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Sample records for source-to-sink sediment flux

  1. Coarse-grained sediment delivery and distribution in the Holocene Santa Monica Basin, California: Implications for evaluating source-to-sink flux at millennial time scales

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    Romans, B.W.; Normark, W.R.; McGann, M.M.; Covault, J.A.; Graham, S.A.

    2009-01-01

    Utilizing accumulations of coarse-grained terrigenous sediment from deep-marine basins to evaluate the relative contributions of and history of controls on sediment flux through a source-to-sink system has been difficult as a result of limited knowledge of event timing. In this study, six new radiocarbon (14C) dates are integrated with five previously published dates that have been recalibrated from a 12.5-m-thick turbidite section from Ocean Drilling Program (ODP) Site 1015 in Santa Monica Basin, offshore California. This borehole is tied to high-resolution seismic-reflection profiles that cover an 1100 km2 area of the middle and lower Hueneme submarine fan and most of the basin plain. The resulting stratigraphic framework provides the highest temporal resolution for a thick-bedded Holocene turbidite succession to date, permitting an evaluation of source-to-sink controls at millennial (1000 yr) scales. The depositional history from 7 ka to present indicates that the recurrence interval for large turbidity-current events is relatively constant (300-360 yr), but the volume of sediment deposited on the fan and in the basin plain has increased by a factor of 2 over this period. Moreover, the amount of sand per event on the basin plain during the same interval has increased by a factor of 7. Maps of sediment distribution derived from correlation of seismic-reflection profiles indicate that this trend cannot be attributed exclusively to autogenic processes (e.g., progradation of depocenters). The observed variability in sediment accumulation rates is thus largely controlled by allogenic factors, including: (1) increased discharge of Santa Clara River as a result of increased magnitude and frequency of El Ni??o-Southern Oscillation (ENSO) events from ca. 2 ka to present, (2) an apparent change in routing of coarse-grained sediment within the staging area at ca. 3 ka (i.e., from direct river input to indirect, littoral cell input into Hueneme submarine canyon), and (3

  2. Analysis of Source-to-Sink-Fluxes and Sediment Budgets in Changing High-Latitude and High-Altitude Cold Environments: SEDIFLUX Manual

    Energy Technology Data Exchange (ETDEWEB)

    Beylich, Achim A; Warburton, Jeff

    2007-07-01

    This First Edition of the SEDIFLUX Manual is an outcome of the European Science Foundation (ESF) Network SEDIFLUX - Sedimentary Source-to-Sink-Fluxes in Cold Environments (2004 - 2006) (http://www.ngu.no/sediflux, http://www.esf.org/sediflux). The development of this publication has been based on four ESF SEDIFLUX Science Meetings, which were held in Saudarkrokur (Iceland), June 18. - 21., 2004, Clermont-Ferrand (France), January 20. - 22., 2005, Durham (UK), December 16. - 19., 2005 and Trondheim (Norway), October 29. - November 2., 2006. The aim of this Manual is to provide guidance on developing quantitative frameworks for characterising catchment (field-based) sediment budget studies, so that: (1) baseline measurements at SEDIFLUX/SEDIBUD key test catchments are standardised thus enabling intersite comparisons, and (2) long-term changes in catchment geosystems as related to climate change are well documented. The main focus is on non-glacial processes, although within the context of glacierised catchments glacial sediment transfer processes are assumed as inputs/outputs of the periglacial / paraglacial system. This First Edition of the SEDIFLUX Manual will be further developed within the I.A.G./A.I.G. Working Group SEDIBUD - Sediment Budgets in Cold Environments (http://www.geomorph.org/wg/wgsb.html).(auth)

  3. Source-to-sink cycling of aeolian sediment in the north polar region of Mars

    Science.gov (United States)

    Ewing, R. C.; Kocurek, G.

    2012-12-01

    Aeolian sand dunes are prominent features on the landscapes of Earth, Mars, Venus and Titan and sedimentary deposits interpreted as aeolian in origin are found in the rock records of Earth and Mars. The widespread occurrence of aeolian dunes on the surface of these worlds and within their deep-time depositional records suggests that aeolian systems are and likely have been a default depositional environment for the Solar System. Within an aeolian source-to-sink context, we hypothesize that planet-specific boundary conditions strongly impact production, transport, accumulation and preservation of aeolian sediment, whereas dunes and dune-field patterns remain largely similar. This hypothesis is explored within the north polar region of Mars, which hosts the most extensive aeolian dune fields and aeolian sedimentary deposits yet recognized on Mars and appears to be a region of dynamic source-to-sink cycling of aeolian sediments. The Planum Boreum Cavi Unit rests beneath north polar ice cap of Mars and is composed of several hundred meters of niveo-aeolian dune cross-stratification. The overall architecture of the unit consists of sets of preserved dune topography with an upward increase in the abundance of ice. Dune sets are defined by stabilized, polygonally fractured bounding surfaces, erosional bounding surfaces and typical internal lee foresets made of sediment and ice. The accumulation of the Cavi Unit is interpreted as occurring through freezing and serves as an example of a cold temperature boundary condition on aeolian sediment accumulation. Preservation of the Cavi Unit arises because of deposition of the overlying ice cap and contrasts with preservation of aeolian sediment on Earth, which is largely driven by eustasy and tectonics. The Cavi Unit is thought to be one source of sediment for the north polar Olympia Undae Dune Field. The region of Olympia Undae near the Cavi Unit shows a reticulate dune field pattern composed of two sets of nearly orthogonal

  4. Magnetic properties as tracers for source-to-sink dispersal of sediments: A case study in the Taiwan Strait

    Science.gov (United States)

    Horng, Chorng-Shern; Huh, Chih-An

    2011-09-01

    Different lithologies between Taiwan and southeastern China lead to diverse mineralogical composition for weathering products derived from the two shores of the Taiwan Strait. Pyrrhotite and magnetite are respectively the dominant magnetic minerals associated with fluvial sediments from western Taiwan and southeastern China. While magnetite commonly co-exists with pyrrhotite in sediments sourced from Taiwan, pyrrhotite has not been found in sediments sourced from mainland China. Associated with such a distinction are vast differences in magnetic properties, including magnetic susceptibility (χ), SIRM, HIRM and the S-ratio, which can be used to study the provenances of sediments in the Taiwan Strait and adjoining marginal seas. Based on any two of these parameters, the magnetic characteristics of much of the Taiwan Strait sediment can be explained using a two-endmember mixing model. Source-to-sink dispersal of sediments in the Taiwan Strait can then be traced from the distribution of these parameters. The results not only corroborate an earlier study based on radionuclides and particle size distribution ( Huh et al., 2011) but reveal more diagnostic details. Besides spatial distribution based on a large number (216) of surface sediments, we also analyzed temporal variation of magnetic properties in six well-dated cores collected at key sites along the sediment source-to-sink pathways. From profiles of these parameters in cores from the middle of the northern Taiwan Strait, it is calculated that sediment supply from Taiwan has increased substantially in the past five decades, which may very well be related to accelerated land use and increased frequency of intense rainfalls in Taiwan during the same period. The approach described in this work may be extended to other source-to-sink systems around the world and through time, especially the mountainous islands fringing the Pacific and Indian Oceans in southeastern Asia. As with Taiwan, these islands have high

  5. A unified framework for modelling sediment fate from source to sink and its interactions with reef systems over geological times.

    Science.gov (United States)

    Salles, Tristan; Ding, Xuesong; Webster, Jody M; Vila-Concejo, Ana; Brocard, Gilles; Pall, Jodie

    2018-03-27

    Understanding the effects of climatic variability on sediment dynamics is hindered by limited ability of current models to simulate long-term evolution of sediment transfer from source to sink and associated morphological changes. We present a new approach based on a reduced-complexity model which computes over geological time: sediment transport from landmasses to coasts, reworking of marine sediments by longshore currents, and development of coral reef systems. Our framework links together the main sedimentary processes driving mixed siliciclastic-carbonate system dynamics. It offers a methodology for objective and quantitative sediment fate estimations over regional and millennial time-scales. A simulation of the Holocene evolution of the Great Barrier Reef shows: (1) how high sediment loads from catchments erosion prevented coral growth during the early transgression phase and favoured sediment gravity-flows in the deepest parts of the northern region basin floor (prior to 8 ka before present (BP)); (2) how the fine balance between climate, sea-level, and margin physiography enabled coral reefs to thrive under limited shelf sedimentation rates after ~6 ka BP; and, (3) how since 3 ka BP, with the decrease of accommodation space, reduced of vertical growth led to the lateral extension of reefs consistent with available observational data.

  6. Large-scale dam removal on the Elwha River, Washington, USA: source-to-sink sediment budget and synthesis

    Science.gov (United States)

    Warrick, Jonathan A.; Bountry, Jennifer A.; East, Amy E.; Magirl, Christopher S.; Randle, Timothy J.; Gelfenbaum, Guy R.; Ritchie, Andrew C.; Pess, George R.; Leung, Vivian; Duda, Jeff J.

    2015-01-01

    Understanding landscape responses to sediment supply changes constitutes a fundamental part of many problems in geomorphology, but opportunities to study such processes at field scales are rare. The phased removal of two large dams on the Elwha River, Washington, exposed 21 ± 3 million m3, or ~ 30 million tonnes (t), of sediment that had been deposited in the two former reservoirs, allowing a comprehensive investigation of watershed and coastal responses to a substantial increase in sediment supply. Here we provide a source-to-sink sediment budget of this sediment release during the first two years of the project (September 2011–September 2013) and synthesize the geomorphic changes that occurred to downstream fluvial and coastal landforms. Owing to the phased removal of each dam, the release of sediment to the river was a function of the amount of dam structure removed, the progradation of reservoir delta sediments, exposure of more cohesive lakebed sediment, and the hydrologic conditions of the river. The greatest downstream geomorphic effects were observed after water bodies of both reservoirs were fully drained and fine (silt and clay) and coarse (sand and gravel) sediments were spilling past the former dam sites. After both dams were spilling fine and coarse sediments, river suspended-sediment concentrations were commonly several thousand mg/L with ~ 50% sand during moderate and high river flow. At the same time, a sand and gravel sediment wave dispersed down the river channel, filling channel pools and floodplain channels, aggrading much of the river channel by ~ 1 m, reducing river channel sediment grain sizes by ~ 16-fold, and depositing ~ 2.2 million m3 of sand and gravel on the seafloor offshore of the river mouth. The total sediment budget during the first two years revealed that the vast majority (~ 90%) of the sediment released from the former reservoirs to the river passed through the fluvial system and was discharged to the coastal

  7. The I.A.G. / A.I.G. SEDIBUD Book Project: Source-to-Sink Fluxes in Undisturbed Cold Environments

    Science.gov (United States)

    Beylich, Achim A.; Dixon, John C.; Zwolinski, Zbigniew

    2015-04-01

    The currently prepared SEDIBUD Book on "Source-to-Sink Fluxes in Undisturbed Cold Environments" (edited by Achim A. Beylich, John C. Dixon and Zbigniew Zwolinski and published by Cambridge University Press) is summarizing and synthesizing the achievements of the International Association of Geomorphologists` (I.A.G./A.I.G.) Working Group SEDIBUD (Sediment Budgets in Cold Environments), which has been active since 2005 (http://www.geomorph.org/wg/wgsb.html). Amplified climate change and ecological sensitivity of largely undisturbed polar and high-altitude cold climate environments have been highlighted as key global environmental issues. The effects of projected climate change will change surface environments in cold regions and will alter the fluxes of sediments, nutrients and solutes, but the absence of quantitative data and coordinated geomorphic process monitoring and analysis to understand the sensitivity of the Earth surface environment in these largely undisturbed environments is acute. Our book addresses this existing key knowledge gap. The applied approach of integrating comparable and longer-term field datasets on contemporary solute and sedimentary fluxes from a number of different defined cold climate catchment geosystems for better understanding (i) the environmental drivers and rates of contemporary denudational surface processes and (ii) possible effects of projected climate change in cold regions is unique in the field of geomorphology. Largely undisturbed cold climate environments can provide baseline data for modeling the effects of environmental change. The book synthesizes work carried out by numerous SEDIBUD Members over the last decade in numerous cold climate catchment geosystems worldwide. For reaching a global cover of different cold climate environments the book is - after providing an introduction part and a basic part on climate change in cold environments and general implications for solute and sedimentary fluxes - dealing in different

  8. Multi-scale constraints of sediment source to sink systems in frontier basins: a forward stratigraphic modeling case study of the Levant region

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    Hawie, Nicolas; Deschamps, Remy; Granjeon, Didier; Nader, Fadi-Henri; Gorini, Christian; Müller, Carla; Montadert, Lucien; Baudin, François

    2015-04-01

    Recent scientific work underlined the presence of a thick Cenozoic infill in the Levant Basin reaching up to 12 km. Interestingly; restricted sedimentation was observed along the Levant margin in the Cenozoic. Since the Late Eocene successive regional geodynamic events affecting Afro-Arabia and Eurasia (collision and strike slip deformation)induced fast marginal uplifts. The initiation of local and long-lived regional drainage systems in the Oligo-Miocene period (e.g. Lebanon versus Nile) provoked a change in the depositional pattern along the Levant margin and basin. A shift from carbonate dominated environments into clastic rich systems has been observed. Through this communication we explore the importance of multi-scale constraints (i.e.,seismic, well and field data) in the quantification of the subsidence history, sediment transport and deposition of a Middle-Upper Miocene "multi-source" to sink system along the northernLevant frontier region. We prove through a comprehensive forward stratigraphic modeling workflow that the contribution to the infill of the northern Levant Basin (offshore Lebanon) is split in between proximal and more distal clastic sources as well as in situ carbonate/hemipelagic deposition. In a wider perspective this work falls under the umbrella of multi-disciplinary source to sink studies that investigate the impact of geodynamic events on basin/margin architectural evolutions, consequent sedimentary infill and thus on petroleum systems assessment.

  9. Source-to-sink sediment transfers, environmental engineering and hazard mitigation in the steep Var River catchment, French Riviera, southeastern France

    Science.gov (United States)

    Anthony, Edward J.; Julian, Maurice

    1999-12-01

    Steep coastal margins are potentially subject to mass wasting processes involving notable landslide activity and sediment evacuation downstream by steep-gradient streams. Sediment transfer from short source-to-sink segments, coupled with mountain hydrological regimes, regulate patterns of river channel aggradation and coastal sediment supply in such geomorphic settings. On the steep French Riviera margin, sediment transfers from existing landslides or from various minor mass wasting processes to stream channels may result following bursts of heavy, concentrated rainfall. High-magnitude flooding and massive sediment transport downstream are generally related to unpredictable extreme rainfalls. Both mass movements and channel sediment storage pose serious hazards to downvalley settlements and infrastructure. A consideration of channel sediment storage patterns in the Var River catchment, the most important catchment in this area, highlights two important shortcomings relative to environmental engineering and hazard mitigation practices. In the first place, the appreciation of geomorphic processes is rather poor. This is illustrated by the undersized nature of engineering works constructed to mitigate hazards in the upstream bedload-dominated channels, and by the unforeseen effects that ten rock dams, constructed in the early 1970s, have had on downstream and coastal sediment storage and on sediment dispersal patterns and, consequently, valley flooding. Secondly, planners and environmental engineers have lacked foresight in valley and coastal management issues on this steep setting, notably as regards the reclaimed areas of the lower Var channel and delta liable to flooding. Urbanization and transport and environmental engineering works have progressively affected patterns of storage and transport of fine-grained sediments in the lower Var channel and delta. Meanwhile the problems raised by these changes have not been adequately addressed in terms of scientific

  10. Clay mineralogy and source-to-sink transport processes of Changjiang River sediments in the estuarine and inner shelf areas of the East China Sea

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    Zhao, Yifei; Zou, Xinqing; Gao, Jianhua; Wang, Chenglong; Li, Yali; Yao, Yulong; Zhao, Wancang; Xu, Min

    2018-02-01

    We examined the source-to-sink sediment transport processes from the Changjiang River to the estuarine coastal shelf area by analyzing the clay mineral assemblages in suspended sediment samples from the Changjiang River catchment and surface samples from the estuarine coastal shelf area following the impoundment of the Three Gorges Dam (TGD) in 2003. The results indicate that the clay mineral compositions throughout the study area are dominated by illite, with less abundant kaolinite and chlorite and scarce smectite. The clay minerals display distinct differences in the tributaries and exhibit obvious changes in the trunk stream compared with the periods before 2003, and the source of sediment has largely shifted to the mid- to lower reaches of the river after 2003. Spatially, the clay mineral assemblages in the estuarine area define two compositionally distinct provinces. Province I covers the mud area of the Changjiang River estuary and the Zhe-Min coastal region, where sediment is primarily supplied by the Changjiang River. Province II includes part of the Changjiang River estuary and the southeastern portion of the study area, where the sediment is composed of terrestrial material from the Changjiang River and re-suspended material from the Huanghe River carried by the Jiangsu coastal current. Moreover, the other smaller rivers in China (including the Oujiang and Minjiang rivers of mainland China and the rivers of West Taiwan) also contribut sediments to the estuarine and inner shelf areas. In general, the clay mineral assemblages in the Changjiang River estuarine area are have mainly been controlled by sediment supplied from upstream of the Changjiang River tributaries. However, since the completion of the TGD in 2003, the mid- to downstream tributaries have become the main source of sediments from the Changjiang catchment into the East China Sea. These analyses further demonstrate that the coastal currents and the decrease in the sediment load of the river

  11. Shoreline erosion and decadal sediment accumulation in the Tar-Pamlico estuary, North Carolina, USA: A source-to-sink analysis

    Science.gov (United States)

    Eulie, Devon O.; Corbett, D. Reide; Walsh, J. P.

    2018-03-01

    Estuaries contain vital habitats and it is important to understand how these areas respond to human activities and natural processes such as sea-level rise and wave attack. As estuarine shorelines erode or become modified with hard structures, there is potential for significantly altering the availability of sediment and the filling of coastal systems. This study used a source-to-sink approach and quantified rates of shoreline erosion in the Tar-Pamlico sub-estuary, a tributary of the larger Albemarle-Pamlico Estuarine System (APES). The average shoreline change rate (SCR) determined using an end-point method was -0.5 ± 0.9 m yr-1 for the Tar-Pamlico. Incorporating bulk density estimates, this contributes 0.6 × 105 tons of fine sediment to the system annually, or after accounting for fluvial input, about 40% of the total sediment supply to the sub-estuary. The role of the Tar-Pamlico as a sink for these sediments was addressed using the radionuclide tracers 210Pb and 137Cs. Radionuclide activities and sediment accumulation rates identified several depositional regions, in particular in the middle of the estuary. Linear sediment accumulation rates ranged from 0.10 ± 0.02 to 0.38 ± 0.02 g cm-2 yr-1, and total storage of fine sediment in the system was 1.6 × 105 t yr-1. It was not possible to confidently discern a change in the rate of shoreline erosion or seabed accumulation. A preliminary budget for fine sediments (grain-size <63 μm) was then calculated to compare erosional sources with sedimentary sinks. Almost all (∼93.0%) of the fine sediment entering the system was accumulated and stored, while only about 7.0% was exported to Pamlico Sound.

  12. U-Pb ages of detrital zircon from Cenozoic sediments in the southwestern Tarim Basin, NW China: Implications for Eocene-Pliocene source-to-sink relations and new insights into Cretaceous-Paleogene magmatic sources

    Science.gov (United States)

    Yang, Wei; Fu, Ling; Wu, Chaodong; Song, Yan; Jiang, Zhenxue; Luo, Qun; Zhang, Ziya; Zhang, Chen; Zhu, Bei

    2018-05-01

    A detailed investigation of potential provenance is still lacking in the southwestern Tarim Basin, which restricts our complete understanding of Cenozoic source-to-sink relations between the basin interior and the Pamir salient - western Kunlun Mountain Range. Debate also exists concerning the potential sources of the Paleogene and Cretaceous igneous detritus present in the Cenozoic sedimentary sequences. Here, we present U-Pb (LA-ICP-MS) ages of detrital zircons from the continuous Eocene-Pliocene sediment series in the well-exposed Aertashi section to investigate changes in sediment provenance through time. The U-Pb detrital zircon ages range widely from 45 to 3204 Ma and can be divided into seven main groups: 45-65 Ma (sub-peak at 49 Ma), 67-103 Ma (sub-peak at 95 Ma), 196-251 Ma (sub-peak at 208 Ma), 252-416 Ma (sub-peak at 296 Ma), 417-540 Ma (sub-peak at 446 Ma), 550-1429 Ma (sub-peaks at 614 Ma, 828 Ma and 942 Ma) and 1345-3204 Ma (sub-peaks at 1773 Ma and 2480 Ma). These zircons were mainly derived from the western Kunlun Mountain Range and northern Pamir salient to the west and south. The evolution of the provenance and source-to-sink relationship patterns in the southwestern Tarim Basin can be divided into three stages: (1) The Middle Eocene to Lower Oligocene sediments display a wide variety of detrital zircon ages, suggesting that the source area was extensive. (2) A major change in provenance occurred during the Late Oligocene to Early Miocene and was characterized by an abrupt increase in the proportion of Triassic and Lower Paleozoic igneous components, implying a significant adjustment in topography induced by the initial uplift and exhumation of the western Kunlun Mountain Range and northern Pamir salient. (3) In the Late Miocene, the source-to-sink system transformed again, and contributions of Triassic to Lower Paleozoic material weakened substantially due to the sufficient indentation of the Pamir salient. Our integrated analyses of zircon

  13. 3D Reconstruction of a Fluvial Sediment Slug from Source to Sink: reach-scale modeling of the Dart River, NZ

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    Brasington, J.; Cook, S.; Cox, S.; James, J.; Lehane, N.; McColl, S. T.; Quincey, D. J.; Williams, R. D.

    2014-12-01

    Following heavy rainfall on 4/1/14, a debris flow at Slip Stream (44.59 S 168.34 E) introduced >106 m3 of sediment to the Dart River valley floor in NZ Southern Alps. Runout over an existing fan dammed the Dart River causing a sudden drop in discharge downstream. This broad dam was breached quickly; however the temporary loss of conveyance impounded a 3 km lake with a volume of 6 x 106 m3 and depths that exceed 10 m. Quantifying the impact of this large sediment pulse on the Dart River is urgently needed to assess potential sedimentation downstream and will also provide an ideal vehicle to test theories of bed wave migration in large, extensively braided rivers. Recent advances in geomatics offer the opportunity to study these impacts directly through the production of high-resolution DEMs. These 3D snapshots can then be compared through time to quantify the morphodynamic response of the channel as it adjusts to the change in sediment supply. In this study we describe the methods and results of a novel survey strategy designed to capture of the complex morphology of the Dart River along a remote 40 km reach, from the upstream landslide source to its distal sediment sink in Lake Wakatipu. The scale of this system presents major logistical and methodological challenges, and hitherto would have conventionally be addressed with airborne laser scanning, bringing with it significant deployment constraints and costs. By contrast, we present sub-metre 3D reconstructions of the system (Figure 1), derived from highly redundant aerial photography shot with a non-metric camera from a helicopter survey that extended over an 80 km2 area. Structure-from-Motion photogrammetry was used to solve simultaneously camera position, pose and derive a 3D point cloud based on over 4000 images. Reconstructions were found to exhibit significant systematic error resulting from the implicit estimation of the internal camera orientation parameters, and we show how these effects can be minimized

  14. Source-to-Sink: An Earth/Mars Comparison of Boundary Conditions for Eolian Dune Systems

    OpenAIRE

    Kocurek, Gary; Ewing, Ryan C.

    2012-01-01

    Eolian dune fields on Earth and Mars evolve as complex systems within a set of boundary conditions. A source-to-sink comparison indicates that although differences exist in sediment production and transport, the systems largely converge at the dune-flow and pattern-development levels, but again differ in modes of accumulation and preservation. On Earth, where winds frequently exceed threshold speeds, dune fields are sourced primarily through deflation of subaqueous deposits as these sediments...

  15. Source to sink transport and regulation by environmental factors

    Directory of Open Access Journals (Sweden)

    Remi eLemoine

    2013-07-01

    Full Text Available Source-to-sink transport of sugar is one of the major determinants of plant growth and relies on the efficient and controlled distribution of sucrose (and some other sugars such as raffinose and polyols across plant organs through the phloem. However, sugar transport through the phloem can be affected by many environmental factors that alter source/sink relationships. In this paper, we summarize current knowledge about the phloem transport mechanisms and review the effects of several abiotic (water and salt stress, mineral deficiency, CO2, light, temperature, air and soil pollutants and biotic (mutualistic and pathogenic microbes, viruses, aphids and parasitic plants factors. Concerning abiotic constraints, alteration of the distribution of sugar among sinks is often reported, with some sinks as roots favoured in case of mineral deficiency. Many of these constraints impair the transport function of the phloem but the exact mechanisms are far from being completely known. Phloem integrity can be disrupted (e.g. by callose deposition and under certain conditions, phloem transport is affected, earlier than photosynthesis. Photosynthesis inhibition could result from the increase in sugar concentration due to phloem transport decrease. Biotic interactions (aphids, fungi, viruses… also affect crop plant productivity. Recent breakthroughs have identified some of the sugar transporters involved in these interactions on the host and pathogen sides. The different data are discussed in relation to the phloem transport pathways. When possible, the link with current knowledge on the pathways at the molecular level will be highlighted.

  16. Mass Balance of Cenozoic Andes-Amazon Source to Sink System—Marañón Basin, Peru

    Directory of Open Access Journals (Sweden)

    Gérôme Calvès

    2018-05-01

    Full Text Available We investigate the mass balance of the Cenozoic Andes-Amazon source to sink system using rock uplift proxies and solid sedimentation of the Marañón Basin in Peru. The evolution of sedimentation rates is calibrated with regional structural restored cross-section. The quantification of eroded sediments from reliefs to sedimentary basin is achieved with ×10 Myr resolution and compared to present day proxies from the HYBAM (HYdrologie et Biogéochimie du Bassin Amazonien Critical Zone Observatory. Erosion of the early Andean landforms started during the Upper Mesozoic period, but sediment rates significantly increase during the Neogene. This is in agreement with the calibrated increase of rock uplift in the Andean orogenic belt.

  17. Source-to-Sink constraints on tectonic and sedimentary evolution of the Central Range, Cenderawasih Bay (Indonesia) and Gulf of Papua (Papua New Guinea)

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    Babault, J.; Viaplana-Muzas, M.; Legrand, X.; Van Den Driessche, J.; González-Quijano, M.; Mudd, S. M.; Kergaravat, C.; Ringenbach, J. C.; Callot, J. P.; Vetel, W.; Dhont, D.

    2017-12-01

    The island of Papua New Guinea is the result of continent-arc collision that began building the island's Central Range during the late Miocene. The tectono-sedimentary evolution of the Cenderawasih Bay, in the northwestern part of the island of Papua New Guinea (Indonesia), which links the Kepala Burung block to the Central Range is still poorly understood. Previous studies have shown that this bay contains a thick (> 8 km) sequence of undated sediments. Hypothesis claim that the embayment resulted from a 3 Ma aperture created by anticlockwise rotation of the Kepala Burung block with respect to the northern rim of the Australian plate, or from the southwest drift of a slice of volcanics/oceanic crust between 8 and 6 Ma. Using a source-to-sink approach, based on i) a geomorphologic analysis of the drainage network dynamics, ii) a reassessment of available thermochronological data, and iii) seismic lines interpretation, we suggest that sediments started to accumulate in the Cenderawasih Bay and onshore in the Waipoga Basin in the late Miocene since the beginning of the Central Range building at 12 Ma, resulting in sediment accumulation of up to 12200 m. At first order, we predict that infilling is mainly composed of siliciclastics sourced in the graphite-bearing Ruffaer Metamorphic Belt and its equivalent in the Weyland Overthrust. From the unroofing paths in the Central Range we deduce two rates of solid phase accumulation (SPAR) since 12 Ma, the first one at a mean SPAR ranging between 0.12-0.25 mm/a with a maximum SPAR of 0.23-0.58 mm/a, and the second during the last 3 Ma, at a mean SPAR ranging between 0.93-1.62 mm/a and with a maximum SPAR between 2.13-3.17 mm/a, i.e., 6700-10000 m of Plio-Pleistocene sediment accumulation. Local transtensional tectonics may explain these unusually high rates of sedimentation in an overall sinistral oblique convergence setting. We further extended this approach to the Gulf of Papua (Papua New Guinea), a foreland basin developed

  18. Sedimentary mercury (Hg) in the marginal seas adjacent to Chinese high-Hg emissions: Source-to-sink, mass inventory, and accumulation history.

    Science.gov (United States)

    Kim, Jihun; Lim, Dhongil; Jung, Dohyun; Kang, Jeongwon; Jung, Hoisoo; Woo, Hanjun; Jeong, Kapsik; Xu, Zhaokai

    2018-03-01

    We comprehensively investigated sedimentary Hg in Yellow and East China Seas (YECSs), which constitute potentially important depocenters for large anthropogenic Hg emissions from mainland China. A large dataset of Al-TOC-Hg concentrations led to an in-depth understanding of sedimentary Hg in the entire YECSs, including distribution and its determinants, source-to-sink, background levels, inventory in flux and budget, and accumulation history. Especially, the net atmospheric Hg flux to the sediments was estimated to be 1.3 × 10 -5  g/m 2 /yr, which corresponded reasonably well to that calculated using a box model. About 21.2 tons of atmospheric Hg (approximately 4% of the total anthropogenic atmospheric Hg emissions from China) were buried annually in the YECS basin. This result implies that most of atmospheric Hg from China is transferred to the surface of the Pacific (including the East/Japan Sea and South China Sea) by the westerlies and, consequently, can play a critical role in open-sea aquatic ecosystems. Copyright © 2018 Elsevier Ltd. All rights reserved.

  19. Second workshop of I.A.G./A.I.G. SEDIBUD - Sediment Budgets in Cold Environments: Sediment fluxes and sediment budgets in changing high-latitude and high-altitude cold environments

    Energy Technology Data Exchange (ETDEWEB)

    Beylich, Achim A; Lamoureux, Scott F; Decaulne, Armelle

    2007-07-01

    This Second Workshop of the I.A.G./A.I.G. Working Group SEDIBUD (Sediment Budgets in Cold Environments) builds on four previous ESF SEDIFLUX Science Meetings held in Saudarkrokur (Iceland) in June 2004, Clermont-Ferrand (France) in January 2005, Durham (UK) in December 2005 and Trondheim (Norway) in the end of October/beginning of November 2006. A first kick-off Meeting of the new I.A.G./A.I.G. SEDIBUD Workshop. The theme of this Second I.A.G./A.I.G. SEDIBUD Workshop is Sediment FLuxes and Sediment Budgets in Changing High-Latitude Cold Environments. The Workshop is split between scientific paper and poster presentations, presentation and discussion of SEDIBUD key test sites, discussions within defined work groups and guided field trip to Kaerkevagge. This workshop will address the key aim of SEDIBUD to discuss Source-to-Sink-Fluxes and Sediment Budgets in Changing Cold Environments. Major emphasis will be given to consequences of climate change, scaling issues and source-to-sink correlations. Central issues will be presentation and discussion of the SEDIFLUX Manual (First Edition), the selection of SEDIBUD key test sites, the discussion and development of further ideas to extend the scientific activities within SEDIBUD in a global framework.(auth)

  20. A shift of thermokarst lakes from carbon sources to sinks during the Holocene epoch

    Science.gov (United States)

    Walter Anthony, K. M.; Zimov, S. A.; Grosse, G.; Jones, Miriam C.; Anthony, P.; Chapin, F. S.; Finlay, J. C.; Mack, M. C.; Davydov, S.; Frenzel, P.F.; Frolking, S.

    2014-01-01

    Thermokarst lakes formed across vast regions of Siberia and Alaska during the last deglaciation and are thought to be a net source of atmospheric methane and carbon dioxide during the Holocene epoch1,2,3,4. However, the same thermokarst lakes can also sequester carbon5, and it remains uncertain whether carbon uptake by thermokarst lakes can offset their greenhouse gas emissions. Here we use field observations of Siberian permafrost exposures, radiocarbon dating and spatial analyses to quantify Holocene carbon stocks and fluxes in lake sediments overlying thawed Pleistocene-aged permafrost. We find that carbon accumulation in deep thermokarst-lake sediments since the last deglaciation is about 1.6 times larger than the mass of Pleistocene-aged permafrost carbon released as greenhouse gases when the lakes first formed. Although methane and carbon dioxide emissions following thaw lead to immediate radiative warming, carbon uptake in peat-rich sediments occurs over millennial timescales. We assess thermokarst-lake carbon feedbacks to climate with an atmospheric perturbation model and find that thermokarst basins switched from a net radiative warming to a net cooling climate effect about 5,000 years ago. High rates of Holocene carbon accumulation in 20 lake sediments (47±10 grams of carbon per square metre per year; mean±standard error) were driven by thermokarst erosion and deposition of terrestrial organic matter, by nutrient release from thawing permafrost that stimulated lake productivity and by slow decomposition in cold, anoxic lake bottoms. When lakes eventually drained, permafrost formation rapidly sequestered sediment carbon. Our estimate of about 160petagrams of Holocene organic carbon in deep lake basins of Siberia and Alaska increases the circumpolar peat carbon pool estimate for permafrost regions by over 50 per cent (ref. 6). The carbon in perennially frozen drained lake sediments may become vulnerable to mineralization as permafrost disappears7

  1. Source-to-sink transport of sugar and regulation by environmental factors.

    Science.gov (United States)

    Lemoine, Remi; La Camera, Sylvain; Atanassova, Rossitza; Dédaldéchamp, Fabienne; Allario, Thierry; Pourtau, Nathalie; Bonnemain, Jean-Louis; Laloi, Maryse; Coutos-Thévenot, Pierre; Maurousset, Laurence; Faucher, Mireille; Girousse, Christine; Lemonnier, Pauline; Parrilla, Jonathan; Durand, Mickael

    2013-01-01

    Source-to-sink transport of sugar is one of the major determinants of plant growth and relies on the efficient and controlled distribution of sucrose (and some other sugars such as raffinose and polyols) across plant organs through the phloem. However, sugar transport through the phloem can be affected by many environmental factors that alter source/sink relationships. In this paper, we summarize current knowledge about the phloem transport mechanisms and review the effects of several abiotic (water and salt stress, mineral deficiency, CO2, light, temperature, air, and soil pollutants) and biotic (mutualistic and pathogenic microbes, viruses, aphids, and parasitic plants) factors. Concerning abiotic constraints, alteration of the distribution of sugar among sinks is often reported, with some sinks as roots favored in case of mineral deficiency. Many of these constraints impair the transport function of the phloem but the exact mechanisms are far from being completely known. Phloem integrity can be disrupted (e.g., by callose deposition) and under certain conditions, phloem transport is affected, earlier than photosynthesis. Photosynthesis inhibition could result from the increase in sugar concentration due to phloem transport decrease. Biotic interactions (aphids, fungi, viruses…) also affect crop plant productivity. Recent breakthroughs have identified some of the sugar transporters involved in these interactions on the host and pathogen sides. The different data are discussed in relation to the phloem transport pathways. When possible, the link with current knowledge on the pathways at the molecular level will be highlighted.

  2. Chesapeake Bay Sediment Flux Model

    Science.gov (United States)

    1993-06-01

    1988; Van der Molen , -88- 1991; Yoshida, 1981.) The model developed below is based on both of these approaches. It incorporates the diagenetic...288: pp. 289-333. Van der Molen , D.T. (1991): A simple, dynamic model for the simulation of the release of phosphorus from sediments in shallow...1974; Berner, 1980; van Cappellen and Berner, 1988). These relate the diagenetic production of phosphate to the resulting pore water concentration

  3. Resilience in Source to Sink Systems: A Millennial Record of Watershed Responses to Disturbance in Loon Lake, Umpqua River Basin, Oregon

    Science.gov (United States)

    Guerrero, F. J.; Richardson, K.; Hatten, J. A.

    2017-12-01

    Small mountainous watersheds are disproportionate sources of particulate organic matter (POM) to long-term sinks like lake bottoms and the ocean. Thus, alterations in sediment routing resulting from disturbances (e.g. earthquakes, fires, and timber harvesting) have profound consequences on watershed's (biogeochemical) resilience. The assessment of these biogeochemical impacts is complicated by the episodic signal propagation along these source-to-sink systems and therefore is seldom attempted. We report on a 1500-year record of historical changes in Loon Lake, a local sedimentary sink (1.2 km2) for a 230 km2 watershed in the Oregon Coast Range. Particle size distributions and POM elemental composition (C, N) were sampled at high temporal resolution ( 3 years). Stable isotopic composition and lignin biomarkers were sampled with varying temporal resolution depending on the period analyzed: 1939-2013 (3-year resolution); 515-1939 (15-year resolution). Disturbance history in Loon Lake catchment is recorded as a sequence of event beds deposited in sharp contrast within a matrix of background sedimentation. At least 8 out of 23 event beds were associated with >8.2 magnitude earthquakes (including the 9.0 megathrust earthquake in 1700). Forest fires in 1770 and 1890 were also recorded as event beds. After 1939, event beds record the impacts of landscape destabilization due to the interaction between intense storms and timber harvesting. At the onset of each event, %C, %N, and C:N ratios increased reflecting the input of coarse POM from surficial soil horizons. Top layers bracketing event beds are rich in clays and have low %C, suggesting a deep-soil sediment source. Isotopic signatures (i.e. δ13C, δ15N) confirm the allochthony of sediment inputs during events and lignin biomarkers suggest a replacement of riparian inputs by a strong gymnosperm signal, particularly after 1945. Thus, event beds record changes in the relative importance of different sediment sources within

  4. Chinese-U.S. sediment source-to-sink research in the east China and Yellow Seas: a brief history

    Science.gov (United States)

    Milliman, John D.; Zuosheng, Yang

    2014-11-01

    In the autumn of 1979, US oceanographers were offered a unique and in many respects a once-in-a-lifetime opportunity, as were, in hindsight, Chinese oceanographers: to help formulate and participate in the initial US-China cooperative joint oceanographic research study, as part of a cooperative research agreement signed earlier that year by the US National Oceanographic and Atmospheric Administration (NOAA) and the Chinese National Bureau of Oceanology (NBO; now known as the State Ocean Administration-SOA). Ten oceanographers from nine US oceanographic institutions and agencies traveled to China in late November with the hope-at this early stage of Chinese-US scientific relations, it was no more than a hope-to begin discussions about the possibility of a cooperative investigation of the river-estuary-shelf interactions from the Yangtze River to the adjacent East China Sea. Two years of cooperative research (1980-82) were envisioned.

  5. Composition and Realization of Source-to-Sink High-Performance Flows: File Systems, Storage, Hosts, LAN and WAN

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Chase Qishi [Univ. of Tennessee, Memphis, TN (United States)

    2016-12-01

    A number of Department of Energy (DOE) science applications, involving exascale computing systems and large experimental facilities, are expected to generate large volumes of data, in the range of petabytes to exabytes, which will be transported over wide-area networks for the purpose of storage, visualization, and analysis. To support such capabilities, significant progress has been made in various components including the deployment of 100 Gbps networks with future 1 Tbps bandwidth, increases in end-host capabilities with multiple cores and buses, capacity improvements in large disk arrays, and deployment of parallel file systems such as Lustre and GPFS. High-performance source-to-sink data flows must be composed of these component systems, which requires significant optimizations of the storage-to-host data and execution paths to match the edge and long-haul network connections. In particular, end systems are currently supported by 10-40 Gbps Network Interface Cards (NIC) and 8-32 Gbps storage Host Channel Adapters (HCAs), which carry the individual flows that collectively must reach network speeds of 100 Gbps and higher. Indeed, such data flows must be synthesized using multicore, multibus hosts connected to high-performance storage systems on one side and to the network on the other side. Current experimental results show that the constituent flows must be optimally composed and preserved from storage systems, across the hosts and the networks with minimal interference. Furthermore, such a capability must be made available transparently to the science users without placing undue demands on them to account for the details of underlying systems and networks. And, this task is expected to become even more complex in the future due to the increasing sophistication of hosts, storage systems, and networks that constitute the high-performance flows. The objectives of this proposal are to (1) develop and test the component technologies and their synthesis methods to

  6. Nares Abyssal Plain Sediment Flux Studies, FY 1985 Annual Report

    International Nuclear Information System (INIS)

    Dymond, J.; Collier, R.

    1987-01-01

    The sediment trap NAP-1 was successfully recovered and the materials have been analyzed for a set of bio- and geochemical components. The trap mooring NAP-2 was deployed and recovered but no analyses have been completed. The bulk fluxes are relatively low at this site and are approximately 50% biogenic and 50% terrigenous. The flux of terrigenous material is very high due to primary atmospheric inputs and horizontal transport of resuspended sediments. The buoyant particle fluxes are also extremely low. The accumulation of material in the sediments reflects the crustal nature of the vertical flux and also shows the normal loss of labile biogenic phases

  7. Tropical Cyclones as a Driver of Global Sediment Flux

    Science.gov (United States)

    Leyland, J.; Darby, S. E.; Cohen, S.

    2017-12-01

    The world's rivers deliver 19 billion tonnes of sediment to the coastal zone annually. The sediment supplied to the coastal zone is of significant importance for a variety of reasons, for example in acting as a vector for nutrients as well as in supplying sediment to coastal landforms such as deltas and beaches that can buffer those landforms from erosion and flooding. A greater understanding of the factors governing sediment flux to the oceans is therefore a key research gap. The non-linear relationship between river discharge and sediment flux implies that the global sediment flux may be disproportionately driven by large floods. Indeed, in our recent empirical research we have demonstrated that changes in the track locations, frequency and intensity of tropical storms in recent decades exert a significant control on the sediment flux emanating from the Mekong River. Since other large rivers potentially affected by tropical storms are known to make a significant contribution to the global sediment flux, this raises the question of the extent to which such storms play a significant role in controlling sediment loads at the global scale. In this paper we address that question by employing a global hydrological model (WBMsed) in order to predict runoff and sediment load forced by recent historical climate scenarios `with' and `without' tropical cyclones. We compare the two scenarios to (i) make the first estimate of the global contribution of sediment load forced by tropical storms; (ii) evaluate how that contribution has varied in recent decades and to (iii) explore variations in tropical-storm driven sediment loads in selected major river basins that are significantly affected by such storms.

  8. Patterns of Cenozoic sediment flux from western Scandinavia

    DEFF Research Database (Denmark)

    Gołędowski, Bartosz; Nielsen, S.B.; Clausen, O.R.

    2012-01-01

    deposits in the North Sea, the post-mid-Miocene Molo and Kai Formations of the Norwegian Shelf, the southern North Sea delta system and large volumes of the Late Pliocene-Holocene Naust Formation. The sediment flux from Scandinavia during the Cenozoic is in general agreement with the detrital flux...

  9. Source-to-Sink System Evolution as Recorded in Clastic Facies in Two New Zealand Examples: the Bounty System of South Island and the Waipaoa System of North Island

    Science.gov (United States)

    Marsaglia, K. M.

    2010-12-01

    New Zealand river sources and their submarine sinks are excellent examples for modeling source-to-sink systems. In particular, the sand fractions of these systems can be used as tracers to document links and/or disconnects between fluvial, shelf, slope, and bathyal components. Within any given system, the ability to use sand as a tracer depends on the nature of the rocks exposed in source river drainage basins. In evolving systems, the potential for erosional unroofing, change of outcrop lithology through time, can be important. Additionally, the ability of a given lithology to generate sediment of a certain size may also vary. For example in the New Zealand examples, Cenozoic mudstones generate mostly mud but can liberate recycled sand grains (if present), as well as a smaller proportion of mudstone lithic fragments depending on degree of mudstone induration; schist generates copious sand and quartz-vein pebbles; and thin-bedded sandy turbidites can generate significant gravel, as well as mud and sand. Sediment production mode also comes into play with glacial processes (South Island) generating rock flour, as well as coarser debris. The major outcropping unit across both islands is a sedimentary to metasedimentary forearc succession, the Torlesse Terrane. It served as the protolith of the Otago schist (South Island) and the source of detritus for Cretaceous and Cenozoic sedimentary units on both islands. Local magmatism also supplied sand-sized material: intraplate (South Island) volcanism produced intrabasinal epiclastic debris and magmatic arc (North Island) volcanism produced extrabasinal pyroclastic debris. Various lithologies have characteristic detrital signatures. For example, in the Cenozoic units of the Waipaoa system, Pliocene calcareous mudstone fragments are key lithic components in tracing sediment transport from source-to sink, whereas the major fingerprint of Otago schist input into the Bounty System of South Island is mica. Critical to defining

  10. Near bed suspended sediment flux by single turbulent events

    Science.gov (United States)

    Amirshahi, Seyed Mohammad; Kwoll, Eva; Winter, Christian

    2018-01-01

    The role of small scale single turbulent events in the vertical mixing of near bed suspended sediments was explored in a shallow shelf sea environment. High frequency velocity and suspended sediment concentration (SSC; calibrated from the backscatter intensity) were collected using an Acoustic Doppler Velocimeter (ADV). Using quadrant analysis, the despiked velocity time series was divided into turbulent events and small background fluctuations. Reynolds stress and Turbulent Kinetic Energy (TKE) calculated from all velocity samples, were compared to the same turbulent statistics calculated only from velocity samples classified as turbulent events (Reevents and TKEevents). The comparison showed that Reevents and TKEevents was increased 3 and 1.6 times, respectively, when small background fluctuations were removed and that the correlation with SSC for TKE could be improved through removal of the latter. The correlation between instantaneous vertical turbulent flux (w ‧) and SSC fluctuations (SSC ‧) exhibits a tidal pattern with the maximum correlation at peak ebb and flood currents, when strong turbulent events appear. Individual turbulent events were characterized by type, strength, duration and length. Cumulative vertical turbulent sediment fluxes and average SSC associated with individual turbulent events were calculated. Over the tidal cycle, ejections and sweeps were the most dominant events, transporting 50% and 36% of the cumulative vertical turbulent event sediment flux, respectively. Although the contribution of outward interactions to the vertical turbulent event sediment flux was low (11%), single outward interaction events were capable of inducing similar SSC ‧ as sweep events. The results suggest that on time scales of tens of minutes to hours, TKE may be appropriate to quantify turbulence in sediment transport studies, but that event characteristics, particular the upward turbulent flux need to be accounted for when considering sediment transport

  11. Global diffusive fluxes of methane in marine sediments

    Science.gov (United States)

    Egger, Matthias; Riedinger, Natascha; Mogollón, José M.; Jørgensen, Bo Barker

    2018-06-01

    Anaerobic oxidation of methane provides a globally important, yet poorly constrained barrier for the vast amounts of methane produced in the subseafloor. Here we provide a global map and budget of the methane flux and degradation in diffusion-controlled marine sediments in relation to the depth of the methane oxidation barrier. Our new budget suggests that 45-61 Tg of methane are oxidized with sulfate annually, with approximately 80% of this oxidation occurring in continental shelf sediments (methane in steady-state diffusive sediments, we calculate that 3-4% of the global organic carbon flux to the seafloor is converted to methane. We further report a global imbalance of diffusive methane and sulfate fluxes into the sulfate-methane transition with no clear trend with respect to the corresponding depth of the methane oxidation barrier. The observed global mean net flux ratio between sulfate and methane of 1.4:1 indicates that, on average, the methane flux to the sulfate-methane transition accounts for only 70% of the sulfate consumption in the sulfate-methane transition zone of marine sediments.

  12. Source-to-sink constraints on tectonic and sedimentary evolution of the western Central Range and Cenderawasih Bay (Indonesia)

    Science.gov (United States)

    Babault, Julien; Viaplana-Muzas, Marc; Legrand, Xavier; Van Den Driessche, Jean; González-Quijano, Manuel; Mudd, Simon M.

    2018-05-01

    The island of New Guinea is the result of continent-arc collision that began building the island's Central Range during the late Miocene. Recent studies have shown that rapid subduction, uplift and exhumation events took place in response to rapid, oblique convergence between the Pacific and the Australian plates. The tectonic and sedimentary evolution of Cenderawasih Bay, in the northwestern part of the New Guinea Island is still poorly understood: this bay links a major structural block, the Kepala Burung block, to the island's Central Ranges. Previous studies have shown that Cenderawasih Bay contains a thick (>8 km) sequence of undated sediments. One hypothesis claims that the embayment resulted from a 3 Ma opening created by anticlockwise rotation of the Kepala Burung block with respect to the northern rim of the Australian plate. Alternatively, the current configuration of Cenderawasih Bay could have resulted from the southwest drift of a slice of volcanics and oceanic crust between 8 and 6 Ma. We test these hypotheses using (i) a geomorphologic analysis of the drainage network dynamics, (ii) a reassessment of available thermochronological data, and (iii) seismic lines interpretation. We suggest that sediments started to accumulate in Cenderawasih Bay and onshore in the Waipoga Basin in the late Miocene since the inception of growth of the Central Range, beginning at 12 Ma, resulting in sediment accumulation of up to 12,200 m. This evidence is more consistent with the second hypothesis, and the volume of sediment accumulated means it is unlikely that the embayment was the result of recent (2-3 Ma) rotation of structural blocks. At first order, we predict that infilling is mainly composed of siliciclastics sourced in the graphite-bearing Ruffaer Metamorphic Belt and its equivalent in the Weyland Overthrust. Ophiolites, volcanic arc rocks and diorites contribute minor proportions. From the unroofing paths in the Central Range we deduce two rates of solid phase

  13. Global diffusive fluxes of methane in marine sediments

    NARCIS (Netherlands)

    Egger, M.; Riedinger, N.; Mogollón, J.M.; Jørgensen, B.B.

    2018-01-01

    Anaerobic oxidation of methane provides a globally important, yet poorly constrained barrier for the vast amounts of methane produced in the subseafloor. Here we provide a global map and budget of the methane flux and degradation in diffusion-controlled marine sediments in relation to the depth of

  14. Source to Sink Tectonic Fate of Large Oceanic Turbidite Systems and the Rupturing of Great and Giant Megathrust Earthquakes (Invited)

    Science.gov (United States)

    Scholl, D. W.; Kirby, S. H.; von Huene, R.

    2010-12-01

    OCEAN FLOOR OBSERVATIONS: Oceanic turbidite systems accumulate above igneous oceanic crust and are commonly huge in areal and volumetric dimensions. For example, the volume of the Zodiac fan of the Gulf of Alaska is roughly 300,000 cubic km. Other large oceanic systems construct the Amazon cone, flood the Bay of Bengal abyss, and accumulate along trench axes to thickness of 1 to 7 km and lengths of 1000 to 3000 km, e.g., the Aleutian-Alaska, Sumatra-Andaman, Makran, and south central Chile Trenches. THE ROCK RECORD: Despite the large dimensions of oceanic turbidite systems, they are poorly preserved in the rock record. This includes oceanic systems deposited in passive-margin oceans, e.g., the Paleozoic Iapetus and Rheric oceans of the Atlantic realm, This circumstance does not apply to Cretaceous and E. Tertiary rock sequences of the north Pacific rim where oceanic turbidite deposits are preserved as accretionary complexes, e.g., the Catalina-Pelona-Orocopia-Rand schist of California and the Chugach-Kodiak complex of Alaska. These rock bodies are exhumed crustal underplates of once deeply (15-30 km) subducted oceanic turbidite systems. PATH FROM SOURCE TO TECTONIC SINK: The fate of most oceanic turbidite systems is to be removed from the sea floor and, ultimately, destroyed. This circumstance is unavoidable because most of them are deposited on lower plate crust destined for destruction in a subduction zone. During the past 4-5 myr alone a volume of 1-1.5 million cubic km of sediment sourced from the glaciated drainages of the Gulf of Alaska flooded the 3000-km-long Aleutian-Alaska trench axis. A small part of this volume accumulated tectonically as a narrow, 10-30-km wide accretionary frontal prism. But about 80 percent was subducted and entered the subduction channel separating the two plates. The subduction channel, roughly 1 km thick, conveys the trench turbidite deposits landward down dip along the rupturing width of the seismogenic zone. SEISMIC CONSEQUENCE

  15. Sediment Equilibrium and Diffusive Fluxes in Relation to Phosphorus Dynamics in the Turbid Minnesota River

    National Research Council Canada - National Science Library

    James, William F

    2009-01-01

    ...) concentration in large river systems. However, in-stream processes such as equilibrium P flux from suspended sediment and diffusive P flux from deposited sediment stored in river channels may also play a role in soluble P control...

  16. Final Project Report: Composition and Realization of Source-to-Sink High-Performance Flows: File Systems, Storage, Hosts, LAN and WAN

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Chase [New Jersey Inst. of Technology, Newark, NJ (United States)

    2017-09-06

    A number of Department of Energy (DOE) science applications, involving exascale computing systems and large experimental facilities, are expected to generate large volumes of data, in the range of petabytes to exabytes, which will be transported over wide-area networks for the purpose of storage, visualization, and analysis. The objectives of this proposal are to (1) develop and test the component technologies and their synthesis methods to achieve source-to-sink high-performance flows, and (2) develop tools that provide these capabilities through simple interfaces to users and applications. In terms of the former, we propose to develop (1) optimization methods that align and transition multiple storage flows to multiple network flows on multicore, multibus hosts; and (2) edge and long-haul network path realization and maintenance using advanced provisioning methods including OSCARS and OpenFlow. We also propose synthesis methods that combine these individual technologies to compose high-performance flows using a collection of constituent storage-network flows, and realize them across the storage and local network connections as well as long-haul connections. We propose to develop automated user tools that profile the hosts, storage systems, and network connections; compose the source-to-sink complex flows; and set up and maintain the needed network connections.

  17. 210Pb and Mass Flux Imbalance Between the Settling Particulates and Sediments at a Sediment Trap

    Science.gov (United States)

    Wu, C.; Chung, Y.; Hung, G.

    2005-05-01

    In order to evaluate the mass balance problems between the settling particulates and the underlying sediments, sediment traps were deployed at M1 site (21o32¡¦N, 119o28¡¦E; 2948m) where a box core was taken recently. The sediment trap results were previously published (Chung et al., 2004: Continental Shelf Research). We report here the 210Pb profile measured on this box core by determining its daughter, 210Po, with alpha spectrometry, assuming the paired nuclides are in radioactive equilibrium. The box core (33 cm long, taken in June, 2004) was analyzed for the distributions of its water content, loss on ignition (LOI), and 210Pb. The water content decreases with depth and averages about 55 percent; the LOI as a measure of the total organic matter (TOM) is fairly constant at about 12 percent. The 210Pb profile shows a general exponential decrease with depth, yielding a maximum sedimentation rate of 0.26cm/y, applying a constant flux and constant sedimentation rate model. This rate translates to a mass flux of 0.31g/cm2/y or about 8.5g/m2/d with a dry bulk density of 1.2g/cm3. Based on the excess 210Pb inventory integrated over the core length, the 210Pb flux is estimated at about 19.2dpm/cm2/y or 526dpm/cm2/d assuming at steady state. The 210Pb and mass fluxes obtained from the deepest trap at M1 were only 129dpm/m2/d and 0.55g/m2/d, respectively. The large ¡excess¡" of the 210Pb and mass fluxes in the sediments over those measured from the sediment trap (4 times in 210Pb flux and 14 times in mass flux) suggests either the sedimentation rate was overestimated due to neglect of the mixing effect, and/or large additional particulates, as resuspended sediments which contain less 210Pb, have been transported laterally near the bottom from elsewhere.

  18. Thiourea, a ROS scavenger, regulates source-to-sink relationship to enhance crop yield and oil content in Brassica juncea (L..

    Directory of Open Access Journals (Sweden)

    Manish Pandey

    Full Text Available In the present agricultural scenario, the major thrust is to increase crop productivity so as to ensure sustainability. In an earlier study, foliar application of thiourea (TU; a non physiological thiol based ROS scavenger has been demonstrated to enhance the stress tolerance and yield of different crops under field condition. Towards this endeavor, present work deals with the effect of TU on photosynthetic efficiency and source-to-sink relationship of Indian mustard (Brassica juncea for understanding its mode of action. The application of TU increased the efficiency of both PSI and PSII photosystems and vegetative growth of plant. The comparative analysis of sucrose to starch ratio and expression level of sugar transporters confirmed the higher source and sink strength in response to TU treatment. The biochemical evidence in support of this was derived from higher activities of sucrose phosphate synthase and fructose-1,6-bis-phosphatase at source; and sucrose synthase and different classes of invertases at both source and sink. This indicated an overall increase in photoassimilate level at sink. An additional contribution through pod photosynthesis was confirmed through the analysis of phosphoenol pyruvate carboxylase enzyme activity and level of organic acids. The increased photoassimilate level was also co-ordinated with acetyl coA carboxylase mediated oil biosynthesis. All these changes were ultimately reflected in the form of 10 and 20% increase in total yield and oil content, respectively under TU treatment as compared to control. Additionally, no change was observed in oil composition of seeds derived from TU treated plants. The study thus signifies the co-ordinated regulation of key steps of photosynthesis and source-to-sink relationship through the external application of TU resulting in increased crop yield and oil content.

  19. Advancement in Watershed Modelling Using Dynamic Lateral and Longitudinal Sediment (Dis)connectivity Prediction

    Science.gov (United States)

    Mahoney, D. T.; al Aamery, N. M. H.; Fox, J.

    2017-12-01

    The authors find that sediment (dis)connectivity has seldom taken precedence within watershed models, and the present study advances this modeling framework and applies the modeling within a bedrock-controlled system. Sediment (dis)connectivity, defined as the detachment and transport of sediment from source to sink between geomorphic zones, is a major control on sediment transport. Given the availability of high resolution geospatial data, coupling sediment connectivity concepts within sediment prediction models offers an approach to simulate sediment sources and pathways within a watershed's sediment cascade. Bedrock controlled catchments are potentially unique due to the presence of rock outcrops causing longitudinal impedance to sediment transport pathways in turn impacting the longitudinal distribution of the energy gradient responsible for conveying sediment. Therefore, the authors were motivated by the need to formulate a sediment transport model that couples sediment (dis)connectivity knowledge to predict sediment flux for bedrock controlled catchments. A watershed-scale sediment transport model was formulated that incorporates sediment (dis)connectivity knowledge collected via field reconnaissance and predicts sediment flux through coupling with the Partheniades equation and sediment continuity model. Sediment (dis)connectivity was formulated by coupling probabilistic upland lateral connectivity prediction with instream longitudinal connectivity assessments via discretization of fluid and sediment pathways. Flux predictions from the upland lateral connectivity model served as an input to the instream longitudinal connectivity model. Disconnectivity in the instream model was simulated via the discretization of stream reaches due to barriers such as bedrock outcroppings and man-made check dams. The model was tested for a bedrock controlled catchment in Kentucky, USA for which extensive historic water and sediment flux data was available. Predicted sediment

  20. Vertical suspsended sediment fluxes observed from ocean gliders

    Science.gov (United States)

    Merckelbach, Lucas; Carpenter, Jeffrey

    2016-04-01

    Many studies trying to understand a coastal system in terms of sediment transport paths resort to numerical modelling - combining circulation models with sediment transport models. Two aspects herein are crucial: sediment fluxes across the sea bed-water column interface, and the subsequent vertical mixing by turbulence. Both aspects are highly complex and have relatively short time scales, so that the processes involved are implemented in numerical models as parameterisations. Due to the effort required to obtain field observations of suspended sediment concentrations (and other parameters), measurements are scarce, which makes the development and tuning of parameterisations a difficult task. Ocean gliders (autonomous underwater vehicles propelled by a buoyancy engine) provide a platform complementing more traditional methods of sampling. In this work we present observations of suspended sediment concentration (SSC) and dissipation rate taken by two gliders, each equipped with optical sensors and a microstructure sensor, along with current observations from a bottom mounted ADCP, all operated in the German Bight sector of the North Sea in Summer 2014. For about two weeks of a four-week experiment, the gliders were programmed to fly in a novel way as Lagrangian profilers to water depths of about 40 m. The benefit of this approach is that the rate of change of SSC - and other parameters - is local to the water column, as opposed to an unknown composition of temporal and spatial variability when gliders are operated in the usual way. Therefore, vertical sediment fluxes can be calculated without the need of the - often dubious - assumption that spatial variability can be neglected. During the experiment the water column was initially thermally stratified, with a cross-pycnocline diffusion coefficient estimated at 7\\cdot10-5 m2 s-1. Halfway through the experiment the remnants of tropical storm Bertha arrived at the study site and caused a complete mixing of the water

  1. Aeolian dune sediment flux heterogeneity in Meridiani Planum, Mars.

    Science.gov (United States)

    Chojnacki, Matthew; Urso, Anna; Fenton, Lori K; Michaels, Timothy I

    2017-06-01

    It is now known unambiguously that wind-driven bedform activity is occurring on the surface of Mars today, including early detections of active sand dunes in Meridiani Planum's Endeavour crater. Many of these reports are only based on a few sets of observations of relatively isolated bedforms and lack regional context. Here, we investigate aeolian activity across central Meridiani Planum and test the hypothesis that dune sites surrounding Endeavour crater are also active and part of region-wide sediment migration driven by northwesterly winds. All 13 dune fields investigated clearly showed evidence for activity and the majority exhibited dune migration (average rates of 0.6 m/Earth-year). Observations indicate substantial geographic and temporal heterogeneity of dune crest fluxes across the area and per site. Locations with multiple time steps indicate dune sand fluxes can vary by a factor of five, providing evidence for short periods of rapid migration followed by near-stagnation. In contrast, measurements at other sites are nearly identical, indicating that some dunes are in a steady-state as they migrate. The observed sediment transport direction was consistent with a regional northeasterly-to-northwesterly wind regime, revealing more variations than were appreciated from earlier, more localized studies. Craters containing shallow, degraded, flat-floored interiors tended to have dunes with high sediment fluxes/activity, whereas local kilometer-scale topographic obstructions (e.g., central peaks, yardangs) were found to be inversely correlated with dune mobility. Finally, the previous, more limited detections of dune activity in Endeavour crater have been shown to be representative of a broader, region-wide pattern of dune motion.

  2. Balanced Sediment Fluxes in Southern California's Mediterranean-climate Zone Salt Marshes

    Science.gov (United States)

    Rosencranz, J. A.; Dickhudt, P.; Ganju, N. K.; Thorne, K.; Takekawa, J.; Ambrose, R. F.; Guntenspergen, G. R.; Brosnahan, S.; MacDonald, G. M.

    2015-12-01

    Salt marsh elevation and geomorphic stability depends on mineral sedimentation. Many southern California, USA salt marshes import sediment during El Niño storm events, but sediment fluxes and mechanisms during dry weather are also potentially important for marsh stability. We calculated tidal creek sediment fluxes within a sediment starved 1.5 km2 salt marsh (Seal Beach) and a less modified 1 km2 marsh (Mugu) with a watershed sediment supply. We measured salt marsh plain suspended sediment concentration and vertical accretion using single stage samplers and marker horizons. At Seal Beach, a 2014 storm yielded 39 and 28 g/s mean sediment fluxes and imported 12000 and 8800 kg in a western channel. This offset 8700 kg export during two months of dry weather, while landward net fluxes in the eastern channel accounted for 33% of the import. During the storm, suspended sediment concentrations on the marsh plain increased by a factor of four; accretion was 1-2 mm near creek levees. An exceptionally high tide sequence at Mugu yielded 4.4 g/s mean sediment flux, importing 1700 kg, accounting for 20% of dry weather fluxes. Overall, low sediment fluxes were observed, suggesting that these salt marshes are currently geomorphically stable. Our results suggest that storms and exceptionally high lunar tides may play large roles, importing sediment and maintaining dry weather sediment flux balances for southern California salt marshes. However, under future climate change and sea-level rise scenarios, results suggest that balanced sediment fluxes may lead to marsh elevational instability, based on estimated mineral sediment deficits.

  3. Calibration of an estuarine sediment transport model to sediment fluxes as an intermediate step for simulation of geomorphic evolution

    Science.gov (United States)

    Ganju, N.K.; Schoellhamer, D.H.

    2009-01-01

    Modeling geomorphic evolution in estuaries is necessary to model the fate of legacy contaminants in the bed sediment and the effect of climate change, watershed alterations, sea level rise, construction projects, and restoration efforts. Coupled hydrodynamic and sediment transport models used for this purpose typically are calibrated to water level, currents, and/or suspended-sediment concentrations. However, small errors in these tidal-timescale models can accumulate to cause major errors in geomorphic evolution, which may not be obvious. Here we present an intermediate step towards simulating decadal-timescale geomorphic change: calibration to estimated sediment fluxes (mass/time) at two cross-sections within an estuary. Accurate representation of sediment fluxes gives confidence in representation of sediment supply to and from the estuary during those periods. Several years of sediment flux data are available for the landward and seaward boundaries of Suisun Bay, California, the landward-most embayment of San Francisco Bay. Sediment flux observations suggest that episodic freshwater flows export sediment from Suisun Bay, while gravitational circulation during the dry season imports sediment from seaward sources. The Regional Oceanic Modeling System (ROMS), a three-dimensional coupled hydrodynamic/sediment transport model, was adapted for Suisun Bay, for the purposes of hindcasting 19th and 20th century bathymetric change, and simulating geomorphic response to sea level rise and climatic variability in the 21st century. The sediment transport parameters were calibrated using the sediment flux data from 1997 (a relatively wet year) and 2004 (a relatively dry year). The remaining years of data (1998, 2002, 2003) were used for validation. The model represents the inter-annual and annual sediment flux variability, while net sediment import/export is accurately modeled for three of the five years. The use of sediment flux data for calibrating an estuarine geomorphic

  4. Residual fluxes of water, salt and suspended sediment in the Beypore Estuary

    Digital Repository Service at National Institute of Oceanography (India)

    AnilKumar, N.; Revichandran, C.; Sankaranarayanan, V.N.; Josanto, V.

    The monthly trends of the residual fluxes of salt and water and the transportation of suspended sediments in the Beypore estuarine system, Kerala, India were examined. At the river mouth the water flux was directed seaward during the postmonsoon...

  5. Annual sediment flux estimates in a tidal strait using surrogate measurements

    Science.gov (United States)

    Ganju, N.K.; Schoellhamer, D.H.

    2006-01-01

    Annual suspended-sediment flux estimates through Carquinez Strait (the seaward boundary of Suisun Bay, California) are provided based on surrogate measurements for advective, dispersive, and Stokes drift flux. The surrogates are landward watershed discharge, suspended-sediment concentration at one location in the Strait, and the longitudinal salinity gradient. The first two surrogates substitute for tidally averaged discharge and velocity-weighted suspended-sediment concentration in the Strait, thereby providing advective flux estimates, while Stokes drift is estimated with suspended-sediment concentration alone. Dispersive flux is estimated using the product of longitudinal salinity gradient and the root-mean-square value of velocity-weighted suspended-sediment concentration as an added surrogate variable. Cross-sectional measurements validated the use of surrogates during the monitoring period. During high freshwater flow advective and dispersive flux were in the seaward direction, while landward dispersive flux dominated and advective flux approached zero during low freshwater flow. Stokes drift flux was consistently in the landward direction. Wetter than average years led to net export from Suisun Bay, while dry years led to net sediment import. Relatively low watershed sediment fluxes to Suisun Bay contribute to net export during the wet season, while gravitational circulation in Carquinez Strait and higher suspended-sediment concentrations in San Pablo Bay (seaward end of Carquinez Strait) are responsible for the net import of sediment during the dry season. Annual predictions of suspended-sediment fluxes, using these methods, will allow for a sediment budget for Suisun Bay, which has implications for marsh restoration and nutrient/contaminant transport. These methods also provide a general framework for estimating sediment fluxes in estuarine environments, where temporal and spatial variability of transport are large. ?? 2006 Elsevier Ltd. All rights

  6. Balanced sediment fluxes in southern California’s Mediterranean-climate zone salt marshes

    Science.gov (United States)

    Rosencranz, Jordan A.; Ganju, Neil K.; Ambrose, Richard F.; Brosnahan, Sandra M.; Dickhudt, Patrick J.; Guntenspergen, Glenn R.; MacDonald, Glen M.; Takekawa, John Y.; Thorne, Karen M.

    2016-01-01

    Salt marsh elevation and geomorphic stability depends on mineral sedimentation. Many Mediterranean-climate salt marshes along southern California, USA coast import sediment during El Niño storm events, but sediment fluxes and mechanisms during dry weather are potentially important for marsh stability. We calculated tidal creek sediment fluxes within a highly modified, sediment-starved, 1.5-km2 salt marsh (Seal Beach) and a less modified 1-km2marsh (Mugu) with fluvial sediment supply. We measured salt marsh plain suspended sediment concentration and vertical accretion using single stage samplers and marker horizons. At Seal Beach, a 2014 storm yielded 39 and 28 g/s mean sediment fluxes and imported 12,000 and 8800 kg in a western and eastern channel. Western channel storm imports offset 8700 kg exported during 2 months of dry weather, while eastern channel storm imports augmented 9200 kg imported during dry weather. During the storm at Mugu, suspended sediment concentrations on the marsh plain increased by a factor of four; accretion was 1–2 mm near creek levees. An exceptionally high tide sequence yielded 4.4 g/s mean sediment flux, importing 1700 kg: 20 % of Mugu’s dry weather fluxes. Overall, low sediment fluxes were observed, suggesting that these salt marshes are geomorphically stable during dry weather conditions. Results suggest storms and high lunar tides may play large roles, importing sediment and maintaining dry weather sediment flux balances for southern California salt marshes. However, under future climate change and sea level rise scenarios, results suggest that balanced sediment fluxes lead to marsh elevational instability based on estimated mineral sediment deficits.

  7. Source-to-Sink: An implicit and O(n) landscape evolution model and its application to the Ogooue Delta, Gabon

    Science.gov (United States)

    Yuan, X.; Braun, J.; Guerit, L.; Simon, B.

    2017-12-01

    Limited attention has been given to linking continental erosion to transport and deposition of sediments in the marine environment in large-scale landscape evolution models. Although both environments have been thoroughly investigated, the details of how erosional or climatic events are recorded in the sedimentary and stratigraphic records have not been studied in a consistent quantitative manner. Here we propose a new numerical model for marine multi-lithology (sand and silt) coupling transport and deposition that is directly coupled to FastScape, a landscape evolution model that solves the continental stream power law and hillslope diffusion equation using implicit and O(n) algorithms. Marine transport and deposition is simulated by a nonlinear 2D diffusion model that incorporates a dual lithology (sand and slit) and where source terms represent the sediment flux from continental river erosion. Sediment compaction effects are also incorporated, taking into account the dual lithology, and are important to properly compute the details of the synthetic stratigraphic record. The algorithm used to represent marine transport and deposition is also implicit and O(n). The main purpose of our work is to invert stratigraphic data from offshore marginal basins to provide constraints on the tectonic, climatic and sea-level conditions that have affected the adjacent continental areas. In order to do so, we have incorporated the new model into a Bayesian inversion and optimisation scheme and tested and validated the approach with synthetic data. This is made possible due to the high efficient of the forward model. We are in the process of applying the inversion scheme to stratigraphic data from the Ogooue Delta (Gabon). By comparing real and synthetic stratigraphic geometries along cross-section of the delta, the shape and slope of seismic/time markers, and the sand to silt fraction in wells, we hope to obtain good constraints, not only of the value of the transport

  8. Heavy metals in marine coastal sediments: assessing sources, fluxes, history and trends.

    Science.gov (United States)

    Frignani, Mauro; Bellucci, Luca Giorgio

    2004-01-01

    Examples are presented from the Adriatic Sea, the Ligurian Sea and the Venice Lagoon to illustrate different approaches to the study of anthropogenic metals in marine coastal sediments. These examples refer to studies of areal distribution and transport mechanisms, individuation of the sources, sediment dating, chronology of the fluxes, present and past trends. In particular, some of the findings achieved in studying the Venice Lagoon are discussed from the point of view of anthropogenic changes both in sediment composition and contaminant fluxes.

  9. Provenance and sediment fluxes in the Irrawaddy (Ayeyarwadi) River

    Science.gov (United States)

    Garzanti, Eduardo; Wang, Jiangang; Vezzoli, Giovanni; Limonta, Mara

    2016-04-01

    .5 and 2.0 Ga (Limonta et al., 2016). Forward mixing calculations based on integrated petrographic and heavy-mineral data (Garzanti et al., 2012) indicate that 60±10% of the total sediment flux is supplied by the Chindwin River and that upper Irrawaddy sand is supplied mainly by the Nmai headwater branch but also significantly from the Mali branch and left-bank tributaries sourced in the northern Shan Plateau. CITED REFERENCES Garzanti E., Resentini A., Vezzoli G., Andò S., Malusà M., Padoan M. 2012. Forward compositional modelling of Alpine orogenic sediments. Sedimentary Geology 280:149-164. Garzanti E., Limonta M., Resentini A., Bandopadhyay P. C., Najman Y., Andò S., Vezzoli G. 2013. Sediment recycling at convergent plate margins (Indo-Burman Ranges and Andaman-Nicobar Ridge). Earth-Science Reviews 123:113-132. Limonta M., Resentini A., Carter A., Bandopadhyay P.C., Garzanti E. 2016. Provenance of Oligocene Andaman Sandstones (Andaman-Nicobar islands): Ganga-Brahmaputra or Irrawaddy derived? In: Bandyopadhyay P., Carter A. (Eds.). The Andaman-Nicobar accretionary ridge geology, tectonics and hazards, Geological Society of London Memoir, in review. Robinson R.A.J., Bird M.I., Oo N.W., Hoey T.B., Aye M.M., Higgitt D.L., Lu X.X., Swe A., Tun T., Win S. L. 2007. The Irrawaddy River sediment flux to the Indian Ocean: the original nineteenth-century data revisited. The Journal of Geology 115:629-640. Wang J.G., Wu F.Y., Tan X.C., Liu C.Z. 2014. Magmatic evolution of the Western Myanmar Arc documented by U-Pb and Hf isotopes in detrital zircon. Tectonophysics 612:97-105.

  10. Event-driven sediment flux in Hueneme and Mugu submarine canyons, southern California

    Science.gov (United States)

    Xu, J. P.; Swarzenski, P.W.; Noble, M.; Li, A.-C.

    2010-01-01

    Vertical sediment fluxes and their dominant controlling processes in Hueneme and Mugu submarine canyons off south-central California were assessed using data from sediment traps and current meters on two moorings that were deployed for 6 months during the winter of 2007. The maxima of total particulate flux, which reached as high as 300+ g/m2/day in Hueneme Canyon, were recorded during winter storm events when high waves and river floods often coincided. During these winter storms, wave-induced resuspension of shelf sediment was a major source for the elevated sediment fluxes. Canyon rim morphology, rather than physical proximity to an adjacent river mouth, appeared to control the magnitude of sediment fluxes in these two submarine canyon systems. Episodic turbidity currents and internal bores enhanced sediment fluxes, particularly in the lower sediment traps positioned 30 m above the canyon floor. Lower excess 210Pb activities measured in the sediment samples collected during periods of peak total particulate flux further substantiate that reworked shelf-, rather than newly introduced river-borne, sediments supply most of the material entering these canyons during storms.

  11. Sedimentation in the Three Gorges Dam and the future trend of Changjiang (Yangtze River sediment flux to the sea

    Directory of Open Access Journals (Sweden)

    Guogang Li

    2009-11-01

    Full Text Available The Three Gorges Dam (TGD on the upper Changjiang (Yangtze River, China, disrupts the continuity of Changjiang sediment delivery to downstream and coastal areas. In this study, which was based on 54 years of annual water and sediment data from the mainstream and major tributaries of Changjiang, sediment deposition induced by the TGD in 2003–2008 was quantified. Furthermore, we determined the theoretical trapping efficiency of the cascade reservoir upstream of the TGD. Its impact on Changjiang sediment flux in the coming decades is discussed. Results show that about 172 million tons (Mt of sediment was trapped annually by the TGD in 2003–2008, with an averaged trapping efficiency of 75%. Most of the total sediment deposition, as induced by the TGD (88%, accumulated within the region between the TGD site and Cuntan. However, significant siltation (12% of the total sediment deposition also occurred upstream of Cuntan as a consequence of the upstream extended backwater region of the TGD. Additionally, the Changjiang sediment flux entered a third downward step in 2001, prior to operation of the TGD. This mainly resulted from sediment reduction in the Jinshajiang tributary since the late 1990s. As the cascade reservoir is put into full operation, it could potentially trap 91% of the Jinshajiang sediment discharge and, therefore, the Jinshajiang sediment discharge would most likely further decrease to 14 Mt/yr in the coming decades. Consequently, the Changjiang sediment flux to the sea is expected to continuously decrease to below 90 Mt/yr in the near future, or only 18% of the amount observed in the 1950s. In the presence of low sediment discharge, profound impacts on the morphology of estuary, delta and coastal waters are expected.

  12. The effect of sediment thermal conductivity on vertical groundwater flux estimates

    Science.gov (United States)

    Sebok, Eva; Müller, Sascha; Engesgaard, Peter; Duque, Carlos

    2015-04-01

    The interaction between groundwater and surface water is of great importance both from ecological and water management perspective. The exchange fluxes are often estimated based on vertical temperature profiles taken from shallow sediments assuming a homogeneous standard value of sediment thermal conductivity. Here we report on a field investigation in a stream and in a fjord, where vertical profiles of sediment thermal conductivity and temperatures were measured in order to, (i) define the vertical variability in sediment thermal conductivity, (ii) quantify the effect of heterogeneity in sediment thermal conductivity on the estimated vertical groundwater fluxes. The study was carried out at field sites located in Ringkøbing fjord and Holtum stream in Western Denmark. Both locations have soft, sandy sediments with an upper organic layer at the fjord site. First 9 and 12 vertical sediment temperature profiles up to 0.5 m depth below the sediment bed were collected in the fjord and in the stream, respectively. Later sediment cores of 0.05 m diameter were removed at the location of the temperature profiles. Sediment thermal conductivity was measured in the sediment cores at 0.1 m intervals with a Decagon KD2 Pro device. A 1D flow and heat transport model (HydroGeoSphere) was set up and vertical groundwater fluxes were estimated based on the measured vertical sediment temperature profiles by coupling the model with PEST. To determine the effect of heterogeneity in sediment thermal conductivity on estimated vertical groundwater fluxes, the model was run by assigning (i) a homogeneous thermal conductivity for all sediment layers, calculated as the average sediment thermal conductivity of the profile, (ii) measured sediment thermal conductivities to the different model layers. The field survey showed that sediment thermal conductivity over a 0.5 m profile below the sediment bed is not uniform, having the largest variability in the fjord where organic sediments were also

  13. Clastic sediment flux to tropical Andean lakes: records of glaciation and soil erosion

    Science.gov (United States)

    Rodbell, Donald T.; Seltzer, Geoffrey O.; Mark, Bryan G.; Smith, Jacqueline A.; Abbott, Mark B.

    2008-08-01

    We developed records of clastic sediment flux to 13 alpine lakes in Peru, Ecuador, and Bolivia, and compared these with independently dated records of regional glaciation. Our objectives are to determine whether a strong relationship exists between the extent of ice cover in the region and the rate of clastic sediment delivery to alpine lakes, and thus whether clastic sediment records serve as reliable proxies for glaciation during the late Pleistocene. We isolated the clastic component in lake sediment cores by removing the majority of the biogenic and authigenic components from the bulk sediment record, and we dated cores by a combination of radiocarbon and tephrochronology. In order to partially account for intra-basin differences in sediment focusing, bedrock erosivity, and sediment availability, we normalized each record to the weighted mean value of clastic sediment flux for each respective core. This enabled the stacking of all 13 lake records to produce a composite record that is generally representative of the tropical Andes. There is a striking similarity between the composite record of clastic sediment flux and the distribution of ˜100 cosmogenic radionuclide (CRN) exposure ages for erratics on moraine crests in the central Peruvian and northern Bolivian Andes. The extent of ice cover thus appears to be the primary variable controlling the delivery of clastic sediment to alpine lakes in the region, which bolsters the increasing use of clastic sediment flux as a proxy for the extent of ice cover in the region. The CRN moraine record and the stacked lake core composite record together indicate that the expansion of ice cover and concomitant increase in clastic sediment flux began at least 40 ka, and the local last glacial maximum (LLGM) culminated between 30 and 20 ka. A decline in clastic sediment flux that began ˜20 ka appears to mark the onset of deglaciation from the LLGM, at least one millennium prior to significant warming in high latitude regions

  14. 210 Pb fluxes in sediment layers sampled from Northern Patagonia lakes

    International Nuclear Information System (INIS)

    Ribeiro Guevara, S.; Sanchez, R.; Arribere, M.; Rizzo, A.

    2003-01-01

    Unsupported 210 Pb fluxes were determined from sediment core inventories in lakes located in Northern Patagonia, Argentina. Total 210 Pb, 226 Ra, associated with supported 210 Pb, and 137 Cs specific activity profiles were measured by gamma-ray spectrometry. Unsupported 210 Pb fluxes showed very low values when compared to other regions, with a 12 fold variation, ranging from 4 to 48 Bq m -2 x y -1 . The linear correlation observed between the 210 Pb fluxes and 137 Cs cumulative fluxes in sediment cores sampled from water bodies within a zone with similar precipitation demonstrated that both radioisotopes behave in the same manner in these systems concerning the processes occurred from fallout to sediment deposition, and that there are no appreciable local or regional sources of unsupported 210 Pb. Positive correlation of 210 Pb fluxes with organic matter contents of the uppermost sediment core layers was also observed. (author)

  15. Effect of water flux and sediment discharge of the Yangtze River on PAHs sedimentation in the estuary.

    Science.gov (United States)

    Li, Rufeng; Feng, Chenghong; Wang, Dongxin; He, Maozhi; Hu, Lijuan; Shen, Zhenyao

    2016-12-01

    Historical distribution characteristics of polycyclic aromatic hydrocarbons (PAHs) and their carriers (i.e., organic matter and mineral particles) in the sediment cores of the Yangtze Estuary were investigated, with emphasis laid on the role of the Yangtze River. Grain size component of sediments (clay, silt, and sand) and organic carbon (black carbon and total organic carbon) in the sediment cores were markedly affected by water flux and sediment discharge of the Yangtze River. Qualitative and quantitative analysis results showed that sands and black carbon acted as the main carriers of PAHs. The sedimentation of two-ring to three-ring PAHs in the estuary had significant correlations with water flux and sediment discharge of the Yangtze River. The relative lower level of the four-ring and five-ring to six-ring PAHs concentrations appeared around the year 2003 and remained for the following several years. This time period accorded well with the water impoundment time of the Three Gorges Reservoir. The decreased level of two-ring to three-ring PAHs occurred in the year 1994, and the peak points around the year 2009 indicated that PAHs sedimentation in the estuary also had close relationship to severe drought and flood in the catchments. The findings presented in this paper could provide references for assessing the impacts of water flux and sediment discharge on the historical deposition of PAHs and their carriers in the Yangtze Estuary.

  16. Climatic and geologic controls on suspended sediment flux in the Sutlej River Valley, western Himalaya

    Directory of Open Access Journals (Sweden)

    H. Wulf

    2012-07-01

    Full Text Available The sediment flux through Himalayan rivers directly impacts water quality and is important for sustaining agriculture as well as maintaining drinking-water and hydropower generation. Despite the recent increase in demand for these resources, little is known about the triggers and sources of extreme sediment flux events, which lower water quality and account for extensive hydropower reservoir filling and turbine abrasion. Here, we present a comprehensive analysis of the spatiotemporal trends in suspended sediment flux based on daily data during the past decade (2001–2009 from four sites along the Sutlej River and from four of its main tributaries. In conjunction with satellite data depicting rainfall and snow cover, air temperature and earthquake records, and field observations, we infer climatic and geologic controls of peak suspended sediment concentration (SSC events. Our study identifies three key findings: First, peak SSC events (≥ 99th SSC percentile coincide frequently (57–80% with heavy rainstorms and account for about 30% of the suspended sediment flux in the semi-arid to arid interior of the orogen. Second, we observe an increase of suspended sediment flux from the Tibetan Plateau to the Himalayan Front at mean annual timescales. This sediment-flux gradient suggests that averaged, modern erosion in the western Himalaya is most pronounced at frontal regions, which are characterized by high monsoonal rainfall and thick soil cover. Third, in seven of eight catchments, we find an anticlockwise hysteresis loop of annual sediment flux variations with respect to river discharge, which appears to be related to enhanced glacial sediment evacuation during late summer. Our analysis emphasizes the importance of unconsolidated sediments in the high-elevation sector that can easily be mobilized by hydrometeorological events and higher glacial-meltwater contributions. In future climate change scenarios, including continuous glacial retreat and

  17. Incision and Landsliding Lead to Coupled Increase in Sediment Flux and Grain Size Export

    Science.gov (United States)

    Roda-Boluda, D. C.; Brooke, S.; D'Arcy, M. K.; Whittaker, A. C.; Armitage, J. J.

    2017-12-01

    The rates and grain sizes of sediment fluxes modulate the dynamics and timing of landscape response to tectonics, and dictate the depositional patterns of sediment in basins. Over the last decades, we have gained a good quantitative understanding on how sediment flux and grain size may affect incision and basin stratigraphy. However, we comparably still have limited knowledge on how these variables change with varying tectonic rates. To address this question, we have studied 152 catchments along 8 normal fault-bounded ranges in southern Italy, which are affected by varying fault slip rates and experiencing a transient response to tectonics. Using a data set of 38 new and published 10Be erosion rates, we calibrate a sediment flux predictive equation (BQART), in order to estimate catchment sediment fluxes. We demonstrate that long-term sediment flux is governed by fault slip rates and the tectonically-controlled transient incision, and that sediment flux estimates from the BQART, steady-state assumptions, and incised volumes are highly correlated. This is supported by our 10Be erosion rates, which are controlled by fault slip and incision rates, and the associated landsliding. Based on a new landslide inventory, we show that erosion rate differences are likely due to differences in incision-related landslide activity across these catchments, and that landslides are a major component of sediment fluxes. From a data set of >13000 grain size counts on hillslope grain size supply and fluvial sediment at catchment outlets, we observe that landslides deliver material 20-200% coarser than other sediment sources, and that this coarse supply has an impact on the grain size distributions being exported from the catchments. Combining our sediment flux and grain size data sets, we are able to show that for our catchments, and potentially also for any areas that respond to changes in climate or tectonics via enhanced landsliding, sediment flux and grain size export increase

  18. Sediment fluxes and the littoral drift along northeast Andhra Pradesh Coast, India: estimation by remote sensing.

    Science.gov (United States)

    Kunte, Pravin D; Alagarsamy, R; Hursthouse, A S

    2013-06-01

    The littoral drift regime along the northeastern coast of India was investigated by analyzing coastal drift indicators and shoreline changes based on multitemporal satellite images. The study of offshore turbidity patterns and quantitative estimation of suspended sediments was undertaken to understand the magnitude and direction of movement of sediment fluxes. The study revealed that: (1) the character of coastal landforms and sedimentation processes indicate that the sediment transport is bidirectional and monsoon dependent; (2) multidate, multitemporal analysis of satellite images helps to show the nature of sediment transport along the coast. The dominant net sediment transport is in a NE direction along the eastern coast of India. Finally, this assessment demonstrates the potential of remote sensing technology in understanding the coastal morphometric changes, long-term sediment transport, shoreline changes, and offshore turbidity distribution pattern and the implications for the transport of sediment-associated pollutants.

  19. Statistical modelling of variability in sediment-water nutrient and oxygen fluxes

    Science.gov (United States)

    Serpetti, Natalia; Witte, Ursula; Heath, Michael

    2016-06-01

    Organic detritus entering, or produced, in the marine environment is re-mineralised to inorganic nutrient in the seafloor sediments. The flux of dissolved inorganic nutrient between the sediment and overlying water column is a key process in the marine ecosystem, which binds the biogeochemical sub-system to the living food web. These fluxes are potentially affected by a wide range of physical and biological factors and disentangling these is a significant challenge. Here we develop a set of General Additive Models (GAM) of nitrate, nitrite, ammonia, phosphate, silicate and oxygen fluxes, based on a year-long campaign of field measurements off the north-east coast of Scotland. We show that sediment grain size, turbidity due to sediment re-suspension, temperature, and biogenic matter content were the key factors affecting oxygen consumption, ammonia and silicate fluxes. However, phosphate fluxes were only related to suspended sediment concentrations, whilst nitrate fluxes showed no clear relationship to any of the expected drivers of change, probably due to the effects of denitrification. Our analyses show that the stoichiometry of nutrient regeneration in the ecosystem is not necessarily constant and may be affected by combinations of processes. We anticipate that our statistical modelling results will form the basis for testing the functionality of process-based mathematical models of whole-sediment biogeochemistry.

  20. Particle fluxes in the Bay of Bengal measurEd. by sediment traps

    Digital Repository Service at National Institute of Oceanography (India)

    Ramaswamy, V.; Parthiban, G.

    Particle fluxes were measured between October, 1987 and March, 1988 using six automated time series sediment traps at three locations in the northern, central and southern Bay of Bengal. Particle fluxes varied between 16.8 and 345 mg m/2 day/1...

  1. Changing trends of rainfall and sediment fluxes in the Kinta River catchment, Malaysia

    Directory of Open Access Journals (Sweden)

    W. R. Ismail

    2015-03-01

    Full Text Available The Kinta River, draining an area of 2566 km2, originates in the Korbu Mountain in Perak, Malaysia, and flows through heterogeneous, mixed land uses ranging from extensive forests to mining, rubber and oil palm plantations, and urban development. A land use change analysis of the Kinta River catchment was carried out together with assessment of the long-term trend in rainfall and sediment fluxes. The Mann-Kendall test was used to examine and assess the long-term trends in rainfall and its relationship with the sediment discharge trend. The land use analysis shows that forests, water bodies and mining land declined whilst built and agricultural land use increased significantly. This has influenced the sediment flux of the catchment. However, most of the rainfall stations and river gauging stations are experiencing an increasing trends, except at Kinta river at Tg. Rambutan. Sediment flux shows a net erosion for the period from 1961 to 1969. The total annual sediment discharge in the Kinta River catchment was low with an average rate of 1,757 t/km2/year. From 1970 to 1985, the annual sediment yield rose to an average rate of 4062 t/km2/year. Afterwards, from 1986 to 1993, the total annual sediment discharge decreased to an average rate of 1,306 t/km2/year and increased back during the period 1994 to 2000 to 2109 t/km2/year. From 2001 to 2006 the average sediment flux rate declined to 865 t/km2/year. The decline was almost 80% from the 1970s. High sediment flux in the early 1970s is partly associated with reduced tin mining activities in the area. This decreasing trend in sediment delivery leaving the Kinta River catchment is expected to continue dropping in the future.

  2. Changing trends of rainfall and sediment fluxes in the Kinta River catchment, Malaysia

    Science.gov (United States)

    Ismail, W. R.; Hashim, M.

    2015-03-01

    The Kinta River, draining an area of 2566 km2, originates in the Korbu Mountain in Perak, Malaysia, and flows through heterogeneous, mixed land uses ranging from extensive forests to mining, rubber and oil palm plantations, and urban development. A land use change analysis of the Kinta River catchment was carried out together with assessment of the long-term trend in rainfall and sediment fluxes. The Mann-Kendall test was used to examine and assess the long-term trends in rainfall and its relationship with the sediment discharge trend. The land use analysis shows that forests, water bodies and mining land declined whilst built and agricultural land use increased significantly. This has influenced the sediment flux of the catchment. However, most of the rainfall stations and river gauging stations are experiencing an increasing trends, except at Kinta river at Tg. Rambutan. Sediment flux shows a net erosion for the period from 1961 to 1969. The total annual sediment discharge in the Kinta River catchment was low with an average rate of 1,757 t/km2/year. From 1970 to 1985, the annual sediment yield rose to an average rate of 4062 t/km2/year. Afterwards, from 1986 to 1993, the total annual sediment discharge decreased to an average rate of 1,306 t/km2/year and increased back during the period 1994 to 2000 to 2109 t/km2/year. From 2001 to 2006 the average sediment flux rate declined to 865 t/km2/year. The decline was almost 80% from the 1970s. High sediment flux in the early 1970s is partly associated with reduced tin mining activities in the area. This decreasing trend in sediment delivery leaving the Kinta River catchment is expected to continue dropping in the future.

  3. Interstitial water chemistry and nutrients fluxes from tropical intertidal sediment

    Digital Repository Service at National Institute of Oceanography (India)

    Ram, A.; Zingde, M.D.

    temporal changes in relation to their con- centrations in the overlying creek water. The high chlorinity creek water infiltrating in the bed after September, progres- sively pushed down the monsoonal low chlorinity water trapped in the sediment resulting....4-2.5%), the trend of decreasing con- centration with depth indicated some accumulation in the sediment over the years. The 1.0-2.5% Corgin core 2 commonly occurs in silty-clay sediment along the centra] west coast of India16 even in areas where there is no apparent...

  4. A comparative study of the flux and fate of the Mississippi and Yangtze river sediments

    Directory of Open Access Journals (Sweden)

    K. Xu

    2015-03-01

    Full Text Available Large rivers play a key role in delivering water and sediment into the global oceans. Large-river deltas and associated coastlines are important interfaces for material fluxes that have a global impact on marine processes. In this study, we compare water and sediment discharge from Mississippi and Yangtze rivers by assessing: (1 temporal variation under varying climatic and anthropogenic impacts, (2 delta response of the declining sediment discharge, and (3 deltaic lobe switching and Holocene sediment dispersal patterns on the adjacent continental shelves. Dam constructions have decreased both rivers’ sediment discharge significantly, leading to shoreline retreat along the coast. The sediment dispersal of the river-dominated Mississippi Delta is localized but for the tide-dominated Yangtze Delta is more diffuse and influenced by longshore currents. Sediment declines and relative sea level rises have led to coastal erosion, endangering the coasts of both rivers.

  5. Sediment carbon and nutrient fluxes from cleared and intact temperate mangrove ecosystems and adjacent sandflats.

    Science.gov (United States)

    Bulmer, Richard H; Schwendenmann, Luitgard; Lohrer, Andrew M; Lundquist, Carolyn J

    2017-12-01

    The loss of mangrove ecosystems is associated with numerous impacts on coastal and estuarine function, including sediment carbon and nutrient cycling. In this study we compared in situ fluxes of carbon dioxide (CO 2 ) from the sediment to the atmosphere, and fluxes of dissolved inorganic nutrients and oxygen across the sediment-water interface, in intact and cleared mangrove and sandflat ecosystems in a temperate estuary. Measurements were made 20 and 25months after mangrove clearance, in summer and winter, respectively. Sediment CO 2 efflux was over two-fold higher from cleared than intact mangrove ecosystems at 20 and 25months after mangrove clearance. The higher CO 2 efflux from the cleared site was explained by an increase in respiration of dead root material along with sediment disturbance following mangrove clearance. In contrast, sediment CO 2 efflux from the sandflat site was negligible (≤9.13±1.18mmolm -2 d -1 ), associated with lower sediment organic matter content. The fluxes of inorganic nutrients (NH 4 + , NO x and PO 4 3- ) from intact and cleared mangrove sediments were low (≤20.37±18.66μmolm -2 h - 1 ). The highest NH 4 + fluxes were measured at the sandflat site (69.21±13.49μmolm -2 h - 1 ). Lower inorganic nutrient fluxes within the cleared and intact mangrove sites compared to the sandflat site were associated with lower abundance of larger burrowing macrofauna. Further, a higher fraction of organic matter, silt and clay content in mangrove sediments may have limited nutrient exchange. Copyright © 2017 Elsevier B.V. All rights reserved.

  6. Evaluation of suspended sediment concentrations, sediment fluxes and sediment depositions along a reservoir by using laser diffraction and acoustic backscatter data

    Science.gov (United States)

    Lizano, Laura; Haun, Stefan

    2015-04-01

    The construction of dams and reservoirs disturb the natural morphological behavior of rivers. A natural settling effect occurs due to the reduced turbulences and flow velocities. As a consequence, reservoirs fill up with sediments which results in a reduction of storage volume, influences the operation of hydropower plants and leads in several cases to flood protection problems. The sediment depositions in reservoirs are standardly evaluated by using bathymetric data, obtained by a single beam sonar from pre-defined cross sections or by an extensive evaluation of the reservoir bed by a side scan sonar. However, a disadvantage of this method is that it is not possible to evaluate the pore water content of the depositions, which may lead as consequence to an uncertainty in the measured amount of deposited sediments. Given that a major part of sediments entering reservoirs are transported in suspension, sediment flux measurements along defined transects could give more reliable information on the settled amount of sediments and additional information on the sediment transport mechanism within the reservoir. An evaluation of the sediment fluxes is in practice often conducted by a single suspended sediment concentration (SSC) measurement in combination with a cross sectional calibration factor to take changes in the SSC along the transect into account. However, these calibration factors are often developed only for one specific in-situ condition and may give unreliable results in case that the boundaries change e.g. the hydraulic conditions. Hence an evaluation of the sediment fluxes along the whole transect would give a more reliable number for the amount of transported sediments through the reservoir. This information can afterwards be used to calculate the amount of settled sediments in different sections of the reservoir and the amount of sediments which will enter the intake. For this study the suspended sediment transport within the Peñas Blancas reservoir in

  7. Increased terrestrial to ocean sediment and carbon fluxes in the northern Chesapeake Bay associated with twentieth century land alteration

    Science.gov (United States)

    Saenger, C.; Cronin, T. M.; Willard, D.; Halka, J.; Kerhin, R.

    2008-01-01

    We calculated Chesapeake Bay (CB) sediment and carbon fluxes before and after major anthropogenic land clearance using robust monitoring, modeling and sedimentary data. Four distinct fluxes in the estuarine system were considered including (1) the flux of eroded material from the watershed to streams, (2) the flux of suspended sediment at river fall lines, (3) the burial flux in tributary sediments, and (4) the burial flux in main CB sediments. The sedimentary maximum in Ambrosia (ragweed) pollen marked peak land clearance (~1900 a.d.). Rivers feeding CB had a total organic carbon (TOC)/total suspended solids of 0.24??0.12, and we used this observation to calculate TOC fluxes from sediment fluxes. Sediment and carbon fluxes increased by 138-269% across all four regions after land clearance. Our results demonstrate that sediment delivery to CB is subject to significant lags and that excess post-land clearance sediment loads have not reached the ocean. Post-land clearance increases in erosional flux from watersheds, and burial in estuaries are important processes that must be considered to calculate accurate global sediment and carbon budgets. ?? 2008 Coastal and Estuarine Research Federation.

  8. Tidal wetland fluxes of dissolved organic carbon and sediment at Browns Island, California: initial evaluation

    Science.gov (United States)

    Ganju, N.K.; Bergamaschi, B.; Schoellhamer, D.H.

    2003-01-01

    Carbon and sediment fluxes from tidal wetlands are of increasing concern in the Sacramento-San Joaquin River Delta (Delta), because of drinking water issues and habitat restoration efforts. Certain forms of dissolved organic carbon (DOC) react with disinfecting chemicals used to treat drinking water, to form disinfection byproducts (DBPs), some of which are potential carcinogens. The contribution of DBP precursors by tidal wetlands is unknown. Sediment transport to and from tidal wetlands determines the potential for marsh accretion, thereby affecting habitat formation.Water, carbon, and sediment flux were measured in the main channel of Browns Island, a tidal wetland located at the confluence of Suisun Bay and the Delta. In-situ instrumentation were deployed between May 3 and May 21, 2002. Water flux was measured using acoustic Doppler current profilers and the index-velocity method. DOC concentrations were measured using calibrated ultraviolet absorbance and fluorescence instruments. Suspended-sediment concentrations were measured using a calibrated nephelometric turbidity sensor. Tidally averaged water flux through the channel was dependent on water surface elevations in Suisun Bay. Strong westerly winds resulted in higher water surface elevations in the area east of Browns Island, causing seaward flow, while subsiding winds reversed this effect. Peak ebb flow transported 36% more water than peak flood flow, indicating an ebb-dominant system. DOC concentrations were affected strongly by porewater drainage from the banks of the channel. Peak DOC concentrations were observed during slack after ebb, when the most porewater drained into the channel. Suspended-sediment concentrations were controlled by tidal currents that mobilized sediment from the channel bed, and stronger tides mobilized more sediment than the weaker tides. Sediment was transported mainly to the island during the 2-week monitoring period, though short periods of export occurred during the spring

  9. Bioturbation and dissolved organic matter enhance contaminant fluxes from sediment treated with powdered and granular activated carbon

    NARCIS (Netherlands)

    Kupryianchyk, D.; Noori, A.; Rakowska, M.I.; Grotenhuis, J.T.C.; Koelmans, A.A.

    2013-01-01

    Sediment amendment with activated carbon (AC) is a promising technique for in situ sediment remediation. To date it is not clear whether this technique sufficiently reduces sediment-to-water fluxes of sediment-bound hydrophobic organic chemicals (HOCs) in the presence of bioturbators. Here, we

  10. Human impact on sediment fluxes within the Blue Nile and Atbara River basins

    Science.gov (United States)

    Balthazar, Vincent; Vanacker, Veerle; Girma, Atkilt; Poesen, Jean; Golla, Semunesh

    2013-01-01

    A regional assessment of the spatial variability in sediment yields allows filling the gap between detailed, process-based understanding of erosion at field scale and empirical sediment flux models at global scale. In this paper, we focus on the intrabasin variability in sediment yield within the Blue Nile and Atbara basins as biophysical and anthropogenic factors are presumably acting together to accelerate soil erosion. The Blue Nile and Atbara River systems are characterized by an important spatial variability in sediment fluxes, with area-specific sediment yield (SSY) values ranging between 4 and 4935 t/km2/y. Statistical analyses show that 41% of the observed variation in SSY can be explained by remote sensing proxy data of surface vegetation cover, rainfall intensity, mean annual temperature, and human impact. The comparison of a locally adapted regression model with global predictive sediment flux models indicates that global flux models such as the ART and BQART models are less suited to capture the spatial variability in area-specific sediment yields (SSY), but they are very efficient to predict absolute sediment yields (SY). We developed a modified version of the BQART model that estimates the human influence on sediment yield based on a high resolution composite measure of local human impact (human footprint index) instead of countrywide estimates of GNP/capita. Our modified version of the BQART is able to explain 80% of the observed variation in SY for the Blue Nile and Atbara basins and thereby performs only slightly less than locally adapted regression models.

  11. Decadal-scale Evolution of Sediment Flux in the Aulne Estuary

    Science.gov (United States)

    Moskalski, S. M.; Deschamps, A.; Floc'h, F.; Verney, R.; Piete, H.; Fromant, G.; Delacourt, C.

    2013-12-01

    Estuarine sediment transport processes have the potential to evolve over time in response to alterations in various factors both internal and external to the estuary, such as sediment supply, river discharge, tidal forcing, or changes to bathymetry. Changes in sediment transport can affect many estuarine processes (e.g. budgets of sediment-adsorbed contaminants or nutrients) and ecosystem services, such as aquaculture, primary production and the need to dredge shipping channels. Most studies of decadal-scale changes in estuaries focus on geomorphology or bathymetry, or are performed using models calibrated by a limited set of observational studies. Because of the potential for sediment flux to both affect and be affected by geomorphology and bathymetry, observational studies oriented to sediment flux evolution are needed. This study focuses on two intensive observational studies separated by 30 years to quantify change in suspended sediment concentration (SSC) in the Aulne river, a shallow macrotidal estuary in western Brittany. Moored and vessel-mounted acoustic Doppler current profilers and YSIs were deployed over a three-week period in the winter of 2013 to examine hydrodynamic and sediment transport processes. The results of the modern study were compared to a 1977 investigation of currents, suspended sediment concentration, and erosion/deposition. The 1977 study found that SSC during spring tide and average river discharge was less than 30 mg/L near the mouth and above 300 mg/L landward, with near-bottom concentrations in the turbidity maximum zone occasionally greater than 1000 mg/L. SSC was highest during low tide and remained elevated throughout, in the upstream part of the estuary. Sediment deposition was stronger after flood tide due to a longer slack period, which implies landward sediment transport in the estuary. In the 2013 study, near-bottom SSC during spring tide and average river discharge was also highest during low tide, but SSC was above 1000 mg

  12. Simulating Spatial Variability of Fluvial Sediment Fluxes Within the Magdalena Drainage Basin, Colombia.

    Science.gov (United States)

    Kettner, A. J.; Syvitski, J. P.; Restrepo, J. D.

    2008-12-01

    This study explores the application of an empirical sediment flux model BQART, to simulate long-term sediment fluxes of major tributaries of a river system based on a limited number of input parameters. We validate model results against data of the 1612 km long Magdalena River, Colombia, South America, which is well monitored. The Magdalena River, draining a hinterland area of 257,438 km2, of which the majority lies in the Andes before reaching the Atlantic coast, is known for its high sediment yield, 560 t kg- 2 yr-1; higher than nearby South American rivers like the Amazon or the Orinoco River. Sediment fluxes of 32 tributary basins of the Magdalena River were simulated based on the following controlling factors: geomorphic influences (tributary-basin area and relief) derived from high-resolution Shuttle Radar Topography Mission data, tributary basin-integrated lithology based on GIS analysis of lithology data, 30year temperature data, and observed monthly mean discharge data records (varying in record length of 15 to 60 years). Preliminary results indicate that the simulated sediment flux of all 32 tributaries matches the observational record, given the observational error and the annual variability. These simulations did not take human influences into account yet, which often increases sediment fluxes by accelerating erosion, especially in steep mountainous area similar to the Magdalena. Simulations indicate that, with relatively few input parameters, mostly derived from remotely-sensed data or existing compiled GIS datasets, it is possible to predict: which tributaries in an arbitrary river drainage produce relatively high contributions to sediment yields, and where in the drainage basin you might expect conveyance loss.

  13. Sediment fluxes from California Coastal Rivers: the influences of climate, geology, and topography

    Science.gov (United States)

    Andrews, E.D.; Antweiler, Ronald C.

    2012-01-01

    The influences of geologic and climatic factors on erosion and sedimentation processes in rivers draining the western flank of the California Coast Range are assessed. Annual suspended, bedload, and total sediment fluxes were determined for 16 river basins that have hydrologic records covering all or most of the period from 1950 to 2006 and have been relatively unaffected by flow storage, regulation, and depletion, which alter the downstream movement of water and sediment. The occurrence of relatively large annual sediment fluxes are strongly influenced by the El Nino–Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO). The frequency of relatively large annual sediment fluxes decreases from north to south during La Nina phases and increases from north to south during El Nino phases. The influence of ENSO is modulated over a period of decades by the PDO, such that relatively large annual sediment fluxes are more frequent during a La Nina phase in conjunction with a cool PDO and during an El Nino phase in conjunction with a warm PDO. Values of mean annual sediment flux, , were regressed against basin and climatic characteristics. Basin area, bedrock erodibility, basin relief, and precipitation explain 87% of the variation in from the 16 river basins. Bedrock erodibility is the most significant characteristic influencing . Basin relief is a superior predictor of compared with basin slope. is nearly proportional to basin area and increases with increasing precipitation. For a given percentage change, basin relief has a 2.3-fold greater effect on than a similar change in precipitation. The estimated natural from all California coastal rivers for the period 1950–2006 would have been approximately 85 million tons without flow storage, regulation, and depletion; the actual has been approximately 50 million tons, because of the effects of flow storage, regulation, and depletion.

  14. Trace element fluxes in sediments of an environmentally impacted river from a coastal zone of Brazil.

    Science.gov (United States)

    da Silva, Yuri Jacques Agra Bezerra; Cantalice, José Ramon Barros; Singh, Vijay P; do Nascimento, Clístenes Williams Araújo; Piscoya, Victor Casimiro; Guerra, Sérgio M S

    2015-10-01

    Data regarding trace element concentrations and fluxes in suspended sediments and bedload are scarce. To fill this gap and meet the international need to include polluted rivers in future world estimation of trace element fluxes, this study aimed to determine the trace element fluxes in suspended sediment and bedload of an environmentally impacted river in Brazil. Water, suspended sediment, and bedload from both the upstream and the downstream cross sections were collected. To collect both the suspended sediment and water samples, we used the US DH-48. Bedload measurements were carried out using the US BLH 84 sampler. Concentrations of Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn were determined by inductively coupled plasma (ICP-OES). As and Hg were determined by an atomic absorption spectrophotometer (AA-FIAS). The suspended sediments contributed more than 99 % of the trace element flux. By far Pb and to a less extent Zn at the downstream site represents major concerns. The yields of Pb and Zn in suspended sediments were 4.20 and 2.93 kg km(2) year(-1), respectively. These yields were higher than the values reported for Pb and Zn for Tuul River (highly impacted by mining activities), 1.60 and 1.30 kg km(2) year(-1), respectively, as well as the Pb yield (suspended + dissolved) to the sea of some Mediterranean rivers equal to 3.4 kg km(2) year(-1). Therefore, the highest flux and yield of Pb and Zn in Ipojuca River highlighted the importance to include medium and small rivers-often overlooked in global and regional studies-in the future estimation of world trace element fluxes in order to protect estuaries and coastal zones.

  15. Temporal variations of water and sediment fluxes in the Cointzio river basin, central Mexico

    Science.gov (United States)

    Duvert, C.; Gratiot, N.; Navratil, O.; Esteves, M.; Prat, C.; Nord, G.

    2009-04-01

    The STREAMS program (Sediment TRansport and Erosion Across MountainS) was launched in 2006 to study suspended sediment dynamics in mountainous areas. Two watersheds were selected as part of the program: the Bléone river basin in the French Alps, and the Cointzio river basin (636 km2), located in the mountainous region of Michoacán, in central Mexico. The volcanic soils of the Cointzio catchment undergo important erosion processes, especially during flashflood events. Thus, a high-frequency monitoring of sediment transport is highly required. The poster presents the high-frequency database obtained from the 2008 hydrological season at the Santiago Undameo gauged station, located at the basin's outlet. Suspended Sediment Concentration (SSC) was estimated every 10 minutes by calibrating turbidity measurements with bottle sampling acquired on a double-daily basis. Water discharge time-series was approximated with continuous water-level measurements (5 minutes time-step), and a stage-discharge rating curve. Our investigation highlights the influence of sampling frequency on annual water and sediment fluxes estimate. A daily or even a weekly water-level measurement provides an unexpectedly reliable assessment of the seasonal water fluxes, with an under-estimation of about 5 % of the total flux. Concerning sediment fluxes, a high-frequency SSC survey appears to be necessary. Acquiring SSC data even twice a day leads to a significant (over 30 %) under-estimation of the seasonal sediment load. These distinct behaviors can be attributed to the fact that sediment transport almost exclusively occurs during brief night flood events, whereas exfiltration on the watershed always provides a base flow during the daily water-level measurements.

  16. Nutrient fluxes across sediment-water interface in Bohai Bay Coastal Zone, China.

    Science.gov (United States)

    Mu, Di; Yuan, Dekui; Feng, Huan; Xing, Fangwei; Teo, Fang Yenn; Li, Shuangzhao

    2017-01-30

    Sediment cores and overlying water samples were collected at four sites in Tianjin Coastal Zone, Bohai Bay, to investigate nutrient (N, P and Si) exchanges across the sediment-water interface. The exchange fluxes of each nutrient species were estimated based on the porewater profiles and laboratory incubation experiments. The results showed significant differences between the two methods, which implied that molecular diffusion alone was not the dominant process controlling nutrient exchanges at these sites. The impacts of redox conditions and bioturbation on the nutrient fluxes were confirmed by the laboratory incubation experiments. The results from this study showed that the nutrient fluxes measured directly from the incubation experiment were more reliable than that predicted from the porewater profiles. The possible impacts causing variations in the nutrient fluxes include sewage discharge and land reclamation. Copyright © 2016 Elsevier Ltd. All rights reserved.

  17. Inferring tidal wetland stability from channel sediment fluxes: observations and a conceptual model

    Science.gov (United States)

    Ganju, Neil K.; Nidzieko, Nicholas J.; Kirwan, Matthew L.

    2013-01-01

    Anthropogenic and climatic forces have modified the geomorphology of tidal wetlands over a range of timescales. Changes in land use, sediment supply, river flow, storminess, and sea level alter the layout of tidal channels, intertidal flats, and marsh plains; these elements define wetland complexes. Diagnostically, measurements of net sediment fluxes through tidal channels are high-temporal resolution, spatially integrated quantities that indicate (1) whether a complex is stable over seasonal timescales and (2) what mechanisms are leading to that state. We estimated sediment fluxes through tidal channels draining wetland complexes on the Blackwater and Transquaking Rivers, Maryland, USA. While the Blackwater complex has experienced decades of degradation and been largely converted to open water, the Transquaking complex has persisted as an expansive, vegetated marsh. The measured net export at the Blackwater complex (1.0 kg/s or 0.56 kg/m2/yr over the landward marsh area) was caused by northwesterly winds, which exported water and sediment on the subtidal timescale; tidally forced net fluxes were weak and precluded landward transport of suspended sediment from potential seaward sources. Though wind forcing also exported sediment at the Transquaking complex, strong tidal forcing and proximity to a turbidity maximum led to an import of sediment (0.031 kg/s or 0.70 kg/m2/yr). This resulted in a spatially averaged accretion of 3.9 mm/yr, equaling the regional relative sea level rise. Our results suggest that in areas where seaward sediment supply is dominant, seaward wetlands may be more capable of withstanding sea level rise over the short term than landward wetlands. We propose a conceptual model to determine a complex's tendency toward stability or instability based on sediment source, wetland channel location, and transport mechanisms. Wetlands with a reliable portfolio of sources and transport mechanisms appear better suited to offset natural and

  18. Inferring tidal wetland stability from channel sediment fluxes: Observations and a conceptual model

    Science.gov (United States)

    Ganju, Neil K.; Nidzieko, Nicholas J.; Kirwan, Matthew L.

    2013-12-01

    and climatic forces have modified the geomorphology of tidal wetlands over a range of timescales. Changes in land use, sediment supply, river flow, storminess, and sea level alter the layout of tidal channels, intertidal flats, and marsh plains; these elements define wetland complexes. Diagnostically, measurements of net sediment fluxes through tidal channels are high-temporal resolution, spatially integrated quantities that indicate (1) whether a complex is stable over seasonal timescales and (2) what mechanisms are leading to that state. We estimated sediment fluxes through tidal channels draining wetland complexes on the Blackwater and Transquaking Rivers, Maryland, USA. While the Blackwater complex has experienced decades of degradation and been largely converted to open water, the Transquaking complex has persisted as an expansive, vegetated marsh. The measured net export at the Blackwater complex (1.0 kg/s or 0.56 kg/m2/yr over the landward marsh area) was caused by northwesterly winds, which exported water and sediment on the subtidal timescale; tidally forced net fluxes were weak and precluded landward transport of suspended sediment from potential seaward sources. Though wind forcing also exported sediment at the Transquaking complex, strong tidal forcing and proximity to a turbidity maximum led to an import of sediment (0.031 kg/s or 0.70 kg/m2/yr). This resulted in a spatially averaged accretion of 3.9 mm/yr, equaling the regional relative sea level rise. Our results suggest that in areas where seaward sediment supply is dominant, seaward wetlands may be more capable of withstanding sea level rise over the short term than landward wetlands. We propose a conceptual model to determine a complex's tendency toward stability or instability based on sediment source, wetland channel location, and transport mechanisms. Wetlands with a reliable portfolio of sources and transport mechanisms appear better suited to offset natural and anthropogenic loss.

  19. Water and sediment temperature dynamics in shallow tidal environments: The role of the heat flux at the sediment-water interface

    Science.gov (United States)

    Pivato, M.; Carniello, L.; Gardner, J.; Silvestri, S.; Marani, M.

    2018-03-01

    In the present study, we investigate the energy flux at the sediment-water interface and the relevance of the heat exchanged between water and sediment for the water temperature dynamics in shallow coastal environments. Water and sediment temperature data collected in the Venice lagoon show that, in shallow, temperate lagoons, temperature is uniform within the water column, and enabled us to estimate the net heat flux at the sediment-water interface. We modeled this flux as the sum of a conductive component and of the solar radiation reaching the bottom, finding the latter being negligible. We developed a "point" model to describe the temperature dynamics of the sediment-water continuum driven by vertical energy transfer. We applied the model considering conditions characterized by negligible advection, obtaining satisfactory results. We found that the heat exchange between water and sediment is crucial for describing sediment temperature but plays a minor role on the water temperature.

  20. Environmental Drivers of Benthic Flux Variation and Ecosystem Functioning in Salish Sea and Northeast Pacific Sediments.

    Directory of Open Access Journals (Sweden)

    Rénald Belley

    Full Text Available The upwelling of deep waters from the oxygen minimum zone in the Northeast Pacific from the continental slope to the shelf and into the Salish Sea during spring and summer offers a unique opportunity to study ecosystem functioning in the form of benthic fluxes along natural gradients. Using the ROV ROPOS we collected sediment cores from 10 sites in May and July 2011, and September 2013 to perform shipboard incubations and flux measurements. Specifically, we measured benthic fluxes of oxygen and nutrients to evaluate potential environmental drivers of benthic flux variation and ecosystem functioning along natural gradients of temperature and bottom water dissolved oxygen concentrations. The range of temperature and dissolved oxygen encountered across our study sites allowed us to apply a suite of multivariate analyses rarely used in flux studies to identify bottom water temperature as the primary environmental driver of benthic flux variation and organic matter remineralization. Redundancy analysis revealed that bottom water characteristics (temperature and dissolved oxygen, quality of organic matter (chl a:phaeo and C:N ratios and sediment characteristics (mean grain size and porosity explained 51.5% of benthic flux variation. Multivariate analyses identified significant spatial and temporal variation in benthic fluxes, demonstrating key differences between the Northeast Pacific and Salish Sea. Moreover, Northeast Pacific slope fluxes were generally lower than shelf fluxes. Spatial and temporal variation in benthic fluxes in the Salish Sea were driven primarily by differences in temperature and quality of organic matter on the seafloor following phytoplankton blooms. These results demonstrate the utility of multivariate approaches in differentiating among potential drivers of seafloor ecosystem functioning, and indicate that current and future predictive models of organic matter remineralization and ecosystem functioning of soft-muddy shelf and

  1. Experimental study of sediment fluxes on Barcelona's nearshore

    OpenAIRE

    Armengou Gallardo, Carla

    2011-01-01

    The presence of suspended sediment in marine waters has several impacts, such as a degradation of the coastal ecosystem, pollution or a damaging effect on the tourism-oriented economies. FIELD_AC is a European project that aims to provide an improved operational service for coastal areas and generate added value for GMES predictions. This is achieved by the analysis of field cases. In this context, this minor thesis is based on the study of the information obtained in a field campaign car...

  2. Sediment nitrous oxide fluxes are dominated by uptake in a temperate estuary

    Directory of Open Access Journals (Sweden)

    Sarah Quinn Foster

    2016-03-01

    Full Text Available Coastal marine ecosystems are generally considered important sources of nitrous oxide (N2O, a powerful greenhouse gas and ozone depleting substance. To date most studies have focused on the environmental factors controlling N2O production although N2O uptake has been observed in a variety of coastal ecosystems. In this study, we examined sediment fluxes of N2O during two years (2012-2013 in a shallow temperate estuary (Waquoit Bay, MA, USA. Overall sediments were a net N2O sink (-23 ±5.2 nmol m-2 h-1, mean ±SE, significantly less than zero p<0.0001. N2O fluxes were significantly correlated to water column dissolved N2O (% saturation (p<0.0001, inorganic phosphorus (DIP (p=0.0017 and nitrogen (DIN (p=0.0019, as well as to temperature (p=0.0192. Additionally, there was a positive correlation between sediment N2O uptake and both oxygen (O2 and DIP uptake (p=0.0002 and p<0.0001, O2 and DIP sediment uptake, respectively. Results from this study indicate that sediments in shallow coastal ecosystems can be a strong sink of dissolved N2O, and therefore may mitigate N2O efflux to the atmosphere and export to the coastal ocean. Establishing the nature and strength of relationships between environmental conditions and sediment N2O fluxes moves us towards better-constrained models that will improve ecosystem management strategies, N2O budgets, and our ability to predict the response of coastal ecosystems to local and global change. Establishing the nature and strength of relationships between environmental conditions and sediment N2O fluxes moves us towards better-constrained models that will improve ecosystem management strategies, N2O budgets, and our ability to predict the response of coastal ecosystems to local and global change.

  3. Budgeting suspended sediment fluxes in tropical monsoonal watersheds with limited data: the Lake Tana basin

    Directory of Open Access Journals (Sweden)

    Zimale Fasikaw A.

    2018-03-01

    Full Text Available Soil erosion decreases soil fertility of the uplands and causes siltation of lakes and reservoirs; the lakes and reservoirs in tropical monsoonal African highlands are especially affected by sedimentation. Efforts in reducing loads by designing management practices are hampered by lack of quantitative data on the relationship of erosion in the watersheds and sediment accumulation on flood plains, lakes and reservoirs. The objective of this study is to develop a prototype quantitative method for estimating sediment budget for tropical monsoon lakes with limited observational data. Four watersheds in the Lake Tana basin were selected for this study. The Parameter Efficient Distributed (PED model that has shown to perform well in the Ethiopian highlands is used to overcome the data limitations and recreate the missing sediment fluxes. PED model parameters are calibrated using daily discharge data and the occasionally collected sediment concentration when establishing the sediment rating curves for the major rivers. The calibrated model parameters are then used to predict the sediment budget for the 1994-2009 period. Sediment retained in the lake is determined from two bathymetric surveys taken 20 years apart whereas the sediment leaving the lake is calculated based on measured discharge and observed sediment concentrations. Results show that annually on average 34 t/ha/year of sediment is removed from the gauged part of the Lake Tana watersheds. Depending on the up-scaling method from the gauged to the ungauged part, 21 to 32 t/ha/year (equivalent to 24-38 Mt/year is transported from the upland watersheds of which 46% to 65% is retained in the flood plains and 93% to 96% is trapped on the flood plains and in the lake. Thus, only 4-7% of all sediment produced in the watersheds leaves the Lake Tana Basin.

  4. DEVELOPMENT AND DEMONSTRATION OF A BIDIRECTIONAL ADVECTIVE FLUX METER FOR SEDIMENT-WATER INTERFACE

    Science.gov (United States)

    A bidirectional advective flux meter for measuring water transport across the sediment-water interface has been successfully developed and field tested. The flow sensor employs a heat-pulse technique combined with a flow collection funnel for the flow measurement. Because the dir...

  5. Long-term kinematics and sediment flux of an active earthflow, Eel River, California

    Science.gov (United States)

    B. H. Mackey; J. J. Roering; J. A. McKean

    2009-01-01

    Although earthflows are the dominant erosion mechanism in many mountainous landscapes, estimates of long-term earthflow-driven sediment flux remain elusive because landslide displacement data are typically limited to contemporary time periods. Combining high-resolution topography from airborne LiDAR (light detection and ranging), total station surveying, orthorectified...

  6. Sediment flux and airflow on the stoss slope of a barchan dune

    Science.gov (United States)

    Lancaster, N.; Nickling, W. G.; Neuman, C. K. McKenna; Wyatt, V. E.

    1996-09-01

    Measurements of sediment flux on the windward slope of an isolated barchan using an array of 30 sand traps provide new data that can constrain models of dune dynamics. The data show that at low wind incident speeds, flux increases up the dune exponentially, whereas at higher wind speeds the increase with distance approaches linearity. Wind profile measurements, conducted at the same time as the flux measurements, indicate that, although wind speed at a given height increases by 1.2 times from dune toe to brinkline, wind shear velocity derived from the profile data decreases up the dune and is in many cases below transport threshold values. This demonstrates that conventional wind profiles, derived from anemometry on dunes, do not measure the part of the boundary layer that is significant for sediment transport.

  7. Estimation of suspended sediment flux in streams using continuous turbidity and flow data coupled with laboratory concentrations

    Science.gov (United States)

    Jack Lewis

    2002-01-01

    The widening use of sediment surrogate measurements such as turbidity necessitates consideration of new methods for estimating sediment flux. Generally, existing methods can be simply be used in new ways. The effectiveness of a method varies according to the quality of the surrogate data and its relation to suspended sediment concentration (SSC). For this discussion,...

  8. Analysis of factors controlling sediment phosphorus flux potential of wetlands in Hulun Buir grassland by principal component and path analysis method.

    Science.gov (United States)

    He, Jing; Su, Derong; Lv, Shihai; Diao, Zhaoyan; Ye, Shengxing; Zheng, Zhirong

    2017-11-08

    Phosphorus (P) flux potential can predict the trend of phosphorus release from wetland sediments to water and provide scientific parameters for further monitoring and management for phosphorus flux from wetland sediments to overlying water. Many studies have focused on factors affecting sediment P flux potential in sediment-water interface, but rarely on the relationship among these factors. In the present study, experiment on sediment P flux potential in sediment-water interface was conducted in six wetlands in Hulun Buir grassland, China and the relationships among sediment P flux potential in sediment-water interface, sediment physical properties, and sediment chemical characteristics were examined. Principal component analysis and path analysis were used to discuss these data in correlation coefficient, direct, and indirect effects on sediment P flux potential in sediment-water interface. Results indicated that the major factors affecting sediment P flux potential in sediment-water interface were amount of organophosphate-degradation bacterium in sediment, Ca-P content, and total phosphorus concentrations. The factors of direct influence sediment P flux potential were sediment Ca-P content, Olsen-P content, SOC content, and sediment Al-P content. The indirect influence sediment P flux potential in sediment-water interface was sediment Olsen-P content, sediment SOC content, sediment Ca-P content, and sediment Al-P content. And the standard multiple regression describing the relationship between sediment P flux potential in sediment-water interface and its major effect factors was Y = 5.849 - 1.025X 1  - 1.995X 2  + 0.188X 3  - 0.282X 4 (r = 0.9298, p < 0.01, n = 96), where Y is sediment P flux potential in sediment-water interface, X 1 is sediment Ca-P content, X 2 is sediment Olsen-P content, X 3 is sediment SOC content, and X 4 is sediment Al-P content. Therefore, future research will focus on these sediment properties to analyze the

  9. A closed-chamber method to measure greenhouse gas fluxes from dry aquatic sediments

    Science.gov (United States)

    Lesmeister, Lukas; Koschorreck, Matthias

    2017-06-01

    Recent research indicates that greenhouse gas (GHG) emissions from dry aquatic sediments are a relevant process in the freshwater carbon cycle. However, fluxes are difficult to measure because of the often rocky substrate and the dynamic nature of the habitat. Here we tested the performance of different materials to seal a closed chamber to stony ground both in laboratory and field experiments. Using on-site material consistently resulted in elevated fluxes. The artefact was caused both by outgassing of the material and production of gas. The magnitude of the artefact was site dependent - the measured CO2 flux increased between 10 and 208 %. Errors due to incomplete sealing proved to be more severe than errors due to non-inert sealing material.Pottery clay as sealing material provided a tight seal between the chamber and the ground and no production of gases was detected. With this approach it is possible to get reliable gas fluxes from hard-substrate sites without using a permanent collar. Our test experiments confirmed that CO2 fluxes from dry aquatic sediments are similar to CO2 fluxes from terrestrial soils.

  10. A closed-chamber method to measure greenhouse gas fluxes from dry aquatic sediments

    Directory of Open Access Journals (Sweden)

    L. Lesmeister

    2017-06-01

    Full Text Available Recent research indicates that greenhouse gas (GHG emissions from dry aquatic sediments are a relevant process in the freshwater carbon cycle. However, fluxes are difficult to measure because of the often rocky substrate and the dynamic nature of the habitat. Here we tested the performance of different materials to seal a closed chamber to stony ground both in laboratory and field experiments. Using on-site material consistently resulted in elevated fluxes. The artefact was caused both by outgassing of the material and production of gas. The magnitude of the artefact was site dependent – the measured CO2 flux increased between 10 and 208 %. Errors due to incomplete sealing proved to be more severe than errors due to non-inert sealing material.Pottery clay as sealing material provided a tight seal between the chamber and the ground and no production of gases was detected. With this approach it is possible to get reliable gas fluxes from hard-substrate sites without using a permanent collar. Our test experiments confirmed that CO2 fluxes from dry aquatic sediments are similar to CO2 fluxes from terrestrial soils.

  11. Accumulation of phosphorus in coastal marine sediments: relationship to benthic and diffusive fluxes

    Directory of Open Access Journals (Sweden)

    Rocio Ponce

    2010-11-01

    Full Text Available Sedimentary phosphorus was characterized in sediment cores from 3 coastal ecosystems of the Gulf of Cadiz. High spatial variability was observed in total phosphorus (from 445 to 20291 μg g.sed-1 and in the other phosphorus phases studied. This variability correlates with the proximity of the 10 sampling stations to sources of urban and/or industrial effluent in the zone. The benthic and diffusive fluxes were measured concurrently with sediment collection at these stations. The measured values of benthic fluxes range between –14 and 6 mmol m-2 d-1. Generally, stations that showed increased interstitial phosphate concentrations with increasing depth were characterized by positive values in phosphate benthic fluxes and by high percentages of reactive forms of sedimentary phosphorus. Negative benthic fluxes were associated with stations receiving more anthropogenic matter, which showed progressively decreasing phosphate concentrations in the interstitial water with depth. In these anthropogenic areas, the non-reactive forms of phosphorus (those associated with ferric oxyhydroxide and authigenic carbonate fluorapatite are abundant, and reach values exceeding 75% of total phosphorus in sediment.

  12. Tidal modulated flow and sediment flux through Wax Lake Delta distributary channels: Implications for delta development

    Directory of Open Access Journals (Sweden)

    K. Hanegan

    2015-03-01

    Full Text Available In this study, a Delft3D model of the Wax Lake Delta was developed to simulate flow and sediment flux through delta distributary channels. The model was calibrated for tidal constituents as well as velocity and sediment concentration across channel transects. The calibrated model was then used to simulate full spring–neap tidal cycles under constant low flow upstream boundary conditions, with grain size variation in suspended load represented using two sediment fractions. Flow and sediment flux results through distributary channel cross-sections were examined for spatial and temporal variability with the goal of characterizing the role of tides in sediment reworking and delta development. The Wax Lake Delta has prograded through channel extension, river mouth bar deposition, and channel bifurcation. Here we show that tidal modulation of currents influences suspended sand transport, and spatial acceleration through distributary channels at low tides is sufficient to suspend sand in distal reaches during lower flows. The basinward-increasing transport capacity in distributary channels indicates that erosive channel extension could be an important process, even during non-flood events.

  13. Partitioning sediment flux by provenance and tracing erosion patterns in Taiwan

    Science.gov (United States)

    Resentini, Alberto; Goren, Liran; Castelltort, Sébastien; Garzanti, Eduardo

    2017-07-01

    We critically evaluate the potential and limitations of an alternative way to calculate erosion rates based on petrographic and mineralogical fingerprints of fluvial sediments coupled with gauged sediment fluxes. Our approach allows us to apportion sediment loads to different lithological units, and consequently to discriminate erosion rates in different tectonic domains within each catchment. Our provenance data on modern Taiwanese sands indicate focused erosion in the Backbone Range and Tananao Complex of the retrowedge. Lower rates are inferred for the northern part of the island characterized by tectonic extension and for the western foothills in the prowedge. The principal factor of uncertainty affecting our estimates is the inevitably inaccurate evaluation of total sediment load, because only the suspended flux was measured. Another is the assumption that suspended load and bed load are derived from the same sources in fixed proportions. Additional errors are caused by the insufficiently precise definition of lithologically similar compositional end-members and by the temporal variability of sediment composition at the outlet of each catchment related to the spatial variability of erosional processes and triggering agents such as earthquakes, typhoons, and landslides. To evaluate the robustness of our findings, we applied a morphometric technique based on the stream-power model. The results obtained are broadly consistent, with local discrepancies ascribed to poorly constrained assumptions and choices of scaling parameters. Our local erosion estimates are consistent with GPS uplift rates measured on a decadal timescale and generally higher than basin-wide results inferred from cosmogenic-nuclide and thermochronology data.

  14. Trace element fluxes during the last 100 years in sediment near a nuclear power plant

    Science.gov (United States)

    Bojórquez-Sánchez, S.; Marmolejo-Rodríguez, A. J.; Ruiz-Fernández, A. C.; Sánchez-González, A.; Sánchez-Cabeza, J. A.; Bojórquez-Leyva, H.; Pérez-Bernal, L. H.

    2017-11-01

    The Salada coastal lagoon is located in Veracruz (Mexico) near the Laguna Verde Nuclear Power Plant (LVNPP). Currently, the lagoon receives the cooling waters used in the LVNPP. To evaluate the fluxes and mobilization of trace elements due to human activities in the area, two sediment cores from the coastal flood plains of Salada Lagoon were analysed. Cores were collected using PVC tubes. Sediments cores were analysed every centimetre for dating (210Pb by alpha detector) and trace metal analysis using ICP-Mass Spectrometry. The dating of both sediment cores covers the period from 1900 to 2013, which includes the construction of the LVNPP (1970's). The Normalized Enrichment Factor shows enrichment of Ag, As and Cr in both sediment cores. These enrichments correspond to the extent of mining activity (which reached a maximum in the 1900's) and to the geological setting of the coastal zone. The profiles of the element fluxes in both sediment cores reflected the construction and operation of the LVNPP; however, the elements content did not show evidence of pollution coming from the LVNPP.

  15. Lithogenic fluxes in the Bay of Bengal measured by sediment traps

    Digital Repository Service at National Institute of Oceanography (India)

    Ramaswamy, V.; VijayKumar, B.; Parthiban, G.; Ittekkot, V.; Nair, R.R.

    -Sea Research I, Vol. 44, No. 5, pp. 793410, 1997 0 1997 Elsevier Science Ltd PII: S0967-0637(96)00117-3 All tights reserved. Printed in Great Britain 09674x37/97 917.00+0.00 Lithogenic fluxes in the Bay of Bengal measured by sediment traps V. RAMASWAMY,* B... of amorphous silica in marine sediments. Journal of Sedimentary Petrology, 50, 215-225. Emmel, F. J. and Curray, J. R. (1984) The Bengal submarine fan, northeastern Indian Ocean. Geo-Marine Letters, 3, 119-124. Goldberg, E. D. and Griffin, J. J. (1970...

  16. Lithogenic fluxes to the deep Arabian Sea measurEd. by sediment traps

    Digital Repository Service at National Institute of Oceanography (India)

    Ramaswamy, V.; Nair, R.R; Manganini, S.J.; Haake, B.; Ittekkot, V.

    . 38. No. 2. pp 1~g-\\[~44 It,lqt. fllC~g...4)i49tql $31~) 4- 0.till Pnnted m Great Britain. ~ lg~t Pergamon Press pie Lithogenic fluxes to the deep Arabian Sea measured by sediment traps V. RAMASWAMY,* R. R. NAIR,* S. MANGANINI,# B. HAAKE~. and V... (MIct, lrdAN et al., 1984). Most of the present suspended sediment discharge is in July and August, during the peak of the southwest monsoon period, with negligible discharge during other times (I'rrEKKO'r and ARAIN, 1986). The Narmada and Tapti...

  17. Effects of salt pond restoration on benthic flux: Sediment as a source of nutrients to the water column

    Science.gov (United States)

    Topping, Brent R.; Kuwabara, James S.; Carter, James L.; Garrettt, Krista K.; Mruz, Eric; Piotter, Sarah; Takekawa, John Y.

    2016-01-01

    Understanding nutrient flux between the benthos and the overlying water (benthic flux) is critical to restoration of water quality and biological resources because it can represent a major source of nutrients to the water column. Extensive water management commenced in the San Francisco Bay, Beginning around 1850, San Francisco Bay wetlands were converted to salt ponds and mined extensively for more than a century. Long-term (decadal) salt pond restoration efforts began in 2003. A patented device for sampling porewater at varying depths, to calculate the gradient, was employed between 2010 and 2012. Within the former ponds, the benthic flux of soluble reactive phosphorus and that of dissolved ammonia were consistently positive (i.e., moving out of the sediment into the water column). The lack of measurable nitrate or nitrite concentration gradients across the sediment-water interface suggested negligible fluxes for dissolved nitrate and nitrite. The dominance of ammonia in the porewater indicated anoxic sediment conditions, even at only 1 cm depth, which is consistent with the observed, elevated sediment oxygen demand. Nearby openestuary sediments showed much lower benthic flux values for nutrients than the salt ponds under resortation. Allochthonous solute transport provides a nutrient advective flux for comparison to benthic flux. For ammonia, averaged for all sites and dates, benthic flux was about 80,000 kg/year, well above the advective flux range of −50 to 1500 kg/year, with much of the variability depending on the tidal cycle. By contrast, the average benthic flux of soluble reactive phosphorus was about 12,000 kg/year, of significant magnitude, but less than the advective flux range of 21,500 to 30,000 kg/year. These benthic flux estimates, based on solute diffusion across the sediment-water interface, reveal a significant nutrient source to the water column of the pond which stimulates algal blooms (often autotrophic). This benthic source may be

  18. Stratigraphic controls on fluid and solute fluxes across the sediment-water interface of an estuary

    Science.gov (United States)

    Sawyer, Audrey H.; Lazareva, Olesya; Kroeger, Kevin D.; Crespo, Kyle; Chan, Clara S.; Stieglitz, Thomas; Michael, Holly A.

    2014-01-01

    Shallow stratigraphic features, such as infilled paleovalleys, modify fresh groundwater discharge to coastal waters and fluxes of saltwater and nutrients across the sediment–water interface. We quantify the spatial distribution of shallow surface water–groundwater exchange and nitrogen fluxes near a paleovalley in Indian River Bay, Delaware, using a hand resistivity probe, conventional seepage meters, and pore-water samples. In the interfluve (region outside the paleovalley) most nitrate-rich fresh groundwater discharges rapidly near the coast with little mixing of saline pore water, and nitrogen transport is largely conservative. In the peat-filled paleovalley, fresh groundwater discharge is negligible, and saltwater exchange is deep (∼1 m). Long pore-water residence times and abundant sulfate and organic matter promote sulfate reduction and ammonium production in shallow sediment. Reducing, iron-rich fresh groundwater beneath paleovalley peat discharges diffusely around paleovalley margins offshore. In this zone of diffuse fresh groundwater discharge, saltwater exchange and dispersion are enhanced, ammonium is produced in shallow sediments, and fluxes of ammonium to surface water are large. By modifying patterns of groundwater discharge and the nature of saltwater exchange in shallow sediments, paleovalleys and other stratigraphic features influence the geochemistry of discharging groundwater. Redox reactions near the sediment–water interface affect rates and patterns of geochemical fluxes to coastal surface waters. For example, at this site, more than 99% of the groundwater-borne nitrate flux to the Delaware Inland Bays occurs within the interfluve portion of the coastline, and more than 50% of the ammonium flux occurs at the paleovalley margin.

  19. Enhancing sediment flux control and natural hazard risk mitigation through a structured conceptual planning approach

    Science.gov (United States)

    Simoni, S.; Vignoli, G.; Mazzorana, B.

    2017-08-01

    Sediment fluxes from mountain rivers contribute to shape the geomorphologic features of lowland rivers and to establish the physical basis for an optimal set of ecosystem functions and related services to people. Through significant public funding, the hydro-morphological regimes of mountain rivers in the European Alps have been progressively altered over the last century, with the aim to provide a safe dwelling space, to boost transport, mobility and to support economic growth. We claim that the underlying planning weaknesses contribute to determine these inefficient resource allocations, since flood risk is still high and the ecosystem services are far from being optimal. Hence, with the overall aim to enhance sediment flux control and hazard risk mitigation in such heavily modified alpine streams, we propose a structured design workflow which guides the planner through system analysis and synthesis. As a first step the proposed workflow sets the relevant planning goals and assesses the protection structure functionality. Then a methodology is proposed to achieve the goals. This methodology consists in characterising the hydrologic basin of interest and the sediment availability and determining the sediment connectivity to channels. The focus is set on the detailed analysis of existing river cross sections where the sediment continuity is interrupted (e.g. slit and check dams). By retaining relevant sediment volumes these structures prevent the reactivation of hydro-morphological and associated ecological functionalities. Since their actual performance can be unsatisfying with respect to flood risk mitigation (e.g. mainly old structures), we introduce specific efficiency indicators as a support for the conceptual design stage to quantify effects related to sediment flux control and risk management. The proposed planning approach is then applied to the Gadria system (stream, slit dam, retention basin and culvert), located in South Tyrol, Italy. This case study

  20. Suspended Sediment Dynamics in the Macrotidal Seine Estuary (France): 2. Numerical Modeling of Sediment Fluxes and Budgets Under Typical Hydrological and Meteorological Conditions

    Science.gov (United States)

    Schulz, E.; Grasso, F.; Le Hir, P.; Verney, R.; Thouvenin, B.

    2018-01-01

    Understanding the sediment dynamics in an estuary is important for its morphodynamic and ecological assessment as well as, in case of an anthropogenically controlled system, for its maintenance. However, the quantification of sediment fluxes and budgets is extremely difficult from in-situ data and requires thoroughly validated numerical models. In the study presented here, sediment fluxes and budgets in the lower Seine Estuary were quantified and investigated from seasonal to annual time scales with respect to realistic hydro- and meteorological conditions. A realistic three-dimensional process-based hydro- and sediment-dynamic model was used to quantify mud and sand fluxes through characteristic estuarine cross-sections. In addition to a reference experiment with typical forcing, three experiments were carried out and analyzed, each differing from the reference experiment in either river discharge or wind and waves so that the effects of these forcings could be separated. Hydro- and meteorological conditions affect the sediment fluxes and budgets in different ways and at different locations. Single storm events induce strong erosion in the lower estuary and can have a significant effect on the sediment fluxes offshore of the Seine Estuary mouth, with the flux direction depending on the wind direction. Spring tides cause significant up-estuary fluxes at the mouth. A high river discharge drives barotropic down-estuary fluxes at the upper cross-sections, but baroclinic up-estuary fluxes at the mouth and offshore so that the lower estuary gains sediment during wet years. This behavior is likely to be observed worldwide in estuaries affected by density gradients and turbidity maximum dynamics.

  1. Numerical modelling of landscape and sediment flux response to precipitation rate change

    Science.gov (United States)

    Armitage, John J.; Whittaker, Alexander C.; Zakari, Mustapha; Campforts, Benjamin

    2018-02-01

    Laboratory-scale experiments of erosion have demonstrated that landscapes have a natural (or intrinsic) response time to a change in precipitation rate. In the last few decades there has been growth in the development of numerical models that attempt to capture landscape evolution over long timescales. However, there is still an uncertainty regarding the validity of the basic assumptions of mass transport that are made in deriving these models. In this contribution we therefore return to a principal assumption of sediment transport within the mass balance for surface processes; we explore the sensitivity of the classic end-member landscape evolution models and the sediment fluxes they produce to a change in precipitation rates. One end-member model takes the mathematical form of a kinetic wave equation and is known as the stream power model, in which sediment is assumed to be transported immediately out of the model domain. The second end-member model is the transport model and it takes the form of a diffusion equation, assuming that the sediment flux is a function of the water flux and slope. We find that both of these end-member models have a response time that has a proportionality to the precipitation rate that follows a negative power law. However, for the stream power model the exponent on the water flux term must be less than one, and for the transport model the exponent must be greater than one, in order to match the observed concavity of natural systems. This difference in exponent means that the transport model generally responds more rapidly to an increase in precipitation rates, on the order of 105 years for post-perturbation sediment fluxes to return to within 50 % of their initial values, for theoretical landscapes with a scale of 100×100 km. Additionally from the same starting conditions, the amplitude of the sediment flux perturbation in the transport model is greater, with much larger sensitivity to catchment size. An important finding is that

  2. Numerical modelling of landscape and sediment flux response to precipitation rate change

    Directory of Open Access Journals (Sweden)

    J. J. Armitage

    2018-02-01

    Full Text Available Laboratory-scale experiments of erosion have demonstrated that landscapes have a natural (or intrinsic response time to a change in precipitation rate. In the last few decades there has been growth in the development of numerical models that attempt to capture landscape evolution over long timescales. However, there is still an uncertainty regarding the validity of the basic assumptions of mass transport that are made in deriving these models. In this contribution we therefore return to a principal assumption of sediment transport within the mass balance for surface processes; we explore the sensitivity of the classic end-member landscape evolution models and the sediment fluxes they produce to a change in precipitation rates. One end-member model takes the mathematical form of a kinetic wave equation and is known as the stream power model, in which sediment is assumed to be transported immediately out of the model domain. The second end-member model is the transport model and it takes the form of a diffusion equation, assuming that the sediment flux is a function of the water flux and slope. We find that both of these end-member models have a response time that has a proportionality to the precipitation rate that follows a negative power law. However, for the stream power model the exponent on the water flux term must be less than one, and for the transport model the exponent must be greater than one, in order to match the observed concavity of natural systems. This difference in exponent means that the transport model generally responds more rapidly to an increase in precipitation rates, on the order of 105 years for post-perturbation sediment fluxes to return to within 50 % of their initial values, for theoretical landscapes with a scale of 100×100 km. Additionally from the same starting conditions, the amplitude of the sediment flux perturbation in the transport model is greater, with much larger sensitivity to catchment size. An

  3. Reconciling surface ocean productivity, export fluxes and sediment composition in a global biogeochemical ocean model

    Directory of Open Access Journals (Sweden)

    M. Gehlen

    2006-01-01

    Full Text Available This study focuses on an improved representation of the biological soft tissue pump in the global three-dimensional biogeochemical ocean model PISCES. We compare three parameterizations of particle dynamics: (1 the model standard version including two particle size classes, aggregation-disaggregation and prescribed sinking speed; (2 an aggregation-disaggregation model with a particle size spectrum and prognostic sinking speed; (3 a mineral ballast parameterization with no size classes, but prognostic sinking speed. In addition, the model includes a description of surface sediments and organic carbon early diagenesis. Model output is compared to data or data based estimates of ocean productivity, pe-ratios, particle fluxes, surface sediment bulk composition and benthic O2 fluxes. Model results suggest that different processes control POC fluxes at different depths. In the wind mixed layer turbulent particle coagulation appears as key process in controlling pe-ratios. Parameterization (2 yields simulated pe-ratios that compare well to observations. Below the wind mixed layer, POC fluxes are most sensitive to the intensity of zooplankton flux feeding, indicating the importance of zooplankton community composition. All model parameters being kept constant, the capability of the model to reproduce yearly mean POC fluxes below 2000 m and benthic oxygen demand does at first order not dependent on the resolution of the particle size spectrum. Aggregate formation appears essential to initiate an intense biological pump. At great depth the reported close to constant particle fluxes are most likely the result of the combined effect of aggregate formation and mineral ballasting.

  4. What fraction of the total metal flux into lakes is retained in the sediments

    Energy Technology Data Exchange (ETDEWEB)

    Nriagu, J O; Wong, H K.T.

    1986-12-01

    The concentrations of, and deposition rates for, the pollutant metals (Pb, Cu, Zn, Ni, and Cd) and the rare earth elements are reported for the sediments and settling particulates in a large, remote lake (Lake Opeongo) in the Algonquin Provincial Park, Ontario. Using a mass conservation model based on the rare earth elements, it is estimated that only 40 to 60% of pollutant metals getting into the lake is retained by the sediments. The low retention rate may explain the widely reported intrabasin and intra-lake differences in metal contents of sediments and casts some doubt on the use of pollutant metal profiles in retrospective assessment of the human contribution to the metal flux into many lake basins. 22 references.

  5. Role of land use change in landslide-related sediment fluxes in tropical mountain regions

    Science.gov (United States)

    Guns, M.; Vanacker, V.; Demoulin, A.

    2012-04-01

    Tropical mountain regions are characterised by high denudation rates. Landslides are known to be recurrent phenomena in active mountain belts, but their contribution to the overall sedimentary fluxes is not yet well known. Previous studies on sedimentary cascades have mostly focused on natural environments, without considering the impact of human and/or anthropogenic disturbances on sedimentary budgets. In our work, we hypothesise that human-induced land use change might alter the sediment cascade through shifts in the landslide magnitude-frequency relationship. We have tested this assumption in the Virgen Yacu catchment (approximately 11km2), in the Ecuadorian Cordillera Occidental. Landslide inventories and land use maps were established based on a series of sequential aerial photos (1963, 1977, 1984 and 1989), a HR Landsat image (2001) and a VHR WorldView2 image (2010). Aerial photographs were ortho-rectified, and coregistred with the WorldView2 satellite image. Field campaigns were realised in 2010 and 2011 to collect field-based data on landslide type and geometry (depth, width and length). This allowed us to establish an empirical relationship between landslide area and volume, which was then applied to the landslide inventories to estimate landslide-related sediment production rates for various time periods. The contribution of landslides to the overall sediment flux of the catchment was estimated by comparing the landslide-related sediment production to the total sediment yield. The empirical landslide area-volume relationship established here for the Ecuadorian Andes is similar to that derived for the Himalayas. It suggests that landslides are the main source of sediment in this mountainous catchment. First calculations indicate that human-induced land use change alters the magnitude-frequency relationship through strong increase of small landslides.

  6. Asymmetric fluxes of water and sediments in a mesotidal mudflat channel

    Science.gov (United States)

    Mariotti, G.; Fagherazzi, S.

    2011-01-01

    The hydrodynamics of a small tributary channel and its adjacent mudflat is studied in Willapa Bay, Washington State, USA. Velocity profiles and water levels are simultaneously measured at different locations in the channel and on the mudflat for two weeks. The above tidal flat and channel hydrodynamics differ remarkably during the tidal cycle. When the water surface level is above the tidal flat elevation, the channel is inactive. At this stage, the above tidal flat flow is predominantly aligned along the Bay axis, oscillating with the tide as a standing wave with peak velocities up to 0.3 m/s. When the mudflat becomes emergent, the flow concentrates in the channel. During this stage, current velocities up to 1 m/s are measured during ebb; and up to 0.6 m/s during flood. Standard equations for open-channel flow are utilized to study the channel hydrodynamics. From the continuity equation, a lateral inflow is predicted during ebb, which likely originates from the drainage of the mudflat through the lateral runnels. Both advective acceleration and lateral discharge terms, estimated directly from the velocity profiles, play a significant role in the momentum equation. The computed drag coefficient for bottom friction is small, due to an absence of vegetation and bottom bedforms in the channel. Sediment fluxes are calculated by combining flow and suspended sediment concentration estimated using the acoustic backscatter signal of the instruments. A net export of the sediment from the channel is found during ebb, which is not balanced by the sediment import during flood. When the mudflat is submerged, ebb-flood asymmetries in suspended sediment concentration are present, leading to a net sediment flux toward the inner part of the Willapa Bay. Finally, a residual flow is detected inside the channel at high slack water, probably associated with the thermohaline circulation.

  7. Suspended sediment flux modeling with artificial neural network: An example of the Longchuanjiang River in the Upper Yangtze Catchment, China

    Science.gov (United States)

    Zhu, Yun-Mei; Lu, X. X.; Zhou, Yue

    2007-02-01

    Artificial neural network (ANN) was used to model the monthly suspended sediment flux in the Longchuanjiang River, the Upper Yangtze Catchment, China. The suspended sediment flux was related to the average rainfall, temperature, rainfall intensity and water discharge. It is demonstrated that ANN is capable of modeling the monthly suspended sediment flux with fairly good accuracy when proper variables and their lag effect on the suspended sediment flux are used as inputs. Compared with multiple linear regression and power relation models, ANN can generate a better fit under the same data requirement. In addition, ANN can provide more reasonable predictions for extremely high or low values, because of the distributed information processing system and the nonlinear transformation involved. Compared with the ANNs that use the values of the dependent variable at previous time steps as inputs, the ANNs established in this research with only climate variables have an advantage because it can be used to assess hydrological responses to climate change.

  8. Link between concentrations of sediment flux and deep crustal processes beneath the European Alps.

    Science.gov (United States)

    Garefalakis, Philippos; Schlunegger, Fritz

    2018-01-09

    Large sediment fluxes from mountain belts have the potential to cause megafans to prograde into the neighbouring sedimentary basins. These mechanisms have been documented based from numerical modelling and stratigraphic records. However, little attention has been focused on inferring temporal changes in the concentrations of supplied sediment from coarse-grained deposits. Here, we extract changes of this variable in the field from a Late Oligocene, c. 4 km-thick suite of fluvial conglomerates situated in the North Alpine foreland basin, which evolved in response to the tectonic and erosional history of the Alps. We measure a decrease in channel depths from >2 m to 20 cm from the base to the top of the suite. These constraints are used to calculate an increase in fan surface slopes from 1.0° based on the Shields criteria for sediment entrainment. We combine slope and bulk grain size data with the Bagnold equation for sediment transport to infer higher concentrations of the supplied sediment. We use these shifts to propose a change towards faster erosion and a steeper landscape in the Alpine hinterland, driven by mantle-scale processes beneath the Alps.

  9. Nitrous Oxide Production and Fluxes from Coastal Sediments under Varying Environmental Conditions

    Science.gov (United States)

    Ziebis, W.; Wankel, S. D.; de Beer, D.; Dentinger, J.; Buchwald, C.; Charoenpong, C.

    2014-12-01

    Although coastal zones represent important contributors to the increasing levels of atmospheric nitrous oxide (N2O), it is still unclear which role benthic processes play and whether marine sediments represent sinks or sources for N2O, since interactions among closely associated microbial groups lead to a high degree of variability. In addition, coastal areas are extremely dynamic regions, often exposed to increased nutrient loading and conditions of depleted oxygen. We investigated benthic N2O fluxes and how environmental conditions affect N2O production in different sediments at 2 different geographical locations (German Wadden Sea, a California coastal lagoon). At each location, a total of 32 sediment cores were taken in areas that differed in sediment type, organic content and pore-water nutrient concentrations, as well as in bioturbation activity. Parallel cores were incubated under in-situ conditions, low oxygen and increased nitrate levels for 10 days. Zones of N2O production and consumption were identified in intact cores by N2O microprofiles at the beginning and end of the experiments. In a collaborative effort to determine the dominant sources of N2O, samples were taken throughout the course of the experiments for the determination of the isotopic composition of N2O (as well as nitrate, nitrite and ammonium). Our results indicate that both, nitrate addition and low oxygen conditions in the overlying water, caused an increase of subsurface N2O production in most sediments, with a high variability between different sediment types. N2O production in the sediments was accompanied by N2O consumption, reducing the fluxes to the water column. In general, organic rich sediments showed the strongest response to environmental changes with increased production and efflux of N2O into the overlying water. Bioturbation activity added to the complexity of N2O dynamics by an increase in nitrification-denitrification processes, as well as enhanced pore-water transport

  10. Stable carbon isotope analysis of fluvial sediment fluxes over two contrasting C(4) -C(3) semi-arid vegetation transitions.

    Science.gov (United States)

    Puttock, Alan; Dungait, Jennifer A J; Bol, Roland; Dixon, Elizabeth R; Macleod, Christopher J A; Brazier, Richard E

    2012-10-30

    Globally, many drylands are experiencing the encroachment of woody vegetation into grasslands. These changes in ecosystem structure and processes can result in increased sediment and nutrient fluxes due to fluvial erosion. As these changes are often accompanied by a shift from C(4) to C(3) vegetation with characteristic δ(13) C values, stable isotope analysis provides a promising mechanism for tracing these fluxes. Input vegetation, surface sediment and fluvially eroded sediment samples were collected across two contrasting C(4) -C(3) dryland vegetation transitions in New Mexico, USA. Isotope ratio mass spectrometric analyses were performed using a Carlo Erba NA2000 analyser interfaced to a SerCon 20-22 isotope ratio mass spectrometer to determine bulk δ(13) C values. Stable isotope analyses of contemporary input vegetation and surface sediments over the monitored transitions showed significant differences (p fluvially eroded sediment from each of the sites, with no significant variation between surface sediment and eroded sediment values. The significant differences in bulk δ(13) C values between sites were dependent on vegetation input. Importantly, these values were robustly expressed in fluvially eroded sediments, suggesting that stable isotope analysis is suitable for tracing sediment fluxes. Due to the prevalent nature of these dryland vegetation transitions in the USA and globally, further development of stable isotope ratio mass spectrometry has provided a valuable tool for enhanced understanding of functional changes in these ecosystems. Copyright © 2012 John Wiley & Sons, Ltd.

  11. Benthic Nutrient Fluxes from Mangrove Sediments of an Anthropogenically Impacted Estuary in Southern China

    Directory of Open Access Journals (Sweden)

    David Kaiser

    2015-06-01

    Full Text Available Mangroves serve as either sinks or sources for inorganic and organic nutrients and can mitigate anthropogenic nutrient pollution, control the production in adjacent systems, and prevent eutrophication. To better understand the nutrient dynamics in a subtropical mangrove, we employed a three-way approach in the Nanliu River Estuary, southern China: Pore water profiles and sediment incubations revealed benthic early diagenesis as well as sediment–water exchange of dissolved nutrients and oxygen, while tidal sampling of estuarine and mangrove water identified source and sink functions of the entire mangrove forest. Fluxes of oxygen during incubations were always directed into the sediment, indicating heterotrophy of the system. There was a net uptake of dissolved inorganic nitrogen, mainly caused by nitrate influx, while ammonium and nitrite showed variable flux direction. Despite high pore water concentrations, phosphate and silica showed net uptake. Fluxes of dissolved organic carbon were generally low except for high efflux in the dark following a storm event. Due to the combination of small forest area and strong anthropogenic nutrient input, the net sink function for dissolved nitrogen and phosphorus provides no significant buffer against the eutrophication of coastal waters.

  12. Comparison of depth-averaged concentration and bed load flux sediment transport models of dam-break flow

    Directory of Open Access Journals (Sweden)

    Jia-heng Zhao

    2017-10-01

    Full Text Available This paper presents numerical simulations of dam-break flow over a movable bed. Two different mathematical models were compared: a fully coupled formulation of shallow water equations with erosion and deposition terms (a depth-averaged concentration flux model, and shallow water equations with a fully coupled Exner equation (a bed load flux model. Both models were discretized using the cell-centered finite volume method, and a second-order Godunov-type scheme was used to solve the equations. The numerical flux was calculated using a Harten, Lax, and van Leer approximate Riemann solver with the contact wave restored (HLLC. A novel slope source term treatment that considers the density change was introduced to the depth-averaged concentration flux model to obtain higher-order accuracy. A source term that accounts for the sediment flux was added to the bed load flux model to reflect the influence of sediment movement on the momentum of the water. In a one-dimensional test case, a sensitivity study on different model parameters was carried out. For the depth-averaged concentration flux model, Manning's coefficient and sediment porosity values showed an almost linear relationship with the bottom change, and for the bed load flux model, the sediment porosity was identified as the most sensitive parameter. The capabilities and limitations of both model concepts are demonstrated in a benchmark experimental test case dealing with dam-break flow over variable bed topography.

  13. Spatial analysis of soil erosion and sediment fluxes: a paired watershed study of two Rappahannock River tributaries, Stafford County, Virginia.

    Science.gov (United States)

    Ricker, Matthew C; Odhiambo, Ben K; Church, Joseph M

    2008-05-01

    Soil erosion is a serious problem in areas with expanding construction, agricultural production, and improper storm water management. It is important to understand the major processes affecting sediment delivery to surficial water bodies in order to tailor effective mitigation and outreach activities. This study analyzes how naturally occurring and anthropogenic influences, such as urbanization and soil disturbance on steep slopes, are reflected in the amount of soil erosion and sediment delivery within sub-watershed-sized areas. In this study, two sub-watersheds of the Rappahannock River, Horsepen Run and Little Falls Run, were analyzed using the Revised Universal Soil Loss Equation (RUSLE) and a sediment delivery ratio (SDR) to estimate annual sediment flux rates. The RUSLE/SDR analyses for Horsepen Run and Little Falls Run predicted 298 Mg/y and 234 Mg/y, respectively, but nearly identical per-unit-area sediment flux rates of 0.15 Mg/ha/y and 0.18 Mg/ha/y. Suspended sediment sampling indicated greater amounts of sediment in Little Falls Run, which is most likely due to anthropogenic influences. Field analyses also suggest that all-terrain vehicle crossings represent the majority of sediment flux derived from forested areas of Horsepen Run. The combined RUSLE/SDR and field sampling data indicate that small-scale anthropogenic disturbances (ATV trails and construction sites) play a major role in overall sediment flux rates for both basins and that these sites must be properly accounted for when evaluating sediment flux rates at a sub-watershed scale.

  14. What is the Source? Post-glacial sediment flux from the Waipaoa Catchment, New Zealand

    Science.gov (United States)

    Bilderback, E. L.; Pettinga, J. R.; Litchfield, N. J.; Quigley, M.; Marden, M.

    2011-12-01

    In the Waipaoa, and for much of the eastern North Island, the shift from the last glacial coldest period to the current interglacial climatic regime resulted in Late Pleistocene-Holocene catchment-wide channel incision (Berryman et al., 2000; Litchfield and Berryman, 2005). Only ~25% of the total post 18 ka sediment yield for the Waipaoa Catchment can be accounted for by channel incision, one of the most widespread and most effective erosive processes in the catchment (Orpin et al., 2006; Marden et al., 2008). We find that deep-seated landslides, which are pervasive, cannot make up this apparent source area sediment deficit. This presents a challenge to our current understanding of the Waipaoa Sedimentary System. New high resolution topographic data sets (lidar and photogrammetry) combined with tephrochronology and field mapping have enabled us to approximate the sediment flux from post 18 ka deep-seated landslides. The sediment delivered to the offshore sink from these upper Waipaoa landslides is likely to be less than 20% of the sediment volume calculated for channel incision. A further GIS analysis of the ~2500 km2 Waipaoa catchment using work from Crosby and Whipple (2006) delineating relict topography and Marden et al. (2008) accounting for river incision and slopes stabilized behind terrace remnants indicates that only about half of the available catchment area could have contributed additional large volumes of sediment to the offshore post 18 ka sink. The presence of tephra cover older than 18 ka on landforms ranging from flat ridgelines to steep (>30 degree) slopes in this remaining terrestrial source area suggests that it has not been eroded en mass. The apparent source deficit remains even though many of the major erosive processes available to fill this deficit have been studied and the potentially contributing catchment area is dramatically reduced by these studies. This analysis raises questions about erosive processes and our ability to balance large

  15. Humin to Human: Organic carbon, sediment, and water fluxes along river corridors in a changing world

    Energy Technology Data Exchange (ETDEWEB)

    Sutfin, Nicholas Alan [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-11-20

    This is a presentation with slides on What does it mean to be human? ...humin?; River flow and Hydrographs; Snake River altered hydrograph (Marston et al., 2005); Carbon dynamics are important in rivers; Rivers and streams as carbon sink; Reservoirs for organic carbon; Study sites in Colorado; River morphology; Soil sample collection; Surveys at RMNP; Soil organic carbon content at RMNP; Abandoned channels and Cutoffs; East River channel migration and erosion; Linking hydrology to floodplain sediment flux; Impact of Extreme Floods on Floodplain Sediment; Channel Geometry: RMNP; Beavers dams and multithread channels; Geomorphology and carbon in N. St. Vrain Creek; Geomorphology and carbon along the East River; Geomorphology and carbon in N. St. Vrain Creek; San Marcos River, etc.

  16. Morphodynamic Modeling of the Lower Yellow River, China: Flux (Equilibrium) Form or Entrainment (Nonequilibrium) Form of Sediment Mass Conservation?

    Science.gov (United States)

    An, C.; Parker, G.; Ma, H.; Naito, K.; Moodie, A. J.; Fu, X.

    2017-12-01

    Models of river morphodynamics consist of three elements: (1) a treatment of flow hydraulics, (2) a formulation relating some aspect of sediment transport to flow hydraulics, and (3) a description of sediment conservation. In the case of unidirectional river flow, the Exner equation of sediment conservation is commonly described in terms of a flux-based formulation, in which bed elevation variation is related to the streamwise gradient of sediment transport rate. An alternate formulation of the Exner equation, however, is the entrainment-based formulation in which bed elevation variation is related to the difference between the entrainment rate of bed sediment into suspension and the deposition rate of suspended sediment onto the bed. In the flux-based formulation, sediment transport is regarded to be in a local equilibrium state (i.e., sediment transport rate locally equals sediment transport capacity). However, the entrainment-based formulation does not require this constraint; the sediment transport rate may lag in space and time behind the changing flow conditions. In modeling the fine-grained Lower Yellow River, it is usual to treat sediment conservation in terms of an entrainment-based (nonequilibrium) rather than a flux-based (equilibrium) formulation with the consideration that fine-grained sediment may be entrained at one place but deposited only at some distant location downstream. However, the differences in prediction between the two formulations are still not well known, and the entrainment formulation may not always be necessary for the Lower Yellow River. Here we study this problem by comparing the results of flux-based and entrainment-based morphodynamics under conditions typical of the Yellow River, using sediment transport equations specifically designed for the Lower Yellow River. We find, somewhat unexpectedly, that in a treatment of a 200-km reach using uniform sediment, there is little difference between the two formulations unless the

  17. Influence of the macrotidal environment on the source to sink pathways of suspended flux in the Gulf of Kachchh, India: Evidence from the Ocean Colour Monitor (IRS-P4)

    Digital Repository Service at National Institute of Oceanography (India)

    Chauhan, O.S.; Menezes, A.A.A.; Jayakumar, S.; Malik, M.A.; Pradhan, Y.; Rajawat, A.S.; Nayak, S.R.; Bandekar, G.; Almeida, C.; Talaulikar, M.; Ramanamurty, M.V.; Subramanian, B.R.

    and sources of total suspended matter (TSM) in the Gulf of Kachchh, a macrotidal system with insignificant freshwater inputs. Strong alongshore currents are prevalent at the mouth that move in (out) clockwise during flood (ebb) and undergo cyclic, dynamic...

  18. Driving forces and their contribution to the recent decrease in sediment flux to ocean of major rivers in China.

    Science.gov (United States)

    Li, Tong; Wang, Shuai; Liu, Yanxu; Fu, Bojie; Zhao, Wenwu

    2018-09-01

    Understanding the mechanisms behind land-ocean sediment transport processes is crucial, due to the resulting impacts on the sustainable management of water and soil resources. This study investigated temporal trends and historical phases of sediment flux delivered to the sea by nine major rivers in China, while also quantifying the contribution of key anthropogenic and natural driving forces. During the past six decades, sediment flux from these nine major rivers exhibited a statistically significant negative trend, decreasing from 1.92Gtyr -1 during 1954-1968 to 1.39Gtyr -1 , 0.861Gtyr -1 and 0.335Gtyr -1 during 1969-1985, 1986-1999 and 2000-2016, respectively. We used a recently developed Sediment Identity approach and found that the sharp decrease in sediment load observed across China was mainly (~95%) caused by a reduction in sediment concentration. Reservoir construction exerted the strongest influence on land-ocean sediment fluxes, while soil conservation measures represented a secondary driver. Before 1999, soil erosion was not controlled effectively in China and reservoirs, especially large ones, played a dominant role in reducing riverine sediments. After 1999, soil erosion has gradually been brought under control across China, so that conservation measures directly accounted for ~40% of the observed decrease in riverine sediments. With intensifying human activities, it is predicted that the total sediment flux delivered to the sea by the nine major rivers will continue to decrease in the coming decades, although at a slower rate, resulting in severe challenges for the sustainable management of drainage basins and river deltas. Copyright © 2018 Elsevier B.V. All rights reserved.

  19. Effects of Hyporheic Water Fluxes and Sediment Grain Size on the Concentration and Diffusive Flux of Heavy Metals in the Streambed.

    Science.gov (United States)

    Liu, Qi; Song, Jinxi; Zhang, Guotao; Wang, Weize; Guo, Weiqiang; Tang, Bin; Kong, Feihe; Huo, Aidi

    2017-09-06

    The hyporheic zone regulates physicochemical processes in surface-groundwater systems and can be an important source of heavy metals in fluvial systems. This study assesses the pore water concentrations and diffusive fluxes of heavy metals with respect to the vertical water exchange flux (VWEF) and sediment grain size. Water and sediment samples were collected on August 2016 from upstream Site 1 and downstream Site 2 along the Juehe River in Shaanxi Province, China. Streambed vertical hydraulic conductivity (Kv) and the VWEF were estimated via the standpipe permeameter test method and Darcy's law. The heavy metal concentrations in the pore water were measured and the diffusive fluxes were calculated using Fick's first law. The VWEF patterns were dominated by upward flow, and Site 1 featured higher values of Kv and VWEF. Higher Cu and Zn concentrations occurred near the channel centre with coarse sand and gravel and greater upward VWEFs because coarser sediment and greater upward VWEFs cause stronger metal desorption capacity. Additionally, Cu and Zn at the two sites generally diffused from pore water to surface water, potentially due to the upward VWEF. The VWEF and sediment grain size are likely crucial factors influencing the heavy metal concentrations and diffusive fluxes.

  20. Bioturbation and dissolved organic matter enhance contaminant fluxes from sediment treated with powdered and granular activated carbon.

    Science.gov (United States)

    Kupryianchyk, D; Noori, A; Rakowska, M I; Grotenhuis, J T C; Koelmans, A A

    2013-05-21

    Sediment amendment with activated carbon (AC) is a promising technique for in situ sediment remediation. To date it is not clear whether this technique sufficiently reduces sediment-to-water fluxes of sediment-bound hydrophobic organic chemicals (HOCs) in the presence of bioturbators. Here, we report polychlorobiphenyl (PCB) pore water concentrations, fluxes, mass transfer coefficients, and survival data of two benthic species, for four treatments: no AC addition (control), powdered AC addition, granular AC addition and addition and subsequent removal of GAC (sediment stripping). AC addition decreased mass fluxes but increased apparent mass transfer coefficients because of dissolved organic carbon (DOC) facilitated transport across the benthic boundary layer (BBL). In turn, DOC concentrations depended on bioturbator activity which was high for the PAC tolerant species Asellus aquaticus and low for AC sensitive species Lumbriculus variegatus. A dual BBL resistance model combining AC effects on gradients, DOC facilitated transport and biodiffusion was evaluated against the data and showed how the type of resistance differs with treatment and chemical hydrophobicity. Data and simulations illustrate the complex interplay between AC and contaminant toxicity to benthic organisms and how differences in species tolerance affect mass fluxes from sediment to the water column.

  1. The influence of neap-spring tidal variation and wave energy on sediment flux in salt marsh tidal creeks

    Science.gov (United States)

    Lacy, Jessica; Ferner, Matthew C.; Callaway, John C.

    2018-01-01

    Sediment flux in marsh tidal creeks is commonly used to gage sediment supply to marshes. We conducted a field investigation of temporal variability in sediment flux in tidal creeks in the accreting tidal marsh at China Camp State Park adjacent to northern San Francisco Bay. Suspended-sediment concentration (SSC), velocity, and depth were measured near the mouths of two tidal creeks during three six-to-ten-week deployments: two in winter and one in summer. Currents, wave properties and SSC were measured in the adjacent shallows. All deployments spanned the largest spring tides of the season. Results show that tidally-averaged suspended-sediment flux (SSF) in the tidal creeks decreased with increasing tidal energy, and SSF was negative (bayward) for tidal cycles with maximum water surface elevation above the marsh plain. Export during the largest spring tides dominated the cumulative SSF measured during the deployments. During ebb tides following the highest tides, velocities exceeded 1 m/s in the narrow tidal creeks, resulting in negative tidally-averaged water flux, and mobilizing sediment from the creek banks or bed. Storm surge also produced negative SSF. Tidally-averaged SSF was positive in wavey conditions with moderate tides. Spring-tide sediment export was about 50% less at a station 130 m further up the tidal creek than at the creek mouth. The negative tidally-averaged water flux near the creek mouth during spring tides indicates that in the lower marsh, some of the water flooding directly across the bay--marsh interface drains through the tidal creeks, and suggests that this interface may be a pathway for sediment supply to the lower marsh as well.

  2. A framework for using connectivity to measure and model water and sediment fluxes

    Science.gov (United States)

    Keessta, Saskia; Saco, Patricia; Nunes, Joao; Parsons, Tony; Poeppl, Ronny; Pereira, Paulo; Novara, Agata; Rodrigo Comino, Jesús; Jordán, Antonio; Masselink, Rens; Cerdà, Artemi

    2017-04-01

    For many years, scientists have tried to understand, describe and quantify water and sediment fluxes at multiple scales (Cerdà et al., 2013; Parsons et al., 2015; Poeppl et al., 2016; Masselink et al., 2016a; Rodrigo Comino et al., 2016). In the past two decades, a new concept called connectivity has been used by Earth Scientists as a means to describe and quantify the influences on the fluxes of water and sediment on different scales: aggregate, pedon, location on the slope, slope, watershed, and basin (Baartman et al., 2013; Parsons et al., 2015; López-Vicente et al., 2015; 2016; Masselink 2016b; Marchamalo et al., 2016; Mekonnen et al., 2016). A better understanding of connectivity can enhance our comprehension of landscape processes and provide a basis for the development of better measurement and modelling approaches, further leading to a better potential for implementing this concept as a management tool. Our research provides a short review of the State-of-the-Art of the connectivity concept, from which we conclude that scientists have been struggling to find a way to quantify connectivity so far. We adapt the knowledge of connectivity to better understand and quantify water and sediment transfers in catchment systems. First, we introduce a new approach to the concept of connectivity to study water and sediment transfers. In this approach water and sediment dynamics are divided in two parts: the system consists of phases and fluxes, each being separately measurable. This approach enables us to: i) better conceptualize our understanding of system dynamics at different timescales, including long timescales; ii) identify the main parameters driving system dynamics, and devise monitoring strategies which capture them; and, iii) build models with a holistic approach to simulate system dynamics without excessive complexity. Secondly, we discuss the role of system boundaries in designing measurement schemes and models. Natural systems have boundaries within which

  3. Dissolved inorganic carbon and alkalinity fluxes from coastal marine sediments: Model estimates for different shelf environments and sensitivity to global change

    NARCIS (Netherlands)

    Krumins, V.; Gehlen, M.; Arndt, S.; Van Cappellen, P.; Regnier, P.

    2013-01-01

    We present a one-dimensional reactive transport model to estimate benthic fluxes of dissolved inorganic carbon (DIC) and alkalinity (AT) from coastal marine sediments. The model incorporates the transport processes of sediment accumulation, molecular diffusion, bioturbation and bioirrigation,

  4. Sediment Buffering and Transport in the Holocene Indus River System

    Science.gov (United States)

    Clift, P. D.; Giosan, L.; Henstock, T.; Tabrez, A. R.; Vanlaningham, S.; Alizai, A. H.; Limmer, D. R.; Danish, M.

    2009-12-01

    Submarine fans are the largest sediment bodies on Earth and potentially hold records of erosion that could be used to assess the response of continents to changing climate in terms of both physical erosion and chemical weathering. However, buffering between the mountain sources and the abyssal plain may make detailed correlation of climate and erosion records difficult. We investigated the nature of sediment transport in the Indus drainage in SW Asia. Through trenching in the flood plain, drilling in the delta and new seismic and coring data from the shelf and canyon we can now constrain sediment transport from source to sink since the Last Glacial Maximum (LGM). The Indus was affected by intensification of the summer monsoon during the Early Holocene and subsequent weakening since ca. 8 ka. Sediment delivery to the delta was very rapid at 12-8 ka, but slowed along with the weakening monsoon. At the LGM erosion in the Karakoram dominated the supply of sandy material, while the proportion of Lesser Himalayan flux increased with strengthening summer rainfall after 12 ka. Total load also increased at that time. Since 5 ka incision of rivers into the upper parts of the flood plain has reworked Lower Holocene sediments, although the total flux slowed. Coring in the Indus canyon shows that sediment has not reached the lower canyon since ca. 7 ka, but that sedimentation has recently been very rapid in the head of the canyon. We conclude that variations in sealevel and terrestrial climate have introduced a lag of at least 7 k.y. into the deep sea fan record and that monsoon strength is a primary control on whether sediment is stored or released in the flood plain.

  5. The Role of Infragravity Waves in Near-Bed Cross-Shore Sediment Flux in the Breaker Zone

    Directory of Open Access Journals (Sweden)

    Samantha Kularatne

    2014-08-01

    Full Text Available Results from a series of field experiments, conducted to investigate the influence of infragravity waves (from wave groups, ripple type and location relative to the breaker line on cross-shore suspended sediment flux close to the sea bed in nearshore environments, are presented. The field data were collected from Cable Beach (Broome and Mullaloo Beach in Western Australia and Chilaw in Sri Lanka. These beaches experience different incident wave, tidal and morphological conditions, with Cable Beach having a 10-m spring tidal range, whilst the other two beaches have tidal ranges <1.0 m. Measurements included simultaneous records of surface elevation, two-dimensional horizontal current velocities and suspended sediment concentrations, together with half-hourly observations of the seabed topography. Although most of the data sets were obtained just outside of the surf zone, a few results from inside of the surf zone were also included. A significant correlation between wave groups and suspended sediment concentration was found at all of the measurement sites, either with or without bed ripples. The direction and magnitude of cross-shore suspended sediment flux varied with location with respect to the breaker line; however, other parameters, such as bed ripples and velocity skewness, could have influenced this result. In Broome, where the measurement location with respect to the breaker line varied with the tidal cycle, the cross-shore sediment flux due to swell waves was shoreward inside and just outside of the surf zone and seaward farther offshore of the breaker line. Further, sediment flux due to swell waves was onshore when the seabed was flat and offshore over post-vortex ripples. Sediment flux due to swell waves was onshore when the normalised velocity skewness towards the shore was high (positive; the flux was offshore when the skewness was lower, but positive, suggesting the influence of other parameters, such as ripples and grain size. The

  6. Polyphosphates as a source of enhanced P fluxes in marine sediments overlain by anoxic waters: Evidence from 31P NMR

    Directory of Open Access Journals (Sweden)

    Ingall Ellery

    2005-06-01

    Full Text Available Sedimentary phosphorus (P composition was investigated in Effingham Inlet, a fjord located on the west coast of Vancouver Island in Barkley Sound. Solid-state 31P nuclear magnetic resonance (NMR spectroscopy was applied to demineralized sediment samples from sites overlain by oxic and anoxic bottom waters. The two sites were similar in terms of key diagenetic parameters, including the mass accumulation rate, integrated sulfate reduction rate, and bulk sediment organic carbon content. In contrast, P benthic fluxes were much higher at the anoxic site. 31P NMR results show that P esters and phosphonates are the major organic P species present at the surface and at depth in sediments at both sites. Polyphosphates were only found in the surface sediment of the site overlain by oxic waters. The varying stability of polyphosphates in microorganisms under different redox conditions may, in part, explain their distribution as well as differences in P flux between the two sites.

  7. Sources of suspended-sediment flux in streams of the chesapeake bay watershed: A regional application of the sparrow model

    Science.gov (United States)

    Brakebill, J.W.; Ator, S.W.; Schwarz, G.E.

    2010-01-01

    We describe the sources and transport of fluvial suspended sediment in nontidal streams of the Chesapeake Bay watershed and vicinity. We applied SPAtially Referenced Regressions on Watershed attributes, which spatially correlates estimated mean annual flux of suspended sediment in nontidal streams with sources of suspended sediment and transport factors. According to our model, urban development generates on average the greatest amount of suspended sediment per unit area (3,928 Mg/km2/year), although agriculture is much more widespread and is the greatest overall source of suspended sediment (57 Mg/km2/year). Factors affecting sediment transport from uplands to streams include mean basin slope, reservoirs, physiography, and soil permeability. On average, 59% of upland suspended sediment generated is temporarily stored along large rivers draining the Coastal Plain or in reservoirs throughout the watershed. Applying erosion and sediment controls from agriculture and urban development in areas of the northern Piedmont close to the upper Bay, where the combined effects of watershed characteristics on sediment transport have the greatest influence may be most helpful in mitigating sedimentation in the bay and its tributaries. Stream restoration efforts addressing floodplain and bank stabilization and incision may be more effective in smaller, headwater streams outside of the Coastal Plain. ?? 2010 American Water Resources Association. No claim to original U.S. government works.

  8. Vertical Distribution and Flux of Nutrients in the Sediments of the Mangrove Reclamation Region of Muara Angke Kapuk, Jakarta

    Directory of Open Access Journals (Sweden)

    Anna Ida Sunaryo Purwiyanto

    2012-12-01

    Full Text Available The reclaimed mangrove estuary in Muara Angke Kapuk is a reclaimed area that has not evaded the impacted of pollution and waste in the areas surrounding Cengkareng, Jakarta. This is apparent from the fact that almost all sediments under the mangrove trees are buried under heaps of plastic trash. However, the reclaimed region still has variety of organism, which indicating that the region still has an internal carrying capacity, especially nutrients from sediment. The purpose of this research was to examine the condition of sediment nutrients in this mangrove reclamation region. The research was conducted by taking water samples using a modification of the stratified cup at a sediment depth of 0-15 cm with depth intervals of 2.5 cm, and taking sediment samples using the sediment ring. Pore water samples were measured for dissolved oxygen (DO and concentrations of ammonia, nitrite, nitrate, and phosphate. Sediment samples were used to obtain porosity values. The data obtained is used to make vertical concentration profiles and analysis of vertical nutrient flux. Vertical nutrient flux analysis was performed with the aid of QUAL2K software version 2.11. The results showed different vertical distributions and flux of nutrients, where influx for ammonia and phosphate and an increase in line with increasing sediment depth, while nitrate efflux and a decreased concentration. The flux calculation of nitrite as transitory nutrient was not done, but the concentration decreased after a depth of 2.5 cm. This indicates that the high contamination on the surface does not prevent the natural chemical processes so the reclaimed region can still provide nutritional support for its organism.

  9. Bulk and export production fluxes from sediment traps in the Gulf of Aqaba, north Red Sea

    Science.gov (United States)

    Torfstein, A.; Kienast, S.; Shaked, Y.

    2016-12-01

    Real time observations of the dynamics between dust input, primary production, and export production in deep oligotrophic waters are extremely rare. This is especially true in the context of the direct response and lag time between nutrient supply (e.g., dust), the oceanic biogeochemical response and the signal transfer from the water to sedimentary record. Here, we present the first direct measurments of bulk and export production fluxes in the deep oligotrophic Gulf of Aqaba (GOA), northern Red Sea, located between the hyper-arid Sahara and Arabia Deserts. This study is based on a coupled sediment trap array that provides daily- and monthly- resolution since January 2014. This coupled configuration allows for a unique collection of marine particulates, whereby the annual and seasonal patterns can be evaluated in the context of discrete (daily-timescale) events such as abrupt dust storms, floods and biological blooms. The marine organic C and N fluxes range annually between 0.02-0.25 and 0.001-0.1 g d-1 m-2, respectively. Both show a sharp decay with depth, corresponding to the "Martin curve" (Martin et al., 1987, Deep-Sea Research, 34, 267-285). Importantly, the daily-resolution sampling provides insights to the seasonal increase in export production during the winter and early spring. Rather than a smooth seasonal cycle, this increase is driven by only very few short events, lasting no more than a few days, during which export production increases by an order of magnitude above the baseline. Yet, the nature of these export production "spikes" is non-unique because they reflect different "trigger" events such as dust storms or water column mixing. Accordingly, we present a quantitative evaluation of the observations in the context of coeval dust flux records and the physical and chemical configuration of the GOA over the time of sampling period, and present and quantitative mass balance of particle fluxes in this deep yet land-locked marine setting.

  10. Landsliding and sediment flux in the Central Swiss Alps: A photogrammetric study of the Schimbrig landslide, Entlebuch

    Science.gov (United States)

    Schwab, Marco; Rieke-Zapp, Dirk; Schneider, Heinz; Liniger, Markus; Schlunegger, Fritz

    2008-05-01

    This study explores the effects of hillslope mass failure on the sediment flux in the Waldemme drainage basin, Central Swiss Alps, over decadal time scales. This area is characterized by abundant landslides affecting principally flysch units and is therefore an important sediment source. The analysis concentrates on the Schimbrig landslide that potentially contributes up to 15% to the sediment budget of the Waldemme drainage basin. Volumetric changes are quantified using high-resolution elevation models that were extracted using digital photogrammetric techniques. Sediment discharge data were used to constrain the significance of the landslide for sediment flux in the channel network. The temporal extent of the photogrammetric analysis ranges from 1962 to 1998, including an earth slide event in 1994. The analyses reveal that during periods of low slip rates of the landslide, nearly all of the displaced sediments were eroded and supplied to the channel network. In contrast, during active periods, only a fraction of the displaced landslide mass was exported to the trunk stream. Interestingly, the 1994 earth slide event did not disturb the long-term sediment discharge pattern of the channel network, nor did it influence the sediment flux at a weekly scale. However, suspended sediment pulses correlate with higher-than-average precipitation events. This was especially the case in August 2005 when a storm event (> 100 years return period) triggered several debris flows and earth flows in the whole drainage basin and in the Schimbrig area. This storm did not result in a significant increase in the slip rates of the entire landslide's main body. It is therefore proposed that debris flows and earth flows perform the connectivity between hillslope processes (e.g. landsliding) and the trunk stream during and between phases of landslide activity in this particular setting.

  11. Comparison of two regression-based approaches for determining nutrient and sediment fluxes and trends in the Chesapeake Bay watershed

    Science.gov (United States)

    Moyer, Douglas; Hirsch, Robert M.; Hyer, Kenneth

    2012-01-01

    Nutrient and sediment fluxes and changes in fluxes over time are key indicators that water resource managers can use to assess the progress being made in improving the structure and function of the Chesapeake Bay ecosystem. The U.S. Geological Survey collects annual nutrient (nitrogen and phosphorus) and sediment flux data and computes trends that describe the extent to which water-quality conditions are changing within the major Chesapeake Bay tributaries. Two regression-based approaches were compared for estimating annual nutrient and sediment fluxes and for characterizing how these annual fluxes are changing over time. The two regression models compared are the traditionally used ESTIMATOR and the newly developed Weighted Regression on Time, Discharge, and Season (WRTDS). The model comparison focused on answering three questions: (1) What are the differences between the functional form and construction of each model? (2) Which model produces estimates of flux with the greatest accuracy and least amount of bias? (3) How different would the historical estimates of annual flux be if WRTDS had been used instead of ESTIMATOR? One additional point of comparison between the two models is how each model determines trends in annual flux once the year-to-year variations in discharge have been determined. All comparisons were made using total nitrogen, nitrate, total phosphorus, orthophosphorus, and suspended-sediment concentration data collected at the nine U.S. Geological Survey River Input Monitoring stations located on the Susquehanna, Potomac, James, Rappahannock, Appomattox, Pamunkey, Mattaponi, Patuxent, and Choptank Rivers in the Chesapeake Bay watershed. Two model characteristics that uniquely distinguish ESTIMATOR and WRTDS are the fundamental model form and the determination of model coefficients. ESTIMATOR and WRTDS both predict water-quality constituent concentration by developing a linear relation between the natural logarithm of observed constituent

  12. [Sediment-water flux and processes of nutrients and gaseous nitrogen release in a China River Reservoir].

    Science.gov (United States)

    Chen, Zhu-hong; Chen, Neng-wang; Wu, Yin-qi; Mo, Qiong-li; Zhou, Xing-peng; Lu, Ting; Tian, Yun

    2014-09-01

    The key processes and fluxes of nutrients (N and P) and gaseous N (N2 and N2O) across the sediment-water interface in a river reservoir (Xipi) of the Jiulong River watershed in southeast China were studied. Intact core sediment incubation of nutrients exchange, in-situ observation and lab incubation of excess dissolved N2 and N2O (products of nitrification, denitrification and Anammox), and determination of physiochemical and microbe parameters were carried out in 2013 for three representative sites along the lacustrine zone of the reservoir. Results showed that ammonium and phosphate were generally released from sediment to overlying water [with averaged fluxes of N (479.8 ± 675.4) mg. (m2. d)-1 and P (4. 56 ± 0.54) mg. (m2 d) -1] , while nitrate and nitrite diffused into the sediment. Flood events in the wet season could introduce a large amount of particulate organic matter that would be trapped by the dam reservoir, resulting in the high release fluxes of ammonium and phosphate observed in the following low-flow season. No clear spatial variation of sediment nutrient release was found in the lacustrine zone of the reservoir. Gaseous N release was dominated by excess dissolved N2 (98% of total), and the N2 flux from sediment was (15.8 ± 12. 5) mg (m2. d) -1. There was a longitudinal and vertical variation of excess dissolved N2, reflecting the combined results of denitrification and Anammox occurring in anoxic sediment and fluvial transport. Nitrification mainly occurred in the lower lacustrine zone, and the enrichment of N2O was likely regulated by the ratio of ammonium to DIN in water.

  13. Vertical and lateral flux on the continental slope off Pakistan: correlation of sediment core and trap results

    Science.gov (United States)

    Schulz, H.; von Rad, U.

    2014-06-01

    Due to the lack of bioturbation, the varve-laminated muds from the oxygen minimum zone (OMZ) off Pakistan provide a unique opportunity to precisely determine the vertical and lateral sediment fluxes in the nearshore part of the northeastern Arabian Sea. West of Karachi (Hab area), the results of two sediment trap stations (EPT and WPT) were correlated with 16 short sediment cores on a depth transect crossing the OMZ. The top of a distinct, either reddish- or light-gray silt layer, 210Pb-dated as AD 1905 ± 10, was used as an isochronous stratigraphic marker bed to calculate sediment accumulation rates. In one core, the red and gray layer were separated by a few (5-10) thin laminae. According to our varve model, this contributes water column above. All traps on the steep Makran continental slope show exceptionally high, pulsed winter fluxes of up to 5000 mg m-2 d-1. Based on core results, the flux at the seafloor amounts to 4000 mg m-2 d-1 and agrees remarkably well with the bulk winter flux of material, as well as with the flux of the individual bulk components of organic carbon, calcium carbonate and opal. However, due to the extreme mass of remobilized matter, the high winter flux events exceeded the capacity of the shallow traps. Based on our comparisons, we argue that high-flux events must occur regularly during winter within the upper OMZ off Pakistan to explain the high accumulations rates. These show distribution patterns that are a negative function of water depth and distance from the shelf. Some of the sediment fractions show marked shifts in accumulation rates near the lower boundary of the OMZ. For instance, the flux of benthic foraminifera is lowered but stable below ~1200-1300 m. However, flux and sedimentation in the upper eastern Makran area are dominated by the large amount of laterally advected fine-grained material and by the pulsed nature of the resuspension events at the upper margin during winter.

  14. Methane Flux and Authigenic Carbonate in Shallow Sediments Overlying Methane Hydrate Bearing Strata in Alaminos Canyon, Gulf of Mexico

    Directory of Open Access Journals (Sweden)

    Joseph P. Smith

    2014-09-01

    Full Text Available In June 2007 sediment cores were collected in Alaminos Canyon, Gulf of Mexico across a series of seismic data profiles indicating rapid transitions between the presence of methane hydrates and vertical gas flux. Vertical profiles of dissolved sulfate, chloride, calcium, magnesium, and dissolved inorganic carbon (DIC concentrations in porewaters, headspace methane, and solid phase carbonate concentrations were measured at each core location to investigate the cycling of methane-derived carbon in shallow sediments overlying the hydrate bearing strata. When integrated with stable carbon isotope ratios of DIC, geochemical results suggest a significant fraction of the methane flux at this site is cycled into the inorganic carbon pool. The incorporation of methane-derived carbon into dissolved and solid inorganic carbon phases represents a significant sink in local carbon cycling and plays a role in regulating the flux of methane to the overlying water column at Alaminos Canyon. Targeted, high-resolution geochemical characterization of the biogeochemical cycling of methane-derived carbon in shallow sediments overlying hydrate bearing strata like those in Alaminos Canyon is critical to quantifying methane flux and estimating methane hydrate distributions in gas hydrate bearing marine sediments.

  15. Variability of residual fluxes of suspended sediment in a multiple tidal-inlet system : the Dutch Wadden Sea

    NARCIS (Netherlands)

    Sassi, M.; Duran-Matute, M.; van Kessel, Th.; Gerkema, Th.

    2015-01-01

    In multiple tidal-inlet systems such as the Dutch Wadden Sea, the exchange of sediments between the coastal lagoon and the adjacent sea is controlled by the combined effect of the tides, wind-driven flows, and density-driven flows. We investigate the variability of residual (tidally averaged) fluxes

  16. Continuous In Situ Measurements of Near Bottom Chemistry and Sediment-Water Fluxes with the Chimney Sampler Array (CSA)

    Science.gov (United States)

    Martens, C. S.; Mendlovitz, H. P.; White, B. L.; Hoer, D.; Sleeper, K.; Chanton, J.; Wilson, R.; Lapham, L.

    2011-12-01

    The Chimney Sampler Array (CSA) was designed to measure in situ chemical and physical parameters within the benthic boundary layer plus methane and oxygen sediment-water chemical fluxes at upper slope sites in the northern Gulf of Mexico. The CSA can monitor temporal changes plus help to evaluate oceanographic and sub-seafloor processes that can influence the formation and stability of gas hydrates in underlying sediments. The CSA consists of vertical cylinders (chimneys) equipped with internal chemical sensors and with laboratory flume-calibrated washout rates. Chimney washout rates multiplied by chimney mean versus ambient concentrations allow calculation of net O2 and methane sediment-water fluxes. The CSA is emplaced on the seafloor by a ROVARD lander using a ROV for chimney deployments. The CSA presently includes two 30 cm diameter by 90 cm length cylinders that seal against the sediment with lead pellet beanbags; within each chimney cylinder are optode, conductivity and methane sensors. The CSA's data logger platform also includes pressure and turbidity sensors external to the chimneys along with an acoustic Doppler current meter to measure temporal variation in ambient current velocity and direction. The CSA was deployed aboard a ROVARD lander on 9/13/2010 in the northern Gulf of Mexico (Lat. 28 51.28440, Long. 088 29.39421) on biogeochemically active sediments within Block MC-118. A ROV was utilized for chimney deployment away from the ROVARD lander. The CSA monitored temporal changes in water column physical parameters, obtained near-bottom chemical data to compare with pore fluid and sediment core measurements and measured temporal variability in oxygen and methane sediment-water fluxes at two closely spaced stations at MC-118. A continuous, three-week data set was obtained that revealed daily cycles in chemical parameters and episodic flux events. Lower than ambient chimney dissolved O2 concentrations controlled by temporal variability in washout rates

  17. Over one hundred years of trace metal fluxes in the sediments of the Pearl River Estuary, South China

    International Nuclear Information System (INIS)

    Ip, C.C.M.; Li, X.D.; Zhang, G.; Farmer, J.G.; Wai, O.W.H.; Li, Y.S.

    2004-01-01

    The rapid economic development in the Pearl River Delta (PRD) region in South China in the last three decades has had a significant impact on the local environment. Estuarine sediment is a major sink for contaminants and nutrients in the surrounding ecosystem. The accumulation of trace metals in sediments may cause serious environmental problems in the aquatic system. Thirty sediment cores were collected in the Pearl River Estuary (PRE) in 2000 for a study on trace metal pollution in this region. Heavy metal concentrations and Pb isotopic compositions in the four 210 Pb-dated sediment cores were determined to assess the fluxes in metal deposits over the last one hundred years. The concentrations of Cu, Pb and Zn in the surface sediment layers were generally elevated when compared with the sub-surface layers. There has been a significant increase in inputs of Cu, Pb and Zn in the PRE since the 1970s. The results also showed that different sampling locations in the estuary received slightly different types of inputs. Pb isotopic composition data indicated that the increased Pb in the recent sediments was of anthropogenic origin. The results of trace metal influxes showed that about 30% of total Pb and 15% of total Zn in the sediments in the 1990s were from anthropogenic sources. The combination of trace metal analysis, Pb isotopic composition and 210 Pb dating in an estuary can provide vital information on the long-term accumulation of metals in sediments

  18. Estimating sediment and caesium-137 fluxes in the Ribble Estuary through time-series airborne remote sensing

    International Nuclear Information System (INIS)

    Wakefield, R.; Tyler, A.N.; McDonald, P.; Atkin, P.A.; Gleizon, P.; Gilvear, D.

    2011-01-01

    High spatial and temporal resolution airborne imagery were acquired for the Ribble Estuary, North West England in 1997 and 2003, to assess the application of time-series airborne remote sensing to quantify total suspended sediment and radionuclide fluxes during a flood and ebb tide sequence. Concomitant measurements of suspended particulate matter (SPM) and water column turbidity were obtained during the time-series image acquisition for the flood and ebb tide sequence on the 17th July 2003 to verify the assumption of a vertically well mixed estuary and thus justifying the vertical extrapolation of spatially integrated estimate of surface SPM. The 137 Cs activity concentrations were calculated from a relatively stable relationship between SPM and 137 Cs for the Ribble Estuary. Total estuary wide budgets of sediment and 137 Cs were obtained by combining the image-derived estimates of surface SPM and 137 Cs with estimates of water volume from a two-dimensional hydrodynamic model (VERSE) developed for the Ribble Estuary. These indicate that around 10,000 tonnes of sediment and 2.72 GBq of 137 Cs were deposited over the tidal sequence monitored in July 2003. This compared favourably with bed height elevation change estimated from field work. An uncertainty analysis on the total sediment and 137 Cs flux yielded a total budget of the order of 40% on the final estimate. The results represent a novel approach to providing a spatially integrated estimate of the total net sediment and radionuclide flux in an intertidal environment over a flood and ebb tide sequence. - Research highlights: → This paper provides a rare insight into the next flux of sediment and associated radionuclide loading into an estuary over and ebb and flood tide sequence. → The paper uses high temporal resolution airborne imagery coupled with concomitant sampling to convert total suspended sediment flux to 137 Cs loading. → For the estuary and date studied, it is estimate that an 10,000 tonnes of

  19. Annual suspended sediment and trace element fluxes in the Mississippi, Columbia, Colorado, and Rio Grande drainage basins

    Science.gov (United States)

    Horowitz, A.J.; Elrick, K.A.; Smith, J.J.

    2001-01-01

    Suspended sediment, sediment-associated, total trace element, phosphorus (P), and total organic carbon (TOC) fluxes were determined for the Mississippi, Columbia, Rio Grande, and Colorado Basins for the study period (the 1996, 1997, and 1998 water years) as part of the US Geological Survey's redesigned National Stream Quality Accounting Network (NASQAN) programme. The majority (??? 70%) of Cu, Zn, Cr, Ni, Ba, P, As, Fe, Mn, and Al are transported in association with suspended sediment; Sr transport seems dominated by the dissolved phase, whereas the transport of Li and TOC seems to be divided equally between both phases. Average dissolved trace element levels are markedly lower than reported during the original NASQAN programme; this seems due to the use of 'clean' sampling, processing, and analytical techniques rather than to improvements in water quality. Partitioning between sediment and water for Ag, Pb, Cd, Cr, Co, V, Be, As, Sb, Hg, and Ti could not be estimated due to a lack of detectable dissolved concentrations in most samples. Elevated suspended sediment-associated Zn levels were detected in the Ohio River Basin and elevated Hg levels were detected in the Tennessee River, the former may affect the mainstem Mississippi River, whereas the latter probably do not. Sediment-associated concentrations of Ag, Cu, Pb, Zn, Cd, Cr, Co, Ba, Mo, Sb, Hg, and Fe are markedly elevated in the upper Columbia Basin, and appear to be detectable (Zn, Cd) as far downstream as the middle of the basin. These elevated concentrations seem to result from mining and/or mining-related activities. Consistently detectable concentrations of dissolved Se were found only in the Colorado River Basin. Calculated average annual suspended sediment fluxes at the mouths of the Mississippi and Rio Grande Basins were below, whereas those for the Columbia and Colorado Basins were above previously published annual values. Downstream suspended sediment-associated and total trace element fluxes

  20. The Role of Water Movement and Spatial Scaling for Measurement of Dissolved Inorganic Nitrogen Fluxes in Intertidal Sediments

    Science.gov (United States)

    Asmus, R. M.; Jensen, M. H.; Jensen, K. M.; Kristensen, E.; Asmus, H.; Wille, A.

    1998-02-01

    Fluxes of dissolved inorganic nitrogen (ammonium and nitrate) across the sediment-water interface were determined at intertidal locations in Königshafen, northern Wadden Sea, North Sea. Three different incubation techniques were compared: closed sediment cores (small scale), closed bell jars (medium scale) and an open flow system (Sylt flume, large scale). Water movement in the two closed systems was maintained below the resuspension limit by spinning magnets (cores, incubated in the laboratory) or by transfer of wave action through flexible plastic foil (bell jars,in situ), whereas in the flume system (in situ) water movement was unidirectional, driven by currents and waves. Data sets from several years of core measurements (1992-94), bell jar measurements (1980) and flume campaigns (1990-93) served as the basis for a comparison of dissolved inorganic nitrogen fluxes. Fluxes of ammonium and nitrate were within the same order of magnitude in closed cores and bell jars, while flume rates of ammonium were considerably higher. The high flume rates were caused by advective flushing due to tidal water movement and wave action. The release of ammonium increased significantly with current velocity between 1 and 13 cm s-1. Fluxes of ammonium were higher in sediments withArenicola marinacompared to those without this bioturbating species. The influence of benthic microalgae was evident only in the small and medium scale core and bell jar systems as reduced ammonium release during light exposure. Nitrate was consumed by sediments in both closed systems at a rate proportional to the nitrate concentration in the overlying water. Nitrate fluxes in the large scale Sylt flume were low with an average of only 7% of the ammonium fluxes, probably due to low concentrations in tidal waters during measurements (summer). Both closed, small scale or open, large scale techniques can be applied successfully for benthic flux studies, but the actual choice depends on the purpose of the

  1. Organic carbon mass accumulation rate regulates the flux of reduced substances from the sediments of deep lakes

    Directory of Open Access Journals (Sweden)

    T. Steinsberger

    2017-07-01

    Full Text Available The flux of reduced substances, such as methane and ammonium, from the sediment to the bottom water (Fred is one of the major factors contributing to the consumption of oxygen in the hypolimnia of lakes and thus crucial for lake oxygen management. This study presents fluxes based on sediment porewater measurements from different water depths of five deep lakes of differing trophic states. In meso- to eutrophic lakes Fred was directly proportional to the total organic carbon mass accumulation rate (TOC-MAR of the sediments. TOC-MAR and thus Fred in eutrophic lakes decreased systematically with increasing mean hypolimnion depth (zH, suggesting that high oxygen concentrations in the deep waters of lakes were essential for the extent of organic matter mineralization leaving a smaller fraction for anaerobic degradation and thus formation of reduced compounds. Consequently, Fred was low in the 310 m deep meso-eutrophic Lake Geneva, with high O2 concentrations in the hypolimnion. By contrast, seasonal anoxic conditions enhanced Fred in the deep basin of oligotrophic Lake Aegeri. As TOC-MAR and zH are based on more readily available data, these relationships allow estimating the areal O2 consumption rate by reduced compounds from the sediments where no direct flux measurements are available.

  2. The Effect of Nitrogen Enrichment on C1-Cycling Microorganisms and Methane Flux in Salt Marsh Sediments

    Directory of Open Access Journals (Sweden)

    Irina Catherine Irvine

    2012-03-01

    Full Text Available Methane (CH4 flux from ecosystems is driven by C1-cycling microorganisms – the methanogens and the methylotrophs. Little is understood about what regulates these communities, complicating predictions about how global change drivers such as nitrogen enrichment will affect methane cycling. Using a nitrogen addition gradient experiment in three Southern California salt marshes, we show that sediment CH4 flux increased linearly with increasing nitrogen addition (1.23 µg CH4 m-2 d-1 for each g N m-2 yr-1 applied after seven months of fertilization. To test the reason behind this increased CH4 flux, we conducted a microcosm experiment altering both nitrogen and carbon availability under aerobic and anaerobic conditions. Methanogenesis appeared to be both nitrogen and carbon (acetate limited. N and C each increased methanogenesis by 18%, and together by 44%. In contrast, methanotrophy was stimulated by carbon (methane addition (830%, but was unchanged by nitrogen addition. Sequence analysis of the sediment methylotroph community with the methanol dehydrogenase gene (mxaF revealed three distinct clades that fall outside of known lineages. However, in agreement with the microcosm results, methylotroph abundance (assayed by qPCR and composition (assayed by T-RFLP did not vary across the experimental nitrogen gradient in the field. Together, these results suggest that nitrogen enrichment to salt marsh sediments increases methane flux by stimulating the methanogen community.

  3. Regulation of CO2 Air Sea Fluxes by Sediments in the North Sea

    Science.gov (United States)

    Burt, William; Thomas, Helmuth; Hagens, Mathilde; Brenner, Heiko; Pätsch, Johannes; Clargo, Nicola; Salt, Lesley

    2016-04-01

    A multi-tracer approach is applied to assess the impact of boundary fluxes (e.g. benthic input from sediments or lateral inputs from the coastline) on the acid-base buffering capacity, and overall biogeochemistry, of the North Sea. Analyses of both basin-wide observations in the North Sea and transects through tidal basins at the North-Frisian coastline, reveal that surface distributions of the δ13C signature of dissolved inorganic carbon (DIC) are predominantly controlled by a balance between biological production and respiration. In particular, variability in metabolic DIC throughout stations in the well-mixed southern North Sea indicates the presence of an external carbon source, which is traced to the European continental coastline using naturally-occurring radium isotopes (224Ra and 228Ra). 228Ra is also shown to be a highly effective tracer of North Sea total alkalinity (AT) compared to the more conventional use of salinity. Coastal inputs of metabolic DIC and AT are calculated on a basin-wide scale, and ratios of these inputs suggest denitrification as a primary metabolic pathway for their formation. The AT input paralleling the metabolic DIC release prevents a significant decline in pH as compared to aerobic (i.e. unbuffered) release of metabolic DIC. Finally, long-term pH trends mimic those of riverine nitrate loading, highlighting the importance of coastal AT production via denitrification in regulating pH in the southern North Sea.

  4. Modelling biogeochemical processes in sediments from the north-western Adriatic Sea: response to enhanced particulate organic carbon fluxes

    Science.gov (United States)

    Brigolin, Daniele; Rabouille, Christophe; Bombled, Bruno; Colla, Silvia; Vizzini, Salvatrice; Pastres, Roberto; Pranovi, Fabio

    2018-03-01

    This work presents the result of a study carried out in the north-western Adriatic Sea, by combining two different types of biogeochemical models with field sampling efforts. A longline mussel farm was taken as a local source of perturbation to the natural particulate organic carbon (POC) downward flux. This flux was first quantified by means of a pelagic model of POC deposition coupled to sediment trap data, and its effects on sediment bioirrigation capacity and organic matter (OM) degradation pathways were investigated constraining an early diagenesis model by using original data collected in sediment porewater. The measurements were performed at stations located inside and outside the area affected by mussel farm deposition. Model-predicted POC fluxes showed marked spatial and temporal variability, which was mostly associated with the dynamics of the farming cycle. Sediment trap data at the two sampled stations (inside and outside of the mussel farm) showed average POC background flux of 20.0-24.2 mmol C m-2 d-1. The difference of organic carbon (OC) fluxes between the two stations was in agreement with model results, ranging between 3.3 and 14.2 mmol C m-2 d-1, and was primarily associated with mussel physiological conditions. Although restricted, these changes in POC fluxes induced visible effects on sediment biogeochemistry. Observed oxygen microprofiles presented a 50 % decrease in oxygen penetration depth (from 2.3 to 1.4 mm), accompanied by an increase in the O2 influx at the station below the mussel farm (19-31 versus 10-12 mmol O2 m-2 d-1) characterised by higher POC flux. Dissolved inorganic carbon (DIC) and NH4+ concentrations showed similar behaviour, with a more evident effect of bioirrigation underneath the farm. This was confirmed through constraining the early diagenesis model, of which calibration leads to an estimation of enhanced and shallower bioirrigation underneath the farm: bioirrigation rates of 40 yr-1 and irrigation depth of 15 cm were

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

    Science.gov (United States)

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

    2013-04-01

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

  6. Suspended-sediment flux and retention in a backwater tidal slough complex near the landward boundary of an estuary

    Science.gov (United States)

    Morgan-King, Tara L.; Schoellhamer, David H.

    2013-01-01

    Backwater tidal sloughs are commonly found at the landward boundary of estuaries. The Cache Slough complex is a backwater tidal region within the Upper Sacramento–San Joaquin Delta that includes two features that are relevant for resource managers: (1) relatively high abundance of the endangered fish, delta smelt (Hypomesus transpacificus), which prefers turbid water and (2) a recently flooded shallow island, Liberty Island, that is a prototype for habitat restoration. We characterized the turbidity around Liberty Island by measuring suspended-sediment flux at four locations from July 2008 through December 2010. An estuarine turbidity maximum in the backwater Cache Slough complex is created by tidal asymmetry, a limited tidal excursion, and wind-wave resuspension. During the study, there was a net export of sediment, though sediment accumulates within the region from landward tidal transport during the dry season. Sediment is continually resuspended by both wind waves and flood tide currents. The suspended-sediment mass oscillates within the region until winter freshwater flow pulses flush it seaward. The hydrodynamic characteristics within the backwater region such as low freshwater flow during the dry season, flood tide dominance, and a limited tidal excursion favor sediment retention.

  7. Suspended sediment fluxes in a tropical estuary, west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    AnilKumar, N.; DineshKumar, P.K.; Srinivas, K.

    Annual transport processes of suspended sediments in Beypore estuary - a tropical estuary along the south west coast of India - were investigated based on time series measurements within the system. It's observed that the sediment transport...

  8. Sediment-water chemical exchange in the coastal zone traced by in situ radon-222 flux measurements

    International Nuclear Information System (INIS)

    Martens, C.S.; Kipphut, G.W.; Klump, J.V.

    1980-01-01

    In situ radon-222 flux experiments conducted in benthic chambers in Cape Lookout Bight, a small marine basin on the North Carolina coast, reveal that enhanced chemical transport across the sediment-water interface during summer months is caused by abiogenic bubble tube structures. Transport rates for dissolved radon, methane, and ammonium more than three times greater than those predicted on the basis of molecular diffusion occur when open tubes are maintained by semidiurnal low-tide bubbling

  9. Anthropogenic radionuclide fluxes and distribution in bottom sediments of the cooling basin of the Ignalina Nuclear Power Plant

    International Nuclear Information System (INIS)

    Marčiulionienė, D.; Mažeika, J.; Lukšienė, B.; Jefanova, O.; Mikalauskienė, R.; Paškauskas, R.

    2015-01-01

    anthropogenic factors resulting in mixing, resuspension and remobilization of sediments and radionuclides. The associated with particles 137 Cs flux was 129 Bq/(m 2  year). The 137 Cs transfer rate from water into bottom sediments was 14.3 year −1 (or, the removal time was 25 days). The K d value for 137 Cs in situ estimated from trap material was 80 m 3 /kg. The associated with particles 60 Co flux was 21 Bq/(m 2  year), when 60 Co activity concentration in sediment trap particles was 15.7 ± 5 Bq/kg. 60 Co activity concentration in soluble form was less than the minimum detectable activity (MDA = 1.3 Bq/m 3 ). Then, the conservatively derived K d value for 60 Co was >90 m 3 /kg. - Highlights: • Radionuclides activity concentrations in bottom sediments were studied during the entire operational period of the INPP. • Activation products ( 60 Co and 54 Mn) were already observed in the impact zones of effluent channels in 1988. • 137 Cs was distributed quite evenly in the bottom sediments at the investigated monitoring stations. • The highest activity concentrations of 137 Cs in 1988–1989 may have been the result of inputs from the Chernobyl accident. • The vertical distribution of radionuclides in bottom sediments revealed complicated sedimentation features

  10. Research on the neutron flux, secular equilibrium of chlorine-36 and groundwater age of the deep quaternary sediments, Hebei plain

    International Nuclear Information System (INIS)

    Dong Yuean; He Ming; Jiang Songsheng; Wu Shaoyong; Jiang Shan

    2001-01-01

    For the study of the neutron flux, secular equilibrium of chlorine-36 in the deep quaternary sediments of Hebei plain, the main chemical composition of water sand and confining bed was determined by neutron activation analysis. The mean neutron flux is 2.79 x 10 -5 cm -2 s -1 which was calculated by the chemical composition of the strata. The mean 36 Cl/Cl ratio in secular equilibrium is 1.27 x 10 -14 in the deep quaternary sediments, Hebei Plain. For the study of the groundwater age of the deep Quaternary sediments of Hebei Plain, the 36 Cl/Cl ratio of groundwater samples were determined by tandem accelerator mass spectrometry. The mixed groundwater 36 Cl/Cl ratio of the second and the third aquifer of Quaternary sediments in Baoding district is 247 x 10 -15 , that of the fourth aquifer in Baoding city is 224 x 10 -15 and the third aquifer in Cangzhou district is 40.5 x 10 -15 . The groundwater age of Baoding district was young and that of the third aquifer in Cangzhou was 229.2 ka

  11. Diffusive flux of PAHs across sediment-water and water-air interfaces at urban superfund sites.

    Science.gov (United States)

    Minick, D James; Anderson, Kim A

    2017-09-01

    Superfund sites may be a source of polycyclic aromatic hydrocarbons (PAHs) to the surrounding environment. These sites can also act as PAH sinks from present-day anthropogenic activities, especially in urban locations. Understanding PAH transport across environmental compartments helps to define the relative contributions of these sources and is therefore important for informing remedial and management decisions. In the present study, paired passive samplers were co-deployed at sediment-water and water-air interfaces within the Portland Harbor Superfund Site and the McCormick and Baxter Superfund Site. These sites, located along the Willamette River (Portland, OR, USA), have PAH contamination from both legacy and modern sources. Diffusive flux calculations indicate that the Willamette River acts predominantly as a sink for low molecular weight PAHs from both the sediment and the air. The sediment was also predominantly a source of 4- and 5-ring PAHs to the river, and the river was a source of these same PAHs to the air, indicating that legacy pollution may be contributing to PAH exposure for residents of the Portland urban center. At the remediated McCormick and Baxter Superfund Site, flux measurements highlight locations within the sand and rock sediment cap where contaminant breakthrough is occurring. Environ Toxicol Chem 2017;36:2281-2289. © 2017 SETAC. © 2017 SETAC.

  12. Soil erosion and sediment fluxes analysis: a watershed study of the Ni Reservoir, Spotsylvania County, VA, USA.

    Science.gov (United States)

    Pope, Ian C; Odhiambo, Ben K

    2014-03-01

    Anthropogenic forces that alter the physical landscape are known to cause significant soil erosion, which has negative impact on surface water bodies, such as rivers, lakes/reservoirs, and coastal zones, and thus sediment control has become one of the central aspects of catchment management planning. The revised universal soil loss equation empirical model, erosion pins, and isotopic sediment core analyses were used to evaluate watershed erosion, stream bank erosion, and reservoir sediment accumulation rates for Ni Reservoir, in central Virginia. Land-use and land cover seems to be dominant control in watershed soil erosion, with barren land and human-disturbed areas contributing the most sediment, and forest and herbaceous areas contributing the least. Results show a 7 % increase in human development from 2001 (14 %) to 2009 (21.6 %), corresponding to an increase in soil loss of 0.82 Mg ha(-1) year(-1) in the same time period. (210)Pb-based sediment accumulation rates at three locations in Ni Reservoir were 1.020, 0.364, and 0.543 g cm(-2) year(-1) respectively, indicating that sediment accumulation and distribution in the reservoir is influenced by reservoir configuration and significant contributions from bedload. All three locations indicate an increase in modern sediment accumulation rates. Erosion pin results show variability in stream bank erosion with values ranging from 4.7 to 11.3 cm year(-1). These results indicate that urban growth and the decline in vegetative cover has increased sediment fluxes from the watershed and poses a significant threat to the long-term sustainability of the Ni Reservoir as urbanization continues to increase.

  13. Dynamics of dissolved organic matter in riverine sediments affected by weir impoundments: Production, benthic flux, and environmental implications.

    Science.gov (United States)

    Chen, Meilian; Kim, Sung-Han; Jung, Heon-Jae; Hyun, Jung-Ho; Choi, Jung Hyun; Lee, Hyo-Jin; Huh, In-Ae; Hur, Jin

    2017-09-15

    In order to understand the characteristics and dynamics of dissolved organic matter (DOM) in the sediment of rivers affected by impoundments, we examined the vertical profiles and the benthic fluxes of DOM in four different core sediments located at upstream sites of weirs in major rivers of South Korea. In three out of four sites, exponential accumulation of dissolved organic carbon (DOC) with depth was observed with the signature of seasonal variability. Except for the site displaying a below-detection limit of Fe(II), the general accumulation trends of DOC with depth was concurrent with the increases of Fe(II) and NH 4 + and the decrease of PO 4 3- , signifying a close linkage of the DOM dynamics with anaerobic respiration via iron reduction, an important early diagenesis pathway. The estimated benthic fluxes from the cores revealed that the sediments likely serve as DOC, chromophoric DOM (CDOM), and fluorescent DOM (FDOM) sources to the overlying water. The benthic effluxes based on DOC were comparable to the ranges previously reported in lake and coastal areas, and those of CDOM and FDOM showed even higher levels. These findings imply that impoundment-affected river systems would change the DOM composition of the overlying water, ultimately influencing the subsequent water treatment processes such as disinfection byproducts production and membrane fouling. A simple mass balance model indicated that the impoundment-affected river sediments may operate as a net carbon sink in the environments due to a greater extent of sedimentation compared to the estimated benthic efflux and sediment biological respiration. Copyright © 2017 Elsevier Ltd. All rights reserved.

  14. Benthic flux of dissolved organic matter from lake sediment at different redox conditions and the possible effects of biogeochemical processes.

    Science.gov (United States)

    Yang, Liyang; Choi, Jung Hyun; Hur, Jin

    2014-09-15

    The benthic fluxes of dissolved organic carbon (DOC), chromophoric and fluorescent dissolved organic matter (CDOM and FDOM) were studied for the sediment from an artificial lake, based on laboratory benthic chamber experiments. Conservative estimates for the benthic flux of DOC were 71 ± 142 and 51 ± 101 mg m(-2) day(-1) at hypoxic and oxic conditions, respectively. Two humic-like (C1 and C2), one tryptophan-like (C3), and one microbial humic-like (C4) components were identified from the samples using fluorescence excitation emission matrices and parallel factor analysis (EEM-PARAFAC). During the incubation period, C3 was removed while C4 was accumulated in the overlying water with no significant difference in the trends between the redox conditions. The humification index (HIX) increased with time. The combined results for C3, C4 and HIX suggested that microbial transformation may be an important process affecting the flux behaviors of DOM. In contrast, the overall accumulations of CDOM, C1, and C2 in the overlying water occurred only for the hypoxic condition, which was possibly explained by their enhanced photo-degradation and sorption to redox-sensitive minerals under the oxic condition. Our study demonstrated significant benthic flux of DOM in lake sediment and also the possible involvement of biogeochemical transformation in the processes, providing insight into carbon cycling in inland waters. Copyright © 2014 Elsevier Ltd. All rights reserved.

  15. Radiolarian fluxes from the southern Bay of Bengal: sediment trap results

    Digital Repository Service at National Institute of Oceanography (India)

    Gupta, S.M.; Mohan, R; Guptha, M.V.S.

    the monsoonal rainfall. Higher radiolarian fluxes occurred during March-May, when moderate salinity and a high sea surface temperature (SST) regime prevailed at the trap site. R-mode cluster analysis of the radiolarian flux data revealed three assemblages...

  16. Comparisons between POC and zooplankton swimmer flux from sediment traps in the subarctic and subtropical North Pacific

    Science.gov (United States)

    Yokoi, Naoya; Abe, Yoshiyuki; Kitamura, Minoru; Honda, Makio C.; Yamaguchi, Atsushi

    2018-03-01

    Seasonal changes in zooplankton swimmer (ZS) abundance, biomass and community structure were evaluated based on samples collected by moored sediment traps at a depth of 200 m in the subarctic (SA) and subtropical (ST) western North Pacific. Based on these samples, we made comparisons on two topics: 1) latitudinal (subarctic vs. subtropical) changes in ZS abundance, biomass and community and 2) quantitative differences between the ZS and particle organic carbon (POC) fluxes based on data from moored or drifting sediment traps. The results showed that the ZS flux was greater in the SA (annual mean: 311 ind. m-2 day-1 or 258 mg C m-2 day-1) than in the ST (135 ind. m-2 day-1 or 38 mg C m-2 day-1). The peak ZS flux was observed from July-August in the SA and from April-May in the ST. The dominant taxa were Copepoda and Chaetognatha in the SA and Ostracoda and Mollusca in the ST. These latitudinal differences are likely related to the dominance of large-sized Copepoda in the SA, regional differences in the timing of the spring phytoplankton bloom, and the magnitude and size structure of primary producers. The percent composition of ZS to the total C flux (= ZS+POC flux) varied by region: 85-95% in the SA and 47-75% in the ST. These differences between the ZS composition and the total C flux are most likely caused by the dominance of large-sized Copepoda (Neocalanus spp. and Eucalanus bungii) in the SA.

  17. Sediment Flux and Storage in a Rural Southeastern Piedmont River System

    Science.gov (United States)

    Jackson, C. R.; Martin, J. K.

    2001-12-01

    A sediment budget was developed for a representative rural southeastern Piedmont watershed to provide information on the relative importance of sediment sources. Sediment issues in the southeastern Piedmont are complicated by the so-called legacy sediment produced by poor farming practices during the cotton-farming era, approximately 1810-1930. The Murder Creek basin near Monticello, GA was chosen because: it featured forestry and agriculture as the principal land uses; a USGS gage provided a flow record; and the creek deposited in a reservoir built in 1948. Suspended load export was calculated using a sediment rating curve and the USGS flow time series. Bed load export was determined by estimating the volume of sediment deposited in the reservoir since construction. Unpaved road erosion was estimated using the WEPP model, and other surface erosion was estimated using USLE and delivery ratios. Historical floodplain storage was determined by coring floodplain deposits, measuring the depth to the pre-historic/historic sediment interface, and multiplying by the area of the floodplain. Recent accretion rates were estimated using dendrogeomorphology. Results showed that the practices of the cotton farming era deposited an average of 1.6 meters of sediment on the floodplains. This depth was relatively uniform across the watershed. The cotton-farming sediment in storage exceeds the current annual export by a factor of about 5000. Approximately half of the current export comes from current inputs, and half comes from remobilized floodplain sediments.

  18. An update of the sediment fluxes investigation in the Rio Cordon (Italy after 25 years of monitoring

    Directory of Open Access Journals (Sweden)

    Lorenzo Picco

    2012-12-01

    Full Text Available Quantification of bed-load transport in high-gradient mountain streams is important, but the field data needed to test transport models are scarce and difficult to obtain. In the present study, we describe the experimental station for monitoring water and sediment fluxes built in 1985 on the Rio Cordon, a small step-pool channel in the eastern Italian Alps. The measuring station consists of an inclined frame that separates fine from coarse sediments (D>20 mm, which are continuously measured by a series of ultrasonic sensors fitted above a storage area. The acquired 25-year dataset, which comprises a high-magnitude/ low-recurrence flood event, has allowed a magnitude-frequency analysis of bed-load volumes to be performed. Results from a combined frequency analysis of peak water discharge and total bed-load volumes are presented. In addition, the integration between the sediment transport dataset and the repeated surveys of sediment sources and of channel changes allowed us to assess the geomorphological effectiveness of different flood events. Despite the importance of the experimental station for making these bed-load observations possible, its maintenance costs are not low and these may have an impact on its future existence. At the same time, improving current instrumentation and future installations with novel technology would make the station an ideal location for calibrating surrogate techniques for sediment transport monitoring.

  19. Persistent toxic substances in remote lake and coastal sediments from Svalbard, Norwegian Arctic: Levels, sources and fluxes

    International Nuclear Information System (INIS)

    Jiao Liping; Zheng, Gene J.; Minh, Tu Binh; Richardson, Bruce; Chen Liqi; Zhang Yuanhui; Yeung, Leo W.; Lam, James C.W.; Yan, Xulin; Lam, Paul K.S.; Wong, Ming H.

    2009-01-01

    Surface sediments from remote lakes and coastal areas from Ny-Alesund, Svalbard, Norwegian Arctic were analyzed for polycyclic aromatic hydrocarbons (PAHs), polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs). Relatively high levels of PAHs were encountered from several lakes from Ny-Alesund, which were within the range of levels reported for European high mountain lakes and some urban/industrialized areas in the world, pointing to the role of remote Arctic lakes as potential reservoir of semi-volatile organic compounds. Specific patterns of PBDEs were observed, showing higher concentrations of lower brominated compounds such as BDE-7, 17 and 28. Estimated surface sediment fluxes of PAHs in Ny-Alesund remote lakes were similar to those observed for some European high mountain lakes. The current PAH levels in sediments from three lakes exceeded Canadian sediment quality guidelines, suggesting the presence of possible risks for aquatic organisms and the need for further studies. - High levels of PAHs and specific patterns of PBDEs were found in sediments from the remote Norwegian Arctic lakes

  20. Catch and Release: A dense, longitudinal array of water quality sondes reveals spatial and temporal complexities in suspended sediment flux

    Science.gov (United States)

    Guilinger, J. J.; Crosby, B. T.

    2017-12-01

    Excessive suspended sediment in streams is one of the most common causes for industrial, ecological and recreational stream impairment in the US. Identifying the primary geomorphic or anthropogenic sources of sediment is a key step in the effective mitigation of impairment. This study seeks to identify sources of suspended sediment in an agriculturally impaired watershed, Marsh Creek, in southeast Idaho. We employ thirteen multi-parameter water quality sensors to simultaneously measure stage, turbidity, temperature and conductivity every 15 minutes over a full calendar year. Examined at both the event and annual scale, these data enable mass balance calculations for mainstem and tributary contributions. Revealed in this monitoring is an approximately eight-fold longitudinal increase in sediment flux over 74 km that is largely augmented by eroding mainstem banks in reaches with higher stream power in the lower 30 km, with less than 20% contributed from tributaries. Independent data confirming the bank source were acquired through cost-effective sediment fingerprinting using 15N and C:N signatures from potential soil endmembers. Additionally, Google Street View-type longitudinal imagery of banks was collected via a kayak survey to confirm the spatial extent and magnitude of bank erosion along Marsh Creek. These data converge on bank erosion as the primary source of fine sediment. Sediment load at various hierarchical temporal and spatial scales is impacted by in-stream storage and remobilization, especially over shorter timescales ranging from daily to seasonal periods. Once averaged over the annual scale, local, temporary in-channel storage is overcome and these data reveal source reaches that can be prioritized for restoration and mitigation projects.

  1. Direct contribution of clams (Ruditapes philippinarum) to benthic fluxes, nitrification, denitrification and nitrous oxide emission in a farmed sediment

    Science.gov (United States)

    Welsh, David T.; Nizzoli, Daniele; Fano, Elisa A.; Viaroli, Pierluigi

    2015-03-01

    The influence of the manila clam (Ruditapes philippinarum) on N-cycle processes, and oxygen and nutrient fluxes in a farmed sediment was investigated using a multiple core incubation approach and parallel incubations of individual clams. Clam population/biomass density varied ∼8-fold between cores and all sediment-water column solute (O2. N2, N2O, NH4+, NOX and DIN) fluxes and benthic process (N-regeneration, nitrification and denitrification) rates were strongly and significantly correlated with clam density/biomass. Isolated clams exhibited high rates of respiration, N-excretion, nitrification and denitrification of 2050 ± 70, 395 ± 49, 201 ± 42 and 235 ± 40 nmol individual-1 h-1, respectively. The direct contribution of the clams and their associated microbiota to benthic processes was estimated by multiplying the per individual rates by the number of clams in each incubated core. The clams on average directly accounted for 64-133% of total rates of sediment oxygen demand, N-regeneration, nitrification and denitrification, indicating that they regulated processes primarily through their own metabolic activity and that of bacteria that colonise them. Clams and the farmed sediments were significant sources of the greenhouse gas N2O, but this was primarily due to their high nitrification and denitrification rates, rather than high specific N2O yields, as N2O emissions represented farmed sediments had a high denitrification efficiency of 67 ± 10%, but this ecosystem service came at the environmental cost of increased N-regeneration and N2O emission rates. The measured N2O emissions indicate that bivalve aquaculture may be a significant source of N2O. It is therefore recommended that N2O emissions should be included in the impact assessments of current and future bivalve-farming projects.

  2. Bathypelagic particle flux signatures from a suboxic eddy in the oligotrophic tropical North Atlantic: production, sedimentation and preservation

    Science.gov (United States)

    Fischer, G.; Karstensen, J.; Romero, O.; Baumann, K.-H.; Donner, B.; Hefter, J.; Mollenhauer, G.; Iversen, M.; Fiedler, B.; Monteiro, I.; Körtzinger, A.

    2015-11-01

    Particle fluxes at the Cape Verde Ocean Observatory (CVOO) in the eastern tropical North Atlantic for the period December 2009 until May 2011 are discussed based on bathypelagic sediment trap time series data collected at 1290 and 3439 m water depth. The typically oligotrophic particle flux pattern with weak seasonality is modified by the appearance of a highly productive and low oxygen anticyclonic modewater eddy (ACME) in winter 2010. The eddy passage was accompanied by unusually high mass fluxes, lasting from December 2009 to May 2010. Distinct biogenic silica (BSi) and organic carbon flux peaks were observed in February-March 2010 when the eddy approached CVOO. The flux of the lithogenic component, mostly mineral dust, was well correlated to that of organic carbon in particular in the deep trap samples, suggesting a close coupling. The lithogenic ballasting obviously resulted in high particle settling rates and, thus, a fast transfer of epi-/mesopelagic signatures to the bathypelagic traps. Molar C : N ratios of organic matter during the ACME passage were around 18 and 25 for the upper and lower trap samples, respectively. This suggests that some production under nutrient (nitrate) limitation in the upper few tens of meters above the zone of suboxia might have occurred in the beginning of 2010. The δ15N record showed a decrease from January to March 2010 while the organic carbon and N fluxes increased. The causes of enhanced sedimentation from the eddy in February/March 2010 remain elusive but nutrient depletion and/or a high availability of dust as ballast mineral for organic-rich aggregates might have contributed to the elevated fluxes during the eddy passage. Remineralization of sinking organic-rich particles could have contributed to the formation of a suboxic zone at shallow depth. Although the eddy has been formed in the African coastal area in summer 2009, no indication of coastal flux signatures were found in the sediment traps, suggesting an

  3. Sedimentary record of water column trophic conditions and sediment carbon fluxes in a tropical water reservoir (Valle de Bravo, Mexico).

    Science.gov (United States)

    Carnero-Bravo, Vladislav; Merino-Ibarra, Martín; Ruiz-Fernández, Ana Carolina; Sanchez-Cabeza, Joan Albert; Ghaleb, Bassam

    2015-03-01

    Valle de Bravo (VB) is the main water reservoir of the Cutzamala hydraulic system, which provides 40% of the drinking water consumed in the Mexico City Metropolitan Area and exhibits symptoms of eutrophication. Nutrient (C, N and P) concentrations were determined in two sediment cores to reconstruct the water column trophic evolution of the reservoir and C fluxes since its creation in 1947. Radiometric methods ((210)Pb and (137)Cs) were used to obtain sediment chronologies, using the presence of pre-reservoir soil layers in one of the cores as an independent chronological marker. Mass accumulation rates ranged from 0.12 to 0.56 g cm(-2) year(-1) and total organic carbon (TOC) fluxes from 122 to 380 g m(-2) year(-1). Total N ranged 4.9-48 g m(-2) year(-1), and total P 0.6-4.2 g m(-2) year(-1). The sedimentary record shows that all three (C, N and P) fluxes increased significantly after 1991, in good agreement with the assessed trophic evolution of VB and with historic and recent real-time measurements. In the recent years (1992-2006), the TOC flux to the bottom of VB (average 250 g m(-2) year(-1), peaks 323 g m(-2) year(-1)) is similar to that found in highly eutrophic reservoirs and impoundments. Over 1/3 of the total C burial since dam construction, circa 70,000 t, has occurred in this recent period. These results highlight the usefulness of the reconstruction of carbon and nutrient fluxes from the sedimentary record to assess carbon burial and its temporal evolution in freshwater ecosystems.

  4. The flux of 226Ra from estuarine and continental shelf sediments

    International Nuclear Information System (INIS)

    Li, Y.H.; Mathieu, G.; Biscaye, P.; Simpson, H.J.

    1977-01-01

    A pronounced desorption phenomenon of 226 Ra from sediment was observed in the Hudson River estuary. Mass balance calculations indicate that the desorption of 226 Ra from the river-borne sediment in estuarine environment is an important source of 226 Ra to the oceans. (Auth.)

  5. The impact of electrogenic sulfide oxidation on elemental cycling and solute fluxes in coastal sediment

    NARCIS (Netherlands)

    Rao, A.M.F.; Malkin, S.Y.; Hidalgo-Martinez, S.; Meysman, Filip

    2016-01-01

    Filamentous sulfide oxidizing cable bacteria are capable of linking the oxidation of free sulfide in deep anoxic layers of marine sediments to the reduction of oxygen or nitrate in surface sediments by conducting electrons over centimeter-scale distances. Previous studies have shown that this newly

  6. Super(210) Pb based trace element fluxes in the nearshore and estuarine sediments off Bombay, India

    Digital Repository Service at National Institute of Oceanography (India)

    Sharma, P.; Borole, D.V.; Zingde, M.D.

    Seven sediment cores from the Thana Creek-Bombay harbour complex (THC) have been studied for excess super(210) Pb (super(210) Pb sub(exc), that portion of super(210) Pb not supported by decay of super(226) Ra in sediment), C sub(org), Mn, Fe, Co, Ni...

  7. Norway and adjacent sedimentary basins during Cenozoic times - sediment fluxes, accumulation rates and mass balance

    DEFF Research Database (Denmark)

    Gołędowski, Bartosz; Nielsen, S.B.; Clausen, O.R.

    2011-01-01

    use offshore data from adjacent sedimentary basins (the North Sea and the Norwegian shelf) to calculate the amount of erosion. We have used a broad dataset of seismic 2D lines to map depositional units and a well dataset for the stratigraphic control and the velocity distribution in the sediments. We...... have therefore obtained accumulation rates in meters per million years for 5 depositional units in three areas - Southern North Sea, Central and Northern North Sea and the Norwegian shelf. Furthermore, taking into account the decay of porosity in sediments with burial depth, we have estimated...... the sediment volumes at the time of their deposition. Such calculation gives minimum values of erosion rates onshore and a mass balance can be approximated, when considering uncertainties like deposition of sediments outside study area, post-depositional sediment removal and loss of mass due to chemical...

  8. Estimation of annual suspended-sediment fluxes, 1931-95, and evaluation of geomorphic changes, 1950-2010, in the Arkansas River near Tulsa, Oklahoma

    Science.gov (United States)

    Lewis, Jason M.; Smith, S. Jerrod; Buck, Stephanie D.; Strong, Scott A.

    2011-01-01

    An understanding of fluvial sediment transport and changing channel morphology can assist planners in making responsible decisions with future riverine development or restoration projects. Sediment rating curves can serve as simple models and can provide predictive tools to estimate annual sediment fluxes. Sediment flux models can aid in the design of river projects by providing insight to past and potential future sediment fluxes. Historical U.S. Geological Survey suspended-sediment and discharge data were evaluated to estimate annual suspended-sediment fluxes for two stations on the Arkansas River located downstream from Keystone Dam in Tulsa County. Annual suspended-sediment fluxes were estimated from 1931-95 for the Arkansas River at Tulsa streamflow-gaging station (07164500) and from 1973-82 for the Arkansas River near Haskell streamflow-gaging station (07165570). The annual flow-weighted suspended-sediment concentration decreased from 1,970 milligrams per liter to 350 milligrams per liter after the completion of Keystone Dam at the Tulsa station. The streambed elevation at the Arkansas River at Tulsa station has changed less than 1 foot from 1970 to 2005, but the thalweg has shifted from a location near the right bank to a position near the left bank. There was little change in the position of most of the banks of the Arkansas River channel from 1950 to 2009. The most substantial change evident from visual inspection of aerial photographs was an apparent decrease in sediment storage in the form of mid-channel and meander bars. The Arkansas River channel between Keystone Dam and the Tulsa-Wagoner County line showed a narrowing and lengthening (increase in sinuosity) over the transition period 1950-77 followed by a steady widening and shortening of the river channel (decrease in sinuosity) during the post-dam (Keystone) periods 1977-85, 1985-2003, and 2003-10.

  9. Flux

    DEFF Research Database (Denmark)

    Ravn, Ib

    . FLUX betegner en flyden eller strømmen, dvs. dynamik. Forstår man livet som proces og udvikling i stedet for som ting og mekanik, får man et andet billede af det gode liv end det, som den velkendte vestlige mekanicisme lægger op til. Dynamisk forstået indebærer det gode liv den bedst mulige...... kanalisering af den flux eller energi, der strømmer igennem os og giver sig til kende i vore daglige aktiviteter. Skal vores tanker, handlinger, arbejde, samvær og politiske liv organiseres efter stramme og faste regelsæt, uden slinger i valsen? Eller skal de tværtimod forløbe ganske uhindret af regler og bånd...

  10. Modelling biogeochemical processes in sediments from the north-western Adriatic Sea: response to enhanced particulate organic carbon fluxes

    Directory of Open Access Journals (Sweden)

    D. Brigolin

    2018-03-01

    Full Text Available This work presents the result of a study carried out in the north-western Adriatic Sea, by combining two different types of biogeochemical models with field sampling efforts. A longline mussel farm was taken as a local source of perturbation to the natural particulate organic carbon (POC downward flux. This flux was first quantified by means of a pelagic model of POC deposition coupled to sediment trap data, and its effects on sediment bioirrigation capacity and organic matter (OM degradation pathways were investigated constraining an early diagenesis model by using original data collected in sediment porewater. The measurements were performed at stations located inside and outside the area affected by mussel farm deposition. Model-predicted POC fluxes showed marked spatial and temporal variability, which was mostly associated with the dynamics of the farming cycle. Sediment trap data at the two sampled stations (inside and outside of the mussel farm showed average POC background flux of 20.0–24.2 mmol C m−2 d−1. The difference of organic carbon (OC fluxes between the two stations was in agreement with model results, ranging between 3.3 and 14.2 mmol C m−2 d−1, and was primarily associated with mussel physiological conditions. Although restricted, these changes in POC fluxes induced visible effects on sediment biogeochemistry. Observed oxygen microprofiles presented a 50 % decrease in oxygen penetration depth (from 2.3 to 1.4 mm, accompanied by an increase in the O2 influx at the station below the mussel farm (19–31 versus 10–12 mmol O2 m−2 d−1 characterised by higher POC flux. Dissolved inorganic carbon (DIC and NH4+ concentrations showed similar behaviour, with a more evident effect of bioirrigation underneath the farm. This was confirmed through constraining the early diagenesis model, of which calibration leads to an estimation of enhanced and shallower bioirrigation underneath the farm

  11. Flux Meter Assesses the Effects of Groundwater, Surface Water, and Contaminated Sediment Interactions on Ecosystems

    Science.gov (United States)

    The slow flow of water between groundwater (GW) and surface water (SW) is often referred to as seepage, or in scientific terms, advective flux. This slow flow at the GW/SW interface presents measurement difficulties. This project was conducted to develop a durable advective flux ...

  12. Flocculation alters the distribution and flux of melt-water supplied sediments and nutrients in the Arctic

    DEFF Research Database (Denmark)

    Markussen, Thor Nygaard; Andersen, Thorbjørn Joest; Ernstsen, Verner Brandbyge

    In the Arctic, thawing permafrost and increased melting of glaciers are important drivers for changes in fine-grained sediment supply and biogeochemical fluxes from land to sea. Flocculation of particles is a controlling factor for the magnitude of fluxes and deposition rates in the marine...... environment but comparatively little is known about the flocculation processes in the Arctic. We investigated flocculation dynamics from a melt-water river in the inner Disko Fjord, West Greenland. A novel, laser-illuminated camera system significantly improved the particle size measurement capabilities...... and settling tubes were sampled to enable sub-sampling of different floc size fractions. Flocculation was observed during periods with low turbulent shear and also at the front of the fresh water plume resulting in significant volumes of large sized flocs at depth below the plume. The floc sizes and volumes...

  13. Influence of tubificid worms on nutrient fluxes across water-sediment interface in fish farm settling ponds

    Directory of Open Access Journals (Sweden)

    Puigagut J.

    2014-04-01

    Full Text Available The influence of tubificid worms on nutrient translocation from water to fish farm sediments accumulating in settling ponds was addressed under laboratory conditions. Small microcosms of 0.5 L were filled up with 35 g of sludge from a fish farm settling pond and 0.15 L of filtered settling pond water. The experimental set up consisted of one control line (no worms added, a second experimental line with 1 mg of tubificid worms·g-1 fresh sediment (550 individuals·m-2 and a third experimental line with 40 mg of tubificid worms·g-1 fresh sediment (22 000 individuals·m-2. Nutrients translocation was determined by monitoring overlaying water concentration of ammonia, nitrate and phosphate for ten days. Results showed that abundances of 550 individuals·m-2 had no significant influence on the fluxes of nutrients here considered. However, the influence of higher abundances of tubificids (22 000 individuals·m-2 was of significant extent on the translocation of nitrate and phosphate. Accordingly, bioturbation of tubificids caused 55% lower nitrate uptake by the sediment when compared to control conditions. Phosphorus released by the sediments of the control condition was ca. 90% higher than that recorded under abundances of tubificids (22 000 individuals·m-2. Results obtained allowed us to estimate that fish farm settling ponds highly colonized by tubificid worms (22 000 individuals·m-2 may contribute to decrease phosphorus discharge (in terms of soluble phosphorus in ca. 5 g of P·ton-1 of fish produced.

  14. Research Note:Effects of human activities on the Yangtze River suspended sediment flux into the estuary in the last century

    Directory of Open Access Journals (Sweden)

    S. L. Yang

    2004-01-01

    Full Text Available The surface erosion area in the Yangtze River basin increased from 364×103 km2 in the 1950s to 707×103 km2 in 2001 due to a great increase in population. Based on the regression relationship between surface erosion area and population, the surface erosion area was predicted to be about 280×103 km2 at the beginning of the 20th century. The sediment yield, which increased by about 30% during the first six decades of the 20th century, was closely related to the surface erosion area in this river basin. The Yangtze annual suspended sediment flux into the estuary was about 395×106 t a-1 at the beginning of the century, and this gradually increased to an average of 509×106 t a-1 in the 1960s. The increase in the suspended sediment flux into the estuary was accelerated in the 1950s and the 1960s due to the rapid increase in population and land use immediately after the Second World War and the Liberation War. After the riverine suspended sediment flux reached its maximum in the 1960s, it decreased to 6 t a-1 in 2003. Construction of dams was found to be the principal cause for this decreasing trend because, during the same period, (a the riverine water discharge did not show a decreasing trend, (b water diversion was not influential and (c sedimentation in lakes and canals of the middle and lower reaches did not increase. The total storage capacity of reservoirs has increased dramatically over the past half century. The amount of sediment trapped in reservoirs has increased to more than half a billion t a-1. As a result, the suspended sediment flux into the estuary dramatically decreased, even though the sediment yield from many areas of the basin increased in recent decades. Human activities gradually increased the suspended sediment flux into the estuary before the 1960s and then rapidly decreased it. The last century was a period when the Yangtze suspended sediment flux into the estuary was dramatically affected by human activities. Keywords

  15. The flux and recovery of bioactive substances in the surface sediments of deep basins off southern California

    Energy Technology Data Exchange (ETDEWEB)

    Jahnke, R.A.

    1990-06-11

    Sediment microbial community biomass and activity in Santa Monica Basin, a nearshore basin in the California Continental Borderland, were examined in October 1985, 1986 and 1987, May 1986, April 1987 and January 1990. Millimeter-scale ATP profiles and incubation of intact cores with {sup 3}H-adenine indicated a high-biomass interface microbial population in the low-oxygen central basin, which was absent in samples from the basin slope sediments. A majority of microbial activity and organic matter mineralization occurred in the top cm of sediment. Comparison of measured ATP and total organic carbon profiles suggest that the C:ATP ratio (wt:wt) ranges between 47:1 and 77:1 in central basin interfacial populations, substantially lower than reported for other aquatic environments. Carbon production estimated from DNA synthesis measurements via {sup 3}H-adenine incorporation was compared with TCO{sub 2} fluxes measured by in situ benthic chamber experiments. Within the uncertainty of the C:ATP ratio, an overall microbial carbon assimilation efficiency of 75--90% was indicated. The low C:ATP ratios and high carbon assimilation efficiencies significantly affect estimates of microbial growth and respiration and are substantially different than those often assumed in the literature. These results suggest that without independent knowledge of these ratios, the uncertainty in tracer-derived microbial growth and respiration rates may be larger than previously reported. 66 refs., 8 figs., 3 tabs.

  16. The flux and recovery of bioactive substances in the surface sediments of deep basins off southern California

    International Nuclear Information System (INIS)

    Jahnke, R.A.

    1990-01-01

    Sediment microbial community biomass and activity in Santa Monica Basin, a nearshore basin in the California Continental Borderland, were examined in October 1985, 1986 and 1987, May 1986, April 1987 and January 1990. Millimeter-scale ATP profiles and incubation of intact cores with 3 H-adenine indicated a high-biomass interface microbial population in the low-oxygen central basin, which was absent in samples from the basin slope sediments. A majority of microbial activity and organic matter mineralization occurred in the top cm of sediment. Comparison of measured ATP and total organic carbon profiles suggest that the C:ATP ratio (wt:wt) ranges between 47:1 and 77:1 in central basin interfacial populations, substantially lower than reported for other aquatic environments. Carbon production estimated from DNA synthesis measurements via 3 H-adenine incorporation was compared with TCO 2 fluxes measured by in situ benthic chamber experiments. Within the uncertainty of the C:ATP ratio, an overall microbial carbon assimilation efficiency of 75--90% was indicated. The low C:ATP ratios and high carbon assimilation efficiencies significantly affect estimates of microbial growth and respiration and are substantially different than those often assumed in the literature. These results suggest that without independent knowledge of these ratios, the uncertainty in tracer-derived microbial growth and respiration rates may be larger than previously reported. 66 refs., 8 figs., 3 tabs

  17. Fluvial export of radionuclides: impact on sediment storages of the Rhone River and fluxes towards the Mediterranean Sea

    International Nuclear Information System (INIS)

    Rolland, B.

    2006-02-01

    This study deals with the behaviour of trace contaminants originating from chronic liquid releases within fluvial aquatic systems. It focuses on some particle reactive artificial radionuclides that were released by the Marcoule nuclear fuel reprocessing plant during several years mainly prior the end of the nineties and that are still detected in the lower Rhone river. It underlines the decrease of 137 Cs, 238 Pu and 239+240 Pu fluxes to the Mediterranean Sea in relation with the variations in the chronic liquid releases from Marcoule. The role of flood events on radionuclides exports processes is particularly considered. Over the years 2002 to 2004, floods contributed for 67%, 55%, 68%, 49% and 56% of the mean annual fluxes of 137 Cs, 238 Pu and 239+240 Pu and natural 7 Be et 210 Pbxs, although these events only represented 5% of time. The removal, during floods, of sediments contaminated by the Marcoule releases contributes on the average for 19%, 44% and 22% of the annual exports of 137 Cs, 238 Pu and 239+240 Pu towards the Sea. Thus, such sedimentary stocks act as a delayed source term of artificial radioactivity that is currently significant. Determination of the sediments residence times before removal allows to evaluate the Rhone capacity to clear its contaminated stocks. Residence times of 200 years, 100 years and 900 years are estimated to be necessary to totally remove the accumulated 137 Cs, 238 Pu and 239+240 Pu, respectively. The location typologies of sediment storages within fluvial systems are also specified. These location are represented on one hand by dams, and on the other hand by river banks and oxbow lakes. Stocks accumulated in dams seem to be removed more easily than those trapped in banks. (author)

  18. Sedimentation

    Digital Repository Service at National Institute of Oceanography (India)

    Rixen, T.; Guptha, M.V.S.; Ittekkot, V.

    opal ratios. Such changes are assumed to have lowered the atmospheric CO sub(2) concentration significantly during glacial times. The differences between estimated deep ocean fluxes derived from satellite data and measured deep fluxes are lower than...

  19. Muddied Waters: the case for mitigating sediment and nutrient flux to optimise restoration response in the Murray-Darling Basin, Australia.

    Directory of Open Access Journals (Sweden)

    Peter Andrew Gell

    2016-03-01

    Full Text Available The waters of the Murray Darling Basin, Australia, have endured multiple stressors for more than a century. Detectable salinisation impacts are evident from 1880 CE and elevated fluxes of sediments and nutrients are now widespread. Most wetlands examined paleolimnologically have shown increased sedimentation rates or have lost aquatic plant communities due to the shading effect of increased turbidity, prompting the observation that the waterways of the Murray Darling Basin are among ten Australian ecosystems most at risk from tipping points. This post-European heightened sediment flux threatens the potential ecological recovery from the application of scarce and expensive environmental water. Nutrients and fine sediments are implicated as drivers of regime shifts that advantage phytoplankton and inhibit the growth of productive macrophyte beds. However, with the river channels identified as likely sources of sediments and sediment-bound phosphorous, it remains possible that the documented ecological changes represent an ongoing response from continued doses from the River. Syntheses of multiple paleolimnological records provide evidence for the management focus to be on sediment supply to maximise the ecological benefit from environmental flow allocations. Here we use paleolimnology to examine in detail the nature and magnitude of the response in a subset of 17 wetlands, to propose means of optimising the ecological bounce from the release of river waters, encumbered with high doses of sediments and nutrients, to wetlands and floodplains.

  20. Nitrous oxide and methane fluxes vs. carbon, nitrogen and phosphorous burial in new intertidal and saltmarsh sediments

    Energy Technology Data Exchange (ETDEWEB)

    Adams, C.A., E-mail: christopher.adams@uea.ac.uk; Andrews, J.E.; Jickells, T.

    2012-09-15

    Carbon (C), nitrogen (N) and phosphorous (P) burial rates were determined within natural saltmarsh (NSM) and 'managed realignment' (MR) sediments of the Blackwater estuary, UK. Methane (CH{sub 4}) and nitrous oxide (N{sub 2}O) fluxes were measured along with their ability to offset a portion of the C burial to give net C sequestration. C and N densities (C{rho} and N{rho}) of NSM sediments (0.022 and 0.0019 g cm{sup -3}) are comparable to other UK NSM sediments. Less vegetationally developed MR sediments have lower C{rho} and N{rho} (0.012 and 0.0011 g cm{sup -3}) while the more vegetationally developed sites possess higher C{rho} and N{rho} (0.023 and 0.0030 g cm{sup -3}) than NSM. Both NSM and MR areas were small CH{sub 4} (0.10-0.40 g m{sup -2} yr{sup -1}) and N{sub 2}O (0.03-0.37 g m{sup -2} yr{sup -1}) sources. Due to their large Global Warming Potentials, even these relatively small greenhouse gas (GHG) fluxes reduced the net C sequestration within MR marshes by as much as 49%, but by only 2% from NSM. Potential MR areas within the Blackwater estuary (29.5 km{sup 2} saltmarsh and 23.7 km{sup 2} intertidal mudflat) could bury 5478 t C yr{sup -1} and 695.5 t N yr{sup -1}, with a further 476 t N yr{sup -1} denitrified. The saltmarsh MR would also sequester 139.4 t P yr{sup -1}. GHG fluxes would reduce the C burial benefit by 24% giving a C sequestration rate of 4174 t C yr{sup -1}. Similar areas within the Humber estuary (74.95 km{sup 2}) could bury 3597 t C yr{sup -1} and 180 t N yr{sup -1}, with a further 442 t N yr{sup -1} denitrified. GHG fluxes would reduce the C burial benefit by 31% giving a C sequestration rate of 2492 t C yr{sup -1}. Overall, MR sites provide sustainable coastal defence options with significant biogeochemical value and, despite being net sources of CH{sub 4} and N{sub 2}O, can sequester C and reduce estuarine nutrient loads. -- Highlights: Black-Right-Pointing-Pointer We investigated C, N, P, CH{sub 4} and N{sub 2}O fluxes

  1. Using UAVSAR Interferometry to Quantify the Geometry and Sediment Flux of Slow-moving Landslides in the Eel River Catchment, Northern California

    Science.gov (United States)

    Handwerger, A. L.; Huang, M. H.; Booth, A. M.; Fielding, E. J.

    2017-12-01

    Slow-moving, deep-seated landslides are highly erosive features that can remain active for periods of decades to centuries, playing a major role in landscape evolution. In the Eel River catchment, Northern California, slow-moving landslides are the primary contributor of sediment to the channel network, delivering >50% of the regional sediment flux despite occupying mass conservation techniques to 1) invert for landslide thickness and 2) solve for landslide rheology (i.e. depth-averaged velocity), which enables us to better constrain both volume and sediment flux. Our preliminary results indicate that the landslide thickness is highly variable with changes up to tens of meters along the landslide body. We also find that the landslides have a power law rheology with a plug-flow vertical velocity profile. Estimates of sediment flux contributed by individual landslides ranges from 103 to 104 m3/yr. The application of UAVSAR data represents a major advance from previous InSAR studies in this region and provides one of the first datasets containing 3D displacement measurements for multiple landslides occurring under nearly identical environmental conditions. Future work is aimed at using these subsurface and kinematic data to calculate landslide erosion rates and regional sediment flux and to better understand the controls on landslide dynamics over short- and long-timescales.

  2. Research Note:Effects of human activities on the Yangtze River suspended sediment flux into the estuary in the last century

    Science.gov (United States)

    Yang, S. L.; Shi, Z.; Zhao, H. Y.; Li, P.; Dai, S. B.; Gao, A.

    The surface erosion area in the Yangtze River basin increased from 364×103 km2 in the 1950s to 707×103 km2 in 2001 due to a great increase in population. Based on the regression relationship between surface erosion area and population, the surface erosion area was predicted to be about 280×103 km2 at the beginning of the 20th century. The sediment yield, which increased by about 30% during the first six decades of the 20th century, was closely related to the surface erosion area in this river basin. The Yangtze annual suspended sediment flux into the estuary was about 395×106 t a-1 at the beginning of the century, and this gradually increased to an average of 509×106 t a-1 in the 1960s. The increase in the suspended sediment flux into the estuary was accelerated in the 1950s and the 1960s due to the rapid increase in population and land use immediately after the Second World War and the Liberation War. After the riverine suspended sediment flux reached its maximum in the 1960s, it decreased to cause for this decreasing trend because, during the same period, (a) the riverine water discharge did not show a decreasing trend, (b) water diversion was not influential and (c) sedimentation in lakes and canals of the middle and lower reaches did not increase. The total storage capacity of reservoirs has increased dramatically over the past half century. The amount of sediment trapped in reservoirs has increased to more than half a billion t a-1. As a result, the suspended sediment flux into the estuary dramatically decreased, even though the sediment yield from many areas of the basin increased in recent decades. Human activities gradually increased the suspended sediment flux into the estuary before the 1960s and then rapidly decreased it. The last century was a period when the Yangtze suspended sediment flux into the estuary was dramatically affected by human activities.

  3. Amino acid and hexosamine in the equatorial western Pacific: vertical fluxes and individual preservation through water column to surface sediments

    Science.gov (United States)

    Kawahata, H.; Gupta, L. P.; Ishizuka, T.

    2002-12-01

    Amino acids (AA) and hexosamines (HA) are major constituents for all living organisms, constituting important fractions of labile organic carbon and nitrogen. They usually decompose rapidly than bulk OM and must be expected to be closely linked to biogeochemical processes. In spite of such importance, our understanding of degradation processes of labile components is still limited. Therefore vertical fluxes and preservation of AA and HA from water column to surface sediments are investigated at the western equatorial Pacific. The settling particles were composed of fairly fresh AA, which could be derived from siliceous diatom with less amount of calcareous plankton. In contrast, AA were degraded in sediments and porewaters. Each AA showed highly variable preservation ratio from settling to sedimentary particles. Compared with glycine, the calculated preservation ratio was the lowest (0%) for cysteine, followed by phenylalanine (6%), tyrosine (17%), methionine (47%), leucine (60%), isoleucine (65%), proline (67%), valine (91%), serine (99%), arginine (107%), threonine (112%), alanine (115%), glutamic acid (114%), aspartic acid (150%), lysine (166%) and histidine (186%). Beta-alanine and gamma-aminobutyric acid were the least labile AA. Probably they are so difficult to degrade for bacteria to get biochemical energy that the degradation proceeds fairly slowly. In contrast, after burial, even most labile, aromatic and sulfur-containing AA, degrade at a rate similar to the other protein AA. In spite of complicated reactions, most of the AA showed first-order reaction kinetics during the degradation in the sediments. The decomposition rate constant k (kyr-1) in this study was 2-3 orders lower than those in coastal marine environments. Better preservation of HA over AA in the sediments was probably due to the general incorporation of HA into structural biopolymer matrices, such as bacterial cell-walls and chitinous material. Abundant glycine in the AA in the sediments is

  4. Sedimentation

    Science.gov (United States)

    Cliff R. Hupp; Michael R. Schening

    2000-01-01

    Sedimentation is arguably the most important water-quality concern in the United States. Sediment trapping is cited frequently as a major function of riverine-forested wetlands, yet little is known about sedimcntation rates at the landscape scale in relation to site parameters, including woody vegetation type, elevation, velocity, and hydraulic connection to the river...

  5. Benthic fluxes of mercury during redox changes in pristine coastal marine sediments from the Gulf of Trieste (northern Adriatic Sea)

    Energy Technology Data Exchange (ETDEWEB)

    Koron, Neza [National Institute of Biology, Piran (Slovenia). Marine Biological Section; Faganeli, Jadran [National Institute of Biology, Piran (Slovenia). Marine Biological Section; Jozef Stefan Institute, Ljubljana (Slovenia). Dept. of Environmental Sciences

    2012-12-15

    Purpose: The Gulf of Trieste (northern Adriatic Sea) is an example of a coastal environment contaminated with mercury (Hg). Contamination is a consequence of nearly 500 years of activity at the Idrija Mine (western Slovenia), which is the second largest Hg mine in the world. Oxygen depletion can be common in the Gulf of Trieste due to late summer stratification of the water column and accumulation of labile organic matter. Since changing redox conditions can have an impact on Hg transformations, we studied the effect of oxygen depletion, in parallel with sulphide, iron (Fe), manganese (Mn), fluorescent dissolved organic matter (FDOM) and nitrogen (N) and phosphorus (P) availability, on total Hg and methylmercury (MeHg) fluxes from sediments. Materials and methods: Pore water concentrations and benthic fluxes of total dissolved Hg and MeHg were studied in situ and in microcosm laboratory experiments using flux chambers encompassing three different stages: oxic, anoxic and reoxidation. Results and discussion: Our experiments showed that in the oxic stage there were small effluxes of MeHg to the water column, which increased in the anoxic stage and dropped rapidly in a subsequent reoxic stage, showing influx. Our results support the hypothesis that MeHg desorption from reduced metal hydroxides under anoxic conditions, and co-precipitation with Fe-oxides and MeHg demethylation in the reoxidation stage, may play a major role in determining MeHg benthic fluxes. For Hg and MeHg, it appears that there is little relationship between their pore water distribution and flux and that of FDOM, i.e. humics. Conclusions: The results indicate that there was no significant difference in Hg and MeHg pore water levels and their benthic fluxes between the contaminated northern and central parts of the Gulf of Trieste and the pristine southern part. This suggests that shallow and stratified coastal marine environments, in general, represent areas with a risk of high benthic release of

  6. Understanding the Role of the Co-Play between Land Use and Climate on Sediment Flux Laws in Intensively Managed Landscapes

    Science.gov (United States)

    Abban, B. K.; Papanicolaou, T.; Wilson, C. G.; Giannopoulos, C.; Sivapalan, M.

    2017-12-01

    In intensively managed landscapes (IMLs), changes in the land cover from what were previously grasslands, and their associated management practices, have led to a high degree of spatial heterogeneity and temporal variability in landscape processes that were absent pre-settlement. This has fundamentally altered terrestrial and instream sediment flux characteristics in regards to net amounts and proportions of source contributions, at shorter time scales. Sediment flux laws are now highly impacted by event-based dynamics. Whereas some events result in highly intermittent fluxes, others result in fluxes that largely propagate in the form of waves. This behavior is governed by the extent of land cover at the given time of the season, as well as the magnitude of the storm event. In addition, flux behavior changes as one moves from the plot scale to the watershed scale, and also with crop rotation. Thus, fluxes are now non-stationary due to continued human activity and its co-play with climate. The goal of this study is to develop a better understanding of the non-stationarity in sediment flux laws that arise from the co-play between land use and climate. Our approach involves the development of a modeling framework that considers all the exchanges between terrestrial and instream sources and addresses the issue of equifinality regarding terrestrial and instream source contributions on net sediment fluxes. The modeling framework couples an established terrestrial erosion model with an established in-stream sediment transport model. As a first step, our study focuses on the Clear Creek Watershed, IA, which is part of the Critical Zone Observatory for Intensively Managed Landscapes. We complement our modeling efforts with extensive terrestrial and instream field observations gathered at different times of the growing season, and in different years. We also used Bayesian sediment sourcing techniques to determine the provenance of transported material as well as the

  7. Geomagnetic modulation of the late Pleistocene cosmic-ray flux as determined by 10Be from Blake Outer Ridge marine sediments

    International Nuclear Information System (INIS)

    McHargue, L.R.; Donahue, D.; Damon, P.E.; Sonett, C.P.; Biddulph, D.; Burr, G.

    2000-01-01

    The cosmic-ray flux incident upon the Earth during the late Pleistocene, 20-60 kyr B.P., was studied by measuring the cosmogenic radionuclide 10 Be from a marine sediment core at site CH88-10P on the Blake Outer Ridge. The paleointensity of the geomagnetic field for this core was determined by various methods. The variance in the concentration of 10 Be in the authigenic fraction of the sediments from Blake Ridge closely correlates with the inverse of the variance in the paleointensity of the geomagnetic field. The 10 Be signal lags, up to 1000 years of sedimentation, the measured paleointensity of the sediments. In contrast, the data from several other elements, some climatically sensitive, and from beryllium show relationship neither to 10 Be nor to the paleomagnetic data. The relationship between 10 Be concentration and the dipole field intensity (M/M o ) as measured in the sediments is consistent with theoretical models

  8. Upper ocean carbon flux determined by the 234Th approach and sediment traps using size-fractionated POC and 234Th data from the Golf of Mexico

    International Nuclear Information System (INIS)

    Hung, Chin-Chang; Roberts, Kimberly A.; Santschi, Peter H.; Guo, Laodong

    2004-01-01

    Size-fractionated particulate 234 Th and particulate organic carbon (POC) fluxes were measured in the Gulf of Mexico during 2000 and 2001 in order to obtain a better estimation of upper ocean organic carbon export out of the euphotic zone within cold core and warm core rings, and to assess the relative merit of sediment trap and POC/ 234 Th methods. In 2000, the flux of POC measured by sediment traps at 120 m ranged from 60 to 148 mg C m -2 d -1 , while 234 Th-derived POC fluxes in large particles (>53 μm) varied from 18 to 61 mg C m -2 d -1 using the ratio of POC/ 234 Th at 120 m, and from 51 to 163 mg C m -2 d -1 using an average ratio of POC/ 234 Th for the upper 120 m water column. In 2001, the fluxes of POC measured by traps deployed at 120 m water depth ranged from 39 to 48 mg C m -2 d -1 , while the 234 Th-derived POC fluxes in large particles (>53 μm) varied from 7 to 37 mg C m -2 d -1 using a ratio of POC/ 234 Th at 120 m, and from 37 to 45 mg C m -2 d -1 using an average ratio of POC/ 234 Th within the 0-120 m interval. The results show that POC fluxes estimated by the 234 Th method using the average ratio of POC/ 234 Th within the euphotic zone are similar to those measured by sediment traps. Furthermore, the results demonstrate that the variability in POC export fluxes estimated by the 234 Th/ 238 U disequilibrium approach is strongly related to the ratio of POC/ 234 Th that is taken, and for which we have independent evidence that it may be controlled by the chemical composition of the suspended particles. The results also reveal that using POC/ 234 Th ratios in small particles may result in an estimate of the POC export flux that is considerably higher than when using POC/ 234 Th ratios in large particles (>53 μm). The POC flux calculated from ratios in large particles is, however, more comparable to the POC flux determined directly by sediment traps, but both of these estimates are much lower than that determined by using the POC/ 234 Th ratios in

  9. A new estimate of detrital redox-sensitive metal concentrations and variability in fluxes to marine sediments

    Science.gov (United States)

    Cole, Devon B.; Zhang, Shuang; Planavsky, Noah J.

    2017-10-01

    The enrichment and depletion of redox sensitive trace metals in marine sediments have been used extensively as paleoredox proxies. The trace metals in shale are comprised of both detrital (transported or particulate) and authigenic (precipitated, redox-driven) constituents, potentially complicating the use of this suite of proxies. Untangling the influence of these components is vital for the interpretation of enrichments, depletions, and isotopic signals of iron (Fe), chromium (Cr), uranium (U), and vanadium (V) observed in the rock record. Traditionally, a single crustal average is used as a cutoff for detrital input, and concentrations above or below this value are interpreted as redox derived authigenic enrichment or depletion, while authigenic isotopic signals are frequently corrected for an assumed detrital contribution. Building from an extensive study of soils across the continental United States - which upon transport will become marine sediments - and their elemental concentrations, we find large deviations from accepted crustal averages in redox-sensitive metals (Fe, Cr, U, V) compared to typical detrital tracers (Al, Ti, Sc, Th) and provide new estimates for detrital contributions to the ocean. The variability in these elemental ratios is present over large areas, comparable to the catchment-size of major rivers around the globe. This heterogeneity in detrital flux highlights the need for a reevaluation of how the detrital contribution is assessed in trace metal studies, and the use of confidence intervals rather than single average values, especially in local studies or in the case of small authigenic enrichments.

  10. Application of an eddy correlation system for the estimation of oxygen benthic fluxes in coastal permeable sediments impacted by submarine groundwater discharge

    Science.gov (United States)

    Donis, D.; Janssen, F.; Böttcher, M.; McGinnis, D.; Holtappels, M.; Wenzhöfer, F.

    2012-04-01

    Measurements of solute exchange across the sediment-water interface are crucial for marine environment monitoring. This interface has fundamental filter functions for the mass exchange between the seafloor and the water column. Being a non-invasive technique, the eddy correlation method, is probably the most accurate measurement for benthic fluxes. It does not interfere with local hydrodynamics and integrates over large areas, showing considerable advantages compared to traditional methods, i.e., microprofiles and benthic chambers. One of the most important exchange processes across the sediment-water interface is flux of oxygen, which is a predominant control factor for the biogeochemical activity in the sediment, carbon processing and the composition of benthic communities. The eddy correlation method performs simultaneous recordings of vertical velocities and oxygen concentrations at a specific distance to the seafloor and is becoming a standard method for resolving dissolved oxygen fluxes in aquatic systems. However, data treatment and interpretation, especially in shallow environments, is still challenging. One major concern in eddy correlation studies of coastal environments is how to consider surface wave motions that can dominate the turbulence range and that may bias flux calculations. A critical part of the data treatment thus is the removal of wave biases from the vertical velocity component, by separating the wave frequency oscillations (due to a tilted or miss-aligned sensor) from those containing meaningful flux contributions. Here we present in situ benthic oxygen exchange rates as determined by an eddy correlation system (ECS) and simultaneously deployed stirred benthic chambers. The study was carried out in a coastal ecosystem of the southern Baltic Sea that was impacted by low salinity groundwater discharge (Hel peninsula, Poland). Oxygen fluxes determined with ECS compared well with results from benthic chambers. Flux data and seepage rates are

  11. Flux of nitrogen, phosphorus, and suspended sediment from the Susquehanna River Basin to the Chesapeake Bay during Tropical Storm Lee, September 2011, as an indicator of the effects of reservoir sedimentation on water quality

    Science.gov (United States)

    Hirsch, Robert M.

    2012-01-01

    Concentrations of nitrogen, phosphorus, and suspended sediment are measured at the U.S. Geological Survey streamgage at Conowingo Dam at the downstream end of the Susquehanna River Basin in Maryland, where the river flows into the Chesapeake Bay. During the period September 7-15, 2011, in the aftermath of Tropical Storm Lee, concentrations of these three constituents were among the highest ever measured at this site. These measurements indicate that sediment-storage processes behind the three dams on the lower Susquehanna River are evolving. In particular, they indicate that scouring of sediment (and the nitrogen and phosphorus attached to that sediment) may be increasing with time. Trends in flow-normalized fluxes at the Susquehanna River at Conowingo, Maryland, streamgage during 1996-2011 indicate a 3.2-percent decrease in total nitrogen, but a 55-percent increase in total phosphorus and a 97-percent increase in suspended sediment. These large increases in the flux of phosphorus and sediment from the Susquehanna River to the Chesapeake Bay have occurred despite reductions in the fluxes of these constituents from the Susquehanna River watershed upstream from the reservoirs. Although the Tropical Storm Lee flood event contributed about 1.8 percent of the total streamflow from the Susquehanna River to the Chesapeake Bay over the past decade (water years 2002-11), it contributed about 5 percent of the nitrogen, 22 percent of the phosphorus, and 39 percent of the suspended sediment during the same period. These results highlight the importance of brief high-flow events in releasing nitrogen, phosphorus, and sediment derived from the Susquehanna River watershed and stored in the Conowingo Reservoir to the Chesapeake Bay.

  12. Sources and burial fluxes of soot black carbon in sediments on the Mackenzie, Chukchi, and Bering Shelves

    Science.gov (United States)

    Yang, Weifeng; Guo, Laodong

    2018-03-01

    Black carbon (BC) has been recognized as a climate forcing and a major component in the global carbon budget. However, studies on BC in the Arctic Ocean remain scarce. We report here variations in the abundance, sources and burial fluxes of sedimentary soot black carbon (soot-BC) in the western Arctic Ocean. The soot-BC contents averaged 1.6 ± 0.3, 0.46 ± 0.04 and 0.56 ± 0.10 mg-C g-1 on the Mackenzie, Chukchi and Bering Shelves, respectively, accounting for 16.6%, 10.2% and 10.4% of the total organic carbon in surface sediment. Temporally, contents of soot-BC remained fairly stable before 1910, but increased rapidly after the 1970s on the Mackenzie Shelf, indicating enhanced source input related to warming. Comparable δ13C signatures of soot-BC (- 24.95‰ to - 24.57‰) to C3 plants pointed to a major biomass source of soot-BC to the Beaufort Sea. Soot-BC showed similar temporal patterns with large fluctuations in the Chukchi/Bering shelf regions, implying the same source terms for soot-BC in these areas. Two events with elevated soot-BC corresponded to a simultaneous increase in biomass combustion and fossil fuel (coal and oil) consumption in Asia. The similar temporal variability in sedimentary soot-BC between the Arctic shelves and Asian lakes and the comparable δ13C values manifested that anthropogenic emission from East Asia was an important source of soot-BC in the western Arctic and subarctic regions. The burial fluxes of soot-BC, estimated from both 137Cs- and 210Pb-derived sedimentation rates, were 2.43 ± 0.42 g-C m-2 yr-1 on the Mackenzie Shelf, representing an efficient soot-BC sink. Soot-BC showed an increase in buried fluxes from 0.56 ± 0.02 g-C m-2 yr-1 during 1963-1986 to 0.88 ± 0.05 g-C m-2 yr-1 after 1986 on the Chukchi Shelf, and from 1.00 ± 0.18 g-C m-2 yr-1 to 2.58 ± 1.70 g-C m-2 yr-1 on the Bering Shelf, which were consistent with recent anthropogenically enhanced BC input observed especially in Asia. Overall, the three Arctic

  13. Sediment-water oxygen, ammonium and soluble reactive phosphorus fluxes in a turbid freshwater estuary (Curonian lagoon, Lithuania: evidences of benthic microalgal activity

    Directory of Open Access Journals (Sweden)

    Marco Bartoli

    2012-07-01

    Full Text Available Seasonal measurements of total and diffusive benthic fluxes were performed during the ice-free period in the Curonian Lagoon (Lithuania. This mostly freshwater hypertrophic basin exhibits wide seasonal variations of water temperature (1-22°C and inorganic nitrogen availability and it is subjected to dramatic blooms of diatoms and cyanobacteria (>100 μg chl a l-1. In this shallow lagoon, nutrient exchanges at the sediment-water interface and the regulating factors have been poorly explored. Overall aim of the present work is to demonstrate that the activity of benthic microalgae, generally neglected in turbid systems, can be a relevant regulator of sedimentary processes. To this purpose, light and dark fluxes of oxygen, ammonium and soluble reactive phosphorus were measured seasonally by intact core laboratory incubation and diffusive fluxes were calculated from sediment profiles. We investigated sandy sediments that were collected from the central area lagoon, that is representative of the most of the shallower lagoon area. Oxygen and ammonium fluxes were significantly different under light and dark incubations, suggesting an active role of benthic microalgae at the sediment-water interface. In the light net oxygen production was measured in three out of four samplings, with July as only exception, and ammonium was retained within sediments. In the dark sediment respiration displayed a temperature-dependent pattern while ammonium efflux increased from March to October. Fluxes of reactive phosphorus varied significantly with sampling seasons but were less affected by the incubation condition. Diffusive fluxes peaked in July, where highest concentration gradients at the interface and theoretical efflux of ammonium and reactive phosphorous were calculated. The marked differences between diffusive and total nutrient fluxes are probably due to photosynthetic activity by benthic microalgae, and thus oxygen production, enhancement of aerobic

  14. Use of flux and morphologic sediment budgets for sandbar monitoring on the Colorado River in Marble Canyon, Arizona

    Science.gov (United States)

    Grams, Paul E.; Buscombe, Daniel D.; Topping, David J.; Hazel, Joseph E.; Kaplinski, Matt

    2015-01-01

    ., 2000) and depends entirely on infrequent tributary floods, monitoring of both sandbars and gross sand storage (the sand budget) is required to evaluate whether the high-flow protocol is having the intended effect of increasing sandbar size without progressively depleting sand from the system.There are many challenges associated with monitoring sand storage and active sand deposits in a river system as large and complex as the 450-km segment of the Colorado River between Glen Canyon Dam and Lake Mead. Previous studies have demonstrated the temporal variation in sand storage associated with sand-supply limitation (Topping et al., 2000) and the spatial variability in the amount of sand stored in eddies and the channel associated with channel hydraulics (Grams et al., 2013). In this study, we report on companion measurements of sand flux and morphologic change to quantify, for the first time, the relation between changes in sand mass balance, changes in within-channel sand storage, and changes in sandbars comprehensively for a 50-km river segment of the Colorado River in lower Marble Canyon within Grand Canyon National Park.We show that, when measured over the scale of a 50-km river segment, these complementary measurements of the sand budget agree within measurement uncertainty and provide a rare opportunity to integrate the temporally rich sand-flux record with the spatially rich morphologic measurements. Both methods show that sediment was evacuated from lower Marble Canyon over the 3-year study period. The flux-based budget shows the timing of changes in storage relative to dam-release patterns, while the morphologic measurements depict the spatial distribution of erosion and deposition among different depositional settings.

  15. Fine-scale community structure analysis of ANME in Nyegga sediments with high and low methane flux

    Directory of Open Access Journals (Sweden)

    Irene eRoalkvam

    2012-06-01

    Full Text Available To obtain knowledge on how regional variations in methane seepage rates influence the stratification, abundance and diversity of anaerobic methanotrophs (ANME we analyzed the vertical microbial stratification in a gravity core from a methane micro-seeping area at Nyegga by using 454-pyrosequencing of 16S rRNA gene tagged amplicons and quantitative PCR. The results were compared with previously obtained data from the more active G11 pockmark, characterized by higher methane flux. A downcore stratification and high relative abundance of ANME was observed in both cores, with transition from an ANME-2a/b dominated community in low-sulfide and low-methane horizons to ANME-1 dominance in horizons near the sulfate methane transition zone (SMTZ. The stratification was over a wider spatial region and at greater depth in the core with lower methane flux, and the total 16S rRNA copy numbers were two orders of magnitude lower than in the sediments at G11 pockmark. A fine-scale view into the ANME communities at each location was achieved through OTU clustering of ANME-affiliated sequences. The majority of ANME-1 sequences from both sampling sites clustered within one OTU, while ANME-2a/b sequences were represented in unique OTUs. We suggest that free living ANME-1 is the most abundant taxon in Nyegga cold seeps, and also the main consumer of methane. The specific ANME-2a/b ecotypes could reflect adaptations to the geochemical composition at each location, with different affinities to methane. Given that the ANME-2a/b population could be sustained in less active seepage areas, this subgroup could be potential seed populations in newly developed methane-enriched environments.

  16. A Hydrodynamic and Sediment Transport Model for the Waipaoa Shelf, New Zealand: Sensitivity of Fluxes to Spatially-Varying Erodibility and Model Nesting

    Directory of Open Access Journals (Sweden)

    Julia M. Moriarty

    2014-04-01

    Full Text Available Numerical models can complement observations in investigations of marine sediment transport and depositional processes. A coupled hydrodynamic and sediment transport model was implemented for the Waipaoa River continental shelf offshore of the North Island of New Zealand, to complement a 13-month field campaign that collected seabed and hydrodynamic measurements. This paper described the formulations used within the model, and analyzed the sensitivity of sediment flux estimates to model nesting and seabed erodibility. Calculations were based on the Regional Ocean Modeling System—Community Sediment Transport Modeling System (ROMS-CSTMS, a primitive equation model using a finite difference solution to the equations for momentum and water mass conservation, and transport of salinity, temperature, and multiple classes of suspended sediment. The three-dimensional model resolved the complex bathymetry, bottom boundary layer, and river plume that impact sediment dispersal on this shelf, and accounted for processes including fluvial input, winds, waves, tides, and sediment resuspension. Nesting within a larger-scale, lower resolution hydrodynamic model stabilized model behavior during river floods and allowed large-scale shelf currents to impact sediment dispersal. To better represent observations showing that sediment erodibility decreased away from the river mouth, the seabed erosion rate parameter was reduced with water depth. This allowed the model to account for the observed spatial pattern of erodibility, though the model held the critical shear stress for erosion constant. Although the model neglected consolidation and swelling processes, use of a spatially-varying erodibility parameter significantly increased export of fluvial sediment from Poverty Bay to deeper areas of the shelf.

  17. PAH fluxes in the Laja Lake of south central Chile Andes over the last 50 years: Evidence from a dated sediment core

    International Nuclear Information System (INIS)

    Quiroz, Roberto; Popp, Peter; Urrutia, Roberto; Bauer, Coretta; Araneda, Alberto; Treutler, Hanns-Christian; Barra, Ricardo

    2005-01-01

    This paper reports the occurrence of polyaromatic hydrocarbons (PAHs) deposition inferred from a sediment core of an Andean lake in south central Chile. Sediments were carefully collected from one of the deepest section of the lake and sliced every 1 cm. The samples were analyzed for PAHs, 137 Cs, 210 Pb, organic carbon and grain-size. The stratigraphic chronology and the sedimentation rates were estimated using the sedimentary signature left by the 137 Cs and 210 Pb fallout as temporal markers. PAHs were quantified by HPLC-fluorescence detection (HPLC-Fluorescence). 15 priority EPA PAHs were analyzed in this study. Based on these results, PAH deposition over the last 50 years was estimated (a period characterized by an important intervention in the area). PAH concentration ranged from 226 to 620 ng g -1 d.w. The highest concentrations of PAHs were found in the core's bottom. The PAH profile is dominated by the presence of perylene indicating a natural source of PAH. In addition, two clear PAH deposition periods could be determined: the most recent with two-four rings PAHs, the older one with five-seven rings predomination. Determined fluxes where 71 to 972 μg m -2 year -1 , dominated by perylene deposition. PAH levels and fluxes are lower compared to the levels found in sediments from remote lakes in Europe and North America. It is concluded that the main source of PAHs into the Laja Lake sediments are of natural origin

  18. Regional patterns of labile organic carbon flux in North American Arctic Margin (NAAM) as reflected by redox sensitive-elements distributions in sediments

    Science.gov (United States)

    Gobeil, C.; Kuzyk, Z. Z. A.; Goni, M. A.; Macdonald, R. W.

    2016-02-01

    Concentrations of elements (S, Mn, Mo, U, Cd, Re) providing insights on organic C metabolized through oxidative processes at the sea floor were measured in 27 sediment cores collected along a section extending from the North Bering Sea to Davis Strait via the Canadian Archipelago. Sedimentary distributions and accumulation rates of these elements were used to i) document the relative importance of aerobic versus anaerobic degradation of organic C in NAAM sediments, ii) infer variations in water column carbon flux and iii) estimate the importance of this margin as a sink for key elements in the Arctic and global ocean. Distributions of Mn, total S and reduced inorganic S demonstrated that most sediments along the NAAM had relatively thick (>1 cm) surface oxic layers, underlain by sediments with weakly reducing conditions and limited sulphate reduction. Strongly reducing conditions accompanied by substantial sedimentary pyrite burial occurred only in certain subregions, including the Bering-Chukchi Shelves, shallow portions of Barrow Canyon. Estimated accumulation rates of authigenic S, Mo, Cd and U, and total Re displayed marked spatial variability that was related to sedimentary redox conditions induced by the supply of labile C to the seabed, as shown by significant relationships between the accumulation rates and vertical C flux, estimated from regional primary production values and water depth at the coring sites. High primary production combined with shallow water columns drive elevated rates of authigenic trace element accumulation in sediments from the Bering-Chukchi Shelves whereas low production combined with moderately deep conditions drive low rates of accumulation in sediments in the Beaufort Shelf, Davis Strait and Canadian Archipelago. Using the average authigenic trace element accumulation rates in sediments from the various regions, we submit that the shelves along the NAAM margin are important sinks in global marine biogeochemical budgets.

  19. Application of a Weighted Regression Model for Reporting Nutrient and Sediment Concentrations, Fluxes, and Trends in Concentration and Flux for the Chesapeake Bay Nontidal Water-Quality Monitoring Network, Results Through Water Year 2012

    Science.gov (United States)

    Chanat, Jeffrey G.; Moyer, Douglas L.; Blomquist, Joel D.; Hyer, Kenneth E.; Langland, Michael J.

    2016-01-13

    In the Chesapeake Bay watershed, estimated fluxes of nutrients and sediment from the bay’s nontidal tributaries into the estuary are the foundation of decision making to meet reductions prescribed by the Chesapeake Bay Total Maximum Daily Load (TMDL) and are often the basis for refining scientific understanding of the watershed-scale processes that influence the delivery of these constituents to the bay. Two regression-based flux and trend estimation models, ESTIMATOR and Weighted Regressions on Time, Discharge, and Season (WRTDS), were compared using data from 80 watersheds in the Chesapeake Bay Nontidal Water-Quality Monitoring Network (CBNTN). The watersheds range in size from 62 to 70,189 square kilometers and record lengths range from 6 to 28 years. ESTIMATOR is a constant-parameter model that estimates trends only in concentration; WRTDS uses variable parameters estimated with weighted regression, and estimates trends in both concentration and flux. WRTDS had greater explanatory power than ESTIMATOR, with the greatest degree of improvement evident for records longer than 25 years (30 stations; improvement in median model R2= 0.06 for total nitrogen, 0.08 for total phosphorus, and 0.05 for sediment) and the least degree of improvement for records of less than 10 years, for which the two models performed nearly equally. Flux bias statistics were comparable or lower (more favorable) for WRTDS for any record length; for 30 stations with records longer than 25 years, the greatest degree of improvement was evident for sediment (decrease of 0.17 in median statistic) and total phosphorus (decrease of 0.05). The overall between-station pattern in concentration trend direction and magnitude for all constituents was roughly similar for both models. A detailed case study revealed that trends in concentration estimated by WRTDS can operationally be viewed as a less-constrained equivalent to trends in concentration estimated by ESTIMATOR. Estimates of annual mean flow

  20. Land-use effects on fluxes of suspended sediment, nitrogen and phosphorus from a river catchment of the Great Barrier Reef, Australia

    Science.gov (United States)

    Hunter, Heather M.; Walton, Richard S.

    2008-07-01

    SummaryA 6-year study was conducted in the Johnstone River system in the wet tropics of north-eastern Australia, to address concerns that the Great Barrier Reef is at risk from elevated levels of suspended sediment (SS) and nutrients discharged from its river catchments. Aims were to quantify: (i) fluxes of SS, phosphorus (P) and nitrogen (N) exported annually from the catchment and (ii) the influence of rural land uses on these fluxes. Around 55% of the 1602 km2 catchment was native rainforest, with the reminder developed mainly for livestock and crop production. Water quality and stream flow were monitored at 16 sites, with the emphasis on sampling major runoff events. Monitoring data were used to calibrate a water quality model for the catchment (HSPF), which was run with 39 years of historical precipitation and evaporation data. Modelled specific fluxes from the catchment of 1.2 ± 1.1 t SS ha-1 y-1, 2.2 ± 1.8 kg P ha-1 y-1 and 11.4 ± 7.3 kg N ha-1y-1 were highly variable between and within years. Fluxes of SS and P were strongly dominated by major events, with 91% of SS and 84% of P exported during the highest 10% of daily flows. On average, sediment P comprised 81% of the total P flux. The N flux was less strongly dominated by major events and sediment N comprised 46% of total N exports. Specific fluxes of SS, N and P from areas receiving precipitation of 3545 mm y-1 were around 3-4 times those from areas receiving 1673 mm y-1. For a given mean annual precipitation, specific fluxes of SS and P from beef pastures, dairy pastures and unsewered residential areas were similar to those from rainforest, while fluxes from areas of sugar cane and bananas were 3-4 times higher. Specific fluxes of N from areas with an annual precipitation of 3545 mm ranged from 8.9 ± 6.5 kg N ha-1 y-1 (rainforest) to 72 ± 50 kg N ha-1 y-1 (unsewered residential). Aggregated across the entire catchment, disproportionately large fluxes of SS, total P and total N were derived from

  1. Residual fluxes and suspended sediment transport in the lower reaches of Muvattupuzha River, southwest coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Revichandran, C.; Balachandran, K.K.; Xavier, J.K.; Rejendran, N.C.

    Spatial and seasonal variation of different physical processes governing the transport of salt and sediment of the Muvattupuzha River, in Kerala, India are discussed. Salt and suspended sediment due to tidal pumping was directed upstream, salt...

  2. Benthic metal fluxes and sediment diagenesis in a water reservoir affected by acid mine drainage: A laboratory experiment and reactive transport modeling

    Science.gov (United States)

    Torres, E.; Ayora, C.; Jiménez-Arias, J. L.; García-Robledo, E.; Papaspyrou, S.; Corzo, A.

    2014-08-01

    Reservoirs are one of the primary water supply sources. Knowledge of the metal fluxes at the water-sediment interfaces of reservoirs is essential for predicting their ecological quality. Redox oscillations in the water column are promoted by stratification; turnover events may significantly alter metal cycling, especially in reservoirs impacted by acid mine drainage (AMD). To study this phenomenon, an experiment was performed under controlled laboratory conditions. Sediment cores from an AMD-affected reservoir were maintained in a tank with reservoir water for approximately two months and subjected to alternating oxic-hypoxic conditions. A detailed metal speciation in solid phases of the sediment was initially performed by sequential extraction, and pore water was analyzed at the end of each redox period. Tank water metals concentrations were systematically monitored throughout the experiment. The experimental results were then used to calibrate a diffusion-reaction model and quantify the reaction rates and sediment-water fluxes. Under oxic conditions, pH, Fe and As concentrations decreased in the tank due to schwertmannite precipitation, whereas the concentrations of Al, Zn, Cu, Ni, and Co increased due to Al(OH)3 and sulfide dissolution. The reverse trends occurred under hypoxic conditions. Under oxic conditions, the fluxes calculated by applying Fick’s first law to experimental concentration gradients contradicted the fluxes expected based on the evolution of the tank water. According to the reactive transport calculations, this discrepancy can be attributed to the coarse resolution of sediment sampling. The one-cm-thick slices failed to capture effectively the notably narrow (1-2 mm) concentration peaks of several elements in the shallow pore water resulting from sulfide and Al(OH)3 dissolution. The diffusion-reaction model, extended to the complete year, computed that between 25% and 50% of the trace metals and less than 10% of the Al that precipitated under

  3. Concentrations and fluxes of dissolved uranium in the Yellow River estuary: seasonal variation and anthropogenic (Water-Sediment Regulation Scheme) impact

    International Nuclear Information System (INIS)

    Juanjuan, Sui; Zhigang, Yu; Bochao, Xu; Wenhua, Dong; Dong, Xia; Xueyan, Jiang

    2014-01-01

    The Water-Sediment Regulation Scheme (WSRS) of the Yellow River is a procedure implemented annually from June to July to expel sediments deposited in Xiaolangdi and other large middle-reach reservoirs and to scour the lower reaches of the river, by controlling water and sediment discharges. Dissolved uranium isotopes were measured in river waters collected monthly as well as daily during the 2010 WSRS (June 19–July 16) from Station Lijin (a hydrologic station nearest to the Yellow River estuary). The monthly samples showed dissolved uranium concentrations of 3.85–7.57 μg l −1 and 234 U/ 238 U activity ratios of 1.24–1.53. The concentrations were much higher than those reported for other global major rivers, and showed seasonal variability. Laboratory simulation experiments showed significant uranium release from bottom and suspended sediment. The uranium concentrations and activity ratios differed during the two stages of the WSRS, which may reflect desorption/dissolution of uranium from suspended river sediments of different origins. An annual flux of dissolved uranium of 1.04 × 10 8 g y −1 was estimated based on the monthly average water discharge and dissolved uranium concentration in the lower reaches of the Yellow River. The amount of dissolved uranium (2.65 × 10 7 g) transported from the Yellow River to the sea during the WSRS constituted about 1/4 of the annual flux. -- Highlights: • Dissolved U in the Yellow River estuary has distinct seasonal variability. • Geochemistry of dissolved U influenced by the WSRS has been analyzed. • Uranium flux during the WSRS has been evaluated

  4. Quantifying the Effects of Near-Bed Concentration on the Sediment Flux after the Operation of the Three Gorges Dam, Yangtze River

    Directory of Open Access Journals (Sweden)

    Li He

    2017-12-01

    Full Text Available The regime of sediment transport in the Jingjiang Reach has significantly changed from quasi-equilibrium to sub-saturation since the impoundment of the Three Gorges Dam (TGD, and vertical profiles of suspended sediment concentration (SSC have changed accordingly. Vertical profiles of SSC data measured at three hydrological stations in the Jingjiang Reach (Zhicheng, Shaishi, and Jianli, before and after the impoundment of TGD, were collected and analyzed. Analytic results indicate a remarkably large concentration in the near-bed zone (within 10% of water depth from the river-bed in a sub-saturated channel. The maximum measured concentration was up to 15 times the vertical average concentration, while the ratio in quasi-equilibrium channel was less than four times that. Concentrations normalized with reference concentration at the same height, and may decrease with increasing values of suspension index (settling velocity over shear velocity. In addition, concentration near the water surface may be larger than concentration in the near-bed region when the suspension index is smaller than 0.01. Sediment flux transported in the near-bed zone may be up to 35% of the total sediment flux in unsaturated flows. The relationship between deviations of estimating sediment flux when ignoring the near-bed concentration and discharge in flood season and non-flood season are different in unsaturated and quasi-equilibrium channels. Analysis indicates that, in the quasi-equilibrium channel, more attention should be paid to near-bed concentration during non-flood season, the same as measurements during flood season with larger discharge.

  5. Constraining the Spatial Extent of Marine Oil Snow Sedimentation and Flocculent Accumulation Following the Deepwater Horizon Event Using an Excess 210Pb Flux Approach.

    Science.gov (United States)

    Schwing, P T; Brooks, G R; Larson, R A; Holmes, C W; O'Malley, B J; Hollander, D J

    2017-06-06

    Following the Deepwater Horizon (DWH) event in 2010, there were several lines of evidence indicating the presence of marine oil snow sedimentation and flocculent accumulation (MOSSFA). A significant amount of marine oil snow formed in the water column of the northern Gulf of Mexico (nGoM), settled rapidly, and ultimately accumulated in the sediments of the nGoM. This study utilized a commonly used radioisotope tracer (excess 210 Pb, 210 Pb xs ) from 32 sediment cores collected from 2010 to 2013 to characterize the spatial extent of MOSSFA on the seafloor. Relative to pre-DWH conditions, an increase in 210 Pb xs flux occurred in two distinct regions: (1) in the western portion of the study area on an east-northeast to west-southwest axis, stretching 230 km southwest and 140 km northeast of the DWH wellhead, and (2) in the eastern portion of the study area on a 70 km northeast to southwest axis near the DeSoto Canyon. The total sedimentary spatial extent of MOSSFA, as calculated by increased 210 Pb xs flux after 2010, ranged from 12 805 to 35 425 km 2 . 210 Pb xs flux provides a valuable tool for documenting the spatial extent of MOSSFA following DWH and will continue to aid in the determination of advective transport and ultimate depocenters of MOSSFA material.

  6. Using high-performance mathematical modelling tools to predict erosion and sediment fluxes in peri-urban catchments

    Science.gov (United States)

    Pereira, André; Conde, Daniel; Ferreira, Carla S. S.; Walsh, Rory; Ferreira, Rui M. L.

    2017-04-01

    Deforestation and urbanization generally lead to increased soil erosion andthrough the indirect effect of increased overland flow and peak flood discharges. Mathematical modelling tools can be helpful for predicting the spatial distribution of erosion and the morphological changes on the channel network. This is especially useful to predict the impacts of land-use changes in parts of the watershed, namely due to urbanization. However, given the size of the computational domain (normally the watershed itself), the need for high spatial resolution data to model accurately sediment transport processes and possible need to model transcritical flows, the computational cost is high and requires high-performance computing techniques. The aim of this work is to present the latest developments of the hydrodynamic and morphological model STAV2D and its applicability to predict runoff and erosion at watershed scale. STAV2D was developed at CEris - Instituto Superior Técnico, Universidade de Lisboa - as a tool particularly appropriated to model strong transient flows in complex and dynamic geometries. It is based on an explicit, first-order 2DH finite-volume discretization scheme for unstructured triangular meshes, in which a flux-splitting technique is paired with a reviewed Roe-Riemann solver, yielding a model applicable to discontinuous flows over time-evolving geometries. STAV2D features solid transport in both Euleran and Lagrangian forms, with the aim of describing the transport of fine natural sediments and then the large individual debris. The model has been validated with theoretical solutions and laboratory experiments (Canelas et al., 2013 & Conde et al., 2015). STAV-2D now supports fully distributed and heterogeneous simulations where multiple different hardware devices can be used to accelerate computation time within a unified Object-Oriented approach: the source code for CPU and GPU has the same compilation units and requires no device specific branches, like

  7. Modeling the Effects of Reservoir Releases on the Bed Material Sediment Flux of the Colorado River in western Colorado and eastern Utah

    Science.gov (United States)

    Pitlick, J.; Bizzi, S.; Schmitt, R. J. P.

    2017-12-01

    Warm-water reaches of the upper Colorado River have historically provided important habitat for four endangered fishes. Over time these habitats have been altered or lost due to reductions in peak flows and sediment loads caused by reservoir operations. In an effort to reverse these trends, controlled reservoir releases are now used to enhance sediment transport and restore channel complexity. In this presentation, we discuss the development of a sediment routing model designed to assess how changes in water and sediment supply can affect the mass balance of sediment. The model is formulated for ten reaches of the Colorado River spanning 250 km where values of bankfull discharge, width, and reach-average slope have been measured. Bed surface grain size distributions (GSDs) have also been measured throughout the study area; these distributions are used as a test of the model, not as input, except as an upstream boundary condition. In modeling fluxes and GSDs, we assume that the bed load transport capacity is determined by local hydraulic conditions and bed surface grain sizes. Estimates of the bankfull bed load transport capacity in each reach are computed for 14 size fractions of the surface bed material, and the fractional transport rates are summed to get the total transport capacity. In the adjacent reach, fluxes of each size fraction from upstream are used to determine the mean grain size, and the fractional transport capacity of that reach. Calculations proceed downstream and illustrate how linked changes in discharge, shear stress and mean grain size affect (1) the total bed load transport capacity, and (2) the size distribution of the bed surface sediment. The results show that model-derived GSDs match measured GSDs very closely, except for two reaches in the lower part of the study area where slope is affected by uplift associated with salt diapirs; here the model significantly overestimates the transport capacity in relation to the supply. Except for these

  8. Seasonality and variability of coccolithophore fluxes in response to diverse oceanographic regimes in the Bay of Bengal: Sediment trap results

    Digital Repository Service at National Institute of Oceanography (India)

    Mergulhao, L.P.; Guptha, M.V.S.; Unger, D.; Murty, V.S.N.

    carbonate and diatom opal fluxes continued to increase. Tanaka and Kawahata (2001) reported that the calculated coccolith- CaCO3 fluxes ranged between 6.8 and 49.6 mg m-2day-1 and contributed 23.3% of total CaCO3 flux in the west Caroline Basin...

  9. Short-term changes in particulate fluxes measured by drifting sediment traps during end summer oligotrophic regime in the NW Mediterranean Sea

    Directory of Open Access Journals (Sweden)

    J. C. Marty

    2009-05-01

    Full Text Available Short-term changes in the flux of particulate matter were determined in the central north western Mediterranean Sea (near DYFAMED site using drifting sediment traps at 200 m depth in the course of the DYNAPROC 2 cruise (14 September–17 October 2004. In this period of marked water column stratification, POC fluxes varied by an order of magnitude, in the range of 0.03–0.29 mgC m−2 h−1 over the month and showed very rapid and high variations. Particulate carbon export represented less than 5% of integrated primary production, suggesting that phytoplankton production was essentially sustained by internal recycling of organic matter and retained within the photic zone. While PON and POP fluxes paralleled one another, the elemental ratios POC/PON and POC/POP, varied widely over short-term periods. Values of these ratios generally higher than the conventional Redfield ratio, together with the very low chlorophyll a flux recorded in the traps (mean 0.017 μg m−2 h−1, and the high phaeopigment and acyl lipid hydrolysis metabolite concentrations of the settling material, indicated that the organic matter reaching 200 m depth was reworked (by grazing, fecal pellets production, degradation and that algal sinking, dominated by nano- and picoplankton, made a small contribution to the downward flux. Over time, the relative abundance of individual lipid classes in organic matter (OM changed from glycolipids-dominated to neutral (wax esters, triacylglycerols and phospholipids-dominated, suggesting ecosystem maturation as well as rapid and continual exchanges between dissolved, suspended and sinking pools. Our most striking result was documenting the rapid change in fluxes of the various measured parameters. In the situation encountered here, with dominant regenerated production, a decrease of fluxes was noticed during windy periods (possibly through reduction of grazing. But fluxes increased as soon as calm

  10. Using a Near-Bed Sediment Flux Sensor to Measure Wave Formed Bedform Migrations and Formation Processes

    National Research Council Canada - National Science Library

    Traykovski, Peter A

    2007-01-01

    My research program focuses on identifying and quantifying sediment erosion, transport, and deposition processes on the continental shelf through state of the art observational techniques in both fine...

  11. Concentrations and fluxes of dissolved uranium in the Yellow River estuary: seasonal variation and anthropogenic (Water-Sediment Regulation Scheme) impact.

    Science.gov (United States)

    Juanjuan, Sui; Zhigang, Yu; Bochao, Xu; Wenhua, Dong; Dong, Xia; Xueyan, Jiang

    2014-02-01

    The Water-Sediment Regulation Scheme (WSRS) of the Yellow River is a procedure implemented annually from June to July to expel sediments deposited in Xiaolangdi and other large middle-reach reservoirs and to scour the lower reaches of the river, by controlling water and sediment discharges. Dissolved uranium isotopes were measured in river waters collected monthly as well as daily during the 2010 WSRS (June 19-July 16) from Station Lijin (a hydrologic station nearest to the Yellow River estuary). The monthly samples showed dissolved uranium concentrations of 3.85-7.57 μg l(-1) and (234)U/(238)U activity ratios of 1.24-1.53. The concentrations were much higher than those reported for other global major rivers, and showed seasonal variability. Laboratory simulation experiments showed significant uranium release from bottom and suspended sediment. The uranium concentrations and activity ratios differed during the two stages of the WSRS, which may reflect desorption/dissolution of uranium from suspended river sediments of different origins. An annual flux of dissolved uranium of 1.04 × 10(8) g y(-1) was estimated based on the monthly average water discharge and dissolved uranium concentration in the lower reaches of the Yellow River. The amount of dissolved uranium (2.65 × 10(7) g) transported from the Yellow River to the sea during the WSRS constituted about 1/4 of the annual flux. Copyright © 2013 Elsevier Ltd. All rights reserved.

  12. Modern and historical fluxes of halogenated organic contaminants to a lake in the Canadian arctic, as determined from annually laminated sediment cores

    International Nuclear Information System (INIS)

    Stern, G.A.; Braekevelt, E.; Helm, P.A.; Bidleman, T.F.; Outridge, P.M.; Lockhart, W.L.; McNeeley, R.; Rosenberg, B.; Ikonomou, M.G.; Hamilton, P.; Tomy, G.T.; Wilkinson, P.

    2005-01-01

    Two annually laminated cores collected from Lake DV09 on Devon Island in May 1999 were dated using 210 Pb and 137 Cs, and analyzed for a variety of halogenated organic contaminants (HOCs), including polychlorinated biphenyls (PCBs), organochlorine pesticides, short-chain polychlorinated n-alkanes (sPCAs), polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), and polybrominated diphenyl ethers (PBDEs). Dry weight HOC concentrations in Lake DV09 sediments were generally similar to other remote Arctic lakes. Maximum HOC fluxes often agreed well with production maxima, although many compound groups exhibited maxima at or near the sediment surface, much later than peak production. The lower than expected HOC concentrations in older sediment slices may be due to anaerobic degradation and possibly to dilution resulting from a temporary increase in sedimentation rate observed between the mid-1960s and 1970s. Indeed, temporal trends were more readily apparent for those compound classes when anaerobic metabolites were also analyzed, such as for DDT and toxaphene. However, it is postulated here for the first time that the maximum or increasing HOC surface fluxes observed for many of the major compound classes in DV09 sediments may be influenced by climate variation and the resulting increase in algal primary productivity which could drive an increasing rate of HOC scavenging from the water column. Both the fraction (F TC ) and enantiomer fraction (EF) of trans-chlordane (TC) decreased significantly between 1957 and 1997, suggesting that recent inputs to the lake are from weathered chlordane sources. PCDD/Fs showed a change in sources from pentachlorophenol (PeCP) in the 1950s and 1960s to combustion sources into the 1990s. Improvements in combustion technology may be responsible for the reducing the proportion of TCDF relative to OCDD in the most recent slice

  13. A novel method for sampling the suspended sediment load in the tidal environment using bi-directional time-integrated mass-flux sediment (TIMS) samplers

    Science.gov (United States)

    Elliott, Emily A.; Monbureau, Elaine; Walters, Glenn W.; Elliott, Mark A.; McKee, Brent A.; Rodriguez, Antonio B.

    2017-12-01

    Identifying the source and abundance of sediment transported within tidal creeks is essential for studying the connectivity between coastal watersheds and estuaries. The fine-grained suspended sediment load (SSL) makes up a substantial portion of the total sediment load carried within an estuarine system and efficient sampling of the SSL is critical to our understanding of nutrient and contaminant transport, anthropogenic influence, and the effects of climate. Unfortunately, traditional methods of sampling the SSL, including instantaneous measurements and automatic samplers, can be labor intensive, expensive and often yield insufficient mass for comprehensive geochemical analysis. In estuaries this issue is even more pronounced due to bi-directional tidal flow. This study tests the efficacy of a time-integrated mass sediment sampler (TIMS) design, originally developed for uni-directional flow within the fluvial environment, modified in this work for implementation the tidal environment under bi-directional flow conditions. Our new TIMS design utilizes an 'L' shaped outflow tube to prevent backflow, and when deployed in mirrored pairs, each sampler collects sediment uniquely in one direction of tidal flow. Laboratory flume experiments using dye and particle image velocimetry (PIV) were used to characterize the flow within the sampler, specifically, to quantify the settling velocities and identify stagnation points. Further laboratory tests of sediment indicate that bidirectional TIMS capture up to 96% of incoming SSL across a range of flow velocities (0.3-0.6 m s-1). The modified TIMS design was tested in the field at two distinct sampling locations within the tidal zone. Single-time point suspended sediment samples were collected at high and low tide and compared to time-integrated suspended sediment samples collected by the bi-directional TIMS over the same four-day period. Particle-size composition from the bi-directional TIMS were representative of the array of

  14. Benthic fluxes of oxygen and inorganic nutrients in the archipelago of Gulf of Finland, Baltic Sea - Effects of sediment resuspension measured in situ

    Science.gov (United States)

    Niemistö, Juha; Kononets, Mikhail; Ekeroth, Nils; Tallberg, Petra; Tengberg, Anders; Hall, Per O. J.

    2018-05-01

    Benthic fluxes of oxygen and dissolved inorganic nutrients; phosphate (DIP), ammonium (NH4), nitrate + nitrite (NOx), and silicate (DSi); and the effects of resuspension on these were studied in situ with the Göteborg benthic landers in the Gulf of Finland archipelago, Baltic Sea. The benthic fluxes were examined at two shallow stations at depths of 7 m and 20 m in May and August 2014. Resuspension altered benthic fluxes of oxygen and nutrients in most of the experiments in August, but not in May, which was mainly due to weaker resuspension treatments in spring. Additionally, the benthic nutrient regeneration rates were higher and redox conditions lower in August when the water was warmer. In August, resuspension increased the benthic oxygen uptake by 33-35%, which was, in addition to stronger resuspension treatment, attributed to higher amounts of dissolved reduced substances in the sediment pore water in comparison to conditions in May. Adsorption onto newly formed iron oxyhydroxides could explain the uptake of DIP by the sediment at the 20 m station and the lowering of the DSi efflux by 31% at the 7 m station during resuspension in August. In addition, resuspension promoted nitrification, as indicated by increased NOx fluxes at both stations (by 30% and 27% at the 7 m and 20 m station, respectively) and a lowered NH4 flux (by 48%) at the 7 m station. Predicted increases in the magnitude and frequency of resuspension will thus markedly affect the transport of phosphorus and silicon and the cycling of nitrogen in the shallow areas of the Gulf of Finland.

  15. Climate-driven unsteady denudation and sediment flux in a high-relief unglaciated catchment-fan using 26Al and 10Be: Panamint Valley, California

    Science.gov (United States)

    Mason, Cody C.; Romans, Brian W.

    2018-06-01

    Environmental changes within erosional catchments of sediment routing systems are predicted to modulate sediment transfer dynamics. However, empirical and numerical models that predict such phenomena are difficult to test in natural systems over multi-millennial timescales. Tectonic boundary conditions and climate history in the Panamint Range, California, are relatively well-constrained by existing low-temperature thermochronology and regional multi-proxy paleoclimate studies, respectively. Catchment-fan systems present there minimize sediment storage and recycling, offering an excellent natural laboratory to test models of climate-sedimentary dynamics. We used stratigraphic characterization and cosmogenic radionuclides (CRNs; 26Al and 10Be) in the Pleasant Canyon complex (PCC), a linked catchment-fan system, to examine the effects of Pleistocene high-magnitude, high-frequency climate change on CRN-derived denudation rates and sediment flux in a high-relief, unglaciated catchment-fan system. Calculated 26Al/10Be burial ages from 13 samples collected in an ∼180 m thick outcropping stratigraphic succession range from ca. 1.55 ± 0.22 Ma in basal strata, to ca. 0.36 ± 0.18-0.52 ± 0.20 Ma within the uppermost part of the succession. The mean long-term CRN-derived paleodenudation rate, 36 ± 8 mm/kyr (1σ), is higher than the modern rate of 24 ± 0.6 mm/kyr from Pleasant Canyon, and paleodenudation rates during the middle Pleistocene display some high-frequency variability in the high end (up to 54 ± 10 mm/kyr). The highest CRN-derived denudation rates are associated with stratigraphic evidence for increased precipitation during glacial-pluvial events after the middle Pleistocene transition (post ca. 0.75 Ma), suggesting 100 kyr Milankovitch periodicity could drive the observed variability. We investigated the potential for non-equilibrium sedimentary processes, i.e. increased landslides or sediment storage/recycling, to influence apparent paleodenudation rates

  16. Stochastic Modeling of Sediment Connectivity for Reconstructing Sand Fluxes and Origins in the Unmonitored Se Kong, Se San, and Sre Pok Tributaries of the Mekong River

    Science.gov (United States)

    Schmitt, R. J. P.; Bizzi, S.; Castelletti, A. F.; Kondolf, G. M.

    2018-01-01

    Sediment supply to rivers, subsequent fluvial transport, and the resulting sediment connectivity on network scales are often sparsely monitored and subject to major uncertainty. We propose to approach that uncertainty by adopting a stochastic method for modeling network sediment connectivity, which we present for the Se Kong, Se San, and Sre Pok (3S) tributaries of the Mekong. We quantify how unknown properties of sand sources translate into uncertainty regarding network connectivity by running the CASCADE (CAtchment Sediment Connectivity And DElivery) modeling framework in a Monte Carlo approach for 7,500 random realizations. Only a small ensemble of realizations reproduces downstream observations of sand transport. This ensemble presents an inverse stochastic approximation of the magnitude and variability of transport capacity, sediment flux, and grain size distribution of the sediment transported in the network (i.e., upscaling point observations to the entire network). The approximated magnitude of sand delivered from each tributary to the Mekong is controlled by reaches of low transport capacity ("bottlenecks"). These bottlenecks limit the ability to predict transport in the upper parts of the catchment through inverse stochastic approximation, a limitation that could be addressed by targeted monitoring upstream of identified bottlenecks. Nonetheless, bottlenecks also allow a clear partitioning of natural sand deliveries from the 3S to the Mekong, with the Se Kong delivering less (1.9 Mt/yr) and coarser (median grain size: 0.4 mm) sand than the Se San (5.3 Mt/yr, 0.22 mm) and Sre Pok (11 Mt/yr, 0.19 mm).

  17. Spatial and temporal variations in landscape evolution: historic and longer-term sediment flux through global catchments

    Science.gov (United States)

    Covault, Jacob A.; Craddock, William H.; Romans, Brian W.; Fildani, Andrea; Gosai, Mayur

    2013-01-01

    Sediment generation and transport through terrestrial catchments influence soil distribution, geochemical cycling of particulate and dissolved loads, and the character of the stratigraphic record of Earth history. To assess the spatiotemporal variation in landscape evolution, we compare global compilations of stream gauge–derived () and cosmogenic radionuclide (CRN)–derived (predominantly 10Be; ) denudation of catchments (mm/yr) and sediment load of rivers (Mt/yr). Stream gauges measure suspended sediment loads of rivers during several to tens of years, whereas CRNs provide catchment-integrated denudation rates at 102–105-yr time scales. Stream gauge–derived and CRN-derived sediment loads in close proximity to one another (temporary storage of sediment in flood plains can provide stream gauge–based sediment loads and denudation rates that are applicable over longer periods than the durations of gauge measurements. The buffering capacity of catchments also has implications for interpreting the stratigraphic record; delayed sediment transfer might complicate the stratigraphic record of external forcings and catchment modification.

  18. The influence of hypercapnia and the infaunal brittlestar Amphiura filiformis on sediment nutrient flux – will ocean acidification affect nutrient exchange?

    Directory of Open Access Journals (Sweden)

    S. Widdicombe

    2009-10-01

    Full Text Available Rising levels of atmospheric carbon dioxide and the concomitant increased uptake of this by the oceans is resulting in hypercapnia-related reduction of ocean pH. Research focussed on the direct effects of these physicochemical changes on marine invertebrates has begun to improve our understanding of impacts at the level of individual physiologies. However, CO2-related impairment of organisms' contribution to ecological or ecosystem processes has barely been addressed. The burrowing ophiuroid Amphiura filiformis, which has a physiology that makes it susceptible to reduced pH, plays a key role in sediment nutrient cycling by mixing and irrigating the sediment, a process known as bioturbation. Here we investigate the role of A. filiformis in modifying nutrient flux rates across the sediment-water boundary and the impact of CO2- related acidification on this process. A 40 day exposure study was conducted under predicted pH scenarios from the years 2100 (pH 7.7 and 2300 (pH 7.3, plus an additional treatment of pH 6.8. This study demonstrated strong relationships between A. filiformis density and cycling of some nutrients; activity increases the sediment uptake of phosphate and the release of nitrite and nitrate. No relationship between A. filiformis density and the flux of ammonium or silicate were observed. Results also indicated that, within the timescale of this experiment, effects at the individual bioturbator level appear not to translate into reduced ecosystem influence. However, long term survival of key bioturbating species is far from assured and changes in both bioturbation and microbial processes could alter key biogeochemical processes in future, more acidic oceans.

  19. Impact of open-ocean convection on particle fluxes and sediment dynamics in the deep margin of the Gulf of Lions

    Directory of Open Access Journals (Sweden)

    M. Stabholz

    2013-02-01

    Full Text Available The deep outer margin of the Gulf of Lions and the adjacent basin, in the western Mediterranean Sea, are regularly impacted by open-ocean convection, a major hydrodynamic event responsible for the ventilation of the deep water in the western Mediterranean Basin. However, the impact of open-ocean convection on the flux and transport of particulate matter remains poorly understood. The variability of water mass properties (i.e., temperature and salinity, currents, and particle fluxes were monitored between September 2007 and April 2009 at five instrumented mooring lines deployed between 2050 and 2350-m depth in the deepest continental margin and adjacent basin. Four of the lines followed a NW–SE transect, while the fifth one was located on a sediment wave field to the west. The results of the main, central line SC2350 ("LION" located at 42°02.5′ N, 4°41′ E, at 2350-m depth, show that open-ocean convection reached mid-water depth (≈ 1000-m depth during winter 2007–2008, and reached the seabed (≈ 2350-m depth during winter 2008–2009. Horizontal currents were unusually strong with speeds up to 39 cm s−1 during winter 2008–2009. The measurements at all 5 different locations indicate that mid-depth and near-bottom currents and particle fluxes gave relatively consistent values of similar magnitude across the study area except during winter 2008–2009, when near-bottom fluxes abruptly increased by one to two orders of magnitude. Particulate organic carbon contents, which generally vary between 3 and 5%, were abnormally low (≤ 1% during winter 2008–2009 and approached those observed in surface sediments (≈ 0.6%. Turbidity profiles made in the region demonstrated the existence of a bottom nepheloid layer, several hundred meters thick, and related to the resuspension of bottom sediments. These observations support the view that open-ocean deep convection events in the Gulf of Lions can cause significant remobilization

  20. Spider-mediated flux of PCBs from contaminated sediments to terrestrial ecosystems and potential risks to arachnivorous birds

    Science.gov (United States)

    We investigated aquatic insect utilization and PCB exposure in riparian spiders at the Lake Hartwell superfund site (Clemson, SC , USA). We sampled sediments, adult chironomids, terrestrial insects, riparian spiders (Tetragnathidae, Araneidae, and Mecynogea lemniscata), and upla...

  1. Enhanced particle fluxes and heterotrophic bacterial activities in Gulf of Mexico bottom waters following storm-induced sediment resuspension

    Science.gov (United States)

    Ziervogel, K.; Dike, C.; Asper, V.; Montoya, J.; Battles, J.; D`souza, N.; Passow, U.; Diercks, A.; Esch, M.; Joye, S.; Dewald, C.; Arnosti, C.

    2016-07-01

    Bottom nepheloid layers (BNLs) in the deep sea transport and remobilize considerable amounts of particulate matter, enhancing microbial cycling of organic matter in cold, deep water environments. We measured bacterial abundance, bacterial protein production, and activities of hydrolytic enzymes within and above a BNL that formed in the deep Mississippi Canyon, northern Gulf of Mexico, shortly after Hurricane Isaac had passed over the study area in late August 2012. The BNL was detected via beam attenuation in CTD casts over an area of at least 3.5 km2, extending up to 200 m above the seafloor at a water depth of 1500 m. A large fraction of the suspended matter in the BNL consisted of resuspended sediments, as indicated by high levels of lithogenic material collected in near-bottom sediment traps shortly before the start of our sampling campaign. Observations of suspended particle abundance and sizes throughout the water column, using a combined camera-CTD system (marine snow camera, MSC), revealed the presence of macroaggregates (>1 mm in diameter) within the BNL, indicating resuspension of canyon sediments. A distinct bacterial response to enhanced particle concentrations within the BNL was evident from the observation that the highest enzymatic activities (peptidase, β-glucosidase) and protein production (3H-leucine incorporation) were found within the most particle rich sections of the BNL. To investigate the effects of enhanced particle concentrations on bacterial activities in deep BNLs more directly, we conducted laboratory experiments with roller bottles filled with bottom water and amended with experimentally resuspended sediments from the study area. Macroaggregates formed within 1 day from resuspended sediments; by day 4 of the incubation bacterial cell numbers in treatments with resuspended sediments were more than twice as high as in those lacking sediment suspensions. Cell-specific enzymatic activities were also generally higher in the sediment

  2. Soil erosion processes and sediment fluxes in a Mediterranean landscape of marls, Campina de Cadiz, SW Spain

    International Nuclear Information System (INIS)

    Faust, D.; Schmidt, M.

    2009-01-01

    Marl landscapes, especially in the Mediterranean, show evident traces of high present-day and past soil erosion rates. The tendency to develop hill slope channels leads even at moderate rainstorm magnitudes to a significant increase of slope-to-slope connectivity, resulting in high amounts of mass transfer from upper parts of the hill slopes towards foot slopes and valley floors. To analyse the intensity of this transfer a study was conducted focussing on late Holocene sediments correlative to modern-time soil erosion in the marl landscape of SW Spain. Based of field observations and sediment analysis several landscape positions within a medium-scale catchment were explored. Depending on landscape constellation, the sediment characteristics reflect either hill slope processes or alluvial processes or an interchange of them. For a temporal context a method to trace young sediments by analysing nutrients originating from modern-time application of mineral fertiliser was applied. Results show high rates of sedimentation (>1 cm/year) for this young period in several profiles. By identifying the predominant geomorphic components and processes in the study area a conceptual model of the studied system was developed. (Author) 17 refs.

  3. Establishing a tracer-based sediment budget to preserve wetlands in Mediterranean mountain agroecosystems (NE Spain)

    Energy Technology Data Exchange (ETDEWEB)

    Navas, Ana, E-mail: anavas@eead.csic.es [Department of Soil and Water, Estación Experimental de Aula Dei, EEAD-CSIC, Avda. Montañana 1005, 50059 Zaragoza (Spain); López-Vicente, Manuel, E-mail: mvicente@eead.csic.es [Department of Soil and Water, Estación Experimental de Aula Dei, EEAD-CSIC, Avda. Montañana 1005, 50059 Zaragoza (Spain); Gaspar, Leticia, E-mail: leticia.gaspar@plymouth.ac.uk [School of Geography, Earth and Environmental Science, Plymouth University, Plymouth, Devon PL4 8AA (United Kingdom); Palazón, Leticia, E-mail: lpalazon@eead.csic.es [Department of Soil and Water, Estación Experimental de Aula Dei, EEAD-CSIC, Avda. Montañana 1005, 50059 Zaragoza (Spain); Quijano, Laura, E-mail: lquijano@eead.cisc.es [Department of Soil and Water, Estación Experimental de Aula Dei, EEAD-CSIC, Avda. Montañana 1005, 50059 Zaragoza (Spain)

    2014-10-15

    Mountain wetlands in Mediterranean regions are particularly threatened in agricultural environments due to anthropogenic activity. An integrated study of source-to-sink sediment fluxes was carried out in an agricultural catchment that holds a small permanent lake included in the European NATURA 2000 Network. More than 1000 yrs of human intervention and the variety of land uses pose a substantial challenge when attempting to estimate sediment fluxes which is the first requirement to protect fragile wetlands. To date, there have been few similar studies and those that have been carried out have not addressed such complex terrain. Geostatistical interpolation and GIS tools were used to derive the soil spatial redistribution from point {sup 137}Cs inventories, and to establish the sediment budget in a catchment located in the Southern Pyrenees. The soil redistribution was intense and soil erosion predominated over soil deposition. On the areas that maintained natural vegetation the median soil erosion and deposition rates were moderate, ranging from 2.6 to 6 Mg ha yr{sup −1} and 1.5 to 2.1 Mg ha yr{sup −1}, respectively. However, in cultivated fields both erosion and deposition were significantly higher (ca. 20 Mg ha yr{sup −1}), and the maximum rates were always associated with tillage practices. Farming activities in the last part of the 20th century intensified soil erosion, as evidenced by the 1963 {sup 137}Cs peaks in the lake cores and estimates from the sediment budget indicated a net deposition of 671 Mg yr{sup −1}. Results confirm a siltation risk for the lake and provide a foundation for designing management plans to preserve this threatened wetland. This comprehensive approach provides information useful for understanding processes that influence the patterns and rates of soil transfer and deposition within fragile Mediterranean mountain wetlands subjected to climate and anthropogenic stresses. - Highlights: • Soil erosion threatens long

  4. Monitoring to assess progress toward meeting the Assabet River, Massachusetts, phosphorus total maximum daily load - Aquatic macrophyte biomass and sediment-phosphorus flux

    Science.gov (United States)

    Zimmerman, Marc J.; Qian, Yu; Yong Q., Tian

    2011-01-01

    In 2004, the Total Maximum Daily Load (TMDL) for Total Phosphorus in the Assabet River, Massachusetts, was approved by the U.S. Environmental Protection Agency. The goal of the TMDL was to decrease the concentrations of the nutrient phosphorus to mitigate some of the instream ecological effects of eutrophication on the river; these effects were, for the most part, direct consequences of the excessive growth of aquatic macrophytes. The primary instrument effecting lower concentrations of phosphorus was to be strict control of phosphorus releases from four major wastewatertreatment plants in Westborough, Marlborough, Hudson, and Maynard, Massachusetts. The improvements to be achieved from implementing this control were lower concentrations of total and dissolved phosphorus in the river, a 50-percent reduction in aquatic-plant biomass, a 30-percent reduction in episodes of dissolved oxygen supersaturation, no low-flow dissolved oxygen concentrations less than 5.0 milligrams per liter, and a 90-percent reduction in sediment releases of phosphorus to the overlying water. In 2007, the U.S. Geological Survey, in cooperation with the Massachusetts Department of Environmental Protection, initiated studies to evaluate conditions in the Assabet River prior to the upgrading of wastewater-treatment plants to remove more phosphorus from their effluents. The studies, completed in 2008, implemented a visual monitoring plan to evaluate the extent and biomass of the floating macrophyte Lemna minor (commonly known as lesser duckweed) in five impoundments and evaluated the potential for phosphorus flux from sediments in impounded and free-flowing reaches of the river. Hydrologically, the two study years 2007 and 2008 were quite different. In 2007, summer streamflows, although low, were higher than average, and in 2008, the flows were generally higher than in 2007. Visually, the effects of these streamflow differences on the distribution of Lemna were obvious. In 2007, large amounts of

  5. Chironomus plumosus larvae increase fluxes of denitrification products and diversity of nitrate-reducing bacteria in freshwater sediment

    DEFF Research Database (Denmark)

    Poulsen, Morten; W. V. Kofoed, Michael; H. Larsen, Lone

    2014-01-01

    , respectively, which was mostly due to stimulation of sedimentary denitrification; incomplete denitrification in the guts accounted for up to 20% of the N2O efflux. Phylotype richness of the nitrate reductase gene narG was significantly higher in sediment with than without larvae. In the gut, 47 narG phylotypes...... were found expressed, which may contribute to higher phylotype richness in colonized sediment. In contrast, phylotype richness of the nitrous oxide reductase gene nosZ was unaffected by the presence of larvae and very few nosZ phylotypes were expressed in the gut. Gene abundance of neither narG, nor...... nosZ wasdifferent in sediments with and without larvae. Hence, C. plumosus increases activity and diversity, but not overall abundance of nitrate-reducing bacteria, probably by providing additional ecological niches in its burrow and gut....

  6. Discharge controls on the sediment and dissolved nutrient transport flux of the lowermost Mississippi River: Implications for export to the ocean and for delta restoration

    Science.gov (United States)

    Allison, Mead A.; Pratt, Thad C.

    2017-12-01

    Lagrangian longitudinal surveys and fixed station data are utilized from the lowermost Mississippi River reach in Louisiana at high and low discharge in 2012-2013 to examine the changing stream power, sediment transport capacity, and nitrate conveyance in this backwater reach of the river. Nitrate appears to remain conservative through the backwater reach at higher discharges (>15,000 m3/s), thus, nitrate levels supplied from the catchment are those exported to the Gulf of Mexico, fueling coastal hypoxia. At lower discharges, interaction with fine sediments and organic matter stored on the bed due to estuarine and tidal processes, likely elevates nitrate levels prior to entering the Gulf: a further 1-2 week long spike in nitrate concentrations is associated with the remobilization of this sediments during the rising discharge phase of the Mississippi. Backwater characteristics are clearly observed in the study reach starting at river kilometer 703 (Vicksburg) in both longitudinal study periods. Stream power at the lowermost station is only 16% of that at Vicksburg in the high discharge survey, and 0.6% at low flow. The high-to-low discharge study differential in unit stream power at a station increases between Vicksburg and the lowermost station from a factor of 3 to 47-50 times. At high discharge, ∼30% of this energy loss can be ascribed to the removal of water to the Atchafalaya at Old River Control. Suspended sediment flux decreases downstream in the studied reach in both studies: the lowermost station has 75% of the flux at Vicksburg in the high discharge study, and 0.9% in the low discharge study. The high discharge values, given that this study was conducted during the highest rising hydrograph of the water year, are augmented by sediment resuspended from the bed that was deposited in the previous low discharge phase. Examination of this first detailed field observation studies of the backwater phenomenon in a major river, shows that observed suspended

  7. Can hydrocarbons in coastal sediments be related to terrestrial flux? A case study of Godavari river discharge (Bay of Bengal)

    Digital Repository Service at National Institute of Oceanography (India)

    Rayaprolu, K.; GopalaKrishna, V.V.J.; Naik, B.G.; Mahalakshmi, G.; Rengarajan, R.; Mazumdar, A; Sarma, N.S.

    A sediment core aged ~250 years and deposition rate of ~2.4 mm yr-1 raised from the coastal region receiving inputs from the Godavari river was examined for n-alkanes The carbon preference index (CPI) of shortchain hydrocarbons (SHC...

  8. Nineteen-year time-series sediment trap study of Coccolithus pelagicus and Emiliania huxleyi (calcareous nannoplankton) fluxes in the Bering Sea and subarctic Pacific Ocean

    Science.gov (United States)

    Tsutsui, Hideto; Takahashi, Kozo; Asahi, Hirofumi; Jordan, Richard W.; Nishida, Shiro; Nishiwaki, Niichi; Yamamoto, Sumito

    2016-03-01

    Coccolithophore fluxes at two sediment trap stations, Station AB in the Bering Sea and Station SA in the subarctic Pacific Ocean, were studied over a nineteen-year (August 1990-July 2009) interval. Two major species, Coccolithus pelagicus and Emiliania huxleyi, occur at both stations, with Gephyrocapsa oceanica, Umbilicosphaera sibogae, Braarudosphaera bigelowii, and Syracosphaera spp. as minor components. The mean coccolithophore fluxes at Stations AB and SA increased from 28.9×106 m2 d-1 and 61.9×106 m2 d-1 in 1990-1999 to 54.4×106 m2 d-1 and 130.2×106 m2 d-1 in 2002-2009, respectively. Furthermore, in late 1999 to early 2000, there was a significant shift in the most dominant species from E. huxleyi to C. pelagicus. High abundances of E. huxleyi correspond to the positive mode of the Pacific Decadal Oscillation (PDO), while those of C. pelagicus respond to the PDO negative mode and are related to water temperature changes at huxleyi. At both stations the mean seawater temperature in the top 45 m from August to October increased ca. 1 °C with linear recurrence from 1990 to 2008. The coccosphere fluxes after Year 2000 at Stations AB and SA, and the shift in species dominance, may have been influenced by this warming.

  9. Effects of wind farm construction on concentrations and fluxes of dissolved organic carbon and suspended sediment from peat catchments at Braes of Doune, central Scotland

    Directory of Open Access Journals (Sweden)

    I. Grieve

    2008-07-01

    Full Text Available This paper assesses the impacts of disturbance associated with the construction of a wind farm on fluxes of dissolved organic carbon (DOC and suspended sediment from a blanket peat catchment in central Scotland during the period immediately following completion of construction. Six streams draining the site were sampled on six dates from October 2006, when construction was completed, and an additional three control streams to the west of the site were sampled on the same dates. Turbidity and stage were recorded semi-continuously in the two largest streams (one disturbed and one control, which were also sampled during storm events. Absorbance (400 nm and DOC concentrations were determined on all samples, and suspended sediment was determined on the event samples. Absorbance and DOC were closely correlated in both the disturbed and undisturbed streams, with slightly greater absorbance per unit DOC in the disturbed streams. DOC concentrations in disturbed tributaries were always greater than those in undisturbed streams, with mean differences ranging from 2 to around 5 mg L-1. DOC and stage were positively correlated during events with maximum concentrations in excess of 30 mg L 1 at peak flow. Suspended sediment concentrations were markedly elevated in the disturbed stream with maximum concentrations at peak flow some 4–5 times greater than in the control. The colour of the sediment suggested that it was highly organic in nature at peak flow, and suspended particulate organic carbon represented a further loss of C from the site. Using flow-weighted mean DOC concentrations calculated for the storms monitored in autumn 2007, dissolved carbon losses can be estimated for the catchments of the disturbed and control streams. From these data the additional DOC loss related to disturbance associated with the wind farm is estimated at 5 g m-2.

  10. Nutrient Fluxes From Profundal Sediment of Ultra-Oligotrophic Lake Tahoe, California/Nevada: Implications for Water Quality and Management in a Changing Climate

    Science.gov (United States)

    Beutel, Marc W.; Horne, Alexander J.

    2018-03-01

    A warming climate is expected to lead to stronger thermal stratification, less frequent deep mixing, and greater potential for bottom water anoxia in deep, temperate oligotrophic lakes. As a result, there is growing interest in understanding nutrient cycling at the profundal sediment-water interface of these rare ecosystems. This paper assessed nutrient content and nutrient flux rates from profundal sediment at Lake Tahoe, California/Nevada, USA. Sediment is a large reservoir of nutrients, with the upper 5 cm containing reduced nitrogen (˜6,300 metric tons) and redox-sensitive phosphorus (˜710 metric tons) equivalent to ˜15 times the annual external load. Experimental results indicate that if deep water in Lake Tahoe goes anoxic, profundal sediment will release appreciable amounts of phosphate (0.13-0.29 mg P/m2·d), ammonia (0.49 mg N/m2·d), and iron to overlaying water. Assuming a 10 year duration of bottom water anoxia followed by a deep-water mixing event, water column phosphate, and ammonia concentrations would increase by an estimated 1.6 µg P/L and 2.9 µg N/L, nearly doubling ambient concentrations. Based on historic nutrient enrichment assays this could lead to a ˜40% increase in algal growth. Iron release could have the dual effect of alleviating nitrate limitation on algal growth while promoting the formation of fine iron oxyhydroxide particles that degrade water clarity. If the depth and frequency of lake mixing decrease in the future as hydrodynamic models suggest, large-scale in-lake management strategies that impede internal nutrient loading in Lake Tahoe, such as bottom water oxygen addition or aluminum salt addition, may need to be considered.

  11. Using Passive Polyethylene Samplers to Evaluate Chemical Activities Controlling Fluxes and Bioaccumulation of Organic Contaminants in Bed Sediments

    Science.gov (United States)

    2010-11-01

    often yielding uncertain information regarding the degree of hazard and the spatial extent of the problem. Subsequent remediation commonly involves...suited to sampling organic contaminants across bed-water interfaces and down into the sediment bed. The methodology must yield data that are more...surrogate standards were Soxhlet extracted for 24 hr using 450 mL of dichloromethane. Extracts were reduced to approximately 10 mL using the rotary

  12. Quantifying suspended sediment flux in a mixed-land-use urbanizing watershed using a nested-scale study design.

    Science.gov (United States)

    Zeiger, Sean; Hubbart, Jason A

    2016-01-15

    Suspended sediment (SS) remains the most pervasive water quality problem globally and yet, despite progress, SS process understanding remains relatively poor in watersheds with mixed-land-use practices. The main objective of the current work was to investigate relationships between suspended sediment and land use types at multiple spatial scales (n=5) using four years of suspended sediment data collected in a representative urbanized mixed-land-use (forest, agriculture, urban) watershed. Water samples were analyzed for SS using a nested-scale experimental watershed study design (n=836 samples×5 gauging sites). Kruskal-Wallis and Dunn's post-hoc multiple comparison tests were used to test for significant differences (CI=95%, p<0.05) in SS levels between gauging sites. Climate extremes (high precipitation/drought) were observed during the study period. Annual maximum SS concentrations exceeded 2387.6 mg/L. Median SS concentrations decreased by 60% from the agricultural headwaters to the rural/urban interface, and increased by 98% as urban land use increased. Multiple linear regression analysis results showed significant relationships between SS, annual total precipitation (positive correlate), forested land use (negative correlate), agricultural land use (negative correlate), and urban land use (negative correlate). Estimated annual SS yields ranged from 16.1 to 313.0 t km(-2) year(-1) mainly due to differences in annual total precipitation. Results highlight the need for additional studies, and point to the need for improved best management practices designed to reduce anthropogenic SS loading in mixed-land-use watersheds. Copyright © 2015 Elsevier B.V. All rights reserved.

  13. Sources, vertical fluxes and accumulation of petroleum hydrocarbons in sediments from the Mandovi Estuary, west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Veerasingam, S.; Vethamony, P.; ManiMurali, R.; Babu, M.T.

    in surficial sediments from the Scotian Shelf. Geochimica et Cosmochimica Acta, 60, 3151–3159. Kennicutt, MCJr., Brooks, J.M., Atlas, E.L., and Giam, C.S. (1989). Organic compounds of environmental concern in the Gulf of Mexico: a review. Aquatic Toxicology... Location PHC (µg/g) References Narragansett Bay, USA 50–120 Farrington and Quinn, 1973 Scotian shelf, Canada 1.0–94.0 Keizer et al., 1978 Liverpool Bay, UK 29.0 Law 1981 Gulf of Mexico 0.02–190 Kennicutt et al., 1989 Guipuzcoan coast 0.21–0.80 Grimalt...

  14. Application of Tools to Measure PCB Microbial Dechlorination and Flux into Water During In-situ Treatment of Sediments

    Science.gov (United States)

    2011-08-01

    removal of sulfur. The copper treated extract was passed through a 3% deactivated silica gel column using hexane ( pesticide grade) as the eluting...the addition of microorganisms and/or chemicals to the sediments to initiate or enhance bioremediation . In situ solidification/stabilization...and a floc contact area. The detail settings are shown in Table 1……………………………………...……...87 Figure 6.5: Using Lick et al. (1996) experiment data to

  15. The interaction between land use change, sediment fluxes and carbon dynamics: evaluating an integrated soil-landscape model at the millennial time-scale.

    Science.gov (United States)

    Bouchoms, Samuel; Van Oost, Kristof; Vanacker, Veerle

    2015-04-01

    Soil-landscape modelling has received growing attention as it allows us to evaluate the interaction between earth surface and soil bio-physical processes. At the landscape scale, human-induced land use change has altered the balance between soil erosion and production, and largely modified sediment fluxes. Intensification in soil redistribution rates affects the interaction between soil chemical, physical and biological processes at the landscape scale. Here, we evaluate the SPEROS-LT model, a spatially explicit 3D model combining a dynamic representation of land use, soil erosion and deposition and the soil carbon cycle. We assess the impact of millennial-scale human-induced land use change on sediment fluxes and carbon dynamics in the Dijle catchement (central Belgium). The watershed has undergone a 3000 years continuous human-induced alteration of the vegetation covers for agricultural characterized by Our study is based on land use reconstructions for the last 3000 years, including massive deforestation for agriculture in Roman Times and the Middle Ages followed by urbanization in the last 150 years. Land use reconstructions rely on simple land use allocation rules based on slope gradients. SPEROS-LT is parametrized for erosion rates against available figures in the literature by changing the transport capacity and the transfer coefficient which defines the amount of flux transferred between different land uses. Carbon content profiles at steady state (i.e. without influence of erosion or deposition) are calibrated for each land use and for the first upper meter of soil by comparing modeled profiles to an averaged observed profiles in stable areas of the pedologic region. We present a model sensitivity analysis and a full validation of the predicted soil carbon storage (horizontally, i.e. in space, and vertically, i.e. with depth) using a large database of observational data. The results indicate (i) a good agreement of the erosion rates. Speros LT modeled

  16. Effects of cyanobacterial-driven pH increases on sediment nutrient fluxes and coupled nitrification-denitrification in a shallow fresh water estuary

    Directory of Open Access Journals (Sweden)

    Y. Gao

    2012-07-01

    Full Text Available Summer cyanobacterial blooms caused an elevation in pH (9 to ~10.5 that lasted for weeks in the shallow and tidal-fresh region of the Sassafras River, a tributary of Chesapeake Bay (USA. Elevated pH promoted desorption of sedimentary inorganic phosphorus and facilitated conversion of ammonium (NH4+ to ammonia (NH3. In this study, we investigated pH effects on exchangeable NH4+ desorption, pore water diffusion and the flux rates of NH4+, soluble reactive phosphorus (SRP and nitrate (NO3, nitrification, denitrification, and oxygen consumption. Elevated pH enhanced desorption of exchangeable NH4+ through NH3 formation from both pore water and adsorbed NH4+ pools. Progressive penetration of high pH from the overlying water into sediment promoted the mobility of SRP and the release of total ammonium (NH4+ and NH3 into the pore water. At elevated pH levels, high sediment-water effluxes of SRP and total ammonium were associated with reduction of nitrification, denitrification and oxygen consumption rates. Alkaline pH and the toxicity of NH3 may inhibit nitrification in the thin aerobic zone, simultaneously constraining coupled nitrification–denitrification with limited NO3 supply and high pH penetration into the anaerobic zone. Geochemical feedbacks to pH elevation, such as enhancement of dissolved nutrient effluxes and reduction in N2 loss via denitrification, may enhance the persistence of cyanobacterial blooms in shallow water ecosystems.

  17. A test of the ADV-based Reynolds flux method for in situ estimation of sediment settling velocity in a muddy estuary

    Science.gov (United States)

    Cartwright, Grace M.; Friedrichs, Carl T.; Smith, S. Jarrell

    2013-12-01

    Under conditions common in muddy coastal and estuarine environments, acoustic Doppler velocimeters (ADVs) can serve to estimate sediment settling velocity ( w s) by assuming a balance between upward turbulent Reynolds flux and downward gravitational settling. Advantages of this method include simple instrument deployment, lack of flow disturbance, and relative insensitivity to biofouling and water column stratification. Although this method is being used with increasing frequency in coastal and estuarine environments, to date it has received little direct ground truthing. This study compared in situ estimates of w s inferred by a 5-MHz ADV to independent in situ observations from a high-definition video settling column over the course of a flood tide in the bottom boundary layer of the York River estuary, Virginia, USA. The ADV-based measurements were found to agree with those of the settling column when the current speed at about 40 cm above the bed was greater than about 20 cm/s. This corresponded to periods when the estimated magnitude of the settling term in the suspended sediment continuity equation was four or more times larger than the time rate of change of concentration. For ADV observations restricted to these conditions, ADV-based estimates of w s (mean 0.48±0.04 mm/s) were highly consistent with those observed by the settling column (mean 0.45±0.02 mm/s). However, the ADV-based method for estimating w s was sensitive to the prescribed concentration of the non-settling washload, C wash. In an objective operational definition, C wash can be set equal to the lowest suspended solids concentration observed around slack water.

  18. Modeling the influence of long term human-induced land use conversion on sediment fluxes and carbon dynamics at the catchment scale

    Science.gov (United States)

    Bouchoms, Samuel; Van Oost, Kristof; Vanacker, Veerle

    2014-05-01

    Over the past 20 years, there has been increasing evidence of the strong impact of human activities on the landscape, specifically on soil erosion due to the removal of natural vegetation cover for agricultural and urban purposes. The results question the widespread hypothesis of a steady state landscape since it appears that the balance between soil production and erosion may be broken altering the interactions between chemical, physical and biological processes in both soil and landscape system. Yet, the relationship between this accelerated erosion and the carbon dynamics at the landscape scale remains an important area of investigation. Recent attempts to combine geomorphic models, soil redistribution and carbon dynamic has proved themselves valuable in term of supporting the importance of lateral fluxes as a crucial control of carbon dynamic at the landscape scale. We use the SPEROS LT model, a modified version of SPEROS-C which includes dynamic land use and soil physical properties, to assess the impact of historical land use conversion on sediment and carbon fluxes in the Dijle catchment. This particular location has experienced a significant human impact since the Roman period, undergoing heavy deforestation and expansion of agricultural lands followed by a period of abandonment. The last 400 to 500 years saw a dramatic increase in the intensity of land use conversion associated to population growth leading to forest cleaning and urbanization. Our main objective is to validate the combined geomorphic and soil carbon turnover process descriptions of the model. Historical land use proportions are based on existing literature estimations and spatial assignation of the land conversion relies on simple allocation rules based on criteria such as slope or soil texture. Land use scenarios are constructed for the last 2000 years. We confront the model results with observations and perform a sensitivity analysis. The results indicate that the general trends in

  19. Particle Fluxes and Bulk Geochemical Characterization of the Cabo Frio Upwelling System in Southeastern Brazil: Sediment Trap Experiments between Spring 2010 and Summer 2012

    Directory of Open Access Journals (Sweden)

    ANA LUIZA S. ALBUQUERQUE

    2014-06-01

    Full Text Available Physical and biogeochemical processes in continental shelves act synergistically in both transporting and transforming suspended material, and ocean dynamics control the dispersion of particles by the coastal zone and their subsequent mixing and dilution within the shelf area constrained by oceanic boundary currents, followed by their gradual settling in a complex sedimentary scenario. One of these regions is the Cabo Frio Upwelling System located in a significantly productive area of Southeastern Brazil, under the control of the nutrient-poor western boundary Brazil Current but also with a wind-driven coastal upwelling zone, inducing cold-water intrusions of South Atlantic Central Water on the shelf. To understand these synergic interactions among physical and biogeochemical processes in the Cabo Frio shelf, a series of four experiments with a total of 98 discrete samples using sediment traps was performed from November 2010 to March 2012, located on the 145 m isobath on the edge of the continental shelf. The results showed that lateral transport might be relevant in some cases, especially in deep layers, although no clear seasonal cycle was detected. Two main physical-geochemical coupling scenarios were identified: singular downwelling events that can enhance particles fluxes and are potentially related to the Brazil Current oscillations; and events of significant fluxes related to the intrusion of the 18°C isotherm in the euphotic zone. The particulate matter settling in the Cabo Frio shelf area seems to belong to multiple marine and terrestrial sources, in which both Paraiba do Sul River and Guanabara Bay could be potential land-sources, although the particulate material might subject intense transformation (diagenesis during its trajectory to the shelf edge.

  20. Particle Fluxes and Bulk Geochemical Characterization of the Cabo Frio Upwelling System in Southeastern Brazil: Sediment Trap Experiments between Spring 2010 and Summer 2012.

    Science.gov (United States)

    Albuquerque, Ana Luiza S; Belém, André L; Zuluaga, Francisco J B; Cordeiro, Livia G M; Mendoza, Ursula; Knoppers, Bastiaan A; Gurgel, Marcio H C; Meyers, Philip A; Capilla, Ramsés

    2014-05-14

    Physical and biogeochemical processes in continental shelves act synergistically in both transporting and transforming suspended material, and ocean dynamics control the dispersion of particles by the coastal zone and their subsequent mixing and dilution within the shelf area constrained by oceanic boundary currents, followed by their gradual settling in a complex sedimentary scenario. One of these regions is the Cabo Frio Upwelling System located in a significantly productive area of Southeastern Brazil, under the control of the nutrient-poor western boundary Brazil Current but also with a wind-driven coastal upwelling zone, inducing cold-water intrusions of South Atlantic Central Water on the shelf. To understand these synergic interactions among physical and biogeochemical processes in the Cabo Frio shelf, a series of four experiments with a total of 98 discrete samples using sediment traps was performed from November 2010 to March 2012, located on the 145 m isobath on the edge of the continental shelf. The results showed that lateral transport might be relevant in some cases, especially in deep layers, although no clear seasonal cycle was detected. Two main physical-geochemical coupling scenarios were identified: singular downwelling events that can enhance particles fluxes and are potentially related to the Brazil Current oscillations; and events of significant fluxes related to the intrusion of the 18°C isotherm in the euphotic zone. The particulate matter settling in the Cabo Frio shelf area seems to belong to multiple marine and terrestrial sources, in which both Paraiba do Sul River and Guanabara Bay could be potential land-sources, although the particulate material might subject intense transformation (diagenesis) during its trajectory to the shelf edge.

  1. Contemporary suspended sediment yield of a partly glaciated catchment, Riffler Bach (Tyrol, Austria)

    Science.gov (United States)

    Weber, Martin; Baewert, Henning; Morche, David

    2015-04-01

    locate sediment sources both approaches underline the fact that SSC does not always depends on discharge but also on sediment availability. The comparison of both approaches shows that in well investigated areas the results are strongly determined by the choice of the analysis method. References Geilhausen, M., Morche, D., Otto, J.-C. and Schrott, L. (2013): Sediment discharge from the proglacial zone of a retreating Alpine glacier. Z Geomorphol Supplementary Issue 57 (2), 29-53. DOI: 10.1127/0372-8854/2012/S-00122 Orwin, J., Lamoureux, S.F., Warburton, J. and Beylich, A., (2010): A framework for characterizing fluvial sediment fluxes from source to sink in cold environments. Geogr. Ann. 92 A (2): 155-176. Orwin, J.F. and Smart, C.C. (2004): Short-term spatial and temporal patterns of suspended sediment transfer in proglacial channels, Small River Glacier, Canada. Hydrol. Process. 18, 1521-1542.

  2. Organo-halogenated contaminants (OHCs) in the sediments from the Soan River, Pakistan: OHCs(adsorbed TOC) burial flux, status and risk assessment.

    Science.gov (United States)

    Malik, Riffat Naseem; Mehboob, Fouzia; Ali, Usman; Katsoyiannis, Athanasios; Schuster, Jasmin K; Moeckel, Claudia; Jones, Kevin C

    2014-05-15

    In this study, regression analysis revealed that TOC is the principal factor in controlling the fate of organo-halogenated contaminants (OHCs: PCBs, PBDEs, OCPs) in Soan River, Pakistan. The OHCs(adsorbed TOC) burial flux (OHCs(adsorbed TOC)Bf; mg/cm(2)·yr) was calculated in the following ranges: ∑PCBs (0.07-0.31), ∑PBDEs (0.005-0.029), ∑HCHs (0.015-0.046) and ∑DDTs (0.007-0.039). Apart from OHCs(adsorbed TOC)Bf, the levels of OHCs were in the following order: PCBs>DDTs>PBDEs>HCH>Chlordane>HCB. PBDEs and PCB congener patterns showed following order respectively: BDE-149>-153>-18>-138>-44 and PCB-149>-153>-18>-138>-44. DDT isomers and metabolites' pattern were p,p'-DDT>p,p'-DDD>p,p'-DDE>o,p'-DDT>o,p'-DDD>o,p'-DDE and HCHs were β-HCH>α-HCH>γ-HCH>δ-HCH. PBDE composition had similarities to penta-BDE and DE-71 mixtures and PCBs with commercial products Aroclor-1254 and -1260. (DDE+DDD)/∑DDTs and p,p'-DDT/p,p'-DDE suggested the recent input of DDTs in sediments while α/γ-HCH indicated past usage of lindane and technical mixtures. Risk assessment suggested that Soan River and its tributaries are potentially at risk against most of the OHCs. Copyright © 2014 Elsevier B.V. All rights reserved.

  3. Miocene-Recent sediment flux in the south-central Alaskan fore-arc basin governed by flat-slab subduction

    Science.gov (United States)

    Finzel, Emily S.; Enkelmann, Eva

    2017-04-01

    The Cook Inlet in south-central Alaska contains the early Oligocene to Recent stratigraphic record of a fore-arc basin adjacent to a shallowly subducting oceanic plateau. Our new measured stratigraphic sections and detrital zircon U-Pb geochronology and Hf isotopes from Neogene strata and modern rivers illustrate the effects of flat-slab subduction on the depositional environments, provenance, and subsidence in fore-arc sedimentary systems. During the middle Miocene, fluvial systems emerged from the eastern, western, and northern margins of the basin. The axis of maximum subsidence was near the center of the basin, suggesting equal contributions from subsidence drivers on both margins. By the late Miocene, the axis of maximum subsidence had shifted westward and fluvial systems originating on the eastern margin of the basin above the flat-slab traversed the entire width of the basin. These mud-dominated systems reflect increased sediment flux from recycling of accretionary prism strata. Fluvial systems with headwaters above the flat-slab region continued to cross the basin during Pliocene time, but a change to sandstone-dominated strata with abundant volcanogenic grains signals a reactivation of the volcanic arc. The axis of maximum basin subsidence during late Miocene to Pliocene time is parallel to the strike of the subducting slab. Our data suggest that the character and strike-orientation of the down-going slab may provide a fundamental control on the nature of depositional systems, location of dominant provenance regions, and areas of maximum subsidence in fore-arc basins.

  4. Rates and fluxes of centennial-scale carbon storage in the fine-grained sediments from the central South Yellow Sea and Min-Zhe belt, East China Sea

    Science.gov (United States)

    Wang, Jianghai; Xiao, Xi; Zhou, Qianzhi; Xu, Xiaoming; Zhang, Chenxi; Liu, Jinzhong; Yuan, Dongliang

    2018-01-01

    The global carbon cycle has played a key role in mitigating global warming and climate change. Long-term natural and anthropogenic processes influence the composition, sources, burial rates, and fluxes of carbon in sediments on the continental shelf of China. In this study, the rates, fluxes, and amounts of carbon storage at the centennial scale were estimated and demonstrated using the case study of three fine-grained sediment cores from the central South Yellow Sea area (SYSA) and Min-Zhe belt (MZB), East China Sea. Based on the high-resolution temporal sequences of total carbon (TC) and total organic carbon (TOC) contents, we reconstructed the annual variations of historical marine carbon storage, and explored the influence of terrestrial and marine sources on carbon burial at the centennial scale. The estimated TC storage over 100 years was 1.18×108 t in the SYSA and 1.45×109 t in the MZB. The corrected TOC storage fluxes at the centennial scale ranged from 17 to 28 t/(km2·a)in the SYSA and from 56 to 148 t/(km2·a) in the MZB. The decrease of terrestrial materials and the increase of marine primary production suggest that the TOC buried in the sediments in the SYSA and MZB was mainly derived from the marine autogenetic source. In the MZB, two depletion events occurred in TC and TOC storage from 1985 to 1987 and 2003 to 2006, which were coeval with the water impoundment in the Gezhouba and Three Gorges dams, respectively. The high-resolution records of the carbon storage rates and fluxes in the SYSA and MZB reflect the synchronous responses to human activities and provide an important reference for assessing the carbon sequestration capacity of the marginal seas of China.

  5. Sediment transport patterns in the San Francisco Bay Coastal System from cross-validation of bedform asymmetry and modeled residual flux

    Science.gov (United States)

    Barnard, Patrick L.; Erikson, Li H.; Elias, Edwin P.L.; Dartnell, Peter; Barnard, P.L.; Jaffee, B.E.; Schoellhamer, D.H.

    2013-01-01

    The morphology of ~ 45,000 bedforms from 13 multibeam bathymetry surveys was used as a proxy for identifying net bedload sediment transport directions and pathways throughout the San Francisco Bay estuary and adjacent outer coast. The spatially-averaged shape asymmetry of the bedforms reveals distinct pathways of ebb and flood transport. Additionally, the region-wide, ebb-oriented asymmetry of 5% suggests net seaward-directed transport within the estuarine-coastal system, with significant seaward asymmetry at the mouth of San Francisco Bay (11%), through the northern reaches of the Bay (7–8%), and among the largest bedforms (21% for λ > 50 m). This general indication for the net transport of sand to the open coast strongly suggests that anthropogenic removal of sediment from the estuary, particularly along clearly defined seaward transport pathways, will limit the supply of sand to chronically eroding, open-coast beaches. The bedform asymmetry measurements significantly agree (up to ~ 76%) with modeled annual residual transport directions derived from a hydrodynamically-calibrated numerical model, and the orientation of adjacent, flow-sculpted seafloor features such as mega-flute structures, providing a comprehensive validation of the technique. The methods described in this paper to determine well-defined, cross-validated sediment transport pathways can be applied to estuarine-coastal systems globally where bedforms are present. The results can inform and improve regional sediment management practices to more efficiently utilize often limited sediment resources and mitigate current and future sediment supply-related impacts.

  6. From Source to Sink: Mechanistic Reasoning Using the Electron-Pushing Formalism

    Science.gov (United States)

    Bhattacharyya, Gautam

    2013-01-01

    Since the introduction of Morrison and Boyd's textbook in organic chemistry over 50 years ago, reaction mechanisms and mechanistic reasoning using the electron-pushing formalism (EPF) have become a mainstay of organic chemistry courses. In recent years there have even been several papers in this Journal and others detailing research on how…

  7. The I.A.G. / A.I.G. SEDIBUD (Sediment Budgets in Cold Environments) Programme: Current and future activities

    Science.gov (United States)

    Beylich, Achim A.; Lamoureux, Scott; Decaulne, Armelle

    2013-04-01

    Projected climate change in cold regions is expected to alter melt season duration and intensity, along with the number of extreme rainfall events, total annual precipitation and the balance between snowfall and rainfall. Similarly, changes to the thermal balance are expected to reduce the extent of permafrost and seasonal ground frost and increase active layer depths. These effects will undoubtedly change surface environments in cold regions and alter the fluxes of sediments, nutrients and solutes, but the absence of quantitative data and coordinated geomorphic process monitoring and analysis to understand the sensitivity of the Earth surface environment is acute in cold climate environments. The International Association of Geomorphologists (I.A.G. / A.I.G. ) SEDIBUD (Sediment Budgets in Cold Environments) Programme was formed in 2005 to address this existing key knowledge gap. SEDIBUD currently has about 400 members worldwide and the Steering Committee of this international programme is composed of ten scientists from eight different countries: Achim A. Beylich (Chair) (Norway), Armelle Decaulne (Secretary) (France), John C. Dixon (USA), Scott F. Lamoureux (Vice-Chair) (Canada), John F. Orwin (Canada), Jan-Christoph Otto (Austria), Irina Overeem (USA), Thorsteinn Sæmundsson (Iceland), Jeff Warburton (UK) and Zbigniew Zwolinski (Poland). The central research question of this global group of scientists is to: Assess and model the contemporary sedimentary fluxes in cold climates, with emphasis on both particulate and dissolved components. Initially formed as European Science Foundation (ESF) Network SEDIFLUX (Sedimentary Source-to-Sink Fluxes in Cold Environments) (2004 - ), SEDIBUD has further expanded to a global group of researchers with field research sites located in polar and alpine regions in the northern and southern hemisphere. Research carried out at each of the close to 50 defined SEDIBUD key test sites varies by programme, logistics and available

  8. Settling fluxes of U- and Th-series nuclides in the Bay of Bengal: Results from time-series sediment trap studies

    Digital Repository Service at National Institute of Oceanography (India)

    Sarin, M.M.; Krishnaswami, S.; Dalai, T.K.; Ramaswamy, V.; Ittekkot, V.

    their production. Enhanced particle aggregation in the intermediate waters, resuspension of "nascent" sedimentary material and focussing of particles in the region of the deep traps can all account for these observations. The particulate flux in the deep trap...

  9. Extreme mass flux from the glaciated, collisional St. Elias Orogen: Preliminary results from IODP Expedition 341 (Invited)

    Science.gov (United States)

    Gulick, S. P.; Jaeger, J. M.

    2013-12-01

    Integrated Ocean Drilling Program Expedition 341 drilled a cross-margin transect to investigate the linkages between global climate change, modification of the dynamics of surficial processes, and subsequent tectonic responses. The Gulf of Alaska (GoA) borders the St. Elias orogen, the highest coastal mountain range on Earth. Exp. 341 drilled five sites within a regional seismic reflection grid that spans from the distal Surveyor Fan to the continental shelf. More than 3000 m of high-quality core coupled with seismic reflection profiles collected with nested vertical resolution allows us to address the major objectives of drilling in the GoA. These objectives were to: 1) document the tectonic response of an active orogenic system to late Miocene to recent climate change; 2) establish the timing of advance/retreat phases of the northern Cordilleran ice sheet to test its relation to dynamics of other global ice sheets; 3) implement an expanded source-to-sink study of the interactions between glacial, tectonic, and oceanographic processes responsible for creation of one of the thickest Neogene high-latitude continental margin sequences; 4) understand the dynamics of productivity, nutrients, freshwater input to the ocean, and ocean circulation in the northeast Pacific and their role in the global carbon cycle, and 5) document the spatial and temporal behavior of the geomagnetic field at extremely high temporal resolution in an under-sampled region of the globe. The Exp. 341 cross-margin transect discovered transitions in sediment accumulation rates from >100 m/Ma at the distal site to > 1000 m/Ma in the proximal fan, slope and on the continental shelf that provide a telescoping view of strata formation from the Miocene to the Holocene. Complete recovery and development of spliced sedimentary records of the Pleistocene through Holocene were achieved at the distal, proximal, and slope Sites U1417, U1418, and U1419, respectively, because of exceptional piston core

  10. Fluvial export of radionuclides: impact on sediment storages of the Rhone River and fluxes towards the Mediterranean Sea; Transfert des radionucleides artificiels par voie fluviale: consequences sur les stocks sedimentaires rhodaniens et les exports vers la Mediterranee

    Energy Technology Data Exchange (ETDEWEB)

    Rolland, B

    2006-02-15

    This study deals with the behaviour of trace contaminants originating from chronic liquid releases within fluvial aquatic systems. It focuses on some particle reactive artificial radionuclides that were released by the Marcoule nuclear fuel reprocessing plant during several years mainly prior the end of the nineties and that are still detected in the lower Rhone river. It underlines the decrease of {sup 137}Cs, {sup 238}Pu and {sup 239+240}Pu fluxes to the Mediterranean Sea in relation with the variations in the chronic liquid releases from Marcoule. The role of flood events on radionuclides exports processes is particularly considered. Over the years 2002 to 2004, floods contributed for 67%, 55%, 68%, 49% and 56% of the mean annual fluxes of {sup 137}Cs, {sup 238}Pu and {sup 239+240}Pu and natural {sup 7}Be et {sup 210}Pbxs, although these events only represented 5% of time. The removal, during floods, of sediments contaminated by the Marcoule releases contributes on the average for 19%, 44% and 22% of the annual exports of {sup 137}Cs, {sup 238}Pu and {sup 239+240}Pu towards the Sea. Thus, such sedimentary stocks act as a delayed source term of artificial radioactivity that is currently significant. Determination of the sediments residence times before removal allows to evaluate the Rhone capacity to clear its contaminated stocks. Residence times of 200 years, 100 years and 900 years are estimated to be necessary to totally remove the accumulated {sup 137}Cs, {sup 238}Pu and {sup 239+240}Pu, respectively. The location typologies of sediment storages within fluvial systems are also specified. These location are represented on one hand by dams, and on the other hand by river banks and oxbow lakes. Stocks accumulated in dams seem to be removed more easily than those trapped in banks. (author)

  11. Physical Forcing-Driven Productivity and Sediment Flux to the Deep Basin of Northern South China Sea: A Decadal Time Series Study

    Directory of Open Access Journals (Sweden)

    Hon-Kit Lui

    2018-03-01

    Full Text Available Understanding the driving forces of absorption of anthropogenic CO2 by the oceans is critical for a sustainable ocean carbon cycle. Decadal sinking particle flux data collected at 1000 m, 2000 m, and 3500 m at the South East Asia Time Series Study (SEATS Station (18° N, 116° E, which was located in the northern South China Sea (nSCS, show that the fluxes undergo strong seasonal and interannual variability. Changes in the flux data are correlated with the satellite-derived chlorophyll-a concentration, indicating that the mass fluxes of the sinking particles are largely controlled by the export production at or near the SEATS station. The cooling of seawater and the strengthening of wind in winter increase the nutrient inventories in the euphotic zone, thus also increasing export production in the nSCS. This study reveals that the intrusion of low-nutrient seawater from the West Philippine Sea into the nSCS significantly reduces the productivity, and hence the flux, of sinking particles.

  12. The clay mineral and Sr-Nd isotopic composition for fine-grained fraction of sediments from northwestern South China Sea: implications for sediment provenance

    Science.gov (United States)

    Cai, G.

    2013-12-01

    *Guanqiang Cai caiguanqiang@sina.com Guangzhou Marine Geological Survey, Guangzhou, 510760, P.R. China As the largest marginal sea in the western pacific, the South China Sea (SCS) receives large amount of terrigenous material annually through numerous rivers from surrounding continents and islands, which make it as the good place for the study of source to sink process. Yet few studies put emphasis on the northwestern continental shelf and slope in the SCS, even though most of the detrital materials derived from the Red River and Hainan Island are deposited in this area, and northwestern shelf plays a significant role in directly linking the South China, the Indochina and the South China Sea and thus controlling the source to sink process of terrestrial sediment. We presented the clay mineral and Sr-Nd isotopic composition of fine-grained fraction for sediments from northwestern SCS, in order to identify sediment source and transportation. The results show that the clay mineral of northwestern SCS sediments are mainly illite (30%~59%), smectite (20%~40%) and kaolinite (8%~35%), with minor chlorite. The illite chemical index varies between 0.19 and 0.75 with an average of 0.49, indicating an intensive hydrolysis in the source region. The 87Sr/86Sr ratios of sediments range from 0.716288 to 0.734416 (average of 0.724659), and ɛ Nd(0) values range from -10.31 to -11.62 (average of -10.93), which suggest that the source rocks of these sediments are derived from continental crust. The Hainan Island is an important source for sediments deposited in the nearshore and western shelf, especially for illite, kaolinite and smectite clay minerals. Furthermore, the relatively high contents of kaolinite and smectite in sediments from eastern shelf and southern slope of Hainan Island are also controlled by the supply of terrigenous materials from Hainan, which cannot be resulted from sedimentary differentiation of the Pearl and Red river sediments. And the correlation analysis

  13. Interplay between spatially explicit sediment sourcing, hierarchical river-network structure, and in-channel bed material sediment transport and storage dynamics

    Science.gov (United States)

    Czuba, Jonathan A.; Foufoula-Georgiou, Efi; Gran, Karen B.; Belmont, Patrick; Wilcock, Peter R.

    2017-05-01

    Understanding how sediment moves along source to sink pathways through watersheds—from hillslopes to channels and in and out of floodplains—is a fundamental problem in geomorphology. We contribute to advancing this understanding by modeling the transport and in-channel storage dynamics of bed material sediment on a river network over a 600 year time period. Specifically, we present spatiotemporal changes in bed sediment thickness along an entire river network to elucidate how river networks organize and process sediment supply. We apply our model to sand transport in the agricultural Greater Blue Earth River Basin in Minnesota. By casting the arrival of sediment to links of the network as a Poisson process, we derive analytically (under supply-limited conditions) the time-averaged probability distribution function of bed sediment thickness for each link of the river network for any spatial distribution of inputs. Under transport-limited conditions, the analytical assumptions of the Poisson arrival process are violated (due to in-channel storage dynamics) where we find large fluctuations and periodicity in the time series of bed sediment thickness. The time series of bed sediment thickness is the result of dynamics on a network in propagating, altering, and amalgamating sediment inputs in sometimes unexpected ways. One key insight gleaned from the model is that there can be a small fraction of reaches with relatively low-transport capacity within a nonequilibrium river network acting as "bottlenecks" that control sediment to downstream reaches, whereby fluctuations in bed elevation can dissociate from signals in sediment supply.

  14. Impact of PAH [Polycyclic Aromatic Hydrocarbons] outlets from an oil refinery on the receiving water area - sediment trap fluxes and multivariate statistical analysis

    International Nuclear Information System (INIS)

    Pettersen, Harald; Naef, Carina; Broman, Dag

    1997-01-01

    PAH concentrations (15 compounds) in settling particulate matter (SPM) collected in the waters outside a petroleum refinery on the Swedish Baltic coast, and in samples of particulate and dissolved fractions in the wastewater from the refinery were determined. SPM concentrations varied between 550 and 4250 ng x gdw -1 and the corresponding calculated fluxes varied between 0.1 and 3.7 ng x cm -2 x day -1 . Both concentrations and fluxes did not differ significantly from background coastal or offshore locations in the Baltic. PAH profiles of the SPM samples were compared with the wastewater samples and SPM samples from background areas in the Baltic, using pattern recognition techniques. This analysis showed that the SPM samples from the petroleum refinery displayed a PAH composition similar to that found in background reference sites in the Baltic, and that the SPM samples could not be connected to the wastewater samples from the refinery. This indicates that Nynas AB is not a significant source of PAHs to the waters in its immediate surroundings, i.e. the waters in the Nynashamn area, and/or that the hydraulic residence time of the water outside the refinery is low. A budget calculation showed that the wastewater outlet from Nynas AB is only a minor contributor of the PAH load to the waters outside the refinery. (Author)

  15. A Nanoscale Study of Carbon and Nitrogen Fluxes in Mats of Purple Sulfur Bacteria: Implications for Carbon Cycling at the Surface of Coastal Sediments

    Directory of Open Access Journals (Sweden)

    Cédric Hubas

    2017-10-01

    Full Text Available Mass blooms of purple sulfur bacteria growing seasonally on green stranded macroalgae have a major impact on the microbial composition and functionality of intertidal mats. To explore the active anoxygenic phototrophic community in purple bacterial mats from the Roscoff Aber Bay (Brittany, France, we conducted a combined approach including molecular and high-resolution secondary ion mass spectrometry (NanoSIMS analyses. To investigate the dynamics of carbon and nitrogen assimilation activities, NanoSIMS was coupled with a stable isotope probing (SIP experiment and a compound specific isotope analysis (CSIA of fatty acid methyl ester (FAME. Sediment samples were incubated with 13C- and/or 15N-labeled acetate, pyruvate, bicarbonate and ammonium. NanoSIMS analysis of 13C - and 15N -incubated samples showed elevated incorporations of 13C - and 15N in the light and of 13C -acetate in the dark into dense populations of spherical cells that unambiguously dominated the mats. These results confirmed CSIA data that ranked vaccenic acid, an unambiguous marker of purple sulfur bacteria, as the most strongly enriched in the light after 13C -acetate amendment and indicated that acetate uptake, the most active in the mat, was not light-dependent. Analysis of DNA- and cDNA-derived pufM gene sequences revealed that Thiohalocapsa-related clones dominated both libraries and were the most photosynthetically active members of the mat samples. This study provides novel insights into the contribution of purple sulfur bacteria to the carbon cycle during their seasonal developments at the sediment surface in the intertidal zone.

  16. The impact of reforestation on discharge and sediment fluxes in drylands: long-term evidences from the Western Rift Valley Escarpment (Northern Ethiopia)

    Science.gov (United States)

    Asfaha, Tesfaalem; Frankl, Amaury; Zenebe, Amanuel; Haile, Mitiku; Nyssen, Jan

    2014-05-01

    Deforestation and land degradation have been common problems in the Northern Ethiopian highlands, including for the Western Rift Valley Escarpment. In particular, the rapid deforestation of the steep catchments (average slope gradient of 44% ± 10%) in the second half of 20th century, together with rainfall variability and over-cultivation, resulted in the development of dense gully and scar networks. Subsequently, huge amounts sediment were taken to the densely populated graben bottoms. In response, extensive reforestation interventions were carried out as of the 1980s, resulting in improvements of vegetation cover in many catchments. This study analyses the spatio-temporal changes in vegetation cover and rainfall variability and their impact on discharge and sediment transport in escarpment catchments. Degree of rehabilitation was examined in 20 adjacent catchments by correlating the density of scar networks incised down to the bed rock with Normalize Difference Vegetation Index (NDVI) and slope gradient. Based on these results, 11 contrasting catchments were selected for detailed investigation. To study the current spatio-temporal variability in rainfall and its relation with daily peak discharge, 7 rain gauges were installed at different locations and altitudes. Trendlines of decadal rainfall variability since 1996 will be established based on the analysis of NOAA's rainfall estimates, and long-term rainfall variability will be explored by correlating the field data to long-term rainfall measurements in nearby synoptic stations. The changes in land use and cover will be detected from aerial photos of the 1935, 1965 and 1986. Peak discharges were monitored using 11 crest stage gauges. Fixed boulders were painted in stream reaches to quantify the transport of bedload. This was done by photographing the stream reaches and by measuring the displacement of painted boulders after flood events. In a multiple regression analysis, scar density was negatively related

  17. Evaluating the use of in-situ turbidity measurements to quantify fluvial sediment and phosphorus concentrations and fluxes in agricultural streams.

    Science.gov (United States)

    Stutter, Marc; Dawson, Julian J C; Glendell, Miriam; Napier, Fiona; Potts, Jacqueline M; Sample, James; Vinten, Andrew; Watson, Helen

    2017-12-31

    Accurate quantification of suspended sediments (SS) and particulate phosphorus (PP) concentrations and loads is complex due to episodic delivery associated with storms and management activities often missed by infrequent sampling. Surrogate measurements such as turbidity can improve understanding of pollutant behaviour, providing calibrations can be made cost-effectively and with quantified uncertainties. Here, we compared fortnightly and storm intensive water quality sampling with semi-continuous turbidity monitoring calibrated against spot samples as three potential methods for determining SS and PP concentrations and loads in an agricultural catchment over two-years. In the second year of sampling we evaluated the transferability of turbidity calibration relationships to an adjacent catchment with similar soils and land cover. When data from nine storm events were pooled, both SS and PP concentrations (all in log space) were better related to turbidity than they were to discharge. Developing separate calibration relationship for the rising and falling limbs of the hydrograph provided further improvement. However, the ability to transfer calibrations between adjacent catchments was not evident as the relationships of both SS and PP with turbidity differed both in gradient and intercept on the rising limb of the hydrograph between the two catchments. We conclude that the reduced uncertainty in load estimation derived from the use of turbidity as a proxy for specific water quality parameters in long-term regulatory monitoring programmes, must be considered alongside the increased capital and maintenance costs of turbidity equipment, potentially noisy turbidity data and the need for site-specific prolonged storm calibration periods. Copyright © 2017 Elsevier B.V. All rights reserved.

  18. Long-term nutrient addition differentially alters community composition and diversity of genes that control nitrous oxide flux from salt marsh sediments

    Science.gov (United States)

    Kearns, Patrick J.; Angell, John H.; Feinman, Sarah G.; Bowen, Jennifer L.

    2015-03-01

    Enrichment of natural waters, soils, and sediments by inorganic nutrients, including nitrogen, is occurring at an increasing rate and has fundamentally altered global biogeochemical cycles. Salt marshes are critical for the removal of land-derived nitrogen before it enters coastal waters. This is accomplished via multiple microbially mediated pathways, including denitrification. Many of these pathways, however, are also a source of the greenhouse gas nitrous oxide (N2O). We used clone libraries and quantative PCR (qPCR) to examine the effect of fertilization on the diversity and abundance of two functional genes associated with denitrification and N2O production (norB and nosZ) in experimental plots at the Great Sippewissett Salt Marsh (Falmouth, MA, USA) that have been enriched with nutrients for over 40 years. Our data showed distinct nosZ and norB community structures at different nitrogen loads, especially at the highest level of fertilization. Furthermore, calculations of the Shannon Diversity Index and Chao1 Richness Estimator indicated that nosZ gene diversity and richness increased with increased nitrogen supply, however no such relationship existed with regard to richness and diversity of the norB gene. Results from qPCR demonstrated that nosZ gene abundance was an order of magnitude lower in the extra-highly fertilized plots compared to the other plots, but the abundance of norB was not affected by fertilization. The majority of sequences obtained from the marsh plots had no close cultured relatives and they were divergent from previously sequenced norB and nosZ fragments. Despite their divergence from any cultured representatives, most of the norB and nosZ sequences appeared to be from members of the Alpha- and Betaproteobacteria, suggesting that these classes are particularly important in salt marsh nitrogen cycling. Our results suggest that both norB and nosZ containing microbes are affected by fertilization and that the Great Sippewissett Marsh may

  19. The I.A.G./A.I.G. SEDIBUD (Sediment Budgets in Cold Environments) Program (2005 - 2017): Key activities and outcomes

    Science.gov (United States)

    Beylich, Achim A.

    2017-04-01

    Amplified climate change and ecological sensitivity of high-latitude and high-altitude cold climate environments has been highlighted as a key global environmental issue. Projected climate change in largely undisturbed cold regions is expected to alter melt-season duration and intensity, along with the number of extreme rainfall events, total annual precipitation and the balance between snowfall and rainfall. Similarly, changes to the thermal balance are expected to reduce the extent of permafrost and seasonal ground frost and increase active-layer depths. These combined effects will undoubtedly change Earth surface environments in cold regions and will alter the fluxes of sediments, solutes and nutrients. However, the absence of quantitative data and coordinated analysis to understand the sensitivity of the Earth surface environment are acute in cold regions. Contemporary cold climate environments generally provide the opportunity to identify solute and sedimentary systems where anthropogenic impacts are still less important than the effects of climate change. Accordingly, it is still possible to develop a library of baseline fluvial yields and sedimentary budgets before the natural environment is completely transformed. The SEDIBUD (Sediment Budgets in Cold Environments) Program, building on the European Science Foundation (ESF) Network SEDIFLUX (Sedimentary Source-to-Sink Fluxes in Cold Environments, since 2004) was formed in 2005 as a new Program (Working Group) of the International Association of Geomorphologists (I.A.G./A.I.G.) to address this still existing key knowledge gap. SEDIBUD (2005-2017) has currently about 400 members worldwide and the Steering Committee of this international program is composed of eleven scientists from ten different countries. The central research question of this global program is to: Assess and model the contemporary sedimentary fluxes in cold climates, with emphasis on both particulate and dissolved components. Research carried

  20. Algal stabilisation of estuarine sediments

    International Nuclear Information System (INIS)

    1992-01-01

    The presence of benthic microalgae can increase the stability of intertidal sediments and influence sediment fluxes within an estuarine environment. Therefore the relative importance of algal stabilisation needs to be understood to help predict the effects of a tidal barrage. The objectives of this study are: to assess the significance of stabilisation of sediments by algae, in relation to the changes in hydrodynamic and sedimentological regimes arising from the construction of tidal power barrages; to identify a reliable and meaningful method of measuring the effectiveness, including duration, of algal binding on sediment stability, and to relate this method to other methods of measuring critical erosion velocity and sediment shear strength; to undertake a series of field experiments investigating the effect of algae on binding sediments and the parameters which could potentially influence such binding and to develop a predictive method for the assessment of sediment stabilisation by algal binding. This report contains plates, figures and tables. (author)

  1. Algal stabilisation of estuarine sediments

    International Nuclear Information System (INIS)

    1992-01-01

    The presence of benthic microalgae can increase the stability of intertidal sediments and influence sediment fluxes within an estuarine environment. Therefore the relative importance of algal stabilisation needs to be understood to help predict the effects of a tidal barrage. The biogenic stabilisation of intertidal estuarine sediments by epipelic diatom films and the macrophyte Vaucheria was studied at three sites on the Severn Estuary. The cohesive strength meter (CSM) was developed to measure surface critical shear stress with varied algal density. A number of techniques have been used to determine the general in situ erodibility of cohesive estuarine sediments. The measurements of sediment shear strength and critical erosion velocity were investigated. Field experiments were undertaken to investigate the effect of algae on binding sediments, and a predictive method for the assessment of sediment stabilisation by algal binding was developed. (author)

  2. Characterizing Feedbacks Between Environmental Forcing and Sediment Characteristics in Fluvial and Coastal Systems

    Science.gov (United States)

    Feehan, S.; Ruggiero, P.; Hempel, L. A.; Anderson, D. L.; Cohn, N.

    2016-12-01

    Characterizing Feedbacks Between Environmental Forcing and Sediment Characteristics in Fluvial and Coastal Systems American Geophysical Union, 2016 Fall Meeting: San Francisco, CA Authors: Scott Feehan, Peter Ruggiero, Laura Hempel, and Dylan Anderson Linking transport processes and sediment characteristics within different environments along the source to sink continuum provides critical insight into the dominant feedbacks between grain size distributions and morphological evolution. This research is focused on evaluating differences in sediment size distributions across both fluvial and coastal environments in the U.S. Pacific Northwest. The Cascades' high relief is characterized by diverse flow regimes with high peak/flashy flows and sub-threshold flows occurring in relative proximity and one of the most energetic wave climates in the world. Combining analyses of both fluvial and coastal environments provides a broader understanding of the dominant forces driving differences between each system's grain size distributions, sediment transport processes, and resultant evolution. We consider sediment samples taken during a large-scale flume experiment that simulated floods representative of both high/flashy peak flows analogous to runoff dominated rivers and sub-threshold flows, analogous to spring-fed rivers. High discharge flows resulted in narrower grain size distributions while low flows where less skewed. Relative sediment size showed clear dependence on distance from source and the environments' dominant fluid motion. Grain size distributions and sediment transport rates were also quantified in both wave dominated nearshore and aeolian dominated backshore portions of Long Beach Peninsula, Washington during SEDEX2, the Sandbar-aEolian-Dune EXchange Experiment of summer 2016. The distributions showed spatial patterns in mean grain size, skewness, and kurtosis dependent on the dominant sediment transport process. The feedback between these grain size

  3. Modern Sedimentation off the Kaoping River, SW Taiwan: A Comparison with Eel River's S2S System

    Science.gov (United States)

    Huh, C.; Lin, H.; Lin, S.

    2006-12-01

    The Kaoping (KP) River in SW Taiwan has a watershed area of 3257 km2 and an annual sediment discharge of 49 MT. Although the sediment yield of the KP River basin (1.5×104 ton km-2 yr^{- 1}) is the 4th highest among Taiwan's catchment basins, it is nearly one order of magnitude higher than that of the Eel River's basin (~1.8×103 ton km-2 yr-1; the highest in the U.S.). The KP canyon extends almost immediately seaward from the river's mouth and terminates in the northwestern corner of the South China Sea. The head of the canyon is characterized by high and steep walls exceeding 600 m. The KP river's source-to-sink system offers a dramatic case of mountainous rivers at active margins for S2S study. Here we report some results about modern sedimentation in KP river's dispersal system. Seventy-six sediment cores collected from an area of ~3000 km2 were analyzed for fallout nuclides 7Be, 137Cs and 210Pb by gamma spectrometry. From profiles of excess 210Pb and 137Cs sediment accumulation rates in the coring sites were estimated, which vary from 0.06 to 1.6 cm/yr, with the highest rates (>1 cm/yr) distributed in the upper slope (exported out of the study area via the KP canyon to the deep sea by gravity-driven turbidity or hyperpycnal flows.

  4. The making of giant pumpkins: how selective breeding changed the phloem of Cucurbita maxima from source to sink.

    Science.gov (United States)

    Savage, Jessica A; Haines, Dustin F; Holbrook, N Michele

    2015-08-01

    Despite the success of breeding programmes focused on increasing fruit size, relatively little is known about the anatomical and physiological changes required to increase reproductive allocation. To address this gap in knowledge, we compared fruit/ovary anatomy, vascular structure and phloem transport of two varieties of giant pumpkins, and their smaller fruited progenitor under controlled environmental conditions. We also modelled carbon transport into the fruit of competitively grown plants using data collected in the field. There was no evidence that changes in leaf area or photosynthetic capacity impacted fruit size. Instead, giant varieties differed in their ovary morphology and contained more phloem on a cross-sectional area basis in their petioles and pedicels than the ancestral variety. These results suggest that sink activity is important in determining fruit size and that giant pumpkins have an enhanced capacity to transport carbon. The strong connection observed between carbon fixation, phloem structure and fruit growth in field-grown plants indicates that breeding for large fruit has led to changes throughout the carbon transport system that could have important implications for how we think about phloem transport velocity and carbon allocation. © 2014 John Wiley & Sons Ltd.

  5. Diversity in Betasatellites Associated with Cotton Leaf Curl Disease During Source-To-Sink Movement Through a Resistant Host

    Directory of Open Access Journals (Sweden)

    Iftikhar Ali Khan

    2016-02-01

    Full Text Available Cotton leaf curl is devastating disease of cotton characterized by leaf curling, vein darkening and enations. The disease symptoms are induced by DNA satellite known as Cotton leaf curl Multan betasatellite (CLCuMuB, dominant betasatellite in cotton but another betasatellite known as Chili leaf curl betasatellite (ChLCB is also found associated with the disease. Grafting experiment was performed to determine if host plant resistance is determinant of dominant population of betasatellite in cotton (several distinct strains of CLCuMuB are associated with the disease. Infected scion of Gossypium hirsutum collected from field (the source was grafted on G. arboreum, a diploid cotton species, resistant to the disease. A healthy scion of G. hirsutum (sink was grafted at the top of G. arboreum to determine the movement of virus/betasatellite to upper susceptible scion of G. hirsutum. Symptoms of disease appeared in the upper scion and presence of virus/betasatellite in the upper scion was confirmed via molecular techniques, showing that virus/betasatellite was able to move to upper scion through resistant G. arboreum. However, no symptoms appeared on G. arboreum. Betasatelites were cloned and sequenced from lower scion, upper scion and G. arboreum which show that the lower scion contained both CLCuMuB and ChLCB, however only ChLCB was found in G. arboreum. The upper scion contained CLCuMuB with a deletion of 78 nucleotides (nt in the non-coding region between A-rich sequence and βC1 gene and insertion of 27 nt in the middle of βC1 ORF. This study may help in investigating molecular basis of resistance in G. arboreum.

  6. Damping Effect of an Unsaturated-Saturated System on Tempospatial Variations of Pressure Head and Specific Flux

    Science.gov (United States)

    Yang, C.; Zhang, Y. K.; Liang, X.

    2014-12-01

    Damping effect of an unsaturated-saturated system on tempospatialvariations of pressurehead and specificflux was investigated. The variance and covariance of both pressure head and specific flux in such a system due to a white noise infiltration were obtained by solving the moment equations of water flow in the system and verified with Monte Carlo simulations. It was found that both the pressure head and specific flux in this case are temporally non-stationary. The variance is zero at early time due to a deterministic initial condition used, then increases with time, and approaches anasymptotic limit at late time.Both pressure head and specific flux arealso non-stationary in space since the variance decreases from source to sink. The unsaturated-saturated systembehavesasa noise filterand it damps both the pressure head and specific flux, i.e., reduces their variations and enhances their correlation. The effect is stronger in upper unsaturated zone than in lower unsaturated zone and saturated zone. As a noise filter, the unsaturated-saturated system is mainly a low pass filter, filtering out the high frequency components in the time series of hydrological variables. The damping effect is much stronger in the saturated zone than in the saturated zone.

  7. Radiocarbon constraints on the coupled growth of sediment and organic carbon reservoirs in fluvial systems

    Science.gov (United States)

    Torres, M. A.; Kemeny, P. C.; Fischer, W. W.; Lamb, M. P.

    2017-12-01

    Vast amounts of sediments are stored transiently in fluvial deposits as they move in rivers from source to sink. The timescale(s) of transient storage have the potential to set the cadence for biogeochemical reactions to occur in river sediments. However, the extent to which storage modulates the chemical composition of river sediments remains unclear. In case of the organic carbon (OC) cycle, transient sediment storage may leave an imprint in the radiocarbon (14C) content of riverine particulate OC (POC), offering a potential tool to trace the coupling of sediment storage and biogeochemical cycling in river systems. We investigated the modern and ancient budgets of sediments and POC in the Efi Haukadalsá River catchment in West Iceland to provide new empirical constraints on the role of sediment storage in the terrestrial OC cycle. This field site is attractive because the basaltic bedrock is free of rock-derived (i.e. "petrogenic") POC such that bulk 14C measurements can be interpreted more directly as constraints on catchment OC storage timescales. Additionally, Lake Haukadalsvatn at the outlet of the river catchment has captured sediment for nearly 13 ka, which offers a complementary record of the evolution of climate-sediment-OC linkages since deglaciation. New 14C measurements show that bulk POC in fine grained fluvial deposits within the Haukadalsá catchment is remarkably old (model ages between 1 and 10 ka). This evidence for "aged" POC in floodplain storage is consistent with previous measurements from Lake Haukadalsvatn, which show that POC is aged in the river system by thousands of years prior to deposition in the lake. Additionally, our estimate of the mean transit time of sediments through the river system matches the millennial-scale reservoir age of riverine POC derived from 14C, which implies a tight coupling between sediment storage and the OC cycle. We interpret the long-term increase in the 14C reservoir age of riverine POC over the last 10 ka

  8. Distribution and dynamics of radionuclides and stable elements in the coastal waters off Rokkasho Village, Japan, prior to the opening of a nuclear reprocessing facility. Part 1. Sedimentation flux of suspended particles and elimination of radionuclides and stable elements from seawater

    International Nuclear Information System (INIS)

    Kondo, K.; Kawabata, H.; Ueda, S.; Hasegawa, H.; Inaba, J.; Ohmomo, Y.; Mitamura, O.; Seike, Y.

    2004-01-01

    A nuclear fuel reprocessing facility is currently under construction in Rokkasho Village, Aomori, Japan. After completion and start-up, this facility will discharge radionuclides into the Pacific Ocean through an outlet pipe set on the seafloor offshore. For future assessments of the stability of these radionuclides in the environment, a sufficient understanding of the behavior of radionuclides in this ocean ecosystem before the start-up of the facility is necessary. To understand the processes by which radionuclides and various other types of elements are eliminated from seawater, we measured the sedimentation flux of suspended particles in the coastal waters off Rokkasho Village where the sea emissions pipes will be placed. (author)

  9. Estimating Western U.S. Reservoir Sedimentation

    Science.gov (United States)

    Bensching, L.; Livneh, B.; Greimann, B. P.

    2017-12-01

    Reservoir sedimentation is a long-term problem for water management across the Western U.S. Observations of sedimentation are limited to reservoir surveys that are costly and infrequent, with many reservoirs having only two or fewer surveys. This work aims to apply a recently developed ensemble of sediment algorithms to estimate reservoir sedimentation over several western U.S. reservoirs. The sediment algorithms include empirical, conceptual, stochastic, and processes based approaches and are coupled with a hydrologic modeling framework. Preliminary results showed that the more complex and processed based algorithms performed better in predicting high sediment flux values and in a basin transferability experiment. However, more testing and validation is required to confirm sediment model skill. This work is carried out in partnership with the Bureau of Reclamation with the goal of evaluating the viability of reservoir sediment yield prediction across the western U.S. using a multi-algorithm approach. Simulations of streamflow and sediment fluxes are validated against observed discharges, as well as a Reservoir Sedimentation Information database that is being developed by the US Army Corps of Engineers. Specific goals of this research include (i) quantifying whether inter-algorithm differences consistently capture observational variability; (ii) identifying whether certain categories of models consistently produce the best results, (iii) assessing the expected sedimentation life-span of several western U.S. reservoirs through long-term simulations.

  10. On contemporary sedimentation at the titanic survey area

    Science.gov (United States)

    Lukashin, V. N.

    2009-12-01

    The basic parameters of the sedimentation environment are considered: the Western Boundary Deep Current that transports sedimentary material and distributes it on the survey area; the nepheloid layer, its features, and the distribution of the concentrations and particulate standing crop in it; the distribution of the horizontal and vertical fluxes of the sedimentary material; and the bottom sediments and their absolute masses. The comparison of the vertical fluxes of the particulate matter and the absolute masses of the sediments showed that the contemporary fluxes of sedimentary material to the bottom provided the distribution of the absolute masses of the sediments in the survey area during the Holocene.

  11. Sediment Transport

    DEFF Research Database (Denmark)

    Liu, Zhou

    Flow and sediment transport are important in relation to several engineering topics, e.g. erosion around structures, backfilling of dredged channels and nearshore morphological change. The purpose of the present book is to describe both the basic hydrodynamics and the basic sediment transport...... mechanics. Chapter 1 deals with fundamentals in fluid mechanics with emphasis on bed shear stress by currents, while chapter 3 discusses wave boundary layer theory. They are both written with a view to sediment transport. Sediment transport in rivers, cross-shore and longshore are dealt with in chapters 2......, 4 and 5, respectively. It is not the intention of the book to give a broad review of the literature on this very wide topic. The book tries to pick up information which is of engineering importance. An obstacle to the study of sedimentation is the scale effect in model tests. Whenever small...

  12. Dating of sediments and determination of sedimentation rate. Proceedings

    Energy Technology Data Exchange (ETDEWEB)

    Illus, E [ed.

    1998-08-01

    The Second NKS (Nordic Nuclear Safety Research)/EKO-1 Seminar was held at the Finnish Centre for Radiation and Nuclear Safety (STUK) on April 2-3, 1997. The work of the NKS is based on 4-year programmes; the current programme having been planned for the years 1994-1997. The programme comprises 3 major fields, one of them being environmental effects (EKO). Under this umbrella there are 4 main projects. The EKO-1 project deals with marine radioecology, in particular bottom sediments and sediment processes. The programme of the second seminar consisted of 8 invited lecturers and 6 other scientific presentations. Dating of sediments and determination of sedimentation rate are important in all types of sedimentological study and model calculations of fluxes of substances in the aquatic environment. In many cases these tasks have been closely related to radioecological studies undertaken in marine and fresh water environments, because they are often based on measured depth profiles of certain natural or artificial radionuclides present in the sediments. During recent decades Pb-210 has proved to be very useful in dating of sediments, but some other radionuclides have also been successfully used, e.g. Pu-239,240, Am-241 and Cs-137. The difficulties existing and problems involved in dating of sediments, as well as solutions for resolving these problems are discussed in the presentations

  13. Dating of sediments and determination of sedimentation rate. Proceedings

    International Nuclear Information System (INIS)

    Illus, E.

    1998-01-01

    The Second NKS (Nordic Nuclear Safety Research)/EKO-1 Seminar was held at the Finnish Centre for Radiation and Nuclear Safety (STUK) on April 2-3, 1997. The work of the NKS is based on 4-year programmes; the current programme having been planned for the years 1994-1997. The programme comprises 3 major fields, one of them being environmental effects (EKO). Under this umbrella there are 4 main projects. The EKO-1 project deals with marine radioecology, in particular bottom sediments and sediment processes. The programme of the second seminar consisted of 8 invited lecturers and 6 other scientific presentations. Dating of sediments and determination of sedimentation rate are important in all types of sedimentological study and model calculations of fluxes of substances in the aquatic environment. In many cases these tasks have been closely related to radioecological studies undertaken in marine and fresh water environments, because they are often based on measured depth profiles of certain natural or artificial radionuclides present in the sediments. During recent decades Pb-210 has proved to be very useful in dating of sediments, but some other radionuclides have also been successfully used, e.g. Pu-239,240, Am-241 and Cs-137. The difficulties existing and problems involved in dating of sediments, as well as solutions for resolving these problems are discussed in the presentations

  14. Analysis of sup(210)Pb in sediment trap samples and sediments from the northern Arabian Sea: Evidence for boundary scavenging

    Digital Repository Service at National Institute of Oceanography (India)

    Borole, D.V.

    . The sup(210)Pb flux exhibited a strong seasonal pattern associated with variations in the sediment mass flux and organic carbon (C sub(org)) flux except during early southwest monsoon in the 3024 m trap. This could be due to enhanced scavenging of sup(210...

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

    Science.gov (United States)

    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.

  16. Terrestrial Sediments of the Earth: Development of a Global Unconsolidated Sediments Map Database (GUM)

    Science.gov (United States)

    Börker, J.; Hartmann, J.; Amann, T.; Romero-Mujalli, G.

    2018-04-01

    Mapped unconsolidated sediments cover half of the global land surface. They are of considerable importance for many Earth surface processes like weathering, hydrological fluxes or biogeochemical cycles. Ignoring their characteristics or spatial extent may lead to misinterpretations in Earth System studies. Therefore, a new Global Unconsolidated Sediments Map database (GUM) was compiled, using regional maps specifically representing unconsolidated and quaternary sediments. The new GUM database provides insights into the regional distribution of unconsolidated sediments and their properties. The GUM comprises 911,551 polygons and describes not only sediment types and subtypes, but also parameters like grain size, mineralogy, age and thickness where available. Previous global lithological maps or databases lacked detail for reported unconsolidated sediment areas or missed large areas, and reported a global coverage of 25 to 30%, considering the ice-free land area. Here, alluvial sediments cover about 23% of the mapped total ice-free area, followed by aeolian sediments (˜21%), glacial sediments (˜20%), and colluvial sediments (˜16%). A specific focus during the creation of the database was on the distribution of loess deposits, since loess is highly reactive and relevant to understand geochemical cycles related to dust deposition and weathering processes. An additional layer compiling pyroclastic sediment is added, which merges consolidated and unconsolidated pyroclastic sediments. The compilation shows latitudinal abundances of sediment types related to climate of the past. The GUM database is available at the PANGAEA database (https://doi.org/10.1594/PANGAEA.884822).

  17. Critical flux determination by flux-stepping

    DEFF Research Database (Denmark)

    Beier, Søren; Jonsson, Gunnar Eigil

    2010-01-01

    In membrane filtration related scientific literature, often step-by-step determined critical fluxes are reported. Using a dynamic microfiltration device, it is shown that critical fluxes determined from two different flux-stepping methods are dependent upon operational parameters such as step...... length, step height, and.flux start level. Filtrating 8 kg/m(3) yeast cell suspensions by a vibrating 0.45 x 10(-6) m pore size microfiltration hollow fiber module, critical fluxes from 5.6 x 10(-6) to 1.2 x 10(-5) m/s have been measured using various step lengths from 300 to 1200 seconds. Thus......, such values are more or less useless in itself as critical flux predictors, and constant flux verification experiments have to be conducted to check if the determined critical fluxes call predict sustainable flux regimes. However, it is shown that using the step-by-step predicted critical fluxes as start...

  18. Earth's portfolio of extreme sediment transport events

    Science.gov (United States)

    Korup, Oliver

    2012-05-01

    Quantitative estimates of sediment flux and the global cycling of sediments from hillslopes to rivers, estuaries, deltas, continental shelves, and deep-sea basins have a long research tradition. In this context, extremely large and commensurately rare sediment transport events have so far eluded a systematic analysis. To start filling this knowledge gap I review some of the highest reported sediment yields in mountain rivers impacted by volcanic eruptions, earthquake- and storm-triggered landslide episodes, and catastrophic dam breaks. Extreme specific yields, defined here as those exceeding the 95th percentile of compiled data, are ~ 104 t km- 2 yr- 1 if averaged over 1 yr. These extreme yields vary by eight orders of magnitude, but systematically decay with reference intervals from minutes to millennia such that yields vary by three orders of magnitude for a given reference interval. Sediment delivery from natural dam breaks and pyroclastic eruptions dominate these yields for a given reference interval. Even if averaged over 102-103 yr, the contribution of individual disturbances may remain elevated above corresponding catchment denudation rates. I further estimate rates of sediment (re-)mobilisation by individual giant terrestrial and submarine mass movements. Less than 50 postglacial submarine mass movements have involved an equivalent of ~ 10% of the contemporary annual global flux of fluvial sediment to Earth's oceans, while mobilisation rates by individual events rival the decadal-scale sediment discharge from tectonically active orogens such as Taiwan or New Zealand. Sediment flushing associated with catastrophic natural dam breaks is non-stationary and shows a distinct kink at the last glacial-interglacial transition, owing to the drainage of very large late Pleistocene ice-marginal lakes. Besides emphasising the contribution of high-magnitude and low-frequency events to the global sediment cascade, these findings stress the importance of sediment storage

  19. Evolution of cyclonic eddies and biogenic fluxes in the northern Bay of Bengal

    Digital Repository Service at National Institute of Oceanography (India)

    Nuncio, M.; PrasannaKumar, S.

    in the sediment trap location. Cyclonic eddy-induced down ward biogenic flux in the sediment trap location was larger than the amplitude, ~40 mg m-2 d-1, of the seasonal cycle. The magnitude of the peak episodic fluxes were one...

  20. Sediment dynamics in Alpine basins

    Science.gov (United States)

    Habersack, Helmut; Liébault, Fred; Comiti, Francesco

    2017-08-01

    In rivers and streams and of the European Alps, sediment transport processes are of great relevance due to their ecological (e.g. aquatic habitats), energy (e.g. reservoir sedimentation) and risk-related (floods and debris flows) consequences. In fact, sediment fluxes are crucial to maintain a good ecological status of watercourses (required by the EU ;Water Framework Directive;, WFD, 2000), as they provide the hydromorphological conditions supporting dynamic aquatic ecosystems (Fryirs and Brierley, 2013; Wohl et al., 2015; Gurnell et al., 2016). Indeed, the key issue to ameliorate river hydrogeomorphological - and thus ecological - status and to comply with WFD provisions lies in allowing the natural processes of sediment and wood supply and transport to take place as much as possible, given the constraints imposed by the non-eliminable uses of each river (Comiti, 2012; Liébault et al., 2013). Specifically river continuity is mentioned in the WFD not only for biota but also sediments, which is hardly discussed in river management so far and almost no concrete measures to improve sediment continuity have been implemented so far (Habersack et al., 2016).

  1. Sources of polycyclic aromatic hydrocarbons to sediments of the Bohai and Yellow Seas in East Asia

    Science.gov (United States)

    Lin, Tian; Hu, Limin; Guo, Zhigang; Qin, Yanwen; Yang, Zuosheng; Zhang, Gan; Zheng, Mei

    2011-12-01

    The coasts of Bohai Sea (BS) and Yellow Sea (YS) in China support almost one-quarter of its population and provide more than one-third of the national GDP. BS and YS are downwind of the Asian continental outflow in spring and winter as influenced by the East Asian monsoon. This makes the two seas important sinks of land-based pollutants associated with the Asian continental outflow. The sixteen U.S. EPA proposed priority polycyclic aromatic hydrocarbons (PAHs) in 130 surface sediment samples collected from BS and YS were measured. Combined with our previous PAH data of 90 PM2.5 samples from the upwind areas, the sources of the PAHs in BS and YS were apportioned using positive matrix factorization (PMF) modeling. Four sources were identified: petroleum residue, vehicular emissions, coal combustion and biomass burning. Petroleum residue was the dominant contributor of PAHs in the coast of the Bohai Bay probably due to Haihe River runoff, oil leakage from ships and offshore oil fields. The contribution of vehicular emissions in BS was higher than that in YS, and the reverse was true for coal combustion and biomass burning. This difference in the source patterns in the sediments of the two seas could be attributed to the different PAH emission features of the upwind area related to demographic and economic conditions, as well as the marine geography. The ratios of selected 4-6 ring PAHs in the sediments compared well with those of the PM2.5 of the upwind areas, implicating that the particle phase PAHs in the atmosphere play an important role in the source to sink process of the pyrogenic PAHs in the region.

  2. Regional variations in the fluxes of foraminifera carbonate, coccolithophorid carbonate and biogenic opal in the northern Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Ramaswamy, V.; Gaye, B.

    Mass fluxes of diatom opal, planktonic foraminifera carbonate and coccolithophorid carbonate were measured with time-series sediment traps at six sites in the Arabian Sea, Bay of Bengal and Equatorial Indian Ocean (EIOT). The above fluxes were...

  3. Mineral Fractionation during Sediment Comminution and Transport in Fluvio-Deltaic and Lacustrine Rocks of the Bradbury Group, Gale Crater, Mars

    Science.gov (United States)

    Siebach, K. L.; Baker, M. B.; Grotzinger, J. P.; McLennan, S. M.; Gellert, R.; Thompson, L. M.; Hurowitz, J.

    2017-12-01

    Mineral distribution patterns in sediments of the Bradbury group in Gale crater, interpreted from observations by the Mars Science Laboratory rover Curiosity, show the importance of transport mechanics in source-to-sink processes on Mars. The Bradbury group is comprised of basalt-derived mudstones to conglomerates exposed along the modern floor of Gale crater and analyzed along a 9-km traverse of the Curiosity rover. Over 110 bulk chemistry analyses of the rocks were acquired, along with two XRD mineralogical analyses of the mudstone. These rocks are uniquely suited for analysis of source-to-sink processes because they exhibit a wide range of compositions, but (based on multiple chemical weathering proxies) they appear to have experienced negligible cation-loss during weathering and erosion. Chemical variations between analyses correlate with sediment grain sizes, with coarser-grained rocks enriched in plagioclase components SiO2, Al2O3, and Na2O, and finer-grained rocks enriched in components of mafic minerals, consistent with grain-size sorting of mineral fractions during sediment transport. Further geochemical and mineralogical modeling supports the importance of mineral fractionation: even though the limited XRD data suggests that some fraction (if not all) of the rocks contain clays and an amorphous component, models show that 90% of the compositions measured are consistent with sorting of primary igneous minerals from a plagioclase-phyric subalkaline basalt (i.e., no corrections for cation-loss are required). The distribution of K2O, modeled as a potassium feldspar component, is an exception to the major-element trends because it does not correlate with grain size, but has an elevation-dependent signal likely correlated with the introduction of a second source material. However, the dominant compositional trends within the Bradbury group sedimentary rocks are correlated with grain size and consistent with mineral fractionation of minimally

  4. Seasonal variations in suspended-sediment dynamics in the tidal reach of an estuarine tributary

    Science.gov (United States)

    Downing-Kunz, Maureen A.; Schoellhamer, David H.

    2013-01-01

    Quantifying sediment supply from estuarine tributaries is an important component of developing a sediment budget, and common techniques for estimating supply are based on gages located above tidal influence. However, tidal interactions near tributary mouths can affect the magnitude and direction of sediment supply to the open waters of the estuary. We investigated suspended-sediment dynamics in the tidal reach of Corte Madera Creek, an estuarine tributary of San Francisco Bay, using moored acoustic and optical instruments. Flux of both water and suspended-sediment were calculated from observed water velocity and turbidity for two periods in each of wet and dry seasons during 2010. During wet periods, net suspended-sediment flux was seaward; tidally filtered flux was dominated by the advective component. In contrast, during dry periods, net flux was landward; tidally filtered flux was dominated by the dispersive component. The mechanisms generating this landward flux varied; during summer we attributed wind–wave resuspension in the estuary and subsequent transport on flood tides, whereas during autumn we attributed increased spring tide flood velocity magnitude leading to local resuspension. A quadrant analysis similar to that employed in turbulence studies was developed to summarize flux time series by quantifying the relative importance of sediment transport events. These events are categorized by the direction of velocity (flood vs. ebb) and the magnitude of concentration relative to tidally averaged conditions (relatively turbid vs. relatively clear). During wet periods, suspended-sediment flux was greatest in magnitude during relatively turbid ebbs, whereas during dry periods it was greatest in magnitude during relatively turbid floods. A conceptual model was developed to generalize seasonal differences in suspended-sediment dynamics; model application to this study demonstrated the importance of few, relatively large events on net suspended-sediment flux

  5. Magnetic-flux pump

    Science.gov (United States)

    Hildebrandt, A. F.; Elleman, D. D.; Whitmore, F. C. (Inventor)

    1966-01-01

    A magnetic flux pump is described for increasing the intensity of a magnetic field by transferring flux from one location to the magnetic field. The device includes a pair of communicating cavities formed in a block of superconducting material, and a piston for displacing the trapped magnetic flux into the secondary cavity producing a field having an intense flux density.

  6. Radon flux measurement methodologies

    International Nuclear Information System (INIS)

    Nielson, K.K.; Rogers, V.C.

    1984-01-01

    Five methods for measuring radon fluxes are evaluated: the accumulator can, a small charcoal sampler, a large-area charcoal sampler, the ''Big Louie'' charcoal sampler, and the charcoal tent sampler. An experimental comparison of the five flux measurement techniques was also conducted. Excellent agreement was obtained between the measured radon fluxes and fluxes predicted from radium and emanation measurements

  7. Vision for a worldwide fluvial-sediment information network

    Science.gov (United States)

    Gray, J.R.; Osterkamp, W.R.

    2007-01-01

    The nations of the world suffer both from the deleterious effects of some natural and human-altered fluxes of fluvial sediment and a lack of consistent and reliable information on the temporal and spatial occurrence of fluvial sediments. Decades ago, this difficulty was unavoidable due to a lack of understanding of the magnitude and scope of environmental influences exerted by fluvial sediment coupled with a dearth of tools for monitoring and studying the data. Such is no longer the case.

  8. Clay mineralogy indicates the muddy sediment provenance in the estuarine-inner shelf of the East China Sea

    Science.gov (United States)

    Zhao, Yifei; Zou, Xinqing; Liu, Qing; Wang, Chenglong; Ge, Chendong; Xu, Min

    2018-02-01

    The estuarine-inner shelf mud regions of the East China Sea (ECS) are valuable for studying the source-to-sink processes of fluvial sediments deposited since the Holocene. In this study, we present evidence of the provenance and environmental evolution of two cores (S5-2 and JC07) from the estuarine-inner shelf regions of the ECS over the past 100 years based on 210Pb dating, high-resolution grain size measurements and clay mineral analyses. The results indicate that the clay mineral assemblages of cores S5-2 and JC07 are dominated by illite, followed by kaolinite and chlorite, and present scarce amounts of smectite. A comparison of these clay mineral assemblages with several major sources reveals that the fine sediments on the estuarine-inner shelf of the ECS represent a mixture of provenances associated with the Yangtze and Yellow Rivers, as well as smaller rivers. However, the contribution of each provenance has varied greatly over the past hundred years, as indicated by the down-core variability due to strong sediment reworking and transport on the inner shelf and the reduction of the sediment load from the Yangtze River basin. In the mud region of the Yangtze River estuary, the sediment from 1930 to 1956 was primarily derived from the Yangtze River, although the Yellow River was also an important influence. From 1956 to 2013, the Yellow River contribution decreased, whereas the Yangtze River contribution correspondingly increased. In the Zhe-Min mud region, the Yangtze River contributed more sediment than did other rivers from 1910 to 1950; however, the Yangtze River contribution gradually decreased from 1950 to 2013. Moreover, the other small rivers accounted for minor contributions, and the East Asian winter monsoon (EAWM) played an important role in the sediment transport process in the ECS. Our results indicate that the weakening/strengthening of the EAWM and a decrease in the sediment load of the Yangtze River influenced the transport and fate of sediment

  9. Estimating suspended sediment yield, sedimentation controls and impacts in the Mellah Catchment of Northern Algeria

    International Nuclear Information System (INIS)

    Khanchoul, Kamel; Assassi Fella; Altschul, Robert

    2009-01-01

    This paper is an assessment of the suspended sediment yield in the Mellah Catchment of northern Algeria. We use discharge-sediment load relationships to explore the variability of water discharge and sediment load, and to investigate the impact of geomorphic factors disturbance on erosion and sedimentation. Suspended sediment load was analyzed in the Mellah Catchment (550 squre kms ) which was controlled by a gauging station to measure discharge and sediment transport. The relations between daily mean sediment concentration and daily mean water discharge were analyzed to develop sediment rating curves. For storms with no water samples, a sediment rating curve was developed. The technique involves stratification of data into discharge-based classes, the mean of which are used to fit a rating curve according to single flow data and season to provide various rating relationships. The mean annual sediment yield during the 24 years of the study period was 562 T km -2 in the Mellah Catchment. This drainage basin had high rainfall and runoff, the erosion was high. The high sediment yield in the Mellah basin could be explained by a high percentage of sparse grassland and cultivation developed on shallow marly silty-clayey soils with steep slopes often exceeding 12%. Almost all suspended sediment loads are transported during storm events that mainly occur in the winter and spring heavy and medium downpours. The scarceness of these events leads to a very large interseasonal variability of the wadi sediment fluxes. The negative impacts of this enhanced sediment mobility are directly felt in the western part of the basin which shows many mass movements, bank and gully erosion because cultivated areas are often bared during autumnal brief flash floods and furrowed downslope during the winter season. (author)

  10. Measurements of gaseous mercury exchanges at the sediment-water, water-atmosphere and sediment-atmosphere interfaces of a tidal environment (Arcachon Bay, France).

    Science.gov (United States)

    Bouchet, Sylvain; Tessier, Emmanuel; Monperrus, Mathilde; Bridou, Romain; Clavier, Jacques; Thouzeau, Gerard; Amouroux, David

    2011-05-01

    The elemental mercury evasion from non-impacted natural areas is of significant importance in the global Hg cycle due to their large spatial coverage. Intertidal areas represent a dynamic environment promoting the transformations of Hg species and their subsequent redistribution. A major challenge remains in providing reliable data on Hg species variability and fluxes under typical transient tidal conditions found in such environment. Field experiments were thus carried out to allow the assessment and comparison of the magnitude of the gaseous Hg fluxes at the three interfaces, sediment-water, sediment-atmosphere and water-atmosphere of a mesotidal temperate lagoon (Arcachon Bay, Aquitaine, France) over three distinct seasonal conditions. The fluxes between the sediment-water and the sediment-atmosphere interfaces were directly evaluated with field flux chambers, respectively static or dynamic. Water-atmosphere fluxes were evaluated from ambient concentrations using a gas exchange model. The fluxes at the sediment-water interface ranged from -5.0 to 5.1 ng m(-2) h(-1) and appeared mainly controlled by diffusion. The occurrence of macrophytic covers (i.e.Zostera noltii sp.) enhanced the fluxes under light radiations. The first direct measurements of sediment-atmosphere fluxes are reported here. The exchanges were more intense and variable than the two other interfaces, ranging between -78 and 40 ng m(-2) h(-1) and were mostly driven by the overlying atmospheric Hg concentrations and superficial sediment temperature. The exchanges between the water column and the atmosphere, computed as a function of wind speed and gaseous mercury saturation ranged from 0.4 to 14.5 ng m(-2) h(-1). The flux intensities recorded over the intertidal sediments periodically exposed to the atmosphere were roughly 2 to 3 times higher than the fluxes of the other interfaces. The evasion of elemental mercury from emerged intertidal sediments is probably a significant pathway for Hg evasion in

  11. Does historical wildfire activity alter metal fluxes to northern lakes?

    Science.gov (United States)

    Pelletier, N.; Chetelat, J.; Vermaire, J. C.; Palmer, M.; Black, J.; Pellisey, J.; Tracz, B.; van der Wielen, S.

    2017-12-01

    Current drought conditions in northwestern Canada are conducive to more frequent and severe wildfires that may mobilize mercury and other metals accumulated in soil and biomass. There is evidence that wildfires can remobilize and transport mercury within and outside catchments by atmospheric volatilization, particulate emissions and catchment soil erosion. However, the effect of fires on mercury fluxes to nearby lake sediments remains unclear. In this study, we use a combination of 10 dated lake sediment cores and four nearby ombrotrophic peatland cores to investigate the effects of wildfires on mercury fluxes to lake sediments. Lakes varying in catchment size and distance from recent fire events were sampled. Mercury concentrations in the environmental archives were measured, and macroscopic charcoal particles (>100 um) were counted at high resolution in the sediments to observe the co-variation of the local fire history and mercury fluxes. Mercury flux recorded in ombrotrophic peat cores provided an estimate of the historical atmospheric mercury flux from local and regional atmospheric deposition. The mercury flux recorded in lake sediments corresponds to the sum of direct atmospheric deposition and catchment transport. In combination, these archives will allow for the partitioning of mercury loading attributable to catchment transport from direct atmospheric deposition. After correcting the fluxes for particle focusing and terragenic elements input, flux from different lakes will be compared based on their catchment size and their temporal and spatial proximity known fire events. Altogether, our preliminary results using these paleolimnological methods will provide new insights on mercury transport processes that are predicted to become more important under a changing climate.

  12. Effect of redox conditions on bacterial community structure in Baltic Sea sediments with contrasting redox conditions

    NARCIS (Netherlands)

    Steenbergh, A.K.; Bodelier, P.L.E.; Slomp, C.P; Laanbroek, H.J.

    2014-01-01

    Phosphorus release from sediments can exacerbate the effect of eutrophication in coastal marine ecosystems. The flux of phosphorus from marine sediments to the overlying water is highly dependent on the redox conditions at the sediment-water interface. Bacteria are key players in the biological

  13. Fluvial sediment in the environment: a national challenge

    Science.gov (United States)

    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.

  14. Triassic North American paleodrainage networks and sediment dispersal of the Chinle Formation: A quantitative approach utilizing detrital zircons

    Science.gov (United States)

    Blum, M. D.; Umbarger, K.

    2017-12-01

    The Triassic Chinle Formation is a fluvial succession deposited in a backarc setting across the present-day Colorado Plateau of the southwestern United States. Existing studies have proposed various mechanisms responsible for the unique stratigraphic architecture and depositional sequences of the Chinle. However, these studies lack necessary age control to correlate stratigraphic patterns with contemporaneous mechanisms. This study will collect new samples for detrital zircon analysis, as well as upgrade existing samples (to n=300) from Dickinson and Gehrels (2008), to improve the resolution of Triassic sediment provenance from source-to-sink. The improved dataset allows appraisal of the multiple provenance terranes that contributed to the Chinle depositional system to delineate and reconstruct paleodrainage patterns. The additional samples will be collected systematically from the base of the Chinle, and vertically throughout the section to capture a regional story of how the continental scale drainage reorganized through time. U-Pb ages of detrital zircons will be utilized to provide quantitative fingerprinting information to constrain interpretations for the origin and transport history of the Chinle fluvial succession in time and space.

  15. Combining sediment fingerprinting and a conceptual model for erosion and sediment transfer to explore sediment sources in an Alpine catchment

    Science.gov (United States)

    Costa, A.; Stutenbecker, L.; Anghileri, D.; Bakker, M.; Lane, S. N.; Molnar, P.; Schlunegger, F.

    2017-12-01

    In Alpine basins, sediment production and transfer is increasingly affected by climate change and human activities, specifically hydropower exploitation. Changes in sediment sources and pathways significantly influence basin management, biodiversity and landscape evolution. We explore the dynamics of sediment sources in a partially glaciated and highly regulated Alpine basin, the Borgne basin, by combining geochemical fingerprinting with the modelling of erosion and sediment transfer. The Borgne basin in southwest Switzerland is composed of three main litho-tectonic units, which we characterised following a tributary-sampling approach from lithologically characteristic sub-basins. We analysed bulk geochemistry using lithium borate fusion coupled with ICP-ES, and we used it to discriminate the three lithologic sources using statistical methods. Finally, we applied a mixing model to estimate the relative contributions of the three sources to the sediment sampled at the outlet. We combine results of the sediment fingerprinting with simulations of a spatially distributed conceptual model for erosion and transport of fine sediment. The model expresses sediment erosion by differentiating the contributions of erosional processes driven by erosive rainfall, snowmelt, and icemelt. Soil erodibility is accounted for as function of land-use and sediment fluxes are linearly convoluted to the outlet by sediment transfer rates for hillslope and river cells, which are a function of sediment connectivity. Sediment connectivity is estimated on the basis of topographic-hydraulic connectivity, flow duration associated with hydropower flow abstraction and permanent storage in hydropower reservoirs. Sediment fingerprinting at the outlet of the Borgne shows a consistent dominance (68-89%) of material derived from the uppermost, highly glaciated reaches, while contributions of the lower part (10-25%) and middle part (1-16%), where rainfall erosion is predominant, are minor. This result is

  16. Quantifying tidally driven benthic oxygen exchange across permeable sediments

    DEFF Research Database (Denmark)

    McGinnis, Daniel F.; Sommer, Stefan; Lorke, Andreas

    2014-01-01

    Continental shelves are predominately (approximate to 70%) covered with permeable, sandy sediments. While identified as critical sites for intense oxygen, carbon, and nutrient turnover, constituent exchange across permeable sediments remains poorly quantified. The central North Sea largely consists...... of permeable sediments and has been identified as increasingly at risk for developing hypoxia. Therefore, we investigate the benthic O-2 exchange across the permeable North Sea sediments using a combination of in situ microprofiles, a benthic chamber, and aquatic eddy correlation. Tidal bottom currents drive...... the variable sediment O-2 penetration depth (from approximate to 3 to 8 mm) and the concurrent turbulence-driven 25-fold variation in the benthic sediment O-2 uptake. The O-2 flux and variability were reproduced using a simple 1-D model linking the benthic turbulence to the sediment pore water exchange...

  17. Observations and modeling of fjord sedimentation during the 30 year retreat of Columbia Glacier, AK

    Science.gov (United States)

    Love, Katherine B; Hallet, Bernard; Pratt, Thomas L.; O'Neel, Shad

    2016-01-01

    To explore links between glacier dynamics, sediment yields and the accumulation of glacial sediments in a temperate setting, we use extensive glaciological observations for Columbia Glacier, Alaska, and new oceanographic data from the fjord exposed during its retreat. High-resolution seismic data indicate that 3.2 × 108 m3 of sediment has accumulated in Columbia Fjord over the past three decades, which corresponds to ~5 mm a−1 of erosion averaged over the glaciated area. We develop a general model to infer the sediment-flux history from the glacier that is compatible with the observed retreat history, and the thickness and architecture of the fjord sediment deposits. Results reveal a fivefold increase in sediment flux from 1997 to 2000, which is not correlated with concurrent changes in ice flux or retreat rate. We suggest the flux increase resulted from an increase in the sediment transport capacity of the subglacial hydraulic system due to the retreat-related steepening of the glacier surface over a known subglacial deep basin. Because variations in subglacial sediment storage can impact glacial sediment flux, in addition to changes in climate, erosion rate and glacier dynamics, the interpretation of climatic changes based on the sediment record is more complex than generally assumed.

  18. Clustering of Emerging Flux

    Science.gov (United States)

    Ruzmaikin, A.

    1997-01-01

    Observations show that newly emerging flux tends to appear on the Solar surface at sites where there is flux already. This results in clustering of solar activity. Standard dynamo theories do not predict this effect.

  19. Chemistry of marine sediments

    International Nuclear Information System (INIS)

    Yen, T.F.

    1977-01-01

    Some topics considered are as follows: characterization of sediments in the vicinity of offshore petroleum production; thermal alteration experiments on organic matter in recent marine sediments as a model for petroleum genesis; composition of polluted bottom sediments in Great Lakes harbors; distribution of heavy metals in sediment fractions; recent deposition of lead off the coast of southern California; release of trace constituents from sediments resuspended during dredging operations; and migration of chemical constituents in sediment-seawater interfaces

  20. Post-disturbance sediment recovery: Implications for watershed resilience

    Science.gov (United States)

    Rathburn, Sara L.; Shahverdian, Scott M.; Ryan, Sandra E.

    2018-03-01

    Sediment recovery following disturbances is a measure of the time required to attain pre-disturbance sediment fluxes. Insight into the controls on recovery processes and pathways builds understanding of geomorphic resilience. We assess post-disturbance sediment recovery in three small (1.5-100 km2), largely unaltered watersheds within the northern Colorado Rocky Mountains affected by wildfires, floods, and debris flows. Disturbance regimes span 102 (floods, debris flows) to 103 years (wildfires). For all case studies, event sediment recovery followed a nonlinear pattern: initial high sediment flux during single precipitation events or high annual snowmelt runoff followed by decreasing sediment fluxes over time. Disturbance interactions were evaluated after a high-severity fire within the South Fork Cache la Poudre basin was followed by an extreme flood one year post-fire. This compound disturbance hastened suspended sediment recovery to pre-fire concentrations 3 years after the fire. Wildfires over the last 1900 YBP in the South Fork basin indicate fire recurrence intervals of 600 years. Debris flows within the upper Colorado River basin over the last two centuries have shifted the baseline of sediment recovery caused by anthropogenic activities that increased debris flow frequency. An extreme flood on North St. Vrain Creek with an impounding reservoir resulted in extreme sedimentation that led to a physical state change. We introduce an index of resilience as sediment recovery/disturbance recurrence interval, providing a relative comparison between sites. Sediment recovery and channel form resilience may be inversely related because of high or low physical complexity in streams. We propose management guidelines to enhance geomorphic resilience by promoting natural processes that maintain physical complexity. Finally, sediment connectivity within watersheds is an additional factor to consider when establishing restoration treatment priorities.

  1. Abrasion-set limits on Himalayan gravel flux.

    Science.gov (United States)

    Dingle, Elizabeth H; Attal, Mikaël; Sinclair, Hugh D

    2017-04-26

    Rivers sourced in the Himalayan mountain range carry some of the largest sediment loads on the planet, yet coarse gravel in these rivers vanishes within approximately 10-40 kilometres on entering the Ganga Plain (the part of the North Indian River Plain containing the Ganges River). Understanding the fate of gravel is important for forecasting the response of rivers to large influxes of sediment triggered by earthquakes or storms. Rapid increase in gravel flux and subsequent channel bed aggradation (that is, sediment deposition by a river) following the 1999 Chi-Chi and 2008 Wenchuan earthquakes reduced channel capacity and increased flood inundation. Here we present an analysis of fan geometry, sediment grain size and lithology in the Ganga Basin. We find that the gravel fluxes from rivers draining the central Himalayan mountains, with upstream catchment areas ranging from about 350 to 50,000 square kilometres, are comparable. Our results show that abrasion of gravel during fluvial transport can explain this observation; most of the gravel sourced more than 100 kilometres upstream is converted into sand by the time it reaches the Ganga Plain. These findings indicate that earthquake-induced sediment pulses sourced from the Greater Himalayas, such as that following the 2015 Gorkha earthquake, are unlikely to drive increased gravel aggradation at the mountain front. Instead, we suggest that the sediment influx should result in an elevated sand flux, leading to distinct patterns of aggradation and flood risk in the densely populated, low-relief Ganga Plain.

  2. Provenance discrimination of sediments in the Zhejiang-Fujian mud belt, East China Sea: Implications for the development of the mud depocenter

    Science.gov (United States)

    Liu, Xiting; Li, Anchun; Dong, Jiang; Lu, Jian; Huang, Jie; Wan, Shiming

    2018-01-01

    In the past decade, the 800 km elongated mud belt off Zhejiang-Fujian coast, East China Sea (ECS), has been extensively studied for understanding the source to sink processes on the East Asian continental margin in the context of the Asian monsoon. However, to better understand the sediment source and dispersal pattern, the existing mineralogical and geochemical data of adjacent river systems, including the Changjiang River (CJR) and local rivers in Zhejiang, Fujian and Taiwan, need to be systematically reviewed. Therefore, various indicators from published literatures for the provenance discrimination in the mud belt have been summarised in this article. The results show that high diversity of clay mineral assemblages in fluvial sediments being supplied into the mud belt, e.g., dominant illite and chlorite in the CJR, absence of smectite in Taiwan rivers, similar amounts of the four clay mineral species in Zhejiang rivers, and dominant kaolinite in Fujian rivers. On heavy mineralogy, the CJR is dominated by dolomite, hornblende, and flaky minerals; and among of them, dolomite is distinctive for the CJR. For geochemical approaches, elemental compositions, combined with strontium and neodymium isotopes, reflect strong provenance control. However, geochemical and mineralogical compositions are found to vary with grain size, and thus extra caution should be taken when using these parameters as provenance indicator to discriminate the marine sediments with variety of grain-size fractions. In addition, pyrrhotite, occurred in fluvial sediments from western Taiwan, has not been found in sediments derived from mainland China, indicating that magnetic parameters could be used to discriminate sediment provenance. The mud belt formed during sea-level highstand, when modern current system in the ECS has been established, resulting in sediments derived from the CJR have been transported southward since 8 ka. In addition, sediment provenances have not been constant since

  3. Fatty acids in sediments and phytoplankton data were collected from the Equatorial Pacific Ocean as part of the Joint Global Ocean Flux Study/Equatorial Pacific Basin Study (JGOFS/EQPAC) project., from 1992-02-03 to 1992-12-13 (NODC Accession 9700180)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Fatty acids in sediments and phytoplankton data were collected using plankton tow, sediments sampler - corer, pump and CTD casts from the R/V THOMAS THOMPSON in the...

  4. 10Be/230Th ratios as proxy for particle flux in the equatorial Pacific ocean

    International Nuclear Information System (INIS)

    Anderson, R.F.; Fleisher, M.Q.; Kubik, P.W.; Suter, M.

    1997-01-01

    Particulate 10 Be/ 230 Th ratios collected by sediment traps in the central equatorial Pacific Ocean exhibit a positive correlation with particle flux, but little or no correlation with particle composition. (author) 1 fig., 4 refs

  5. Sediment Transport Over Run-of-River Dams

    Science.gov (United States)

    O'Brien, M.; Magilligan, F. J.; Renshaw, C. E.

    2016-12-01

    Dams have numerous documented effects that can degrade river habitat downstream. One significant effect of large dams is their ability to trap sediment delivered from upstream. This trapping can alter sediment transport and grain size downstream - effects that often motivate dam removal decisions. However, recent indirect observations and modeling studies indicate that small, run-of-river (ROR) dams, which do not impede discharge, may actually leak sediment downstream. However, there are no direct measurements of sediment flux over ROR dams. This study investigates flow and sediment transport over four to six different New England ROR dams over a summer-fall field season. Sediment flux was measured using turbidity meters and tracer (RFID) cobbles. Sediment transport was also monitored through an undammed control site and through a river where two ROR dams were recently removed. These data were used to predict the conditions that contribute to sediment transport and trapping. Year 1 data show that tracer rocks of up to 61 mm were transported over a 3 m ROR dam in peak flows of 84% of bankfull stage. These tracer rocks were transported over and 10 m beyond the dam and continue to move downstream. During the same event, comparable suspended sediment fluxes of up to 81 g/s were recorded both upstream and downstream of the dam at near-synchronous timestamps. These results demonstrate the potential for sediment transport through dammed rivers, even in discharge events that do not exceed bankfull. This research elucidates the effects of ROR dams and the controls on sediment transport and trapping, contributions that may aid in dam management decisions.

  6. Determining the sources of fine-grained sediment using the Sediment Source Assessment Tool (Sed_SAT)

    Science.gov (United States)

    Gorman Sanisaca, Lillian E.; Gellis, Allen C.; Lorenz, David L.

    2017-07-27

    A sound understanding of sources contributing to instream sediment flux in a watershed is important when developing total maximum daily load (TMDL) management strategies designed to reduce suspended sediment in streams. Sediment fingerprinting and sediment budget approaches are two techniques that, when used jointly, can qualify and quantify the major sources of sediment in a given watershed. The sediment fingerprinting approach uses trace element concentrations from samples in known potential source areas to determine a clear signature of each potential source. A mixing model is then used to determine the relative source contribution to the target suspended sediment samples.The computational steps required to apportion sediment for each target sample are quite involved and time intensive, a problem the Sediment Source Assessment Tool (Sed_SAT) addresses. Sed_SAT is a user-friendly statistical model that guides the user through the necessary steps in order to quantify the relative contributions of sediment sources in a given watershed. The model is written using the statistical software R (R Core Team, 2016b) and utilizes Microsoft Access® as a user interface but requires no prior knowledge of R or Microsoft Access® to successfully run the model successfully. Sed_SAT identifies outliers, corrects for differences in size and organic content in the source samples relative to the target samples, evaluates the conservative behavior of tracers used in fingerprinting by applying a “Bracket Test,” identifies tracers with the highest discriminatory power, and provides robust error analysis through a Monte Carlo simulation following the mixing model. Quantifying sediment source contributions using the sediment fingerprinting approach provides local, State, and Federal land management agencies with important information needed to implement effective strategies to reduce sediment. Sed_SAT is designed to assist these agencies in applying the sediment fingerprinting

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

    Science.gov (United States)

    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

  8. sup(234) Th scavenging and particle export fluxes from the upper 100 m of the Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Sarin, M.M.; Rengarajan, R.; Ramaswamy, V.

    of column primary productivity. Using the sup(234) Th export fluxes and the measured specific activity of sup(234) Th in the sediment traps, we have computed th eparticle and carbon fluxes at 100 m. These results reveal that the particle fluxes determined...

  9. Rapid sedimentation and overpressure in shallow sediments of the Bering Trough, offshore southern Alaska

    Science.gov (United States)

    Daigle, Hugh; Worthington, Lindsay L.; Gulick, Sean P. S.; Van Avendonk, Harm J. A.

    2017-04-01

    Pore pressures in sediments at convergent margins play an important role in driving chemical fluxes and controlling deformation styles and localization. In the Bering Trough offshore Southern Alaska, extreme sedimentation rates over the last 140 kyr as a result of glacial advance/retreats on the continental shelf have resulted in elevated pore fluid pressures in slope sediments overlying the Pamplona Zone fold and thrust belt, the accretionary wedge resulting from subduction of the Yakutat microplate beneath the North American Plate. Based on laboratory experiments and downhole logs acquired at Integrated Ocean Drilling Program Site U1421, we predict that the overpressure in the slope sediments may be as high as 92% of the lithostatic stress. Results of one-dimensional numerical modeling accounting for changes in sedimentation rate over the last 130 kyr predicted overpressures that are consistent with our estimates, suggesting that the overpressure is a direct result of the rapid sedimentation experienced on the Bering shelf and slope. Comparisons with other convergent margins indicate that such rapid sedimentation and high overpressure are anomalous in sediments overlying accretionary wedges. We hypothesize that the shallow overpressure on the Bering shelf/slope has fundamentally altered the deformation style within the Pamplona Zone by suppressing development of faults and may inhibit seismicity by focusing faulting elsewhere or causing deformation on existing faults to be aseismic. These consequences are probably long-lived as it may take several million years for the excess pressure to dissipate.

  10. Auto consolidated cohesive sediments erosion

    International Nuclear Information System (INIS)

    Ternat, F.

    2007-02-01

    Pollutants and suspended matters of a river can accumulate into the sedimentary column. Once deposited, they are submitted to self-weight consolidation processes, ageing and burying, leading to an increase of their erosion resistance. Pollutant fluxes can be related to sedimentary fluxes, determined by threshold laws. In this work, an erosion threshold model is suggested by introducing a cohesion force into the usual force balance. A model of cohesion is developed on the basis of interactions between argillaceous cohesive particles (clays), particularly the Van der Waals force, whose parameterization is ensured by means of granulometry and porosity. Artificial erosion experiments were performed in a recirculating erosion flume with natural cored sediments where critical shear stress measurements were performed. Other analyses provided granulometry and porosity. The results obtained constitute a good database for the literature. The model is then applied to the experimental conditions and gives good agreement with measurements. An example of the accounting for self-weight consolidation processes is finally suggested, before finishing on a Mohr like diagram dedicated to soft cohesive sediment erosion. (author)

  11. Quantifying benthic nitrogen fluxes in Puget Sound, Washington: a review of available data

    Science.gov (United States)

    Sheibley, Richard W.; Paulson, Anthony J.

    2014-01-01

    Understanding benthic fluxes is important for understanding the fate of materials that settle to the Puget Sound, Washington, seafloor, as well as the impact these fluxes have on the chemical composition and biogeochemical cycles of marine waters. Existing approaches used to measure benthic nitrogen flux in Puget Sound and elsewhere were reviewed and summarized, and factors for considering each approach were evaluated. Factors for selecting an appropriate approach for gathering information about benthic flux include: availability of resources, objectives of projects, and determination of which processes each approach measures. An extensive search of literature was undertaken to summarize known benthic nitrogen fluxes in Puget Sound. A total of 138 individual flux chamber measurements and 38 sets of diffusive fluxes were compiled for this study. Of the diffusive fluxes, 35 new datasets were located, and new flux calculations are presented in this report. About 65 new diffusive flux calculations are provided across all nitrogen species (nitrate, NO3-; nitrite, NO2-; ammonium, NH4+). Data analysis of this newly compiled benthic flux dataset showed that fluxes beneath deep (greater than 50 meters) water tended to be lower than those beneath shallow (less than 50 meters) water. Additionally, variability in flux at the shallow depths was greater, possibly indicating a more dynamic interaction between the benthic and pelagic environments. The overall range of bottom temperatures from studies in the Puget Sound area were small (5–16 degrees Celsius), and only NH4+ flux showed any pattern with temperature. For NH4+, flux values and variability increased at greater than about 12 degrees Celsius. Collection of additional study site metadata about environmental factors (bottom temperature, depth, sediment porosity, sediment type, and sediment organic matter) will help with development of a broader regional understanding benthic nitrogen flux in the Puget Sound.

  12. Mercury in Long Island Sound sediments

    Science.gov (United States)

    Varekamp, J.C.; Buchholtz ten Brink, Marilyn 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.

  13. Compact neutron flux monitor

    International Nuclear Information System (INIS)

    Madhavi, V.; Phatak, P.R.; Bahadur, C.; Bayala, A.K.; Jakati, R.K.; Sathian, V.

    2003-01-01

    Full text: A compact size neutron flux monitor has been developed incorporating standard boards developed for smart radiation monitors. The sensitivity of the monitors is 0.4cps/nV. It has been tested up to 2075 nV flux with standard neutron sources. It shows convincing results even in high flux areas like 6m away from the accelerator in RMC (Parel) for 106/107 nV. These monitors have a focal and remote display, alarm function with potential free contacts for centralized control and additional provision of connectivity via RS485/Ethernet. This paper describes the construction, working and results of the above flux monitor

  14. Sedimentation of Particulate Organic Matter in the Dona Paula Bay, West Coast of India during November to May 1995-97.

    Digital Repository Service at National Institute of Oceanography (India)

    Bhaskar, P.V.; Cardozo, E.; Giriyan, A.; Garg, A.; Bhosle, N.B.

    particle flux study in the Santa Monica San Pedro Basin off Los Angeles: particle flux, primary production and transmissometer study. Continental Shelf Research 7: 307-328. Olesen, M. and Lundsgaard, C. 1996 Seasonal sedimentation of autochthonous...

  15. SEDIMENT PROPERTIES and Other Data from FIXED PLATFORM From NE Atlantic (limit-40 W) from 19890403 to 19900409 (NODC Accession 9200155)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The data in this accession contains files of Joint Global Ocean Flux Study (JGOFS) North Atlantic Bloom Experiment Biogenic Sediment Trap Flux data collected by Dr....

  16. Lithogenic fluxes to the northern Indian Ocean - An overview

    Digital Repository Service at National Institute of Oceanography (India)

    Ramaswamy, V.

    Lithogenic fluxes to the northern Indian Ocean, measurEd. by time-series sediment traps, exhibit a strong seasonality with the bulk of the material (40 to 80 %) being deposited during the southwest monsoon period. This seasonality is more pronounced...

  17. Increased particle flux to the deep ocean related to monsoons

    Digital Repository Service at National Institute of Oceanography (India)

    Nair, R.R.; Ittekkot, V.; Manganini, S.J.; Ramaswamy, V.; Haake, B.; Degens, E.T.; Desai, B.N.; Honjo, S.

    . To assess the impact of monsoon-driven processes on the downward particle flux variations in the open ocean we deployed three moored arrays consisting of six time-series sediment traps at selected locations in the western, central and eastern parts...

  18. Coastal hypoxia and sediment biogeochemistry

    Directory of Open Access Journals (Sweden)

    J. J. Middelburg

    2009-07-01

    Full Text Available The intensity, duration and frequency of coastal hypoxia (oxygen concentration <63 μM are increasing due to human alteration of coastal ecosystems and changes in oceanographic conditions due to global warming. Here we provide a concise review of the consequences of coastal hypoxia for sediment biogeochemistry. Changes in bottom-water oxygen levels have consequences for early diagenetic pathways (more anaerobic at expense of aerobic pathways, the efficiency of re-oxidation of reduced metabolites and the nature, direction and magnitude of sediment-water exchange fluxes. Hypoxia may also lead to more organic matter accumulation and burial and the organic matter eventually buried is also of higher quality, i.e. less degraded. Bottom-water oxygen levels also affect the organisms involved in organic matter processing with the contribution of metazoans decreasing as oxygen levels drop. Hypoxia has a significant effect on benthic animals with the consequences that ecosystem functions related to macrofauna such as bio-irrigation and bioturbation are significantly affected by hypoxia as well. Since many microbes and microbial-mediated biogeochemical processes depend on animal-induced transport processes (e.g. re-oxidation of particulate reduced sulphur and denitrification, there are indirect hypoxia effects on biogeochemistry via the benthos. Severe long-lasting hypoxia and anoxia may result in the accumulation of reduced compounds in sediments and elimination of macrobenthic communities with the consequences that biogeochemical properties during trajectories of decreasing and increasing oxygen may be different (hysteresis with consequences for coastal ecosystem dynamics.

  19. OU3 sediment dating and sedimentation rates

    International Nuclear Information System (INIS)

    Blair, R.B.; Wolaver, H.A.; Burger, V.M.

    1994-01-01

    Environmental Technologies at Rocky Flats Environmental Technology Site (RFS) investigated the sediment history of Standley Lake, Great Western Reservoir, and Mower Reservoir using 137 Cs and 239,240 Pu global fall-out as dating indicators. These Colorado Front Range reservoirs have been the subject of study by various city, state and national agencies due to suspected Department of Energy Rocky Flats Plant impacts. We performed sediment dating as part of the RCRA Facility Investigation/Remedial Investigation Report for Operable Unit 3. A sediment chronology profile assists scientist in determining the year of sedimentation for a particular peak concentration of contaminants. Radioisotope sediment dating for the three reservoirs indicated sedimentation rates of 0.7 to 0.8 in./yr. for Standley Lake (SL), 0.9 in./yr. for Great Western Reservoir (GWR), and 0.3 in./yr. in Mower Reservoir (MR). RFS sediment dating for Operable Unit 3 compared favorably with the Hardy, Livingston, Burke, and Volchok Standley Lake study. This report describes the cesium/plutonium sediment dating method, estimates sedimentation rates for Operable Unit 3 reservoirs, and compares these results to previous investigations

  20. Radionuclide fluxes in the Arabian Sea: The role of particle composition

    Digital Repository Service at National Institute of Oceanography (India)

    Scholten, J.C.; Fietzke, J.; Mangini, A.; Stoffers, P.; Rixen, T.; Gaye-Haake, B.; Blanz, T.; Ramaswamy, V.; Sirocko, F.; Schulz, H.; Ittekkot, V.

    scavenging. 2. Methods Sediment trap samples were obtained from loca- tions WAST, CAST and EAST. Details on the locations, sampling intervals and average composition of the sediment trap material are given in Table 1. investigated Collection interruptions Ca... as they sink through the water column [11]. One of the basic methods when applying radio- high ratios are expected at continental margins (high particle flux), and such a boundary scavenging was observed in the surface sediments of the Pacific Ocean [13...

  1. Nares Abyssal Plain sediment flux studies, FY 1986 annual report

    International Nuclear Information System (INIS)

    Dymond, J.; Collier, R.W.

    1987-01-01

    On 21 September, 1984, a mooring (NAP-2) was deployed at 23 0 14.5'N, 64 0 02.1'W with an approximate bottom depth of 5835 meters. This mooring contained 6 upward looking traps (at 720, 1420, 2870, 3785, 4770, 5780 meters) and two inverted traps (at 2900 and 4800 meters). This mooring was successfully recovered on 21 November, 1985. The details of this recovery and the samples are presented. On 22 November, 1985, another shorter trap mooring (NAP-3) was deployed. The mooring was similar in design to NAP-1 and has two normal traps at 750 and 4800 meters and an inverted trap at 4830 meters

  2. Coupling climate conditions, sediment sources and sediment transport in an alpine basin

    Science.gov (United States)

    Rainato, Riccardo; Picco, Lorenzo; Cavalli, Marco; Mao, Luca; Neverman, Andrew J.; Tarolli, Paolo

    2017-04-01

    In a fluvial system, mountain basins control sediment export to the lowland rivers. Hence, the analysis of the erosion processes and sediment delivery patterns that act in mountain basins is important. Several studies have investigated the alterations triggered by recent climatic change on the hydrological regime, whilst only a few works have explored the consequences on the sediment dynamics. Here we combined and analyzed the quasi-unique dataset of climatic conditions, landscape response, and sediment export produced, since 1986 in the Rio Cordon basin (5 km2, Eastern Italian Alps) to examine the sediment delivery processes occurring in the last three decades. The temperature, precipitation, and fluvial sediment fluxes in the basin were analyzed using continuous measurement executed by a permanent monitoring station, while the landscape evolution was investigated by three sediment source inventories established in 1994, 2006, and 2016. Thus, the analysis focused on the trends exhibited during the periods 1986-1993, 1994-2006, and 2007-2015. In terms of climatic conditions, three distinct climate forcing stages can be observed in the periods analyzed: a relatively stable phase (1986-1993), a period characterized by temperature and rainfall fluctuations (1994-2006), and a more recent warmer and wetter phase (2007-2015). In the 1986-1993 period, the fluvial sediment fluxes reflected the stable trend exhibited by the climatic conditions. In the subsequent 1994-2006 period, the average temperature and precipitation were in line with that previously observed, although with higher interannual variability. Notwithstanding the climate forcing and the occurrence of high magnitude/low frequency floods that strongly influenced the source areas, between 1994 and 2006 the Rio Cordon basin showed relatively limited erosion activity. Hence, the climatic conditions and the landscape response can only partially explain the strong increase of sediment export recorded in the 1994

  3. Linking nutrient enrichment, sediment erodibility and biofilms

    Science.gov (United States)

    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.

  4. Primary cosmic ray flux

    Energy Technology Data Exchange (ETDEWEB)

    Stanev, Todor

    2001-05-01

    We discuss the primary cosmic ray flux from the point of view of particle interactions and production of atmospheric neutrinos. The overall normalization of the cosmic ray flux and its time variations and site dependence are major ingredients of the atmospheric neutrino predictions and the basis for the derivation of the neutrino oscillation parameters.

  5. Flux cutting in superconductors

    International Nuclear Information System (INIS)

    Campbell, A M

    2011-01-01

    This paper describes experiments and theories of flux cutting in superconductors. The use of the flux line picture in free space is discussed. In superconductors cutting can either be by means of flux at an angle to other layers of flux, as in longitudinal current experiments, or due to shearing of the vortex lattice as in grain boundaries in YBCO. Experiments on longitudinal currents can be interpreted in terms of flux rings penetrating axial lines. More physical models of flux cutting are discussed but all predict much larger flux cutting forces than are observed. Also, cutting is occurring at angles between vortices of about one millidegree which is hard to explain. The double critical state model and its developments are discussed in relation to experiments on crossed and rotating fields. A new experiment suggested by Clem gives more direct information. It shows that an elliptical yield surface of the critical state works well, but none of the theoretical proposals for determining the direction of E are universally applicable. It appears that, as soon as any flux flow takes place, cutting also occurs. The conclusion is that new theories are required. (perspective)

  6. Assessing the transport of PAH in the surficial sediment layer by passive sampler approach.

    Science.gov (United States)

    Belles, Angel; Alary, Claire; Criquet, Justine; Ivanovsky, Anastasia; Billon, Gabriel

    2017-02-01

    A new method based on passive samplers has been developed to assess the diffusive flux of fluorene, fluoranthene and pyrene in the sediment bed and across the sediment-water interface. The dissolved compound concentration gradient in the sediment in the vertical direction was measured at the outlet of a storm water pond by using polyethylene strips as passive samplers. Simultaneously, the dissipation of a set of tracer compounds preloaded in the passive samplers was measured to estimate the effective diffusion coefficients of the pollutants in the sediment. Both measurements were used to evaluate the diffusive flux of the compounds according to Fick's first law. The diffusive fluxes of the 3 studied compounds have been estimated with a centimetre-scale resolution in the upper 44cm of the sediment. According to the higher compound diffusion coefficient and the steeper concentration gradient in the surficial sediment layer, the results show that the net flux of compounds near the sediment interface (1cm depth) is on average 500 times higher than in the deep sediment, with average fluxes at 1cm depth on the order of 5, 0.1 and 0.1ng/m 2 /y for fluorene, fluoranthene and pyrene, respectively. Copyright © 2016 Elsevier B.V. All rights reserved.

  7. A sediment budget for the southern reach in San Francisco Bay, CA: Implications for habitat restoration

    Science.gov (United States)

    Shellenbarger, Gregory; Wright, Scott A.; Schoellhamer, David H.

    2013-01-01

    The South Bay Salt Pond Restoration Project is overseeing the restoration of about 6000 ha of former commercial salt-evaporation ponds to tidal marsh and managed wetlands in the southern reach of San Francisco Bay (SFB). As a result of regional groundwater overdrafts prior to the 1970s, parts of the project area have subsided below sea-level and will require between 29 and 45 million m3 of sediment to raise the surface of the subsided areas to elevations appropriate for tidal marsh colonization and development. Therefore, a sufficient sediment supply to the far south SFB subembayment is a critical variable for achieving restoration goals. Although both major tributaries to far south SFB have been seasonally gaged for sediment since 2004, the sediment flux at the Dumbarton Narrows, the bayward boundary of far south SFB, has not been quantified until recently. Using daily suspended-sediment flux data from the gages on Guadalupe River and Coyote Creek, combined with continuous suspended-sediment flux data at Dumbarton Narrows, we computed a sediment budget for far south SFB during Water Years 2009–2011. A Monte Carlo approach was used to quantify the uncertainty of the flux estimates. The sediment flux past Dumbarton Narrows from the north dominates the input to the subembayment. However, environmental conditions in the spring can dramatically influence the direction of springtime flux, which appears to be a dominant influence on the net annual flux. It is estimated that up to several millennia may be required for natural tributary sediments to fill the accommodation space of the subsided former salt ponds, whereas supply from the rest of the bay could fill the space in several centuries. Uncertainty in the measurement of sediment flux is large, in part because small suspended-sediment concentration differences between flood and ebb tides can lead to large differences in total mass exchange. Using Monte Carlo simulations to estimate the random error associated with

  8. Heat flux microsensor measurements

    Science.gov (United States)

    Terrell, J. P.; Hager, J. M.; Onishi, S.; Diller, T. E.

    1992-01-01

    A thin-film heat flux sensor has been fabricated on a stainless steel substrate. The thermocouple elements of the heat flux sensor were nickel and nichrome, and the temperature resistance sensor was platinum. The completed heat flux microsensor was calibrated at the AEDC radiation facility. The gage output was linear with heat flux with no apparent temperature effect on sensitivity. The gage was used for heat flux measurements at the NASA Langley Vitiated Air Test Facility. Vitiated air was expanded to Mach 3.0 and hydrogen fuel was injected. Measurements were made on the wall of a diverging duct downstream of the injector during all stages of the hydrogen combustion tests. Because the wall and the gage were not actively cooled, the wall temperature reached over 1000 C (1900 F) during the most severe test.

  9. A method to quantify and value floodplain sediment and nutrient retention ecosystem services

    Science.gov (United States)

    Hopkins, Kristina G.; Noe, Gregory; Franco, Fabiano; Pindilli, Emily J.; Gordon, Stephanie; Metes, Marina J.; Claggett, Peter; Gellis, Allen; Hupp, Cliff R.; Hogan, Dianna

    2018-01-01

    Floodplains provide critical ecosystem services to local and downstream communities by retaining floodwaters, sediments, and nutrients. The dynamic nature of floodplains is such that these areas can both accumulate sediment and nutrients through deposition, and export material downstream through erosion. Therefore, estimating floodplain sediment and nutrient retention should consider the net flux of both depositional and erosive processes. An ecosystem services framework was used to quantify and value the sediment and nutrient ecosystem service provided by floodplains in the Difficult Run watershed, a small (151 km2) suburban watershed located in the Piedmont of Virginia (USA). A sediment balance was developed for Difficult Run and two nested watersheds. The balance included upland sediment delivery to streams, stream bank flux, floodplain flux, and stream load. Upland sediment delivery was estimated using geospatial datasets and a modified Revised Universal Soil Loss Equation. Predictive models were developed to extrapolate field measurements of the flux of sediment, sediment-bound nitrogen (N), and sediment-bound phosphorus (P) from stream banks and floodplains to 3232 delineated stream segments in the study area. A replacement cost approach was used to estimate the economic value of the sediment and nutrient retention ecosystem service based on estimated net stream bank and floodplain flux of sediment-bound N for all streams in the study area. Results indicated the net fluvial fluxes of sediment, sediment-bound N, and sediment-bound P were −10,439 Mg yr−1 (net export), 57,300 kg-N yr−1(net trapping), and 98 kg-P yr−1(net trapping), respectively. For sediment, floodplain retention was offset by substantial losses from stream bank erosion, particularly in headwater catchments, resulting in a net export of sediment. Nutrient retention in the floodplain exceeded that lost through stream bank erosion resulting in net retention of nutrients (TN and

  10. Suspended-sediment dynamics in the tidal reach of a San Francisco Bay tributary

    Science.gov (United States)

    Shellenbarger, Gregory; Downing-Kunz, Maureen; Schoellhamer, David H.

    2015-01-01

    To better understand suspended-sediment transport in a tidal slough adjacent to a large wetland restoration project, we deployed continuously measuring temperature, salinity, depth, turbidity, and velocity sensors in 2010 at a near-bottom location in Alviso Slough (Alviso, California, USA). Alviso Slough is the downstream reach of the Guadalupe River and flows into the far southern end of San Francisco Bay. River flow is influenced by the Mediterranean climate, with high flows (∼90 m3 s−1) correlated to episodic winter storms and low base flow (∼0.85 m3 s−1) during the summer. Storms and associated runoff have a large influence on sediment flux for brief periods, but the annual peak sediment concentrations in the slough, which occur in April and May, are similar to the rest of this part of the bay and are not directly related to peak discharge events. Strong spring tides promote a large upstream sediment flux as a front associated with the passage of a salt wedge during flood tide. Neap tides do not have flood-directed fronts, but a front seen sometimes during ebb tide appears to be associated with the breakdown of stratification in the slough. During neap tides, stratification likely suppresses sediment transport during weaker flood and ebb tides. The slough is flood dominant during spring tides, and ebb dominant during neap tides. Extreme events in landward (salt wedge) and bayward (rainfall events) suspended-sediment flux account for 5.0 % of the total sediment flux in the slough and only 0.55 % of the samples. The remaining 95 % of the total sediment flux is due to tidal transport, with an imbalance in the daily tidal transport producing net landward flux. Overall, net sediment transport during this study was landward indicating that sediment in the sloughs may not be flushed to the bay and are available for sedimentation in the adjacent marshes and ponds.

  11. Seismologically determined bedload flux during the typhoon season.

    Science.gov (United States)

    Chao, Wei-An; Wu, Yih-Min; Zhao, Li; Tsai, Victor C; Chen, Chi-Hsuan

    2015-02-05

    Continuous seismic records near river channels can be used to quantify the energy induced by river sediment transport. During the 2011 typhoon season, we deployed a seismic array along the Chishan River in the mountain area of southern Taiwan, where there is strong variability in water discharge and high sedimentation rates. We observe hysteresis in the high-frequency (5-15 Hz) seismic noise level relative to the associated hydrological parameters. In addition, our seismic noise analysis reveals an asymmetry and a high coherence in noise cross-correlation functions for several station pairs during the typhoon passage, which corresponds to sediment particles and turbulent flows impacting along the riverbed where the river bends sharply. Based on spectral characteristics of the seismic records, we also detected 20 landslide/debris flow events, which we use to estimate the sediment supply. Comparison of sediment flux between seismologically determined bedload and derived suspended load indicates temporal changes in the sediment flux ratio, which imply a complex transition process from the bedload regime to the suspension regime between typhoon passage and off-typhoon periods. Our study demonstrates the possibility of seismologically monitoring river bedload transport, thus providing valuable additional information for studying fluvial bedrock erosion and mountain landscape evolution.

  12. The contribution of bank and surface sediments to fluvial sediment ...

    African Journals Online (AJOL)

    The contribution of bank and surface sediments to fluvial sediment transport of the Pra River. ... the relative contribution of surface and bank sediments to the fluvial sediment transport. ... EMAIL FREE FULL TEXT EMAIL FREE FULL TEXT

  13. Morphodynamics and Sediment connectivity in the Kosi River basin in the Himalaya and their implications for river management

    Science.gov (United States)

    Sinha, R.; Mishra, K.; Swrankar, S.; Jain, V.; Nepal, S.; Uddin, K.

    2017-12-01

    Sediment flux of large tropical rivers is strongly influenced by the degree of linkage between the sediments sources and sink (i.e. sediment connectivity). Sediment connectivity, especially at the catchment scale, depends largely on the morphological characteristics of the catchment such as relief, terrain roughness, slope, elevation, stream network density and catchment shape and the combined effects of land use, particularly vegetation. Understanding the spatial distribution of sediment connectivity and its temporal evolution can be useful for the characterization of sediment source areas. Specifically, these areas represent sites of instability and their connectivity influences the probability of sediment transfer at a local scale that will propagate downstream through a feedback system. This paper evaluates the morphodynamics and sediment connectivity of the Kosi basin in Nepal and India at various spatial and temporal scales. Our results provide the first order assessment of the spatial sediment connectivity in terms of the channel connectivity (IC outlet) and source to channel connectivity (IC channel) of the upstream and midstream Kosi basin. This assessment helped in the characterization of sediment dynamics in the complex morphological settings and in a mixed environment. Further, Revised Universal Soil Loss Equation (RUSLE) was used to quantify soil erosion and sediment transport capacity equation is used to quantify sediment flux at each cell basis. Sediment Delivery Ratio (SDR) was calculated for each sub-basin to identify the sediment production and transport capacity limited sub-basin. We have then integrated all results to assess the sediment flux in the Kosi basin in relation to sediment connectivity and the factors controlling the pathways of sediment delivery. Results of this work have significant implications for sediment management of the Kosi river in terms of identification of hotspots of sediment accumulation that will in turn be manifested

  14. Mercury in dated Greenland marine sediments

    DEFF Research Database (Denmark)

    Asmund, G.; Nielsen, S.P.

    2000-01-01

    Twenty marine sediment cores from Greenland were analysed for mercury, and dated by the lead-210 method. In general the cores exhibit a mercury profile with higher mercury concentrations in the upper centimetres of the core. The cores were studied by linear regression of In Hg vs, age of the sedi......Twenty marine sediment cores from Greenland were analysed for mercury, and dated by the lead-210 method. In general the cores exhibit a mercury profile with higher mercury concentrations in the upper centimetres of the core. The cores were studied by linear regression of In Hg vs, age...... indicating that the mercury mainly originates from atmospheric washout. But the large variability indicates that other processes also influence the mercury flux to Arctic marine sediments. (C) 2000 Elsevier Science B.V. All rights reserved....

  15. Diversity, Persistence and Evolution in Marine Sediments

    DEFF Research Database (Denmark)

    Starnawski, Piotr

    2016-01-01

    on the marine sediments communities was reviewed, it became apparent that there are some global trends in these populations ob- served in deep and shallow, organic rich and poor sediments. We have observed the same, often uncultured, organisms with very similar relative abundance profiles in reviewed sites...... communities as they transition from actively growing surface populations to barely dividing subsurface ones; (ii) evolutionary consequences of the prolonged residence in such environments and (iii) inferring function of the dominant groups found in deep sediments. When the current state of our knowledge....... In order to better understand this pattern we’ve reviewed the assembly processes that may lead to such situations, keeping in mind the limitations imposed by the environment.We’ve concluded, that due to low energy fluxes, and consequently low number of pos- sible cell divisions, selective survival of pre...

  16. Sediment transfer dynamics in the Illgraben

    Science.gov (United States)

    Bennett, G. L.; Molnar, P.; McArdell, B. W.; Schlunegger, F.; Burlando, P.

    2012-04-01

    resumed. During this time hillslope erosion exceeded channel erosion by 0.14myr¯ 1 indicating that hillslopes eroded independently of channel incision. Channel sediment transfer was transport-limited at the scale of the study as suggested by the aggradation of the channel in periods of very high hillslope flux and its apparent relation to variables connected to runoff generation such as precipitation and snowmelt. We have developed a conceptual model of sediment transfer based on our data set with which to investigate sediment transfer dynamics in a probabilistic sense. A stochastic sediment input from the hillslopes is generated from our magnitude-frequency model of landslides. Sediment is fed into a hillslope storage component, where a fraction is redeposited in long-term storage. Sediment in short-term storage is subsequently fed into the channel system and is only removed given a transport event (rainfall or snowmelt) of sufficient magnitude and sufficient available sediment. Transport events are generated stochastically using a weather generator. We calibrate the model with available data. Despite its simplicity the model reproduces the storage and discharge behavior of the channel system observed over the study period and enables us to test the sensitivity of the system to different parameters and system structures.

  17. Sedimentation rates and erosion changes recorded in recent sediments of Lake Piaseczno, south-eastern Poland

    Science.gov (United States)

    Tylmann, Wojciech; Turczyński, Marek; Kinder, Małgorzata

    2009-10-01

    This paper presents the dating results and basic analyses of recent sediments from Lake Piaseczno. The age of sediments was determined using the 210Pb method and constant flux: constant sedimentation (CF: CS) model. The estimated timescale was in agreement with the AMS14C date from the base of the core. The mean sediment accumulation rate during the last 100 years was calculated as 0.025 g cm-2 a-1. Based on the radiocarbon date, the rate of sediment accumulation below the 210Pb dating horizon was estimated as 0.066 g cm-2 a-1. The variability of main physical properties and sediment components along the core was analysed as well. The sediments were characterised by a very high water content (>80%). Carbonates were either not present or at a very low level (interesting record of increasing erosion intensity in the catchment area. Analysis of archival cartographic materials demonstrated that the most likely reason for the enhanced transport of minerogenic matter to the lake was deforestation caused by human activity in the beginning of the 20th century.

  18. Ocean Sediment Thickness Contours

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Ocean sediment thickness contours in 200 meter intervals for water depths ranging from 0 - 18,000 meters. These contours were derived from a global sediment...

  19. Center for Contaminated Sediments

    Data.gov (United States)

    Federal Laboratory Consortium — The U.S. Army Corps of Engineers Center for Contaminated Sediments serves as a clearinghouse for technology and expertise concerned with contaminated sediments. The...

  20. Geochemistry of sediments

    Digital Repository Service at National Institute of Oceanography (India)

    Nath, B.N.

    Considering the potential of elemental data in marine sediments as diagnostic tools of various geological and oceanographic processes, sediment geochemical data from the Indian Ocean region has been reviewed in this article. Emphasis is laid...

  1. Indicators: Sediment Enzymes

    Science.gov (United States)

    Sediment enzymes are proteins that are produced by microorganisms living in the sediment or soil. They are indicators of key ecosystem processes and can help determine which nutrients are affecting the biological community of a waterbody.

  2. Electrodialytic remediation of sediments

    DEFF Research Database (Denmark)

    Jensen, Pernille Erland

    Sediments of harbors and freshwaters are regularly dredged for various reasons: maintenance of navigational depths, recovery of recreational locations, and even environmental recovery. In the past, sediments dredged from harbors have been dumped at sea, however, environmental regulations now, in ...

  3. Moessbauer, X-ray fluorescence and paleomagnetic studies of deep-sea sediments from Peru Basin: two million years of sedimentation history

    International Nuclear Information System (INIS)

    Drodt, M.; Trautwein, A.X.; Dekkers, M.J.

    1996-01-01

    Sediment cores with different sub-bottom depths (I: 45 cm and II: 700 cm) from the Peru Basin have been investigated. From the depth profile of the relative amount of Fe(II) a redox zone is obtained which correlates with the organic carbon flux into the sediment (core I). Moessbauer parameters suggest that the iron in the sediments is mainly contained in clay minerals and to varying extent also in goethite

  4. Effects of Sediment Chemical Properties on Phosphorus Release Rates in the Sediment-Water Interface of the Steppe Wetlands.

    Science.gov (United States)

    He, Jing; Su, Derong; Lv, Shihai; Diao, Zhaoyan; Xie, Jingjie; Luo, Yan

    2017-11-22

    Rising temperature causes a process of phosphorus release, which can be characterized well using phosphorus release rates (V P ). The objective of the present study was to investigate the major factors affecting sediment phosphorus release rates through a wetland habitat simulation experiment. The results showed that the V P of different wetland sediments were different and changed with the order of W-R (river wetland) > W-L (lake wetland) > W-M (grassy marsh wetland) > W-A (reservoir wetland). The main driving factors which influenced sediment phosphorus flux velocity in the sediment-water interface were sediment B-SO₄ 2- , B-MBN and A-MBP content. Path analysis and determination coefficient analysis indicated the standard multiple regression equation for sediment phosphorus release rates in the sediment-water interface, and each main factor was Y = -0.105 + 0.096X₁ + 0.275X₂ - 0.010X₃ ( r = 0.416, p phosphorus release rates; X₁ is sediment B-SO₄ 2- content; X₂ is sediment B-MBN; and X₃ is sediment A-MBP content. Sediment B-SO₄ 2- , B-MBN and A-MBP content and the interaction between them were the main factors affecting sediment phosphorus release rates in the sediment-water interface. Therefore, these results suggest that soil chemical properties and microbial activities likely play an important role in phosphorus release rates in the sediment-water interface. We hope to provide effective scientific management and control methods for relevant environmental protection departments.

  5. Sediment-water gas exchange in two Swedish lakes measured by Eddy Correlation

    Science.gov (United States)

    Kokic, J.; Sahlee, E.; Brand, A.; Sobek, S.

    2014-12-01

    Lake sediments are hotspots for carbon (C) cycling, acting both as sinks and sources through C burial and production of carbon dioxide (CO2) and methane. The fate of this CO2 in the water column is controlled by bottom water turbulence, a factor not accounted for in current estimates of sediment CO2 fluxes. This study is aimed to quantify the turbulent CO2 flux across the sediment-water interface (SWI) by measuring the oxygen (O2) flux with the non-invasive Eddy Correlation (EC) method that combines measurements of 3D velocity (ADV) and O2 fluctuations with a microsensor. Using the metabolic relation (respiratory quotient, RQ) of O2 and CO2 derived from a sediment incubation experiment we present the first estimates of turbulent lake sediment CO2 flux from two boreal lakes in Sweden (Erssjön and Erken, 0.07 km2 and 23.7 km2 respectively). Only ~10 % of the total dataset was extracted for flux calculations due to poor signal-to-noise ratio in the velocity and O2 signals. The sediment in Lake Erssjön was both consuming and producing O2, related to bacterial respiration and photosynthesis. Mean O2 flux was -0.19 and 0.17 μmol O2 m-2 sec-1, comparing to 0.04 μmol O2 m-2 sec-1 derived from the sediment incubation experiment. Fluxes for Lake Erken are still to be determined. Experimentally derived RQ of the both lake sediments were close to unity implying that in-situ CO2 fluxes are of similar magnitude as O2 fluxes, varying between -0.15 and 0.18 μmol C m-2 sec-1. The first measurement of turbulent sediment O2 flux and estimate of turbulent CO2 flux from a small boreal lake show higher and more variable fluxes than previously found in experimental studies. The low amount of data extracted for flux calculations (~10%) point towards the difficulties in EC measurement in low-turbulence environments. On-going work focuses on the turbulence structure in lakes and its influence on the gas fluxes at the SWI.

  6. Sediment Budget in the Taiwan Strait with High Fluvial Sediment Inputs from Mountainous Rivers: New Observations and Synthesis

    Directory of Open Access Journals (Sweden)

    Shuh-Ji Kao

    2008-01-01

    Full Text Available The shallow Taiwan Strait at the southern opening of the East China Sea (ECS receives abundant sediments from turbid mountainous rivers in Taiwan. The volume of sediment is among the highest sediment yields on the global surface. This large amount of sediment discharged from modern Taiwan (range: 175 - 380 Mt y-1 based on 50-yr data is comparable to that discharged from Changjaing (500 Mt y-1-decreasing in recent decades, underscoring the importance of sediment budget in the Taiwan Strait and sediment flux from Taiwan into the ECS.We documented fluvial mud and sand concentrations during flash flooding with our observations indicating that fluvial materials in Taiwan¡¦s rivers are chiefly composed of mud (> 70 and up to 98 . By contrast, sand fraction dominates (> 85 for most stations surface sediments in the Taiwan Strait. Super typhoon Herb alone delivered 130 Mt of sediments from Choshui, the largest river in Taiwan, yet only insignificant amounts of mud were found at the river mouth six months later. The actions of waves, tides, and currents apparently prevent the deposition of fine grained sediments. Assuming sand occupied 30 (the maximum of the 60 Mt y-1 total sediment input from major western Taiwanese rivers, our annual budget estimate shows that the amount of sand input (18 5 Mt y-1 is comparable to the burial output of sand (12 10 Mt y-1. However, mud burial (6 5 Mt y-1 in the strait is far below the estimated mud input (42 11 Mt y-1, resulting in a significant shortfall. Hydrodynamic conditions were synthesized to explain the distribution pattern of limited mud patches in the strait and to reveal potential pathways by which fine-grain sediment transportation takes place in the seas surrounding Taiwan. A significant shortfall in the mud budget in the Taiwan Strait suggests that ~85 of the fluvial mud left the strait. Alternatively, the 50-year modern sediment flux data used in this study reflects exacerbated sediment flux due to human

  7. Fate modeling of mercury species and fluxes estimation in an urban river

    International Nuclear Information System (INIS)

    Tong, Yindong; Zhang, Wei; Chen, Cen; Chen, Long; Wang, Wentao; Hu, Xindi; Wang, Huanhuan; Hu, Dan; Ou, Langbo; Wang, Xuejun; Wang, Qiguang

    2014-01-01

    The fate and transfer of mercury in urban river is an important environmental concern. In this study, QWASI (Quantitative Water–Air–Sediment Interaction) model was selected to estimate the levels of total mercury and three mercury species in water and sediment, and was used to quantify the fluxes of mercury at water/air and sediment/water interfaces of an urban river. The predicted mercury levels in water and sediments were closed to the measured values. Water inflow, re-suspension of sediment and diffusion from sediment to water are major input sources of mercury in water. The net mercury transfer flux from water to air was 0.16 ng/(m 2 h). At the sediment/water interface, a net total mercury transfer of 1.32 ng/(m 2 h) from water to sediment was seen. In addition to the existing dynamic flux chambers measurement, this model method could provide a new perspective to identify the distribution and transfer of mercury in the urban river. -- Highlights: • QWASI could be a good tool to quantify transfer and fate of mercury in environment. • Distribution and flux of mercury species in an urban river was modeled. • Mercury in water mainly came from water inflow, sediment re-suspension and diffusion. • Net mercury transfer from water to air and sediment were 0.16 and 1.32 ng/(m 2 h). -- Quantitative Water–Air–Sediment Interaction model was used to quantify the transfer and fate of mercury in an urban river

  8. Human impacts on sediment in the Yangtze River: A review and new perspectives

    Science.gov (United States)

    Yang, H. F.; Yang, S. L.; Xu, K. H.; Milliman, J. D.; Wang, H.; Yang, Z.; Chen, Z.; Zhang, C. Y.

    2018-03-01

    Changes in riverine suspended and riverbed sediments have environmental, ecological and social implications. Here, we provide a holistic review of water and sediment transport and examine the human impacts on the flux, concentration and size of sediment in the Yangtze River in recent decades. We find that most of the fluvial sediment has been trapped in reservoirs, except for the finest portion. Furthermore, soil-conservation since the 1990s has reduced sediment yield. From 1956-1968 (pre-dam period) to 2013-2015 (post-dams and soil-conservation), the sediment discharge from the sub-basins decreased by 91%; in the main river, the sediment flux decreased by 99% at Xiangjiaba (upper reach), 97% at Yichang (transition between upper and middle reaches), 83% at Hankou (middle reach), and 77% at Datong (tidal limit). Because the water discharge was minimally impacted, the suspended sediment concentration decreased to the same extent as the sediment flux. Active erosion of the riverbed and coarsening of surficial sediments were observed in the middle and lower reaches. Fining of suspended sediments was identified along the river, which was counteracted by downstream erosion. Along the 700-km-long Three Gorges Reservoir, which retained 80% of the sediment from upstream, the riverbed gravel or rock was buried by mud because of sedimentation after impoundment. Along with these temporal variations, the striking spatial patterns of riverine suspended and riverbed sediments that were previously exhibited in this large basin were destroyed or reversed. Therefore, we conclude that the human impacts on sediment in the Yangtze River are strong and systematic.

  9. Boundary Conditions and the Aeolian Sediment State of the Olympia Undae Dune Field, Mars

    Science.gov (United States)

    Middlebrook, W.; Ewing, R. C.; Ayoub, F.; Bridges, N. T.; Smith, I.; Spiga, A.

    2015-05-01

    We evaluate the boundary conditions in Olympia Undae. We map two and three dimensional dune parameters from two locations proximal and distal to Planum Boreum and constrain sediment fluxes. We compare our results with a mesoscale atmospheric model.

  10. Pb-210 and Pu-239,240 in nearshore Gulf of Mexico sediments

    International Nuclear Information System (INIS)

    Rotter, R.J.

    1985-05-01

    Pb-210, Ra-226, and Pu-239,240 activities were measured in nearshore Gulf of Mexico sediments. Sediment cores were collected from the Mississippi delta, and the western Gulf of Mexico shelf. Mississippi delta cores which exhibit significantly higher sedimentation rates show larger inventories of Pb-210. The measured Pu levels from the western shelf are lower than from the delta at comparable depths. In three of the western shelf cores, the observed Pu inventory is considerably less than predicted from atmospheric flux. Therefore, Pu is not being removed to the sediment, or is being released following deposition. A key difference between these isotopes is that Pu exists in a less particle-reactive state. The ratio of excess Pb-210 to Pu levels increases with water depth in the delta and the western shelf. Water depth acts as an integrator of depth-sensitive processes. Pu scavenging is more sensitive to these processes. A sub-surface Pu maximum has been observed. Excess Pb-210 and Pu levels correlate well with sedimentation rates. This suggests that particle flux is important in removal of Pb-210 and Pu to the sediment. The flux of Mn out of the sediment is correlated with inventory data, suggesting that redox cycling of Mn may play a role in increasing Pb-210 and Pu sediment inventories. It is unclear whether the effects of increased sedimentation rates and increased Mn fluxes can be evaluated independently. Mixing of surface sediment correlates with inventory data. Increased sediment mixing allows for additional scavenging of Pb-210 and Pu from overlying waters. Mixing of sediment at depths below the mixed surface layer may play a role in increasing sediment inventories of Pb-210 and Pu

  11. Inverse modelling of fluvial sediment connectivity identifies characteristics and spatial distribution of sediment sources in a large river network.

    Science.gov (United States)

    Schmitt, R. J. P.; Bizzi, S.; Kondolf, G. M.; Rubin, Z.; Castelletti, A.

    2016-12-01

    Field and laboratory evidence indicates that the spatial distribution of transport in both alluvial and bedrock rivers is an adaptation to sediment supply. Sediment supply, in turn, depends on spatial distribution and properties (e.g., grain sizes and supply rates) of individual sediment sources. Analyzing the distribution of transport capacity in a river network could hence clarify the spatial distribution and properties of sediment sources. Yet, challenges include a) identifying magnitude and spatial distribution of transport capacity for each of multiple grain sizes being simultaneously transported, and b) estimating source grain sizes and supply rates, both at network scales. Herein, we approach the problem of identifying the spatial distribution of sediment sources and the resulting network sediment fluxes in a major, poorly monitored tributary (80,000 km2) of the Mekong. Therefore, we apply the CASCADE modeling framework (Schmitt et al. (2016)). CASCADE calculates transport capacities and sediment fluxes for multiple grainsizes on the network scale based on remotely-sensed morphology and modelled hydrology. CASCADE is run in an inverse Monte Carlo approach for 7500 random initializations of source grain sizes. In all runs, supply of each source is inferred from the minimum downstream transport capacity for the source grain size. Results for each realization are compared to sparse available sedimentary records. Only 1 % of initializations reproduced the sedimentary record. Results for these realizations revealed a spatial pattern in source supply rates, grain sizes, and network sediment fluxes that correlated well with map-derived patterns in lithology and river-morphology. Hence, we propose that observable river hydro-morphology contains information on upstream source properties that can be back-calculated using an inverse modeling approach. Such an approach could be coupled to more detailed models of hillslope processes in future to derive integrated models

  12. The internal strength of rivers: autogenic processes in control of the sediment load (Tana River, Kenya)

    Science.gov (United States)

    Geeraert, Naomi; Ochieng Omengo, Fred; Tamooh, Fredrick; Paron, Paolo; Bouillon, Steven; Govers, Gerard

    2014-05-01

    The construction of sediment rating curves for monitoring stations is a widely used technique to budget sediment fluxes. Changes in the relationship between discharge and sediment concentrations over time are often attributed to human-induced changes in catchment characteristics, such as land use change, dam construction or soil conservation measures and many models have been developed to quantitatively link catchment characteristics and river sediment load. Conversely, changes in river sediment fluxes are often interpreted as indications of major changes in the catchment. By doing so, autogenic processes, taking place within the river channel, are overlooked despite the increasing awareness of their importance. We assessed the role of autogenic processes on the sediment load of Tana River (Kenya). The Tana river was impacted by major dam construction between 1968 and 1988, effectively blocking at least 80% of the sediment transfer from the highlands to the lower river reaches. However, a comparison of pre-dam sediment fluxes at Garissa (located 250 km downstream of the dams) with recent measurements shows that sediment fluxes have not changed significantly. This suggests that most of the sediment in the post-dam period has to originate from inside the alluvial plain of the river, as tributaries downstream of the dams are scarce and intermittent. Several observations are consistent with this hypothesis. We observed that, during the wet season, sediment concentrations rapidly increased below the dams and are not controlled by inputs from tributaries. Also, sediment concentrations were high at the beginning of the wet season, which can be attributed to channel adjustment to the higher discharges. The river sediment does not contain significant amounts of 137Cs or 210Pbxs, suggesting that sediments are not derived from topsoil erosion. Furthermore, we observed a counter clockwise hysteresis during individual events which can be explained by the fact that sediment

  13. Continuous magnetic flux pump

    Science.gov (United States)

    Hildebrandt, A. F.; Elleman, D. D.; Whitmore, F. C. (Inventor)

    1966-01-01

    A method and means for altering the intensity of a magnetic field by transposing flux from one location to the location desired fro the magnetic field are examined. The device described includes a pair of communicating cavities formed in a block of superconducting material, is dimensioned to be insertable into one of the cavities and to substantially fill the cavity. Magnetic flux is first trapped in the cavities by establishing a magnetic field while the superconducting material is above the critical temperature at which it goes superconducting. Thereafter, the temperature of the material is reduced below the critical value, and then the exciting magnetic field may be removed. By varying the ratios of the areas of the two cavities, it is possible to produce a field having much greater flux density in the second, smaller cavity, into which the flux transposed.

  14. Flux in Tallinn

    Index Scriptorium Estoniae

    2004-01-01

    Rahvusvahelise elektroonilise kunsti sümpoosioni ISEA2004 klubiõhtu "Flux in Tallinn" klubis Bon Bon. Eestit esindasid Ropotator, Ars Intel Inc., Urmas Puhkan, Joel Tammik, Taavi Tulev (pseud. Wochtzchee). Klubiõhtu koordinaator Andres Lõo

  15. Flux shunts for undulators

    International Nuclear Information System (INIS)

    Hoyer, E.; Chin, J.; Hassenzahl, W.V.

    1993-05-01

    Undulators for high-performance applications in synchrotron-radiation sources and periodic magnetic structures for free-electron lasers have stringent requirements on the curvature of the electron's average trajectory. Undulators using the permanent magnet hybrid configuration often have fields in their central region that produce a curved trajectory caused by local, ambient magnetic fields such as those of the earth. The 4.6 m long Advanced Light Source (ALS) undulators use flux shunts to reduce this effect. These flux shunts are magnetic linkages of very high permeability material connecting the two steel beams that support the magnetic structures. The shunts reduce the scalar potential difference between the supporting beams and carry substantial flux that would normally appear in the undulator gap. Magnetic design, mechanical configuration of the flux shunts and magnetic measurements of their effect on the ALS undulators are described

  16. Salp contributions to vertical carbon flux in the Sargasso Sea

    Science.gov (United States)

    Stone, Joshua P.; Steinberg, Deborah K.

    2016-07-01

    We developed a one-dimensional model to estimate salp contributions to vertical carbon flux at the Bermuda Atlantic Time-series Study (BATS) site in the North Atlantic subtropical gyre for a 17-yr period (April 1994 to December 2011). We based the model parameters on published rates of salp physiology and experimentally determined sinking and decomposition rates of salp carcasses. Salp grazing was low during non-bloom conditions, but routinely exceeded 100% of chlorophyll standing stock and primary production during blooms. Fecal pellet production was the largest source of salp carbon flux (78% of total), followed by respiration below 200 m (19%), sinking of carcasses (3%), and DOC excretion below 200 m (salp-mediated carbon flux. Seasonally, salp flux was higher during spring-summer than fall-winter, due to seasonal changes in species composition and abundance. Salp carbon export to 200 m was on average 2.3 mg C m-2 d-1 across the entire time series. This is equivalent to 11% of the mean 200 m POC flux measured by sediment traps in the region. During years with significant salp blooms, however, annually-averaged salp carbon export was the equivalent of up to 60% of trap POC flux at 200 m. Salp carbon flux attenuated slowly, and at 3200 m the average modeled carbon from salps was 109% of the POC flux measured in sediment traps at that depth. Migratory and carcass carbon export pathways should also be considered (alongside fecal pellet flux) as facilitating carbon export to sequestration depths in future studies.

  17. Spatial and stress-related variation in benthic microbial gas flux in northeastern Alberta wetlands

    International Nuclear Information System (INIS)

    Ciborowski, J.; Gardner Costa, J.

    2010-01-01

    This study investigated the effects of oil sands process material (OSPM) on the sediment microbial respiration in newly constructed wetlands located in northeastern Alberta. The sediment gas flux in 10 wetlands with various sediment characteristics and ages was studied. Analyses of variance (ANOVA) were used to contrast the mean wetland production of methane (CH 4 ) and carbon dioxide (CO 2 ) with season, wetland status, wetland age, and wetland zones. The study showed that CH 4 was significantly higher in reference wetlands than in OSPM-impacted wetlands. A significant relationship between the status and zone of the wetland was observed for CH 4 fluxes in reference wetlands. CH 4 fluxes were higher in the non-vegetated zones of reference wetlands than in the vegetated zones of reference wetlands. CO 2 fluxes were low and not significantly different in any of the studied sites. Results indicated that the wetlands contributed little atmospheric carbon.

  18. Neutron flux monitor

    International Nuclear Information System (INIS)

    Oda, Naotaka.

    1993-01-01

    The device of the present invention greatly saves an analog processing section such as an analog filter and an analog processing circuit. That is, the device of the present invention comprises (1) a neutron flux detection means for detecting neutron fluxed in the reactor, (2) a digital filter means for dividing signals corresponding to the detected neutron fluxes into predetermined frequency band regions, (3) a calculation processing means for applying a calculation processing corresponding to the frequency band regions to the neutron flux detection signals divided by the digital filter means. With such a constitution, since the neutron detection signals are processed by the digital filter means, the accuracy is improved and the change for the property of the filter is facilitated. Further, when a neutron flux level is obtained, a calculation processing corresponding to the frequency band region can be conducted without the analog processing circuit. Accordingly, maintenance and accuracy are improved by greatly decreasing the number of parts. Further, since problems inherent to the analog circuit are solved, neutron fluxes are monitored at high reliability. (I.S.)

  19. Neutron flux monitoring device

    International Nuclear Information System (INIS)

    Shimazu, Yoichiro.

    1995-01-01

    In a neutron flux monitoring device, there are disposed a neutron flux measuring means for outputting signals in accordance with the intensity of neutron fluxes, a calculation means for calculating a self power density spectrum at a frequency band suitable to an object to be measured based on the output of the neutron flux measuring means, an alarm set value generation means for outputting an alarm set value as a comparative reference, and an alarm judging means for comparing the alarm set value with the outputted value of the calculation means to judge requirement of generating an alarm and generate an alarm in accordance with the result of the judgement. Namely, the time-series of neutron flux signals is put to fourier transformation for a predetermined period of time by the calculation means, and from each of square sums for real number component and imaginary number component for each of the frequencies, a self power density spectrum in the frequency band suitable to the object to be measured is calculated. Then, when the set reference value is exceeded, an alarm is generated. This can reliably prevent generation of erroneous alarm due to neutron flux noises and can accurately generate an alarm at an appropriate time. (N.H.)

  20. Global Soil and Sediment transfer during the Anthropocene

    Science.gov (United States)

    Hoffmann, Thomas; Vanacker, Veerle; Stinchcombe, Gary; Penny, Dan; Xixi, Lu

    2016-04-01

    The vulnerability of soils to human-induced erosion and its downstream effects on fluvial and deltaic ecosystems is highly variable in space and time; dependent on climate, geology, the nature and duration of land use, and topography. Despite our knowledge of the mechanistic relationships between erosion, sediment storage, land-use and climate change, the global patterns of soil erosion, fluvial sediment flux and storage throughout the Holocene remain poorly understood. The newly launched PAGES working group GloSS aims to determine the sensitivity of soil resources and sediment routing systems to varying land use types during the period of agriculture, under contrasting climate regimes and socio-ecological settings. Successfully addressing these questions in relation to the sustainable use of soils, sediments and river systems requires an understanding of past human-landscape interactions. GloSS, therefore, aims to: Develop proxies for, or indices of, human impact on rates of soil erosion and fluvial sediment transfer that are applicable on a global scale and throughout the Holocene; Create a global database of long-term (102-104 years) human-accelerated soil erosion and sediment flux records; Identify hot spots of soil erosion and sediment deposition during the Anthropocene, and Locate data-poor regions where particular socio-ecological systems are not well understood, as strategic foci for future work. This paper will present the latest progress of the PAGES GloSS working group.

  1. Influence of macrobenthos on chemical diagenesis of marine sediments

    Energy Technology Data Exchange (ETDEWEB)

    Aller, R.C.

    1977-05-01

    Diagenetic reactions involving the decomposition of organic matter and the dissolution, mobilization, and reprecipitation of metals sensitive to oxidation-reduction reactions, are most intense and rapid in the upper 1 m and especially the upper 10 cm of marine sediment. It is in this upper zone where most benthic organisms live and interact with sediments and where exchange rates of dissolved and particulate material between sediment and overlying water are largely determined. In Long Island Sound, U.S.A., both spatial and temporal trends in sediment chemistry and the flux of material out of the bottom demonstrate the control of diagenesis by bottom fauna. /sup 234/Th//sup 238/U disequilibrium studies demonstrate that particle reworking rates near the sediment-water interface vary both temporally and spatially in the Sound. The most rapid reworking occurs in protobranch-inhabited bottom areas as do the highest /sup 234/Th inventories. Excess /sup 234/Th profiles in the sediment allow determination of the rates of selected diagenetic reactions, such as Mn/sup + +/ production, near the sediment surface. Both the /sup 234/Th disequilibrium and flux measurements indicate that intra-estuarine redistribution of metals continually takes place.

  2. Overview of selected surrogate technologies for high-temporal resolution suspended-sediment monitoring

    Science.gov (United States)

    Gray, John R.; Gartner, Jeffrey W.

    2010-01-01

    Traditional methods for characterizing selected properties of suspended sediments in rivers are being augmented and in some cases replaced by cost-effective surrogate instruments and methods that produce a temporally dense time series of quantifiably accurate data for use primarily in sediment-flux computations. Turbidity is the most common such surrogate technology, and the first to be sanctioned by the U.S. Geological Survey for use in producing data used in concert with water-discharge data to compute sediment concentrations and fluxes for storage in the National Water Information System. Other technologies, including laser-diffraction, digital photo-optic, acoustic-attenuation and backscatter, and pressure-difference techniques are being evaluated for producing reliable sediment concentration and, in some cases, particle-size distribution data. Each technology addresses a niche for sediment monitoring. Their performances range from compelling to disappointing. Some of these technologies have the potential to revolutionize fluvial-sediment data collection, analysis, and availability.

  3. Sediment biogeochemistry in an East African mangrove forest (Gazi Bay, Kenya)

    NARCIS (Netherlands)

    Middelburg, J.J.; Nieuwenhuize, J.; Slim, F.J.; Ohowa, B.

    1996-01-01

    The biogeochemistry of mangrove sediments was investigated in several mangrove forest communities in Gazi Bay, a coastal lagoon in Kenya, Africa. Carbon dioxide fluxes, sediment median grain sizes, sedimentary organic carbon, nitrogen and phosphorus contents and pore-water characteristics (ammonium,

  4. Comparison of manufactured and black carbon nanoparticle concentrations in aquatic sediments

    NARCIS (Netherlands)

    Koelmans, A.A.; Nowack, B.; Wiesner, M.

    2009-01-01

    In this paper, we show that concentrations of manufactured carbon-based nanoparticles (MCNPs) in aquatic sediments will be negligible compared to levels of black carbon nanoparticles (BCNPs). This is concluded from model calculations accounting for MCNP sedimentation fluxes, removal rates due to

  5. Distribution of longshore sediment transport along the Indian coast based on empirical model

    Digital Repository Service at National Institute of Oceanography (India)

    Chandramohan, P.; Nayak, B.U.

    An empirical sediment transport model has been developed based on longshore energy flux equation. Study indicates that annual gross sediment transport rate is high (1.5 x 10 super(6) cubic meters to 2.0 x 10 super(6) cubic meters) along the coasts...

  6. The Open Flux Problem

    Science.gov (United States)

    Linker, J. A.; Caplan, R. M.; Downs, C.; Riley, P.; Mikic, Z.; Lionello, R.; Henney, C. J.; Arge, C. N.; Liu, Y.; Derosa, M. L.; Yeates, A.; Owens, M. J.

    2017-10-01

    The heliospheric magnetic field is of pivotal importance in solar and space physics. The field is rooted in the Sun’s photosphere, where it has been observed for many years. Global maps of the solar magnetic field based on full-disk magnetograms are commonly used as boundary conditions for coronal and solar wind models. Two primary observational constraints on the models are (1) the open field regions in the model should approximately correspond to coronal holes (CHs) observed in emission and (2) the magnitude of the open magnetic flux in the model should match that inferred from in situ spacecraft measurements. In this study, we calculate both magnetohydrodynamic and potential field source surface solutions using 14 different magnetic maps produced from five different types of observatory magnetograms, for the time period surrounding 2010 July. We have found that for all of the model/map combinations, models that have CH areas close to observations underestimate the interplanetary magnetic flux, or, conversely, for models to match the interplanetary flux, the modeled open field regions are larger than CHs observed in EUV emission. In an alternative approach, we estimate the open magnetic flux entirely from solar observations by combining automatically detected CHs for Carrington rotation 2098 with observatory synoptic magnetic maps. This approach also underestimates the interplanetary magnetic flux. Our results imply that either typical observatory maps underestimate the Sun’s magnetic flux, or a significant portion of the open magnetic flux is not rooted in regions that are obviously dark in EUV and X-ray emission.

  7. The Open Flux Problem

    Energy Technology Data Exchange (ETDEWEB)

    Linker, J. A.; Caplan, R. M.; Downs, C.; Riley, P.; Mikic, Z.; Lionello, R. [Predictive Science Inc., 9990 Mesa Rim Road, Suite 170, San Diego, CA 92121 (United States); Henney, C. J. [Air Force Research Lab/Space Vehicles Directorate, 3550 Aberdeen Avenue SE, Kirtland AFB, NM (United States); Arge, C. N. [Science and Exploration Directorate, NASA/GSFC, Greenbelt, MD 20771 (United States); Liu, Y. [W. W. Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305 (United States); Derosa, M. L. [Lockheed Martin Solar and Astrophysics Laboratory, 3251 Hanover Street B/252, Palo Alto, CA 94304 (United States); Yeates, A. [Department of Mathematical Sciences, Durham University, Durham, DH1 3LE (United Kingdom); Owens, M. J., E-mail: linkerj@predsci.com [Space and Atmospheric Electricity Group, Department of Meteorology, University of Reading, Earley Gate, P.O. Box 243, Reading RG6 6BB (United Kingdom)

    2017-10-10

    The heliospheric magnetic field is of pivotal importance in solar and space physics. The field is rooted in the Sun’s photosphere, where it has been observed for many years. Global maps of the solar magnetic field based on full-disk magnetograms are commonly used as boundary conditions for coronal and solar wind models. Two primary observational constraints on the models are (1) the open field regions in the model should approximately correspond to coronal holes (CHs) observed in emission and (2) the magnitude of the open magnetic flux in the model should match that inferred from in situ spacecraft measurements. In this study, we calculate both magnetohydrodynamic and potential field source surface solutions using 14 different magnetic maps produced from five different types of observatory magnetograms, for the time period surrounding 2010 July. We have found that for all of the model/map combinations, models that have CH areas close to observations underestimate the interplanetary magnetic flux, or, conversely, for models to match the interplanetary flux, the modeled open field regions are larger than CHs observed in EUV emission. In an alternative approach, we estimate the open magnetic flux entirely from solar observations by combining automatically detected CHs for Carrington rotation 2098 with observatory synoptic magnetic maps. This approach also underestimates the interplanetary magnetic flux. Our results imply that either typical observatory maps underestimate the Sun’s magnetic flux, or a significant portion of the open magnetic flux is not rooted in regions that are obviously dark in EUV and X-ray emission.

  8. {sup 10}Be/{sup 230}Th ratios as proxy for particle flux in the equatorial Pacific ocean

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, R.F.; Fleisher, M.Q. [LDEO of Columbia Univ. (United States); Kubik, P.W. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Suter, M. [Eidgenoessische Technische Hochschule, Zurich (Switzerland)

    1997-09-01

    Particulate {sup 10}Be/{sup 230}Th ratios collected by sediment traps in the central equatorial Pacific Ocean exhibit a positive correlation with particle flux, but little or no correlation with particle composition. (author) 1 fig., 4 refs.

  9. Seasonal variability of the vertical fluxes of Globigerina bulloides (D'Orbigny) in the northern Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Guptha, M.V.S.; Mohan, R.

    Settling particles intercepted using time-series sediment traps at seven locations in the northern Indian Ocean have been examined for the spatial and temporal variability in the distribution and fluxes of Globigerina bulloides (D'Orbigny...

  10. Seasonal variability of the vertical fluxes of @iGlobigerina bulloides@@ (D'Orbigny) in the northern Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Guptha, M.V.S.; Mohan, R.

    Settling particles intercepted using time-series sediment traps at seven locations in the northern Indian Ocean have been examined for the spatial and temporal variability in the distribution and fluxes of @iGlobigerina bulloides@@ (@i...

  11. Seasonal variability of the vertical fluxes of Globigerina bulloides (D'Orbigny) in the northern Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Guptha, M.V.S.; Mohan, R.

    Settling particles intercepted using time-series sediment traps at seven locations in the northern Indian Ocean have been examined for the spatial and temporal variability in the distribution and fluxes of Globigerina bulloides (D...

  12. Temperature signal in suspended sediment export from an Alpine catchment

    Science.gov (United States)

    Costa, Anna; Molnar, Peter; Stutenbecker, Laura; Bakker, Maarten; Silva, Tiago A.; Schlunegger, Fritz; Lane, Stuart N.; Loizeau, Jean-Luc; Girardclos, Stéphanie

    2018-01-01

    Suspended sediment export from large Alpine catchments ( > 1000 km2) over decadal timescales is sensitive to a number of factors, including long-term variations in climate, the activation-deactivation of different sediment sources (proglacial areas, hillslopes, etc.), transport through the fluvial system, and potential anthropogenic impacts on the sediment flux (e.g. through impoundments and flow regulation). Here, we report on a marked increase in suspended sediment concentrations observed near the outlet of the upper Rhône River Basin in the mid-1980s. This increase coincides with a statistically significant step-like increase in basin-wide mean air temperature. We explore the possible explanations of the suspended sediment rise in terms of changes in water discharge (transport capacity), and the activation of different potential sources of fine sediment (sediment supply) in the catchment by hydroclimatic forcing. Time series of precipitation and temperature-driven snowmelt, snow cover, and ice melt simulated with a spatially distributed degree-day model, together with erosive rainfall on snow-free surfaces, are tested to explore possible reasons for the rise in suspended sediment concentration. We show that the abrupt change in air temperature reduced snow cover and the contribution of snowmelt, and enhanced ice melt. The results of statistical tests show that the onset of increased ice melt was likely to play a dominant role in the suspended sediment concentration rise in the mid-1980s. Temperature-driven enhanced melting of glaciers, which cover about 10 % of the catchment surface, can increase suspended sediment yields through an increased contribution of sediment-rich glacial meltwater, increased sediment availability due to glacier recession, and increased runoff from sediment-rich proglacial areas. The reduced extent and duration of snow cover in the catchment are also potential contributors to the rise in suspended sediment concentration through

  13. [Impacts of Asian clams (Corbicula fluminea) on lake sediment properties and phosphorus movement].

    Science.gov (United States)

    Zhang, Lei; Gu, Xiao-Zhi; Shao, Shi-Guang; Hu, Hai-Yan; Zhong, Ji-Cheng; Fan, Cheng-Xin

    2011-01-01

    To examine the impact of Corbicula fluminea on sediment properties and phosphorus dynamics across sediment-water interface in lake, the microcosm experiment was carried out with sediment and lake water from the estuary of Dapu River, a eutrophic area in Taihu Lake. Rhizon samplers were used to acquire pore water, and soluble reactive phosphorus (SRP) flux across sediment-water interface and sediment properties were determined. The activity of C. fluminea destroyed the initial sediment structure, mixed sediment in different depths, increased oxygen penetration depth, sediment water content, and total microbial activity in sediment. The downward movement of overlying water was enhanced by the activity of C. fluminea, which decreased Fe2+ in pore water by oxidation. The production of ferric iron oxyhydroxide adsorbed SRP from pore water and decreased SRP concentration in pore water, and this increased iron bound phosphorus in corresponding sediment. The emergence of C. fluminea accelerated SRP release from sediment to overlying water, and enhanced SRP flux increased with the rise of introduced C. fluminea density. Metabolization of C. fluminea might play an important role in accelerating SRP release.

  14. Meromorphic flux compactification

    Energy Technology Data Exchange (ETDEWEB)

    Damian, Cesar [Departamento de Ingeniería Mecánica, Universidad de Guanajuato,Carretera Salamanca-Valle de Santiago Km 3.5+1.8 Comunidad de Palo Blanco,Salamanca (Mexico); Loaiza-Brito, Oscar [Departamento de Física, Universidad de Guanajuato,Loma del Bosque No. 103 Col. Lomas del Campestre C.P 37150 León, Guanajuato (Mexico)

    2017-04-26

    We present exact solutions of four-dimensional Einstein’s equations related to Minkoswki vacuum constructed from Type IIB string theory with non-trivial fluxes. Following https://www.doi.org/10.1007/JHEP02(2015)187; https://www.doi.org/10.1007/JHEP02(2015)188 we study a non-trivial flux compactification on a fibered product by a four-dimensional torus and a two-dimensional sphere punctured by 5- and 7-branes. By considering only 3-form fluxes and the dilaton, as functions on the internal sphere coordinates, we show that these solutions correspond to a family of supersymmetric solutions constructed by the use of G-theory. Meromorphicity on functions constructed in terms of fluxes and warping factors guarantees that flux and 5-brane contributions to the scalar curvature vanish while fulfilling stringent constraints as tadpole cancelation and Bianchi identities. Different Einstein’s solutions are shown to be related by U-dualities. We present three supersymmetric non-trivial Minkowski vacuum solutions and compute the corresponding soft terms. We also construct a non-supersymmetric solution and study its stability.

  15. Meromorphic flux compactification

    International Nuclear Information System (INIS)

    Damian, Cesar; Loaiza-Brito, Oscar

    2017-01-01

    We present exact solutions of four-dimensional Einstein’s equations related to Minkoswki vacuum constructed from Type IIB string theory with non-trivial fluxes. Following https://www.doi.org/10.1007/JHEP02(2015)187; https://www.doi.org/10.1007/JHEP02(2015)188 we study a non-trivial flux compactification on a fibered product by a four-dimensional torus and a two-dimensional sphere punctured by 5- and 7-branes. By considering only 3-form fluxes and the dilaton, as functions on the internal sphere coordinates, we show that these solutions correspond to a family of supersymmetric solutions constructed by the use of G-theory. Meromorphicity on functions constructed in terms of fluxes and warping factors guarantees that flux and 5-brane contributions to the scalar curvature vanish while fulfilling stringent constraints as tadpole cancelation and Bianchi identities. Different Einstein’s solutions are shown to be related by U-dualities. We present three supersymmetric non-trivial Minkowski vacuum solutions and compute the corresponding soft terms. We also construct a non-supersymmetric solution and study its stability.

  16. Flux Pinning in Superconductors

    CERN Document Server

    Matsushita, Teruo

    2007-01-01

    The book covers the flux pinning mechanisms and properties and the electromagnetic phenomena caused by the flux pinning common for metallic, high-Tc and MgB2 superconductors. The condensation energy interaction known for normal precipitates or grain boundaries and the kinetic energy interaction proposed for artificial Nb pins in Nb-Ti, etc., are introduced for the pinning mechanism. Summation theories to derive the critical current density are discussed in detail. Irreversible magnetization and AC loss caused by the flux pinning are also discussed. The loss originally stems from the ohmic dissipation of normal electrons in the normal core driven by the electric field induced by the flux motion. The readers will learn why the resultant loss is of hysteresis type in spite of such mechanism. The influence of the flux pinning on the vortex phase diagram in high Tc superconductors is discussed, and the dependencies of the irreversibility field are also described on other quantities such as anisotropy of supercondu...

  17. Fluvial fluxes from the Magdalena River into Cartagena Bay, Caribbean Colombia: Trends, future scenarios, and connections with upstream human impacts

    Science.gov (United States)

    Restrepo, Juan D.; Escobar, Rogger; Tosic, Marko

    2018-02-01

    Fluxes of continental runoff and sediments as well as downstream deposition of eroded soils have severely altered the structure and function of fluvial and deltaic-estuarine ecosystems. The Magdalena River, the main contributor of continental fluxes into the Caribbean Sea, delivers important amounts of water and sediments into Cartagena Bay, a major estuarine system in northern Colombia. Until now, trends in fluvial fluxes into the bay, as well as the relationship between these tendencies in fluvial inputs and associated upstream changes in the Magdalena catchment, have not been studied. Here we explore the interannual trends of water discharge and sediment load flowing from the Magdalena River-Canal del Dique system into Cartagena Bay during the last three decades, forecast future scenarios of fluxes into the bay, and discuss possible connections between observed trends in fluvial inputs and trends in human intervention in the Magdalena River basin. Significant upward trends in annual runoff and sediment load during the mid-1980s, 1990s, and post-2000 are observed in the Magdalena and in the Canal del Dique flowing into Cartagena Bay. During the last decade, Magdalena streamflow and sediment load experienced increases of 24% and 33%, respectively, compared to the pre-2000 year period. Meanwhile, the Canal del Dique witnessed increases in water discharge and sediment load of 28% and 48%, respectively. During 26 y of monitoring, the Canal del Dique has discharged 177 Mt of sediment to the coastal zone, of which 52 Mt was discharged into Cartagena Bay. Currently, the Canal drains 6.5% and transports 5.1% of the Magdalena water discharge and sediment load. By 2020, water discharge and sediment flux from the Canal del Dique flowing to the coastal zone will witness increments of 164% and 260%, respectively. Consequently, sediment fluxes into Cartagena Bay will witness increments as high as 8.2 Mt y- 1 or 317%. Further analyses of upstream sediment load series for 21

  18. The use of modeling and suspended sediment concentration measurements for quantifying net suspended sediment transport through a large tidally dominated inlet

    Science.gov (United States)

    Erikson, Li H.; Wright, Scott A.; Elias, Edwin; Hanes, Daniel M.; Schoellhamer, David H.; Largier, John; Barnard, P.L.; Jaffee, B.E.; Schoellhamer, D.H.

    2013-01-01

    Sediment exchange at large energetic inlets is often difficult to quantify due complex flows, massive amounts of water and sediment exchange, and environmental conditions limiting long-term data collection. In an effort to better quantify such exchange this study investigated the use of suspended sediment concentrations (SSC) measured at an offsite location as a surrogate for sediment exchange at the tidally dominated Golden Gate inlet in San Francisco, CA. A numerical model was calibrated and validated against water and suspended sediment flux measured during a spring–neap tide cycle across the Golden Gate. The model was then run for five months and net exchange was calculated on a tidal time-scale and compared to SSC measurements at the Alcatraz monitoring site located in Central San Francisco Bay ~ 5 km from the Golden Gate. Numerically modeled tide averaged flux across the Golden Gate compared well (r2 = 0.86, p-value

  19. Neutron flux monitoring device

    International Nuclear Information System (INIS)

    Goto, Yasushi; Mitsubori, Minehisa; Ohashi, Kazunori.

    1997-01-01

    The present invention provides a neutron flux monitoring device for preventing occurrence of erroneous reactor scram caused by the elevation of the indication of a start region monitor (SRM) due to a factor different from actual increase of neutron fluxes. Namely, judgement based on measured values obtained by a pulse counting method and a judgment based on measured values obtained by a Cambel method are combined. A logic of switching neutron flux measuring method to be used for monitoring, namely, switching to an intermediate region when both of the judgements are valid is adopted. Then, even if the indication value is elevated based on the Cambel method with no increase of the counter rate in a neutron source region, the switching to the intermediate region is not conducted. As a result, erroneous reactor scram such as 'shorter reactor period' can be avoided. (I.S.)

  20. Simulation of suspended sediment transport initialized with satellite ...

    Indian Academy of Sciences (India)

    Sediment dynamics like deposition, erosion and dispersion are explained with the simu- lated tidal currents and .... P and q=the flux in the x and y directions, respec- tively, h=water ..... Babu K S, Dwarakish G S and Jayakumar S 2003 Model-.

  1. Why would we use the Sediment Isotope Tomography (SIT) model to establish a 210Pb-based chronology in recent-sediment cores?

    International Nuclear Information System (INIS)

    Abril Hernández, José-María

    2015-01-01

    After half a century, the use of unsupported 210 Pb ( 210 Pb exc ) is still far off from being a well established dating tool for recent sediments with widespread applicability. Recent results from the statistical analysis of time series of fluxes, mass sediment accumulation rates (SAR), and initial activities, derived from varved sediments, place serious constraints to the assumption of constant fluxes, which is widely used in dating models. The Sediment Isotope Tomography (SIT) model, under the assumption of non post-depositional redistribution, is used for dating recent sediments in scenarios in that fluxes and SAR are uncorrelated and both vary with time. By using a simple graphical analysis, this paper shows that under the above assumptions, any given 210 Pb exc profile, even with the restriction of a discrete set of reference points, is compatible with an infinite number of chronological lines, and thus generating an infinite number of mathematically exact solutions for histories of initial activity concentrations, SAR and fluxes onto the SWI, with these two last ranging from zero up to infinity. Particularly, SIT results, without additional assumptions, cannot contain any statistically significant difference with respect to the exact solutions consisting in intervals of constant SAR or constant fluxes (both being consistent with the reference points). Therefore, there is not any benefit in its use as a dating tool without the explicit introduction of additional restrictive assumptions about fluxes, SAR and/or their interrelationship. - Highlights: • The 210 Pb-based method for dating recent sediments is of a widespread use. • Recent results limit the use of the simplifying assumption of constant fluxes. • SIT model claims to solve scenarios where fluxes and SAR independently vary with time. • The paper shows how SIT model lacks of sound physical basis. • A dating tool is only possible by introducing additional restrictive assumptions

  2. Recent sediment transport and deposition in the Nazaré Canyon, Portuguese continental margin.

    NARCIS (Netherlands)

    de Stigter, H.C.; Boer, W.; de Jesus Mendes, P.A.; Jesus, C.C.; Thomsen, L.; van den Bergh, G.D.; van Weering, T.C.E.

    2007-01-01

    Processes, pathways and fluxes of sediment transport and deposition in the Nazaré submarine canyon, Portuguese continental margin, were investigated by water column profiling of suspended particulate matter, recording of near-bottom currents and suspended particulate matter fluxes with benthic

  3. U- and Th-series nuclides in settling particles: implications to sediment transport through surface waters and interior ocean

    International Nuclear Information System (INIS)

    Sarin, M.M.

    2012-01-01

    The Bay of Bengal is a unique ocean basin receiving large quantities of fresh water and sediment supply from several rivers draining the Indian subcontinent. The annual flux of suspended sediments discharged into the Bay of Bengal is one billion tons, about one-tenth of the global sediment discharge into the ocean. The water and sediment discharge to the Bay, show significant seasonal variation, with maximum transport coinciding with the SW-monsoon (July-September). Earlier studies on the distribution of clay minerals in sediments have led to the suggestion that the sediments of the western Bengal Fan are mainly derived from the Peninsular rivers, whereas rest of the Fan sediments is influenced by the Himalayan rivers. Settling fluxes of particulate matter through the water column of the Bay of Bengal show seasonal trends resulting from monsoon enhanced sediment supply via rivers and biological processes in the water column. It is, thus, important to understand the influence of the seasonally varying particle fluxes on the solute-particle interactions and chemical scavenging processes in the surface and deep waters of the Bay of Bengal. In this context, measurements of U- and Th-series nuclides in the settling particles are most relevant. The radionuclide fluxes ( 230 Th, 228 Th and 210 Pb) in the settling particles provide insight into the role of their removal by vertical particle flux and/or lateral transport (removal at the ocean boundaries). A study carried out in the Northern Bay of Bengal documents that the authigenic flux of 230 Th, as measured in sediment trap samples from deep waters, is balanced by its production in the overhead water column. The sediment mass flux, Al and 228 Th fluxes are similar in the settling particles through shallow and deep waters, suggesting predominant removal by vertical particle flux in the North Bay of Bengal. In the Central Bay, particulate mass, Al and 228 Th fluxes are higher in the trap material from deep waters relative

  4. Atmospheric neutrino fluxes

    International Nuclear Information System (INIS)

    Honda, M.; Kasahara, K.; Hidaka, K.; Midorikawa, S.

    1990-02-01

    A detailed Monte Carlo simulation of neutrino fluxes of atmospheric origin is made taking into account the muon polarization effect on neutrinos from muon decay. We calculate the fluxes with energies above 3 MeV for future experiments. There still remains a significant discrepancy between the calculated (ν e +antiν e )/(ν μ +antiν μ ) ratio and that observed by the Kamiokande group. However, the ratio evaluated at the Frejus site shows a good agreement with the data. (author)

  5. The inverse Numerical Computer Program FLUX-BOT for estimating Vertical Water Fluxes from Temperature Time-Series.

    Science.gov (United States)

    Trauth, N.; Schmidt, C.; Munz, M.

    2016-12-01

    Heat as a natural tracer to quantify water fluxes between groundwater and surface water has evolved to a standard hydrological method. Typically, time series of temperatures in the surface water and in the sediment are observed and are subsequently evaluated by a vertical 1D representation of heat transport by advection and dispersion. Several analytical solutions as well as their implementation into user-friendly software exist in order to estimate water fluxes from the observed temperatures. Analytical solutions can be easily implemented but assumptions on the boundary conditions have to be made a priori, e.g. sinusoidal upper temperature boundary. Numerical models offer more flexibility and can handle temperature data which is characterized by irregular variations such as storm-event induced temperature changes and thus cannot readily be incorporated in analytical solutions. This also reduced the effort of data preprocessing such as the extraction of the diurnal temperature variation. We developed a software to estimate water FLUXes Based On Temperatures- FLUX-BOT. FLUX-BOT is a numerical code written in MATLAB which is intended to calculate vertical water fluxes in saturated sediments, based on the inversion of measured temperature time series observed at multiple depths. It applies a cell-centered Crank-Nicolson implicit finite difference scheme to solve the one-dimensional heat advection-conduction equation. Besides its core inverse numerical routines, FLUX-BOT includes functions visualizing the results and functions for performing uncertainty analysis. We provide applications of FLUX-BOT to generic as well as to measured temperature data to demonstrate its performance.

  6. Sediment supply to beaches

    DEFF Research Database (Denmark)

    Aagaard, Troels

    2014-01-01

    Many beaches have been built by an onshore supply of sand from the shoreface, and future long-term coastal evolution critically depends on cross-shore sediment exchange between the upper and the lower shorefaces. Even so, cross-shore sediment supply remains poorly known in quantitative terms...... and this reduces confidence in predictions of long-term shoreline change. In this paper, field measurements of suspended sediment load and cross-shore transport on the lower shoreface are used to derive a model for sediment supply from the lower to the upper shoreface at large spatial and temporal scales. Data...

  7. Sediment Core Laboratory

    Data.gov (United States)

    Federal Laboratory Consortium — FUNCTION: Provides instrumentation and expertise for physical and geoacoustic characterization of marine sediments.DESCRIPTION: The multisensor core logger measures...

  8. The dirt on sediments

    Science.gov (United States)

    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.

  9. The 137Cs distribution in sediment profiles from the Yangtze River estuary: a comparison of modeling and experimental results

    International Nuclear Information System (INIS)

    Pan, S.M.; Xu, Y.H.; Wang, A.; Povinec, P.P.

    2012-01-01

    It has been generally accepted when estimating sedimentation rates using the 137 Cs dating method that the position of the 137 Cs maximum in a sediment profile represents the year 1963. In this paper we validated this approach by developing a model in which the annual 137 Cs global fallout flux for the Yangtze River estuary was established on the basis of the Tokyo flux corrected for precipitation rates observed in Shanghai. As the 137 Cs maxima in the sediment deposition profiles depend on the sedimentation rates, the sub-sampling intervals were calculated accordingly. Higher measured than the calculated values were found in some cores, what may be due to fluctuating sedimentation rates and an additional deposition of 137 Cs from land-based sources. The study provides useful information on the reliability of the measured 137 Cs maxima in sediment profiles frequently used for dating of sediments in marine (coastal regions, open seas) as well as in terrestrial (lakes) environments. (author)

  10. Fluxes of particulate organic carbon in the East China Sea in summer

    Directory of Open Access Journals (Sweden)

    C.-C. Hung

    2013-10-01

    Full Text Available To understand carbon cycling in marginal seas better, particulate organic carbon (POC concentrations, POC fluxes and primary production (PP were measured in the East China Sea (ECS in summer 2007. Higher concentrations of POC were observed in the inner shelf, and lower POC values were found in the outer shelf. Similar to POC concentrations, elevated uncorrected POC fluxes (720–7300 mg C m−2 d−1 were found in the inner shelf, and lower POC fluxes (80–150 mg C m−2 d−1 were in the outer shelf, respectively. PP values (~ 340–3380 mg C m−2 d−1 had analogous distribution patterns to POC fluxes, while some of PP values were significantly lower than POC fluxes, suggesting that contributions of resuspended particles to POC fluxes need to be appropriately corrected. A vertical mixing model was used to correct effects of bottom sediment resuspension, and the lowest and highest corrected POC fluxes were in the outer shelf (58 ± 33 mg C m−2 d−1 and the inner shelf (785 ± 438 mg C m−2 d−1, respectively. The corrected POC fluxes (486 to 785 mg C m−2 d−1 in the inner shelf could be the minimum value because we could not exactly distinguish the effect of POC flux from Changjiang influence with turbid waters. The results suggest that 27–93% of the POC flux in the ECS might be from the contribution of resuspension of bottom sediments rather than from the actual biogenic carbon sinking flux. While the vertical mixing model is not a perfect model to solve sediment resuspension because it ignores biological degradation of sinking particles, Changjiang plume (or terrestrial inputs and lateral transport, it makes significant progress in both correcting the resuspension problem and in assessing a reasonable quantitative estimate of POC flux in a marginal sea.

  11. Connections between sedimentary basins during continental collision: how tectonic, surface and sedimentary processes shaped the Paratethys

    NARCIS (Netherlands)

    ter Borgh, M.M.

    2013-01-01

    The aim of this thesis is to improve the understanding of source to sink systems in general and the Danube River Basin - Black Sea source to sink system in particular. The sediment sources of this system are formed by a number of mountain chains, including the Alps, Dinarides and Carpathians; a

  12. Legacy Sediments in U.S. River Environments: Atrazine and Aggradation to Zinc and Zoobenthos

    Science.gov (United States)

    Wohl, E.

    2014-12-01

    Legacy sediments are those that are altered by human activities. Alterations include (i) human-caused aggradation (and subsequent erosion), such as sediment accumulating upstream from relict or contemporary dams, (ii) human-caused lack of continuing deposition that results in changing moisture and nutrient levels within existing sediments, such as on floodplains that no longer receive lateral or vertical accretion deposits because of levees, bank stabilization, and other channel engineering, and (iii) human-generated contaminants such as PCBs and pesticides that adsorb to fine sediment. Existing estimates of human alterations of river systems suggest that legacy sediments are ubiquitous. Only an estimated 2% of river miles in the United States are not affected by flow regulation that alters sediment transport, for example, and less than half of major river basins around the world are minimally altered by flow regulation. Combined with extensive but poorly documented reduction in floodplain sedimentation, as well as sediment contamination by diverse synthetic compounds, excess nutrients, and heavy metals, these national and global estimates suggest that legacy sediments now likely constitute a very abundant type of fluvial sediment. Because legacy sediments can alter river form and function for decades to centuries after the cessation of the human activity that created the legacy sediments, river management and restoration must be informed by accurate knowledge of the distribution and characteristics of legacy sediments. Geomorphologists can contribute understanding of sediment dynamics, including: the magnitude, frequency, and duration of flows that mobilize sediments with adsorbed contaminants; sites where erosion and deposition are most likely to occur under specified flow and sediment supply; residence time of sediments; and the influence of surface and subsurface water fluxes on sediment stability and geochemistry.

  13. Sediment transport by runoff on debris-mantled dryland hillslopes

    Science.gov (United States)

    Michaelides, Katerina; Martin, Gareth J.

    2012-09-01

    Hillslopes supply sediment to river channels, and therefore impact drainage basin functioning and evolution. The relationship between hillslope attributes and sediment flux forms the basis of geomorphic transport laws used to model the long-term topographic evolution of drainage basins, but their specific interactions during individual storm events are not well understood. Runoff-driven erosion of coarse particles, prevalent in dryland environments, presents a particular set of conditions for sediment transport that is poorly resolved in current models. In order to address this gap, we developed a particle-based, force-balance model for sheetwash sediment transport on coarse, debris-mantled hillslopes within a rainfall-runoff model. We use the model to examine how the interplay between hillslope attributes (gradient, length and grain size distribution) and runoff characteristics affects sediment transport, grain-size changes on the hillslope, and sediment supply to the slope base. The relationship between sediment flux and hillslope gradient was found to transition from linear above a threshold to sigmoidal depending on hillslope length, initial grain sizes, and runoff characteristics. Grain sizes supplied to the slope base vary in a complex manner with hillslope attributes but an overall coarsening of the hillslopes is found to occur with increasing gradient, corroborating previous findings from field measurements. Intense, short duration storms result in within-hillslope sediment redistribution and equifinality in sediment supply for different hillslope characteristics, which explain the lack of field evidence for any systematic relationships. Our model findings provide insights into hillslope responses to climatic forcing and have theoretical implications for modeling hillslope evolution in dry lands.

  14. Radiation flux measuring device

    International Nuclear Information System (INIS)

    Corte, E.; Maitra, P.

    1977-01-01

    A radiation flux measuring device is described which employs a differential pair of transistors, the output of which is maintained constant, connected to a radiation detector. Means connected to the differential pair produce a signal representing the log of the a-c component of the radiation detector, thereby providing a signal representing the true root mean square logarithmic output. 3 claims, 2 figures

  15. Soluble organic nutrient fluxes

    Science.gov (United States)

    Robert G. Qualls; Bruce L. Haines; Wayne Swank

    2014-01-01

    Our objectives in this study were (i) compare fluxes of the dissolved organic nutrients dissolved organic carbon (DOC), DON, and dissolved organic phosphorus (DOP) in a clearcut area and an adjacent mature reference area. (ii) determine whether concentrations of dissolved organic nutrients or inorganic nutrients were greater in clearcut areas than in reference areas,...

  16. Flux vacua and supermanifolds

    Energy Technology Data Exchange (ETDEWEB)

    Grassi, Pietro Antonio [CERN, Theory Unit, CH-1211 Geneva, 23 (Switzerland); Marescotti, Matteo [Dipartimento di Fisica Teorica, Universita di Torino, Via Giuria 1, I-10125, Turin (Italy)

    2007-01-15

    As been recently pointed out, physically relevant models derived from string theory require the presence of non-vanishing form fluxes besides the usual geometrical constraints. In the case of NS-NS fluxes, the Generalized Complex Geometry encodes these informations in a beautiful geometrical structure. On the other hand, the R-R fluxes call for supergeometry as the underlying mathematical framework. In this context, we analyze the possibility of constructing interesting supermanifolds recasting the geometrical data and RR fluxes. To characterize these supermanifolds we have been guided by the fact topological strings on supermanifolds require the super-Ricci flatness of the target space. This can be achieved by adding to a given bosonic manifold enough anticommuting coordinates and new constraints on the bosonic sub-manifold. We study these constraints at the linear and non-linear level for a pure geometrical setting and in the presence of p-form field strengths. We find that certain spaces admit several super-extensions and we give a parameterization in a simple case of d bosonic coordinates and two fermionic coordinates. In addition, we comment on the role of the RR field in the construction of the super-metric. We give several examples based on supergroup manifolds and coset supermanifolds.

  17. Flux vacua and supermanifolds

    International Nuclear Information System (INIS)

    Grassi, Pietro Antonio; Marescotti, Matteo

    2007-01-01

    As been recently pointed out, physically relevant models derived from string theory require the presence of non-vanishing form fluxes besides the usual geometrical constraints. In the case of NS-NS fluxes, the Generalized Complex Geometry encodes these informations in a beautiful geometrical structure. On the other hand, the R-R fluxes call for supergeometry as the underlying mathematical framework. In this context, we analyze the possibility of constructing interesting supermanifolds recasting the geometrical data and RR fluxes. To characterize these supermanifolds we have been guided by the fact topological strings on supermanifolds require the super-Ricci flatness of the target space. This can be achieved by adding to a given bosonic manifold enough anticommuting coordinates and new constraints on the bosonic sub-manifold. We study these constraints at the linear and non-linear level for a pure geometrical setting and in the presence of p-form field strengths. We find that certain spaces admit several super-extensions and we give a parameterization in a simple case of d bosonic coordinates and two fermionic coordinates. In addition, we comment on the role of the RR field in the construction of the super-metric. We give several examples based on supergroup manifolds and coset supermanifolds

  18. Atmospheric neutrino fluxes

    International Nuclear Information System (INIS)

    Perkins, D.H.

    1984-01-01

    The atmospheric neutrino fluxes, which are responsible for the main background in proton decay experiments, have been calculated by two independent methods. There are discrepancies between the two sets of results regarding latitude effects and up-down asymmetries, especially for neutrino energies Esub(ν) < 1 GeV. (author)

  19. Flux scaling: Ultimate regime

    Indian Academy of Sciences (India)

    First page Back Continue Last page Overview Graphics. Flux scaling: Ultimate regime. With the Nusselt number and the mixing length scales, we get the Nusselt number and Reynolds number (w'd/ν) scalings: and or. and. scaling expected to occur at extremely high Ra Rayleigh-Benard convection. Get the ultimate regime ...

  20. A carbon isotope budget for an anoxic marine sediment

    International Nuclear Information System (INIS)

    Boehme, S.E.; Blair, N.E.

    1991-01-01

    A carbon isotope budget has been determined for the coastal marine site, Cape Lookout Bight, NC. Isotope measurements of methane and σCO 2 fluxing out and buried in these sediments were applied to previously measured flux data (Martens et al., in press) to predict the isotopic composition of the incoming metabolizable organic matter. Methane leaves the sediment predominantly via ebullition with an isotopic composition of -60 per mil. Less than 2% of the methane produced is buried with an average diffusional flux value of -17 per mil and a burial value of +11 per mil. The isotope budget predicts a metabolizable organic carbon isotope signature of -19.3 per mil which is in excellent agreement with the measured total organic carbon value of -19.2 ± 0.3 per mil implying that the dominant remineralization processes have been identified

  1. Desorption of Ba and 226Ra from river-borne sediments in the Hudson estuary

    International Nuclear Information System (INIS)

    Li, Y.-H.

    1979-01-01

    The pronounced desorption of Ba and 226 Ra from river-borne sediments in the Hudson estuary can be explained quantitatively by the drastic decrease in the distribution coefficients of both elements from a fresh to a salty water medium. The desorption in estuaries can augment, at least, the total global river fluxes of dissolved Ba and 226 Ra by one and nine times, respectively. The desorption flux of 226 Ra from estuaries accounts for 17-43% of the total 226 Ra flux from coastal sediments. Two mass balance models depicting mixing and adsorption-desorption processes in estuaries are discussed. (Auth.)

  2. Floodplains as a source of fine sediment in grazed landscapes: tracing the source of suspended sediment in the headwaters of an intensively managed agricultural landscape

    Science.gov (United States)

    Yu, M.; Rhoads, B. L.; Stumpf, A.

    2017-12-01

    The flux of fine sediment within agricultural watersheds is an important factor determining the environmental quality of streams and rivers. Despite this importance, the contributions of sediment sources to suspended sediment loads within intensively managed agricultural watersheds remain poorly understood. This study assesses the provenance of fine suspended sediment in the headwater portion of a river flowing through an agricultural landscape in Illinois. Sediment source samples were collected from five potential sources: streambanks, forested floodplain, grassland, and grazed floodplains. Event-based and aggregated suspended sediment samples were collected from the stream at the watershed outlet. Quantitative geochemical fingerprinting techniques and a mixing model were employed to estimate the relative contributions of sediment from five potential sources to the suspended sediment loads. Organic matter content, trace elements, and fallout radionuclides were used as potential tracers. Principal Component analysis was employed to complement the results and Monte Carlo random sampling routine was used to test the uncertainty in estimated contributions of sources to in-stream sediment loads. Results indicate that the majority of suspended sediment is derived from streambanks and grazed floodplains. Erosion of the floodplain both by surface runoff and by streambank erosion from lateral channel migration contributes to the production of fine sediment within the stream system. These results suggest that human activities, in this case grazing, have converted portions of floodplains, normally net depositional environments, into sources of fine sediments. Efforts to reduce fluxes of fine sediment in this intensively managed landscape should focus on degraded floodplain surfaces and eroding channel banks within heavily grazed reaches of the stream.

  3. Methanotrophy in surface sediments of streams

    Science.gov (United States)

    Bagnoud, Alexandre; Pramateftaki, Paraskevi; Peter, Hannes; Battin, Tom

    2017-04-01

    Because streams are often found to be supersaturated in methane (CH4), they are considered as atmospheric sources of this greenhouse gas. However, little is known about the processes driving CH4 cycling in these environments, i.e. production, consumption and fluxes. CH4 is thought to be produced in deeper anoxic sediments, before it migrates up to reach the oxic stream water, where it can be oxidized by methanotrophs. In order to gain insights into this process, we investigated 14 different streams across Switzerland. We characterized the chemistry of surface and sediment waters by measuring dissolved chemical profiles. We also sampled surface sediments and determined methanotrophic rates with laboratory incubations and Michaelis-Menten modeling. Interestingly, rates were strongly correlated with the CH4 concentrations in stream waters, rather than in sediment waters. This indicates that methantrophic populations feed on CH4 from the surface streamwater, even though CH4 concentrations are higher in the sediment waters. Methanotrophy rates were also correlated with Crenothrix counts (based on 16S rRNA sequencing), a strict methanotroph, while this latter was correlated with pmoA counts (based on quantitative PCR), a gene involved in methanotrophy. These results show that Crenothrix genera are the most active methanotrophs in surface sediments of streams, and can represent more than 2% of microbial communities. Remarkably, the dominating Crenothrix species was detected in all 14 samples. This work allows the assessment of in situ methanotrophic rates, of the environmental parameters driving this process, and of the microbial populations carrying it out, and thus brings useful insights about carbon cycling in streams.

  4. Dynamics of Cohesive Sediments

    DEFF Research Database (Denmark)

    Johansen, Claus

    The present thesis considers the transport processes of cohesive sediments. The cohesive sediment used in the laboratory experiments was kaolinite, a clay mineral, in order to be able to reproduce the individual experiments. In the first part of the thesis, the theoretical considerations regarding...

  5. A Tidally Averaged Sediment-Transport Model for San Francisco Bay, California

    Science.gov (United States)

    Lionberger, Megan A.; Schoellhamer, David H.

    2009-01-01

    A tidally averaged sediment-transport model of San Francisco Bay was incorporated into a tidally averaged salinity box model previously developed and calibrated using salinity, a conservative tracer (Uncles and Peterson, 1995; Knowles, 1996). The Bay is represented in the model by 50 segments composed of two layers: one representing the channel (>5-meter depth) and the other the shallows (0- to 5-meter depth). Calculations are made using a daily time step and simulations can be made on the decadal time scale. The sediment-transport model includes an erosion-deposition algorithm, a bed-sediment algorithm, and sediment boundary conditions. Erosion and deposition of bed sediments are calculated explicitly, and suspended sediment is transported by implicitly solving the advection-dispersion equation. The bed-sediment model simulates the increase in bed strength with depth, owing to consolidation of fine sediments that make up San Francisco Bay mud. The model is calibrated to either net sedimentation calculated from bathymetric-change data or measured suspended-sediment concentration. Specified boundary conditions are the tributary fluxes of suspended sediment and suspended-sediment concentration in the Pacific Ocean. Results of model calibration and validation show that the model simulates the trends in suspended-sediment concentration associated with tidal fluctuations, residual velocity, and wind stress well, although the spring neap tidal suspended-sediment concentration variability was consistently underestimated. Model validation also showed poor simulation of seasonal sediment pulses from the Sacramento-San Joaquin River Delta at Point San Pablo because the pulses enter the Bay over only a few days and the fate of the pulses is determined by intra-tidal deposition and resuspension that are not included in this tidally averaged model. The model was calibrated to net-basin sedimentation to calculate budgets of sediment and sediment-associated contaminants. While

  6. Effects of zinc pyrithione and copper pyrithione on microbial community function and structure in sediments

    DEFF Research Database (Denmark)

    Petersen, DG; Dahllof, I.; Nielsen, LP

    2004-01-01

    incorporation) were used, whereas molecular fingerprinting methods (polymerase chain reaction/ denaturing gradient gel electrophoresis) were used to describe the bacterial community structure. The lowest-observed-effect concentration (LOEC) for ZPT was 0.001 nmol/g dry sediment for the phosphate flux and total...... DNA content, whereas the LOEC for CPT was 0.1 nmol/g dry sediment for the nitrate flux and total DNA content. Nitrate fluxes increased significantly following additions of both ZPT and CPT, whereas ammonium fluxes decreased significantly after ZPT addition, suggesting changes in the nitrification...... and denitrification processes. The total DNA content decreased significantly following addition of both ZPT and CPT, but at the highest addition of ZPT (10 nmol ZPT/g dry sediment), an increase in total DNA content was found. Increased protein synthesis and bacterial diversity were also observed at this concentration...

  7. Biogeochemistry in highly reduced mussel farm sediments during macrofaunal recolonization by Amphiura filiformis and Nephtys sp.

    Science.gov (United States)

    Lindqvist, Stina; Norling, Karl; Hulth, Stefan

    2009-04-01

    Mussel farming is considered a viable means for reducing coastal eutrophication. This study assessed the importance of bioturbation by recolonizing fauna for benthic solute fluxes and porewater distributions in manipulated mussel farm sediments. Three consecutive time-series flux incubations were performed during an experimental period of three weeks in sieved farm sediment treated with the brittle star Amphiura filiformis and the polychaete Nephtys sp. The functional behavior of Nephtys sp. and interactions between Nephtys sp. and the spontaneously colonizing spionid Malacoceros fuliginosus determined the biogeochemical response in the Nephtys sp. treatment. For example, the oxic zone was restricted and benthic nitrate and silicate fluxes were reduced compared to the brittle star treatment. A. filiformis seemed to enhance the bioadvective solute transport, although an increased supply of oxygen was due to the highly reducing conditions of the sediment mainly seen as secondary effects related to porewater distributions and benthic nutrient fluxes.

  8. Effects of Sediment Chemical Properties on Phosphorus Release Rates in the Sediment-Water Interface of the Steppe Wetlands

    Directory of Open Access Journals (Sweden)

    Jing He

    2017-11-01

    Full Text Available Rising temperature causes a process of phosphorus release, which can be characterized well using phosphorus release rates (VP. The objective of the present study was to investigate the major factors affecting sediment phosphorus release rates through a wetland habitat simulation experiment. The results showed that the VP of different wetland sediments were different and changed with the order of W–R (river wetland > W–L (lake wetland > W–M (grassy marsh wetland > W–A (reservoir wetland. The main driving factors which influenced sediment phosphorus flux velocity in the sediment–water interface were sediment B-SO42−, B-MBN and A-MBP content. Path analysis and determination coefficient analysis indicated the standard multiple regression equation for sediment phosphorus release rates in the sediment–water interface, and each main factor was Y = −0.105 + 0.096X1 + 0.275X2 − 0.010X3 (r = 0.416, p < 0.01, n = 144, where Y is sediment phosphorus release rates; X1 is sediment B-SO42− content; X2 is sediment B-MBN; and X3 is sediment A-MBP content. Sediment B-SO42−, B-MBN and A-MBP content and the interaction between them were the main factors affecting sediment phosphorus release rates in the sediment–water interface. Therefore, these results suggest that soil chemical properties and microbial activities likely play an important role in phosphorus release rates in the sediment–water interface. We hope to provide effective scientific management and control methods for relevant environmental protection departments.

  9. The truth is out there: measured, calculated and modelled benthic fluxes.

    Science.gov (United States)

    Pakhomova, Svetlana; Protsenko, Elizaveta

    2016-04-01

    In a modern Earth science there is a great importance of understanding the processes, forming the benthic fluxes as one of element sources or sinks to or from the water body, which affects the elements balance in the water system. There are several ways to assess benthic fluxes and here we try to compare the results obtained by chamber experiments, calculated from porewater distributions and simulated with model. Benthic fluxes of dissolved elements (oxygen, nitrogen species, phosphate, silicate, alkalinity, iron and manganese species) were studied in the Baltic and Black Seas from 2000 to 2005. Fluxes were measured in situ using chamber incubations (Jch) and at the same time sediment cores were collected to assess the porewater distribution at different depths to calculate diffusive fluxes (Jpw). Model study was carried out with benthic-pelagic biogeochemical model BROM (O-N-P-Si-C-S-Mn-Fe redox model). It was applied to simulate biogeochemical structure of the water column and upper sediment and to assess the vertical fluxes (Jmd). By the behaviour at the water-sediment interface all studied elements can be divided into three groups: (1) elements which benthic fluxes are determined by the concentrations gradient only (Si, Mn), (2) elements which fluxes depend on redox conditions in the bottom water (Fe, PO4, NH4), and (3) elements which fluxes are strongly connected with organic matter fate (O2, Alk, NH4). For the first group it was found that measured fluxes are always higher than calculated diffusive fluxes (1.5disadvantages and the main facing us question is - which value should be taken for calculation the balance? This research is funded by VISTA - a basic research program and collaborative partnership between the Norwegian Academy of Science and Letters and Statoil.

  10. Design of a flux buffer based on the flux shuttle

    International Nuclear Information System (INIS)

    Gershenson, M.

    1991-01-01

    This paper discusses the design considerations for a flux buffer based on the flux-shuttle concept. Particular attention is given to the issues of flux popping, stability of operation and saturation levels for a large input. Modulation techniques used in order to minimize 1/f noise, in addition to offsets are also analyzed. Advantages over conventional approaches using a SQUID for a flux buffer are discussed. Results of computer simulations are presented

  11. Lobotomy of flux compactifications

    Energy Technology Data Exchange (ETDEWEB)

    Dibitetto, Giuseppe [Institutionen för fysik och astronomi, University of Uppsala,Box 803, SE-751 08 Uppsala (Sweden); Guarino, Adolfo [Albert Einstein Center for Fundamental Physics, Institute for Theoretical Physics,Bern University, Sidlerstrasse 5, CH-3012 Bern (Switzerland); Roest, Diederik [Centre for Theoretical Physics, University of Groningen,Nijenborgh 4 9747 AG Groningen (Netherlands)

    2014-05-15

    We provide the dictionary between four-dimensional gauged supergravity and type II compactifications on T{sup 6} with metric and gauge fluxes in the absence of supersymmetry breaking sources, such as branes and orientifold planes. Secondly, we prove that there is a unique isotropic compactification allowing for critical points. It corresponds to a type IIA background given by a product of two 3-tori with SO(3) twists and results in a unique theory (gauging) with a non-semisimple gauge algebra. Besides the known four AdS solutions surviving the orientifold projection to N=4 induced by O6-planes, this theory contains a novel AdS solution that requires non-trivial orientifold-odd fluxes, hence being a genuine critical point of the N=8 theory.

  12. Role of organic phosphorus in sediment in a shallow eutrophic lake

    Science.gov (United States)

    Shinohara, Ryuichiro; Hiroki, Mikiya; Kohzu, Ayato; Imai, Akio; Inoue, Tetsunori; Furusato, Eiichi; Komatsu, Kazuhiro; Satou, Takayuki; Tomioka, Noriko; Shimotori, Koichi; Miura, Shingo

    2017-08-01

    We tested the hypothesis that mineralization of molybdenum unreactive phosphorus (MUP) in pore water is the major pathway for the changes in the concentration of molybdenum-reactive P (MRP) in pore water and inorganic P in sediment particles. The concentration of inorganic P in the sediment particles increased from December to April in Lake Kasumigaura, whereas concentrations of organic P in the sediment particles and MUP in pore water decreased. These results suggest that MUP mineralization plays a key role as the source of MRP, whereas desorption of inorganic P from the sediment particles into the pore water is a minor process. One-dimensional numerical simulation of sediment particles and the pore water supported the hypothesis. Diffusive flux of MUP was small in pore water, even in near-surface layers, so mineralization was the dominant process for changing the MUP concentration in the pore water. For MRP, diffusion was the dominant process in the surface layer, whereas adsorption onto the sediment was the dominant process in deeper layers. Researchers usually ignore organic P in the sediment, but organic P in sediment particles and the pore water is a key source of inorganic P in the sediment particles and pore water; our results suggest that in Lake Kasumigaura, organic P in the sediment is an important source, even at depths more than 1 cm below the sediment surface. In contrast, the large molecular size of MUP in pore water hampers diffusion of MUP from the sediment into the overlying water.

  13. [Effect of the Runoff-sediment Control of the Xiaolangdi Reservoir on DOC Transport].

    Science.gov (United States)

    Zhang, Yong-ling; Wang, Ming-shi; Dong, Yu-long

    2015-04-01

    The sampling was carried out in Sanmenxia hydrological station, Xiaolangdi hydrological station and Huayuankou hydrological station from November 2011 to October 2012. The impact of the runoff-sediment control of the Xiaolangdi reservoir on DOC transport,was analyzed. The results were as follows. DOC contents in Sanmenxia station, Xiaolangdi station and Huayuankou station were 1.97-2.71 mg-L(-1), 1.87-2.76 mg x L(-1) and 2.07-2.93 mg x L(-1), respectively, during the normal operation period of Xiaolangdi Reservoir and Sanmenxia reservoir, and the DOC content in the three reservoirs had obvious seasonal change. DOC contents in the three stations were 2.14-3.32 mg x L(-1), 2.21-2.84 mg x L(-1) and 2.11-2.84 mg x L(-1), respectively, during the runoff-sediment control, and the DOC content in the sediment-releasing period of reservoir was higher than that in the water-releasing period of reservoir. DOC content had no significant correlation with TSS and flow either during the normal operation or during the water-sediment regulation of the reservoir. But the DOC content had significant correlation with water temperature during the normal operation of the reservoir. DOC flux in Sanmenxia station was similar to that in Xiaolangdi station from November to March. DOC flux in Sanmenxia station was obviously less than that in Xiaolangdi station from April to July. And the DOC flux in Sanmenxia station was much higher than that in Xiaolangdi station from August to October. The result showed that DOC was retained from August to October by Xiaolangdi reservoir and discharged from Xiaolangdi reservoir from April to July. The yearly DOC fluxes were 8.6 x 10(10), 9.0 x 10(10) and 9.7 x 10(10) g respectively in Sanmenxia station, Xiaolangdi station and Huayuankou station. The DOC flux of Sanmenxia station was the highest in September, which accounted for 22.0% of the yearly DOC flux, and the DOC flux of Xiaolangdi station was the highest in June, which accounted for 17.6% of the

  14. Quantifying postfire aeolian sediment transport using rare earth element tracers

    Science.gov (United States)

    Dukes, David; Gonzales, Howell B.; Ravi, Sujith; Grandstaff, David E.; Van Pelt, R. Scott; Li, Junran; Wang, Guan; Sankey, Joel B.

    2018-01-01

    Grasslands, which provide fundamental ecosystem services in many arid and semiarid regions of the world, are undergoing rapid increases in fire activity and are highly susceptible to postfire-accelerated soil erosion by wind. A quantitative assessment of physical processes that integrates fire-wind erosion feedbacks is therefore needed relative to vegetation change, soil biogeochemical cycling, air quality, and landscape evolution. We investigated the applicability of a novel tracer technique—the use of multiple rare earth elements (REE)—to quantify soil transport by wind and to identify sources and sinks of wind-blown sediments in both burned and unburned shrub-grass transition zone in the Chihuahuan Desert, NM, USA. Results indicate that the horizontal mass flux of wind-borne sediment increased approximately threefold following the fire. The REE tracer analysis of wind-borne sediments shows that the source of the horizontal mass flux in the unburned site was derived from bare microsites (88.5%), while in the burned site it was primarily sourced from shrub (42.3%) and bare (39.1%) microsites. Vegetated microsites which were predominantly sinks of aeolian sediments in the unburned areas became sediment sources following the fire. The burned areas showed a spatial homogenization of sediment tracers, highlighting a potential negative feedback on landscape heterogeneity induced by shrub encroachment into grasslands. Though fires are known to increase aeolian sediment transport, accompanying changes in the sources and sinks of wind-borne sediments may influence biogeochemical cycling and land degradation dynamics. Furthermore, our experiment demonstrated that REEs can be used as reliable tracers for field-scale aeolian studies.

  15. Physics of magnetic flux ropes

    Science.gov (United States)

    Russell, C. T.; Priest, E. R.; Lee, L. C.

    The present work encompasses papers on the structure, waves, and instabilities of magnetic flux ropes (MFRs), photospheric flux tubes (PFTs), the structure and heating of coronal loops, solar prominences, coronal mass ejections and magnetic clouds, flux ropes in planetary ionospheres, the magnetopause, magnetospheric field-aligned currents and flux tubes, and the magnetotail. Attention is given to the equilibrium of MFRs, resistive instability, magnetic reconnection and turbulence in current sheets, dynamical effects and energy transport in intense flux tubes, waves in solar PFTs, twisted flux ropes in the solar corona, an electrodynamical model of solar flares, filament cooling and condensation in a sheared magnetic field, the magnetopause, the generation of twisted MFRs during magnetic reconnection, ionospheric flux ropes above the South Pole, substorms and MFR structures, evidence for flux ropes in the earth magnetotail, and MFRs in 3D MHD simulations.

  16. Geodynamics of sediments in stream and river environments. Value of a policy for regional management of sediments

    International Nuclear Information System (INIS)

    Quelennec, R.E.

    1984-01-01

    The description of processes associated with the genesis, mobilization and transport of sediments in catchments and in hydrographic networks makes it easier to understand, from the ''hydrosedimentary'' viewpoint, the part played by sediments in the build-up and transport of radioactive pollutants in continental waters. In order to evaluate the flux of sediments passing through a watercourse, the author puts forward a number of semi-empirical equations and established mathematical models, while specifying the conditions under which they should be applied. The paper ends with a reminder of the principal objectives of a policy for ''regional management of sediments'' as defined by the author and presented during the Propriano Seminar (France) in May 1981. (author)

  17. Floodplains as a source of fine sediment in grazed landscapes: Tracing the source of suspended sediment in the headwaters of an intensively managed agricultural landscape

    Science.gov (United States)

    Yu, Mingjing; Rhoads, Bruce L.

    2018-05-01

    The flux of fine sediment within agricultural watersheds is an important factor determining the environmental quality of streams and rivers. Despite this importance, the contributions of sediment sources to suspended sediment loads within intensively managed agricultural watersheds remain poorly understood. This study assesses the provenance of fine suspended sediment in the headwater portion of a river flowing through an agricultural landscape in Illinois. Sediment source samples were collected from five sources: croplands, forested floodplains, grasslands, upper grazed floodplains, and lower grazed floodplains. Event-based and aggregated suspended sediment samples were collected from the stream at the watershed outlet. Quantitative geochemical fingerprinting techniques and a mixing model were employed to estimate the relative contributions of sediment from the five sources to the suspended sediment loads. To account for possible effects of small sample sizes, the analysis was repeated with only two sources: grazed floodplains and croplands/grasslands/forested floodplains. Results based on mean values of tracers indicate that the vast majority of suspended sediment within the stream (>95%) is derived from erosion of channel banks and the soil surface within areas of grazed floodplains. Uncertainty analysis based on Monte Carlo simulations indicates that mean values of tracer properties, which do not account for sampling variability in these properties, probably overestimate contributions from the two major sources. Nevertheless, this analysis still supports the conclusion that floodplain erosion accounts for the largest percentage of instream sediment (≈55-75%). Although grazing occurs over only a small portion of the total watershed area, grazed floodplains, which lie in close proximity to the stream channel, are an important source of sediment in this headwater steam system. Efforts to reduce fluxes of fine sediment in this intensively managed landscape should

  18. Estuarine abandoned channel sedimentation rates record peak fluvial discharge magnitudes

    Science.gov (United States)

    Gray, A. B.; Pasternack, G. B.; Watson, E. B.

    2018-04-01

    Fluvial sediment deposits can provide useful records of integrated watershed expressions including flood event magnitudes. However, floodplain and estuarine sediment deposits evolve through the interaction of watershed/marine sediment supply and transport characteristics with the local depositional environment. Thus extraction of watershed scale signals depends upon accounting for local scale effects on sediment deposition rates and character. This study presents an examination of the balance of fluvial sediment dynamics and local scale hydro-geomorphic controls on alluviation of an abandoned channel in the Salinas River Lagoon, CA. A set of three sediment cores contained discrete flood deposits that corresponded to the largest flood events over the period of accretion from 1969 to 2007. Sedimentation rates scaled with peak flood discharge and event scale sediment flux, but were not influenced by longer scale hydro-meteorological activities such as annual precipitation and water yield. Furthermore, the particle size distributions of flood deposits showed no relationship to event magnitudes. Both the responsiveness of sedimentation and unresponsiveness of particle size distributions to hydro-sedimentological event magnitudes appear to be controlled by aspects of local geomorphology that influence the connectivity of the abandoned channel to the Salinas River mainstem. Well-developed upstream plug bar formation precluded the entrainment of coarser bedload into the abandoned channel, while Salinas River mouth conditions (open/closed) in conjunction with tidal and storm surge conditions may play a role in influencing the delivery of coarser suspended load fractions. Channel adjacent sediment deposition can be valuable records of hydro-meteorological and sedimentological regimes, but local depositional settings may dominate the character of short term (interdecadal) signatures.

  19. Simulation of contaminated sediment transport in White Oak Creek basin

    International Nuclear Information System (INIS)

    Bao, Y.; Clapp, R.B.; Brenkert, A.L.; Moore, T.D.; Fontaine, T.A.

    1995-01-01

    This paper presents a systematic approach to management of the contaminated sediments in the White Oak Creek watershed at Oak Ridge National Laboratory near Oak Ridge, Tennessee. The primary contaminant of concern is radioactive cesium-137 ( 137 Cs), which binds to soil and sediment particles. The key components in the approach include an intensive sampling and monitoring system for flood events; modeling of hydrological processes, sediment transport, and contaminant flux movement; and a decision framework with a detailed human health risk analysis. Emphasis is placed on modeling of watershed rainfall-runoff and contaminated sediment transport during flooding periods using the Hydrologic Simulation Program- Fortran (HSPF) model. Because a large number of parameters are required in HSPF modeling, the major effort in the modeling process is the calibration of model parameters to make simulation results and measured values agree as closely as possible. An optimization model incorporating the concepts of an expert system was developed to improve calibration results and efficiency. Over a five-year simulation period, the simulated flows match the observed values well. Simulated total amount of sediment loads at various locations during storms match with the observed values within a factor of 1.5. Simulated annual releases of 137 Cs off-site locations match the data within a factor of 2 for the five-year period. The comprehensive modeling approach can provide a valuable tool for decision makers to quantitatively analyze sediment erosion, deposition, and transport; exposure risk related to radionuclides in contaminated sediment; and various management strategies

  20. Distribution and flux of 226Ra and 228Ra in the Amazon River estuary

    International Nuclear Information System (INIS)

    Key, R.M.; Sarmiento, J.L.; Stallard, R.F.; Moore, W.S.

    1985-01-01

    Measurements of 226 Ra and 228 Ra in the Amazon River estuary show that desorption from riverborne suspended particulate matter in the estuary increases the riverine flux of both isotopes to the ocean by a factor of approximately 5 over the flux attributable to radium dissolved in the river water alone. The total Amazon flux supplies approximately 0.20% of the 226 Ra and approximately 2.6% of the 228 Ra standing crops in the near-surface Atlantic (0-200 m). Diffusive flux from estuarine and shelf sediments and desorption from resuspended sediments in the region of the estuary approximately double the estuarine 226 Ra concentration and quadruple the estuarine 228 Ra concentration above that caused by the dissolved and desorbed river components alone

  1. Spatially explicit modeling of particulate nutrient flux in Large global rivers

    Science.gov (United States)

    Cohen, S.; Kettner, A.; Mayorga, E.; Harrison, J. A.

    2017-12-01

    Water, sediment, nutrient and carbon fluxes along river networks have undergone considerable alterations in response to anthropogenic and climatic changes, with significant consequences to infrastructure, agriculture, water security, ecology and geomorphology worldwide. However, in a global setting, these changes in fluvial fluxes and their spatial and temporal characteristics are poorly constrained, due to the limited availability of continuous and long-term observations. We present results from a new global-scale particulate modeling framework (WBMsedNEWS) that combines the Global NEWS watershed nutrient export model with the spatially distributed WBMsed water and sediment model. We compare the model predictions against multiple observational datasets. The results indicate that the model is able to accurately predict particulate nutrient (Nitrogen, Phosphorus and Organic Carbon) fluxes on an annual time scale. Analysis of intra-basin nutrient dynamics and fluxes to global oceans is presented.

  2. Effects of ghost shrimp on zinc and cadmium in sediments from Tampa Bay, FL

    Science.gov (United States)

    Klerks, P.L.; Felder, D.L.; Strasser, K.; Swarzenski, P.W.

    2007-01-01

    This study investigated the effects that ghost shrimp have on the distribution of metals in sediment. We measured levels of HNO3-extractable zinc and cadmium in surface sediment, in ghost shrimp burrow walls and in sediment ejected by the ghost shrimp from their burrows, at five sandy intertidal sites in Tampa Bay. Ghost shrimp densities and their rate of sediment ejection were also quantified, as were sediment organic content and silt + clay content. Densities of ghost shrimp (Sergio trilobata and Lepidophthalmus louisianensis) averaged 33/m2 at our sites, and they ejected sediment at an average rate of 28 g/burrow/day. Levels of both Zn and Cd were significantly higher in burrow walls than in surface sediments. Sediment ejected by the shrimp from their burrows had elevated levels of Zn (relative to surface sediments) at one of the sites. Sediment organic content and silt + clay content were higher in burrow-wall sediments than in ejected sediment, which in turn tended to have values above those of surface sediments. Differences in levels of HNO3-extractable Zn and Cd among sediment types may be a consequence of these sediments differing in other physiochemical characteristics, though the differences in metal levels remained statistically significant for some sites after correcting for differences in organic content and silt + clay content. We conclude that the presence of ghost shrimp burrows contributes to spatial heterogeneity of sedimentary metal levels, while the ghost shrimp bioturbation results in a significant flux of metals to the sediment surface and is expected to decrease heterogeneity of metal levels in sedimentary depth profiles.

  3. Suspended sediment in a high-Arctic river

    DEFF Research Database (Denmark)

    Ladegaard-Pedersen, Pernille; Sigsgaard, Charlotte; Kroon, Aart

    2017-01-01

    -2012) of daily measurements from the high-Artic Zackenberg River in Northeast Greenland to estimate annual suspended sediment fluxes based on four commonly used methods: M1) is the discharge weighted mean and uses direct measurements, while M2-M4) are one uncorrected and two bias corrected rating curves......-1 and 61,000±16,000ty-1. Extreme events with high discharges had a mean duration of 1day. The average suspended sediment flux during extreme events was 17,000±5000ty-1, which constitutes a year-to-year variation of 20-37% of the total annual flux. The most accurate sampling strategy was bi...... extrapolating a continuous concentration trace from measured values. All methods are tested on complete and reduced datasets. The average annual runoff in the period 2005-2012 was 190±25mio·m3 y-1. The different estimation methods gave a range of average annual suspended sediment fluxes between 43,000±10,000ty...

  4. 3D stratigraphic modeling of the Congo turbidite system since 210 ka: an investigation of factors controlling sedimentation

    Science.gov (United States)

    Laurent, Dimitri; Picot, Marie; Marsset, Tania; Droz, Laurence; Rabineau, Marina; Granjeon, Didier; Molliex, Stéphane

    2017-04-01

    intensity. These external forcing factors are responsible for the evolution of the capacity of turbidity currents by directly acting on the river runoff magnitude and the sediment budget according to the balance between mechanical and chemical erosion. If the sediment supply is the key parameter for the large scale sedimentary cycles, a steep increase of the sand/mud ratio leads to the development of sub-cycles characterized by middle fan avulsions. We identified these events as related to abrupt destabilizations of river mouth bars linked to periodic Congo River floods. Finally, the local slope gradient only plays a role in the maximal length of the turbidity currents and deposition in the most distal part of the basin. To conclude, the stratigraphic modeling allows us to propose an evolutionary "source to sink" model of the Quaternary Congo Fan, emphasizing the interconnection through time between drainage basin responses to climate change and sedimentary transfers in the deep-water environment. Picot, M. et al., 2016. Controls on turbidite sedimentation: Insights from a quantitative approach of submarine channel and lobe architecture (Late Quaternary Congo Fan). Marine and Petroleum Geology, 72, 423-446. Keywords: Congo, sedimentary basin, Quaternary, turbidite system, sedimentary cycles, geophysical data, stratigraphic modeling, DionisosFlow

  5. The Effects of Salinity on Nitrogen Losses from an Oligohaline Estuarine Sediment

    DEFF Research Database (Denmark)

    Giblin, Anne E.; Weston, Nathaniel B.; Banta, Gary Thomas

    2010-01-01

    Benthic respiration, sediment–water nutrient fluxes, denitrification and dissimilatory nitrate reduction to ammonium (DNRA) were measured in the upper section of the Parker River Estuary from 1993 to 2006. This site experiences large changes in salinity over both short and long time scales....... Sediment respiration ranged from 6 to 52 mmol m−2 day−1 and was largely controlled by temperature. Nutrient fluxes were dominated by ammonium fluxes, which ranged from a small uptake of −0.3 to an efflux of over 8.2 mmol N m−2 day−1. Ammonium fluxes were most highly correlated with salinity and laboratory...... related to salinity, ranging from 1 mmol m−2 day−1 during the spring and fall to less than 0.2 mmol m−2 day−1 in late summer. Salinity appears to exert a major control on the nitrogen cycle at this site, and partially decouples sediment ammonium fluxes from organic matter decomposition....

  6. The influence of turbulent bursting on sediment resuspension under unidirectional currents

    Directory of Open Access Journals (Sweden)

    S. Salim

    2017-07-01

    Full Text Available Laboratory experiments were conducted in an open channel flume with a flat sandy bed to examine the role of turbulence on sediment resuspension. An acoustic Doppler velocimeter (ADV was used to measure the instantaneous three-dimensional velocity components and acoustic backscatter as a proxy to suspended sediment concentration. Estimates of sediment transport assume that there is a mean critical velocity that needs to be exceeded before sediment transport is initiated. This approach does not consider the turbulent flow field that may initiate sediment resuspension through event-based processes such as the bursting phenomenon. In this paper, laboratory measurements were used to examine the sediment resuspension processes below and above the mean critical velocity. The results within a range above and below the measured mean critical velocity suggested that (1 the contribution of turbulent bursting events remained identical in both experimental conditions, (2 ejection and sweep events contributed more to the total sediment flux than up-acceleration and down-deceleration events, and (3 wavelet transform revealed a correlation between the momentum and sediment flux in both test conditions. Such similarities in conditions above and below the measured mean critical velocity highlight the need to re-evaluate the accuracy of a single time-averaged mean critical velocity for the initiation of sediment entrainment.

  7. Use of spatially distributed time-integrated sediment sampling networks and distributed fine sediment modelling to inform catchment management.

    Science.gov (United States)

    Perks, M T; Warburton, J; Bracken, L J; Reaney, S M; Emery, S B; Hirst, S

    2017-11-01

    Under the EU Water Framework Directive, suspended sediment is omitted from environmental quality standards and compliance targets. This omission is partly explained by difficulties in assessing the complex dose-response of ecological communities. But equally, it is hindered by a lack of spatially distributed estimates of suspended sediment variability across catchments. In this paper, we demonstrate the inability of traditional, discrete sampling campaigns for assessing exposure to fine sediment. Sampling frequencies based on Environmental Quality Standard protocols, whilst reflecting typical manual sampling constraints, are unable to determine the magnitude of sediment exposure with an acceptable level of precision. Deviations from actual concentrations range between -35 and +20% based on the interquartile range of simulations. As an alternative, we assess the value of low-cost, suspended sediment sampling networks for quantifying suspended sediment transfer (SST). In this study of the 362 km 2 upland Esk catchment we observe that spatial patterns of sediment flux are consistent over the two year monitoring period across a network of 17 monitoring sites. This enables the key contributing sub-catchments of Butter Beck (SST: 1141 t km 2 yr -1 ) and Glaisdale Beck (SST: 841 t km 2 yr -1 ) to be identified. The time-integrated samplers offer a feasible alternative to traditional infrequent and discrete sampling approaches for assessing spatio-temporal changes in contamination. In conjunction with a spatially distributed diffuse pollution model (SCIMAP), time-integrated sediment sampling is an effective means of identifying critical sediment source areas in the catchment, which can better inform sediment management strategies for pollution prevention and control. Copyright © 2017 Elsevier Ltd. All rights reserved.

  8. Sediment Resuspension Data

    Data.gov (United States)

    U.S. Environmental Protection Agency — The full report on sediment resuspension in drinking water storage tanks and a link to an animation of results. This dataset is associated with the following...

  9. Sediments and aquatic indicators

    International Nuclear Information System (INIS)

    1987-01-01

    Determinations of 90 Sr, certain gamma emitting nuclides and 239,240 Pu in bottom sediment in the Baltic Sea area and in sedimenting material and biota near the Loviisa and Olkiluoto nuclear power stations were continued in 1984 and 1985. In the bottom sediments of the deep Baltic basins, the total amounts of 90 Sr, 137 Cs and Pu were 8.5-80 Bq m -2 , 83-3200 Bq m -2 and 4.7-190 Bq m -2 , respectively. The ranges were about the same as in the earlier reports 1,2 . In sedimenting material and biota the conentrations of 90 Sr and 239,240 Pu were roughly the same as in 1983. The amounts and selection of reactor originated activation products were not changed in the vicinity of the two nuclear power stations. Small amounts of 137 Cs and 134 Cs released from the Loviisa nuclear power station were detected in 1985

  10. Offshore Surficial Sediment

    Data.gov (United States)

    California Natural Resource Agency — This data layer (PAC_EXT.txt and PAC_PRS.txt) represents two of five point coverages of known sediment samples, inspections, and probes from the usSEABED data...

  11. Towards integrated assessment of the northern Adriatic Sea sediment budget using remote sensing

    Science.gov (United States)

    Taramelli, A.; Filipponi, F.; Valentini, E.; Zucca, F.; Gutierrez, O. Q.; Liberti, L.; Cordella, M.

    2014-12-01

    Understanding the factors influencing sediment fluxes is a key issue to interpret the evolution of coastal sedimentation under natural and human impact and relevant for the natural resources management. Despite river plumes represent one of the major gain in sedimentary budget of littoral cells, knowledge of factors influencing complex behavior of coastal plumes, like river discharge characteristics, wind stress and hydro-climatic variables, has not been yet fully investigated. Use of Earth Observation data allows the identification of spatial and temporal variations of suspended sediments related to river runoff, seafloor erosion, sediment transport and deposition processes. Objective of the study is to investigate sediment fluxes in northern Adriatic Sea by linking suspended sediment patterns of coastal plumes to hydrologic and climatic forcing regulating the sedimentary cell budget and geomorphological evolution in coastal systems and continental shelf waters. Analysis of Total Suspended Matter (TSM) product, derived from 2002-2012 MERIS time series, was done to map changes in spatial and temporal dimension of suspended sediments, focusing on turbid plume waters and intense wind stress conditions. From the generated multi temporal TSM maps, dispersal patterns of major freshwater runoff plumes in northern Adriatic Sea were evaluated through spatial variability of coastal plumes shape and extent. Additionally, sediment supply from river distributary mouths was estimated from TSM and correlated with river discharge rates, wind field and wave field through time. Spatial based methodology has been developed to identify events of wave-generated resuspension of sediments, which cause variation in water column turbidity, occurring during intense wind stress and extreme metocean conditions, especially in the winter period. The identified resuspension events were qualitatively described and compared with to hydro-climatic variables. The identification of spatial and

  12. Uptake, translocation, and elimination in sediment-rooted macrophytes: a model-supported analysis of whole sediment test data.

    Science.gov (United States)

    Diepens, Noël J; Arts, Gertie H P; Focks, Andreas; Koelmans, Albert A

    2014-10-21

    Understanding bioaccumulation in sediment-rooted macrophytes is crucial for the development of sediment toxicity tests using macrophytes. Here, we explore bioaccumulation in sediment-rooted macrophytes by tracking and modeling chemical flows of chlorpyrifos, linuron, and six PCBs in water-sediment-macrophyte systems. Chemical fluxes across the interfaces between pore water, overlying water, shoots, and roots were modeled using a novel multicompartment model. The modeling yielded the first mass-transfer parameter set reported for bioaccumulation by sediment-rooted macrophytes, with satisfactory narrow confidence limits for more than half of the estimated parameters. Exposure via the water column led to rapid uptake by Elodea canadensis and Myriophyllum spicatum shoots, followed by transport to the roots within 1-3 days, after which tissue concentrations gradually declined. Translocation played an important role in the exchange between shoots and roots. Exposure via spiked sediment led to gradual uptake by the roots, but subsequent transport to the shoots and overlying water remained limited for the chemicals studied. These contrasting patterns show that exposure is sensitive to test set up, chemical properties, and species traits. Although field-concentrations in water and sediment will differ from those in the tests, the model parameters can be assumed applicable for modeling exposure to macrophytes in the field.

  13. Underwater Sediment Sampling Research

    Science.gov (United States)

    2017-01-01

    impacted sediments was found to be directly related to the concentration of crude oil detected in the sediment pore waters . Applying this mathematical...Kurt.A.Hansen@uscg.mil. 16. Abstract (MAXIMUM 200 WORDS ) The USCG R&D Center sought to develop a bench top system to determine the amount of total...scattered. The approach here is to sample the interstitial water between the grains of sand and attempt to determine the amount of oil in and on

  14. Australian methane fluxes

    International Nuclear Information System (INIS)

    Williams, D.J.

    1990-01-01

    Estimates are provided for the amount of methane emitted annually into the atmosphere in Australia for a variety of sources. The sources considered are coal mining, landfill, motor vehicles, natural gas suply system, rice paddies, bushfires, termites, wetland and animals. This assessment indicates that the major sources of methane are natural or agricultural in nature and therefore offer little scope for reduction. Nevertheless the remainder are not trival and reduction of these fluxes could play a significant part in any Australian action on the greenhouse problem. 19 refs., 7 tabs., 1 fig

  15. {sup 137}Cs and {sup 210}Pb inventories in soils and sediments from Chapala Lake (Mexico)

    Energy Technology Data Exchange (ETDEWEB)

    Ruiz-Fernandez, A.C.; Perez-Bernal, L.H. [Unidad Academica Mazatlan, Instituto de Ciencias del Mar y Limnologia, Universidad Nacional Autonoma de Mexico (Mexico); Sanchez-Cabeza, J.A. [Unidad Academica de Procesos Oceanicos y Costeros, Instituto de Ciencias del Mar y Limnologia, Universidad Nacional Autonoma de Mexico (Mexico); Ontiveros-Cuadras, J.F. [Posgrado en Ciencias del Mar y Limnologia, Instituto de Ciencias del Mar y Limnologia, Universidad Nacional Autonoma de Mexico (Mexico)

    2014-07-01

    Chapala Lake is the largest natural freshwater reservoir in Mexico and it is located in Central Mexico, at 1524 m above sea level. The lake is considered to be fairly anthropized and it has experienced periods of extremely low water level as a result of recent climate change and water extraction. The study of recent manifestations of global change in Chapala Lake requires accurate {sup 210}Pb chronological reconstructions, taking into account the expected variability of sediment accumulation rates by using the Constant Flux model. For a reliable application of this dating model, it is important that {sup 210}Pb flux values in the lacustrine sedimentary record are in correspondence with the local atmospheric fluxes. With the aim to estimate the fluxes of the fallout radionuclides {sup 210}Pb and {sup 137}Cs in the region, sediment and soil cores were collected in the Chapala Lake. Sediment profiles were evaluated and estimated fluxes in sediments and soils were compared. Some geochemical properties (e.g. grain size distribution, organic matter concentration, XRF-derived elemental composition and magnetic susceptibility) were also evaluated to understand how diagenesis changes and sediment provenance can affect the {sup 210}Pb and {sup 137}Cs depth profiles and inventories. Document available in abstract form only. (authors)

  16. Measuring hypoxia induced metal release from highly contaminated estuarine sediments during a 40 day laboratory incubation experiment

    Energy Technology Data Exchange (ETDEWEB)

    Banks, Joanne L., E-mail: jlbanks@student.unimelb.edu.au [Department of Zoology, University of Melbourne, Victoria, 3010 Australia (Australia); Ross, D. Jeff, E-mail: Jeff.Ross@utas.edu.au [Institute of Marine and Antarctic Studies, Nubeena Crescent, Taroona, Tasmania, 7053 Australia (Australia); Keough, Michael J., E-mail: mjkeough@unimelb.edu.au [Department of Zoology, University of Melbourne, Victoria, 3010 Australia (Australia); Eyre, Bradley D., E-mail: bradley.eyre@scu.edu.au [Centre for Coastal Biogeochemistry, School of Environmental Science and Management, Southern Cross University, PO Box 157, Lismore, NSW, 2480 Australia (Australia); Macleod, Catriona K., E-mail: Catriona.Macleod@utas.edu.au [Institute of Marine and Antarctic Studies, Nubeena Crescent, Taroona, Tasmania, 7053 Australia (Australia)

    2012-03-15

    Nutrient inputs to estuarine and coastal waters worldwide are increasing and this in turn is increasing the prevalence of eutrophication and hypoxic and anoxic episodes in these systems. Many urbanised estuaries are also subject to high levels of anthropogenic metal contamination. Environmental O{sub 2} levels may influence whether sediments act as sinks or sources of metals. In this study we investigated the effect of an extended O{sub 2} depletion event (40 days) on fluxes of trace metals (and the metalloid As) across the sediment-water interface in sediments from a highly metal contaminated estuary in S.E. Tasmania, Australia. We collected sediments from three sites that spanned a range of contamination and measured total metal concentration in the overlying water using sealed core incubations. Manganese and iron, which are known to regulate the release of other divalent cations from sub-oxic sediments, were released from sediments at all sites as hypoxia developed. In contrast, the release of arsenic, cadmium, copper and zinc was comparatively low, most likely due to inherent stability of these elements within the sediments, perhaps as a result of their refractory origin, their association with fine-grained sediments or their being bound in stable sulphide complexes. Metal release was not sustained due to the powerful effect of metal-sulphide precipitation of dissolved metals back into sediments. The limited mobilisation of sediment bound metals during hypoxia is encouraging, nevertheless the results highlight particular problems for management in areas where hypoxia might occur, such as the release of metals exacerbating already high loads or resulting in localised toxicity. - Highlights: Black-Right-Pointing-Pointer Metal contaminated sediments exposed to long-term hypoxia released Mn and Fe pulses. Black-Right-Pointing-Pointer As flux increased under anoxic conditions Cd, Cu and Zn fluxes occurred only during the first week of hypoxia. Black

  17. Numerical modelling of hydro-morphological processes dominated by fine suspended sediment in a stormwater pond

    Science.gov (United States)

    Guan, Mingfu; Ahilan, Sangaralingam; Yu, Dapeng; Peng, Yong; Wright, Nigel

    2018-01-01

    Fine sediment plays crucial and multiple roles in the hydrological, ecological and geomorphological functioning of river systems. This study employs a two-dimensional (2D) numerical model to track the hydro-morphological processes dominated by fine suspended sediment, including the prediction of sediment concentration in flow bodies, and erosion and deposition caused by sediment transport. The model is governed by 2D full shallow water equations with which an advection-diffusion equation for fine sediment is coupled. Bed erosion and sedimentation are updated by a bed deformation model based on local sediment entrainment and settling flux in flow bodies. The model is initially validated with the three laboratory-scale experimental events where suspended load plays a dominant role. Satisfactory simulation results confirm the model's capability in capturing hydro-morphodynamic processes dominated by fine suspended sediment at laboratory-scale. Applications to sedimentation in a stormwater pond are conducted to develop the process-based understanding of fine sediment dynamics over a variety of flow conditions. Urban flows with 5-year, 30-year and 100-year return period and the extreme flood event in 2012 are simulated. The modelled results deliver a step change in understanding fine sediment dynamics in stormwater ponds. The model is capable of quantitatively simulating and qualitatively assessing the performance of a stormwater pond in managing urban water quantity and quality.

  18. Critical heat flux evaluation

    International Nuclear Information System (INIS)

    Banner, D.

    1995-01-01

    Critical heat flux (CHF) is of importance for nuclear safety and represents the major limiting factors for reactor cores. Critical heat flux is caused by a sharp reduction in the heat transfer coefficient located at the outer surface of fuel rods. Safety requires that this phenomenon also called the boiling crisis should be precluded under nominal or incidental conditions (Class I and II events). CHF evaluation in reactor cores is basically a two-step approach. Fuel assemblies are first tested in experimental loops in order to determine CHF limits under various flow conditions. Then, core thermal-hydraulic calculations are performed for safety evaluation. The paper will go into more details about the boiling crisis in order to pinpoint complexity and lack of fundamental understanding in many areas. Experimental test sections needed to collect data over wide thermal-hydraulic and geometric ranges are described CHF safety margin evaluation in reactors cores is discussed by presenting how uncertainties are mentioned. From basic considerations to current concerns, the following topics are discussed; knowledge of the boiling crisis, CHF predictors, and advances thermal-hydraulic codes. (authors). 15 refs., 4 figs

  19. Neutron flux monitor

    International Nuclear Information System (INIS)

    Seki, Eiji; Tai, Ichiro.

    1984-01-01

    Purpose: To maintain the measuring accuracy and the reponse time within an allowable range in accordance with the change of neutron fluxes in a nuclear reactor pressure vessel. Constitution: Neutron fluxes within a nuclear reactor pressure vessel are detected by detectors, converted into pulse signals and amplified in a range switching amplifier. The amplified signals are further converted through an A/D converter and digital signals from the converter are subjected to a square operation in an square operation circuit. The output from the circuit is inputted into an integration circuit to selectively accumulate the constant of 1/2n, 1 - 1/2n (n is a positive integer) respectively for two continuing signals to perform weighing. Then, the addition is carried out to calculate the integrated value and the addition number is changed by the chane in the number n to vary the integrating time. The integrated value is inputted into a control circuit to control the value of n so that the fluctuation and the calculation time for the integrated value are within a predetermined range and, at the same time, the gain of the range switching amplifier is controlled. (Seki, T.)

  20. Detrital Zircon Geo- and Thermochronologic Constraints on Late Mississippian-Early Pennsylvanian Sediment Transport and Tectonics, Southwestern Kansas and Northwestern Arkansas

    Science.gov (United States)

    Bidgoli, T. S.; Wang, W.; Moeller, A.; Stockli, D. F.; Watney, L.

    2017-12-01

    The Late Mississippian to Early Pennsylvanian is a critical time interval across the globe, with major changes in tectonics, climate, and eustacy. Transcontinental sediment transport in North America, from the Appalachians to Great Canyon, has been proposed to initiate at this time (Gehrels et al., 2011). In the midcontinent, clastic influx to the Hugoton Embayment and Arkoma Shelf, during widespread carbonate platform deposition, may record evidence for this model, but the limited number of provenance studies has hindered interpretations. To test this model and further constrain sediment dispersal and source-to-sink systems in the midcontinent, we evaluate the provenance of upper Mississippian to middle Pennsylvanian siliciclastic intervals, in two areas, using sandstone component analysis and detrital zircon U-Pb and (U-Th)/He double dating. (1) For the Hugoton Embayment in southwestern Kansas, we focus on sandstones deposited in two valley-filling intervals, the Chester and Morrow. A total of 1100 zircon U-Pb ages have been acquired from samples from 10 boreholes, 6 from Chester and 4 from Morrow. Preliminary analysis suggests that the Chester is characterized by two major zircon U-Pb age clusters of 900-1295 Ma (Grenville) and 390-475 Ma, consistent with sediment delivery from the Appalachian orogen. Morrow strata record a change in provenance, with the presence of two additional age groups, 1300-1500 Ma (24.5%) and 1600-1800 Ma (17.9%), that correspond well with the age of basement rocks in the Granite-Rhyolite and Yavapai-Maztzal provinces, respectively. We ascribe changes in the zircon age spectra and introduction of these grains to the development of local uplifts, like the Nemaha Ridge, in the early Pennsylvanian. Double dating of zircons from these peaks may reveal additional information about these basement sources and the timing of denudation of these uplifts. (2) For the Arkoma shelf, we are analyzing 11 samples, collected from outcrops in northwestern

  1. Understanding Long-term, Large-scale Shoreline Change and the Sediment Budget on Fire Island, NY, using a 3D hydrodynamics-based model

    Science.gov (United States)

    List, J. H.; Safak, I.; Warner, J. C.; Schwab, W. C.; Hapke, C. J.; Lentz, E. E.

    2016-02-01

    The processes responsible for long-term (decadal) shoreline change and the related imbalance in the sediment budget on Fire Island, a 50 km long barrier island on the south coast of Long Island, NY, has been the subject of debate. The estimated net rate of sediment leaving the barrier at the west end of the island is approximately double the estimated net rate of sediment entering in the east, but the island-wide average sediment volume change associated with shoreline change is near zero and cannot account for this deficit. A long-held hypothesis is that onshore sediment flux from the inner continental shelf within the western half of the island is responsible for balancing the sediment budget. To investigate this possibility, we use a nested, 3-D, hydrodynamics-based modeling system (COAWST) to simulate the island-wide alongshore and cross-shore transport, in combination with shoreline change observations. The modeled, net alongshore transport gradients in the nearshore predict that the central part of Fire Island should be erosional, yet shoreline change observations show this area to be accretionary. We compare the model-predicted alongshore transport gradients with the flux gradients that would be required to generate the observed shoreline change, to give the pattern of sediment volume gains or losses that cannot be explained by the modeled alongshore transport gradients. Results show that the western 30 km of coast requires an input of sediment, supporting the hypothesis of onshore flux in this area. The modeled cross-shore flux of sediment between the shoreface and inner shelf is consistent these results, with onshore-directed bottom currents creating an environment more conducive to onshore sediment flux in the western 30 km of the island compared to the eastern 20 km. We conclude that the cross-shore flux of sediment can explain the shoreline change observations, and is an integral component of Fire Island's sediment budget.

  2. 1992 Progress report on sediment-related aspects of northern hydrocarbon development

    Energy Technology Data Exchange (ETDEWEB)

    1993-01-01

    The Mackenzie Delta is ecologically important for its outflow of warm, sediment-laden water to the Arctic Ocean. Lack of knowledge and clear understanding of delta processes raise serious concerns over potential impacts from development of local hydrocarbon resources on Delta ecosystems. The Northern Oil and Gas Program is sponsoring research on Mackenzie Delta hydrology and hydraulics, sediment flux, contaminant levels, and other issues relevant to impacts of hydrocarbon development. A compendium of five reports on the sediment-related aspects of this research is presented. The topics of the reports are: suspended sediment sampling; sedimentation measurement; channel stability; hydraulic and morphologic surveys; and sediment station data. A separate abstract has been prepared for each of the five reports.

  3. The exceptional sediment load of fine-grained dispersal systems: Example of the Yellow River, China

    Science.gov (United States)

    Ma, Hongbo; Nittrouer, Jeffrey A.; Naito, Kensuke; Fu, Xudong; Zhang, Yuanfeng; Moodie, Andrew J.; Wang, Yuanjian; Wu, Baosheng; Parker, Gary

    2017-01-01

    Sedimentary dispersal systems with fine-grained beds are common, yet the physics of sediment movement within them remains poorly constrained. We analyze sediment transport data for the best-documented, fine-grained river worldwide, the Huanghe (Yellow River) of China, where sediment flux is underpredicted by an order of magnitude according to well-accepted sediment transport relations. Our theoretical framework, bolstered by field observations, demonstrates that the Huanghe tends toward upper-stage plane bed, yielding minimal form drag, thus markedly enhancing sediment transport efficiency. We present a sediment transport formulation applicable to all river systems with silt to coarse-sand beds. This formulation demonstrates a remarkably sensitive dependence on grain size within a certain narrow range and therefore has special relevance to silt-sand fluvial systems, particularly those affected by dams. PMID:28508078

  4. The exceptional sediment load of fine-grained dispersal systems: Example of the Yellow River, China.

    Science.gov (United States)

    Ma, Hongbo; Nittrouer, Jeffrey A; Naito, Kensuke; Fu, Xudong; Zhang, Yuanfeng; Moodie, Andrew J; Wang, Yuanjian; Wu, Baosheng; Parker, Gary

    2017-05-01

    Sedimentary dispersal systems with fine-grained beds are common, yet the physics of sediment movement within them remains poorly constrained. We analyze sediment transport data for the best-documented, fine-grained river worldwide, the Huanghe (Yellow River) of China, where sediment flux is underpredicted by an order of magnitude according to well-accepted sediment transport relations. Our theoretical framework, bolstered by field observations, demonstrates that the Huanghe tends toward upper-stage plane bed, yielding minimal form drag, thus markedly enhancing sediment transport efficiency. We present a sediment transport formulation applicable to all river systems with silt to coarse-sand beds. This formulation demonstrates a remarkably sensitive dependence on grain size within a certain narrow range and therefore has special relevance to silt-sand fluvial systems, particularly those affected by dams.

  5. Eddy correlation measurements of oxygen uptake in deep ocean sediments

    DEFF Research Database (Denmark)

    Berg, P.; Glud, Ronnie Nøhr; Hume, A.

    2010-01-01

    .62 +/- 0.23 (SE, n = 7), 1.65 +/- 0.33 (n = 2), and 1.43 +/- 0.15 (n = 25) mmol m(-2) d(-1). The very good agreement between the eddy correlation flux and the chamber flux serves as a new, important validation of the eddy correlation technique. It demonstrates that the eddy correlation instrumentation......Abstract: We present and compare small sediment-water fluxes of O-2 determined with the eddy correlation technique, with in situ chambers, and from vertical sediment microprofiles at a 1450 m deep-ocean site in Sagami Bay, Japan. The average O-2 uptake for the three approaches, respectively, was 1...... available today is precise and can resolve accurately even very small benthic O-2 fluxes. The correlated fluctuations in vertical velocity and O-2 concentration that give the eddy flux had average values of 0.074 cm s(-1) and 0.049 mu M. The latter represents only 0.08% of the 59 mu M mean O-2 concentration...

  6. The effects of wastewater effluent and river discharge on benthic heterotrophic production,