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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. Roles of the outer membrane protein AsmA of Salmonella enterica in the control of marRAB expression and invasion of epithelial cells.

    PubMed

    Prieto, Ana I; Hernández, Sara B; Cota, Ignacio; Pucciarelli, M Graciela; Orlov, Yuri; Ramos-Morales, Francisco; García-del Portillo, Francisco; Casadesús, Josep

    2009-06-01

    A genetic screen for suppressors of bile sensitivity in DNA adenine methylase (dam) mutants of Salmonella enterica serovar Typhimurium yielded insertions in an uncharacterized locus homologous to the Escherichia coli asmA gene. Disruption of asmA suppressed bile sensitivity also in phoP and wec mutants of S. enterica and increased the MIC of sodium deoxycholate for the parental strain ATCC 14028. Increased levels of marA mRNA were found in asmA, asmA dam, asmA phoP, and asmA wec strains of S. enterica, suggesting that lack of AsmA activates expression of the marRAB operon. Hence, asmA mutations may enhance bile resistance by inducing gene expression changes in the marRAB-controlled Mar regulon. In silico analysis of AsmA structure predicted the existence of one transmembrane domain. Biochemical analysis of subcellular fractions revealed that the asmA gene of S. enterica encodes a protein of approximately 70 kDa located in the outer membrane. Because AsmA is unrelated to known transport and/or efflux systems, we propose that activation of marRAB in asmA mutants may be a consequence of envelope reorganization. Competitive infection of BALB/c mice with asmA(+) and asmA isogenic strains indicated that lack of AsmA attenuates Salmonella virulence by the oral route but not by the intraperitoneal route. Furthermore, asmA mutants showed a reduced ability to invade epithelial cells in vitro.

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

    PubMed

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

    2012-09-01

    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 Re(I) tricarbonyl precursor yielded fac-Re(CO)3(ASMA) as a mixture of diastereomers. The chemistry is analogous to that of the Tc(I) tricarbonyl complex, which yields fac-(99m)Tc(CO)3(ASMA) under similar conditions. The formation, structure, and isomerization of fac-Re(CO)3(ASMA) products were characterized by HPLC, (1)H 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 (99m)Tc(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 (99m)Tc radiopharmaceuticals.

  5. Análisis del espectro infrarrojo del polvo interestelar asociado con cúmulos globulares y de su evolución temporal

    NASA Astrophysics Data System (ADS)

    Pellizza, L. J.; Forte, J. C.; Carpintero, D.

    El trabajo que se presenta investiga la dinámica de las partículas de polvo interestelar eyectadas por estrellas gigantes rojas en un cúmulo globular utilizando simulaciones numéricas de su interacción con el campo gravitatorio y con la radiación electromagnética de las estrellas. Se pretende con ello determinar la distribución espacial de ese material como una función del tiempo en un sistema similar a NGC 104 (47 Tuc). A partir de la distribución espacial resultante se obtuvo el espectro infrarrojo integrado el cual sugiere que el máximo contraste con la radiación estelar ocurre en longitudes de onda cercanas a 300 μm y que decrece rápidamente hacia longitudes de onda menores, en las que suelen realizarse las observaciones.

  6. 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.

  7. 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

  8. 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)

  9. Aquatic sediments

    SciTech Connect

    Bonner, J.S.; Autenrieth, R.L.; Schreiber, L. )

    1990-06-01

    The authors present a literature review concerning sediment properties, interactions, and conditions. Topics of discussion include the following: biological activity and toxicity; nutrients; metals; organic compounds; dredging; radionuclides; oxygen demand and organic carbon; mathematical modeling; sediment transport and suspension; and paleolimnology.

  10. 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 ...

  11. 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...

  12. Fluvial sediment concepts

    USGS Publications Warehouse

    Guy, Harold P.

    1970-01-01

    This report is the first of a series concerned with the measurement of and recording of information about fluvial sediment and with related environmental data needed to maintain and improve basic sediment knowledge. Concepts presented in this report involve (1) the physical characteristics of sediment which include aspects relative 'to weathering, soils, resistance to erosion, and particle size, (2) sediment erosion, transport, and deposition characteristics, which include aspects relative to fine sediment and overland flow, coarse sediment and streamflow, variations in stream sediment concentration, deposition, and denudation, (3) geomorphic considerations, which include aspects relative to the drainage basin, mass wasting, and channel properties, (4) economic aspects, and (5) data needs and program objectives to be attained through the use of several kinds of sediment records.

  13. 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

  14. 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.

  15. Sediment Budget and Sediment Fingerprinting as Management Strategies to Understand Sediment Contributions to Receiving Waters

    NASA Astrophysics Data System (ADS)

    Gellis, A.; Fitzpatrick, F.; Gorman-Sanisaca, L.

    2015-12-01

    A sound understanding of the sediment sources contributing to the sediment flux and the overall sediment budget of a watershed is key to total maximum daily load (TMDL) management strategies that focus on reducing sediment and sediment-related nutrient loadings to streams. This understanding can be provided by performing complementary sediment-source fingerprinting and sediment-budgeting investigations. The sediment fingerprinting approach quantifies the relative proportion of the potential sediment sources and the delivery of sediment from these sources. Sediment budget approaches provide information on the magnitude and location of the fluxes and the links between sources, sinks, and sediment output. Sediment budget approaches can include field based, photogrammetric, GIS, and modeling approaches to identify the important sources, erosion, and storage areas of sediment within a watershed. Combining sediment budget and sediment fingerprinting approaches provides resource managers with information on where to target mitigation measures that reduce erosion, and sediment delivery. Many watersheds across the U.S. have or are soon implementing TMDL allocations to reduce sediment and nutrient loadings. Streambank erosion is typically not accounted for in statistical, empirical, and process-based models, yet it is a major source of sediment in many watersheds. We present several examples of sediment budget and sediment fingerprinting studies from the Chesapeake Bay watershed and the Driftless Area, Wisconsin where information on loading of streambank sediment has been used (successfully) to shape upland and stream corridor management practices.

  16. The dirt on sediments

    USGS Publications Warehouse

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

    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.

  17. 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 ...

  18. Cell aggregation and sedimentation.

    PubMed

    Davis, R H

    1995-01-01

    The aggregation of cells into clumps or flocs has been exploited for decades in such applications as biological wastewater treatment, beer brewing, antibiotic fermentation, and enhanced sedimentation to aid in cell recovery or retention. More recent research has included the use of cell aggregation and sedimentation to selectively separate subpopulations of cells. Potential biotechnological applications include overcoming contamination, maintaining plasmid-bearing cells in continuous fermentors, and selectively removing nonviable hybridoma cells from perfusion cultures.

  19. 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...

  20. Sedimentation of prairie wetlands

    USGS Publications Warehouse

    Gleason, Robert A.; Euliss, Ned H.

    1998-01-01

    Many wetlands in the prairie pothole region are embedded within an agricultural landscape where they are subject to varying degrees of siltation. Cultivation of wetland catchment areas has exacerbated soil erosion; wetlands in agricultural fields receive more sediment from upland areas than wetlands in grassland landscapes and hence are subject to premature filling (i.e., they have shorter topographic lives). Associated impacts from increased turbidity, sediment deposition, and increased surface water input likely have impaired natural wetland functions. Although trapping of sediments by wetlands is often cited as a water quality benefit, sediment input from agricultural fields has potential to completely fill wetlands and shorten their effective life-span. Thus, the value placed on wetlands to trap sediments is in conflict with maximizing the effective topographic life of wetlands. Herein, we provide an overview of sedimentation, identify associated impacts on wetlands, and suggest remedial management strategies. We also highlight the need to evaluate the impact of agricultural practices on wetland functions from an interdisciplinary approach to facilitate development of best management practices that benefit both wetland and agricultural interests.

  1. 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.

  2. 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.

  3. 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.

  4. Sedimentation of knotted polymers

    NASA Astrophysics Data System (ADS)

    Piili, J.; Marenduzzo, D.; Kaski, K.; Linna, R. P.

    2013-01-01

    We investigate the sedimentation of knotted polymers by means of stochastic rotation dynamics, a molecular dynamics algorithm that takes hydrodynamics fully into account. We show that the sedimentation coefficient s, related to the terminal velocity of the knotted polymers, increases linearly with the average crossing number nc of the corresponding ideal knot. This provides direct computational confirmation of this relation, postulated on the basis of sedimentation experiments by Rybenkov [J. Mol. Biol.10.1006/jmbi.1996.0876 267, 299 (1997)]. Such a relation was previously shown to hold with simulations for knot electrophoresis. We also show that there is an accurate linear dependence of s on the inverse of the radius of gyration Rg-1, more specifically with the inverse of the Rg component that is perpendicular to the direction along which the polymer sediments. When the polymer sediments in a slab, the walls affect the results appreciably. However, Rg-1 remains to a good precision linearly dependent on nc. Therefore, Rg-1 is a good measure of a knot's complexity.

  5. 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.

  6. Sediment impacts on marine sponges.

    PubMed

    Bell, James J; McGrath, Emily; Biggerstaff, Andrew; Bates, Tracey; Bennett, Holly; Marlow, Joseph; Shaffer, Megan

    2015-05-15

    Changes in sediment input to marine systems can influence benthic environments in many ways. Sponges are important components of benthic ecosystems world-wide and as sessile suspension feeders are likely to be impacted by changes in sediment levels. Despite this, little is known about how sponges respond to changes in settled and suspended sediment. Here we review the known impacts of sedimentation on sponges and their adaptive capabilities, whilst highlighting gaps in our understanding of sediment impacts on sponges. Although the literature clearly shows that sponges are influenced by sediment in a variety of ways, most studies confer that sponges are able to tolerate, and in some cases thrive, in sedimented environments. Critical gaps exist in our understanding of the physiological responses of sponges to sediment, adaptive mechanisms, tolerance limits, and the particularly the effect of sediment on early life history stages.

  7. 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.

  8. 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

  9. 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

  10. Reservoir sedimentation research at the National Sedimentation Laboratory

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Researchers at the National Sedimentation Laboratory have made important contributions to reservoir sedimentation research for most of the 50 years that the laboratory has existed. Early publications from the mid 1960s to the mid 1970s reported work on the development of gamma ray sediment measurem...

  11. 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...

  12. 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

  13. SULFIDE MINERALS IN SEDIMENTS

    EPA Science Inventory

    The formation processes of metal sulfides in sediments, especially iron sulfides, have been the subjects of intense scientific research because of linkages to the global biogeochemical cycles of iron, sulfur, carbon, and oxygen. Transition metal sulfides (e.g., NiS, CuS, ZnS, Cd...

  14. 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.

  15. Sediment delivery after a wildfire

    USGS Publications Warehouse

    Reneau, S.L.; Katzman, D.; Kuyumjian, G.A.; Lavine, A.; Malmon, D.V.

    2007-01-01

    We use a record of sedimentation a small reservoir within the Cerro Grande burn area, New Mexico, to document postfire delivery of ash, other fine-grained sediment carried in suspension within floods, and coarse-grained sediment transported as bedload over a five-year period. Ash content of sediment layers is estimated using fallout 137Cs as a tracer, and ash concentrations are shown to rapidly decrease through a series of moderate-intensity convective storms in the first rainy season after the fire. Over 90% of the ash was delivered to the reservoir in the first year, and ash concentrations in suspended sediment were negligible after the second year. Delivery of the remainder of the fine sediment also declined rapidly after the first year despite the occurrence of higher-intensity storms in the second year. Fine sediment loads after five years remained significantly above prefire averages. Deposition of coarse-grained sediment was irregular in time and was associated with transport by snowmelt runoff of sediment stored along the upstream channel during short-duration summer floods. Coarse sediment delivery in the first four years was strongly correlated with snowmelt volume, suggesting a transport-limited system with abundant available sediment. Transport rates of coarse sediment declined in the fifth year, consistent with a transition to a more stable channel as the accessible sediment supply was depleted and the channel bed coarsened. Maximum impacts from ash and other fine-grained sediment therefore occurred soon after the fire, whereas the downstream impacts from coarse-grained sediment were attenuated by the more gradual process of bedload sediment transport. ?? 2007 Geological Society of America.

  16. 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.

  17. 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...

  18. Anomalous Sediment Mixing by Bioturbation

    NASA Astrophysics Data System (ADS)

    Roche, K. R.; Aubeneau, A. F.; Xie, M.; Packman, A. I.

    2013-12-01

    Bioturbation, the reworking of sediments by animals and plants, is the dominant mode of sediment mixing in low-energy environments, and plays an important role in sedimentary biogeochemical processes. Mixing resulting from bioturbation has historically been modeled as a diffusive process. However, diffusion models often do not provide a sufficient description of sediment mixing due to bioturbation. Stochastic models, such as the continuous time random walk (CTRW) model, provide more general descriptions of mixing behavior that are applicable even when regular diffusion assumptions are not met. Here we present results from an experimental investigation of anomalous sediment mixing by bioturbation in freshwater sediments. Clean and heavy-metal-contaminated sediments were collected from Lake DePue, a backwater lake of the Illinois River. The burrowing worm species Lumbriculus variegatus was introduced to homogenized Lake DePue sediments in aerated aquaria. We then introduced inert fine fluorescent particles to the sediment-water interface. Using time-lapse photography, we observed the mixing of the fluorescent particles into the sediment bed over a two-week period. We developed image analysis software to characterize the concentration distribution of the fluorescent particles as a function of sediment depth, and applied this to the time-series of images to evaluate sediment mixing. We fit a one-dimensional CTRW model to the depth profiles to evaluate the underlying statistical properties of the mixing behavior. This analysis suggests that the sediment mixing caused by L. variegatus burrowing is subdiffusive in time and superdiffusive in space. We also found that heavy metal contamination significantly reduces L. variegatus burrowing, causing increasingly anomalous sediment mixing. This result implies that there can be important feedbacks between sediment chemistry, organism behavior, and sediment mixing that are not considered in current environmental models.

  19. 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.

  20. 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).

  1. Magnetism of quaternary sediments

    NASA Astrophysics Data System (ADS)

    Heller, Friedrich

    Magnetism of Quaternary sediments was the topic of a well-attended symposium held during the 13th INQUA (International Union of Quaternary Research) congress in Beijing, China, August 2-9. More than 40 papers were delivered by scientists from Belgium, England, France, Germany, Japan, New Zealand, Sweden, Switzerland, Taiwan, the United States, the Soviet Union, Yugoslavia, and other countries. The host country contributed to a productive session that was part of the first large scientific meeting to take place in Beijing after the June 4, 1989, upheaval.Nearly half of the studies focused on paleomagnetic and rock magnetic properties of loess in Alaska, Central Asia, China, and New Zealand. Magnetostratigraphic polarity dating was done at some sections in the western (Shaw et al.) and central Chinese loess plateau (Bai and Hus; Wang and Evans; Yue). The interpretation of the polarity pattern found in the western loess plateau still is not unambiguous. In the central part, certain polarity boundaries, such as the Brunhes/Matuyama (B/M) boundary, are found in slightly different stratigraphic positions (Hus et al.; Yue). In deep-sea sediments the lock-in depth of natural remanent magnetization (NRM) at the B/M boundary seems to be a linear function of sedimentation rate (de Menocal et al.). Although the magnetization process in the Chinese loess is not well understood, detailed records of polarity transitions have been reported for the B/M and the Jaramillo R→N transition (Ma et al.; Rolph).

  2. 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

  3. [Bacterial diversity in Lianyungang marine sediment and Qinghai Lake sediment].

    PubMed

    Hou, Mei-Feng; He, Shi-Long; Li, Dong; Zhang, Jie; Zhao, Yun

    2011-09-01

    The 16S rRNA clone libraries of two different saline environments the Lianyungang marine sediment and the Qinghai Lake sediment were constructed. The Shannon diversity index, Chao and ACE richness index and Simpson dominance index of the bacterial communities in the two samples was compared, and the analysis for the bacterial community structures of this two samples was conducted. The results showed that the Shannon diversity index of Lianyungang marine sediment achieved 3.53, and that of Qinghai Lake sediment achieved 3.05, it was concluded that the bacterial communities in the two samples were diverse. The main bacterial communities in Lianyungang marine sediment included Proteobacteria (49.2%) and Bacteroidetes (29.2%), and Bacteroidetes (60.0%) and Firmicutes (26.0%) were the main bacterial communities in Qinghai Lake sediment. Some halotolerant and halophilic bacteria were found, which were important for industrial production and high saline wastewater treatment.

  4. Cyclic Sediment Trading Between Channel and River Bed Sediments

    NASA Astrophysics Data System (ADS)

    Haddadchi, A.

    2015-12-01

    Much of the previous work on sediment tracing has focused on determining either the initial sources of the sediment (soils derive from a particular rock type) or the erosion processes generating the sediment. However, alluvial stores can be both a source and sink for sediment transported by streams. Here geochemical and fallout radionuclide tracing of river-bed and alluvial sediments are used to determine the role of secondary sources, sediment stores, as potential sources of sediment leaving Emu Creek catchment, southeastern Queensland, Australia. Activity concentrations of 137Cs on the river sediments are consistent with channel erosion being the dominant source at all sites sampled along the river. To characterise the deposition and remobilisation cycles in the catchment, a novel geochemical tracing approach was used. Successive pockets of alluvium were treated as discrete sink terms within geochemical mixing models and their source contributions compared with those of river bed sediments collected adjacent to each alluvial pocket. Three different size fractions were examined; silts and clays (<10 μm), silts (10-63 μm), and fine sands (63-212 μm). The contribution of the initial soil/rock type sources to river bed and alluvial sediments at each sampling site was identical for all three different size fractions, but varied along the stream. Combining these findings it is concluded that proximal alluvial stores dominated the supply of sediment to the river at each location, with this being particularly evident at the catchment outlet. Identical contribution of rock type sources to both river bed and alluvial pockets together with the dominant erosion being from channel banks indicates a high degree of 'trading' between the fluvial space and the alluvial space. Hence, management works aimed at primarily reducing the supply of sediments to the outlet of Emu Creek should focus on rehabilitation of channel banks in the lower catchment.

  5. Optical sedimentation recorder

    SciTech Connect

    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.

  6. 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

  7. 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...

  8. 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.

  9. 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...

  10. 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...

  11. SEDIMENTATION IN THE ANGLE CENTRIFUGE.

    PubMed

    Pickels, E G

    1943-01-20

    1. Using hemocyanin from Limulus polyphemus as a test material, the process of sedimentation in the angle centrifuge, operating both in vacuum and in the open air, has been investigated. 2. Sedimentation in a given field of force was found less efficient when centrifugation was conducted in the open air, because of thermal convection. 3. Correlations have been made with results obtained in the analytical ultracentrifuge, and a theory of sedimentation in inclined tubes has been presented to explain the experimental results. 4. It has been shown that under proper conditions the angle centrifuge may be used for approximate determinations of particle size. 5. Recommendations, based mostly on experimental evidence, have been made for improving sedimentation and interpreting results. 6. To counteract convective disturbances of either thermal or inertial origin, a satisfactory method has been developed which consists of furnishing the fluid under study with a synthetic density gradient, formed with sucrose or some other non-sedimentable material.

  12. 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

  13. 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

  14. Coastal sediment dynamics in Spitsbergen

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

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

  15. 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...

  16. 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.

  17. 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...

  18. 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.

  19. AsMA journal covers, a history.

    PubMed

    Day, Pamela C

    2014-01-01

    The cover of our journal has changed quite often over the years. As we look forward to changing the name and design of the journal, it seems appropriate to reflect on the previous journal titles and covers. A brief history follows.

  20. 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.

  1. 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.

  2. 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...

  3. 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...

  4. 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.

  5. Measuring suspended sediment: Chapter 10

    USGS Publications Warehouse

    Gray, J.R.; Landers, M.N.

    2013-01-01

    Suspended sediment in streams and rivers can be measured using traditional instruments and techniques and (or) surrogate technologies. The former, as described herein, consists primarily of both manually deployed isokinetic samplers and their deployment protocols developed by the Federal Interagency Sedimentation Project. They are used on all continents other than Antarctica. The reliability of the typically spatially rich but temporally sparse data produced by traditional means is supported by a broad base of scientific literature since 1940. However, the suspended sediment surrogate technologies described herein – based on hydroacoustic, nephelometric, laser, and pressure difference principles – tend to produce temporally rich but in some cases spatially sparse datasets. The value of temporally rich data in the accuracy of continuous sediment-discharge records is hard to overstate, in part because such data can often overcome the shortcomings of poor spatial coverage. Coupled with calibration data produced by traditional means, surrogate technologies show considerable promise toward providing the fluvial sediment data needed to increase and bring more consistency to sediment-discharge measurements worldwide.

  6. 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.

  7. Relationship of sediment discharge to streamflow

    USGS Publications Warehouse

    Colby, B.R.

    1956-01-01

    The relationship between rate of sediment discharge and rate of water discharge at a cross section of a stream is frequently expressed by an average curve. This curve is the sediment rating curve. It has been widely used in the computation of average sediment discharge from water discharge for periods when sediment samples were not collected. This report discusses primarily the applications of sediment rating curves for periods during which at least occasional sediment samples were collected. Because sediment rating curves are of many kinds, the selection of the correct kind for each use is important. Each curve should be carefully prepared. In particular, the correct dependent variable must be used or the slope of the sediment rating curve may be incorrect for computing sediment discharges. Sediment rating curves and their applications were studied for the following gaging stations: 1. Niobrara River near Cody, Nebr. 2. Colorado River near Grand Canyon, Ariz. 3. Rio Grande at San Martial, N. Mex. 4. Rio Puerto near Bernardo, N. Mex. 5. White River near Kadoka, S. Dak. 6. Sandusky River near Fremont, Ohio Except for the Sandusky River and the Rio Puerco, which transport mostly fine sediment, one instantaneous sediment rating curve was prepared for the discharge of suspended sands, at each station, and another for the discharge of sediment finer than 0.082 millimeter. Each curve was studied separately, and by trial-end-error multiple correlation some of the factors that cause scatter from the sediment rating curves were determined. Average velocity at the cross section, Water temperature, and erratic fluctuations in concentration seemed to be the three major factors that caused departures from the sediment rating curves for suspended sands. The concentration of suspended sands varied with about the 2.8 power of the mean velocity for the four sediment, rating curves for suspended sands. The effect of water temperature was not so consistent as that of velocity and

  8. Sediment transported by Georgia streams

    USGS Publications Warehouse

    Kennedy, Vance C.

    1964-01-01

    A reconnaissance investigation of the sediment transported by selected Georgia streams during the period December 1957 to June 1959 was made to provide a general understanding of the physical quality of stream water in Georgia and to supply facts needed in planning more detailed work. The investigation was made by studying the variation of sediment concentration and sediment load with stream discharge at 33 sites and by relating the available data to topographic, geologic, climatic, and soil conditions in the State. In the Blue Ridge Mountains area of northern Georgia the great relief, moderately heavy precipitation, fast runoff, and loamy soils cause sediment concentrations and sediment loads which are above average for the State. During periods of moderate to low streamflow, the concentration of suspended sediment ranges from 1 to 25 ppm (parts per million). After heavy rainfall, sediment concentration increases rapidly as water discharge rises, and occasionally exceeds 1,000 ppm before decreasing again. The concentration may reach a maximum and decrease before the discharge peak is reached. A major part of the annual sediment load can be carried during a short period of time because of the great increase in both water discharge and sediment concentration during floods. The lower Coastal Plain differs from the mountainous areas in several respects. The topography is gently rolling to almost level, precipitation and runoff are less than average for the State, and topsoils generally consist of hard and loamy sand. Concentration of suspended sediment in streamflow commonly ranges from 1 to 20 ppm during periods of low to moderate discharge and increases to 15 to 60 ppm at high discharge. Because of the small increase in concentration with increasing stream discharge, the sediment load varies approximately in proportion to the discharge. The sediment characteristics of streams in the Piedmont, the Valley and Ridge area. and the upper Coastal Plain are intermediate

  9. 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.

  10. 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

  11. 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.

  12. Azaarenes in Puget sound sediments

    NASA Astrophysics Data System (ADS)

    Furlong, Edward T.; Carpenter, Roy

    1982-08-01

    The first quantitative measurements of azaarenes in marine sediments are reported for Puget Sound, in northwestern Washington State, U.S.A. Two- to four-ring azaarenes, in concentrations as low as 50 ppb (relative to organic carbon), are measured in 210Pb dated sediments using glass capillary gas chromatography combined with nitrogen-selective detection. Azaarene distributions are geographically and temporally variable. Azaarene distributions in upper sediment layers suggest that total azaarene concentrations are related to proximity to urban areas, and may be anthropogenically derived. Subsurface maxima between 6 and 17 cm in several cores resemble similar maxima in PAH and organo-sulfur compounds. Trace quantities of azaarenes present in sediments, deposited prior to urbanization of the Puget Sound region, suggest low-level natural azaarene sources. One core containing particulate coal produced a concentrated and complex azaarene mixture, suggesting either introduction of mined coal or erosion of regional coal deposits. Analyses of possible azaarene sources indicate that although azaarene compositions vary between sources, coal azaarenes can be distinguished from petroleum azaarenes by their ratios of 2-ring to 3-ring azaarenes, and may identify predominant azaarene inputs in environmental samples. Gross differences in azaarene composition exist between European and American air particulates and sediments, suggesting differences in azaarene sources.

  13. Modeling microalgal flocculation and sedimentation.

    PubMed

    Salim, S; Gilissen, L; Rinzema, A; Vermuë, M H; Wijffels, R H

    2013-09-01

    In this study, a combined flocculation and sedimentation model is developed. The model predicts the time needed to reach a desired concentration of microalgal suspension in a sedimentation tank. The concentration of the particles as function of the time and the position in the tank is described. The model was validated with experimental data for Ettlia texensis. The concentration changes measured in time at different heights in the sedimentation vessel corresponded well with model predictions. The model predicts that it takes 25 h to reach a final concentration of 5.2 gDW L(-1), when the initial concentration is 0.26 gDW L(-1) and the tank height is 1m. This example illustrates the use of this model for the design of the settling tank needed for pre-concentration of microalgal biomass before further dewatering.

  14. Ancient aqueous sedimentation on Mars

    NASA Astrophysics Data System (ADS)

    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.

  15. 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.

  16. 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.

  17. Hydroxyatrazine in soils and sediments

    USGS Publications Warehouse

    Lerch, R.N.; Thurman, E.M.; Blanchard, P.E.

    1999-01-01

    Hydroxyatrazine (HA) is the major metabolite of atrazine in most surface soils. Knowledge of HA sorption to soils, and its pattern of stream water contamination suggest that it is persistent in the environment. Soils with different atrazine use histories were collected from four sites, and sediments were collected from an agricultural watershed. Samples were exhaustively extracted with a mixed-mode extractant, and HA was quantitated using high performance liquid chromatography with UV detection. Atrazine, deethylatrazine (DEA), and deisopropylatrazine (DIA) were also measured in all samples. Concentrations of HA were considerably greater than concentrations of atrazine, DEA, and DIA in all soils and sediments studied. Soil concentrations of HA ranged from 14 to 640 ??g/kg with a median concentration of 84 ??g/kg. Sediment concentrations of HA ranged from 11 to 96 ??g/kg, with a median concentration of 14 ??g/kg. Correlations of HA and atrazine concentrations to soil properties indicated that HA levels in soils were controlled by sorption of atrazine. Because atrazine hydrolysis is known to be enhanced by sorption and pH extremes, soils with high organic matter (OM) and clay content and low pH will result in greater atrazine sorption and subsequent hydrolysis. Significant correlation of HA concentrations to OM, pH, and cation exchange capacity of sediments indicated that mixed-mode sorption (i.e., binding by cation exchange and hydrophobic interactions) was the mechanism controlling HA levels in sediment. The presence of HA in soils and stream sediments at the levels observed support existing hypotheses regarding its transport in surface runoff. These results also indicated that persistence of HA in terrestrial and aquatic ecosystems is an additional risk factor associated with atrazine usage.

  18. Preliminary design of sedimentation ponds

    SciTech Connect

    Wilson, L.C.; Wayland, L.D.

    1982-12-01

    Almost one-hundred sedimentation ponds were conceptually designed for a large surface mining study are in northeast Texas. An approximate procedure was developed to economically estimate construction quantities in order to predict surface water control costs. This procedure utilized site-specific empirical relationships developed from detailed analyses on a representative number of proposed sedimentation ponds. Use of these equations provided earthwork volumes, and spillway pipe lengths. The procedure developed for this study is presented along with the results of a verification analysis.

  19. 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

  20. 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

  1. Regulatory applications of sediment criteria. Final report

    SciTech Connect

    Not Available

    1987-06-23

    The report briefly describes the development of sediment criteria, discusses their utility and appropriate regulatory applications, and recommends steps to enhance the acceptance of sediment criteria by the regulatory and regulated communities.

  2. 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)

  3. 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.

  4. Digital model of evaporite sedimentation.

    PubMed

    Briggs, L I; Pollack, H N

    1967-01-27

    A deterministic digital model to simulate evaporite sedimentation permits experimentation with depth of water, shape of salt basin, number, position, and strength of the inlets, and rate of evaporation. It provides a reasonable fit to salt thickness and distribution in the Upper Silurian Salina Formation of Michigan. PMID:17737562

  5. 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 ...

  6. 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

  7. 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.

  8. Sediment availability on burnt hillslopes

    NASA Astrophysics Data System (ADS)

    Nyman, Petter; Sheridan, Gary; Moody, John; Smith, Hugh; Noske, Philip; Lane, Patrick

    2013-04-01

    In general, erosion has been modeled as being proportional to some form of energy or force (such as shear stress or stream power) with the proportionality constant being erodibility, which is a characterization of sediment availability. It is unclear if erodibility is constant with depth on recently burnt hillslopes. This study used both field- and laboratory based experiments to quantify sediment availability as a depth-dependent parameter on burnt hillslopes. An explicit representation of fire-effect on sediment availability was achieved by assuming that fire-effects produce a non-cohesive soil layer of variable depth. This depth is characterized as a probability density function with a single parameter that changed during recovery (0-3 years) as the available soil was depleted. Measurements in southeastern Australia found that initially after a wildfire the hillslope had a layer (0.75-0.91 cm in depth) of non-cohesive soil, which represented 97-117 t/ha of transport limited sediment. The thickness of this layer decreased exponentially with time since the wildfire. Additional results showed that fine roots (< 2-mm diameter) reduce the erodibility of surface soils for depths < 2 cm. The soil depth and root density accounted for ~60 % of variation in the erodibility at soil depths < 2 cm. At greater depths the root effect diminished and other soil properties (% silt and clay in particular) became more important as predictors of erodibility. The results are organized into a conceptual framework for modeling fire-effects on sediment availability for systems with low and high pre-fire erodibility. The fire-effect produces an equal depth of non-cohesive soil for both systems but this represents a greater perturbation for systems with low pre-fire erodibility than for those systems with a high pre-fire erodibility.

  9. Discos de polvo en sistemas exoplanetarios múltiples

    NASA Astrophysics Data System (ADS)

    Hobson, M.; Gómez, M.

    2016-08-01

    We investigate the spectral energy distributions of 486 stars hosting multiple exoplanetary systems, seeking infrared excesses that could indicate the presence of debris disks. These disks would be leftovers of the planetary formation process, and could be considered as analogues of the Solar System's asteroid or Kuiper belts. We estimate disk temperatures and radii for 79 systems with excesses in two or more filters. We find that 77 of the disks possess warm dust with a temperature in the range K, while 22 have cold dust with . Only one system has hot dust with K. 80 of the disks are within 10 au of the stars, and 35 at distances comparable to that of the asteroid belt; however, 96 are external to the planets.

  10. 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...

  11. Suspended Sediment Monitoring Strategies Reduce Model Uncertainties

    NASA Astrophysics Data System (ADS)

    Eads, R.; O'Connor, M.

    2007-12-01

    Regulatory agencies require development and implementation of Total Maximum Daily Loads for watersheds listed under section 303d of the Clean Water Act. For rivers identified as sediment impaired, methods are required to identify sediment sources and to estimate loading capacities, and models, such as sediment budgets, are often employed. Models can be tested and improved when stream monitoring provides accurate estimates of sediment loads. Motivated by proposed vineyard development on forested ridges in a sediment-listed watershed in the Coast Range of northern California, four tributaries to Gualala River ranging in size from 300 to 800 ha2 were monitored over two winter seasons. More than 1850 samples were analyzed for suspended sediment concentration. Inter- annual variability of sediment loads from wet and dry years is compared. Traditional methods for estimating suspended sediment loads often rely on measurements, such as water discharge, that are not well correlated to sediment concentration due to the highly variable routing of sediment to the channel from hillslopes, roads, and landslides. A method, such as Turbidity Threshold Sampling, that employs a parameter well correlated to suspended sediment concentration can improve sampling efficiency by collecting samples that are distributed over a range of rising and falling concentrations. The resulting set of samples can be used to estimate sediment loads by establishing a relationship between concentration and turbidity for any sampled period and applying it to the continuous turbidity record.

  12. Modern Reservoir Sedimentation Management Techniques with Examples

    NASA Astrophysics Data System (ADS)

    Annandale, G. W.

    2014-12-01

    Implementation of reservoir sedimentation management approaches results in a win-win scenario, it assists in enhancing the environment by preserving river function downstream of dams while concurrently providing opportunities to sustainably manage water resource infrastructure. This paper summarizes the most often used reservoir sedimentation management techniques with examples of where they have been implemented. Three categories can be used to classify these technologies, i.e. catchment management, sediment routing and sediment removal. The objective of catchment management techniques is to minimize the amount of sediment that may discharge into a reservoir, thereby reducing the loss of storage space due to sedimentation. Reservoir routing is a set of techniques that aim at minimizing the amount of sediment that may deposit in a reservoir, thereby maximizing the amount of sediment that may be passed downstream. The third group consists of techniques that may be used to remove previously deposited sediment from reservoirs. The selection of reservoir sedimentation management approaches is site specific and depends on various factors, including dam height, reservoir volume, reservoir length, valley shape, valley slope, sediment type and hydrology. Description of the different reservoir sedimentation management techniques that are used in practice will be accompanied by case studies, including video, illustrating criteria that may be used to determine the potential success of implementing the techniques.

  13. 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...

  14. Subsurface hydrologic effects on sediment deposition

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Quantification of soil erosion processes has been traditionally focused on soil detachment and sediment transport while efforts in quantifying sediment deposition process are relatively minor. Nevertheless, most sediment generated on the hill slopes are deposited within the field and only a small am...

  15. 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...

  16. EFFECTS OF HIGH SEDIMENT CONCENTRATIONS ON VELOCITY AND SEDIMENT DISTRIBUTIONS.

    USGS Publications Warehouse

    McCutcheon, Steve C.; Bradley, Jeffrey B.; ,

    1984-01-01

    Several classifications are required to describe sediment-transporting flow. The flow may be turbulent or laminar, Newtonian or non-Newtonian, and may also have a uniform or nonuniform concentration profile. As sediment concentration or transport increases, the character of flow changes. Generally, fall velocity and effective fall diameter decrease. The viscosity of the mixture increases. The flow becomes non-Newtonian when particle interaction becomes dominant. In the lowest concentration ranges, flows are Newtonian, generally nonuniform by concentration, and almost exclusively turbulent. Mudflows are non-Newtonian and usually laminar flows of a nearly uniform concentration. In the interim ranges are found transitions to non-Newtonian and laminar flows and uniform concentration profiles.

  17. Dimpling in loose granular sediments

    NASA Astrophysics Data System (ADS)

    Díaz-Hernández, Jose Luis; Yepes, Jorge

    2010-05-01

    Dimpling is the name given to the centimetre-scale collapse of granular deposits covering the interior of alteration shelters in semi-arid badlands. The development of micro-collapses is favoured by the stable conditions found in these shelters, where they are safe from water flows, rain impact, and animal or human traffic. The floor of these shelters is usually covered by several centimetres of sandy sediment resulting from the alteration of the rocky substratum and characterised by apparently very low density and high porosity. We have observed that the dimpling phenomenon does not depend on the mineralogy of the sands and occurs in dry conditions. The dimples are the shapes resulting from this process and are fragile, conical depressions ranging from 1 to 12 cm in diameter. They are generally over 3 cm in depth, depending on the depth of the sandy layer. The dimples can be classified into three groups by diameter (Ø): Ø≤1cm, 1cm≤Ø≤10 cm and Ø≥10 cm. These three morphometrical ranges suggest three evolutionary stages of the shapes. The main mechanisms of evolution are the coalescence of neighbouring dimples and the accommodation of the lateral walls towards more open, stable shapes. In this process, the slope of the dimple walls decreases to the angle of equilibrium, or internal friction angle of the sediment, when they acquire a more stable, dense structure. This evolution occurs naturally over several months. The process begins when sufficient sediment with low apparent density accumulates. This takes place by vertical accretion of particles from the shelter walls, which pile up in a stack-of-cards type structure. The increase in weight of the sediment column causes punctual micro-collapses when the limit of the sediment's self-supporting capacity is reached. The process is gravitational. Thermal variations can also condition the structural instability of the sediment due to the dilation-retraction changes undergone by the sediment grains. We can

  18. A Sediment Budget Case Study: Comparing Watershed Scale Erosion Estimates to Modeled and Empirical Sediment Loads

    NASA Astrophysics Data System (ADS)

    McDavitt, B.; O'Connor, M.

    2003-12-01

    The Pacific Lumber Company Habitat Conservation Plan requires watershed analyses to be conducted on their property. This paper summarizes a portion of that analysis focusing on erosion and sedimentation processes and rates coupled with downstream sediment routing in the Freshwater Creek watershed in northwest California. Watershed scale erosion sources from hillslopes, roads, and channel banks were quantified using field surveys, aerial photo interpretation, and empirical modeling approaches for different elements of the study. Sediment transport rates for bedload were modeled, and sediment transport rates for suspended sediment were estimated based on size distribution of sediment inputs in relation to sizes transported in suspension. Recent short-term, high-quality estimates of suspended sediment yield that a community watershed group collected with technical assistance from the US Forest Service were used to validate the resulting sediment budget. Bedload yield data from an adjacent watershed, Jacoby Creek, provided another check on the sediment budget. The sediment budget techniques and bedload routing models used for this study generated sediment yield estimates that are in good agreement with available data. These results suggest that sediment budget techniques that require moderate levels of fieldwork can be used to provide relatively accurate technical assessments. Ongoing monitoring of sediment sources coupled with sediment routing models and reach scale field data allows for predictions to be made regarding in-channel sediment storage.

  19. 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.

  20. 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.

  1. Sediment problems in urban areas

    USGS Publications Warehouse

    Guy, Harold P.

    1970-01-01

    One obstacle to a scientific recognition and an engineering solution to sediment-related environmental problems is that such problems are bound in conflicting and generally undefinable political and institutional restraints. Also, some of the difficulty may involve the fact that the scientist or engineer, because of his relatively narrow field of investigation, cannot always completely envision the less desirable effects of his work and communicate alternative solutions to the public. For example, the highway and motor-vehicle engineers have learned how to provide the means by which one can transport himself from one point to another with such great efficiency that a person's employment in this country is now commonly more than 5 miles from his residence. However, providing such efficient personal transport has created numerous serious environmental problems. Obstacles to recognition of and action to control sediment problems in and around urban areas are akin to other environmental problems with respect to the many scientific, engineering, economic, and social aspects.

  2. 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.

  3. 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

  4. 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.

  5. Sediment transport measurements: Chapter 5

    USGS Publications Warehouse

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

    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.

  6. 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.

  7. 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.

  8. Mercury dynamics in lake sediments

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

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

  9. 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

  10. 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

  11. 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.

  12. Reconnaissance study of stream sedimentation, southern Guam

    USGS Publications Warehouse

    Shade, P.J.

    1983-01-01

    This study uses limited available data to estimate sediment yields for three basins in southern Guam. The flow-duration sediment-rating curve method, reservoir survey data, and Pacific southwest Inter-Agency Committee (PSIAC) formula were used. Daily suspended-sediment samples were collected at USGS gaging stations on the Ylig and Ugum Rivers for one year. Intermittent samples were collected from the Talofofo River for six months. Although limited, these data are used in the flow-duration sediment-rating-curve method to estimate mean suspended-sediment yields. Fena Reservoir sedimentation data are used to test the applicability of the PSIAC formula in the three basins. Estimates of suspended-sediment yields are 467 to 845, 678 to 977, and 634 to 855 tons per year per square mile for the Talofofo, Ylig, and Ugum basins, respectively. PSIAC estimates of total sediment yield are 1,200 tons/yr/mi2 for the Talofofo, 1,385 tons/yr/mi2 for the Ylig, and 1,210 tons/yr/mi2 for the Ugum basins. These values are comparable to estimates of sediment yields from several similar basins on Oahu, Hawaii. It appears that the PSIAC method can be a useful tool in estimating sediment yields in some tropical areas. (USGS)

  13. Deposition of fine sediment in turbulent conditions

    NASA Astrophysics Data System (ADS)

    Capapé, Sergi; Martín-Vide, Juan Pedro; Colombo, Ferran

    2015-04-01

    Sediment transport is the responsible for reshaping the stream bed. There are multiple studies on the bedform formation, but data is scarce when the bed originates from a sediment-laden flow and the sediment is in the very fine range. The aim of this work is to evaluate the suspended sediment concentration at which deposition starts to occur. Specifically, non-cohesive fine sediment made of silica particles (D50 = 0.004 mm, σg = 2.45) is used to assess the transport of sediment in the wash-load size range. The second objective arises as a consequence of studying the first one: to analyse the relation between the flow properties and a developed bed composed of very fine sediment. The experiments are performed in a 15 m-long 0.37 m-wide flume (SIMGEO UB-CSIC, Faculty of Geology, University of Barcelona). Water and sediment are recirculated. The clean smooth metal surface of the flume is set to be the initial condition in each run. Hydraulic conditions in the flume are quasi-uniform. Flow parameters are controlled by the use of an ADV Vectrino, a current meter, a thermometer and siphons to collect samples of the suspension. Preliminary results show that very fine sediment transported in suspension settles on the bed as function of the elapsed time and the suspended sediment concentration. Bedform development may show the typical stages unless for the first partial-covered bed stage in which solitary lunate ripples migrate downstream.

  14. 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

  15. 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.

  16. 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.

  17. 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.

    2016-07-11

    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.

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

    USGS Publications Warehouse

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

    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).

  19. Selecting Color-based Tracers and Classifying Sediment Sources in the Assessment of Sediment Dynamics Using Sediment Source Fingerprinting.

    PubMed

    Barthod, Louise R M; Liu, Kui; Lobb, David A; Owens, Philip N; Martínez-Carreras, Núria; Koiter, Alexander J; Petticrew, Ellen L; McCullough, Gregory K; Liu, Cenwei; Gaspar, Leticia

    2015-09-01

    The use of sediment color as a fingerprint property to determine sediment sources is an emerging technique that can provide a rapid and inexpensive means of investigating sediment sources. The present study aims to test the feasibility of color fingerprint properties to apportion sediment sources within the South Tobacco Creek Watershed (74 km) in Manitoba, Canada. Suspended sediment from 2009 to 2011 at six monitoring stations and potential source samples along the main stem of the creek were collected. Reflectance spectra of sediments and source materials were quantified using a diffuse reflectance spectrometry, and 16 color coefficients were derived from several color space models. Canonical discriminant analysis was used to reclassify and downsize sediment source groups. After the linear additive test and stepwise discriminant function analysis, four color coefficients were chosen to fit the Stable Isotope Analysis in R model. Consistent with the conventional fingerprinting approach, the color fingerprint results demonstrated a switch in the dominant sediment source between the headwaters and the outlet of the watershed, with the main sources being topsoil in the upper reaches, whereas outcrop shale and stream bank materials dominated in the lower reaches. The color fingerprinting approach can be integrated with conventional fingerprints (e.g., geochemical and fallout radionuclide properties) to improve source discrimination, which is a key component for source ascription modeling. We concluded that the use of color fingerprints is a promising, cost-effective technique for sediment source fingerprinting. PMID:26436277

  20. 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

  1. 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.

  2. 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.

  3. Sediment ingestion of two sympatric shorebird species

    USGS Publications Warehouse

    Hui, C.A.; Beyer, W.N.

    1998-01-01

    Black-bellied Plovers (Pluvialis squatarola) have short bills and primarily peck while foraging whereas Willets (Catoptrophorus semipalmatus) have long bills and primarily probe with bills open in sediments. Intestinal digesta were collected from these species at sympatric overwintering sites in southern California near San Diego to relate sediment ingestion to bill length and feeding behavior. Plover digesta contained an estimated 29% sediment, and Willet digesta an estimated 3% sediment. Techniques based on acid insoluble ash and on the elemental markers of Al, Fe, and Ti in digesta provided similar results. High Ca concentrations in Willet digesta and our observations suggested that the willets in our sample fed primarily on molluscs and crustaceans. Sediment ingestion may be species specific, not necessarily linked to bill length or probing behaviors, and may greatly affect a bird?s exposure to environmental contaminants in sediment.

  4. 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

  5. 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.

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

    USGS Publications Warehouse

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

  7. Glacial marine sedimentation: Paleoclimatic significance

    SciTech Connect

    Anderson, J.B.; Ashley, G.M.

    1991-01-01

    This publication resulted from a symposium held during the 1988 Annual Meeting of the Geological Society of America. Many, but not all, contributors to the symposium have papers in this volume. This Special Paper consists of 14 chapters and a Subject/Geographic index. Each chapter has is own list of references. The papers cover a wide range of modem climate/ ocean environments, including papers on glacial marine sediments from Antarctica, the fiords of Alaska, and sediments from the Canadian High Arctic. In addition, three papers discuss [open quote]old[close quotes] glacial marine records (i.e., pre-Tertiary), and one paper discusses the Yakataga Formation of the Gulf of Alaska which is a Miocene-to-late-Pleistocene sequence. The last chapter in the book includes a survey and summary of the evidence for the paleoclimatic significance of glacial marine sediments by the two editors, John Anderson and Gail Ashley. It is worth noting that Anderson and Domack state in the Foreword that there is a considerable variation in terminology; hence they employ a series of definitions which they urge the other authors to employ. They define and explain what they mean by [open quotes]polar ice cap,[close quotes] [open quote]polar tundra (subpolar),[close quotes] and [open quotes]temperate oceanic and boreal[close quotes] in terms of the dominant glacial and glacial marine processes. Although one might quarrel with the terminology, the broad differences between these three glaciological regimes are indeed fundamental and need to be sought in the geological record. The flavor of the volume can be judged by some of the chapter titles. Contributions on Antarctica include a paper by Anderson and other entitled [open quote]Sedimentary facies associated with Antarctica's floating ice masses[close quotes] and a companion paper by Anderson and Domack which deals with the extremely complex glacial marine facies (13 facies are delimited) in McMurdo Sound, Antarctica.

  8. 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.

  9. 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.

  10. 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...

  11. 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

  12. Suspended sediments limit coral sperm availability.

    PubMed

    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

  13. Modelling sediment input in large river basins

    NASA Astrophysics Data System (ADS)

    Scherer, U.

    2012-04-01

    Erosion and sediment redistribution play a pivotal role in the terrestrial ecosystem as they directly influence soil functions and water quality. In particular surface waters are threatened by emissions of nutrients and contaminants via erosion. The sustainable management of sediments is thus a key challenge in river basin management. Beside the planning and implementation of mitigation measures typically focusing on small and mesoscale catchments, the knowledge of sediment emissions and associated substances in large drainage basins is of utmost importance for water quality protection of large rivers and the seas. The objective of this study was thus to quantify the sediment input into the large drainage basins of Germany (Rhine, Elbe, Odra, Weser, Ems, Danube) as a basis for nutrient and contaminant emissions via erosion. The sediment input was quantified for all watersheds of Germany and added up along the flow paths of the river systems. Due to the large scale, sediment production within the watersheds was estimated based on the USLE for cultivated land and naturally covered areas and on specific erosion rates for mountainous areas without vegetation cover. To quantify the sediment delivery ratio a model approach was developed using data on calculated sediment production rates and long term sediment loads observed at monitoring stations of 13 watersheds located in different landscape regions of Germany. A variety of morphological parameters and catchment properties such as slope, drainage density, share of morphological sinks, hypsometric integral, flow distance between sediment source areas and the next stream as well as soil and land use properties were tested to explain the variation in the sediment delivery ratios for the 13 watersheds. The sediment input into streams is mainly controlled by the location of sediment source areas and the morphology along the flow pathways to surface waters. Thus, this complex interaction of spatially distributed catchment

  14. 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.

  15. Dams on the Mekong: Cumulative sediment starvation

    NASA Astrophysics Data System (ADS)

    Kondolf, G. M.; Rubin, Z. K.; Minear, J. T.

    2014-06-01

    The Mekong River, largely undeveloped prior to 1990, is undergoing rapid dam construction. Seven dams are under construction on the mainstem in China and 133 proposed for the Lower Mekong River and tributaries. We delineated nine distinct geomorphic regions, for which we estimated sediment yields based on geomorphic characteristics, tectonic history, and the limited sediment transport data available. We then applied the 3W model to calculate cumulative sediment trapping by these dams, accounting for changing trap efficiency over time and multiple dams on a single river system. Under a "definite future" scenario of 38 dams (built or under construction), cumulative sediment reduction to the Delta would be 51%. Under full build-out of all planned dams, cumulative sediment trapping will be 96%. That is, once in-channel stored sediment is exhausted, only 4% of the predam sediment load would be expected to reach the Delta. This scenario would have profound consequences on productivity of the river and persistence of the Delta landform itself, and suggests that strategies to pass sediment through/around dams should be explored to prevent the consequences of downstream sediment starvation.

  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. 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.

  18. Palaeoclimate, Sedimentation and Continental Accretion

    NASA Astrophysics Data System (ADS)

    Ziegler, A. M.; Barrett, S. F.; Scotese, C. R.

    1981-05-01

    Climate has a pervasive effect on sedimentation today, and the same climatic patterns are reflected in the distribution of lithofacies through the Palaeozoic, as the continents migrate beneath the climatic zones. The low-latitude hot wet zone is represented by thick clastics, coals and carbonates and is best developed along east coasts where prevailing winds bring moisture and heated surface waters toward the continent. The desert zones occur on the west sides of continents centred at 20 degrees north and south, and these dry belts are represented in the geological record by evaporites. Tillites, thick clastics and coals occur in the temperate rainy belts, especially on the windward, west sides of continents above 40 degrees latitude. Continental accretion occurs where subduction zones coincide with rainy zones, such that the products of erosion are transported to the trench, and thus thrust back, extending the margin of the continent. The opposite process of `tectonic erosion', wherein the descending oceanic slab continually `rasps' away the margin of the continental crust, may occur in areas where rainfall and surface run-off is insufficient to provide trench sediments. This process has been operating adjacent to the Atacama Desert in South America during the past 200 Ma. To judge by the eastward migration of the calc-alkaline intrusive foci, about 250 km of the margin of South America have been transported down the subduction zone during this period.

  19. 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...

  20. 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

  1. 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

  2. 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.

  3. 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.

  4. 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

  5. Calibration of biological lake sediment records: Tracing diatom assemblages through the water column into the sediment

    NASA Astrophysics Data System (ADS)

    Maier, Dominique; Gälman, Veronika; Bigler, Christian; Renberg, Ingemar

    2013-04-01

    Paleolimnological studies rely on sediment cores taken from the deepest point of a lake. The deposited sediment and its embedded biological record are expected to be chronological and to display the lakes ecological past. Therefore many studies use micropalaeontological approaches, since, e. g., unicellular organisms like diatoms are directly dependent on habitat changes and thus mirror the prevailing weather conditions. In this study we combine a set of diatom samples from freeze cores of a varved sediment, a sediment trap and bi-weekly plankton survey data with environmental data to calibrate the biological sediment record of a lake. The annually laminated sediment of the boreal forest lake Nylandssjön in northern Sweden provides a very high temporal resolution, which allows us, even on a seasonal scale, a gapless comparison between in situ production and the sediment deposition. Analysis of the diatom assemblages through the water column into the sediment is expected to reveal quantitative and qualitative miss match in deposition, resuspension, seasonal and interannual delays caused by physical events or autochtonous interactions such as grazing in the water column. The overall comparison of the ten year plankton net record and the corresponding sediment trap samples reveals large shifts from season to season but also from year to year. The sediment trap diatom record indicates comparable abundance patterns for the main taxa (Asterionella formosa and Tabellaria flocculosa). Peaks and seasonal shifts are less pronounced in the sediment trap compared to the plankton data. An overall difficulty lies in the comparison of volumes of water and sediment, concentrations and fluxes, which needs to be solved. However, subsequent comparison with the sediment diatom assemblage is expected to lead us to understand interannual taphonomic processes affecting diatom records within ten years in the naturally formed sediment layers. More importantly we will be able to discover

  6. 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.

  7. 7 CFR 58.134 - Sediment content.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... Specifications for Dairy Plants Approved for USDA Inspection and Grading Service 1 Quality Specifications for Raw Milk § 58.134 Sediment content. (a) Method of testing. Methods for determining the sediment content of the milk of individual producers shall be those described in the latest edition of Standard...

  8. Repeated erosion of cohesive sediments with biofilms

    NASA Astrophysics Data System (ADS)

    Valentine, K.; Mariotti, G.; Fagherazzi, S.

    2014-04-01

    This study aims to explore the interplay between biofilms and erodability of cohesive sediments. Erosion experiments were run in four laboratory annular flumes with natural sediments. After each erosion the sediment was allowed to settle, mimicking intermittent physical processes like tidal currents and waves. The time between consecutive erosion events ranged from 1 to 12 days. Turbidity of the water column caused by sediment resuspension was used to determine the erodability of the sediments with respect to small and moderate shear stresses. Erodability was also compared on the basis of the presence of benthic biofilms, which were quantified using a Pulse-Amplitude Modulation (PAM) Underwater Fluorometer. We found that frequent erosion lead to the establishment of a weak biofilm, which reduced sediment erosion at small shear stresses (around 0.1 Pa). If prolonged periods without erosion were present, the biofilm fully established, resulting in lower erosion at moderate shear stresses (around 0.4 Pa). We conclude that an unstructured extracellular polymeric substances (EPS) matrix always affect sediment erodability at low shear stresses, while only a fully developed biofilm mat can reduce sediment erodability at moderate shear stresses.

  9. 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.

  10. Transformation of benzothiazole in estuarine sediments.

    PubMed

    Catallo, W James; Junk, T

    2005-01-01

    Benzothiazole (BT) is a natural and synthetic compound occurring in aquatic sediments and wastewater. The purpose of this work was to investigate BT biogeochemistry in controlled Eh/pH microcosms (CEPMs) containing estuarine sediments of different particle sizes (coarse, intermediate, fine) under oxidized and reduced conditions vs. killed controls, and tide simulation mesocosms (TSMs) containing plants and meiofauna under well-drained (oxidized), consistently saturated/flooded (reduced), and tidal (alternating oxidized/reduced) conditions. Benzothiazole was transformed into complex product mixtures under all conditions. Benzothiazole transformation rates in CEPMs were slower under reduced conditions vs. oxidized conditions in the fine- and intermediate-grain sediments, but the same in the coarse sediment. Quiescent (unstirred) CEPMs showed greatly reduced BT transformation rates in all sediments, with half-lives on the order of 2200 to >4000 h (unstirred) vs. 640 to 1000 h in the continuously stirred systems. The TSM data showed that tidal and drained systems processed BT at identical rates, far exceeding those observed in statically flooded (reduced) TSMs. Mixing was found to be a more significant variable in BT transformation rate than either Eh or sediment particle size breakdown, with constant stirring increasing observed degradation appreciably. Otherwise, BT was transformed more readily on sediments of high surface area under oxidized conditions vs. coarser sediments and those under reducing electrochemical conditions. PMID:16151226

  11. 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...

  12. METHYL MERCURY IN LAKE MICHIGAN SURFICIAL SEDIMENTS

    EPA Science Inventory

    Sediment samples were collected from Lake Michigan between 1994 and 1996. One purpose of the sampling was to define the horizontal distribution of methyl mercury in the surficial 1 cm of sediment. Samples were collected from 51 stations using a box core from which subcores for ...

  13. Determination of sedimentation coefficients for small peptides.

    PubMed Central

    Schuck, P; MacPhee, C E; Howlett, G J

    1998-01-01

    Direct fitting of sedimentation velocity data with numerical solutions of the Lamm equations has been exploited to obtain sedimentation coefficients for single solutes under conditions where solvent and solution plateaus are either not available or are transient. The calculated evolution was initialized with the first experimental scan and nonlinear regression was employed to obtain best-fit values for the sedimentation and diffusion coefficients. General properties of the Lamm equations as data analysis tools were examined. This method was applied to study a set of small peptides containing amphipathic heptad repeats with the general structure Ac-YS-(AKEAAKE)nGAR-NH2, n = 2, 3, or 4. Sedimentation velocity analysis indicated single sedimenting species with sedimentation coefficients (s(20,w) values) of 0.37, 0.45, and 0.52 S, respectively, in good agreement with sedimentation coefficients predicted by hydrodynamic theory. The described approach can be applied to synthetic boundary and conventional loading experiments, and can be extended to analyze sedimentation data for both large and small macromolecules in order to define shape, heterogeneity, and state of association. PMID:9449347

  14. 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...

  15. Field methods for measurement of fluvial sediment

    USGS Publications Warehouse

    Edwards, Thomas K.; Glysson, G. Douglas

    1999-01-01

    This chapter describes equipment and procedures for collection and measurement of fluvial sediment. The complexity of the hydrologic and physical environments and man's ever-increasing data needs make it essential for those responsible for the collection of sediment data to be aware of basic concepts involved in processes of erosion, transport, deposition of sediment, and equipment and procedures necessary to representatively collect sediment data. In addition to an introduction, the chapter has two major sections. The 'Sediment-Sampling Equipment' section encompasses discussions of characteristics and limitations of various models of depth- and point-integrating samplers, single-stage samplers, bed-material samplers, bedload samplers, automatic pumping samplers, and support equipment. The 'Sediment-Sampling Techniques'` section includes discussions of representative sampling criteria, characteristics of sampling sites, equipment selection relative to the sampling conditions and needs, depth and point-integration techniques, surface and dip sampling, determination of transit rates, sampling programs and related data, cold-weather sampling, bed-material and bedload sampling, measuring total sediment discharge, and measuring reservoir sedimentation rates.

  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. 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.

  18. 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...

  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 sulfur

  20. Geochemistry of Peruvian near-surface sediments

    NASA Astrophysics Data System (ADS)

    Böning, Philipp; Brumsack, Hans-Jürgen; Böttcher, Michael E.; Schnetger, Bernhard; Kriete, Cornelia; Kallmeyer, Jens; Borchers, Sven Lars

    2004-11-01

    Sixteen short sediment cores were recovered from the upper edge (UEO), within (WO) and below (BO) the oxygen minimum zone (OMZ) off Peru during cruise 147 of R/V Sonne. Solids were analyzed for major/trace elements, total organic carbon, total inorganic carbon, total sulfur, the stable sulfur isotope composition (δ 34S) of pyrite, and sulfate reduction rates (SRR). Pore waters were analyzed for dissolved sulfate/sulfide and δ 34S of sulfate. In all cores highest SRR were observed in the top 5 cm where pore water sulfate concentrations varied little due to resupply of sulfate by sulfide oxidation and/or diffusion of sulfate from bottom water. δ 34S of dissolved sulfate showed only minor downcore increases. Strong 32S enrichments in sedimentary pyrite (to -48‰ vs. V-CDT) are due to processes in the oxidative part of the sulfur cycle in addition to sulfate reduction. Manganese and Co are significantly depleted in Peruvian upwelling sediments most likely due to mobilization from particles settling through the OMZ, whereas release of both elements from reducing sediments only seems to occur in near-coastal sites. Cadmium, Mo and Re are exceptionally enriched in WO sediments (<600 m water depth). High Re and moderate Cd and Mo enrichments are seen in BO sediments (>600 m water depth). Re/Mo ratios indicate anoxic and suboxic conditions for WO and BO sediments, respectively. Cadmium and Mo downcore profiles suggest considerable contribution to UEO/WO sediments by a biodetrital phase, whereas Re presumably accumulates via diffusion across the sediment-water interface to precipitation depth. Uranium is distinctly enriched in WO sediments (due to sulfidic conditions) and in some BO sediments (due to phosphorites). Silver transfer to suboxic BO sediments is likely governed by diatomaceous matter input, whereas in anoxic WO sediments Ag is presumably trapped due to sulfide precipitation. Cadmium, Cu, Zn, Ni, Cr, Ag, and T1 predominantly accumulate via biogenic pre

  1. 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

  2. FIELD VALIDATION OF SEDIMENT TOXCITY IDENTIFCATION AND EVALUATION METHODS

    EPA Science Inventory

    Sediment Toxicity Identification and Evaluation (TIE) methods have been developed for both porewaters and whole sediments. These relatively simple laboratory methods are designed to identify specific toxicants or classes of toxicants in sediments; however, the question of whethe...

  3. 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 ...

  4. 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...

  5. Uncertainty in tsunami sediment transport modeling

    USGS Publications Warehouse

    Jaffe, Bruce E.; Goto, Kazuhisa; Sugawara, Daisuke; Gelfenbaum, Guy R.; La Selle, SeanPaul M.

    2016-01-01

    Erosion and deposition from tsunamis record information about tsunami hydrodynamics and size that can be interpreted to improve tsunami hazard assessment. We explore sources and methods for quantifying uncertainty in tsunami sediment transport modeling. Uncertainty varies with tsunami, study site, available input data, sediment grain size, and model. Although uncertainty has the potential to be large, published case studies indicate that both forward and inverse tsunami sediment transport models perform well enough to be useful for deciphering tsunami characteristics, including size, from deposits. New techniques for quantifying uncertainty, such as Ensemble Kalman Filtering inversion, and more rigorous reporting of uncertainties will advance the science of tsunami sediment transport modeling. Uncertainty may be decreased with additional laboratory studies that increase our understanding of the semi-empirical parameters and physics of tsunami sediment transport, standardized benchmark tests to assess model performance, and development of hybrid modeling approaches to exploit the strengths of forward and inverse models.

  6. Physical properties of hydrate-bearing sediments

    NASA Astrophysics Data System (ADS)

    Waite, W. F.; Santamarina, J. C.; Cortes, D. D.; Dugan, B.; Espinoza, D. N.; Germaine, J.; Jang, J.; Jung, J. W.; Kneafsey, T. J.; Shin, H.; Soga, K.; Winters, W. J.; Yun, T.-S.

    2009-12-01

    Methane gas hydrates, crystalline inclusion compounds formed from methane and water, are found in marine continental margin and permafrost sediments worldwide. This article reviews the current understanding of phenomena involved in gas hydrate formation and the physical properties of hydrate-bearing sediments. Formation phenomena include pore-scale habit, solubility, spatial variability, and host sediment aggregate properties. Physical properties include thermal properties, permeability, electrical conductivity and permittivity, small-strain elastic P and S wave velocities, shear strength, and volume changes resulting from hydrate dissociation. The magnitudes and interdependencies of these properties are critically important for predicting and quantifying macroscale responses of hydrate-bearing sediments to changes in mechanical, thermal, or chemical boundary conditions. These predictions are vital for mitigating borehole, local, and regional slope stability hazards; optimizing recovery techniques for extracting methane from hydrate-bearing sediments or sequestering carbon dioxide in gas hydrate; and evaluating the role of gas hydrate in the global carbon cycle.

  7. Plutonium fractionation in southern Baltic Sea sediments.

    PubMed

    Strumińska-Parulska, Dagmara I; Skwarzec, Bogdan; Pawlukowska, Magdalena

    2012-01-01

    In this study, different chemical plutonium fractions (dissolved in water, connected to carbonates, connected to oxides, complexed with organic matter, mineral acids soluble and the rest) in sediments from the Vistula River estuary, the Gdańsk Basin and the Bornholm Deep were determined. The distribution of (239+240)Pu in analysed sediments samples was not uniform but dependent on its chemical form, depth and the sediment geomorphology. The highest amount of plutonium exists in middle parts of sediments and comes from the global atmospheric fallout from nuclear tests in 1958-1961. According to all analysed fractions, the biggest amount of (239+240)Pu was in the mobile form, connected to carbonate fractions from the Vistula River estuary, the Gulf of Gdańsk and the Bornholm Deep sediments. PMID:22612422

  8. Mixed sediment beach processes: Kachemak Bay, Alaska

    USGS Publications Warehouse

    Ruggiero, P.; Adams, P.N.; Warrick, J.A.

    2007-01-01

    Mixed sediment beaches are morphologically distinct from and more complex than either sand or gravel only beaches. Three digital imaging techniques are employed to quantify surficial grain size and bedload sediment transport rates along the mixed sediment beaches of Kachemak Bay, Alaska. Applying digital imaging procedures originally developed for quickly and efficiently quantifying grain sizes of sand to coarse sediment classes gives promising results. Hundreds of grain size estimates lead to a quantitative characterization of the region's sediment at a significant reduction in cost and time as compared to traditional techniques. Both the sand and coarse fractions on this megatidal beach mobilize into self-organized bedforms that migrate alongshore with a seasonally reflecting the temporal pattern of the alongshore component of wave power. In contrast, the gravel bedforms also migrate in the cross-shore without significant seasonally suggesting that swash asymmetry is sufficient to mobilize the gravel even during low energy summer conditions. ?? 2007 ASCE.

  9. 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.

  10. 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.

  11. Sediment data sources and estimated annual suspended-sediment loads of rivers and streams in Colorado

    USGS Publications Warehouse

    Elliott, J.G.; DeFeyter, K.L.

    1986-01-01

    Sources of sediment data collected by several government agencies through water year 1984 are summarized for Colorado. The U.S. Geological Survey has collected suspended-sediment data at 243 sites; these data are stored in the U.S. Geological Survey 's water data storage and retrieval system. The U.S. Forest Service has collected suspended-sediment and bedload data at an additional 225 sites, and most of these data are stored in the U.S. Environmental Protection Agency 's water-quality-control information system. Additional unpublished sediment data are in the possession of the collecting entities. Annual suspended-sediment loads were computed for 133 U.S. Geological Survey sediment-data-collection sites using the daily mean water-discharge/sediment-transport-curve method. Sediment-transport curves were derived for each site by one of three techniques: (1) Least-squares linear regression of all pairs of suspended-sediment and corresponding water-discharge data, (2) least-squares linear regression of data sets subdivided on the basis of hydrograph season; and (3) graphical fit to a logarithm-logarithm plot of data. The curve-fitting technique used for each site depended on site-specific characteristics. Sediment-data sources and estimates of annual loads of suspended, bed, and total sediment from several other reports also are summarized. (USGS)

  12. Cell sedimentation with gravity activation.

    PubMed

    Czerlinski, G; Goldman-Leikin, R; Reid, D

    1988-12-01

    Murine monoclonal antibody T101 has been coupled to thinly polymer-coated heavy alloy particles (LaMn2Ge2). These conjugates are coupled to cultured cells of the human T-cell leukemia line RPMI 8402 (T8402). The sedimentation velocities of cells, of particles, and of cells with particles attached are measured. After determining the mean radii of cells, of particles, and of cells with particles attached, one may compute a mean number of 33 particles attached to a cell. Independently one may compute a mean number of 144 particles/cell for surface saturation. The Appendix handles the underlying theory in three parts: number of particles/cell, saturation number of particles/cell, and resolution for gravity activation. Regarding the latter, cell radii from 4 to 10 microns and particle radii from 0.01 to 1 micron are considered.

  13. 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.

  14. Interstitial brines in playa sediments

    USGS Publications Warehouse

    Jones, B.F.; Van Denburgh, A.S.; Truesdell, A.H.; Rettig, S.L.

    1969-01-01

    Study of several closed drainages in the Great Basin has shown that the interstitial solutions of shallow, fine-grained playa deposits store a large quantity of dissolved solids and are often more concentrated than associated lakes and ponds, except in peripheral zones of stream or ground-water inflow. These interstitial fluids, when compared with local runoff, impoundments, or spring waters, commonly have a distinctive ionic composition which sometimes cannot be explained by either simple mixing of surface and subsurface inflow or by evaporative concentration. At Abert Lake, Oregon, the interstitial solute concentrations increased with depth to values as much as five times greater than the lake, except where springs indicate significant ground-water input. Where Na+, Cl, and CO2 species constitute more than 90% of the solutes, Na+ Cl- ratios in the lake water are lower than in interstitial solutions of bottom cores and higher than in playa fluids. At the same time, Na+ K+ ratios are highest in the fluids of lake bottom muds and lowest in playa interstitials. In deeper playa profiles, interstitial Na+ Cl- tended to decrease with depth (5 ft. maximum). In the Abert Lake area, as in other parts of the western Great Basin, Na+ Cl- ratios are indicative of total CO2 in solution and the effects of organic decay in surficial sediments. These ratios, coupled with data on silica and bulk density, show that higher PCO2 accompanying decay promotes silicate dissolution and hydrogen ion exchange, stripping alkalis from sediment which had preferentially adsorbed K+ when entering the lake. On subsequent loss of pore fluid in the playa regime, silica initially released to solution in the lake environment is readsorbed on dissolution products. ?? 1969.

  15. 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.

  16. 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.

  17. Numerical modelling of mixed-sediment consolidation

    NASA Astrophysics Data System (ADS)

    Grasso, Florent; Le Hir, Pierre; Bassoullet, Philippe

    2015-04-01

    Sediment transport modelling in estuarine environments, characterised by cohesive and non-cohesive sediment mixtures, has to consider a time variation of erodibility due to consolidation. Generally, validated by settling column experiments, mud consolidation is now fairly well simulated; however, numerical models still have difficulty to simulate accurately the sedimentation and consolidation of mixed sediments for a wide range of initial conditions. This is partly due to the difficulty to formulate the contribution of sand in the hindered settling regime when segregation does not clearly occur. Based on extensive settling experiments with mud-sand mixtures, the objective of this study was to improve the numerical modelling of mixed-sediment consolidation by focusing on segregation processes. We used constitutive relationships following the fractal theory associated with a new segregation formulation based on the relative mud concentration. Using specific sets of parameters calibrated for each test—with different initial sediment concentration and sand content—the model achieved excellent prediction skills for simulating sediment height evolutions and concentration vertical profiles. It highlighted the model capacity to simulate properly the segregation occurrence for mud-sand mixtures characterised by a wide range of initial conditions. Nevertheless, calibration parameters varied significantly, as the fractal number ranged from 2.64 to 2.77. This study investigated the relevance of using a common set of parameters, which is generally required for 3D sediment transport modelling. Simulations were less accurate but remained satisfactory in an operational approach. Finally, a specific formulation for natural estuarine environments was proposed, simulating correctly the sedimentation-consolidation processes of mud-sand mixtures through 3D sediment transport modelling.

  18. Advancing knowledge gained from sediment budgets through sediment age dating and fingerprinting in small watersheds

    NASA Astrophysics Data System (ADS)

    Skalak, K.; Benthem, A.; Gellis, A.; Harvey, J. W.; Hupp, C. R.; Larsen, L.; Noe, G. B.; Pizzuto, J. E.; Schenk, E.

    2013-12-01

    Dynamics and long-term trajectories of fine sediment generally remain poorly quantified in rivers, which have implications for nutrient and contaminant transport and remediation strategies. Here we focus on two streams within the Chesapeake Bay watershed, Difficult Run and Accotink Creek. These streams have varying degrees of urbanization and diverse best management practices, making possible a comparison of sediment sources, sinks, and residence times to illuminate how land management impacts fine sediment transport. Bank erosion and floodplain accumulation in Difficult Run has been previously determined and is ongoing in Accotink Creek. Current work advances sediment budgets by quantifying the role of in-channel fine sediment storage in the bed and margins. To understand the relative storage timescales for various geomorphic features (floodplain, in-channel, etc.) and develop age distributions, sediment is dated using radionuclides of varying half-lives such as Pb-210, Cs-137, Be-7, bomb radiocarbon, and optically stimulated luminescence (OSL). To determine the source of sediment that is transported in suspension, sediment fingerprinting has been completed in Difficult Run and initiated in Accotink Creek. Furthermore, the present study furthers our understanding of fine sediment dynamics by fingerprinting sources of stored sediment and evaluating how they evolve over storm events and stream size. For this, we sampled sediment in storage zones before and after storm events of a specified magnitude to determine their chemical signatures with respect to various source-tracking elements and isotopes. This study represents the first such work to integrate sediment dating, sediment fingerprinting and an analysis of storage zones to understand fine sediment dynamics and long-term trajectories.

  19. 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

  20. Effects of tubificid bioturbation on pore structures in sediment and the migration of sediment particles.

    PubMed

    Li, Yaorui; Hua, Xiuyi; Zheng, Fang; Dong, Deming; Liang, Dapeng; Guo, Zhiyong

    2016-04-01

    In this study, the effects of tubificid bioturbation near the water-sediment interface on pore structures and the migration of sediment particles were evaluated using a series of simulations. In these experiments, the distribution and variation of the tubificid burrows and the macropores in the sediment were investigated by X-ray computed tomography (CT) and digital image collecting, without sampling or disturbing the sediment. The migration of the sediment particles was also determined using CT by adding BaSO4 microspheres to the sediment as a tracer. The effects of tubificid bioturbation on the distribution and migration of contaminants in the sediment were verified by adding Pb-containing sediment layers to the sediment. The results indicate that after the addition of the tubificids, both the burrows and the macropores in the sediments increased with time, and the rate of increase slowed gradually. With the increased worm density, the burrows and the pore structures also increased. The in-depth distribution of the burrows and macropores was determined by the settlement time of the worms: with the settlement time increasing from 3 to 19 days, the depth of the zone with the highest density of burrows and macropores increased from 0-30 to 30-50 mm and from 0-10 to 30-60 mm, respectively. The distribution of the burrows and macropores was closely related to the distribution of the tubificids. Thickening of the oxidized zones in the superficial sediments in the presence of tubificid bioturbation was also observed. The main action of tubificids on the sediment particles was the transport of particles from the inner sediment (especially in the range of 30-50 mm in depth) to the water-sediment interface. The migration of Pb in the contaminated sediment with tubificid bioturbation could be interpreted by the variation in the burrows and macropores and the migration of sediment particles. Both the formation and the variation in the burrows and macropores, as well as

  1. 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.

  2. 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

  3. 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

  4. 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.

  5. Sediment characteristics and sedimentation rates in Lake Michie, Durham County, North Carolina, 1990-92

    USGS Publications Warehouse

    Weaver, J.C.

    1994-01-01

    A reservoir sedimentation study was conducted at 508-acre Lake Michie, a municipal water-supply reservoir in northeastern Durham County, North Carolina, during 1990-92. The effects of sedimentation in Lake Michie were investigated, and current and historical rates of sedimentation were evaluated. Particle-size distributions of lake-bottom sediment indicate that, overall, Lake Michie is rich in silt and clay. Nearly all sand is deposited in the upstream region of the lake, and its percentage in the sediment decreases to less than 2 percent in the lower half of the lake. The average specific weight of lake-bottom sediment in Lake Michie is 73.6 pounds per cubic foot. The dry-weight percentage of total organic carbon in lake-bottom sediment ranges from 1.1 to 3.8 percent. Corresponding carbon-nitrogen ratios range form 8.6 to 17.6. Correlation of the total organic carbon percentages with carbon-nitrogen ratios indicates that plant and leaf debris are the primary sources of organic material in Lake Michie. Sedimentation rates were computed using comparisons of bathymetric volumes. Comparing the current and previous bathymetric volumes, the net amount of sediment deposited (trapped) in Lake Michie during 1926-92 is estimated to be about 2,541 acre-feet or slightly more than 20 percent of the original storage volume computed in 1935. Currently (1992), the average sedimentation rate is 38 acre-feet per year, down from 45.1 acre-feet per year in 1935. To confirm the evidence that sedimentation rates have decreased at Lake Michie since its construction in 1926, sediment accretion rates were computed using radionuclide profiles of lake-bottom sediment. Sediment accretion rates estimated from radiochemical analyses of Cesium-137 and lead-210 and radionuclides in the lake-bottom sediment indicate that rates were higher in the lake?s early years prior to 1962. Estimated suspended-sediment yields for inflow and outflow sites during 1983-91 indicate a suspended-sediment trap

  6. 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.

  7. Chemical profile of Plomin Bay sediments.

    PubMed

    Orescanin, Visnja; Nad, Karlo; Bartolincić, Anamarija; Valković, Vladivoj

    2009-09-01

    Granulometric, chemical, and leaching properties of sediments dredged in the Plomin Bay (Northern Adriatic Sea, Croatia) were investigated in order to asses the risk of remobilisation of heavy metals into the water column. In total 65 samples from 65 sampling sites were taken from different sediment depths within the bay. Analysis of variance confirmed the homogeneity of granulometric and elemental composition of the investigated sediment throughout its volume. Granulometric analysis showed that all samples corresponded to a pelitic fraction (<0.063 mm). Bulk elemental mass fractions in the sediments were similar to literature data on relatively unpolluted areas of the Adriatic Sea. High sedimentation rate caused by constant inflow of material from the Boljuncica River drainage may be responsible for low levels of heavy metals and negligible influence of fly and bottom ash from a nearby disposal site on the chemical composition of the sediments. In contact with sea water only 0.29 mg kg-1 of V, 0.04 mg kg-1 of Cr, 0.07 mg kg-1 of Ni, 0.33 mg kg-1 of Cu, 0.67 mg kg-1 of Zn and 0.06 mg kg-1 of Pb could be remobilised from sediment material into the water column. However, these values increased three to ten times in case of leaching with organic acids.

  8. 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.

  9. A process-based model for aeolian sediment transport and spatiotemporal varying sediment availability

    NASA Astrophysics Data System (ADS)

    Hoonhout, Bas M.; Vries, Sierd de

    2016-08-01

    Aeolian sediment transport is influenced by a variety of bed surface properties, like moisture, shells, vegetation, and nonerodible elements. The bed surface properties influence aeolian sediment transport by changing the sediment transport capacity and/or the sediment availability. The effect of bed surface properties on the transport capacity and sediment availability is typically incorporated through the velocity threshold. This approach appears to be a critical limitation in existing aeolian sediment transport models for simulation of real-world cases with spatiotemporal variations in bed surface properties. This paper presents a new model approach for multifraction aeolian sediment transport in which sediment availability is simulated rather than parameterized through the velocity threshold. The model can cope with arbitrary spatiotemporal configurations of bed surface properties that either limit or enhance the sediment availability or sediment transport capacity. The performance of the model is illustrated using four prototype cases, the simulation of two wind tunnel experiments from literature and a sensitivity analysis of newly introduced parameters.

  10. 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.

  11. 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.

  12. Site-specific sediment clean-up objectives developed by the sediment quality triad

    SciTech Connect

    Redman, S.; Janisch, T.

    1995-12-31

    Sediment chemistry, sediment toxicity, and benthic macroinvertebrate community data were collected and evaluated in concert (1) to characterize adverse effects of hydrocarbon and metal contaminants in the sediments of a small inlet of Superior Bay, Lake Superior and a tributary creek and (2) to derive numeric objectives for the clean up of this system. Sediments from reference locations and eight study sites were analyzed for a range of contaminants, including hydrocarbons (measured both as diesel range organics (DRO) and oil and grease), lead, chromium, and ammonia. A range of sediment toxicity was observed across the eight study sites using a variety of tests and endpoints: Hyalella azteca (10 day survival and growth), Chironomus tentans (10 day survival and growth), Ceriodaphnia dubia (48 hour survival), and Daphnia magna (48 hour survival and 10 day survival and reproduction). A range of alterations of the benthic macroinvertebrate community compared with communities from reference locations were observed. Benthic community alterations were summarized quantitatively by taxa richness and Shannon-Weiner mean diversity. Lowest effect levels determined through this study included 150 {micro}g/g dry sediment for DRO (as measured in this study) and 40 {micro}g/g dry sediment for lead. Effects thresholds determined through this study included 1,500 {micro}g/g dry sediment for DRO and 90 {micro}g/g dry sediment for lead. These levels and concentrations measured in relevant reference locations are being used to define objectives for sediment clean up in the inlet and creek.

  13. 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.

  14. 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

  15. Hydraulic potential in Lake Michigan bottom sediments

    USGS Publications Warehouse

    Cartwright, K.; Hunt, C.S.; Hughes, G.M.; Brower, R.D.

    1979-01-01

    The magnitude and direction of groundwater flux in the bottom sediments of Lake Michigan were deduced from measurements made during three shipboard cruises between 1973 and 1975. These factors affect the geochemical environment of the sediments and therefore the distribution of trace elements reported to be present. The near-shore, sandy-bottom and fine-grained, soft, deep-lake sediments were investigated; areas of hard till or bedrock were not included in the study. Thirty-three piezometers were placed in near-shore sands in waters 5-15 m deep. The piezometers were placed an average of 3 m into the bottom sediment. Water levels from the piezometers averaged 0.6 cm above the lake level, equivalent to an upward hydraulic gradient of about 0.002 cm/cm. Water samples taken from the piezometers have a distinctly different chemical composition from that of the lake water. The total dissolved mineral content and hardness of the groundwater are about twice those of the lake water. Twenty-two hydraulic gradient measurements were made in the fine-grained soft deep-lake sediments in waters 48-140 m deep by using a differential-pressure transducer dropped into the sediments. These measurements show an upward gradient averaging 0.2 cm/cm. No chemical data were obtained for the groundwater in the deep-lake sediments. The results of this study indicate that the groundwater flux is upward through the bottom sediments into Lake Michigan and that there is a chemical change in the water near the water-sediment contact. ?? 1979.

  16. Numerical Experiments on Sediment Pulse Dynamics

    NASA Astrophysics Data System (ADS)

    Morgan, J. A.; Nelson, P. A.

    2015-12-01

    Local channel morphology is highly dependent on sediment supply from upstream reaches. Sediment pulses are introduced to channels during natural and anthropogenic disturbances such as landslides, dam removal, or gravel augmentation. Flume studies have shown that sediment pulses tend to evolve through some combination of translation and dispersion, but the relative importance of the sediment pulse size, the grain size of the pulse material, flow unsteadiness, and channel nonuniformity is poorly understood. Here we use a one-dimensional morphodynamic model to simulate the evolution of various sediment pulses in a straight, rectangular channel. The model is capable of determining transcritical flows, using the energy equation for subcritical nodes and a reduced momentum equation for supercritical nodes. Bed evolution and grain size sorting are handled with the mixed-grain-size Exner equation for sediment continuity. A stratigraphy submodel allows the vertical grain size distribution created during deposition to provide feedbacks on morphodynamic processes encountered during degradation. We explore how pulse characteristics such as total mass, feed timing, and grain size distribution affect pulse translation and dispersion. We also consider the influence of steady versus unsteady water discharge and the existence of background sediment feed. Finally, we examine the effect of variations in channel width by varying the amplitude and wavelength of downstream sinusoidal width undulations. Preliminary results suggest that smaller sediment pulses experience a greater degree of translation than larger pulses. Width variations, particularly those of larger amplitudes, were found to result in increased pulse dispersion. Our results suggest that morphodynamic models can facilitate understanding of what controls sediment pulse dynamics, and they may improve predictions and the potential effectiveness of river restoration techniques such as dam removal and gravel augmentation.

  17. Sediment mediated species interactions in coastal waters

    NASA Astrophysics Data System (ADS)

    Reise, Karsten

    2002-10-01

    Self-structuring in marine sediment communities is achieved by the mobility of the organisms, the trophic web, and biogenic transformations of the habitat. The latter are: bioconstruction and bioturbations, sediment stabilisation and destabilisation, with facilitating and inhibiting effects. This cursory overview intends to show that in near-shore mud and sand, biogenic habitat transformations pervade all community interactions. Consequently these deserve as much attention in benthic ecosystem analyses as do trophic pathways. Abundant phototrophs and suspension feeders tend to accumulate sediment and organic matter. Underneath phototrophic mats, composite layers of anaerobic microorganisms abound. Benthic animals provide anchorage to tufts of algae, and these in turn provide shelter and food for mobile benthos. Rooted plants slow down hydrodynamics and generate complex habitats above the sediment surface but below a meshwork of roots may inhibit burrowing animals. Abundant suspension feeders stabilise sediments, and may build loose hummocks, multi-species epibenthic thickets or solid reefs, accommodating diverse epibenthic assemblages. Their raised and rough surfaces enhance turbulence. Below the sediment surface, tubes and burrows of sessile or discretely motile animals provide microoxic habitats for diverse assemblages of small organisms. At the surface, mucus of motile organisms increases sediment cohesion. Accumulated dead hardparts of the benthos support epibionts when at the surface but cause resistance to the burrowers below. Reworking and irrigation of the sediment by the infauna increases oxygenation, and particulate and solute fluxes with the overlying water. Mounds and pits generated by resident burrowers as well as by large visiting grazers and predators further diversify the benthos. All these bioengineered structures and processes generate dynamic and complex habitat-mediated interaction webs, affecting and meshed into the trophic web, which they may

  18. 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.

  19. 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).

  20. Climate, Hydrology, and Lake Sediment

    NASA Astrophysics Data System (ADS)

    Ito, E.; Forester, R. M.

    2008-12-01

    Components of lake sediment such as endogenic minerals, organic compounds, and fossils as well as chemistry and isotopes of those components are sources of information about past continental climate. No matter the size of the lake, the components of their sedimentary records reflect some integration of catchment processes operating on the landscape, within the ground water, and in the lake. Climate change influences and often drives change among these processes, yet the integration of the processes commonly yields unique records in lakes residing under the same climate. An estimate of the actual climate history from lake records as opposed to the apparent climate history from a given lake depends on how well we understand the modern system, or in the absence of a modern system, making use of known modern systems. We single out the effect of hydrology on lake records to illustrate the importance of understanding the modern system. The Waubay Lakes Chain in NE South Dakota is a series of lakes at different elevations and spill points that may be hydrologically connected, even coalescing, or may be isolated, though some remain hydrologically open (Niehus et al. 1999). Pickerel is an "upland" open freshwater lake whose level remains nearly constant, while Waubay is a shallow lake at intermediate elevation having more changes in level and salinity. Bitter, at the lowest elevation, receives spillover from Waubay during high water periods, exhibits wide ranges of salinity and elevation including going dry. Pickerel has a short residence time with lower δ18O and TDS than Waubay and Bitter (08/1991: -4.1 permil, -1.5 permil, and -1.8 permil; 204 mg/L, 6,420 mg/L, and 13,128mg/L respectively). The three lakes see the same climate, but their hydrologies lead to these different characteristics that interpreted in climate terms would suggest Pickerel resides under a wet climate while Bitter resides under a dry climate. The sediment records from these lakes though incompletely

  1. Sedimentation in mountain streams: A review of methods of measurement

    USGS Publications Warehouse

    Hedrick, Lara B.; Anderson, James T.; Welsh, Stuart; Lin, Lian-Shin

    2013-01-01

    The goal of this review paper is to provide a list of methods and devices used to measure sediment accumulation in wadeable streams dominated by cobble and gravel substrate. Quantitative measures of stream sedimentation are useful to monitor and study anthropogenic impacts on stream biota, and stream sedimentation is measurable with multiple sampling methods. Evaluation of sedimentation can be made by measuring the concentration of suspended sediment, or turbidity, and by determining the amount of deposited sediment, or sedimentation on the streambed. Measurements of deposited sediments are more time consuming and labor intensive than measurements of suspended sediments. Traditional techniques for characterizing sediment composition in streams include core sampling, the shovel method, visual estimation along transects, and sediment traps. This paper provides a comprehensive review of methodology, devices that can be used, and techniques for processing and analyzing samples collected to aid researchers in choosing study design and equipment.

  2. 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.

  3. 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

  4. 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.

  5. 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.

  6. Wetland sedimentation from hurricanes Katrina and Rita.

    PubMed

    Turner, R Eugene; Baustian, Joseph J; Swenson, Erick M; Spicer, Jennifer S

    2006-10-20

    More than 131 x 10(6) metric tons (MT) of inorganic sediments accumulated in coastal wetlands when Hurricanes Katrina and Rita crossed the Louisiana coast in 2005, plus another 281 x 10(6) MT when accumulation was prorated for open water area. The annualized combined amount of inorganic sediments per hurricane equals (i) 12% of the Mississippi River's suspended load, (ii) 5.5 times the inorganic load delivered by overbank flooding before flood protection levees were constructed, and (iii) 227 times the amount introduced by a river diversion built for wetland restoration. The accumulation from hurricanes is sufficient to account for all the inorganic sediments in healthy saltmarsh wetlands.

  7. 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.

  8. Sediment storage and yield in an urbanized karst watershed

    NASA Astrophysics Data System (ADS)

    Hart, Evan A.; Schurger, Stephen G.

    2005-08-01

    In karst watersheds, sinkholes and other drainage features control the temporal and spatial pattern of sediment storage across the landscape. However, studies dealing with sedimentation in karst watersheds are scarce and the sediment storage function of sinkholes and caves has not been investigated using a sediment budget approach. In this study, we use estimates of channel erosion, sinkhole sedimentation, and suspended sediment yield to examine changes in sediment storage in the 9 km 2 Upper Pigeon Roost Creek fluviokarst watershed near Cookeville, TN. The study watershed has undergone urbanization over the last ˜ 50 years, and sinkholes and caves in the area show signs of recent sedimentation (buried tree roots, buried cultural artifacts, etc.). While sinkholes are generally considered to be sediment sinks, sinkholes examined in this study are shown to cycle between periods of net sediment storage and net sediment loss. Using copyright dates on trash items buried in sinkhole deposits, we estimated the residence time of sinkhole-stored sediment to range from 6 to 10 years. However, other evidence indicates that some sinkholes may store sediment for several centuries. We propose that sediment storage within sinkholes is controlled by several factors including sinkhole drainage area, sinkhole morphology, and basin sediment yield. In addition, changes in sediment storage in karst watersheds are contingent upon random events such as sinkhole collapses. Annual sediment yield was estimated to be 111 Mg km - 2 year - 1 for the entire study watershed and ranged from 11 to 128 Mg km - 2 year - 1 for 3 sub-watersheds. Sediment eroded from the watershed, perhaps during historic settlement of the area, is stored within a large cave system underlying the city. However, the results of a partial sediment budget indicate that the cave is presently a net sediment source. Overall, the findings indicate that the sediment storage function of caves and sinkholes varies spatially and

  9. 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.

  10. Sediment availability on burned hillslopes

    NASA Astrophysics Data System (ADS)

    Nyman, Petter; Sheridan, Gary J.; Moody, John A.; Smith, Hugh G.; Noske, Philip J.; Lane, Patrick N. J.

    2013-12-01

    describes the inherent resistance of soil to erosion. Hillslope erosion models typically consider erodibility to be constant with depth. This may not be the case after wildfire because erodibility is partly determined by the availability of noncohesive soil and ash at the surface. This study quantifies erodibility of burned soils using methods that explicitly capture variations in soil properties with depth. Flume experiments on intact cores from three sites in western United States showed that erodibility of fire-affected soil was highest at the soil surface and declined exponentially within the top 20 mm of the soil profile, with root density and soil depth accounting for 62% of the variation. Variation in erodibility with depth resulted in transient sediment flux during erosion experiments on bounded field plots. Material that contributed to transient flux was conceptualized as a layer of noncohesive material of variable depth (dnc). This depth was related to shear strength measurements and sampled spatially to obtain the probability distribution of noncohesive material as a function of depth below the surface. After wildfire in southeast Australia, the initial dnc ranged from 7.5 to 9.1 mm, which equated to 97-117 Mg ha-1 of noncohesive material. The depth decreased exponentially with time since wildfire to 0.4 mm (or < 5 Mg ha-1) after 3 years of recovery. The results are organized into a framework for modeling fire effects on erodibility as a function of the production and depletion of the noncohesive layer overlying a cohesive layer.

  11. 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.

  12. 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.

  13. 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...

  14. 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...

  15. 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...

  16. 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

  17. 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...

  18. Microplastic pollution in deep-sea sediments.

    PubMed

    Van Cauwenberghe, Lisbeth; Vanreusel, Ann; Mees, Jan; Janssen, Colin R

    2013-11-01

    Microplastics are small plastic particles (<1 mm) originating from the degradation of larger plastic debris. These microplastics have been accumulating in the marine environment for decades and have been detected throughout the water column and in sublittoral and beach sediments worldwide. However, up to now, it has never been established whether microplastic presence in sediments is limited to accumulation hot spots such as the continental shelf, or whether they are also present in deep-sea sediments. Here we show, for the first time ever, that microplastics have indeed reached the most remote of marine environments: the deep sea. We found plastic particles sized in the micrometre range in deep-sea sediments collected at four locations representing different deep-sea habitats ranging in depth from 1100 to 5000 m. Our results demonstrate that microplastic pollution has spread throughout the world's seas and oceans, into the remote and largely unknown deep sea.

  19. 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.

  20. Ecological benefits of contaminated sediment remediation.

    PubMed

    Zarull, Michael A; Hartig, John H; Krantzberg, Gail

    2002-01-01

    Contaminated sediment has been identified as a source of ecological impacts in marine and freshwater systems throughout the world, and the importance of the contaminated sediment management issue continues to increase in all industrialized countries. In many areas, dredging or removal of sediments contaminated with nutrients, metals, oxygen-demanding substances, and persistent toxic organic chemicals has been employed as a form of environmental remediation. In most situations, however, the documentation of the sediment problem has not been quantitatively coupled to ecological impairments. In addition, the lack of long-term, postactivity research and monitoring for most projects has impeded a better understanding of the ecological significance of sediment contamination. Establishing quantitatively the ecological significance of sediment-associated contamination in any area is a difficult time- and resource-consuming exercise. It is, however, absolutely essential that it be done. Such documentation will likely be used as the justification for remedial and rehabilitative action(s) and also as the rationale for proposing when intervention is necessary in one place but not another. Bounding the degree of ecological impact (at least semiquantitatively) provides for realistic expectations for improvement if sediment remediation is to be pursued. It should also provide essential information on linkages that could be used in rehabilitating other ecosystem components such as fish or wildlife habitat. The lack of information coupling contaminated sediment to specific ecological impairments has, in many instances, precluded a clear estimate of how much sediment requires action to be taken, why, and what improvements can be expected to existing impairment(s) over time. Also, it has likely resulted in either a delay in remedial action or abandonment of the option altogether. A clear understanding of ecological links not only provides adequate justification for a cleanup program

  1. 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

  2. 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.

  3. 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

  4. Classification of lake sediments using a hydrocyclone.

    PubMed

    Park, J H; Jo, Y M; Oh, J M

    2003-01-01

    The present work is a preliminary experiment for hydrocyclones as a primary process in lake sediment thickening. A few cyclones based on the Rietema standard geometry were prepared, and sample particles were sediments from a local lake and waste coal fly ash for a reference test. As a result of the chemical analysis, more organic contaminants were found in smaller particles. The experimental tests showed that physical characteristics of particles, configuration of the cyclone and operation conditions could affect the separation efficiency.

  5. 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.

  6. 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.

  7. Oceanic sediment volumes and continental drift.

    PubMed

    Gilluly, J

    1969-11-21

    The volume of sediment off the Atlantic Coast of the United States is at least six times as great as that off the Pacific Coast. This disparity is readily accounted for if the continent is drifting westward and has overrun large volumes of sediment on a former Benioff zone. Such an overrunning is also consonant with many features of the geology of the western United States.

  8. 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.

  9. Phosphorus flux from wetland ditch sediments.

    PubMed

    Hill, C R; Robinson, J S

    2012-10-15

    The accumulation of phosphorus (P) in the bottom sediment of field drainage ditches poses a threat to the ecology both of the ditch water and downstream water courses. We investigated the amounts, forms and internal loading of sediment-bound P along two drainage ditches that regulate water levels in a basin fen (~200 ha) supporting a mixture of restored wetland and drained agricultural fields. Water levels in the Lady's Drove Rhyne are currently managed to enhance the biodiversity of the wetland (Catcott Lows Reserve - an area formerly cultivated for arable crop production); whereas, the East Ditch is managed to drain adjoining land that remains under arable and livestock production. Laboratory-based chemical fractionation schemes were used to characterise the forms and potential mobility of the sediment-bound P, whilst pore-water equilibrators were employed in situ to evaluate the diffusive flux of P through the sediment-water column, and to characterise the corresponding redox conditions. Along both ditches, sediment pore-water profiles indicated conditions ranging from weakly to very reducing conditions with increasing depth, and net fluxes of P from the sediment to overlying water. P flux values ranged from 0.33 to 1.30 mg m(-2) day(-1). Both the degree of P saturation (DPS) of the sediment and NaOH extractable (Fe/Al-bound) P correlated significantly (P<0.05) with P flux. Both in the wetland and agricultural ditches, by far the highest values for P flux were recorded at sites closest to points of drainage water entry from the corresponding, adjoining land. Although the P flux data were obtained from only a single sampling event, this study highlights the contribution of historical as well as ongoing agricultural land use on the sustained elevated P status of ditch sediments in lowland catchments.

  10. Stream sediment sampling and analysis. Final report

    SciTech Connect

    Means, J.L.; Voris, P.V.; Headington, G.L.

    1986-04-01

    The objectives were to sample and analyze sediments from upstream and downstream locations (relative to the Goodyear Atomic plant site) of three streams for selected pollutants. The three streams sampled were the Scioto River, Big Beaver Creek, and Big Run Creek. Sediment samples were analyzed for EPA's 129 priority pollutants (Clean Water Act) as well as isotopic uranium (/sup 234/U, /sup 235/U, and /sup 238/U) and technetium-99.

  11. Sulfide and methane production in sewer sediments.

    PubMed

    Liu, Yiwen; Ni, Bing-Jie; Ganigué, Ramon; Werner, Ursula; Sharma, Keshab R; Yuan, Zhiguo

    2015-03-01

    Recent studies have demonstrated significant sulfide and methane production by sewer biofilms, particularly in rising mains. Sewer sediments in gravity sewers are also biologically active; however, their contribution to biological transformations in sewers is poorly understood at present. In this study, sediments collected from a gravity sewer were cultivated in a laboratory reactor fed with real wastewater for more than one year to obtain intact sediments. Batch test results show significant sulfide production with an average rate of 9.20 ± 0.39 g S/m(2)·d from the sediments, which is significantly higher than the areal rate of sewer biofilms. In contrast, the average methane production rate is 1.56 ± 0.14 g CH4/m(2)·d at 20 °C, which is comparable to the areal rate of sewer biofilms. These results clearly show that the contributions of sewer sediments to sulfide and methane production cannot be ignored when evaluating sewer emissions. Microsensor and pore water measurements of sulfide, sulfate and methane in the sediments, microbial profiling along the depth of the sediments and mathematical modelling reveal that sulfide production takes place near the sediment surface due to the limited penetration of sulfate. In comparison, methane production occurs in a much deeper zone below the surface likely due to the better penetration of soluble organic carbon. Modelling results illustrate the dependency of sulfide and methane productions on the bulk sulfate and soluble organic carbon concentrations can be well described with half-order kinetics.

  12. 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

  13. 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.

  14. 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.

  15. Determining annual suspended sediment and sediment-associated trace element and nutrient fluxes

    USGS Publications Warehouse

    Horowitz, A.J.

    2008-01-01

    Suspended sediment is a major factor in the biological and geochemical cycling of trace elements and nutrients in aquatic systems. The design of effective studies involving the collection, processing, and subsequent chemical analysis of suspended sediment requires a clear understanding of the problems associated with using this sample medium. This review summarizes the current state of knowledge relative to the various issues/problems associated with the collection of representative suspended sediment samples in fluvial systems. It also addresses issues associated with accurately determining the concentrations and fluxes of sediment-associated trace elements and nutrients.

  16. Mechanistic sediment quality guidelines based on contaminant bioavailability: equilibrium partitioning sediment benchmarks.

    PubMed

    Burgess, Robert M; Berry, Walter J; Mount, David R; Di Toro, Dominic M

    2013-01-01

    Globally, estimated costs to manage (i.e., remediate and monitor) contaminated sediments are in the billions of U.S. dollars. Biologically based approaches for assessing the contaminated sediments which pose the greatest ecological risk range from toxicity testing to benthic community analysis. In addition, chemically based sediment quality guidelines (SQGs) provide a relatively inexpensive line of evidence for supporting these assessments. The present study summarizes a mechanistic SQG based on equilibrium partitioning (EqP), which uses the dissolved concentrations of contaminants in sediment interstitial waters as a surrogate for bioavailable contaminant concentrations. The EqP-based mechanistic SQGs are called equilibrium partitioning sediment benchmarks (ESBs). Sediment concentrations less than or equal to the ESB values are not expected to result in adverse effects and benthic organisms should be protected, while sediment concentrations above the ESB values may result in adverse effects to benthic organisms. In the present study, ESB values are reported for 34 polycyclic aromatic hydrocarbon, 32 other organic contaminants, and seven metals (cadmium, chromium, copper, nickel, lead, silver, zinc). Also included is an overview of EqP theory, ESB derivation, examples of applying ESB values, and considerations when using ESBs. The ESBs are intended as a complement to existing sediment-assessment tools, to assist in determining the extent of sediment contamination, to help identify chemicals causing toxicity, and to serve as targets for pollutant loading control measures.

  17. 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.

  18. 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.

  19. 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 ...

  20. Gravitational sedimentation of flocculated waste activated sludge.

    PubMed

    Chu, C P; Lee, D J; Tay, J H

    2003-01-01

    The sedimentation characteristics of flocculated wastewater sludge have not been satisfactorily explored using the non-destructive techniques, partially owing to the rather low solid content (ca. 1-2%) commonly noted in the biological sediments. This paper investigated, for the first time, the spatial-temporal gravitational settling characteristics of original and polyelectrolyte flocculated waste activated sludge using Computerized Axial Tomography Scanner. The waste activated sludge possessed a distinct settling characteristic from the kaolin slurries. The waste activated sludges settled more slowly and reached a lower solid fraction in the final sediment than the latter. Flocculation markedly enhanced the settleability of both sludges. Although the maximum achievable solid contents for the kaolin slurries were reduced, flocculation had little effects on the activated sludge. The purely plastic rheological model by Buscall and White (J Chem Soc Faraday Trans 1(83) (1987) 873) interpreted the consolidating sediment data, while the purely elastic model by Tiller and Leu (J. Chin. Inst. Chem. Eng. 11 (1980) 61) described the final equilibrated sediment. Flocculation produced lower yield stress during transient settling, thereby resulting in the more easily consolidated sludge than the original sample. Meanwhile, the flocculated activated sludge was stiffer in the final sediment than in the original sample. The data reported herein are valuable to the theories development for clarifier design and operation.

  1. Sedimentation of athermal particles in clay suspensions

    NASA Astrophysics Data System (ADS)

    Clotet, Xavier; Kudrolli, Arshad

    2015-03-01

    We discuss sedimentation of athermal particles in dense clay suspensions which appear liquid-like to glass-like. These studies are motivated by the physics important to a diverse range of problems including remediation of oil sands after the extraction of hydrocarbons, and formation of filter cakes in bore wells. We approach this problem by first considering collective sedimentation of athermal spherical particles in a viscous liquid in quasi-two dimensional and three dimensional containers. We examine the system using optical and x-ray tomography techniques which gives particle level information besides global information on the evolution of the volume fraction. Unlike sediments in the dilute limit - which can be modeled as isolated particles that sediment with a constant velocity and slow down exponentially as they approach the bottom of the container - we find interaction between the particles through the viscous fluids leads to qualitatively differences. We find significant avalanching behavior and cooperative motion as the grains collectively settle, and non-exponential increase in settling time. We discuss the effect of stirring caused by the sedimenting particles on their viscosity and consequently the sedimentation rates as a function of particle concentration. Supported by Petroleum Research Fund Grant PRF # 54045-ND9.

  2. Linking nutrient enrichment, sediment erodibility and biofilms

    NASA Astrophysics Data System (ADS)

    Conrad, B.; Mahon, R.; Sojka, S. L.

    2014-12-01

    Sediment movement in coastal lagoons affects nutrient flux and primary producer growth. Previous research has shown that sediment erodibility is affected by biofilm concentration and that growth of benthic organisms, which produce biofilm, is affected by nutrient enrichment. However, researchers have not examined possible links between nutrient addition and sediment erodibility. We manipulated nutrient levels in the water column of 16 microcosms filled with homogenized sediment from a shallow coastal lagoon and artificial seawater to determine the effects on biofilm growth, measured through chlorophyll a and colloidal carbohydrate concentrations. Erosion tests using a Gust microcosm were conducted to determine the relationship between sediment erodibility and biofilm concentration. Results show that carbohydrate levels decreased with increasing nutrient enrichment and were unrelated to chlorophyll concentrations and erodibility. The nutrient levels did not predictably affect the chlorophyll levels, with lower chlorophyll concentrations in the control and medium enrichment treatments than the low and high enrichment treatments. Controls on biofilm growth are still unclear and the assumed relationship between carbohydrates and erodibility may be invalid. Understanding how biofilms respond to nutrient enrichment and subsequent effects on sediment erodibility is essential for protecting and restoring shallow coastal systems.

  3. Acoustic filtration and sedimentation of soot particles

    NASA Astrophysics Data System (ADS)

    Martin, K. M.; Ezekoye, O. A.

    Removal of soot particles from a static chamber by an intense acoustic field is investigated. Combustion of a solid fuel fills a rectangular chamber with small soot particles, which sediment very slowly. The chamber is then irradiated by an intense acoustic source to produce a three dimensional standing wave field in the chamber. The acoustic excitation causes the soot particles to agglomerate, forming larger particles which sediment faster from the system. The soot also forms 1-2 cm disks, with axes parallel to the axis of the acoustic source, which are levitated by the sound field at half-wavelength spacing within the chamber. Laser extinction measurements are made to determine soot volume fractions as a function of exposure time within the chamber. The volume fraction is reduced over time by sedimentation and by particle migration to the disks. The soot disks are considered to be a novel mechanism for particle removal from the air stream, and this mechanism has been dubbed acoustic filtration. An experimental method is developed for comparing the rate of soot removal by sedimentation alone with the rate of soot removal by sedimentation and acoustic filtration. Results show that acoustic filtration increases the rate of soot removal by a factor of two over acoustically-induced sedimentation alone.

  4. Dispersion of plutonium from contaminated pond sediments

    USGS Publications Warehouse

    Rees, T.F.; Cleveland, J.M.; Carl, Gottschall W.

    1978-01-01

    Sediment-water distributions of plutonium as a function of pH and contact time are investigated in a holding pond at the Rocky Flats plant of the Department of Energy. Although plutonium has been shown to sorb from natural waters onto sediments, the results of this study indicate that under the proper conditions it can be redispersed at pH 9 and above. Concentrations greater than 900 pCi Pu/L result after 34 h contact at pH 11 or 12 and the distribution coefficient, defined as the ratio of concentration in the sediment to that in the liquid, decreases from 1.1 ?? 105 at pH 7 to 1.2 ?? 103 at pH 11. The plutonium is probably dispersed as discrete colloids or as hydrolytic species adsorbed onto colloidal sediment particles whose average size decreases with increasing pH above pH 9. About 5% of the total plutonium is dispersed at pH 12, and the dispersion seems to readsorb on the sediment with time. Consequently, migration of plutonium from the pond should be slow, and it would be difficult to remove this element completely from pond sediment by leaching with high pH solutions. ?? 1978 American Chemical Society.

  5. Sedimentation and sustainability of western American reservoirs

    NASA Astrophysics Data System (ADS)

    Graf, William L.; Wohl, Ellen; Sinha, Tushar; Sabo, John L.

    2010-12-01

    Reservoirs are sustainable only as long as they offer sufficient water storage space to achieve their design objectives. Life expectancy related to sedimentation is a measure of reservoir sustainability. We used data from the Army Corps of Engineers, U.S. Bureau of Reclamation, and U.S. Geological Survey (Reservoir Sedimentation Survey Information System II (RESIS II)) to explore the sustainability of American reservoirs. Sustainability varied by region, with the longest life expectancies in New England and the Tennessee Valley and the shortest in the interior west. In the Missouri and Colorado River basins, sedimentation and rates of loss of reservoir storage capacity were highly variable in time and space. In the Missouri River Basin, the larger reservoirs had the longest life expectancies, with some exceeding 1000 years, while smaller reservoirs in the basin had the shortest life expectancies. In the Colorado River Basin at the site of Glen Canyon Dam, sediment inflow varied with time, declining by half beginning in 1942 because of hydroclimate and upstream geomorphic changes. Because of these changes, the estimated life expectancy of Lake Powell increased from 300 to 700 years. Future surprise changes in sedimentation delivery and reservoir filling area are expected. Even though large western reservoirs were built within a limited period, their demise will not be synchronous because of varying sedimentation rates. Popular literature has incorrectly emphasized the possibility of rapid, synchronous loss of reservoir storage capacity and underestimated the sustainability of the water control infrastructure.

  6. Sediment transport in the nearshore area of Phoenix Island

    NASA Astrophysics Data System (ADS)

    Hu, Rijun; Ma, Fang; Wu, Jianzheng; Zhang, Wei; Jiang, Shenghui; Xu, Yongchen; Zhu, Longhai; Wang, Nan; Liu, Aijiang

    2016-10-01

    Based on the measured data, suspended sediment concentration, surface sediment grain size, current and waves, the sediment transport mechanisms and pathways in the Phoenix Island area were analyzed using methods of flux decomposition and Grain Size Trend Analysis (GSTA). The results show that net suspended sediment is mainly transported by average current, Stokes drift, and gravitational circulation. The transport direction of suspended sediment is varying and basically following the direction of residual tidal currents. Surface sediment transport pathways are primarily parallel to the coastline along with two convergent centers. Waves and longshore currents have a significant influence on sediment transport, but the influence is limited due to a steep and deep underwater bank. Tidal current is the main controlling factor for sediment transport, especially in the deep water area. Neither suspended nor surface sediment is transported towards the southwest. The South Shandong Coastal Current (SSCC) has little effect on sediment transport processes in the nearshore area of Phoenix Island.

  7. Geochemical indices of fine sediment transport, northwest Gulf of Mexico.

    USGS Publications Warehouse

    Holmes, C.W.

    1982-01-01

    The 210Pb distribution, the clay mineralogy distribution, and the distribution of three trace metals, Ba, Pb, and Mn, in the sediments of the south Texas shelf are related to the dynamics of the sedimentary transport process. 210Pb, whose concentration is time dependent, defines three loci of recent sediment accumulations. The variation of 210Pb activity at the sediment-water interface delineates areas of terrestrial sedimentation from hemipelagic sedimentation. Ba tags sediment movement from areas of hydrocarbon exploration. Pb concentrations tag the sediment derived from metropolitan complexes. Mn is concentrated in areas of very slow sediment accumulation. A model of sediment transport and deposition which relates currents, wind, tides, sediment flux, and precipitation has been formulated. -from Author

  8. Bunker Hill Sediment Characterization Study

    SciTech Connect

    Neal A. Yancey; Debby F. Bruhn

    2009-12-01

    The long history of mineral extraction in the Coeur d’Alene Basin has left a legacy of heavy metal laden mine tailings that have accumulated along the Coeur d’Alene River and its tributaries (U.S. Environmental Protection Agency, 2001; Barton, 2002). Silver, lead and zinc were the primary metals of economic interest in the area, but the ores contained other elements that have become environmental hazards including zinc, cadmium, lead, arsenic, nickel, and copper. The metals have contaminated the water and sediments of Lake Coeur d’Alene, and continue to be transported downstream to Spokane Washington via the Spokane River. In 1983, the EPA listed the Bunker Hill Mining and Metallurgical Complex on the National Priorities List. Since that time, many of the most contaminated areas have been stabilized or isolated, however metal contaminants continue to migrate through the basin. Designation as a Superfund site causes significant problems for the economically depressed communities in the area. Identification of primary sources of contamination can help set priorities for cleanup and cleanup options, which can include source removal, water treatment or no action depending on knowledge about the mobility of contaminants relative to water flow. The mobility of contaminant mobility under natural or engineered conditions depends on multiple factors including the physical and chemical state (or speciation) of metals and the range of processes, some of which can be seasonal, that cause mobilization of metals. As a result, it is particularly important to understand metal speciation (National Research Council, 2005) and the link between speciation and the rates of metal migration and the impact of natural or engineered variations in flow, biological activity or water chemistry.

  9. Sustainably Managing Sediment in Regulated Rivers: Recent Developments

    NASA Astrophysics Data System (ADS)

    Kondolf, G. M.; Gao, Y.; Annandale, G. W.; Morris, G. L.; Sumi, T.

    2014-12-01

    Inspired by the current drought and concerns about maintaining water storage capacity, California State Senate this year passed SB1259, directing the Department of Water Resources to assess the state's reservoirs for sedimentation problems. The need to actively manage sediment in reservoirs is increasingly recognized, as valuable reservoir storage capacity is lost and downstream reaches suffer from sediment starvation, manifesting problems such as channel incision, accelerated erosion of deltas, and loss of gravels important for habitat. With increased dam construction globally, these impacts will be widespread. Despite the opportunities to pass sediment through or around reservoirs (to preserve reservoir capacity and to minimize downstream impacts), these sustainable approaches to managing sediment are not applied in many situations where they would be effective. From a workshop involving international and Chinese experts and review of recent literature, collective global experience in managing reservoir sediments and mitigating downstream sediment starvation suggest that sediment management can be classified as catchment management (to reduce sediment inflow), sediment removal, and sediment routing through or around the reservoir. Sediment routing has the virtues of maintaining sediment flows to downstream reaches, as well as preserving reservoir capacity. Where geometry is favorable, sediment can often be bypassed around the reservoir (avoiding reservoir sedimentation and supplying sediment to downstream reaches) or sluiced through large-capacity outlets after flowing rapidly through the reservoir to avoid sedimentation. In narrow reservoirs with steep longitudinal gradients, sediments accumulated in the reservoir can often be re-suspended and flushed through when the reservoir is drawn down. Turbidity currents can often be 'vented' through the dam, with the advantage that the reservoir need not be drawn down to pass sediment. In planning dams, the expert group

  10. Earthflow sediment production and Holocene sediment record in a large Apennine catchment

    NASA Astrophysics Data System (ADS)

    Simoni, Alessandro; Ponza, Alessio; Picotti, Vincenzo; Berti, Matteo; Dinelli, Enrico

    2013-04-01

    Landscape evolution in active mountain chains can be dominated by gravitational slope movements. This is observed in a large portion of the Reno river catchment, Apennines, Italy, where weak rocks, such as clayshales, are subject to earthflows that control hillslope morphology and supply sediments to the channel network. In this paper, we evaluate the sediment flux generated by earthflows and compare it with Holocene-averaged deposition rates to assess the contribution of mass movements to landscape evolution. Present-day hillslope sediment flux is estimated by combining measured displacement rates (72 inclinometers) and spatial attributes of earthflows and historical frequency of reactivations. Averaged sediment yield (~ 1.6 x 103 t/km2/yr) compares well with similar studies on earthflow-dominated landscapes, despite notable differences in methodology. In the study area, the connectivity between hillslopes and the stream network is well developed and no significant sediment sinks influence the sediment transport processes. We document best estimates of regional sediment fluxes and related uncertainties, based on available data. Coarse limestone fragments, present in the clayshales, are used as a natural sediment tracer to allow a comparison with sedimentation rates taking place at the mouth of the intramontane catchment. Here, available borehole logs, 14C datings and stratigraphic correlations of the alluvial fan are used to obtain an estimate of the deposition that took place during Holocene times. Taking also into account the role of solute transport, sedimentation rates are compared to earthflow sediment production rates. Results show a good agreement and demonstrate that earthflows are the primary mass wasting process in these weak rock lithologies. We document best estimates of regional sediment fluxes and related uncertainties. Present earthflow sediment production outpaces Holocene-averaged sedimentation rates by a factor of two. The gap between sediment

  11. Large-scale suspended sediment transport and sediment deposition in the Mekong Delta

    NASA Astrophysics Data System (ADS)

    Manh, N. V.; Dung, N. V.; Hung, N. N.; Merz, B.; Apel, H.

    2014-08-01

    Sediment dynamics play a major role in the agricultural and fishery productivity of the Mekong Delta. However, the understanding of sediment dynamics in the delta, one of the most complex river deltas in the world, is very limited. This is a consequence of its large extent, the intricate system of rivers, channels and floodplains, and the scarcity of observations. This study quantifies, for the first time, the suspended sediment transport and sediment deposition in the whole Mekong Delta. To this end, a quasi-2D hydrodynamic model is combined with a cohesive sediment transport model. The combined model is calibrated using six objective functions to represent the different aspects of the hydraulic and sediment transport components. The model is calibrated for the extreme flood season in 2011 and shows good performance for 2 validation years with very different flood characteristics. It is shown how sediment transport and sediment deposition is differentiated from Kratie at the entrance of the delta on its way to the coast. The main factors influencing the spatial sediment dynamics are the river and channel system, dike rings, sluice gate operations, the magnitude of the floods, and tidal influences. The superposition of these factors leads to high spatial variability of sediment transport, in particular in the Vietnamese floodplains. Depending on the flood magnitude, annual sediment loads reaching the coast vary from 48 to 60% of the sediment load at Kratie. Deposited sediment varies from 19 to 23% of the annual load at Kratie in Cambodian floodplains, and from 1 to 6% in the compartmented and diked floodplains in Vietnam. Annual deposited nutrients (N, P, K), which are associated with the sediment deposition, provide on average more than 50% of mineral fertilizers typically applied for rice crops in non-flooded ring dike floodplains in Vietnam. Through the quantification of sediment and related nutrient input, the presented study provides a quantitative basis for

  12. Estimating suspended sediment loads in the Pearl River Delta region using sediment rating curves

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Wei, Xiaoyan; Jinhai, Zheng; Yuliang, Zhu; Zhang, Yanjing

    2012-04-01

    In this study, sediment rating curves are employed to study the variations in relationships between water discharge and suspended sediment concentration based on the recent 50 years of monthly data set in the three major rivers of the Pearl River Delta. Results show that sediment rating parameters vary with time. The lowest rating coefficient, ln(a), and the highest rating exponent, b, mostly occur in the 1980s, indicating that sediment transport reached its peak in this decade at the same level as water discharge. This upward shift of sediment load is probably caused by exacerbated karst rocky desertification in the upper reaches of the Pearl River. However, since the beginning of the 1990s sediment loads from the Pearl River to its estuary began to show a dramatically decreasing trend, which is attributed mainly to deposition in the reservoirs, leading to an increase of ln(a) and a decrease of b. Furthermore, the sediment rating curve in 1957 to1970 is applied to estimate potential sediment load (1971 to 2006) in the absence of human influences. It is also estimated quantitatively by the sediment rating curves that in the 1980s, the annual sediment load decreased by 7.59×106 t/yr because of natural factors, while sediment increase induced by human activities was 20.07×106 t/yr, which resulted in an actual increased sediment load of 12.47×106 t/yr compared with the reference level in 1957 to 1970. In the last two decades, the difference between measured and estimated sediment loads became considerable, and the annual deficit sharply increased to 26.80×106 t/yr in the 1990s, and 50.46×106 t/yr in the 2000s, indicating that human activities, mainly referring to dam and reservoir construction, play a dominant role in the decrease of sediment load. The decrease in sediment supply from the Pearl River should be paid special attention because it may cause serious impacts on the river delta and the coastal ocean.

  13. Incorporation of Fine-Grained Sediment Erodibility Measurements into Sediment Transport Modeling, Capitol Lake, Washington

    USGS Publications Warehouse

    Stevens, Andrew W.; Gelfenbaum, Guy; Elias, Edwin; Jones, Craig

    2008-01-01

    Capitol Lake was created in 1951 with the construction of a concrete dam and control gate that prevented salt-water intrusion into the newly formed lake and regulated flow of the Deschutes River into southern Puget Sound. Physical processes associated with the former tidally dominated estuary were altered, and the dam structure itself likely caused an increase in retention of sediment flowing into the lake from the Deschutes River. Several efforts to manage sediment accumulation in the lake, including dredging and the construction of sediment traps upriver, failed to stop the lake from filling with sediment. The Deschutes Estuary Feasibility Study (DEFS) was carried out to evaluate the possibility of removing the dam and restoring estuarine processes as an alternative ongoing lake management. An important component of DEFS was the creation of a hydrodynamic and sediment transport model of the restored Deschutes Estuary. Results from model simulations indicated that estuarine processes would be restored under each of four restoration alternatives, and that over time, the restored estuary would have morphological features similar to the predam estuary. The model also predicted that after dam-removal, a large portion of the sediment eroded from the lake bottom would be deposited near the Port of Olympia and a marina located in lower Budd Inlet seaward of the present dam. The volume of sediment transported downstream was a critical piece of information that managers needed to estimate the total cost of the proposed restoration project. However, the ability of the model to predict the magnitude of sediment transport in general and, in particular, the volume of sediment deposition in the port and marina was limited by a lack of information on the erodibility of fine-grained sediments in Capitol Lake. Cores at several sites throughout Capitol Lake were collected between October 31 and November 1, 2007. The erodibility of sediments in the cores was later determined in the

  14. Sediment properties influencing the bioavailability of uranium to Chironomus dilutus larvae in spiked field sediments.

    PubMed

    Crawford, Sarah E; Liber, Karsten

    2016-04-01

    The partitioning of metals between dissolved and solid phases directly affects metal bioavailability to benthic invertebrates and is influenced by metal-binding properties of sediment phases. Little research has been done examining the effects of sediment properties on the bioavailability of uranium (U) to freshwater benthic invertebrates. In the present study, 18 field sediments with a wide range of properties (total organic carbon, fine fraction, cation exchange capacity, and iron content) were amended with the same concentrations of U to characterize the effects of these sediment properties on U bioavailability to freshwater midge, Chironomus dilutus. Bioaccumulation of U by C. dilutus larvae varied by over an order of magnitude when exposed to sediments spiked with 50 mg U kg(-1) d.w. (5-69 mg U kg(-1) d.w.) and 500 mg U kg(-1) d.w. (20-452 mg U kg(-1) d.w.), depending on the type of sediment. Variance in U bioaccumulation was best explained by differences in the cation exchange capacity, fine fraction (≤50 μm particle size), and Fe content of U-spiked sediment, with generated regression equations predicting observed bioaccumulation within a factor of two. The presented regression equations offer an easy-to-apply method for accounting for the influence of sediment properties on U bioavailability in freshwater sediment, with fine fraction being the single most practical variable. This research strongly supports that risk assessments and guidelines for U-contaminated sediments should not ignore the influence of sediment properties that can result in substantial differences in the bioaccumulation of U in benthic invertebrates. PMID:26802266

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  16. Sediment properties influencing the bioavailability of uranium to Chironomus dilutus larvae in spiked field sediments.

    PubMed

    Crawford, Sarah E; Liber, Karsten

    2016-04-01

    The partitioning of metals between dissolved and solid phases directly affects metal bioavailability to benthic invertebrates and is influenced by metal-binding properties of sediment phases. Little research has been done examining the effects of sediment properties on the bioavailability of uranium (U) to freshwater benthic invertebrates. In the present study, 18 field sediments with a wide range of properties (total organic carbon, fine fraction, cation exchange capacity, and iron content) were amended with the same concentrations of U to characterize the effects of these sediment properties on U bioavailability to freshwater midge, Chironomus dilutus. Bioaccumulation of U by C. dilutus larvae varied by over an order of magnitude when exposed to sediments spiked with 50 mg U kg(-1) d.w. (5-69 mg U kg(-1) d.w.) and 500 mg U kg(-1) d.w. (20-452 mg U kg(-1) d.w.), depending on the type of sediment. Variance in U bioaccumulation was best explained by differences in the cation exchange capacity, fine fraction (≤50 μm particle size), and Fe content of U-spiked sediment, with generated regression equations predicting observed bioaccumulation within a factor of two. The presented regression equations offer an easy-to-apply method for accounting for the influence of sediment properties on U bioavailability in freshwater sediment, with fine fraction being the single most practical variable. This research strongly supports that risk assessments and guidelines for U-contaminated sediments should not ignore the influence of sediment properties that can result in substantial differences in the bioaccumulation of U in benthic invertebrates.

  17. Utilizing Turbidity and Measurements of Suspended Sediment Concentrations to Better Understand Sediment Transport within Urban Streams

    NASA Astrophysics Data System (ADS)

    Elkins, T. M.; Napieralski, J. A.

    2009-12-01

    The Rouge River watershed in Southeast Michigan is an urban watershed, which has been exposed to more than 100 years of anthropogenic activities related to industrialization and urbanization. This urbanization has degraded water quality by increasing erosion and altering the transport mechanism and chemistry of bed and suspended sediments. This study aims to explore the relationship between development within the Lower Rouge watershed and watershed hydrology through an examination of USGS discharge data, stream water quality and suspended sediment loads during storm and base flow. Two YSI dataloggers are used to continuously measure water quality parameters during baseflow and storm events (varying hydrologic conditions), including: turbidity, dissolved oxygen, conductivity, salinity, total dissolved solids, and temperature. Depth-integrated sediment samples are collected and analyzed for sediment concentration using Imhoff cones and filtration methods. Correlations between discharge weighted continuous turbidity measurements and discharge weighted suspended sediment samples are used to estimate sediment loads; essentially, turbidity readings and measured sediment concentrations form a near-linear relationship. In addition, sediment samples are analyzed for inorganic heavy metal contaminants common to Southeast Michigan to characterize both suspended sediments and sediments frequently deposited on adjacent floodplains. These metals (i.e. Lead, Copper, Chromium, Nickle) are commonly known as the “Michigan Metals” and represent indicator species of mobilized and deposited contaminants associated with urbanization and industrialization. The results will provide a baseline for better understanding the transport and fate of contaminated sediments within the Rouge watershed, as well as guide ongoing development and management practices along the Rouge River.

  18. Mapping intertidal surface sediment type distribution with retrieved sedimental components using EO-1 Hyperion data

    NASA Astrophysics Data System (ADS)

    Li, Huan; Zhang, Dong; Zhang, Ying; Xu, Yong

    2010-11-01

    Sediment type was one of the most important parameters of intertidal zone. The hydrodynamics and morphological changes could be indicated by sediment types very well, and the understanding of their distribution and stability could provide an important insight into littoral marine ecology. The way of conventional survey for sediment types was expensive and time-consuming. The objective of this study was to develop a method to distinguish sediment types using remote sensing, and enable which to be an alternative to traditional methods. Intertidal zone sediments were sampled at the south of Dafeng port, Yancheng city, Jiangsu province, China. Samples were collected from the upper 3cm surface of intertidal zone. The laboratory spectral reflectance data were obtained using a spectrometer. Particle-size of sediment samples were measured by Mastersizer 2000. Through analyzing characteristics of spectral reflectance for sediment samples, we found that two bands were sensitive to content of sediment components (sand, silt and clay) with central wavelengths at 864 and 1034 nm. However, the position of sensitive bands changed as moisture varied. In order to eliminate the impact of moisture on sediment spectral reflectance, moisture was introduced as a crucial factor to build regression equations with reflectance of sensitive bands to get contents of different sediment components, and then Shepard classification system was applied to acquire spatial distribution of sediment types. This way provided a quick, non-destructive and nonpolluting survey method. Meanwhile, this intelligent way of extracting information from muddy coastal zone will contribute to constructing digital earth, the huge system which benefits human beings.

  19. Mapping intertidal surface sediment type distribution with retrieved sedimental components using EO-1 Hyperion data

    NASA Astrophysics Data System (ADS)

    Li, Huan; Zhang, Dong; Zhang, Ying; Xu, Yong

    2009-09-01

    Sediment type was one of the most important parameters of intertidal zone. The hydrodynamics and morphological changes could be indicated by sediment types very well, and the understanding of their distribution and stability could provide an important insight into littoral marine ecology. The way of conventional survey for sediment types was expensive and time-consuming. The objective of this study was to develop a method to distinguish sediment types using remote sensing, and enable which to be an alternative to traditional methods. Intertidal zone sediments were sampled at the south of Dafeng port, Yancheng city, Jiangsu province, China. Samples were collected from the upper 3cm surface of intertidal zone. The laboratory spectral reflectance data were obtained using a spectrometer. Particle-size of sediment samples were measured by Mastersizer 2000. Through analyzing characteristics of spectral reflectance for sediment samples, we found that two bands were sensitive to content of sediment components (sand, silt and clay) with central wavelengths at 864 and 1034 nm. However, the position of sensitive bands changed as moisture varied. In order to eliminate the impact of moisture on sediment spectral reflectance, moisture was introduced as a crucial factor to build regression equations with reflectance of sensitive bands to get contents of different sediment components, and then Shepard classification system was applied to acquire spatial distribution of sediment types. This way provided a quick, non-destructive and nonpolluting survey method. Meanwhile, this intelligent way of extracting information from muddy coastal zone will contribute to constructing digital earth, the huge system which benefits human beings.

  20. Sediment fingerprinting to determine the source of suspended sediment in a southern Piedmont stream.

    PubMed

    Mukundan, R; Radcliffe, D E; Ritchie, J C; Risse, L M; McKinley, R A

    2010-01-01

    Thousands of stream miles in the southern Piedmont region are impaired because of high levels of suspended sediment. It is unclear if the source is upland erosion from agricultural sources or bank erosion of historic sediment deposited in the flood plains between 1830 and 1930 when cotton farming was extensive. The objective of this study was to determine the source of high stream suspended sediment concentrations in a typical southern Piedmont watershed using sediment fingerprinting techniques. Twenty-one potential tracers were tested for their ability to discriminate between sources, conservative behavior, and lack of redundancy. Tracer concentrations were determined in potential sediment sources (forests, pastures, row crop fields, stream banks, and unpaved roads and construction sites), and suspended sediment samples collected from the stream and analyzed using mixing models. Results indicated that 137Cs and 15N were the best tracers to discriminate potential sediment sources in this watershed. The delta15N values showed distinct signatures in all the potential suspended sediment sources, and delta15N was a unique tracer to differentiate stream bank soil from upland subsurface soils, such as soil from construction sites, unpaved roads, ditches, and field gullies. Mixing models showed that about 60% of the stream suspended sediment originated from eroding stream banks, 23 to 30% from upland subsoil sources (e.g., construction sites and unpaved roads), and about 10 to 15% from pastures. The results may be applicable to other watersheds in the Piedmont depending on the extent of urbanization occurring in these watersheds. Better understanding of the sources of fine sediment has practical implications on the type of sediment control measures to be adopted. Investment of resources in improving water quality should consider the factors causing stream bank erosion and erosion from unpaved roads and construction sites to water quality impairment.

  1. Shifting Sediment Sources in the Quaternary Nile

    NASA Astrophysics Data System (ADS)

    Woodward, Jamie; Macklin, Mark; Fielding, Laura; Millar, Ian; Williams, Martin

    2016-04-01

    Invited Paper The Nile basin contains the longest river channel system in the world and drains about one tenth of the African continent. A dominant characteristic of the modern Nile is the marked spatial and temporal variability in the flux of water and sediment. Because the major headwater basins of the Nile are linked to key elements of the global climate system, the sedimentary records in the basin have attracted good deal of attention from the Quaternary palaeoclimate and palaeohydrology communities. Various approaches (from heavy minerals to strontium isotopes) have been employed to examine present and past patterns of sediment yield in the basin. A good deal of work has been carried out on the long sediment records in the delta and offshore which provide high resolution archives of hydrological changes in the upstream basin as well fluctuations in the input of dust from the desert. The sediment load of the modern desert Nile (downstream of Khartoum) is dominated by sediment inputs from the Blue Nile (61 +/- 5%) and Atbara (35 +/- 4%), whilst the White Nile contribution is meagre (3 +/- 2%) (Padoan et al. 2011). Recent work has shown that these values were very different during humid phases of the Quaternary when stronger Northern Hemisphere summer insolation produced wetter conditions across North Africa. In the early Holocene, for example, the Nile floodplain in Northern Sudan shows a tributary wadi input of 40-50%. This paper will review three decades of work on the sediment delivery dynamics of the Quaternary Nile and explore their palaeoclimatic implications. Padoan, M., Garzanti, E., Harlavan, Y., Villa, I.M. (2011) Tracing Nile sediment sources by Sr and Nd isotope signatures (Uganda, Ethiopia, Sudan). Geochim. Cosmochim. Acta 75 (12), 3627-3644.

  2. The evolution of sediment acoustic models

    NASA Astrophysics Data System (ADS)

    Chotiros, Nicholas P.; Isakson, Marcia J.

    2012-11-01

    Sediment acoustic models contain two connected components, the geo-physical description of the sediment and the model of acoustic processes. Geo-physical descriptors are used in the classification of sediments, and they are based on grain size, density and other physical descriptors. Acoustic sediment models were initially fluid approximations that were simple to implement. As the need for accuracy increased, the fluid model was extended to stratified fluid and visco-elastic models. The latter, with five frequency-independent parameters, appeared to be consistent with sediment acoustic data up to the 1980s. More recent experimental data have revealed discrepancies in the frequency-dependence of attenuation and sound speed, particularly in the case of sandy sediments, which cover a large fraction of the continental shelves. Broad-band acoustic measurements of wave speeds and attenuations are more consistent with a poro-elastic model, consisting of Biot's theory with extensions to account for the physics of granular media. Aside from terminology, there is a fundamental difference between visco-elastic and poro-elastic theories. The former is based on two types of waves, a compressional wave and a shear wave, while the latter has an additional compressional wave, often called the Biot wave. There are currently two approaches to the development of sediment acoustic models: (a) visco-elastic models with frequency dependent parameters that mimic the observed behavior, and (b) poro-elastic models that reflect the physical processes. It is shown that (a) would be a significant improvement over existing models, but (b) is the preferred solution.

  3. Mercury in Long Island Sound sediments

    USGS Publications Warehouse

    Varekamp, J.C.; Bucholtz ten Brink, M. R.; Mecray, E.I.; Kreulen, B.

    2000-01-01

    Mercury (Hg) concentrations were measured in 394 surface and core samples from Long Island Sound (LIS). The surface sediment Hg concentration data show a wide spread, ranging from 600 ppb Hg in westernmost LIS. Part of the observed range is related to variations in the bottom sedimentary environments, with higher Hg concentrations in the muddy depositional areas of central and western LIS. A strong residual trend of higher Hg values to the west remains when the data are normalized to grain size. Relationships between a tracer for sewage effluents (C. perfringens) and Hg concentrations indicate that between 0-50 % of the Hg is derived from sewage sources for most samples from the western and central basins. A higher percentage of sewage-derived Hg is found in samples from the westernmost section of LIS and in some local spots near urban centers. The remainder of the Hg is carried into the Sound with contaminated sediments from the watersheds and a small fraction enters the Sound as in situ atmospheric deposition. The Hg-depth profiles of several cores have well-defined contamination profiles that extend to pre-industrial background values. These data indicate that the Hg levels in the Sound have increased by a factor of 5-6 over the last few centuries, but Hg levels in LIS sediments have declined in modern times by up to 30 %. The concentrations of C. perfringens increased exponentially in the top core sections which had declining Hg concentrations, suggesting a recent decline in Hg fluxes that are unrelated to sewage effluents. The observed spatial and historical trends show Hg fluxes to LIS from sewage effluents, contaminated sediment input from the Connecticut River, point source inputs of strongly contaminated sediment from the Housatonic River, variations in the abundance of Hg carrier phases such as TOC and Fe, and focusing of sediment-bound Hg in association with westward sediment transport within the Sound.

  4. Sedimentation pattern of the southeastern Weddell Sea

    NASA Astrophysics Data System (ADS)

    Huang, Xiaoxia; Jokat, wilfried; gohl, karsten

    2014-05-01

    An improved understanding of the sedimentation processes of the southeast Weddell Sea helps in refined reconstructions of paleo-ice sheet dynamics in conjunction with paleoceanographic processes. We re-investigated a series of sedimentary features of the continental rise, such as contourite drifts, which were reworked by glacial erosional and ocean-current activity from the middle Miocene to the present. New unconformities WS-u5 (middle Miocene), WS-u6 (late Miocene), WS-u7 (Pliocene) were interpreted by correlating records of the ODP Leg 113 Site 693 and existing seismostratigraphic and chronological models. We focused on the Crary trough mouth fan and channel system as well as giant sediment drifts and analysed published and unpublished high-resolution seismic reflection, sub-bottom profiler (Parasound) and swath-bathymetry data. Four types of sediment drifts (channel related drifts, elongate drifts, contourite drifts, and levee drifts), mass wasting deposits and sediment waves were recognized from analyses of seismic characteristics. The formation of the different types of sediment drifts can be related to the upslope/downslope Antarctica Bottom Water (AABW) and Weddell Sea Bottom Water (WSBW) activity as well as interaction with the westward Weddell Gyre and Coriolis force. Mass wasting deposits and sediment waves were caused by large scale slumping and sliding from the continental slope and by contour currents, respectively. The large size of the three main channels and their infill consisting of seismically chaotic facies indicate that these channels formed by shelf slope collapses at the Dronning Maud Land margin and large volume mass wasting through the Crary trough mouth fan. Finally, we compare the sedimentation processes of the Crary fan with other submarine fans, such as Belgica fan of West Antarctica, Prydz Bay fan of East Antarctica and Scoresby fan of East Greenland.

  5. Development of a standardized sediment reference toxicant test using formulated sediment and copper sulfate

    SciTech Connect

    Suedel, B.C.; Hartzell, R.S.; Williams, C.W.; Connelly, R.A.

    1994-12-31

    The lack of suitable reference toxicant tests to assess the condition or health of populations of benthic test organisms is problematic because the precision and accuracy of definitive whole sediment tests cannot be assessed without this reference. To address this need, formulated sediment was prepared to provide a consistent substrate with respect to percent solids, particle size distribution, cation exchange capacity, organic carbon, organic matter, redox potential, and pH. Hyalella azteca and Chironomus tentans were exposed for 96-h to formulated sediment amended with serial dilutions of copper sulfate. Results indicate that (1) formulated sediments can be prepared consistently between batches with minimal variability with respect to sediment characteristics, providing a consistent test substrate; (2) when combined with formulated sediment, copper sulfate is a suitable sediment reference toxicant for assessing the condition and health of H. azteca and C tentans populations; and (3) formulated sediment provides a suitable substrate for H. azteca and C tentans (control survival > 80%). This method provides a means by which the health and sensitivity of benthic test organisms can be assessed and provides a measure of precision within and among laboratories through time.

  6. Nature and changes in organic matter in organic sediments. [organic matter in ocean sediments

    NASA Technical Reports Server (NTRS)

    Kaplan, I. R.

    1973-01-01

    A series of isoprenoid compounds were isolated from a heat treated marine sediment (from Tanner Basin) which were not present in the original sediment. Among the compounds identified were: phytol, dihydrophytol, C-18-isoprenoid ketone, phytanic and pristanic acids, C-19- and C-10-monoolefines, and the alkanes pristane and phytane. The significance and possible routes leading to these compounds is discussed.

  7. Mechanistic Sediment Quality Guidelines Based on Contaminant Bioavailability: Equilibrium Partitioning Sediment Benchmarks

    EPA Science Inventory

    Globally, billions of metric tons of contaminated sediments are present in aquatic systems representing a potentially significant ecological risk. Estimated costs to manage (i.e., remediate and monitor) these sediments are in the billions of U.S. dollars. Biologically-based app...

  8. PREDICTING SEDIMENT METAL TOXICITY USING A SEDIMENT BIOTIC LIGAND MODEL: METHODOLOGY AND INITIAL APPLICATION

    EPA Science Inventory

    An extension of the simultaneously extracted metals/acid-volatile sulfide (SEM/AVS) procedure is presented that predicts the acute and chronic sediment metals effects concentrations. A biotic ligand model (BLM) and a pore water–sediment partitioning model are used to predict the ...

  9. Reservoir Sedimentation and Upstream Sediment Sources: Perspectives and Future Research Needs on Streambank and Gully Erosion.

    PubMed

    Fox, G A; Sheshukov, A; Cruse, R; Kolar, R L; Guertault, L; Gesch, K R; Dutnell, R C

    2016-05-01

    The future reliance on water supply and flood control reservoirs across the globe will continue to expand, especially under a variable climate. As the inventory of new potential dam sites is shrinking, construction of additional reservoirs is less likely compared to simultaneous flow and sediment management in existing reservoirs. One aspect of this sediment management is related to the control of upstream sediment sources. However, key research questions remain regarding upstream sediment loading rates. Highlighted in this article are research needs relative to measuring and predicting sediment transport rates and loading due to streambank and gully erosion within a watershed. For example, additional instream sediment transport and reservoir sedimentation rate measurements are needed across a range of watershed conditions, reservoir sizes, and geographical locations. More research is needed to understand the intricate linkage between upland practices and instream response. A need still exists to clarify the benefit of restoration or stabilization of a small reach within a channel system or maturing gully on total watershed sediment load. We need to better understand the intricate interactions between hydrological and erosion processes to improve prediction, location, and timing of streambank erosion and failure and gully formation. Also, improved process-based measurement and prediction techniques are needed that balance data requirements regarding cohesive soil erodibility and stability as compared to simpler topographic indices for gullies or stream classification systems. Such techniques will allow the research community to address the benefit of various conservation and/or stabilization practices at targeted locations within watersheds.

  10. Tsunami inundation and sediment transport in a sediment-limited embayment on American Samoa

    USGS Publications Warehouse

    Apotsos, A.; Gelfenbaum, G.; Jaffe, B.; Watt, Sebastian; Peck, B.; Buckley, M.; Stevens, A.

    2011-01-01

    Field observations and numerical simulations are used to explore tsunami inundation and sediment transport in an embayment (Fagafue Bay) on the north side of Tutuila, American Samoa during the 29 September 2009 South Pacific tsunami. Field observations of the nearshore bathymetry and topography, tsunami flow depth and sediment deposition, and extent of movable sandy sediment remaining on the beach were collected during two field surveys approximately two and five weeks after the tsunami. Onshore measurements of flow depth at forty-eight locations indicate the wave inundated almost 250. m onshore with a depth exceeding 7. m locally. The tsunami deposited patchy areas of sediment up to 0.2. m thick interspersed with a thin dusting (< 0.01 m) of sandy sediment throughout most of the inundated area. A numerical simulation based on the best available topography and bathymetry and a simplified offshore wave forcing is calibrated with the onshore flow observations. The calibrated model is used to simulate tsunami-induced sediment transport within and onshore of both the actual embayment and several idealized embayments. The simulations show that the onshore deposition of sediment can be affected by more than 50% by both the amount of sediment available for transport and the steepness of the onshore topography, suggesting these effects may need to be considered when interpreting tsunami deposits.

  11. A COMPARISON OF BULK SEDIMENT TOXICITY TESTING METHODS AND SEDIMENT ELUTRIATE TOXICITY

    EPA Science Inventory

    Bulk sediment toxicity tests are routinely used to assess the level and extent of contamination in natural sediments. While reliable, these tests can be resource intensive, requiring significant outlays of time and materials. The purpose of this study was to compare the results ...

  12. Reservoir Sedimentation and Upstream Sediment Sources: Perspectives and Future Research Needs on Streambank and Gully Erosion.

    PubMed

    Fox, G A; Sheshukov, A; Cruse, R; Kolar, R L; Guertault, L; Gesch, K R; Dutnell, R C

    2016-05-01

    The future reliance on water supply and flood control reservoirs across the globe will continue to expand, especially under a variable climate. As the inventory of new potential dam sites is shrinking, construction of additional reservoirs is less likely compared to simultaneous flow and sediment management in existing reservoirs. One aspect of this sediment management is related to the control of upstream sediment sources. However, key research questions remain regarding upstream sediment loading rates. Highlighted in this article are research needs relative to measuring and predicting sediment transport rates and loading due to streambank and gully erosion within a watershed. For example, additional instream sediment transport and reservoir sedimentation rate measurements are needed across a range of watershed conditions, reservoir sizes, and geographical locations. More research is needed to understand the intricate linkage between upland practices and instream response. A need still exists to clarify the benefit of restoration or stabilization of a small reach within a channel system or maturing gully on total watershed sediment load. We need to better understand the intricate interactions between hydrological and erosion processes to improve prediction, location, and timing of streambank erosion and failure and gully formation. Also, improved process-based measurement and prediction techniques are needed that balance data requirements regarding cohesive soil erodibility and stability as compared to simpler topographic indices for gullies or stream classification systems. Such techniques will allow the research community to address the benefit of various conservation and/or stabilization practices at targeted locations within watersheds. PMID:26885658

  13. EMAP SEDIMENTATION INDEX: LAND USE AND NATURAL HYDRAULIC CONTROLS ON STREAM SEDIMENTATION

    EPA Science Inventory

    Excessive erosion, transport and deposition of sediment in streams and rivers is a major problem in surface waters throughout the United States. It is important to have a reliable measure of stream sedimentation that properly accounts for natural controls on the amount of fine p...

  14. Reservoir Sedimentation and Upstream Sediment Sources: Perspectives and Future Research Needs on Streambank and Gully Erosion

    NASA Astrophysics Data System (ADS)

    Fox, G. A.; Sheshukov, A.; Cruse, R.; Kolar, R. L.; Guertault, L.; Gesch, K. R.; Dutnell, R. C.

    2016-05-01

    The future reliance on water supply and flood control reservoirs across the globe will continue to expand, especially under a variable climate. As the inventory of new potential dam sites is shrinking, construction of additional reservoirs is less likely compared to simultaneous flow and sediment management in existing reservoirs. One aspect of this sediment management is related to the control of upstream sediment sources. However, key research questions remain regarding upstream sediment loading rates. Highlighted in this article are research needs relative to measuring and predicting sediment transport rates and loading due to streambank and gully erosion within a watershed. For example, additional instream sediment transport and reservoir sedimentation rate measurements are needed across a range of watershed conditions, reservoir sizes, and geographical locations. More research is needed to understand the intricate linkage between upland practices and instream response. A need still exists to clarify the benefit of restoration or stabilization of a small reach within a channel system or maturing gully on total watershed sediment load. We need to better understand the intricate interactions between hydrological and erosion processes to improve prediction, location, and timing of streambank erosion and failure and gully formation. Also, improved process-based measurement and prediction techniques are needed that balance data requirements regarding cohesive soil erodibility and stability as compared to simpler topographic indices for gullies or stream classification systems. Such techniques will allow the research community to address the benefit of various conservation and/or stabilization practices at targeted locations within watersheds.

  15. Assessment of Density Variations of Marine Sediments with Ocean and Sediment Depths

    PubMed Central

    Tenzer, R.; Gladkikh, V.

    2014-01-01

    We analyze the density distribution of marine sediments using density samples taken from 716 drill sites of the Deep Sea Drilling Project (DSDP). The samples taken within the upper stratigraphic layer exhibit a prevailing trend of the decreasing density with the increasing ocean depth (at a rate of −0.05 g/cm3 per 1 km). Our results confirm findings of published studies that the density nonlinearly increases with the increasing sediment depth due to compaction. We further establish a 3D density model of marine sediments and propose theoretical models of the ocean-sediment and sediment-bedrock density contrasts. The sediment density-depth equation approximates density samples with an average uncertainty of about 10% and better represents the density distribution especially at deeper sections of basin sediments than a uniform density model. The analysis of DSDP density data also reveals that the average density of marine sediments is 1.70 g/cm3 and the average density of the ocean bedrock is 2.9 g/cm3. PMID:24744686

  16. Effects of sediment composition on inorganic mercury partitioning, speciation and bioavailability in oxic surficial sediments.

    PubMed

    Zhong, Huan; Wang, Wen-Xiong

    2008-01-01

    Artificially prepared sediments were used to assess the effects of sediment composition on inorganic Hg partitioning, speciation and bioavailability. Organic coating in sediment greatly increased the Hg partitioning and the amount of bioavailable Hg bound with the clay and the Fe and Mn oxides, but had little effect on that bound with the quartz and calcium carbonate as a result of weaker binding of humic acids and fulvic acids. The clay content increased the concentration of Hg in the sediments but inhibited the gut juice extraction due to the strong binding of Hg-organic matter (OM) complexes. Most Hg in the sediments was complexed by OM (mainly distributed in the organo-complexed phase and the strongly complexed phase), and the Hg-OM complexes (especially Hg in the strongly complexed phase) in sediments contributed much to gut juice extraction. Redistribution of Hg-OM complexes between sediments and gut juices may occur during gut juice extraction and modify Hg bioavailability and speciation in sediments.

  17. Tephra transport, sedimentation and hazards

    NASA Astrophysics Data System (ADS)

    Volentik, Alain C. M.

    Tephra deposits are one of the possible outcomes of explosive volcanic eruptions and are the result of vertical settling of volcanic particles that have been expelled from the volcanic vent into the atmosphere, following magma fragmentation within the volcanic conduit. Tephra fallout represents the main volcanic hazard to populated areas and critical facilities. Therefore, it is crucial to better understand processes that lead to tephra transport, sedimentation and hazards. In this study, and based on detailed mapping and sampling of the tephra deposit of the 2450BP Plinian eruption of Pululagua volcano (Ecuador), I investigate tephra deposits through a variety of approaches, including empirical and analytical modeling of tephra thickness and grain size data to infer important eruption source parameters (e.g. column height, total mass ejected, total grain size distribution of the deposit). I also use a statistical approach (smoothed bootstrap with replacement method) to assess the uncertainty in the eruptive parameters. The 2450BP Pululagua volcanic plume dynamics were also explored through detailed grain size analysis and 1D modeling of tephra accumulation. Finally, I investigate the influence of particle shape on tephra accumulation on the ground through a quantitative and comprehensive study of the shape of volcanic ash. As the global need for energy is expected to grow in the future, many future natural hazard studies will likely involve the assessment of volcanic hazards at critical facilities, including nuclear power plants. I address the potential hazards from tephra fallout, pyroclastic flows and lahars for the Bataan Nuclear Power Plant (Philippines) posed by three nearby volcanoes capable of impacting the site during an explosive eruption. I stress the need for good constraints (stratigraphic analysis and events dating) on past eruptive events to better quantify the probability of future events at potentially active volcanoes, the need for probabilistic

  18. Sediment contributions from floodplains and legacy sediments to Piedmont streams of Baltimore County, Maryland

    NASA Astrophysics Data System (ADS)

    Donovan, Mitchell; Miller, Andrew; Baker, Matthew; Gellis, Allen

    2015-04-01

    Disparity between watershed erosion rates and downstream sediment delivery has remained an important theme in geomorphology for many decades, with the role of floodplains in sediment storage as a common focus. In the Piedmont Province of the eastern USA, upland deforestation and agricultural land use following European settlement led to accumulation of thick packages of overbank sediment in valley bottoms, commonly referred to as legacy deposits. Previous authors have argued that legacy deposits represent a potentially important source of modern sediment loads following remobilization by lateral migration and progressive channel widening. This paper seeks to quantify (1) rates of sediment remobilization from Baltimore County floodplains by channel migration and bank erosion, (2) proportions of streambank sediment derived from legacy deposits, and (3) potential contribution of net streambank erosion and legacy sediments to downstream sediment yield within the Mid-Atlantic Piedmont. We calculated measurable gross erosion and deposition rates within the fluvial corridor along 40 valley segments from 18 watersheds with drainage areas between 0.18 and 155 km2 in Baltimore County, Maryland. We compared stream channel and floodplain morphology from lidar-based digital elevation data collected in 2005 with channel positions recorded on 1:2400 scale topographic maps from 1959-1961 in order to quantify 44-46 years of channel change. Sediment bulk density and particle size distributions were characterized from streambank and channel deposit samples and used for volume to mass conversions and for comparison with other sediment sources. Average annual lateral migration rates ranged from 0.04 to 0.19 m/y, which represented an annual migration of 2.5% (0.9-4.4%) channel width across all study segments, suggesting that channel dimensions may be used as reasonable predictors of bank erosion rates. Gross bank erosion rates varied from 43 to 310 Mg/km/y (median = 114) and were

  19. Applying sediment quality guidelines on soft sediments of the Gulf of Finland, Baltic Sea.

    PubMed

    Vallius, Henry

    2015-09-15

    The Gulf of Finland is known to have been rather largely contaminated by heavy metals during the last half of the 20th century, but indications of recovery have been reported. In order to investigate the recent levels of heavy metals and arsenic in the uppermost soft sediments of the off-shore Gulf of Finland coring of altogether 23 sites were performed. The subsamples of the cores are 605 in total and thus give a good picture of heavy metal levels in the surface sediments during the first decade of this century. In order to evaluate methods and predict sediment toxicity the sediment concentrations are compared to American SQG:s. Majority of the subsamples exceeded the threshold levels of both used SQG:s, but some exceeded also the midrange effects quality guidelines. As, Cd, Hg, and Zn concentrations still occur at unacceptably high levels in sediments of the off-shore Gulf of Finland.

  20. Sediment Burial Intolerance of Marine Macroinvertebrates.

    PubMed

    Hendrick, Vicki J; Hutchison, Zoë L; Last, Kim S

    2016-01-01

    The marine environment contains suspended particulate matter which originates from natural and anthropogenic sources. Settlement of this material can leave benthic organisms susceptible to smothering, especially if burial is sudden i.e. following storms or activities such as dredging. Their survival will depend on their tolerance to, and their ability to escape from burial. Here we present data from a multi-factorial experiment measuring burial responses incorporating duration, sediment fraction and depth. Six macroinvertebrates commonly found in sediment rich environments were selected for their commercial and/or conservation importance. Assessments revealed that the brittle star (Ophiura ophiura), the queen scallop (Aequipecten opercularis) and the sea squirt (Ciona intestinalis) were all highly intolerant to burial whilst the green urchin (Psammichinus miliaris) and the anemone (Sagartiogeton laceratus), showed intermediate and low intolerance respectively, to burial. The least intolerant, with very high survival was the Ross worm (Sabellaria spinulosa). With the exception of C. intestinalis, increasing duration and depth of burial with finer sediment fractions resulted in increased mortality for all species assessed. For C. intestinalis depth of burial and sediment fraction were found to be inconsequential since there was complete mortality of all specimens buried for more than one day. When burial emergence was assessed O. ophiura emerged most frequently, followed by P. miliaris. The former emerged most frequently from the medium and fine sediments whereas P. miliaris emerged more frequently from coarse sediment. Both A. opercularis and S. laceratus showed similar emergence responses over time, with A. opercularis emerging more frequently under coarse sediments. The frequency of emergence of S. laceratus increased with progressively finer sediment and C. intestinalis did not emerge from burial irrespective of sediment fraction or depth. Finally, and perhaps

  1. Micro-facies of Dead Sea sediments

    NASA Astrophysics Data System (ADS)

    Neugebauer, Ina; Schwab, Markus J.; Brauer, Achim; Frank, Ute; Dulski, Peter; Kitagawa, Hiroyuki; Enzel, Yehouda; Waldmann, Nicolas; Ariztegui, Daniel; Drilling Party, Dsddp

    2013-04-01

    Lacustrine sediments infilling the Dead Sea basin (DSB) provide a rare opportunity to trace changing climates in the eastern Mediterranean-Levant region throughout the Pleistocene and Holocene. In this context, high-resolution investigation of changes in sediment micro- facies allow deciphering short-term climatic fluctuations and changing environmental conditions in the Levant. The Dead Sea is a terminal lake with one of the largest drainage areas in the Levant, located in the Mediterranean climate zone and influenced also by the Saharo-Arabian deserts. Due to drastic climatic changes in this region, an exceptionally large variety of lacustrine sediments has been deposited in the DSB. These sediments, partially the results of changing lake levels, primarily represent changes in precipitation (e.g. Enzel et al., 2008). Evaporites (halite and gypsum) reflect dry climatic conditions during interglacials, while alternated aragonite-detritus (AAD) is deposited during glacial lake level high-stands. Here we present the first micro-facies inventory of a ~450 m long sediment profile from the deepest part of the northern DSB (ICDP site 5017-1, ~300 m water depth). The sediment record comprises the last two glacial-interglacial cycles, with mainly AAD facies in the upper part of the Amora Formation (penultimate glacial) and the last glacial Lisan Formation. The last interglacial Samra and the Holocene Zeelim Formations are predominantly characterized by thick bedded halite deposits, intercalated by partly laminated detrital marl sequences. Representative sections of the different facies types have been analyzed for micro-facies on petrographic thin sections, supported by high-resolution µXRF element scanning, magnetic susceptibility measurements and microscopic fluorescence analysis. Furthermore, Holocene sediments retrieved at the deep basin core site have been compared to their shallow-water counterpart at the western margin of the lake (core DSEn; Migowski et al., 2004

  2. Sediment fluxes in transboundary Selenga river basin

    NASA Astrophysics Data System (ADS)

    Belozerova, Ekaterina

    2013-04-01

    Gathering reliable information on transboundary river systems remains a crucial task for international water management and environmental pollution control. Countries located in the lower parts of the river basins depend on water use and management strategies in adjacent upstream countries. One important issue in this context is sediment transport and associated contaminant fluxes across the state borders. The mass flows of dissolved ions, biogens, heavy metal concentrations, as far as suspended sediment concentration (SSC, mg/l) along upper Selenga river and its tributaries based on the literature review and results of field campaigns 2011-2012 were estimated. Based on the water discharges measurements Q, suspended load WR (t/day) and dissolved loads WL were calculated. In the Selenga basin the minimal WR (1,34-3,74 t/day) were found at small rivers. Maximal sediment loads (WR = 15 000 t/day) were found at the upper Orkhon river during flood event. The downstream point (Mongolia-Russia border) was characterized 2 220 t/day in 2011. Generally the prevalence of the accumulation is found through calculating sediment budget for all rivers (ΔW = WR (downstream) - WR (upstream) < 0). Downstream of Orkhon river (below confluence with Tuul) ΔW = - 1145 t/day. Below Selenga-Orkhon confluence sediment yield reached 2515 t/day, which is corresponded to transboundary sediment flux. Silt sediments (0,001 - 0,05 mm) form the main portion of the transported material. The maximal value of sand flux (302 t/day) was reported for middle stream station of Selenga river (upstream from confluence with Orkhon). The increase of human activities (mining and pastures) increases the portion of clay particles in total sediment load (e.g. at the downstream point of most polluted Orkhon river it reached 207,8 t/day). The existed estimates are compared with distribution of the main matter sources within basin: mining and industry, river-bank erosion and slope wash. The heaviest increase of

  3. Sediment Burial Intolerance of Marine Macroinvertebrates

    PubMed Central

    Hendrick, Vicki J.; Hutchison, Zoë L.; Last, Kim S.

    2016-01-01

    The marine environment contains suspended particulate matter which originates from natural and anthropogenic sources. Settlement of this material can leave benthic organisms susceptible to smothering, especially if burial is sudden i.e. following storms or activities such as dredging. Their survival will depend on their tolerance to, and their ability to escape from burial. Here we present data from a multi-factorial experiment measuring burial responses incorporating duration, sediment fraction and depth. Six macroinvertebrates commonly found in sediment rich environments were selected for their commercial and/or conservation importance. Assessments revealed that the brittle star (Ophiura ophiura), the queen scallop (Aequipecten opercularis) and the sea squirt (Ciona intestinalis) were all highly intolerant to burial whilst the green urchin (Psammichinus miliaris) and the anemone (Sagartiogeton laceratus), showed intermediate and low intolerance respectively, to burial. The least intolerant, with very high survival was the Ross worm (Sabellaria spinulosa). With the exception of C. intestinalis, increasing duration and depth of burial with finer sediment fractions resulted in increased mortality for all species assessed. For C. intestinalis depth of burial and sediment fraction were found to be inconsequential since there was complete mortality of all specimens buried for more than one day. When burial emergence was assessed O. ophiura emerged most frequently, followed by P. miliaris. The former emerged most frequently from the medium and fine sediments whereas P. miliaris emerged more frequently from coarse sediment. Both A. opercularis and S. laceratus showed similar emergence responses over time, with A. opercularis emerging more frequently under coarse sediments. The frequency of emergence of S. laceratus increased with progressively finer sediment and C. intestinalis did not emerge from burial irrespective of sediment fraction or depth. Finally, and perhaps

  4. Sediment Burial Intolerance of Marine Macroinvertebrates.

    PubMed

    Hendrick, Vicki J; Hutchison, Zoë L; Last, Kim S

    2016-01-01

    The marine environment contains suspended particulate matter which originates from natural and anthropogenic sources. Settlement of this material can leave benthic organisms susceptible to smothering, especially if burial is sudden i.e. following storms or activities such as dredging. Their survival will depend on their tolerance to, and their ability to escape from burial. Here we present data from a multi-factorial experiment measuring burial responses incorporating duration, sediment fraction and depth. Six macroinvertebrates commonly found in sediment rich environments were selected for their commercial and/or conservation importance. Assessments revealed that the brittle star (Ophiura ophiura), the queen scallop (Aequipecten opercularis) and the sea squirt (Ciona intestinalis) were all highly intolerant to burial whilst the green urchin (Psammichinus miliaris) and the anemone (Sagartiogeton laceratus), showed intermediate and low intolerance respectively, to burial. The least intolerant, with very high survival was the Ross worm (Sabellaria spinulosa). With the exception of C. intestinalis, increasing duration and depth of burial with finer sediment fractions resulted in increased mortality for all species assessed. For C. intestinalis depth of burial and sediment fraction were found to be inconsequential since there was complete mortality of all specimens buried for more than one day. When burial emergence was assessed O. ophiura emerged most frequently, followed by P. miliaris. The former emerged most frequently from the medium and fine sediments whereas P. miliaris emerged more frequently from coarse sediment. Both A. opercularis and S. laceratus showed similar emergence responses over time, with A. opercularis emerging more frequently under coarse sediments. The frequency of emergence of S. laceratus increased with progressively finer sediment and C. intestinalis did not emerge from burial irrespective of sediment fraction or depth. Finally, and perhaps

  5. Resuspension of sediment, a new approach for remediation of contaminated sediment.

    PubMed

    Pourabadehei, Mehdi; Mulligan, Catherine N

    2016-06-01

    Natural events and anthropogenic activities are the reasons of undesirable resuspension of contaminated sediments in aquatic environment. Uncontrolled resuspension could remobilize weakly bound heavy metals into overlying water and pose a potential risk to aquatic ecosystem. Shallow harbours, with contaminated sediments are subjected to the risk of uncontrolled resuspension. Remediation of sediments in these areas cannot be performed by conventional in situ methods (e.g. capping with or without reactive amendment). Ex situ remediation also requires dredging of sediment, which could increase the risk of spreading contaminants. Alternatively, the resuspension technique was introduced to address these issues. The concept of the resuspension method is that finer sediments have a greater tendency to adsorb the contamination. Therefore, finer sediments, believed carry more concentration of contaminants, were targeted for removal from aquatic environment by a suspension mechanism in a confined water column. The objective of this study was to evaluate the feasibility of the resuspension technique as a new approach for remediation of contaminated sediment and a viable option to reduce the risk of remobilization of contaminants in harbours due to an undesirable resuspension event. Unlike the common in situ techniques, the resuspension method could successfully reduce the total concentration of contaminants in almost all samples below the probable effect level (PEL) with no significant change in the quality of overlying water. The results indicated that removal efficiency could be drastically enhanced for metals in sediment with a higher enrichment factor. Moreover, availability of metals (e.g. Cd and Pb) with a high concentration in labile fractions was higher in finer sediments with a high enrichment factor. Consequently, removal of contaminants from sediment through the resuspension method could reduce the risk of mobility and availability of metals under changing

  6. An evaluation of sediment rating curves for estimating suspended sediment concentrations for subsequent flux calculations

    USGS Publications Warehouse

    Horowitz, A.J.

    2003-01-01

    In the absence of actual suspended sediment concentration (SSC) measurements, hydrologists have used sediment rating (sediment transport) curves to estimate (predict) SSCs for subsequent flux calculations. Various evaluations of the sediment rating-curve method were made using data from long-term, daily sediment-measuring sites within large (>1 000 000 km2), medium ( 1000 km2), and small (<1000 km2) river basins in the USA and Europe relative to the estimation of suspended sediment fluxes. The evaluations address such issues as the accuracy of flux estimations for various levels of temporal resolution as well as the impact of sampling frequency on the magnitude of flux estimation errors. The sediment rating-curve method tends to underpredict high, and overpredict low SSCs. As such, the range of errors associated with concomitant flux estimates for relatively short time-frames (e.g. daily, weekly) are likely to be substantially larger than those associated with longer time-frames (e.g. quarterly, annually) because the over- and underpredictions do not have sufficient time to balance each other. Hence, when error limits must be kept under ??20%, temporal resolution probably should be limited to quarterly or greater. The evaluations indicate that over periods of 20 or more years, errors of <1% can be achieved using a single sediment rating curve based on data spanning the entire period. However, somewhat better estimates for the entire period, and markedly better annual estimates within the period, can be obtained if individual annual sediment rating curves are used instead. Relatively accurate (errors sediment fluxes can be obtained from hydrologically based monthly measurements/samples. For 5-year periods or longer, similar results can be obtained from measurements/samples collected once every 2 months. In either case, hydrologically based sampling, as opposed to calendar-based sampling is likely to limit the magnitude of flux estimation

  7. Using Distributed Continuous Turbidity Monitoring to Inform Sediment and Sediment-bound Nutrient Budgets

    NASA Astrophysics Data System (ADS)

    Rizzo, D.; Hamshaw, S. D.; Underwood, K. L.; Wemple, B. C.; Dewoolkar, M.

    2014-12-01

    The State of Vermont is experiencing changing hydrological regimes due to increased precipitation resulting from climate change. Understanding the impacts this change may cause to river corridors and the water quality of receiving waters is a critical need. Estimating the loading of sediment and sediment-bound nutrients such as phosphorous from various sources is a key aspect. In particular, the proportion attributable to main stem bank erosion is of concern as it is suspected to be a significant source in river basins in the Northeast. Sediment and nutrient budgets have been utilized for many years to provide a conceptual framework for proportioning loading to different sources. In this study, a continuous turbidity monitoring station network informs the creation of a watershed sediment budget in a small watershed. Monitoring stations placed on select upstream tributaries as well as the downstream watershed outlet are used to characterize overall watershed yield as well as loading to the main stem from tributaries. Analysis of differential unit area loading from tributary and downstream monitoring sites estimate the proportion of the overall watershed sediment yield that could be attributed to main stem bank erosion. Regression models of suspended sediment and total phosphorous enable the quantification of sediment-bound phosphorous loadings from stream banks. To characterize loadings and overall watershed sediment and nutrient yields, a probabilistic framework is created using a Bayesian approach that enables updating of continuously-collected data and provides estimates of uncertainty resulting in credible ranges of sediment and phosphorous loading. These sediment and nutrient budget estimates along with their associated uncertainties help inform water resource managers of loading sources and enable prioritization of mitigation efforts.

  8. Phosphorus and nitrogen in coral reef sediments

    SciTech Connect

    Entsch, B.; Boto, K.G.; Sim, R.G.; Wellington, J.T.

    1983-05-01

    The occurrence of P and N in the sediments has been investigated on Davies Reef in the central region of the Great Barrier Reef Complex. Concentrations of inorganic P and N in the water were typical of nutrient-depleted tropical surface water. Carbonate sediments were found to contain a uniform pool of P (300 ppm by wt), principally in the form of inorganic phosphate. The interstitial water of the surface layer of sediment contained micromolar concentrations of inorganic P and even higher concentrations of inorganic N, principally as ammonium. These nutrient concentrations were considered too low to compete significantly with the uptake of available phasphate into algae. The presence of ammonium and soluble P was associated with anaerobic redox potentials in the sediments just below the surface. Soluble phosphorus was in equilibrium with a small, rapidly exchangeable fraction of the sedimentary pool of inorganic phosphate. Analyses of P in growing tips of Halimeda and corals (which supply more than half of reef sediments) suggested that the skeletons provide a biological mechanism for the replenishment of at least some of the sedimentary pool. Ratios of C:N:P for a selection of benthic algae were used as a preliminary indicator of thier N and P status.

  9. Reduction of perchlorate in river sediment.

    PubMed

    Simon, Rupert; Weber, Eric J

    2006-04-01

    The transformation of perchlorate was investigated in river sediment during laboratory batch and column studies to determine if reduction of perchlorate is a viable pathway in natural sediment without previous exposure to perchlorate. Perchlorate at an initial concentration of 10 microM was reduced quantitatively to chloride in 3 d after a lag phase of 2 d in sediment slurries amended with lactate. Raising the initial concentration of perchlorate to 1,000 microM increased the lag phase to 20 d before reduction occurred. At perchlorate concentrations greater than 1,000 microM, the reduction of perchlorate was not observed within 40 d. We speculate that the high concentration of perchlorate specifically was problematic to the microbes mediating the reduction of perchlorate. High levels of nitrate inhibited the reduction of perchlorate as well. In sediment slurries amended with 870 microM sodium nitrate, the reduction of perchlorate at an initial concentration of 100 microM did not occur before day 15 of the experiment, but complete removal of nitrate had occurred by day four. Sediment column studies further demonstrated the dependence of perchlorate reduction on endogenous nitrate levels.

  10. Sediment isotope tomography (SIT) model version 1

    SciTech Connect

    Carroll, J.; Abraham, J.D.

    1996-03-08

    Geochronology using {sup 210}Pb is the principal method used to quantify sediment accumulation in rapidly depositing aquatic environments such as lakes, estuaries, continental shelves, and submarine canyons. This method is based on the radioactive decay of {sup 210}Pb with depth in a column of sediment. The decay through time of {sup 210}Pb P(t) is governed by the exponential law P(t) = P{sub 0} exp( -{lambda}t) where P{sub 0} is the surficial concentration at time t = 0, and {lambda} is the decay constant (3.114 {sm_bullet} 10{sup -2} year [yr]{sup -1} for {sup 210}Pb). If the sedimentation rate is constant, then elapsed time t is connected to burial depth x, through x = Vt where V is the sedimentation velocity. Accordingly, P(x) = P{sub 0}exp( -{lambda}x/V). The sedimentation velocity is obtained from an exponential fit to the measured {sup 210}Pb data P(x), with depth x.

  11. Mesoscale eddies transport deep-sea sediments

    PubMed Central

    Zhang, Yanwei; Liu, Zhifei; Zhao, Yulong; Wang, Wenguang; Li, Jianru; Xu, Jingping

    2014-01-01

    Mesoscale eddies, which contribute to long-distance water mass transport and biogeochemical budget in the upper ocean, have recently been taken into assessment of the deep-sea hydrodynamic variability. However, how such eddies influence sediment movement in the deepwater environment has not been explored. Here for the first time we observed deep-sea sediment transport processes driven by mesoscale eddies in the northern South China Sea via a full-water column mooring system located at 2100 m water depth. Two southwestward propagating, deep-reaching anticyclonic eddies passed by the study site during January to March 2012 and November 2012 to January 2013, respectively. Our multiple moored instruments recorded simultaneous or lagging enhancement of suspended sediment concentration with full-water column velocity and temperature anomalies. We interpret these suspended sediments to have been trapped and transported from the southwest of Taiwan by the mesoscale eddies. The net near-bottom southwestward sediment transport by the two events is estimated up to one million tons. Our study highlights the significance of surface-generated mesoscale eddies on the deepwater sedimentary dynamic process. PMID:25089558

  12. Assessment of sediment monitoring at LLNL

    SciTech Connect

    Gallegos, G.

    1994-03-17

    Three separate sediment monitoring studies have been conducted at the Lawrence Livermore National Laboratory (LLNL) Livermore site. ``Sediment`` is defined here as finely divided solid materials that have settled out of an active stream or standing water. Sediment samples from all three studies were analyzed for a number of contaminants including {sup 239}pu, {sup 3}H, gamma emitting radionuclides, heavy metals, volatile organic compounds and pesticides. The analytical results for metals and organic compounds were compared to limits for disposal of hazardous waste, the tritium values were compared to drinking water standards, and the other radionuclides were compared to soils monitoring values. No tritium values were above (or were greater than 55% of drinking water standards), and no other radionuclides in sediments were above soils values. In all of the studies, only two metals, lead and mercury, and six organic compounds, benzo(a)-pyrene, Dieldrin, p,p{prime}-DDT, Endosulfan L endosulfan sulfate, and vinyl chloride were above waste disposal limits. Three of the high contaminants, mercury, benzo(a)-pyrene, and vinyl chloride, were found at one sampling location; the others were not connected by drainage channels or physical proximity to each other. Overall, a total of 247 samples were analyzed, and the sporadic identification of materials over disposal limits demonstrates that there is negligible contamination of sediment.

  13. Sedimentation profiles in Lake Tuscaloosa, Alabama, 2000

    USGS Publications Warehouse

    Stricklin, Victor E.

    2001-01-01

    Lake Tuscaloosa, created in 1969 by the impoundment of North River, is the primary water supply for the cities of Tuscaloosa and Northport, Alabama, and surrounding areas. In 1982, 17 cross-sections were established in the principal tributaries of the lake, which include North River, Dry Creek, Turkey Creek, Binion Creek, Tierce Creek, Carroll Creek, and Brush Creek. These cross-sections were resurveyed in 1986 to determine the amount of sedimentation or scour occurring in the lake at these areas. In May 2000, 14 of the 17 cross-sections were located for resurveying to determine the amount of sedimentation or scour since 1986. The maximum amount of sediment deposition determined from the 2000 survey occurred in the upper end of the Carroll Creek tributary at cross-section CC8 (3.0 feet). The maximum amount of scour occurred in the Turkey Creek tributary at cross-section TRC2 (7.0 feet). Of the 14 cross-sections, 6 indicated increased amounts of sediment deposition, 5 indicated scouring of bottom sediments, and 3 indicated little or no change.

  14. Amyloplast sedimentation kinetics in gravistimulated maize roots

    NASA Technical Reports Server (NTRS)

    Sack, F. D.; Suyemoto, M. M.; Leopold, A. C.

    1985-01-01

    Amyloplast sedimentation in gravistimulated maize (Zea mays L.) roots was measured using the change in angle from the center of the cell to each amyloplast as an index of sedimentation. Using tissue fixed after gravistimulation, the relationship between mean amyloplast angle and the duration of gravistimulation was found to be linear when plotted on a logarithmic time scale. Extrapolated values for the onset of angular change are 5.9 s after the start of gravistimulation for the entire population of amyloplasts and 11.8 s for lead amyloplasts. By multiplying the instantaneous angular velocity (in radians) by the cell center to amyloplast radius, it is possible to calculate the initial sedimentation velocity to be 19.1 micrometers min-1 at 5.9 s. During sedimentation, the mean amyloplast angles surpass the calculated cell corner angle of 123 at 2.2 min for all amyloplasts and at 19 s for lead amyloplasts near the new lower wall. Thus, substantial sedimentation occurs within the presentation time, calculated to be 4.1 min. These kinetics are consistent with several hypotheses of graviperception.

  15. Mesoscale eddies transport deep-sea sediments.

    PubMed

    Zhang, Yanwei; Liu, Zhifei; Zhao, Yulong; Wang, Wenguang; Li, Jianru; Xu, Jingping

    2014-01-01

    Mesoscale eddies, which contribute to long-distance water mass transport and biogeochemical budget in the upper ocean, have recently been taken into assessment of the deep-sea hydrodynamic variability. However, how such eddies influence sediment movement in the deepwater environment has not been explored. Here for the first time we observed deep-sea sediment transport processes driven by mesoscale eddies in the northern South China Sea via a full-water column mooring system located at 2100 m water depth. Two southwestward propagating, deep-reaching anticyclonic eddies passed by the study site during January to March 2012 and November 2012 to January 2013, respectively. Our multiple moored instruments recorded simultaneous or lagging enhancement of suspended sediment concentration with full-water column velocity and temperature anomalies. We interpret these suspended sediments to have been trapped and transported from the southwest of Taiwan by the mesoscale eddies. The net near-bottom southwestward sediment transport by the two events is estimated up to one million tons. Our study highlights the significance of surface-generated mesoscale eddies on the deepwater sedimentary dynamic process.

  16. Sediment, land use, and freshwater mussels: Prospects and problems

    USGS Publications Warehouse

    Brim-Box, J.; Mossa, J.

    1999-01-01

    The decline in freshwater mussel populations in many river basins throughout North America has been attributed, in part, to land-use modifications that cause changes in sediment regimes. However, the specific associations that mussels have with stream sediments are poorly understood, making it difficult to assess the impacts of changes in sedimentation rates on unionid mussels. Both bed and suspended materials, and concomitant changes in channel form associated with changes in sediment supply, may affect mussels in numerous ways at various stages in their life cycle. Considerable debate and uncertainty remains regarding the strength of associations between sediments and mussels, including whether increased sedimentation is a cause of recent mussel declines. It is important to be aware of appropriate procedures for sampling and analyzing fluvial sediments, and the nature of sediment sources, to adequately assess relationships between unionid mussels and fluvial sediments.

  17. Air emissions from exposed contaminated sediments and dredged material

    SciTech Connect

    Valsaraj, K.T.; Ravikrishna, R.; Reible, D.D.; Thibodeaux, L.J.; Choy, B.; Price, C.B.; Brannon, J.M.; Myers, T.E.; Yost, S.

    1999-01-01

    The sediment-to-air fluxes of two polycyclic aromatic hydrocarbons (phenanthrene and pyrene) and a heterocyclic aromatic hydrocarbon (dibenzofuran) from a laboratory-contaminated sediment and those of three polycyclic aromatic hydrocarbons (naphthalene, phenanthrene, and pyrene) from three field sediments were investigated in experimental microcosms. The flux was dependent on the sediment moisture content, air-filled porosity, and the relative humidity of the air flowing over the sediment surface. The mathematical model predictions of flux from the laboratory-spiked sediment agreed with observed values. The fluxes of compounds with higher hydrophobicity were more air-side resistance controlled. Conspicuous differences were observed between the fluxes from the laboratory-spiked and two of the three field sediments. Two field sediments showed dramatic increases in mass-transfer resistances with increasing exposure time and had significant fractions of oil and grease. The proposed mathematical model was inadequate for predicting the flux from the latter field sediments. Sediment reworking enhanced the fluxes from the field sediments due to exposure of fresh solids to the air. Variations in flux from the lab-spiked sediment as a result of change in air relative humidity were due to differences in retardation of chemicals on a dry or wet surface sediment. High moisture in the air over the dry sediment increased the competition for sorption sites between water and contaminant and increased the contaminant flux.

  18. Carotenoid diagenesis in a marine sediment

    NASA Technical Reports Server (NTRS)

    Watts, C. D.; Maxwell, J. R.

    1977-01-01

    The major carotenoids at three levels (3, 40, and 175 m below the sediment-water interface) in a core from a marine sediment (Cariaco Trench, off Venezuela) have been examined. Mass and electronic spectral data have provided evidence for the onset of a progressive reduction of carotenoids in the geological column. The time scale of the process appears to depend on the particular carotenoid. Reduction of up to two double bonds is observed for the diol, zeaxanthin, in the oldest sediment (about 340,000 years old) but no reduction is observed in the younger samples (about 5000 and 56,000 years old). The diketone, canthaxanthin, shows evidence of reduction of up to two double bonds in the 56,000-yr sample and up to five double bonds in the oldest sample. No reduction of beta-carotene was observed in any of the samples.

  19. Toxicity of sediment-incorporated drilling fluids

    SciTech Connect

    Clark, J.R.; Patrick, J.M.

    1987-01-01

    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 calculate EC50s at the same times that LC50s were determined. Observations of the burrowing behavior allowed quantitation of effects after 24-h exposures to each of the drilling fluids whereas lancelet mortality was sufficient to calculate 24-h LC50s for only one drilling fluid. Drilling fluids were less toxic to lancelets when incorporated into sediments than to mysids (Mysidopsis bahia) or benthic invertebrate communities in water-column exposures.

  20. Degradation of methyl bromide in anaerobic sediments

    USGS Publications Warehouse

    Oremland, R.S.; Miller, L.G.; Strohmaler, F.E.

    1994-01-01

    Methyl bromide (MeBr) was anaerobically degraded in saltmarsh sediments after reaction with sulfide. The product of this nucleophilic substitution reaction was methanethiol, which underwent further chemical and bacterial reactions to form dimethyl sulfide. These two gases appeared transiently during sediment incubations because they were metabolized by methanogenic and sulfate-reducing bacteria. A second, less significant reaction of MeBr was the exchange with chloride, forming methyl chloride, which was also susceptible to attack by sulfide. Incubation of 14C-labeled methyl iodide as an analogue of MeBr resulted in the formation of 14CH4 and 14CO2 and also indicated that sulfate-reducing bacteria as well as methanogens metabolized the methylated sulfur intermediates. These results suggest that exposed sediments with abundant free sulfide, such as coastal salt-marshes, may constitute a sink for atmospheric MeBr.

  1. Marine clathrate mining and sediment separation

    DOEpatents

    Borns, David J.; Hinkebein, Thomas E.; Lynch, Richard W.; Northrop, David A.

    2001-01-01

    A method and apparatus for mining of hydrocarbons from a hydrocarbon-containing clathrate such as is found on the ocean floor. The hydrocarbon containing clathrate is disaggregated from sediment by first disrupting clathrate-containing strata using continuous mining means such as a rotary tilling drum, a fluid injector, or a drill. The clathrate-rich portion of sediment thus disrupted from the sea floor strata are carried through the apparatus to regions of relative lower pressure and/or relative higher temperature where the clathrate further dissociates into component hydrocarbons and water. The hydrocarbon is recovered with the assistance of a gas that is injected and buoys the hydrocarbon containing clathrate helping it to rise to regions of lower pressure and temperature where hydrocarbon is released. The sediment separated from the hydrocarbon returns to the ocean floor.

  2. History of the Federal Interagency Sedimentation Project

    USGS Publications Warehouse

    Skinner, John V.

    1989-01-01

    Since 1939, the date of the Project's inception, the team has operated under the direction of two lead agencies - the U.S. Geological Survey and U.S. Army Corps of Engineers. The supporting agencies are the Agricultural Research Service, Bureau of Reclamation, U.S. Forest Service, Bureau of Land Management, Federal Highway Administration, and the Tennessee Valley Authority. Overall direction of the Project rests with the Subcommittee on Sedimentation, Interagency Advisory Committee on Water Data. The Project's goals focus on improving and maintaining the quality of fluvial sediment data by (1) developing sediment samplers, laboratory analyzers, and automatic gages (2) evaluating methods, (3) standardizing equipment and methods and (4) procuring, calibrating and selling equipment.

  3. Meiofauna increases bacterial denitrification in marine sediments

    PubMed Central

    Bonaglia, S.; Nascimento, F. J. A; Bartoli, M.; Klawonn, I.; Brüchert, V.

    2014-01-01

    Denitrification is a critical process that can alleviate the effects of excessive nitrogen availability in aquatic ecosystems subject to eutrophication. An important part of denitrification occurs in benthic systems where bioturbation by meiofauna (invertebrates <1 mm) and its effect on element cycling are still not well understood. Here we study the quantitative impact of meiofauna populations of different abundance and diversity, in the presence and absence of macrofauna, on nitrate reduction, carbon mineralization and methane fluxes. In sediments with abundant and diverse meiofauna, denitrification is double that in sediments with low meiofauna, suggesting that meiofauna bioturbation has a stimulating effect on nitrifying and denitrifying bacteria. However, high meiofauna densities in the presence of bivalves do not stimulate denitrification, while dissimilatory nitrate reduction to ammonium rate and methane efflux are significantly enhanced. We demonstrate that the ecological interactions between meio-, macrofauna and bacteria are important in regulating nitrogen cycling in soft-sediment ecosystems. PMID:25318852

  4. Lipids of aquatic sediments, recent and ancient

    NASA Technical Reports Server (NTRS)

    Eglinton, G.; Hajibrahim, S. K.; Maxwell, J. R.; Quirke, J. M. E.; Shaw, G. J.; Volkman, J. K.; Wardroper, A. M. K.

    1979-01-01

    Computerized gas chromatography-mass spectrometry (GC-MS) is now an essential tool in the analysis of the complex mixtures of lipids (geolipids) encountered in aquatic sediments, both 'recent' (less than 1 million years old) and ancient. The application of MS, and particularly GC-MS, has been instrumental in the rapid development of organic geochemistry and environmental organic chemistry in recent years. The techniques used have resulted in the identification of numerous compounds of a variety of types in sediments. Most attention has been concentrated on molecules of limited size, mainly below 500 molecular mass, and of limited functionality, for examples, hydrocarbons, fatty acids and alcohols. Examples from recent studies (at Bristol) of contemporary, 'recent' and ancient sediments are presented and discussed.

  5. Sediment Budgeting in Dam-Affected Rivers: Assessing the Influence of Damming, Tributaries, and Alluvial Valley Sediment Storage on Sediment Regimes

    NASA Astrophysics Data System (ADS)

    Wilcox, A. C.; Dekker, F. J.; Riebe, C. S.

    2014-12-01

    Although sediment supply is recognized as a fundamental driver of fluvial processes, measuring how dams affect sediment regimes and incorporating such knowledge into management strategies remains challenging. To determine the influences of damming, tributary supply, and valley morphology and sediment storage on downstream sediment supply in a dryland river, the Bill Williams River (BWR) in western Arizona, we measured basin erosion rates using cosmogenic nuclide analysis of beryllium-10 (10Be) at sites upstream and downstream of a dam along the BWR, as well as from tributaries downstream of the dam. Riverbed sediment mixing calculations were used to test if the dam, which blocks sediment supply from the upper 85% of the basin's drainage area, increases the proportion of tributary sediment to residual upstream sediment in mainstem samples downstream of the dam. Erosion rates in the BWR watershed are more than twice as large in the upper catchment (136 t km-2 yr-1) than in tributaries downstream of Alamo Dam (61 t km-2 yr-1). Tributaries downstream of the dam have little influence on mainstem sediment dynamics. The effect of the dam on reducing sediment supply is limited, however, because of the presence of large alluvial valleys along the mainstem BWR downstream of the dam that store substantial sediment and mitigate supply reductions from the upper watershed. These inferences, from our 10Be derived erosion rates and mixing calculations, are consistent with field observations of downstream changes in bed material size, which suggest that sediment-deficit conditions are restricted to a 10 km reach downstream of the dam, and limited reservoir bathymetry data. Many studies have suggested that tributary sediment inputs downstream of dams play a key role in mitigating dam-induced sediment deficits, but here we show that in a dryland river with ephemeral tributaries, sediment stored in alluvial valleys can also play a key role and in some cases trumps the role of

  6. Sediment thickness in the southern Canada Basin

    USGS Publications Warehouse

    May, S.D.; Grantz, A.

    1990-01-01

    Multichannel seismic reflection data are used, in conjunction with deep crustal seismic refraction data, to estimate the thickness of sediments in the southern Canada Basin of the Arctic Ocean north of Alaska. The sediments are interpreted to be of Hauterivian (mid-Early Cretaceous) to Holocene age. Comparison of the seismic reflection character of seismic reflections in the study area with that in other basins indicates that a base-of-sediment-top of oceanic layer 2 reflection is not present above the depth at which the water-bottom multiple obscures all deeper arrivals, which is in conflict with the conclusions drawn from aeromagnetic, refraction, and other reflection studies. Seismic velocity structure, determined from the reflection data, indicates that the reflections above the multiple are from sedimentary strata. In the absence of seismic reflection evidence for the top of layer 2 above the multiple, we estimate total sediment thickness by using the layer 3 refractions and subtracting an average assumed layer 2 thickness from the top of layer 3. Assuming that an average thickness of oceanic layer 2 (1.4 km) overlies layer 3 in the southern Canada Basin, sediment thickness in the study area is estimated to range between 6.5 km where water depth is 3.8 km to greater than 11 km where the water depth is 2 km. This is nearly double that of any previous estimates and should have a significant effect on calculations such as the age of Canada Basin, regional heat flow, and long-term sedimentation rates. ?? 1990.

  7. Metal and sediment ingestion by dabbling ducks

    USGS Publications Warehouse

    Beyer, W.N.; Spann, J.; Day, D.

    1999-01-01

    The chemical analysis of intestinal digesta from hunter-killed carcasses or of wildlife scat is a promising means of estimating the exposure of wildlife to those environmental contaminants that, like lead, are poorly absorbed in the digestive tract. When evaluating contaminants at a site, biologists may find the results of this non-destructive approach more straightforward to interpret in terms of exposure to wildlife than would be analyses of soils, sediments, water, or wildlife tissues. To illustrate the approach, we collected digesta from 47 waterfowl shot by hunters at Prime Hook National Wildlife Refuge, in Delaware, USA. The waterfowl digesta contained an average of approximately 2.4% sediment, estimated from the Al concentrations in the digesta, a marker for sediment. Al concentrations were significantly correlated with concentrations of Cr (Spearman's rank correlation coefficient, r=0.57), V (r=0.70), Ni (r=0.31), and Pb (r=0.55), and we concluded that these metals were ingested mainly with sediment. American widgeon (Anas americana) ingested sediment at a rate of about four times that of three other species of dabbling ducks (Anas crecca, A. acuta, A. rubripes) and had several times the exposure to the sediment-associated metals. The digesta of one American black duck contained a high concentration of lead (70 mg/kg, dry wt.), presumably from lead shot, but none of the other samples had notably elevated metal concentrations. We suggest that scat and digesta be analyzed more widely by biologists and resource managers seeking a simple, inexpensive assessment of contaminants in local wildlife habitat.

  8. Dating sediment cores from Hudson River marshes

    SciTech Connect

    Robideau, R.; Bopp, R.F. . Dept. of Earth and Environmental Sciences)

    1993-03-01

    There are several methods for determining sediment accumulation rates in the Hudson River estuary. One involves the analysis of the concentration of certain radionuclides in sediment core sections. Radionuclides occur in the Hudson River as a result of: natural sources, fallout from nuclear weapons testing and low level aqueous releases from the Indian Point Nuclear Power Facility. The following radionuclides have been studied in the authors work: Cesium-137, which is derived from global fallout that started in the 1950's and has peaked in 1963. Beryllium-7, a natural radionuclide with a 53 day half-life and found associated with very recently deposited sediments. Another useful natural radionuclide is Lead-210 derived from the decay of Radon-222 in the atmosphere. Lead-210 has a half-life of 22 years and can be used to date sediments up to about 100 years old. In the Hudson River, Cobalt-60 is a marker for Indian Point Nuclear Reactor discharges. The author's research involved taking sediment core samples from four sites in the Hudson River Estuarine Research Reserve areas. These core samples were sectioned, dried, ground and analyzed for the presence of radionuclides by the method of gamma-ray spectroscopy. The strength of each current pulse is proportional to the energy level of the gamma ray absorbed. Since different radionuclides produce gamma rays of different energies, several radionuclides can be analyzed simultaneously in each of the samples. The data obtained from this research will be compared to earlier work to obtain a complete chronology of sediment deposition in these Reserve areas of the river. Core samples may then by analyzed for the presence of PCB's, heavy metals and other pollutants such as pesticides to construct a pollution history of the river.

  9. Meiofauna Metabolism in Suboxic Sediments: Currently Overestimated

    PubMed Central

    Braeckman, Ulrike; Vanaverbeke, Jan; Vincx, Magda; van Oevelen, Dick; Soetaert, Karline

    2013-01-01

    Oxygen is recognized as a structuring factor of metazoan communities in marine sediments. The importance of oxygen as a controlling factor on meiofauna (32 µm-1 mm in size) respiration rates is however less clear. Typically, respiration rates are measured under oxic conditions, after which these rates are used in food web studies to quantify the role of meiofauna in sediment carbon turnover. Sediment oxygen concentration ([O2]) is generally far from saturated, implying that (1) current estimates of the role of meiofauna in carbon cycling may be biased and (2) meiofaunal organisms need strategies to survive in oxygen-stressed environments. Two main survival strategies are often hypothesized: 1) frequent migration to oxic layers and 2) morphological adaptation. To evaluate these hypotheses, we (1) used a model of oxygen turnover in the meiofauna body as a function of ambient [O2], and (2) performed respiration measurements at a range of [O2] conditions. The oxygen turnover model predicts a tight coupling between ambient [O2] and meiofauna body [O2] with oxygen within the body being consumed in seconds. This fast turnover favors long and slender organisms in sediments with low ambient [O2] but even then frequent migration between suboxic and oxic layers is for most organisms not a viable strategy to alleviate oxygen limitation. Respiration rates of all measured meiofauna organisms slowed down in response to decreasing ambient [O2], with Nematoda displaying the highest metabolic sensitivity for declining [O2] followed by Foraminifera and juvenile Gastropoda. Ostracoda showed a behavioral stress response when ambient [O2] reached a critical level. Reduced respiration at low ambient [O2] implies that meiofauna in natural, i.e. suboxic, sediments must have a lower metabolism than inferred from earlier respiration rates conducted under oxic conditions. The implications of these findings are discussed for the contribution of meiofauna to carbon cycling in marine sediments

  10. Redistribution of intertidal sediment contaminants by microphytobenthos

    NASA Astrophysics Data System (ADS)

    Becker, Amani; Copplestone, David; Tyler, Andrew; Smith, Nick; Sneddon, Christopher

    2014-05-01

    Microphytobenthos (MPB) is a mixed community of microscopic algae inhabiting the top few millimetres of bottom sediment in the intertidal zone. It is a key component of the estuarine ecosystem, interacting with the sediment and fauna to influence sediment distribution and resuspension and forming the base of the estuarine food chain. Estuarine sediments, with which the MPB is closely associated, are a significant sink for contaminants from both fluvial and marine sources. Algae are known to have the capacity to take up contaminants, and the phytoplankton has been well studied in this respect, however there has been little research involving MPB. The extent to which contaminant uptake by MPB occurs and under what conditions is therefore very poorly understood. It seems probable that the paucity of research in this area is due to the complexity of the bioavailability of contaminants in the intertidal zone coupled with difficulties in separating MPB from the sediment. A series of experiments are proposed in which we will investigate (at a range of spatial scales) contaminant partitioning in the presence of MPB; the effect of changing temperatures on contaminant uptake and toxicity to MPB; effects of sediment resuspension on contaminant availability and uptake to MPB; and the uptake of contaminants from MPB to molluscs. A mesocosm (or experimental enclosure) is being constructed to replicate the natural system and enable manipulation of conditions of interest. This will attain greater realism than laboratory toxicity tests, with more statistical power than can be achieved through field studies. By gaining a better understanding of processes governing contaminant bioavailability and mechanisms for uptake by MPB it will be possible to relate these to projected climate change effects and ascertain potential consequences for contaminant redistribution.

  11. Regulating contaminated sediments in aquatic environments: A hydrologic perspective

    NASA Astrophysics Data System (ADS)

    Marcus, W. Andrew

    1989-11-01

    A number of state and federal agencies are presently attempting to develop management strategies for contaminated aquatic sediments. Until now, research and debate on sediment guidelines and regulations has focused almost exclusively on biological and chemical techniques for determining when sediments pose an environmental risk. Hydrologic factors must also be considered, however, if these biochemically based techniques for establishing sediment quality standards are to be feasible. Hydrologic issues that need to be addressed include how to define the boundaries of the aquatic environment, the scope of sediment regulations in ephemeral waters, regulations and sampling procedures in heterogeneous sediments, and timing of samples for monitoring and enforcement purposes

  12. Sediment sources and their contribution along northern coast of the South China Sea: Evidence from clay minerals of surface sediments

    NASA Astrophysics Data System (ADS)

    Liu, Jianguo; Yan, Wen; Chen, Zhong; Lu, Jun

    2012-09-01

    Clay minerals of surface sediment samples from nine bays/harbors along northern coast of the South China Sea (SCS) are used for sediment sources and contribution estimation in the study areas. Results reveal that sediments in the study bays/harbors seem to be a mixture of sediments from the Pearl, Hanjiang River and local islands/rivers, but their clay mineral assemblage is distinct from that of Luzon and Taiwan sediments, indicating that sediments are derived mainly from the neighboring sources through riverine input and partly from localized sediments. Due to input of local sediments in the northern SCS, sediments from both east of the Leizhou Peninsula (Area IV) and next to the Pearl River estuary (PRE, Area II) have high smectite percent. Affected by riverine input of the Pearl and Hanjiang Rivers, sediments in west of the PRE (Area III) and east of the PRE (Area I) have high illite (average 47%) and kaolinite (54%) percents, respectively. Sediment contributions of various major sources to the study areas are estimated as the following: (1) the Hanjiang River provide 95% and 84% sediments in Areas I and II, respectively, (2) the Pearl River supply 79% and 29% sediments in Areas III and IV, respectively and (3) local sediments contribute the rest and reach the maximum (˜71%) in Area IV.

  13. Estimated post-Messinian sediment supply and sedimentation rates on the Ebro continental margin, Spain

    USGS Publications Warehouse

    Nelson, C.H.

    1990-01-01

    Because of the extensive data base of seismic profiles, radiometric ages, and stratigraphic time markers such as the subaerial Messinian surface, sedimentation rates and Ebro River sediment discharge can be estimated for different periods and environments of the Ebro continental margin. New values for sediment discharge (i.e., 6.2 versus previous estimates of 2-3.5 million t/yr) for the Holocene highstand are more reliable but remain minimum estimates because a small proportion of Ebro sediment advected to the Balearic Rise and Abyssal Plain cannot be accounted for, especially during lowstands. The general highstand conditions of the Pliocene, which were similar to those of the Holocene, resulted in a low discharge of Ebro River sediment (ca. 6.5 million t/yr) and an even thickness of sediment across the margin that deposited at rates of about 24-40 cm/ky. In contrast, sediment supply increased two-three times during the Pleistocene, the margin prograded rapidly and deposition occurred at rates of 101-165 cm/ky on the outer shelf and slope, but basin floor rates remained anomalously low (21-26 cm/ky) because sediment was drained and broadly dispersed eastward in Valencia Trough. During the late Pleistocene rise of sea level, the main depocenters progressively shifted shoreward and sedimentation rates greatly decreased from 175 cm/ky on the upper slope during the early transgression to 106 cm/ky on the outer shelf and then to 63 cm/ky on the mid-shelf during the late transgression as the river sediment discharge dropped to half by Holocene time. Maximal sedimentation rates occurred in active depocenters of sediment dispersal such as the Holocene delta (370 cm/ky) or the youngest Pleistocene Oropesa channel-levee complex (705 cm/ky) where deposition rates increased by an order of magnitude or more compared to average Ebro shelf (38 cm/ky) or base-of-slope rates in the Pleistocene (21 cm/ky). The sedimentation rates verify the importance of sea-level control on the

  14. 300 Area process trench sediment analysis report

    SciTech Connect

    Zimmerman, M.G.; Kossik, C.D.

    1987-12-01

    This report describes the results of a sampling program for the sediments underlying the Process Trenches serving the 300 Area on the Hanford reservation. These Process Trenches were the subject of a Closure Plan submitted to the Washington State Department of Ecology and to the US Environmental Protection Agency in lieu of a Part B permit application on November 8, 1985. The closure plan described a proposed sampling plan for the underlying sediments and potential remedial actions to be determined by the sample analyses results. The results and proposed remedial action plan are presented and discussed in this report. 50 refs., 6 figs., 8 tabs.

  15. Anthropopression markers in lake bottom sediments

    NASA Astrophysics Data System (ADS)

    Nadolna, Anna; Nowicka, Barbara

    2014-05-01

    Lakes are vulnerable to various types of anthropogenic disturbances. Responses of lake ecosystems to environmental stressors are varied and depend not only on the type of a factor but also on the lake natural resistance to degradation. Within the EULAKES project an evaluation of anthropogenic stress extent in a flow-through, postglacial, ribbon lake (Lake Charzykowskie) was carried out. It was assumed, that this impact manifests unevenly, depending on a type and degree of the pressure on the shore zones, water quality of tributaries, lake basin shape and dynamics of a water movement. It was stated, that anthropogenic markers are substances accumulated in bottom sediments as a result of allochthonous substances inflow from the catchment and atmosphere. Along the selected transects 105 samples from the top layer of sediments (about 20 cm) was collected representing the contemporary accumulation (about 15 years). The content of selected chemical elements and compounds was examined, including nutrients (TN and TP), heavy metals (arsenic, cadmium, lead, chromium, nickel, copper, zinc, mercury, iron, and manganese) and pesticides (DDT, DDD, DDE, DMDT , γ-HCH). The research was conducted in the deepest points of each lake basin and along the research transects - while choosing the spots, the increased intensity of anthropogenic impact (ports, roads with heavy traffic, wastewater discharge zones, built-up areas) was taken into consideration. The river outlets to the lake, where there are ecotonal zones between limnic and fluvial environment, were also taken into account. Analysis of the markers distribution was carried out against the diversity of chemical characteristics of limnic sediments. Ribbon shape of the lake basin and the dominant wind direction provide an opportunity of easy water mixing to a considerable depth. Intensive waving processes cause removal of the matter from the littoral zone towards lake hollows (separated by the underwater tresholds), where the

  16. Lutocline Mixing and sediment wave interaction

    NASA Astrophysics Data System (ADS)

    Medina, P.; Gonzalez/Nieto, P. L.

    2010-05-01

    Coastal mixing induced by waves is modeled experimentally by means of an oscillating grid, [1,2]when the boundary layer is turbulent as when waves generated by a storm break and spill, or when wind interacts with wave stirring, then a strong turbulence lifts off bottom sediments and these often form a distinct sediment laden region capped by a sharp density interface called in this case a Lutocline. These particle layer may be transported to deeper regions by compensation or gravity currents[3,4]. Point velocity distributions created by wind, waves and sloping currents are dominated by breaker areas which act as strong attractors for the sediments in suspension, because at the same time there is a higher mean water level near the coast due to wave radiation[5]. The combination of offshore and onshore together with the longshore and crosshore strong currents due to wave radiation imbalance produce the strongest local shear induced morphological sediment transport. The use of a circular Couette flow to hold sediments in suspension using a vortex generator (producing shear) or an oscilating grid is used to investigate the parameter range of sediment lift off. [1] Crespo A. and Redondo J.M.(1989) A simple experiment on the interaction between gravity currents and sediment transport, Rev. de Geofisica 45, 203-210. [2] Redondo J.M. and Cantalapiedra I.R. (1993) Mixing in horizontally heterogeneous flows", Applied Scientific Research, 51, 217-222 [3] J.E. Simpson (1997) Gravity Currents: In the Environment and the Laboratory, 2nd Edition, Cambridge University Press, Cambridge, England. [4] R.S.J. Sparks, R.T. Bonnecaze, H.E. Huppert, J.R. Lister, M.A. Hallworth, H. Mader, J. Phillips (1993) Sediment-laden gravity currents with reversing buoyancy, Earth Planet. Sci. Lett. 114. 243-257. [5] Bezerra M.O., Diez M., Medeiros C. Rodriguez A., Bahia E., Sanchez Arcilla A and Redondo J.M. (1998) Study on the influence of waves on coastal diffusion using image analysis. Applied

  17. Sediment studies at Bikini Atoll part 2. inventories of transuranium elements in surface sediments

    SciTech Connect

    Noshkin, V.E.; Eagle, R.J.; Wong, K.M.; Robison, W.L.

    1997-10-01

    This is the second of three reports on Bikini sediment studies, which discusses the concentrations and inventories of {sup 241}Am and {sup 239+240}Pu in sediments from the lagoon. Surface sediment samples were collected from 87 locations over the entire lagoon at Bikini Atoll during 1979. The collections were made to map the distribution of long-lived radionuclides associated with the bottom material and to show what modifications occurred in the composition of the sediment as a result of the testing program. Present inventories for {sup 241}Am and {sup 239+240}Pu in the surface 2 cm of sediment are estimated to be 14 and 17 TBq, respectively. These values are estimated to represent only 14% of the total inventory in the sediment column. Sediment inventories of {sup 239+240}Pu and {sup 241}Am are changing only slowly with time through chemical- physical processes that continuously mobilize small amounts of the transuranics to the water column. The lowest concentrations and inventories are associated with deposits logoonward of the eastern reef.

  18. Modeling methane bubble growth in fine-grained muddy aquatic sediments: correlation with sediment properties

    NASA Astrophysics Data System (ADS)

    Katsman, Regina

    2015-04-01

    Gassy sediments contribute to destabilization of aquatic infrastructure, air pollution, and global warming. In the current study a precise shape and size of the buoyant mature methane bubble in fine-grained muddy aquatic sediment is defined by numerical and analytical modeling, their results are in a good agreement. A closed-form analytical solution defining the bubble parameters is developed. It is found that the buoyant mature bubble is elliptical in its front view and resembles an inverted tear drop in its cross-section. The size and shape of the mature bubble strongly correlate with sediment fracture toughness. Bubbles formed in the weaker sediments are smaller and characterized by a larger surface-to volume ratio that induces their faster growth and may lead to their faster dissolution below the sediment-water interface. This may prevent their release to the water column and to the atmosphere. Shapes of the bubbles in the weaker sediments deviate further from the spherical configuration, than those in the stronger sediments. Modeled bubble characteristics, important for the acoustic applications, are in a good agreement with field observations and lab experiments.

  19. Evaluation of sediment yield and sediment data-collection network in the Piceance basin, northwestern Colorado

    USGS Publications Warehouse

    Kircher, J.E.; Von Guerard, Paul

    1982-01-01

    Statistical relationships were developed between suspended-sediment discharge and several regional factors of climate, physiography, and land use in the Piceance basin, northwestern Colorado. The purpose of the study was to evaluate the existing sediment collection network, especially in regard to detecting changes in suspended-sediment discharge due to the development in the basin. Spatial- and time variability were examined using multiple linear regression techniques. Because of the short period of record, monthly mean sediment loads were used to determine shifts or changes in trends due to mining and related activities in the basin. Dummy variable analysis was used to detect these premining and postmining differences in the regression lines and also to detect seasonal differences in the sediment discharge. Differences did exist in the sediment discharge from season to season and before and after mining; however, due to the variability and short period of record the cause of these differences could not be adequately determined. Part of the high variability in sediment discharge was due to variability in the water discharge. Therefore, if the network is to be improved, the emphasis needs to be on improvement of the water-discharge. The results of the monthly mean regression analysis were used in the mean monthly and mean annual analysis for determination of initial network design equations. These were only preliminary in nature and could be improved with additional data. (USGS)

  20. Sediment mixing and accumulation rate effects on radionuclide depth profiles in Hudson estuary sediments

    SciTech Connect

    Olsen, C.R.; Simpson, H.J.; Peng, T.H.; Bopp, R.F.; Trier, R.M.

    1981-11-01

    Measured anthropogenic radionuclide profiles in sediment cores from the Hudson River estuary were compared with profiles computed by using known input histories of radionuclides to the estuary and mixing coefficients which decreased exponentially with depth in the sediment. Observed /sup 134/Cs sediment depth profiles were used in the mixing rate computation because reactor releases were the only significant source for this nuclide, whereas the inputs of /sup 137/Cs and /sup 239,240/Pu to the estuary were complicated by runoff or erosion in upstream areas, in addition to direct fallout from precipitation. Our estimates for the rates of surface sediment mixing in the low salinity reach of the estuary range from 0.25 to 1 cm/sup 2//yr, or less. In some areas of the harbor adjacent to New York City, where fine-particle accumulation rates are generally 3 cm/yr, and often as high as 10 to 20 cm/yr, sediment mixing rates as high as 10 cm/sup 2//yr would have little effect on radionuclide peak distributions. Consequently, anthropogenic radionuclide maximum activities in subsurface sediments of the Hudson appear to be useful as time-stratigraphic reference levels, which can be correlated with periods of maximum radionuclide inputs for estimating rates and patterns of sediment accumulation. 10 figures.

  1. Sediment mixing and accumulation rate effects on radionuclide depth profiles in Hudson estuary sediments

    SciTech Connect

    Olsen, C.R.; Simpson, H.J.; Peng, T.; Bopp, R.F.; Trier, R.M.

    1981-11-20

    Measured anthropogenic radionuclide profiles in sediment cores from the Hudson River estuary were compared with profiles computed by using known input histories of radionuclides to the estuary and mixing coefficients which decreased exponentially with depth in the sediment. Observed /sup 134/Cs sediment depth profiles were used in the mixing rate computation because reactor releases were the only significant source for this nuclide, whereas the inputs of /sup 137/Cs and /sup 239.240/Pu to the estuary were complicated by runoff or erosion in upstream areas, in addition to direct fallout from precipitation. Our estimates for the rates of surface sediment mixing in the low salinity reach of the estuary range from 0.25 to 1 cm/sup 2//yr, or less. In some areas of the harbor adjacent to New York City, were fine-particle accumulation rates are generally >3 cm/yr, and often as high as 10 to 20 cm/yr, sediment mixing rates as high as 10 cm/sup 2//yr would have little effect on radionuclide peak distributions. Consequently, anthropogenic radionuclide maximum activities in subsurface sediments of the Hudson appear to be useful as time-stratigraphic reference levels, which can be correlated with periods of maximum radionuclide inputs for estimating rates and patterns of sediment accumulation.

  2. Colorado River sediment transport 1. Natural sediment supply limitation and the influence of Glen Canyon Dam

    USGS Publications Warehouse

    Topping, D.J.; Rubin, D.M.; Vierra, L.E.

    2000-01-01

    Analyses of flow, sediment-transport, bed-topographic, and sedimentologic data suggest that before the closure of Glen Canyon Dam in 1963, the Colorado River in Marble and Grand Canyons was annually supply-limited with respect to fine sediment (i.e., sand and finer material). Furthermore, these analyses suggest that the predam river in Glen Canyon was not supply-limited to the same degree and that the degree of annual supply limitation increased near the head of Marble Canyon. The predam Colorado River in Grand Canyon displays evidence of four effects of supply limitation: (1) seasonal hysteresis in sediment concentration, (2) seasonal hysteresis in sediment grain size coupled to the seasonal hysteresis in sediment concentration, (3) production of inversely graded flood deposits, and (4) development or modification of a lag between the time of a flood peak and the time of either maximum or minimum (depending on reach geometry) bed elevation. Analyses of sediment budgets provide additional support for the interpretation that the predam river was annually supply-limited with respect to fine sediment, but it was not supply-limited with respect to fine sediment during all seasons. In the average predam year, sand would accumulate and be stored in Marble Canyon and upper Grand Canyon for 9 months of the year (from July through March) when flows were dominantly below 200-300 m3/s; this stored sand was then eroded during April through June when flows were typically higher. After closure of Glen Canyon Dam, because of the large magnitudes of the uncertainties in the sediment budget, no season of substantial sand accumulation is evident. Because most flows in the postdam river exceed 200-300 m3/s, substantial sand accumulation in the postdam river is unlikely.

  3. Toxicity of silicon carbide nanowires to sediment-dwelling invertebrates in water or sediment exposures

    USGS Publications Warehouse

    Mwangi, Joseph N.; Wang, Ning; Ritts, Andrew; Kunz, James L.; Ingersoll, Christopher G.; Li, Hao; Deng, Baolin

    2011-01-01

    Silicon carbide nanowires (SiCNW) are insoluble in water. When released into an aquatic environment, SiCNW would likely accumulate in sediment. The objective of this study was to assess the toxicity of SiCNW to four freshwater sediment-dwelling organisms: amphipods (Hyalella azteca), midges (Chironomus dilutus), oligochaetes (Lumbriculus variegatus), and mussels (Lampsilis siliquoidea). Amphipods were exposed to either sonicated or nonsonicated SiCNW in water (1.0 g/L) for 48 h. Midges, mussels, and oligochaetes were exposed only to sonicated SiCNW in water for 96 h. In addition, amphipods were exposed to sonicated SiCNW in whole sediment for 10 d (44% SiCNW on dry wt basis). Mean 48-h survival of amphipods exposed to nonsonicated SiCNW in water was not significantly different from the control, whereas mean survival of amphipods exposed to sonicated SiCNW in two 48-h exposures (0 or 15% survival) was significantly different from the control (90 or 98% survival). In contrast, no effect of sonicated SiCNW was observed on survival of midges, mussels, or oligochaetes. Survival of amphipods was not significantly reduced in 10-d exposures to sonicated SiCNW either mixed in the sediment or layered on the sediment surface. However, significant reduction in amphipod biomass was observed with the SiCNW either mixed in sediment or layered on the sediment surface, and the reduction was more pronounced for SiCNW layered on the sediment. These results indicated that, under the experimental conditions, nonsonicated SiCNW in water were not acutely toxic to amphipods, sonicated SiCNW in water were acutely toxic to the amphipods, but not to other organisms tested, and sonicated SiCNW in sediment affected the growth but not the survival of amphipods.

  4. Heating Unsaturated Sediments Using Solar Energy to Enhance Passive Sediment Remediation Technologies

    NASA Astrophysics Data System (ADS)

    Rossman, A.

    2002-12-01

    Sediment heating has been shown to enhance passive sediment remediation technologies such as bioremediation and barometric pumping (passive soil venting). Sediment heating raises the slow remediation rates that often limit the widespread use of these technologies. In bioremediation applications, a 10 degree C increase in subsurface temperature is expected to double the microbial activity, and thus the remediation rate. The removal rate of tetracholorethylene (PCE - a common subsurface contaminant) by passive soil vapor extraction is expected to nearly double in low-permeable sediments when the subsurface is heated 10 degree C from ambient temperatures due to an increased vapor pressure in the PCE. When the sediment is heated using renewable energy sources, these thermally enhanced remediation technologies can be environmentally benign alternatives to conventional remediation techniques that rely on large external energy inputs. The thermally enhanced passive technologies may be particularly useful for remediating unsaturated, low-permeable lenses that are troublesome to most conventional remediation technologies such as conventional soil vapor extraction and co-solvent flushes. The main objective of this work was to quantify subsurface sediment heating using a solar powered heat injection well. To do this, a pilot sediment heating system was installed in Vermont and high resolution meteorological and sediment temperature data were collected using a stand-alone data acquisition system. Unsaturated, silty sediments were heated in-situ by converting the direct and indirect solar energy available at the surface to heat energy in the subsurface using stand-alone renewable energy sources and a resistive element heat injection well. The heat injection well was powered by a 600-W passively tracking photovoltaic (PV) array and a small 1.2-m swept area wind turbine. It is envisioned that the heat injection well would be placed directly into an area of high subsurface

  5. Characteristics of resuspended sediment from Georges Bank collected with a sediment trap

    USGS Publications Warehouse

    Parmenter, C.M.; Bothner, Michael H.; Butman, B.

    1983-01-01

    A sediment trap was deployed 3 m from the bottom at a water depth of 62 m on the southern flank of Georges Bank (41??02??2???N, 67??33??5???W) from 30 September 1978 to 10 March 1979 to qualitatively determine the size of sediments resuspended from the bottom by winter storms and to determine if seasonal changes in the phytoplankton could be observed in the trapped sediment. Bulk X-ray analyses of the trapped sediment showed layers of distinctly different textures preserved in the collection vessel. The median grain size of sampled layers ranged from 2??7 to 6??5 ?? (fine sand to silt), but all layers contained a pronounced mode in the 3 ?? (fine sand) range. Nine layers containing relatively large amounts of sand were present. The sand content was 75% in the coarest layers and about 32% in the fine layers. The median grain size of bottom sediments at the deployment site was considerably coarser than the trap samples, although the dominant grain size was also 3 ??. Average bottom-current speeds during the deployment period were about 30 cm s-1 with a range of 10 to 50 cm s-1. Bottom stress, computed from the observed currents and waves, suggest that 11 storms caused sufficient stress to resuspend 3 ??-sized sediments, in good agreement with the nine layers of relatively coarse sediments collected in the trap. Surface waves had to be included in the calculation of bottom stress because the bottom currents alone were insufficient to cause the resuspension of 3 ??-sized sediment. The trapped sediments contain numerous diatoms and coccoliths that are typical of late fall and winter assemblages. No clear seasonal difference in the flora was noted among sampled layers, probably due to the large influx of resuspended material and a reduced primary flux during this period. An undescribed species of Thalassiosira (G. Fryxell, personal communication), and siliceous scales of unknown systematic position were observed at all levels. ?? 1983.

  6. Numerical simulation of turbidity current flow and sedimentation

    SciTech Connect

    Zeng, J.

    1992-01-01

    A computer-based numerical model of turbidity-current flow and sedimentation has been developed by integrating geological observations with basic equations for fluid and sediment motion. The model emphasizes water mixing across the upper boundary, particle-concentration controls on sediment support and flow dynamics, and sediment fractionation during sedimentation. The model includes three numerical components: (1) a sedimentation/fluidization model for quantifying sediment-size fractionation in sedimenting multi-component suspensions; (2) a concentration-viscosity model for quantifying the changes in density and viscosity of high-concentrated sediment suspensions; and (3) a layer-averaged flow model for tracing downslope flow evolution using continuity and momentum equations. The resulting simulation monitors the sedimentation history of layer-averaged turbidity flows over submarine slopes in terms of the evolution of flow velocity, thickness, and sediment concentration and the resulting rate of sedimentation and sediment size fractionation in a longitudinal section of the flow. The model generates turbidites and outputs downslope variations in their thickness and grain-size structuring. The model is tested by reference to modern turbidity currents in Bute Inlet, British Columbia. Using initial and boundary conditions approximating those of Bute Inlet yields model flows that show downslope evolutions and deposit turbidites closely resembling their natural counterparts. Additional flow experiments provide quantitative evaluation of the effects of basin geometry, sediment concentration, and sediment sources on the formation and properties of turbidites. Experimental high-concentration flows show much higher downslope velocities and lower sediment-setting velocities than more dilute flows, resulting in longer sediment-transport. Model turbidites formed by high-concentration and low-concentration flows show both distribution and coarse-tail grading.

  7. Sources of suspended sediment in the Lower Roanoke River, NC

    NASA Astrophysics Data System (ADS)

    Jalowska, A. M.; McKee, B. A.; Rodriguez, A. B.; Laceby, J. P.

    2015-12-01

    The Lower Roanoke River, NC, extends 220 km from the fall line to the bayhead delta front in the Albemarle Sound. The Lower Roanoke is almost completely disconnected from the upper reaches by a series of dams, with the furthest downstream dam located at the fall line. The dams effectively restrict the suspended sediment delivery from headwaters, making soils and sediments from the Lower Roanoke River basin, the sole source of suspended sediment. In flow-regulated rivers, bank erosion, especially mass wasting, is the major contributor to the suspended matter. Additional sources of the suspended sediment considered in this study are river channel, surface soils, floodplain surface sediments, and erosion of the delta front and prodelta. Here, we examine spatial and temporal variations in those sources. This study combined the use of flow and grain size data with a sediment fingerprinting method, to examine the contribution of surface and subsurface sediments to the observed suspended sediment load along the Lower Roanoke River. The fingerprinting method utilized radionuclide tracers 210Pb (natural atmospheric fallout), and 137Cs (produced by thermonuclear bomb testing). The contributions of surface and subsurface sources to the suspended sediment were calculated with 95% confidence intervals using a Monte-Carlo numerical mixing model. Our results show that with decreasing river slope and changing hydrography along the river, the contribution of surface sediments increases and becomes a main source of sediments in the Roanoke bayhead delta. At the river mouth, the surface sediment contribution decreases and is replaced by sediments eroded from the delta front and prodelta. The area of high surface sediment contribution is within the middle and upper parts of the delta, which are considered net depositional. Our study demonstrates that floodplains, often regarded to be a sediment sink, are also a sediment source, and they should be factored into sediment, carbon and

  8. The role of reservoirs in global sediment budgets

    NASA Astrophysics Data System (ADS)

    Verstraeten, G.; Renwick, W.; Poesen, J.; de Vente, J.; Vinogradova, N.; Bazzoffi, P.; Lajczak, A.; Radoane, M.; Rey, F.

    2009-04-01

    Man-made reservoirs are an important sink for sediment eroded from the land and thus constitute an important aspect of the sediment budget. Their impact has mostly been assessed at the scale of an individual river basin but rarely on a continental or even a global scale. Although there are recent estimates of global sediment retention by dams, these studies have solely focussed on the role reservoirs play in controlling sediment fluxes to the oceans, thus on their net impact for global sediment budgets. However, the net impact of reservoirs is much larger than the gross amount of sediment stored within all reservoirs on the globe. Furthermore, the impact of smaller waterholding structures is mostly neglected. In this paper, we present a first comprehensive assessment of global annual sediment storage within reservoirs based on sedimentation rates obtained from over 3700 reservoirs, representing nearly 25% of the global storage capacity. We argue that at least 27 petagrams (Pg) sediment are stored annually in all larger reservoirs, with possible sediment retention of an additional 27 Pg in smaller man-made water bodies. These values are 2 to 4 times larger than the estimated sediment mass transported annually to the global coastal ocean, and 8 to 15 times larger than the net reduction of sediment flux to the oceans attributed to reservoirs. These estimates provide minimum annual continental erosion rates and comparison with soil erosion data suggest that soil erosion on agricultural land is not the dominant source of sediment deposited in reservoirs or exported to the ocean. In recent decades, reservoir sedimentation has become as least as important as floodplain sediment storage and can nowadays be considered as one of the most important sediment sinks in continental sediment budgets.

  9. Influences of microbial activity and sediment disturbance on hyporheic exchange in sandy sediments

    NASA Astrophysics Data System (ADS)

    Mendoza-Lera, C.; Mutz, M.

    2012-04-01

    Besides the vertical hydraulic gradient, sediment permeability is the main controlling factor of water exchange across the stream bed. Reduction of permeability by microbial activity is reported from unidirectional percolated sediment columns. We investigated effects of algal and bacterial activity on hyporheic exchange (vertical water flux, VWF) under semi-natural stream conditions in 16 outdoor sand-bed flumes during 30 day. Variability of bedform was considered by 8 flumes having plane-bed and 8 flumes ripple-bed. To gain information on the relative significance of algae and heterotrophic microorganisms, half of the flumes were operated under constant dark conditions (no-light flumes), while the others were exposed to daylight. After 21 days, the upper 2 cm of the sediments was manually disturbed simulating moderate sediment dynamics which frequently occurs in natural sand-bed streams. VWF was measured by tracing loss of uranine from the water column while flumes were operating in re-circulating mode. Algae and bacterial abundance, organic matter, and CaCO3 content in sediments were determined. Sediment potential respiration (SPR) was measured in flow through respiration chambers and oxygen bubbles from primary production were sampled. As expected, initial VWF was higher in ripple-bed. After 13 days, VWF was completely inhibited in both plane and ripple-bed flumes under daylight conditions. In no-light flumes reduction of VWF was moderate. Microbial precipitation of calcium carbonate and production of oxygen bubbles in the uppermost sediments blocked the pore space. After 3 weeks, abundance and biomass of algae and SPR in the upper 2 cm of sediment were higher in daylight flumes than in no-light flumes, while bacterial abundance was higher in no-light flumes. The sediment disturbance at day 21 released the oxygen bubbles increased bed permeability and therefore restored VWF to initial rates in day-light flumes. SPR was unaffected by the sediment disturbance. In

  10. Catchment sediment flux: a lake sediment perspective on the onset of the Anthropocene?

    NASA Astrophysics Data System (ADS)

    Chiverrell, Richard

    2014-05-01

    Definitions of the Anthropocene are varied but from a geomorphological perspective broadly can be described as the interval of recent Earth history during which 'humans have had an 'overwhelming' effect on the Earth system' (Brown et al., 2013). Identifying the switch to a human-dominated geomorphic process regime is actually a challenging process, with in the 'Old World' ramping up of human populations and impacts on earth surface processes since the Neolithic/Mesolithic transition and the onset of agriculture. In the terrestrial realm lakes offer a unique window on changes in human forcing of earth surface processes from a sedimentary flux perspective, because unlike alluvial and hill-slope systems sedimentation is broadly continuous and uninterrupted. Dearing and Jones (2003) showed for a global dataset of lakes a 5-10 fold increase in sediment delivery comparing pre- and post-anthropogenic disturbance. Here sediment records from several lakes in lowland agricultural landscapes are presented to examine the changes in the flux and composition of materials delivered from their catchments. By definition the lakes record the switch to a human dominated system, but not necessary in accelerated sediment accumulation rates with changes in sediment composition equally important. Data from Crose, Hatch and Peckforton Meres, in lowland northwest England are interrogated producing quantitative land-cover reconstructions from pollen spectra calculated using the REVEALS model (Sugita, 2007), geochemical evidence for changes sediment provenance and flux, and 14C and stable Pb pollutant based chronological models detecting changes in sediment accumulation rate. The lake sediment geochemistry points to several phases of heightened human impact within these small agricultural catchments. Following small-in-scale forest cover reductions and limited impacts in terms of sediment flux during the Neolithic, the Bronze to Iron Age saw the first substantial reductions in forest cover

  11. Fluvial sediment in the environment: a national challenge

    USGS Publications Warehouse

    Larsen, Matthew C.; Gellis, Allen C.; Glysson, G. Douglas; Gray, John R.; Horowitz, Arthur J.

    2010-01-01

    Sediment and sediment-associated constituents can contribute substantially to water-quality impairment. In the past, sediment was viewed mainly as an engineering problem that affected reservoir storage capacity, shipping channel maintenance, and bridge scour, as well as the loss of agricultural soil. Sediment is now recognized as a major cause of aquatic system degradation in many rivers and streams as a result of light attenuation, loss of spawning substrate due to fine-grained sediment infilling, reduction in primary productivity, decreases in biotic diversity, and effects from sediment-associated chemical constituents. Recent advances in sediment measurement, assessment, source-identification, and analytical protocols provide new capabilities to quantify sediment and solid-phase chemical fluxes in aquatic systems. Developing, maintaining, and augmenting current sediment- and water-quality-monitoring networks is essential for determining the health of U.S. waterways and for evaluating the effectiveness of management actions in reducing sediment-related problems. The application of new scientific capabilities that address the adverse effects of sediment and sediment- associated constituents represents a major step in managing the Nation’s water quality. A robust Federal, national-scale eff rt, in collaboration with vested stakeholders, is needed to address these sediment-related water-quality issues across the United States.

  12. Probability forecast of the suspended sediment concentration using copula

    NASA Astrophysics Data System (ADS)

    Yu, Kun-xia; Li, Peng; Li, Zhanbin

    2016-04-01

    An approach for probability forecast of the suspended sediment loads is presented in our research. Probability forecast model is established based on the joint probability distribution of water discharge and suspended sediment concentration. The conditional distribution function of suspended sediment concentration given water discharge is evaluated provided the joint probability distribution between water discharge and suspended sediment concentration is constructed, and probability forecast of suspended sediment concentration is implemented in terms of conditional probability function. This approach is exemplified using annual data set of ten watersheds in the middle Yellow River which is characterized by heavy sediment. The three-parameter Gamma distribution is employed to fit the marginal distribution of annual water discharge and annual suspended sediment concentration, and the Gumbel copula can well describe the dependence structure between annual water discharge and annual suspended sediment concentration. Annual suspended sediment concentration estimated from the conditional distribution function with forecast probability of 50 percent agree better with the observed suspended sediment concentration values than the traditional sediment rating curve method given water discharge values. The overwhelming majority of observed suspended sediment concentration points lie between the forecast probability of 5 percent and 95 percent, which can be considered as the lower and upper 95th percent uncertainty bound of the predicted observation respectively. The results indicate that probability forecast on the basis of conditional distribution function is a potential alternative in suspended sediment and other hydrological variables estimation.

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

    PubMed

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

    2014-08-01

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

  14. Sediment calibration strategies of Phase 5 Chesapeake Bay watershed model

    USGS Publications Warehouse

    Wu, J.; Shenk, G.W.; Raffensperger, J.; Moyer, D.; Linker, L.C.; ,

    2005-01-01

    Sediment is a primary constituent of concern for Chesapeake Bay due to its effect on water clarity. Accurate representation of sediment processes and behavior in Chesapeake Bay watershed model is critical for developing sound load reduction strategies. Sediment calibration remains one of the most difficult components of watershed-scale assessment. This is especially true for Chesapeake Bay watershed model given the size of the watershed being modeled and complexity involved in land and stream simulation processes. To obtain the best calibration, the Chesapeake Bay program has developed four different strategies for sediment calibration of Phase 5 watershed model, including 1) comparing observed and simulated sediment rating curves for different parts of the hydrograph; 2) analyzing change of bed depth over time; 3) relating deposition/scour to total annual sediment loads; and 4) calculating "goodness-of-fit' statistics. These strategies allow a more accurate sediment calibration, and also provide some insightful information on sediment processes and behavior in Chesapeake Bay watershed.

  15. Sediment transport-based metrics of wetland stability

    USGS Publications Warehouse

    Ganju, Neil K.; Kirwan, Matthew L.; Dickhudt, Patrick J.; Guntenspergen, Glenn R.; Cahoon, Donald R.; Kroeger, Kevin D.

    2015-01-01

    Despite the importance of sediment availability on wetland stability, vulnerability assessments seldom consider spatiotemporal variability of sediment transport. Models predict that the maximum rate of sea level rise a marsh can survive is proportional to suspended sediment concentration (SSC) and accretion. In contrast, we find that SSC and accretion are higher in an unstable marsh than in an adjacent stable marsh, suggesting that these metrics cannot describe wetland vulnerability. Therefore, we propose the flood/ebb SSC differential and organic-inorganic suspended sediment ratio as better vulnerability metrics. The unstable marsh favors sediment export (18 mg L−1 higher on ebb tides), while the stable marsh imports sediment (12 mg L−1 higher on flood tides). The organic-inorganic SSC ratio is 84% higher in the unstable marsh, and stable isotopes indicate a source consistent with marsh-derived material. These simple metrics scale with sediment fluxes, integrate spatiotemporal variability, and indicate sediment sources.

  16. IDENTIFICATION OF TOXICANTS IN WHOLE MARINE SEDIMENTS: METHODS AND RESULTS

    EPA Science Inventory

    Identification of stressors in aquatic systems is critical to sound assessment and management of our nation's waterways. Information from stressor identification can be useful in designing effective sediment remediation methods, assessing options for sediment disposal, allowing m...

  17. APPLYING TOXICITY IDENTIFICATION PROCEDURES TO FIELD COLLECTED SEDIMENTS

    EPA Science Inventory

    Identification of specific causes of sediment toxicity can allow for much more focused risk assessment and management decision making. We have been developing toxicity identification evaluation (TIE) methods for contaminated sediments and focusing on three toxicant groups (ammoni...

  18. RESULTS OF APPLYING TOXICITY IDENTIFICATION PROCEDURES TO FIELD COLLECTED SEDIMENTS

    EPA Science Inventory

    Identification of specific causes of sediment toxicity can allow for much more focused risk assessment and management decision making. We have been developing toxicity identification evaluation TIE) methods for contaminated sediments and are focusing on three toxicant groups (amm...

  19. USDA-ARS National Sedimentation Laboratory: A historic perspective

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Sediment from soil erosion is conceded by most authorities to be the largest single stream pollutant. Physical damage from sediment include reservoir storage loss, navigation channel filling, stream channel morphology alterations, ecological impacts, and clogging of drainage pathways. Ultimately, so...

  20. Quantitative centrifugation to extract benthic protozoa from freshwater sediments.

    PubMed

    Starink, M; Bär-Gilissen, M J; Bak, R P; Cappenberg, T E

    1994-01-01

    TWO METHODS FOR EXTRACTING PROTISTS FROM FRESHWATER SEDIMENT ARE DESCRIBED: (i) an adapted isopycnic centrifugation technique for sandy and gyttja-like sediments and (ii) a rate zonal centrifugation technique for sediments rich in particulate organic material (litter-like sediments). The recoveries of protists during isopycnic centrifugation in media of several densities were compared. No significant losses in sodium diatrizoate and Percoll were recorded. After known amounts of nanoflagellates were added to azoic sediments, the protists were extracted and counted. For sandy sediments, we found 100% recovery, and for the gyttja-like sediments we found a maximum recovery of 94%. The recovery of protozoa extracted from litter-like sediments, characteristic of littoral systems, depends on a given centrifugal force, on time, and on the dimensions of the flagellates. A recovery model which takes into account cell dimensions and centrifugation characteristics gives the minimum expected recovery.

  1. Role of porosity in filtration. 12: Filtration with sedimentation

    SciTech Connect

    Tiller, F.M.; Hsyung, N.B.; Cong, D.Z.

    1995-05-01

    Filtration on horizontal surfaces facing upward is accompanied by sedimentation. Materials balances that are based solely on the volume of filtrate and neglect sedimentation flux lead to an understatement of the solids deposited in the cake and potentially large errors in calculated values of the average specific resistance {alpha}{sub av} neglecting sedimentation was 3.75 times greater than the value including the effect of sedimentation. In addition to errors due to neglect of sedimentation, CATSCAN studies show that the slurry concentration above the cake increases with time, contrary to usual assumptions. In a manner similar to batch sedimentation in a closed cylinder, characteristics of constant composition arose from the cake surface. Approximate predictions based on a combination of traditional sedimentation and filtration theory were in accord with the CATSCAN data. Existing filtration theory must be substantially modified to account for the effect of sedimentation.

  2. Impact Of Groundwater Discharge On Contaminant Behavior In Sediments

    EPA Science Inventory

    The discharge of groundwater into surface water may influence the concentrations and availability of contaminants in sediments. There are three predominant pathways by which groundwater may affect the characteristics of contaminated sediments: 1) direct contribution of contamin...

  3. Quantifying Seepage Flux using Sediment Temperatures

    EPA Science Inventory

    This report provides a demonstration of different modeling approaches that use sediment temperatures to estimate the magnitude and direction of water flux across the groundwater-surface water transition zone. Analytical models based on steady-state or transient temperature solut...

  4. Seismoelectric Phenomena in Fluid-Saturated Sediments

    SciTech Connect

    Block, G I; Harris, J G

    2005-04-22

    Seismoelectric phenomena in sediments arise from acoustic wave-induced fluid motion in the pore space, which perturbs the electrostatic equilibrium of the electric double layer on the grain surfaces. Experimental techniques and the apparatus built to study this electrokinetic (EK) effect are described and outcomes for studies of seismoelectric phenomena in loose glass microspheres and medium-grain sand are presented. By varying the NaCl concentration in the pore fluid, we measured the conductivity dependence of two kinds of EK behavior: (1) the electric fields generated within the samples by the passage of transmitted acoustic waves, and (2) the electromagnetic wave produced at the fluid-sediment interface by the incident acoustic wave. Both phenomena are caused by relative fluid motion in the sediment pores--this feature is characteristic of poroelastic (Biot) media, but not predicted by either viscoelastic fluid or solid models. A model of plane-wave reflection from a fluid-sediment interface using EK-Biot theory leads to theoretical predictions that compare well to the experimental data for both sand and glass microspheres.

  5. Synchrotron Analysis Of Metal Immobilization In Sediments

    EPA Science Inventory

    Heavy metal contamination is a problem at many marine and fresh water environments as a result of industrial and military activities. Metals such as lead (Pb), zinc (Zn), copper (Cu), and chromium (Cr) are common contaminants in sediments due to many Navy activities. The mobile...

  6. Par Pond Fish, Water, and Sediment Chemistry

    SciTech Connect

    Paller, M.H.; Wike, L.D.

    1996-06-01

    The objectives of this report are to describe the Par Pond fish community and the impact of the drawdown and refill on the community, describe contaminant levels in Par Pond fish, sediments, and water and indicate how contaminant concentrations and distributions were affected by the drawdown and refill, and predict possible effects of future water level fluctuations in Par Pond.

  7. A Field Exercise in Fluvial Sediment Transport.

    ERIC Educational Resources Information Center

    Tharp, Thomas M.

    1983-01-01

    Describes an investigation which introduces the mathematical principles of stream hydraulics and fluvial sediment in a practical context. The investigation has four stages: defining hydrology of the stream; defining channel hydraulics in a study reach; measuring grain size; and calculating transportable grain size and comparing measure stream-bed…

  8. Elastic properties of overpressured and unconsolidated sediments

    USGS Publications Warehouse

    Lee, Myung W.

    2003-01-01

    Differential pressure affects elastic velocities and Poisson?s ratio of sediments in such a way that velocities increase as differential pressure increases. Overpressured zones in sediments can be detected by observing an increase in Poisson?s ratio with a corresponding drop in elastic velocities. In highly overpressured sands, such as shallow water flow sands, the P-to S-wave velocity ratio (Vp/Vs) is very high, on the order of 10 or higher, due to the unconsolidated and uncemented nature of sediments. In order to predict elastic characteristics of highly overpressured sands, Biot-Gassmann theory by Lee (BGTL) is used with a variable exponent n that depends on differential pressure and the degree of consolidation/compaction. The exponent n decreases as differential pressure and the degree of consolidation increases, and, as n decreases, velocity increases and Vp/Vs decreases. The predicted velocity ratio by BGTL agrees well with the measured velocity ratio at low differential pressure for unconsolidated sediments.

  9. Nonlinear compressional waves in marine sediments

    NASA Astrophysics Data System (ADS)

    McDonald, B. Edward

    2005-09-01

    A theory for nonlinear waves in marine sediments must account for the presence of a granular frame filled with water and possibly gas bubbles. When grains are in full contact, the stress-strain relation for the sediment contains a contribution varying as strain to the power 3/2, referred to as the Hertz force. The quadratic nonlinearity parameter derived from the second pressure derivative with respect to density thus diverges in the limit of small strain. We present a simple nonlinear wave equation model (a variant of the NPE) for compressional waves in marine sediments that avoids Taylor expansion and the problem of diverging nonlinearity parameter. An equation of state for partially consolidated sediments is derived from consolidation test results. Pressure is found to increase with overdensity to the power 5/2, indicating an increase in the number of contacts per grain as density increases. Numerical results for nonlinear compressional waves show agreement with analytic self-similar profiles derived from the nonlinear wave equation. [Work supported by the ONR.

  10. Distribution of radionuclides in Dardanelle Reservoir sediments.

    PubMed

    Forgy, J R; Epperson, C E; Swindle, D L

    1984-02-01

    Natural and reactor-discharged gamma-ray emitting radionuclides were measured in Dardanelle Reservoir surface sediments taken near the Arkansas Nuclear One Power Plant site. Samples represented several water depths and particle sizes, at 33 locations, in a field survey conducted in early September 1980. Radionuclide contents of dry sediments ranged as follows: natural radioactivity (40K as well as uranium and thorium decay products) 661-1210 Bq/kg; and reactor discharged radioactivity (137Cs, 134Cs, 60Co,, 58Co, 54Mn), no detectable activity to 237 Bq/kg. In general, radionuclide contents were positively correlated with decreasing sediment particle size. The average external whole-body and skin doses from all measurable reactor-discharged radionuclides were calculated according to the mathematical formula for determining external dose from sediment given by the U.S. Nuclear Regulatory Commission (NRC). Inside the discharge embayment near the reactor discharge canal, the doses were 1.7 X 10(-3) mSv/yr to the whole body and 2.0 X 10(-3) mSv/yr to the skin. Outside this area, the doses were 0.15 X 10(-3) and 0.18 X 10(-3) mSv/yr to the whole body and skin, respectively. PMID:6693264

  11. Chlorinated organic compounds in urban river sediments

    SciTech Connect

    Soma, Y.; Shiraishi, H.; Inaba, K.

    1995-12-31

    Among anthropogenic chemicals, many chlorinated organic compounds have been used as insecticides and detected frequently as contaminants in urban river sediments so far. However, the number and total amount of chemicals produced commercially and used are increasing year by year, though each amount of chemicals is not so high. New types of contaminants in the environment may be detected by the use of newly developed chemicals. Chlorinated organic compounds in the urban river sediments around Tokyo and Kyoto, large cities in Japan, were surveyed and recent trends of contaminants were studied. Contaminants of the river sediments in industrial areas had a variety, but PCB (polychlorinated biphenyls) was detected in common in industrial areas. Concentration of PCB related well to the number of factories on both sides of rivers, although the use of PCB was stopped 20 years ago. In domestic areas, Triclosan (5-chloro-2-(2,4-dichlorophenoxy)-phenol) and Triclocarban (3,4,4{prime}-trichlorocarbanilide)(both are contained in soap or shampoo for fungicides), p-dichlorobenzene (insecticides for wears) and TCEP(tris-chloroethyl phosphate) were detected. EOX(extracted organic halogen) in the sediments was 5 to 10 times of chlorinated organic compounds detected by GC/MS. Major part of organic halogen was suggested to be included in chlorinated organics formed by bleaching or sterilization.

  12. SEDIMENT TOXICOLOGY TESTING, ISSUES AND METHODS

    EPA Science Inventory

    The significant role that sediments play in aquatic ecosystems is well known. They serve as both a sink and a source of organic and inorganic materials, where critical cycling processes for organic matter and the critical elements (e.g., C, N, P, and S). The majority of decomposi...

  13. Upper Washita River experimental watersheds: Sediment Database

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Improving the scientific understanding of the effectiveness of watershed conservation practices and floodwater-retardation structures to control floods and soil erosion is one of the primary objectives for sediment studies in the upper Washita River Experimental Watersheds. This paper summarizes se...

  14. Electrical properties of methane hydrate + sediment mixtures

    USGS Publications Warehouse

    Du Frane, Wyatt L.; Stern, Laura A.; Weitemeyer, Karen A.; Constable, Steven; Roberts, Jeffery J.

    2011-01-01

    As part of our DOE-funded proposal to characterize gas hydrate in the Gulf of Mexico using marine electromagnetic methods, a collaboration between SIO, LLNL, and USGS with the goal of measuring the electrical properties of lab-created methane (CH4) hydrate and sediment mixtures was formed. We examined samples with known characteristics to better relate electrical properties measured in the field to specific gas hydrate concentration and distribution patterns. Here we discuss first-ever electrical conductivity (σ) measurements on unmixed CH4 hydrate (Du Frane et al., 2011): 6 x 10-5 S/m at 5 °C, which is ~5 orders of magnitude lower than seawater. This difference allows electromagnetic (EM) techniques to distinguish highly resistive gas hydrate deposits from conductive water saturated sediments in EM field surveys. More recently, we performed measurements on CH4 hydrate mixed with sediment and we also discuss those initial findings here. Our results on samples free of liquid water are important for predicting conductivity of sediments with pores highly saturated with gas hydrate, and are an essential starting point for comprehensive mixing models.

  15. Carbonate to siliciclastic periplatform sediments: southwest Florida

    USGS Publications Warehouse

    Holmes, Charles W.

    1988-01-01

    Geophysical, geochemical, and sedimentological data suggest that the spatial relationships of these deposits are related to sea-level variations. During extreme lowstands, with much of the shelf exposed, the dominant sedimentation was in the form of siliciclastic deposition on the abyssal floor, and slope talus development at the edge of the shelf. During a subsequent rise in sea level, after carbonate production on the shelf was initiated, sediment was transported southward to the head of the canyons and funneled to the abyssal floor. Subsequent rising sea level shifted the axis of transport farther to the shelf, bypassing the canyons and funneling the sediment through breaks in the carbonate reef banks at the southern edge of the platform. At the sites of both the hemipelagic and the turbidite deposition, high-resolution seismic data indicate that at least three cycles of deposition have occurred. In the abyss, this cyclic nature has produced alternating layers of carbonate and noncarbonate sediments, recognizable in the sedimentary record as limestone units interlayered with fine shales. In the geologic record the hemipelagic deposits would be almost indistinguishable from deep-sea foraminiferal oozes.  

  16. Roughness configuration matters for aeolian sediment flux

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The parameterisation of surface roughness effects on aeolian sediment transport is a key source of uncertainty in wind erosion models. Roughness effects are typically represented by bulk drag-partitioning schemes that scale the threshold friction velocity (u*t) for soil entrainment by the ratio of s...

  17. Heat production by sediment: ecological significance

    SciTech Connect

    Pamatmat, M.M.

    1982-01-22

    Sediments held at constant temperature evolve heat at rates that can be measured by direct calorimetry. The heat production rates decrease with depth from the surface layer. Total heat flux is an indication of the rate of degradation of potential chemical energy originally fixed by photosynthesis and represents benthic energy flow.

  18. Conceptualizing hillslope sediment connectivity as virtual velocity

    NASA Astrophysics Data System (ADS)

    Parsons, Anthony; Cooper, James; Onda, Yuichi; Patin, Jérémy; Wainwright, John

    2015-04-01

    The extent and speed of sediment delivery from catchment hillslopes to stream channels are products of the connectivity between the two. This relationship has often been expressed in terms of sediment sources and sinks. Here we reconceptualize the relationship as an expression of the virtual velocity (distance of travel per unit of time including periods when the particle is at rest) of eroded soil particles. This conceptualization has the advantage of being employable over a range of temporal and spatial scales and is applicable to any process, or combination of processes, of sediment transport operating on a hillslope. In this study we apply the conceptualization to examine hillslope connectivity of interrill erosion at three temporal scales. We use data from plot experiments to determine the virtual velocity of soil particles at the scale of a single event, at the scale of a season of runoff events, and at the decadal scale. These data allow us to infer what proportions of the hillslopes are supplying interrill sediment at these temporal scales.

  19. A Sedimentation Experiment Using a Preparative Ultracentrifuge

    ERIC Educational Resources Information Center

    Boudreau, Raymond E.; And Others

    1975-01-01

    Describes an experiment that illustrates the use of the preparative ultracentrifuge in isolating and purifying bacterial ribosomes, determines the sedimentation coefficients of the ribonucleoprotein particles, and demonstrates the subunit structure of the 70-S ribosome and the role of the magnesium ion in the association of subunits. (Author/GS)

  20. TOXICITY TESTS FOR SEDIMENT QUALITY ASSESSMENTS

    EPA Science Inventory

    Toxic sediments have contributed to a wide-variety of environmental problems around the world. The observed effects include direct toxic effects to aquatic life, bio-magnification of toxicants in the food chain, and economic impacts. This chapter discusses the use of toxicity...

  1. Organic carbon accumulation in Brazilian mangal sediments

    NASA Astrophysics Data System (ADS)

    Sanders, Christian J.; Smoak, Joseph M.; Sanders, Luciana M.; Sathy Naidu, A.; Patchineelam, Sambasiva R.

    2010-12-01

    This study reviews the organic carbon (OC) accumulation rates in mangrove forests, margins and intertidal mudflats in geographically distinct areas along the Brazilian coastline (Northeastern to Southern). Our initial results indicate that the mangrove forests in the Northeastern region of Brazil are accumulating more OC (353 g/m 2/y) than in the Southeastern areas (192 g/m 2/y) being that the sediment accumulation rates, 2.8 and 2.5 mm/y, and OC content ˜7.1% and ˜5.8% (dry sediment weight) were contributing factors to the discrepancies between the forests. The intertidal mudflats on the other hand showed substantially greater OC accumulation rates, sedimentation rates and content 1129 g/m 2/y and 234 g/m 2/y; 7.3 and 3.4 mm/y; 10.3% and ˜2.7% (OC of dry sediment weight content), respectively, in the Northeastern compared to the Southeastern region. Mangrove forests in the South-Southeastern regions of Brazil may be more susceptible to the rising sea level, as they are geographically constricted by the vast mountain ranges along the coastline.

  2. Contaminated sediment dynamics in peatland headwaters

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  3. Nontronite Stability in Near-Surface Sediments

    NASA Astrophysics Data System (ADS)

    Home, C.; Baker, L.

    2015-12-01

    The purpose of this study is to examine how long nontronite clays persist in soil, by studying samples collected from a sediment cone weathering out of crack in a basalt outcrop near Moscow Idaho. Nontronite, a dioctahedral ferric smectite clay, is a frequent weathering product of basaltic rocks. However, it is rarely described in surface soils, even in basaltic terrains. At our field site, nontronite formed by basalt weathering is eroding from cracks in the basalt and forming small talus cones. We are examining samples collected from a trench and several soil cores to determine the clay mineralogy at different depths in the talus cone. Bulk and clay mineralogy is being determined using X-ray Diffractometry (XRD) analysis and Fourier Transform Infrared Spectroscopy (FT-IR) analysis. Bulk chemical analyses, and selective extractions with acid oxalate and citrate-bicarbonate-dithionite reagents, are being used to analyze Fe mineralogy and amorphous constituents. Preliminary observations suggest that iron mineralogy may vary with depth in the sediments, and that older, deeper sediments may contain more Fe in oxide phases. We hypothesize that nontronite in the sediments is decomposing over time to form low-Fe smectites + Fe oxides. The results of this study will help determine whether nontronite is stable to erosion and redeposition in a surficial environment, as well as the timescale of its possible decomposition. These results may be useful in assessing proposed models of nontronite transport and redeposition on Mars.

  4. The effect of manipulations of freshwater sediments on responses of benthic invertebrates in whole-sediment toxicity tests

    SciTech Connect

    Day, K.E.; Kirby, R.S.; Reynoldson, T.B.

    1995-08-01

    Manipulations of freshwater sediment were performed to remove indigenous organisms prior to conducting toxicity tests with three species of benthic invertebrates. The effects of these treatments on end points in bioassays were compared within and between two sediments, i.e., a ``clean`` sediment and a ``contaminated`` sediment. In addition, the effects of manipulations on the physicochemical structure of the two sediments and the presence of metals, PAHs, and PCBs in the contaminated sediment were examined. The amphipod Hyalella azteca was most sensitive to the manipulations and had low survival in sediment that was sterilized. Growth (milligrams dry weight per individual) was affected by the presence of contaminants. Survival of Chironomus riparius was not affected by any manipulation but was reduced by contaminants as well as indigenous organisms. Growth of C. riparius was higher in autoclaved sediment but lower in sediment containing endemic tubificid worms. Production of young by Tubifex tubifex increased in sediment that was irradiated, possibly due to increased detrital material. Particle size distribution, metals, nutrients, and PAHs varied little as a function of manipulation; however, sieving of sediment through 250-{micro}m mesh did reduce percent total organic carbon (TOC), percent loss on ignition (LOI), and concentrations of some PCBs in either clean or contaminated sediment. Manipulation of sediments to remove endemic species should be determined on a case-by-case basis and is specific to the organisms used in toxicity tests.

  5. Aeolian sediment transport in vegetation canopies

    NASA Astrophysics Data System (ADS)

    Gromke, C.; Walter, B.; Burri, K.; Graf, F.; Lehning, M.

    2011-12-01

    Wind erosion experiments in grass canopies performed in the atmospheric boundary layer wind tunnel of the WSL Institute for Snow and Avalanche Research SLF in Davos / Switzerland are presented. The experiments were made using an 8 m long vegetation on sand (grain size 0.4 - 0.8 mm) fetch such that a naturally turbulent boundary layer could develop. The vegetation canopy consisted of regularly arrayed artificial grass tussocks which adequately mimic the aerodynamic and structural characteristics of vegetation with regard to flexibility and porosity. Three canopy densities and an unplanted, bare sand surface for reference were investigated. High speed imaging techniques were employed to study aeolian sediment transport over the final meter of the wind tunnel fetch. Moving particle trajectories were analysed by means of Particle Tracking Velocimetry (PTV). Sediment mass flux and concentration profiles were analysed using Shadow Imaging. The results of the particle trajectory analysis are presented in a statistical framework in terms of ejection and impact angle, trajectory length and curvature and particle velocity. Differences between aeolian sediment transport in / over vegetation canopies and the reference bare sand surface are pointed out. The previous observations of Burri et al. (2011), which revealed characteristic differences in the sediment mass flux profiles above a bare and vegetated surface, are now quantitatively explained by the trajectory analysis. Whereas the mass flux profile was steadily decreasing with height above ground for the bare surface, a peak at about twice the canopy height was found for the vegetated surface. The particle trajectory analysis plays a key role in distinguishing the diverse mechanisms leading to this elevated peak. The sediment mass flux and concentration profiles are additionally evaluated with respect to the height-dependency of particle size distributions. The trajectory analysis results are considered to have a high

  6. Geophysical Constraints on Sediment Dispersal Systems

    NASA Astrophysics Data System (ADS)

    Johnstone, Elizabeth Anne Carruthers

    Geophysical and geological approaches were employed to understand sediment dispersal systems and their response to various forcing functions (i.e., sea level fluctuations, tectonic deformation, sediment supply, and climate change). Two end member marine environments were studied; one with high precipitation and sediment discharge (Gulf of Papua, Papua New Guinea) and the other with low precipitation and sediment discharge (Oceanside Littoral Cell). The high-sedimentation rate in the Gulf of Papua (GoP) yields high-fidelity records of Earth history. As part of the NSF Margins Source-to-Sink (S2S) program, we acquired CHIRP and core data across the GoP continental shelf that complemented onshore and offshore research in the region. CHIRP seismic data imaged three Holocene sedimentary lobes. The older Central lobe is downlapped by two younger lobes to the north and south. Sediment analysis showed that the older Central lobe has an elemental signature similar to the younger Northern lobe with both sourced from the Purari River watershed and lobe migration appears to be climatically controlled. The Southern lobe has elemental signatures more consistent with the Fly River watershed. Our results suggest the northern rivers began depositing sediments on the shelf during the Holocene sea level rise in the central region of the GoP and migrated abruptly north at ~2 kybp. Conversely, during the early Holocene transgression, sediments in the Fly drainage system were sequestered onshore infilling accommodation created in the large low-relief coastal plain during the sea level rise. Upon infilling the onshore accommodation, the Fly River delivered sediment to the ocean and formed the Southern lobe. Such differences in onshore storage capacity may introduce a lag between low-gradient rivers (Type I) with a large coastal plain versus high-gradient river systems (Type II) with small coastal plains. The second study site is in the sediment-starved Oceanside Littoral Cell (OCL) of

  7. Comparisons of Sediment Test Volumes for Freshwater Solid Phase Sediment Toxicity Tests

    EPA Science Inventory

    Laboratory tests with benthic macroinvertebrates are commonly used to assess the potential toxicity of contaminated sediments, and detailed standard test procedures have been developed for various species. For freshwater, two benthic organisms, Hyalella azteca and Chironomus dil...

  8. Purification of Tetrahymena nuclei by sedimentation at unit gravity.

    PubMed

    Sweet, Melody T; Allis, C David

    2010-04-01

    This protocol provides a method for purification of Tetrahymena nuclei using sedimentation at unit gravity. It is useful for applications where purity of micro- and macronuclei is required beyond that which is typically achieved by differential sedimentation alone. When differential sedimentation is followed by sedimentation at unit gravity, micro- and macronuclei can be purified to virtual homogeneity. This method also permits the purification of homogeneous populations of developing new macronuclei (anlagen) and distinct classes of micronuclei from various stages of conjugation.

  9. /sup 137/Cs radioactive dating of Lake Ontario sediment cores

    SciTech Connect

    Ward, T.E.; Breeden, J.; Komisarcik, K.; Porter, R.; Czuczwa, J.; Kaminski, R.; McVeety, B.D.

    1987-12-01

    The distribution of /sup 137/Cs in sediment cores from Lake Ontario provides estimates of the sediment accumulation rates. Geochronology with /sup 210/Pb dating and distribution of Ambrosia (ragweed) pollen compare well with /sup 137/Cs dating. These methods can determine with precision, changes in sedimentation occurring over the past 100 years or so. Typical sedimentation rates of 0.18-0.36 cm/yr were measured. 16 refs., 3 figs., 2 tabs.

  10. Erythrocyte sedimentation rate and C-reactive protein.

    PubMed

    Harrison, Michael

    2015-06-01

    C-reactive protein is a better indicator of inflammation than the erythrocyte sedimentation rate. It is more sensitive and responds more quickly to changes in the clinical situation. False negative and false positive results are more common when measuring the erythrocyte sedimentation rate. Renal disease, female sex and older age increase the erythrocyte sedimentation rate. The erythrocyte sedimentation rate has value in detecting low-grade bone infection, and in monitoring some patients with systemic lupus erythematosus.

  11. Contaminants in Chesapeake Bay sediments, 1984-1991

    SciTech Connect

    Eskin, R.A.; Rowland, K.H.; Alegre, D.Y.

    1996-05-01

    This report presents data on sediment chemical contaminant concentrations in the Chesapeake Bay and its tidal tributaries collected between 1984 and 1991. The majority of this data collection was coordinated by Maryland and Virginia with support from the Chesapeake Bay Program. The primary objectives of this report are to describe the spatial patterns in the distribution of sediment chemical contaminants in Chesapeake Bay to sediment quality guidelines in order to identify areas where sediment chemical contaminants may adversely impact aquatic biota.

  12. Comparison of Erosion Rates Estimated by Sediment Budget Techniques and Suspended Sediment Monitoring and Regulatory Implications

    NASA Astrophysics Data System (ADS)

    O'Connor, M.; Eads, R.

    2007-12-01

    Watersheds in the northern California Coast Range have been designated as "impaired" with respect to water quality because of excessive sediment loads and/or high water temperature. Sediment budget techniques have typically been used by regulatory authorities to estimate current erosion rates and to develop targets for future desired erosion rates. This study examines erosion rates estimated by various methods for portions of the Gualala River watershed, designated as having water quality impaired by sediment under provisions of the Clean Water Act Section 303(d), located in northwest Sonoma County (~90 miles north of San Francisco). The watershed is underlain by Jurassic age sedimentary and meta-sedimentary rocks of the Franciscan formation. The San Andreas Fault passes through the western edge of watershed, and other active faults are present. A substantial portion of the watershed is mantled by rock slides and earth flows, many of which are considered dormant. The Coast Range is geologically young, and rapid rates of uplift are believed to have contributed to high erosion rates. This study compares quantitative erosion rate estimates developed at different spatial and temporal scales. It is motivated by a proposed vineyard development project in the watershed, and the need to document conditions in the project area, assess project environmental impacts and meet regulatory requirements pertaining to water quality. Erosion rate estimates were previously developed using sediment budget techniques for relatively large drainage areas (~100 to 1,000 km2) by the North Coast Regional Water Quality Control Board and US EPA and by the California Geological Survey. In this study, similar sediment budget techniques were used for smaller watersheds (~3 to 8 km2), and were supplemented by a suspended sediment monitoring program utilizing Turbidity Threshold Sampling techniques (as described in a companion study in this session). The duration of the monitoring program to date

  13. Sediment source fingerprinting to quantify fine sediment sources in forested catchments, Chile.

    NASA Astrophysics Data System (ADS)

    Schuller, P.; Walling, D. E.; Iroume, A.; Castillo, A.; Quilodran, C.

    2012-04-01

    A study to improve the understanding of the primary sediment sources and transfer pathways in catchments disturbed following forest plantation harvesting is being undertaken in South-Central Chile. The study focuses on two sets of paired experimental catchments (treatment and control), located about 400 km apart, with similar soil type but contrasting mean annual rainfall: Nacimiento (1,200 mm year-1) and Los Ulmos (2,500 mm year-1). Sediment source fingerprinting techniques are being used to document the primary fine sediment sources. In each catchment, three potential sediment sources were defined: clearcut slopes (Z1), forest roads (Z2) and the stream channel (Z3). In each catchment, multiple representative composite samples of the different potential source materials were collected before harvest operations from the upper 1 cm layer in Z1, Z2, and from the channel bank and bed for Z3. A time-integrating trap sampler installed in the discharge monitoring station constructed at the outlet of each catchment has been used to collect samples of the suspended sediment and these have been supplemented by sediment collected from the weir pools. Total suspended sediment load is been quantified in the monitoring stations using discharge records and integrated water sampling. Caesium-137 (137Cs), excess lead-210 (210Pbex) and other sediment properties are being used as fingerprints. After air-drying, oven-drying at 40°C and disaggregation, both the source material samples and the sediment samples collected in the discharge monitoring stations were sieved through a 63-μm sieve and the <63-μm fractions were used for subsequent analyses. For radionuclide assay, the samples were sealed in Petri dishes and after 4 weeks the mass activity density (activity concentration) of 137Cs and 210Pbex was determined by gamma analysis, using an ORTEC extended range Ge detector of 53% relative efficiency. The 137Cs and 210Pbex activity and organic carbon (Corg) concentration associated

  14. In Situ Sediment Treatment Using Activated Carbon: A Demonstrated Sediment Cleanup Technology

    PubMed Central

    Patmont, Clayton R; Ghosh, Upal; LaRosa, Paul; Menzie, Charles A; Luthy, Richard G; Greenberg, Marc S; Cornelissen, Gerard; Eek, Espen; Collins, John; Hull, John; Hjartland, Tore; Glaza, Edward; Bleiler, John; Quadrini, James

    2015-01-01

    This paper reviews general approaches for applying activated carbon (AC) amendments as an in situ sediment treatment remedy. In situ sediment treatment involves targeted placement of amendments using installation options that fall into two general approaches: 1) directly applying a thin layer of amendments (which potentially incorporates weighting or binding materials) to surface sediment, with or without initial mixing; and 2) incorporating amendments into a premixed, blended cover material of clean sand or sediment, which is also applied to the sediment surface. Over the past decade, pilot- or full-scale field sediment treatment projects using AC—globally recognized as one of the most effective sorbents for organic contaminants—were completed or were underway at more than 25 field sites in the United States, Norway, and the Netherlands. Collectively, these field projects (along with numerous laboratory experiments) have demonstrated the efficacy of AC for in situ treatment in a range of contaminated sediment conditions. Results from experimental studies and field applications indicate that in situ sequestration and immobilization treatment of hydrophobic organic compounds using either installation approach can reduce porewater concentrations and biouptake significantly, often becoming more effective over time due to progressive mass transfer. Certain conditions, such as use in unstable sediment environments, should be taken into account to maximize AC effectiveness over long time periods. In situ treatment is generally less disruptive and less expensive than traditional sediment cleanup technologies such as dredging or isolation capping. Proper site-specific balancing of the potential benefits, risks, ecological effects, and costs of in situ treatment technologies (in this case, AC) relative to other sediment cleanup technologies is important to successful full-scale field application. Extensive experimental studies and field trials have shown that when

  15. Improved understanding of Diatom stratigraphy in a varved sediment through lake monitoring and sediment trap data

    NASA Astrophysics Data System (ADS)

    Maier, Dominique Beatrice; Bigler, Christian

    2016-04-01

    Biological remains in lake sediments reflect past conditions in the lake itself and within its catchment. However, it is difficult to disentangle to which extent the environmental drivers are natural (e.g. population dynamics, climate) or human-induced (e.g. agriculture, forestry). Therefore, comprehensive lake monitoring is crucial to understand taphonomy and sediment formation, and enhances the value of the paleolimnological archive. In this study, we analyze survey data of a varved lake in northern Sweden (Nylandssjön, Nordingrå) with special focus on the diatom record. Different monitoring components are combined, i.e. (1) bi-weekly data of chemical parameters (chlorophyll a, nutrients) covering the period from 2012 to 2015, (2) physical parameters (temperature, oxygen, ice-cover) covering the period from 2000-2015, (3) high-resolution data from a sequential sediment trap covering the period from 2000-2015 and (4) annually resolved diatom data from the sediment varves. Early and intense spring mixing in 2012 translates into a short but vertically pervasive chlorophyll a band which is simultaneously recorded in the sequential trap with a high diatom peak (500 000 valves cm2 d-1). The years 2013 and 2014 show higher chlorophyll a concentrations in the water column, but diatoms do not form a peak flux (>100 000 diatoms cm2 d-1) at any time in the sediment trap, probably due to stratification patterns. The trap record from 2012 indicates a spring bloom dominating the sediment signal, but this is not repeated in 2013 and 2014. Future analyses will be directed towards linking the monitored in-lake processes to annually or even seasonally resolved environmental characteristics. The multiplicity of potential ecological and environmental drivers led us to reverse our analytical view by starting with the diatom stratigraphy in the varved sediment, continuing through the data from sediment trap and water column into the lake catchment to identify deviations (timing

  16. Habitat heterogeneity reflected in mesophotic reef sediments

    NASA Astrophysics Data System (ADS)

    Weinstein, D. K.; Klaus, J. S.; Smith, T. B.

    2015-11-01

    Modern reef sediments reflect the physical and chemical characteristics of the environment as well as the local reef fauna. Analysis of sedimentary reef facies can thus provide a powerful tool in interpreting ancient reef deposits. However, few studies have attempted to differentiate sedimentary facies in mesophotic coral ecosystems, low light habitats defined as residing 30-150 m below sea level. The low-angle shelf mesophotic coral ecosystem south of the northern U.S. Virgin Islands (USVI) consists of reefs with different structural characteristics ideal for studying the relationship between habitat variability and sedimentary facies. Textural, compositional, and geochemical analyses of surface sediments were used to identify mesophotic reef subfacies associated with distinct benthic communities and structural habitats. Sediment grain composition and bulk geochemistry were found to broadly record the distribution and abundance of coral and macroalgae communities, foundational mesophotic reef benthic organisms. Overall, sediment composition was found to be a good indicator of specific reef environments in low-angle mesophotic reef habitats. Sedimentological analyses indicate that hydrodynamic forces do not transport a significant amount of allochthonous sediment or potentially harmful terrigenous material to USVI mesophotic reefs. Episodic, maximum current velocities prevented deposition of most silt-size grains and smaller, but biological processes were found to have a greater influence on subfacies partitioning than hydrodynamic processes. Results provide a new analog for studies of ancient mesophotic coral ecosystem geological history and document the relationship between mesophotic reef subfacies, structural complexity, and habitat heterogeneity. They also demonstrate how mesophotic reefs along the same shelf system do not always share similar sedimentary characteristics and thus record a diverse set of ecological and environmental conditions.

  17. A Sound Approach to Soft Sediment Resolution

    NASA Astrophysics Data System (ADS)

    Snoek, M.

    2005-06-01

    The last few years has seen a surge in research activities directed towards investigating properties and dynamics of young marine, limnic and fluvial sediments. It is by now a well established fact that the sequence of sediments ranging from concentrated benthic suspension over fluid mud to un-consolidated material summarized as liquid sediments (LS), act as carriers for a wide range of pollutants discharged or migrated into waterways. Knowledge of the transport and fate of LS allows determining the transport and fate of adsorbed constituents (e.g., heavy metals, pesticides, PCBs, PAHs). To assess the environmental impact of LS, efforts have to be made to better understand the processes in relation to hydrodynamics and the chemical and physical properties of the layers. Since physical laws limit the resolution and detection power of conventional seismo-acoustic systems in respect of LS, alternative measurement, data analysis and processing approaches have to be found. Adapted acoustic procedures initially developed for shallow water marine environments to extreme shallow water regimes using matched field inversion techniques can reveal geoacoustic parameters including density, compressional wave speed and attenuation as a function of depth and time. The paper outlines the effects of sediment mobility upon the environment followed by a short overview of techniques commonly used to investigate sediments and other freshwater/marine events. The problems faced and limitations of existing systems are briefly outlined. Results obtained with recently developed and refined geoacoustic inversion methods are presented highlighting their potential for long-term study of physical properties and dynamics of LS.

  18. Karst is a repository for old sediments

    SciTech Connect

    Hobbs, H.C. )

    1994-04-01

    The Paleozoic plateau of southeastern Minnesota has been repeatedly glaciated, and has accumulated several sheets of loess. In the eastern part of this area, most of the older sediments have been eroded away and the late Wisconsinan Peoria loess directly overlies limestone. A lag of erratics from one or more older tills occurs sporadically on the bedrock surface. A more complete record is preserved in some sinkholes and solution cavities. Sinkholes (surface depressions) contain material that washed or collapsed into the hole, as well as material that was deposited directly (such as loess). Solution cavities contain only material sorted by water. Sinkhole fills exposed in roadcuts and quarry walls commonly lack the surface expression and black-dirt funnel'' of active sinkholes. Several of these contain erratic-bearing sediment interpreted as slopewash and mudflow. One appears to contain actual till--unsorted, unbedded pebble-loam that is not mixed with other materials commonly found on the limestone surface, such as red clay or loess. It cannot be determined whether this material was deposited directly or collapsed in later. Solution cavities are typically packed with sediment right up to the top. The bulk of such deposits is typically clay and silt; however, erratic pebbles are present in some. The fine sediment is sorted and bedded, at least in places. In one large cavity fill, a layer of rip-up clay clasts occurs near the top. Study of the stratigraphy of karst sediments in southeastern Minnesota is still preliminary. Techniques which are used to correlate them include: physical characteristics, texture analysis (on material that has not been sorted), sand and pebble lithology, and magnetic polarity. Techniques that could be used include clay mineralogy, geochemical analysis, and thermoluminescence.

  19. Indices of benthic community tolerance in contaminated Great Lakes sediments: Relations with sediment contaminant concentrations, sediment toxicity, and the sediment quality triad

    USGS Publications Warehouse

    Wildhaber, M.L.; Schmitt, C.J.

    1998-01-01

    We evaluated the toxic-units model developed by Wildhaber and Schmitt (1996) as a predictor of indices of mean tolerance to pollution (i.e., Lenat, 1993; Hilsenhoff, 1987) and other benthic community indices from Great Lakes sediments containing complex mixtures of environmental contaminants (e.g., polychlorinated biphenyls - PCBs, polycyclic aromatic hydrocarbons PAHs, pesticides, chlorinated dioxins, and metals). Sediment toxic units were defined as the ratio of the estimated pore-water concentration of a contaminant to its chronic toxicity as estimated by U.S. Environmental Protection Agency Ambient Water Quality Criteria (AWQC) or other applicable standard. The total hazard of a sediment to aquatic life was assessed by summing toxic units for all contaminants quantified. Among the benthic community metrics evaluated, total toxic units were most closely correlated with Lenat's (1993) and Hilsenhoff's (1987) indices of community tolerance (T(L), and T(H), respectively); toxic units accounted for 42% (T(L)) and 53% (T(H)) of variability in community tolerance as measured by Ponar grabs. In contrast, taxonomic richness and Shannon-Wiener diversity were not correlated (P > 0.05) with toxic units. Substitution of order- or family-level identifications for lowest possible (mostly genus- or species-) level identifications in the calculation of T(L) and T(H) indices weakened the relationships with toxic units. Tolerance values based on order- and family-level identifications of benthos for artificial substrate samples were more strongly correlated with toxic units than tolerance values for benthos from Ponar grabs. The ability of the toxic-units model to predict the other two components (i.e., laboratory-measured sediment toxicity and benthic community composition) of the Sediment Quality Triad (SQT) may obviate the need for the SQT in some situations.

  20. Magneto-Chemotaxis in Sediment: First Insights

    PubMed Central

    Mao, Xuegang; Egli, Ramon; Petersen, Nikolai; Hanzlik, Marianne; Liu, Xiuming

    2014-01-01

    Magnetotactic bacteria (MTB) use passive alignment with the Earth magnetic field as a mean to increase their navigation efficiency in horizontally stratified environments through what is known as magneto-aerotaxis (M-A). Current M-A models have been derived from MTB observations in aqueous environments, where a >80% alignment with inclined magnetic field lines produces a one-dimensional search for optimal living conditions. However, the mean magnetic alignment of MTB in their most widespread living environment, i.e. sediment, has been recently found to be <1%, greatly reducing or even eliminating the magnetotactic advantage deduced for the case of MTB in water. In order to understand the role of magnetotaxis for MTB populations living in sediment, we performed first M-A observations with lake sediment microcosms. Microcosm experiments were based on different combinations of (1) MTB position with respect to their preferred living depth (i.e. above, at, and below), and (2) magnetic field configurations (i.e. correctly and incorrectly polarized vertical fields, horizontal fields, and zero fields). Results suggest that polar magnetotaxis is more complex than implied by previous experiments, and revealed unexpected differences between two types of MTB living in the same sediment. Our main findings are: (1) all investigated MTB benefit of a clear magnetotactic advantage when they need to migrate over macroscopic distances for reaching their optimal living depth, (2) magnetotaxis is not used by all MTB under stationary, undisturbed conditions, (3) some MTB can rely only on chemotaxis for macroscopic vertical displacements in sediment while other cannot, and (4) some MTB use a fixed polar M-A mechanisms, while other can switch their M-A polarity, performing what can be considered as a mixed polar-axial M-A. These observations demonstrate that sedimentary M-A is controlled by complex mechanical, chemical, and temporal factors that are poorly reproduced in aqueous

  1. Rapid Sediment Accumulation Results in High Methane Effluxes from Coastal Sediments

    PubMed Central

    Lenstra, Wytze; Jong, Dirk; Meysman, Filip J. R.; Sapart, Célia J.; van der Veen, Carina; Röckmann, Thomas; Gonzalez, Santiago; Slomp, Caroline P.

    2016-01-01

    Globally, the methane (CH4) efflux from the ocean to the atmosphere is small, despite high rates of CH4 production in continental shelf and slope environments. This low efflux results from the biological removal of CH4 through anaerobic oxidation with sulfate in marine sediments. In some settings, however, pore water CH4 is found throughout the sulfate-bearing zone, indicating an apparently inefficient oxidation barrier for CH4. Here we demonstrate that rapid sediment accumulation can explain this limited capacity for CH4 removal in coastal sediments. In a saline coastal reservoir (Lake Grevelingen, The Netherlands), we observed high diffusive CH4 effluxes from the sediment into the overlying water column (0.2–0.8 mol m-2 yr-1) during multiple years. Linear pore water CH4 profiles and the absence of an isotopic enrichment commonly associated with CH4 oxidation in a zone with high rates of sulfate reduction (50–170 nmol cm-3 d-1) both suggest that CH4 is bypassing the zone of sulfate reduction. We propose that the rapid sediment accumulation at this site (~ 13 cm yr-1) reduces the residence time of the CH4 oxidizing microorganisms in the sulfate/methane transition zone (< 5 years), thus making it difficult for these slow growing methanotrophic communities to build-up sufficient biomass to efficiently remove pore water CH4. In addition, our results indicate that the high input of organic matter (~ 91 mol C m-2 yr-1) allows for the co-occurrence of different dissimilatory respiration processes, such as (acetotrophic) methanogenesis and sulfate reduction in the surface sediments by providing abundant substrate. We conclude that anthropogenic eutrophication and rapid sediment accumulation likely increase the release of CH4 from coastal sediments. PMID:27560511

  2. Sediment storage dam: A structural gully erosion control and sediment trapping measure, northern Ethiopia

    NASA Astrophysics Data System (ADS)

    Mekonnen, Mulatie; Keesstra, Saskia; Baartman, Jantiene; Ritsema, Coen

    2014-05-01

    Gully erosion is a prime problem in Ethiopia. This study assessed the severity of gully erosion and the role of sediment storage dams (SSD) in restoring gullies and preventing further gully development, its sediment trapping efficacy (STE) and its capacity in converting degraded gully lands to productive land. On average 2.5 m deep, 6.6 m wide and 28.3 m long gullies were formed in Minizr watershed, northwest Ethiopia, in 2013. Concentrated surface runoff, traditional ditches, graded terraces without suitable water ways and road construction are the main causes of such serious gully erosion. Over grazing, tunnel flow and lack of proper immediate gully treatment actions after gully initiation are found to be additional causes of the problem. Gully erosion was also found as the major source of sediment for downstream rivers and water reservoirs. The annual volume of soil eroded from only four gullies was 1941.3 m3. To control gully erosion, SSDs were found to be important physical structures, which can trap significant amount of sediment within gullies and they can convert unproductive gully land to productive agricultural land for fruit and crop production. Eight SSDs trapped about 44*103 m3 of sediment within 2 to 8 years. Two representative SSDs constructed using gabion and stone were tested for their STE. Results showed that their efficacy was 74.1% and 66.4% for the gabion and stone SSDs, respectively. Six of the older SSDs were already full of sediment and created 0.75 ha of productive land within 2 to 8 years. SSDs best fits to treat large size and deep gullies where other gully control measures, check dams, could not function well. To prevent gully formation, controlling its causes that is avoiding traditional ditches, practicing grassed water ways to safely remove runoff water from graded terraces, integrated watershed and road side management practices are important solutions. KEY WORDS: Sediment storage dam, gully erosion, sediment trapping efficacy

  3. Rapid Sediment Accumulation Results in High Methane Effluxes from Coastal Sediments.

    PubMed

    Egger, Matthias; Lenstra, Wytze; Jong, Dirk; Meysman, Filip J R; Sapart, Célia J; van der Veen, Carina; Röckmann, Thomas; Gonzalez, Santiago; Slomp, Caroline P

    2016-01-01

    Globally, the methane (CH4) efflux from the ocean to the atmosphere is small, despite high rates of CH4 production in continental shelf and slope environments. This low efflux results from the biological removal of CH4 through anaerobic oxidation with sulfate in marine sediments. In some settings, however, pore water CH4 is found throughout the sulfate-bearing zone, indicating an apparently inefficient oxidation barrier for CH4. Here we demonstrate that rapid sediment accumulation can explain this limited capacity for CH4 removal in coastal sediments. In a saline coastal reservoir (Lake Grevelingen, The Netherlands), we observed high diffusive CH4 effluxes from the sediment into the overlying water column (0.2-0.8 mol m-2 yr-1) during multiple years. Linear pore water CH4 profiles and the absence of an isotopic enrichment commonly associated with CH4 oxidation in a zone with high rates of sulfate reduction (50-170 nmol cm-3 d-1) both suggest that CH4 is bypassing the zone of sulfate reduction. We propose that the rapid sediment accumulation at this site (~ 13 cm yr-1) reduces the residence time of the CH4 oxidizing microorganisms in the sulfate/methane transition zone (< 5 years), thus making it difficult for these slow growing methanotrophic communities to build-up sufficient biomass to efficiently remove pore water CH4. In addition, our results indicate that the high input of organic matter (~ 91 mol C m-2 yr-1) allows for the co-occurrence of different dissimilatory respiration processes, such as (acetotrophic) methanogenesis and sulfate reduction in the surface sediments by providing abundant substrate. We conclude that anthropogenic eutrophication and rapid sediment accumulation likely increase the release of CH4 from coastal sediments. PMID:27560511

  4. Partitioning studies of dioxin between sediment and water: The measurement of Koc for Lake Ontario sediment

    SciTech Connect

    Lodge, K.B.; Cook, P.M.

    1989-01-01

    A desorption experiment is described in which the sediment-to-water partition coefficient for 2,3,7,8-tetrachlorodibenzo-p-dioxin is measured for a sample from Lake Ontario. After a contact period of 4 days, the logarithm of the partition coefficient on an organic carbon basis, LogKoc, ranges from 7.25 to 7.59. Information on the partitioning behavior of dioxin between water and dissolved or suspended matter derived from the sediment is provided.

  5. Computations of total sediment discharge, Niobrara River near Cody, Nebraska

    USGS Publications Warehouse

    Colby, Bruce R.; Hembree, C.H.

    1955-01-01

    A natural chute in the Niobrara River near Cody, Nebr., constricts the flow of the river except at high stages to a narrow channel in which the turbulence is sufficient to suspend nearly the total sediment discharge. Because much of the flow originates in the sandhills area of Nebraska, the water discharge and sediment discharge are relatively uniform. Sediment discharges based on depth-integrated samples at a contracted section in the chute and on streamflow records at a recording gage about 1,900 feet upstream are available for the period from April 1948 to September 1953 but are not given directly as continuous records in this report. Sediment measurements have been made periodically near the gage and at other nearby relatively unconfined sections of the stream for comparison with measurements at the contracted section. Sediment discharge at these relatively unconfined sections was computed from formulas for comparison with measured sediment discharges at the contracted section. A form of the Du Boys formula gave computed tonnages of sediment that were unsatisfactory. Sediment discharges as computed from the Schoklitsch formula agreed well with measured sediment discharges that were low, but they were much too low at measured sediment discharges that were higher. The Straub formula gave computed discharges, presumably of bed material, that were several times larger than measured discharges of sediment coarser than 0.125 millimeter. All three of these formulas gave computed sediment discharges that increased with water discharges much less rapidly than the measured discharges of sediment coarser than 0.125 millimeter. The Einstein procedure when applied to a reach that included 10 defined cross sections gave much better agreement between computed sediment discharge and measured sediment discharge than did anyone of the three other formulas that were used. This procedure does not compute the discharge of sediment that is too small to be found in the stream bed in

  6. Sediment bioaccumulation test with Lumbriculus variegatus: Effects of feeding

    EPA Science Inventory

    Sediment bioaccumulation tests with Lumbriculus variegatus were performed on seven sediments with a series of ratios of total organic carbon in sediment to L. variegatus (dry weight) (TOC/Lv) that spanned the recommendation of no less than 50:1. With increasing loading of organi...

  7. SEDIMENTS: A RESERVOIR OF HISTORIC CONTAMINATION OF THE ENVIRONMENT

    EPA Science Inventory

    Sediments contain contaminants derived from past activities that seriously degraded the environment.

    During low water, sediments are subject to natural erosion or removal for navigation.

    Erosion or dredging of sediment will release contaminants into the environment ...

  8. Lead Speciation And Bioavailability In Apatite-Amended Sediments

    EPA Science Inventory

    The in situ sequestration of lead (Pb) in sediment with a phosphate amendment was investigated by Pb speciation and bioavailability. Sediment Pb in preamendment samples was identified as galena (PbS) with trace amounts of absorbed Pb. Sediment exposed to atmospheric conditions ...

  9. LITERATURE REVIEW AND REPORT: SURFACE-SEDIMENT SAMPLER DATABASE

    EPA Science Inventory

    A literature review was conducted to identify available surface sediment sampling technologies with an ability to collect undisturbed sediments to depths of up to 1 meter below the water sediment interface. This survey was conducted using published literature and references, Envi...

  10. ASSESSING STREAM BED STABILITY AND EXCESS SEDIMENTATION IN MOUNTAIN STREAMS

    EPA Science Inventory

    Land use and resource exploitation in headwaters catchments?such as logging, mining, and road building?often increase sediment supply to streams, potentially causing excess sedimentation. Decreases in mean substrate size and increases in fine stream bed sediments can lead to inc...

  11. Riparian Sediment Delivery Ratio: Stiff Diagrams and Artifical Neural Networks

    EPA Science Inventory

    Various methods are used to estimate sediment transport through riparian buffers and grass jilters with the sediment delivery ratio having been the most widely applied. The U.S. Forest Service developed a sediment delivery ratio using the stiff diagram and a logistic curve to int...

  12. Virginia Erosion and Sediment Control Handbook. Standards, Criteria and Guidelines.

    ERIC Educational Resources Information Center

    Virginia State Soil and Water Conservation Commission, Richmond, VA.

    Guidelines and technical standards for development of local erosion and sediment control programs and conservation standards to meet the goals established by the Virginia Erosion and Sediment Control law are presented in this handbook. Part I defines natural and manmade erosion, sedimentation, and the hazards of uncontrolled wear and damage to the…

  13. Sediment Bioaccumulation Test with Lumbriculus variegatus: Effects of Organism Loading

    EPA Science Inventory

    Sediment bioaccumulation tests with Lumbriculus variegatus were performed on seven sediments with a series of ratios of total organic carbon in sediment to L. variegatus (dry weight) (TOC/Lv) that spanned the recommendation of no less than 50:1. With increasing loading of organi...

  14. Sediment source determination using fallout Cesium-137 in arid rangelands.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Sediment source identification in arid rangelands is necessary to understanding rangeland conditions and developing management practices to improve rangeland health and reduce sediment load to streams. The purpose of this research was to use Cesium-137 to identify sources of sediments in an arid ran...

  15. Mixture design and treatment methods for recycling contaminated sediment.

    PubMed

    Wang, Lei; Kwok, June S H; Tsang, Daniel C W; Poon, Chi-Sun

    2015-01-01

    Conventional marine disposal of contaminated sediment presents significant financial and environmental burden. This study aimed to recycle the contaminated sediment by assessing the roles and integration of binder formulation, sediment pretreatment, curing method, and waste inclusion in stabilization/solidification. The results demonstrated that the 28-d compressive strength of sediment blocks produced with coal fly ash and lime partially replacing cement at a binder-to-sediment ratio of 3:7 could be used as fill materials for construction. The X-ray diffraction analysis revealed that hydration products (calcium hydroxide) were difficult to form at high sediment content. Thermal pretreatment of sediment removed 90% of indigenous organic matter, significantly increased the compressive strength, and enabled reuse as non-load-bearing masonry units. Besides, 2-h CO2 curing accelerated early-stage carbonation inside the porous structure, sequestered 5.6% of CO2 (by weight) in the sediment blocks, and acquired strength comparable to 7-d curing. Thermogravimetric analysis indicated substantial weight loss corresponding to decomposition of poorly and well crystalline calcium carbonate. Moreover, partial replacement of contaminated sediment by various granular waste materials notably augmented the strength of sediment blocks. The metal leachability of sediment blocks was minimal and acceptable for reuse. These results suggest that contaminated sediment should be viewed as useful resources.

  16. Incorporating Contaminant Bioavailability into Sediment Quality Assessment Frameworks

    EPA Science Inventory

    The recently adopted sediment quality assessment framework for evaluating bay and estuarine sediments in the State of California incorporates bulk sediment chemistry as a key line of evidence(LOE) but does not address the bioavailability of measured contaminants. Thus, the chemis...

  17. Mixture design and treatment methods for recycling contaminated sediment.

    PubMed

    Wang, Lei; Kwok, June S H; Tsang, Daniel C W; Poon, Chi-Sun

    2015-01-01

    Conventional marine disposal of contaminated sediment presents significant financial and environmental burden. This study aimed to recycle the contaminated sediment by assessing the roles and integration of binder formulation, sediment pretreatment, curing method, and waste inclusion in stabilization/solidification. The results demonstrated that the 28-d compressive strength of sediment blocks produced with coal fly ash and lime partially replacing cement at a binder-to-sediment ratio of 3:7 could be used as fill materials for construction. The X-ray diffraction analysis revealed that hydration products (calcium hydroxide) were difficult to form at high sediment content. Thermal pretreatment of sediment removed 90% of indigenous organic matter, significantly increased the compressive strength, and enabled reuse as non-load-bearing masonry units. Besides, 2-h CO2 curing accelerated early-stage carbonation inside the porous structure, sequestered 5.6% of CO2 (by weight) in the sediment blocks, and acquired strength comparable to 7-d curing. Thermogravimetric analysis indicated substantial weight loss corresponding to decomposition of poorly and well crystalline calcium carbonate. Moreover, partial replacement of contaminated sediment by various granular waste materials notably augmented the strength of sediment blocks. The metal leachability of sediment blocks was minimal and acceptable for reuse. These results suggest that contaminated sediment should be viewed as useful resources. PMID:25464304

  18. Bedded Sediment Conditions and Macroinvertebrate Responses in New Mexico Streams: A First Step in Establishing Sediment Criteria

    EPA Science Inventory

    Aquatic life protection was the impetus for a New Mexico Environment Department (NMED) effort to define bedded sediment conditions in streams that were natural and tolerable, especially to benthic macroinvertebrates. Sediments were measured using surveys of streambed particles to...

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

    EPA Science Inventory

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

  20. ESTIMATION OF BIOTA SEDIMENT ACCUMULATION FACTOR (BSAF) FROM PAIRED OBSERVATIONS OF CHEMICAL CONCENTRATIONS IN BIOTA AND SEDIMENT (FINAL REPORT)

    EPA Science Inventory

    Biota Sediment Accumulation Factor (BSAF) is a parameter describing bioaccumulation of sediment-associated organic compounds or metals into tissues of ecological receptors. The report provides information on methodologies to estimate BSAF for nonionic organic chemicals.

  1. Evaluation of Deposited Sediment and Macroinvertebrate Metrics Used to Quantify Biological Response to Excessive Sedimentation in Agricultural Streams

    NASA Astrophysics Data System (ADS)

    Sutherland, Andrew B.; Culp, Joseph M.; Benoy, Glenn A.

    2012-07-01

    The objective of this study was to evaluate which macroinvertebrate and deposited sediment metrics are best for determining effects of excessive sedimentation on stream integrity. Fifteen instream sediment metrics, with the strongest relationship to land cover, were compared to riffle macroinvertebrate metrics in streams ranging across a gradient of land disturbance. Six deposited sediment metrics were strongly related to the relative abundance of Ephemeroptera, Plecoptera and Trichoptera and six were strongly related to the modified family biotic index (MFBI). Few functional feeding groups and habit groups were significantly related to deposited sediment, and this may be related to the focus on riffle, rather than reach-wide macroinvertebrates, as reach-wide sediment metrics were more closely related to human land use. Our results suggest that the coarse-level deposited sediment metric, visual estimate of fines, and the coarse-level biological index, MFBI, may be useful in biomonitoring efforts aimed at determining the impact of anthropogenic sedimentation on stream biotic integrity.

  2. The Materosion project, a sediment cascade modeling for torrential sediment transfers: final results and perspectives

    NASA Astrophysics Data System (ADS)

    Rudaz, Benjamin; Loye, Alexandre; Mazotti, Benoit; Bardou, Eric; Jaboyedoff, Michel

    2013-04-01

    The Materosion project, conducted between the swiss canton of Valais (CREALP) and University of Lausanne (CRET) aims at forecasting sediment transfer in alpine torrents using the sediment cascade concept. The study site is the high Anniviers valley, around the village of Zinal (Valais). The torrents are divided in homogeneous reaches, to and from which sediments are transported by debris flows and bedload transport events. The model runs simulations of 100 years, with a 1-month time step, each with a given a random meteorological event ranging from no activity up to high magnitude debris flows. These events are calibrated using local rain data and observed corresponding debris flow frequencies. The model is applied to ten torrent systems with variable geological context, watershed geometries and sediment supplies. Given the high number of possible event scenarios, 10'000 simulations per torrent are performed, giving a statistical distribution of cumulated volumes and an event size distribution. A way to visualize the complex results data is proposed, and a back-analysis of the internal sediment cascade dynamic is performed. The back-analysis shows that the results' distribution stabilize after ~5'000 simulations. The model results, especially the range of debris flow volumes are crucial to maintain mitigation measures such as retention dams, and give clues for future sediment cascade modeling.

  3. Field performance of self-siphon sediment cleansing set for sediment removal in deep CSO chamber.

    PubMed

    Zhou, Yongchao; Zhang, Yiping; Tang, Ping

    2013-01-01

    This paper presents a study of the self-siphon sediment cleansing set (SSCS), a system designed to remove sediment from the deep combined sewer overflow (CSO) chamber during dry-weather periods. In order to get a better understanding of the sediment removal effectiveness and operational conditions of the SSCS system, we carried out a full-scale field study and comparison analysis on the sediment depth changes in the deep CSO chambers under the conditions with and without the SSCS. The field investigation results demonstrated that the SSCS drains the dry-weather flow that accumulated for 50-57 min from the sewer channel to the intercepting system in about 10 min. It is estimated that the bed shear stress in the CSO chamber and sewer channel is improved almost 25 times on average. The SSCS acts to remove the near bed solids with high pollution load efficiently. Moreover, it cleans up not only the new sediment layer but also part of the previously accumulated sediment.

  4. Heavy metal concentrations and toxicity in water and sediment from stormwater ponds and sedimentation tanks.

    PubMed

    Karlsson, Kristin; Viklander, Maria; Scholes, Lian; Revitt, Mike

    2010-06-15

    Sedimentation is a widely used technique in structural best management practices to remove pollutants from stormwater. However, concerns have been expressed about the environmental impacts that may be exerted by the trapped pollutants. This study has concentrated on stormwater ponds and sedimentation tanks and reports on the accumulated metal concentrations (Cd, Cr, Ni, Pb, and Zn) and the associated toxicity to the bacteria Vibrio fischeri. The metal concentrations are compared with guidelines and the toxicity results are assessed in relation to samples for which metal concentrations either exceed or conform to these values. The water phase metal concentrations were highest in the ponds whereas the sedimentation tanks exhibited a distinct decrease towards the outlet. However, none of the water samples demonstrated toxicity even though the concentrations of Cu, Pb, and Zn exceeded the threshold values for the compared guidelines. The facilities with higher traffic intensities had elevated sediment concentrations of Cr, Cu, Ni, and Zn which increased towards the outlet for the sedimentation tanks in agreement with the highest percentage of fine particles. The sediments in both treatment facilities exhibited the expected toxic responses in line with their affinity for heavy metals but the role of organic carbon content is highlighted.

  5. Cosmogenic nuclide budgeting of floodplain sediment transfer

    NASA Astrophysics Data System (ADS)

    Wittmann, H.; von Blanckenburg, F.

    2009-08-01

    Cosmogenic nuclides produced in quartz may either decay or accumulate while sediment is moved through a river basin. A change in nuclide concentration resulting from storage in a floodplain is potentially important in large drainage basins in which sediment is prone to repeated burial and remobilization as a river migrates through its floodplain. We have modeled depth- and time-dependent cosmogenic nuclide concentration changes for 10Be, 26Al, and 14C during sediment storage and mixing in various active floodplain settings ranging from confined, shallow rivers with small floodplains to foreland-basin scale floodplains traversed by deep rivers. Floodplain storage time, estimated from channel migration rates, ranges from 0.4 kyr for the Beni River basin (Bolivia) to 7 kyr for the Amazon River basin, while floodplain storage depth, estimated from channel depth, ranges from 1 to 25 m. For all modeled active floodplain settings, the long-lived nuclides 10Be and 26Al show neither significant increase in nuclide concentration from irradiation nor decrease from decay. We predict a hypothetical response time after which changes in 10Be or 26Al concentrations become analytically resolvable. This interval ranges from 0.07 to 2 Myr and exceeds in all cases the typical residence time of sediment in a floodplain. Due to the much shorter half life of 14C, nuclide concentrations modeled for the in situ-produced variety of this nuclide are, however, sensitive to floodplain storage on residence times of < 20 kyr. The cosmogenic nuclide composition of old deposits in currently inactive floodplains that have been isolated for periods of millions of years from the river that once deposited them is predicted to either increase or decrease in 10Be and 26Al concentration, depending on the depositional depth. These conditions can be evaluated using the 26Al/ 10Be ratio that readily discloses the depth and duration of storage. We illustrate these models with examples from the Amazon basin

  6. Sediment quality in freshwater impoundments at Savannah National Wildlife Refuge

    USGS Publications Warehouse

    Winger, P.V.; Lasier, P.J.

    2004-01-01

    Freshwater impoundments at Savannah National Wildlife Refuge (NWR), South Carolina, provide an important habitat for wildlife species, but degraded sediment quality in the Savannah River downstream of the discharge from two impoundments have caused concern about potential contaminant problems within the impoundments. The quality of sediments from five impoundments (impoundments no. 1, 2, 6, 7, and 17) on the NWR was evaluated using physical and chemical characterization, contaminant concentrations (metals, organochlorine pesticides, polychlorinated biphenyls, and polycyclic aromatic hydrocarbons), and toxicity testing. Survival of Hyalella azteca (freshwater amphipod) exposed for 28 days to solid-phase sediments was not significantly different from controls, but growth was significantly decreased at several sites. Survival in 96-hour exposures to sediment pore water was significantly decreased at most sites. Factors contributing to the toxic responses were low pH (3.7 to 4.1), ammonia (20 mg/L), and increased concentrations of cations in the pore water. The excess of simultaneously extracted metals over the acid volatile sulfides in the sediments was also typical of sites displaying decreased sediment quality. Elemental concentrations in pore water were negatively correlated with pH, and the highest concentrations were observed in impoundment no. 7. The acidic nature of the sediment in this impoundment was exacerbated by recent draining, burning, and disking, which allowed oxidation of the previously anoxic wetland sediment. Sediment disturbance and mixing of vegetation into the sediments by disking may also have contributed to the formation of ammonia caused by microbial decomposition of the fragmented organic matter. Contaminants were not detected in sediments from the impoundments, but releases of acidic water with increased levels of sediment cations from the impoundments may have contributed to the degraded sediment conditions previously observed in the river

  7. Protecting sediment-sensitive aquatic species inmountain streams through the application of biologically based streambed sediment criteria

    EPA Science Inventory

    We evaluated several lines of evidence to identify bedded fine sediment levels that should protect and maintain self-sustaining populations of native sediment-sensitive aquatic species in the western US. To identify these potential criterion values for streambed sediments ≤0.06 ...

  8. Let's Bet on Sediments! Hudson Canyon Cruise--Grades 9-12. Focus: Sediments of Hudson Canyon.

    ERIC Educational Resources Information Center

    National Oceanic and Atmospheric Administration (DOC), Rockville, MD.

    These activities are designed to teach about the sediments of Hudson Canyon. Students investigate and analyze the patterns of sedimentation in the Hudson Canyon, observe how heavier particles sink faster than finer particles, and learn that submarine landslides are avalanches of sediment in deep ocean canyons. The activity provides learning…

  9. A Stochastic Model For Extracting Sediment Delivery Timescales From Sediment Budgets

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    Watershed managers need to quantify sediment storage and delivery timescales to understand the time required for best management practices to improve downstream water quality. To address this need, we route sediment downstream using a random walk through a series of valley compartments spaced at 1 km intervals. The probability of storage within each compartment, q, is specified from a sediment budget and is defined as the ratio of the volume deposited to the annual sediment flux. Within each compartment, the probability of sediment moving directly downstream without being stored is p=1-q. If sediment is stored within a compartment, its "resting time" is specified by a stochastic exponential waiting time distribution with a mean of 10 years. After a particle's waiting time is over, it moves downstream to the next compartment by fluvial transport. Over a distance of "n" compartments, a sediment particle may be stored from 0 to n times with the probability of each outcome (store or not store) specified by the binomial distribution. We assign q = 0.02, a stream velocity of 0.5 m/s, an event "intermittency "of 0.01, and assume a balanced sediment budget. Travel time probability density functions have a steep peak at the shortest times, representing rapid transport in the channel of the fraction of sediment that moves downstream without being stored. However, the probability of moving downstream "n" km without storage is pn (0.90 for 5 km, 0.36 for 50 km, 0.006 for 250 km), so travel times are increasingly dominated by storage with increasing distance. Median travel times for 5, 50, and 250 km are 0.03, 4.4, and 46.5 years. After a distance of approximately 2/q or 100 km (2/0.02/km), the median travel time is determined by storage timescales, and active fluvial transport is irrelevant. Our model extracts travel time statistics from sediment budgets, and can be cast as a differential equation and solved numerically for more complex systems.

  10. Geomorphic coupling and sediment connectivity in an alpine catchment — Exploring sediment cascades using graph theory

    NASA Astrophysics Data System (ADS)

    Heckmann, Tobias; Schwanghart, Wolfgang

    2013-01-01

    Through their relevance for sediment budgets and the sensitivity of geomorphic systems, geomorphic coupling and (sediment) connectivity represent important topics in geomorphology. Since the introduction of the systems perspective to physical geography by Chorley and Kennedy (1971), a catchment has been perceived as consisting of landscape elements (e.g. landforms, subcatchments) that are coupled by geomorphic processes through sediment transport. In this study, we present a novel application of mathematical graph theory to explore the network structure of coarse sediment pathways in a central alpine catchment. Numerical simulation models for rockfall, debris flows, and (hillslope and channel) fluvial processes are used to establish a spatially explicit graph model of sediment sources, pathways and sinks. The raster cells of a digital elevation model form the nodes of this graph, and simulated sediment trajectories represent the corresponding edges. Model results are validated by visual comparison with the field situation and aerial photos. The interaction of sediment pathways, i.e. where the deposits of a geomorphic process form the sources of another process, forms sediment cascades, represented by paths (a succession of edges) in the graph model. We show how this graph can be used to explore upslope (contributing area) and downslope (source to sink) functional connectivity by analysing its nodes, edges and paths. The analysis of the spatial distribution, composition and frequency of sediment cascades yields information on the relative importance of geomorphic processes and their interaction (however regardless of their transport capacity). In the study area, the analysis stresses the importance of mass movements and their interaction, e.g. the linkage of large rockfall source areas to debris flows that potentially enter the channel network. Moreover, it is shown that only a small percentage of the study area is coupled to the channel network which itself is

  11. Diagenetic regimes in Arctic Ocean sediments: Implications for sediment geochemistry and core correlation

    NASA Astrophysics Data System (ADS)

    Meinhardt, A.-K.; März, C.; Schuth, S.; Lettmann, K. A.; Schnetger, B.; Wolff, J.-O.; Brumsack, H.-J.

    2016-09-01

    Dark brown sediment layers are a potential stratigraphic tool in Quaternary Arctic Ocean sediments. They are rich in Mn, Fe, and trace metals scavenged from the water column and were most likely deposited during interglacial intervals. In this study, we combine sediment and pore water data from sediment cores taken in different parts of the Arctic Ocean to investigate the influence of early diagenetic processes on sediment geochemistry. In most studied cores, Mn, Co, and Mo are released into the pore waters from Mn oxide dissolution in deeper (>1.5 m) sediment layers. The relationship between sedimentary Mn, Co, and Mo contents in excess of the lithogenic background (elementxs) shows that Coxs/Moxs values are a diagnostic tool to distinguish between layers with diagenetic metal addition from the pore waters (Coxs/Moxs < 1), layers affected by Mn oxide dissolution and metal release (Coxs/Moxs > 10), and unaffected layers (Coxs/Moxs from 1 to 10). Steady-state calculations based on current pore water profiles reveal that in the studied cores, the diagenetic addition of these metals from the pore water pool alone is not sufficient to produce the sedimentary metal enrichments. However, it seems evident that dissolution of Mn oxides in the Mn reduction zone can permanently alter the primary geochemical signature of the dark brown layers. Therefore, pore water data and Coxs/Moxs values should be considered before core correlation when this correlation is solely based on Mn contents and dark sediment color. In contrast to the mostly non-lithogenic origin of Mn in the dark brown layers, sedimentary Fe consists of a large lithogenic (80%) and a small non-lithogenic fraction (20%). Our pore water data show that diagenetic Fe remobilization is not currently occurring in the sediment. The dominant Fe sources are coastal erosion and river input. Budget calculations show that Fe seems to be trapped in the modern Arctic Ocean and accumulates in shelf and basin sediments. The Fe

  12. Hourly and daily variation of sediment redox potential in tidal wetland sediments

    USGS Publications Warehouse

    Catallo, W. James

    1999-01-01

    Variation of electrochemical oxidation-reduction (redox) potential was examined in surface salt march sediments under conditions of flooding and tidal simulation in mesocosms and field sites. Time series were generated of redox potential measured in sediment profiles at 2-10 cm depth using combination Pt-Ag/AgCl (ORP) electrodes. Redox potential data were acquired at rapid rates (1-55 samples/h) over extended periods (3-104 days) along with similar times series of temperature (water, air, soil) and pH. It was found that redox potential vaired as a result of water level changes and was unrelated to diurnal changes in temperature or pH, the latter of which changed by 370 mV redox potential decrease in under 48 hours). Attenuatoin of microbial activity by [gamma] y-radiation and toxic chemicals elimintated this response. In tidal salt marsh mesocosms where the sediment-plant assemblages were exposed to a simulated diurnal tide, redox potenial oscillations of 40-300 mV amplitude were recoded that has the same periodicity as the flood-drain cycle. Periodic redoc potential time series were observed repeatedly in sediments receiving tidal pulsing but not in those sediments exposed to static hydrological conditions. Data collected over 12 days from a coastal marsh site experiencing diurnal tides showed similar fluctuations in redox potential. Data from the experimentents indicated that (a) redox potential can be a dynamic, nonlinear variable in coastal and estuarine wetland sediments over hourly and daily scales, and the designs of biogeochemical experiments should reflect this, (b) redox potential can change rapidly and signigicantly in coastal wetland sediments in response of flooding and draining, (c) microbial community processes are primarily determinants of the time course of redox potential in wetland sediments, and elimination of inhibition of microbial activity (e.g. by pollutants) can significantly alter that behavior, and (d) fast redox potential dynamics appear

  13. Estimating the fluvial sediment input to the coastal sediment budget: A case study of Ghana

    NASA Astrophysics Data System (ADS)

    Boateng, Isaac; Bray, Malcolm; Hooke, Janet

    2012-02-01

    Knowledge of fluvial sediment supply to the coastal sediment budget is important for the assessment of the impacts on coastal stability. Such knowledge is valuable for designing coastal engineering schemes and the development of shoreline management planning policies. It also facilitates understanding of the connection between rivers in the hinterland and adjoining coastal systems. Ghana's coast has many fluvial sediment sources and this paper provides the first quantitative assessments of their contributions to the coastal sediment budget. The methods use largely existing data and attempt to cover all of Ghana's significant coastal rivers. Initially work was hindered by insufficient direct measured data. However, the problem was overcome by the application of a regression approach, which provides an estimated sediment yield for non-gauged rivers based on data from gauged rivers with similar characteristics. The regression approach was effective because a regional coherence in behaviour was determined between those rivers, where direct measured data were available. The results of the assessment revealed that Ghana's coast is dissected by many south-draining rivers, stream and lagoons. These rivers, streams and lagoons supply significant amounts of sediment to coastal lowlands and therefore contribute importantly to beaches. Anthropogenic impoundment of fluvial sediment, especially the Akosombo dam on the Volta River, has reduced the total fluvial sediment input to the coast from about 71 × 10 6 m 3/a before 1964 (pre-Akosombo dam) to about 7 × 10 6 m 3/a at present (post-Akosombo dam). This sharp reduction threatened the stability of the east coast and prompted an expensive ($83 million) defence scheme to be implemented to protect 8.4 km-long coastline at Keta. Sections of Ghana's coast are closely connected to the hinterland through the fluvial sediment input from local rivers. Therefore, development in the hinterland that alters the fluvial sediment input from

  14. Sediment contaminant surveillance in Milford Haven Waterway.

    PubMed

    Little, D I; Bullimore, B; Galperin, Y; Langston, W J

    2016-01-01

    Sediment contaminants were monitored in Milford Haven Waterway (MHW) since 1978 (hydrocarbons) and 1982 (metals), with the aim of providing surveillance of environmental quality in one of the UK's busiest oil and gas ports. This aim is particularly important during and after large-scale investment in liquefied natural gas (LNG) facilities. However, the methods inevitably have changed over the years, compounding the difficulties of coordinating sampling and analytical programmes. After a review by the MHW Environmental Surveillance Group (MHWESG), sediment hydrocarbon chemistry was investigated in detail in 2010. Natural Resources Wales (NRW) contributed their MHW data for 2007 and 2012, collected to assess the condition of the Special Area of Conservation (SAC) designated under the European Union Habitats Directive. Datasets during 2007-2012 have thus been more comparable. The results showed conclusively that a MHW-wide peak in concentrations of sediment polycyclic aromatic hydrocarbons (PAHs), metals and other contaminants occurred in late 2007. This was corroborated by independent annual monitoring at one centrally located station with peaks in early 2008 and 2011. The spatial and temporal patterns of recovery from the 2007 peak, shown by MHW-wide surveys in 2010 and 2012, indicate several probable causes of contaminant trends, as follows: atmospheric deposition, catchment runoff, sediment resuspension from dredging, and construction of two LNG terminals and a power station. Adverse biological effects predictable in 2007 using international sediment quality guidelines were independently tested by data from monitoring schemes of more than a decade duration in MHW (starfish, limpets) and in the wider SAC (grey seals). Although not proving cause and effect, many of these potential biological receptors showed a simultaneous negative response to the elevated 2007 contamination following intense dredging activity in 2006. Wetland bird counts were typically at a peak in

  15. Methane Recovery from Hydrate-bearing Sediments

    SciTech Connect

    J. Carlos Santamarina; Costas Tsouris

    2011-04-30

    Gas hydrates are crystalline compounds made of gas and water molecules. Methane hydrates are found in marine sediments and permafrost regions; extensive amounts of methane are trapped in the form of hydrates. Methane hydrate can be an energy resource, contribute to global warming, or cause seafloor instability. This study placed emphasis on gas recovery from hydrate bearing sediments and related phenomena. The unique behavior of hydrate-bearing sediments required the development of special research tools, including new numerical algorithms (tube- and pore-network models) and experimental devices (high pressure chambers and micromodels). Therefore, the research methodology combined experimental studies, particle-scale numerical simulations, and macro-scale analyses of coupled processes. Research conducted as part of this project started with hydrate formation in sediment pores and extended to production methods and emergent phenomena. In particular, the scope of the work addressed: (1) hydrate formation and growth in pores, the assessment of formation rate, tensile/adhesive strength and their impact on sediment-scale properties, including volume change during hydrate formation and dissociation; (2) the effect of physical properties such as gas solubility, salinity, pore size, and mixed gas conditions on hydrate formation and dissociation, and it implications such as oscillatory transient hydrate formation, dissolution within the hydrate stability field, initial hydrate lens formation, and phase boundary changes in real field situations; (3) fluid conductivity in relation to pore size distribution and spatial correlation and the emergence of phenomena such as flow focusing; (4) mixed fluid flow, with special emphasis on differences between invading gas and nucleating gas, implications on relative gas conductivity for reservoir simulations, and gas recovery efficiency; (5) identification of advantages and limitations in different gas production strategies with

  16. Archaea in Arctic Thermokarst Lake Sediments

    NASA Astrophysics Data System (ADS)

    Matheus Carnevali, P. B.; Rohrssen, M.; Dodsworth, J. A.; Kuhn, E.; Williams, M.; Adams, H. E.; Berisford, D. F.; Hand, K. P.; Priscu, J. C.; Walter Anthony, K.; Love, G. D.; Hedlund, B. P.; Murray, A. E.

    2011-12-01

    Thermokarst lakes in the Northern Slope of Alaska are known to emit ebullient methane (CH4), some of which is of biogenic origin. Thawing of permafrost in the margins and bottom of these lakes, as a result of climate change, releases sources of carbon that could be used by methanogenic Archaea. However, the composition of Archaea inhabiting these lakes is not known. We have chosen a subset of Thermokarst lakes near Barrow Alaska to determine if there are methanogenic and methane oxidizing Archaea in these lake sediments. To describe the diversity of the archaeal community in the sediments we profiled the variable 3 (v3) region of the 16S rRNA gene of Archaea. The v3 profiles indicated surprisingly high levels of diversity, with 20 to 36 bands in the 10 sample horizons over the upper 100 cm of sediments surveyed in four lakes, at two times of the year. One of v3 rRNA gene bands was common to all lakes, and most phylotypes were grouped by depth (1-40 cm or 41-105 cm) within a lake. Likewise, cluster analysis indicated partitioning of archaeal communities between lakes. To specifically detect methanogens and anaerobic methanotrophs (ANME) in the sediments, DNA was surveyed by PCR to detect the methyl coenzyme M reductase (mcrA) gene, which is specific to the pathways of methanogenesis and anaerobic methane oxidation (AMO). An array of methanogen enrichment cultures was also set up. The expected 464-491 bp amplification product predicted for the mcrA gene was detected in all sediment samples. Assays of enrichment cultures incubated at 2 and 10 °C with substrates used in the main pathways for methanogenesis have produced positive growth and CH4 production results. Most cultures produced CH4 from carbon dioxide (CO2) reduction with hydrogen (H2), although methanol and acetate were also utilized as methanogenic substrates by a few cultures. From the experiments conducted to date we conclude that there is a great diversity of Archaea inhabiting these Thermokarst lakes

  17. Bedload transport of a bimodal sediment bed

    NASA Astrophysics Data System (ADS)

    Houssais, M.; Lajeunesse, E.

    2012-12-01

    Despite several decades of investigations, accounting for the effect of the wide range of grain sizes composing the bed of rivers on bedload transport remains a challenging problem. We investigate this problem by studying experimentally the influence of grain size distribution on bedload transport in the simple configuration of a bimodal sediment bed composed of a mixture of 2 populations of quartz grains of sizes D1 = 0.7 ± 0.1 mm and D2 = 2.2 ± 0.4 mm, respectively. The experiments are carried out in a tilted rectangular flume inside which the sediment bed is sheared by a steady and spatially uniform turbulent flow. Using a high-speed video imaging system, we focus on the measurement of the average particle velocity and the surface density of moving particles, defined as the number of moving particles per unit surface of the bed. These two quantities are measured separately for each population of grains as a function of the dimensionless shear stress (or Shields number) and the fraction of the bed surface covered with small grains. We show that the average velocity and the surface density of moving particles obey the same equations as those reported by Lajeunesse et al. (2010) for a bed of homogeneous grain size. Once in motion, the grains follow therefore similar laws whether the bed is made of uniform sediment or of a bimodal mixture. This suggests that the erosion-deposition model established by Lajeunesse et al. (2010) for a bed of uniform sediment can be generalized to the case of a bimodal one. The only difference evidenced by our experiments concerns the critical Shields number for incipient sediment motion. Above a uniform sediment bed, the latter depends on the particle Reynolds number through the Shields curve. In the case of a bimodal bed, our experiments show that the critical Shields numbers of both populations of grains decrease linearly with the fraction of the bed surface covered with small grains. We propose a simple model to account for this

  18. Sediment contaminant surveillance in Milford Haven Waterway.

    PubMed

    Little, D I; Bullimore, B; Galperin, Y; Langston, W J

    2016-01-01

    Sediment contaminants were monitored in Milford Haven Waterway (MHW) since 1978 (hydrocarbons) and 1982 (metals), with the aim of providing surveillance of environmental quality in one of the UK's busiest oil and gas ports. This aim is particularly important during and after large-scale investment in liquefied natural gas (LNG) facilities. However, the methods inevitably have changed over the years, compounding the difficulties of coordinating sampling and analytical programmes. After a review by the MHW Environmental Surveillance Group (MHWESG), sediment hydrocarbon chemistry was investigated in detail in 2010. Natural Resources Wales (NRW) contributed their MHW data for 2007 and 2012, collected to assess the condition of the Special Area of Conservation (SAC) designated under the European Union Habitats Directive. Datasets during 2007-2012 have thus been more comparable. The results showed conclusively that a MHW-wide peak in concentrations of sediment polycyclic aromatic hydrocarbons (PAHs), metals and other contaminants occurred in late 2007. This was corroborated by independent annual monitoring at one centrally located station with peaks in early 2008 and 2011. The spatial and temporal patterns of recovery from the 2007 peak, shown by MHW-wide surveys in 2010 and 2012, indicate several probable causes of contaminant trends, as follows: atmospheric deposition, catchment runoff, sediment resuspension from dredging, and construction of two LNG terminals and a power station. Adverse biological effects predictable in 2007 using international sediment quality guidelines were independently tested by data from monitoring schemes of more than a decade duration in MHW (starfish, limpets) and in the wider SAC (grey seals). Although not proving cause and effect, many of these potential biological receptors showed a simultaneous negative response to the elevated 2007 contamination following intense dredging activity in 2006. Wetland bird counts were typically at a peak in

  19. Suspended sediment dynamics in the Kromme Rijn river: indication for intense fine sediment exchange between water column and streambed

    NASA Astrophysics Data System (ADS)

    Van den Boomen, R.; Zweers, A. J.; Van der Perk, M.

    2012-04-01

    The limited transparency of the river water of the Kromme Rijn, a dammed distributary of the Rhine River in the Netherlands, restricts the ecological function of the stream and the achievement of the EU-Water Framework Directive targets. To increase water transparency in this river, the 'Hoogheemraadschap De Stichtse Rijnlanden' (HDSR) water authority considers to design one or more large-scale sediment traps. For an optimal design of these possible sediment traps, further knowledge about the local sediment characteristics and sedimentation and resuspension rates is a prerequisite. At the request of the HDSR water authority, we studied the fine sediment characteristics and dynamics in the Kromme Rijn river and its tributaries. Between summer 2010 and summer 2011, eleven monthly water samples were collected from six monitoring locations in the 25 km long reach of the Kromme Rijn river between the inlet from the Nederrijn river and Utrecht. Additional samples were collected from seven monitoring locations in streams and canals discharging into the Kromme Rijn river. The water samples were analysed for suspended sediment concentration and the suspended sediment was analysed for loss on ignition and particle size distribution by laser diffraction. In addition, at these monitoring locations, small sediment traps with an 8 cm circular opening were installed at 0.7 m below the water surface to measure the gross long-term sedimentation rate. These sediment traps were emptied every two months. During the monitoring period, the average sediment load in the Kromme Rijn near the inlet was 112 g/s and decreased to about 90 g/s near Utrecht. The vast majority of the sediment load (91%) in the main branch of the Kromme Rijn originates from the inlet from the Nederrijn river. The 2-16 μm and 16-63 μm particle size classes comprise about 80% of the suspended sediment. The average organic fraction of the suspended sediment was 36%. The sediment collected from the sediment traps

  20. Dispersal of fine sediment in nearshore coastal waters

    USGS Publications Warehouse

    Warrick, Jonathan A.

    2013-01-01

    Fine sediment (silt and clay) plays an important role in the physical, ecological, and environmental conditions of coastal systems, yet little is known about the dispersal and fate of fine sediment across coastal margin settings outside of river mouths. Here I provide simple physical scaling and detailed monitoring of a beach nourishment project near Imperial Beach, California, with a high portion of fines (40% silt and clay by weight). These results provide insights into the pathways and residence times of fine sediment transport across a wave-dominated coastal margin. Monitoring of the project used physical, optical, acoustic, and remote sensing techniques to track the fine portion of the nourishment sediment. The initial transport of fine sediment from the beach was influenced strongly by longshore currents of the surf zone that were established in response to the approach angles of the waves. The mean residence time of fine sediment in the surf zone—once it was suspended—was approximately 1 hour, and rapid decreases in surf zone fine sediment concentrations along the beach resulted from mixing and offshore transport in turbid rip heads. For example, during a day with oblique wave directions and surf zone longshore currents of approximately 25 cm/s, the offshore losses of fine sediment in rips resulted in a 95% reduction in alongshore surf zone fine sediment flux within 1 km of the nourishment site. However, because of the direct placement of nourishment sediment on the beach, fine suspended-sediment concentrations in the swash zone remained elevated for several days after nourishment, while fine sediment was winnowed from the beach. Once offshore of the surf zone, fine sediment settled downward in the water column and was observed to transport along and across the inner shelf. Vertically sheared currents influenced the directions and rates of fine sediment transport on the shelf. Sedimentation of fine sediment was greatest on the seafloor directly offshore

  1. Sediment Transport in Streams in the Umpqua River Basin, Oregon

    USGS Publications Warehouse

    Onions, C. A.

    1969-01-01

    This report presents tables of suspended-sediment data collected from 1956 to 1967 at 10 sites in the Umpqua River basin. Computations based on these data indicate that average annual suspended-sediment yields at these sites range from 137 to 822 tons per square mile. Because available data for the Umpqua River basin are generally inadequate for accurate determinations of sediment yield and for the definition of characteristics of fluvial sediments, recommendations are made for the collection and analysis of additional sediment data.

  2. Fatty acids in recent sediments in the St. Lawrence estuary

    NASA Astrophysics Data System (ADS)

    Rodier, L.; Khalil, M. F.

    1982-11-01

    Surface sediments along the Rimouski section in the St. Lawrence estuary were sampled at the surface and at 10 cm depth. Fatty acids were extracted and analysed. Saturated and unsaturated fatty acid contents at the two depths vary with the nature of the sediments. The clay sediments rich in organic matter contain more fatty acids than the corresponding sand or gravel. Unsaturated fatty acids were more abundant in the surface sediments. Some iso- and anteiso-odd carbon fatty acids were detected in the sediments; these acids could indicate a microbial activity. Correlation is made with the fatty acid contents of the water column together with the surface microlayer of the estuarine water.

  3. Sediment erodability in sediment transport modelling: Can we account for biota effects?

    NASA Astrophysics Data System (ADS)

    Le Hir, P.; Monbet, Y.; Orvain, F.

    2007-05-01

    Sediment erosion results from hydrodynamic forcing, represented by the bottom shear stress (BSS), and from the erodability of the sediment, defined by the critical erosion shear stress and the erosion rate. Abundant literature has dealt with the effects of biological components on sediment erodability and concluded that sediment processes are highly sensitive to the biota. However, very few sediment transport models account for these effects. We provide some background on the computation of BSS, and on the classical erosion laws for fine sand and mud, followed by a brief review of biota effects with the aim of quantifying the latter into generic formulations, where applicable. The effects of macrophytes, microphytobenthos, and macrofauna are considered in succession. Marine vegetation enhances the bottom dissipation of current energy, but also reduces shear stress at the sediment-water interface, which can be significant when the shoot density is high. The microphytobenthos and secreted extracellular polymeric substances (EPS) stabilise the sediment, and an increase of up to a factor of 5 can be assigned to the erosion threshold on muddy beds. However, the consequences with respect to the erosion rate are debatable since, once the protective biofilm is eroded, the underlying sediment probably has the same erosion behaviour as bare sediment. In addition, the development of benthic diatoms tends to be seasonal, so that stabilising effects are likely to be minimal in winter. Macrofaunal effects are characterised by extreme variability. For muddy sediments, destabilisation seems to be the general trend; this can become critical when benthic communities settle on consolidated sediments that would not be eroded if they remained bare. Biodeposition and bioresuspension fluxes are mentioned, for comparison with hydrodynamically induced erosion rates. Unlike the microphytobenthos, epifaunal benthic organisms create local roughness and are likely to change the BSS generated

  4. N Isotopes in Nile Sediments (ethiopia, Sudan)

    NASA Astrophysics Data System (ADS)

    Padoan, M.; Villa, I. M.; Garzanti, E.; Galbusera, M.; Quistini, S.; Peruta, L.; El Kammar, A.

    2009-04-01

    The Nile is the most important river of the Eastern Mediterranean. Its water and sediment fluxes have greatly influenced marine circulation throughout the Quaternary, and are widely considered as possible causes for stagnation and formation of sapropel (Krom et al., 1999a; 2002; Talbot et al., 2000; Freydier et al., 2001; Weldeab et al., 2002; Scrivner et al., 2004). Variations in annual flooding and baseflow of the river Nile, controlled by climate changes, had major impact on the rise and demise of Egyptian dynasties (Stanley et al., 2003). In order to better define sedimentary sources of the Nile system and to obtain more robust results, we have analyzed Nd isotopes in sediments of all its major Sudanese and Ethiopian tributaries (Atbara, Gash, Abay, Didesa, Dabus, White Nile, Bahr Ez Zeraf) in several replicate samples. Analyses were carried out on distinct mud and sand fractions (<40 microns and 125-180 microns) of 30 samples, and systematic changes related to grain size and hydraulic-sorting processes could thus be investigated. On the same samples, companion studies are being carried out on Sr isotopes (Padoan et al., 2007) and on Pb isotopes at the Geological Survey of Israel (Harlavan et al., in preparation). Overall, isotopic signals are markedly different between the White Nile system, derived from largely Archean to Paleoproterozoic basement rocks, and Ethiopian tributaries, derived in diverse proportions from largely Neoproterozoic rift-shoulder basements and overlying Oligocene flood basalts. Isotopic signals of Main Nile sediments downstream of the Atbara confluence are close to those of Blue Nile sediments, indicating that detritus is mainly provided by the latter (Garzanti et al., 2006). In the White Nile branch, the 143Nd/144Nd ratio of the mud fraction is lower in the Bahr Ez Zeraf (0.51167) than in the White Nile downstrean of the Sobat confluence (0.51219), revealing significant sediment influx from the latter. In Blue Nile and Atbara branches

  5. Effect of physical sediments reworking on hydrocarbon degradation and bacterial community structure in marine coastal sediments.

    PubMed

    Duran, Robert; Bonin, Patricia; Jezequel, Ronan; Dubosc, Karine; Gassie, Claire; Terrisse, Fanny; Abella, Justine; Cagnon, Christine; Militon, Cecile; Michotey, Valérie; Gilbert, Franck; Cuny, Philippe; Cravo-Laureau, Cristiana

    2015-10-01

    The present study aimed to examine whether the physical reworking of sediments by harrowing would be suitable for favouring the hydrocarbon degradation in coastal marine sediments. Mudflat sediments were maintained in mesocosms under conditions as closer as possible to those prevailing in natural environments with tidal cycles. Sediments were contaminated with Ural blend crude oil, and in half of them, harrowing treatment was applied in order to mimic physical reworking of surface sediments. Hydrocarbon distribution within the sediment and its removal was followed during 286 days. The harrowing treatment allowed hydrocarbon compounds to penetrate the first 6 cm of the sediments, and biodegradation indexes (such as n-C18/phytane) indicated that biodegradation started 90 days before that observed in untreated control mesocosms. However, the harrowing treatment had a severe impact on benthic organisms reducing drastically the macrofaunal abundance and diversity. In the harrowing-treated mesocosms, the bacterial abundance, determined by 16S rRNA gene Q-PCR, was slightly increased; and terminal restriction fragment length polymorphism (T-RFLP) analyses of 16S rRNA genes showed distinct and specific bacterial community structure. Co-occurrence network and canonical correspondence analyses (CCA) based on T-RFLP data indicated the main correlations between bacterial operational taxonomic units (OTUs) as well as the associations between OTUs and hydrocarbon compound contents further supported by clustered correlation (ClusCor) analysis. The analyses highlighted the OTUs constituting the network structural bases involved in hydrocarbon degradation. Negative correlations indicated the possible shifts in bacterial communities that occurred during the ecological succession.

  6. Effect of physical sediments reworking on hydrocarbon degradation and bacterial community structure in marine coastal sediments.

    PubMed

    Duran, Robert; Bonin, Patricia; Jezequel, Ronan; Dubosc, Karine; Gassie, Claire; Terrisse, Fanny; Abella, Justine; Cagnon, Christine; Militon, Cecile; Michotey, Valérie; Gilbert, Franck; Cuny, Philippe; Cravo-Laureau, Cristiana

    2015-10-01

    The present study aimed to examine whether the physical reworking of sediments by harrowing would be suitable for favouring the hydrocarbon degradation in coastal marine sediments. Mudflat sediments were maintained in mesocosms under conditions as closer as possible to those prevailing in natural environments with tidal cycles. Sediments were contaminated with Ural blend crude oil, and in half of them, harrowing treatment was applied in order to mimic physical reworking of surface sediments. Hydrocarbon distribution within the sediment and its removal was followed during 286 days. The harrowing treatment allowed hydrocarbon compounds to penetrate the first 6 cm of the sediments, and biodegradation indexes (such as n-C18/phytane) indicated that biodegradation started 90 days before that observed in untreated control mesocosms. However, the harrowing treatment had a severe impact on benthic organisms reducing drastically the macrofaunal abundance and diversity. In the harrowing-treated mesocosms, the bacterial abundance, determined by 16S rRNA gene Q-PCR, was slightly increased; and terminal restriction fragment length polymorphism (T-RFLP) analyses of 16S rRNA genes showed distinct and specific bacterial community structure. Co-occurrence network and canonical correspondence analyses (CCA) based on T-RFLP data indicated the main correlations between bacterial operational taxonomic units (OTUs) as well as the associations between OTUs and hydrocarbon compound contents further supported by clustered correlation (ClusCor) analysis. The analyses highlighted the OTUs constituting the network structural bases involved in hydrocarbon degradation. Negative correlations indicated the possible shifts in bacterial communities that occurred during the ecological succession. PMID:25847440

  7. Role of sediment resuspension in the remobilization of particulate-phase metals from coastal sediments

    USGS Publications Warehouse

    Kalnejais, Linda H.; Martin, William R.; Signell, Richard P.; Bothner, Michael H.

    2007-01-01

    The release of particulate-phase trace metals due to sediment resuspension has been investigated by combining erosion chamber experiments that apply a range of shear stresses typically encountered in coastal environments with a shear stress record simulated by a hydrodynamic model. Two sites with contrasting sediment chemistry were investigated. Sediment particles enriched in silver, copper, and lead, 4−50 times greater than the bulk surface-sediment content, were the first particles to be eroded. As the shear-stress level was increased in the chamber, the total mass eroded increased, but the enrichment of these trace metals fell, approaching the bulk-sediment content. From the temporal distribution of shear stress generated by the hydrodynamic model for a site in Boston Harbor, resuspension fluxes were estimated. The erosion threshold of this site is exceeded during spring tides, releasing the particles enriched in trace metals into the water column. Due to the higher trace metal content and the regularity of resuspension, low-energy resuspension events (up to a shear stress of 0.2 N/m2) contribute up to 60% of the resuspension metal flux in an average year. The estimated annual quantity of copper and lead resuspended into the water column is higher than estimates of the total riverine flux for these metals. These results indicate that sediment resuspension is a very important mechanism for releasing metals into the water column and provide new insight into the chemical and physical processes controlling the long-term fate of trace metals in contaminated sediments.

  8. Sediment Transport in the Lower Yampa River, Northwestern Colorado

    USGS Publications Warehouse

    Elliott, John G.; Kircher, James E.; Von Guerard, Paul

    1984-01-01

    Discharge measurements and sediment samples were taken at streamflow-gaging station 09260050 Yampa River at Deerlodge Park in 1982 and 1983 to determine the annual sediment supply to the Yampa Canyon in Dinosaur National Monument. Forty-three years of discharge records at two tributary sites were combined to determine the historic discharge of the Yampa River at Deerlodge Park. A mean annual hydrograph and flow-duration curve were derived from these data. Sediment-transport equations were derived for total sediment discharge, suspended-sediment discharge, bedload dischagre, and the discharge of sediment in several particle-sizes. Annual sediment discharge were determined by the flow-duration, sediment-rating-curve method and indicated annual total sediment discharge was approximately 2.0 million tons per year of which 0.8 million tons per year was sand-sized material. Bedload was almost entirely sand, and annual bedload discharge was 0.1 million tons per year. Development of water resources in the Yampa River basin could effect the geomorphic character of the Yampa River at Deerlodge Park and the Yampa Canyon. Several scenarios of altered streamflow frequency distribution, reduced streamflow volume, and reduced sediment supply are examined to estimate the effect on the sediment budget at Deerlodge Park. (USGS)

  9. The algal lift: Buoyancy-mediated sediment transport

    NASA Astrophysics Data System (ADS)

    Mendoza-Lera, Clara; Federlein, Laura L.; Knie, Matthias; Mutz, Michael

    2016-01-01

    The role of benthic algae as biostabilizers of sediments is well-known, however, their potential to lift and transport sediments remains unclear. Under low-flow conditions, matured algal mats may detach from the bed and may lift up sediment, thereby causing disturbance to the uppermost streambed sediment. We tested the potential of algal mats to lift sediments in 12 indoor flumes filled with sand (0.2 - 0.8 mm), gravel (2 - 8 mm) or a sand-gravel mixture (25/75% mass). After four weeks, the algal mats covered about 50% of the flumes area. Due to the accumulation of oxygen gas bubbles in the mats, that developed from high primary production at 4.5 weeks, about half of the algal mats detached from the bed carrying entangled sediments. Both the area covered by algal mats and detached area were similar among sediment types, but the amount of sediment transported tended to be higher for sand and sand-gravel mixture compared to gravel. Our results reveal that biologically mediated sediment transport mainly depends on the development of a dense filamentous algal matrix, that traps gas bubbles, increasing the mats buoyancy. This novel mechanism of sediment transport will occur in shallow ecosystems during low-flow periods, with the highest impact for sandy sediments.

  10. Assessing Sediment-Related Effects of Dam Removals

    NASA Astrophysics Data System (ADS)

    Wallick, J. Rose; Randle, Timothy

    2009-04-01

    Subcommittee on Sedimentation: Sediment Management and Dam Removal Workshop; Portland, Oregon, 14-16 October 2008; For a host of reasons including dam safety, maintenance costs, and ecological concerns, more dams are currently being removed each year in the United States than are being constructed. Because many reservoirs have accumulated sediments within their pools, dam removal can potentially impose a variety of sediment-related risks, including downstream effects on habitat, water quality, infrastructure, and flood storage. Sediment-related risks are particularly heightened when the sediment stored behind a dam is contaminated. Currently no standard procedure exists for assessing sediment-related risks associated with dam removal. As a result, there are wide-ranging levels of analysis used to predict and monitor sediment impacts after a dam is removed. To develop a decision framework for assessing sediment-related effects from dam removals, the U.S. Federal Subcommittee on Sedimentation (SOS) held a workshop in October on the campus of Portland State University, in Oregon, hosted by the U.S. Geological Survey's (USGS) Oregon Water Science Center. At the meeting, attendees crafted a decision framework that will help standardize data collection and analysis methods necessary for understanding sediment-related effects associated with dam removals.

  11. Watershed sediment source fingerprinting: a view under the hood

    NASA Astrophysics Data System (ADS)

    Smith, H.

    2015-12-01

    Sediment source fingerprinting procedures involve the discrimination of sediment sources based on physical and chemical properties and estimation of the contributions from those sources to mixtures of fine-grained sediment transported within watersheds. Sources of sediment widely considered include agricultural land uses, channel banks and geological zones. There has been a tendency in the literature for sediment fingerprinting to be presented as a technique that can deliver accurate and precise information on source contributions to sediment across a range of environments. However, recent research indicates that such a view of sediment fingerprinting cannot presently be supported. Furthermore, many past papers lack transparency in data processing and presentation that prevents the critical assessment of results and hinders wider uptake of the technique. Therefore, this contribution aims to delve 'under the hood' of sediment fingerprinting to promote further discussion and debate over future research needs and method limitations. It draws on important developments from the last two years concerning the effect of (i) tracer selection, (ii) tracer behaviour during transport, (iii) corrections to tracer datasets and (iv) the choice of mixing model on predictions of sediment source contributions. Sediment fingerprinting has the potential to make a very significant contribution to the measurement of contemporary sediment sources in watersheds, but cannot be viewed as an 'off-the-shelf' technique for widespread application until important challenges have been addressed.

  12. Hydrocarbon Bioaccumulation from contaminated sediment by a deposit feeding polychaete

    SciTech Connect

    Weston, D.P. )

    1990-01-09

    This study examined the role of sediment organic carbon content in aromatic hydrocarbon bioaccumulation and assessed the importance of two routes of hydrocarbon uptake: (1) uptake of the dissolved contaminant fraction from interstitial or overlying water; and (2) uptake of the particulate contaminant fraction from ingested sediments. The lugworm, Abarenicola pacifica, was exposed to three sediments contaminated with [[sup 3]H] benzo(a)pyrene (BaP). By manipulating the organic content of these sediments it was possible to establish three treatments with similar BaP concentrations in the interstitial water, but differing in the amount of BaP in the bulk sediment. BaP bioaccumulation over the first few days of exposure was correlated with feeding rate, implicating ingested sediments as a source of implicating ingested sediments as a source of BaP. The greatest body burden, however, was attained in those individuals held in sediments with the lowest organic carbon content and the lowest BaP concentration. Body burden at steady state was not correlated with either BaP concentrations in bulk sediment (dry weight or organic normalized basis) or the interstitial water. Increased organic matter decreased BaP bioavailability in a non-linear fashion. Bioaccumulation factors relative to water and organic content were relatively constant between 1 and 2% organic carbon in the sediment, but these same accumulation factors substantially underestimated body burden if applied to sandy sediments with little (0.3%) organic carbon.

  13. Two-dimensional sediment transport modeling for reservoir sediment management: Reventazón River, Costa Rica

    NASA Astrophysics Data System (ADS)

    Dubinski, I. M.

    2012-12-01

    Sedimentation is an ongoing concern for reservoirs that may be addressed using a variety of sediment management options. Sedimentation in reservoirs reduces reservoir storage and alters the sediment supply downstream. The objective of this study is to estimate the spatial and temporal distribution of deposited sediment in a proposed reservoir in the Reventazón River, Costa Rica over long-term operation (40 years) under different sediment management scenarios. The two-dimensional sediment transport model MIKE 21C by DHI is used to simulate sediment deposition for the base case (i.e., no sediment management) and assess the anticipated effectiveness of two sediment management strategies (i.e., full drawdown flushing and partial drawdown flushing). Incoming total sediment load is estimated using measured and estimated suspended sediment load combined with bed load estimated using the BAGS model with the Wilcock and Crowe (2003) equation. The base case simulation indicates that the anticipated storage loss in the absence of sediment management would amount to about 35% of the total and 33% of the active storage volume over a 40-year period. The predicted storage losses are significantly less when the performance of full drawdown flushing and partial drawdown flushing was simulated. In the case of full drawdown flushing the total anticipated storage loss is about 22%, while the loss in active storage is only 7%. In the case of partial drawdown flushing the predicted loss in total storage is 26%, while the anticipated loss in active storage is 8% after 40 years of operation. The simulations indicate that flushing is a viable and sustainable sediment management option for maintaining active storage in the proposed reservoir and passing through sediment.

  14. Tolerance of freshwater test organisms to formulated sediments for use as control materials in whole-sediment toxicity tests

    SciTech Connect

    Kemble, N.E.; Dwyer, F.J.; Ingersoll, C.G.; Dawson, T.D.; Norberg-King, T.J.

    1999-02-01

    A method is described for preparing formulated sediments for use in toxicity testing. Ingredients used to prepare formulated sediments included commercially available silt, clay, sand, humic acid, dolomite, and {alpha}-cellulose (as a source of organic carbon). {alpha}-Cellulose was selected as the source of organic carbon because it is commercially available, consistent from batch to batch, and low in contaminant concentrations. The tolerance of freshwater test organisms to formulated sediments for use as control materials in whole-sediment toxicity testing was evaluated. Sediment exposures were conducted for 10 d with the amphipod Hyalella azteca, the midges Chironomus riparius and C. tentans, and the oligochaete Lumbriculus variegatus and for 28 d with H. azteca. Responses of organisms in formulated sediments was compared with a field-collected control sediment that has routinely been used to determine test acceptability. Tolerance of organisms to formulated sediments was evaluated by determining responses to varying levels of {alpha}-cellulose, to varying levels of grain size, to evaluation of different food types, or to evaluation of different sources of overlying water. In the 10-d exposures, survival of organisms exposed to the formulated sediments routinely met or exceeded the responses of test organisms exposed to the control sediment and routinely met test acceptability criteria required in standard methods. Growth of amphipods and oligochaetes in 10-d exposures with formulated sediment was often less than growth of organisms in the field-collected control sediment. Additional research is needed, using the method employed to prepare formulated sediment, to determine if conditioning formulated sediments before starting 10-d tests would improve the growth of amphipods. In the 28-d exposures, survival of H. azteca was low when reconstituted water was used as the source of overlying water. However, when well water was used as the source of overlying water in

  15. Tolerance of freshwater test organisms to formulated sediments for use as control materials in whole-sediment toxicity tests

    USGS Publications Warehouse

    Kemble, N.E.; Dwyer, F.J.; Ingersoll, C.G.; Dawson, T.D.; Norberg-King, T. J.

    1999-01-01

    A method is described for preparing formulated sediments for use in toxicity testing. Ingredients used to prepare formulated sediments included commercially available silt, clay, sand, humic acid, dolomite, and ??- cellulose (as a source of organic carbon). ??-Cellulose was selected as the source of organic carbon because it is commercially available, consistent from batch to batch, and low in contaminant concentrations. The tolerance of freshwater test organisms to formulated sediments for use as control materials in whole-sediment toxicity testing was evaluated. Sediment exposures were conducted for 10 d with the amphipod Hyalella azteca, the midges Chironomus riparius and C. tentans, and the oligochaete Lumbriculus variegatus and for 28 d with H. azteca. Responses of organisms in formulated sediments was compared with a field-collected control sediment that has routinely been used to determine test acceptability. Tolerance of organisms to formulated sediments was evaluated by determining responses to varying levels of ??-cellulose, to varying levels of grain size, to evaluation of different food types, or to evaluation of different sources of overlying water. In the 10-d exposures, survival of organisms exposed to the formulated sediments routinely met or exceeded the responses of test organisms exposed to the control sediment and routinely met test acceptability criteria required in standard methods. Growth of amphipods and oligochaetes in 10-d exposures with formulated sediment was often less than growth of organisms in the field-collected control sediment. Additional research is needed, using the method employed to prepare formulated sediment, to determine if conditioning formulated sediments before starting 10-d tests would improve the growth of amphipods. In the 28-d exposures, survival of H. azteca was low when reconstituted water was used as the source of overlying water. However, when well water was used as the source of overlying water in 28-d exposures

  16. Sediments Contamination with Organic Micropollutants: Current State and Perspectives

    NASA Astrophysics Data System (ADS)

    Popenda, Agnieszka; Włodarczyk-Makuła, Maria

    2016-06-01

    This study focused on the sediment contamination with some organic micropollutants based on the monitoring data together with available literature in Poland. The following persistent organic pollutants (POPs): polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and chlorinated pesticides (CP) were characterized in sediments with respect to current legislations in force. Based on accessible data, higher PAHs, PCBs and CP concentrations were found in river sediments than in lake sediments. Especially, sediments of the Oder River and its tributary in the southern part of Poland, were highly polluted. In order to minimize the risk of the secondary pollution of surface waters, it is necessary to introduce consolidated management system with sediments proceeding. Furthermore, it is also of great importance to elaborate specific regulations concerning conditions of sediments management.

  17. Overview of sediment quality in the United States. Final report

    SciTech Connect

    Lyman, W.J.; Glazer, A.E.; Ong, J.H.; Coons, S.F.

    1987-06-01

    This report provides an overview of sediment quality in waters of the United States. The focus is on describing qualitatively the nature and extent of contaminated sediments, i.e., bottom deposits in rivers, lakes, harbors and oceans that have been polluted with heavy metals, organic chemicals and other materials from anthropogenic sources. Such materials, also called in-place pollutants, may be significantly impacting aquatic ecosystems in some areas, and may be degrading the quality of the overlying water to the extent that water quality criteria are exceeded and that uses of the water - by both aquatic life and humans - are impaired. Major sections of the report provide information on: (1) the nature of sediment contamination problems; (2) sources of contaminated sediments; (3) available responses to sediment contamination; and (4) an overview of sediment quality criteria, used to classify sediments as polluted or not. There are appendices.

  18. Ecotoxicological evaluation of sediments applied to environmental forensic investigation.

    PubMed

    Alves, R H; Rietzler, A C

    2015-11-01

    The present study aimed to evaluate the potential for using toxicity assays with sediment samples for the detection of water pollution caused by the discharge of tannery effluents into water bodies and its application to environmental forensic investigation. The study included ecotoxicological evaluation of sediments, survey of benthic organisms in the field, as well as chromium, cadmium and lead dosage which provided data for a sediment quality triad evaluation. The sediment samples showed acute and chronic toxicity to the bioindicators, low biodiversity of benthic macrofauna and high chromium concentration, reaching up to 4365 mg.Kg-1. A close relationship was observed between the separate results of ecotoxicological sediment evaluation and the sediment quality triad. The sediment ecotoxicological assessment proved to be applicable to tracking sources of contamination related to tanneries and similar activities in environmental forensics. PMID:26675905

  19. Nematode communities in contaminated river sediments.

    PubMed

    Heininger, Peter; Höss, Sebastian; Claus, Evelyn; Pelzer, Jürgen; Traunspurger, Walter

    2007-03-01

    Nematode communities of eight sites from three river catchments were investigated in terms of the genera composition, feeding types, and life-history strategists. The sampling sites showed a gradient of anthropogenic contamination with heavy metals and organic pollutants being important factors in differentiating the sites. Nematode community structure was related to sediment pollution and the hydro-morphological structure of the sampling sites. Heavily contaminated sites were characterized by communities with high relative abundances of omnivorous and predacious nematodes (Tobrilus, c-p 3; Mononchus, c-p 4), while sites with low to medium contamination were dominated by bacterivorous nematodes (Monhystera, Daptonema; c-p 2) or suction feeders (Dorylaimus, c-p 4). The relatively high Maturity Index values in the heavily polluted sites were surprising. Nematodes turned out to be a suitable organism group for monitoring sediment quality, with generic composition being the most accurate indicator for assessing differences in nematode community structure. PMID:16905227

  20. Rio Grande sediment study -- Supply and transport

    SciTech Connect

    Diniz, E.; Eidson, D.; Bourgeois, M.

    1995-12-31

    The 1992 New Mexico State Legislature directed the Interstate Stream Commission (ISC) to study the feasibility of clearing and deepening the channel of the Rio Grande between Albuquerque and Elephant Butte to improve water conveyance and water conservation. The ISC requested the US Army Corps of Engineers-Albuquerque District (COE) to undertake this study under the Planning Assistance to States Program. The study was divided into two phases. Phase 1 consisted of an analysis of the sediment contribution to the Rio grande from the tributaries and an evaluation of the existing US Geological Survey (USGS) sediment gage data. Phase 2 will be an analysis, through the use of an HEC-6, Scour and Deposition in Rivers and Reservoirs, computer model, to determine the long-term performance of any Rio Grande channel improvements. This narrative presents the Phase 1 methods and results.

  1. Beryllium in sediments of Nagoya harbor estuaries

    SciTech Connect

    Itoh, K.

    1986-06-01

    Beryllium occurs naturally in minerals and oils. Other than the natural sources, considerable quantity of beryllium has been discharged from its smelting industry. Soil pollutants caused by beryllium in the circumference of its smelting industry on the banks of Nagoya harbor estuaries have been reported. Several methods for the spectroscopic determination of beryllium can not eliminate the interference caused by fluoride ion which remains in the digestion solution when hydrofluoric acid is used to degradate the silicate lattice. Accordingly, the authors attempted to improve the pretreatment in order to eliminate the effect of fluoride ion, and to make the procedure simpler and faster with high precision. A simple and sensitive method is presented for the determination of beryllium in sediments by atomic absorption spectroscopy using methylisobutylketone extraction with acetylacetone. They have carried out an extensive investigation on the pollution of sea water and sediments of Nagoya harbor estuaries, which is located in one of the most active industrial areas in Japan.

  2. Geomechanical Modeling of Gas Hydrate Bearing Sediments

    NASA Astrophysics Data System (ADS)

    Sanchez, M. J.; Gai, X., Sr.

    2015-12-01

    This contribution focuses on an advance geomechanical model for methane hydrate-bearing soils based on concepts of elasto-plasticity for strain hardening/softening soils and incorporates bonding and damage effects. The core of the proposed model includes: a hierarchical single surface critical state framework, sub-loading concepts for modeling the plastic strains generally observed inside the yield surface and a hydrate enhancement factor to account for the cementing effects provided by the presence of hydrates in sediments. The proposed framework has been validated against recently published experiments involving both, synthetic and natural hydrate soils, as well as different sediments types (i.e., different hydrate saturations, and different hydrates morphologies) and confinement conditions. The performance of the model in these different case studies was very satisfactory.

  3. Biological Remnants in a Precambrian Sediment.

    PubMed

    Meinschein, W G; Barghoorn, E S; Schopf, J W

    1964-07-17

    A billion-year-old shale from the Nonesuch formation at White Pine Mine, Michigan, contains microfossils, porphyrins, and optically active alkanes. Pristane and phytane, which are isoprenoid hydrocarbons found in living plants and animals, are constituents of the ancient alkanes in the Nonesuch shale; the presence of porphyrins in this Precambrian sediment suggests that photosynthetic organisms have existed for more than a billion years.

  4. Seasonal sediment and nutrient transport patterns.

    PubMed

    Moriasi, D N; Guzman, J A; Steiner, J L; Starks, P J; Garbrecht, J D

    2014-07-01

    It is essential to understand sediment and nutrient sources and their spatial and temporal patterns 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 determine seasonal patterns of suspended sediment (SS), total N (TN), and total P (TP) concentrations and loadings for three USGS gauge sites located at the Fort Cobb Reservoir Experimental watershed (FCREW) located in southwestern Oklahoma. Measured instantaneous discharge, SS, TN, and TP concentration data were used to develop lognormal water quality-discharge relationships. The water quality-discharge relationships were used to generate estimated seasonal concentrations and loads based on hourly or 30-min interval discharge. The estimated concentrations and loads were used to determine seasonal patterns for SS, TN, and TP relative to the respective state water quality criteria. Decreasing and increasing monotonic trends were observed for the seasonal time series loads for all three sites, but they were insignificant based on the Spearman test (α = 0.05). The largest loads were estimated during the wet springs and summers. The study SS, TN, and TP target concentrations were exceeded in one season or another. The study results showed that the priority locations to implement the TN and TP conservation practices were the Lake Creek and Willow Creek subwatersheds during the winter and spring seasons. Common practices to mitigate nutrients and suspended sediments include nutrient management, no-till, conversion of cultivated land to pasture, riparian buffers, and animal exclusion.

  5. Remanent magnetism of sediment governs magnetofossil alignment

    NASA Astrophysics Data System (ADS)

    Wendel, JoAnna

    2014-04-01

    Most bacteria navigate by reacting to different chemical signals in their surroundings, but some bacteria have another navigational tool in their arsenal—the Earth's magnetic field. Nestled inside these magnetotactic bacteria (MTB) are organelles called magnetosomes, filled with tiny magnetic crystals and arranged in chains, which form nano-sized compass needles. When MTB die and degrade, these tiny crystals can remain in sediment and eventually become magnetic fossils called magnetofossils.

  6. Thermal conductivity of hydrate-bearing sediments

    USGS Publications Warehouse

    Cortes, D.D.; Martin, A.I.; Yun, T.S.; Francisca, F.M.; Santamarina, J.C.; Ruppel, C.

    2009-01-01

    A thorough understanding of the thermal conductivity of hydrate-bearing sediments is necessary for evaluating phase transformation processes that would accompany energy production from gas hydrate deposits and for estimating regional heat flow based on the observed depth to the base of the gas hydrate stability zone. The coexistence of multiple phases (gas hydrate, liquid and gas pore fill, and solid sediment grains) and their complex spatial arrangement hinder the a priori prediction of the thermal conductivity of hydrate-bearing sediments. Previous studies have been unable to capture the full parameter space covered by variations in grain size, specific surface, degree of saturation, nature of pore filling material, and effective stress for hydrate-bearing samples. Here we report on systematic measurements of the thermal conductivity of air dry, water- and tetrohydrofuran (THF)-saturated, and THF hydrate-saturated sand and clay samples at vertical effective stress of 0.05 to 1 MPa (corresponding to depths as great as 100 m below seafloor). Results reveal that the bulk thermal conductivity of the samples in every case reflects a complex interplay among particle size, effective stress, porosity, and fluid-versus-hydrate filled pore spaces. The thermal conductivity of THF hydrate-bearing soils increases upon hydrate formation although the thermal conductivities of THF solution and THF hydrate are almost the same. Several mechanisms can contribute to this effect including cryogenic suction during hydrate crystal growth and the ensuing porosity reduction in the surrounding sediment, increased mean effective stress due to hydrate formation under zero lateral strain conditions, and decreased interface thermal impedance as grain-liquid interfaces are transformed into grain-hydrate interfaces. Copyright 2009 by the American Geophysical Union.

  7. Seasonal sediment and nutrient transport patterns.

    PubMed

    Moriasi, D N; Guzman, J A; Steiner, J L; Starks, P J; Garbrecht, J D

    2014-07-01

    It is essential to understand sediment and nutrient sources and their spatial and temporal patterns 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 determine seasonal patterns of suspended sediment (SS), total N (TN), and total P (TP) concentrations and loadings for three USGS gauge sites located at the Fort Cobb Reservoir Experimental watershed (FCREW) located in southwestern Oklahoma. Measured instantaneous discharge, SS, TN, and TP concentration data were used to develop lognormal water quality-discharge relationships. The water quality-discharge relationships were used to generate estimated seasonal concentrations and loads based on hourly or 30-min interval discharge. The estimated concentrations and loads were used to determine seasonal patterns for SS, TN, and TP relative to the respective state water quality criteria. Decreasing and increasing monotonic trends were observed for the seasonal time series loads for all three sites, but they were insignificant based on the Spearman test (α = 0.05). The largest loads were estimated during the wet springs and summers. The study SS, TN, and TP target concentrations were exceeded in one season or another. The study results showed that the priority locations to implement the TN and TP conservation practices were the Lake Creek and Willow Creek subwatersheds during the winter and spring seasons. Common practices to mitigate nutrients and suspended sediments include nutrient management, no-till, conversion of cultivated land to pasture, riparian buffers, and animal exclusion. PMID:25603081

  8. Monitoring of suspended sediment in South Tyrol

    NASA Astrophysics Data System (ADS)

    Nadalet, Rudi; Dinale, Roberto; Pernter, Martin; Maraldo, Luca; Peterlin, Dieter; Richter, Arnold; Comiti, Francesco

    2016-04-01

    In the context of the EU Water Framework Directive (WFD), which aims to achieve a good status of European water bodies, the Hydrographic Office of the Autonomous Province of Bolzano (Italy) extended in 2014 its institutional activities including the monitoring of suspended sediment in the river channel network. Currently, the only active monitoring station is on the Adige River at the gauging station of Ponte Adige near Bolzano (drainage area 2705 km2). The applied monitoring strategy and the data analysis concept are both based on the guidelines issued by the Austrian Federal Ministry of Agriculture, Forestry, Environment and Water Management (BMLFUW). The results indicates that the temporal variability strongly differs during the investigated period (2014-2015). In addition to the analysis of precipitation and water discharge, temperature and lightning activity were also included to better understand the sediment transport dynamics observed at the station. In summer 2015, the combination of constantly high daily temperature throughout the Adige basin (which drove intense glacier melting in the headwaters) with a high frequency of convective rainfall events (90% more than in 2014, obtained through lightning detection), led to an annual mass of transported suspended sediment of 260000 t. Interestingly, this value is similar to the one estimated for 2014 (300000 t), which was characterized by very different meteorological conditions (colder and wetter summer), but with the occurrence of an important flood in August, which transported half of the annual amount. Finally, we can conclude that the adopted monitoring strategy is applicable for institutional aims in terms of costs as well as in terms of time effort. During the next years, other stations for suspended sediment monitoring are planned to be installed in the Province to cover the most important river segments.

  9. Sediment Interfaces: Ecotones on a Microbial Scale

    NASA Astrophysics Data System (ADS)

    Borchers, M. R.; Colwell, F. S.; D'Angelo, G.; Thurber, A. R.; Graw, M. F.

    2015-12-01

    Ecotones - transitions between different biomes - often support greater faunal diversity than the adjacent ecological systems. For subseafloor microorganisms, defined geological and chemical gradients have been shown to affect population sizes and community structure, but the role that sediment interfaces play is still unclear. Here, we test the hypothesis that zones of transition between two distinct sediment types increase microbial diversity and change community composition. Concurrently, we explore those factors that drive deep-subsurface microbial community structure (e.g., depth, interstitial water chemistry, methane concentrations, clay content). Samples from IODP Expedition 349 - South China Sea Tectonics - had interfaces of either ash/clay or turbidite/clay boundaries sampled , DNA extracted, and the 16S rRNA gene analyzed on an Illumina MiSeq platform. Initial analyses reveal that microbial communities in sediment samples are distinct from communities in drilling fluid, indicating that contamination is unlikely. In four of the eight complete interfaces currently analyzed we found an increase in diversity (based on the chao1 index), in certain cases doubling the diversity of the adjacent rock types. The pattern was not uniform across all interfaces. While some posit that ecotones provide a mixing of the two adjacent communities, we were surprised to find an abundance (mean = 392 OTUs) of unique microbial taxa within the ecotone itself when compared to adjacent sediment (mean=282 unique OTUs). Thus while diversity was not uniformly increased in ecotones, the interface led to divergent microbial communities that were not simply mixtures of those adjacent. We will discuss the ability of abiotic factors in explaining the among ecotone variance that we observed. Our investigation helps to characterize the factors that drive microbial community structure of the subseafloor while highlighting the need to focus on habitat heterogeneity at a scale pertinent to

  10. Preliminary cross section of Englebright Lake sediments

    USGS Publications Warehouse

    Snyder, Noah P.; Hampton, Margaret A.

    2003-01-01

    Overview -- The Upper Yuba River Studies Program is a CALFED-funded, multidisciplinary investigation of the feasibility of introducing anadromous fish species to the Yuba River system upstream of Englebright Dam. Englebright Lake (Figure 1 on poster) is a narrow, 14-km-long reservoir located in the northern Sierra Nevada, northeast of Marysville, CA. The dam was completed in 1941 for the primary purpose of trapping sediment derived from mining operations in the Yuba River watershed. Possible management scenarios include lowering or removing Englebright Dam, which could cause the release of stored sediments and associated contaminants, such as mercury used extensively in 19th-century hydraulic gold mining. Transport of released sediment to downstream areas could increase existing problems including flooding and mercury bioaccumulation in sport fish. To characterize the extent, grain size, and chemistry of this sediment, a coring campaign was done in Englebright Lake in May and June 2002. More than twenty holes were drilled at 7 different locations along the longitudinal axis of the reservoir (Figure 4 on poster), recovering 6 complete sequences of post-reservoir deposition and progradation. Here, a longitudinal cross section of Englebright Lake is presented (Figure 5 on poster), including pre-dam and present-day topographic profiles, and sedimentologic sections for each coring site. This figure shows the deltaic form of the reservoir deposit, with a thick upper section consisting of sand and gravel overlying silt, a steep front, and a thinner lower section dominated by silt. The methodologies used to create the reservoir cross section are discussed in the lower part of this poster.

  11. Sedimentation basin performance at highway construction sites.

    PubMed

    Kalainesan, Sujaya; Neufeld, Ronald D; Quimpo, Rafael; Yodnane, Precha

    2009-02-01

    Sedimentation basins (SBs) are commonly used during highway construction for erosion and sedimentation pollution control as well as for attenuation of overland storm waters. In order to evaluate the sediment removal capacity of these SBs, four basins were selected for monitoring from a new highway construction that extends I-99 to I-80, in Pennsylvania. Between September 2004 and August 2005, ten sampling trips were conducted during which basin inlet and outlet water samples were obtained. The SB samples were analyzed for pH, color, turbidity, total suspended solids (TSS), volatile suspended solids (VSS), total and dissolved iron, magnesium, manganese, aluminum, calcium, sulfate and phosphate. The data showed peaks in concentrations of TSS, total aluminum, total manganese, total iron and total phosphate that closely correlated to localized rainfall peaks. For certain samples, the concentration of TSS in the outlet was higher than the TSS concentration at the basin inlet, suggesting sediment re-suspension. In general SBs managed high flows during wet weather events, but were not effective in capturing particulates. This paper discusses the need for Best Management Practices (BMPs) for the design of SBs that reflect contemporary concerns for management of particle removal and to control the release of particulate-bound metals. This paper also evaluates the water quality impacts of naturally occurring acidic drainages into SBs, as several acidic seeps with pH in the range of 5-6 and having high dissolved concentrations of metals (Fe, Mn, Mg and Ca), sulfate and phosphate were observed draining into the SBs.

  12. Discrete element modelling of subglacial sediment deformation

    NASA Astrophysics Data System (ADS)

    Christensen, A. D.; Egholm, D. L.; Piotrowski, J. A.; Tulaczyk, S.

    2012-04-01

    Soft, deformable sediments are often present under glaciers. Subglacial sediments deform under the differential load of the ice, and this causes the overlying glacier to accelerate its motion. Understanding the rheology of subglacial sediment is therefore important for models of glacial dynamics. Previous studies of the mechanical behaviour of subglacial sediments have primarily relied on analytical considerations and laboratory shearing experiments. As a novel approach, the Discrete Element Method (DEM) is used to explore the highly nonlinear dynamics of a granular bed that is exposed to stress conditions comparable to subglacial environments. The numerical approach allows close monitoring of the mechanical and rheological behaviour under a range of conditions. Of special interest is bed shear strength, strain distribution and -localization, mode of deformation, and role of effective normal pressure during shearing. As a calibration benchmark, results from laboratory ring-shear experiments on granular material are compared to similar numerical experiments. The continuously recorded stress dynamics in the laboratory shear experiments are compared to DEM experiments, and the micro-mechanical parameters in the contact model of the DEM code are calibrated to match the macroscopic Mohr-Coulomb failure criteria parameters, constrained from successive laboratory shear tests under a range of normal pressures. The data-parallel nature of the basic DEM formulation makes the problem ideal for utilizing the high arithmetic potential of modern general-purpose GPUs. Using the Nvidia Cuda C toolkit, the algorithm is formulated for spherical particles in three dimensions with a soft-body contact model. Scene rendering is performed using a custom Cuda ray-tracing algorithm. Efforts on optimization of the particle algorithm are discussed, and future plans of expansion are presented.

  13. Dissolved and particulate carbohydrates in contrasting marine sediments

    NASA Astrophysics Data System (ADS)

    Burdige, D. J.; Skoog, A.; Gardner, K.

    2000-03-01

    Dissolved and particulate carbohydrates were examined in contrasting Chesapeake Bay (estuarine) and mid-Atlantic shelf/slope break (continental margin) sediments. Particulate carbohydrates (PCHOs) represented ˜5-9% of the total sediment particulate organic carbon (POC), and PCHO remineralization appeared to be a similar fraction of total sediment carbon oxidation (or C ox). When these results are compared with results from other coastal sediments and a pelagic turbidite, PCHO remineralization (as a percentage of C ox) did not vary by more than a factor of ˜2-3 over a 3-4 order of magnitude range in C ox values. The causes of this are not well understood, but may be related to specific effects associated with the remineralization of highly altered organic matter mixtures under aerobic conditions. Dissolved carbohydrates (DCHOs) in these sediment pore waters ranged from ˜30 to 400 μM, increased with depth in a manner similar to total DOC, and represented ˜10 to 55% of pore water DOC. In Chesapeake Bay sediments this percentage decreased with sediment depth, while in these continental margin sediments it was constant (upper 30 cm). Of the DCHOs in these pore waters ˜30 to 50% could be identified as individual aldoses (monomeric neutral sugars), and total aldose yields (individual aldoses as a percentage of total DOC) were higher in these continental margin sediment pore waters (>9%) than they were in the estuarine sediment pore waters (<5%). A comparison of DCHO and PCHO concentrations in these sediments indicates that their concentrations are uncoupled, and that pore water DCHO concentrations are primarily controlled by sediment remineralization processes. Pore water DCHOs appeared to be preferentially found in the high molecular weight (HMW) DOC pool, and likely occur as some of the initial HMW intermediates produced and consumed during sediment POC remineralization. These results also support past suggestions about the differing controls on carbon

  14. Toxicity of lead-contaminated sediment to mallards

    USGS Publications Warehouse

    Heinz, G.H.; Hoffman, D.J.; Sileo, L.; Audet, D.J.; LeCaptain, L.J.

    1999-01-01

    Because consumption of lead-contaminated sediment has been suspected as the cause of waterfowl mortality in the Coeur d?Alene River basin in Idaho, we studied the bioavailability and toxicity of this sediment to mallards (Anas platyrhynchos). In experiment 1, one of 10 adult male mallards died when fed a pelleted commercial duck diet that contained 24% lead-contaminated sediment (with 3,400 μg/g lead in the sediment). Protoporphyrin levels in the blood increased as the percentage of lead-contaminated sediment in the diet increased. Birds fed 24% lead-contaminated sediment exhibited atrophy of the breast muscles, green staining of the feathers around the vent, viscous bile, green staining of the gizzard lining, and renal tubular intranuclear inclusion bodies. Mallards fed 24% lead-contaminated sediment had means of 6.1 μg/g of lead in the blood and 28 μg/g in the liver (wet-weight basis) and 1,660 μg/g in the feces (dry-weight basis). In experiment 2, we raised the dietary concentration of the lead-contaminated sediment to 48%, but only about 20% sediment was actually ingested due to food washing by the birds. Protoporphyrin levels were elevated in the lead-exposed birds, and all of the mallards fed 48% lead-contaminated sediment had renal tubular intranuclear inclusion bodies. The concentrations of lead in the liver were 9.1 μg/g for mallards fed 24% lead-contaminated sediment and 16 μg/g for mallards fed 48% lead-contaminated sediment. In experiment 3, four of five mallards died when fed a ground corn diet containing 24% lead-contaminated sediment (with 4,000 μg/g lead in this sample of sediment), but none died when the 24% lead-contaminated sediment was mixed into a nutritionally balanced commercial duck diet; estimated actual ingestion rates for sediment were 14% and 17% for the corn and commercial diets. Lead exposure caused elevations in protoporphyrin, and four of the five mallards fed 24% lead-contaminated sediment in a commercial diet and all five

  15. Phytoplankton and sediments in Gulf of Mexico

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Affected both by terrestrial factors like agriculture, deforestation, and erosion, and by marine factors like salinity levels, ocean temperature and water pollution, coastal environments are the dynamic interface between land and sea. In this MODIS image from January 15, 2002, the Gulf of Mexico is awash in a mixture of phytoplankton and sediment. Tan-colored sediment is flowing out into the Gulf from the Mississippi River, whose floodplain cuts a pale, wide swath to the right of center in the image, and also from numerous smaller rivers along the Louisiana coast (center). Mixing with the sediment are the multi-colored blue and green swirls that reveal the presence of large populations of marine plants called phytoplankton. Phytoplankton populations bloom and then fade, and these cycles affect fish and mammals-including humans-higher up the food chain. Certain phytoplankton are toxic to both fish and humans, and coastal health departments must monitor ecosystems carefully, often restricting fishing or harvesting of shellfish until the blooms have subsided.

  16. Photochemical source of metals for sediments.

    PubMed

    Kopácek, Jirí; Maresová, Marie; Norton, Stephen A; Porcal, Petr; Veselý, Josef

    2006-07-15

    A mass budget study of major in-lake Al fluxes, palaeolimnological data on a >10,000 year old sediment record, and in situ photochemical experiments performed at Plesné Lake (Czech Republic) suggest that photochemical liberation of organically bound aluminum (Al) and iron (Fe) by solar radiation is a significant natural source of their ionic species for lakes and subsequent oxyhydroxides for sediments. The results show that photochemically induced transformation of dissolved Al and Fe to solid oxyhydroxides deposited to Plesné Lake sediment dominated (91 and 73%, respectively) their sedimentary flux throughout the preindustrial era, since soil formation initiated in the catchment. The following sequence of processes occurs: (i) soil organic acids dissolve and bind metals and export them from terrestrial to aquatic systems. (ii) Photochemical decomposition of organic-metal complexes liberates a significant portion (approximately 50% in Pleseé Lake) of organically bound Al and Fe as inorganic ions. (iii) The liberated ionic Al and Fe hydrolyze, precipitate as oxyhydroxide particles, and settle. We hypothesise that the same Al and Fe transporting process occurs in other lakes and coastal marine areas and is ecologically important because Al and Fe oxyhydroxides can bind trace metals and phosphorus.

  17. Compost treatment of contaminated pond sediment

    SciTech Connect

    Francis, M.; Gukert, D. |

    1995-12-31

    This paper summarizes an experiment involving compost treatment of pond sediment contaminated with hydrocarbons. Experimental variables included the size, shape, and aeration of the compost pile. Pile temperature measurements and hydrocarbon analyses were made periodically. Temperatures in the pyramid shaped compost piles rose quickly and remained elevated above ambient for about one month; during this period, hydrocarbon loss from the piles was greatest. The flat pile did not show elevated temperatures at any time, and total hydrocarbon losses by volatilization were 19.1 g. Total losses from the passively aerated pile were 1.02 g, while the actively aerated pile had losses of 0.08 g. Individual identified component compounds in the sediment included polycyclic aromatic hydrocarbons (PAHs). Final levels were in the 2 to 20 ppM range compared to 100 to 400 ppM in the original sediment. Composting removed PAH components and other light organics, and the composted material can be stored onsite or landfilled without leaching concerns.

  18. Sediment resuspension in Lake St. Clair

    SciTech Connect

    Hawley, N. ); Lesht, B.M. )

    1992-12-01

    Time-series measurements of water transparency, wave conditions, and current speed were made at several different sites in Lake St. Clair during five different 1-month periods in 1985 and 1986. Observed changes in suspended sediment concentration were modeled with a simple zero-dimensional, spatially averaged, mass balance model in which local bottom erosion was expressed as a linear function of the bottom shear stress. Estimates of the three parameters required by the model (particle settling velocity, resuspension concentration, and background suspended material concentration) are reasonably consistent for the various data sets, suggesting that the properties of the lake bottom do not change significantly through either space or time. The modeled settling velocities agree with the observed suspended particle size data and the erosion rates are comparable to laboratory results for freshwater sediments. The results show that a simple mass flux model can be used to model local sediment resuspension events in Lake St. Clair with reasonable accuracy. 23 refs., 5 figs., 3 tabs.

  19. Metals Retention in Constructed Wetland Sediments

    SciTech Connect

    KNOX, ANNA

    2004-10-27

    The A-01 wetland treatment system (WTS) was designed to remove metals from the effluent at the A-01 NPDES outfall at the Savannah River Site, Aiken, SC. Sequential extraction data was used to evaluate remobilization and retention of Cu, Pb, Zn, Mn, and Fe in the wetland sediment. Remobilization of metals was determined by the Potentially Mobile Fraction (PMF) and metal retention by the Recalcitrant Factor (RF). The PMF, which includes water soluble, exchangeable, and oxides fractions, is the contaminant fraction that has the potential to enter into the mobile aqueous phase under changeable environmental conditions. PMF values were low for Cu, Zn and Pb (about 20 percent) and high for Fe and Mn (about 60 to 70 percent). The RF, which includes crystalline oxides, sulfides or silicates and aluminosilicates, is the ratio of strongly bound fractions to the total concentration of elements in sediment. RF values were about 80 percent for Cu, Zn and Pb, indicating high retention in the sediment and 30 percent to above 40 percent for Fe and Mn indication low retention.

  20. Flume simulation of sedimentation in recirculating flow

    SciTech Connect

    Schmidt, J.C. ); Rubin, D.M. ); Ikeda, H. )

    1990-05-01

    A 4-m-wide flume at the University of Tsukuba Environmental Research Center was used to simulate flow conditions near debris fans in bedrock gorges. Flow was constricted to 2 m by a semicircular obstruction. During the authors experiments (discharge = 600 L/sec; Froude number of constricted flow = 1) a zone of recirculating current extended 25-30 m downstream from the separation point at the constriction. The pattern and velocity of surface flow was determined using time-lapse photography; subsurface velocity was measured with a two-dimensional electromagnetic current meter. During 32-hr of run time, a fine, very coarse sand mixture was fed into the flow at a rate between 0.5-1 kg/sec. Oscillation ripples developed beneath the separation surface that bounds the recirculation zone, and upstream-migrating dunes and ripples developed within the recirculation zone upstream from the reattachment point. A mid-channel expansion bar was deposited downstream from the reattachment point. Sedimentation within the recirculation zone continued by vertical aggradation and by upstream migration of dunes and ripples. Sediments within the recirculation zone were areally sorted with the finest sediment deposited near the separation point. These patterns are consistent with field observations of bars along the Colorado River in the Grand Canyon.

  1. Sediment from the Tigris and Euphrates

    NASA Technical Reports Server (NTRS)

    2002-01-01

    There is a large amount of sediment clearly visible in the true-color image of the Persian Gulf, acquired on November 1, 2001, by the Moderate-resolution Imaging Spectroradiometer (MODIS). Carried by the confluence of the Tigris and Euphrates Rivers (at center), the sediment-laden waters appear light brown where they enter the northern end of the Persian Gulf and then gradually dissipate into turquoise swirls as they drift southward. The nutrients these sediments carry are helping to support a phytoplankton bloom in the region, which adds some darker green hues in the rich kaleidoscope of colors on the surface (see the high resolution image). The confluence of the Tigris and Euphrates Rivers marks the southernmost boundary between Iran (upper right) and Iraq (upper left). South of Iraq are the countries of Kuwait and Saudi Arabia. The red dots indicate the probable locations of fires burning at oil refineries. Thin black plumes of smoke can be seen streaming away from several of these. Image courtesy Jacques Descloitres, MODIS Land Rapid Response Team at NASA GSFC

  2. Riverside morphological response to pulsed sediment diversions

    NASA Astrophysics Data System (ADS)

    Meselhe, Ehab A.; Sadid, Kazi M.; Allison, Mead A.

    2016-10-01

    Sediment diversions deliver sediment and fresh water from rivers to surrounding wetland areas as a strategy to build and sustain coastal wetland areas. Numerical modeling of the lower Mississippi River, USA, coupled with detailed field observations are used to provide quantitative information about the morphodynamic behavior of river channels in response to diverting large quantities of water and sediment. This study suggests that reduction in river stream power caused by the extraction of significant amounts of water discharge results in river channel aggradation in the vicinity and downstream of diversions. The aggradation quantities depend on the diversion sand capture efficiency and the diverted water discharge relative to the main river discharge. Additional factors observed to influence the sand capture efficiency include the invert elevation of the diversion intake, placement of the diversion intake on top of a lateral or point bars, and the local degree of the river channel curvature. Notably, the capture efficiency of fine material (silt and clay), to a large degree, is not site specific and is rather influenced by the timing of the diversion structure operations relative to the incoming fine-material hydrograph.

  3. Irreversible sediment formation in green tea infusions.

    PubMed

    Xu, Yong-Quan; Chen, Gen-Sheng; Wang, Qiu-Shuang; Yuan, Hai-Bo; Feng, Chun-Hong; Yin, Jun-Feng

    2012-03-01

    The formation of irreversible tea sediment (IRS) and its chemical components in green tea infusions were investigated. The results showed that the amounts of IRS in the green tea infusions from various tea cultivars ranged from 0.10 to 1.47 mg/mL. The amount of IRS was influenced remarkably by the chemical components in the green tea infusion. Principal component analysis and regression analysis indicated that gallated catechins, Mn, Ca, caffeine, Na, and (-)-gallocatechin gallate (GCG) were the principal components. IRS (mg/mL) = -4.226 + 0.275 gallated catechins + 79.551 Na + 7.321 Mn + 21.055 Ca + 0.513 caffeine - 0.129 GCG (R2 = 0.697). The contents of the main chemical components in the reversible tea sediment (RTS) and IRS were markedly different, especially the minerals. Large amount of minerals participated in the formation of irreversible green tea sediment. The amount of IRS increased with the extraction temperature. PMID:22329921

  4. Sediment cascade modelling for stochastic torrential sediment transfers forecasting in a changing alpine climate

    NASA Astrophysics Data System (ADS)

    Rudaz, Benjamin; Bardou, Eric; Jaboyedoff, Michel

    2015-04-01

    Alpine ephemeral streams act as links between high altitude erosional processes, slope movements and valley-floor fluvial systems or fan storage. Anticipating future mass wasting from these systems is crucial for hazard mitigation measures. Torrential activity is highly stochastic, with punctual transfers separating long periods of calm, during which the system evolves internally and recharges. Changes can originate from diffuse (rock faces, sheet erosion of bared moraines), concentrated external sources (rock glacier front, slope instabilities) or internal transfers (bed incision or aggradation). The proposed sediment cascade model takes into account those different processes and calculates sediment transfer from the slope to the channel reaches, and then propagates sediments downstream. The two controlling parameters are precipitation series (generated from existing rain gauge data using Gumbel and Extreme Probability Distribution functions) and temperature (generated from local meteorological stations data and IPCC scenarios). Snow accumulation and melting, and thus runoff can then be determined for each subsystem, to account for different altitudes and expositions. External stocks and sediment sources have each a specific response to temperature and precipitation. For instance, production from rock faces is dependent on frost-thaw cycles, in addition to precipitations. On the other hand, landslide velocity, and thus sediment production is linked to precipitations over longer periods of time. Finally, rock glaciers react to long-term temperature trends, but are also prone to sudden release of material during extreme rain events. All those modules feed the main sediment cascade model, constructed around homogeneous torrent reaches, to and from which sediments are transported by debris flows and bedload transport events. These events are determined using a runoff/erosion curve, with a threshold determining the occurrence of debris flows in the system. If a debris

  5. Overview of current methods in sedimentation velocity and sedimentation equilibrium analytical ultracentrifugation.

    PubMed

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

    2013-02-01

    Modern computational strategies have allowed for the direct modeling of the sedimentation process of heterogeneous mixtures, resulting in sedimentation velocity (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 analytical ultracentrifugation (AUC), such as the study of protein self- and hetero-association, the study of membrane proteins, and applications in biotechnology. New global multisignal modeling and mass conservation approaches in SV and sedimentation equilibrium (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 multiprotein 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 unit is to describe the current tools for the study of soluble proteins, detergent-solubilized membrane proteins and their interactions by SV and SE.

  6. Sediment Surface Areas, Organic Content, and Metal Fractionation of Point Mugu Sediments

    NASA Astrophysics Data System (ADS)

    Becerra, C. A.; Wong, N.; Khachikian, C. S.

    2002-12-01

    Point Mugu contains one of the largest coastal wetlands ecosystems in California, which includes a Naval Air station, several sewage oxidation ponds and a partly dredged lagoon. Remediation efforts include investigating the feasibility of using the present sewage pond sludge to restore a dredged area in the lagoon. A problem with this approach is the potential release and subsequent environmental impact of the toxic substances from the sludge. Contaminants may become unavailable once sorbed onto particles. In general, this process is a direct function of surface area and organic carbon sorbed onto the sediment. The goal of the current investigation is to provide insight into the biological availability of a suite of metal contaminants in Pt. Mugu marsh sediments by studying changes in the physical and chemical properties of the sediments at horizontal and vertical spatial scales. The surface area and organic carbon for eight cores were measured as well as the first three sequential extraction of a host of metals. We have found that a direct correlation exists between surface area and the organic content of sediments as a function of depth. Surface area and the amount of organic carbon decreases with depth, which could result in higher availability of metals with increasing depth into the sediments.

  7. Sediment studies at Bikini Atoll part 1. distribution of fine and coarse components in surface sediments

    SciTech Connect

    Noshkin, V. E.; Eagle, R.J.; Robison, W.L.

    1997-01-01

    In 1979, 21 years after the moratorium on nuclear testing in the Marshall Islands, surface sediment samples (to depths of 2 and 4 cm) were collected from 87 locations over the floor of Bikini lagoon. The main purpose for the collections was to map the distribution of long- lived man-made radionuclides associated with the bottom material. In addition the samples were processed to estimate the fraction of fine and coarse components to show what modifications occurred since the sediment composition was first described in samples collected before testing in 1946. In this report a comparison is made of the amount and distribution of fine material associated with the lagoon surface sediment before and after the testing of nuclear devices. Nuclear testing produced more finely divided material in-the surface sediment layer over large areas of the lagoon and especially in regions of the lagoon and reef adjacent to test sites. Five cratering events at Bikini Atoll generated sufficient material to account for the inventory of new fine material found over the bottom surface of the lagoon. Although the fraction of fine material in the bottom sediments was altered by the nuclear events, the combined processes of formation, transport and deposition were not sufficiently dynamic to alter the geographical features of the major sedimentary components over most of the lagoon floor.

  8. Accumulation and effects of sediment-associated silver nanoparticles to sediment-dwelling invertebrates.

    PubMed

    Ramskov, Tina; Forbes, Valery E; Gilliland, Douglas; Selck, Henriette

    2015-09-01

    Sediment is increasingly recognized as the major sink for contaminants including nanoparticles (NPs). Thus, sediment-living organisms are especially susceptible to NP exposure. Studies of the fate and effects of NPs in the sediment matrix are still in their infancy, and data from such studies are in high demand. Here, we examine the effects of exposure to sediment mixed with either aqueous Ag (administered as AgNO3) or Ag NPs (13nm, citrate-capped) at a nominal exposure concentration of 100μg Ag/g dry weight sediment on four benthic invertebrates: two clones of the gastropod Potamopyrgus antipodarum (clones A and B) and two polychaete species (Capitella teleta, Capitella sp. S). Our results show that both species sensitivity and Ag form (aqueous Ag, Ag NPs) play a role in bioaccumulation and effects. Following two weeks of exposure, both clones of P. antipodarum were found to be insensitive towards both Ag forms (generally low Ag accumulation, no toxicity). In contrast, the two Capitella species varied widely with respect to Ag uptake and observed toxicity. Capitella sp. S was adversely affected by both aqueous Ag (mortality) and Ag NPs (growth), whereas C. teleta was not affected by either Ag form. For neither polychaete species was the observed toxicity directly related to bioaccumulation. Therefore, future nano-ecotoxicological research should focus on understanding differences in uptake and handling mechanisms among species and the relationship between bioaccumulation and toxicity. PMID:26256765

  9. Assessment of sediments in lakes at the Rocky Mountain Arsenal using the sediment quality triad

    SciTech Connect

    Pearson, M.S.; Clements, W.H.

    1995-12-31

    The authors used the sediment quality triad to assess toxicity of sediments from three lakes located at the Rocky Mountain Arsenal (Superfund site), Denver, CO. The primary contaminants of concern are aldrin, endrin, dieldrin, DDT, DDE, As, and Hg. Preliminary results indicated lower macroinvertebrate density at stations in Lower Derby Lake compared to stations in Ladora and Mary Lakes. Mean diversity, as measured by the Shannon-Weaver Index, at Lower Derby was < 1.0, while Lakes Mary and Ladora were 2.0 and 2.2 respectively. Invertebrate communities were dominated by Chironomidae (Diptera) in all three lakes (> 80%). Chironomus tentans laboratory toxicity tests showed that mortality was highly variable among lakes and stations, and ranged from 0 to 93%. Lake sediment had the greatest toxic effects, as chironomids exposed to six of 10 stations exhibited > 70% mortality. In Lower Derby Lake four of 12 stations had > 50% mortality while no site at Lake Mary showed > 40% mortality. Results of acute toxicity tests with pore water generally agreed with the trends of the sediment toxicity tests. Results of toxicity tests and benthic sampling may have been influenced by differences in sediment characteristics among stations.

  10. Reservoir sedimentation and environmental degradation: assessing trends in sediment-associated trace elements in Grenada Lake, Mississippi.

    PubMed

    Bennett, Sean J; Rhoton, Fred E

    2007-01-01

    Sediments impounded within flood control reservoirs are potentially important archives of environmental and geomorphic processes occurring within drainage basins. The concentrations of select sediment-associated trace elements were assessed within the impoundment of Grenada Lake, a relatively large flood control reservoir in Mississippi with a history of contaminant bioaccumulation in fish. The post-construction sediments (after 1954) are discriminated from the pre-construction sediments (before 1954) based on depth variations in sediment texture and 137Cs emissions. The concentrations of select trace elements of the post-1954 sediments all are statistically greater than the pre-1954 sediments, and these same sediments also are enriched in clay. Once these concentrations are normalized by clay content, all trace elements in the post-1954 sediments are lower in concentration than the pre-1954 normalized sediments. Moreover, the trace elements when normalized by clay or Al content show virtually no change vertically (over time) within the reservoir impoundment. This suggests that the sources of these sediment-associated trace elements within Grenada Lake, whether natural or anthropogenic, have not changed appreciably over the lifespan of the reservoir and that the degradation of sedimentologic and ecologic indices within the lake are due to the sequestration of clay or clay-sized materials.

  11. Storm Event Suspended Sediment-Discharge Hysteresis and Controls in Agricultural Watersheds: Implications for Watershed Scale Sediment Management.

    PubMed

    Sherriff, Sophie C; Rowan, John S; Fenton, Owen; Jordan, Philip; Melland, Alice R; Mellander, Per-Erik; hUallacháin, Daire Ó

    2016-02-16

    Within agricultural watersheds suspended sediment-discharge hysteresis during storm events is commonly used to indicate dominant sediment sources and pathways. However, availability of high-resolution data, qualitative metrics, longevity of records, and simultaneous multiwatershed analyses has limited the efficacy of hysteresis as a sediment management tool. This two year study utilizes a quantitative hysteresis index from high-resolution suspended sediment and discharge data to assess fluctuations in sediment source location, delivery mechanisms and export efficiency in three intensively farmed watersheds during events over time. Flow-weighted event sediment export was further considered using multivariate techniques to delineate rainfall, stream hydrology, and antecedent moisture controls on sediment origins. Watersheds with low permeability (moderately- or poorly drained soils) with good surface hydrological connectivity, therefore, had contrasting hysteresis due to source location (hillslope versus channel bank). The well-drained watershed with reduced connectivity exported less sediment but, when watershed connectivity was established, the largest event sediment load of all watersheds occurred. Event sediment export was elevated in arable watersheds when low groundcover was coupled with high connectivity, whereas in the grassland watershed, export was attributed to wetter weather only. Hysteresis analysis successfully indicated contrasting seasonality, connectivity and source availability and is a useful tool to identify watershed specific sediment management practices.

  12. Storm Event Suspended Sediment-Discharge Hysteresis and Controls in Agricultural Watersheds: Implications for Watershed Scale Sediment Management.

    PubMed

    Sherriff, Sophie C; Rowan, John S; Fenton, Owen; Jordan, Philip; Melland, Alice R; Mellander, Per-Erik; hUallacháin, Daire Ó

    2016-02-16

    Within agricultural watersheds suspended sediment-discharge hysteresis during storm events is commonly used to indicate dominant sediment sources and pathways. However, availability of high-resolution data, qualitative metrics, longevity of records, and simultaneous multiwatershed analyses has limited the efficacy of hysteresis as a sediment management tool. This two year study utilizes a quantitative hysteresis index from high-resolution suspended sediment and discharge data to assess fluctuations in sediment source location, delivery mechanisms and export efficiency in three intensively farmed watersheds during events over time. Flow-weighted event sediment export was further considered using multivariate techniques to delineate rainfall, stream hydrology, and antecedent moisture controls on sediment origins. Watersheds with low permeability (moderately- or poorly drained soils) with good surface hydrological connectivity, therefore, had contrasting hysteresis due to source location (hillslope versus channel bank). The well-drained watershed with reduced connectivity exported less sediment but, when watershed connectivity was established, the largest event sediment load of all watersheds occurred. Event sediment export was elevated in arable watersheds when low groundcover was coupled with high connectivity, whereas in the grassland watershed, export was attributed to wetter weather only. Hysteresis analysis successfully indicated contrasting seasonality, connectivity and source availability and is a useful tool to identify watershed specific sediment management practices. PMID:26784287

  13. Development, Evaluation, and Application of Sediment Quality Targets for Assessing and Managing Contaminated Sediments in Tampa Bay, Florida

    USGS Publications Warehouse

    MacDonald, D.D.; Carr, R.S.; Eckenrod, D.; Greening, H.; Grabe, S.; Ingersoll, C.G.; Janicki, S.; Janicki, T.; Lindskoog, R.A.; Long, E.R.; Pribble, R.; Sloane, G.; Smorong, D.E.

    2004-01-01

    Tampa Bay is a large, urban estuary that is located in west central Florida. Although water quality conditions represent an important concern in this estuary, information from numerous sources indicates that sediment contamination also has the potential to adversely affect aquatic organisms, aquatic-dependent wildlife, and human health. As such, protecting relatively uncontaminated areas of the bay from contamination and reducing the amount of toxic chemicals in contaminated sediments have been identified as high-priority sediment management objectives for Tampa Bay. To address concerns related to sediment contamination in the bay, an ecosystem-based framework for assessing and managing sediment quality conditions was developed that included identification of sediment quality issues and concerns, development of ecosystem goals and objectives, selection of ecosystem health indicators, establishment of metrics and targets for key indicators, and incorporation of key indicators, metrics, and targets into watershed management plans and decision-making processes. This paper describes the process that was used to select and evaluate numerical sediment quality targets (SQTs) for assessing and managing contaminated sediments. These SQTs included measures of sediment chemistry, whole-sediment and pore-water toxicity, and benthic invertebrate community structure. In addition, the paper describes how the SQTs were used to develop site-specific concentration-response models that describe how the frequency of adverse biological effects changes with increasing concentrations of chemicals of potential concern. Finally, a key application of the SQTs for defining sediment management areas is discussed.

  14. Evaluation of PCB and hexachlorobenzene biota-sediment accumulation factors based on ingested sediment in a deposit-feeding clam

    SciTech Connect

    Boese, B.L.; Lee, H. II; Specht, D.T.; Randall, R.; Pelletier, J.

    1996-09-01

    Contaminated sediment exposure experiments were conducted using a marine deposit-feeding clam (Macoma nasuta) to determine biota-sediment accumulation factors (BSAFs) based on ingested sediment and fecal organic carbon. Internal, or gut, BSAFs were determined for hexachlorobenzene and 13 polychlorinated biphenyl congeners and were compared to those found with the standard method of calculating BSAFs, which uses the organic carbon and contaminant concentration of the whole or external sediment. The results of these experiments indicated that gut BSAFs were consistently smaller and less variable across sediment types than the corresponding standard BSAFs. Although these results indicate that using ingested sediment concentrations and fecal total organic carbon to calculate gut BSAFs might improve the predictive ability of the standard BSAF model, the benefit is small when compared to the difficulty in measuring the contaminant concentration on ingested sediment and the organic carbon content of feces.

  15. Remobilization of barium in continental margin sediments

    NASA Astrophysics Data System (ADS)

    McManus, James; Berelson, William M.; Klinkhammer, Gary P.; Kilgore, Tammy E.; Hammond, Douglas E.

    1994-11-01

    The rate of Ba release from California continental margin sediments has been measured, using an in situ benthic flux chamber, and the range of values (25-50 nmol cm -2 y -1) is larger than any previously published benthic flux estimate for this element. The magnitude of the Ba flux suggests that a significant fraction of the Ba raining from the euphotic zone is recycled at the seafloor. Ba:Si regeneration ratios from these margin sediments increase with depth, demonstrating that Ba is decoupled from Si during the earliest stages of diagenesis. On the other hand, Ba regeneration rates and CaCO 3 dissolution rates covary; the coupling between these two constituents is supported by the observation that the Ba: CaCO 3 dissolution flux ratio (1.7 ± 0.4 × 10 -3) is independent of bottomwater depth—even in sediments underlying the oxygen minimum zone along the continental margin. Furthermore, this flux ratio is consistent with both the water column Ba:alkalinity ratio for the world's ocean, as well as the Ba:CaCO 3 ratio in sediment-trap solid phases from the Equatorial Pacific (1.1-2.2 × 10 -3). However, the constancy of the Ba:alkalinity ratio over geologic time remains in question, because the mechanism that controls this relationship remains a mystery. Our flux measurements suggest that diagenesis does not significantly influence the Ba:Ca ratio in the upper 0.5 mm of Pacific sediments, thereby supporting the idea of using the Ba concentration in surface-dwelling benthic forams as a proxy for deep-water chemical conditions ( LEA and BOYLE, 1989, 1990). On the other hand, we predict that if a foraminifer lives 0.5 mm or more below this interface, then diagenetic effects could influence the Ba:Ca ratio that foram species would record. The carrier phase of the particulate Ba reactive during early diagenesis does not appear to be organic matter, oxyhydroxides, or calcium carbonate, but rather a mineral phase related to marine barite or perhaps celestite.

  16. Parameterisation of clastic sediments including benthic structures

    NASA Astrophysics Data System (ADS)

    Bobertz, B.; Harff, J.; Bohling, B.

    2009-02-01

    The sediment transport processes in the south-western Baltic Sea are predicted by means of a numerical model in the project DYNAS. There are two sediment parameters that influence the results of modelling remarkably: critical shear stress velocity and bottom roughness. This paper presents the way how to parameterise these factors and extrapolate them into the investigation area. The critical shear stress velocity is parameterised basing on grain size data, combining approximations after Hjulström [Hjulström, F., 1935: Studies in the morphological activity of rivers as illustrated by the river Fyris. Geological Institution of University of Uppsala: Bulletin (25): 221-528.], Shields [Shields, A., 1936: Anwendung der Ähnlichkeits-Mechanik und der Turbulenzforschung auf die Geschiebebewegung. Mitteilungen der Preussischen Versuchsanstalt für Wasserbau und Schiffahrt (26): 26 pp.] and Bohling [Bohling, B., 2003: Untersuchungen zur Mobilität natürlicher und anthropogener Sedimente in der Mecklenburger Bucht. unpublished doctoral thesis, Mathematisch-Naturwissenschaftliche Fakultät, Ernst-Moritz-Arndt-Universität Greifswald/Germany, 156 pp.]. The roughness length, in the case of absence of macro zoo-benthos and their structures, is parameterised basing on grain size too employing Soulsby [Soulsby, R.L., 1997: Dynamics of Marine Sands: a Manual for Practical Applications. London, Thomas Telford Publications. 249 pp.], Nielsen [Nielsen, P., 1983: Analytical determination of nearshore wave height variation due to refraction shoaling and friction. Coastal Engineering 7, 233-251.] and Yalin [Yalin, M.S., 1977: Mechanics of Sediment Transport. Pergamon Press, New York. 298 pp.]. No equivalent simple parameterisations for biologically caused bed roughness exist. Here, findings of Friedrichs [Friedrichs, M., 2004: Flow-induced effects of macro zoo-benthic structures on the near-bed sediment transport. Dissertation, Universität Rostock, 80 S.] and estimations by the DYNAS

  17. Varves in lake sediments - a review

    NASA Astrophysics Data System (ADS)

    Zolitschka, Bernd; Francus, Pierre; Ojala, Antti E. K.; Schimmelmann, Arndt

    2015-06-01

    Downcore counting of laminations in varved sediments offers a direct and incremental dating technique for high-resolution climatic and environmental archives with at least annual and sometimes even seasonal resolution. The pioneering definition of varves by De Geer (1912) had been restricted to rhythmically deposited proglacial clays. One century later the meaning of 'varve' has been expanded to include all annually deposited laminae in terrestrial and marine settings. Under favourable basin configurations and environmental conditions, limnic varves are formed due to seasonality of depositional processes from the lake's water column and/or transport from the catchment area. Subsequent to deposition of topmost laminae, the physical preservation of the accumulating varved sequence requires the sustained absence of sediment mixing, for example via wave action or macrobenthic bioturbation. Individual (sub)laminae in varved lake sediments typically express contrasting colours, always differ in terms of their organic, chemical and/or mineralogical compositions, and often also differ with regard to grain-size. Various predominating climatic and depositional conditions may result in clastic, biogenic or endogenic (incl. evaporitic) varved sediments and their mixtures. To reliably establish a varve chronology, the annual character of laminations needs to be determined and verified in a multidisciplinary fashion. Sources and influences of possible errors in varve chronologies are best determined and constrained by repeated varve counts, and by including radioisotopes and correlation with historically documented events. A well-established varve chronology greatly enhances the scientific value of laminated limnic archives by securely anchoring the wealth of multi-proxy palaeoenvironmental information in the form of time-series for multidisciplinary investigations. Applications of varved records are discussed with special reference to advances since the 1980s. These span fields

  18. Sediment Movement Near a Tropical Wood Jam

    NASA Astrophysics Data System (ADS)

    Cadol, D.; Wohl, E.

    2008-12-01

    One mechanism by which wood interacts with sediment transport is the trapping of sediment behind jams. In tropical streams, higher discharge per unit of contributing area and higher microbial diversity relative to temperate zones are likely to cause in-stream wood to be more transient. This may reduce the residence time of jams, also reducing wood-induced sediment storage. To begin to evaluate this possibility, tracer clasts, scour chains, and wood pieces were surveyed four times from June 2007 to June 2008 at a wood jam in a stream in Costa Rica. At the study site the moderate gradient (3.2%) stream drains 1.6 km2 of preserved old-growth tropical wet forest of La Selva Biological Station. The mean grain size of the bed material is 205 mm, ranging from coarse sand to boulders, with discontinuous bedrock outcrops on both banks. Distance traveled by the tracer clasts was positively correlated with both maximum and average daily rainfall during the time between surveys. Between the first two surveys, a new accumulation of wood in the jam blocked the thalweg and redirected the majority of flow around the side of the jam. A 15-cm-thick wedge of sediment was deposited behind the blockage, and gravel bars adjacent to and immediately downstream of the jam were scoured by as much as 30 cm. The majority of the gravel sized tracer clasts placed upstream of the jam were not recovered and were presumably incorporated into the sediment wedge. Tracer clasts placed in the portion of the channel affected by the redirected flow were transported downstream as much as 47 m. Clasts larger than D55 (220 mm) were not transported in the course of the study. The jam and key pieces persisted for the entire study period, and the number of pieces in the jam stayed nearly constant. However, the structure was modified and only 46% of the original pieces were retained for the full year. The clast transport distance was positively correlated with wood turnover rate for the three inter

  19. Assessing the integrated sediment trapping role of man-made and natural sediment sinks, Minizr catchment, Ethiopia

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

    To enhance sedimentation within a catchment, man-made sediment trapping (ST) measures and natural sediment sinks are playing a vital role. To evaluate the ST role of such measures, this study was conducted at Minizr catchment, northwest Ethiopian highlands. Man-made soil and water conservation (SWC) structures constructed within the catchment and natural sediment sinks (floodplain and wetland) were digitized and quantified from Google earth imagery. Sediment pins, vertical cut measurements through the deposit (after the rainy season) and SWC structures dimension measurements (before and after the rainy seasons) were used to estimate the trapped sediment depth. Inflow and outflow suspended sediment measurements were done to calculate sediment trapping efficacies (STEs). On average, SWC structures trapped ~7922 t yr-1 (56 kg m-1 yr-1) and micro-trenches trapped ~13260 kg yr-1 (a micro-trench trapped 23 kg yr-1). A floodplain located near the centre of the catchment trapped ~ 9971 t yr-1 (59 kg m-2 yr-1) and a wetland located near the outlet of the catchment trapped ~ 8715 t yr-1 (36 kg m-2 yr-1). The STEs of the wetland and the floodplain were found to be 85 % and 77 %, respectively. Substantial difference was observed between the STE of grassed and un-grassed waterways, 75 % and 21 %, respectively. About ~40 % of the transported sediment was trapped by major sediment traps (both man-made and natural) and ~60 % is still leaving the catchment and entering into Koga reservoir. Although man-made structures and natural sediment sinks trapped large amount of sediment, the rate of sediment red-deposition is lower than the rate of sediment export at the outlet of the catchment, which is because of lack of an integrated ST approach.

  20. Tracking multiple sediment cascades at the river network scale identifies controls and emerging patterns of sediment connectivity

    NASA Astrophysics Data System (ADS)

    Schmitt, Rafael J. P.; Bizzi, Simone; Castelletti, Andrea

    2016-05-01

    Sediment connectivity in fluvial networks results from the transfer of sediment between multiple sources and sinks. Connectivity scales differently between all sources and sinks as a function of distance, source grain size and sediment supply, network topology and topography, and hydrologic forcing. In this paper, we address the challenge of quantifying sediment connectivity and its controls at the network scale. We expand the concept of a single, catchment-scale sediment cascade toward representing sediment transport from each source as a suite of individual cascading processes. We implement this approach in the herein presented CAtchment Sediment Connectivity And DElivery (CASCADE) modeling framework. In CASCADE, each sediment cascade establishes connectivity between a specific source and its multiple sinks. From a source perspective, the fate of sediment is controlled by its detachment and downstream transport capacity, resulting in a specific trajectory of transfer and deposition. From a sink perspective, the assemblage of incoming cascades defines provenance, sorting, and magnitude of sediment deliveries. At the network scale, this information reveals emerging patterns of connectivity and the location of bottlenecks, where disconnectivity occurs. In this paper, we apply CASCADE to quantitatively analyze the sediment connectivity of a major river system in SE Asia. The approach provides a screening model that can support analyses of large, poorly monitored river systems. We test the sensitivity of CASCADE to various parameters and identify the distribution of energy between the multiple, simultaneously active sediment cascades as key control behind network sediment connectivity. To conclude, CASCADE enables a quantitative, spatially explicit analysis of network sediment connectivity with potential applications in both river science and management.

  1. Timber Harvest Effects on Sediment and Water Yields and Analysis of Sediment Load Calculation Methods in the Interior Pacific Northwest

    NASA Astrophysics Data System (ADS)

    Elverson, C.; Karwan, D. L.

    2015-12-01

    Timber harvest practices have a long-standing association with changes in water and sediment yields. We quantify the trends in water and sediment yields in the Mica Creek Experimental Watershed (MCEW) in relation to management practices with linear regression and analysis of covariance (ANCOVA). From 1991 to 2013, an increase in water yield resulted from both clearcutting and thinning treatments, with monthly water yield rate increases of 13-57% and annual water yield increases up to 210 mm (40%) in the clearcut watershed. Following treatment, annual sediment yields increased in the clearcut watershed by 40-131% and the thinned watershed by 33-163%, both relative to the control watershed, with statistically-significant monthly load increases in the year immediately following treatment. Water and sediment yield changes do not follow the same post-treatment patterns. Water yields increased immediately following treatment and, over time, gradually dropped towards pre-harvest levels. Annual sediment yields increased in some years after the harvest, but in some cases the increase was years after treatment. Monthly sediment yields increased in the first year following the clearcut harvest, but elevated monthly loads following the partial cut harvest came years later. Hence, we investigate the changes in sediment yield through an examination of water yield and sediment concentration and in response to events. We test the sensitivity of our results to different methods for computing sediment yields based on total suspended solids concentration and continuous discharge measurements. Flow-weighted sediment yield averaged 24% higher than sediment yield computed from linear-interpolated total suspended solids concentration values. During typical summer and fall conditions, flow-weighting was found to overweight storm measurements and produce large sediment yield estimates. Further work is suggested to test methods of calculating monthly sediment yields with irregularly

  2. A cell extraction method for oily sediments

    NASA Astrophysics Data System (ADS)

    Lappé, M.; Kallmeyer, J.

    2