Michael E.; Lager, Claire V.; Lager, Dan

    2014-01-01

    A long-term (10 month exposure) experiment on effects of suspended sediment on the mortality, growth, and recruitment of the reef corals Montipora capitata and Porites compressa was conducted on the shallow reef flat off south Molokaʻi, Hawaiʻi. Corals were grown on wire platforms with attached coral recruitment tiles along a suspended solid concentration (SSC) gradient that ranged from 37 mg l−1 (inshore) to 3 mg l−1 (offshore). Natural coral reef development on the reef flat is limited to areas with SSCs less than 10 mg l−1 as previously suggested in the scientific literature. However, the experimental corals held at much higher levels of turbidity showed surprisingly good survivorship and growth. High SSCs encountered on the reef flat reduced coral recruitment by one to three orders of magnitude compared to other sites throughout Hawaiʻi. There was a significant correlation between the biomass of macroalgae attached to the wire growth platforms at the end of the experiment and percentage of the corals showing mortality. We conclude that lack of suitable hard substrate, macroalgal competition, and blockage of recruitment on available substratum are major factors accounting for the low natural coral coverage in areas of high turbidity. The direct impact of high turbidity on growth and mortality is of lesser importance. PMID:25653896

  7. Response of reef corals on a fringing reef flat to elevated suspended-sediment concentrations: Moloka'i, Hawai'i.

    PubMed

    Jokiel, Paul L; Rodgers, Kuʻulei S; Storlazzi, Curt D; Field, Michael E; Lager, Claire V; Lager, Dan

    2014-01-01

    A long-term (10 month exposure) experiment on effects of suspended sediment on the mortality, growth, and recruitment of the reef corals Montipora capitata and Porites compressa was conducted on the shallow reef flat off south Moloka'i, Hawai'i. Corals were grown on wire platforms with attached coral recruitment tiles along a suspended solid concentration (SSC) gradient that ranged from 37 mg l(-1) (inshore) to 3 mg l(-1) (offshore). Natural coral reef development on the reef flat is limited to areas with SSCs less than 10 mg l(-1) as previously suggested in the scientific literature. However, the experimental corals held at much higher levels of turbidity showed surprisingly good survivorship and growth. High SSCs encountered on the reef flat reduced coral recruitment by one to three orders of magnitude compared to other sites throughout Hawai'i. There was a significant correlation between the biomass of macroalgae attached to the wire growth platforms at the end of the experiment and percentage of the corals showing mortality. We conclude that lack of suitable hard substrate, macroalgal competition, and blockage of recruitment on available substratum are major factors accounting for the low natural coral coverage in areas of high turbidity. The direct impact of high turbidity on growth and mortality is of lesser importance. PMID:25653896

  8. Response of reef corals on a fringing reef flat to elevated suspended-sediment concentrations: Moloka‘i, Hawai‘i

    USGS Publications Warehouse

    Jokiel, Paul L.; Rodgers, Ku'ulei S.; Storlazzi, Curt D.; Field, Michael E.; Lager, Claire V.; Lager, Dan

    2014-01-01

    A long-term (10 month exposure) experiment on effects of suspended sediment on the mortality, growth, and recruitment of the reef corals Montipora capitata and Porites compressa was conducted on the shallow reef flat off south Molokaʻi, Hawaiʻi. Corals were grown on wire platforms with attached coral recruitment tiles along a suspended solid concentration (SSC) gradient that ranged from 37 mg l−1 (inshore) to 3 mg l−1(offshore). Natural coral reef development on the reef flat is limited to areas with SSCs less than 10 mg l−1 as previously suggested in the scientific literature. However, the experimental corals held at much higher levels of turbidity showed surprisingly good survivorship and growth. High SSCs encountered on the reef flat reduced coral recruitment by one to three orders of magnitude compared to other sites throughout Hawaiʻi. There was a significant correlation between the biomass of macroalgae attached to the wire growth platforms at the end of the experiment and percentage of the corals showing mortality. We conclude that lack of suitable hard substrate, macroalgal competition, and blockage of recruitment on available substratum are major factors accounting for the low natural coral coverage in areas of high turbidity. The direct impact of high turbidity on growth and mortality is of lesser importance.

  9. Biogeochemical dynamics in 20 m deep coastal sediments: The transition between the shallow subsurface and the marine deep biosphere

    NASA Astrophysics Data System (ADS)

    Beck, Melanie; Riedel, Thomas; Graue, Jutta; Brumsack, Hans-Jürgen; Engelen, Bert

    2010-05-01

    At present a large tidal flat area extends along the coastline of the southern North Sea. On longer geological time scales this area has, however, transformed from a terrestrial- to a marine-dominated landscape owing to changes in sea level. Biogeochemistry and microbial abundance have been intensively studied in the present tidal-flat sediments, down to about 5 m depth. However, very little is known about biogeochemical and microbial processes in deeper sediment layers, which were deposited before the establishment of today's tidal flat area. To study whether the geological history of sediment accumulation and thus the paleo-environment has an impact on pore water biogeochemistry and microbial abundance, Quaternary coastal deposits were investigated down to 20 m depth. In the tidal flat area of Spiekeroog Island (NW Germany) two geological settings were selected which are located close to each other but differ in sediment age and paleo-environmental conditions: A paleo-channel filled with mainly Holocene sediments and a sedimentary succession with the oldest sediments deposited during the Saalian glaciation ca. 130,000 years ago. The interdisciplinary analysis clearly shows that microorganisms are more abundant in the Holocene sediments. Here, almost all Archaea appear to be methanogenic as indicated by the presence of the mcrA-gene. About 12% of the Bacteria harbor the key gene for sulfate reduction. In contrast, only 1% methanogens and 0.5% sulfate-reducing bacteria were found in the older sediments. Furthermore, this study supports the concept that certain biogeochemical and microbiological features show astonishing similarities between the upper 5 meters of tidal-flat sediments and the upper hundred meters of deep-sea sediments. In the investigated 20 m-long sediment cores, the microbiological and geochemical response to sedimentary settings is transitional between the shallow subsurface of tidal-flat sediments and the marine deep biosphere.

  10. Cosmological dynamics of spatially flat Einstein-Gauss-Bonnet models in various dimensions: Vacuum case

    NASA Astrophysics Data System (ADS)

    Pavluchenko, Sergey A.

    2016-07-01

    In this paper we perform a systematic study of vacuum spatially flat anisotropic [(3 +D )+1 ]-dimensional Einstein-Gauss-Bonnet cosmological models. We consider models that topologically are the product of two flat isotropic submanifolds with different scale factors. One of these submanifolds is three dimensional and represents our 3D space and the other is D dimensional and represents extra dimensions. We consider no Ansatz on the scale factors, which makes our results quite general. With both Einstein-Hilbert and Gauss-Bonnet contributions in play and with the symmetry involved, the cases with D =1 , D =2 , D =3 , and D ≥4 have different dynamics due to the different structures of the equations of motion. We analytically analyze equations of motion in all cases and describe all possible regimes. It appears that the only regimes with nonsingular future asymptotes are the Kasner regime in general relativity and exponential regimes. As of the past asymptotes, for a smooth transition only the Kasner regime in Gauss-Bonnet is an option. With this at hand, we are down to only two viable regimes: the "pure" Kasner regime [transition from a high-energy (Gauss-Bonnet) to a low-energy (general relativity) Kasner regime] and a transition from a high-energy Kasner regime to an anisotropic exponential solution. It appears that these regimes take place for different signs of the Gauss-Bonnet coupling α : the "pure" Kasner regime occurs for α >0 at low D and α <0 for high D ; the anisotropic exponential regime is reached only for α >0 . So if we restrain ourselves with α >0 solutions (which would be the case, say, if we identify α with inverse string tension in heterotic string theory), the only late-time regimes are Kasner for D =1 , 2 and anisotropic exponential for D ≥2 . Also, low-energy Kasner regimes [a (t )∝tp] have expansion rates for (3 +1 )-dimensional subspace ("our Universe") ranging from p =0.5 (D =1 ) to p =1 /√{3 }≈0.577 (D →∞ ), which

  11. A novel tracer technique for the assessment of fine sediment dynamics in urban water management systems.

    PubMed

    Spencer, K L; Droppo, I G; He, C; Grapentine, L; Exall, K

    2011-04-01

    Urban storm water run off can reduce the quality of receiving waters due to high sediment load and associated sediment-bound contaminants. Consequently, urban water management systems, such as detention ponds, that both modify water quantity through storage and improve water quality through sediment retention are frequently-used best management practices. To manage such systems effectively and to improve their efficiency, there is a need to understand the dynamics (transport and settling) of sediment, and in particular the fine sediment fraction (<63 μm) and its associated contaminants within urban storm water management systems. This can be difficult to achieve, as modelling the transport behaviour of fine-grained and cohesive sediment is problematic and field-based measurements can be costly, time-consuming and unrepresentative. The aim of this study was to test the application of a novel cohesive sediment tracer and to determine fine sediment transport dynamics within a storm water detention pond. The cohesive sediment tracer used was a holmium labelled montmorillonite clay which flocculated and had similar size and settling velocity to the natural pond sediment it was intended to mimic. The tracer demonstrated that fine sediment was deposited across the entire pond, with the presence of reed beds and water depth being important factors for maximising sediment retention. The results of the sediment tracer experiment were in good agreement with those of a mathematical sediment transport model. Here, the deposited sediment tracer was sampled by collecting and analysing surface pond sediments for holmium. However, analysis and sampling of the three dimensional suspended tracer 'cloud' may provide more accurate information regarding internal pond sediment dynamics. PMID:21420140

  12. Quantifying the eroded volume of mercury-contaminated sediment using terrestrial laser scanning at Stocking Flat, Deer Creek, Nevada County, California, 2010–13

    USGS Publications Warehouse

    Howle, James F.; Alpers, Charles N.; Bawden, Gerald W.; Bond, Sandra

    2016-01-01

    High-resolution ground-based light detection and ranging (lidar), also known as terrestrial laser scanning, was used to quantify the volume of mercury-contaminated sediment eroded from a stream cutbank at Stocking Flat along Deer Creek in the Sierra Nevada foothills, about 3 kilometers west of Nevada City, California. Terrestrial laser scanning was used to collect sub-centimeter, three-dimensional images of the complex cutbank surface, which could not be mapped non-destructively or in sufficient detail with traditional surveying techniques.The stream cutbank, which is approximately 50 meters long and 8 meters high, was surveyed on four occasions: December 1, 2010; January 20, 2011; May 12, 2011; and February 4, 2013. Volumetric changes were determined between the sequential, three-dimensional lidar surveys. Volume was calculated by two methods, and the average value is reported. Between the first and second surveys (December 1, 2010, to January 20, 2011), a volume of 143 plus or minus 15 cubic meters of sediment was eroded from the cutbank and mobilized by Deer Creek. Between the second and third surveys (January 20, 2011, to May 12, 2011), a volume of 207 plus or minus 24 cubic meters of sediment was eroded from the cutbank and mobilized by the stream. Total volumetric change during the winter and spring of 2010–11 was 350 plus or minus 28 cubic meters. Between the third and fourth surveys (May 12, 2011, to February 4, 2013), the differencing of the three-dimensional lidar data indicated that a volume of 18 plus or minus 10 cubic meters of sediment was eroded from the cutbank. The total volume of sediment eroded from the cutbank between the first and fourth surveys was 368 plus or minus 30 cubic meters.

  13. Turbulent Sediment Suspension and Induced Ripple Dynamics Absent Mean Shear

    NASA Astrophysics Data System (ADS)

    Johnson, B. A.; Cowen, E.

    2014-12-01

    sediment beds to explore the source of the ripples, which we were surprised to find in absence of mean shear. By varying the details of the random jet-firing algorithm and using alternate jet spacing configurations, we investigate the relationship between the characteristic metrics of turbulence and the induced ripple dynamics.

  14. Dynamics of peat accumulation and marl flat formation in a calcareous fen, midwestern United States

    USGS Publications Warehouse

    Miner, J.J.; Ketterling, D.B.

    2003-01-01

    The age and sequence of peat accumulation were investigated at a calcareous fen in northeastern Illinois, USA. The purpose of this study was to identify the processes that form and sustain marl flats, which are areas of marl or tufa substrate within the fen that contain numerous rare plant species. Geomorphic, stratigraphic, and radiocarbon evidence was used to establish the processes and chronology of peat accumulation and erosion adjacent to each marl flat. The age of the base of the peat deposit varies greatly throughout the fen, ranging from 14,679 calibrated years before present (cal. years BP) to nearly modern, indicating that colonization of the sand and gravel substrate by peat occurred throughout the period from the Late Pleistocene to present. Adjacent to one marl flat, trends in basal peat age and thickness show that peat accumulation has progressed laterally inward from both sides, suggesting that the marl flat has been infilling with peat progressively by accumulation at the margins since at least 5,370 cal. years BP or longer. A second marl flat in the fen is surrounded by older, thick peat of differing ages on either edge and is bounded by fresh scarps, indicating that the marl flat currently is expanding laterally by erosion into the preexisting peat blanket. These two examples suggest a continuously repeating process, where erosion of the accumulated peat blanket forms a marl flat, which is later covered by peat accumulation. Trends in basal peat age elsewhere in the fen suggest that other marl flats may have existed in the past that have been completely infilled with peat. This study suggests that marl flat formation is a natural process that has been occurring for millennia, continuously creating habitat for the rare plant species that occupy marl flats. There is no evidence that the marl flats at this site are indicative of anthropogenic disturbance, so that management options for these areas are limited to maintaining the quality and quantity

  15. Dynamics of the contact between a ruthenium surface with a single nanoasperity and a flat ruthenium surface: Molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    de Oliveira, Alan Barros; Fortini, Andrea; Buldyrev, Sergey V.; Srolovitz, David

    2011-04-01

    We study the dynamics of the contact between a pair of surfaces (with properties designed to mimic ruthenium) via molecular dynamics simulations. In particular, we study the contact between a ruthenium surface with a single nanoasperity and a flat ruthenium surface. The results of such simulations suggest that contact behavior is highly variable. The goal of this study is to investigate the source and degree of this variability. We find that during compression, the behavior of the contact force displacement curves is reproducible, while during contact separation, the behavior is highly variable. Examination of the contact surfaces suggests that two separation mechanisms are in operation and give rise to this variability. One mechanism corresponds to the formation of a bridge between the two surfaces that plastically stretches as the surfaces are drawn apart and eventually separate in shear. This leads to a morphology after separation in which there are opposing asperities on the two surfaces. This plastic separation/bridge formation mechanism leads to a large work of separation. The other mechanism is a more brittle-like mode in which a crack propagates across the base of the asperity (slightly below the asperity/substrate junction) leading to most of the asperity on one surface or the other after separation and a slight depression facing this asperity on the opposing surface. This failure mode corresponds to a smaller work of separation. This failure mode corresponds to a smaller work of separation. Furthermore, contacts made from materials that exhibit predominantly brittle-like behavior will tend to require lower work of separation than those made from ductile-like contact materials.

  16. Nitrite isotope dynamics in coastal sediments: An intricate link between nitrogen and oxygen cycling

    NASA Astrophysics Data System (ADS)

    Charoenpong, C.; Buchwald, C.; Ziebis, W.; Wankel, S. D.

    2014-12-01

    Marine sediments often exhibit strong redox gradients, hosting a range of important nitrogen transformation processes. While the interplay among these microbially catalyzed nitrogen transformations has been well studied in the water column, the sharp redox transition in sediments often makes it far more difficult to unravel the complexity underpinning the cycling of nitrogen. Although often low in concentration, nitrite represents an important 'crossroad' in the nitrogen cycle as a reactive intermediate of both reductive and oxidative N transformations, including nitrification, dissimilatory nitrate reduction to ammonium and denitrification. Here we focus on the dual isotopic composition of nitrite (δ15N and δ18O), in concert with nitrate and ammonium data, as a means for constraining the sedimentary N cycling. Intact flow-through core incubations were performed on sediments collected from intertidal flats on the island of Sylt, Germany. Three types of substrate (i.e., sand, silt, and clay) were collected and subjected to different oxygen (i.e., ambient vs depleted) and nitrogen (i.e., ambient vs highly loaded) regimes. In addition to the measurement of natural abundance N and O stable isotopes, we also amended cores with nitrate having a positive ∆17O in our high nitrogen treatment, which offers yet an additional tracer to further constrain these transformations. While the concentration and isotopic composition (δ15N and δ18O) of nitrite act to integrate the influence of major N redox reactions, the N and O isotope systematics are decoupled. Although nitrogen atoms are generally conserved among these transformations, oxygen isotopes of nitrite are subject to a different set of processes. For example, the loss of an oxygen atom during the reductive processes of NO3- and NO2- reduction, the gain of oxygen atoms from O2 and water during nitrification, and oxygen isotopic equilibration between nitrite and water are all reflected in the δ18O of NO2-. Thus, the

  17. Farallon plate dynamics prior to the Laramide orogeny: Numerical models of flat subduction

    NASA Astrophysics Data System (ADS)

    Liu, Sibiao; Currie, Claire A.

    2016-01-01

    The Laramide orogeny (~ 80-50 Ma) was an anomalous period of mountain-building in the western United States that occurred more than 1000 km inboard of the Farallon Plate subduction margin. It is widely believed that this orogeny is coincident with a period of flat (subhorizontal) subduction. However, the factors that caused the Farallon Plate to evolve from a normal (steep) geometry to flat subduction are not well understood. Three proposed factors are: (1) a westward (trenchward) increase in North America motion, (2) an increased slab suction force owing to the presence of thick Colorado Plateau lithosphere, and (3) subduction of a low-density oceanic plateau. This study uses 2D upper mantle scale numerical models to investigate these factors. The models show that trenchward continental motion is the primary control on subduction geometry, with decreasing slab dip as velocity increases. However, this can only create low-angle subduction, as the Farallon Plate was old (> 100 Myr) and denser than the mantle. A transition to flat subduction requires: (1) subduction of a buoyant oceanic plateau that includes an 18-km-thick crust that does not undergo metamorphic densification and an underlying depleted harzburgite layer, and (2) a slab break-off at the landward side of the plateau. The break-off removes the dense frontal slab, and flat subduction develops as the buoyant plateau deflects the slab upward. The slab suction force has only a minor effect on slab flattening, but the thickness of the Colorado Plateau lithosphere controls the depth of the flat slab. With a continental velocity of 4 cm/yr and a 400-km-wide oceanic plateau, flat subduction develops within 15 Ma after plateau subduction. The flat slab underthrusts the continent at ~ 200 km depth, eventually extending > 1500 km inboard of the trench.

  18. Carbonate sediment dynamics and compartmentalisation of a highly modified coast: Geraldton, Western Australia

    NASA Astrophysics Data System (ADS)

    Tecchiato, Sira; Collins, Lindsay; Stevens, Alexandra; Soldati, Michela; Pevzner, Roman

    2016-02-01

    The coastal zone off Geraldton in temperate Midwestern Australia was investigated to identify sediment dynamics and sediment budget components of two main embayments. An integrated analysis of hydrodynamics, geomorphology, sediments and habitat data was required to overcome a lack of previous examinations of sediment dynamics in the region. The seaward extent of the nearshore transport system was assessed. An improved understanding of coastal sediment dynamics and its relationship to coastal stability and assets was also achieved. The system is complex, with biogenic sediment input, as well as carbonate dune and river-derived sediments. Coastal erosion at Geraldton is mitigated by nourishment activities which require sand bypassing. Natural and artificial sediment sinks were identified, and are mainly located in the northern embayment where beach erosion is more significant. A dredged shipping channel needed to provide access to port facilities modifies the local sediment dynamics. This study provides new information for managing the Geraldton coast, which may be applicable to similar regions of Western Australia and carbonate coasts elsewhere.

  19. Making and Remaking Dynamic 3D Structures by Shining Light on Flat Liquid Crystalline Vitrimer Films without a Mold.

    PubMed

    Yang, Yang; Pei, Zhiqiang; Li, Zhen; Wei, Yen; Ji, Yan

    2016-02-24

    Making dynamic three-dimensional (3D) structures capable of reversible shape changes or locomotion purely out of dry polymers is very difficult. Meanwhile, no previous dynamic 3D structures can be remade into new configurations while being resilient to mechanical damages and low temperature. Here, we show that light-activated transesterification in carbon nanotube dispersed liquid crystalline vitrimers enables flexible design and easy building of dynamic 3D structures out of flat films upon irradiation of light without screws, glues, or molds. Shining light also enables dynamic 3D structures to be quickly modified on demand, restored from distortion, repaired if broken, in situ healed when microcrack appears, assembled for more sophisticated structures, reconfigured, and recycled after use. Furthermore, the fabrication, reconfiguration, actuation, reparation, and assembly as well as healing can be performed even at extremely low temperatures (e.g., -130 °C). PMID:26840838

  20. Controls of Sediment Nitrogen Dynamics in Tropical Coastal Lagoons

    PubMed Central

    Enrich-Prast, Alex; Figueiredo, Viviane; Esteves, Francisco de Assis; Nielsen, Lars Peter

    2016-01-01

    Sediment denitrification rates seem to be lower in tropical environments than in temperate environments. Using the isotope pairing technique, we measured actual denitrification rates in the sediment of tropical coastal lagoons. To explain the low denitrification rates observed at all study sites (<5 μmol N2 m-2 h-1), we also evaluated potential oxygen (O2) consumption, potential nitrification, potential denitrification, potential anammox, and estimated dissimilatory nitrate (NO3-) reduction to ammonium (NH4+; DNRA) in the sediment. 15NO3- and 15NH4+ conversion was measured in oxic and anoxic slurries from the sediment surface. Sediment potential O2 consumption was used as a proxy for overall mineralization activity. Actual denitrification rates and different potential nitrogen (N) oxidation and reduction processes were significantly correlated with potential O2 consumption. The contribution of potential nitrification to total O2 consumption decreased from contributing 9% at sites with the lowest sediment mineralization rates to less than 0.1% at sites with the highest rates. NO3- reduction switched completely from potential denitrification to estimated DNRA. Ammonium oxidation and nitrite (NO2-) reduction by potential anammox contributed up to 3% in sediments with the lowest sediment mineralization rates. The majority of these patterns could be explained by variations in the microbial environments from stable and largely oxic conditions at low sediment mineralization sites to more variable conditions and the prevalences of anaerobic microorganisms at high sediment mineralization sites. Furthermore, the presence of algal and microbial mats on the sediment had a significant effect on all studied processes. We propose a theoretical model based on low and high sediment mineralization rates to explain the growth, activity, and distribution of microorganisms carrying out denitrification and DNRA in sediments that can explain the dominance or coexistence of DNRA and

  1. Controls of Sediment Nitrogen Dynamics in Tropical Coastal Lagoons.

    PubMed

    Enrich-Prast, Alex; Figueiredo, Viviane; Esteves, Francisco de Assis; Nielsen, Lars Peter

    2016-01-01

    Sediment denitrification rates seem to be lower in tropical environments than in temperate environments. Using the isotope pairing technique, we measured actual denitrification rates in the sediment of tropical coastal lagoons. To explain the low denitrification rates observed at all study sites (<5 μmol N2 m-2 h-1), we also evaluated potential oxygen (O2) consumption, potential nitrification, potential denitrification, potential anammox, and estimated dissimilatory nitrate (NO3-) reduction to ammonium (NH4+; DNRA) in the sediment. 15NO3- and 15NH4+ conversion was measured in oxic and anoxic slurries from the sediment surface. Sediment potential O2 consumption was used as a proxy for overall mineralization activity. Actual denitrification rates and different potential nitrogen (N) oxidation and reduction processes were significantly correlated with potential O2 consumption. The contribution of potential nitrification to total O2 consumption decreased from contributing 9% at sites with the lowest sediment mineralization rates to less than 0.1% at sites with the highest rates. NO3- reduction switched completely from potential denitrification to estimated DNRA. Ammonium oxidation and nitrite (NO2-) reduction by potential anammox contributed up to 3% in sediments with the lowest sediment mineralization rates. The majority of these patterns could be explained by variations in the microbial environments from stable and largely oxic conditions at low sediment mineralization sites to more variable conditions and the prevalences of anaerobic microorganisms at high sediment mineralization sites. Furthermore, the presence of algal and microbial mats on the sediment had a significant effect on all studied processes. We propose a theoretical model based on low and high sediment mineralization rates to explain the growth, activity, and distribution of microorganisms carrying out denitrification and DNRA in sediments that can explain the dominance or coexistence of DNRA and

  2. Dynamic sediment trapping and episodic sediment accretion in fluviodeltaic environments: Implications for coastal restoration

    NASA Astrophysics Data System (ADS)

    Shen, Z.; Tornqvist, T. E.; Chamberlain, E. L.; Esposito, C. R.; Marshak, J.; Nijhuis, A.; Sandoval, L.; Mauz, B.

    2013-12-01

    Many large river deltas are experiencing severe land loss because of various natural and anthropogenic causes. This is truly the case for the Mississippi Delta where ~40 km2/yr land loess have been documented for the last 25 years. A solid understanding about fluviodeltaic sediment dispersion and accretion is essential to improve management of fluviodeltaic landscapes. Here we present field data collected from the Bayou Lafourche subdelta in the Mississippi Delta to investigate the sedimentary and chronologic development of the Bayou Lafourche floodplain. The textural composition of the floodplain deposits shows dramatic changes along Bayou Lafourche. In the upstream portion where Bayou Lafourche cut through swamp environments, the floodplain deposits are dominantly mud, similar in composition to sediment load of the Lower Mississippi River. This suggests that the floodplain in this reach has a relatively high sediment trapping efficiency, which is confirmed by a >50% sediment trapping efficiency estimated for a crevasse splay there. In contrast, Bayou Lafourche floodplain deposits are sand dominant in the downstream portion where the subdelta extended into an open water environment, which suggests a relatively low sediment trapping efficiency in open water environments, similar to the Wax Lake Delta in the Mississippi Delta. Optical chronology for the Bayou Lafourche floodplain deposits demonstrates that fluviodeltaic sedimentation is episodic at a centennial time scale. As a consequence of relatively high sediment trapping efficiency and the episodic pattern of fluviodeltaic deposition, sediment accretion rates on the upstream portion of Bayou Lafourche are on the order of cm/yr at a centennial time scale. Our data suggest that mud, which constitutes ~80% of the Lower Mississippi River sediment load, can be used efficiently for wetland creation if being diverted to locations favor a high trapping efficiency, such as inland vegetated swamps. The sediment accretion

  3. Multiple-method approaches for quantifying fine sediment dynamics in river catchments over contemporary timescales

    NASA Astrophysics Data System (ADS)

    Smith, Hugh

    2015-04-01

    Understanding the patterns and processes of contemporary fine sediment dynamics in river catchments constitutes a key research challenge for catchment scientists. Such knowledge has considerable value for the targeting of management resources to reduce excess fine sediment supply and its impacts on water resources and aquatic ecosystems. Many past studies tended to focus on a single compartment of the fine sediment cascade and utilised a limited range of research methods. For more holistic understanding, the use of multiple-method approaches is required to provide data on the sources, transfer, storage, and transit times of fine sediment in river catchments. Such approaches would allow scientists to better conceptualise catchment processes controlling the movement of fine sediment across a range of spatial scales. It may also enhance the scientific quality of catchment-scale studies through the acquisition of multiple lines of evidence concerning a particular research problem. The specific combination of fine sediment tracing and fingerprinting procedures with catchment sediment flux measurements and sediment budget modelling has considerable potential to enhance our knowledge of contemporary sediment dynamics. This combination of techniques offers complementary information and the opportunity to compare datasets, such as estimates of catchment sediment source contributions obtained using sediment tracers with direct measurements of sediment fluxes or catchment model outputs. This contribution explores the potential for such combinations of methods to yield distinctive insights not otherwise available from the use of only one of these techniques. It draws on published examples of multiple-method studies by the author from small agricultural and wildfire-affected forest catchments (1-2 km2) in south-east Australia and from larger agricultural river catchments (38-920 km2) in south-west England. It will also identify possible directions for catchment research based

  4. Predicting fine sediment dynamics along a pool-riffle mountain channel

    NASA Astrophysics Data System (ADS)

    Rathburn, Sara; Wohl, Ellen

    2003-09-01

    Fine sediment dynamics in mountain rivers are of concern because of implications for aquatic habitat, channel stability, and downstream sediment yields. Many mountain river systems have episodic fine sediment transport because of infrequent, point-source sediment inputs from landslides; basin instability triggered by land uses such as logging; or infrequent mobilization of the coarse surface layer in channels. Dam removal, which is now more likely along mountain rivers, may also provide a substantial fine sediment input to downstream channel reaches. Fine sediment storage in the interstices of spawning gravels and within pools along mountain rivers is of particular interest because of impacts to aquatic organisms. In this study we focus on sediment dynamics within pools of the North Fork Poudre River in Colorado as an example of the processes controlling fine sediment deposition, storage, and transport within laterally constricted pools. The 1996 release of ˜7000 m 3 of silt-to gravel-sized sediment from a reservoir on the North Fork provided an opportunity to develop a field data set of fine sediment dynamics and to test the predictions of three different one- or two-dimensional sediment transport and hydraulic models against the field observations. The models were calibrated against quantitative measurements of pool scour and fill. One-dimensional HEC-6 results indicate that robust simulations yield the greatest agreement between predicted and measured pool bed elevation change. Model calibration on two pools and validation on one pool indicate that at least 58% of observed bed changes after the sediment release were predicted by HEC-6. Modeling accuracy using quasi-two-dimensional GSTARS 2.0 was considerably more variable, and no pool-wide trends were obtained. The two-dimensional model RMA2 substantially improved the representation of eddy pool hydraulics within a compound pool of the North Fork. Results from the hydraulic modeling, coupled with bed load and

  5. Elephant trail runoff and sediment dynamics in northern Thailand.

    PubMed

    Sidle, Roy C; Ziegler, Alan D

    2010-01-01

    Although elephants may exert various impacts on the environment, no data are available on the effects of elephant trails on runoff, soil erosion, and sediment transport to streams during storms. We monitored water and sediment fluxes from an elephant trail in northern Thailand during seven monsoon storms representing a wide range of rainfall energies. Runoff varied from trivial amounts to 353 mm and increased rapidly in tandem with expanding contributing areas once a threshold of wetting occurred. Runoff coefficients during the two largest storms were much higher than could be generated from the trail itself, implying a 4.5- to 7.9-fold increase in the drainage areas contributing to storm runoff. Clockwise hysteresis patterns of suspended sediment observed during most storms was amplified by a "first flush" of sediment early on the hydrograph in which easily entrained sediment was transported. As runoff areas expanded during the latter part of large storms, discharge increased but sediment concentrations declined. Thus, sediment flux was better correlated to kinetic energy of rainfall on the falling limbs of most storm hydrographs compared to rising limbs. Based on a power function relationship between sediment flux and storm kinetic energy, the estimated annual sediment yield from the trail for 135 storms in 2005 was 308 to 375 Mg ha(-1) yr(-1), higher than from most disturbed land surfaces in the tropics. The eight largest storms (30% of total storm energy) in 2005 transported half of the total annual sediment. These measurements together with site investigations reveal that highly interconnected elephant trails, together with other source areas, directly link runoff and sediment to streams. PMID:20400583

  6. Modelling of cohesive sediment dynamics in tidal estuarine systems: Case study of Tagus estuary, Portugal

    NASA Astrophysics Data System (ADS)

    Franz, G.; Pinto, L.; Ascione, I.; Mateus, M.; Fernandes, R.; Leitão, P.; Neves, R.

    2014-12-01

    Cohesive sediment dynamics in estuarine systems is a major issue in water quality and engineering problems. Numerical models can help to assess the complex dynamics of cohesive sediments, integrating the information collected in monitoring studies. Following a numerical approach we investigated the main factors that influence the cohesive sediment dynamics in an estuarine system composed of large mudflats (Tagus estuary, Portugal). After a spin up period of the bottom layer and considering the combined effect of waves and currents on the bottom shear stress, the dynamics of cohesive sediment during the fortnightly and daily erosion-sedimentation cycle was properly reproduced by the model. The results of cohesive suspended sediments were validated with data from sixteen monitoring stations located along the estuary and turbidity data measured by two multiparametric probes. The hydrodynamics were previously validated by harmonic analysis and with ADCP data. Although tidal currents are the major cause of cohesive sediment erosion, the results suggest that wind waves also play an important role. The simulated sediment mass involved in the fortnightly tidal cycle was in the same order of magnitude of the annual load from the rivers, as observed in previous studies based on field data.

  7. The Dynamics of Coarse Sediment Transfer in an Upland Bedrock River

    NASA Astrophysics Data System (ADS)

    Warburton, J.; Hardy, R. J.; Ferguson, R. I.; Cray, A.

    2010-12-01

    Bedrock channels in UK environments have received relatively little attention despite their importance within upland river systems and their influence on controlling the conveyance of sediment downstream. This poster describes the transfer of coarse sediment through Trout Beck, an upland bedrock reach in the North Pennines, UK. The transport of coarse sediment has been quantified through field monitoring of sediment characteristics, repeat magnetic tracer surveys and in-situ bed load impact sensors. This was carried out in conjunction with surveys of channel morphology (using terrestrial laser scanning and repeat dGPS measurements) and continuous flow monitoring. The interaction between mobile sediment and channel morphology is partly conditioned by the extent of alluvial sediment cover. Sediment storage is patchy with partially alluvial and alluvial sections of the channel, interspersed with bedrock reaches containing very little sediment except in hydraulically sheltered sites. There are notable differences in sediment dynamics between these different sections of the river channel which have a considerable influence on conveyance of sediment through the reach. In bedrock sections the low resistance to flow and stable channel boundaries result in little sediment storage and during periods when flow is competent there is downstream conveyance of the full grain-size distribution of sediment. Detailed morphological survey has provided the necessary boundary conditions, along with the flow data, to apply a one-dimensional hydraulic model (HEC-RAS) of the bedrock study reach. The modelling results have quantified the hydraulic regime of the channel. Using local shear stress as a proxy for sediment transport, sediment transport potential for the dominant grain-size distribution of the reach (16-256 mm) has been assessed for different locations in the channel. There are significant differences in the critical threshold of shear stress for sediment transport down the

  8. Examining Sediment-bound Radiocesium Dynamics in Two Fukushima Coastal Catchments with Sediment Fingerprinting Techniques

    NASA Astrophysics Data System (ADS)

    Laceby, J. P.; Lepage, H.; Bonté, P.; Joron, J. L.; Onda, Y.; Lefèvre, I.; Ayrault, S.; Evrard, O.

    2015-12-01

    The Fukushima Dai-ichi nuclear power plant accident resulted in the significant fallout of radiocesium (137Cs and 134Cs) over the Fukushima region. After deposition on the soil surface, radiocesium is primarily bound to fine soil particles. Subsequently, rainfall and snow melt run-off events result in the downstream migration of radiocesium. Understanding the spatial distribution and relative contribution of different sediment sources is therefore fundamental to the management of radiocesium migration. Sediment fingerprinting techniques were used to determine the location and relative contributions of different sediment sources in the Mano and Niida Rivers, in the Fukushima region. First, we modelled the relative contributions of radiocesium from the upstream portions of the catchment, that received greater proportions of the fallout (e.g. >20 kBq kg-1), to sediment sampled in the downstream coastal regions. Second, we examined the elemental geochemistry of the major soil types (e.g. Andosols, Cambisols, Fluvisols) within these catchments and modelled their relative contribution to sediment sampled throughout these catchments. Elemental composition was measured with neutron activation analysis, radiocesium with gamma-spectrometry and a distribution modelling approach quantified source contributions. In the Mano River ~20% of the radiocesium sampled was modelled to be derived from the upstream area compared to ~50% in the Niida River. The highest contribution of upstream radiocesium was modelled after the typhoon seasons in 2011 and 2013. Fluvisols were found to be the dominant source of sediment (76%). The dominance of Fluvisols indicates that sediments are likely derived from sources that are highly connected to the river network (e.g. rice paddy fields). Understanding the relative contributions of these different sediment sources will allow for more direct management of sediment and thus radiocesium transfers in these Fukushima coastal catchments.

  9. Application of wave mechanics theory to fluid dynamics problems: Flat plate flow

    NASA Technical Reports Server (NTRS)

    Krzywoblocki, M. Z. V.

    1974-01-01

    The characteristics of the flow in the laminar boundary layer along an infinitely long flat plate are discussed. The flow may be disturbed or not, depending on the situation. The physical, natural aspects of the flow, either a laminar flow free from disturbances or a flow which originally is a laminar one with disturbances superimposed upon it. Oscillograms of turbulence in wind tunnel tests and in the wake of a cylinder are presented.

  10. Chemical lake restoration products: sediment stability and phosphorus dynamics.

    PubMed

    Egemose, Sara; Reitzel, Kasper; Andersen, Frede Ø; Flindt, Mogens R

    2010-02-01

    Laboratory experiments with sediments from three shallow Danish lakes were conducted to evaluate the effects of chemical lake restoration products during resuspension. Phosphorus (P) removal, sediment stability, sediment consolidation and color reduction were studied over time. The investigated products were aluminum (Al), Phoslock (a commercial bentonite product coated with lanthanum) and a combination of Al covered with bentonite (Al/Ben). All treatments effectively reduced the P concentration in the water. However, the treatments containing Al reduced the P concentration immediately after resuspension, whereas Phoslock required several days after resuspension to reduce the P concentration. Especially Phoslock, but also Al/Ben, increased the sediment stability threshold by 265% and 101%, respectively, whereas Al had no stabilizing effect. The fresh Al floc was resuspended 5x easier than untreated sediment. The largest consolidation of the sediment occurred with addition of Phoslock, followed by Al/Ben, while Al alone had no effect. Enhanced consolidation may be of importance for macrophyte colonisation of organic sediment. Phoslock improved the light climate moderately by removing color, whereas Al was very effective in removing color. Ben/Al showed intermediate effects on color reduction. These findings are important when decisions are made on restoration method for a specific lake, which may be more or less wind exposed. PMID:20055487

  11. Effects of sedimentation on soil nutrient dynamics in riparian forests.

    PubMed

    Lockaby, B G; Governo, R; Schilling, E; Cavalcanti, G; Hartsfield, C

    2005-01-01

    The influence of sedimentation rates on biogeochemistry of riparian forests was studied near ephemeral streams at Fort Benning, GA. Upper reaches of seven ephemeral streams had received varying rates of sedimentation stemming from erosion along unpaved roadways at the military installation. Two reference catchments were also included in the study. Decomposition of foliar litter, microbial C and N, N mineralization, and arthropod populations were compared within and among catchments. Rates of sedimentation over the past 25 yr ranged from 0 in references to 4.0 cm yr(-1). Decomposition rates declined exponentially with sedimentation rates as low as 0.20 to 0.32 cm yr(-1) and appeared to reach an equilibrium at a sedimentation rate of 0.5 cm yr(-1). Nitrogen mineralization and microbial C and N followed the same trend. Sedimentation had no discernible effect on arthropod populations. These data suggest that biogeochemical cycles may be altered by sedimentation rates that commonly occur in some floodplain forests. PMID:15647569

  12. Aestuariicola saemankumensis gen. nov., sp. nov., a member of the family Flavobacteriaceae, isolated from tidal flat sediment.

    PubMed

    Yoon, Jung-Hoon; Kang, So-Jung; Jung, Yong-Taek; Oh, Tae-Kwang

    2008-09-01

    A Gram-negative, non-motile, pleomorphic bacterial strain, designated SMK-142(T), was isolated from a tidal flat of the Yellow Sea, Korea, and was subjected to a polyphasic taxonomic study. Strain SMK-142(T) grew optimally at pH 7.0-8.0, 25 degrees C and in the presence of 2% (w/v) NaCl. Phylogenetic analyses based on 16S rRNA gene sequences showed that strain SMK-142(T) clustered with Lutibacter litoralis with which it exhibited a 16S rRNA gene sequence similarity value of 91.2%. This cluster joined the clade comprising the genera Tenacibaculum and Polaribacter at a high bootstrap resampling value. Strain SMK-142(T) contained MK-6 as the predominant menaquinone and iso-C(15:0), iso-C(15:1) and iso-C(17:0) 3-OH as the major fatty acids. The DNA G+C content was 37.2 mol%. Strain SMK-142(T) was differentiated from three phylogenetically related genera, Lutibacter, Tenacibaculum and Polaribacter, on the basis of low 16S rRNA gene sequence similarity values and differences in fatty acid profiles and in some phenotypic properties. On the basis of phenotypic, chemotaxonomic and phylogenetic data, strain SMK-142(T) represents a novel genus and species for which the name Aestuariicola saemankumensis gen. nov., sp. nov. is proposed (phylum Bacteroidetes, family Flavobacteriaceae). The type strain of the type species, Aestuariicola saemankumensis sp. nov., is SMK-142(T) (=KCTC 22171(T)=CCUG 55329(T)). PMID:18768617

  13. Lutibacter litoralis gen. nov., sp. nov., a marine bacterium of the family Flavobacteriaceae isolated from tidal flat sediment.

    PubMed

    Choi, Dong H; Cho, Byung C

    2006-04-01

    A rod-shaped marine bacterium, designated strain CL-TF09T, isolated from a tidal flat in Ganghwa, Korea, was characterized based on its physiological and biochemical features, fatty acid profile and phylogenetic position. 16S rRNA gene sequence analysis revealed a clear affiliation with the family Flavobacteriaceae. Strain CL-TF09T showed the closest phylogenetic relationship with the genera Tenacibaculum and Polaribacter; sequence similarities between CL-TF09T and the type strains of Tenacibaculum and Polaribacter species ranged from 90.7 to 91.8 %. Cells of strain CL-TF09T were non-motile and grew on solid media as yellow colonies. The strain grew in the presence of 1-5 % sea salts, within a temperature range of 5-30 degrees C and at pH 7-8. The strain had iso-C(15 : 0) 3-OH (17.4 %), iso-C(15 : 0) (16.7 %), anteiso-C(15 : 0) (15.1 %) and iso-C(16 : 0) 3-OH (13.4 %) as predominant fatty acids. The DNA G+C content was 33.9 mol%. Based on the physiological, fatty acid composition and phylogenetic data presented, strain CL-TF09T is considered to represent a novel genus and species of the family Flavobacteriaceae, for which the name Lutibacter litoralis gen. nov., sp. nov. is proposed. The type strain is CL-TF09T (=KCCM 42118T = JCM 13034T). PMID:16585692

  14. Trace metals dynamics in surface sediments investigated by DGT micro-scale measurements

    NASA Astrophysics Data System (ADS)

    Motelica-Heino, M.; Davison, W.

    2003-05-01

    In surface sediments, metal mobility is controlled by the recruitment and turn-over of organic matter whereas sulphide is thought to control the concentration of metals in sediment pore water by removing them from the solution. DGT is a dynamic probe that measures the kinetically available fraction of metals or sulphide. DGT uses a credit card size probe inserted into the sediment that provides a snapshot of the metal distribution in the sediment, which can be uncovered by spectrochemical analytical techniques. In-situ vertical profiles and horizontal maps of trace metals at high (mm scale) and ultra-high resolution (100 μm) together with Fe, Mn and sulphide were generated from DGT probes deployed in surface sediments. Collectively, the results showed that besides vertical gradients, associated with the depletion of oxygen with depth and the degradation of organic matter by a succession of electron acceptors, small scale remobilisation of metals associated with sediment heterogeneity take place.

  15. The use of lipid markers to define sources of organic matter in sediment and food web of the intertidal salt-marsh-flat ecosystem of Mont-Saint-Michel Bay, France

    NASA Astrophysics Data System (ADS)

    Meziane, Tarik; Bodineau, Laurent; Retiere, Christian; Thoumelin, Guy

    1997-12-01

    Salt marsh plants and seven surface sediment samples along a transect in the intertidal flat area of Mont-Saint-Michel Bay were analysed for fatty acids and sterols. The presence of lipid markers of halophytes (long-chain fatty acids, 18:3ω3, and phytosterols) in the surface layers of the sediment confirms the export of organic matter from the salt marsh to the intertidal flat. The spatial distribution of this organic matter over the tidal-flat area was controlled by the tidal currents and the presence of mussel beds. Lipid markers of diatoms (20:5ω3 and brassicasterol) and bacteria (18:1ω7 and odd, linear and branched, fatty acids) were also found in the surface sediments. Diatoms and benthic bacteria as well as organic matter from the salt marsh were the significant food sources available to the macrozoobenthos on the intertidal flat. The ingestion of these food types by the dominant species of the macrozoobenthos was confirmed by the presence of their respective lipid markers in the animals. The presence of these markers in animals subjected to a starvation experiment confirmed that these food types are really assimilated. The lipid composition of the starved animals indicated that the species studied were able to accumulate the fatty acid 20:5ω3 (considered to be a diatom marker), and that the annelid Nereis diversicolor supported an internal bacterial population.

  16. Dynamic transport of suspended sediment by solitary wave: Experimental study

    NASA Astrophysics Data System (ADS)

    cho, JaeNam; Kim, DongHyun; Hwang, KyuNam; Lee, SeungOh

    2016-04-01

    Solitary waves are able to transport a large amount of suspended sediment when approaching on the beach, which sometimes causes - serious beach erosion, especially in the east and south coastal lines in Korea. But it has rarely been known about the method how to evaluate or estimate the amount of beach erosion caused by solitary waves. Experimental assessment is necessary to comprehend the process of sediment transport on a slope. The prismatic rectangular channel is 12 m long, 0.8 m wide, and 0.75 m high. A sluice gate is applied at prismatic channel in order to produce the solitary waves. Upstream water depth is more than channel water depth and the sluice gate is suddenly opened to simulate conditions of solitary waves. A sand slope with a 1/6 and a sediment thickness is 0.03 m. The experimental sediments are used anthracite (d_50=1.547 mm ,C_u=1.38) and Jumoonjin sand (d_50=0.627 mm ,C_u=1.68). Specific laboratory equipment are designed to collect suspended sediment samples at the same time along the wave propagation at 5 points with evenly space. Each amount of sampling is approximately 25 ml and they are completely dried in oven over 24 hours according to the USGS (Guideline and standard techniques and method 3-C4). Two video cameras (Model No. : Sony, HDR-XR550) are mounted for capturing images at top and side-view when the processes of solitary wave and run up/down on slope. Also, this study are analyzed the correlation between Suspended sediment concentration and turbidity. Also, this study are analyzed the correlation between suspended sediment concentration and turbidity. Turbidity is used to verify suspended sediment concentration. Dimensionless analyses of experimental results carried out in this study. One dimensionless parameter is expressed with pressure of solitary wave on a slope to suspended sediment concentration, which is concerned about lifting force. The other is relate to drag force presenting with run up/down velocity on a slope and

  17. Sediment Dynamics Within Buffer Zone and Sinkhole Splay Areas Under Extreme Soil Disturbance Conditions

    NASA Astrophysics Data System (ADS)

    Schoonover, Jon E.; Crim, Jackie F.; Williard, Karl W. J.; Groninger, John W.; Zaczek, James J.; Pattumma, Klairoong

    2015-09-01

    Sedimentation dynamics were assessed in sinkholes within training areas at Ft. Knox Military Installation, a karst landscape subjected to decades of tracked vehicle use and extreme soil disturbance. Sinkholes sampled were sediment-laden and behaved as intermittent ponds. Dendrogeomorphic analyses were conducted using willow trees ( Salix spp.) located around the edge of 18 sinkholes to estimate historical sedimentation rates, and buried bottles were installed in 20 sinkholes at the center, outer edge, and at the midpoint between the center and edge to estimate annual sedimentation rates. Sedimentation data were coupled with vegetation characteristics of sinkhole buffers to determine relationships among these variables. The dendrogeomorphic method estimated an average accumulation rate of 1.27 cm year-1 translating to a sediment loss rate of 46.1 metric ton year-1 from the training areas. However, sediment export to sinkholes was estimated to be much greater (118.6 metric ton year-1) via the bottle method. These data suggest that the latter method provided a more accurate estimate since accumulation was greater in the center of sinkholes compared to the periphery where dendrogeomorphic data were collected. Vegetation data were not tightly correlated with sedimentation rates, suggesting that further research is needed to identify a viable proxy for direct measures of sediment accumulation in this extreme deposition environment. Mitigation activities for the sinkholes at Ft. Knox's tank training area, and other heavily disturbed karst environments where extreme sedimentation exists, should consider focusing on flow path and splay area management.

  18. Sediment Dynamics Within Buffer Zone and Sinkhole Splay Areas Under Extreme Soil Disturbance Conditions.

    PubMed

    Schoonover, Jon E; Crim, Jackie F; Williard, Karl W J; Groninger, John W; Zaczek, James J; Pattumma, Klairoong

    2015-09-01

    Sedimentation dynamics were assessed in sinkholes within training areas at Ft. Knox Military Installation, a karst landscape subjected to decades of tracked vehicle use and extreme soil disturbance. Sinkholes sampled were sediment-laden and behaved as intermittent ponds. Dendrogeomorphic analyses were conducted using willow trees (Salix spp.) located around the edge of 18 sinkholes to estimate historical sedimentation rates, and buried bottles were installed in 20 sinkholes at the center, outer edge, and at the midpoint between the center and edge to estimate annual sedimentation rates. Sedimentation data were coupled with vegetation characteristics of sinkhole buffers to determine relationships among these variables. The dendrogeomorphic method estimated an average accumulation rate of 1.27 cm year(-1) translating to a sediment loss rate of 46.1 metric ton year(-1) from the training areas. However, sediment export to sinkholes was estimated to be much greater (118.6 metric ton year(-1)) via the bottle method. These data suggest that the latter method provided a more accurate estimate since accumulation was greater in the center of sinkholes compared to the periphery where dendrogeomorphic data were collected. Vegetation data were not tightly correlated with sedimentation rates, suggesting that further research is needed to identify a viable proxy for direct measures of sediment accumulation in this extreme deposition environment. Mitigation activities for the sinkholes at Ft. Knox's tank training area, and other heavily disturbed karst environments where extreme sedimentation exists, should consider focusing on flow path and splay area management. PMID:25975438

  19. Human impacts on sediment dynamics within the Rhine delta, the Netherlands

    NASA Astrophysics Data System (ADS)

    Hobo, Noortje; Middelkoop, Hans; Makaske, Bart

    2015-04-01

    The Rhine delta in the Netherlands has a long history of human impacts, of which large-scale land reclamation, drainage, embankment and river channelization have been the most prominent. On-going plans for river and floodplain restoration will lead to renewed - but yet unknown - sediment dynamics along the lower Rhine branches in the coming century. Here we address the consequences of human impacts for the sediment dynamics in the Rhine delta during three major phases in the past: 1) the pristine high-stand delta before land reclamation and embankment (~4000 BP - 1300 AD, 2) the period of embanked rivers (~1350-1850 AD), and 3) the period after the river channels were normalized to a fixed standard width by arrays of groynes and riprap (~1870 AD-present). For each of these periods we quantitatively reconstructed the amounts of sediment deposited within the delta, internal sediment reworking, and associated sediment residence times. The results show that sediment trapping varied across the delta during the pre-embankment period, and demonstrate how avulsions caused small sediment pulses within the system. Estimated average residence times of overbank fines were in the order of 10 ka. Embankment has dramatically reduced the spatial extent where sediment deposition occurred, while internal sediment reworking along the embanked rivers remained locally very active. Channel normalization not only ceased re-erosion of previously deposited floodplain sediment along the channel banks, but implied an ultimate shift of the depo-centre of both overbank and channel sediments from the floodplain to the lower river channels and the estuary. To date, the Rhine sediment has to be dredged from its lower reaches, while the old floodplain surface presently protected by embankments suffers from increasing soil subsidence.

  20. Molecular Approaches to Understanding C & N Dynamics in MArine Sediments

    SciTech Connect

    Arturo Massol; James Tiedje; Jizhong Zhou; Allan Devol

    2007-05-16

    Continental margin sediments constitute only about 10% of the total sediment surface area in the world’s oceans, nevertheless they are the dominant sites of nitrogen (N) cycling. Recent studies suggest that the oceanic nitrogen budget is unbalanced, primarily due to a higher nitrogen removal rate in contrast to the fixation rate, and it has been suggested that denitrification activity contributes significantly to this imbalance. Although denitrification in marine environments has been studied intensively at the process level, little is known about the species abundance, composition, distribution, and functional differences of the denitrifying population. Understanding the diversity of microbial populations in marine environments, their responses to various environmental factors such as NO3-, and how this impact the rate of denitrification is critical to predict global N dynamics. Environmental Microbiology has the prompt to study the influence of each microbial population on a biogeochemical process within a given ecosystem. Culture-dependent and –independent techniques using nucleic acid probes can access the identity and activity of cultured and uncultured microorganisms. Nucleic acid probes can target distintict genes which set phylogenetic relationships, such as rDNA 16S, DNA gyrase (gyrB) and RNA polymerase sigma 70 factor (rpoD). In the other hand, the genetic capabilities and their expression could be tracked using probes that target several functional genes, such as nirS, nirK, nosZ, and nifH, which are genes involved in denitrification. Selective detection of cells actively expressing functional genes within a community using In Situ Reverse Transcription-PCR (ISRT-PCR) could become a powerful culture-independent technique in microbial ecology. Here we describe an approach to study the expression of nirS genes in denitrifying bacteria. Pure cultures of Pseudomonas stutzeri and Paracoccus denitrificans, as well as co-cultures with non

  1. Vortex dynamics and wall shear stress behaviour associated with an elliptic jet impinging upon a flat plate

    NASA Astrophysics Data System (ADS)

    Long, J.; New, T. H.

    2016-07-01

    Vortical structures and dynamics of a Re h = 2100 elliptic jet impinging upon a flat plate were studied at H/ d h = 1, 2 and 4 jet-to-plate separation distances. Flow investigations were conducted along both its major and minor planes using laser-induced fluorescence and digital particle image velocimetry techniques. Results show that the impingement process along the major plane largely consists of primary jet ring-vortex and wall-separated secondary vortex formations, where they subsequently separate from the flat plate at smaller H/ d h = 1 and 2 separation distances. Key vortex formation locations occur closer to the impingement point as the separation distance increases. Interestingly, braid vortices and rib structures begin to take part in the impingement process at H/ d h = 4 and wave instabilities dominate the flow field. In contrast, significantly more coherent primary and secondary vortices with physically larger vortex core sizes and higher vortex strengths are observed along the minor plane, with no signs of braid vortices and rib structures. Lastly, influences of these different flow dynamics on the major and minor plane instantaneous and mean skin friction coefficient levels are investigated to shed light on the effects of separation distance on the wall shear stress distributions.

  2. Interfacial anisotropy in the transport of liquid crystals confined between flat, structureless walls: a molecular dynamics simulation approach.

    PubMed

    Mima, Toshiki; Yasuoka, Kenji

    2008-01-01

    Molecular dynamics simulations of uniaxial Gay-Berne ellipsoids as prolate liquid crystal molecules confined between two flat, structureless walls have been carried out in order to investigate anisotropy in their dynamic properties. Several physical quantities are profiled as a function of distance from a wall. The walls stimulate ellipsoids into different behaviors from those of the bulk system. The profiles of self-diffusion coefficients, which are distinguished in each direction of a director-based coordinate system, show that the ellipsoids are more diffusive parallel to the walls and less diffusive perpendicular to the walls with decreasing distance from the walls. According to the self-rotation coefficient and rotational viscosity profiles, ellipsoids are easy to rotate parallel to the walls and hard to rotate in the plane perpendicular to the walls. The analyses of velocity autocorrelation functions, angular velocity autocorrelation functions, director angular velocity autocorrelation functions, and their spectra are useful for the investigation of anisotropy near the walls. We conclude that the flat, structureless wall not only prevents ellipsoids from diffusing and rotating in the plane perpendicular to the walls, but also stimulates them to diffuse and rotate in the plane parallel to the walls. PMID:18351864

  3. Interfacial anisotropy in the transport of liquid crystals confined between flat, structureless walls: A molecular dynamics simulation approach

    NASA Astrophysics Data System (ADS)

    Mima, Toshiki; Yasuoka, Kenji

    2008-01-01

    Molecular dynamics simulations of uniaxial Gay-Berne ellipsoids as prolate liquid crystal molecules confined between two flat, structureless walls have been carried out in order to investigate anisotropy in their dynamic properties. Several physical quantities are profiled as a function of distance from a wall. The walls stimulate ellipsoids into different behaviors from those of the bulk system. The profiles of self-diffusion coefficients, which are distinguished in each direction of a director-based coordinate system, show that the ellipsoids are more diffusive parallel to the walls and less diffusive perpendicular to the walls with decreasing distance from the walls. According to the self-rotation coefficient and rotational viscosity profiles, ellipsoids are easy to rotate parallel to the walls and hard to rotate in the plane perpendicular to the walls. The analyses of velocity autocorrelation functions, angular velocity autocorrelation functions, director angular velocity autocorrelation functions, and their spectra are useful for the investigation of anisotropy near the walls. We conclude that the flat, structureless wall not only prevents ellipsoids from diffusing and rotating in the plane perpendicular to the walls, but also stimulates them to diffuse and rotate in the plane parallel to the walls.

  4. Application of Sediment Trend Analysis in the Examination of Sediment Transport Dynamics of Missisquoi Bay

    NASA Astrophysics Data System (ADS)

    Kraft, M. P.; Manley, P.; Singer, J.; Manley, T.; McLaren, P.

    2013-12-01

    Missisquoi Bay is located between Vermont and Quebec in the northeast sector of the Restricted Arm of Lake Champlain. The average depth of the Bay is slightly less than 3 meters with a surface area covering 77.5 km2. The Bay receives water from eastern and western catchment basins, most notably via the Missisquoi, Rock, and Pike Rivers. Circulation within Missisquoi Bay has been altered by the construction of railroad causeways in the late 19th century and highway construction in the early 20th century. Over the past several decades there have also been changes in land-use practices, including the intensification of agriculture, increased animal husbandry, and urbanization. As a consequence of construction and changing land use, loadings of nitrogen and phosphorus to the Bay have increased seasonal oxygen depletion causing eutrophication. Since monitoring began in 1992, Missisquoi Bay has displayed the highest mean total phosphorus concentrations and chlorophyll a concentrations in Lake Champlain. Various efforts have taken place to reduce nutrient loading to Missisquoi Bay, but persistent release of phosphorus from bottom sediments will continue to delay for decades the recovery from nutrient diversion. To better understand the causes and timing of eutrophication in Missisquoi Bay, one component of a 5-year integrated VT EPSCoR - RACC program included an examination of N and P loadings and their distribution throughout the Bay. Internal circulation patterns are also being studied. To determine the pattern of net sediment transport and determine sediment behavior (erosion and accretion), a Sediment Trend Analysis (STA) was performed using 369 grab samples collected in the Bay. Grain size distributions for the surface sediment samples were determined using a Malvern Mastersizer 2000 particle size analyzer. Sediment maps showing the proportion of gravel, sand, and mud show that near major river distributaries sand-sized sediment was dominant with muds becoming more

  5. The carbon cycle and biogeochemical dynamics in lake sediments

    USGS Publications Warehouse

    Dean, W.E.

    1999-01-01

    The concentrations of organic carbon (OC) and CaCO3 in lake sediments are often inversely related. This relation occurs in surface sediments from different locations in the same lake, surface sediments from different lakes, and with depth in Holocene sediments. Where data on accumulation rates are available, the relation holds for organic carbon and CaCO3 accumulation rates as well. An increase of several percent OC is accompanied by a decrease of several tens of percent CaCO3 indicating that the inverse relation is not due to simple dilution of one component by another. It appears from core data that once the OC concentration in the sediments becomes greater than about 12%, the CO2 produced by decomposition of that OC and production of organic acids lowers the pH of anoxic pore waters enough to dissolve any CaCO3 that reaches the sediment-water interface. In a lake with a seasonally anoxic hypolimnion, processes in the water column also can produce an inverse relation between OC and CaCO3 over time. If productivity of the lake increases, the rain rate of OC from the epilimnion increases. Biogenic removal of CO2 and accompanying increase in pH also may increase the production of CaCO3. However, the decomposition of organic matter in the hypolimnion will decrease the pH of the hypolimnion causing greater dissolution of CaCO3 and therefore a decrease in the rain rate of CaCO3 to the sediment-water interface.

  6. Identifying fermenting bacteria in anoxic tidal-flat sediments by a combination of microcalorimetry and ribosome-based stable-isotope probing.

    PubMed

    Graue, Jutta; Kleindienst, Sara; Lueders, Tillmann; Cypionka, Heribert; Engelen, Bert

    2012-07-01

    A novel approach was developed to follow the successive utilization of organic carbon under anoxic conditions by microcalorimetry, chemical analyses of fermentation products and stable-isotope probing (SIP). The fermentation of (13) C-labeled glucose was monitored over 4 weeks by microcalorimetry in a stimulation experiment with tidal-flat sediments. Based on characteristic heat production phases, time points were selected for quantifying fermentation products and identifying substrate-assimilating bacteria by the isolation of intact ribosomes prior to rRNA-SIP. The preisolation of ribosomes resulted in rRNA with an excellent quality. Glucose was completely consumed within 2 days and was mainly fermented to acetate. Ethanol, formate, and hydrogen were detected intermittently. The amount of propionate that was built within the first 3 days stayed constant. Ribosome-based SIP of fully labeled and unlabeled rRNA was used for fingerprinting the glucose-degrading species and the inactive background community. The most abundant actively degrading bacterium was related to Psychromonas macrocephali (similarity 99%) as identified by DGGE and sequencing. The disappearance of Desulfovibrio-related bands in labeled rRNA after 3 days indicated that this group was active during the first degradation phase only. In summary, ribosome-based SIP in combination with microcalorimetry allows dissecting distinct phases in substrate turnover in a very sensitive manner. PMID:22188432

  7. Modelling-based assessment of suspended sediment dynamics in a hypertidal estuarine channel

    NASA Astrophysics Data System (ADS)

    Amoudry, Laurent O.; Ramirez-Mendoza, Rafael; Souza, Alejandro J.; Brown, Jennifer M.

    2014-05-01

    We investigate the dynamics of suspended sediment transport in a hypertidal estuarine channel which displays a vertically sheared exchange flow. We apply a three-dimensional process-based model coupling hydrodynamics, turbulence and sediment transport to the Dee Estuary, in the north-west region of the UK. The numerical model is used to reproduce observations of suspended sediment and to assess physical processes responsible for the observed suspended sediment concentration patterns. The study period focuses on a calm period during which wave-current interactions can reasonably be neglected. Good agreement between model and observations has been obtained. A series of numerical experiments aim to isolate specific processes and confirm that the suspended sediment dynamics result primarily from advection of a longitudinal gradient in concentration during our study period, combined with resuspension and vertical exchange processes. Horizontal advection of sediment presents a strong semi-diurnal variability, while vertical exchange processes (including time-varying settling as a proxy for flocculation) exhibit a quarter-diurnal variability. Sediment input from the river is found to have very little importance, and spatial gradients in suspended concentration are generated by spatial heterogeneity in bed sediment characteristics and spatial variations in turbulence and bed shear stress.

  8. Acoustic measurement of sediment dynamics in the coastal zones using wireless sensor networks

    NASA Astrophysics Data System (ADS)

    Sudhakaran, A., II; Paramasivam, A.; Seshachalam, S.; A, C.

    2014-12-01

    Analyzing of the impact of constructive or low energy waves and deconstructive or high energy waves in the ocean are very much significant since they deform the geometry of seashore. The deformation may lead to productive result and also to the end of deteriorate damage. Constructive waves results deposition of sediment which widens the beach where as deconstructive waves results erosion which narrows the beach. Validation of historic sediment transportation and prediction of the direction of movement of seashore is essential to prevent unrecoverable damages by incorporating precautionary measurements to identify the factors that influence sediment transportation if feasible. The objective of this study is to propose a more reliable and energy efficient Information and communication system to model the Coastal Sediment Dynamics. Various factors influencing the sediment drift at a particular region is identified. Consequence of source depth and frequency dependencies of spread pattern in the presence of sediments is modeled. Property of source depth and frequency on sensitivity to values of model parameters are determined. Fundamental physical reasons for these sediment interaction effects are given. Shallow to deep water and internal and external wave model of ocean is obtained intended to get acoustic data assimilation (ADA). Signal processing algorithms are used over the observed data to form a full field acoustic propagation model and construct sound speed profile (SSP). The inversions of data due to uncertainties at various depths are compared. The impact of sediment drift over acoustic data is identified. An energy efficient multipath routing scheme Wireless sensor networks (WSN) is deployed for the well-organized communication of data. The WSN is designed considering increased life time, decreased power consumption, free of threats and attacks. The practical data obtained from the efficient system to model the ocean sediment dynamics are evaluated with remote

  9. Methane Dynamics in Sediments from Mangrove-dominated Costal Lagoons

    NASA Astrophysics Data System (ADS)

    Chuang, P. C.; Paytan, A.; Young, M. B.

    2014-12-01

    Porewater methane and sulfate concentrations from cored sediments have been measured in two coastal mangrove ecosystems (Celestún and Chelem Lagoons) on the Yucatán Peninsula, Mexico. Methane exists in shallow sediments while sulfate is not depleted and stable carbon isotopes of methane (-87.27‰ ~ -62.08‰) imply high methane fluxes/production rates below and within the cored sediment depths. The preliminary results from a transport-reaction model show that methane emitted to the water column from these sediments could be 17.8 mg m-2 d-1 in Celestún Lagoon and much higher (565 mg m-2 d-1) in Chelem Lagoon. Since the water depths are shallow (mostly less than 100 cm), the high fluxes of methane could contribute to the atmosphere. The objectives of this study will aim to understand the biogeochemical cycles for methane and sulfate in sediments. A numerical transport-reaction model will be applied to the sedimentary geochemical data (methane, sulfate, chloride, particulate organic carbon (POC) and stable carbon isotopes of headspace methane) from the two lagoons to estimate sulfate reduction, methane oxidation and production rates and advective methane fluxes. The modeled results will be used to discuss the role of methane from mangrove areas and their potential contribution to the global methane cycle.

  10. Sediment transport dynamics in the swash zone under large-scale laboratory conditions

    NASA Astrophysics Data System (ADS)

    Ruju, Andrea; Conley, Daniel; Masselink, Gerd; Puleo, Jack

    2016-06-01

    A laboratory experiment was carried out to study sediment transport dynamics occurring in the swash zone of a coarse-sandy beach built in a large-scale wave flume. Hydro- and morpho-dynamic as well as sediment transport data were collected using sensors mounted on a scaffold rig deployed in the lower swash zone close to the moving bed. The high resolution of near-bed data permitted quantitative evaluation of suspended and sheet flow contributions to the total sediment transport. Although sheet flow sediment fluxes were higher than suspended fluxes, the vertically integrated suspended sediment load overcame the sheet flow load during uprush and it was on the same order of magnitude during backwash. The observed cumulative sediment transport was generally larger than the morphological changes occurring shoreward of the rig location implying either an underestimation of the offshore sediment transport or an overestimation of the onshore fluxes obtained from concentration and velocity profile data. Low correlations were found between net swash profile changes and runup parameters suggesting that local hydrodynamic parameters provide little or no predictability of accretion and erosion of an upper beach which is near equilibrium. The balance between erosion and deposition induced by individual swash events brought a dynamic equilibrium with small differences between the profiles measured at the start and at the end of the run.

  11. Sediment dynamics within the intertidal floodplain of the lower Amazon River

    NASA Astrophysics Data System (ADS)

    Fricke, A. T.; Nittrouer, C. A.; Ogston, A. S.; Nowacki, D. J.; Asp, N. E.; Souza Filho, P. W.

    2014-12-01

    Tidal influence extends ~800 kilometers upstream of the Amazon River mouth, producing semidiurnal oscillations in water elevation and slowing or reversing the flow of the world's largest river. This tidally influenced reach, known as the tidal river, is flanked by an expansive intertidal floodplain, and includes confluences with two large tributaries, the Xingu and Tapajós. The relative magnitude of the seasonal and tidal signals changes along the length of the tidal river, yielding diverse floodplain environments that span a range of seasonal and tidal influence. Near the upstream limit of tides, natural levees isolate the river from the floodplain during low to moderate flows, while in the lower tidal river, natural levees are absent and river-floodplain exchange is dominated by the tides rather than seasonal variation in river stage. This difference between fluvial and tidal systems strongly affects the nature of sediment exchange between the channel and floodplain, including frequency, duration, and depth of inundation. Here we present data on the impact of this fluvial-tidal continuum on sedimentary processes in the floodplain and resultant depositional signatures. Changes in levee prominence, grain size, and sediment accumulation combine to produce the distinct morphologies of floodplain lakes, intertidal backswamps, and intertidal flats. In addition to sediment accumulation on the periodically exposed floodplain, Amazon River sediment accumulates within the drowned tributary confluences of the Xingu and Tapajós Rivers. Here seasonal and tidal changes in water temperature, discharge, and suspended-sediment concentration drive barotropic and baroclinic flows that transport Amazon River sediment into tributary basins. These findings help to constrain the fate of sediment within the ungauged Amazon tidal river, and will help in understanding the response of the lower Amazon River to changes in accommodation space associated with rising sea level, and changes

  12. New chronology for the southern Kalahari Group sediments with implications for sediment-cycle dynamics and early hominin occupation

    NASA Astrophysics Data System (ADS)

    Matmon, Ari; Hidy, Alan J.; Vainer, Shlomy; Crouvi, Onn; Fink, David; Erel, Yigal; Arnold, M.; Aumaître, G.; Bourlès, D.; Keddadouche, K.; Horwitz, Liora K.; Chazan, Michael

    2015-07-01

    Kalahari Group sediments accumulated in the Kalahari basin, which started forming during the breakup of Gondwana in the early Cretaceous. These sediments cover an extensive part of southern Africa and form a low-relief landscape. Current models assume that the Kalahari Group accumulated throughout the entire Cenozoic. However, chronology has been restricted to early-middle Cenozoic biostratigraphic correlations and to OSL dating of only the past ~ 300 ka. We present a new chronological framework that reveals a dynamic nature of sedimentation in the southern Kalahari. Cosmogenic burial ages obtained from a 55 m section of Kalahari Group sediments from the Mamatwan Mine, southern Kalahari, indicate that the majority of deposition at this location occurred rapidly at 1-1.2 Ma. This Pleistocene sequence overlies the Archaean basement, forming a significant hiatus that permits the possibility of many Phanerozoic cycles of deposition and erosion no longer preserved in the sedimentary record. Our data also establish the existence of a shallow early-middle Pleistocene water body that persisted for > 450 ka prior to this rapid period of deposition. Evidence from neighboring archeological excavations in southern Africa suggests an association of high-density hominin occupation with this water body.

  13. New chronology for the southern Kalahari Group sediments - implications for sediment-cycle dynamics and basin development

    NASA Astrophysics Data System (ADS)

    Matmon, Ari; Hidy, Alan; Vainer, Shlomy; Crouvi, Onn; Fink, David; Erel, Yigal; Aster Team; Horwitz, Liora; Chazan, Michael

    2016-04-01

    Kalahari Group sediments accumulated in the Kalahari basin, which started forming during the breakup of Gondwana in the early Cretaceous. These sediments cover an extensive part of southern Africa and form a low-relief landscape. Current models assume that the Kalahari Group accumulated throughout the entire Cenozoic. However, chronology has been restricted to early-middle Cenozoic biostratigraphic correlations and to OSL dating of only the past ~300 ka. We present a new chronological framework that reveals a dynamic nature of sedimentation in the southern Kalahari. Cosmogenic burial ages obtained from a 55 m section of Kalahari Group sediments from the Mamatwan Mine, southern Kalahari, indicate that the majority of deposition at this location occurred rapidly at 1-1.2 Ma. This Pleistocene sequence overlies the Archaean basement, forming a significant hiatus that permits the possibility of many Phanerozoic cycles of deposition and erosion no longer preserved in the sedimentary record. Our data also establish the existence of a shallow early-middle Pleistocene water body that persisted for >450 ka prior to this rapid period of deposition and suggesting an Okavango-like environment. Evidence from neighboring archaeological excavations in southern Africa suggests an association of high-density hominin occupation with this water body.

  14. Coral reef metabolism and carbon chemistry dynamics of a coral reef flat

    NASA Astrophysics Data System (ADS)

    Albright, Rebecca; Benthuysen, Jessica; Cantin, Neal; Caldeira, Ken; Anthony, Ken

    2015-05-01

    Global carbon emissions continue to acidify the oceans, motivating growing concern for the ability of coral reefs to maintain net positive calcification rates. Efforts to develop robust relationships between coral reef calcification and carbonate parameters such as aragonite saturation state (Ωarag) aim to facilitate meaningful predictions of how reef calcification will change in the face of ocean acidification. Here we investigate natural trends in carbonate chemistry of a coral reef flat over diel cycles and relate these trends to benthic carbon fluxes by quantifying net community calcification and net community production. We find that, despite an apparent dependence of calcification on Ωarag seen in a simple pairwise relationship, if the dependence of net calcification on net photosynthesis is accounted for, knowing Ωarag does not add substantial explanatory value. This suggests that, over short time scales, the control of Ωarag on net calcification is weak relative to factors governing net photosynthesis.

  15. Asymptotically locally flat spacetimes and dynamical nonspherically-symmetric black holes in three dimensions

    NASA Astrophysics Data System (ADS)

    Barnich, Glenn; Troessaert, Cédric; Tempo, David; Troncoso, Ricardo

    2016-04-01

    The theory of massive gravity proposed by Bergshoeff, Hohm and Townsend is considered in the special case of the pure irreducibly fourth-order quadratic Lagrangian. It is shown that the asymptotically locally flat black holes of this theory can be consistently deformed to "black flowers" that are no longer spherically symmetric. Moreover, we construct radiating spacetimes settling down to these black flowers in the far future. The generic case can be shown to fit within a relaxed set of asymptotic conditions as compared to the ones of general relativity at null infinity, while the asymptotic symmetries remain the same. Conserved charges as surface integrals at null infinity are constructed following a covariant approach, and their algebra represents BMS3 , but without central extensions. For solutions possessing an event horizon, we derive the first law of thermodynamics from these surface integrals.

  16. Hydrologic characteristics and suspended sediment dynamics in the Gradašica river basin

    NASA Astrophysics Data System (ADS)

    Kogoj, Mojca; Rusjan, Simon; Vidmar, Andrej; Mikoš, Matjaž

    2013-04-01

    Sediment transport in catchments is an important aspect of environmental research because of its role in the transport of sediment-associated nutrients, pesticides and other contaminants. High turbidity levels in water bodies affect stream morphology, aquatic organisms and their habitats, cause siltation of water reservoirs and have other side effects. For maintaining adequate water quality, reducing excessive soil erosion and proper estimation of the amount of transported material it is necessary to define and understand main factors that control sediment production and transport in rivers. Understanding the hydrological response of catchments on hydrometeorological phenomena and their influences on changes in suspended sediment concentrations require measurements of the processes at time scales that correspond to hydrological dynamics of a catchment. Our research aims to investigate hydrological and seasonal controls over suspended sediment production and obtain an insight into a suspended sediment concentration dynamics and total loads in a forested catchment. For this purpose, we study several factors actively controlling suspended sediment mobilization and transport in a small experimental catchment in Polhov Gradec mountainous area in the central part of Slovenia, drained by the Gradaščica river. Steep slopes, relatively high altitudes and abundance of precipitation (average yearly sums between 1600 to 1700 mm) result in a quick rise in the water level and consequently, in torrential response of the Gradaščica river. The studied headwaters lay on dolomite and limestone with a mainly natural land cover. The area is a subject to erosion with debris sources in the dolomite and additional catchment characteristics that contribute to high sediment transport rates. The main categories of factors that actively control sediment mobilization and transport from catchments, studied in our research, are hydrological and meteorological controls, physiographic factors

  17. Flow Dynamics and Sediment Entrainment in Natural Turbidity Currents Inferred from Numerical Modeling

    NASA Astrophysics Data System (ADS)

    Traer, M. M.; Hilley, G. E.; Fildani, A.

    2009-12-01

    Submarine turbidity currents derive their momentum from gravity acting upon the density contrast between sediment-laden and clear water, and so unlike fluvial systems, the dynamics of such flows are inextricably linked to the rates at which they deposit and entrain sediment. We have analyzed the sensitivity of the growth and maintenance of turbidity currents to sediment entrainment and deposition using the layer-averaged equations of conservation of fluid and sediment mass, and conservation of momentum and turbulent kinetic energy. Our model results show that the dynamics of turbidity currents are extremely sensitive to the functional form and empirical constants of the relationship between sediment entrainment and friction velocity. Data on the relationship between sediment entrainment and friction velocity for submarine density flows are few and as a result, entrainment formulations are populated with data from sub-aerial flows not driven by the density contrast between clear and turbid water. If we entertain the possibility that sediment entrainment in sub-aerial rivers is different than in dense underflows, flow parameters such as velocity, height, and concentration were found nearly impossible to predict beyond a few hundred meters based on the limited laboratory data available that constrain the sediment entrainment process in turbidity currents. The sensitivity of flow dynamics to the functional relationship between friction velocity and sediment entrainment indicates that independent calibration of a sediment entrainment law in the submarine environment is necessary to realistically predict the dynamics of these flows and the resulting patterns of erosion and deposition. To calibrate such a relationship, we have developed an inverse methodology that utilizes existing submarine channel morphology as a means of constraining the sediment entrainment function parameters. We use a Bayesian Metropolis-Hastings sampler to determine the sediment entrainment

  18. Sandia National Laboratories environmental fluid dynamics code : sediment transport user manual.

    SciTech Connect

    Grace, Matthew D.; Thanh, Phi Hung X.; James, Scott Carlton

    2008-09-01

    This document describes the sediment transport subroutines and input files for the Sandia National Laboratories Environmental Fluid Dynamics Code (SNL-EFDC). Detailed descriptions of the input files containing data from Sediment Erosion at Depth flume (SEDflume) measurements are provided along with the description of the source code implementing sediment transport. Both the theoretical description of sediment transport employed in SNL-EFDC and the source code are described. This user manual is meant to be used in conjunction with the EFDC manual (Hamrick 1996) because there will be no reference to the hydrodynamics in EFDC. Through this document, the authors aim to provide the necessary information for new users who wish to implement sediment transport in EFDC and obtain a clear understanding of the source code.

  19. Temporal variation of trace metal geochemistry in floodplain lake sediment subject to dynamic hydrological conditions.

    PubMed

    van Griethuysen, Corine; Luitwieler, Marloes; Joziasse, Jan; Koelmans, Albert A

    2005-09-01

    Climate change and land use may significantly influence metal cycling in dynamic river systems. We studied temporal variation of sediment characteristics in a floodplain lake, including concentrations of dissolved organic carbon, acid volatile sulfide and trace metals. The sampling period included a severe winter inundation and a dramatic water level drop during summer. Temporal changes were interpreted using multivariate analysis and chemical equilibrium calculations. Metal concentrations in sediment increased with depth, indicating a gradual improvement of sediment quality. In contrast, dissolved metal concentrations were highest in top layers due to mobilization from oxyhydroxides and precipitation with sulfides in deeper layers. Inundation had a mobilizing effect as it stimulated resuspension and oxygenation of sediment top layers. Water table lowering combined with organic matter decomposition led to immobilization due to sulfide formation. The chemistry of the sediments was consistent with model calculations, especially for macro-elements. The results illustrate the importance of seasonality for metal risk assessment. PMID:15963368

  20. Grazing Land Management Strongly Controls Water Quality, Sediment and Channel Dynamics in Tallgrass Prairie Headwater Networks

    NASA Astrophysics Data System (ADS)

    Grudzinski, B. G.; Daniels, M. D.

    2013-12-01

    In the prairie remnants of North America, watershed sediment regimes are heavily influenced by livestock grazing practices. Despite dramatic declines in stream water quality and ecosystem function concomitant with increasing gazing pressures, there have been no studies to quantitatively assess the relationship between various grazing treatments and sediment production in natural grassland ecosystems. In this study, we evaluate suspended sediment transport and channel morphology in the Flint Hills physiographic province using a paired whole-watershed approach, including 2 replicates of high density cattle grazing, 2 replicates of low density cattle grazing, 3 replicates of bison grazing and 3 replicates of no grazing. As expected, results demonstrate that cattle grazing operations increase e-coli, sediment concentrations and increase channel width. However, no significant differences in e-coli, suspended sediment dynamics or channel geomorphology were found between bison grazed and ungrazed watersheds.

  1. Benthic activity in sediments of the northwestern Adriatic Sea: sediment oxygen consumption, macro- and meiofauna dynamics

    NASA Astrophysics Data System (ADS)

    Moodley, Leon; Heip, Carlo H. R.; Middelburg, Jack J.

    1998-12-01

    Benthic activity was examined at three stations (18 m water depth) in the northwestern Adriatic Sea. Carbon mineralisation rates, as based on sediment oxygen consumption rates, ranged from 54 to 89 g C m -2 y -1. The relatively high carbon mineralisation rates, large macrofaunal biomass (9 to 16 g C m -2) and macrofaunal production (11 to 19 g C m -2 y -1) provide evidence of high organic-matter input and intense benthic-pelagic coupling. This is further supported by the high dominance of the suspension-feeding bivalve Corbula gibba, which accounts for 52 to 63% of the total annual macrofaunal biomass production. Although the infaunal distribution of total macrofauna showed a sharp decline in densities and biomass with depth into the sediment, different patterns within the dominant taxa were observed. Whilst the bivalve Corbula gibba and the amphipod Ampelisca sp. were restricted to the surface layer, other species such as the dominant bivalve Mysella sp. and the gastropod Hyala sp. were not confined to a specific depth level and the majority of the populations occurred deeper than 5 cm into the sediment. Bioturbation, based on the occurrence of macrofauna, extended to at least 20 cm. Nematodes and foraminifera together formed 80 to 90% of the meiofaunal community in the upper 5 cm of the sediment. Annual mean densities ranged from 3.40 to 6.07×10 6 ind. m -2. Maximum abundance of meiofauna was not encountered at the station where maximum macrofaunal activity was recorded, and this could reflect the negative effect of biological interaction on meiofaunal densities in areas that have a high food supply.

  2. Sediment dynamics in the lower Mekong River: Transition from tidal river to estuary

    NASA Astrophysics Data System (ADS)

    Nowacki, Daniel J.; Ogston, Andrea S.; Nittrouer, Charles A.; Fricke, Aaron T.; Van, Pham Dang Tri

    2015-09-01

    A better understanding of flow and sediment dynamics in the lowermost portions of large-tropical rivers is essential to constraining estimates of worldwide sediment delivery to the ocean. Flow velocity, salinity, and suspended-sediment concentration were measured for 25 h at three cross sections in the tidal Song Hau distributary of the Mekong River, Vietnam. Two campaigns took place during comparatively high-seasonal and low-seasonal discharge, and estuarine conditions varied dramatically between them. The system transitioned from a tidal river with ephemeral presence of a salt wedge during high flow to a partially mixed estuary during low flow. The changing freshwater input, sediment sources, and estuarine characteristics resulted in seaward sediment export during high flow and landward import during low flow. The Dinh An channel of the Song Hau distributary exported sediment to the coast at a rate of about 1 t s-1 during high flow and imported sediment in a spatially varying manner at approximately 0.3 t s-1 during low flow. Scaling these values results in a yearly Mekong sediment discharge estimate about 65% smaller than a generally accepted estimate of 110 Mt yr-1, although the limited temporal and spatial nature of this study implies a relatively high degree of uncertainty for the new estimate. Fluvial advection of sediment was primarily responsible for the high-flow sediment export. Exchange-flow and tidal processes, including local resuspension, were principally responsible for the low-flow import. The resulting bed-sediment grain size was coarser and more variable during high flow and finer during low, and the residual flow patterns support the maintenance of mid-channel islands. This article was corrected on 7 OCT 2015. See the end of the full text for details.

  3. Assessing sediment connectivity to understand dynamics of contaminated sediment within coastal catchments of Fukushima Prefecture (Japan)

    NASA Astrophysics Data System (ADS)

    Chartin, Caroline; Evrard, Olivier; Onda, Yuichi; Ottlé, Catherine; Brossoni, Camille; Lefèvre, Irène; Lepage, Hugo; Bonté, Philippe; Patin, Jeremy; Ayrault, Sophie

    2013-04-01

    The Fukushima Dai-ichi Nuclear Power Plant accident has led to the release of large radionuclide quantities (e.g., about 20 PBq of Cs-137 and 200 PBq of I-131) into the atmosphere. About 80% of the release was blown out and over the Pacific Ocean. The remaining 20% of emissions were deposited as wet and dry deposits on soils of Fukushima Prefecture, mainly between 15-16 March. As most radionuclides are strongly sorbed by fine particles, they are likely to be redistributed within the landscape in association with soil and sediment particles transported by runoff and erosion processes. A spatial analysis of Ag-110m:Cs-137 ratio in soils and river sediments provided a way to trace those transfers. This fingerprinting study showed that particles eroded from inland mountain ranges exposed to the highest initial radionuclide fallout were already dispersed along coastal rivers, most likely during summer typhoons and spring snowmelt. Those results suggest that hillslopes and rivers have become a perennial source of radioactive contaminants to the Pacific Ocean off Fukushima Prefecture. This study aims to specify the location and nature of the preferential sources supplying contaminated material to the main rivers draining the Fukushima contamination plume. To this end, important parameters controlling soil erosion and sediment transfers within catchments, i.e. landscape morphology and land use characteristics, were preliminary derived from DEM data and satellite images for the River Mano, Nitta and Ota catchments (ca. 525 km²) draining the most radioactive part of the contamination plume that formed across Fukushima Prefecture. Then, those data were used to compute indices assessing the potential sediment connectivity (i) between hillslopes and rivers and (ii) between hillslopes and catchment outlets. Finally, spatially-distributed values of connectivity indices were confronted to gamma-emitting radionuclide activities (Cs-134, Cs-137 and Ag-110m) measured in riverbed

  4. Impact of frontal systems on estuarine sediment and pollutant dynamics.

    PubMed

    Duck, R W; Wewetzer, S F

    2001-02-01

    In this paper, a brief description of frontal systems, their modes of occurrence and impact on the estuarine environment, is presented. Previous studies of estuarine fronts have largely focused on the water surface and within the water column. New observations in the Tay Estuary, Scotland have shown that the presence of fronts within the water column may be marked, not only by surface foam bands, but also by abrupt (i.e. non-gradational) changes in the underlying bedform morphology and/or sediment facies, as detected using side-scan sonar. This preliminary evidence suggests that fronts may exert a control, not only on the surface and intra-water column sediment and pollutant partitioning, but also on the distribution and persistence of bedload transport pathways. PMID:11258822

  5. On the modeling and nonlinear dynamics of autonomous Silva-Young type chaotic oscillators with flat power spectrum

    SciTech Connect

    Kengne, Jacques; Kenmogne, Fabien

    2014-12-15

    The nonlinear dynamics of fourth-order Silva-Young type chaotic oscillators with flat power spectrum recently introduced by Tamaseviciute and collaborators is considered. In this type of oscillators, a pair of semiconductor diodes in an anti-parallel connection acts as the nonlinear component necessary for generating chaotic oscillations. Based on the Shockley diode equation and an appropriate selection of the state variables, a smooth mathematical model (involving hyperbolic sine and cosine functions) is derived for a better description of both the regular and chaotic dynamics of the system. The complex behavior of the oscillator is characterized in terms of its parameters by using time series, bifurcation diagrams, Lyapunov exponents' plots, Poincaré sections, and frequency spectra. It is shown that the onset of chaos is achieved via the classical period-doubling and symmetry restoring crisis scenarios. Some PSPICE simulations of the nonlinear dynamics of the oscillator are presented in order to confirm the ability of the proposed mathematical model to accurately describe/predict both the regular and chaotic behaviors of the oscillator.

  6. On the modeling and nonlinear dynamics of autonomous Silva-Young type chaotic oscillators with flat power spectrum.

    PubMed

    Kengne, Jacques; Kenmogne, Fabien

    2014-12-01

    The nonlinear dynamics of fourth-order Silva-Young type chaotic oscillators with flat power spectrum recently introduced by Tamaseviciute and collaborators is considered. In this type of oscillators, a pair of semiconductor diodes in an anti-parallel connection acts as the nonlinear component necessary for generating chaotic oscillations. Based on the Shockley diode equation and an appropriate selection of the state variables, a smooth mathematical model (involving hyperbolic sine and cosine functions) is derived for a better description of both the regular and chaotic dynamics of the system. The complex behavior of the oscillator is characterized in terms of its parameters by using time series, bifurcation diagrams, Lyapunov exponents' plots, Poincaré sections, and frequency spectra. It is shown that the onset of chaos is achieved via the classical period-doubling and symmetry restoring crisis scenarios. Some PSPICE simulations of the nonlinear dynamics of the oscillator are presented in order to confirm the ability of the proposed mathematical model to accurately describe/predict both the regular and chaotic behaviors of the oscillator. PMID:25554054

  7. On the modeling and nonlinear dynamics of autonomous Silva-Young type chaotic oscillators with flat power spectrum

    NASA Astrophysics Data System (ADS)

    Kengne, Jacques; Kenmogne, Fabien

    2014-12-01

    The nonlinear dynamics of fourth-order Silva-Young type chaotic oscillators with flat power spectrum recently introduced by Tamaseviciute and collaborators is considered. In this type of oscillators, a pair of semiconductor diodes in an anti-parallel connection acts as the nonlinear component necessary for generating chaotic oscillations. Based on the Shockley diode equation and an appropriate selection of the state variables, a smooth mathematical model (involving hyperbolic sine and cosine functions) is derived for a better description of both the regular and chaotic dynamics of the system. The complex behavior of the oscillator is characterized in terms of its parameters by using time series, bifurcation diagrams, Lyapunov exponents' plots, Poincaré sections, and frequency spectra. It is shown that the onset of chaos is achieved via the classical period-doubling and symmetry restoring crisis scenarios. Some PSPICE simulations of the nonlinear dynamics of the oscillator are presented in order to confirm the ability of the proposed mathematical model to accurately describe/predict both the regular and chaotic behaviors of the oscillator.

  8. Investigation of image lag and modulation transfer function in fluoroscopy images obtained with a dynamic flat-panel detector.

    PubMed

    Kawashima, Hiroki; Tanaka, Rie; Ichikawa, Katsuhiro; Matsubara, Kosuke; Iida, Hiroji; Sanada, Shigeru

    2013-07-01

    Digital imaging with a dynamic flat-panel detector (FPD) is commonly used in clinical practice. However, several factors reduce the accuracy of target tracking in fluoroscopic imaging, including image lag and blurring. There have been several reports focusing on the modulation transfer function (MTF), noise power spectrum (NPS), and detective quantum efficiency (DQE) in different types of FPD. However, there have been no studies comparing image lag and MTF properties in dynamic images obtained with indirect- and direct-conversion FPDs. We investigated the image lag and MTF under several imaging conditions in fluoroscopic images obtained with an indirect-conversion and a direct-conversion FPD system. The measurements of image lag and MTF were obtained under several conditions according to IEC 62220-1-3 standards. We examined whether the image lag and MTF were influenced by the dose level and target movement speed. Indirect-conversion FPD showed dependence on the dose level, which was not observed for direct-conversion FPD. Furthermore, there were large differences in MTF between images of static and moving plate with indirect-conversion FPD in comparison to the differences observed with direct-conversion FPD. These results will be useful for the determination of imaging conditions for target tracking and other types of dynamic imaging. PMID:23568338

  9. Development of a national, dynamic reservoir-sedimentation database

    USGS Publications Warehouse

    Gray, J.R.; Bernard, J.M.; Stewart, D.W.; McFaul, E.J.; Laurent, K.W.; Schwarz, G.E.; Stinson, J.T.; Jonas, M.M.; Randle, T.J.; Webb, J.W.

    2010-01-01

    The importance of dependable, long-term water supplies, coupled with the need to quantify rates of capacity loss of the Nation’s re servoirs due to sediment deposition, were the most compelling reasons for developing the REServoir- SEDimentation survey information (RESSED) database and website. Created under the auspices of the Advisory Committee on Water Information’s Subcommittee on Sedimenta ion by the U.S. Geological Survey and the Natural Resources Conservation Service, the RESSED database is the most comprehensive compilation of data from reservoir bathymetric and dry-basin surveys in the United States. As of March 2010, the database, which contains data compiled on the 1950s vintage Soil Conservation Service’s Form SCS-34 data sheets, contained results from 6,616 surveys on 1,823 reservoirs in the United States and two surveys on one reservoir in Puerto Rico. The data span the period 1755–1997, with 95 percent of the surveys performed from 1930–1990. The reservoir surface areas range from sub-hectare-scale farm ponds to 658 km2 Lake Powell. The data in the RESSED database can be useful for a number of purposes, including calculating changes in reservoir-storage characteristics, quantifying sediment budgets, and estimating erosion rates in a reservoir’s watershed. The March 2010 version of the RESSED database has a number of deficiencies, including a cryptic and out-of-date database architecture; some geospatial inaccuracies (although most have been corrected); other data errors; an inability to store all data in a readily retrievable manner; and an inability to store all data types that currently exist. Perhaps most importantly, the March 2010 version of RESSED database provides no publically available means to submit new data and corrections to existing data. To address these and other deficiencies, the Subcommittee on Sedimentation, through the U.S. Geological Survey and the U.S. Army Corps of Engineers, began a collaborative project in

  10. The Dynamics of Suspended Sediment over Bedforms in Mixed Sand-Clay-EPS

    NASA Astrophysics Data System (ADS)

    Ye, Leiping; Parsons, Daniel; Schindler, Robert; Manning, Andrew

    2014-05-01

    Quantifying and modeling sediment dynamics in flows, including the complexities of sediment mixtures and their biological status, is a key to parameterizing physical processes at the flow-bed interface and ultimately to predicting natural sediment transport (French, 2010). Such predictions rely strongly on accurate knowledge of relationships between hydrodynamics and sediment properties. The work presented here describes laboratory experiments that have been conducted using mixed cohesive and non-cohesive sediment and Xanthan gum as a proxy for the biological stickiness of Extracellular Polymeric Substances (EPS) (Vardy et al., 2007). The dynamics of suspended sediments and bed morphology were monitored and analyzed continuously in a set of experiments in a laboratory flume (at the University of Hull's Total Environment Simulator) facility. The tank was sectioned into a 10 x 2 m channel and during the study period, a total of 16 runs with varying bed sediment compositions were used (various ratios of sand, clay and EPS). Unidirectional flow rates were generated via recirculated pumped saline water (at 15 PSU). Suspended sediments were observed through (1) physical water samples (via pump) (2) vertically spaced OBS sensors, (3) LISST-100X, (4) ABS profiles. In addition, water samples were analyzed for flocculation properties using LabSFLOC (e.g. Manning et al., 2002), allowing the effects of varying suspended sands, clays and EPS on flocculation were monitored throughout. The results revealed a strong temporal variability in suspended sediment transport with the various proportions of substrate sand, clay and EPS. Work is ongoing and more details will be presented.

  11. Suspended sediment dynamics in a tidal channel network under peak river flow

    NASA Astrophysics Data System (ADS)

    Achete, Fernanda Minikowski; van der Wegen, Mick; Roelvink, Dano; Jaffe, Bruce

    2016-05-01

    Peak river flows transport fine sediment, nutrients, and contaminants that may deposit in the estuary. This study explores the importance of peak river flows on sediment dynamics with special emphasis on channel network configurations. The Sacramento-San Joaquin Delta, which is connected to San Francisco Bay (California, USA), motivates this study and is used as a validation case. Besides data analysis of observations, we applied a calibrated process-based model (D-Flow FM) to explore and analyze high-resolution (˜100 m, ˜1 h) dynamics. Peak river flows supply the vast majority of sediment into the system. Data analysis of six peak flows (between 2012 and 2014) shows that on average, 40 % of the input sediment in the system is trapped and that trapping efficiency depends on timing and magnitude of river flows. The model has 90 % accuracy reproducing these trapping efficiencies. Modeled deposition patterns develop as the result of peak river flows after which, during low river flow conditions, tidal currents are not able to significantly redistribute deposited sediment. Deposition is quite local and mainly takes place at a deep junction. Tidal movement is important for sediment resuspension, but river induced, tide residual currents are responsible for redistributing the sediment towards the river banks and to the bay. We applied the same forcing for four different channel configurations ranging from a full delta network to a schematization of the main river. A higher degree of network schematization leads to higher peak-sediment export downstream to the bay. However, the area of sedimentation is similar for all the configurations because it is mostly driven by geometry and bathymetry.

  12. Dynamic Sediment Modeling in Iowa Streams and Rivers: A Case Study at Walnut Creek

    NASA Astrophysics Data System (ADS)

    Li, Z.; Zhang, Y.; Skopec, M.

    2004-12-01

    Deep channel bed incision and severe channel bank erosion, which have strong effects on the evolution of channel and watershed morphology, are becoming serious problems in natural rivers and streams in Iowa as a result of wide distribution of loess soil material, agricultural activity, river training and human intervention. Consequent high sediment concentration can also cause low water quality and jeopardize aquatic habitat. Dynamic modeling of sediment transport in rivers and streams provides a useful tool for monitoring, controlling and forecasting the morphology change and water quality in channels and watersheds. In order to gain insight into sediment transport process, a dynamic sediment model is built for a 7-mile segment of Walnut Creek in Jasper County, Iowa. This creek was intensively surveyed by Iowa Geological Survey Bureau (IGSB) as part of the Walnut Creek Nonpoint Source Monitoring Project. Besides channel geometry data from the survey, hydraulic and sediment data were collected at two gauges upstream and downstream operated by USGS. A software GSTARS3 developed by USGS is adopted to model both channel bed incision and bank erosion which are typical phenomena in Iowa. The dynamic sediment model is calibrated using channel bathymetry data from recent survey conducted by IGSB. Finally, based on forecasting of flow and sediment discharge time series at the upstream and stage time series at the downstream, a sediment forecasting model is developed to see if the stream can go back to the clarity and morphology of original creek. The study on this small surveyed and controlled creek will benefit our research in other Iowa rivers and streams.

  13. Holocene sediment dynamics on a cool-water carbonate shelf: Otway, southeastern Australia

    SciTech Connect

    Boreen, T.D.; James, N.P. )

    1993-07-01

    The Otway Shelf is covered by cool waters and veneered by bryozoan-dominated carbonate sediments. Radiocarbon dating and stratigraphy of shelf vibracores and slope gravity cores document late Pleistocene/Holocene deposition. Shelf sediments of the late Pleistocene high-stand are rare, either never having been deposited or having been removed during the following sea-level fall. During the subsequent lowstand the shelf was exposed, facies shifted basinward, and beach/dune complexes were constructed near the shelf edge. The deep shelf was characterized by nondeposition and hardground formation, and the shelf margin became locally erosional. Upper-slope bryozoan/sponge assemblages continued to grow actively, and lower-slope foraminifera and nannofossil ooze was increasingly enriched in hemipelagic terrigenous mud swept off the wide shelf. Coarse shelf debris and lowstand dune sands were erosively reworked and transported onto the upper slope and redistributed to deep-slope aprons during early transgression. The late Quaternary shelf record resembles that of flat-topped, warm-water platforms with Holocene sediment overlying Pleistocene/Tertiary limestone, but for different reasons. The slow growth potential, uniform profile of sediment production and distribution, and inability of constituent organisms to construct rigid frameworks favor maintenance of a shallow ramp profile and makes the cool-water carbonate system an excellent modern analog for interpretation of many ancient ramp successions.

  14. Sediment Retention Dynamics and Vegetation Along Three Tributaries of the Chesapeake Bay

    NASA Astrophysics Data System (ADS)

    Ross, K.; Ross, K.; Hupp, C.; Alexander, L.; Alexander, L.

    2001-12-01

    Coastal Plain riparian wetlands in the Mid-Atlantic United States are the last place for sediment and contaminant storage before reaching critical estuarine and marine environments. The deteriorating health of the Chesapeake Bay has been attributed in part to elevated sediment loads. The purpose of this study is to investigate the effects of channelization and urbanization on sediment deposition and geomorphic processes along the Pocomoke and Chickahominy Rivers and Dragon Run, three Coastal Plain tributaries. Floodplain microtopography was surveyed in 100 x 100 m grids at three characteristic reaches along each river and woody vegetation analyses were conducted. Floodplain suspended sediment concentrations and short and long-term sedimentation rates were estimated at each reach using single stage sediment sampler arrays, clay pads and dendrogeomorphic techniques, respectively. Site hydroperiod and flow characteristics were determined from USGS gaging station records, floodplain water level recorders, and field observations. Channelized floodplain reaches along the Pocomoke River are flooded less frequently, have lower mineral sedimentation rates (2 mm/yr to 6 mm/yr) and woody species diversity than the unchannelized reaches. Along the Chickahominy River, floodplain wetlands close to urban centers are flooded more frequently, but have shorter hydroperiods (3.5 days/yr compared to more than 45 days/yr), lower sedimentation rates (1.8 mm/yr to 6.8 mm/yr), and lower woody species diversity (0.51 to 1.95 on the Shannon-Weiner diversity index) than floodplains further downstream. Suspended sediment delivery and deposition rates are significantly influenced by floodplain hydroperiod duration and channel-floodplain connectivity. These results suggest that understanding floodplain sediment dynamics and geomorphic processes with respect to dominant watershed landuse patterns is critical for effective water quality management and restoration efforts.

  15. Analog Modeling of the Juan Fernández Ridge, Central Chile, and Implications for Flat-Slab Subduction Dynamics

    NASA Astrophysics Data System (ADS)

    Woodell, D.; Anderson, M. L.

    2009-12-01

    This study compares the strain experienced by the subducting lithosphere in analog models to the strain recorded by earthquakes in the subduction zone that includes the Juan Fernández Ridge (JFR), near 33 S, 73 W, off the coast of central Chile. The JFR is an aseismic hot spot ridge that has a thickened oceanic crust. The overthickened crust reduces the total density of the slab when compared to the surrounding slab areas, and thus increases the buoyancy of the subducting Nazca plate at this particular location. It is hypothesized that the Nazca plate experiences “flat-slab” subduction at the JFR subduction zone due to this buoyancy. Brudzinski and Chen (2005) argue that, due to the poorly aligned direction of maximum extension (T axes) for earthquakes in the subducting slab in flat-slab subduction zones, the theory of “slab pull” may not be valid for flat-slab subduction zones, and there must be other forces at work. However, Anderson et al. (2007) develop new, more precise slab contours from newly determined earthquake locations and use these contours to qualitatively compare the earthquake data to slab dip directions and thus expected slab-pull directions. They conclude that T axes are parallel to slab dip, and thus slab pull is the only force necessary for explaining the T axis direction. In this study, we quantitatively compare extension produced in analog "flat-slab" models in the laboratory to T axes from the Anderson et al. (2007) study, extending and further testing their idea. Several materials comprise the analog models. Light corn syrup represents the asthenosphere, while silicon putty represents the lithosphere. Recreating the dynamics of the buoyant JFR necessitates two different densities of silly putty: a denser one for the bulk of the slab, and a less dense one for the buoyant ridge. Shallow circular indentations (strain ellipses) on the slab facilitate recording of the strain in the subducting slab. Video and still pictures record each

  16. Model tracks sediment dynamics for highly curved meandering rivers

    NASA Astrophysics Data System (ADS)

    Schultz, Colin

    2013-07-01

    Understanding the dynamics of meandering rivers—the twisting, turning, and wandering of waterways over time—is of concern to water managers and civil engineers. How curved a river is affects how it moves, and Ottevanger et al. built on existing models to improve representations of meandering dynamics for highly curved rivers.

  17. Approaching a flat boundary with a block copolymer coated emulsion drop: late stage drainage dynamics

    NASA Astrophysics Data System (ADS)

    Rozairo, Damith; Croll, Andrew

    Understanding the dynamics of the formation and drainage of the thin fluid film that becomes trapped by a deformable droplet as it approaches another object is crucial to the advancement of many industrial and biomedical applications. Adding amphiphilic diblock copolymers, which are becoming more commonly used in drug delivery and oil recovery, only add to the complexity. Despite their increased use, little is known about how long polymer chains fill an emulsion drop's interface or how the molecules influence hydrodynamic processes. We study the drainage dynamics of a thin water film trapped between mica and a diblock copolymer saturated oil droplet. Specifically, we examine several different polystyrene-b-poly(ethylene oxide) (PS-PEO) molecules self-assembled at a toluene-water interface using laser scanning confocal microscopy. Our experiments reveal that the molecular details of the polymer chains deeply influence the drainage times, indicating that they are not acting as a 'simple' surfactant. The presence of the chains creates a much slower dynamic as fluid is forced to drain through an effective polymer brush, the brush itself determined by chain packing at the interface. We present a simple model which accounts for the basic physics of the interface.

  18. Trailing-edge dynamics and morphing of a deformable flat plate at high Reynolds number by time-resolved PIV

    NASA Astrophysics Data System (ADS)

    Chinaud, M.; Rouchon, J. F.; Duhayon, E.; Scheller, J.; Cazin, S.; Marchal, M.; Braza, M.

    2014-05-01

    The present paper investigates the turbulent wake structure in the near-region past the trailing edge of a deformable inclined plate. The plate is actuated by shape memory alloys. Using these actuators a significant deformation (bending) can be achieved (≈10% of the chord) under the aerodynamic loads corresponding to a Reynolds number of 200 000. The shear-layer dynamics as well as the mean velocity and turbulent stresses have been quantified for a reference case (flat plate inclined at 10°). The present study investigates the modification of the shear-layer and near-wake dynamics achieved by means of the dynamic deformation of the plate compared with static cases that include three intermediate positions of the deformed plate. The comparison of the static cases with the dynamic regime discusses the validity of the quasi-static hypothesis for the present low frequency actuation. It is found that the present actuation enhances the shearing mechanisms past the trailing-edge and modifies the von-Kármán mode as well as the structure of the shear-layer, Kelvin-Helmholtz eddies. Moreover, the increase of the bending enhances the appearance of the pairing mechanism between successive shear-layer eddies and the interaction between the von-Kármán and shear-layer instability modes. Furthermore, it has been found that the increase of the plate's curvature leads to an attenuation of the shear-layer amplitude and of the overall spectral energy, concerning the most deformed position.

  19. Sediment yield in human-induced degraded catchments of the Northern Ethiopian Highlands: magnitude and dynamics

    NASA Astrophysics Data System (ADS)

    Vanmaercke, M.; Zenebe, A.; Poesen, J.; Nyssen, J.; Verstraeten, G.; Deckers, J.; Govers, G.

    2009-04-01

    The Northern Ethiopian Highlands are a fragile environment, characterised by steep slopes, intense rainfall and a sparse vegetation cover. The extreme poverty, stagnating technology and high population and livestock densities induce serious soil erosion problems. This not only leads to lower crop yields but also reduces the life expectancy of many dams and reservoirs (used for power generation or water supply in the dry season) as a result of massive sedimentation. Although these problems demand for a thorough solution, little is known about the magnitude and dynamics of sediment transport in the Northern Ethiopian Highlands. Therefore an intensive measuring campaign was conducted during the rainy season of 2006 in 10 subcatchments of the Geba (drainage area: 5180 km2), a tributary of the Tekeze (Atbara) river. These subcatchments range in size from 120 km2 to 4330 km2 and represent contrasting environments typical for the Northern Ethiopian Highlands. In this paper, the results of this measuring campaign are discussed. The sediment yield for the 10 subcatchments range between 400 and 2500 t km-2 a-1, with an average value of 1400 t km-2 a-1. The uncertainties on these sediment yields were assessed by Monte Carlo simulations. Important spatial and temporal variations in suspended sediment export were noted. A few flash floods were recorded in detail for which clear positive hysteresis effects in sediment concentration were found. The environmental factors, causing the large differences in sediment yield between the studied catchments were assessed by means of a semi-quantitative model.

  20. Impact of ice-shelf sediment content on the dynamics of plumes under melting ice shelves

    NASA Astrophysics Data System (ADS)

    Wells, A.

    2015-12-01

    When a floating ice shelf melts into an underlying warm salty ocean, the resulting fresh meltwater can rise in a buoyant Ice-Shelf-Water plume under the ice. In certain settings, ice flowing across the grounding line carries a basal layer of debris rich ice, entrained via basal freezing around till in the upstream ice sheet. Melting of this debris-laden ice from floating ice shelves provides a flux of dense sediment to the ocean, in addition to the release of fresh buoyant meltwater. This presentation considers the impact of the resulting suspended sediment on the dynamics of ice shelf water plumes, and identifies two key flow regimes depending on the sediment concentration frozen into the basal ice layer. For large sediment concentration, melting of the debris-laden ice shelf generates dense convectively unstable waters that drive convective overturning into the underlying ocean. For lower sediment concentration, the sediment initially remains suspended in a buoyant meltwater plume rising along the underside of the ice shelf, before slowly depositing into the underlying ocean. A theoretical plume model is used to evaluate the significance of the negatively buoyant sediment on circulation strength and the feedbacks on melting rate, along with the expected depositional patterns under the ice shelf.

  1. Assessing surface sediment dynamics along the north-west coast of Marsa Dhouiba (Tunisia, southern Mediterranean)

    NASA Astrophysics Data System (ADS)

    Khiari, Nouha; Atoui, Abdelfattah; Brahim, Mouldi; Sammari, Chérif; Charef, Abdelkrim; Aleya, Lotfi

    2016-04-01

    An investigation was conducted from summer 2012 to winter 2013 at 25 stations along the Tunisian coast near Kef Abbed at Marsa Dhouiba (north-east Mediterranean Sea) to analyse grain size, sediment mineralogy and currents. Particle-size analysis shows that sand deposits at shallow depths are characterised by S-shaped curves, indicating a degree of agitation and possible transport by rip currents near the bottom. At greater depths (between 10 and 30 m), the bottom is covered by coarse sand and gravel. A current was observed transporting sediment eastward along the coast; another seaward current was also noted. Generated by wind, swell and especially waves from west to north-west, the two currents transport clay and silt-sized sediment seaward. An Acoustic Doppler Current Profiler showed Marsa Dhouiba's coastal current to follow a direction 175° East, with its main axis running north/north-west parallel to the coast and its minor axis also running north/north-west. Analysis of current components indicates that the velocities u and v are oriented north to south. Sediment evolution in shallow waters is dependent on detrital inputs from streams and winds. The coarse fraction of surface sediments in Marsa Dhouiba presents 87% of total sediments and is located at depths of 10-30 m. Sediment dynamics in the Marsa Dhouiba region are closely related to the west/north-west swell.

  2. In-Well Sediment Incubators to Evaluate Microbial Community Stability and Dynamics following Bioimmobilization of Uranium

    SciTech Connect

    Baldwin, Brett R.; Peacock, Aaron D.; Gan, M.; Resch, Charles T.; Arntzen, Evan V.; Smithgall, A. N.; Pfiffner, S.; Freifeld, Barry M.; White, D. C.; Long, Philip E.

    2009-09-23

    An in-situ incubation device (ISI) was developed in order to investigate the stability and dynamics of sediment associated microbial communities to prevailing subsurface oxidizing or reducing conditions. Here we describe the use of these devices at the Old Rifle Uranium Mill Tailings Remedial Action (UMTRA) site. During the 7 month deployment oxidized Rifle aquifer background sediments (RABS) were deployed in previously biostimulated wells under iron reducing conditions, cell densities of known iron reducing bacteria including Geobacteraceae increased significantly showing the microbial community response to local subsurface conditions. PLFA profiles of RABS following in situ deployment were strikingly similar to those of adjacent sediment cores suggesting ISI results could be extrapolated to the native material of the test plots. Results for ISI deployed reduced sediments showed only slight changes in community composition and pointed toward the ability of the ISIs to monitor microbial community stability and response to subsurface conditions.

  3. Dynamics and recovery of a sediment-exposed Chironomus riparius population: A modelling approach.

    PubMed

    Diepens, Noël J; Beltman, Wim H J; Koelmans, Albert A; Van den Brink, Paul J; Baveco, Johannes M

    2016-06-01

    Models can be used to assess long-term risks of sediment-bound contaminants at the population level. However, these models usually lack the coupling between chemical fate in the sediment, toxicokinetic-toxicodynamic processes in individuals and propagation of individual-level effects to the population. We developed a population model that includes all these processes, and used it to assess the importance of chemical uptake routes on a Chironomus riparius population after pulsed exposure to the pesticide chlorpyrifos. We show that particle ingestion is an important additional exposure pathway affecting C. riparius population dynamics and recovery. Models ignoring particle ingestion underestimate the impact and the required recovery times, which implies that they underestimate risks of sediment-bound chemicals. Additional scenario studies showed the importance of selecting the biologically relevant sediment layer and showed population effects in the long term. PMID:27031571

  4. Dynamics of the Laschamp geomagnetic excursion from Black Sea sediments

    NASA Astrophysics Data System (ADS)

    Nowaczyk, N. R.; Arz, H. W.; Frank, U.; Kind, J.; Plessen, B.

    2012-10-01

    Investigated sediment cores from the southeastern Black Sea provide a high-resolution record from mid latitudes of the Laschamp geomagnetic polarity excursion. Age constraints are provided by 16 AMS 14C ages, identification of the Campanian Ignimbrite tephra (39.28±0.11 ka), and by detailed tuning of sedimentologic parameters of the Black Sea sediments to the oxygen isotope record from the Greenland NGRIP ice core. According to the derived age model, virtual geomagnetic pole (VGP) positions during the Laschamp excursion persisted in Antarctica for an estimated 440 yr, making the Laschamp excursion a short-lived event with fully reversed polarity directions. The reversed phase, centred at 41.0 ka, is associated with a significant field intensity recovery to 20% of the preceding strong field maximum at ˜50 ka. Recorded field reversals of the Laschamp excursion, lasting only an estimated ˜250 yr, are characterized by low relative paleointensities (5% relative to 50 ka). The central, fully reversed phase of the Laschamp excursion is bracketed by VGP excursions to the Sargasso Sea (˜41.9 ka) and to the Labrador Sea (˜39.6 ka). Paleomagnetic results from the Black Sea are in excellent agreement with VGP data from the French type locality which facilitates the chronological ordering of the non-superposed lavas that crop out at Laschamp-Olby. In addition, VGPs between 34 and 35 ka reach low northerly to equatorial latitudes during a clockwise loop, inferred to be the Mono lake excursion.

  5. Earth Flats

    NASA Astrophysics Data System (ADS)

    Bohlin, R. C.; Mack, J.; Hartig, G.; Sirianni, M.

    2005-10-01

    Since the last ISR 2003-02 on the use of Earth observations for a source of flat field illumination, several hundred more observations have been obtained with the full set of HRC standard filters and four narrow band WFC filters. While most of these observation show streaks or other nonuniform illumination, a significant subset are defect free and can be used to construct complete LP-flats. Many of the existing pipeline flats are confirmed to a precision of ~1%, which validates the stellar L-flat technique. Exceptions are the WFC, where a shutter light leak causes a systematic central contamination of a few percent and limits the verification accuracy to ~2%. Other exceptions are the four longest wavelength HRC filters, which show systematic differences with the pipeline flats. This discrepancy is apparently caused by stray light originating from the detector surface, where most of the longest wavelength photons are reflected and then scattered back from nearby focal plane structures. Because this complete set of HRC Earth flats is more appropriate than the pipeline flats for large diffuse objects such as the Moon, Jupiter, or the Orion Nebula, the set is now available on the STScI/ACS website. Earth flats also measure the small and intermediate scale P-flat structure. Due to slight deviations from OTA like illumination in the lab, the flat field corrections in the dust mote regions are 1-2% better with Earth flats. The trend found in ACS ISR 2005-09 for an increase toward the UV for more pixels with non-Poisson statistical distributions is confirmed for the F330W Earth flats, where up to 3% of the pixels are in error by >1%. Most of this newly discovered population of deviant pixels are dark with low responses; however, the effect of these erroneous P-flat values on stellar photometry is less than 0.1%.

  6. Experimental Validation Data for Computational Fluid Dynamics of Forced Convection on a Vertical Flat Plate

    SciTech Connect

    Harris, Jeff R.; Lance, Blake W.; Smith, Barton L.

    2015-08-10

    We present computational fluid dynamics (CFD) validation dataset for turbulent forced convection on a vertical plate. The design of the apparatus is based on recent validation literature and provides a means to simultaneously measure boundary conditions (BCs) and system response quantities (SRQs). Important inflow quantities for Reynolds-Averaged Navier-Stokes (RANS). CFD are also measured. Data are acquired at two heating conditions and cover the range 40,000 < Rex < 300,000, 357 < Reδ2 < 813, and 0.02 < Gr/Re2 < 0.232.

  7. Experimental Validation Data for Computational Fluid Dynamics of Forced Convection on a Vertical Flat Plate

    DOE PAGESBeta

    Harris, Jeff R.; Lance, Blake W.; Smith, Barton L.

    2015-08-10

    We present computational fluid dynamics (CFD) validation dataset for turbulent forced convection on a vertical plate. The design of the apparatus is based on recent validation literature and provides a means to simultaneously measure boundary conditions (BCs) and system response quantities (SRQs). Important inflow quantities for Reynolds-Averaged Navier-Stokes (RANS). CFD are also measured. Data are acquired at two heating conditions and cover the range 40,000 < Rex < 300,000, 357 < Reδ2 < 813, and 0.02 < Gr/Re2 < 0.232.

  8. Spatial patterns of sediment dynamics within a medium-sized watershed over an extreme storm event

    NASA Astrophysics Data System (ADS)

    Gao, Peng; Zhang, Zhirou

    2016-08-01

    In this study, we quantified spatial patterns of sediment dynamics in a watershed of 311 km2 over an extreme storm event using watershed modeling and statistical analyses. First, we calibrated a watershed model, Dynamic Watershed Simulation Model (DWSM) by comparing the predicted with calculated hydrograph and sedigraph at the outlet for this event. Then we predicted values of event runoff volume (V), peak flow (Qpeak), and two types of event sediment yields for lumped morphological units that contain 42 overland elements and 21 channel segments within the study watershed. Two overland elements and the connected channel segment form a first-order subwatershed, several of which constitute a larger nested subwatershed. Next we examined (i) the relationships between these variables and area (A), precipitation (P), mean slope (S), soil erodibility factor, and percent of crop and pasture lands for all overland elements (i.e., the small spatial scale, SSS), and (ii) those between sediment yield, Qpeak, A, P, and event runoff depth (h) for the first-order and nested subwatersheds along two main creeks of the study watershed (i.e., the larger spatial scales, LSS). We found that at the SSS, sediment yield was nonlinearly well related to A and P, but not Qpeak and h; whereas at the LSS, linear relationships between sediment yield and Qpeak existed, so did the Qpeak-A, and Qpeak-P relationships. This linearity suggests the increased connectivity from the SSS to LSS, which was caused by ignorance of channel processes within overland elements. It also implies that sediment was transported at capacity during the extreme event. So controlling sediment supply from the most erodible overland elements may not efficiently reduce the downstream sediment load.

  9. Water and sediment dynamics in a small Mediterranean cultivated catchment under cracking soils

    NASA Astrophysics Data System (ADS)

    Inoubli, Nesrine; Raclot, Damien; Moussa, Roger; Habaieb, Hamadi; Le Bissonnais, Yves

    2016-04-01

    Shrink-swell soils, such as those in a Mediterranean climate regime, can cause changes in terms of hydrological and erosive responses due to the changing soil water storage conditions. Only a limited number of long-term studies have focused on the impacts on both hydrological and erosive responses and their interactions in an agricultural environment. In this context, this study aims to document the dynamics of cracks, runoff and soil erosion within a small Mediterranean cultivated catchment and to quantify the influence of crack processes on the water and sediment supplied to a reservoir located at the catchment outlet. Detailed monitoring of the presence of topsoil cracks was conducted within the Kamech catchment (ORE OMERE, Tunisia), and runoff and suspended sediment loads were continuously measured over a long period of time (2005-2012) at the outlets of a field (1.32 ha) and a catchment (263 ha). Analysis of the data showed that topsoil cracks were open approximately half of the year and that the rainfall regime and water table level conditions locally control the seasonal cracking dynamics. Topsoil cracks appeared to seriously affect the generation of runoff and sediment concentrations and, consequently, sediment yields, with similar dynamics observed at the field and catchment outlets. A similar time lag in the seasonality between water and sediment delivery was observed at these two scales: although the runoff rates were globally low during the presence of topsoil cracks, most sediment transport occurred during this period associated with very high sediment concentrations. This study underlines the importance of a good prediction of runoff during the presence of cracks for reservoir siltation considerations. In this context, the prediction of cracking effects on runoff and soil erosion is a key factor for the development of effective soil and water management strategies and downstream reservoir preservation.

  10. Phosphorus dynamics in lake sediments: Insights from field study and reactive-transport modeling

    NASA Astrophysics Data System (ADS)

    Dittrich, Maria; Markovic, Stefan; Cadena, Sandra; Doan, Phuong T. K.; Watson, Sue; Mugalingam, Shan

    2016-04-01

    Phosphorus is an indispensable nutrient for organisms in aquatic systems and its availability often controls primary productivity. At the sediment-water interface, intensive microbiological, geochemical and physical processes determine the fraction of organic matter, nutrients and pollutants released into the overlying water. Therefore, detailed understanding of the processes occurring in the top centimeters of the sediment is essential for the assessment of water quality and the management of surface waters. In cases where measurements are impossible or expensive, diagenetic modelling is required to investigate the interplay among the processes, verify concepts and predict potential system behavior. The main aims of this study are to identify and predict the dynamics of phosphorus (P) in sediments and gain insight into the mechanism of P release from sediments under varying environmental conditions. We measured redox, O2 and pH profiles with micro-sensors at the sediment-water interface; analyzed phosphate and metals (Fe, Mn, Al, Ca) content in pore waters collected using in situ samplers, so called "peepers"; determined P binding forms using sequential extraction and analyzed metals associated with each fraction. Following the sediment analysis, P binding forms were divided in five groups: inert, carbonate-bound, organic, redox-sensitive, and labile P. Using the flux of organic and inorganic matter as dynamic boundary conditions, the diagenetic model simulates P internal loading and predicts P retention. This presentation will discuss the results of two years studies on P dynamics at the sediment-water interface in three different lakes ranging from heavy-polluted Hamilton Harbor and Bay of Quinte to pristine Georgian Bay in Ontario, Canada.

  11. Better budgeting by redundancy, context, and coupling of coarse and fine sediment dynamics (Invited)

    NASA Astrophysics Data System (ADS)

    Belmont, P.

    2013-12-01

    The core principles of sediment budgeting are simple, involving a careful accounting of sediment sources and sinks over a specified spatial extent and time period. However, a long history of sediment budgeting has shown that such numbers are difficult to constrain due to uncertainty in measurements and immense variability in water and sediment fluxes in time and space. As a result, many budgets compiled at the reach or watershed scales are indeterminate with respect to net erosion or deposition. Further, budgets can be highly sensitive to bias if critical processes or contingencies in the landscape are not considered. Over the past decade many new tools and techniques have been developed that can be used to constrain sediment budgets, including software for analysis of high resolution topography data and imagery, in situ monitoring instrumentation, geochemical fingerprinting and particle tracking devices, and increasingly sophisticated models that describe erosion, transport, and deposition in a physically meaningful way. These approaches have the potential to substantially advance budgeting capabilities by providing multiple, redundant sources of information that must be reconciled within the hard constraint of a mass balance. Each independent source of information can add to the level of certainty with which the budget can inform our understanding of sediment inputs, outputs and net change in storage. However, a key technical challenge lies in developing meaningful estimates of uncertainty for each approach. Once developed, rigorous estimates of uncertainty can serve as scaling factors to close the budget in a transparent and parsimonious manner. More broadly, two key conceptual challenges for the future of sediment budgeting include a) placing the components of the budget into the appropriate landscape context with a focus on identifying critical locations where erosion and deposition processes may be amplified or dampened, and b) linking the dynamics of coarse

  12. Phosphorus Dynamics in Soil, Runoff, and Sediment from Three Management Systems

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Land application of poultry litter can lead to increased phosphorus (P) level in surface runoff and sediment, which in turn, potentially accelerates the eutrophication in the water bodies. The objective of this research was to study the P dynamics in two poultry litter amended soils using three mana...

  13. REMOVAL OF TANK AND SEWER SEDIMENT BY GATE FLUSHING: COMPUTATIONAL FLUID DYNAMICS MODEL STUDIES

    EPA Science Inventory

    This presentation will discuss the application of a computational fluid dynamics 3D flow model to simulate gate flushing for removing tank/sewer sediments. The physical model of the flushing device was a tank fabricated and installed at the head-end of a hydraulic flume. The fl...

  14. Algoriphagus aestuarii sp. nov., a member of the Cyclobacteriaceae isolated from a tidal-flat sediment of the Yellow Sea in Korea.

    PubMed

    Jung, Yong-Taek; Lee, Jung-Sook; Yoon, Jung-Hoon

    2015-10-01

    A Gram-strain-negative, coccoid or oval-shaped, non-motile bacterial strain, designated MDM-1T, was isolated from a tidal-flat sediment on the Korean peninsula. Strain MDM-1T was found to grow optimally at pH 7.0-8.0, at 30 °C and in the presence of 2-3 % (w/v) NaCl. A neighbour-joining phylogenetic tree based on 16S rRNA gene sequences showed that strain MDM-1T falls within the clade comprising species of the genus Algoriphagus, clustering with the type strains of Algoriphagus halophilus, A. lutimaris, A. chungangensis and A. machipongonensis, with which it exhibited 97.2-98.5 % 16S rRNA gene sequence similarity. Sequence similarities to the type strains of the other recognized species of the genus Algoriphagus were 92.8-97.6 %. Strain MDM-1T was found to contain MK-7 as the predominant menaquinone and iso-C15 : 0 and summed feature 3 (C16 : 1ω6c and/or C16 : 1ω7c) as the major fatty acids. The major polar lipids were identified as phosphatidylcholine, phosphatidylethanolamine and two unidentified lipids. The DNA G+C content of strain MDM-1T was determined to be 42.7 mol% and the mean DNA-DNA relatedness with A. halophilus KCTC 12051T, A. lutimaris S1-3T, A. chungangensis KCTC 23759T, A. machipongonensis DSM 24695T and A. ratkowskyi CIP 107452T was 19.7-5.2 %. Differential phenotypic properties, together with the phylogenetic and genetic distinctiveness, revealed that strain MDM-1T is distinguishable from recognized species of the genus Algoriphagus. On the basis of the data presented, strain MDM-1T is proposed to represent a novel species of the genus Algoriphagus, for which the name Algoriphagus aestuarii sp. nov. is proposed. The type strain is MDM-1T ( = KCTC 42199T = NBRC 110552T). PMID:26297134

  15. Nonlinear Dynamics of Biofilm Growth on Sediment Surfaces

    NASA Astrophysics Data System (ADS)

    Molz, F. J.; Murdoch, L. C.; Faybishenko, B.

    2013-12-01

    Bioclogging often begins with the establishment of small colonies (microcolonies), which then form biofilms on the surfaces of a porous medium. These biofilm-porous media surfaces are not simple coatings of single microbes, but complex assemblages of cooperative and competing microbes, interacting with their chemical environment. This leads one to ask: what are the underlying dynamics involved with biofilm growth? To begin answering this question, we have extended the work of Kot et al. (1992, Bull. Mathematical Bio.) from a fully mixed chemostat to an idealized, one-dimensional, biofilm environment, taking into account a simple predator-prey microbial competition, with the prey feeding on a specified food source. With a variable (periodic) food source, Kot et al. (1992) were able to demonstrate chaotic dynamics in the coupled substrate-prey-predator system. Initially, deterministic chaos was thought by many to be mainly a mathematical phenomenon. However, several recent publications (e.g., Becks et al, 2005, Nature Letters; Graham et al. 2007, Int. Soc Microb. Eco. J.; Beninca et al., 2008, Nature Letters; Saleh, 2011, IJBAS) have brought together, using experimental studies and relevant mathematics, a breakthrough discovery that deterministic chaos is present in relatively simple biochemical systems. Two of us (Faybishenko and Molz, 2013, Procedia Environ. Sci)) have numerically analyzed a mathematical model of rhizosphere dynamics (Kravchenko et al., 2004, Microbiology) and detected patterns of nonlinear dynamical interactions supporting evidence of synchronized synergetic oscillations of microbial populations, carbon and oxygen concentrations driven by root exudation into a fully mixed system. In this study, we have extended the application of the Kot et al. model to investigate a spatially-dependent biofilm system. We will present the results of numerical simulations obtained using COMSOL Multi-Physics software, which we used to determine the nature of the

  16. Computational Fluid Dynamics Uncertainty Analysis Applied to Heat Transfer over a Flat Plate

    NASA Technical Reports Server (NTRS)

    Groves, Curtis Edward; Ilie, Marcel; Schallhorn, Paul A.

    2013-01-01

    There have been few discussions on using Computational Fluid Dynamics (CFD) without experimental validation. Pairing experimental data, uncertainty analysis, and analytical predictions provides a comprehensive approach to verification and is the current state of the art. With pressed budgets, collecting experimental data is rare or non-existent. This paper investigates and proposes a method to perform CFD uncertainty analysis only from computational data. The method uses current CFD uncertainty techniques coupled with the Student-T distribution to predict the heat transfer coefficient over a at plate. The inputs to the CFD model are varied from a specified tolerance or bias error and the difference in the results are used to estimate the uncertainty. The variation in each input is ranked from least to greatest to determine the order of importance. The results are compared to heat transfer correlations and conclusions drawn about the feasibility of using CFD without experimental data. The results provide a tactic to analytically estimate the uncertainty in a CFD model when experimental data is unavailable

  17. Sediment dynamics over multiple time scales in Dyke Marsh Preserve (Potomac River, VA)

    NASA Astrophysics Data System (ADS)

    Palinkas, C. M.; Walters, D.

    2010-12-01

    Tidal freshwater marshes are critical components of fluvial and estuarine ecosystems, yet sediment dynamics within them have not received as much attention as their saltwater counterparts. This study examines sedimentation in Dyke Marsh Preserve, located on the Potomac River (VA), focusing on understanding the spatial variability present over multiple time scales. Bimonthly sediment data were collected using ceramic tiles, and seasonal- and decadal-scale sedimentation was determined via 7Be (half-life 53.3 days) and 210Pb (half-life 22.3 years), respectively. Results were also compared to SET data collected by the National Park Service since 2006. Preliminary data indicate that sites at lower elevations have higher sedimentation rates, likely related to their close proximity to the sediment source. Mass accumulation rates generally decreased with increasing time scale, such that the seasonal rates were greater than the SET-derived accretion rates, which were in turn greater than the decadal-scale rates. However, the bimonthly rates were the lowest observed, probably because the sampling period (May-October 2010) did not include the main depositional period of the year, which would be integrated by the other techniques.

  18. Sediment Transport Dynamic in a Meandering Fluvial System: Case Study of Chini River

    NASA Astrophysics Data System (ADS)

    Nazir, M. H. M.; Awang, S.; Shaaban, A. J.; Yahaya, N. K. E. M.; Jusoh, A. M.; Arumugam, M. A. R. M. A.; Ghani, A. A.

    2016-07-01

    Sedimentation in river reduces the flood carrying capacity which lead to the increasing of inundation area in the river basin. Basic sediment transport can predict the fluvial processes in natural rivers and stream through modeling approaches. However, the sediment transport dynamic in a small meandering and low-lying fluvial system is considered scarce in Malaysia. The aim of this study was to analyze the current riverbed erosion and sedimentation scenarios along the Chini River, Pekan, Pahang. The present study revealed that silt and clay has potentially been eroded several parts of the river. Sinuosity index (1.98) indicates that Chini River is very unstable and continuous erosion process in waterways has increase the riverbank instability due to the meandering factors. The riverbed erosional and depositional process in the Chini River is a sluggish process since the lake reduces the flow velocity and causes the deposited particles into the silt and clay soil at the bed of the lake. Besides, the bed layer of the lake comprised of cohesive silt and clayey composition that tend to attach the larger grain size of sediment. The present study estimated the total sediment accumulated along the Chini River is 1.72 ton. The HEC-RAS was employed in the simulations and in general the model performed well, once all parameters were set within their effective ranges.

  19. Sediment dynamics in restored riparian forest with different widths and agricultural surroundings

    NASA Astrophysics Data System (ADS)

    Stucchi Boschi, Raquel; Simões da Silva, Laura; Ribeiro Rodrigues, Ricardo; Cooper, Miguel

    2016-04-01

    The riparian forests are essential to maintaining the quality of water resources, aquifer recharge and biodiversity. Due to the ecological services provided by riparian forests, these areas are considered by the law as Permanent Preservation Areas, being mandatory maintenance and restoration. However, the obligation of restoration and the extent of the Permanent Preservation Areas as defined by the Brazilian Forest Code, based on water body width, elucidates the lack of accurate scientific data on the influence of the size of the riparian forest in maintaining their ecological functions, particularly regarding the retention of sediments. Studies that evaluate the ideal width of riparian forests to guarantee their ecological functions are scarce and not conclusive, especially when we consider newly restored forests, located in agricultural areas. In this study, we investigate the dynamics of erosion and sedimentation in restored riparian forests with different widths situated in agricultural areas. The two study areas are located in a Semideciduous Tropical Forest inserted in sugarcane landscapes of São Paulo state, Brazil. The installed plots had 60 and 100 m in length and the riparian forest has a width of 15, 30 and 50 m. The characteristics of the sediments inside the plots were evaluated by detailed morphological and micromorphological studies as well as physical characterization. The dynamics of deposition and the amount of deposited sediments have been assessed with graded metal stakes partially buried inside the plots. The intensity, frequency and distribution of rainfall, as well as the occurrence of extreme events, have been evaluated by data collected from rain gauges installed in the areas. We expect that smaller widths are not able to retain sediments originated from the adjacent sugarcane areas. We also believe that extreme events are responsible for generating most of the sediments. The results will be important to support the discussion about an

  20. Towards a Holistic Model for Simulating Sediment Dynamics at Watershed Scales: Partitioning of Sediment Sources and Uncertainty Quantification

    NASA Astrophysics Data System (ADS)

    Abban, Benjamin; Papanicolaou, Thanos; Cowles, Kate; Wilson, Christopher; Abaci, Ozan; Wacha, Kenneth

    2016-04-01

    The challenge remains to understand watershed sediment source dynamics for planning and evaluating mitigation measures on anthropogenic activities such as intensive agriculture, which exacerbates soil erosion from the landscape. To this end, our research aims to develop a cross-scale model, capable of simulating sediment transport from the plot scale to the watershed scale while effectively capturing the important feedback effects across the scales. Our approach combines numerical modeling with physical observations and measurements to not only provide a tool capable of mimicking cause and effect relationships, but also capable of quantifying uncertainty related to source dynamics predictions. We present herein a key component of the cross-scale model that quantifies source partitioning and the associated uncertainty. This component is based on a Bayesian un-mixing framework and is particularly useful for watersheds characterized by considerable spatiotemporal heterogeneity. The Bayesian un-mixing framework utilizes two key parameters, namely α and β, that explicitly accounts for spatial origin attributes and the time history of sediments delivered to the watershed outlet, respectively. These parameters are treated probabilistically so as to account for variability in source erosion processes, as well as the delivery times and storage of eroded material within the watershed. The use of Markov Chain Monte Carlo simulations for determining posterior probability density functions in the framework allows uncertainty in source contribution estimates to be quantified naturally as part of the solution process. We demonstrate the utility of the Bayesian un-mixing framework in a predominantly agricultural watershed in the US Midwest known as the Clear Creek Watershed, IA, which is part of the Critical Zone Observatory for Intensively Managed Landscapes (IML-CZO). Stable isotopes of Carbon and Nitrogen are used as tracers since they have been found to be appropriate for

  1. Sediment Dynamics in Shallow Tidal Landscapes: The Role of Wind Waves and Tidal Currents

    NASA Astrophysics Data System (ADS)

    Carniello, L.; D'Alpaos, A.

    2014-12-01

    A precise description of sediment dynamics (resuspension and re-distribution of sediments) is crucial when investigating the long term evolution of the different morphological entities characterizing tidal landscapes. It has been demonstrated that wind waves are the main responsible for sediment resuspension in shallow micro-tidal lagoons where tidal currents, which produce shear stresses large enough to carry sediments into suspension only within the main channels, are mainly responsible for sediment redistribution. A mathematical model has been developed to describe sediment entrainment, transport and deposition due to the combined effect of tidal currents and wind waves in shallow lagoons considering both cohesive and non-cohesive sediments. The model was calibrated and tested using both in situ point observations and turbidity maps obtained analyzing satellite images. Once calibrated the model can integrate the high temporal resolution of point observations with the high spatial resolution of remote sensing, overcoming the intrinsic limitation of these two types of observations. The model was applied to the specific test case of the Venice lagoon simulating an entire year (2005) which was shown to be a "representative" year for wind and tide characteristics. The time evolution of the computed total bottom shear stresses (BSS) and suspended sediment concentration (SSC) was analyzed on the basis of a "Peaks Over Threshold" method once a critical value for shear stress and turbidity were chosen. The analyses of the numerical results enabled us to demonstrate that resuspension events can be modeled as marked Poisson processes: interarrival time, intensity of peak excesses and duration being exponentially distributed random variable. The probability distributions of the interarrival time of overthreshold exceedances in both BSS and SSC as well as their intensity and duration can be used in long-term morphodynamic studies to generate synthetic series statistically

  2. Headwater sediment dynamics in a debris flow catchment constrained by high-resolution topographic surveys

    NASA Astrophysics Data System (ADS)

    Loye, Alexandre; Jaboyedoff, Michel; Theule, Joshua Isaac; Liébault, Frédéric

    2016-06-01

    Debris flows have been recognized to be linked to the amounts of material temporarily stored in torrent channels. Hence, sediment supply and storage changes from low-order channels of the Manival catchment, a small tributary valley with an active torrent system located exclusively in sedimentary rocks of the Chartreuse Massif (French Alps), were surveyed periodically for 16 months using terrestrial laser scanning (TLS) to study the coupling between sediment dynamics and torrent responses in terms of debris flow events, which occurred twice during the monitoring period. Sediment transfer in the main torrent was monitored with cross-section surveys. Sediment budgets were generated seasonally using sequential TLS data differencing and morphological extrapolations. Debris production depends strongly on rockfall occurring during the winter-early spring season, following a power law distribution for volumes of rockfall events above 0.1 m3, while hillslope sediment reworking dominates debris recharge in spring and autumn, which shows effective hillslope-channel coupling. The occurrence of both debris flow events that occurred during the monitoring was linked to recharge from previous debris pulses coming from the hillside and from bedload transfer. Headwater debris sources display an ambiguous behaviour in sediment transfer: low geomorphic activity occurred in the production zone, despite rainstorms inducing debris flows in the torrent; still, a general reactivation of sediment transport in headwater channels was observed in autumn without new debris supply, suggesting that the stored debris was not exhausted. The seasonal cycle of sediment yield seems to depend not only on debris supply and runoff (flow capacity) but also on geomorphic conditions that destabilize remnant debris stocks. This study shows that monitoring the changes within a torrent's in-channel storage and its debris supply can improve knowledge on recharge thresholds leading to debris flow.

  3. Sediment Dynamics and Southern Steelhead Habitat (Oncorhynchus mykiss) in the Matilija Creek Watershed, Southern California

    NASA Astrophysics Data System (ADS)

    Minear, J. T.; Kondolf, G. M.

    2003-12-01

    Matilija Creek, one of two principal forks of the Ventura River, drains 142 km2 in the Transverse Ranges of southern California. Thanks to rapid tectonic uplift and weak clastic rocks, sediment yields exceed 1200 m3/km2 annually. Matilija Dam was built in 1947 with an initial capacity of 8 million m3 and is now nearly full of sediment. The dam is structurally unsafe, blocks anadromous fish migration, and is being considered for removal. The Ventura River has one of the southernmost runs of steelhead trout (Oncorhynchus mykiss), with an average of approximately 2,500 annually migrating up Matilija Creek before the dam was built. The high sediment yields and highly variable flow regime have raised questions about the interactions among high flows, sediment transfer from lower order tributaries to the third order channels used by the fish, and fish life history. Previous studies in Southern California have documented sediment yields (especially following debris flows and fires, and mostly in the San Gabriel Mountains), but the interaction of geomorphic processes and aquatic habitat in this highly episodic environment is not well understood. We used a combination of mapping and survey techniques, sediment traps, grain size analysis, lithologic analysis and scour rods to study intra-annual geomorphic processes and sediment dynamics affecting Southern Steelhead habitat in the Matilija Creek area in 16 study pools over the 2002 and 2003 flow seasons (dry and "normal", respectively) and found little sediment was deposited or scoured from pools. However, other processes not previously recognized significantly affected the steelhead habitat in the study pools including tufa cementation (carbonate deposition) and alder root growth in spawning gravels, as well as seasonal desiccation of some reaches. Removal of Matilija Dam will reopen suitable habitat to steelhead trout, but managers should recognize that habitat quality is likely to vary considerably from year

  4. Denoising and artefact reduction in dynamic flat detector CT perfusion imaging using high speed acquisition: first experimental and clinical results.

    PubMed

    Manhart, Michael T; Aichert, André; Struffert, Tobias; Deuerling-Zheng, Yu; Kowarschik, Markus; Maier, Andreas K; Hornegger, Joachim; Doerfler, Arnd

    2014-08-21

    Flat detector CT perfusion (FD-CTP) is a novel technique using C-arm angiography systems for interventional dynamic tissue perfusion measurement with high potential benefits for catheter-guided treatment of stroke. However, FD-CTP is challenging since C-arms rotate slower than conventional CT systems. Furthermore, noise and artefacts affect the measurement of contrast agent flow in tissue. Recent robotic C-arms are able to use high speed protocols (HSP), which allow sampling of the contrast agent flow with improved temporal resolution. However, low angular sampling of projection images leads to streak artefacts, which are translated to the perfusion maps. We recently introduced the FDK-JBF denoising technique based on Feldkamp (FDK) reconstruction followed by joint bilateral filtering (JBF). As this edge-preserving noise reduction preserves streak artefacts, an empirical streak reduction (SR) technique is presented in this work. The SR method exploits spatial and temporal information in the form of total variation and time-curve analysis to detect and remove streaks. The novel approach is evaluated in a numerical brain phantom and a patient study. An improved noise and artefact reduction compared to existing post-processing methods and faster computation speed compared to an algebraic reconstruction method are achieved. PMID:25069101

  5. Denoising and artefact reduction in dynamic flat detector CT perfusion imaging using high speed acquisition: first experimental and clinical results

    NASA Astrophysics Data System (ADS)

    Manhart, Michael T.; Aichert, André; Struffert, Tobias; Deuerling-Zheng, Yu; Kowarschik, Markus; Maier, Andreas K.; Hornegger, Joachim; Doerfler, Arnd

    2014-08-01

    Flat detector CT perfusion (FD-CTP) is a novel technique using C-arm angiography systems for interventional dynamic tissue perfusion measurement with high potential benefits for catheter-guided treatment of stroke. However, FD-CTP is challenging since C-arms rotate slower than conventional CT systems. Furthermore, noise and artefacts affect the measurement of contrast agent flow in tissue. Recent robotic C-arms are able to use high speed protocols (HSP), which allow sampling of the contrast agent flow with improved temporal resolution. However, low angular sampling of projection images leads to streak artefacts, which are translated to the perfusion maps. We recently introduced the FDK-JBF denoising technique based on Feldkamp (FDK) reconstruction followed by joint bilateral filtering (JBF). As this edge-preserving noise reduction preserves streak artefacts, an empirical streak reduction (SR) technique is presented in this work. The SR method exploits spatial and temporal information in the form of total variation and time-curve analysis to detect and remove streaks. The novel approach is evaluated in a numerical brain phantom and a patient study. An improved noise and artefact reduction compared to existing post-processing methods and faster computation speed compared to an algebraic reconstruction method are achieved.

  6. Human impact on late-Holocene hillslope and fluvial sediment dynamics: a field and modeling approach

    NASA Astrophysics Data System (ADS)

    Verstraeten, Gert; Notebaert, Bastiaan; Dusar, Bert; Peeters, Iris; Govers, Gerard; van Rompaey, Anton; Poesen, Jean; Lang, Andreas

    2010-05-01

    The human impact on sediment fluxes is evidenced by numerous integrated field studies. Most of these studies, however, remain qualitative and site-specific, leaving several questions on landscape response unresolved. How intense is the landscape response to human impact compared to the response to natural environmental change ? When did humans took over control and to what extent ? What is the importance of internal catchment dynamics in regulating sediment fluxes ? How do human and natural induced environmental change interact ? Detailed field-based approaches have recently been made for several areas that now provide partial answers to several of these questions. These include time-differentiated catchment sediment budgets, catchment-wide analysis of historic sedimentation rates and cumulative density functions of colluvial and alluvial activity. However, the poor temporal resolution of the sedimentary record makes it in most cases impossible to decipher e.g. the impact of short-lasting climatic events. Spatial modelling techniques could provide a means for estimating the impact of past (and future) environmental change on hillslope and fluvial sediment dynamics. But which model approach needs to be used ? Which variables and process-interactions need to be included ? Here, we present results from the application of the geomorphic WATEM/SEDEM model on two contrasting environments in Belgium and SW Turkey. For the Dijle catchment (Loess Belt, Belgium), this model was combined with a climate reconstruction model and a spatially distributed land use model driven by historical and archaeological data. Model results match the history of sediment dynamics as evidenced by the time-differentiated sediment budget very well. Moreover, the model approach made it possible to estimate the relative importance of human and climatic impact on the Holocene sediment dynamics. Compared to the mid-Holocene time period, human induced land use change increased sediment fluxes by 6000

  7. The symbiotic relationship of sediment and biofilm dynamics at the sediment water interface of oil sands industrial tailings ponds.

    PubMed

    Reid, T; VanMensel, D; Droppo, I G; Weisener, C G

    2016-09-01

    Within the oil sands industry, tailings ponds are used as a means of retaining tailings until a reclamation technology such as end pit lakes (EPLs) can be developed and optimized to remediate such tailings with a water cap (although dry-land strategies for tailing reclamation are also being developed). EPLs have proven successful for other mining ventures (e.g. metal rock mines) in eventually mitigating contaminant loads to receiving waters once biochemical remediation has taken place (although the duration for this to occur may be decades). While the biological interactions at the sediment water interface of tailings ponds or EPLs have been shown to control biogeochemical processes (i.e. chemical fluxes and redox profiles), these have often been limited to static microcosm conditions. Results from such experiments may not tell the whole story given that the sediment water interface often represents a dynamic environment where erosion and deposition may be occurring in association with microbial growth and decay. Mobilization of sediments and associated contaminants may therefore have a profound effect on remediation rates and, as such, may decrease the effectiveness of EPLs as viable reclamation strategies for mining industries. Using a novel core erosion system (U-GEMS), this paper examines how the microbial community can influence sediment water interface stability and how the biofilm community may change with tailings age and after disturbance (biofilm reestablishment). Shear strength, eroded mass measurements, density gradients, high-resolution microscopy, and microbial community analyses were made on 2 different aged tailings (fresh and ∼38 years) under biotic and abiotic conditions. The same experiments were repeated as duplicates with both sets of experiments having consolidation/biostabilization periods of 21 days. Results suggest that the stability of the tailings varies between types and conditions with the fresh biotic tailings experiencing up to 75

  8. Investigating suspended sediment dynamics in contrasting agricultural catchments using ex situ turbidity-based suspended sediment monitoring

    NASA Astrophysics Data System (ADS)

    Sherriff, S. C.; Rowan, J. S.; Melland, A. R.; Jordan, P.; Fenton, O.; hUallachain, D. O.

    2015-08-01

    Soil erosion and suspended sediment (SS) pose risks to chemical and ecological water quality. Agricultural activities may accelerate erosional fluxes from bare, poached or compacted soils, and enhance connectivity through modified channels and artificial drainage networks. Storm-event fluxes dominate SS transport in agricultural catchments; therefore, high temporal-resolution monitoring approaches are required, but can be expensive and technically challenging. Here, the performance of in situ turbidity sensors, conventionally installed submerged at the river bankside, is compared with installations where river water is delivered to sensors ex situ, i.e. within instrument kiosks on the riverbank, at two experimental catchments (Grassland B and Arable B). The in situ and ex situ installations gave comparable results when calibrated against storm-period, depth-integrated SS data, with total loads at Grassland B estimated at 12 800 and 15 400 t, and 22 600 and 24 900 t at Arable B, respectively. The absence of spurious turbidity readings relating to bankside debris around the in situ sensor and its greater security make the ex situ sensor more robust. The ex situ approach was then used to characterise SS dynamics and fluxes in five intensively managed agricultural catchments in Ireland which feature a range of landscape characteristics and land use pressures. Average annual suspended sediment concentration (SSC) was below the Freshwater Fish Directive (78/659/EEC) guideline of 25 mg L-1, and the continuous hourly record demonstrated that exceedance occurred less than 12 % of the observation year. Soil drainage class and proportion of arable land were key controls determining flux rates, but all catchments reported a high degree of inter-annual variability associated with variable precipitation patterns compared to the long-term average. Poorly drained soils had greater sensitivity to runoff and soil erosion, particularly in catchments with periods of bare soils. Well

  9. Sedimentation dynamics of disks in a linearly stratified fluid

    NASA Astrophysics Data System (ADS)

    Mercier, Matthieu; Pemeja, Justin; Ern, Patricia

    2014-11-01

    The settling dynamics of small objects in a stratified fluid is important to understand the fate of the biomass in lakes or oceanic environments, for industrial applications such as waste-water disposal for instance. Recent numerical and theoretical studies dedicated to freely falling (or rising) bodies in stratified environments have shown some important differences compared to the same problem in a homogeneous fluid. Experimental results are still needed for validation, especially at low and moderate values of the Reynolds number, Re = Ud / ν <= 100 , with U the instantaneous vertical velocity of the object, d its characteristic length, and ν the kinematic velocity of the fluid. We present original experimental results of freely falling disks of finite thickness in a linearly stratified fluid. Three-dimensional trajectories and the wake of the object are obtained using a pair of cameras visualizing two perpendicular planes, revealing a strong influence of the stratification on the dynamics of the object. In particular, the stratification enhances the steady drag experienced by the disks when falling broadside; and generates a change of stability for the disk orientation (from horizontal to vertical) when the Re number decreases below a threshold value.

  10. Sediment Dynamics in the Upper McKenzie River Basin, Central Oregon Cascade Range

    NASA Astrophysics Data System (ADS)

    Stallman, J. D.; Bowers, R. J.; Cabrera, N. C.; Real de Asua, R.; Wooster, J. K.

    2005-12-01

    Reference and current sediment budgets were developed to evaluate the extent to which hydroelectric dams alter sediment dynamics in the upper McKenzie River basin of central Oregon. The 647 km2 study area straddles the western boundary of the High Cascades graben separating the High Cascades and Western Cascades geologic terrains. Permeable Quaternary volcanics forming the low-gradient High Cascades plateau promote surface hydrologic disconnection, nearly constant discharge controlled by groundwater emergence, and low sediment yield. In contrast, deeply weathered Tertiary volcanics, rugged topography, and a dense network of steep channels in the Western Cascades terrain promote peaked storm responses and high sediment yield by deep-seated mass movement, debris slides, and debris flows. Three independent estimates of sediment yield (application of published surface process rates, extrapolation of regional suspended load and bedload flux rates, and extrapolation of reservoir sedimentation rates) illustrate the dominant role of geologic terrains in determining the longitudinal pattern of sediment supply to the McKenzie River. Average reference yields from High Cascades and Western Cascades sources were 9 t km-2y-1 and 200 t km-2y-1, respectively. Downstream of Trail Bridge Dam, High Cascades sources (241 km2) account for 12% of the total reference yield, while Western Cascades sources (67 km2) account for 62%. Estimates of current sediment yield illustrate the offsetting effects of reservoir sediment trapping and accelerated yield related to forest management. Average current yields from High Cascades and Western Cascades sources were 17 t km-2y-1 and 300 t km-2y-1, respectively. Current yield to the McKenzie River arm of Trail Bridge Reservoir (42 km2 sourced in High Cascades terrain) was 17 t km-2y-1, while current yield to Smith Reservoir (48 km2 sourced in Western Cascades terrain) was 251 t km-2y-1. The relation between hydroelectric project effects and forest

  11. Measurement of Large-Scale Sediment Transport Dynamics Using Multibeam Sonar

    NASA Astrophysics Data System (ADS)

    Simmons, S. M.; Parsons, D. R.; Best, J. L.; Malzone, C.; Keevil, G.

    2007-12-01

    Multibeam Echo-Sounder (MBES) sonar systems have developed rapidly over recent decades and are now routinely deployed to provide high-resolution object detection and bathymetric surveying in a range of aquatic environments, from the deep-sea to lakes and rivers. MBES systems were developed for bottom-detection and measurement of bed morphology, and have previously discarded the received acoustic back-scatter from the water column after the bottom-detection algorithms have been performed. However, modern data handling and storage technologies have facilitated the logging of this large quantity of acoustic intensity and phase information, and commercial MBES systems are now available that provide this capability. This paper develops a novel methodology to exploit this logging capability to quantify the concentration and dynamics of suspended sediment within the water column. This development provides a multi-purpose tool for the holistic surveying of sediment transport by imaging suspended sediment concentration, associated coherent flow structures and providing concurrent high-resolution bathymetry. This paper presents methods of data analysis and results obtained from deployment of the RESON SeaBat 8125 and 7125 MBES systems in the field and during testing in a controlled environment. The field results were obtained from sites on the Paraná river, Argentina, with the aim of examining the dynamics of suspended sediment transport over dune bedforms and in the region of flow mixing between large rivers of significantly different suspended sediment concentration. Controlled testing was performed in a former ship dry-dock by creating flows density currents of known suspended sediment concentration with different types and mixes of sediment. The results demonstrate the capability of the RESON MBES systems to successfully resolve the contrast in suspended sediment concentration, and hence the spatio-temporal monitoring of the associated coherent flow structures. The

  12. Modelling the effects of Zostera noltei meadows on sediment dynamics: application to the Arcachon lagoon

    NASA Astrophysics Data System (ADS)

    Kombiadou, Katerina; Ganthy, Florian; Verney, Romaric; Plus, Martin; Sottolichio, Aldo

    2014-10-01

    A three-dimensional model has been modified to describe the complex interactions between hydrodynamics, sediment dynamics and biological parameters in the presence of Zostera noltei. The model treats seagrass leafs as flexible blades that bend under hydrodynamic forcing and alter the local momentum and turbulence fluxes and, therefore, the benthic shear conditions; these changes cause related changes to the mass balance at the boundary of the bed, in turn affecting the suspended matter in the column and ultimately primary productivity and the growth of the dwarf-grass. Modelling parameters related to the impact of Z. noltei to the local flow and to erosion and deposition rates were calibrated using flume experimental measurements; results from the calibration of the model are presented and discussed. The coupled model is applied in the Arcachon Bay, an area with high environmental significance and large abundance of dwarf-grass meadows. In the present paper, results from preliminary applications of the model are presented and discussed; the effectiveness of the coupled model is assessed comparing modelling results with available field measurements of suspended sediment concentrations and seagrass growth parameters. The model generally reproduces sediment dynamics and dwarf-grass seasonal growth in the domain efficiently. Investigations regarding the effects of the vegetation to the near-bed hydrodynamics and to the sediment suspension in the domain show that dwarf-grass meadows play an important part to velocity attenuation and to sediment stabilisation, with flow and suspended sediment concentrations damping, compared to an unvegetated state, to reach 35-50 and 65 %, respectively, at peak seagrass growth.

  13. The dynamics of fine-grain sediment dredged from Santa Cruz Harbor

    USGS Publications Warehouse

    Storlazzi, Curt D.; Conaway, Christopher H.; Presto, M. Katherine; Logan, Joshua B.; Cronin, Katherine; van Ormondt, Maarten; Lescinski, Jamie; Harden, E. Lynne; Lacy, Jessica R.; Tonnon, Pieter K.

    2011-01-01

    In the fall and early winter of 2009, a demonstration project was done at Santa Cruz Harbor, California, to determine if 450 m3/day of predominantly (71 percent) mud-sized sediment could be dredged from the inner portion of the harbor and discharged to the coastal ocean without significant impacts to the beach and inner shelf. During the project, more than 7600 m3 of sediment (~5400 m3 of fine-grain material) was dredged during 17 days and discharged approximately 60 m offshore of the harbor at a depth of 2 m on the inner shelf. The U.S. Geological Survey's Pacific Coastal and Marine Science Center was funded by the U.S. Army Corps of Engineers and the Santa Cruz Port District to do an integrated mapping and process study to investigate the fate of the mud-sized sediment dredged from the inner portion of Santa Cruz Harbor and to determine if any of the fine-grain material settled out on the shoreline and/or inner shelf during the fall and early winter of 2009. This was done by collecting highresolution oceanographic and sediment geochemical measurements along the shoreline and on the continental shelf of northern Monterey Bay to monitor the fine-grain sediment dredged from Santa Cruz Harbor and discharged onto the inner shelf. These in place measurements, in conjunction with beach, water column, and seabed surveys, were used as boundary and calibration information for a three-dimensional numerical circulation and sediment dynamics model to better understand the fate of the fine-grain sediment dredged from Santa Cruz Harbor and the potential consequences of disposing this type of material on the beach and on the northern Monterey Bay continental shelf.

  14. Spatio-temporal patterns of soil erosion and suspended sediment dynamics in the Mekong River Basin.

    PubMed

    Suif, Zuliziana; Fleifle, Amr; Yoshimura, Chihiro; Saavedra, Oliver

    2016-10-15

    Understanding of the distribution patterns of sediment erosion, concentration and transport in river basins is critically important as sediment plays a major role in river basin hydrophysical and ecological processes. In this study, we proposed an integrated framework for the assessment of sediment dynamics, including soil erosion (SE), suspended sediment load (SSL) and suspended sediment concentration (SSC), and applied this framework to the Mekong River Basin. The Revised Universal Soil Loss Equation (RUSLE) model was adopted with a geographic information system to assess SE and was coupled with a sediment accumulation and a routing scheme to simulate SSL. This framework also analyzed Landsat imagery captured between 1987 and 2000 together with ground observations to interpolate spatio-temporal patterns of SSC. The simulated SSL results from 1987 to 2000 showed the relative root mean square error of 41% and coefficient of determination (R(2)) of 0.89. The polynomial relationship of the near infrared exoatmospheric reflectance and the band 4 wavelength (760-900nm) to the observed SSC at 9 sites demonstrated the good agreement (overall relative RMSE=5.2%, R(2)=0.87). The result found that the severe SE occurs in the upper (China and Lao PDR) and lower (western part of Vietnam) regions. The SSC in the rainy season (June-November) showed increasing and decreasing trends longitudinally in the upper (China and Lao PDR) and lower regions (Cambodia), respectively, while the longitudinal profile of SSL showed a fluctuating trend along the river in the early rainy season. Overall, the results described the unique spatio-temporal patterns of SE, SSL and SSC in the Mekong River Basin. Thus, the proposed integrated framework is useful for elucidating complex process of sediment generation and transport in the land and river systems of large river basins. PMID:27338846

  15. Sediment dynamics and heavy metal pollution history of the Cruhlig Lake (Danube Delta, Romania).

    PubMed

    Begy, Róbert-Csaba; Preoteasa, Luminita; Timar-Gabor, Alida; Mihăiescu, Radu; Tănăselia, Claudiu; Kelemen, Szabolcs; Simon, Hedvig

    2016-03-01

    This is the first study reporting recent sedimentation rates data (e.g. the past 120-150 years) for the Cruhlig Lake situated in the Danube Delta. The aim of this study is to analyse the recent sedimentation rates using the (210)Pb dating method and identifying the heavy metal pollutants and their variability in time. Five sediment cores were taken with a gravity corer and - after drying the sliced samples-physical parameters, organic material and inorganic carbon content were determined. The total (210)Pb content was measured via (210)Po by alpha spectrometry, while supported (210)Pb was measured by (226)Ra (trough short life (222)Rn daughters) with HPGe detectors. Heavy metals were determined by ICP-MS; from the 64 measured elements, only exceeding values of Al, As, Cd, Co, Cs, Cr, Cu, Fe, Hg, K, Li, Mg, Mn, Ni, Pb and Zn are discussed. After applying the CRS model, ages and sedimentation rates were calculated. The average sedimentation rate of the Cruhlig Lake is 0.21 ± 0.02 g/cm(2)y, Minimum values (0.05 ± 0.003 g/cm(2)y) are registered along the eastern shoreline of the lake before 1913, while maximum values are recorded due to the flooding in 2006 in the western side (1.34 ± 0.12 g/cm(2)y). Recent sedimentation rates divide the lake into three areas: the secluded eastern near shore part (0.63 ± 0.07 g/cm(2)y), the centre of the lake (0.92 ± 0.05 g/cm(2)y) and the dynamic western area, where most sediment transport takes place (1.13 ± 0.01 g/cm(2)y). The sedimentation pattern proves this lake to be very sensitive to fluvial discharge fluctuations. The building of the Iron Gate dams (1972 and 1985) had a negative impact on the sedimentation decreasing it with 58.74%, while after 1989 these values grew 2.25 times. The lake received a quantity of sediment rich in heavy metals in 1992 ± 3 y, which settled mostly on the eastern part. Values for Cd, Co, Cr, Hg, Pb and Zn are up to five times higher in 1980 ± 5 y in the eastern part of the lake, while Cd, Co

  16. Sediment Dynamics of Vengulra-Aravli beach, Central West Coast, India

    NASA Astrophysics Data System (ADS)

    Hanamgond, P.

    2009-04-01

    The beaches are by far the most widely distributed of any of the coastal sedimentary environments. A great many factors are involved in providing sediment for accumulation and development of the beach. The sediment at most places is locally derived, however it can travel and could have traveled long distances shaping the beaches over different season/annual cycles. The granulometric analysis of sediments has long been oriented towards finding environment diagnostic descriptors of grain size distributions (McLaren, 1981) using either the Friedman's (1961, 1967 and 1979) moment method or more commonly the Folk and Ward's (1957) graphic method. It is understood that, the grain size analysis is one of the important tools to delineate littoral drift. The assessment or understanding of this littoral drift and the littoral drift data help to assist in many developmental schemes such as- the harbor development, recreation, tourism development, location of sand traps, growth of coastal bars/spits beach starvation and associated erosion, coastal protection, navigation and so on. In the present study, the sedimnt dynamics of Vengurla-Aravli stretch of beach has been undertaken using the four seasons (Premonsoon, Monsoon & Postmonsoon 2003; and Premonsoon 2004), grain size data alongwith the supporting data on longshore currents and wave parameters collected at 14 study sites. The sediment samples were collected across the beach at every 10 m interval. The study highlights textural variation, sediment movement across and along the beach, energy condition and overall depositional environment of the study area.

  17. Fine-grained suspended sediment dynamics in the Eel River flood plume

    NASA Astrophysics Data System (ADS)

    Curran, Kristian J.; Hill, Paul S.; Milligan, Timothy G.

    2002-11-01

    Small rivers (drainage basins <10 4 km2) discharging runoff from mountainous terrain are major contributors of mud to the marine environment. However, little understanding of the dispersal mechanisms and fate of discharged fine-grained sediments to the continental shelf is known due to the episodic and unpredictable nature of discharge from these rivers. This study used a helicopter-based sampling program to capture unprecedented measures of Eel River, northern California, flood plume events during 1997, 1998, and 1999. In situ measures of floc size and estimated floc fraction show no relationship with concentration, turbulent-kinetic-energy, time from river mouth, wind speed, wave height, or discharge. A relationship apparently does exist between effective settling velocity (bulk mean settling velocity) of plume sediments and wind speed/direction, as well as with tides. Results implicate the energetic nearshore as a source of suspended sediment resupply to the offshore region of the plume. Future studies focusing on surf zone suspended fine-grained sediment dynamics are needed in order to understand the fate of flood plume sediments discharged to exposed, energetic shelves, such as the Eel River margin.

  18. Surface sediment dynamics along the shore of Hammamet Gulf (Tunisia, southern Mediterranean)

    NASA Astrophysics Data System (ADS)

    Atoui, Abdelfattah; Brahim, Mouldi; Sammari, Chérif; Aleya, Lotfi

    2016-09-01

    In the summer of 2015 the authors analysed grain size and surface sediment composition through high spatial resolution from samples taken at 53 stations along the Hammamet coast (southern Mediterranean Sea). The Acoustic Doppler Current Profiler deployed in this study showed that the surface current flows toward the north-east, parallel to the coast at a maximum speed along the main axis of about 5.9 cm s-1. Near the bottom the current flows toward the north-west at a maximum speed of 2.2 cm s-1. The tide plays a relatively small role in water circulation in Hammamet Gulf. Spatial distribution of particle size, along with speed and current direction analysis, furnish an overview of the gulf's sediment dynamics and transport. The sands are categorised as moderately sorted, well sorted or very well sorted. Particle size distribution of surface sediments from the coast to a depth of 25 m offshore shows a decreasing trend in the offshore direction. Mineralogical analysis shows that Hammamet's coastal sands are composed of two main minerals: quartz and calcite. Magnesium calcite and aragonite are present in small amounts. Sediment dynamics along the Hammamet Gulf shores are complex, being subject to the effect of swells and secondarily of tides. We encourage the implementation of responsible environmental management procedures in order to help preserve the site.

  19. DENITRIFICATION AND NITROGEN DYNAMICS IN SEDIMENTS OF A MID-ATLANTIC INCISED STREAM DEPOSITED WITH DEEP LEGACY SEDIMENTS.

    EPA Science Inventory

    Excess legacy sediments deposited in former impounded streams frequently bury Holocene pre-settlement wetlands, decrease in-situ nitrogen removal, and increase nitrogen transport downstream, particularly where deep incised channels limit sediment-water interactions. This has prom...

  20. Future sediment dynamics in the Mekong Delta floodplains: Impacts of hydropower development, climate change and sea level rise

    NASA Astrophysics Data System (ADS)

    Manh, Nguyen Van; Dung, Nguyen Viet; Hung, Nguyen Nghia; Kummu, Matti; Merz, Bruno; Apel, Heiko

    2015-04-01

    The Mekong Delta is under threat due to human activities that are endangering livelihood of millions of people. Hydropower development, climate change and the combined effects of sea level rise and deltaic subsidence are the main drivers impacting future flow regimes and sedimentation patterns in the Mekong Delta. We develop a sensitivity-based approach to assess the response of the floodplain hydrology and sediment dynamics in the delta to these drivers. A quasi-2D hydrodynamic model of suspended sediment dynamics is used to simulate the sediment transport and sediment deposition in the delta, including Tonle Sap Lake, for a baseline (2000-2010) and a future (2050-2060) period. For each driver we derive a plausible range of future states and discretize it into different levels, resulting in 216 combinations. Our results thus cover all plausible future pathways of sediment dynamics in the delta based on current knowledge. Our results indicate that hydropower development dominates the changes in floodplain sediment dynamics of the Mekong Delta, while sea level rise has the smallest effect. The floodplains of the Vietnamese Mekong Delta are much more sensitive to the changes compared to the other subsystems of the delta. The median changes of the three drivers combined indicate that the inundation extent would increase slightly, but the overall floodplain sedimentation would decrease by approximately 40%, and the sediment load to the South China Sea would diminish to half of the current rates. The maximum changes in all drivers would mean a nearly 90% reduction of delta sedimentation and a 95% reduction of the sediment reaching the sea. Our findings provide new and valuable information on the possible future development of floodplain hydraulics and sedimentation in the Mekong Delta and identify the areas that are most vulnerable to these changes.

  1. Effect of secondary particles on image quality of dynamic flat panels in carbon ion scanning beam treatment

    PubMed Central

    Amano, S; Furukawa, T; Shirai, T; Noda, K

    2015-01-01

    Objective: Real-time markerless tumour tracking using radiographic fluoroscopic imaging is one of the better solutions to improving respiratory-gated radiotherapy. However, particle beams cause secondary particles from patients, which could affect radiographs. Here, we evaluated the quality of radiographs during carbon ion pencil beam scanning (CPBS) irradiation for respiratory gating. Methods: A water phantom and chest phantom were used. The phantoms were irradiated with CPBS at 290 MeV n−1 from orthogonal directions. Dose rates were 3.4 × 108, 1.14 × 108 and 3.79 × 107 particles per second. A dynamic flat panel detector (DFPD) was installed on the upstream (DFPD1) or downstream (DFPD2) side of the vertical irradiation port. DFPD images were acquired during CPBS at 15.00, 7.50 and 3.75 frames per second (fps). Charge on the DFPD was cleaned using fast readout technique every 30 fps. DFPD images were acquired during CPBS with radiographic exposure, and results with and without fast readout technique were compared. Results: Secondary particles were visualized as spots or streak-like shapes. Capture of secondary particles from the horizontal beam direction was lower with fast readout technique than without it. With regard to beam irradiation direction dependency, CPBS from the horizontal direction resulted in a greater magnitude of secondary particles reaching DFPD2 than reaching DFPD1. When CPBS was delivered from the vertical direction, however, the magnitude of secondary particles on both DFPDs was very similar. Conclusion: Fast readout technique minimized the effect of secondary particles on DFPD images during CPBS. Advances in knowledge: This technique may be useful for markerless tumour tracking for respiratory gating. PMID:25536444

  2. Oxygen dynamics in periphyton communities and associated effects on phosphorus release from lake sediments

    SciTech Connect

    Carlton, R.G.

    1986-01-01

    Periphyton is typically a heterogeneous assemblage of filamentous and single celled photoautotrophic and heterotrophic micoorganisms suspended in a mucopolysaccharide matrix which they produce. By definition, the assemblage is attached to a substratum such as rock, sediment, or plant in an aquatic environment. Microtechniques with high spatial and temporal resolution are required to define metabolic interactions among the heterotrophic and autotrophic constituents, and between periphyton and its environment. This study used oxygen sensitive microelectrodes with tip diameters of < 30 m to investigate the effects of photosynthesis and respiration on the oxygen dynamics of several diverse periphyton communities both in situ and in laboratory microcosms. A novel flow-through system that utilized TSP radiotracer and that permitted manipulation of the velocity, flushing rate, and oxygen concentration of overlying water was developed to investigate the role of photosynthetic oxygen production on the phosphorus dynamics in lake sediments colonized by epipelic periphyton. 89 refs., 20 figs.

  3. Suspended Sediment Transport Dynamics and Sediment Yields in Relation to Watershed Characteristics, Upper Green River Basin, Kentucky

    NASA Astrophysics Data System (ADS)

    Otoo, J.; Kentworthy, S.; Florea, L.; May, M.; Meier, Q.; Hollon, C.

    2008-12-01

    Sediment delivery is a major problem in the Green River, Kentucky, home of 71 of the state's 103 known mussel species and 151 fish species. The river also provides water for many of its surrounding counties. This research focuses on how suspended sediment loads, grain size, and the temporal co-variation of flow rate and sediment concentration during runoff events are related to watershed characteristics. The link between sediment load and watershed characteristics can help in the planning and development of effective strategies to minimize sediment load and suspended sediment concentration in the Green River, thereby improving the water quality of the river. The primary research objectives were on suspended sediment loads from two watersheds namely: Pitman Creek and Brush Creek in the Upper Green River Basin. Water quality was monitored using data sondes positioned at selected sites in the two watersheds. Water samples were collected and analyzed for concentrations of suspended sediments. The suspended sediments data was then linked to watershed characteristics to determine what factors affect or influence suspended sediment concentration in the Upper Green River Basin. Thus, the research reveals the relationships between suspended sediment loads, grain size, flow rate and the watershed characteristics of interest. We will present hydrologic monitoring results combined with field investigations which indicate that suspended sediment in the Green River is affected by an discharge, relief, geology, watershed area, landuse, and cover conditions.

  4. Long-term agricultural non-point source pollution loading dynamics and correlation with outlet sediment geochemistry

    NASA Astrophysics Data System (ADS)

    Ouyang, Wei; Jiao, Wei; Li, Xiaoming; Giubilato, Elisa; Critto, Andrea

    2016-09-01

    Some agricultural non-point source (NPS) pollutants accumulate in sediments in the outlet sections of watersheds. It is crucial to evaluate the historical interactions between sediment properties and watershed NPS loading. Therefore, a sediment core from the outlet of an agricultural watershed was collected. The core age was dated using the 210Pb method, and sedimentation rates were determined using the constant rate of supply (CRS) model. The total nitrogen (TN), total phosphorus (TP), Cd, Pb, Cu, Ni and Cr accumulations in the sediment generally showed fluctuating increases, with the highest sedimentation fluxes all occurring in approximately 1998. The measurement of specific mass sedimentation rates reflected a record of watershed soil erosion dynamics. Using SWAT (Soil and Water Assessment Tool) to simulate long-term watershed agricultural NPS pollution loadings, the historical interactions between sediment properties and NPS loadings were further evaluated. The N leaching process weakened these interactions, but the historical accumulations of TP and heavy metals in sediments generally correlated well with watershed NPS TP loading. The regression analysis suggested that Pb and Cr were the most suitable indexes for assessing long-term NPS TN and TP pollution, respectively. Assessing the NPS loading dynamics using the vertical characteristics of sediment geochemistry is a new method.

  5. Sediment yield dynamics during the 1950s multi-year droughts from two ungauged basins in the Edwards Plateau, Texas

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Sediment yield dynamics on the Edwards Plateau region of Texas was dramatically influenced by a multi-year drought that occurred there during the 1950s. To assess the effect of this drought on sediment yield, we used the Soil and Water Assessment Tool (SWAT) to identify the factors that contributed...

  6. ANN modelling of sediment concentration in the dynamic glacial environment of Gangotri in Himalaya.

    PubMed

    Singh, Nandita; Chakrapani, G J

    2015-08-01

    The present study explores for the first time the possibility of modelling sediment concentration with artificial neural networks (ANNs) at Gangotri, the source of Bhagirathi River in the Himalaya. Discharge, rainfall and temperature have been considered as the main controlling factors of variations in sediment concentration in the dynamic glacial environment of Gangotri. Fourteen feed forward neural networks with error back propagation algorithm have been created, trained and tested for prediction of sediment concentration. Seven models (T1-T7) have been trained and tested in the non-updating mode whereas remaining seven models (T1a-T7a) have been trained in the updating mode. The non-updating mode refers to the scenario where antecedent time (previous time step) values are not used as input to the model. In case of the updating mode, antecedent time values are used as network inputs. The inputs applied in the models are either the variables mentioned above as individual factors (single input networks) or a combination of them (multi-input networks). The suitability of employing antecedent time-step values as network inputs has hence been checked by comparative analysis of model performance in the two modes. The simple feed forward network has been improvised with a series parallel non-linear autoregressive with exogenous input (NARX) architecture wherein true values of sediment concentration have been fed as input during training. In the glacial scenario of Gangotri, maximum sediment movement takes place during the melt period (May-October). Hence, daily data of discharge, rainfall, temperature and sediment concentration for five consecutive melt periods (May-October, 2000-2004) have been used for modelling. High Coefficient of determination values [0.77-0.88] have been obtained between observed and ANN-predicted values of sediment concentration. The study has brought out relationships between variables that are not reflected in normal statistical analysis. A

  7. Sediment dynamics during the rainy season in tropical highland catchments of central Mexico using fallout radionuclides

    NASA Astrophysics Data System (ADS)

    Evrard, Olivier; Némery, Julien; Gratiot, Nicolas; Duvert, Clément; Ayrault, Sophie; Lefèvre, Irène; Poulenard, Jérôme; Prat, Christian; Bonté, Philippe; Esteves, Michel

    2010-12-01

    Tropical regions are affected by intense soil erosion associated with deforestation, overgrazing, and cropping intensification. This land degradation leads to important on-site (e.g., decrease in soil fertility) and off-site (e.g., reservoir siltation and water pollution) impacts. This study determined the mean soil particle and sediment residence times in soils and rivers of three subcatchments (3-12 km 2) with contrasted land uses (i.e., cropland, forests, and rangelands) draining to a reservoir located in highlands of the transvolcanic Mexican belt. Calculations were based on rainfall amount and river discharges as well as on fallout radionuclide measurements (Be-7, Cs-137, and Pb-210) conducted on rainfall precipitated samples, soil sampled in the catchments, and suspended sediment collected by automatic samplers in the river during most storms recorded throughout the 2009 rainy season. Calculations using a radionuclide two-box balance model showed that the mean residence time of particles in soils ranged between 5000 ± 1500 and 23,300 ± 7000 years. In contrast, sediment residence time in rivers was much shorter, fluctuating between 50 ± 30 and 200 ± 70 days. The shortest mean residence times were measured in a hilly catchment dominated by cropland and rangelands, whereas they were the longest in an undulating catchment dominated by forests and cropland. Calculation of the Be-7/excess-Pb-210 in both rainfall and sediment allowed gaining insight on sediment dynamics throughout the rainy season. The first heavy storms of the year exported the bulk of the sediment stock accumulated in the river channel during the previous year. Then, during the rainy season, the two steeper catchments dominated by cropland and rangelands reacted strongly to rainfall. Sediment was indeed eroded and exported from both catchments during single heavy storms on several occasions in 2009. In contrast, the agro-forested catchment with gentler slopes exported sediment at a constant

  8. A sandpile model of grain blocking and consequences for sediment dynamics in step-pool streams

    NASA Astrophysics Data System (ADS)

    Molnar, P.

    2012-04-01

    Coarse grains (cobbles to boulders) are set in motion in steep mountain streams by floods with sufficient energy to erode the particles locally and transport them downstream. During transport, grains are often blocked and form width-spannings structures called steps, separated by pools. The step-pool system is a transient, self-organizing and self-sustaining structure. The temporary storage of sediment in steps and the release of that sediment in avalanche-like pulses when steps collapse, leads to a complex nonlinear threshold-driven dynamics in sediment transport which has been observed in laboratory experiments (e.g., Zimmermann et al., 2010) and in the field (e.g., Turowski et al., 2011). The basic question in this paper is if the emergent statistical properties of sediment transport in step-pool systems may be linked to the transient state of the bed, i.e. sediment storage and morphology, and to the dynamics in sediment input. The hypothesis is that this state, in which sediment transporting events due to the collapse and rebuilding of steps of all sizes occur, is analogous to a critical state in self-organized open dissipative dynamical systems (Bak et al., 1988). To exlore the process of self-organization, a cellular automaton sandpile model is used to simulate the processes of grain blocking and hydraulically-driven step collapse in a 1-d channel. Particles are injected at the top of the channel and are allowed to travel downstream based on various local threshold rules, with the travel distance drawn from a chosen probability distribution. In sandpile modelling this is a simple 1-d limited non-local model, however it has been shown to have nontrivial dynamical behaviour (Kadanoff et al., 1989), and it captures the essence of stochastic sediment transport in step-pool systems. The numerical simulations are used to illustrate the differences between input and output sediment transport rates, mainly focussing on the magnification of intermittency and

  9. Oxygen dynamics in periphyton communities and associated effects on phosphorus release from lake sediments

    SciTech Connect

    Carlton, R.G.

    1986-01-01

    This study used oxygen sensitive microelectrodes with tip diameters of < 30 um to investigate the effects of photosynthesis and respiration on the oxygen dynamics of several diverse periphyton communities both in situ and in laboratory microcosms. A novel flow-through system that utilized /sup 32/P radiotracer and that permitted manipulation of the velocity, flushing rate, and oxygen concentration of overlying water was developed to investigate the role of photosynthetic oxygen production on the phosphorus dynamics in lake sediments colonized by epipelic periphyton.

  10. Imaging the recent sediment dynamics of the Galicia Bank region (Atlantic, NW Iberian Peninsula)

    NASA Astrophysics Data System (ADS)

    Ercilla, Gemma; Casas, David; Vázquez, Juan T.; Iglesias, Jorge; Somoza, Luís; Juan, Carmen; Medialdea, Teresa; León, Ricardo; Estrada, Ferran; García-Gil, Soledad; Farran, Marcel. Lí; Bohoyo, Fernando; García, Margarita; Maestro, Adolfo

    2011-03-01

    Multibeam bathymetry, high resolution multi-channel, and very high resolution single-channel (3.5 kHz) seismic records were used to depict the complex geomorphology that defines the Galicia Bank region (Atlantic, NW Iberian Peninsula). This region (≈620-5,000 m water depth) is characterized by a great variety of features: structural features (scarps, highs, valleys, fold bulges), fluid dynamics-related features (structural undulations and collapse craters), mass-movement features (gullies, channels, mass-flow deposits, slope-lobe complexes, and mass-transport deposits), bottom-current features (moats, furrows, abraded surface, sediment waves, and drifts), (hemi)pelagic features, mixed features (abraded surfaces associated to mixed sediments) and bioconstructions. These features represent architectural elements of four sedimentary systems: slope apron, contouritic, current-controlled (hemi)pelagic, and (hemi)pelagic. These systems are a reflection of different sedimentary processes: downslope (mass transport, mass flows, turbidity flows), alongslope (bottom currents of Mediterranean Outflow Water, Labrador Sea Water, North Atlantic Deep Water, and Lower Deep Water), vertical settling, and the interplay between them. The architectural and sediment dynamic complexities, for their part, are conditioned by the morphostructural complexity of the region, whose structures (exposed scarps and highs) favor multiple submarine sediment sources, affect the type and evolution of the mass-movement processes, and interact with different water masses. This region and similar sedimentary environments far from the continental sediment sources, as seamounts, are ideal zones for carrying out submarine source-to-sink studies, and can represent areas subject to hazards, both geologic and oceanographic in origin.