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Sample records for polvo sedimentable asma

  1. Polvo en la Región de los Troyanos

    NASA Astrophysics Data System (ADS)

    Gilhutton, R.; Brunini, A.; Coldwell, G.

    La posible existencia de un anillo de polvo en la resonancia 1:1 con Júpiter formado por partículas provenientes de colisiones de asteroides fue propuesta por Liou and Zook (Icarus 113, 403, 1995) y estudiada extensamente por Vieira Martins and Gomes (VIII Reunión Regional Latinoamericana de Astronomía, Montevideo,1995). Si bien las partículas quedarían atrapadas sólo por períodos de algunos miles de años, el proceso colisional continuo en el cinturón de asteroides mantendría constante la densidad, presentándose una mayor concentración en la región de los troyanos. En el presente trabajo se presentan resultados preliminares sobre observaciones polarimétricas realizadas desde CASLEO de la región de L5 que confirmarían la existencia y variaciones de densidad en el anillo de polvo.

  2. Dinámica y crecimiento de los granos de polvo en la nebulosa protoplanetaria

    NASA Astrophysics Data System (ADS)

    de La Fuente Marcos, Carlos

    2001-06-01

    En el escenario estándar de la formación planetaria, los planetesimales (cuerpos de tamaño kilométrico) crecen a partir de granos de polvo, similares a los interestelares, embebidos en un disco gaseoso denominado nebulosa protoplanetaria. Durante esta etapa, los movimientos del gas pueden tener gran influencia en la dinámica y el crecimiento de los granos de polvo, dado que el flujo kepleriano del gas frena el movimiento de los mismos haciendo que caigan hacia el Sol, y la turbulencia inhibe la inestabilidad gravitacional de la capa de polvo. Aunque se acepta que los planetesimales fueron los elementos constituyentes de los planetas, todavía se desconoce cómo se produjo la formación de los mismos. Por esta razón, en los estudios más recientes, existe un renovado interés por comprender mejor la evolución de la capa de polvo inmersa en el disco gaseoso de la Nebulosa. El gas que fluye en el disco puede engendrar estructuras carentes de simetría axial, como por ejemplo ondas espirales y vórtices, a partir de gran variedad de mecanismos de excitación e inestabilidad. En 1995, Barge y Sommeria pusieron de manifiesto que la existencia de vórtices gaseosos persistentes en la nebulosa solar tendría importantes consecuencias sobre la formación de los planetesimales y el posterior crecimiento de los planetas gigantes. La investigación desarrollada en esta Tesis analiza la relación entre el polvo y el gas debida al acoplamiento por fricción dinámica entre ambos; en concreto, se estudia el efecto del flujo medio del gas sobre la dinámica de las partículas de polvo. El primer objetivo es investigar en profundidad los procesos de captura y crecimiento de los granos de polvo dentro de un vórtice y su posible relevancia en cuanto a la formación de los planetesimales. El segundo objetivo es la exploración de los efectos de ondas espirales propagándose en el disco gaseoso sobre la dinámica y el crecimiento de las partículas. La presencia de líneas de

  3. Formación estelar en NGC 6357: viendo a través del polvo con Gemini

    NASA Astrophysics Data System (ADS)

    Bosch, G.; Morrell, N.; Barbá, R.

    Presentamos aquí los primeros resultados de fotometría JHKs obtenidos con Flamingos I en el telescopio Gemini Sur. El mosaico comprendido por tres posiciones adyacentes tomadas a lo largo de varios semestres nos permite caracterizar la población estelar en la zona que presenta una interacción más importante entre las estrellas masivas y la nube molecular que les dió origen. Los diagramas color-magnitud nos permiten identificar numerosas fuentes con exceso infrarrojo, la mayoría de ellas imposible de detectarse en el rango óptico debido a la fuerte absorción del polvo presente en la región. Es altamente probable que la mayoría de estas fuentes con exceso sean protoestrellas, aunque es necesario realizar espectroscopía infrarroja de las mismas para confirmar su naturaleza.

  4. Synthesis and characterization of fac-Re(CO)3-aspartic-N-monoacetic acid, a structural analogue of a potential new renal tracer, fac-99mTc(CO)3(ASMA)

    PubMed Central

    Klenc, Jeffrey; Lipowska, Malgorzata; Taylor, Andrew T.; Marzilli, Luigi G.

    2013-01-01

    The reaction of an aminopolycarboxylate ligand, aspartic-N-monoacetic acid (ASMA), with [Re(CO)3(H2O)3]+ was examined. The tridentate coordination of ASMA to this ReI tricarbonyl precursor yielded fac-Re(CO)3(ASMA) as a mixture of diastereomers. The chemistry is analogous to that of the TcI tricarbonyl complex, which yields fac-99mTc(CO)3(ASMA) under similar conditions. The formation, structure, and isomerization of fac-Re(CO)3(ASMA) products were characterized by HPLC, 1H NMR spectroscopy, and X-ray crystallography. The two major fac-Re(CO)3(ASMA) diastereomeric products each have a linear ONO coordination mode with two adjacent five-membered chelate rings, but they differ in the endo or exo orientation of the uncoordinated acetate group, in agreement with expectations based on previous studies. Conditions have been identified for the expedient isomerization of fac-Re(CO)3(ASMA) to a mixture consisting primarily of one major product. Because different isomeric species typically have different pharmacokinetic characteristics, these conditions may provide for the practical isolation of a single 99mTc(CO)3(ASMA) species, thus allowing the isolation of the isomer that has optimal imaging and pharmacokinetic characteristics. This information will aid in the design of future 99mTc radiopharmaceuticals. PMID:24273448

  5. Towards a consensus-based biokinetic model for green microalgae - The ASM-A.

    PubMed

    Wágner, Dorottya S; Valverde-Pérez, Borja; Sæbø, Mariann; Bregua de la Sotilla, Marta; Van Wagenen, Jonathan; Smets, Barth F; Plósz, Benedek Gy

    2016-10-15

    Cultivation of microalgae in open ponds and closed photobioreactors (PBRs) using wastewater resources offers an opportunity for biochemical nutrient recovery. Effective reactor system design and process control of PBRs requires process models. Several models with different complexities have been developed to predict microalgal growth. However, none of these models can effectively describe all the relevant processes when microalgal growth is coupled with nutrient removal and recovery from wastewaters. Here, we present a mathematical model developed to simulate green microalgal growth (ASM-A) using the systematic approach of the activated sludge modelling (ASM) framework. The process model - identified based on a literature review and using new experimental data - accounts for factors influencing photoautotrophic and heterotrophic microalgal growth, nutrient uptake and storage (i.e. Droop model) and decay of microalgae. Model parameters were estimated using laboratory-scale batch and sequenced batch experiments using the novel Latin Hypercube Sampling based Simplex (LHSS) method. The model was evaluated using independent data obtained in a 24-L PBR operated in sequenced batch mode. Identifiability of the model was assessed. The model can effectively describe microalgal biomass growth, ammonia and phosphate concentrations as well as the phosphorus storage using a set of average parameter values estimated with the experimental data. A statistical analysis of simulation and measured data suggests that culture history and substrate availability can introduce significant variability on parameter values for predicting the reaction rates for bulk nitrate and the intracellularly stored nitrogen state-variables, thereby requiring scenario specific model calibration. ASM-A was identified using standard cultivation medium and it can provide a platform for extensions accounting for factors influencing algal growth and nutrient storage using wastewater resources. PMID:27525381

  6. Aquatic Sediments.

    ERIC Educational Resources Information Center

    Sanville, W. D.; And Others

    1978-01-01

    Presents a literature review of aquatic sediments and its effect upon water quality, covering publications of 1976-77. This review includes: (1) sediment water interchange; (2) chemical and physical characterization; and (3) heavy water in sediments. A list of 129 references is also presented. (HM)

  7. Contaminated Sediment Core Profiling

    EPA Science Inventory

    Evaluating the environmental risk of sites containing contaminated sediments often poses major challenges due in part to the absence of detailed information available for a given location. Sediment core profiling is often utilized during preliminary environmental investigations ...

  8. Sediment Toxicity Identification Evaluation

    EPA Science Inventory

    Approach combining chemical manipulations and aquatic toxicity testing, generally with whole organisms, to systematically characterize, identify and confirm toxic substances causing toxicity in whole sediments and sediment interstitial waters. The approach is divided into thre...

  9. Paonia Reservoir Sediment Management

    NASA Astrophysics Data System (ADS)

    Kimbrel, S.; Collins, K.; Williams, C.

    2014-12-01

    Paonia Dam and Reservoir are located on Muddy Creek, a tributary of the North Fork Gunnison River in western Colorado. Since dam closure in 1962, the 2002 survey estimates an annual sedimentation rate of 153,000 m3/y, resulting in a 25% loss of total reservoir capacity. Long before sediment levels completely fill the reservoir, the outlet works have recently plugged with sediment and debris, adversely impacting operations, and emphasizing the urgency of formulating an effective sediment management plan. Starting in 2010-2011, operations were changed to lower the reservoir and flush sediment through the outlet works in early spring before filling the pool for irrigation. Even though the flushing strategy through the long, narrow reservoir (~5 km long and 0.3 km wide) has prevented outlet works plugging, a long term plan is needed to manage inflowing and deposited sediment more efficiently. Reclamation's Sedimentation and River Hydraulics Group is leading an effort to study the past and current sediment issues at Paonia Dam and Reservoir, evaluate feasible sediment management alternatives, and formulate a plan for future operations and monitoring. The study is building on previously collected data and the existing knowledge base to develop a comprehensive, sustainable sediment management plan. The study is being executed in three phases: Phase 1 consisted of an initial site visit to map and sample existing reservoir bottom sediments, a preliminary site evaluation upstream and downstream of the dam, and establishment of time-lapse photo sites and taking initial ground-based photos. Phase 2 includes a bathymetric survey of entire reservoir and 11 km of the river downstream of the dam, continuous suspended sediment monitoring upstream and downstream of the reservoir, and collection of additional core samples of reservoir bottom sediments. Phase 3 involves the evaluation of current and past operations and sediment management practices, evaluate feasible sediment

  10. The dirt on sediments

    USGS Publications Warehouse

    Smith, Loren M.; Euliss, Ned H. "Chip", Jr.

    2010-01-01

    In the wetland science field, sediment deposition is often thought of as being beneficial especially when one thinks of coastal estuarine systems. For example, sediments deposited from streams and rivers are necessary to naturally build and maintain tidal marshes. These sediments come from eroded upland soils in the interior of the continent. When these sediments are diverted from natural coastal deposition areas, such as occurs from river channelization, we lose marshes through subsidence as is happening throughout coastal Louisiana. However, the value of eroded soils is all a matter of hydrogeomorphic perspective.

  11. Analytical Ultracentrifugation: Sedimentation Velocity and Sedimentation Equilibrium

    PubMed Central

    Cole, James L.; Lary, Jeffrey W.; Moody, Thomas; Laue, Thomas M.

    2009-01-01

    Analytical ultracentrifugation (AUC) is a versatile and powerful method for the quantitative analysis of macromolecules in solution. AUC has broad applications for the study of biomacromolecules in a wide range of solvents and over a wide range of solute concentrations. Three optical systems are available for the analytical ultracentrifuge (absorbance, interference and fluorescence) that permit precise and selective observation of sedimentation in real time. In particular, the fluorescence system provides a new way to extend the scope of AUC to probe the behavior of biological molecules in complex mixtures and at high solute concentrations. In sedimentation velocity, the movement of solutes in high centrifugal fields is interpreted using hydrodynamic theory to define the size, shape and interactions of macromolecules. Sedimentation equilibrium is a thermodynamic method where equilibrium concentration gradients at lower centrifugal fields are analyzed to define molecule mass, assembly stoichiometry, association constants and solution nonideality. Using specialized sample cells and modern analysis software, researchers can use sedimentation velocity to determine the homogeneity of a sample and define whether it undergoes concentration-dependent association reactions. Subsequently, more thorough model-dependent analysis of velocity and equilibrium experiments can provide a detailed picture of the nature of the species present in solution and their interactions. PMID:17964931

  12. Fluvial sedimentation in Kentucky

    USGS Publications Warehouse

    Flint, R.F.

    1983-01-01

    Covering periods 1942-45 and 1951-81, this report documents the characteristics of sediments being transported from 79 drainage areas within the Commonwealth of Kentucky, and from eight stations on the main stem of the Ohio River. The drainage areas range in size from 0.67 square mile at Cane Branch near Parkers Lake to 40,330 square miles at Tennessee River near Paducah. Sediment yields and particle size of suspended and bed sediments are discussed by physiographic province. The Blue Grass had the highest average annual suspended-sediment yield for selected stations of 741 tons per square mile, and the Western Coal Field had the lowest with 197. The Eastern Coal Field had the broadest range of annual suspended-sediment yields. The range was from 25 tons per square mile at Helton Branch near Greenwood to 21,000 tons per square mile at Millers Creek near Phyllis. For selected stations bedload discharge was estimated to be 5 to 10 percent as much as the suspended-sediment discharge. Only three drainage areas had sediment yields that exceeded the average annual erosion rates for cultivated land in Kentucky of 9.93 tons per acre (6,355 tons per square mile). These three were in the Eastern Coal Field. (USGS)

  13. Autonomous sensor manager agents (ASMA)

    NASA Astrophysics Data System (ADS)

    Osadciw, Lisa A.

    2004-04-01

    Autonomous sensor manager agents are presented as an algorithm to perform sensor management within a multisensor fusion network. The design of the hybrid ant system/particle swarm agents is described in detail with some insight into their performance. Although the algorithm is designed for the general sensor management problem, a simulation example involving 2 radar systems is presented. Algorithmic parameters are determined by the size of the region covered by the sensor network, the number of sensors, and the number of parameters to be selected. With straight forward modifications, this algorithm can be adapted for most sensor management problems.

  14. SEDIMENT GEOCHEMICAL MODEL

    EPA Science Inventory

    Until recently, sediment geochemical models (diagenetic models) have been only able to explain sedimentary flux and concentration profiles for a few simplified geochemical cycles (e.g., nitrogen, carbon and sulfur). However with advances in numerical methods, increased accuracy ...

  15. AMBIENT WATER, POREWATER, AND SEDIMENT

    EPA Science Inventory

    Sediment assessments may be performed for a variety of purposes; these include: dredging and dredged sediment disposal, for evaluations of sediments as a capping material, to determine sediment quality, to assess biological impairment and to assess the status of environment monit...

  16. Hydrodynamics of sediment threshold

    NASA Astrophysics Data System (ADS)

    Ali, Sk Zeeshan; Dey, Subhasish

    2016-07-01

    A novel hydrodynamic model for the threshold of cohesionless sediment particle motion under a steady unidirectional streamflow is presented. The hydrodynamic forces (drag and lift) acting on a solitary sediment particle resting over a closely packed bed formed by the identical sediment particles are the primary motivating forces. The drag force comprises of the form drag and form induced drag. The lift force includes the Saffman lift, Magnus lift, centrifugal lift, and turbulent lift. The points of action of the force system are appropriately obtained, for the first time, from the basics of micro-mechanics. The sediment threshold is envisioned as the rolling mode, which is the plausible mode to initiate a particle motion on the bed. The moment balance of the force system on the solitary particle about the pivoting point of rolling yields the governing equation. The conditions of sediment threshold under the hydraulically smooth, transitional, and rough flow regimes are examined. The effects of velocity fluctuations are addressed by applying the statistical theory of turbulence. This study shows that for a hindrance coefficient of 0.3, the threshold curve (threshold Shields parameter versus shear Reynolds number) has an excellent agreement with the experimental data of uniform sediments. However, most of the experimental data are bounded by the upper and lower limiting threshold curves, corresponding to the hindrance coefficients of 0.2 and 0.4, respectively. The threshold curve of this study is compared with those of previous researchers. The present model also agrees satisfactorily with the experimental data of nonuniform sediments.

  17. Influenza-Sediment Interactions

    NASA Astrophysics Data System (ADS)

    Trusiak, A.; Block, K. A.; Katz, A.; Gottlieb, P.; Alimova, A.; Galarza, J.; Wei, H.; Steiner, J. C.

    2013-12-01

    A typical water fowl can secrete 1012 influenza virions per day. Therefore it is not unexpected that influenza virions interact with sediments in the water column. The influence of sediments on avian influenza virions is not known. With the threat of avian influenza emerging into the human population, it is crucial to understand virus survivability and residence time in a body of water. Influenza and clay sediments are colloidal particles and thus aggregate as explained by DLVO (Derjaguin & Landau, Verwey & Overbeek) theory. Of great importance is an understanding of the types of particulate or macromolecular components that bind the virus particles, and whether the virus remains biologically active. We present results of hetero-aggregation and transmission electron microscopy experiments performed with influenza A/PR8/38. Influenza particles are suspended with sediment and minimal nutrients for several days, after which the components are evaluated to determine influenza concentration and survivability. Transmission electron microscopy results are reported on the influenza-sediment aggregates to elucidate structure and morphology of the components.

  18. Fluvial sedimentation in Kentucky

    SciTech Connect

    Flint, R.F.

    1983-12-01

    This report, covering periods 1942-45 and 1951-81, documents the characteristics of sediment being transported from 79 drainage areas within the Commonwealth of Kentucky, and at eight stations on the main stem of the Ohio River. The drainage areas, excluding the Ohio River, range in size from 0.67 square mile on Cane Branch near Parkers Lake to 40,330 square miles on the Tennessee River near Paducah. The drainage areas on the Ohio River range from 62,000 square miles at Greenup Dam to 203,100 square miles at Lock and Dam 53 near Grand Chain, Illinois. Sediment yields and particle size of suspended and bed sediments are discussed for the five major physiographic regions of Kentucky and for the Ohio River stations. The Blue Grass region had the highest average annual suspended-sediment discharge of 741 tons per square mile. The Eastern Coal Field had the broadest range of average annual yields ranging from 25 tons per square mile at Helton Branch near Greenwood to 21,000 tons per square miles at Millers Creek near Phyllis. For sampling stations, the Jackson Purchase region had the highest median value of annual suspended-sediment yield of 535 tons per square mile. 53 refs., 12 figs., 33 tabs.

  19. Subglacial conduits in sediments

    NASA Astrophysics Data System (ADS)

    Hewitt, Ian

    2016-04-01

    Much of the current understanding of subglacial hydrology is based on the R-channel type model, in which turbulent dissipation and melting causes a roughly semi-circular incision upwards into the ice. The prevalence of such R-channels beneath the Greenland and Antarctic ice sheets is poorly known. Beneath sediment-based ice, distributed water flow may prevail, or some form of conduits may still form due to a combination of upwards melting as well as downwards erosion into the subglacial sediments (often referred to as a canal). This study examines the dynamics of such conduits, and implications for large-scale subglacial drainage. Although a relatively standard set of equations has developed to model the evolution and efficiency of R-channels, models of sediment-floored conduits are much less well established; previous models assume steady state, or make ad hoc assumptions about the balance of processes controlling the channel walls. In this study I suggest a (relatively) simple model analogous to that for an R-channel. The model requires consideration of the energy balance that results in melting of the ice roof, and also the erosion, deposition, and creep of the sediments. Implications for the evolution of large-scale drainage systems over subglacial sediment will be discussed, for subglacial floods in Antarctica, and for subglacial erosion and landform development.

  20. Remediation technologies for contaminated sediments

    SciTech Connect

    Swanson, L.M.

    1995-09-01

    Although soil and groundwater remediation has been conducted for many years, sediment remediation is still in its infancy. Regulatory agencies are now beginning to identify areas where contaminated sediments exist and evaluate their environmental impact. As these evaluations are completed, the projects must shift focus to how these sediments can be remediated. Also as the criteria for aquatic disposal of dredged sediments become more stringent, remediation technologies must be developed to address contaminated sediments generated by maintenance dredging.This report describes the various issues and possible technologies for sediment remediation.

  1. Sediment transport mechanics

    NASA Astrophysics Data System (ADS)

    Ballio, Francesco; Tait, Simon

    2012-12-01

    The Editor of Acta Geophysica and the Guest Editors wish to dedicate this Topical Issue on Sediment Transport Mechanics to the memory of Stephen Coleman, who died recently. During his career, Stephen had made an outstanding scientific contribution to the topic of Sediment Transport. The level of his contribution is demonstrated in the paper by Aberle, Coleman, and Nikora included in this issue, on which he started working before becoming aware of the illness that led to his untimely death. For scholars and colleagues Stephen remains an example of intellectual honesty and scientific insight.

  2. 11. MOVABLE BED SEDIMENTATION MODELS. AUTOMATIC SEDIMENT FEEDER DESIGNED AND ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    11. MOVABLE BED SEDIMENTATION MODELS. AUTOMATIC SEDIMENT FEEDER DESIGNED AND BUILT BY WES. - Waterways Experiment Station, Hydraulics Laboratory, Halls Ferry Road, 2 miles south of I-20, Vicksburg, Warren County, MS

  3. Soft-sediment mullions

    NASA Astrophysics Data System (ADS)

    Ortner, Hugo

    2015-04-01

    In this contribution I describe the appearance, formation and significance of soft-sediment mullions. I use several examples from synorogenic turbidites of the Alps and the Pyrenees to show their appearance in the field. Soft-sediment mullions are elongate, slightly irregular bulges at the base of coarse-grained clastic beds (sand to conglomerate), separated by narrow, elongate flames of fine-grained material (mud) protruding into the coarse-grained bed. Various processes may lead to the formation of such structures: (1) longitudinal furrows parallel to the sediment transport direction may form by spiral motion in flow rolls during sediment transport (Dzulinski, 1966; Dzulinski & Simpson, 1966). (2) Loading combined with downslope movement can produce elongate structures parallelling the dowslope direction (Anketell et al., 1970). (3) Soft-sediment mullions are oriented perpendicular or oblique to the downslope direction, and show evidence of bedding-parallel shortening. Thus, they resemble cuspate-lobate folds or mullions, which are well-known in ductile structural geology (e.g. Urai et al., 2001). Soft-sediment mullions have been observed in two cases: Either bedding-parallel shortening can be achieved by slump processes, or by active tectonic shortening. Slumping is characterized by an alternation of stretching and shortening (e.g. Ortner, 2007; Alsop & Marco 2014), and therefore mullions do overprint or are overprinted by normal faults. In active depositional systems that are subject to tectonic shortening growth strata will form, but sediments already deposited will be shortened during lithification. In some cases, the formation of soft-sediment mullions predates folding, but the most widespread expression of syn-lithification shortening seems to be soft-sediment mullions, that form in the inner arcs of fold hinges. In the examples documented so far, the size of soft-sediment mullions is dependent on the grain-size of the coarse-grained layer, in which the

  4. SEDIMENT ASSESSMENT AND REMEDIATION PROGRAM

    EPA Science Inventory

    Assessment and Remediation of Contaminated Sediments (ARCS) is an integrated program for the development and testing of assessment and remedial action alternatives for contaminated sediments. Information from ARCS program activities will be used to guide the development of Remedi...

  5. ULTRASONIC MEASUREMENT OF SEDIMENT RESUSPENSION

    EPA Science Inventory

    Recognizing the need for improved measurement and parameterization of sediment resuspension, this paper presents a review of the major methods now in use for alleviating this need. Special attention is devoted to reviewing methods for obtaining sediment concentration profiles by ...

  6. PHYTOASSESSMENT OF ESTUARINE SEDIMENTS

    EPA Science Inventory

    Most sediment quality assessments and quality guidelines are based on the laboratory response of single animal species and benthic animal community composition. The role of plants in this hazard assessment process is poorly understood despite the fact that plant-dominated habitat...

  7. SEDIMENT SAMPLING GUIDELINES

    EPA Science Inventory

    The guidance document will detail the measures needed to collect and analyze soils/sediments from flood plains, wetlands, bogs, rivers, and streams that are impacted by high moisture content. High moisture in the above matrices can manifest itself as increased detection limits a...

  8. Contaminated Aquatic Sediments.

    PubMed

    Jaglal, Kendrick

    2016-10-01

    A review of the literature published in 2015 relating to the assessment, evaluation and remediation of contaminated aquatic sediments is presented. The review is divided into the following main sections: policy and guidance, methodology, distribution, fate and transport, risk, toxicity and remediation. PMID:27620103

  9. Sulfur diagenesis in marine sediments

    NASA Technical Reports Server (NTRS)

    Goldhaber, M.

    1985-01-01

    Bacterial sulfate reduction occurs in all marine sediments that contain organic matter. Aqueous sulfide (HS-, H2S), one of the initial products of bacterial sulfide reduction, is extremely reactive with iron bearing minerals: sulfur is fixed into sediments as iron sulfide (first FeS and then Fe2S2). A working definition is given of sulfur diagenesis in marine sediments. Controls and consequences of sulfate reduction rates in marine sediments are examined.

  10. Ammonia and sediment toxicity

    SciTech Connect

    Ogle, R.S.; Hansen, S.R.

    1994-12-31

    Ammonia toxicity to aquatic organisms has received considerable study, with most of these studies focusing on water column organisms. However, with the development and implementation of sediment (and pore water) toxicity tests, the toxicity of ammonia to benthic infauna and other sediment toxicity test organisms has become important, especially since sediment/porewater ammonia occurs at higher concentrations than in the water column. Unfortunately, there has been very little of this type information, especially for marine/estuarine organisms. This laboratory determined the toxicity of ammonia to three key marine/estuarine test organisms: the amphipod Eohaustorius estuarius, the bivalve Mytilus edulis, and the echinoderm Strongylocentrotus purpuratus. Because sediment/porewater pH can differ substantially from typical seawater pH, the toxicity evaluations covered a range of pH levels (6, 7, 8, and 9). Eohaustorius results indicate that while Total Ammonia increased in toxicity (measured as EC50) as pH increased (from 460 mg/L at pH 6, to 13 mg/L at pH 9), unionized ammonia toxicity decreased from 0.13 mg/L at pH 6 to 2.8 mg/L at pH 9. The amphipod was much less sensitive to ammonia than were the bivalve and echinoderm, with an unionized ammonia EC50 at pH 8 of 2.14 mg/L relative to 0.43 mg/L for the mussel and 0.13 mg/L for the purple urchin. These results are discussed with respect to design and interpretation of sediment toxicity test results, including an interpretation approach based on partitioning of Toxic Units (TU).

  11. Sediment bioassays with oyster larvae

    SciTech Connect

    Chapman, P.M.; Morgan, J.D.

    1983-10-01

    Tests with naturally-occurring sediments are rare and sediment testing methodology is not standardized. The authors present a simple methodology for undertaking sediment bioassays with oyster larvae, and present data from a recent study to prove the utility of this method.

  12. COLLECTION OF UNDISTURBED SURFACE SEDIMENTS

    EPA Science Inventory

    The National Resource Council identified the need for a capability to collect undisturbed surface sediments. Surface sediments are an important source for most exposure of fish to polychlorinated biphenyls via direct uptake from water in contact with sediments. An innovative sedi...

  13. Influence of sediment storage on downstream delivery of contaminated sediment

    USGS Publications Warehouse

    Malmon, D.V.; Reneau, S.L.; Dunne, T.; Katzman, D.; Drakos, P.G.

    2005-01-01

    Sediment storage in alluvial valleys can strongly modulate the downstream migration of sediment and associated contaminants through landscapes. Traditional methods for routing contaminated sediment through valleys focus on in-channel sediment transport but ignore the influence of sediment exchanges with temporary sediment storage reservoirs outside the channel, such as floodplains. In theory, probabilistic analysis of particle trajectories through valleys offers a useful strategy for quantifying the influence of sediment storage on the downstream movement of contaminated sediment. This paper describes a field application and test of this theory, using 137Cs as a sediment tracer over 45 years (1952-1997), downstream of a historical effluent outfall at the Los Alamos National Laboratory (LANL), New Mexico. The theory is parameterized using a sediment budget based on field data and an estimate of the 137Cs release history at the upstream boundary. The uncalibrated model reasonably replicates the approximate magnitude and spatial distribution of channel- and floodplain-stored 137Cs measured in an independent field study. Model runs quantify the role of sediment storage in the long-term migration of a pulse of contaminated sediment, quantify the downstream impact of upstream mitigation, and mathematically decompose the future 137Cs flux near the LANL property boundary to evaluate the relative contributions of various upstream contaminant sources. The fate of many sediment-bound contaminants is determined by the relative timescales of contaminant degradation and particle residence time in different types of sedimentary environments. The theory provides a viable approach for quantifying the long-term movement of contaminated sediment through valleys. Copyright 2005 by the American Geophysical Union.

  14. Biogeochemistry of Intertidal Sediments

    NASA Astrophysics Data System (ADS)

    Jickells, T. D.; Rae, J. E.

    2005-07-01

    This authoritative volume includes contributions from a wide range of researchers of intertidal sediments. Individual chapters explore the underlying biogeochemical processes controlling the behavior of carbon, the nutrients nitrogen and phosphorus, and contaminants such as toxic organics, trace metals and artificial radionuclides in intertidal environments. The biogeochemistry of these environments is critical to understanding their ecology and management. Each of the chapters includes a comprehensive review and the results of recent research. The contributors are active researchers in this diverse and ecologically important field. This text is mainly for researchers and managers working with intertidal sediments, but it will also serve as a valuable senior undergraduate and graduate reference text in environmental chemistry, environmental science, earth science, and oceanography.

  15. Formulated sediment for use in whole-sediment toxicity testing

    SciTech Connect

    Kemble, N.E.; Dwyer, F.J.; Hardesty, D.K.; Ingersoll, C.G.

    1995-12-31

    A formulated control sediment was developed to provide consistent and acceptable biological endpoints for a variety of species used in whole sediment toxicity testing. In an attempt to develop such a sediment the authors conducted multiple tests to evaluate: (1) {alpha}-cellulose as an organic carbon source, (2) various TOC concentrations, (3) various grain sizes, (4) different food types, and (5) overlying waters. Studies were conducted with the amphipod Hyalella azteca the midges Chironomus riparius, Chironomus tentans and the oligochaete Lumbriculus variegatus in 10 d exposures and H. azteca in 28 d exposures. Sediment from West Bearskin Lake Minnesota was used as a control sediment with each species in each test. Survival of test organisms in all of the 10-d experiments, with the exception of C. riparius, was above the acceptable levels for a control sediment. Survival in the formulated sediments also was not significantly different when compared to the control sediment. Amphipod survival in the 28-d exposures was low; however, the use of reconstituted water in combination with the formulated sediment may have been a problem. The authors are currently evaluating various types of overlying water with formulated sediments and sublethal endpoints in each of the exposures (i.e., growth, sexual maturation or head capsule width).

  16. Beryllium Desorption from Sediments

    NASA Astrophysics Data System (ADS)

    Boschi, V.; Willenbring, J. K.

    2015-12-01

    Beryllium isotopes have provided a useful tool in the field of geochronology and geomorphology over the last 25 years. The amount of cosmogenic meteoric 10Be and native 9Be absorbed to soils often scales with the residence time and chemical weathering of sediments in a landscape, respectively. Thus, the concentrations in river sediment may be used to quantify the denudation of specific watersheds. When deposited in ocean sediment, these concentrations are thought to record the history of denudation on Earth over the last ~10 Ma. The use of both isotopes often relies on the premise of beryllium retention to sediment surfaces in order to preserve a landscape's erosion and weathering signature. Changes in setting, en route from the soil to fluvial system to the ocean, can cause beryllium desorption and may preclude some applications of the 10Be/9Be system. Four mechanisms were tested to determine the desorption potential of beryllium including a reduction in pH, an increase in ionic strength and complexation with soluble organic and inorganic species. These processes have the potential to mobilize beryllium into solution. For example, by both reducing the pH and increasing the ionic strength, competition for adsorption sites increases, potentially liberating beryllium from the sediment surface. In addition, organic and inorganic ligands can complex beryllium causing it to become mobilized. To determine which of these alterations influence beryllium desorption and to quantify the effect, we prepared separate solutions of beryllium bound to minerals and organic compounds and measured beryllium concentrations in solution before and after adjusting the pH, ionic strength, and changing inorganic and organic ligand concentrations. We conclude from our observations that overall, beryllium sorbed to organic compounds was more resistant to desorption relative to mineral-associated beryllium. Among the methods tested, a reduction in pH resulted in the greatest amount of

  17. Hydrocarbons in Washington coastal sediments

    NASA Astrophysics Data System (ADS)

    Prahl, Fredrick G.; Carpenter, Roy

    1984-06-01

    The sources and distributions of polycyclic aromatic hydrocarbons (PAH) and aliphatic hydrocarbons are characterized in seventeen sediments from a highly river-influenced sedimentary environment off the southwestern coast of Washington. The major hydrocarbons are land-derived, introduced as preformed compounds and display long-term stability in sediment cores. A series of PAH of anthropogenic origin and two naturally derived compounds, retene and perylene, dominate the PAH composition in these sediments. Plantwax n-alkanes are the major aliphatic hydrocarbon constituents. Aliphatic hydrocarbons of marine origin, pristane and a series of four acyclic, multibranched C 25 polyolefins, are also observed in many sediments. The concentrations of these marine-derived hydrocarbons decrease to negligible levels rapidly with sediment depth from the sea-sediment interface, suggesting degradation. In general, the major land-derived hydrocarbons are concentrated in the midshelf silt deposit which extends northwestward along the continental shelf from the Columbia River mouth. A quantitatively more minor, natural series of phenanthrene homologs, also of terrestrial origin, is preferentially advected further offshore and deposited in continental slope sediments. These distributions are consistent with recognized particle associations for these compounds and sediment dispersal processes in this coastal environment. Sediment core records suggest the present pattern of dispersal has persisted for at least the past century and possibly since the Late Pleistocene.

  18. Dispersion in Unconsolidated Aquatic Sediments

    NASA Astrophysics Data System (ADS)

    Roychoudhury, A. N.

    2001-11-01

    Inert tracer breakthrough experiments were used to parameterize hydrodynamic dispersion in undisturbed cores of surface sediment from lacustrine, estuarine, and marine depositional environments. The sediments studied cover wide ranges of composition, porosity (46 to 83%), mean grain size (10 -5to 10 -2 cm), and sorting (0·48-1·26). As expected, hydrodynamic dispersion depends on the average longitudinal fluid flow velocity through the sediment plug. At linear flow velocities exceeding 10 -4 cm s -1, mechanical dispersion exceeds diffusion in all sediment cores studied. Compared to the classical studies on dispersion in sand columns, however, Peclet numbers based on particle size measurements do not provide a reliable guide for predicting the transition from molecular diffusion-dominated to mechanical dispersion-dominated flow regimes in the sediments. It is believed that the influence of pore structure on dispersion is much larger than that of particle size and that the characteristic pore lengths in the finest, highly porous sediments are orders of magnitude larger than the mean grain size. Aggregation, microlaminations, and a heterogeneous pore size distribution may all contribute to non-ideal flow conditions in the sediments. Tailing of the breakthrough curve occurred occasionally in fine grain sediment, signifying micro and macro scale dispersion and non-ideal flow behavior. Experiments showing significant non-ideal flow through the sediment plug were not used for calculation of hydrodynamic dispersion coefficient.

  19. Climate variability, soil conservation, and reservoir sedimentation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Rivers carry sediments which, upon entering a reservoir, settle to the bottom. The process of deposition and gradual accumulation of sediments in the reservoir is referred to as reservoir sedimentation. As reservoir sedimentation progresses, the storage capacity allocated for sediment deposition wil...

  20. Optical sedimentation recorder

    DOEpatents

    Bishop, James K.B.

    2014-05-06

    A robotic optical sedimentation recorder is described for the recordation of carbon flux in the oceans wherein both POC and PIC particles are captured at the open end of a submersible sampling platform, the captured particles allowed to drift down onto a collection plate where they can be imaged over time. The particles are imaged using three separate light sources, activated in sequence, one source being a back light, a second source being a side light to provide dark field illumination, and a third source comprising a cross polarized light source to illuminate birefringent particles. The recorder in one embodiment is attached to a buoyancy unit which is capable upon command for bringing the sedimentation recorder to a programmed depth below the ocean surface during recordation mode, and on command returning the unit to the ocean surface for transmission of recorded data and receipt of new instructions. The combined unit is provided with its own power source and is designed to operate autonomously in the ocean for extended periods of time.

  1. MODELING SEDIMENT-NUTRIENT FLUX AND SEDIMENT OXYGEN DEMAND

    EPA Science Inventory

    Depositional flux of particulate organic matter in bottom sediments affects nutrients cycling at the sediment-water interface and consumes oxygen from the overlying water in streams, lakes, and estuaries. This project deals with analytical modeling of nitrogen and carbon producti...

  2. Targeting sediment management strategies using sediment quantification and fingerprinting methods

    NASA Astrophysics Data System (ADS)

    Sherriff, Sophie; Rowan, John; Fenton, Owen; Jordan, Phil; hUallacháin, Daire Ó.

    2016-04-01

    Cost-effective sediment management is required to reduce excessive delivery of fine sediment due to intensive land uses such as agriculture, resulting in the degradation of aquatic ecosystems. Prioritising measures to mitigate dominant sediment sources is, however, challenging, as sediment loss risk is spatially and temporally variable between and within catchments. Fluctuations in sediment supply from potential sources result from variations in land uses resulting in increased erodibility where ground cover is low (e.g., cultivated, poached and compacted soils), and physical catchment characteristics controlling hydrological connectivity and transport pathways (surface and/or sub-surface). Sediment fingerprinting is an evidence-based management tool to identify sources of in-stream sediments at the catchment scale. Potential sediment sources are related to a river sediment sample, comprising a mixture of source sediments, using natural physico-chemical characteristics (or 'tracers'), and contributions are statistically un-mixed. Suspended sediment data were collected over two years at the outlet of three intensive agricultural catchments (approximately 10 km2) in Ireland. Dominant catchment characteristics were grassland on poorly-drained soils, arable on well-drained soils and arable on moderately-drained soils. High-resolution (10-min) calibrated turbidity-based suspended sediment and discharge data were combined to quantify yield. In-stream sediment samples (for fingerprinting analysis) were collected at six to twelve week intervals, using time-integrated sediment samplers. Potential sources, including stream channel banks, ditches, arable and grassland field topsoils, damaged road verges and tracks were sampled, oven-dried (<40oC) and sieved (125 microns). Soil and sediment samples were analysed for mineral magnetics, geochemistry and radionuclide tracers, particle size distribution and soil organic carbon. Tracer data were corrected to account for particle

  3. CHARACTERIZING HUMAN CONTACT WITH SEDIMENT

    EPA Science Inventory

    People contact sediment during a variety of activities such as fishing, wading and boating. A number of default assumptions are used today to characterize dermal contact with sediments in terms of magnitude, frequency and duration. The accuracy of these default values are widel...

  4. GREAT LAKES CONTAMINATED SEDIMENTS PROGRAM

    EPA Science Inventory

    Contaminated sediments are a significant problem in the Great Lakes basin. Although discharges of toxic substances to the Great Lakes have been reduced in the last 20 years, persistent high concentrations of contaminants in the bottom sediments of rivers and harbors have raised...

  5. HANDBOOK: REMEDIATION OF CONTAMINATED SEDIMENTS

    EPA Science Inventory

    Contaminated sediments may pose risks to both human and environmental health. Such sediments may be found in

    large sites, such as the harbors of industrialized ports. However, they are also frequently found in smaller sites, such as streams, lakes, bayous, and rivers. In r...

  6. Sediment flux and the Anthropocene.

    PubMed

    Syvitski, James P M; Kettner, Albert

    2011-03-13

    Data and computer simulations are reviewed to help better define the timing and magnitude of human influence on sediment flux--the Anthropocene epoch. Impacts on the Earth surface processes are not spatially or temporally homogeneous. Human influences on this sediment flux have a secondary effect on floodplain and delta-plain functions and sediment dispersal into the coastal ocean. Human impact on sediment production began 3000 years ago but accelerated more widely 1000 years ago. By the sixteenth century, societies were already engineering their environment. Early twentieth century mechanization has led to global signals of increased sediment flux in most large rivers. By the 1950s, this sediment disturbance signal reversed for many rivers owing to the proliferation of dams, and sediment load reduction below pristine conditions is the dominant signal today. A delta subsidence signal began in the 1930s and is now a dominant signal in terms of sea level for many coastal environments, overwhelming even the global warming imprint on sea level. Humans have engineered how most water and sediment are discharged into the coastal ocean. Hyperpycnal flow events have become more common for some rivers, and less common for other rivers. Bottom trawling is now widespread, suggesting that even continental shelves have received a significant but as yet quantified Anthropocene impact. The Anthropocene attains the level of a geological climate event, such as that seen in the transition between the Pleistocene and the Holocene. PMID:21282156

  7. DESIGN CONSIDERATION INVOLVING ACTIVE SEDIMENT CAPS (PRESENTATION)

    EPA Science Inventory

    When contaminated sediments pose unacceptable risks to human health and the environment, management activities such as removal, treatment, or isolation of contaminated sediments may be required. Various capping designs are being considered for isolating contaminated sediment are...

  8. DESIGN CONSIDERATION INVOLVING ACTIVE SEDIMENT CAPS

    EPA Science Inventory

    When contaminated sediments pose unacceptable risks to human health and the environment, management activities such as removal, treatment, or isolation of contaminated sediments may be required. Various capping designs are being considered for isolating contaminated sediment are...

  9. Ballast water sediment elemental analysis.

    PubMed

    Maglić, Lovro; Zec, Damir; Frančić, Vlado

    2016-02-15

    Sediment samples from the ballast water tanks of ships calling at the port of Rijeka in the Northern Adriatic were analysed using X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectroscopy (SIMS) using caesium, argon and oxygen ion beams. The research was carried out in order to determine the sediment composition and relative abundance of the dominant elements. The results indicate that the sediment samples mostly consisted of compounds that originated from the deterioration of tank plates, tank coating residues and ballast operations such as clay, silt, sand and organic materials. No significant heavy metals or highly toxic elements were found. The research revealed some advantages and significant drawbacks of using XPS and SIMS for the routine analysis of sediment composition as a decision supporting tool for ballast water and sediment management. PMID:26763315

  10. Magnetostratigraphy of Cave Sediments

    NASA Astrophysics Data System (ADS)

    Bosák, P.; Pruner, P.

    2007-05-01

    Karst and cave fills (karst sediments) are relatively special kinds of geologic materials, as the karst environment favors both the preservation of paleontological remains and their destruction: on one hand, karst is well known for its wealth of paleontological sites, on the other hand, most of cave fills are completely sterile (especially the inner-cave facies). Another specific feature is that karst systems can be "frozen" (halted) and then rejuvenated, often for several times. Reactivation processes may degrade the record into an unreadable form, often mixing karst fill of different ages (collapses, reworking, redepositions). Only the last accumulation phase has been dated in caves in most cases. The fossilisation of the cave (fill by deposits) and rejuvenation (exhumation of the fill) reflect changes in resurgence area. The rejuvenation of the karst process can excavate the previous cave fill completely, which is the most common case resulting from the polycyclicity and dynamics of cave environments. Under favorable settings, fills belonging to more infill phases and separated by distinct hiatuses (unconformities) can occur in one sedimentary profile. Such amalgamation is typical especially in ponor part of the cave. During our previous research we found, that owing to the specific character of karst sediments, the use of paleomagnetic methods can bring surprising result, without regards to the character of the method (correlated- ages not providing direct numerical output). The method can serve as helpful tool to interpret not only the age of cave sediments but also to understand the evolution of karst landscape and tectonic history of the region. To obtain more precise results, it is necessary to combine paleomagnetism with other methods of numerical-, relative- or correlated-dating. The analytical results confirmed that the complete step/field procedure offered by the alternating field and thermal demagnetization methods must be applied. The sampling for

  11. Sediments of Arabia

    NASA Technical Reports Server (NTRS)

    2005-01-01

    21 August 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows martian sediment in two basic forms: (1) light-toned, layered, sedimentary rock outcrops and (2) dark, windblown sand dunes. The dark sand of the dunes is most likely composed of grains rich in iron-, magnesium-, aluminum-, and silicon-bearing minerals. The hills and mounds of layered sedimentary rock were once more extensive, covering the entire scene shown here, which occurs on the floor of a crater in western Arabia Terra.

    Location near: 8.9oN, 1.2oW Image width: width: 3 km (1.9 mi) Illumination from: lower left Season: Northern Autumn

  12. Estimating sediment discharge: Appendix D

    USGS Publications Warehouse

    Gray, John R.; Simões, Francisco J. M.

    2008-01-01

    Sediment-discharge measurements usually are available on a discrete or periodic basis. However, estimates of sediment transport often are needed for unmeasured periods, such as when daily or annual sediment-discharge values are sought, or when estimates of transport rates for unmeasured or hypothetical flows are required. Selected methods for estimating suspended-sediment, bed-load, bed- material-load, and total-load discharges have been presented in some detail elsewhere in this volume. The purposes of this contribution are to present some limitations and potential pitfalls associated with obtaining and using the requisite data and equations to estimate sediment discharges and to provide guidance for selecting appropriate estimating equations. Records of sediment discharge are derived from data collected with sufficient frequency to obtain reliable estimates for the computational interval and period. Most sediment- discharge records are computed at daily or annual intervals based on periodically collected data, although some partial records represent discrete or seasonal intervals such as those for flood periods. The method used to calculate sediment- discharge records is dependent on the types and frequency of available data. Records for suspended-sediment discharge computed by methods described by Porterfield (1972) are most prevalent, in part because measurement protocols and computational techniques are well established and because suspended sediment composes the bulk of sediment dis- charges for many rivers. Discharge records for bed load, total load, or in some cases bed-material load plus wash load are less common. Reliable estimation of sediment discharges presupposes that the data on which the estimates are based are comparable and reliable. Unfortunately, data describing a selected characteristic of sediment were not necessarily derived—collected, processed, analyzed, or interpreted—in a consistent manner. For example, bed-load data collected with

  13. Spiking sediment with organochlorines for toxicity testing

    SciTech Connect

    Murdoch, M.H.; Chapman, P.M.; Norman, D.M.; Quintino, V.M.

    1997-07-01

    Sediment toxicity testing integrates responses to sediment variables and hence does not directly indicate cause and effect. One tool for determining cause and effect is sediment spiking, in which relatively uncontaminated sediment is amended with known amounts of contaminants, then tested for toxicity. However, sediment spiking methods vary considerably. The present study details appropriate methodologies (dry and wet spiking) for amending sediments with a range of organic contaminant concentrations, i.e., polychlorinated biphenyl (PCB). Target and actual concentrations were similar. A dose-response was determined, but PCB was not toxic in an acute sediment toxicity test. Chronic testing of these same sediments is reported in a companion article in this issue.

  14. Holocene sediments within lake catchments - testing sediment delivery

    NASA Astrophysics Data System (ADS)

    Dreibrodt, S.; Bork, H.-R.

    2009-04-01

    Results of detailed investigation of soils, colluvia and lake sediments in a lake catchment in northern Germany proves that the input of eroded soil (enabled by agricultural land use) is of a minor amount compared with the storage within colluvial layers. Pre-existing micro- and meso-topography and prehistorical land use patterns as well as precipitation intensity are probable to control the Holocene flux of sediments within the lake catchment area. Therefore we entertain some doubt if sediment delivery ratios- usually applied on larger spatial scales (e. g. river catchment areas)- are useful to produce reliable quantitative data of Holocene soil erosion in central Europe.

  15. 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

  16. Sediment budgeting of German waterways

    NASA Astrophysics Data System (ADS)

    Promny, M.

    2012-04-01

    Waterways today rarely have a sustainable sediment budget. Supply from upstream and lateral sources is blocked by barrages in many places. The transport capacity is strongly modified by means of planform and cross-section alterations. Many free-flowing river sections are subject to bed degradation, while impoundments tend to aggrade. This has consequences for the usability of navigation facilities, stability of structures (like bridge foundations and dykes) and groundwater levels. Consequently, sediment managements operations are commonplace, being challenging in economic and ecologic terms. A first step towards an improved sediment management is to establish the current sediment budget of a river. There are different methods to gain information about the sediment budget: - measurements of bed-load and suspended load transport - deductions from temporal development of bed-level development - deductions from temporal development of streamwise water-level measurements - deductions from temporal development of water-levels at gauges - bed-load tracer analyses - numerical modelling An overview of the methods used in sediment budgeting of German waterways at the Federal Institute of Hydrology will be given. Ongoing research based on the above mentioned methodology will be presented, with a special focus on the possible influence of climate change on sediment budgets.

  17. MODELING SEDIMENT-NUTRIENT FLUX AND SEDIMENT OXYGEN DEMAND

    EPA Science Inventory

    This project builds upon previous advances in modeling bottom sediment processes in eutrophication models. It develops algorithms for simulating processes responsible for nitrogen (nitrate, ammonium, organic-N) and carbon transformation and cycling (organic-N and methane) in bott...

  18. Comparison of bulk sediment and sediment elutriate toxicity testing methods

    EPA Science Inventory

    Elutriate bioassays are among numerous methods that exist for assessing the potential toxicity of sediments in aquatic systems. In this study, interlaboratory results were compared from 96-hour Ceriodaphnia dubia and Pimephales promelas static-renewal acute toxicity tests conduct...

  19. 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.

  20. Elwha River Restoration: Sediment Management

    NASA Astrophysics Data System (ADS)

    Kimbrel, S.; Bountry, J.; Randle, T. J.; Ritchie, A.; Huginin, H.; Torrance, A.

    2013-12-01

    The removal of Elwha and Glines Canyon Dams on the Elwha River relies on controlled reservoir drawdown increments and natural river flows to erode and redistribute the reservoir sediment, estimated to be a total of 23 (× 3) million m3. To mitigate for the predicted sediment effects, facilities have been constructed for water quality and flood protection. A sediment monitoring program is being implemented by an interdisciplinary team from Reclamation and National Park Service to integrate real-time measurements with continually updated numerical model predictions. The most recent numerical reservoir modeling and monitoring results indicate about 20 to 25 percent of the reservoir sediment has been released since the start of dam removal. Monitoring results in 2012 and early 2013 confirmed that controlled reservoir drawdown increments have induced sufficient vertical and lateral erosion of delta surfaces behind both dams. Predam channel and floodplain surface has been exposed in numerous portions of Lake Aldwell, with the release of coarse and fine sediment in the first few pools below Elwha Dam. The material released from Lake Aldwell has included organic material. With the removal of about three quarters of Glines Canyon Dam and the disappearance of Lake Mills, coarse bedload sediment has been continually released into the downstream river since late fall 2012. Field measurements and numerical modeling are being used to track the progression of the sediment wave downstream to the Elwha River mouth. Initial findings are that the aggradation was greatest immediately downstream of Glines Canyon Dam, and filled pools and transformed river planform from step-pool to glide for most of the 7 mile reach between Lake Mills and Lake Aldwell. Although there has not been a major flood, winter flows and spring snowmelt have significantly reworked the released sediment and remnants of the pre-sediment release pools and rapids have re-emerged. Large wood and organics have also

  1. Sedimentation rate control on diagenesis, East China Sea sediments

    NASA Astrophysics Data System (ADS)

    Zheng, Yan; Zheng, Hongbo; Kissel, Catherine; Laj, Carlo

    2011-08-01

    Diagenesis of ferrimagnetic minerals can alter the magnetic properties, erasing partially or entirely the original paleomagnetic and paleoclimatic signals, especially on continental margins where sedimentation rates are usually high. Understanding the mechanisms by which magnetic particles are affected by diagenesis is therefore critical for retrieving paleomagnetic and paleoclimatic information from sediments. High-resolution magnetic analysis was carried out on rapidly deposited (0.4-20 mm/year) Holocene sediments from the East China Sea (ECS) inner continental shelf. The primary magnetic mineral assemblage in the sediment core contains ferrimagnetic minerals, such as magnetite, with minor contributions from hematite. The magnetic properties vary down-core in two steps, due to post-depositional reductive diagenesis. The first occurs at depths of 0.15-1.1 m and is characterized by reduction of both magnetite and hematite in suboxic sediments. The suboxic-sulfate boundary (SSB) is therefore located at 1.1 m. We demonstrate that the depth of the SSB has negative relation to the average sedimentation rate in Chinese marginal seas. The second step change in magnetic properties occurs at 3.2-5.8 m, and contains two intervals with extremely low magnetic mineral content, each corresponding to dissolution fronts associated with the former and present position of the sulfate-methanic transition (SMT). These two intervals correlate well with abrupt changes in sedimentation rate and separate the anoxic zone into two parts: the sulfidic zone and the methanic zone. Our study suggests that sedimentation rate provides a dominant control on magnetic mineral diagenesis, at least in the Chinese marginal seas, which controls not only the type of redox zonation, but also the thicknesses of diagenetic zones.

  2. Inertial Screening in Sedimentation

    NASA Technical Reports Server (NTRS)

    Segre, P. N.; Curreri, Peter A. (Technical Monitor)

    2001-01-01

    Using particle image velocimetry we have measured the sedimentation dynamics of non-Brownian spheres over a wide range of Reynolds numbers (Re) between 0.001 and 2.5. Particle velocity fluctuations about the mean settling velocity show large-scale correlations whose spatial extent and magnitude Delta V/V are independent of Re up to a critical value Re less than Re(sub c). For Re greater than Re(sub c) the fluctuations substantially diminish with increasing Reynolds number due to inertial screening of the long-range hydrodynamic interactions (HI). The onset of inertial affects is found to occur when the Oseen length l(sub o)=v/V becomes of order the correlation length. In the inertial regime, the velocity fluctuations follow -(Delta V/V)(sup 2) approaching ln(Re), in agreement with an integration of the (l/r) HI over a narrow region extending up to the Oseen length l(sub o). A simple "blob" model connects the measured correlation lengths to the magnitudes of the velocity fluctuations.

  3. Dating sediments using luminescence signals

    SciTech Connect

    Wintle, A. )

    1993-05-01

    Before siting a nuclear power station or a nuclear waste repository, it is necessary to establish that the area has been free of earthquake activity for a sufficient period of time. Evidence of past earthquake activity is often provided by faults in surface sediments. Age limits for fault formation can be set by obtaining the depositional ages of the sediment unit in which the fault was formed and the overlying sediment. A useful technique would be one that dating could be applied to the mineral grains that make up the sediments and that would give the time that has passed since the grains were blown or washed into position. Luminescence dating techniques, of which the most well known is thermo-luminescence (TL), provide such information. This approach has been successful in dating movement on the Wasatch Fault in Utah. A combination of TL and radiocarbon dates indicated that three faulting events had occurred within the past 5000 years. 2 refs., 1 fig.

  4. CONTAMINANTS IN WATER AND SEDIMENT

    EPA Science Inventory

    The Detroit River has experienced over a century of heavy contaminant discharges from industry and municipalities. The sources of contaminants vary, and include non-point sources, combined sewer overflows, point sources, tributaries, sediments, and upstream inputs. ---
    Demonst...

  5. 7 CFR 58.134 - Sediment content.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 3 2011-01-01 2011-01-01 false Sediment content. 58.134 Section 58.134 Agriculture... Milk § 58.134 Sediment content. (a) Method of testing. Methods for determining the sediment content of... for the Examination of Dairy Products. Sediment content shall be based on comparison with...

  6. 7 CFR 58.134 - Sediment content.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 3 2012-01-01 2012-01-01 false Sediment content. 58.134 Section 58.134 Agriculture... Milk § 58.134 Sediment content. (a) Method of testing. Methods for determining the sediment content of... for the Examination of Dairy Products. Sediment content shall be based on comparison with...

  7. 7 CFR 58.134 - Sediment content.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 3 2010-01-01 2010-01-01 false Sediment content. 58.134 Section 58.134 Agriculture... Milk § 58.134 Sediment content. (a) Method of testing. Methods for determining the sediment content of... for the Examination of Dairy Products. Sediment content shall be based on comparison with...

  8. Suspended sediment in Minnesota streams

    USGS Publications Warehouse

    Tornes, L.H.

    1986-01-01

    Analysis showed that more than 90 percent of the annual sediment load was carried during 3 to 9 months of the year. On the average, almost 25 percent of the annual sediment load was transported during April. Generally, it was found that less than 4 percent of the average annual load was transported during December, January, and February, which indicates that sampling frequency could be reduced during winter.

  9. Batch gravitational sedimentation of slurries.

    PubMed

    Chu, C P; Ju, S P; Lee, D J; Mohanty, K K

    2002-01-01

    We investigated the batch settling behavior of the kaolin slurry and the UK ball clay slurry at various initial solids fractions (phi(0)s) using a computerized axial tomography scanner (CATSCAN). The spatio-temporal evolutions of solids fractions in the consolidating sediments were continuously monitored. Since the interface between the sediment and the supernatant of the investigated slurries was blurred, an averaging procedure was employed to estimate their null-stress solids fractions (phi(g)s). Besides the rather slow settling for the high-phi(0) slurries, the basic settling characteristics resemble each other regardless of whether phi(0)>phi(g) or vice versa. The above-mentioned experimental data reveal that the investigated slurries are neither purely elastic nor purely plastic in rheological behavior. On contrary to most model works a blurred supernatant-sediment interface makes difficulty in the gel point determination. During initial settling the high-phi(0) slurries clearly exhibit a finite yield stress to resist deformation. That is, the slurries are plastic fluids. However, the network structure in the slurries deteriorates gradually in the subsequent settling stage while the final, equilibrated sediment reveals a continuous distribution in solids fraction. Restated, the final sediment possesses as a purely elastic characteristic. The model parameters of theory by Buscall and White were regressed by the dynamic consolidating sediment data, while those by Tiller and Leu were obtained using the final equilibrated sediment data. Calculations from both models reveal that ball clay slurry is more compressible than is the kaolin slurry. The high-phi(S0) slurry would yield the less compressible sediment. PMID:16290348

  10. Sulfur cycling in freshwater sediments

    NASA Technical Reports Server (NTRS)

    Klug, M. J.

    1985-01-01

    Organic sulfur containing compounds represent greater than 80% of the total sulfur in sediments of eutrophic freshwater lakes. Although sedimentary sulfur is predominantly in the form of organic compounds, more sulfur is transformed by sulfate reduction than by any other process. Rates of sulfate reduction in these sediments average 7 mmol/sq m/day. This rate is 19 times greater than the net rate of production of inorganic sulfur from organic compounds on an annual basis.

  11. 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.

  12. Sediment segregation by biodiffusing bivalves

    NASA Astrophysics Data System (ADS)

    Montserrat, F.; Van Colen, C.; Provoost, P.; Milla, M.; Ponti, M.; Van den Meersche, K.; Ysebaert, T.; Herman, P. M. J.

    2009-08-01

    The selective processing of sediment fractions (sand and mud; >63 μm and ≤63 μm median grain size) by macrofauna was assessed using two size classes of inert, UV-fluorescent sediment fraction tracers (luminophores). The luminophores were applied to the sediment surface in 16 m 2 replicated plots, defaunated and control, and left to be reworked by infauna for 32 days. As the macrofaunal assemblage in the ambient sediment and the control plots was dominated by the common cockle Cerastoderma edule, this species was used in an additional mesocosm experiment. The diversity, abundance and biomass of the defaunated macrobenthic assemblage did not return to control values within the experimental period. Both erosion threshold and bed elevation increased in the defaunated plots as a response to the absence of macrofauna and an increase in microphytobenthos growth. In the absence of macrobenthos, we observed an accretion of 7 mm sediment, containing ca. 60% mud. Image analysis of the vertical distribution of the different luminophore size classes showed that the cockles preferentially mobilised fine material from the sediment, thereby rendering it less muddy and effectively increasing the sand:mud ratio. Luminophore profiles and budgets of the mesocosm experiment under "no waves-no current" conditions support the field data very well.

  13. Marine sediments in the classroom

    NASA Astrophysics Data System (ADS)

    Van Toer, Aurelie; Le Divenah, Claudie

    2013-04-01

    In the present context of global climatic change, studies of the past natural climate variability is critical for the knowledge of the Earth climate mechanism. One of the major climatic reservoir is the ocean which covers more than 70% of the surface of the earth. It exchanges moisture and heat with the atmosphere and plays an important role in the climatic changes at different latitudes. The marine sediments are therefore archives of the past oceanographic/climatic changes. These marine sediments are collected as long cores penetrating into the sediment and therefore giving access to the progressive climatic changes with time. Marine sediments are classically composed of skeleton of micro-organisms and of terrigenous fraction. The main micro-organisms used as tracers of paleoclimatic changes are foraminifera. Their species change with the properties of the water mass in which they live (in particular temperature and salinity). With the aim of showing the students in a classroom how to recognize these species and to reconstruct the past oceanographic changes, "real" sediment has been taken during different cruises in different oceanic basins. We will present here the type of sediments available and the type of analysis/observation which can be made in a class. We will show how to perform the preparation of the samples and what are the possible observations through a binocular microscope. The students will then be able to extract information from their own observation about climate: its variations over time and through the differences between the areas of coring operations. In order to allow this activity to be introduced into your class, a program of distribution of these marine sediments will be proposed and will be presented. A registration form will be available. A limited number of proposals will be accepted and a report of their activity in the classroom will be mandatory a few months after the distribution of samples.

  14. Elwha River Restoration: Sediment Management

    NASA Astrophysics Data System (ADS)

    Randle, T. J.; Bountry, J.; Ritchie, A.; Hugunin, H.; Torrence, A.

    2012-12-01

    The 1 to 2-year removal of Elwha and Glines Canyon Dams on the Elwha River relies on controlled reservoir drawdown increments and natural river flows to erode and redistribute the reservoir sediment, estimated to be a total of 18 million m3. To mitigate for the predicted sediment effects, facilities have been constructed for water quality and flood protection, including water treatment plants, new wells, a new surface water intake, raising the height of existing levees, and the construction of new levees. A sediment monitoring program is being implemented by an interdisciplinary team from Reclamation and National Park Service to integrate real-time measurements with continually updated numerical model predictions. The most recent numerical reservoir modeling and monitoring results indicate about 50 percent of the reservoir sediment will remain in the reservoir while another 50 percent is predicted to be released downstream during dam removal and a few high flood periods following the completion of dam removal. Early monitoring results confirm that lowering the reservoir pool in a controlled increment, and then holding the reservoir pool at constant elevation, is inducing sufficient vertical and lateral erosion of the exposed delta surface. Predam channel and floodplain surface has been exposed in numerous portions of Lake Aldwell. The first major coarse sediment released from Lake Aldwell occurred in mid-April. This sediment release along with continued erosion during spring snowmelt of 2012 has resulted in deposition of the first few river pools below Elwha Dam. Deposition on riffles, where velocities are higher, has not occurred. Therefore, no major change to flood stage is predicted from the initial sediment release. The material released from Lake Aldwell has included organic material. About half of Glines Canyon Dam has been removal and Lake Mills is about one-quarter of its original size. Future monitoring will focus on continued tracking of the lateral

  15. Bedload sheets in heterogeneous sediment

    SciTech Connect

    Whiting, P.J.; Dietrich, W.E.; Leopold, L.B.; Drake, T.G.; Shreve, R.L.

    1988-02-01

    Field observations in streams with beds of coarse sand and fine gravel have revealed that bedload moves primarily as thin, migrating accumulations of sediment, and coarse grains cluster at their leading edge. These accumulations are one or two coarse grains high and are much longer (0.2-0.6 m long in sand; 0.5-2.0 m in fine gravel) than their height. The authors propose the term bedload sheet for these features, and the authors argue that they result from an instability inherent to bedload movement of moderately and poorly sorted sediment. In essence, coarse particles in the bedload slow or stop each other, trap finer particles in their interstices, and thus cause the coarse particles to become mobile again. Bedload sheets develop on the stoss side of dunes, causing the dune to advance incrementally with the arrival of each sheet. Successive deposition of coarse sediment from the leading edge followed by fine sediment may generate the grain-size sorting that distinguishes cross-bedding. Available flume experiments and field observations indicate that bedload sheets are a common, but generally unrecognized, feature of heterogeneous sediment transport.

  16. Cable Bacteria in Freshwater Sediments

    PubMed Central

    Kristiansen, Michael; Frederiksen, Rasmus B.; Dittmer, Anders Lindequist; Bjerg, Jesper Tataru; Trojan, Daniela; Schreiber, Lars; Damgaard, Lars Riis; Schramm, Andreas; Nielsen, Lars Peter

    2015-01-01

    In marine sediments cathodic oxygen reduction at the sediment surface can be coupled to anodic sulfide oxidation in deeper anoxic layers through electrical currents mediated by filamentous, multicellular bacteria of the Desulfobulbaceae family, the so-called cable bacteria. Until now, cable bacteria have only been reported from marine environments. In this study, we demonstrate that cable bacteria also occur in freshwater sediments. In a first step, homogenized sediment collected from the freshwater stream Giber Å, Denmark, was incubated in the laboratory. After 2 weeks, pH signatures and electric fields indicated electron transfer between vertically separated anodic and cathodic half-reactions. Fluorescence in situ hybridization revealed the presence of Desulfobulbaceae filaments. In addition, in situ measurements of oxygen, pH, and electric potential distributions in the waterlogged banks of Giber Å demonstrated the presence of distant electric redox coupling in naturally occurring freshwater sediment. At the same site, filamentous Desulfobulbaceae with cable bacterium morphology were found to be present. Their 16S rRNA gene sequence placed them as a distinct sister group to the known marine cable bacteria, with the genus Desulfobulbus as the closest cultured lineage. The results of the present study indicate that electric currents mediated by cable bacteria could be important for the biogeochemistry in many more environments than anticipated thus far and suggest a common evolutionary origin of the cable phenotype within Desulfobulbaceae with subsequent diversification into a freshwater and a marine lineage. PMID:26116678

  17. Priming effects in marine sediments

    NASA Astrophysics Data System (ADS)

    Gontikaki, Evina; Thornton, Barry; Witte, Ursula

    2013-04-01

    Continental margin sediments (<2000 m) cover merely 15 % of the ocean's seafloor but are responsible for more than 70 % of the global benthic mineralization. Understanding when these systems act as a source or sink of carbon (C) is thus of primary importance if we are to produce reliable global C budgets and predict the effects of future perturbations on the global C cycle. The chemical nature of organic matter (OM) is thought to be one of the major controls on the degradation/preservation balance in sediments; labile and refractory OM pools degrade at different rates but not independently. Priming effects (PE), i.e. changes in the decomposition of refractory organic matter following inputs of labile OM, have the potential to alter the C budget in sediments but have been largely ignored by marine scientists. Climate-driven changes in primary production, and land erosion and run-off are likely to change the quantity and composition of organic matter inputs in marine ecosystems and influence the magnitude and direction of PEs in seawater and sediments. Here, we attempt to evaluate the importance of priming effects on C cycling in marine sediments by use of labelled substrates of different quantity and quality in stable isotope tracer experiments and argue that PEs need to be incorporated in global change models.

  18. Extraterrestrial Matter Chronometry of Sediments

    NASA Astrophysics Data System (ADS)

    Peucker-Ehrenbrink, B.; Waters, C. A.; Hoffman, P. F.; Kurz, M. D.

    2010-12-01

    Tracer records of extraterrestrial matter (ET) accumulation in sediments suggest that ET accretion rates are reasonable constant on time scales relevant to sediment accumulation in terrestrial and marine environments (1000-100,000 years), except during impact events. Geochemical tracers of ET matter in sediments are therefore informative rate indicators applicable to individual samples. This alleviates the need for interpolating rates between known chronometric tie points. The most sensitive tracers of ET accretion include noble gases, particularly helium, and the heavy platinum group elements osmium, iridium and platinum. Helium and osmium have tell-tale isotope signatures that are sensitive indicators of terrestrial vs. extraterrestrial pedigree. Here we investigate the use of coupled helium-osmium isotope and helium, osmium, iridium and platinum concentration analyses to determine sedimentation rates across Neoproterozoic glacial terminations. Bodiselitsch et al. (Science 308, 2005, 239ff) suggested that significant iridium anomalies at transitions from glacial to postglacial sediments constrain the duration of Neoproterozoic Marinoan glaciation to at least 3, and most likely 12 million years. Our data on Marinoan sections from NW Canada and Namibia reveal no large ET matter anomaly, and support a more nuanced interpretation of coupled geochemical indicators of accretion of ET matter across those transitions. Our records provide insights into environmental changes during periods of Neoproterozoic climate change.

  19. Cable Bacteria in Freshwater Sediments.

    PubMed

    Risgaard-Petersen, Nils; Kristiansen, Michael; Frederiksen, Rasmus B; Dittmer, Anders Lindequist; Bjerg, Jesper Tataru; Trojan, Daniela; Schreiber, Lars; Damgaard, Lars Riis; Schramm, Andreas; Nielsen, Lars Peter

    2015-09-01

    In marine sediments cathodic oxygen reduction at the sediment surface can be coupled to anodic sulfide oxidation in deeper anoxic layers through electrical currents mediated by filamentous, multicellular bacteria of the Desulfobulbaceae family, the so-called cable bacteria. Until now, cable bacteria have only been reported from marine environments. In this study, we demonstrate that cable bacteria also occur in freshwater sediments. In a first step, homogenized sediment collected from the freshwater stream Giber Å, Denmark, was incubated in the laboratory. After 2 weeks, pH signatures and electric fields indicated electron transfer between vertically separated anodic and cathodic half-reactions. Fluorescence in situ hybridization revealed the presence of Desulfobulbaceae filaments. In addition, in situ measurements of oxygen, pH, and electric potential distributions in the waterlogged banks of Giber Å demonstrated the presence of distant electric redox coupling in naturally occurring freshwater sediment. At the same site, filamentous Desulfobulbaceae with cable bacterium morphology were found to be present. Their 16S rRNA gene sequence placed them as a distinct sister group to the known marine cable bacteria, with the genus Desulfobulbus as the closest cultured lineage. The results of the present study indicate that electric currents mediated by cable bacteria could be important for the biogeochemistry in many more environments than anticipated thus far and suggest a common evolutionary origin of the cable phenotype within Desulfobulbaceae with subsequent diversification into a freshwater and a marine lineage. PMID:26116678

  20. Ancient aqueous sedimentation on Mars

    SciTech Connect

    Goldspiel, J.M.; Squyres, S.W. )

    1991-02-01

    Viking orbiter images are presently used to calculate approximate volumes for the inflow valleys of the ancient cratered terrain of Mars; a sediment-transport model is then used to conservatively estimate the amount of water required for the removal of this volume of debris from the valleys. The results obtained for four basins with well-developed inflow networks indicate basin sediment thicknesses of the order of tens to hundreds of meters. The calculations further suggest that the quantity of water required to transport the sediment is greater than that which could be produced by a single discharge of the associated aquifer, unless the material of the Martian highlands was very fine-grained and noncohesive to depths of hundreds of meters. 48 refs.

  1. Creep behavior of submarine sediments

    USGS Publications Warehouse

    Silva, Armand J.; Booth, J.S.

    1984-01-01

    A series of experiments on drained creep of marine sediment indicates that strength degradation results from the creep process, which implies an associated reduction in slope stability. Furthermore, the highest creep potential of a sediment may be at its preconsolidation stress. Results from the experiments on samples from Georges Bank continental slope were also used in conjunction with a preliminary theoretical model to predict creep displacements. For the case illustrated in this report, steep slopes (>20??) and thick sections (>30 m) give rise to substantial creep and probable creep rupture; as angles or thicknesses decrease, displacements rapidly become negligible. Creep may be a significant geologic process on many marine slopes. Not only can it cause major displacements of surface sediment, but it may also be the precursor to numerous slope failures. ?? 1985 Springer-Verlag New York Inc.

  2. Ancient aqueous sedimentation on Mars

    NASA Technical Reports Server (NTRS)

    Goldspiel, Jules M.; Squyres, Steven W.

    1991-01-01

    Viking orbiter images are presently used to calculate approximate volumes for the inflow valleys of the ancient cratered terrain of Mars; a sediment-transport model is then used to conservatively estimate the amount of water required for the removal of this volume of debris from the valleys. The results obtained for four basins with well-developed inflow networks indicate basin sediment thicknesses of the order of tens to hundreds of meters. The calculations further suggest that the quantity of water required to transport the sediment is greater than that which could be produced by a single discharge of the associated aquifer, unless the material of the Martian highlands was very fine-grained and noncohesive to depths of hundreds of meters.

  3. Radionuclides in Chesapeake Bay sediments

    NASA Technical Reports Server (NTRS)

    Cressy, P. J., Jr.

    1976-01-01

    Natural and manmade gamma-ray emitting radionuclides were measured in Chesapeake Bay sediments taken near the Calvert Cliffs Nuclear Power Plant site. Samples represented several water depths, at six locations, for five dates encompassing a complete seasonal cycle. Radionuclide contents of dry sediments ranged as follows: Tl-208, 40 to 400 pCi/kg; Bi-214, 200 to 800 pCi/kg; K, 0.04 to 2.1 percent; Cs-137 5 to 1900 pCi/kg; Ru106, 40 to 1000 pCikg Co60, 1 to 27 pCi/kg. In general, radionuclide contents were positively correlated with each other and negatively correlated with sediment grain size.

  4. Rheometry of natural sediment slurries

    USGS Publications Warehouse

    Major, Jon J.

    1993-01-01

    Recent experimental analyses of natural sediment slurries yield diverse results yet exhibit broad commonality of rheological responses under a range of conditions and shear rates. Results show that the relation between shear stress and shear rate is primarily nonlinear, that the relation can display marked hysteresis, that minimum shear stress can occur following yield, that physical properties of slurries are extremely sensitive to sediment concentration, and the concept of slurry yield strength is still debated. New rheometric analyses have probed viscoelastic behavior of sediment slurries. Results show that slurries composed of particles ??? 125 ?? m exhibit viscoelastic responses, and that shear stresses are relaxed over a range of time scales rather than by a single response time.

  5. Criteria for a sediment data set

    USGS Publications Warehouse

    Glysson, Douglas G.

    1989-01-01

    The transport of sediment through a hydrologic system or basin is an extremely complex phenomenon. Many factors affect this movement. Criteria are established for an 'ultimate' or complete sediment data set, and guidelines are given for the collection of alluvial data. The paper describes what parameters need to be measured and stored to obtain a complete sediment and hydraulic data set that could be used to compute sediment transport using any prominently known sediment-transport equation. The criteria address only the collection of data for noncohesive sediment.

  6. Sediment transport and sedimentation along the Amazon floodplain

    SciTech Connect

    Dunne, T.; Mertes, A.K.L.; Meade, R.H.

    1985-01-01

    As the Amazon River leaves the Andean foothills and crosses the structural trough in its Brazilian segment, it receives a large increment of discharge, but a small increase in sediment load from the bounding cratons. The gradient of the river declines gradually from Iquitos, Peru, downstream to Coari, Brazil, before increasing downstream to the vicinity of Manaus as the river crosses a structural arch. Between Manaus and Obidos, the river slope declines sharply. The interplay of the variable gradient and increasing discharge creates a pattern of boundary shear stress and sediment transport which the authors have defined by measurement and calculation. The downstream divergence of suspended and bed load transport is responsible for the patterns of aggradation, channel behavior and floodplain morphology. Aggradation has been computed on the basis of three years of sediment transport measurements; floodplain morphology was documented from radar photography and navigation charts; and channel migration from these charts and from aerial and satellite photography. In the reach between the Peruvian border and Coari, the river deposits sand bars within and alongside the channel and shifts laterally at a relatively rapid rate, forming a scroll-bar floodplain topography with long, narrow lakes. In the middle, steeper reach no net aggradation was measured, sand-bar development and channel shifting are limited. Below Manaus, the rapid decline in gradient and the large influx of Andean sediment from the Rio Madeira result in deposition of almost the entire sand load and a portion of the silt.

  7. Current Methods in Sedimentation Velocity and Sedimentation Equilibrium Analytical Ultracentrifugation

    PubMed Central

    Zhao, Huaying; Brautigam, Chad A.; Ghirlando, Rodolfo; Schuck, Peter

    2013-01-01

    Significant progress in the interpretation of analytical ultracentrifugation (AUC) data in the last decade has led to profound changes in the practice of AUC, both for sedimentation velocity (SV) and sedimentation equilibrium (SE). Modern computational strategies have allowed for the direct modeling of the sedimentation process of heterogeneous mixtures, resulting in SV size-distribution analyses with significantly improved detection limits and strongly enhanced resolution. These advances have transformed the practice of SV, rendering it the primary method of choice for most existing applications of AUC, such as the study of protein self- and hetero-association, the study of membrane proteins, and applications in biotechnology. New global multi-signal modeling and mass conservation approaches in SV and SE, in conjunction with the effective-particle framework for interpreting the sedimentation boundary structure of interacting systems, as well as tools for explicit modeling of the reaction/diffusion/sedimentation equations to experimental data, have led to more robust and more powerful strategies for the study of reversible protein interactions and multi-protein complexes. Furthermore, modern mathematical modeling capabilities have allowed for a detailed description of many experimental aspects of the acquired data, thus enabling novel experimental opportunities, with important implications for both sample preparation and data acquisition. The goal of the current commentary is to supplement previous AUC protocols, Current Protocols in Protein Science 20.3 (1999) and 20.7 (2003), and 7.12 (2008), and provide an update describing the current tools for the study of soluble proteins, detergent-solubilized membrane proteins and their interactions by SV and SE. PMID:23377850

  8. Sediment reworking rates in deep sediments of the Mediterranean Sea.

    PubMed

    Barsanti, M; Delbono, I; Schirone, A; Langone, L; Miserocchi, S; Salvi, S; Delfanti, R

    2011-07-01

    Different pelagic areas of the Mediterranean Sea have been investigated in order to quantify physical and biological mixing processes in deep sea sediments. Herein, results of eleven sediment cores sampled at different deep areas (> 2000 m) of the Western and Eastern Mediterranean Sea are presented. ²¹⁰Pb(xs) and ¹³⁷Cs vertical profiles, together with ¹⁴C dating, are used to identify the main processes characterising the different areas and, finally, controlling mixing depths (SML) and bioturbation coefficients (D(b)). Radionuclide vertical profiles and inventories indicate that bioturbation processes are the dominant processes responsible for sediment reworking in deep sea environments. Results show significant differences in sediment mixing depths and bioturbation coefficients among areas of the Mediterranean Sea characterised by different trophic regimes. In particular, in the Oran Rise area, where the Almeria-Oran Front induces frequent phytoplankton blooms, we calculate the highest values of sediment mixing layers (13 cm) and bioturbation coefficients (0.187 cm² yr⁻¹), and the highest values of ²¹⁰Pb(xs) and ¹³⁷Cs inventories. Intermediate values of SML and D(b) (~6 cm and ~0.040 cm² yr⁻¹, respectively) characterise the mesothrophic Algero-Balearic basin, while in the Southern Tyrrhenian Sea mixing parameters (SML of 3 cm and D(b) of 0.011 cm² yr⁻¹ are similar to those calculated for the oligotrophic Eastern Mediterranean (SML of 2 cm and D(b) of ~0.005 cm² yr⁻¹). PMID:21561644

  9. PREDICTING TOXICITY TO AMPHIPODS FROM SEDIMENT CHEMISTRY

    EPA Science Inventory

    Background

    The contribution of contaminated sediments to effects on sediment-dwelling organisms (including plants and invertebrates), aquatic-dependent wildlife (amphibians, reptiles, fish, birds, and mammals), and human health has become more apparent in recent yea...

  10. DEVELOPMENT OF ECOLOGICAL TOOLS FOR CONTAMINATED SEDIMENTS

    EPA Science Inventory

    Contaminated sediments are of interest to a broad group of programs in the agency. OERR and the Regions are interested in monitoring contaminated sediments to characterize/assess existing conditions, determine remediation alternatives, track spatial and temporal changes, and dete...

  11. Beverage Cans Used for Sediment Collection.

    ERIC Educational Resources Information Center

    Studlick, Joseph R. J.; Trautman, Timothy A.

    1979-01-01

    Beverage cans are well suited for sediment collection and storage containers. Advantages include being free, readily available, and the correct size for many samples. Instruction for selection, preparation, and use of cans in sediment collection and storage is provided. (RE)

  12. PHOXOCEPHALID AMPHIPOD BIOASSAY FOR MARINE SEDIMENT TOXICITY

    EPA Science Inventory

    The relative toxicity of marine sediment can be accurately determined through acute, static bioassays with the phoxocepalid amphipod Repoxynius abronius. Mortality and sublethal effects on emergence from sediment and reburial behavior are determined after ten day exposure in 1-L ...

  13. Chesapeake Bay sediment flux model. Final report

    SciTech Connect

    Di Toro, D.M.; Fitzpatrick, J.J.

    1993-06-01

    Formulation and application of a predictive diagenetic sediment model are described in this report. The model considers two benthic sediment layers: a thin aerobic layer in contact with the water column and a thicker anaerobic layer. Processes represented include diagenesis, diffusion, particle mixing, and burial. Deposition of organic matter, water column concentrations, and temperature are treated as independent variables that influence sediment-water fluxes. Sediment oxygen demand and sediment-water fluxes of sulfide, ammonium, nitrate, phosphate, and silica are predicted. The model was calibrated using sediment-water flux observations collected in Chesapeake Bay 1985-1988. When independent variables were specified based on observations, the model correctly represented the time series of sediment-water fluxes observed at eight stations in the Bay and tributaries.... Chesapeake Bay, Models, Sediments, Dissolved oxygen, Nitrogen Eutrophication, Phosphorus.

  14. Beneficial Use Of Contaminated Sediment

    EPA Science Inventory

    The western portion of the Lake George Branch of the Indian Harbor Canal (IHC) is no longer used for commercial purposes, but contains petroleum contaminated sediments. The IHC is considered an important habitat for many animal species. Several future development projects have ...

  15. Radiotracer Imaging of Sediment Columns

    NASA Astrophysics Data System (ADS)

    Moses, W. W.; O'Neil, J. P.; Boutchko, R.; Nico, P. S.; Druhan, J. L.; Vandehey, N. T.

    2010-12-01

    Nuclear medical PET and SPECT cameras routinely image radioactivity concentration of gamma ray emitting isotopes (PET - 511 keV; SPECT - 75-300 keV). We have used nuclear medical imaging technology to study contaminant transport in sediment columns. Specifically, we use Tc-99m (T1/2 = 6 h, Eγ = 140 keV) and a SPECT camera to image the bacteria mediated reduction of pertechnetate, [Tc(VII)O4]- + Fe(II) → Tc(IV)O2 + Fe(III). A 45 mL bolus of Tc-99m (32 mCi) labeled sodium pertechnetate was infused into a column (35cm x 10cm Ø) containing uranium-contaminated subsurface sediment from the Rifle, CO site. A flow rate of 1.25 ml/min of artificial groundwater was maintained in the column. Using a GE Millennium VG camera, we imaged the column for 12 hours, acquiring 44 frames. As the microbes in the sediment were inactive, we expected most of the iron to be Fe(III). The images were consistent with this hypothesis, and the Tc-99m pertechnetate acted like a conservative tracer. Virtually no binding of the Tc-99m was observed, and while the bolus of activity propagated fairly uniformly through the column, some inhomogeneity attributed to sediment packing was observed. We expect that after augmentation by acetate, the bacteria will metabolically reduce Fe(III) to Fe(II), leading to significant Tc-99m binding. Imaging sediment columns using nuclear medicine techniques has many attractive features. Trace quantities of the radiolabeled compounds are used (micro- to nano- molar) and the half-lives of many of these tracers are short (<1 day). This allows multiple measurements to be made on the same column and thus the sediment biology to be monitored non-invasively over time (i.e. after an augmentation has been introduced) and minimizes long-lived radioactive waste. Different parameters can be measured, depending on the tracer type and delivery. A constant infusion of a conservative tracer, such as the positron emitter Br-76 (T1/2= 16.2 hr), measures the exclusion fraction (as

  16. Prediction of bedload sediment transport for heterogeneous sediments in shape

    NASA Astrophysics Data System (ADS)

    Durafour, Marine; Jarno, Armelle; Le Bot, Sophie; Lafite, Robert; Marin, François

    2015-04-01

    Key words: Particle shape, in-situ measurements, bedload transport, heterogeneous sediments Bedload sediment transport in the coastal area is a dynamic process mainly influenced by the type of hydrodynamic forcings involved (current and/or waves), the flow properties (velocity, viscosity, depth) and sediment heterogeneity (particle size, density, shape). Although particle shape is recognized to be a significant factor in the hydrodynamic behavior of grains, this parameter is not currently implemented in bedload transport formulations: firstly because the mechanisms of initiation of motion according to particle shape are still not fully understood, and secondly due to the difficulties in defining common shape parameters. In March 2011, a large panel of in-situ instruments was deployed on two sites in the Eastern English Channel, during the sea campaign MESFLUX11. Samples of the sediment cover available for transport are collected, during a slack period, per 2cm thick strata by divers and by using a Shipeck grab. Bedload discharges along a tidal cycle are also collected with a Delft Nile Sampler (DNS; Gaweesh and Van Rijn, 1992, 1994) on both sites. The first one is characterized by a sandy bed with a low size dispersion, while the other study area implies graded sediments from fine sands to granules. A detailed analysis of the data is performed to follow the evolution of in-situ bedload fluxes on the seabed for a single current. In-situ measurements are compared to existing formulations according to a single fraction approach, using the median diameter of the mixture, and a fractionwise approach, involving a discretization of the grading curve. Results emphasize the interest to oscillate between these two methods according to the dispersion in size of the site considered. The need to apply a hiding/exposure coefficient (Egiazaroff, 1965) and a hindrance factor (Kleinhans and Van Rijn, 2002) for size heterogeneous sediments is also clearly highlighted. A really good

  17. Erosion and sedimentation in Arab countries

    NASA Astrophysics Data System (ADS)

    This symposium is organized by the Iraqi National Committee for the International Hydrological Program (IHP) and the International Association of Hydrological Sciences (IAHS) International Commission on Continental Erosion (ICCE). It will be held February 15-19, 1986, at the Water Research Center in Baghdad, Iraq. The program will cover a wide range of topics associated with erosion and sedimentation in Arab countries. These topics include soil erosion and sedimentation problems, erosion, transport and deposition processes, sediment yields, reservoir sedimentation, and river training.

  18. The diffusion of ions in unconsolidated sediments

    USGS Publications Warehouse

    Manheim, F. T.

    1970-01-01

    Diffusion in unconsolidated sediments generally proceeds at rates ranging from half to one twentieth of those applying to diffusion of ions and molecules in free solution. Diffusion rates are predictable with respect to porosity and path tortuosity in host sediments, and can be conveniently measured by determinations of electrical resistivity on bulk sediment samples. Net ion flux is further influenced by reactions of diffusing species with enclosing sediments, but such influences should not be confused with or lumped with diffusion processes. ?? 1970.

  19. MODELING FRAMEWORK FOR EVALUATING SEDIMENTATION IN STREAM NETWORKS: FOR USE IN SEDIMENT TMDL ANALYSIS

    EPA Science Inventory

    A modeling framework that can be used to evaluate sedimentation in stream networks is described. This methodology can be used to determine sediment Total Maximum Daily Loads (TMDLs) in sediment impaired waters, and provide the necessary hydrodynamic and sediment-related data t...

  20. Regional Models for Sediment Toxicity Assessment

    EPA Science Inventory

    This paper investigates the use of empirical models to predict the toxicity of sediment samples within a region to laboratory test organisms based on sediment chemistry. In earlier work, we used a large nationwide database of matching sediment chemistry and marine amphipod sedim...

  1. Computation of fluvial-sediment discharge

    USGS Publications Warehouse

    Porterfield, George

    1972-01-01

    This report is one of a series concerning the concepts, measurement, laboratory procedures, and computation of fluvial-sediment discharge. Material in this report includes procedures and forms used to compile and evaluate particle-size and concentration data, to compute fluvial-sediment discharge, and to prepare sediment records for publication.

  2. TOXICANT IDENTIFICATION STUDIES ON A HARBOR SEDIMENT

    EPA Science Inventory

    Presentation summarizes the results of experiments on sediment toxicity identification evaluation (TIE) techniques that allow researchers to characterize and identify chemical causes of acute toxicity in sediments that can be applied using the 10-d solid-phase sediment toxicity t...

  3. Modeling Transport of Flushed Reservoir Sediment

    NASA Astrophysics Data System (ADS)

    Dubinski, I. M.

    2014-12-01

    Drawdown flushing of a reservoir is often part of a reservoir sediment management program. Flushing can deliver higher than normal sediment loads to the river channel located downstream of a reservoir. The flushed sediment may contain a higher proportion of finer sediment than what was delivered to a channel prior to the presence of the reservoir. The extent of long-term impacts caused by the flushed sediment on the channel morphology and habitat will in part depend on the residence time of the sediment within the channel. In this study we used MIKE 21C to model the fate of flushed sediment through a river channel where the bed material consists of an armoring layer of gravels overlying finer sediment. MIKE 21C is a two-dimensional curvilinear morphological model for rivers developed by DHI. Curvilinear means that the model grid may curve to better follow the channel and flow direction, for example in a meandering channel. Multiple bed material layers are included in the model to represent the armoring and underlying layers existing in the bed separately from the overlying flushed sediment. These layers may also mix. The nature of the interactions between these two layers helps regulate transport and deposition of the flushed sediment, thus are critical to assessing the fate of the flushed sediment and associated potential impacts.

  4. Major sedimentation issues for the USGS

    USGS Publications Warehouse

    Jobson, Harvey E.; Andrews, Edmund D.

    1990-01-01

    Historically, sediment information has been used primarily in planning for engineering structures that were designed to meet a single or a very limited number of objectives. Today most water-resource systems are fully developed, but society is asking that the existing systems be operated to meet multiple objectives, which often were not considered in the original system design. Sediment related problems that seem to be of highest priority today include: 1. The relation of sediment transport to the transport and fate of attached pollutants, 2. Documentation of the mean sediment concentration and load as well as the natural variability of instantaneous sediment concentrations and loads as related to land use, and 3. Evaluation of the effect of sediment on fish and wildlife habitat. The sediment program of the U.S. Geological Survey (USGS) is changing in response to these changing priorities as it attempts to remain relevant and responsive to current problems.

  5. San Francisco Bay Sediment Concentration

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This March 3, 2000 image of the San Francisco Bay region shows a 60 by 75 kilometer Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) image in band 1 (near infrared, 0.52-0.60 microns). The color coded suspended sediment image was created from band 1 by blacking out the land, and assigning colors to the relative brightnesses in the water. High values were colored white, then red, yellow, green, and blue. Brighter values in band 1 indicate higher sediment load in the water. The highest values are in Suisun and San Pablo Bays, into which the Sacramento River empties, and along the coast of the San Francisco Peninsula. The Pacific Ocean and San Francisco Bay water are relatively clear. Image courtesy ASTER Science Team

  6. Machine learning in sedimentation modelling.

    PubMed

    Bhattacharya, B; Solomatine, D P

    2006-03-01

    The paper presents machine learning (ML) models that predict sedimentation in the harbour basin of the Port of Rotterdam. The important factors affecting the sedimentation process such as waves, wind, tides, surge, river discharge, etc. are studied, the corresponding time series data is analysed, missing values are estimated and the most important variables behind the process are chosen as the inputs. Two ML methods are used: MLP ANN and M5 model tree. The latter is a collection of piece-wise linear regression models, each being an expert for a particular region of the input space. The models are trained on the data collected during 1992-1998 and tested by the data of 1999-2000. The predictive accuracy of the models is found to be adequate for the potential use in the operational decision making. PMID:16530383

  7. Smoke and Sediments in Sicily

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The waters along the shoreline of Sicily appear bright aquamarine in this image from April 7, 2002. Although other satellite images occasionally show lightening along the coast of Sicily and southern Italy, the water is unusually bright in this image. The bright water may have been caused by a recent storm that either stirred up sediment from relatively shallow sea bottom, or could be a springtime phytoplankton bloom. (Distinguishing phytoplankton from sediment is one of the challenges facing NASA researchers who study life in the oceans from satellites.) Another interesting feature of this image is the smoke plume from Mount Etna that is streaming almost directly to the East (right). Mt. Etna is one of the world's most active volcanos, and erupts up to several times a year. Image courtesy Jacques Descloitres, MODIS Land Rapid Response Team at NASA GSFC

  8. Using sediment particle size distribution to evaluate sediment sources in the Tobacco Creek Watershed

    NASA Astrophysics Data System (ADS)

    Liu, Cenwei; Lobb, David; Li, Sheng; Owens, Philip; Kuzyk, ZouZou

    2014-05-01

    Lake Winnipeg has recently brought attention to the deteriorated water quality due to in part to nutrient and sediment input from agricultural land. Improving water quality in Lake Winnipeg requires the knowledge of the sediment sources within this ecosystem. There are a variety of environmental fingerprinting techniques have been successfully used in the assessment of sediment sources. In this study, we used particle size distribution to evaluate spatial and temporal variations of suspended sediment and potential sediment sources collected in the Tobacco Creek Watershed in Manitoba, Canada. The particle size distribution of suspended sediment can reflect the origin of sediment and processes during sediment transport, deposition and remobilization within the watershed. The objectives of this study were to quantify visually observed spatial and temporal changes in sediment particles, and to assess the sediment source using a rapid and cost-effective fingerprinting technique based on particle size distribution. The suspended sediment was collected by sediment traps twice a year during rainfall and snowmelt periods from 2009 to 2012. The potential sediment sources included the top soil of cultivated field, riparian area and entire profile from stream banks. Suspended sediment and soil samples were pre-wet with RO water and sieved through 600 μm sieve before analyzing. Particle size distribution of all samples was determined using a Malvern Mastersizer 2000S laser diffraction with the measurement range up to 600μm. Comparison of the results for different fractions of sediment showed significant difference in particle size distribution of suspended sediment between snowmelt and rainfall events. An important difference of particle size distribution also found between the cultivated soil and forest soil. This difference can be explained by different land uses which provided a distinct fingerprint of sediment. An overall improvement in water quality can be achieved by

  9. Oxic and Anoxic Regions of Subseafloor Sediment

    NASA Astrophysics Data System (ADS)

    D'Hondt, S.; Pockalny, R. A.; Spivack, A. J.; Inagaki, F.; Murray, R. W.; Adhikari, R. R.; Gribsholt, B.; Kallmeyer, J.; McKinley, C. C.; Morono, Y.; Røy, H.; Sauvage, J.; Ziebis, W.

    2015-12-01

    Dissolved oxygen content defines two broad categories of subseafloor sediment. In areas with high rates of microbial respiration, most of the sediment column is anoxic and active anaerobic microbial communities are present for hundreds of meters or more below the seafloor. In these regions, O2 and aerobic communities penetrate only millimeters to centimeters into the sediment from the sediment-water interface. In some areas of active fluid flow through the underlying basalt, O2 may also penetrate meters upward into the sediment from the basalt. In areas with low sedimentary respiration, O2 and aerobic communities penetrate tens of meters downward from the seafloor and may persist throughout the entire sediment column. IODP Expedition 329 showed that microbial cells and aerobic respiration persist through the entire sediment sequence (to depths of at least 75 meters below seafloor) in the South Pacific Gyre. Extrapolating from these results and a global relationship of O2 penetration depth to sedimentation rate and sediment thickness, we suggest that oxygen and aerobic communities occur throughout the entire sediment sequence in 15-44% of the Pacific and 9-37% of the global seafloor. Subduction of sediment from largely anoxic regions and subduction of sediment and basalt from fully oxic regions are respectively sources of reduced and oxidized material to the mantle. The balance between oxic and anoxic regions has presumably changed considerably throughout Earth history. Regions with largely anoxic sediment and regions with fully oxic sediment present fundamentally different opportunities for understanding of (i) paleoceanographic history and (ii) the nature of microbial life under extreme energy limitations.

  10. Submarine lithification of carbonate sediments.

    PubMed

    Milliman, J D

    1966-08-26

    Recrystallized planktonic limestones from two guyots in the North Atlantic are in oxygen-isotopic equilibrium with their present ambient waters, suggesting submarine lithifica tion and recrystallization. The early stages of submarine lithification of carbonates may involve precipitation of, and replacement by, magnesium-rich calcite; with time this may invert to magnesium-poor calcite. This type of lithification probably requires very low rates of sediment accumulation. PMID:17837254

  11. Integration of Hydrologic, Sediment Yield, Sediment Delivery, Hydrodynamic and Sediment Transport Models in Large Great Lakes Watersheds

    NASA Astrophysics Data System (ADS)

    Brunton, A.; Nairn, R.; Selegean, J.

    2004-12-01

    Computational tools to evaluate surface and subsurface water flow and sediment transport are commonly used by environmental and engineering practitioners. However, different parts of the hydrologic system (e.g. hillslope overland flow, groundwater, river channel flow) are often treated separately and at disparate spatial and temporal scales. Overland flow models typically have no explicit channel representation and vice-versa, making integrated assessments of water and sediment delivery from catchment to channel difficult. This is problematic when appraising the influence of land use change (urbanization, modification of riparian buffer strips, changes in tillage and forestry practices etc.) on catchment sediment movement and river flood hydrographs. A 'budgetary' approach was taken to defining the sources and sinks of water and sediment within large catchments in the Great Lakes area under a variety of land uses. These budgets were derived from existing datasets including digital elevation models, river flow and sediment load records, and dam sedimentation surveys. Numerical models of watershed hydrology and sediment delivery, 2-D river flow and sediment transport were constructed to develop a general understanding of the hydrologic and geomorphic behavior of these systems, and to predict the effects of changing land use and riparian buffer zone modification. Models were calibrated against river flow and sediment transport records, reservoir sedimentation surveys and harbor dredging records. The challenges and benefits of combining these diverse approaches and their implementation in best management practices are discussed.

  12. Sediment detachment by rain power

    NASA Astrophysics Data System (ADS)

    Gabet, Emmanuel J.; Dunne, Thomas

    2003-01-01

    In interrill areas, overland flow is often incapable of detaching soil particles so detachment is primarily by raindrop impact. We derive a mathematical expression, rain power (R, W m-2), relating the energy expenditure of raindrops impacting a soil surface to the rate of detachment of soil particles. Rain power incorporates rainfall, hillslope, and vegetation characteristics and is modulated by flow depths. Rainfall simulation experiments on natural hillslopes were performed to measure detachment rates and across-slope flow depth distributions in surface runoff. Our results indicate that flow depths follow a Poisson distribution, and this observation is used to develop a dimensionless function, A(?, d), that accounts for the interaction of flow depths (h) and raindrop diameter (d) in moderating detachment rates. Rain power correlates well with the detachment rate of fine-grained particles (ψ, g m-2 s-1) so that ψ = 0.011R1.4A(?, d) (n = 44, R2 = 0.88, p < 0.005). We generalize this result to represent natural rainfall conditions and present a method for modeling sediment detachment rates and sediment discharge along entire lengths of hillslopes under the range of conditions where detached sediment is transported as wash load. Modeling simulations demonstrate the temporal and spatial variation in detachment rates caused by increases in flow depth.

  13. Sediment transport measurements: Chapter 5

    USGS Publications Warehouse

    Diplas, P.; Kuhnle, R.; Gray, J.; Glysson, D.; Edwards, T.

    2008-01-01

    Sediment erosion, transport, and deposition in fluvial systems are complex processes that are treated in detail in other sections of this book. Development of methods suitable for the collection of data that contribute to understanding these processes is a still-evolving science. Sediment and ancillary data are fundamental requirements for the proper management of river systems, including the design of structures, the determination of aspects of stream behavior, ascertaining the probable effect of removing an existing structure, estimation of bulk erosion, transport, and sediment delivery to the oceans, ascertaining the long-term usefulness of reservoirs and other public works, tracking movement of solid-phase contaminants, restoration of degraded or otherwise modified streams, and assistance in the calibration and validation of numerical models. This chapter presents techniques for measuring bed-material properties and suspended and bed-load discharges. Well-established and relatively recent, yet adequately tested, sampling equipment and methodologies, with designs that are guided by sound physical and statistical principles, are described. Where appropriate, the theory behind the development of the equipment and guidelines for its use are presented.

  14. Oligocene tectonics and sedimentation, California

    USGS Publications Warehouse

    Nilsen, T.H.

    1984-01-01

    During the Oligocene epoch, California was marked by extensive nonmarine sedimentation, in contrast to its pre-Oligocene and post-Oligocene depositional history. The Oligocene continental deposits are especially widespread in southern California and fill a number of small and generally partly restricted basins. Fluvial facies in many basins prograded over previously deposited lower Tertiary turbidites. Volcanism, from widespread centers, was associated with the nonmarine sedimentation. However, some basins remained marine and a few contain Oligocene turbidites and pelagic sediments deposited at bathyal depths. The Oligocene redbeds of California do not form a post-orogenic molasse sequence comparable to the Old Red Sandstone or Alpine molasse. They are synorogenic and record local uplift of basins and surrounding source areas. Late Cretaceous to contemporary orogenesis in California has been generally characterized by the formation of small restricted basins of variable depth adjacent to small upland areas in response to strike-slip faulting. Deposition of Oligocene redbeds was associated with climatic change from warm and humid to cold and semiarid, and a global lowering of sea level. Oligocene tectonism occurred during the transition from subduction of the Farallon Plate to initiation of the modern San Andreas transform system. However, the major influence that caused uplift, formation of fault-bounded basins, and extensive redbed deposition, especially in southern California, was the approach of the Pacific-Farallon spreading ridge to the western margin of California. ?? 1984.

  15. Oligocene tectonics and sedimentation, California

    NASA Astrophysics Data System (ADS)

    Nilsen, Tor H.

    1984-03-01

    During the Oligocene epoch, California was marked by extensive nonmarine sedimentation, in contrast to its pre-Oligocene and post-Oligocene depositional history. The Oligocene continental deposits are especially widespread in southern California and fill a number of small and generally partly restricted basins. Fluvial facies in many basins prograded over previously deposited lower Tertiary turbidites. Volcanism, from widespread centers, was associated with the nonmarine sedimentation. However, some basins remained marine and a few contain Oligocene turbidites and pelagic sediments deposited at bathyal depths. The Oligocene redbeds of California do not form a post-orogenic molasse sequence comparable to the Old Red Sandstone or Alpine molasse. They are synorogenic and record local uplift of basins and surrounding source areas. Late Cretaceous to contemporary orogenesis in California has been generally characterized by the formation of small restricted basins of variable depth adjacent to small upland areas in response to strike-slip faulting. Deposition of Oligocene redbeds was associated with climatic change from warm and humid to cold and semiarid, and a global lowering of sea level. Oligocene tectonism occurred during the transition from subduction of the Farallon Plate to initiation of the modern San Andreas transform system. However, the major influence that caused uplift, formation of fault-bounded basins, and extensive redbed deposition, especially in southern California, was the approach of the Pacific—Farallon spreading ridge to the western margin of California.

  16. Biotic drivers of fluvial sediment transport: Aggregate effects of sediment mobilisation by crayfish on catchment-scale sediment yield

    NASA Astrophysics Data System (ADS)

    Rice, Stephen; Mathers, Kate; Reeds, Jake; Extence, Chris

    2015-04-01

    Small but prolific organisms may be significant zoogeomorphic agents that make cumulative contributions to the large-scale terrestrial sediment cascade in, as yet, unknown and unquantified ways. One such organism is the signal crayfish (Pacifastacus leniusculus), which has invaded many European rivers. The geographical extent and abundance of this animal ensure innumerable local, small-scale interactions with the fluvial sediment system that have the potential to yield a substantial effect when aggregated across larger spatial and temporal scales. Here we estimate, for the first time, the proportion of the total annual sediment yield associated with crayfish activity in an infested river and examine the variability in crayfish-driven sediment flux integrated across daily, monthly and seasonal time scales. We focused on one of several mechanisms by which crayfish activities affect sediment dynamics: the mobilisation of fine sediments by foraging, fighting and burrowing under hydraulic conditions that are otherwise insufficient to entrain sediment. On the Brampton Branch of the River Nene, UK, a 12-month record of suspended sediment concentration (derived from a calibration of turbidity data against measured SSC) allowed calculation of sediment fluxes and integrated sediment loads at ten-minute intervals. Concurrent measurements of water depth and crayfish movements (using PIT tagging) confirmed that night-time crayfish activity was often associated with increased sediment fluxes in the absence of any change in hydraulic conditions. Sediment loads calculated for these periods of crayfish activity were compared with total loads to estimate the contribution made to sediment mobilisation by crayfish. Crayfish-induced fluxes were most significant during summer low-flows, becoming less important during winter when the crayfish were inactive and competent high flows dominated sediment transport. Nevertheless, the seasonal cumulative effect of crayfish was substantial and

  17. 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

  18. Fluvial sediments a summary of source, transportation, deposition, and measurement of sediment discharge

    USGS Publications Warehouse

    Colby, B.R.

    1963-01-01

    This paper presents a broad but undetailed picture of fluvial sediments in streams, reservoirs, and lakes and includes a discussion of the processes involved in the movement of sediment by flowing water. Sediment is fragmental material that originates from the chemical or physical disintegration of rocks. The disintegration products may have many different shapes and may range in size from large boulders to colloidal particles. In general, they retain about the same mineral composition as the parent rocks. Rock fragments become fluvial sediment when they are entrained in a stream of water. The entrainment may occur as sheet erosion from land surfaces, particularly for the fine particles, or as channel erosion after the surface runoff has accumulated in streams. Fluvial sediments move in streams as bedload (particles moving within a few particle diameters of the streambed) or as suspended sediment in the turbulent flow. The discharge of bedload varies with several factors, which may include particle size and a type of effective shear on the surface of the streambed. The discharge of suspended sediment depends partly on concentration of moving sediment near the streambed and hence on discharge of bedload. However, the concentration of fine sediment near the streambed varies widely, even for equal flows, and, therefore, the discharge of fine sediment normally cannot be computed theoretically. The discharge of suspended sediment also depends on velocity, turbulence, depth of flow, and fall velocity of the particles. In general, the coarse sediment transported by a stream moves intermittently and is discharged at a rate that depends on properties of the flow and of the sediment. If an ample supply of coarse sediment is available at the surface of the streambed, the discharge of the coarse sediment, such as sand, can be roughly computed from properties of the available sediment and of the flow. On the other hand, much of the fine sediment in a stream usually moves nearly

  19. Quantification of Gravel Rural Road Sediment Production

    NASA Astrophysics Data System (ADS)

    Silliman, B. A.; Myers Toman, E.

    2014-12-01

    Unbound rural roads are thought to be one of the largest anthropogenic sources of sediment reaching stream channels in small watersheds. This sediment deposition can reduce water quality in the streams negatively impacting aquatic habitat as well as impacting municipal drinking water sources. These roads are thought to see an increase in construction and use in southeast Ohio due to the expansion of shale gas development in the region. This study set out to quantify the amount of sediment these rural roads are able to produce. A controlled rain event of 12.7 millimeters of rain over a half hour period was used to drive sediment production over a 0.03 kilometer section of gravel rural road. These 8 segments varied in many characteristics and produced from 2.0 to 8.4 kilograms of sediment per 0.03 kilometers of road with the average production over the 8 segments being 5.5 kilograms of sediment. Sediment production was not strongly correlated with road segment slope but traffic was found to increase sediment production from 1.1 to 3.9 times as much sediment after traffic use. These results will help inform watershed scale sediment budgeting, and inform best management practices for road maintenance and construction. This study also adds to the understanding of the impacts of rural road use and construction associated with the changing land use from agricultural to natural gas extraction.

  20. Importance of elemental mercury in lake sediments.

    PubMed

    Bouffard, Ariane; Amyot, Marc

    2009-02-01

    Mercury (Hg) redox changes in sediments are poorly studied and understood, even though they potentially control Hg availability for methylation and can alter sediment-water Hg exchange. Elemental Hg (Hg(0)) concentrations in sediments of two Canadian Shield lakes were assessed by thermodesorption. Hg(0) concentrations in sediments varied between 6.3 and 60.3 pg g(-1) (wet weight) which represented 7.4-28.4% of total mercury (HgT) concentration. Hg(0) concentrations were similar in both lakes. Hg(0) was rapidly adsorbed on sediments in controlled adsorption experiments and surface sediments sampled in summer had a stronger affinity for Hg(0) than deeper sediments and sediments sampled in fall. This adsorption was positively correlated to organic matter content and negatively related to particle grain size, pH and oxygen concentration in overlying water. This study demonstrates that Hg(0) is a prevalent species in sediments, but not in porewater, because of the high sorptive capacity of sediments towards Hg(0). Its potential availability towards Hg methylating bacteria remains to be determined. PMID:19091379

  1. New Zealand sediment toxicity testing methodologies

    SciTech Connect

    Hickey, C.W.; Roper, D.S.; Nipper, M.; Martin, M.L.

    1995-12-31

    Sediment toxicity testing in New Zealand is developing against a background of an increasing public desire for environmental protection and strict legislative requirements that contaminant discharges should not have any significant adverse effects on aquatic life. The importance of sediment contamination and its potential immediate and long term adverse effects on aquatic biota in general is becoming widely recognized, This has lead to an effort to develop acute and chronic sediment toxicity tests with organisms representative of the New Zealand indigenous biota. An amphipod species occurring in both freshwater and estuarine environments, Chaetocorophium cf lucasi, and the marine bivalve Macomona liliana, a common inhabitant of intertidal sandflats, have been evaluated for their sensitivity to natural sediment characteristics. The amphipod and bivalve are presently being used for testing sediment acute (10d) and chronic toxicity (20--30d), with survival and growth as test endpoints, and the bivalve has shown to be a useful organism for behavioral tests with burial and sediment avoidance by movement and drifting as endpoints. The estuarine bivalve Arthritica bifurca, abundant in muddy sediments, is a self-fertilizing hermaphroditic species and its suitability for sediment tests with a reproductive endpoint is underway. Freshwater sphaeriid bivalves, Sphaerium novazelandiae, are also being used for survival, growth, reproduction and behavioral endpoints. Sensitivity to reference toxicants and results for contaminated sediments will be presented and discussed in relation to sediment quality criteria developed elsewhere.

  2. Carbon isotopic composition of Amazon shelf sediments

    SciTech Connect

    Showers, W.J.; Angle, D.G.; Nittrouer, C.A.; Demaster, D.J.

    1985-02-01

    The distribution of carbon isotopes in Amazon shelf sediment is controlled by the same processes that are forming the modern subaqueous delta. The terrestrial (-27 to -25 per thousand) isotopic carbon signal observed in surficial sediments near the river mouth extends over 400 km northwest along the shelf. Terrestrial carbon is associated with areas of rapid sediment accumulation (topset and foreset regions). A sharp boundary between terrestrial (-27 to -25 per thousand) and marine (-23 to -22 per thousand) isotopic carbon values in surficial sediments is associated with a change in depositional conditions (foreset to bottomset regions) and a decrease in sediment accumulation rate. POC water-column isotopic values (-27 per thousand) near the river mouth are similar to the underlying surficial-sediment TOC isotopic values, but POC water-column samples collected 20 km off the river mouth have marine carbon isotopic values (-22 to -19 per thousand) and differ from the underlying surficial-sediment TOC isotopic values. These water column observations are related to variations in turbidity and productivity. Down-core isotopic variation is only observed in cores taken in areas of lower sediment accumulation rates. These observations indicate that the organic carbon in Amazon shelf sediment is dominantly terrestrial in composition, and the location of deposition of this carbon is controlled by modern processes of sediment accumulation. The modern Amazon shelf is similar to large clinoform shale deposits of the Cretaceous in North America. Thus, the stratigraphic setting may help predict the isotopic variations of carbon in ancient deposits.

  3. Issues Relating To Sediment Toxicity Testing And Bioaccumulation Of Persistent Chemicals In SRS Sediments

    SciTech Connect

    WINONA, SPECHT

    2005-03-01

    Many chemical contaminants that enter a water body in an aqueous form are ultimately deposited to the sediments. Over time, the concentrations of contaminants in sediments may build up to concentrations that are much higher than those found in the water column. However, not all chemicals present in sediments are toxic/bioavailable. Factors that affect bioavailability include aqueous solubility, pH, redox, and composition of the sediment matrix (grain size, mineral constituents, organic matter), and for metals, the quantity of acid volatile sulfides that are present in the sediments. Many sediments contain multiple chemical contaminants, which may interact synergistically or antagonistically with respect to toxicity.

  4. Sediment acoustic index method for computing continuous suspended-sediment concentrations

    USGS Publications Warehouse

    Landers, Mark N.; Straub, Timothy D.; Wood, Molly S.; Domanski, Marian M.

    2016-01-01

    Once developed, sediment acoustic index ratings must be validated with additional suspended-sediment samples, beyond the period of record used in the rating development, to verify that the regression model continues to adequately represent sediment conditions within the stream. Changes in ADVM configuration or installation, or replacement with another ADVM, may require development of a new rating. The best practices described in this report can be used to develop continuous estimates of suspended-sediment concentration and load using sediment acoustic surrogates to enable more informed and accurate responses to diverse sedimentation issues.

  5. Sediment supply versus local hydraulic controls on sediment transport and storage in a river with large sediment loads

    NASA Astrophysics Data System (ADS)

    Dean, David J.; Topping, David J.; Schmidt, John C.; Griffiths, Ronald E.; Sabol, Thomas A.

    2016-01-01

    The Rio Grande in the Big Bend region of Texas, USA, and Chihuahua and Coahuila, Mexico, undergoes rapid geomorphic changes as a result of its large sediment supply and variable hydrology; thus, it is a useful natural laboratory to investigate the relative importance of flow strength and sediment supply in controlling alluvial channel change. We analyzed a suite of sediment transport and geomorphic data to determine the cumulative influence of different flood types on changing channel form. In this study, physically based analyses suggest that channel change in the Rio Grande is controlled by both changes in flow strength and sediment supply over different spatial and temporal scales. Channel narrowing is primarily caused by substantial deposition of sediment supplied to the Rio Grande during tributary-sourced flash floods. Tributary floods have large suspended-sediment concentrations, occur for short durations, and attenuate rapidly downstream in the Rio Grande, depositing much of their sediment in downstream reaches. Long-duration floods on the mainstem have the capacity to enlarge the Rio Grande, and these floods, released from upstream dams, can either erode or deposit sediment in the Rio Grande depending upon the antecedent in-channel sediment supply and the magnitude and duration of the flood. Geomorphic and sediment transport analyses show that the locations and rates of sand erosion and deposition during long-duration floods are most strongly controlled by spatial changes in flow strength, largely through changes in channel slope. However, spatial differences in the in-channel sediment supply regulate sediment evacuation or accumulation over time in long reaches (greater than a kilometer).

  6. PROFILE: Management of Sedimentation in Tropical Watersheds.

    PubMed

    NAGLE; FAHEY; LASSOIE

    1999-05-01

    / The sedimentation of reservoirs is a serious problem throughout the tropics, yet most attempts to control sedimentation in large river basins have not been very successful. Reliable information on erosion rates and sources of sediments has been lacking. In regions where geologically unstable terrain combines with high rainfall, natural erosion rates might be so high that the effects of human activity are limited. Estimates of natural erosion in these situations often have been poor because of the episodic nature of most erosion during large storms and because mass-wasting may supply much of the sediment. The predominance of mass-wasting in some watersheds can result in an unexpectedly high ratio of bedload to suspended load, shifting sedimentation to "live" rather than "dead" storage within reservoirs. Furthermore, the inappropriate use of the Universal Soil Loss Equation to assess the effectiveness of erosion control measures has led to inaccurate estimates of the sediment reduction benefits that could accrue to watershed treatment efforts. Although reducing erosion from cultivated areas is desirable for other reasons, efforts aimed at reducing reservoir sedimentation by controlling agricultural sources of erosion may have limited benefits if the principal sources are of natural origin or are associated with construction of the dams and reservoirs and with rural roads and trails. Finally, the most appropriate locations for watershed rehabilitation depend on the magnitude of temporary storage of colluvium and alluvium within the river basin: Where storage volume is large and residence time of sediment very long, reducing agricultural erosion may have limited impacts on sedimentation within the expected life of a reservoir. Systematic development and analysis of sediment budgets for representative watersheds is needed to address these limitations and thereby improve both the planning of river basin development schemes and the allocation of resources towards

  7. Suspended sediment and sediment-associated contaminants in San Francisco Bay

    USGS Publications Warehouse

    Schoellhamer, D.H.; Mumley, T.E.; Leatherbarrow, J.E.

    2007-01-01

    Water-quality managers desire information on the temporal and spatial variability of contaminant concentrations and the magnitudes of watershed and bed-sediment loads in San Francisco Bay. To help provide this information, the Regional Monitoring Program for Trace Substances in the San Francisco Estuary (RMP) takes advantage of the association of many contaminants with sediment particles by continuously measuring suspended-sediment concentration (SSC), which is an accurate, less costly, and more easily measured surrogate for several trace metals and organic contaminants. Continuous time series of SSC are collected at several sites in the Bay. Although semidiurnal and diurnal tidal fluctuations are present, most of the variability of SSC occurs at fortnightly, monthly, and semiannual tidal time scales. A seasonal cycle of sediment inflow, wind-wave resuspension, and winnowing of fine sediment also is observed. SSC and, thus, sediment-associated contaminants tend to be greater in shallower water, at the landward ends of the Bay, and in several localized estuarine turbidity maxima. Although understanding of sediment transport has improved in the first 10 years of the RMP, determining a simple mass budget of sediment or associated contaminants is confounded by uncertainties regarding sediment flux at boundaries, change in bed-sediment storage, and appropriate modeling techniques. Nevertheless, management of sediment-associated contaminants has improved greatly. Better understanding of sediment and sediment-associated contaminants in the Bay is of great interest to evaluate the value of control actions taken and the need for additional controls. ?? 2007 Elsevier Inc. All rights reserved.

  8. Aeolian sediment transport on a beach with a varying sediment supply

    NASA Astrophysics Data System (ADS)

    de Vries, S.; Arens, S. M.; de Schipper, M. A.; Ranasinghe, R.

    2014-12-01

    Variability in aeolian sediment transport rates have traditionally been explain by variability in wind speed. Although it is recognised in literature that limitations in sediment supply can influence sediment transport significantly, most models that predict aeolian sediment transport attribute a dominant role to the magnitude of the wind speed. In this paper it is proposed that spatio-temporal variability of aeolian sediment transport on beaches can be dominated by variations in sediment supply rather than variations in wind speed. A new dataset containing wind speed, direction and sediment transport is collected during a 3 day field campaign at Vlugtenburg beach, The Netherlands. During the measurement campaign, aeolian sediment transport varied in time with the tide while wind speed remained constant. During low tide, measured transport was significantly larger than during high tide. Measured spatial gradients in sediment transport at the lower and upper beaches during fairly constant wind conditions suggest that aeolian sediment transport on beaches may be partly governed by the spatial variability in sediment supply, with relatively large supply in the intertidal zone when exposed and small supply on the upper beach due to sorting processes. The measurements support earlier findings that the intertidal zone can be significant source of sediment for sediment transport on beaches. Both a traditional cubic model (with respect to the wind speed) and a newly proposed linear model are fitted to the field data. The fit quality of both types of models are found to be similar.

  9. Development of formulated reference sediments for freshwater and estuarine sediment testing

    SciTech Connect

    Suedel, B.C.; Rodgers, J.H. Jr. . Dept. of Biology)

    1994-07-01

    Sediments collected at various field locations may have chemical and physical constituents that influence test results and may contain organisms that cannot be readily removed. Thus, reference sediments are needed that can be formulated to match diverse freshwater and estuarine sediments encountered in comprehensive testing programs. This research evaluated formulated reference sediments in terms of (a) their ability to match field-collected sediments both chemically and physically; (b) their suitability as habitant (survival and reproduction) for typical invertebrate toxicity testing species (Hyalella azteca Saussure, Chironomus tentans Fabricius, and Daphnia magna Straus) during chronic exposures; and (c) their suitability as a substrate for Hyalella azteca, Chironomus tentans, Daphnia magna, Ceriodaphnia dubia Richard, and Pimephales promelas Rafinesque in 14-d whole-sediment exposures. Formulated reference sediments were prepared to match naturally occurring sediments with respect to particle-size distribution, organic matter, organic carbon, pH, solids, CEC, but not redox potential. After preparation, a conditioning period of at least 7 d was required for pH stabilization of formulated reference sediments. In culture experiments, formulated reference sediments was suitable for Hyalella azteca, Chironomus tentans, and Daphnia magna survival and reproduction for 56,40, and 28 d, respectively. Hyalella azteca, Chironomus tentans, Daphnia magna, Ceriodaphnia dubia and Pimephales promelas survival was [>=] 88% in 14-d exposures to formulated reference sediment. Formulated reference sediments may reduce some unexplained physical, chemical, or biological toxicity'' of field-collected sediments (e.g., organic matter) that may influence toxicity testing results.

  10. Sediment measurement in estuarine and coastal areas

    NASA Technical Reports Server (NTRS)

    Shelley, P. E.

    1976-01-01

    A survey of uses of estuarine and coastal areas is given. Problems associated with these uses are discussed, and data needs for intelligent management of these valuable areas are outlined. Suspended sediment measurements are seen to be one of the greatest needs. To help understand the complexity of the problem, a brief discussion of sediment mechanics is given, including sediment sources, characteristics, and transport. The impact of sediment mechanics on its direct measurement (sampling and analysis) is indicated, along with recommendations for directly obtaining representative data. Indirect measurement of suspended sediment by remote sensors is discussed both theoretically and in the light of some recent experiences. The need for an integrated, multidisciplinary program to solve the problem of quantitatively measuring suspended sediment with remote sensors is stressed, and several important considerations of such a program and benefits to be derived therefrom are briefly addressed.

  11. South Florida Coastal Sediment Ecological Risk Assessment.

    PubMed

    Julian, Paul

    2015-08-01

    This study evaluated the degree of sediment contamination in several South Florida estuaries. During the 2010 National Condition Assessment, Florida Fish and Wildlife Research Institute collected water column, sediment and biotic data from estuaries across the entire state of Florida. Sediments were analyzed for arsenic, cadmium, chromium, lead, mercury, zinc and total polychlorinated biphenyls and were compared relative to empirically derived sediment quality guidelines. As a result of this data collection and assessment effort, it was determined that the degree of contamination with respect to sediment was low for all southern Florida estuaries assessed, except the Miami River which was determined to be considerably contaminated. However only one monitoring location was used to assess the Miami River, and as such should be viewed with caution. A low degree of contamination was determined for Biscayne Bay sediments, possibly indicating a recovery from its previously reported higher contaminant level. PMID:26084967

  12. Continental margin sedimentation: from sediment transport to sequence stratigraphy

    USGS Publications Warehouse

    Nittrouer, Charles A., (Edited By); Austin, James A.; Field, Michael E.; Kravitz, Joseph H.; Syvitski, James P.M.; Wiberg, Patricia L.

    2007-01-01

    This volume on continental margin sedimentation brings together an expert editorial and contributor team to create a state-of-the-art resource. Taking a global perspective, the book spans a range of timescales and content, ranging from how oceans transport particles, to how thick rock sequences are formed on continental margins. - Summarizes and integrates our understanding of sedimentary processes and strata associated with fluvial dispersal systems on continental shelves and slopes - Explores timescales ranging from particle transport at one extreme, to deep burial at the other - Insights are presented for margins in general, and with focus on a tectonically active margin (northern California) and a passive margin (New Jersey), enabling detailed examination of the intricate relationships between a wide suite of sedimentary processes and their preserved stratigraphy - Includes observational studies which document the processes and strata found on particular margins, in addition to numerical models and laboratory experimentation, which provide a quantitative basis for extrapolation in time and space of insights about continental-margin sedimentation - Provides a research resource for scientists studying modern and ancient margins, and an educational text for advanced students in sedimentology and stratigraphy

  13. Dewatering of contaminated river sediments

    NASA Technical Reports Server (NTRS)

    Church, Ronald H.; Smith, Carl W.; Scheiner, Bernard J.

    1994-01-01

    Dewatering of slurries has been successfully accomplished by the proper use of polymers in flocculating the fine particulate matter suspended in mineral processing streams. The U.S. Bureau of Mines (USBM) entered into a cooperative research effort with the U.S. Army Corps of Engineers (Corps) for the purpose of testing and demonstrating the applicability of mining flocculation technology to dredging activities associated with the removal of sediments from navigable waterways. The Corps has the responsibility for maintaining the navigable waterways in the United States. Current technology relies primarily on dredging operations which excavate the material from the bottom of waterways. The Corps is testing new dredging technology which may reduce resuspension of sediments by the dredging operation. Pilot plant dredging equipment was tested by the Corps which generated larger quantities of water when compared to conventional equipment, such as the clam shell. The transportation of this 'excess' water adds to the cost of sediment removal. The process developed by the USBM consists of feed material from the barge being pumped through a 4-in line by a centrifugal pump and exiting through a 4-in PVC delivery system. A 1,000-gal fiberglass tank was used to mix the polymer concentrate. The polymer was pumped through a 1-in line using a variable speed progressive cavity pump and introduced to the 4-in feed line prior to passing through a 6-in by 2-ft static mixer. The polymer/feed slurry travels to the clarifying tank where the flocculated material settled to the bottom and allowed 'clean' water to exit the overflow. A pilot scale flocculation unit was operated on-site at the Corps' 'Confined Disposal Facility' in Buffalo, NY.

  14. Sulfate reduction and methanogenesis in marine sediments

    NASA Technical Reports Server (NTRS)

    Oremland, R. S.; Taylor, B. F.

    1978-01-01

    Methanogenesis and sulfate-reduction were followed in laboratory incubations of sediments taken from tropical seagrass beds. Methanogenesis and sulfate-reduction occurred simultaneously in sediments incubated under N2, thereby indicating that the two processes are not mutually exclusive. Sediments incubated under an atmosphere of H2 developed negative pressures due to the oxidation of H2 by sulfate-respiring bacteria. H2 also stimulated methanogenesis, but methanogenic bacteria could not compete for H2 with the sulfate-respiring bacteria.

  15. SEDIMENT TOTAL ORGANIC CARBON: IS THIS A USEFUL INDICATOR OF SEDIMENT CONDITION FOR PACIFIC NORTHWEST ESTUARIES?

    EPA Science Inventory

    Total organic carbon (TOC) content of sediments has been used as an indicator of benthic community condition during multiple cycles of the EPA National Coastal Assessment (NCA). Because percent TOC is generally positively correlated with sediment percent fines, previous analyses...

  16. Suspended sediments limit coral sperm availability

    PubMed Central

    Ricardo, Gerard F.; Jones, Ross J.; Clode, Peta L.; Humanes, Adriana; Negri, Andrew P.

    2015-01-01

    Suspended sediment from dredging activities and natural resuspension events represent a risk to the reproductive processes of coral, and therefore the ongoing maintenance of reefal populations. To investigate the underlying mechanisms that could reduce the fertilisation success in turbid water, we conducted several experiments exposing gametes of the corals Acropora tenuis and A. millepora to two sediment types. Sperm limitation was identified in the presence of siliciclastic sediment (230 and ~700 mg L−1), with 2–37 fold more sperm required to achieve maximum fertilisation rates, when compared with sediment-free treatments. This effect was more pronounced at sub-optimum sperm concentrations. Considerable (>45%) decreases in sperm concentration at the water’s surface was recorded in the presence of siliciclastic sediment and a >20% decrease for carbonate sediment. Electron microscopy then confirmed sediment entangled sperm and we propose entrapment and sinking is the primary mechanism reducing sperm available to the egg. Longer exposure to suspended sediments and gamete aging further decreased fertilisation success when compared with a shorter exposure. Collectively, these findings demonstrate that high concentrations of suspended sediments effectively remove sperm from the water’s surface during coral spawning events, reducing the window for fertilisation with potential subsequent flow-on effects for recruitment. PMID:26659008

  17. Mercury Methylation Rates in Prairie Wetland Sediments

    NASA Astrophysics Data System (ADS)

    Hoggarth, C.; Hall, B.

    2011-12-01

    The majority of methylmercury (MeHg) in aquatic ecosystems is likely produced through methylation of Hg(II) by sulfate-reducing and iron-reducing bacteria. Wetland sediments may be significant sites of MeHg production, due to the combination of anoxic conditions and availability of organic matter to support microbial activity. Methylmercury produced by methylation of inorganic mercury within wetland sediments may be transferred to the water column, allowing for bioaccumulation of neurotoxic MeHg in the aquatic food web. Little information is available on sediment MeHg and total mercury concentrations, mercury methylation rates, and MeHg flux to the water column in prairie wetlands. Sediment cores from the St. Denis National Wildlife Area (SDNWA), ~40 km east of Saskatoon in central Saskatchewan, Canada, will be collected to measure sediment mercury methylation rates, total mercury, and MeHg concentrations in prairie wetland sediments. The SDNWA has been a site of prairie wetland research since 1968 and is located near the northern boundary of the Prairie Pothole Region which supports 50-80% of North American waterfowl. Sediment MeHg production will be measured in 2011 through the injection of 201Hg stable isotope to sediment cores from 12 prairie wetlands located within and nearby the SDNWA. Amended sediment cores will be incubated in situ for four hours to allow methylation of a fraction of the inorganic mercury stable isotope to Me201Hg. Analysis of the incubated sediment cores will allow for measurement of MeHg production rates, MeHg, and total mercury concentrations. Additional sediment cores will be taken to determine sediment water content, organic content, and porosity. Water samples from sediment pore water and the wetland water column will be analyzed for MeHg, total mercury, DOC, sulphate, SUVA, and water chemistry. Methylmercury flux from sediment pore water to the overlying water column will be calculated. Sediment MeHg production rates in the 12

  18. Incipient motion of surf zone sediments

    NASA Astrophysics Data System (ADS)

    Frank, Donya; Foster, Diane; Sou, In Mei; Calantoni, Joseph

    2015-08-01

    Incipient motion experiments were conducted with natural gravel, acetate beads, and coarse-gravel-sized electronic grains called Smart Sediment Grains in a Small-Oscillatory Flow Tunnel. Measurements of fluid velocity were made using Particle Image Velocimetry. The strength of the fluid shear stresses and the pressure gradients were examined for a range of oscillatory flow conditions at the onset of motion of the sediment particles to determine which mechanism had induced particle motion. The three sediment types utilized in these experiments facilitated an assessment of the effects of sediment grain size diameter, shape, and density on incipient motion. Results suggested that the onset of sediment motion was dominated by the pressure gradients for flows with small orbital excursion amplitudes, by the shear stresses for flows with large orbital excursion amplitudes and by the combined effects for intermediate flows. The denser, angular gravel required greater free-stream accelerations to trigger sediment motion than the spherical, less dense acetate beads, and Smart Sediment Grains. A combined parameter for incipient motion that accounts for the simultaneous effects of both shear stresses and pressure gradients while depending on the static coefficient of friction and the packing concentration of the mobile bed layer was evaluated for accuracy using a range of sediment types. The results suggested that the combined parameter may be a better indicator of sediment mobilization under oscillatory flows than the typically assumed shear stress criterion.

  19. Sediment Sources in the Persian Gulf

    NASA Astrophysics Data System (ADS)

    Mahoutian, Mehrab

    2014-05-01

    Sediment Constituent Analysis is an effective tool for identifying sediment sources. Based on several sediment samples taken from different sites all over the Iranian coastlines, we have been able to show that an important portion of sediment on the beaches in the Persian Gulf is bio-clastic; that is, biologically created from the coral environment as well as other marine habitats. Unlike mineral (clastic) sediments, carbonate sediments are born not made. Furthermore, carbonate sand constituents are generally less durable than their quartz and mineral counterparts, and break down relatively quickly. Therefore, destruction of reefs and degradation of marine habitat are certain to reduce the sand supply to the shoreline in the Persian Gulf that is necessary to maintain beaches. Carbonate sands are also found on the coastline of the Oman Sea. One of the striking things about the sediments along the coastline of Iran is the high percentage of carbonate material. Molluscan debris is common, even ubiquitous. This reflects the populations living in the offshore waters. Some molluscs thrive in high-energy sandy environments, others like finer sediments. Some live at the surface, while some burrow down as much as a half-metre. A great deal of information can be gained from the study of the species of mollusk and their distribution in the sediments. This paper introduces a few case studies done in different parts of the Persian Gulf by using this method as a general assessment toolbox.

  20. Measuring the acute toxicity of estuarine sediments

    SciTech Connect

    DeWitt, T.H.; Swartz, R.C.; Lanberson, J.O.

    1989-01-01

    Estuarine sediments frequently are repositories and sources of anthropogenic contaminants. Toxicity is one method of assessing the environmental quality of sediments, yet because of the extreme range of salinities that characterize estuaries few infaunal organisms have both the physiological tolerance and sensitivity to chemical contaminants to serve in estuarine sediment toxicity tests. The study describes research on the estuarine burrowing amphipod, Eohaustorius estuarius Bosworth, 1973, whose survival was >95% in control sediments across a 2 to 28% salinity range over 10-d periods. E. estuarius also was acutely sensitive to low sediment concentrations of the polycyclic aromatic hydrocarbon, fluoranthene (LC50 approximately = 10.6 mg/kg), and its sensitivity to fluoranthene was not affected by salinity. E. estuarius was almost as sensitive as Rhepoxynius abronius to fluoranthene and to field-collected sediments from Puget Sound urban and industrial bays. E. estuarius was also more tolerant of very fine, uncontaminated sediments than R. abronius. Furthermore, E. estuarius was more sensitive to sediments spiked with fluoranthene than the freshwater amphipod, Hyalella azteca. E. estuarius, and possibly other estuarine haustoriid species, appears to be an excellent candidate for testing the acute toxicity if estuarine and marine sediments.

  1. Sediment reservoirs and sediment fluxes in high mountain environments: how does sediment move through the system at the decadal scale?

    NASA Astrophysics Data System (ADS)

    Micheletti, Natan; Lambiel, Christophe; Lane, Stuart N.

    2016-04-01

    Faced with rapid climate warming over recent decades, high mountain systems are likely to respond dramatically because of: (1) the vulnerability of permafrost, glacial and nival processes to temperature and precipitation changes; (2) the ample availability of unconsolidated, potentially mobile sediments left after deglaciation; and (3) steep slopes, that potentially aid sediment mobilization. We no surprisingly know little about these processes over the decadal scale because the geomorphic response is often complex, spatially and temporally, and there is little history of decadal scale measurement of these systems. In this paper, we focus upon a number of basins in the Southern Swiss Alps, with a wide range of primary sediment transfer mechanisms and altitude ranges up to 1,800 to 3,600 m asl. We are able to combine a set of unique data on: (1) erosion/deposition processes (derived from combined geomorphological maps and photogrammetrically-derived Digital Elevation Models); (2) sediment flux based upon tracking sediment using image correlation; (3) sediment connection quantified using a new approach to handle DEM noise; (4) changing stream sediment transport capacity derived from hydrodynamic modeling applied to long time series of river flow; and (5) sediment export measured at intakes flushed periodically as part of hydropower management. Results suggest a distinct landscape response to climatic forcing. A progressive acceleration of surface displacements for different landforms is observed throughout the last five decades. We observed that, with the beginning of a warmer period in the 1980s, glacier retreat and enhanced snowmelt caused water yield to increase considerably for various watersheds. This translates into enhancement of sediment transport capacities, which in combination with the intensification of landscape dynamics (greater erosion rates) explains the increase flushing frequency and hence sediment export registered in the basins. However, whilst

  2. Dating sediment in a fast sedimentation reservoir using 137Cs and 210Pb

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Over 10,000 reservoirs have been constructed in agricultural watersheds in the United States since the 1940s to control floods and sediments. Reservoir sedimentation records provide a unique opportunity to retrospectively study the effects of land use changes and climate variations on sediment produ...

  3. Accurate lacustrine and wetland sediment accumulation rates determined from 14c activity of bulk sediment fractions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In the absence of identifiable macrofossils in lacustrine sediments, 14C dating must rely on pollen or bulk sediment fractions. Bulk sediment fractions are not generally preferred because they contain an unknown mixture of organic material of variable age, they may contain dead carbon such as ligni...

  4. [Limnology of high mountain tropical lake, in Ecuador: characteristics of sediments and rate of sedimentation].

    PubMed

    Gunkel, Günter

    2003-06-01

    Equatorial high mountain lakes are a special type of lake occurring mainly in the South American Andes as well as in Central Africa and Asia. They occur at altitudes of a few thousand meters above sea level and are cold-water lakes (< 20 degrees C). Relatively little is known about them. A long-term limnological study was therefore undertaken at Lake San Pablo, Ecuador, to analyze the basic limnological processes of the lake, which has a tendency for eutrophication. Sediment quality of San Pablo Lake is given under consideration of horizontal and vertical distribution using sediment cores. Significance of sediments for eutrophication process of lakes is demonstrated using phosphorus concentration of sediments as well as the phosphorus retention capacity of the sediments by ratio Fe/P. Dating of the sediments is done using 137Cs and 210Pb, but the activity of 137Cs in the sediment was very low nearly at the detection level. Sedimentation rate is determined to be 3.5 mm/year and the sediment cores represent about 110 years. P concentration of the sediments is high (approximately 5 g/kg dry substance), and P retention capacity by Fe is insufficient (Fe/P = 4). The sediment quality did not change significantly during the past decades, and the trophic state of San Pablo Lake was already less or more eutrophic 110 years ago. The contamination of the lake sediments by heavy metals is insignificant. PMID:15162731

  5. BASELINE SEDIMENT CHARACTERISTICS AND SEDIMENTATION PATTERNS ON THE VIRGINIA PORTION OF THE CHESAPEAKE BAY

    EPA Science Inventory

    The distribution patterns of sediment physical properties, deposition patterns, and sediment accumulation rates provide an integrating framework for investigations of toxic substance concentration and distribution. Over 2,000 surface-sediment grab samples (1.4 km grid) reveal tha...

  6. Microcystin elimination during sediment contact.

    PubMed

    Grützmacher, Gesche; Wessel, Gabriele; Klitzke, Sondra; Chorus, Ingrid

    2010-01-15

    Microcystins (MCYSTs) are a group of structurally similar toxic peptides produced by cyanobacteria ("blue-green algae") which occur frequently in surface waters worldwide. Reliable elimination is necessary when using these waters as drinking water sources. Bank filtration and artificial groundwater recharge utilize adsorption and degradation processes in the subsurface, commonly through sand and gravel aquifers, for the elimination of a wide range of substances during drinking water (pre-) treatment. To obtain parameters for estimating whether MCYST breakthrough is likely in field settings, we tested MCYST elimination in laboratory experiments (batch experiments, column experiments) under a range of conditions. Adsorption coefficients (k(d)-values) obtained from batch studies ranged from 0.2 mL/g for filter sand to 11.6 mL/g for fine grained aquifer materials with 2% fine grains (<63 microm) and 0.8% organic matter. First order degradation rates in column studies reached 1.87 d(-1) under aerobic conditions and showed high variations under anoxic conditions (<0.01-1.35 d(-1)). These results show that, next to sediment texture, redox conditions play an important role for MCYST elimination during sediment passage. Biodegradation was identified as the dominating process for MCYST elimination in sandy aquifer material. PMID:20000604

  7. Modern sedimentation and sediment dispersal pattern off southwestern Taiwan

    NASA Astrophysics Data System (ADS)

    Hsu, Sheng-Ting; Su, Chih-Chieh; Tsai, Po-Hsuan; Cheng, Yiya

    2015-04-01

    Taiwan is located at the collision zone between the Eurasian and Philippine Sea Plates and also on the Western North Pacific corridor of typhoons. Every year, three to four typhoons will invaded Taiwan and brought heavy rainfall. The active tectonic setting and climatic conditions create the extremely high sediment yield and export to the ocean. Our study area is located offshore southwestern Taiwan which is mainly composed of a narrow Gaoping Shelf and broad Gaoping Slope. Four major submarine canyons, the Shoshan Submarine Canyon, Kaohsiung Submarine Canyon, Gaoping Submarine Canyon, and Fangliao Submarine Canyon, extended into deep sea, through Penghu Submarine Canyon and subsequently merged into north terminus of Manila Trench. Over 50 box and gravity cores were collected by using R/V Ocean Research 1, 3 and 5 from 2005 to 2014. The cores were split and conducted core description and surface photographs at the Core Laboratory of the Taiwan Ocean Research Institute (TORI). The following analyses, including X-radiography, bulk density, particle size, Pb-210 chronology, were accomplished at the Marine Radioactivity and Sedimentology Lab at the Institute of Oceanography, National Taiwan University. The grain size analysis result shows a finer trend from coastal to deep water , except for the lower Fangliao basin which the grain size is larger than the expected value. According to the previous studies on the Pingtung Earthquake induced submarine geohazard, the Fangliao Submarine Canyon and the Lower Fangliao Basin is an important conduit for gravity flow which triggered large scale submarine cable breakages and left coarse sediments on the passage. By using the excess Pb-210 derived sediment accumulation rates, Huh et al. (2009) suggested the depocenter off the southwestern Taiwan is located at the flank of the Gaoping Canyon over the upper slope with the highest rate >1 cm/yr. In this study we integrate the Pb-210 inventory data which covered the area from the

  8. LABORATORY SEDIMENT TOXICITY TESTS, SEDIMENT CHEMISTRY AND DISTRIBUTION OF BENTHIC MACROINVERTEBRATES IN SEDIMENTS FROM THE KEWEENAW WATERWAY, MICHIGAN

    EPA Science Inventory

    Acute laboratory sediment toxicity tests using the water flea Daphnia magna and the burrowing mayfly nymph Hexagenia limbata were conducted on sediments from two areas of the Keweenaw Waterway, Michigan, to determine whether the tests reflected the condition of benthic macroinver...

  9. Influence of wave and current flow on sediment-carrying capacity and sediment flux at the water-sediment interface.

    PubMed

    Zheng, Jun; Li, Ruijie; Yu, Yonghai; Suo, Anning

    2014-01-01

    In nearshore waters, spatial and temporal scales of waves, tidal currents, and circulation patterns vary greatly. It is, therefore, difficult to combine these factors' effects when trying to predict sediment transport processes. This paper proposes the concept of significant wave velocity, which combines the effects of waves, tides, and ocean currents using the horizontal kinetic energy superposition principle. Through a comparison of the relationship between shear stress at the water-sediment interface and sediment-carrying capacity, assuming equilibrium sediment flux, a new formula for sediment-carrying capacity, which incorporates the concept of significant wave velocities, is derived. Sediment-carrying capacity is a function of the critical velocity, which increases with water depth and decreases with increasing relative roughness of the sea bed. Finally, data from field observation stations and simulations are used to test the proposed formula. The results show that the new formula is in good agreement with both field and simulation data. This new formula for sediment-carrying capacity can be used to simulate nearshore sediment transport. PMID:25259499

  10. Surface sediment analysis and modern sedimentation rates in Flandres Bay, Western Antarctic Peninsula

    NASA Astrophysics Data System (ADS)

    Munoz, Y. P.; Wellner, J. S.; Mead, K. A.

    2012-12-01

    Flandres Bay is located on the west side of the Antarctic Peninsula, where temperatures have risen more than the global average over the last century and where many glaciers have shown signs of retreat in recent decades. The Antarctic Ice Cap drains through tidewater glaciers that flow into bays around the peninsula. In this study, multibeam swath bathymetry data, seismic profiles, and sediment cores were used to determine the distribution of surface sediment types and modern sedimentation rates and compare these to the sediment accumulation down core. The bathymetry of the fjord includes small basins with flat bottoms, highly irregular seamounts, and deep channels in the bedrock as well as subglacial geomorphic features carved by the flow of glaciers. Results of sediment analysis show a variation in sediment type throughout the bay from pebbles with minor matrix close to the glacial calving margin to muddy diatomaceous ooze in the outer bay. Sediment accumulation rates were measured using 137 Cs counts on bulk sediment and 14 C on carbonate, usually forams, found after sieving bulk sediment. Samples for 137 Cs were taken on the top few centimeters of sediment cores and show a higher rate of sediment accumulation compared to rates calculated using 14 C, which measures millennial scale accumulation rates to the base of the core. Density logs of the sediment cores have relatively consistent values, indicating that the change in calculated accumulation rates is not simply due to compaction. As predicted, accumulation rates are higher close to the glaciers, where there is a high occurrence of ice rafted debris and dropstones; the sedimentation rates decrease away from the source and sediment analysis shows an increase in the biogenic component in the sediment, especially diatoms, in the outer bay. Other fjords adjacent to Flandres Bay, including Beascochea to the south, show similar trends of increasing rates of sediment accumulation in the upper portions of cores. In

  11. Suspended sediment yield in Texas watersheds

    NASA Astrophysics Data System (ADS)

    Coonrod, Julia Ellen Allred

    The Texas Water Development Board collected suspended sediment samples across the state of Texas for approximately 60 years. Until this research, no comprehensive analysis of the data had been conducted. This study compiles the suspended sediment data along with corresponding streamflow and rainfall. GIS programs are developed which characterize watersheds corresponding to the sediment gauging stations. The watersheds are characterized according to topography, climate, soils, and land use. All of the data is combined to form several SAS data sets which can subsequently be analyzed using regression. Annual data for all of the stations across the state are classified temporally and spatially to determine trends in the sediment yield. In general, the suspended sediment load increases with increasing runoff but no correlation exists with rainfall. However, the annual average rainfall can be used to classify the watersheds according to climate, which improves the correlation between sediment load and runoff. The watersheds with no dams have higher sediment loads than watersheds with dams. Dams in the drier parts of Texas reduce the sediment load more than dams in the wetter part of the state. Sediment rating curves are developed separately for each basin in Texas. All but one of the curves fall into a band which varies by about two orders of magnitude. The study analyzes daily time series data for the Lavaca River near Edna station. USGS data are used to improve the sediment rating curve by the addition of physically related variables and interaction terms. The model can explain an additional 41% of the variability in sediment concentration compared to a simple bivariate regression of sediment load and flow. The TWDB daily data for the Lavaca River near Edna station are used to quantify temporal trends. There is a high correlation between sediment load and flowrate for the Lavaca River. The correlation can be improved by considering a flow-squared term and by

  12. Managing sediment to minimize environmental impacts

    SciTech Connect

    Sherman, K.

    1995-12-31

    When considering licensing of a hydroelectric project, FERC must give equal consideration to power and nonpower values such as environmental resources. A case study is the existing Rock-Creek Cresta Project, located on the North Fork of the Feather River in northern California, which is in the process of relicensing by the Commission. This project includes two reservoirs - Rock Creek and Cresta Reservoirs, each formed by a dam that diverts water from the river into a tunnel and to a powerhouse. The watershed includes large natural and man-made sediment sources. Rock Creek Reservoir has accumulated 3.9 million cubic yards of sediments since the dam was built in 1950; Cresta Reservoir has accumulated 2.9 million cy of sediments since 1949. Operational problems began in the 1980s. As part of the relicensing process, Pacific Gas & Electric Company (PG&E) initially proposed a combination of dredging 500,000 cy of sediment from each reservoir, land disposal of dredged sediments, followed by sediment pass-through to achieve a long term net balance of sediment inflow and outflow. This proposal had substantial economic costs and environmental impact. Potential environmental effects included impacts to water quality and aquatic organisms and to terrestrial habitat from disposal of a million cy of dredged sediments. PG&E used physical and mathematical models to develop an innovative approach that minimized the amount of sediment needed to be dredged by limiting dredging to the area immediately adjacent to the intake structures. This would also tend to minimize impacts to water quality and aquatic habitat by reducing the area of disturbance within the reservoirs. PG&E proposes to keep the intake areas open and provide for long-term sediment pass-through by providing additional low-level outlet capacity. This would permit reservoir drawdown, which would increase velocities and sediment movement out of the reservoirs.

  13. Quantifying sediment connectivity in Wadi Al-Arab (NW Jordan) using a sediment budget approach

    NASA Astrophysics Data System (ADS)

    Kraushaar, Sabine; Pöppl, Ronald

    2015-04-01

    Due to data scarcity, sediment connectivity most often only qualitatively describes the potential transfer of sediments through a landscape. However, quantitative information on sediment delivery is of special relevance for modelling approaches as well as for sustainable land and water management, especially in water scarce regions such as Jordan, where valuable water reservoirs suffer from sediment pollution. Measurements are needed to quantify sediment outputs of the different land units and to trace their pathways though the catchments. This study uses the outcomes of a multiple response sediment budget approach conducted in the Wadi al-Arab catchment in northwest Jordan (263.5 km²) to quantify sediment connectivity. The catchment shows a Mediterranean to semi arid climate and consists of carbonatic and marly geology of the Upper Cretaceous. The topography ranges from rolling hills in the East to steeper mountainous areas in the North and West were olive orchards are the main agricultural use. Soil erosion measurements in the main land use units and relevant sediment sources, such as olive orchards, agricultural fields, and natural vegetated slopes uncovered the potential ranges of soil erosion rates in these units. Furthermore, the annual sediment yield in the Wadi Al Arab water reservoir was calculated. With the extrapolation of the erosion rates of the main contributing land use units and the annual sediment amount that reaches the sink, a maximum value of lateral sediment connectivity could be quantified, reaching up to 18%. A multiple sediment fingerprint method was used to delineate the relative contribution of each measured source to the sink based on the lake sediment samples. Supported by additional 137Cs analysis of terrace samples and a survey of the Wadi bed a high longitudinal connectivity could be derived. The applied method mix allowed the quantification of lateral sediment connectivity on catchment scale and gave a comprehensive understanding of

  14. Accounting for Long Term Sediment Storage in a Watershed Scale Numerical Model for Suspended Sediment Routing

    NASA Astrophysics Data System (ADS)

    Keeler, J. J.; Pizzuto, J. E.; Skalak, K.; Karwan, D. L.; Benthem, A.; Ackerman, T. R.

    2015-12-01

    Quantifying the delivery of suspended sediment from upland sources to downstream receiving waters is important for watershed management, but current routing models fail to accurately represent lag times in delivery resulting from sediment storage. In this study, we route suspended sediment tagged by a characteristic tracer using a 1-dimensional model that implicitly includes storage and remobilization processes and timescales. From an input location where tagged sediment is added, the model advects suspended sediment downstream at the velocity of the stream (adjusted for the intermittency of transport events). Deposition rates are specified by the fraction of the suspended load stored per kilometer of downstream transport (presumably available from a sediment budget). Tagged sediment leaving storage is evaluated from a convolution equation based on the probability distribution function (pdf) of sediment storage waiting times; this approach avoids the difficulty of accurately representing complex processes of sediment remobilization from floodplain and other deposits. To illustrate the role of storage on sediment delivery, we compare exponential and bounded power-law waiting time pdfs with identical means of 94 years. In both cases, the median travel time for sediment to reach the depocenter in fluvial systems less than 40km long is governed by in-channel transport and is unaffected by sediment storage. As the channel length increases, however, the median sediment travel time reflects storage rather than in-channel transport; travel times do not vary significantly between the two different waiting time functions. At distances of 50, 100, and 200 km, the median travel time for suspended sediment is 36, 136, and 325 years, orders of magnitude slower than travel times associated with in-channel transport. These computations demonstrate that storage can be neglected for short rivers, but for longer systems, storage controls the delivery of suspended sediment.

  15. Modeling a mountain basin sediment cascade

    NASA Astrophysics Data System (ADS)

    Bennett, Georgie; Molnar, Peter; McArdell, Brian; Burlando, Paolo

    2013-04-01

    Mountain basins are most sensitive to climate change because of the dependence of snow and ice melt processes, surface weathering and erosion on air temperature, combined with their rapid rainfall-runoff response. Consequently, sediment yield from mountain basins will also likely be related to climate variability. Constructing sediment budgets is the first step towards understanding the interaction of climate and earth-surface processes. Recently, mountain basin sediment transfer has been conceptualized as a sediment cascade in which, following erosion, sediment travels through multiple cycles of storage and remobilization before exiting the basin. However, few studies have extended this concept beyond the identification and quantification of individual processes and storage units. In this study we have developed a probabilistic sediment cascade model based on a sediment budget spanning more than 4 decades in the Illgraben, an active, debris-flow prone basin in the Swiss Alps. We use this model to investigate the role of thresholds and hydrological and sediment storage dynamics in the transformation of the observed probability distribution of slope failures into that of debris flows. The sediment cascade model consists of a hydrological and sediment module, both of which are based on a spatially lumped storage reservoir representation of the involved physical processes. Water and sediment are generated and routed according to conceptual rules and thresholds which we define and calibrate based on observations. We run simulations with stochastic sediment input drawn from the power-law distribution of slope failures and observed climatic variables (precipitation and air temperature) at the daily resolution for the period 2000-2009, and investigate the outputs of the model in terms of (1) the probability distribution and (2) the timing of sediment discharge events compared to observed debris flows. The triggering of debris flows in our model is conditioned by the

  16. Sediment Source Tracking in the Georgia Piedmont

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Preliminary results on the source of suspended sediment in a southern Piedmont stream are presented. Nuclear fallout radionuclide 137Cs and three other natural tracers were used to estimate the relative contribution of bank and upland sediment sources. Tracer concentrations were determined in potent...

  17. Laboratory theory and methods for sediment analysis

    USGS Publications Warehouse

    Guy, Harold P.

    1969-01-01

    The diverse character of fluvial sediments makes the choice of laboratory analysis somewhat arbitrary and the pressing of sediment samples difficult. This report presents some theories and methods used by the Water Resources Division for analysis of fluvial sediments to determine the concentration of suspended-sediment samples and the particle-size distribution of both suspended-sediment and bed-material samples. Other analyses related to these determinations may include particle shape, mineral content, and specific gravity, the organic matter and dissolved solids of samples, and the specific weight of soils. The merits and techniques of both the evaporation and filtration methods for concentration analysis are discussed. Methods used for particle-size analysis of suspended-sediment samples may include the sieve pipet, the VA tube-pipet, or the BW tube-VA tube depending on the equipment available, the concentration and approximate size of sediment in the sample, and the settling medium used. The choice of method for most bed-material samples is usually limited to procedures suitable for sand or to some type of visual analysis for large sizes. Several tested forms are presented to help insure a well-ordered system in the laboratory to handle the samples, to help determine the kind of analysis required for each, to conduct the required processes, and to assist in the required computations. Use of the manual should further 'standardize' methods of fluvial sediment analysis among the many laboratories and thereby help to achieve uniformity and precision of the data.

  18. Extrapolation of Biota-sediment Accumulation Factors

    EPA Science Inventory

    When assessing risks at sites with contaminated sediments, risk assessors need to estimate residues in fish and other aquatic biota based upon the levels of contaminants in the sediments. Unfortunately, risk assessors are often challenged by data limitations, i.e., i) contaminan...

  19. Climate variations, soil conservation and reservoir sedimentation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The integrated effects of soil conservation and a wetter climate on reservoir sedimentation were investigated for the Fort Cobb Reservoir watershed in west-central Oklahoma. A 12% wetter climate since the mid-1980s led to an increase in soil erosion and downstream sediment yield that offset the redu...

  20. Fine-Sediment Loadings to Lake Tahoe

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Over the past 35 years, a trend of decreasing water clarity has been documented in Lake Tahoe, attributable in part to the delivery of fine-grained sediments emanating from upland and channel sources. The overall objective of the research reported here was to determine the amount of fine sediment de...

  1. Landscape self organisation: Modelling Sediment trains

    NASA Astrophysics Data System (ADS)

    Schoorl, J. M.; Temme, A. J. A. M.; Veldkamp, A.

    2012-04-01

    Rivers tend to develop towards an equilibrium length profile, independently of exogenous factors. In general, although still under debate, this so-called self-organisation is assumed to be caused by simple feedbacks between sedimentation and erosion. Erosion correlates positively with gradient and discharge and sedimentation negatively. With the LAPSUS model, which was run for the catchment of the Sabinal, a small river in the South of Spain, this interplay of erosion and sedimentation results in sediment pulses (sequences of incision and sedimentation through time). These pulses are visualised in a short movie ( see http://www.youtube.com/watch?v=V5LDUMvYZxU). In this case the LAPSUS model run did not take climate, base level nor tectonics into account. Therefore, these pulses can be considered independent of them. Furthermore, different scenarios show that the existence of the pulses is independent of precipitation, erodibility and sedimentation rate, although they control the number and shape of the pulses. A fieldwork check showed the plausibility of the occurrence of these sediment pulses. We conclude that the pulses as modelled with LAPSUS are indeed the consequence of the feedbacks between erosion and sedimentation and are not depending on exogenous factors. Keywords: Landscape self-organisation, Erosion, Deposition, LAPSUS, Modelling

  2. Sediment retention in rangeland riparian buffers.

    PubMed

    Hook, Paul B

    2003-01-01

    Controlling nonpoint-source sediment pollution is a common goal of riparian management, but there is little quantitative information about factors affecting performance of rangeland riparian buffers. This study evaluated the influence of vegetation characteristics, buffer width, slope, and stubble height on sediment retention in a Montana foothills meadow. Three vegetation types (sedge wetland, rush transition, bunchgrass upland) were compared using twenty-six 6- x 2-m plots spanning 2 to 20% slopes. Plots were clipped moderately (10-15 cm stubble) or severely (2-5 cm stubble). Sediment (silt + fine sand) was added to simulated overland runoff 6, 2, or 1 m above the bottom of each plot. Runoff was sampled at 15-s to > 5-min intervals until sediment concentrations approached background levels. Sediment retention was affected strongly by buffer width and moderately by vegetation type and slope, but was not affected by stubble height. Mean sediment retention ranged from 63 to > 99% for different combinations of buffer width and vegetation type, with 94 to 99% retention in 6-m-wide buffers regardless of vegetation type or slope. Results suggest that rangeland riparian buffers should be at least 6 m wide, with dense vegetation, to be effective and reliable. Narrower widths, steep slopes, and sparse vegetation increase risk of sediment delivery to streams. Vegetation characteristics such as biomass, cover, or density are more appropriate than stubble height for judging capacity to remove sediment from overland runoff, though stubble height may indirectly indicate livestock impacts that can affect buffer performance. PMID:12809315

  3. TRACKING SEDIMENT REDISTRIBUTION IN A SMALL WATERSHED

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A new method is used to track erosion, translocation, and re-deposition of sediment in a small watershed, thus allowing for the first time a complete, spatially distributed, sediment balance to be made as a function of landscape position. A 0.68 ha watershed in Coshocton, OH was divided into six mo...

  4. PORTABLE DEVICE FOR MEASURING SEDIMENT RESUSPENSION

    EPA Science Inventory

    A portable device for measuring sediment resuspension has been developed. he device consists of a cylindrical chamber inside of which a horizontal grid oscillates vertically. he sediments whose properties are to be determined are placed at the bottom of the chamber with water ove...

  5. Mean sediment residence time in barchan dunes

    NASA Astrophysics Data System (ADS)

    Zhang, D.; Yang, X.; Rozier, O.; Narteau, C.

    2014-03-01

    When a barchan dune migrates, the sediment trapped on its lee side is later mobilized when exposed on the stoss side. Then sand grains may undergo many dune turnover cycles before their ejection along the horns, but the amount of time a sand grain contributes to the dune morphodynamics remains unknown. To estimate such a residence time, we analyze sediment particle motions in steady state barchans by tracking individual cells of a 3-D cellular automaton dune model. The overall sediment flux may be decomposed into advective and dispersive fluxes to estimate the relative contribution of the underlying physical processes to the barchan shape. The net lateral sediment transport from the center to the horns indicates that dispersion on the stoss slope is more efficient than the convergent sediment fluxes associated with avalanches on the lee slope. The combined effect of these two antagonistic dispersive processes restricts the lateral mixing of sediment particles in the central region of barchans. Then, for different flow strengths and dune sizes, we find that the mean residence time of sediment particles in barchans is equal to the surface of the central longitudinal dune slices divided by the input sand flux. We infer that this central slice contains most of the relevant information about barchan morphodynamics. Finally, we initiate a discussion about sediment transport and memory in the presence of bed forms using the advantages of the particle tracking technique.

  6. Seasonal sediment and nutrients transport patterns

    Technology Transfer Automated Retrieval System (TEKTRAN)

    It is essential to understand sediment and nutrient sources and their spatial and temporal patterns in order to design effective mitigation strategies. However, long-term data sets to determine sediment and nutrient loadings are scarce and expensive to collect. The goal of this study was to determin...

  7. HARBOR ISLAND REMEDIAL INVESTIGATION, MARINE SEDIMENT

    EPA Science Inventory

    The data set contains marine sediment data from a remedial investigation of Harbor Island, a National Priority List (NPL) Superfund site in Washington State. Both surface and subsurface marine sediments were collected. A station data set contain sampling station location and desc...

  8. Sediment transport in a curved channel

    SciTech Connect

    Altunin, V.S.; Larinova, L.V.; Martinkus, A.T.; Novikova, N.M.

    1987-11-01

    The authors construct mathematical and experimental flow models to describe the hydrodynamic behavior of sediments eroding into hydroelectric plant waterways for purposes of arriving at sediment reclamation scenarios as well as optimizing waterway design parameters for the minimization of erosion. The models simulate both straight and curved waterways and also allow the determination of the cross-sectional design.

  9. FIELD VALIDATION OF SEDIMENT TIE METHODS

    EPA Science Inventory

    Sediment toxicity is a widely recognized problem in many regions of the world. Frequently, however, the cause of toxicity is not known. The ability to identify the cause(s) of toxicity in sediments allows managers to determine sources of continuing contamination to support sele...

  10. Phytoplankton and sediments in Yellow Sea

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Sediment and phytoplankton cloud the waters of the Yellow Sea in this true-color MODIS image acquired March 18, 2002. The swirls of sediment appear as a murky brownish blue color, while the phytoplankton are purely blue green and are concentrated around the small island in the lower right corner of the image.

  11. An introduction to carbonate sediments and rocks

    SciTech Connect

    Scoffin, T.P.

    1986-01-01

    This book provides an approach to the study of carbonate sediments and sedimentary rocks. Topics covered include the following: nature and origins of common carbonate grains; processes of sedimentation; the growth and structure of coral reefs; distribution of modern marine carbonates; diagenesis; classification of limestone; facies models and sequences in ancient limestone; economic aspects; and field and laboratory techniques.

  12. TOXICITY OF SEDIMENT-INCORPORATED DRILLING FLUIDS

    EPA Science Inventory

    The 24, 96, or 168-h LC50s of four used drilling fluids or barite incorporated into sediment were determined in toxicity tests with lancelets (Branchiostoma caribaeum), a benthic chordate. The number of lancelets that did not burrow into contaminated sediments was used to calcula...

  13. Radioiodide sorption to sediment minerals

    SciTech Connect

    Kaplan, D.I.; Serne, R.J.; Parker, K.E.; Kutnyakov, I.V.

    1999-07-01

    Laboratory studies were conducted to quantify and understand the processes by which iodide (I{sup {minus}}) sorbs to minerals found in subsurface arid sediments. Little or no I{sup {minus}} sorbed to montmorillonite (K{sub d} = {minus}0.42 {+-} 0.08 mL/g), quartz (K{sub d} = 0.04 {+-} 0.02 mL/g), vermiculite (K{sub d} = 0.56 {+-} 0.21 mL/g), calcite (K{sub d} = 0.04 {+-} 0.01 mL/g), goethite (K{sub d} = 0.10 {+-} 0.03 mL/g), or chlorite (K{sub d} = {minus}0.22 {+-} 0.06 mL/g). A significant amount of I{sup {minus}} sorbed to illite (K{sub d} = 15.14 {+-} 2.84 mL/g). Upon treating the iodide-laden illite with dissolved F{sup {minus}}, Cl{sup {minus}}, Br{sup {minus}}, or {sup 127}I{sup {minus}}, desorption (or isotopic exchange in the case of {sup 127}I) removed, respectively, 43 {+-} 3%, 45 {+-} 0%, 52 {+-} 3, and 83 {+-} 1% of the I{sup {minus}} originally adsorbed to the illite. The fact that such large amounts of I{sup {minus}} could be desorbed suggests that the I{sup {minus}} was weakly adsorbed, and not chemically bonded to a soft metal, such as mercury or silver, that may have existed in the illite structure as trace impurities. Finally, I{sup {minus}} sorption to illite was strongly pH-dependent; the K{sub d} values decreased from 46 to 22 mL/g as the pH values increased from 3.6 to 9.4. Importantly, I{sup {minus}} sorbed to illite even under alkaline conditions. Together, these experiments suggest that illite removed I{sup {minus}} from the aqueous phase predominantly by reversible physical adsorption to the pH-dependent edge sites. Illites may constitute a substantial proportion of the clay-size fraction of many arid sediments and therefore may play an important role in retarding I{sup {minus}} movement in these sediments.

  14. VERTICAL MIXING OF LAKE SEDIMENTS BY TUBIFICID OLIGOCHAETES

    EPA Science Inventory

    Vertical mixing of lake sediments by tubificid oligochaetes was studied in laboratory experiments by using a radioactive (cesium 137 labeled sediment) marker horizon. Results from these experiments were used to develop and test a mathematical model describing tubificid sediment m...

  15. PROCEDURE FOR DETERMINATION OF SEDIMENT PARTICLE SIZE (GRAIN SIZE)

    EPA Science Inventory

    Sediment quality and sediment remediation projects have become a high priority for USEPA. Sediment particle size determinations are used in environmental assessments for habitat characterization, chemical normalization, and partitioning potential of chemicals. The accepted met...

  16. TOXICITY IDENTIFICATION EVALUATION (TIE) RESULTS FOR METAL CONTAMINATED SEDIMENTS

    EPA Science Inventory

    Identification of contaminants in sediment is necessary for sound management decisions on sediment disposal, remediation, determination of ecological risk, and source identification. We have been developing sediment toxicity identification evaluation (TIE) techniques that allow ...

  17. Bioaccumulation of PCBs Across Concentration Gradients in Sediments

    EPA Science Inventory

    Sediment bioaccumulation tests with Lumbriculus variegatus quantify the relationships between the chemical residues in sediments and benthic invertebrates, and these relationships are expressed as biota-sediment accumulation factors (BSAF). At some field sites, BSAFs decr...

  18. Sediment transport through a tidal creek

    NASA Astrophysics Data System (ADS)

    Green, Malcolm O.; Hancock, Nicole J.

    2012-08-01

    A 3-month field experiment was conducted at Henderson Creek, New Zealand. The data show how tidal creeks that are an extension of the freshwater drainage network (as opposed to tidal creeks that are part of an estuarine distributary network with no direct connection to the land) variously import, export and deposit fine sediment sourced from both landward and seaward of the creek, depending on the wind and freshwater runoff, and modulated by the tide. During freshwater spates, saltwater was largely displaced from the tidal creek at low tide, and sediment sourced from the land was deposited inside the tidal creek and exported to the wider estuary beyond the base of the creek. In one spate, during which 80 mm of rain fell in less than one day, 580 t of sediment was sourced from landward of the tidal creek, and a maximum of 33% of this was exported to the wider estuary. Between rainstorms when it was calm, sediment was returned from the wider estuary by tidal currents (but not necessarily the same sediment that was exported during spates), and sediment was also eroded from the middle reaches of the tidal creek and transported to the upper reaches, where it was deposited. The up-estuary deposition is explainable in Lagrangian terms as a type of settling lag, which results in an asymmetrical response of suspended-sediment concentration to current speed in the tidal creek. The return of sediment to the tidal creek between spates was greatly enhanced by wind waves that resuspended sediments from the intertidal flats of the wider estuary, with that sediment being transported by tidal currents into the tidal creek where it was deposited, largely in the middle reaches. There is a broad consensus that waves drive a net loss of sediment from intertidal flats to offshore, which reverses a net accumulation of sediment on intertidal flats during calm weather. In contrast, waves on the intertidal flats outside the mouth of Henderson Creek initiate net landward transport of

  19. Sediment chemoautotrophy in the coastal ocean

    NASA Astrophysics Data System (ADS)

    Vasquez-Cardenas, Diana; Meysman, Filip J. R.; van Breugel, Peter; Boschker, Henricus T. S.

    2016-04-01

    A key process in the biogeochemistry of coastal sediments is the reoxidation of reduced intermediates formed during anaerobic mineralization which in part is performed by chemoautotrophic micro-organisms. These microbes fix inorganic carbon using the energy derived from reoxidation reactions and in doing so can fix up to 32% of the CO2 released by mineralization. However the importance and distribution of chemoautotrophy has not been systematically investigated in these environments. To address these issues we surveyed nine coastal sediments by means of bacterial biomarker analysis (phospholipid derived fatty acids) combined with stable isotope probing (13C-bicarbonate) which resulted in an almost doubling of the number of observations on coastal sedimentary chemoautotrophy. Firstly, sediment chemoautotrophy rates from this study and rates compiled from literature (0.07 to 36 mmol C m‑2 d‑1) showed a power-law relation with benthic oxygen uptake (3.4 to 192 mmol O2 m‑2 d‑1). Benthic oxygen uptake was used as a proxy for carbon mineralization to calculate the ratio of the CO2 fixed by chemoautotrophy over the total CO2 released through mineralization. This CO2 efficiency was 3% in continental shelf, 9% in nearshore and 21% in salt marsh sediments. These results suggest that chemoautotrophy plays an important role in C-cycling in reactive intertidal sediments such as salt marshes rather than in the organic-poor, permeable continental shelf sediments. Globally in the coastal ocean our empirical results show that chemoautotrophy contributes ˜0.05 Pg C y‑1 which is four times less than previous estimates. Secondly, five coastal sediment regimes were linked to the depth-distribution of chemoautotrophy: 1) permeable sediments dominated by advective porewater transport, 2) bioturbated sediments, and cohesive sediments dominated by diffusive porewater transport characterized by either 3) canonical sulfur oxidation, 4) nitrate-storing Beggiatoa, or 5) electrogenic

  20. Quantitative patterns of sediment distribution in oceans

    SciTech Connect

    Ronov, A.B.; Khain, V.E.; Balukhovskii, A.N.

    1986-11-01

    Maps of the lithologic formations of the oceans have been compiled for all the epochs starting from the Late Jurassic to the Pliocene. The recent areas of occurrence of the main types of oceanic sediments have been measured on the maps, and the sediment volumes have been calculated separately for the Pacific, Atlantic, Indian, and Arctic oceans. Reliable estimates of the total volume of sediments of the world ocean and their distribution among stratigraphic complexes have been obtained. The quantitative patterns have been determined of the time variation of the occurrence of oceanic formations and their mean sedimentation rates for the world ocean as a whole and for each ocean separately. Specific features and differences have been revealed in the sedimentation history of young oceans (Atlantic, Indian, and Arctic) and the ancient (rejuvenated) Pacific Ocean.

  1. Bubble growth and rise in soft sediments

    NASA Astrophysics Data System (ADS)

    Boudreau, Bernard P.; Algar, Chris; Johnson, Bruce D.; Croudace, Ian; Reed, Allen; Furukawa, Yoko; Dorgan, Kelley M.; Jumars, Peter A.; Grader, Abraham S.; Gardiner, Bruce S.

    2005-06-01

    The mechanics of uncemented soft sediments during bubble growth are not widely understood and no rheological model has found wide acceptance. We offer definitive evidence on the mode of bubble formation in the form of X-ray computed tomographic images and comparison with theory. Natural and injected bubbles in muddy cohesive sediments are shown to be highly eccentric oblate spheroids (disks) that grow either by fracturing the sediment or by reopening preexisting fractures. In contrast, bubbles in soft sandy sediment tend to be spherical, suggesting that sand acts fluidly or plastically in response to growth stresses. We also present bubble-rise results from gelatin, a mechanically similar but transparent medium, that suggest that initial rise is also accomplished by fracture. Given that muddy sediments are elastic and yield by fracture, it becomes much easier to explain physically related phenomena such as seafloor pockmark formation, animal burrowing, and gas buildup during methane hydrate melting.

  2. Snake and Columbia Rivers Sediment Sampling Project

    SciTech Connect

    Pinza, M. R.; Word, J. Q.; Barrows, E. S.; Mayhew, H. L.; Clark, D. R.

    1992-12-01

    The disposal of dredged material in water is defined as a discharge under Section 404 of the Clean Water Act and must be evaluated in accordance with US Environmental Protection Agency regulation 40 CFR 230. Because contaminant loads in the dredged sediment or resuspended sediment may affect water quality or contaminant loading, the US Army Corps of Engineers (USACE), Walla Walla District, has requested Battelle/Marine Sciences Laboratory to collect and chemically analyze sediment samples from areas that may be dredged near the Port Authority piers on the Snake and Columbia rivers. Sediment samples were also collected at River Mile (RM) stations along the Snake River that may undergo resuspension of sediment as a result of the drawdown. Chemical analysis included grain size, total organic carbon, total volatile solids, ammonia, phosphorus, sulfides, oil and grease, total petroleum hydrocarbons, metals, polynuclear aromatic hydrocarbons, pesticides, polychlorinated biphenyls, and 21 congeners of polychlorinated dibenzodioxins and dibenzofurans.

  3. Speeding up of sedimentation under confinement.

    PubMed

    Heitkam, S; Yoshitake, Y; Toquet, F; Langevin, D; Salonen, A

    2013-04-26

    We show an increase of the sedimentation velocity as small particles are confined in circular capillaries. In general, confinement slows down sedimentation. But, we show that at low Reynolds numbers and in 1D confinement this is not the case. Particle sedimentation velocity is not homogeneous, which can lead to the formation of structures. These structures are enhanced and stabilized in the presence of walls and in the absence of other dissipative mechanisms. As a consequence, it is possible to achieve sedimentation velocities that even exceed the Stokes velocity. The segregation at critical capillary diameters has been directly observed using a large scale model. These simple experiments offer a new insight into the old problem of sedimentation under confinement. PMID:23679787

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

    PubMed

    Le Bihanic, Florane; Perrichon, Prescilla; Landi, Laure; Clérandeau, Christelle; Le Menach, Karyn; Budzinski, Hélène; Cousin, Xavier; Cachot, Jérôme

    2014-12-01

    Most persistent organic pollutants, due to their hydrophobic properties, accumulate in aquatic sediments and represent a high risk for sediment quality. To assess the toxicity of hydrophobic pollutants, a novel approach was recently proposed as an alternative to replace, refine and reduce animal experimentation: the medaka embryo-larval sediment contact assay (MELAc). This assay is performed with Japanese medaka embryos incubated on a natural sediment spiked with the compound being tested. With the aim of improving this assay, our study developed a reference exposure protocol with an artificial sediment specifically designed to limit natural sediment composition uncertainties and preparation variability. The optimum composition of the new artificial sediment was tested using a model polycyclic aromatic hydrocarbon (PAH), fluoranthene. The sediment was then validated with two other model PAHs, benz[a]anthracene and benzo[a]pyrene. Various developmental end points were recorded, including survival, embryonic heartbeat, hatching delay, hatching success, larval biometry and abnormalities. The final artificial sediment composition was set at 2.5 % dry weight (dw) Sphagnum peat, 5 % dw kaolin clay and 92.5 % dw silica of 0.2- to 0.5-mm grain size. In contrast with natural sediments, the chemical components of this artificial matrix are fully defined and readily identifiable. It is totally safe for fish embryos and presents relatively high sorption capacities for hydrophobic compounds. Studies with other hydrophobic and metallic contaminants and mixtures should be performed to further validate this artificial sediment. PMID:24526399

  5. Geochemistry of sediments in cores and sediment traps from Bear Lake, Utah and Idaho

    USGS Publications Warehouse

    Bischoff, James L.; Cummins, Kathleen; Shamp, Donald D.

    2005-01-01

    The present study of Bear Lake began in 1998. Initially, the study utilized sediments from three long cores (up to 5 m) previously collected in 1996 and short cores (up to 40 cm) collected in 1998. The short cores were specifically acquired to preserve the uppermost layers of sediment that may have been lost in the long cores. In addition, three arrays of sediment traps were deployed during the summer of 1998, and sediment from these traps was collected during the summers of 1999 and 2000 (see Dean and others, 2005, for core and sediment trap locations). The cores and sediment traps were sampled, and splits were distributed to various investigators for analyses of a wide variety of sediment parameters. The chemical composition of the acid-soluble component of the sediments is presented in this report. HCl or HNO3 treatment of the sediment quantitatively dissolves the authigenic component of the sediment, a component that includes carbonates, sulfates, and iron-mono sulfides. In the case of Bear Lake, CaCO3 is the major component of the sediment today and for most of the Holocene (Dean and others 2005). The chemical composition of the acid-soluble fraction gives important information on this component and, therefore, insight into the chemical conditions of the lake at the time of carbonate deposition.

  6. [Distributions of phosphorus fractions in suspended sediments and surface sediments of Tiaoxi mainstreams and cause analysis].

    PubMed

    Chen, Hai-Long; Yuan, Xu-Yin; Wang, Huan; Li, Zheng-Yang; Xu, Hai-Yan

    2015-02-01

    Phosphorus is a primary nutrient showing the water quality status of river and inducing eutrophication, and a different phosphorus fraction can make diverse contributions to water quality. Four phosphorus forms of suspended sediments and surface sediments in Tiaoxi mainstreams were measured using a sequential extraction procedure, and the distributions of their forms were discussed. The results showed that the tropic status of Xitiaoxi River was inferior to that of Dongtiaoxi River as a whole, and the water quality in the middle reach of Dongtiaoxi River was better than that in the upper and lower reaches. The contents of nutrient elements in suspended sediments were significantly higher than those in surface sediment, which indicated an enrichment of nutrient in fine sediment. The percentages of the loosely absorbed phosphorus ( NH4Cl-P), the reductant phosphorus (BD-P) and the metal oxide bound phosphorus (NaOH-P) in the suspended sediment were higher than those in surface sediment, while the percentage of the calcium bound phosphorus (HCl-P) showed a reverse trend. Correlation analyses between phosphorus forms and chemical compositions of suspended sediments and surface sediments were performed. The results showed the phosphorus forms in suspended sediments and surface sediments of Xitiaoxi River had weak relationships with mineral components, while those in the Dongtiaoxi River had strong relationships with mineral, especially OM and clay mineral. The cause was associated with the geological setting and material sources in Tiaoxi watershed. PMID:26031071

  7. Martian sediments and sedimentary rocks

    NASA Technical Reports Server (NTRS)

    Markun, C. D.

    1988-01-01

    Martian sediments and sedimentary rocks, clastic and nonclastic, should represent a high priority target in any future return-sample mission. The discovery of such materials and their subsequent analysis in terrestrial laboratories, would greatly increase the understanding of the Martian paleoclimate. The formation of Martian clastic sedimentary rocks, under either present, low-pressure, xeric conditions or a postulated, high-pressure, hydric environment, depends upon the existence of a supply of particles, various cementing agents and depositional basins. A very high resolution (mm-cm range) photographic reconnaissance of these areas would produce a quantum jump in the understanding of Martian geological history. Sampling would be confined to more horizontal (recent) surfaces. Exploration techniques are suggested for various hypothetical Martian sedimentary rocks.

  8. Sediment dispersal in the northwestern Adriatic Sea

    USGS Publications Warehouse

    Harris, C.K.; Sherwood, C.R.; Signell, R.P.; Bever, A.J.; Warner, J.C.

    2008-01-01

    Sediment dispersal in the Adriatic Sea was evaluated using coupled three-dimensional circulation and sediment transport models, representing conditions from autumn 2002 through spring 2003. The calculations accounted for fluvial sources, resuspension by waves and currents, and suspended transport. Sediment fluxes peaked during southwestward Bora wind conditions that produced energetic waves and strengthened the Western Adriatic Coastal Current. Transport along the western Adriatic continental shelf was nearly always to the south, except during brief periods when northward Sirocco winds reduced the coastal current. Much of the modeled fluvial sediment deposition was near river mouths, such as the Po subaqueous delta. Nearly all Po sediment remained in the northern Adriatic. Material from rivers that drain the Apennine Mountains traveled farther before deposition than Po sediment, because it was modeled with a lower settling velocity. Fluvial sediment delivered to areas with high average bed shear stress was more highly dispersed than material delivered to more quiescent areas. Modeled depositional patterns were similar to observed patterns that have developed over longer timescales. Specifically, modeled Po sediment accumulation was thickest near the river mouth with a very thin deposit extending to the northeast, consistent with patterns of modern sediment texture in the northern Adriatic. Sediment resuspended from the bed and delivered by Apennine Rivers was preferentially deposited on the northern side of the Gargano Peninsula, in the location of thick Holocene accumulation. Deposition here was highest during Bora winds when convergences in current velocities and off-shelf flux enhanced delivery of material to the midshelf. Copyright 2008 by the American Geophysical Union.

  9. Assessing the potential toxicity of resuspended sediment

    SciTech Connect

    Bonnet, C.; Babut, M.; Ferard, J.F.; Martel, L.; Garric, J.

    2000-05-01

    Two moderately contaminated freshwater sediments (Sorel Harbour, St. Lawrence River, Canada) were subjected to a suspension event. The objective was to assess the environmental impact of the disposal of dredged material in water, in particular, the short-term effects of dumping on the water column and the long-term effects of dredged sediment deposits. In a series of microcosms, the sediments were left to stand for 25 d under flow-through conditions. In a second series of microcosms, sediments were vigorously suspended for 15 min before being left to settle and were submitted to the same treatment as reference sediments during the following 25 d. Physicochemical and biological parameters (Daphnia magna and Hydra attenuata survival) were measured in overlying water throughout the experiment. Sediment toxicity was assessed with Chironomus tentans and Hyalella azteca exposed to sediments collected at both the beginning and end of the 25-d period. Pore-water toxicity was evaluated with D. magna. During the suspension process, in the Sorel Harbour mixed sediment overlying water, the authors observed effects on H. attenuata survival and ammonia and metals (chromium, copper, and zinc) releases. Meanwhile, in reference (nonmixed) and mixed sediments as well as in associated pore waters, there were no significant chemical modifications no biological effects after the 25-d experiments. The developed approach, which attempts to simulate a dumping process, aims at allowing the assessment of the short- and long-term hazards resulting from a resuspension process in overlying water and in resettled sediments using both chemical and biological measurements.

  10. Relationship of Bacterial Richness to Organic Degradation Rate and Sediment Age in Subseafloor Sediment

    PubMed Central

    Walsh, Emily A.; Kirkpatrick, John B.; Pockalny, Robert; Sauvage, Justine; Spivack, Arthur J.; Murray, Richard W.; Sogin, Mitchell L.

    2016-01-01

    ABSTRACT Subseafloor sediment hosts a large, taxonomically rich, and metabolically diverse microbial ecosystem. However, the factors that control microbial diversity in subseafloor sediment have rarely been explored. Here, we show that bacterial richness varies with organic degradation rate and sediment age. At three open-ocean sites (in the Bering Sea and equatorial Pacific) and one continental margin site (Indian Ocean), richness decreases exponentially with increasing sediment depth. The rate of decrease in richness with increasing depth varies from site to site. The vertical succession of predominant terminal electron acceptors correlates with abundance-weighted community composition but does not drive the vertical decrease in richness. Vertical patterns of richness at the open-ocean sites closely match organic degradation rates; both properties are highest near the seafloor and decline together as sediment depth increases. This relationship suggests that (i) total catabolic activity and/or electron donor diversity exerts a primary influence on bacterial richness in marine sediment and (ii) many bacterial taxa that are poorly adapted for subseafloor sedimentary conditions are degraded in the geologically young sediment, where respiration rates are high. Richness consistently takes a few hundred thousand years to decline from near-seafloor values to much lower values in deep anoxic subseafloor sediment, regardless of sedimentation rate, predominant terminal electron acceptor, or oceanographic context. IMPORTANCE Subseafloor sediment provides a wonderful opportunity to investigate the drivers of microbial diversity in communities that may have been isolated for millions of years. Our paper shows the impact of in situ conditions on bacterial community structure in subseafloor sediment. Specifically, it shows that bacterial richness in subseafloor sediment declines exponentially with sediment age, and in parallel with organic-fueled oxidation rate. This result

  11. Quantity, composition, and source of sediment collected in sediment traps along the fringing coral reef off Molokai, Hawaii

    USGS Publications Warehouse

    Bothner, Michael H.; Reynolds, R.L.; Casso, M.A.; Storlazzi, C.D.; Field, M.E.

    2006-01-01

    Sediment traps were used to evaluate the frequency, cause, and relative intensity of sediment mobility/resuspension along the fringing coral reef off southern Molokai (February 2000–May 2002). Two storms with high rainfall, floods, and exceptionally high waves resulted in sediment collection rates > 1000 times higher than during non-storm periods, primarily because of sediment resuspension by waves. Based on quantity and composition of trapped sediment, floods recharged the reef flat with land-derived sediment, but had a low potential for burying coral on the fore reef when accompanied by high waves. The trapped sediments have low concentrations of anthropogenic metals. The magnetic properties of trapped sediment may provide information about the sources of land-derived sediment reaching the fore reef. The high trapping rate and low sediment cover indicate that coral surfaces on the fore reef are exposed to transient resuspended sediment, and that the traps do not measure net sediment accumulation on the reef surface.

  12. Managing Fine Sediment in Regulated Rivers

    NASA Astrophysics Data System (ADS)

    Schmidt, J. C.

    2015-12-01

    A paradigm useful in managing dams and diversions is that the combined effects of changing flow regime and sediment supply perturb regulated rivers into sediment deficit or sediment surplus. In the U.S. Southwest, large dams constructed on interregional rivers typically create sediment deficit segments >100 km long. Further downstream, sediment surplus may occur if desert tributaries deliver sufficient amounts of fine sediment, such as parts of the Rio Grande, lower Green River, and Colorado River delta. Sediment surplus also occurs on most smaller regional rivers. The protocols for managing rivers perturbed into sediment deficit have been refined for the Colorado River downstream from Glen Canyon Dam but are nonetheless challenged by externally determined water-supply agreements that require annual water deliveries that sometimes occur when there has been little tributary resupply. Virtually all of the naturally supplied sand to the depleted, 100-km long Marble Canyon comes from the Paria River. The sand delivery rate since 2012 was sufficiently large to trigger short-duration controlled floods under the High Flow Experiment (HFE) Protocol. The sand mass balance of Marble Canyon since 2012 when the HFE Protocol was adopted was positive due to the combination of relatively large sand delivery from the Paria River and average total annual flows. Large total annual flows have the potential to export large amounts of sand and create a negative sand mass balance. Despite the challenge of managing a scarce and highly variable sand supply and occasional years of large reservoir releases, the long-term (2006-2015) sand mass balance for the upstream half of Marble Canyon is indeterminant and is positive for the downstream half of Marble Canyon. The apparent success of managing sand in Grand Canyon under deficit conditions suggests that fine sediment management protocols might be developed for other regulated rivers. Implementation would require establishment of networks of

  13. SANDS - Sediment Analysis Network for Decision Support

    NASA Astrophysics Data System (ADS)

    Hardin, D. M.; Hawkins, L.; He, M.; Ebersole, S.

    2010-12-01

    Since the year 2000, Eastern Louisiana, coastal Mississippi, Alabama, and the western Florida panhandle have been affected by 28 tropical storms, seven of which were hurricanes. These tropical cyclones have significantly altered normal coastal processes and characteristics in the Gulf region through sediment disturbance. Although tides, seasonality, and agricultural development influence suspended sediment and sediment deposition over periods of time, tropical storm activity has the capability of moving the largest sediment loads in the shortest periods of time for coastal areas. The SANDS project is also investigating the effects of sediment immersed oil from the Deepwater Horizon disaster in April 2010 which has the potential to resurface as a result of tropical storm activity. The importance of sediments upon water quality, coastal erosion, habitats and nutrients has made their study and monitoring vital to decision makers in the region. Currently agencies such as United States Army Corps of Engineers (USACE), NASA, and Geological Survey of Alabama (GSA) are employing a variety of in-situ and airborne based measurements to assess and monitor sediment loading and deposition. These methods provide highly accurate information but are limited in geographic range, are not continuous over a region and, in the case of airborne LIDAR are expensive and do not recur on a regular basis. Multi-temporal and multi-spectral satellite imagery that shows tropical-storm-induced suspended sediment and storm-surge sediment deposits can provide decision makers with immediate and long-term information about the impacts of tropical storms and hurricanes. It can also be valuable for those conducting research and for projects related to coastal issues such as recovery, planning, management, and mitigation. The Sediment Analysis Network for Decision Support has generated a number of decision support products derived from MODIS, Landsat and SeaWiFS instruments that potentially support

  14. Controls on flood and sediment wave propagation

    NASA Astrophysics Data System (ADS)

    Bakker, Maarten; Lane, Stuart N.; Costa, Anna; Molnar, Peter

    2015-04-01

    The understanding of flood wave propagation - celerity and transformation - through a fluvial system is of generic importance for flood forecasting/mitigation. In association with flood wave propagation, sediment wave propagation may induce local erosion and sedimentation, which will affect infrastructure and riparian natural habitats. Through analysing flood and sediment wave propagation, we gain insight in temporal changes in transport capacity (the flood wave) and sediment availability and transport (the sediment wave) along the river channel. Heidel (1956) was amongst the first to discuss the progressive lag of sediment concentration behind the corresponding flood wave based on field measurements. Since then this type of hysteresis has been characterized in a number of studies, but these were often based on limited amount of floods and measurement sites, giving insufficient insight into associated forcing mechanisms. Here, as part of a project concerned with the hydrological and geomorphic forcing of sediment transfer processes in alpine environments, we model the downstream propagation of short duration, high frequency releases of water and sediment (purges) from a flow intake in the Borgne d'Arolla River in south-west Switzerland. A total of >50 events were measured at 1 minute time intervals using pressure transducers and turbidity probes at a number of sites along the river. We show that flood and sediment wave propagation can be well represented through simple convection diffusion models. The models are calibrated/validated to describe the set of measured waves and used to explain the observed variation in wave celerity and diffusion. In addition we explore the effects of controlling factors including initial flow depth, flood height, flood duration, bed roughness, bed slope and initial sediment concentration, on the wave propagation processes. We show that the effects of forcing mechanisms on flood and sediment wave propagation will lead to different

  15. Using sediment 'fingerprints' to assess sediment-budget errors, north Halawa Valley, Oahu, Hawaii, 1991-92

    USGS Publications Warehouse

    Hill, B.R.; DeCarlo, E.H.; Fuller, C.C.; Wong, M.F.

    1998-01-01

    Reliable estimates of sediment-budget errors are important for interpreting sediment-budget results. Sediment-budget errors are commonly considered equal to sediment-budget imbalances, which may underestimate actual sediment-budget errors if they include compensating positive and negative errors. We modified the sediment 'fingerprinting' approach to qualitatively evaluate compensating errors in an annual (1991) fine (<63 ??m) sediment budget for the North Halawa Valley, a mountainous, forested drainage basin on the island of Oahu, Hawaii, during construction of a major highway. We measured concentrations of aeolian quartz and 137Cs in sediment sources and fluvial sediments, and combined concentrations of these aerosols with the sediment budget to construct aerosol budgets. Aerosol concentrations were independent of the sediment budget, hence aerosol budgets were less likely than sediment budgets to include compensating errors. Differences between sediment-budget and aerosol-budget imbalances therefore provide a measure of compensating errors in the sediment budget. The sediment-budget imbalance equalled 25% of the fluvial fine-sediment load. Aerosol-budget imbalances were equal to 19% of the fluvial 137Cs load and 34% of the fluval quartz load. The reasonably close agreement between sediment- and aerosol-budget imbalances indicates that compensating errors in the sediment budget were not large and that the sediment-budget imbalance as a reliable measure of sediment-budget error. We attribute at least one-third of the 1991 fluvial fine-sediment load to highway construction. Continued monitoring indicated that highway construction produced 90% of the fluvial fine-sediment load during 1992. Erosion of channel margins and attrition of coarse particles provided most of the fine sediment produced by natural processes. Hillslope processes contributed relatively minor amounts of sediment.

  16. Tsunami Sediment Transport and Deposition in a Sediment Limited Environment on American Samoa

    NASA Astrophysics Data System (ADS)

    Apotsos, A. A.; Gelfenbaum, G. R.; Jaffe, B. E.; Watt, S.; Peck, B.; Buckley, M. L.; Richmond, B. M.; Stevens, A. W.

    2009-12-01

    On 29 September 2009 a large tsunami struck the US territory of American Samoa, killing 34 people. However, had it not been for the island’s tsunami preparation, the death toll would have been much higher. An integral part of preparing for a tsunami is knowing how often large tsunamis occur, knowledge that can be improved by using paleo-tsunami sediment deposits to lengthen the historical tsunami record. Doing so requires a detailed understanding of the processes that control sediment transport during tsunamis and thus the patterns of deposition, which may vary substantially in sediment limited and sediment rich environments. As American Samoa is relatively young and composed of volcanic islands surrounded by coral reefs, sandy beaches occur primarily as pocket beaches between volcanic rock headlands. The extent and depth of littoral sediment available for transport is therefore limited. This is in contrast to previous studies which have focused primarily on coastal environments with extensive sand supply. Here, field observations and a numerical model are used to investigate tsunami-induced sediment transport in two sediment limited embayments (Massacre and Fagafue Bays) on the north side of the island of Tutuila in American Samoa. Detailed measurements of bathymetry, topography, tsunami flow depth and direction, sediment deposition, reef and vegetative roughness, and the extent of sediment available for transport were collected approximately two weeks after the tsunami. Both embayments contain sandy sediments that extend all the way (Massacre Bay) and part of the way (Fagafue Bay) along the beach at the head of the embayment. The observed onshore sediment deposit created by the tsunami was limited and patchy in both embayments even though a number of large coral boulders were transported onshore at both locations. The extent to which the limited supply of sediment plays in producing the patterns of deposition observed in these two bays is examined using a three

  17. Modeling sediment deposition from marine outfall jets.

    PubMed

    Terfous, Abdelali; Chiban, Samia; Ghenaim, Abdellah

    2016-08-01

    This paper presents a two-dimensional model to study the sediment deposition from marine outfall jets. The introduced unidirectional coupling (fluid-sediment) is an appropriate choice in the case of low-concentrated particle-laden jets such as municipal wastewater discharge, where the concentration of particles is small enough and does not affect the hydrodynamic development of the jet in the nearfield. The sedimentation model takes advantage of the preferential concentration phenomenon. The deposition criterion states that the deposition of sediments begins when the vertical component of the entrainment velocity becomes smaller than the settling velocity. Once the deposition process begins, it is controlled by the settling velocity, entrainment velocity, volume flux, and sediment concentration. The deposition along the jet trajectory is expressed by an ordinary differential equation coupled with the liquid phase equations. Experiments of Lane-Serff and Moran [Sedimentation from Buoyant jets. J Hyd Eng. 2005;131(3):166-174], Cuthbertson and Davies [Deposition from particle-laden, round, turbulent, horizontal, buoyant jets in stationary and coflowing receiving fluids. J Hydr Eng. 2008;134(4):390-402], and Lee [Mixing of horizontal sediment laden jets [dissertation]. Hong Kong: University of Hong Kong; 2010], chosen from bibliography, are used to validate the model. These experiments cover the cases of horizontal and inclined buoyant jets in stationary ambient, horizontal buoyant jets in co-flow current and nonbuoyant horizontal jets in stationary ambient. Good agreement between the experiments and the obtained simulations is revealed. PMID:26732467

  18. Dense colloidal fluids form denser amorphous sediments

    PubMed Central

    Liber, Shir R.; Borohovich, Shai; Butenko, Alexander V.; Schofield, Andrew B.; Sloutskin, Eli

    2013-01-01

    We relate, by simple analytical centrifugation experiments, the density of colloidal fluids with the nature of their randomly packed solid sediments. We demonstrate that the most dilute fluids of colloidal hard spheres form loosely packed sediments, where the volume fraction of the particles approaches in frictional systems the random loose packing limit, φRLP = 0.55. The dense fluids of the same spheres form denser sediments, approaching the so-called random close packing limit, φRCP = 0.64. Our experiments, where particle sedimentation in a centrifuge is sufficiently rapid to avoid crystallization, demonstrate that the density of the sediments varies monotonically with the volume fraction of the initial suspension. We reproduce our experimental data by simple computer simulations, where structural reorganizations are prohibited, such that the rate of sedimentation is irrelevant. This suggests that in colloidal systems, where viscous forces dominate, the structure of randomly close-packed and randomly loose-packed sediments is determined by the well-known structure of the initial fluids of simple hard spheres, provided that the crystallization is fully suppressed. PMID:23530198

  19. Sediment characteristics of Tennessee streams and reservoirs

    USGS Publications Warehouse

    Trimble, Stanley W.; Carey, William P.

    1984-01-01

    Measured suspended-sediment data and reservoir sedimentation data have been analyzed to determine sediment yields and transport characteristics of Tennessee streams. Measured suspended-sediment is mostly silt and clay size material even in the sand-bed channels of western Tennessee. Unmeasured load accounts for less than 10 percent of the total sediment load in western Tennessee. Unmeasured load in middle and eastern Tennessee streams is believed to be only a small percentage of total load because bed material is generally coarse and quite variable. Sediment of total load because bed material is generally coarse and quite variable. Sediment yields for middle and eastern Tennessee basins generally are less than 800 tons per square mile per year ((tons/mi2)/yr), however, highly disturbed basins can have yields from 1,000 to 3,000 (tons/mi2)/yr. Yields for the heavily agricultural and channelized basins of western Tennessee generally range from 700 to 1,000 (tons/mi2)/yr. Yields for the Hatchie River in western Tennessee are less than 200 (tons/mi2)/yr reflecting the lack of floodplain agriculture and channelization. (USGS)

  20. Global sediment fluxes during the last millennium

    NASA Astrophysics Data System (ADS)

    Naipal, Victoria; Reick, Christian; Van Oost, Kristof; Hoffmann, Thomas; Pongratz, Julia

    2016-04-01

    Soil redistribution plays an important role in the transport of carbon and nutrients between terrestrial ecosystems. However, quantification of soil redistribution and its effects on the global biogeochemical cycles is currently unknown. This study aims at developing new tools and methods to represent soil redistribution on a global scale, and contribute to the quantification of anthropogenic disturbances to the biogeochemical cycles. We present a new large-scale coarse resolution sediment budget model that can simulate spatial patterns and long-term trends in soil redistribution in floodplains and on hillslope, resulting from external forces such as climate and land use change. First, we validated the model for the Rhine catchment using observed Holocene sediment storage data and observed scaling behavior between sediment storage and catchment area. Then, we applied the model on 20 large river catchments globally, using climate and land cover data from the Max Planck Institute Earth System Model (MPI-ESM) for the last millennium (850 - 2005AD). We show that the model can reproduce current observed sediment yields if uncertainty in the observations is taken into account. Furthermore, we find that the change in erosion rates during the last millennium resulted in a significant increase in sediment storage for different global catchments. We identify land use change as the main driver behind this change in sediment storage. Finally, catchments characteristics, such as area and slope, play an important role in buffering or amplifying the effect of land use and other external forces on the change in erosion and sediment storage.

  1. Underwater sediment-contact radiation survey method

    SciTech Connect

    Lee, D.R.; St. Aubin, M.; Welch, S.J. )

    1991-11-01

    The authors are striving to produce a practical system for mapping lateral distributions in gamma activity on submerged sediments. This is in response to the need for quality control and interpretation of data obtainable by sediment sampling and analyses near nuclear utilities. A prototype gamma probe has been constructed and tested. The prototype is essentially a background survey meter packaged in a 53-cm-long {times} 5.4-cm-diam waterproof vehicle. This usage-shaped vehicle is connected to a cable for towing in contact with bottom sediments of lakes, rivers, and coastal waters. This vehicle, or sediment probe as it is called, was initially developed for measuring sediment electrical conductances, a parameter that can be used to locate underwater areas of groundwater and contaminant upwelling. During towing, the probe does not roll or twist around its longitudinal axis by more than 10 deg, so that sensors, which have been fixed within the vehicle, can be oriented to look up, down, or sideways. In over 450 lin-km of underwater survey, only a single sediment probe has been irretrievably snagged on sunken rocks or other debris. Work in the Ottawa River near the Chalk River Laboratories has shown good agreement among point measurements of river sediment with continuous measurements using the moving probe.

  2. Evaluation of sediment transport in steep channels combining sediment impact sensors, tracer stones and TLS

    NASA Astrophysics Data System (ADS)

    Harb, Gabriele; Schneider, Josef; Sass, Oliver; Stangl, Johannes

    2016-04-01

    Torrential floods combined with sediment transport presents major hazards to human life and infrastructure in alpine catchments. Despite the importance of sediment transport due to the large damage caused in case of flood events, we lack data on sediment movement and sediment transport rates in steep channels and torrents to improve the understanding of sediment transport processes in this areas. This paper presents an improved application of sediment impact sensors (SIS) integrated in a unique measurement system in an Alpine catchment in Austria consisting of meteorological stations, runoff gauges and tracer stones. In addition sediment availability, mobilization and accumulation have been mapped and quantified by means of terrestrial laser scanning (TLS) and structure from motion using unmanned aerial vehicles (UAVs). Additionally a numerical model was used to simulate the bed load transport rates in the torrent. This contribution focuses on field measurements of bed load transport rates in steep channels based on SIS data, tracer stone data, bed load measurements, precipitation and discharge data. The measurement data was compared to several sediment transport formulae for steep slopes and validated with the observed deposited amount of sediment in the sediment retention basin at the outlet of the catchment.

  3. Suspended-sediment loads and reservoir sediment trap efficiency for Clinton Lake, Kansas, 2010-12

    USGS Publications Warehouse

    Juracek, Kyle E.

    2013-01-01

    Continuous streamflow and turbidity data collected from October 1, 2010, to September 30, 2012, at a site upstream and downstream from Clinton Lake, Kansas, were used to compute the total suspended-sediment load delivered to and released from the reservoir as well as the sediment trap efficiency for the reservoir. Ongoing sedimentation is inhibiting the ability of Clinton Lake to serve several purposes including flood control, water supply, and recreation. The inflow suspended-sediment load was substantially larger than the outflow load and most of the suspended-sediment load was delivered during short-term, high-discharge periods. Respectively, the total 2-year inflow and outflow suspended-sediment loads were computed to be 44.4 and 1.49 million pounds. Sediment trap efficiency for the reservoir was estimated to be 97 percent. The mean annual suspended-sediment yield from the upstream basin was estimated to be 60,500 pounds per square mile. Because this study was completed during a drought, the estimated inflow suspended-sediment load and suspended-sediment yield likely are substantially less than what would occur during a period of average or above average precipitation and runoff.

  4. Flocculated sediments can reduce the size of sediment basin at construction sites.

    PubMed

    Kang, Jihoon; King, Scott E; McLaughlin, Richard A

    2016-01-15

    Due to stringent water quality regulations on stormwater discharges, there is increasing interest in chemically-assisted settling of suspended sediments at construction sites. This study investigated settling characteristics of flocculated sediment by polyacrylamide (PAM) in a top-loading settling tube. Studied sediment materials were obtained from construction sites in North Carolina, USA: Coastal Plain loamy sand (CPLS), Piedmont sandy clay loam (PSCL), Piedmont silt loam (PSL), and Mountain clay loam (MCL). The four different sediment suspensions mixed with and without dissolved PAM were introduced to the top of the column individually. During a 1-h settling period, samples were taken at 1-m depth from surface at various times and analyzed for total suspended solids (TSS). Flocculated sediment by PAM greatly increased its settled TSS fraction up to 95-97% only in 1-min settling period compared to those of unflocculated sediment (16-72%). The settling improvement by PAM was profound in the finer-textured soils (PSL and MCL) by increasing their median particle settling velocity (>2 cm s(-1)) compared to unflocculated counterparts (<1.1 cm s(-1)). Estimated surface area requirement of sediment basin suggested that the basins receiving flocculated sediment could be reduced in size (surface area) by 2- to 4-times compared to those receiving unflocculated sediment. Our results suggests that current sediment basin design could be modified when chemically-assisted settling is implemented, taking up less space and cost in construction sites. PMID:26555101

  5. The impacts of sediment supply, flow hydrology and channel restoration on floodplain sedimentation

    NASA Astrophysics Data System (ADS)

    Benjankar, R. M.; Yager, E. M.

    2009-12-01

    Physical processes and riparian ecosystems on many floodplains around the world have been severely impacted by human activities. For example, an 80 km long reach of the Kootenai River floodplain in Idaho is completely disconnected from the channel because of levee construction and upstream dam operation. River channelization and reductions in flood magnitudes, frequencies and sediment supplies have decreased floodplain sedimentation rates and significantly impeded the regeneration of riparian forests. To better understand historical (prior to the dam and levees) floodplain processes, we constructed a 2D hydrodynamic model that calculates flow, sediment transport and sedimentation rates on a portion of the Kootenai floodplain. We calculated the historical variability in sediment transport and deposition rates using a range of flow magnitudes and sediment supplies. To assess the errors in our calculations, we used a range of sediment transport equations to calculate sediment flux. The predicted sedimentation rates varied with the flood magnitude, sediment supply and spatial position on the floodplain. These simulations also allowed us to compare historical floodplain processes with those could occur after floodplain restoration. One potential restoration scenario includes the intentional breaching of levees to allow floodplain reconnection. The levees currently channelize a 25 year recurrence interval (RI) flood. After the levee breach, a flood with a historical RI of 1.1 years would reconnect the floodplain to the channel. Our results suggest that floodplain processes may be restored through a combination of dam operational changes and levee removal.

  6. Sediment storage by vegetation in steep bedrock landscapes: Theory, experiments, and implications for postfire sediment yield

    NASA Astrophysics Data System (ADS)

    Lamb, Michael P.; Levina, Mariya; Dibiase, Roman A.; Fuller, Brian M.

    2013-06-01

    models for sediment transport on hillslopes are needed for applications ranging from landscape evolution to debris-flow hazards. Progress has been made for soil-mantled landscapes; however, little is known about sediment production and transport in bedrock landscapes that often maintain a patchy soil mantle, even though slopes exceed the angle of repose. Herein we investigate the hypothesis that patchy soil cover is stable on steep slopes due to local roughness such as vegetation dams that trap sediment upslope. To quantify local sediment storage, we developed a new theory and tested it against tilt-table experiments. Results show that trapped sediment volume scales with the cube of dam width. Where the dam width is less than about fifty grain diameters, particle force chains appear to enhance stability, resulting in greater trapped volumes and sediment-pile slopes that exceed the angle of repose. Trapped volumes are greatest for hillslopes that just exceed the friction slope and are independent of hillslope gradient for gradients greater than about twice the friction slope. For neighboring dams spaced less than about five grain diameters apart, grain bridging results in a single sediment pile that is larger than the sum of individual piles. This work provides a mass-conserving framework for quantifying sediment storage and nonlocal transport in bedrock landscapes. Results may explain the rapid increase in sediment yield following wildfire in steep terrain in the absence of rainfall; as sediment dams are incinerated, particles become gravitationally unstable and move rapidly downslope as dry ravel.

  7. Microbial interactions with naturally occurring hydrophobic sediments: Influence on sediment and associated contaminant mobility.

    PubMed

    Droppo, I G; Krishnappan, B G; Lawrence, J R

    2016-04-01

    The erosion, transport and fate of sediments and associated contaminants are known to be influenced by both particle characteristics and the flow dynamics imparted onto the sediment. The influential role of bitumen containing hydrophobic sediments and the microbial community on sediment dynamics are however less understood. This study links an experimental evaluation of sediment erosion with measured sediment-associated contaminant concentrations and microbial community analysis to provide an estimate of the potential for sediment to control the erosion, transport and fate of contaminants. Specifically the paper addresses the unique behaviour of hydrophobic sediments and the role that the microbial community associated with hydrophobic sediment may play in the transport of contaminated sediment. Results demonstrate that the hydrophobic cohesive sediment demonstrates unique transport and particle characteristics (poor settling and small floc size). Biofilms were observed to increase with consolidation/biostabilization times and generated a unique microbial consortium relative to the eroded flocs. Natural oil associated with the flocs appeared to be preferentially associated with microbial derived extracellular polymeric substances. While PAHs and naphthenic acid increased with increasing shear (indicative of increasing loads), they tended to decrease with consolidation/biostabilization (CB) time at similar shears suggesting a chemical and/or biological degradation. PAH and napthenic acid degrading microbes decreased with time as well, which may suggest that there was a reduced pool of PAHs and naphthenic acids available resulting in their die off. This study emphasizes the importance that any management strategies and operational assessments for the protection of human and aquatic health incorporate the sediment (suspended and bed sediment) and biological (biofilm) compartments and the energy dynamics within the system in order to better predict contaminant

  8. Trend analyses with river sediment rating curves

    USGS Publications Warehouse

    Warrick, Jonathan A.

    2015-01-01

    Sediment rating curves, which are fitted relationships between river discharge (Q) and suspended-sediment concentration (C), are commonly used to assess patterns and trends in river water quality. In many of these studies it is assumed that rating curves have a power-law form (i.e., C = aQb, where a and b are fitted parameters). Two fundamental questions about the utility of these techniques are assessed in this paper: (i) How well to the parameters, a and b, characterize trends in the data? (ii) Are trends in rating curves diagnostic of changes to river water or sediment discharge? As noted in previous research, the offset parameter, a, is not an independent variable for most rivers, but rather strongly dependent on b and Q. Here it is shown that a is a poor metric for trends in the vertical offset of a rating curve, and a new parameter, â, as determined by the discharge-normalized power function [C = â (Q/QGM)b], where QGM is the geometric mean of the Q values sampled, provides a better characterization of trends. However, these techniques must be applied carefully, because curvature in the relationship between log(Q) and log(C), which exists for many rivers, can produce false trends in â and b. Also, it is shown that trends in â and b are not uniquely diagnostic of river water or sediment supply conditions. For example, an increase in â can be caused by an increase in sediment supply, a decrease in water supply, or a combination of these conditions. Large changes in water and sediment supplies can occur without any change in the parameters, â and b. Thus, trend analyses using sediment rating curves must include additional assessments of the time-dependent rates and trends of river water, sediment concentrations, and sediment discharge.

  9. Denitrification in San Francisco Bay intertidal sediments

    USGS Publications Warehouse

    Oremland, Ronald S.; Umberger, Cindy; Culbertson, Charles W.; Smith, Richard L.

    1984-01-01

    The acetylene block technique was employed to study denitrification in intertidal estuarine sediments. Addition of nitrate to sediment slurries stimulated denitrification. During the dry season, sediment-slurry denitrification rates displayed Michaelis-Menten kinetics, and ambient NO3− + NO2− concentrations (≤26 μM) were below the apparent Km (50 μM) for nitrate. During the rainy season, when ambient NO3− + NO2− concentrations were higher (37 to 89 μM), an accurate estimate of the Km could not be obtained. Endogenous denitrification activity was confined to the upper 3 cm of the sediment column. However, the addition of nitrate to deeper sediments demonstrated immediate N2O production, and potential activity existed at all depths sampled (the deepest was 15 cm). Loss of N2O in the presence of C2H2 was sometimes observed during these short-term sediment incubations. Experiments with sediment slurries and washed cell suspensions of a marine pseudomonad confirmed that this N2O loss was caused by incomplete blockage of N2O reductase by C2H2 at low nitrate concentrations. Areal estimates of denitrification (in the absence of added nitrate) ranged from 0.8 to 1.2 μmol of N2 m−2 h−1 (for undisturbed sediments) to 17 to 280 μmol of N2 m−2 h−1 (for shaken sediment slurries).

  10. Suspended-sediment inflows to Watts Bar Reservoir. Revision 1

    SciTech Connect

    Ewing, L.K.

    1993-09-01

    Suspended-sediment inflows to Watts Bar Reservoir are important data that are required in numerical modeling of transport and deposition of sediment in the reservoir. Acceptable numerical modeling requires sediment inflow rates and locations in order to be able to compute the location and quantity of sediment deposited within the reservoir. Therefore, the representativeness of modeling results is highly dependent on the characteristics of sediment input to the model. The following recommendations, that account for suspended-sediment inflows to be used in the numerical modeling of sediment transport and deposition in Watts Bar Reservoir, were developed through an evaluation of available watershed and sediment deposition data. (1) Use the suspended-sediment rating regression equations of Gaydos et al., for Emory River at Oakdale, TN, and for Poplar Creek near Oak Ridge, TN, to represent the suspended-sediment inflows into Watts Bar Reservoir from its tributaries; (2) Use a suspended-sediment rating regression equation that was derived from suspended-sediment and streamflow data of the Little Tennessee River at McGhee, TN, to represent sediment inflow from the Little Tennessee River for simulation of any historical year before the completion of Tellico Dam; (3) Check the appropriateness of any assumption for suspended-sediment inflows from upstream reservoirs by using its long-term relationship to local suspended-sediment inflows and to the suspended-sediment outflow through Watts Bar Dam; and (4) Focus refinements to suspended-sediment inflow rates on the Clinch arm of Watts Bar Reservoir.

  11. A bioaccumulation bioassay for freshwater sediments

    USGS Publications Warehouse

    Mac, Michael J.; Noguchi, George E.; Hesselberg, Robert J.; Edsall, Carol C.; Shoesmith, John A.; Bowker, James D.

    1990-01-01

    A laboratory bioassay is described for determining the bioavailability of contaminants from freshwater sediments. The bioassay consists of 10-d exposures to whole sediments under flow-through conditions. After testing five species, the fathead minnow (Pimephales promelas) and the earthworm (Lubricus terrestris) were recommended for use in the test. When the availability of polychlorinated biphenyls (PCBs), Hg and Zn from Great Lakes sediments was examined in laboratory exposures, only the PCBs were accumulated. A field validation study demonstrated that the magnitude of accumulation in laboratory exposures was similar to that in organisms caged in the field. A protocol is recommended for using the test as a standardized bioaccumulation bioassay.

  12. Remediation technologies for oil-contaminated sediments.

    PubMed

    Agarwal, Ashutosh; Liu, Yu

    2015-12-30

    Oil-contaminated sediments pose serious environmental hazards for both aquatic and terrestrial ecosystems. Innovative and environmentally compatible technologies are urgently required to remove oil-contaminated sediments. In this paper, various physical, chemical and biological technologies are investigated for the remediation of oil-contaminated sediments such as flotation and washing, coal agglomeration, thermal desorption, ultrasonic desorption, bioremediation, chemical oxidation and extraction using ionic liquids. The basic principles of these technologies as well as their advantages and disadvantages for practical application have been discussed. A combination of two or more technologies is expected to provide an innovative solution that is economical, eco-friendly and adaptable. PMID:26414316

  13. Morphology of methane hydrate host sediments

    USGS Publications Warehouse

    Jones, K.W.; Feng, H.; Tomov, S.; Winters, W.J.; Eaton, M.; Mahajan, D.

    2005-01-01

    The morphological features including porosity and grains of methane hydrate host sediments were investigated using synchrotron computed microtomography (CMT) technique. The sediment sample was obtained during Ocean Drilling Program Leg 164 on the Blake Ridge at water depth of 2278.5 m. The CMT experiment was performed at the Brookhaven National Synchrotron Light Source facility. The analysis gave ample porosity, specific surface area, mean particle size, and tortuosity. The method was found to be highly effective for the study of methane hydrate host sediments.

  14. Amyloplast Sedimentation Kinetics in Corn Roots

    NASA Technical Reports Server (NTRS)

    Leopold, A. C.; Sack, F.

    1985-01-01

    Knowledge of the parameters of amyloplast sedimentation is crucial for an evaluation of proposed mechanisms of root graviperception. Early estimates of the rate of root amyloplast sedimentation were as low as 1.2 micron/min which may be too slow for many amyloplasts to reach the vicinity of the new lower wall within the presentation time. On this basis, Haberlandt's classical statolith hypothesis involving amyloplast stimulation of a sensitive surface near the new lower wall was questioned. The aim was to determine the kinetics of amyloplast sedimentation with reference to the presentation time in living and fixed corn rootcap cells as compared with coleoptiles of the same variety.

  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. Bioavailability of sediment-associated PAHs by Lumbriculus variegatus in sediment cores

    SciTech Connect

    Harkey, G.A.; VanHoof, P.L.; Landrum, P.F.

    1994-12-31

    Lumbriculus variegatus were exposed four weeks to sediment core sections. Sediment was taken from Lake George in northern Michigan and known to be historically contaminated with PAHs. Bioaccumulation was maximal at the 12--16 cm depth where sediment PAH concentrations were greatest. Accumulation was minimal in surficial and 44--48 cm sections. Accumulation peaked at about 96 h, then declined over the remainder of the study for some of the lower molecular weight PAHs. For most higher molecular weight compounds, accumulation peaked at 2 weeks, then slightly declined at 4 weeks. Uptake rate coefficients stayed relatively constant for specific PAH congeners over the range of sediment depths, suggesting constant bioavailability with sediment aging. Accumulation factors (AFs) of selected congeners were also consistent among sediment depths and were comparable to those calculated for other species reported in previous studies.

  17. The impact of different sediment concentrations and sediment transport formulas on the simulated floodplain processes

    NASA Astrophysics Data System (ADS)

    Benjankar, Rohan; Yager, Elowyn M.

    2012-07-01

    SummaryOverbank sedimentation is an important process in river floodplain ecosystems and is a component of the floodplain geomorphologic evolution. The impact of suspended sediment supply on floodplain processes is still unclear because sediment deposition can be influenced by many factors. We quantified the effect of sediment supply (suspended sediment) and transport formulas on simulated floodplain processes using a coupled two-dimensional hydrodynamic and sediment transport model (MIKE21C). Erosion and deposition depths, net sedimentation depth and total volume were quantified based on the last time step of the simulation period. The MIKE21C model was validated by comparing simulated water surface elevations to those from a one-dimensional hydrodynamic model. We compared the sediment transport model simulated suspended sediment concentrations (SSCs) to measured concentrations at a gage station. Erosion and deposition processes were simulated using five hydrograph scenarios as a function of high and low SSC and two sediment transport equations, Van Rijn (1984) and Engelund and Hansen (1967). A specific location could be an erosional or depositional zone at different time steps of the simulation. Thus, floodplain deposition is a discontinuous function of river discharge and varies spatially and temporally over the floodplain. Large flows with high SSC were more effective for floodplain deposition than lower discharges, which dominantly caused sediment scour. Coupled hydrodynamic and sediment transport models that account for feedback processes between topography and hydraulics should be given first preference for future floodplain restoration projects. From a restoration perspective, larger flows are required for greater floodplain deposition rates and maintenance of dynamic processes. The Engelund and Hansen (1967) equation simulated higher transport rates than the Van Rijn equation (1984). For future studies, transport equations should be selected based on the

  18. Simulating Sediment Transport Processes in San Francisco Bay Using Coupled Hydrodynamic, Wave, and Sediment Transport Models

    NASA Astrophysics Data System (ADS)

    Bever, A. J.; MacWilliams, M.

    2012-12-01

    Under the conceptual model of sediment transport in San Pablo Bay, a sub-embayment of San Francisco Bay, proposed by Krone (1979), sediment typically enters San Pablo Bay during large winter and spring flows and is redistributed during summer conditions through wind wave resuspension and transport by tidal currents. A detailed understanding of how the waves and tides redistribute sediment within San Francisco Bay is critical for predicting how future sea level rise and a reduction in the sediment supply to the Bay will impact existing marsh and mudflat habitat, tidal marsh restoration projects, and ongoing maintenance dredging of the navigation channels. The three-dimensional UnTRIM San Francisco Bay-Delta Model was coupled with the Simulating WAves Nearshore (SWAN) wave model and the SediMorph morphological model, to develop a three-dimensional hydrodynamic, wind wave, and sediment transport model of the San Francisco Bay and the Sacramento-San Joaquin Delta. Numerical simulations of sediment resuspension due to tidal currents and wind waves and the subsequent transport of this sediment by tidal currents are used to quantify the spatial and temporal variability of sediment fluxes on the extensive shoals in San Pablo Bay under a range of tidal and wind conditions. The results demonstrate that suspended sediment concentration and sediment fluxes within San Pablo Bay are a complex product of tides and waves interacting spatially throughout the Bay, with concentrations responding to local resuspension and sediment advection. Sediment fluxes between the San Pablo Bay shoals and the deeper channel are highest during spring tides, and are elevated for up to a week following wave events, even though the greatest influence of the wave event occurs abruptly.

  19. Temporal adjustments of bed surface texture and sediment mobility to a variable sediment supply regime

    NASA Astrophysics Data System (ADS)

    von Flotow, C. M.; Hassan, M. A.

    2012-12-01

    Mountain streams tend to alternate between supply-limited and transport-limited situations. In a supply-limited situation, fine sediment winnows out of the streambed and surface armor structures develop. Armor structures influence the nature of turbulence in water and thereby mobility of bed sediment. Bed surface evolution under conditions of sediment starvation followed by large sediment loading events is relatively unexplored in an experimental setting. The objective of this research is to evaluate temporal adjustments of a streambed surface due to changes in sediment supply regimes. To achieve our goals, we conducted laboratory experiments in an 18 meter long, one meter wide flume with a three percent slope. The bed was brought to an armored state by running water with no sediment feed before releasing a sequence of sediment pulses. Water discharge and grain size distribution of the sediment feed were held constant over the set of experiments while supply input rates varied. Sediment flux at the outlet of the flume was continuously measured. At a given time interval, flow resistance, bed surface structure, grain size, and bed elevation were measured in detail over a two meter section of the flume bed. Instantaneous three-dimensional observations of flow velocities were made using an Acoustic Doppler Velocimeter in order to calculate Reynolds shear stresses and turbulence intensities. We will present results on temporal changes of the bed surface state, flow properties, and sediment mobility in response to variable rates of sediment input. Flume results will be linked to a 10-year record of observations made in a riffle pool field reach following flood and large sediment input events. Together the data will be used to develop a model for the prediction of bed surface evolution in mountain streams.

  20. Contributions of Sediment Provenance and Sediment Diagenesis to Western Antarctic Peninsula Magnetic Proxy Records

    NASA Astrophysics Data System (ADS)

    Brachfeld, S.; Manley, P.; Gorring, M.; Ryan, P.

    2007-05-01

    We examine the role of sediment provenance, iron-sulfur diagenesis, and iron-silica diagenesis in shaping environmental magnetic proxy records in Antarctic biosiliceous sediments. A 20-m sediment core from the Gerlache Drift, western Antarctic Peninsula, contains an ultra-high resolution record of environmental change spanning the last 4000 years. Magnetic susceptibility and several remanence parameters appear to record regularly repeating patterns in biogenic and terrigenous sedimentation, with a major shift at the Middle Holocene to Late Holocene transition. This shift is manifested as an abrupt downcore decrease in magnetic susceptibility, concomitant with an increase in biogenic silica. However, this record does not show the typical pattern associated with iron-sulfur diagenesis, i.e., selective dissolution of fine particles and coarsening of the residual assemblage. We observe multidomain magnetite above the transition, and PSD-magnetite plus hematite below the transition, which suggests a change in sediment provenance. However, we observe a change in clay mineralogy downcore that is consistent with predictions for iron-silica diagenesis. In order to investigate the role of changing sediment sources vs. post-depositional diagenesis, we have examined bulk sediment geochemistry, total organic carbon and total sulfur content to identify possible diagenetic fronts, and bulk mineralogic assemblages and lithic clast composition to examine sediment sources. In addition, we have examined the lithologic and geochemical characteristics of surface sediment samples and diamict samples from a North- South suite of western AP fjords and inner shelf basins, which we use to fingerprint potential sediment source regions. These tools may be able to distinguish between sediment supplied from local Antarctic Peninsula geologic terranes, Bransfield Basin volcanics entrained in the nearshore countercurrent, or West Antarctic sediment supplied by the Antarctic Circumpolar Current.

  1. SORPTION OF HYDROPHOBIC POLLUTANTS ON NATURAL SEDIMENTS

    EPA Science Inventory

    The sorption of hydrophobic compounds (aromatic hydrocarbons and chlorinated hydrocarbons) spanning a concentration range in water solubility from 500 parts per trillion (ppt) to 1800 parts per million (ppm) on local (North Georgia) pond and river sediments was investigated. The ...

  2. Sediment generation and provenance: processes and pathways

    NASA Astrophysics Data System (ADS)

    Caracciolo, L.; Garzanti, E.; von Eynatten, H.; Weltje, G. J.

    2016-05-01

    The ability to trace sediments from their sources to sedimentary basins is a prerequisite for quantitative analysis of Earth-surface dynamics. The comparatively recent revival of sedimentary provenance analysis goes hand-in-hand with the ever expanding range of analytical tools available for quantifying sediment properties (isotopic, mineral, chemical, and petrographic composition, grain-size and shape distributions, age spectra, etc.), and for interpreting such data in paleo-geographic, -tectonic and -climatic terms. The breakdown of sediment budgets into source-specific contributions - one of the most important tasks of provenance analysis - permits quantification of rates of surface processes in the geological past ("deep time"), even in cases where the source areas themselves have been destroyed by global tectonics. Quantitative sedimentary provenance analysis is therefore crucial to the reconstruction of ancient sediment-routing systems, the fundamental units of mass transfer at the Earth's surface.

  3. Flux Saturation Length of Sediment Transport

    NASA Astrophysics Data System (ADS)

    Pähtz, Thomas; Kok, Jasper F.; Parteli, Eric J. R.; Herrmann, Hans J.

    2013-11-01

    Sediment transport along the surface drives geophysical phenomena as diverse as wind erosion and dune formation. The main length scale controlling the dynamics of sediment erosion and deposition is the saturation length Ls, which characterizes the flux response to a change in transport conditions. Here we derive, for the first time, an expression predicting Ls as a function of the average sediment velocity under different physical environments. Our expression accounts for both the characteristics of sediment entrainment and the saturation of particle and fluid velocities, and has only two physical parameters which can be estimated directly from independent experiments. We show that our expression is consistent with measurements of Ls in both aeolian and subaqueous transport regimes over at least 5 orders of magnitude in the ratio of fluid and particle density, including on Mars.

  4. RECOVERY OF DNA FROM SOILS AND SEDIMENTS

    EPA Science Inventory

    Experiments were performed to evaluate the effectiveness of different methodological approaches for recovering DNA from soil and sediment bacterial communities; cell extraction followed by lysis and DNA recovery (cell extraction method) versus direct cell lysis and alkaline extra...

  5. Sediment Analysis Network for Decision Support (SANDS)

    NASA Astrophysics Data System (ADS)

    Hardin, D. M.; Keiser, K.; Graves, S. J.; Conover, H.; Ebersole, S.

    2009-12-01

    Since the year 2000, Eastern Louisiana, coastal Mississippi, Alabama, and the western Florida panhandle have been affected by 28 tropical storms, seven of which were hurricanes. These tropical cyclones have significantly altered normal coastal processes and characteristics in the Gulf region through sediment disturbance. Although tides, seasonality, and agricultural development influence suspended sediment and sediment deposition over periods of time, tropical storm activity has the capability of moving the largest sediment loads in the shortest periods of time for coastal areas. The importance of sediments upon water quality, coastal erosion, habitats and nutrients has made their study and monitoring vital to decision makers in the region. Currently agencies such as United States Army Corps of Engineers (USACE), NASA, and Geological Survey of Alabama (GSA) are employing a variety of in-situ and airborne based measurements to assess and monitor sediment loading and deposition. These methods provide highly accurate information but are limited in geographic range, are not continuous over a region and, in the case of airborne LIDAR are expensive and do not recur on a regular basis. Multi-temporal and multi-spectral satellite imagery that shows tropical-storm-induced suspended sediment and storm-surge sediment deposits can provide decision makers with immediate and long-term information about the impacts of tropical storms and hurricanes. It can also be valuable for those conducting research and for projects related to coastal issues such as recovery, planning, management, and mitigation. The recently awarded Sediment Analysis Network for Decision Support will generate decision support products using NASA satellite observations from MODIS, Landsat and SeaWiFS instruments to support resource management, planning, and decision making activities in the Gulf of Mexico. Specifically, SANDS will generate decision support products that address the impacts of tropical storms

  6. Flux saturation length of sediment transport.

    PubMed

    Pähtz, Thomas; Kok, Jasper F; Parteli, Eric J R; Herrmann, Hans J

    2013-11-22

    Sediment transport along the surface drives geophysical phenomena as diverse as wind erosion and dune formation. The main length scale controlling the dynamics of sediment erosion and deposition is the saturation length Ls, which characterizes the flux response to a change in transport conditions. Here we derive, for the first time, an expression predicting Ls as a function of the average sediment velocity under different physical environments. Our expression accounts for both the characteristics of sediment entrainment and the saturation of particle and fluid velocities, and has only two physical parameters which can be estimated directly from independent experiments. We show that our expression is consistent with measurements of Ls in both aeolian and subaqueous transport regimes over at least 5 orders of magnitude in the ratio of fluid and particle density, including on Mars. PMID:24313529

  7. BENTHIC COMMUNITY RESPONSE TO SEDIMENT AMENDMENTS

    EPA Science Inventory

    The amendments apatite, organoclay, acetate, chitin, and geotextile reactive mats containing apatite and apatite + organoclay are currently under examination for remediation of contaminated sediments. The objective of this research is to evaluate toxicity to several estuarine an...

  8. Isolation of cellulolytic actinomycetes from marine sediments

    SciTech Connect

    Veiga, M.; Esparis, A.; Fabregas, J.

    1983-07-01

    The cellulolytic activity of 36 actinomycetes strains isolated from marine sediments was investigated by the cellulose-azure method. Approximately 50% of the isolates exhibited various degrees of cellulolytic activity. 13 references.

  9. SEWER AND TANK SEDIMENT FLUSHING: CASE STUDIES

    EPA Science Inventory

    The objective of the report summarized here is to demonstrate that sewer system and storage tank flushing that reduces sediment deposition and accumulation is of prime importance to optimizing performance, maintaining structural integrity, and minimizing pollution of receiving wa...

  10. MEASURING CONTAMINANT RESUSPENSION RESULTING FROM SEDIMENT CAPPING

    EPA Science Inventory

    This Sediment Issue summarizes two studies undertaken at marine sites by the National Risk Management Research Laboratory of U.S. EPA to evaluate the resuspension of surface materials contaminated with polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) b...

  11. Sediment-Associated Reactions of Aromatic Amines

    EPA Science Inventory

    Sorption of aromatic amines to sediments and soils can occur by both reversible physical processes and irreversible chemical processes. To elucidate the significance of these sorption pathways, the sorption kinetics of aniline and pyridine were studied in resaturated pond sedimen...

  12. Cryogenic Structure of Perennially Frozen Lacustrine Sediments

    NASA Astrophysics Data System (ADS)

    Kanevskiy, M.; Shur, Y.; Jorgenson, T.

    2007-12-01

    The existing data on cryogenic structure of lacustrine sediments in various permafrost regions of Eurasia and North America show that these sediments can vary from ice-poor to extremely ice-rich. Complicated cryogenic structure of lacustrine sediments can indicate the conditions of freezing; its study helps to reconstruct the history of permafrost development. There are four mechanisms of lacustrine sediments freezing and formation of their cryogenic structure: 1) epigenetic; 2) syngenetic; 3) para-syngenetic; 4) quasi-syngenetic. Para-syngenetic type of freezing is the most widespread for the lacustrine sediments accumulating in the taliks surrounded by permafrost. The freezing of such sediments goes in various directions (from the surface, from the bottom, from the sides). The ice layers and lenses in para-syngenetic sediments are usually inclined, and the ice content is relatively small in the central parts of the lens-like geological bodies of lacustrine origin. Ice content increases towards top, bottom, and marginal parts of these geological bodies. Such distribution of the ice content is connected with water migration to the multidirectional fronts of freezing. Our study includes the data from several field sites located in Russia and Alaska. One of the most interesting sections was studied in the Kular mining region, Northern Yakutia, where the big lens of lacustrine silts, whose thickness reaches 18-20 m, was observed. This lens was enclosed in the ice-rich syngenetic Late Pleistocene "Yedoma" sediments containing huge ice wedges. The cryogenic structure of the most part of the observed geological body is typical for para-syngenetic sediments. Gravimetric moisture content of lacustrine silts varies in wide range: from 35% up to 130%. At the upper part of the section the ice lenses up to 10-15 cm thick were observed. Ice wedge pseudomorphs were found at the boundary between lacustrine sediments and underlying alluvial gravels. Para-syngenetic part of this

  13. Magnesium Isotopic Composition of Subducting Marine Sediments

    NASA Astrophysics Data System (ADS)

    Hu, Y.; Teng, F. Z.; Plank, T. A.; Huang, K. J.

    2015-12-01

    Subducted marine sediments have recently been called upon to explain the heterogeneous Mg isotopic composition (δ26Mg, ‰) found in mantle wehrlites (-0.39 to +0.09 [1]) in the context of a homogeneous mantle (-0.25 ± 0.07 [2]). However, no systematic measurements of δ26Mg on marine sediments are currently available to provide direct support to this model. To characterize the Mg inputs to global subduction zones, we measured δ26Mg data for a total of 90 marine sediments collected from 12 drill sites outboard of the world's major subduction zones. These sediments span a 1.73‰ range in δ26Mg. The detritus-dominated sediments have δ26Mg (-0.59 to +0.53) comparable to those of weathered materials on continents (e.g. -0.52 to +0.92 [3]), while the calcareous oozes yield δ26Mg (as light as -1.20) more similar to the seawater value (-0.83 [4]). The negative correlation between δ26Mg and CaO/Al2O3 in these sediments indicates the primary control of mineralogy over the Mg isotopic distribution among different sediment types, as carbonates are enriched in light Mg isotopes (-5.10 to -0.40 [5]) whereas clay-rich weathering residues generally have heavier δ26Mg (e.g. up to +0.65 in saprolite [6]). In addition, chemical weathering and grain-size sorting drive sediments to a heavier δ26Mg, as indicated by the broad positive trends between δ26Mg with CIA (Chemical Index of Alteration [7]) and Al2O3/SiO2, respectively. Collectively, the arc systems sampled in this study represent ~30% of global arc length and the extrapolated global Mg flux of subducting marine sediments accounts for ~9% of the yearly Mg riverine input with a flux-weighted average δ26Mg at -0.26. Subduction of these heterogeneous sediments may not cause significant mantle heterogeneity on a global scale, but the highly variable Mg fluxes and δ26Mg of sediments delivered to different trenches are capable of producing local mantle variations. Volcanic rocks sourced from these mantle domains are thus

  14. Assessing upper Mississippi River sediments using benthic invertebrates and the sediment quality triad

    SciTech Connect

    Canfield, T.J.; Brunson, E.L.; Dwyer, F.J.; Ingersoll, C.G.; Kemble, N.E.

    1995-12-31

    Benthic invertebrate samples were collected from 23 pools in the Upper Mississippi River (UMR) and from one station in the Saint Croix River (SCR) as part of study to assess the effects of the extensive flooding of 1993 on sediment contamination in the UMR system. Sediment contamination consists of organic and inorganic contaminants. Samples were collected with a petite ponar grab sampler Oligochaete and Chironomid abundance constituted over 80% of the community in samples from 18 of 23 pools in the UMR and in the SCR sample. Fingernail clams comprised a large portion of the community in 5 of 23 UMR pools. Total abundance values ranged from 333/m{sup 2} at pool 1 to 25,000/m{sup 2} at pool 19. Overall frequency of chironomid mouth part deformities was 3%, which is comparable to literature values for incidence of deformities in uncontaminated sediments. Occurrence of mouth part deformities ranged 0 to 13% at the UMR pools. Sediment contamination was generally low in the UMR pools and the SCR site. The degree of sediment contamination will be evaluated with data from laboratory toxicity exposures, sediment chemistry analyses and benthic community analyses using the Sediment Quality Triad approach. Preliminary evaluations show the sediments from the UMR and SCR are relatively uncontaminated and the flooding of `93 did not adversely effect sediment quality in the UMR system.

  15. Toxicity assessment of sediments from three European river basins using a sediment contact test battery.

    PubMed

    Tuikka, A I; Schmitt, C; Höss, S; Bandow, N; von der Ohe, P C; de Zwart, D; de Deckere, E; Streck, G; Mothes, S; van Hattum, B; Kocan, A; Brix, R; Brack, W; Barceló, D; Sormunen, A J; Kukkonen, J V K

    2011-01-01

    The toxicity of four polluted sediments and their corresponding reference sediments from three European river basins were investigated using a battery of six sediment contact tests representing three different trophic levels. The tests included were chronic tests with the oligochaete Lumbriculus variegatus, the nematode Caenorhabditis elegans and the mudsnail Potamopyrgus antipodarum, a sub-chronic test with the midge Chironomus riparius, an early life stage test with the zebra fish Danio rerio, and an acute test with the luminescent bacterium Vibrio fischeri. The endpoints, namely survival, growth, reproduction, embryo development and light inhibition, differed between tests. The measured effects were compared to sediment contamination translated into toxic units (TU) on the basis of acute toxicity to Daphnia magna and Pimephales promelas, and multi-substance Potentially Affected Fractions of species (msPAF) as an estimate for expected community effects. The test battery could clearly detect toxicity of the polluted sediments with test-specific responses to the different sediments. The msPAF and TU-based toxicity estimations confirmed the results of the biotests by predicting a higher toxic risk for the polluted sediments compared to the corresponding reference sediments, but partly having a different emphasis from the biotests. The results demonstrate differences in the sensitivities of species and emphasize the need for data on multiple species, when estimating the effects of sediment pollution on the benthic community. PMID:20833427

  16. Age Dating Fluvial Sediment Storage Reservoirs to Construct Sediment Waiting Time Distributions

    NASA Astrophysics Data System (ADS)

    Skalak, K.; Pizzuto, J. E.; Benthem, A.; Karwan, D. L.; Mahan, S.

    2015-12-01

    Suspended sediment transport is an important geomorphic process that can often control the transport of nutrients and contaminants. The time a particle spends in storage remains a critical knowledge gap in understanding particle trajectories through landscapes. We dated floodplain deposits in South River, VA, using fallout radionuclides (Pb-210, Cs-137), optically stimulated luminescence (OSL), and radiocarbon dating to determine sediment ages and construct sediment waiting time distributions. We have a total of 14 age dates in two eroding banks. We combine these age dates with a well-constrained history of mercury concentrations on suspended sediment in the river from an industrial release. Ages from fallout radionuclides document sedimentation from the early 1900s to the present, and agree with the history of mercury contamination. OSL dates span approximately 200 to 17,000 years old. We performed a standard Weibull analysis of nonexceedance to construct a waiting time distribution of floodplain sediment for the South River. The mean waiting time for floodplain sediment is 2930 years, while the median is approximately 710 years. When the floodplain waiting time distribution is combined with the waiting time distribution for in-channel sediment storage (available from previous studies), the mean waiting time shifts to approximately 680 years, suggesting that quantifying sediment waiting times for both channel and floodplain storage is critical in advancing knowledge of particle trajectories through watersheds.

  17. Self-sedimentation of fossil phytoplankton blooms, laminated hemipelagic sediments and the oceanic carbon cycle

    SciTech Connect

    Grimm, K.A.; Lange, C.B.

    1996-12-31

    The flux of phytoplankton-derived organic carbon from the surface ocean to the deep sea and underlying sediments is a nonuniform process that significantly impacts biogeochemical cycles, atmospheric pCO{sub 2} / O{sub 2} and organic carbon enrichment in marine sediments. Some marine phytoplankton actively drive the sedimentation process by the formation of sticky transparent gels which facilitate aggregation, rapid sinking and efficient export flux. Here we present fossil evidence of unfragmented, low-diversity phytoplankton assemblages preserved as sedimentary laminations and as preserved aggregates that are attributable to a similar phytoplankton-driven sedimentary mechanism, here termed {open_quotes}self-sedimentation{close_quotes}. Heterogeneities in the texture and/or composition of sediment supply are necessary for the production of laminatedhemipelagic sediments; the absence of hydraulic and biological reworking permits preservation of these sedimentary laminae. Distinctly-laminated core intervals are characterized by large compositional contrasts between adjacent laminae; many such high-bimodality couplets are attributable to self-sedimentation of phytoplankton blooms. Self-sedimentation propels the formation of some conspicuous hemipelagic sedimentary laminations and results in efficient carbon and opal flux to the sediments. These records suggest that phytoplankton-mediated changes in the efficiency of the biological carbon pump may govern many accumulations of organic-rich hydrocarbon source rock as well as many abrupt changes in atmospheric pCO{sub 2} and climate.

  18. Self-sedimentation of fossil phytoplankton blooms, laminated hemipelagic sediments and the oceanic carbon cycle

    SciTech Connect

    Grimm, K.A. ); Lange, C.B. )

    1996-01-01

    The flux of phytoplankton-derived organic carbon from the surface ocean to the deep sea and underlying sediments is a nonuniform process that significantly impacts biogeochemical cycles, atmospheric pCO[sub 2] / O[sub 2] and organic carbon enrichment in marine sediments. Some marine phytoplankton actively drive the sedimentation process by the formation of sticky transparent gels which facilitate aggregation, rapid sinking and efficient export flux. Here we present fossil evidence of unfragmented, low-diversity phytoplankton assemblages preserved as sedimentary laminations and as preserved aggregates that are attributable to a similar phytoplankton-driven sedimentary mechanism, here termed [open quotes]self-sedimentation[close quotes]. Heterogeneities in the texture and/or composition of sediment supply are necessary for the production of laminatedhemipelagic sediments; the absence of hydraulic and biological reworking permits preservation of these sedimentary laminae. Distinctly-laminated core intervals are characterized by large compositional contrasts between adjacent laminae; many such high-bimodality couplets are attributable to self-sedimentation of phytoplankton blooms. Self-sedimentation propels the formation of some conspicuous hemipelagic sedimentary laminations and results in efficient carbon and opal flux to the sediments. These records suggest that phytoplankton-mediated changes in the efficiency of the biological carbon pump may govern many accumulations of organic-rich hydrocarbon source rock as well as many abrupt changes in atmospheric pCO[sub 2] and climate.

  19. Effective particle sizes of cohesive sediment in north Mississippi streams

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Knowledge of the size of cohesive sediment particles transported in streams is important information for predicting how the sediment and contaminants the sediment may be carrying will be transported by the flow. Cohesive sediments (less than 0.062 mm in diameter) generally are not transported in th...

  20. A SEDIMENT TOXICITY METHOD USING LEMNA MINOR, DUCKWEED

    EPA Science Inventory

    We developed a Lemna minor sediment toxicity test method to assess sediment contaminants which may affect plants. This 96-hour test used 15 ml of sediment and 2 ml of overlying water which was renewed after 48 hours. Sand was used as the control sediment and also to dilute test ...

  1. Contaminated aquatic sediments: Geochemical engineering solutions

    SciTech Connect

    Forstner, U.

    1995-12-31

    Risk assessment and management of contaminated sediments requires a holistic approach, i.e., the analytical and experimental parameters should always be related to the potential remediation options for a specific sediment problem. Particular emphasis should be posed on evaluation of redox-sensitive components. Regarding the potential release of metals from sediments changing of pH conditions are of prime importance. To incorporate new experience with non-linear and time-delayed processes, special emphasis should be put on the characteristics of the mineral and organic solid matrices, e.g., to capacity controlling properties, and in particular, the buffer capacity against pH-depression. There is a long retention time for sediments in larger catchment areas. Improvement at the source may need decades to become effective in the sediments at the tower reaches and harbors close to the river mouth. Remediation techniques on contaminated sediments generally are much more limited than for most other solid waste materials, except of mine wastes. The widely diverse contamination sources in larger catchment areas usually produces a mixture of pollutants, which is more difficult to treat than an industrial waste. Only a very small percentage of dredged sediments can undergo treatment in the closer sense -- solvent extraction, bioremediation, thermal desorption, vitrification, etc. Mechanical separation of less strongly contaminated fractions, however, may be an useful step prior to storage of the residues. For most sediments from maintenance dredging, there are more arguments in favor of disposal. Final storage conditions would imply that these materials should be deposited in a favorable geochemical environment. At the actual state of knowledge, this could only mean deposition under permanent anoxic conditions. Such conditions can be made artificially or be selected from natural environments.

  2. Soil conservation through sediment trapping: A review

    NASA Astrophysics Data System (ADS)

    Mekonnen, Mulatie; Keesstra, Saskia; Baartman, Jantiene; Maroulis, Jerry; Stroosnijder, Leo

    2014-05-01

    Preventing the off-site effects of soil erosion is an essential part of good catchment management. Most efforts are in the form of on-site soil and water conservation measures. However, sediment trapping (ST) can be an alternative (or additional) measure to prevent the negative off-site effects of soil erosion. Therefore, not all efforts should focus solely on on-site soil conservation, but also on the safe routing of sediment-laden flows and on creating sites and conditions where sediment can be trapped, preferably in a cost effective or even profitable way. ST can be applied on-site (in-field) and off-site and involves both vegetative and structural measures. The main vegetative measures include grass strips, tree or bush buffers, grassed waterways and restoration of the waterways and their riparian zone; while structural measures include terraces, ponds and check dams. This paper provides a review of studies that have assessed the sediment trapping efficacy (STE) of such vegetative and structural measures. Vegetation type and integration of two or more measures (vegetative as well as structural) are important factors influencing STE. In this review, the STE of most measures was evaluated either individually or in such combinations. In real landscape situations, it is not only important to select the most efficient erosion control measures, but also to determine their optimum location in the catchment. Hence, there is a need for research that shows a more integrated determination of STE at the catchment scale. If integrated measures are implemented at the most appropriate spatial locations within a catchment where they can disconnect landscape units from each other, they will decrease runoff velocity and sediment transport and, subsequently, reduce downstream flooding and sedimentation problems. KEY WORDS: Integrated sediment trapping, sediment trapping efficacy, vegetative, structural, on-site and off-site measures.

  3. Inversion of elastic impedance for unconsolidated sediments

    USGS Publications Warehouse

    Lee, Myung W.

    2006-01-01

    Elastic properties of gas-hydrate-bearing sediments are important for quantifying gas hydrate amounts as well as discriminating the gas hydrate effect on velocity from free gas or pore pressure. This paper presents an elastic inversion method for estimating elastic properties of gas-hydrate-bearing sediments from angle stacks using sequential inversion of P-wave impedance from the zero-offset stack and S-wave impedance from the far-offset stack without assuming velocity ratio.

  4. Interaction of fine sediment with alluvial streambeds

    USGS Publications Warehouse

    Jobson, H.E.; Carey, W.P.

    1989-01-01

    An alluvial streambed can have a large capacity to store fine sediments that are extracted from the flow when instream concentrations are high and it can gradually release fine sediment to the flow when the instream concentrations are low. Several types of storage mechanisms are available depending on the relative size distribution of the suspended load and bed material, as well as the flow hydraulics. -from Authors

  5. Nickel-free iron particles in sediments

    NASA Astrophysics Data System (ADS)

    Pechersky, D. M.; Kuzina, D. M.

    2015-11-01

    The results provided by the microprobe and thermomagnetic studies of native iron in sediments are generalized. It is found that the sediments are abundant in Ni-free iron particles. These particles are shown to have extraterrestrial origin and likely to be parts of cosmic dust. It is suggested that these particles were formed from the mantle and crustal rocks as a result of their fragmentation and melting of the silicates (such as olivine and pyroxene) contained in these rocks.

  6. Sediment transport in two mediterranean regulated rivers.

    PubMed

    Lobera, G; Batalla, R J; Vericat, D; López-Tarazón, J A; Tena, A

    2016-01-01

    Mediterranean climate is characterized by highly irregular rainfall patterns with marked differences between wet and dry seasons which lead to highly variable hydrological fluvial regimes. As a result, and in order to ensure water availability and reduce its temporal variability, a high number of large dams were built during the 20th century (more than 3500 located in Mediterranean rivers). Dams modify the flow regime but also interrupt the continuity of sediment transfer along the river network, thereby changing its functioning as an ecosystem. Within this context, the present paper aims to assess the suspended sediment loads and dynamics of two climatically contrasting Mediterranean regulated rivers (i.e. the Ésera and Siurana) during a 2-yr period. Key findings indicate that floods were responsible for 92% of the total suspended sediment load in the River Siurana, while this percentage falls to 70% for the Ésera, indicating the importance of baseflows on sediment transport in this river. This fact is related to the high sediment availability, with the Ésera acting as a non-supply-limited catchment due to the high productivity of the sources (i.e. badlands). In contrast, the Siurana can be considered a supply-limited system due to its low geomorphic activity and reduced sediment availability, with suspended sediment concentration remaining low even for high magnitude flood events. Reservoirs in both rivers reduce sediment load up to 90%, although total runoff is only reduced in the case of the River Ésera. A remarkable fact is the change of the hydrological character of the River Ésera downstream for the dam, shifting from a humid mountainous river regime to a quasi-invariable pattern, whereas the Siurana experiences the opposite effect, changing from a flashy Mediterranean river to a more constant flow regime below the dam. PMID:26372613

  7. Destabilization of Cohesive Intertidal Sediments by Infauna

    NASA Astrophysics Data System (ADS)

    de Deckere, E. M. G. T.; Tolhurst, T. J.; de Brouwer, J. F. C.

    2001-11-01

    Bioturbation activity was reduced in four plots on an intertidal mudflat in the Humber estuary (UK) during 4 days, by spraying the sediment with an insecticide, namely vydate. Macrofaunal, especially Nereis diversicolor and oligochaeta, and meiofaunal densities decreased, while the diatom biomass did not change. This resulted in a 300% increase in sediment stability, caused by a reduction in bioturbation and grazing pressure and a decrease in the water content.

  8. Sediment transport monitoring for sustainable hydropower development

    NASA Astrophysics Data System (ADS)

    Rüther, Nils; Guerrero, Massimo; Stokseth, Siri

    2015-04-01

    Due to the increasing demand of CO2 neutral energy not only in Europe but also in World, a relatively large amount of new hydro power plants (HPP) are built. In addition, will existing ones refurbished and renewed in order to run them more cost effective. A huge thread to HPPs is incoming sediments in suspension from the rivers upstream. The sediments settle in the reservoir and reduce the effective head and volume and reduce consequently the life time of the reservoir. In addition are the fine sediments causing severe damages to turbines and infrastructure of a HPP. For estimating the amount of incoming sediments in suspension and therefore planning efficient counter measures, it is essential to monitor the rivers within the catchment of the HPP for suspended sediments. This work is considerably time consuming and requires highly educated personnel and is therefore expensive. Consequently will this study present a method to measure suspended sediment concentrations and their grain size distribution with a dual frequency acoustic Doppler current profiler (ADCP). This method is more cost effective and reliable in comparison to traditional measurement methods. Having more detailed information about the sediments being transported in a river, the hydro power plant can be planned, built, and operated much more efficiently and sustainable. The two horizontal ADCPs are installed at a measurement cross section in the Devoll river in Albania. To verify the new method, the suspended load concentrations will be monitored also in the traditional ways at the same cross sections. It is planned to install turbidity measurement devices included with an automatic sampling devices. It is also planned to use an optical in situ measurement device (LISST SL by Sequoia Inc.) to have detailed information of sediment concentration and grain sizes over the depth.

  9. NUMERICAL MODELING OF FINE SEDIMENT PHYSICAL PROCESSES.

    USGS Publications Warehouse

    Schoellhamer, David H.

    1985-01-01

    Fine sediment in channels, rivers, estuaries, and coastal waters undergo several physical processes including flocculation, floc disruption, deposition, bed consolidation, and resuspension. This paper presents a conceptual model and reviews mathematical models of these physical processes. Several general fine sediment models that simulate some of these processes are reviewed. These general models do not directly simulate flocculation and floc disruption, but the conceptual model and existing functions are shown to adequately model these two processes for one set of laboratory data.

  10. The kinetics of denitrification in permeable sediments

    NASA Astrophysics Data System (ADS)

    Evrard, Victor; Glud, Ronnie N.; Cook, Perran L. M.

    2013-04-01

    Permeable sediments comprise the majority of shelf sediments, yet the rates of denitrification remain highly uncertain in these environments. Computational models are increasingly being used to understand the dynamics of denitrification in permeable sediments, which are complex environments to study experimentally. The realistic implementation of such models requires reliable experimentally derived data on the kinetics of denitrification. Here we undertook measurements of denitrification kinetics as a function of nitrate concentration and in the presence and absence of oxygen, in carefully controlled flow through reactor experiments on sediments taken from six shallow coastal sites in Port Phillip Bay, Victoria, Australia. The results showed that denitrification commenced rapidly (within 30 min) after the onset of anoxia and the kinetics could be well described by Michaelis-Menten kinetics with half saturation constants (apparent Km) ranging between 1.5 and 19.8 μM, and maximum denitrification rate (Vmax) were in the range of 0.9-7.5 nmol mL-1 h-1. The production of N2 through anaerobic ammonium oxidation (anammox) was generally found to be less than 10% that of denitrification. Vmax were in the same range as previously reported in cohesive sediments despite organic carbon contents one order of magnitude lower for the sediments studied here. The ratio of sediment O2 consumption to Vmax was in the range of 0.02-0.09, and was on average much lower than the theoretical ratio of 0.8. The most likely explanation for this is that the microbial community is not able to instantaneously shift or optimally use a particular electron acceptor in the highly dynamic redox environment experienced in permeable sediments. Consistent with this explanation, subsequent longer-term experiments over 5 days showed that denitrification rates increased by a factor of 10 within 3 days of the permanent onset of anoxia. In contrast to previous studies, we did not observe any significant