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Sample records for episodic high sediment

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  2. Glacial and nonglacial sediment contributions to Wisconsin episode loess in the Central United States

    USGS Publications Warehouse

    Grimley, D.A.

    2000-01-01

    The relative contributions of various glacial and nonglacial sediments to Wisconsin Episode loess units along the lower Illinois and central Mississippi Valleys are estimated on the basis of a comparison of magnetic susceptibility and silt and clay mineralogy. A mathematical method of source area calculation, using four compositional parameters, was guided by current knowledge of the regional glacial history. On the basis of this technique, the Roxana Silt, along the Illinois and Mississippi River Valleys, is composed of significant Superior lobe sediment (35%-40%) as well as Wadena or Des Moines lobe sediment (about 35%). This can account for its high magnetic susceptibility, feldspar content, kaolinite content, and pink hue. Lower Peoria Silt contains about 25%-35% Lake Michigan lobe sediment with reduced contributions of the other sources. After the Mississippi River's diversion (20.4 ka), the supply of Superior, Des Moines, and Wadena lobe sediment was cut off from the Illinois Valley in favor of Lake Michigan lobe sediment (75%- 80% contribution). This major source area shift accounts for higher dolomite and illite contents and a more yellow hue in approximately the upper two-thirds of Peoria Silt in the study area. In loess south of St. Louis, less pronounced compositional shifts occur because Superior lobe sediment was not cut off and because Des Moines lobe, Wadena lobe, and Missouri River sediments, having more intermediate composition, compose 40%-50% of the loess, thereby diluting other source area changes. Nonglacial sediment, from fluvial and periglacial sources, is estimated to compose 10%-40% of loess in both regions.

  3. Episodic Emplacement of Sediment + Carbon within Large Tropical River Basins

    NASA Astrophysics Data System (ADS)

    Aalto, R.; Aufdenkampe, A.

    2012-04-01

    Application of advanced methods for imaging (sub-bottom sonar and ERGI), dating (high resolution 210-Pb and 14-C from deep cores), and biogeochemical analysis have facilitated the characterization and inter-comparison of floodplain sedimentation rates, styles, and carbon loading across disparate large river basins. Two examples explored here are the near-pristine 72,000 km2 Beni River basin in northern Bolivia and the similarly natural 36,000 km2 Strickland River basin in Papua New Guinea - that are located on either side of the Equatorial Pacific warm pool that drives the ENSO phenomenon. Our published research suggests that large, rapid-rise, cold-phase ENSO floods account for the preponderance of sediment accumulation within these two tropical systems. New results to be presented at EGU further clarify the extent of modern deposits (~100 yrs) within both systems and add a deeper perspective into how these extensive floodplains developed over the Holocene, both in response to external forcing (climate and base level) and internal system morphodynamics. The vast scale of these temporally discrete deposits (typically 100s of millions of tonnes over relatively short time periods) involved equate to high burial rates, which in turn support the high carbon loadings sequestered within the resulting sedimentary deposits. We have identified the principal source of this carbon and sedimentary material to be extensive landslides throughout the high-relief headwaters - failures that deliver huge charges of pulverized rock and soil directly into canyons (in both the Bolivian Andes and the PNG Highlands), where raging floodwaters provide efficient transport to lowland depocentres. We present recent results from our research in these basins, providing insight into the details of such enormous mass budgets that result in a signicant carbon sink within the floodplains. Processes, timing, and rates are compared between the two systems, providing insight into the nature of

  4. Episodic sedimentation on a lower Silurian storm-dominated carbonate ramp, Anticosti Island, Quebec, Canada

    SciTech Connect

    Sami, T.; Desrochers, A.

    1989-03-01

    The 130-170-m thick Becscie Formation represents continuous deposition on a shallow, open-marine carbonate ramp across the Ordovician-Silurian boundary. The sequence reflects a generally quiet, shallow marine environment punctuated by episodic, storm-generated, high-energy events. These events deposited individual storm units, or tempestites, which occur as fining-upward sequences ranging from 0.5 to 80 cm thick. A complete ideal storm deposit consists of a sharp erosional base overlain by intraclastic to bioclastic rudstone fining upward into calcarenite and then into finely laminated calcisiltite grading upward into shale. Tempestites exhibit a variety of storm-generated structures which are today exposed on extensive bedding planes. Gutters and gutter casts occur throughout the sequence and show a range of morphologies and fill/substrate combinations. Hummocky cross-stratification is widespread and restricted exclusively to the calcisiltite-rich tempestites. Flat-pebble conglomerates (intraclastic rudstone) occur through most of the sequence and contain clasts of mudstone, packstone, and grainstone, indicating extensive early sea floor lithification. Tempestite sequences display lateral and vertical variations controlled by water depth and distance from shore. Construction of proximality trends permits recognition of lower order sea level changes within the overall regressive sequence. Sea level changes are believed to be eustatic, yet diastrophic-tectonic influences should not be dismissed due to regional tectonic activity. Paleocurrent data suggest sediment transport by predominantly southwest-oriented geostrophic currents. Together with sedimentologic evidence, this supports a combined-flow model for storm sediment transport in the Anticosti basin.

  5. Particle mobility and bed surface adjustments on episodic sediment supply experiments

    NASA Astrophysics Data System (ADS)

    Ferrer-Boix, C.; Hassan, M. A.

    2015-12-01

    This research aims to explore how episodic sediment supply affects particle mobility and bed surface adjustments in mountain streams. We conducted a set of runs in a 1 m-wide, 18 m-long tilting flume. Seven consecutive runs, each lasting 40 hours, were conducted under constant flow (65 l/s) but varying sediment supply rates for a total duration of 280 hours. The feed rate for the runs was as follow: no feed (runs 1 and 7), constant feed of 2.1 g/m/s (runs 2 and 6), one pulse of 83 g/m/s (run 3), four pulses of 83 g/m/s (run 4) and two pulses of 83 g/m/s (run 5). The total mass of sediment supplied during each of runs 2-6 was 300 kg. The feed texture was identical to that of the original mixture (Dmin = 0.5 mm, Dmax = 64 mm, Dg = 5.65 mm and sg = 3.05) with a bed slope of 0.0218 m/m. Bed surface images of a 2 m-long reach in the middle of the flume were processed. Bed surface areas covered by particle sizes coarser than 5.66 mm were automatically identified. Thus, we can easily obtain fractional particle mobility, i.e. how much bed area covered by a particular grain size changed at a given time. Preliminary analyses of the experiments show that the bed surface texture systematically adjusts to each change in the sediment supply. Thus, (i) bed surface gradually coarsens during no feed runs 1 and 7, (ii) suddenly fines and subsequently coarsens after each episodic sediment supply event (runs 3-5) and (iii) remains approximately constant during runs 2 and 6 under constant feed conditions. Surface coarsening during run 1 was accompanied by the formation of bed structures and particle clusters. However, the amplitude of the changes of the bed surface texture is relatively small compared to the texture obtained after the first 40 h under no feed in run 1. This does not imply that the bed particles remain immobile. Conversely, bed particles on the surface move, bed structures loosen while the bed surface texture maintains, overall, the same grain size distribution

  6. Sediment Dating With Short-Lived Radioisotopes In Monterey Canyon, California Imply Episodes Of Rapid Deposition And Erosion

    NASA Astrophysics Data System (ADS)

    Lorenson, T. D.; Swarzenski, P. W.; Maier, K. L.; Gwiazda, R.; Paull, C. K.; Sumner, E.; Symons, W. O.

    2015-12-01

    Submarine canyons are a major conduit for terrestrial material to the deep sea. To better constrain the timing and rates in which sediment is transported down-canyon, we collected a series of sediment cores along the axis of Monterey Canyon, and quantified mass accumulation rates using short-lived radio-isotopes. A suite of sediment cores were carefully collected perpendicular to the canyon thalweg in water depths of approximately 300m, 500m, 800m, and 1500m using a remotely operated vehicle (ROV). We choose cores that were between 60m and 75m above the canyon thalweg on canyon side bench features for correlation with moored instrument deployments. The sediment cores reveal a complex stratigraphy that includes copious bioturbation features, sand lenses, subtle erosional surfaces, subtle graded bedding, and abrupt changes sediment texture and color. Downcore excess 210Pb and 137Cs profiles imply episodic deposition and remobilization cycles on the canyon benches. Excess 210Pb activities in cores reach depths of up to 1m, implying very rapid sedimentation. Sedimentation rates vary with water depth, generally with the highest sedimentation rate in closest to land, but vary substantially on adjacent canyon benches. Preliminary results demonstrate that sediment movement within Monterey Canyon is both dynamic and episodic on human time-scales and can be reconstructed used short-lived radio-isotopes.

  7. Holocene aeolian sedimentation and episodic mass-wasting events recorded in lacustrine sediments on Langøya in Vesterålen, northern Norway

    NASA Astrophysics Data System (ADS)

    Nielsen, Pål Ringkjøb; Dahl, Svein Olaf; Jansen, Henrik Løseth; Støren, Eivind N.

    2016-09-01

    In this study, the frequency of mass-wasting events and past storminess has been reconstructed throughout the Holocene (11,500 cal yr BP to present) from lacustrine sediments in lake Trehynnvatnet (33 m a.s.l.), which is located in a glacially carved valley at Nykvåg on the outmost coast of western Langøya, Vesterålen, northern Norway. Sediment cores (∼2-5 m long) have been examined by use of high-resolution magnetic susceptibility and XRF-scanning as well as grain size and loss-on-ignition analysis. In total 35 episodic event layers have been identified throughout the Holocene. The majority of these events are characterized as discrete coarse-grained sediment layers followed by normal grading, and are related to past mass-wasting activity within the catchment. Periods with high mass-wasting activity are dated to 11,000-10,500, 5500-4500, 4000-3500, 3000-2500, 2000-1000 and 500-0 cal yr BP. The continuous input of sand grains (>250 μm) has been systematically investigated throughout the sediment cores. The sand grains are related to catchment samples from the sandy beach deposits in Sandvikbukta c. 750 m away in SW direction, and are suggested to indicate (niveo-) aeolian influx to the lake. The content of sand grains varies greatly throughout the record, although there is a clear increase in influx of sand during the last 2800 years. Periods with high aeolian influx are proposed to indicate increased storminess, which occurred between 1600 and 1550 (350-400 CE), 1400-1300 (450-550 CE), 750-550 (1200-1400 CE) and 250-20 cal yr BP (1700-1930 CE), which to some degree coincides with periods of increased storminess and winter precipitation recorded in other studies around the North Eastern Atlantic region.

  8. High number of previous Plasmodium falciparum clinical episodes increases risk of future episodes in a sub-group of individuals.

    PubMed

    Loucoubar, Cheikh; Grange, Laura; Paul, Richard; Huret, Augustin; Tall, Adama; Telle, Olivier; Roussilhon, Christian; Faye, Joseph; Diene-Sarr, Fatoumata; Trape, Jean-François; Mercereau-Puijalon, Odile; Sakuntabhai, Anavaj; Bureau, Jean-François

    2013-01-01

    There exists great disparity in the number of clinical P. falciparum episodes among children of the same age and living in similar conditions. The epidemiological determinants of such disparity are unclear. We used a data-mining approach to explore a nineteen-year longitudinal malaria cohort study dataset from Senegal and identify variables associated with increased risk of malaria episodes. These were then verified using classical statistics and replicated in a second cohort. In addition to age, we identified a novel high-risk group of children in whom the history of P. falciparum clinical episodes greatly increased risk of further episodes. Age and a high number of previous falciparum clinical episodes not only play major roles in explaining the risk of P. falciparum episodes but also are risk factors for different groups of people. Combined, they explain the majority of falciparum clinical attacks. Contrary to what is widely believed, clinical immunity to P. falciparum does not de facto occur following many P. falciparum clinical episodes. There exist a sub-group of children who suffer repeated clinical episodes. In addition to posing an important challenge for population stratification during clinical trials, this sub-group disproportionally contributes to the disease burden and may necessitate specific prevention and control measures.

  9. Effects of episodic sedimentation on the net-spinning caddisflies Hydropsyche betteni and Ceratopsyche sparna (Trichoptera: Hydropsychidae).

    PubMed

    Strand, R M; Merritt, R W

    1997-01-01

    Net-spinning caddisflies commonly inhabit the chronically sedimented waters of midwestern agricultural catchments despite the presumed costs of sedimentation-induced gill-and net-fouling. We conducted a laboratory experiment to determine whether larval growth and survival of Hydropsyche betteni and Ceratopsyche sparna are affected by daily exposure to moderate levels of sedimentation. Sedimentation did not alter the relative growth rate of either species although slight losses by H. betteni and gains by C. sparna produced significant differences between species. H. betteni had a decreased likelihood of survival in sedimentation treatments relative to controls, but significantly outperformed C. sparna overall. Larval C. sparna are reportedly more sensitive than H. betteni to the instream effects of agricultural land use; however, the results of this experiment suggest that this differential sensitivity is probably not caused by episodic increases in suspended sediment concentration.

  10. The role of episodic fire-related debris flows on long-term (103-104) sediment yields in the Middle Fork Salmon River Watershed, in central Idaho

    NASA Astrophysics Data System (ADS)

    Riley, K. E.; Pierce, J. L.; Hopkins, A.

    2010-12-01

    Episodic fire-related debris flows contribute large amounts of sediment and large woody debris to streams. This study evaluates fire-related sedimentation from small steep tributaries of the Middle Fork Salmon River (MFSR) in central Idaho to evaluate the timing, frequency, and magnitude of episodic fire-related sedimentation on long-term (10 3-10 4) sediment yields. The MFSR lies within the Northern Rocky Mountains and encompasses a range of ecosystems including high elevation (~3,000 -1,700 m) subalpine pine and spruce forests, mid-elevation (2650 - 1130 m) montane Douglas-fir and ponderosa pine-dominated forests and low elevation (~ 1,800 - 900 m) sagebrush steppe. Recent debris flow events in tributaries of the MFSR appear to primarily result from increased surface runoff, rilling, and progressive sediment bulking following high severity fires. This study estimates: 1) the volume of sediment delivered by four recent (1997-2008) fire-related debris flow events using real time kinematic GPS surveys, and 2) the timing of Holocene fire-related debris flow events determined by 14C dating charcoal fragments preserved in buried burned soils and within fire-related deposits. Our measured volumes of the four recent debris flow events are compared to two empirically derived volume estimates based on remotely sensed spatial data (burn severity and slope), measured geometric data (longitudinal profile, cross sectional area, flow banking angle), and precipitation records. Preliminary stratigraphic profiles in incised alluvial fans suggest that a large percentage of alluvial fan thickness is composed of fire-related deposits suggesting fire-related hillslope erosion is a major process delivering sediment to alluvial fans and to the MFSR. Fire-related deposits from upper basins compose ~71% of total alluvial fan thickness, while fire-related deposits from lower basins make up 36% of alluvial fan thickness. However, lower basins are less densely vegetated with small diameter

  11. Recent eruptive episodes of the Rungwe volcanic field (Tanzania) recorded in lacustrine sediments of the Northern malawi rift

    NASA Astrophysics Data System (ADS)

    Williams, T. M.; Henney, P. J.; Owen, R. B.

    1993-07-01

    Discrete ash horizons in Holocene sediments from northern Lake Malawi provide evidence of six eruptive episodes within the nearby Rungwe Volcanic Field between c.9000-360 BP. Rare earth element (REE) analyses show the ash layers to be strongly enriched in La, Ce, Pr, Nd, Sm, Tb, Dy, Er, Tm, Yb and Lu, with low Eu/Eu∗ and high La N/Sm N values, relative to the surrounding muds. Mixing calculations suggest possible affinities between the Rungwe ash emissions and silicic volcanics from other important Quaternary centres (e.g. Naivasha) with respect to HREE geochemistry. The LREE spectra are less comparable and may indicate a less fractionated ash assemblage for Rungwe Field. In the absence of clear in situ evidence regarding the timing and frequency of Holocene eruptions at Rungwe, the Lake Malawi sediments may prove a valuable reconstructive tool. However, the direction and extent of ash dispersal is strongly controlled by wind/climatic factors and the retention of a complete record at any single location is unlikely.

  12. Episodic sediment-discharge events in Cascade Springs, southern Black Hills, South Dakota

    USGS Publications Warehouse

    Hayes, Timothy Scott

    1999-01-01

    upper Minnelusa Formation, which is caused by upward leakage of relatively fresh water from the Madison aquifer. The anhydrite dissolution and dedolomitization account for the net removal of minerals that would lead to breccia pipe formation by gravitational collapse. Breccia pipes in the lower Minnelusa Formation are uncommon; however, networks of interconnected breccia layers and breccia dikes are common. These networks, along with vertical fractures and faults, are likely pathways for transmitting upward leakage from the Madison aquifer. It is concluded that suspended sediment discharged at Cascade Springs probably results from episodic collapse brecciation that is caused by subsurface dissolution of anhydrite beds and cements of the upper Minnelusa Formation, accompanied by replacement of dolomite by calcite. It is further concluded that many breccia pipes probably are the throats of artesian springs that have been abandoned and exposed by erosion. The locations of artesian spring-discharge points probably have been shifting outwards from the center of the Black Hills uplift, essentially keeping pace with regional erosion over geologic time. Thus, artesian springflow probably is a factor in controlling water levels in the Madison and Minnelusa aquifers, with hydraulic head declining over geologic time, in response to development of new discharge points. Development of breccia pipes as throats of artesian springs would greatly enhance vertical hydraulic conductivity in the immediate vicinity of spring-discharge points. Horizontal hydraulic conductivity in the Minnelusa Formation also may be enhanced by dissolution processes related to upward leakage from the Madison aquifer. Potential processes could include dissolution resulting from leakage in the vicinity of breccia pipes that are abandoned spring throats, active spring discharge, development of subsurface breccias with no visible surface expression or spring discharge, as well as general areal leakage

  13. Evolution of a Holocene delta driven by episodic sediment delivery and coseismic deformation, Puget Sound, Washington, USA

    USGS Publications Warehouse

    Barnhardt, W.A.; Sherrod, B.L.

    2006-01-01

    Episodic, large-volume pulses of volcaniclastic sediment and coseismic subsidence of the coast have influenced the development of a late Holocene delta at southern Puget Sound. Multibeam bathymetry, ground-penetrating radar (GPR) and vibracores were used to investigate the morphologic and stratigraphic evolution of the Nisqually River delta. Two fluvial–deltaic facies are recognized on the basis of GPR data and sedimentary characteristics in cores, which suggest partial emplacement from sediment-rich floods that originated on Mount Rainier. Facies S consists of stacked, sheet-like deposits of andesitic sand up to 4 m thick that are continuous across the entire width of the delta. Flat-lying, highly reflective surfaces separate the sand sheets and comprise important facies boundaries. Beds of massive, pumice- and charcoal-rich sand overlie one of the buried surfaces. Organic-rich material from that surface, beneath the massive sand, yielded a radiocarbon age that is time-correlative with a series of known eruptive events that generated lahars in the upper Nisqually River valley. Facies CF consists of linear sandbodies or palaeochannels incised into facies S on the lower delta plain. Radiocarbon ages of wood fragments in the sandy channel-fill deposits also correlate in time to lahar deposits in upstream areas. Intrusive, sand-filled dikes and sills indicate liquefaction caused by post-depositional ground shaking related to earthquakes. Continued progradation of the delta into Puget Sound is currently balanced by tidal-current reworking, which redistributes sediment into large fields of ebb- and flood-oriented bedforms.

  14. Mercury Depletion Episode Studies in the Canadian High Arctic

    NASA Astrophysics Data System (ADS)

    Steffen, A.; Schroeder, W.; Hoenniger, G.; Platt, U.; Lawson, G.

    2001-12-01

    Episodic mercury depletion episodes were first recorded in Alert, Canada in 1995. Since this time, considerable research has been undertaken to further study this phenomenon. It has been found that there is an occurrence of fast photo-chemically induced reactions involving the oxidation of Hg (0) to Hg (II) during the springtime period in the high Arctic. Data from a cold regions pyrolysis unit (CRPU) have confirmed that particle-associated mercury (PM) and reactive gaseous mercury (RGM) are still present in the air during a mercury depletion event when Hg (0) concentration levels are very low. These more reactive species are less volatile and are more readily removed in the air and/or are deposited on the snow surfaces than Hg (0). In the winter and spring of 2000 in Alert, snow samples collected showed an almost 20 fold increase in mercury concentrations during the springtime period from the dark period. Air profiling measurements undertaken during the same time period have shown that Hg (0) is re-emitted from the snow pack surfaces both over land and the frozen Arctic Ocean near Alert. It is thought that free radical BrO is responsible for the destruction of ozone depletion episodes in the Arctic during springtime and increased concentrations from satellites have been measured during these times. Ground level in situ measurements taken over the frozen ocean during depletion events showed an anti-correlation between Hg (0) and BrO concentrations during MDEs. In February 2001, continuous automated RGM and PM measurements were initiated to further study this phenomenon in parallel with the CRPU to measure total atmospheric mercury concentrations in ambient air in the Canadian Arctic during springtime depletion events. A summary of findings from these studies will be presented.

  15. Episodic Sediment Failure in Northern Flemish Pass, Eastern Canadian Margin: Interplay of Seismicity, Contour Current Winnowing, and Excess Pore Pressures

    NASA Astrophysics Data System (ADS)

    Piper, D.

    2015-12-01

    Episodic sediment failures are recognised on continental slopes around Flemish Pass and Orphan Basin from multibeam bathymetry, seismic reflection profiles and piston cores. Seismic stratigraphy is tied to published long cores with O-isotope data back to before MIS 6 and carbonate rich Heinrich layers in places produce marker reflections in high-resolution sparker profiles. Heinrich layers, radiocarbon dates and peaks in diatom abundance provide core chronology. Slope sedimentation was strongly influenced by the Labrador Current and the silty muds show architecture characteristic of contourites. Variation in Labrador Current strength is known from the sortable silt proxy over the past 125 ka. Large slope failures were mapped from seismic reflection profiles and their age estimated from seismic stratigraphy (3-5 ka resolution) and in some cases refined from cores (1-3 ka resolution). Large slope failures occurred apparently synchronously over margin lengths of 50-350 km. Such failures were earthquake triggered: other mechanisms for producing laterally extensive synchronous failure do not apply. Triaxial shear measurements show a Su/σ' ratio of typical slope sediment of 0.48, implying considerable stability. However, some silty muds have Atterberg limits that suggest susceptibility to liquefaction under cyclic loading, particularly in Holocene deposits and by analogy those of past full interglacials. Basal failure planes of some large failures correspond with either the last interglacial or the MIS 6 glacial maximum. Comparison with seismological models suggests that the observed slope failures represent earthquakes ranging from Mw ~5.6 to ~7.6. Mean recurrence interval of M = 7 earthquakes at any point on the margin is estimated at 30 ka from seismological models and 40 ka from the sediment failure record. In northern Flemish Pass, a spatial cluster of several failures over 30 ka preceded by a long interval with no failures suggests that some other mechanism has

  16. Highly episodic fire and erosion regime over the past 2,000 y in the Siskiyou Mountains, Oregon

    PubMed Central

    Colombaroli, Daniele; Gavin, Daniel G.

    2010-01-01

    Fire is a primary mode of natural disturbance in the forests of the Pacific Northwest. Increased fuel loads following fire suppression and the occurrence of several large and severe fires have led to the perception that in many areas there is a greatly increased risk of high-severity fire compared with presettlement forests. To reconstruct the variability of the fire regime in the Siskiyou Mountains, Oregon, we analyzed a 10-m, 2,000-y sediment core for charcoal, pollen, and sedimentological data. The record reveals a highly episodic pattern of fire in which 77% of the 68 charcoal peaks before Euro-American settlement cluster within nine distinct periods marked by a 15-y mean interval. The 11 largest charcoal peaks are significantly related to decadal-scale drought periods and are followed by pulses of minerogenic sediment suggestive of rapid sediment delivery. After logging in the 1950s, sediment load was increased fourfold compared with that from the most severe presettlement fire. Less severe fires, marked by smaller charcoal peaks and no sediment pulses, are not correlated significantly with drought periods. Pollen indicators of closed forests are consistent with fire-free periods of sufficient length to maintain dense forest and indicate a fire-triggered switch to more open conditions during the Medieval Climatic Anomaly. Our results indicate that over millennia fire was more episodic than revealed by nearby shorter tree-ring records and that recent severe fires have precedents during earlier drought episodes but also that sediment loads resulting from logging and road building have no precedent in earlier fire events.

  17. Sediment mobilization deposits from episodic subsurface fluid flow - A new tool to reveal long-term earthquake records?

    NASA Astrophysics Data System (ADS)

    Reusch, Anna; Moernaut, Jasper; Anselmetti, Flavio S.; Strasser, Michael

    2016-04-01

    Subsurface fluid flow can be affected by earthquakes: increased spring activity, mud volcano eruptions, groundwater fluctuations, changes in geyser frequency and other forms of altered subsurface fluid flow have been documented during, after, or even prior to earthquakes. Recently discovered giant pockmarks on the bottom of Lake Neuchâtel, Switzerland, are the lake-floor expression of subsurface fluid flow. They discharge karstic groundwater from the Jura Mountains and experience episodically increased subsurface fluid flow documented by subsurface sediment mobilization deposits at the levees of the pockmarks. In this study, we present the spatio-temporal distribution of event deposits from phases of sediment expulsion and their time correlative multiple mass-transport deposits. We report striking evidence for five events of concurrent multiple subsurface sediment deposits and multiple mass-transport deposits since Late Glacial times, for which we propose past earthquakes as trigger. Comparison of this new event catalogue with historic earthquakes and other independent paleoseismic records suggests that initiation of sediment expulsion requires a minimum macroseismic intensity of VII. Thus, our study presents for the first time sedimentary deposits resulting from increased subsurface fluid flow as new paleoseismic proxy. Comparable processes must also be relevant for other mountain front ranges and coastal mountain ranges, where groundwater flow triggers subsurface sediment mobilization and discharges into lacustrine and marine settings.

  18. Episodes of low dissolved oxygen indicated by ostracodes and sediment geochemistry at Crystal Lake, Illinois, USA

    USGS Publications Warehouse

    Curry, B. Brandon; Filippelli, G.M.

    2010-01-01

    Low dissolved oxygen during the summer and early fall controls profundal continental ostracode distribution in Crystal Lake (McHenry County), Illinois, favoring Cypria ophthalmica and Physocypria globula at water depths from 6 to 13 m. These species also thrived in the lake's profundal zone from 14,165 to 9600 calendar year before present (cal yr b.p.) during the late Boiling, Allerod, and Younger Dryas chronozones, and early Holocene. Characterized by sand, cemented tubules, large aquatic gastropod shells, and littoral ostracode valves, thin (1-6 cm) tempestite deposits punctuate thicker deposits of organic gyttja from 16,080 to 11,900 cal yr b.p. The succeeding 2300 yr (11,900-9600 cal yr b.p.) lack tempestites, and reconstructed water depths were at their maximum. Deposition of marl under relatively well-oxygenated conditions occurred during the remainder of the Holocene until the arrival of Europeans, when the lake returned to a pattern of seasonally low dissolved oxygen. Such conditions are also indicated in the lake sediment by the speciation of phosphorus, high concentrations of organic carbon, and abundant iron and manganese occluded to mineral grains. Initial low dissolved oxygen was probably caused by the delivery of dissolved P and Fe in shallow groundwater, the chemistry of which was influenced by Spodosol pedogenesis under a spruce forest. The triggering may have been regionally warm and wet conditions associated with retreat of the Lake Michigan lobe (south-central Laurentide Ice Sheet). ?? 2010, by the American Society of Limnology and Oceanography Inc.

  19. Changes in vegetation and drainage density as controlling factors in the episodicity of Quaternary sediment flux: southwestern United States and Bolivian Eastern Cordillera

    NASA Astrophysics Data System (ADS)

    Barnes, J.; Pelletier, J. D.

    2001-12-01

    Piedmont geomorphic surfaces in the southwestern U.S. primarily represent cut-and-fill cycles resulting from variations in sediment supply from adjacent mountain catchments. Although sparse, precise age control supports the hypothesis that sediment supply in the southwestern U.S. can increase by an order of magnitude during Quaternary humid-to-arid transitions recognized in high-resolution paleoclimatic proxies. As an example, this episodicity is quantified with a time series of sediment flux for the central Gila Mountains, southwestern Arizona, where paleosurfaces outcrop in the modern channel bank, permitting an estimate of deposit volume in conjunction with high-resolution photogrammetric DEMs. Age control is provided by a new method of surface exposure dating based on 3D hillslope diffusion adjacent to gullies penetrating the surface. We propose that episodes of piedmont alluviation result from an increase in drainage density resulting from climatically-induced vegetative successions from mature woodland vegetation to desert shrubs that excavate large amounts of hillslope colluvium stored during the previous humid interval. Analogous vegetative shifts occur in the Bolivian Eastern Cordillera (EC). Field observations and analyses of topographic maps and LANDSAT images suggest that the longitudinal profiles of the major rivers of the EC are dominated by an order-of-magnitude increase in Plio-Quaternary hillslope erosion in the elevation zone between approximately 2.5 and 3.5 kilometers above sea level corresponding to glacial-interglacial vegetational successions from Andean forest (glacial) to Paramo grasslands (interglacial). These vegetation changes resulted in rapid fluctuations in drainage density responsible for a large increase in transport rates that alluviated major valleys and enhanced bedrock incision rates downstream. Areas above and below this elevation have perennial grassland and forest, respectively, whose long-term vegetational stability has

  20. Episodic Memory and Episodic Future Thinking Impairments in High-Functioning Autism Spectrum Disorder: An Underlying Difficulty With Scene Construction or Self-Projection?

    PubMed Central

    2013-01-01

    Objective: There appears to be a common network of brain regions that underlie the ability to recall past personal experiences (episodic memory) and the ability to imagine possible future personal experiences (episodic future thinking). At the cognitive level, these abilities are thought to rely on “scene construction” (the ability to bind together multimodal elements of a scene in mind—dependent on hippocampal functioning) and temporal “self-projection” (the ability to mentally project oneself through time—dependent on prefrontal cortex functioning). Although autism spectrum disorder (ASD) is characterized by diminished episodic memory, it is unclear whether episodic future thinking is correspondingly impaired. Moreover, the underlying basis of such impairments (difficulties with scene construction, self-projection, or both) is yet to be established. The current study therefore aimed to elucidate these issues. Method: Twenty-seven intellectually high-functioning adults with ASD and 29 age- and IQ-matched neurotypical comparison adults were asked to describe (a) imagined atemporal, non-self-relevant fictitious scenes (assessing scene construction), (b) imagined plausible self-relevant future episodes (assessing episodic future thinking), and (c) recalled personally experienced past episodes (assessing episodic memory). Tests of narrative ability and theory of mind were also completed. Results: Performances of participants with ASD were significantly and equally diminished in each condition and, crucially, this diminution was independent of general narrative ability. Conclusions: Given that participants with ASD were impaired in the fictitious scene condition, which does not involve self-projection, we suggest the underlying difficulty with episodic memory/future thinking is one of scene construction. PMID:24015827

  1. Meteorological effects on the evolution of high ozone episodes in the greater Seoul area.

    SciTech Connect

    Ghim, Y. S.; Oh, H. S.; Chang, Y.-S.; Environmental Assessment; Korea Inst. of Science and Tech.

    2001-02-01

    Three high O{sub 3} episodes - 7 days in 1992 (July 3-July 9), 9 days in 1994 (July 21-July 29), and another 3 days in 1994 (August 22-August 24) - were selected on the basis of morning (7:00 a.m.-10:00 a.m.) average wind direction and speed and daily maximum O{sub 3} concentrations in the greater Seoul, Korea, of 1990-1997. To better understand their characteristics and life cycles, surface data from the Seoul Weather Station (SWS) and surface and 850-hPa wind field data covering northeast Asia around the Korean Peninsula were used for the analysis. In the July 1992 episode, westerly winds were most frequent as a result of the influence of a high-pressure system west of the Korean Peninsula behind a trough. In contrast, in the July 1994 episode, easterly winds were most frequent as a result of the effect of a typhoon moving north from the south of Japan. Despite different prevailing wind directions, the peak O{sub 3} concentrations for each episode occurred when a sea/land breeze developed in association with weak synoptic forcing. The August 1994 episode, which was selected as being representative of calm conditions, was another typical example in which a well-developed sea/land breeze helped cause the peak O{sub 3} concentration to rise to a record high of 322 parts per billion by volume (ppbv). All three high O3 episodes ended as a result of precipitation, and subsequent rises in O3 concentrations were also suppressed by a series of precipitation events afterwards. In particular, two heavy rainfalls were the main reason why the August 1994 episode, which had the highest and second-highest O{sub 3} concentrations, lasted only a few days.

  2. Spatial navigation impairments among intellectually high-functioning adults with autism spectrum disorder: exploring relations with theory of mind, episodic memory, and episodic future thinking.

    PubMed

    Lind, Sophie E; Williams, David M; Raber, Jacob; Peel, Anna; Bowler, Dermot M

    2013-11-01

    Research suggests that spatial navigation relies on the same neural network as episodic memory, episodic future thinking, and theory of mind (ToM). Such findings have stimulated theories (e.g., the scene construction and self-projection hypotheses) concerning possible common underlying cognitive capacities. Consistent with such theories, autism spectrum disorder (ASD) is characterized by concurrent impairments in episodic memory, episodic future thinking, and ToM. However, it is currently unclear whether spatial navigation is also impaired. Hence, ASD provides a test case for the scene construction and self-projection theories. The study of spatial navigation in ASD also provides a test of the extreme male brain theory of ASD, which predicts intact or superior navigation (purportedly a systemizing skill) performance among individuals with ASD. Thus, the aim of the current study was to establish whether spatial navigation in ASD is impaired, intact, or superior. Twenty-seven intellectually high-functioning adults with ASD and 28 sex-, age-, and IQ-matched neurotypical comparison adults completed the memory island virtual navigation task. Tests of episodic memory, episodic future thinking, and ToM were also completed. Participants with ASD showed significantly diminished performance on the memory island task, and performance was positively related to ToM and episodic memory, but not episodic future thinking. These results suggest that (contra the extreme male brain theory) individuals with ASD have impaired survey-based navigation skills--that is, difficulties generating cognitive maps of the environment--and adds weight to the idea that scene construction/self-projection are impaired in ASD. The theoretical and clinical implications of these results are discussed.

  3. Numerical modeling of mixed sediment resuspension, transport, and deposition during the March 1998 episodic events in southern Lake Michigan

    SciTech Connect

    Lee, Cheegwan; Schwab, David J.; Beletsky, Dmitry; Stroud, Jonathan; Lesht, B. M.

    2007-02-17

    A two-dimensional sediment transport model capable of simulating sediment resuspension of mixed (cohesive+noncohesive) sediment is developed and applied to quantitatively simulate the March 1998 resuspension events in southern Lake Michigan. Some characteristics of the model are the capability to incorporate several floc size classes, a physically-based settling velocity formula, bed armoring, and sediment availability limitation. Important resuspension parameters were estimated from field and laboratory measurement data. The model reproduced the resuspension plume (observed by the SeaWIFS satellite and field instruments) and recently measured sedimentation rate distribution (using radiotracer techniques) fairly well. Model results were verified with field measurements of suspended sediment concentration and settling flux (by ADCPs and sediment traps). Both wave conditions and sediment bed properties (critical shear stress, fine sediment fraction, and limited sediment availability or source) are the critical factors that determine the concentration distribution and width of the resuspension plume. The modeled sedimentation pattern shows preferential accumulation of sediment on the eastern side of the lake, which agrees with the observed sedimentation pattern despite a predominance of particle sources from the western shoreline. The main physical mechanisms determining the sedimentation pattern are 1) the two counter-rotating circulation gyres producing offshore mass transport along the southeastern coast during northerly wind and 2) the settling velocity of sediment flocs which controls the deposition location.

  4. Numerical modeling of mixed sediment resuspension, transport, and deposition during the March 1998 episodic events in southern Lake Michigan.

    SciTech Connect

    Lee, C.; Schwab, D. J.; Beletsky, D.; Stroud, J.; Lesht, B.; PNNL; NOAA; Univ. of Michigan; Univ. of Pennsylvania

    2007-02-17

    A two-dimensional sediment transport model capable of simulating sediment resuspension of mixed (cohesive plus noncohesive) sediment is developed and applied to quantitatively simulate the March 1998 resuspension events in southern Lake Michigan. Some characteristics of the model are the capability to incorporate several floc size classes, a physically based settling velocity formula, bed armoring, and sediment availability limitation. Important resuspension parameters were estimated from field and laboratory measurement data. The model reproduced the resuspension plume (observed by the SeaWIFS satellite and field instruments) and recently measured sedimentation rate distribution (using radiotracer techniques) fairly well. Model results were verified with field measurements of suspended sediment concentration and settling flux (by ADCPs and sediment traps). Both wave conditions and sediment bed properties (critical shear stress, fine sediment fraction, and limited sediment availability or source) are the critical factors that determine the concentration distribution and width of the resuspension plume. The modeled sedimentation pattern shows preferential accumulation of sediment on the eastern side of the lake, which agrees with the observed sedimentation pattern despite a predominance of particle sources from the western shoreline. The main physical mechanisms determining the sedimentation pattern are (1) the two counter-rotating circulation gyres producing offshore mass transport along the southeastern coast during northerly wind and (2) the settling velocity of sediment flocs which controls the deposition location.

  5. Chemical and mineralogical proxies of erosion episodes in the dried lake sediments (Amik Lake, Southern Turkey): paleoenvironmental implications

    NASA Astrophysics Data System (ADS)

    El Ouahabi, Meriam; Hubert-Ferrari, Aurélia; Lebeau, Héléne; Fagel, Nathalie; Vander Auwera, Jacquelinec; Karabacak, Volkan; Schmidt, Sabine

    2016-04-01

    The Amik Basin in the Eastern Mediterranean region has been continuously occupied since 6000-7000 BC. The landscape has sustained with highly variable anthropic pressure culminating during the Late Roman Period when the Antioch city reached its golden age. The basin also sustained a high seismic activity (M≥7) as it is a releasing step-over along the Dead Sea Fault. The study focuses on the sedimentary record of the Amik Lake occupying the central part of the Basin. Our objective is to constrain major paleo-environmental changes in the area over the last 4000 years and to unravel possible human impacts on the sedimentation. A diverse array of complementary methods was applied on the 6 m long record. High resolution of mineralogical (XRD) and geochemical (XRF) analyses were performed. Quantitative mineralogical phases of sediments by the Rietveld method were computed using Topaz software. The age of the record is constrained combining radionuclide and radiocarbon dating, and checked using the correlation between the earthquake history and rapidly deposited layer identified. A high sedimentation rate of 0.12 cm/yr was inferred at the coring site. The 4000 years old record shows that significant fluctuations of the lake level and the riverine system inflow into the Amik Lake occurred. The Late Bronze lowstand leaded to punctual dryings of the lake at the end of the Bronze/Iron transition marked by the collapse of the Hittite Empire and during the Dark ages. At that time, the riverine was carrying a large terrigenous input linked to strong soil erosion related to deforestation, exploitation of mineral resources and the beginning of upland cultivation. During the Roman Period and in the later periods, upland soils were partly depleted and the riverine system completely transformed by channelization that leaded to a mashification of the Amik Basin. Chemical and mineralogical composition of sediments is quite diversified reflecting the significant geological variation

  6. Low-wind/high particulate matter episodes in the Calexico/Mexicali region.

    PubMed

    Kelly, Kerry E; Jaramillo, Isabel C; Quintero-Núñez, Margarito; Wagner, David A; Collins, Kimberly; Meuzelaar, Henk L C; Lighty, JoAnn S

    2010-12-01

    The U.S. Environmental Protection Agency (EPA) currently classifies Imperial County, CA, as a nonattainment area for PM10 (particulate matter [PM] < or = 10 microm in diameter), and this region suffers from high rates of chronic bronchitis and childhood asthma. Although high annual and daily average PM levels can have negative health and economic effects, recent studies have identified an association between adverse health effects and short-term PM spikes of tens of micrograms per cubic meter. This study identified PM episodes in Calexico/Mexicali that involve PM concentration spikes with concentrations up to 10 times greater than those reported to cause adverse health effects. These episodes appear to be relatively common during the winter months, are associated with wind speeds below 2 m/sec and stable boundary level heights below 500 m, and can comprise a large portion of the 24-hr PM levels. The organic composition of the PM10 samples collected during the low-wind/ high-PM episodes differed from that collected at other times. However, a preliminary source attribution identified only one significant difference between the source classes: agricultural burning accounted for 6.7% of organic-fraction PM10 for low-wind/high-PM episodes versus 0.25% at other times. This preliminary source attribution also revealed that motor vehicles were the most important relative contributor to organic PM10. PMID:21243902

  7. The Effects of Runaway-Homeless Episodes on High School Dropout

    PubMed Central

    Aratani, Yumiko; Cooper, Janice L.

    2013-01-01

    This article uses data from the National Longitudinal Survey of Youth 1997 to examine the relationship between running away from home between the ages of 12 and 14 and dropping from high school among youth. Propensity score matching was conducted in estimating the effect of running away on high school dropout while controlling for confounding factors, such as familial instability and socioemotional health risks. The findings suggest that having runaway-homeless episodes have a detrimental effect on academic achievement. PMID:25641997

  8. Crop harvest in Central Europe causes episodes of high airborne Alternaria spore concentrations in Copenhagen

    NASA Astrophysics Data System (ADS)

    Skjøth, C. A.; Sommer, J.; Frederiksen, L.; Gosewinkel Karlson, U.

    2012-06-01

    This study tests the hypothesis that Danish agricultural areas are the main source to airborne Alternaria spores in Copenhagen, Denmark. We suggest that the source to the overall load is mainly local, but with intermittent Long Distance Transport (LDT) from more remote agricultural areas. This hypothesis is supported by investigating a 10 yr bi-hourly record of Alternaria spores in the air from Copenhagen. This record shows 232 clinically relevant episodes with a distinct daily profile. The data analysis also revealed potential LDT episodes almost every year. A source map and analysis of atmospheric transport suggest that LDT always originates from the main agricultural areas in Central Europe. A dedicated emission study in cereal crops under harvest during 2010 also supports our hypothesis. The emission study showed that although the fields had been treated against fungal infections, harvesting still produced large amounts of airborne fungal spores. It is likely that such harvesting periods can cause clinically relevant levels of fungal spores in the atmosphere. Our findings suggest that crop harvest in Central Europe causes episodes of high airborne Alternaria spore concentrations in Copenhagen as well as other urban areas in this region. It is likely that such episodes could be simulated using atmospheric transport models.

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

    USGS Publications Warehouse

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

    1984-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  11. Episodic high irrigation pressure during surgical neuroendoscopy may cause intermittent intracranial circulatory insufficiency.

    PubMed

    Fàbregas, N; Valero, R; Carrero, E; Tercero, J; Caral, L; Zavala, E; Ferrer, E

    2001-04-01

    Intermittent high peak pressure values inside the endoscope during neuroendoscopic surgical procedures are associated with postoperative morbidity. Unexpected delay in awakening is the complication most frequently observed by the anesthesiologist as a result of high peak pressure values inside the endoscope. During eight neuroendoscopic procedures the authors continuously monitored cerebral hemodynamic function, using a transcranial doppler (TCD) probe fixed on patients' temporal window. We observed that episodes of high peak pressure values inside the endoscope during neuroendoscopic navigation rinsing periods resulted in changes in the TCD wave profile consistent with "near intracranial circulatory arrestlike" wave. No systemic hemodynamic warning signs accompanied these intermittent episodes of severe decrease in cerebral perfusion pressure. When the rinsing liquid was allowed to escape, the pressure inside the endoscope decreased and the TCD wave immediately returned to its previous value. Neuroendoscopic procedures, although classified as minimally invasive surgery, warrant special monitoring that could alert us to a decrease in cerebral perfusion pressure. Middle cerebral artery TCD recording is a reliable and accurate tool for this purpose. PMID:11294458

  12. Continuous deformation versus episodic deformation at high stress - the microstructural record

    NASA Astrophysics Data System (ADS)

    Trepmann, C. A.; Stöckhert, B.

    2009-04-01

    The microstructural record of continuous high stress deformation is compared to that of episodic high stress deformation on two examples: 1. Folding of quartz veins in metagreywacke from Pacheco Pass, California, undergoing deformation by dissolution precipitation creep at temperatures of 300 ± 50°C. The microfabric of the folded quartz veins indicates deformation by dislocation creep accompanied by subgrain rotation. The small recrystallized grain size of ~8±6 µm in average implies relatively high differential stresses of a few hundred MPa. The stress concentration in the vein is due to a high contrast in effective viscosities between the single phase material and the polyphase fine-grained host metagreywacke deforming by dissolution precipitation creep. Smoothly curved, but generally not sutured, grain boundaries as well as the small size and a relatively high dislocation density of recrystallized grains suggest that strain-induced grain boundary migration was of minor importance. This is suspected to be a consequence of low strain gradients, which are due to the relative rates of dynamic recovery and continuous dislocation production during climb-controlled creep, at high stress and the given low temperature. Subgrain rotation recrystallization is thus proposed to be characteristic for continuous deformation at high differential stress. 2. Episodic deformation in the middle crust at the tip of a seismic active fault zone. The microfabric of mid-crustal rocks exhumed in tectonically active regions can record episodic high stress deformation at the base of the seismogenic layer. The quartz veins from St. Paul la Roche in the Massif Central, France, are very coarse grained. On the scale of a thin section they are basically single crystalline. However, they show a very heterogeneous microstructure with a system of healed microcracks that are decorated by subgrains and more rarely by small recrystallized grains. Undulating deformation lamellae that do not show a

  13. High-temporal Resolution Sediment Fingerprinting with Uncertainty: A Bayesian Approach

    NASA Astrophysics Data System (ADS)

    Cooper, Richard; Krueger, Tobi; Hiscock, Kevin; Rawlins, Barry

    2014-05-01

    A high-temporal resolution fluvial sediment source apportionment model, set within an empirical Bayesian framework, is presented for the River Wensum Demonstration Test Catchment (DTC), UK. Direct X-ray fluorescence (XRF) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analysis of sediment covered filter papers were used in conjunction with ISCO automatic water samplers to monitor suspended particulate matter (SPM) geochemistry at high-temporal resolution throughout the progression of five heavy precipitation events during 2012-2013. Exploiting the spatial and temporal variation in four potential sediment source areas and SPM geochemistry respectively, we are able to apportion sediment contributions from eroding stream channel banks, arable topsoils, damaged road verges and agricultural field drains at 60-120 minute resolution. For all monitored precipitation episodes, pre- and post-event conditions are dominated by elevated SPM calcium concentrations that indicate major sediment inputs from carbonate-rich subsurface sources. Conversely, precipitation events coincide with an increase in concentrations of clay-associated elements and a consequent increase in predicted contributions from surface sources. Employing a Gibbs sampling Markov Chain Monte-Carlo mixing model procedure has enabled full characterisation of both spatial geochemical variability and instrument precision to quantify uncertainty around posterior distributions. All model source apportionment estimates correspond favourably with understanding of the regional geology, analysis of hysteresis behaviour, and visual observations of catchment processes. The results presented here demonstrate how to directly analyse SPM trapped on filter papers by spectroscopy to yield the high-temporal resolution source apportionment estimates required by catchment managers to help mitigate the deleterious effects of land-to-river sediment transfer.

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

    PubMed Central

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

    2016-01-01

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

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

    PubMed

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

    2016-01-01

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

  16. Episodic Memories

    ERIC Educational Resources Information Center

    Conway, Martin A.

    2009-01-01

    An account of episodic memories is developed that focuses on the types of knowledge they represent, their properties, and the functions they might serve. It is proposed that episodic memories consist of "episodic elements," summary records of experience often in the form of visual images, associated to a "conceptual frame" that provides a…

  17. High rates of organic carbon burial in fjord sediments globally

    NASA Astrophysics Data System (ADS)

    Smith, Richard W.; Bianchi, Thomas S.; Allison, Mead; Savage, Candida; Galy, Valier

    2015-06-01

    The deposition and long-term burial of organic carbon in marine sediments has played a key role in controlling atmospheric O2 and CO2 concentrations over the past 500 million years. Marine carbon burial represents the dominant natural mechanism of long-term organic carbon sequestration. Fjords--deep, glacially carved estuaries at high latitudes--have been hypothesized to be hotspots of organic carbon burial, because they receive high rates of organic material fluxes from the watershed. Here we compile organic carbon concentrations from 573 fjord surface sediment samples and 124 sediment cores from nearly all fjord systems globally. We use sediment organic carbon content and sediment delivery rates to calculate rates of organic carbon burial in fjord systems across the globe. We estimate that about 18 Mt of organic carbon are buried in fjord sediments each year, equivalent to 11% of annual marine carbon burial globally. Per unit area, fjord organic carbon burial rates are one hundred times as large as the global ocean average, and fjord sediments contain twice as much organic carbon as biogenous sediments underlying the upwelling regions of the ocean. We conclude that fjords may play an important role in climate regulation on glacial-interglacial timescales.

  18. Episodic memory retrieval for story characters in high-functioning autism

    PubMed Central

    2013-01-01

    Background The objective of this study was to examine differences in episodic memory retrieval between individuals with autism spectrum disorder (ASD) and typically developing (TD) individuals. Previous studies have shown that personality similarities between readers and characters facilitated reading comprehension. Highly extraverted participants read stories featuring extraverted protagonists more easily and judged the outcomes of such stories more rapidly than did less extraverted participants. Similarly, highly neurotic participants judged the outcomes of stories with neurotic protagonists more rapidly than did participants with low levels of neuroticism. However, the impact of the similarity effect on memory retrieval remains unclear. This study tested our ‘similarity hypothesis’, namely that memory retrieval is enhanced when readers with ASD and TD readers read stories featuring protagonists with ASD and with characteristics associated with TD individuals, respectively. Methods Eighteen Japanese individuals (one female) with high-functioning ASD (aged 17 to 40 years) and 17 age- and intelligence quotient (IQ)-matched Japanese (one female) TD participants (aged 22 to 40 years) read 24 stories; 12 stories featured protagonists with ASD characteristics, and the other 12 featured TD protagonists. Participants read a single sentence at a time and pressed a spacebar to advance to the next sentence. After reading all 24 stories, they were asked to complete a recognition task about the target sentence in each story. Results To investigate episodic memory in ASD, we analyzed encoding based on the reading times for and readability of the stories and retrieval processes based on the accuracy of and response times for sentence recognition. Although the results showed no differences between ASD and TD groups in encoding processes, they did reveal inter-group differences in memory retrieval. Although individuals with ASD demonstrated the same level of accuracy as did

  19. Recent and episodic volcanic and glacial activity on Mars revealed by the High Resolution Stereo Camera.

    PubMed

    Neukum, G; Jaumann, R; Hoffmann, H; Hauber, E; Head, J W; Basilevsky, A T; Ivanov, B A; Werner, S C; van Gasselt, S; Murray, J B; McCord, T

    2004-12-23

    The large-area coverage at a resolution of 10-20 metres per pixel in colour and three dimensions with the High Resolution Stereo Camera Experiment on the European Space Agency Mars Express Mission has made it possible to study the time-stratigraphic relationships of volcanic and glacial structures in unprecedented detail and give insight into the geological evolution of Mars. Here we show that calderas on five major volcanoes on Mars have undergone repeated activation and resurfacing during the last 20 per cent of martian history, with phases of activity as young as two million years, suggesting that the volcanoes are potentially still active today. Glacial deposits at the base of the Olympus Mons escarpment show evidence for repeated phases of activity as recently as about four million years ago. Morphological evidence is found that snow and ice deposition on the Olympus construct at elevations of more than 7,000 metres led to episodes of glacial activity at this height. Even now, water ice protected by an insulating layer of dust may be present at high altitudes on Olympus Mons.

  20. Episodic High-velocity Outflows from V899 Mon: A Constraint On The Outflow Mechanisms

    NASA Astrophysics Data System (ADS)

    Ninan, J. P.; Ojha, D. K.; Philip, N. S.

    2016-07-01

    We report the detection of large variations in the outflow wind velocity from a young eruptive star, V899 Mon, during its ongoing high accretion outburst phase. Such large variations in the outflow velocity (from -722 to -425 km s-1) have never been reported previously in this family of objects. Our continuous monitoring of this source shows that the multi-component, clumpy, and episodic high velocity outflows are stable in the timescale of a few days, and vary over the timescale of a few weeks to months. We detect significant decoupling in the instantaneous outflow strength to accretion rate. From the comparison of various possible outflow mechanisms in magnetospheric accretion of young stellar objects, we conclude magnetically driven polar winds to be the most consistent mechanism for the outflows seen in V899 Mon. The large scale fluctuations in outflow over the short period makes V899 Mon the most ideal source to constrain various magnetohydrodynamics simulations of magnetospheric accretion. Based on observations made with the Southern African Large Telescope (SALT).

  1. Quantifying the surface energy fluxes in South Greenland during the 2012 high melt episodes using in-situ observations

    NASA Astrophysics Data System (ADS)

    Fausto, Robert; van As, Dirk; Box, Jason; Colgan, William; Langen, Peter

    2016-09-01

    Two high melt episodes occurred on the Greenland ice sheet in July 2012, during which nearly the entire ice sheet surface experienced melting. Observations from an automatic weather station (AWS) in the lower ablation area in South Greenland reveal the largest daily melt rates (up to 28 cm d-1 ice equivalent) ever recorded on the ice sheet. The two melt episodes lasted 6 days, equivalent to 6% of the June-August melt period, but contributed 14 % to the total annual ablation of 8.5 m ice equivalent. We employ a surface energy balance model driven by AWS data to quantify the relative importance of the energy budget components contributing to melt through the melt season. During the days with largest daily melt rates, surface turbulent heat input peaked at 552 Wm-2, 77 % of the surface melt energy, which is otherwise typically dominated by absorbed solar radiation. We find that rain contributed ca. 7 % to melt during these episodes.

  2. Model for episodic flow of high-pressure water in fault zones before earthquakes

    USGS Publications Warehouse

    Byerlee, J.

    1993-01-01

    In this model for the evolution of large crustal faults, water originally from the country rock saturates the porous and permeable fault zone. During shearing, the fault zone compacts and water flows back into the country rock, but the flow is arrested by silicate deposition that forms low permeability seals. The fluid will be confined to seal-bounded fluid compartments of various sizes and porosity that are not hydraulically connected with each other. When the seal between two compartments is ruptured, an electrical streaming potential will be generated by the sudden movement of fluid from the high-pressure compartment to the low-pressure compartment. During an earthquake the width of the fault zone will increase by failure of the geometric irregularities on the fault. This newly created, porous and permeable, wider fault zone will fill with water, and the process described above will be repeated. Thus, the process is episodic with the water moving in and out of the fault zone, and each large earthquake should be preceded by an electrical and/or magnetic signal. -from Author

  3. Modeling sediment delivery from a highly erodible mountain catchment

    NASA Astrophysics Data System (ADS)

    Le Bouteiller, C.; Asif, N. M.; Recking, A.; Liebault, F.

    2015-12-01

    Draix observatory is located in the French Alps on a highly erodible substrate of shale. Most of the observatory is in a badland area characterized by steep gullies and high erosion rates (up to 1cm/year). Within the observatory, the study focuses on the Moulin, which is an 8ha catchment located at an elevation of 850-925m, with 54% of badland area. Available data includes DEM, meteorological data, high-frequency records of discharge and suspended sediment concentration during the floods, cumulative values of bedload transport for each flood, high-frequency records of bedload transport for a few events from a Birkbeck sampler. Modeling sediment delivery in such a catchment is challenging because 1) most available models have been designed for low-relief regions and do not account for steep slope processes such as debris flow and landslides; 2) hydrology (especially flashfloods) in mountainous regions is not well understood; 3) soil properties are very heterogeneous ; 4) multiple time scales are involved: seasonal sediment production on the slopes, storage in the bed and exportation requires to work on yearly times scales, while summer floods and most sediment delivery events occur over a few minutes only. We evaluate the ability of the SHETRAN model to reproduce sediment delivery patterns from the catchment. First, we calibrate the hydrological model using one year of meteorological and hydrological data. We then apply the sediment transport module over several flood events, using in-situ measurements of bed and slope grain-size distributions. Finally we investigate how sediment available on the slopes moves through the catchment over a year. Event-scale volumes of sediment simulated by the model are comparable to observed values within an order of 2. Sediment delivery rates are very sensitive to the slope grain-size distribution. Depending on sediment availability on the slopes and on soil erodibility, the catchment is running either in a supply-limited or

  4. Impaired Presynaptic High-Affinity Choline Transporter Causes a Congenital Myasthenic Syndrome with Episodic Apnea.

    PubMed

    Bauché, Stéphanie; O'Regan, Seana; Azuma, Yoshiteru; Laffargue, Fanny; McMacken, Grace; Sternberg, Damien; Brochier, Guy; Buon, Céline; Bouzidi, Nassima; Topf, Ana; Lacène, Emmanuelle; Remerand, Ganaelle; Beaufrere, Anne-Marie; Pebrel-Richard, Céline; Thevenon, Julien; El Chehadeh-Djebbar, Salima; Faivre, Laurence; Duffourd, Yannis; Ricci, Federica; Mongini, Tiziana; Fiorillo, Chiara; Astrea, Guja; Burloiu, Carmen Magdalena; Butoianu, Niculina; Sandu, Carmen; Servais, Laurent; Bonne, Gisèle; Nelson, Isabelle; Desguerre, Isabelle; Nougues, Marie-Christine; Bœuf, Benoit; Romero, Norma; Laporte, Jocelyn; Boland, Anne; Lechner, Doris; Deleuze, Jean-François; Fontaine, Bertrand; Strochlic, Laure; Lochmuller, Hanns; Eymard, Bruno; Mayer, Michèle; Nicole, Sophie

    2016-09-01

    The neuromuscular junction (NMJ) is one of the best-studied cholinergic synapses. Inherited defects of peripheral neurotransmission result in congenital myasthenic syndromes (CMSs), a clinically and genetically heterogeneous group of rare diseases with fluctuating fatigable muscle weakness as the clinical hallmark. Whole-exome sequencing and Sanger sequencing in six unrelated families identified compound heterozygous and homozygous mutations in SLC5A7 encoding the presynaptic sodium-dependent high-affinity choline transporter 1 (CHT), which is known to be mutated in one dominant form of distal motor neuronopathy (DHMN7A). We identified 11 recessive mutations in SLC5A7 that were associated with a spectrum of severe muscle weakness ranging from a lethal antenatal form of arthrogryposis and severe hypotonia to a neonatal form of CMS with episodic apnea and a favorable prognosis when well managed at the clinical level. As expected given the critical role of CHT for multisystemic cholinergic neurotransmission, autonomic dysfunctions were reported in the antenatal form and cognitive impairment was noticed in half of the persons with the neonatal form. The missense mutations induced a near complete loss of function of CHT activity in cell models. At the human NMJ, a delay in synaptic maturation and an altered maintenance were observed in the antenatal and neonatal forms, respectively. Increased synaptic expression of butyrylcholinesterase was also observed, exposing the dysfunction of cholinergic metabolism when CHT is deficient in vivo. This work broadens the clinical spectrum of human diseases resulting from reduced CHT activity and highlights the complexity of cholinergic metabolism at the synapse. PMID:27569547

  5. Impaired Presynaptic High-Affinity Choline Transporter Causes a Congenital Myasthenic Syndrome with Episodic Apnea.

    PubMed

    Bauché, Stéphanie; O'Regan, Seana; Azuma, Yoshiteru; Laffargue, Fanny; McMacken, Grace; Sternberg, Damien; Brochier, Guy; Buon, Céline; Bouzidi, Nassima; Topf, Ana; Lacène, Emmanuelle; Remerand, Ganaelle; Beaufrere, Anne-Marie; Pebrel-Richard, Céline; Thevenon, Julien; El Chehadeh-Djebbar, Salima; Faivre, Laurence; Duffourd, Yannis; Ricci, Federica; Mongini, Tiziana; Fiorillo, Chiara; Astrea, Guja; Burloiu, Carmen Magdalena; Butoianu, Niculina; Sandu, Carmen; Servais, Laurent; Bonne, Gisèle; Nelson, Isabelle; Desguerre, Isabelle; Nougues, Marie-Christine; Bœuf, Benoit; Romero, Norma; Laporte, Jocelyn; Boland, Anne; Lechner, Doris; Deleuze, Jean-François; Fontaine, Bertrand; Strochlic, Laure; Lochmuller, Hanns; Eymard, Bruno; Mayer, Michèle; Nicole, Sophie

    2016-09-01

    The neuromuscular junction (NMJ) is one of the best-studied cholinergic synapses. Inherited defects of peripheral neurotransmission result in congenital myasthenic syndromes (CMSs), a clinically and genetically heterogeneous group of rare diseases with fluctuating fatigable muscle weakness as the clinical hallmark. Whole-exome sequencing and Sanger sequencing in six unrelated families identified compound heterozygous and homozygous mutations in SLC5A7 encoding the presynaptic sodium-dependent high-affinity choline transporter 1 (CHT), which is known to be mutated in one dominant form of distal motor neuronopathy (DHMN7A). We identified 11 recessive mutations in SLC5A7 that were associated with a spectrum of severe muscle weakness ranging from a lethal antenatal form of arthrogryposis and severe hypotonia to a neonatal form of CMS with episodic apnea and a favorable prognosis when well managed at the clinical level. As expected given the critical role of CHT for multisystemic cholinergic neurotransmission, autonomic dysfunctions were reported in the antenatal form and cognitive impairment was noticed in half of the persons with the neonatal form. The missense mutations induced a near complete loss of function of CHT activity in cell models. At the human NMJ, a delay in synaptic maturation and an altered maintenance were observed in the antenatal and neonatal forms, respectively. Increased synaptic expression of butyrylcholinesterase was also observed, exposing the dysfunction of cholinergic metabolism when CHT is deficient in vivo. This work broadens the clinical spectrum of human diseases resulting from reduced CHT activity and highlights the complexity of cholinergic metabolism at the synapse.

  6. Arsenic sequestration by sorption processes in high-iron sediments

    NASA Astrophysics Data System (ADS)

    Root, Robert A.; Dixit, Suvasis; Campbell, Kate M.; Jew, Adam D.; Hering, Janet G.; O'Day, Peggy A.

    2007-12-01

    High-iron sediments in North Haiwee Reservoir (Olancha, CA), resulting from water treatment for removal of elevated dissolved arsenic in the Los Angeles Aqueduct system, were studied to examine arsenic partitioning between solid phases and porewaters undergoing shallow burial. To reduce arsenic in drinking water supplies, ferric chloride and a cationic polymer coagulant are added to the aqueduct upstream of Haiwee Reservoir, forming an iron-rich floc that scavenges arsenic from the water. Analysis by synchrotron X-ray absorption spectroscopy (XAS) showed that the aqueduct precipitate is an amorphous hydrous ferric oxide (HFO) similar to ferrihydrite, and that arsenic is associated with the floc as adsorbed and/or coprecipitated As(V). Arsenic-rich floc and sediments are deposited along the inlet channel as aqueduct waters enter the reservoir. Sediment core samples were collected in two consecutive years from the edge of the reservoir along the inlet channel using 30- or 90-cm push cores. Cores were analyzed for total and extractable arsenic and iron concentrations. Arsenic and iron speciation and mineralogy in sediments were examined at selected depths by synchrotron XAS and X-ray diffraction (XRD). Sediment-porewater measurements were made adjacent to the core sample sites using polyacrylamide gel probe samplers. Results showed that sediment As(V) is reduced to As(III) in all cores at or near the sediment-water interface (0-4 cm), and only As(III) was observed in deeper sediments. Analyses of EXAFS spectra indicated that arsenic is present in the sediments mostly as a bidentate-binuclear, inner-sphere sorption complex with local atomic geometries similar to those found in laboratory studies. Below about 10 cm depth, XAS indicated that the HFO floc had been reduced to a mixed Fe(II, III) solid with a local structure similar to that of synthetic green rust (GR) but with a slightly contracted average interatomic Fe-Fe distance in the hydroxide layer. There was no

  7. Arsenic Sequestration By Sorption Processes in High-Iron Sediments

    SciTech Connect

    Root, R.A.; Dixit, S.; Campbell, K.M.; Jew, A.D.; Hering, J.G.; O'Day, P.A.

    2009-06-04

    High-iron sediments in North Haiwee Reservoir (Olancha, CA), resulting from water treatment for removal of elevated dissolved arsenic in the Los Angeles Aqueduct system, were studied to examine arsenic partitioning between solid phases and porewaters undergoing shallow burial. To reduce arsenic in drinking water supplies, ferric chloride and a cationic polymer coagulant are added to the aqueduct upstream of Haiwee Reservoir, forming an iron-rich floc that scavenges arsenic from the water. Analysis by synchrotron X-ray absorption spectroscopy (XAS) showed that the aqueduct precipitate is an amorphous hydrous ferric oxide (HFO) similar to ferrihydrite, and that arsenic is associated with the floc as adsorbed and/or coprecipitated As(V). Arsenic-rich floc and sediments are deposited along the inlet channel as aqueduct waters enter the reservoir. Sediment core samples were collected in two consecutive years from the edge of the reservoir along the inlet channel using 30- or 90-cm push cores. Cores were analyzed for total and extractable arsenic and iron concentrations. Arsenic and iron speciation and mineralogy in sediments were examined at selected depths by synchrotron XAS and X-ray diffraction (XRD). Sediment-porewater measurements were made adjacent to the core sample sites using polyacrylamide gel probe samplers. Results showed that sediment As(V) is reduced to As(III) in all cores at or near the sediment-water interface (0--4 cm), and only As(III) was observed in deeper sediments. Analyses of EXAFS spectra indicated that arsenic is present in the sediments mostly as a bidentate-binuclear, inner-sphere sorption complex with local atomic geometries similar to those found in laboratory studies. Below about 10 cm depth, XAS indicated that the HFO floc had been reduced to a mixed Fe(II, III) solid with a local structure similar to that of synthetic green rust (GR) but with a slightly contracted average interatomic Fe-Fe distance in the hydroxide layer. There was no

  8. Episodic bedrock erosion by gully-head migration, Colorado High Plains, USA

    USGS Publications Warehouse

    Rengers, Francis; Tucker, G.E.; Mahan, Shannon

    2016-01-01

    This study explores the frequency of bedrock exposure in a soil-mantled low-relief (i.e. non-mountainous) landscape. In the High Plains of eastern Colorado, gully headcuts are among the few erosional features that will incise through the soil mantle to expose bedrock. We measured the last time of bedrock exposure using optically stimulated luminescence dating of alluvial sediment overlying bedrock in gully headcuts. Our dating suggests that headcuts in adjacent gullies expose bedrock asynchronously, and therefore, the headcuts are unlikely to have been triggered by a base-level drop in the trunk stream. This finding supports the hypothesis that headcuts can develop locally in gullies as a result of focused scour in locations where hydraulic stress during a flash flood is sufficiently high, and/or ground cover is sufficiently weak, to generate a scour hole that undermines vegetation. Alluvium dating also reveals that gullies have been a persistent part of this landscape since the early Holocene. 

  9. Presence of PAHs in water and sediments of the Colombian Cauca River during heavy rain episodes, and implications for risk assessment.

    PubMed

    Sarria-Villa, Rodrigo; Ocampo-Duque, William; Páez, Martha; Schuhmacher, Marta

    2016-01-01

    In Colombia little attention has been paid to river pollution with Polycyclic Aromatic Hydrocarbons (PAHs). Low environmental control and legislation in such emerging region could significantly contribute to high PAHs releases. In this study, we report the presence of PAHs in water and sediments of the Cauca River (Colombia). Three sampling campaigns were carried out between May 2010 and June 2011, and the samples were collected at eight relevant sites. The sampling time included measuring before, during, and after a season of heavy rains, which were influenced by the global coupled ocean-atmospheric phenomenon, which affected tropical countries with huge flooding, commonly called "La Niña", and/or "El Niño" Southern Oscillation (ENSO). The highest mean ∑PAH concentrations were 4476.5 ng/l and 1582.7 ng/g in water and sediments, respectively. The PAHs most detected were Benzo[b]fluoranthene, Benzo[k]fluoranthene, and Pyrene in sediments; and Fluorene, Acenaphtylene, and Anthracene in water. After the season of rains statistically significant higher PAH concentrations were detected. The results of the study were compared to other rivers worldwide at both environmental compartments, and did not show concentrations of special concern. In some sites, concentrations detected of PAHs were higher than screening benchmarks for ecological protection. Estimation of human health risks was carried out, and the results suggested some likely carcinogenic effects due to PAHs especially in children exposed during current recreational swimming and adults working in low technology sand extraction.

  10. The Risk of Tuberculosis Reinfection Soon after Cure of a First Disease Episode Is Extremely High in a Hyperendemic Community

    PubMed Central

    Warren, Robin; van der Spuy, Gian; Hoal, Eileen G.; van Helden, Paul D

    2015-01-01

    Elevated rates of reinfection tuberculosis in various hyperendemic regions have been reported and, in particular, it has been shown that in a high-incidence setting near Cape Town, South Africa, the rate of reinfection tuberculosis (TB) disease after cure of a previous TB disease episode is about four times greater than the rate of first-time TB disease. It is not known whether this elevated rate is caused by a high reinfection rate due, for instance, to living circumstances, or a high rate of progress to disease specific to the patients, or both. In order to address that question we analysed an extensive data set from clinics attended by TB patients in the high-incidence setting near Cape Town, South Africa and found that, in fact, the (average) rate of reinfection (as opposed to the rate of reinfection disease) after cure of a previous TB disease episode is initially about 0.85 per annum. This rate diminishes rapidly over time and after about ten years this rate is similar to the rate of infection in the general population. Also, the rate of progress to disease after reinfection is initially high but declines in subsequent years down to the figure typical for the general population. These findings suggest that the first few months after cure of a TB disease episode form a critical period for controlling reinfection disease in a hyperendemic setting and that monitoring such cured patients could pre-empt a reinfection progressing to active disease. PMID:26649422

  11. High-precision mapping of seismicity in the 2014 Bárdarbunga volcanic episode

    NASA Astrophysics Data System (ADS)

    Vogfjörd, Kristín S.; Hensch, Martin; Gudmundsson, Gunnar B.; Jónsdóttir, Kristín

    2015-04-01

    unbroken crust as the magma intruded. The lateral propagation direction of the seismicity abruptly changes direction along each new segment, sometimes by up to 90 degrees and the propagation was sporadic, advancing with varying speed and sometimes stopping for periods of time. During these times of arrest, continuous low-frequency seismic tremor was sometimes recorded for several hours. A few days following these episodes, depressions appeared on the ice surface, confirming initial assumptions that the tremor was revealing temporary magma-ice interaction on the surface below the glacier. Relative locations of microearthquakes around the caldera rim are much less constrained and their distribution is more diffuse. However, along the southern caldera rim, the events follow the linear trend of the rim and extend to a few km depth. At the northern caldera margin the distribution is more diffuse and appears to dip towards north. An overview will be given of the high-precision locations in the dyke and around the caldera rim and estimation of absolute location accuracies in horizontal and vertical direction discussed. A joint interpretation of the best fitting focal mechanisms with the rifting planes, as defined by the event distribution in the dyke, will also be presented to show the lateral variation in the stress field orientation along the dyke. The high relative, lateral location accuracy in the dyke allows detailed examination of the temporal propagation so some examples of the temporal dyke advance will also be shown. Sigmundsson and 36 others. 2014. Segmented lateral dyke growth in a rifting event at Bárðarbunga volcanic system, Iceland. Nature. doi:10.1038/nature14111.

  12. Multiple episodes of fluid flow in the SW Barents Sea (Loppa High) evidenced by gas flares, pockmarks and gas hydrate accumulation

    NASA Astrophysics Data System (ADS)

    Chand, S.; Thorsnes, T.; Rise, L.; Brunstad, H.; Stoddart, D.; Bøe, R.; Lågstad, P.; Svolsbru, T.

    2012-05-01

    Gas and gas hydrates have gained considerable attention in the last 20 yr due to their possible impact on global climate change from methane escalations. Our study area, the SW Barents Sea, is unique in its evolution due to the effect of glaciations which removed thick layers of sediment from the seabed. Unloading due to erosion and deglaciation resulted in opening of pre-existing faults and creation of new ones, facilitating fluid migration and eventually escape into the water from the subsurface. Expressions of hydrocarbon gas accumulation and fluid flow such as gas hydrates and pockmarks are widely distributed in the Barents Sea. Several gas flares, some of them 200 m high in echograms, occur along a segment of the Ringvassøy Loppa Fault Complex, indicating open fractures and active fluid flow. Observation of gas flares along regional fault complexes outside pockmark regions indicates that present gas escape occurs along faults only. The pockmark formation and gas flares belong to different episodes of fluid flow. The pockmarks are absent outside soft sediment depocentres indicating that their existence is related to the presence of recording medium. The thin sediment cover in pockmarks and their penetration down into glaciomarine sediments indicate that they formed after deposition of these sediments and that fluid escape was active to the very recent past. Methane hydrate stability zone (MHSZ) modelling shows that after the last glacial maximum 18 000-20 000 14C years ago, the MHSZ has thinned from 600 m to zero in most parts of the SW Barents Sea. The fluid expulsion probably happened after retreat of the glaciers causing release of methane from dissociation of methane hydrates through fluid escape processes which lasted until recently. Bottom simulating reflectors (BSR) observed are probably due to structure II hydrates formed from gas containing higher order hydrocarbon components such as ethane, propane, etc. along with methane. The study area falls close

  13. Ionic tracer movement through highly weathered sediments

    NASA Astrophysics Data System (ADS)

    Seaman, J. C.; Bertsch, P. M.; Miller, W. P.

    1995-11-01

    A highly-weathered, sandy aquifer material from the Upper Coastal Plain region of the southeastern U.S.A. (Aiken, South Carolina) was used to determine the impact of ionic strength and solution composition on the determination of physical transport parameters using ionic tracers. The mineralogy of the clay fraction consisted primarily of kaolinite, goethite and mica. Repacked saturated columns (bulk density ˜ 1.5 g cm -3) were leached at a constant rate (˜ 0.25 cm min -1) with a given tracer solution. For comparison, tritium (˜ 200 pCi mL -1) was included in leachate of selected columns and several of the experiments were replicated in columns of acid-washed sand. Pore volume estimates based on tritium breakthrough were consistent with those calculated from the bulk density of the repacked matrix. In contrast, solute breakthrough for the sandy geologic material was dependent on concentration, as well as cation and anion type. At low ionic strenghts (0.0005-0.010 M) that are analogous to conditions that may be encountered ins field-scale transport experiments, neither the cation nor the anion acted conservatively, yielding systematically high estimates of column porosity or low estimates of flow velocity. At the higher ionic strengths (˜ 0.10 M), solute breakthrough was essentially conservative regardless of ionic composition. The impact of cation valence and concentration on Br - breakthrough was determined using MgBr 2 and KBr solutions of varying concentrations (0.001-0.1 N). Bromide breakthrough was substantially delayed for concentrations below 0.10 M and was delayed to a greater extent in the presence of a divalent cation (Mg 2+) than in the presence of a monovalent cation (K +). Failure to recognize these interactions in the field could lead to a false interpretation of Br displacement in terms of physical interactions, i.e. flow velocity, dispersivity, etc.

  14. Better Patient Care At High-Quality Hospitals May Save Medicare Money And Bolster Episode-Based Payment Models.

    PubMed

    Tsai, Thomas C; Greaves, Felix; Zheng, Jie; Orav, E John; Zinner, Michael J; Jha, Ashish K

    2016-09-01

    US policy makers are making efforts to simultaneously improve the quality of and reduce spending on health care through alternative payment models such as bundled payment. Bundled payment models are predicated on the theory that aligning financial incentives for all providers across an episode of care will lower health care spending while improving quality. Whether this is true remains unknown. Using national Medicare fee-for-service claims for the period 2011-12 and data on hospital quality, we evaluated how thirty- and ninety-day episode-based spending were related to two validated measures of surgical quality-patient satisfaction and surgical mortality. We found that patients who had major surgery at high-quality hospitals cost Medicare less than those who had surgery at low-quality institutions, for both thirty- and ninety-day periods. The difference in Medicare spending between low- and high-quality hospitals was driven primarily by postacute care, which accounted for 59.5 percent of the difference in thirty-day episode spending, and readmissions, which accounted for 19.9 percent. These findings suggest that efforts to achieve value through bundled payment should focus on improving care at low-quality hospitals and reducing unnecessary use of postacute care.

  15. Better Patient Care At High-Quality Hospitals May Save Medicare Money And Bolster Episode-Based Payment Models.

    PubMed

    Tsai, Thomas C; Greaves, Felix; Zheng, Jie; Orav, E John; Zinner, Michael J; Jha, Ashish K

    2016-09-01

    US policy makers are making efforts to simultaneously improve the quality of and reduce spending on health care through alternative payment models such as bundled payment. Bundled payment models are predicated on the theory that aligning financial incentives for all providers across an episode of care will lower health care spending while improving quality. Whether this is true remains unknown. Using national Medicare fee-for-service claims for the period 2011-12 and data on hospital quality, we evaluated how thirty- and ninety-day episode-based spending were related to two validated measures of surgical quality-patient satisfaction and surgical mortality. We found that patients who had major surgery at high-quality hospitals cost Medicare less than those who had surgery at low-quality institutions, for both thirty- and ninety-day periods. The difference in Medicare spending between low- and high-quality hospitals was driven primarily by postacute care, which accounted for 59.5 percent of the difference in thirty-day episode spending, and readmissions, which accounted for 19.9 percent. These findings suggest that efforts to achieve value through bundled payment should focus on improving care at low-quality hospitals and reducing unnecessary use of postacute care. PMID:27605651

  16. Using Geochemical Indicators to Distinguish High Biogeochemical Activity in Sediments

    NASA Astrophysics Data System (ADS)

    Kenwell, A. M.; Navarre-Sitchler, A.; Prugue, R.; Spear, J. R.; Williams, K. H.; Maxwell, R. M.

    2014-12-01

    A better understanding of how microbial communities interact with their surroundings in physically and chemically heterogeneous subsurface environments will lead to improved quantification of biogeochemical reactions and associated nutrient cycling. This study develops a methodology to predict elevated rates of biogeochemical activity (microbial "hotspots") in subsurface environments by correlating microbial community structure with the spatial distribution of geochemical indicators in subsurface sediments. Statistical hierarchical cluster analyses (HCA) of X-ray fluorescence (XRF), simulated precipitation leachate, bioavailable Fe and Mn, total organic carbon (TOC), microbial community structure, grain size, bulk density and moisture content data were used to identify regions of the subsurface characterized by biogeochemical hotspots and sample characteristics indicative of these hotspots within fluvially-derived aquifer sediments. The methodology has been applied to (a) alluvial materials collected at a former uranium mill site near Rifle, Colorado and (b) relatively undisturbed floodplain deposits (soils and sediments) collected along the East River near Crested Butte, Colorado. At Rifle, 33 sediment samples were taken from 8 sediment cores and at the East River 33 soil/sediment samples were collected across and perpendicular to 3 active meanders. The East River watershed exhibits characteristic fluvial progression and serves as a representative example of many headwater catchments with the upper Colorado River basin. Initial clustering revealed that operationally defined hotspots were characterized by high organic carbon, bioavailable iron and dark colors but not necessarily low hydraulic conductivity. Applying the method to identify hotspots in both contaminated and natural floodplain deposits and their associated alluvial aquifers demonstrates the broad applicability of a geochemical indicator based approach.

  17. Presence of PAHs in water and sediments of the Colombian Cauca River during heavy rain episodes, and implications for risk assessment.

    PubMed

    Sarria-Villa, Rodrigo; Ocampo-Duque, William; Páez, Martha; Schuhmacher, Marta

    2016-01-01

    In Colombia little attention has been paid to river pollution with Polycyclic Aromatic Hydrocarbons (PAHs). Low environmental control and legislation in such emerging region could significantly contribute to high PAHs releases. In this study, we report the presence of PAHs in water and sediments of the Cauca River (Colombia). Three sampling campaigns were carried out between May 2010 and June 2011, and the samples were collected at eight relevant sites. The sampling time included measuring before, during, and after a season of heavy rains, which were influenced by the global coupled ocean-atmospheric phenomenon, which affected tropical countries with huge flooding, commonly called "La Niña", and/or "El Niño" Southern Oscillation (ENSO). The highest mean ∑PAH concentrations were 4476.5 ng/l and 1582.7 ng/g in water and sediments, respectively. The PAHs most detected were Benzo[b]fluoranthene, Benzo[k]fluoranthene, and Pyrene in sediments; and Fluorene, Acenaphtylene, and Anthracene in water. After the season of rains statistically significant higher PAH concentrations were detected. The results of the study were compared to other rivers worldwide at both environmental compartments, and did not show concentrations of special concern. In some sites, concentrations detected of PAHs were higher than screening benchmarks for ecological protection. Estimation of human health risks was carried out, and the results suggested some likely carcinogenic effects due to PAHs especially in children exposed during current recreational swimming and adults working in low technology sand extraction. PMID:26303092

  18. Non-Verbal Episodic Memory Deficits in Primary Progressive Aphasias are Highly Predictive of Underlying Amyloid Pathology.

    PubMed

    Ramanan, Siddharth; Flanagan, Emma; Leyton, Cristian E; Villemagne, Victor L; Rowe, Christopher C; Hodges, John R; Hornberger, Michael

    2016-01-01

    Diagnostic distinction of primary progressive aphasias (PPA) remains challenging, in particular for the logopenic (lvPPA) and nonfluent/agrammatic (naPPA) variants. Recent findings highlight that episodic memory deficits appear to discriminate these PPA variants from each other, as only lvPPA perform poorly on these tasks while having underlying amyloid pathology similar to that seen in amnestic dementias like Alzheimer's disease (AD). Most memory tests are, however, language based and thus potentially confounded by the prevalent language deficits in PPA. The current study investigated this issue across PPA variants by contrasting verbal and non-verbal episodic memory measures while controlling for their performance on a language subtest of a general cognitive screen. A total of 203 participants were included (25 lvPPA; 29 naPPA; 59 AD; 90 controls) and underwent extensive verbal and non-verbal episodic memory testing, with a subset of patients (n = 45) with confirmed amyloid profiles as assessed by Pittsburgh Compound B and PET. The most powerful discriminator between naPPA and lvPPA patients was a non-verbal recall measure (Rey Complex Figure delayed recall), with 81% of PPA patients classified correctly at presentation. Importantly, AD and lvPPA patients performed comparably on this measure, further highlighting the importance of underlying amyloid pathology in episodic memory profiles. The findings demonstrate that non-verbal recall emerges as the best discriminator of lvPPA and naPPA when controlling for language deficits in high load amyloid PPA cases.

  19. Non-Verbal Episodic Memory Deficits in Primary Progressive Aphasias are Highly Predictive of Underlying Amyloid Pathology.

    PubMed

    Ramanan, Siddharth; Flanagan, Emma; Leyton, Cristian E; Villemagne, Victor L; Rowe, Christopher C; Hodges, John R; Hornberger, Michael

    2016-01-01

    Diagnostic distinction of primary progressive aphasias (PPA) remains challenging, in particular for the logopenic (lvPPA) and nonfluent/agrammatic (naPPA) variants. Recent findings highlight that episodic memory deficits appear to discriminate these PPA variants from each other, as only lvPPA perform poorly on these tasks while having underlying amyloid pathology similar to that seen in amnestic dementias like Alzheimer's disease (AD). Most memory tests are, however, language based and thus potentially confounded by the prevalent language deficits in PPA. The current study investigated this issue across PPA variants by contrasting verbal and non-verbal episodic memory measures while controlling for their performance on a language subtest of a general cognitive screen. A total of 203 participants were included (25 lvPPA; 29 naPPA; 59 AD; 90 controls) and underwent extensive verbal and non-verbal episodic memory testing, with a subset of patients (n = 45) with confirmed amyloid profiles as assessed by Pittsburgh Compound B and PET. The most powerful discriminator between naPPA and lvPPA patients was a non-verbal recall measure (Rey Complex Figure delayed recall), with 81% of PPA patients classified correctly at presentation. Importantly, AD and lvPPA patients performed comparably on this measure, further highlighting the importance of underlying amyloid pathology in episodic memory profiles. The findings demonstrate that non-verbal recall emerges as the best discriminator of lvPPA and naPPA when controlling for language deficits in high load amyloid PPA cases. PMID:26890745

  20. Mudstone sedimentation at high latitudes: Ice as a transport medium for mud and supplier of nutrients

    USGS Publications Warehouse

    Macquaker, J.H.S.; Keller, M.A.

    2005-01-01

    in the Early Cretaceous the outsized grains are interpreted to have been deposited from a combination of melting, dirty anchor, and fast ice. The mud fraction, which forms the bulk of the sediment, is interpreted to have been deposited from melting, sediment-laden frazil ice, and fast ice. After deposition sediments were partially reworked by bottom currents generated by brine rejection during sea ice formation. Sympagic organisms, grazing on algae and bacteria both within and below the ice, pelleted the sediment. Bioturbation, which varies through the succession, indicates that sedimentation probably occurred beneath a predominantly oxic or dysoxic water column. In this setting productivity was fueled by nutrients released from melting sea ice in the marginal ice zone. The good petroleum source potential of these mudstones is attributed to high organic productivity coupled to episodic and rapid sedimentation rather than existence of bottom-water anoxia linked to upwelling. Because sea-ice rafting was probably the dominant sediment transport mechanism it is not appropriate to use sequence stratigraphic methodology to predict lithofacies variability in this environment. Copyright ?? 2005, SEPM (Society for Sedimentary Geology).

  1. Crevasse-splay sedimentation processes revealed through high resolution modelling

    NASA Astrophysics Data System (ADS)

    Hackney, Christopher; Darby, Stephen; Parsons, Daniel; Leyland, Julian; Aalto, Rolf; Nicholas, Andrew; Best, Jim

    2015-04-01

    During rapid rise flood events, crevasse-splay complexes are a dominant conduit through which sediment and water are passed from the main channel onto the floodplain, particularly for large rivers. These crevasse-splay systems are, therefore, key in controlling rates of floodplain sedimentation, as well as conditioning the location of avulsions. Despite recent advances in our capabilities to model the development and evolution of these systems, our understanding of the passage, storage and reworking of water and sediment across them remains relatively poor. A key limitation concerns the point that, since floodplain topography is a first-order control on the hydrodynamics of crevasse-splays, publicly available topographic data sets (e.g. SRTM) are currently unable to resolve key processes at the necessary spatial resolution. Here we employ Structure-from-Motion (SfM) on low-level aerial photography to obtain high-resolution (3m grid cell) georectified topographic data (horizontal error = 0.02 m; vertical error = 0.5 m) for a series of three representative crevasse-splay complexes located along the Mekong River, Cambodia. We use the coupled hydrodynamic and morphodynamic model, Delft-3D to simulate sedimentation patterns for a series of flood events. We model floodplain deposition and erosion and validate simulated spatial and temporal variations against observed patterns. We show how the spatial and temporal patterns of floodplain development via crevasse-splays are conditioned by key hydrological characteristics.

  2. High resolution monitoring of episodic stratification events in an enclosed marine system

    NASA Astrophysics Data System (ADS)

    Sullivan, Timothy; Broszeit, Stefanie; O'Sullivan, Keith P. A.; McAllen, Rob; Davenport, John; Regan, Fiona

    2013-05-01

    While hypoxic and anoxic environments have existed throughout geological time, their frequency of occurrence in shallow coastal and estuarine areas appears to be increasing. However, few data are available on the physicochemical conditions at the boundary between anoxic and normoxic layers, including the conditions required for both formation and dissipation of stratification. Advances in autonomous environmental sensing technology have produced robust sensors capable of detailed measurements under inhospitable conditions created in such environments. In this study, an autonomous sensor approach was used to compare water column properties above and below the stratification before during and after dissipation of the stratification. Further, an investigation into the effect of the stratification on sedimentation rates of organic and inorganic matter and current speeds is reported here. Lough Hyne, a seasonally stratified temperate marine lake provided favourable conditions for this study. It was shown that temperatures dropped rapidly above the oxy-thermocline while increasing rapidly below the stratification, leading to a mixing of the complete water column. This was reflected in oxygen measurements below the stratification, which rose from anoxia to normoxic conditions over the same time period. During summer, the thermocline formed a barrier to organic matter sedimentation, reducing it significantly when present, while inorganic matter sedimentation was unaffected by the presence of thermocline. It also caused a reduction in current speeds below the thermocline.

  3. Investigation of Ground-Level Ozone and High-Pollution Episodes in a Megacity of Eastern China.

    PubMed

    Zhao, Heng; Wang, Shanshan; Wang, Wenxin; Liu, Rui; Zhou, Bin

    2015-01-01

    Differential Optical Absorption Spectroscopy (DOAS) was used for the long-term observation of ground-level ozone (O3) from March 2010 to March 2013 over Shanghai, China. The 1-hour average concentration of O3 was 27.2 ± 17.0 ppbv. O3 level increased during spring, reached the peak in late spring and early summer, and then decreased in autumn and finally dropped to the bottom in winter. The highest monthly average O3 concentration in June (41.1 ppbv) was nearly three times as high as the lowest level recorded in December (15.2 ppbv). In terms of pollution episodes, 56 hourly samples (on 14 separate days) in 2010 exceeded the 1-hour ozone limit of 200 μg/m3 specified by the Grade II of the Chinese Ambient Air Quality Standards (CAAQS, revised GB 3095-2012). Utilizing the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model, the primary contribution to high ozone days (HODs) was identified as the regional transportation of volatile organic compounds (VOC) and high concentrations of O3 from the chemical industrial zone in the Jinshan district of Shanghai. HODs showed higher concentrations of HONO and NO2 than non-episode conditions, implying that HONO at high concentration during HODs was capable of increasing the O3 concentration. The photolysis rate of HONO was estimated, suggesting that the larger number of OH radicals resulting from high concentrations of HONO have a considerable impact on ozone concentrations. PMID:26121146

  4. Investigation of Ground-Level Ozone and High-Pollution Episodes in a Megacity of Eastern China.

    PubMed

    Zhao, Heng; Wang, Shanshan; Wang, Wenxin; Liu, Rui; Zhou, Bin

    2015-01-01

    Differential Optical Absorption Spectroscopy (DOAS) was used for the long-term observation of ground-level ozone (O3) from March 2010 to March 2013 over Shanghai, China. The 1-hour average concentration of O3 was 27.2 ± 17.0 ppbv. O3 level increased during spring, reached the peak in late spring and early summer, and then decreased in autumn and finally dropped to the bottom in winter. The highest monthly average O3 concentration in June (41.1 ppbv) was nearly three times as high as the lowest level recorded in December (15.2 ppbv). In terms of pollution episodes, 56 hourly samples (on 14 separate days) in 2010 exceeded the 1-hour ozone limit of 200 μg/m3 specified by the Grade II of the Chinese Ambient Air Quality Standards (CAAQS, revised GB 3095-2012). Utilizing the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model, the primary contribution to high ozone days (HODs) was identified as the regional transportation of volatile organic compounds (VOC) and high concentrations of O3 from the chemical industrial zone in the Jinshan district of Shanghai. HODs showed higher concentrations of HONO and NO2 than non-episode conditions, implying that HONO at high concentration during HODs was capable of increasing the O3 concentration. The photolysis rate of HONO was estimated, suggesting that the larger number of OH radicals resulting from high concentrations of HONO have a considerable impact on ozone concentrations.

  5. Investigation of Ground-Level Ozone and High-Pollution Episodes in a Megacity of Eastern China

    PubMed Central

    Zhao, Heng; Wang, Shanshan; Wang, Wenxin; Liu, Rui; Zhou, Bin

    2015-01-01

    Differential Optical Absorption Spectroscopy (DOAS) was used for the long-term observation of ground-level ozone (O3) from March 2010 to March 2013 over Shanghai, China. The 1-hour average concentration of O3 was 27.2 ± 17.0 ppbv. O3 level increased during spring, reached the peak in late spring and early summer, and then decreased in autumn and finally dropped to the bottom in winter. The highest monthly average O3 concentration in June (41.1 ppbv) was nearly three times as high as the lowest level recorded in December (15.2 ppbv). In terms of pollution episodes, 56 hourly samples (on 14 separate days) in 2010 exceeded the 1-hour ozone limit of 200 μg/m3 specified by the Grade II of the Chinese Ambient Air Quality Standards (CAAQS, revised GB 3095-2012). Utilizing the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model, the primary contribution to high ozone days (HODs) was identified as the regional transportation of volatile organic compounds (VOC) and high concentrations of O3 from the chemical industrial zone in the Jinshan district of Shanghai. HODs showed higher concentrations of HONO and NO2 than non-episode conditions, implying that HONO at high concentration during HODs was capable of increasing the O3 concentration. The photolysis rate of HONO was estimated, suggesting that the larger number of OH radicals resulting from high concentrations of HONO have a considerable impact on ozone concentrations. PMID:26121146

  6. Rejection episodes.

    PubMed

    Koyama, H; Cecka, J M

    1992-01-01

    Based upon analyses of 40,671 kidney transplants reported to the UNOS Scientific Renal Transplant Registry between October 1987 and August 1992: 1. Twenty-four percent of the 21,923 recipients of first cadaver grafts experienced one or more rejection episodes during their transplant hospitalization, 52% during the first 6 months. At 12 months, only 40% of patients remained rejection-free. Patients who experienced any rejection during the first 6 months had a 72% 1-year graft survival rate compared with 95% for those who remained rejection-free (p < 0.001). 2. Recipients of transplants from living donors had a significantly lower incidence of rejection episodes. There was a clear effect of histocompatibility in comparing the incidence of rejection in HLA-identical sibling transplants (8% at discharge and 32% at 1 year) with that in 1-haplotype disparate transplants (22% at discharge and 52% at 1 year, p < 0.01 at each time point). Rejections were reported for 25% of transplants from other living donors at discharge and for 56% at 1 year, similar to the figures for cadaver transplants. 3. Histocompatibility also influenced the incidence of rejection in first cadaver-donor transplants. Only 15% of recipients of 0-HLA-A,B mismatched kidneys had rejection episodes reported at discharge, compared with 26% of those who received kidneys completely mismatched for HLA-A,B antigens (p < 0.01). At 1 year, 56% of HLA-A,B matched patients remained rejection-free, whereas only 35% of those mismatched for 4 antigens had no reported rejection through the first year (p < 0.01). Considering HLA-DR antigen mismatches, 19% of the 0-antigen mismatched group had rejection episodes at discharge, versus 28% for those with 2 HLA-DR mismatches (p < 0.01), and at 1 year, the percentage who were rejection-free decreased from 48% to 40% and 34% with 0, 1, and 2 HLA-DR mismatches, respectively. 4. The incidence of rejection episodes decreased as the recipient's age increased. Patients under age

  7. Effect of high sedimentation rates on surface sediment dynamics and mangrove growth in the Porong River, Indonesia.

    PubMed

    Sidik, Frida; Neil, David; Lovelock, Catherine E

    2016-06-15

    Large quantities of mud from the LUSI (Lumpur Sidoarjo) volcano in northeastern Java have been channeled to the sea causing high rates of sediment delivery to the mouth of the Porong River, which has a cover of natural and planted mangroves. This study investigated how the high rates of sediment delivery affected vertical accretion, surface elevation change and the growth of Avicennia sp., the dominant mangrove species in the region. During our observations in 2010-2011 (4-5years after the initial volcanic eruption), very high rates of sedimentation in the forests at the mouth of the river gave rise to high vertical accretion of over 10cmy(-1). The high sedimentation rates not only resulted in reduced growth of Avicennia sp. mangrove trees at the two study sites at the Porong River mouth, but also gave rise to high soil surface elevation gains. PMID:27048688

  8. Effect of high sedimentation rates on surface sediment dynamics and mangrove growth in the Porong River, Indonesia.

    PubMed

    Sidik, Frida; Neil, David; Lovelock, Catherine E

    2016-06-15

    Large quantities of mud from the LUSI (Lumpur Sidoarjo) volcano in northeastern Java have been channeled to the sea causing high rates of sediment delivery to the mouth of the Porong River, which has a cover of natural and planted mangroves. This study investigated how the high rates of sediment delivery affected vertical accretion, surface elevation change and the growth of Avicennia sp., the dominant mangrove species in the region. During our observations in 2010-2011 (4-5years after the initial volcanic eruption), very high rates of sedimentation in the forests at the mouth of the river gave rise to high vertical accretion of over 10cmy(-1). The high sedimentation rates not only resulted in reduced growth of Avicennia sp. mangrove trees at the two study sites at the Porong River mouth, but also gave rise to high soil surface elevation gains.

  9. High resolution microprofiling, fractionation and speciation at sediment water interfaces

    NASA Astrophysics Data System (ADS)

    Fabricius, Anne-Lena; Duester, Lars; Ecker, Dennis; Ternes, Thomas A.

    2016-04-01

    Within aquatic environments, the exchange between the sediment and the overlaying water is often driven by steep gradients of, e.g., the oxygen concentration, the redox potential or the pH value at the sediment water interface (SWI). Important transport processes at the SWI are sedimentation and resuspension of particulate matter and diffusional fluxes of dissolved substances. To gain a better understanding of the key factors and processes determining the fate of substances at the SWI, methods with a spatial high resolution are required that enable the investigation of several sediment parameters in parallel to different analytes of interest in the sediment pore water. Moreover, beside the total content, questions concerning the speciation and fractionation are of concern in studying the different (transport) processes. Due to the availability of numerous micro-sensors and -electrodes (e.g., O2, redox potential, pH value, H2S, N2O) and the development of methods for pore water sampling [1], the toolbox to study the heterogeneous and often dynamic conditions at the SWI at a sub-millimetre scale were considerably improved. Nevertheless, the methods available for pore water sampling often require the installation of the sampling devices at the sampling site and/or intensive preparation procedures that may influence the conditions at the area studied and/or the characteristics of the samples taken. By combination of a micro profiling system with a new micro filtration probe head connected to a pump and a fraction collector, a micro profiling and micro sampling system ("missy") was developed that enables for the first time a direct, automate and low invasive sampling of small volumes (<500 μL) at a spatial high resolution of a few millimetres to sub-millimetres [2]. Via the application of different sample preparation procedures followed by inductively plasma-mass spectrometry analyses, it was possible to address not only the total content of metal(loid)s, but also

  10. Unusual carbon and oxygen isotropic ratios of ostracodal calcite from last interglacial (Sangamon episode) lacustrine sediment in Raymond Basin, Illinois, USA

    USGS Publications Warehouse

    Curry, B. Brandon; Anderson, T.F.; Lohmann, K.C.

    1997-01-01

    The stable isotopic records of ostracode valves deposited during the last interglaciation in Raymond Basin, Illinois, have ??13C and ??18O values as high as +16.5??? and +9.2??? respectively, the highest values yet reported from continental ostracodal calcite. Located in south-central Illinois, Raymond, Pittsburgh, Bald Knob, and Hopwood Farm basins collectively have yielded important long pollen and ostracode records that date from about 130 000 years ago to the present. Although fossils from the present-day interglaciation are not well preserved, these records constitute the only described, conformable, fossiliferous successions of this age from the interior of glaciated North America. The high ??13C values from Raymond Basin are attributed to the residual effects of methane loss either by ebullition or by emission through the stems of senescent emergent aquatic vegetation. A mass balance model suggests that an increase in ??13C of dissolved inorganic carbon on the order of +15??? is possible within a few hours given modest rates of methanogenesis of about 0.02 mol m-2 d-1. The ??13C records from other studies of ostracode valves have values approaching, but not exceeding about +14??? suggesting a limiting value to ???13C enrichment due to simultaneous inputs and outputs of dissolved inorganic carbon. Values of ??18O in ostracodal calcite are quite variable (-4 to +9???) in sediment from the late Sangamon subepisode. A model of isotopic enrichment in a desiccating water body implies that a reduction in reservoir volume of 20% could produce this range of isotopic values. High humidity and evaporation probably account for most of the ??18O variability.

  11. Influence of trans-boundary air pollution from China on multi-day high PM10 episodes in Seoul, Korea

    NASA Astrophysics Data System (ADS)

    Oh, H. R.; Ho, C. H.; Kim, J.; Chen, D.; Lee, S.; Choi, Y. S.; Chang, L. S.; Song, C. K.

    2014-12-01

    Air quality problems have become a serious global issue as it causes over 3 million deaths per year all over the world. With generations of massive air pollutants in China, the effects of trans-boundary transports of air pollutants on human health have become a serious international concern in East Asia. However, only a limited number of studies are available for providing scientific evidences for quantifying the sources and transports of air pollutants over major countries in East Asia. Here, it is shown that particulate matters originated from China played major role in the occurrence of multi-day (≥ 4 days) severe air pollution episodes in Seoul, Korea, in which the concentration of particulate matter of diameters ≤ 10 μm exceeds 100 μg m-3. Observations show that these multi-day severe air quality episodes occur when a strong high-pressure system resides over the eastern China - Korea region. Such a weather condition confines air pollutants within the atmospheric boundary layer and spread them by slow westerlies within the boundary layer from China into the neighboring countries. Understanding such dynamical processes is a key for advancing the predictability of trans-boundary air pollutants and their health impacts in East Asia as well as developing international measures to improve air quality for the region.

  12. The Effects of Runaway-Homeless Episodes on High School Dropout

    ERIC Educational Resources Information Center

    Aratani, Yumiko; Cooper, Janice L.

    2015-01-01

    This article uses data from the National Longitudinal Survey of Youth 1997 to examine the relationship between running away from home between the ages of 12 and 14 and dropping from high school among youth. Propensity score matching was conducted in estimating the effect of running away on high school dropout while controlling for confounding…

  13. Changes in distribution of fine sediments in the hyporheic zone during high flow events

    NASA Astrophysics Data System (ADS)

    Kasahara, T.; Yasuda, Y.; Otsuki, K.

    2013-12-01

    Streambed sediments are dynamic, influencing stream-groundwater exchange. Reduction of the exchange flow due to streambed clogging by fine sediments has been reported in impacted agricultural and urban streams. In natural streams, intrusion of fine sediments and subsequent clogging may occur, but its effects are expected to be temporary due to the periodical washout of fine sediments. Understanding the dynamics of fine sediments in shallow streambed in natural streams is important in studying stream-groundwater exchange and in designing of management practices of impacted streams. In this study, we focused on shallow streambed, less than 25cm depth, where hyporheic exchange occurs. The concentrations of fine sediments in interstitial water were measured, using PVC pipes, to study the change in fine sediments distribution in the streambed during high flow events. We also measured the sediment accumulation on the streambed, using mesh, to study the linkage between the locations of surface accumulation and fine sediment intrusion. The study site was located in a 3rd order stream with gravel-cobble bed and base flow of about 80 L/s in northern Kyushu Island of Japan. The concentration of fine sediments in the interstitial water varied considerably among sampling locations, ranging from 38mg/L to over 200mg/L with an average of 120mg/L. The concentrations increased after high flow event, with an average of 3g/L in some event, and they were higher in the locations with negative vertical head gradient, indicating that the downwelling flow carrying fine sediments into the interstitial zone. Streambed sediment accumulation showed relation with fine sediment concentration, and also with water depth and velocity, suggesting that the surface channel condition may indicate the locations of fine sediments intrusion in the interstitial zone. The results of this study showed that fine sediment distribution in the shallow streambed changes considerably during high flow events, and

  14. Can Ultra-violet Mie Lidar Be an Effective Instrument During High Pollution Episode?

    NASA Astrophysics Data System (ADS)

    Liu, Qiaojun; Wang, Zhangjun; Du, Libin; Cheng, Andrew Yuk Sun; Meng, Xiangqian; Chen, Chao; Li, Xianxin; Liu, Xingtao

    2016-06-01

    Vertical profiles of particulates were measured by a 355 nm Mie scattering lidar during a dust-storm event. A high energy pulse laser was employed as the light source to detect the extinction coefficient in the altitude up to 6 km in the day and 9 km at night. The extinction profiles showed layers of high aerosol concentrations in good agreement with ground-based pollution measurements, which indicated that such ultra-violet lidar is a very useful remote sensing instrument for monitoring extinction profiles during extreme high aerosol loading and low visibility atmospheric conditions when low energy lidar systems cannot obtain effective results.

  15. EPISODIC EVENTS: THE EFFECT OF FLOODS ON NUTRIENT TRANSPORT IN A NORTHWESTERN, USA ESTUARY

    EPA Science Inventory

    To estimate the effects of storms on nutrient transport, dissolved nutrients and suspended sediment loads were measured relative to stream discharge in the Yaquina River, OR for three storm events. Episodic events, particularly high rainfall or flood events may transport high di...

  16. Migration of objects and inferences across episodes.

    PubMed

    Hannigan, Sharon L; Reinitz, Mark Tippens

    2003-04-01

    Participants viewed episodes in the form of a series of photographs portraying ordinary routines (e.g., eating at a restaurant) and later received a recognition test. In Experiment 1, it was shown that objects (e.g., a vase of flowers, a pewter lantern) that appeared in a single episode during the study phase migrated between memories of episodes described by the same abstract schema (e.g., from Restaurant Episode A at study to Restaurant Episode B at test), and not between episodes anchored by different schemas. In Experiment 2, it was demonstrated that backward causal inferences from one study episode influenced memories of other episodes described by the same schema, and that high-schema-relevant items viewed in one episode were sometimes remembered as having occurred in another episode of the same schematic type.

  17. Migration of objects and inferences across episodes.

    PubMed

    Hannigan, Sharon L; Reinitz, Mark Tippens

    2003-04-01

    Participants viewed episodes in the form of a series of photographs portraying ordinary routines (e.g., eating at a restaurant) and later received a recognition test. In Experiment 1, it was shown that objects (e.g., a vase of flowers, a pewter lantern) that appeared in a single episode during the study phase migrated between memories of episodes described by the same abstract schema (e.g., from Restaurant Episode A at study to Restaurant Episode B at test), and not between episodes anchored by different schemas. In Experiment 2, it was demonstrated that backward causal inferences from one study episode influenced memories of other episodes described by the same schema, and that high-schema-relevant items viewed in one episode were sometimes remembered as having occurred in another episode of the same schematic type. PMID:12795485

  18. Human intracranial high-frequency activity maps episodic memory formation in space and time.

    PubMed

    Burke, John F; Long, Nicole M; Zaghloul, Kareem A; Sharan, Ashwini D; Sperling, Michael R; Kahana, Michael J

    2014-01-15

    Noninvasive neuroimaging studies have revealed a network of brain regions that activate during human memory encoding; however, the relative timing of such activations remains unknown. Here we used intracranially recorded high-frequency activity (HFA) to first identify regions that activate during successful encoding. Then, we leveraged the high-temporal precision of HFA to investigate the timing of such activations. We found that memory encoding invokes two spatiotemporally distinct activations: early increases in HFA that involve the ventral visual pathway as well as the medial temporal lobe and late increases in HFA that involve the left inferior frontal gyrus, left posterior parietal cortex, and left ventrolateral temporal cortex. We speculate that these activations reflect higher-order visual processing and top-down modulation of attention/semantic information, respectively.

  19. The Meteorology and Chemistry of High Nitric-Acid Episodes at the South Pole

    NASA Astrophysics Data System (ADS)

    Neff, William; Davis, Douglas

    2016-04-01

    Between 1998 and 2007, a series of field experiments carried out at the South Pole and with aircraft over a wider area revealed a very chemically active boundary layer overlying the east Antarctic ice sheet during the Austral summer. An early discovery was unexpectedly high concentrations of nitric acid (NO) at the South Pole. These were argued to be a result of the UV pholoysis of reactive nitrogen in surface and/or near-surface snow followed by subsequent confinement and non-linear HOx/NOx chemistry within a thin stable atmospheric boundary layer. The concentrations of NO also demonstrated daily, intraseasonal, as well as interannual variability as seen in the four field programs. This paper seeks to elucidate the interplay of large-to-small scale meteorology and chemistry at the South Pole that leads to highly variable NO concentrations and to examine boundary layer depth effects on NO in years when no direct measurements were available, in particular during the latest field program in 2006-2007. The importance of the South Pole is that it, unlike other high-latitude sites, has no diurnal cycle to disturb the evolution of the mostly stable boundary layer and its physics and chemistry. In the spring, as the solar elevation angle increases, nitrate photolysis rates increase. At the same time, the stratospheric vortex warms and with its breakup, the total column ozone increases leading to decreased photolysis rates. In addition, following the formation of the thermal tropopause in early spring, the tropospheric circulation over Antarctica changes dramatically, affecting the transport and dominant source regions for warm air and clouds arriving at the South Pole. The timing of the final warming ranged from early-November to mid-December for the four field experiment years. During the 30 days prior to the final increase in column ozone, as the thermal tropopause forms (~100 hPa), the winds at 300 hPa become bimodal, either along the eastern side of the Weddell Sea

  20. High concentration suspended sediment measurments using acontinuous fiber optic in-stream transmissometer

    SciTech Connect

    Campbell, Chris G.; Laycak, Danny T.; Hoppes, William; Tran,Nguyen T.; Shi, Frank G.

    2004-05-26

    Suspended sediment loads mobilized during high flow periods in rivers and streams are largely uncharacterized. In smaller and intermittent streams, a large storm may transport a majority of the annual sediment budget. Therefore monitoring techniques that can measure high suspended sediment concentrations at semi-continuous time intervals are needed. A Fiber optic In-stream Transmissometer (FIT) is presented for continuous measurement of high concentration suspended sediment in storm runoff. FIT performance and precision were demonstrated to be reasonably good for suspended sediment concentrations up to 10g/L. The FIT was compared to two commercially available turbidity devices and provided better precision and accuracy at both high and low concentrations. Both turbidity devices were unable to collect measurements at concentrations greater than 4 g/L. The FIT and turbidity measurements were sensitive to sediment particle size. Particle size dependence of transmittance and turbidity measurement poses the greatest problem for calibration to suspended sediment concentration. While the FIT was demonstrated to provide acceptable measurements of high suspended sediment concentrations, approaches to real-time suspended sediment detection need to address the particle size dependence in concentration measurements.

  1. A high ozone episode in winter 2013 in the Uinta Basin oil and gas region characterized by aircraft measurements

    NASA Astrophysics Data System (ADS)

    Oltmans, S. J.; Karion, A.; Schnell, R. C.; Pétron, G.; Sweeney, C.; Wolter, S.; Neff, D.; Montzka, S. A.; Miller, B. R.; Helmig, D.; Johnson, B. J.; Hueber, J.

    2014-08-01

    During the winter of 2012-2013 atmospheric surface ozone mole fractions exceeded the US 8 h standard of 75 ppb on 39 days in the Uinta Basin of Utah. As part of the Uinta Basin Winter Ozone Study (UBWOS) aircraft flights were conducted throughout the basin with continuous measurements of ozone (O3), methane (CH4), carbon dioxide (CO2), carbon monoxide (CO), nitrogen dioxide (NO2), and discrete whole air flask samples for determination of ∼50 trace gases including a number of non-methane hydrocarbons (NMHCs). During the course of seven flights conducted between 31 January and 7 February 2013, coinciding with strong, multi-day temperature inversions, O3 levels gradually built up in the shallow boundary layer from ∼45 ppb to ∼140 ppb. Near-surface CH4 mole fractions increased during the episode from near background levels of ∼2 ppm to over 10 ppm. Based on elevated levels of CH4 across the basin and high correlations of CH4 with NMHCs from the discrete air samples, O3 precursor NMHCs were also inferred to be elevated throughout the basin. Discrete plumes of high NO2 were observed in the gas production region of the basin suggesting that gas processing plants and compressor facilities were important point sources of reactive nitrogen oxides (NOx). Vertical profiles obtained during the flights showed that the high O3 mole fractions (as well as other elevated constituents) were confined to a shallow layer from near the ground to 300-400 m above ground level (m a.g.l.) capped by a strong temperature inversion. The highest mole fractions of the measured constituents during the study period were in an isothermal cold layer that varied from ∼300 m depth on 4 February to ∼150 m on 5 February. A gradient layer with declining mole fractions with altitude extended above the isothermal layer to ∼1900 m a.s.l. (300-400 m a.g.l.) indicative of some mixing of air out of the boundary layer. O3 mole fractions continued to increase within the basin as the

  2. Eruption dynamics and degassing histories of high fountaining episodes of the Pu`u `O`o eruption in the East Rift Zone of Kilauea, 1983-1986

    NASA Astrophysics Data System (ADS)

    Holt, S. J.; Carey, R.; Houghton, B. F.; Swanson, D. A.; Orr, T. R.; Patrick, M. R.

    2013-12-01

    Between January 1983 and July 1986, activity at Kilauea was localised at Pu`u `O`o in the East Rift Zone. During this time activity was characterised by short (0.2 to 16 days), high intensity fountaining episodes of varying heights, which were separated by lengthy repose periods (10 to 50 days). Microtextural analysis of juvenile pyroclasts produced by eruptions such as these can be highly valuable in providing information on the nature of the evolution of the magma's volatiles in the shallow conduit. The growing literature on microtextural analysis of the vesicles in basaltic pyroclasts suggests that variations in eruption form, duration and intensity is controlled by the degassing and outgassing of the magma, and in variations in the timing and extent of the nucleation, growth and coalescence of bubbles in the magma and the degree in which they are mechanically coupled to the melt (Stovall et al. 2011, Parcheta et al. 2013). We have collected samples from three high fountaining episodes that were well characterised by Hawaiian Volcano Observatory staff at the time of the eruption. These episodes produced fountains with heights between 391-445 m, and volumes of 1.1x107 m3 and 1.7x107 m3 of lava (bulk volume). We describe here microtextural characteristics and matrix glass volatile contents of pyroclasts erupted from the three episodes and we couple this data together with multidisciplinary geophysical and visual datasets collected by HVO staff. The combination of quantitative vesicle microtextures and syn-eruptive volatiles within groundmass glass permit us to quantify the degassing histories of magma erupted in each eruptive episode. This data will be combined with visual observations of fountain height and geophysical data (geodetic and seismic) in order to better define the factors that govern the variations in the eruption intensity of Hawaiian volcanism.

  3. New strategies for upscaling high-resolution flow and overbank sedimentation models to quantify floodplain sediment storage at the catchment scale

    NASA Astrophysics Data System (ADS)

    Nicholas, A. P.; Walling, D. E.; Sweet, R. J.; Fang, X.

    2006-10-01

    SummaryQuantitative models of catchment scale floodplain sediment storage must balance competing demands. For example, such approaches must incorporate a physically-based representation of controls on overbank sedimentation rates at the reach scale, but should also be computationally efficient so that catchment scale analysis remains a realistic goal. This paper reports the development of a novel nested modelling strategy that combines a high-resolution hydraulic model based on the shallow water form of the Navier-Stokes equations, with a reduced complexity overbank sedimentation model and coarse-resolution catchment sediment budget model. The approach is implemented within a Monte-Carlo framework to allow an assessment of uncertainty in the parameterisation of overbank sedimentation processes, and to derive uncertainty-bounded estimates of floodplain sedimentation rates over a range of spatial scales. This strategy is applied to a 26 km reach of the River Culm, Devon, UK. The relative performance of a wide range of model structures is evaluated by comparing model predictions with estimates of actual mean annual sedimentation rates derived by analysis of the caesium-137 content of floodplain sediment cores at 20 locations within each of eight study sites distributed throughout the catchment. The results of the current model application demonstrate the potential of the nested modelling strategy as a means of upscaling physically-based flow and sediment transport codes. Furthermore, the novel reduced-complexity overbank sedimentation model presented here is shown to provide a means of simulating complex patterns of suspended sediment transport and deposition, while reducing computing costs by 2-3 orders of magnitude compared with conventional high-resolution advection-diffusion codes. Uncertainty-bounded estimates of floodplain sediment storage for the River Culm confirm that floodplain sedimentation represents a primary component of the fine sediment budget of

  4. User Friendly Processing of Sediment CT Data: Software and Application in High Resolution Non-Destructive Sediment Core Data Sets

    NASA Astrophysics Data System (ADS)

    Reilly, B. T.; Stoner, J. S.; Wiest, J.; Abbott, M. B.; Francus, P.; Lapointe, F.

    2015-12-01

    Computed Tomography (CT) of sediment cores allow for high resolution images, three dimensional volumes, and down core profiles, generated through the attenuation of X-rays as a function of density and atomic number. When using a medical CT-Scanner, these quantitative data are stored in pixels using the Hounsfield scale, which are relative to the attenuation of X-rays in water and air at standard temperature and pressure. Here we present MATLAB based software specifically designed for sedimentary applications with a user friendly graphical interface to process DICOM files and stitch overlapping CT scans. For visualization, the software allows easy generation of core slice images with grayscale and false color relative to a user defined Hounsfield number range. For comparison to other high resolution non-destructive methods, down core Hounsfield number profiles are extracted using a method robust to coring imperfections, like deformation, bowing, gaps, and gas expansion. We demonstrate the usefulness of this technique with lacustrine sediment cores from the Western United States and Canadian High Arctic, including Fish Lake, Oregon, and Sawtooth Lake, Ellesmere Island. These sites represent two different depositional environments and provide examples for a variety of common coring defects and lithologies. The Hounsfield profiles and images can be used in combination with other high resolution data sets, including sediment magnetic parameters, XRF core scans and many other types of data, to provide unique insights into how lithology influences paleoenvironmental and paleomagnetic records and their interpretations.

  5. Generation of lipid peroxidation products in culinary oils and fats during episodes of thermal stressing: a high field 1H NMR study.

    PubMed

    Claxson, A W; Hawkes, G E; Richardson, D P; Naughton, D P; Haywood, R M; Chander, C L; Atherton, M; Lynch, E J; Grootveld, M C

    1994-11-21

    The oxidative deterioration of glycerol-bound polyunsaturated fatty acids (PUFAs) in culinary oils and fats during episodes of heating associated with normal usage (30-90 min at 180 degrees C) has been monitored by high field 1H NMR spectroscopy. Thermal stressing of PUFA-rich culinary oils generated high levels of n-alkanals, trans-2-alkenals, alka-2,4-dienals and 4-hydroxy-trans-2-alkenals via decomposition of their conjugated hydroperoxydiene precursors, whereas only low concentrations of selected aldehydes were produced in oils with a low PUFA content, lard and dripping when subjected to the above heating episodes. Samples of repeatedly used, PUFA-rich culinary oils obtained from restaurants also contained high levels of each class of aldehyde. The dietary, physiological and toxicological ramifications of the results obtained are discussed.

  6. Mechanism of Arsenic Sequestration in High-Iron Sediments

    NASA Astrophysics Data System (ADS)

    Root, R. A.; Campbell, K. M.; Hering, J. G.; O'Day, P. A.

    2005-12-01

    Naturally occurring elevated concentrations of arsenic in the runoff of the eastern Sierra Nevada and feed waters of the Los Angeles Aqueduct are remediated by the Los Angeles Department of Power and Water (LADPW) up stream of the Haiwee Reservoir (Olancha, CA). To reduce total arsenic in drinking water supplies, the LADPW adds ferric chloride and a cationic polymer coagulant to the aqueduct. The treatment precipitates as an amorphous iron oxide, spectrally similar to 6-line ferrihydrite, that adsorbs and sequesters arsenic as arsenate. As the channeled flow enters North Haiwee Reservoir, the As(V)-enriched iron floc settles as sediments in the inlet channel. Buried As(V) is reduced to As(III) near the sediment-water interface (0-10cm), and only As(III) is observed at depths below the steep (1-2cm) near-surface redox gradient. Sediment samples from 30-cm push cores were collected from the edge of the reservoir along the inlet channel in tandem with in situ porewater measurements using an inert polyacrylamide gel probe sampler. Sediments were analyzed to characterize the redox gradient, host mineralogy, and variation in bulk elemental composition with depth. X-ray absorption spectroscopy (XAS) was used to determine the depth of the microbially driven redox boundary where As (V) is reduced to As (III) and to investigate the molecular bonding of arsenic adsorbed to iron hydroxide surfaces. Specific and characteristic iron and arsenic phases were isolated by sequential extraction; extracted and bulk concentrations were determined by ICP-MS. Splits of specific extraction steps were analyzed by synchrotron EXAFS and XRD to determine the identity of separated phases. The primary mineralogy of sediments along the inlet channel is detrital quartz, plagioclase feldspar, and phyllosilicates weathered from the Sierra Nevada granitic batholith. Notably, crystalline magnetite, hematite, and goethite, phases that would indicate transformation of hydrous iron phases to more stable

  7. Shelfal sediment transport by undercurrents forces turbidity current activity during high sea level, Chile continental margin

    NASA Astrophysics Data System (ADS)

    Bernhardt, Anne; Hebbeln, Dierk; Regenberg, Marcus; Lückge, Andreas; Strecker, Manfred. R.

    2016-04-01

    Understanding the links between terrigenous sediment supply and marine transport and depositional processes along tectonically active margins is essential to decipher turbidite successions as potential archives of climatic and seismic forcings and to comprehend timing and quantity of marine clastic deposition. Sequence stratigraphic models predict coarse-grained terrigenous sediment delivery to deep-marine sites mainly during sea-level fall and lowstand. Marine clastic deposition during periods of transgression and highstand has been attributed to the continued geomorphic connectivity between terrestrial sediment sources and marine sinks (e.g., rivers connected to submarine canyons) often facilitated by narrow shelves, high sediment supply causing delta migration to the shelf edge, and/or abrupt increases in sediment supply due to climatic variability or catastrophic events. To decipher the controls on Holocene highstand turbidite deposition, we analyzed twelve sediment cores of spatially disparate, coeval Holocene turbidite systems along the Chile margin (29-40°S) with changing climatic and geomorphic characteristics but uniform changes of sea level. Intraslope basins in north-central Chile (29-33°S) offshore a narrow to absent shelf record a shut-off of turbidite activity during the Holocene. In contrast, core sites in south-central Chile (36-40°S) offshore a wide continental shelf have repeatedly experienced turbidite deposition during sea-level highstand conditions, even though most of the depocenters are not connected via canyons to sediment sources. The interplay of stable high sediment supply related to strong onshore precipitation in combination with a wide shelf, over which undercurrents move sediment towards the shelf edge, appears to control Holocene turbidite sedimentation and sediment export to the deep sea.

  8. The Sediment Yield of High Mountain Environment Watersheds: Strong Evidence of Transport Capacity Limitation

    NASA Astrophysics Data System (ADS)

    Micheletti, N.; Lane, S. N.; Lambiel, C.

    2015-12-01

    Alpine landscapes are likely to be particularly sensitive to climate change, because of: (1) the vulnerability of permafrost and glacial and nival processes to changes in atmospheric temperature and precipitation; (2) their history, which may have led to high rates of sediment production, and hence high rates of sediment supply; and (3) the steep slopes that may sustain sediment transport. Assessing the effects of climate change upon these processes over the timescale of recent rapid warming (i.e. decades) is difficult because of the lack of available data. Here, we use two unique data sources to assess the relative importance of these three processes for two high mountain basins (altitude range 2'000 to 3'500 m asl): (1) histories of surface change from the late 1950s, based upon construction of digital elevation models from archival imagery; and (2) a long term record, beginning in the early 1960s, of sediment export based upon the flushing of sediment from hydropower intakes. The two basins contain glaciers, rock glaciers, permafrost and the legacy of past glacial activity. These data show that the level of geomorphic activity within both basins is orders of magnitude higher than the volume of sediment exported from the basins. Decadal scale changes in elevation and surface displacement velocities suggest an acceleration of landscape dynamics from the 1980s. Changes in atmospheric temperature remain a key control of this process, but precipitation and snow cover prove critical in controlling rock glacier behaviour and can induce acceleration of surface displacements even under cold atmospheric conditions. However, the analysis of the sediment export data show that despite generally greater within basin dynamics, the rate of export of sediment remains orders of magnitude lower than rates of sediment production. Calculations of sediment transport capacity suggest that this is because the fundamental limit upon sediment yield is the capacity of the stream to

  9. Quantification of subaerial and episodic subglacial erosion rates on high latitude upland plateaus: Cumberland Peninsula, Baffin Island, Arctic Canada

    NASA Astrophysics Data System (ADS)

    Margreth, Annina; Gosse, John C.; Dyke, Arthur S.

    2016-02-01

    Long-term rates of subaerial and episodic subglacial erosion by predominately cold-based ice cover are determined for tors on weathered plateaus on Cumberland Peninsula. By measuring terrestrial cosmogenic nuclide concentrations in differentially weathered surfaces on a given tor, we reconstruct the complex exposure and erosion history involving recurring cold-based ice cover. The style and rate of subaerial and subglacial erosion at multiple tor sites on Cumberland Peninsula are assessed with a Monte Carlo approach that computes plausible exposure histories based on a proxy record of global ice volume. Constant subaerial erosion rates by weathering are low (<2 mm ka-1), corroborated by nuclide concentrations measured on two tors located on coastal ridge crests that have likely never been glaciated. Summit plateaus intermittently covered by cold-based ice throughout the Quaternary have experienced episodic subglacial erosion by plucking of fractured bedrock with rates between 1 and 16 mm ka-1. Variation of episodic erosion rates is associated with topographic position of the sampled tors and bedrock fracture density. Most of the tors were last glacially plucked in pre-ultimate glaciations, not during the Wisconsinan glaciation. Furthermore, the new approach provides evidence for the extent of ice coverage during the late Wisconsinan, which is significant if no erratics are available for exposure dating. Despite late Pleistocene intervals of ice cover and glacial plucking, tor-studded landscapes of Cumberland Peninsula are of considerable antiquity.

  10. Associations of hippocampal metabolism and regional brain grey matter in neuroleptic-naïve ultra-high-risk subjects and first-episode schizophrenia.

    PubMed

    Nenadic, Igor; Maitra, Raka; Basu, Soumyajit; Dietzek, Maren; Schönfeld, Nils; Lorenz, Carsten; Gussew, Alexander; Amminger, G Paul; McGorry, Patrick; Reichenbach, Jürgen R; Sauer, Heinrich; Gaser, Christian; Smesny, Stefan

    2015-10-01

    Hippocampal pathology has been shown to be central to the pathophysiology of schizophrenia and a putative risk marker for developing psychosis. We applied both (1)H MRS (proton magnetic resonance spectroscopy) at 3Tesla and voxel-based morphometry (VBM) of high-resolution brain structural images in order to study the association of the metabolites glutamate (Glu) and N-acetyl-aspartate (NAA) in the hippocampus with whole-brain morphometry in 31 persons at ultra-high-risk for psychosis (UHR), 18 first-episode schizophrenia patients (Sz), and 42 healthy controls (all subjects being neuroleptic-naïve). Significantly diverging associations emerged for UHR subjects hippocampal glutamate showed positive correlation with the left superior frontal cortex, not seen in Sz or controls, while in first-episode schizophrenia patients a negative correlation was significant between glutamate and a left prefrontal area. For NAA, we observed different associations for left prefrontal and caudate clusters bilaterally for both high-risk and first-episode schizophrenia subjects, diverging from the pattern seen in healthy subjects. Our results suggest that associations of hippocampal metabolites in key areas of schizophrenia might vary due to liability to or onset of the disorder.

  11. Associations of hippocampal metabolism and regional brain grey matter in neuroleptic-naïve ultra-high-risk subjects and first-episode schizophrenia.

    PubMed

    Nenadic, Igor; Maitra, Raka; Basu, Soumyajit; Dietzek, Maren; Schönfeld, Nils; Lorenz, Carsten; Gussew, Alexander; Amminger, G Paul; McGorry, Patrick; Reichenbach, Jürgen R; Sauer, Heinrich; Gaser, Christian; Smesny, Stefan

    2015-10-01

    Hippocampal pathology has been shown to be central to the pathophysiology of schizophrenia and a putative risk marker for developing psychosis. We applied both (1)H MRS (proton magnetic resonance spectroscopy) at 3Tesla and voxel-based morphometry (VBM) of high-resolution brain structural images in order to study the association of the metabolites glutamate (Glu) and N-acetyl-aspartate (NAA) in the hippocampus with whole-brain morphometry in 31 persons at ultra-high-risk for psychosis (UHR), 18 first-episode schizophrenia patients (Sz), and 42 healthy controls (all subjects being neuroleptic-naïve). Significantly diverging associations emerged for UHR subjects hippocampal glutamate showed positive correlation with the left superior frontal cortex, not seen in Sz or controls, while in first-episode schizophrenia patients a negative correlation was significant between glutamate and a left prefrontal area. For NAA, we observed different associations for left prefrontal and caudate clusters bilaterally for both high-risk and first-episode schizophrenia subjects, diverging from the pattern seen in healthy subjects. Our results suggest that associations of hippocampal metabolites in key areas of schizophrenia might vary due to liability to or onset of the disorder. PMID:26088723

  12. Evolution of a high-latitude sediment drift inside a glacially-carved trough based on high-resolution seismic stratigraphy (Kveithola, NW Barents Sea)

    NASA Astrophysics Data System (ADS)

    Rebesco, Michele; Özmaral, Asli; Urgeles, Roger; Accettella, Daniela; Lucchi, Renata G.; Rüther, Denise; Winsborrow, Monica; Llopart, Jaume; Caburlotto, Andrea; Lantzsch, Hendrik; Hanebuth, Till J. J.

    2016-04-01

    Kveithola is a glacially-carved, E-W trending trough located in the NW Barents Sea, an epicontinental shelf sea of the Arctic Ocean located off northern Norway and Russia. A set of confined sediment drifts (the "Kveithola Drift") is located in the inner part of the trough. In general, drift deposits are commonly characterized by high lateral continuity, restricted occurrence of hiatuses and relatively high accumulation rates, and thus represent excellent repositories of paleo-environmental information. We provide for the first time a detailed morphological and seismostratigraphic insight into this sediment drift, which is further supported by some preliminary lithological and sedimentological analyses. The complex morphology of the drift, imaged by combining all available multibeam data, includes a main and a minor drift body, two drift lenses in the outer part of the trough, more or less connected drift patches in the innermost part and small perched sediment patches in a structurally-controlled channel to the north. The seismic (PARASOUND) data show that the main and minor drift bodies are mainly well-stratified, characterized by sub-parallel reflections of moderate to high amplitude and good lateral continuity. The reflectors show an abrupt pinch-out on the northern edge where a distinct moat is present, and a gradual tapering to the south. Internally we identify the base of the drift and four internal horizons, which we correlate throughout the drift. Facies typical for contourite deposition are found in the sediment cores, with strongly bioturbated sediments and abundant silty/sandy mottles that contain shell fragments. These characteristics, along with the morphological and seismic information, suggest a strong control by a bottom current flowing along the moat on the northern edge of the drift. Though both Atlantic and Arctic waters are known to enter the trough, from the west and the north respectively, brine-enriched shelf water (BSW) produced during

  13. A high throughout semi-quantification method for screening organic contaminants in river sediments.

    PubMed

    Bu, Qingwei; Wang, Donghong; Liu, Xin; Wang, Zijian

    2014-10-01

    A high throughout semi-quantification method for screening nearly 900 organic contaminants (OCs) in river sediments has been developed. For most OCs tested, concentrations calculated from the proposed semi-quantification method deviated from actual values by a factor of 4. The overall recovery tests indicated that most OCs can be successfully extracted from sediments with recovery rates from 84.1 to 128.6%. To demonstrate the effectiveness of our method towards OC quantification, we screened OCs from sediments collected from the Haihe River basin. Seventy unregulated OCs (including pesticides, flame retardants, PPCPs, etc.) were identified and quantified at concentrations up to 2600 ng/g from 24 sediment samples. From these results, it is confirmed that the developed method is a useful way to fulfill a comprehensive analysis of OCs in sediments and would be valuable for the identification and prioritization of priority pollutants in watershed management.

  14. Evaluation of marine sediments as microbial sources for methane production from brown algae under high salinity.

    PubMed

    Miura, Toyokazu; Kita, Akihisa; Okamura, Yoshiko; Aki, Tsunehiro; Matsumura, Yukihiko; Tajima, Takahisa; Kato, Junichi; Nakashimada, Yutaka

    2014-10-01

    Various marine sediments were evaluated as promising microbial sources for methane fermentation of Saccharina japonica, a brown alga, at seawater salinity. All marine sediments tested produced mainly acetate among volatile fatty acids. One marine sediment completely converted the produced volatile fatty acids to methane in a short period. Archaeal community analysis revealed that acetoclastic methanogens belonging to the Methanosarcina genus dominated after cultivation. Measurement of the specific conversion rate at each step of methane production under saline conditions demonstrated that the marine sediments had higher conversion rates of butyrate and acetate than mesophilic methanogenic granules. These results clearly show that marine sediments can be used as microbial sources for methane production from algae under high-salt conditions without dilution.

  15. High-precision measurements of wetland sediment elevation. I. Recent improvements to the sedimentation--erosion table

    USGS Publications Warehouse

    Cahoon, D.R.; Lynch, J.C.; Hensel, P.; Boumans, R.; Perez, B.C.; Segura, B.; Day, J.W.

    2002-01-01

    The sedimentation-erosion table (SET) developed by Boumans and Day (1993) is herein renamed the surface elevation table (SET) to better reflect the conceptual view of the processes being measured. The SET was designed for making high-resolution measurements of small-scale changes in elevation of loose, unconsolidated sediments in shallow water and mudflat habitats. The SET has undergone three major improvements to increase precision and so that it can be used to measure sediment elevation in vegetated wetlands as well as shallow water habitats. The remote-release 'sliding plate' mechanism has been replaced with a single plate, collars (first 2.5 cm then 7.5 cm in length) have been attached to the plate to reduce play in the placement of the measuring pins, and the brass measuring pins have been replaced with fiberglass pins to reduce bending and consequent loss of precision. Under ideal laboratory conditions, the 95% confidence limit for individual pin measurements averaged about A? 1.4 mm (range A? 0.7 to A? 1.9 mm). These modifications have resulted in a reduction of error by about 50%.

  16. Arsenic redistribution between sediments and water near a highly contaminated source.

    PubMed

    Keimowitz, Alison R; Zheng, Yan; Chillrud, Steven N; Mailloux, Brian; Jung, Hun Bok; Stute, Martin; Simpson, H James

    2005-11-15

    Mechanisms controlling arsenic partitioning between sediment, groundwater, porewaters, and surface waters were investigated at the Vineland Chemical Company Superfund site in southern New Jersey. Extensive inorganic and organic arsenic contamination at this site (historical total arsenic > 10 000 microg L(-1) or > 130 microM in groundwater) has spread downstream to the Blackwater Branch, Maurice River, and Union Lake. Stream discharge was measured in the Blackwater Branch, and water samples and sediment cores were obtained from both the stream and the lake. Porewaters and sediments were analyzed for arsenic speciation as well as total arsenic, iron, manganese, and sulfur, and they indicate that geochemical processes controlling mobility of arsenic were different in these two locations. Arsenic partitioning in the Blackwater Branch was consistent with arsenic primarily being controlled by sulfur, whereas in Union Lake, the data were consistent with arsenic being controlled largely by iron. Stream discharge and arsenic concentrations indicate that despite large-scale groundwater extraction and treatment, > 99% of arsenic transport away from the site results from continued discharge of high arsenic groundwater to the stream, rather than remobilization of arsenic in stream sediments. Changing redox conditions would be expected to change arsenic retention on sediments. In sulfur-controlled stream sediments, more oxic conditions could oxidize arsenic-bearing sulfide minerals, thereby releasing arsenic to porewaters and streamwaters; in iron-controlled lake sediments, more reducing conditions could release arsenic from sediments via reductive dissolution of arsenic-bearing iron oxides.

  17. First High-Resolution Record of Late Quaternary Environmental Changes in the Amundsen Sea, West Antarctica, Revealed by Multi-proxy Analysis of Drift Sediments

    NASA Astrophysics Data System (ADS)

    Horrocks, J.; Ó Cofaigh, C.; Lloyd, J. M.; Hillenbrand, C. D.; Kuhn, G.; Smith, J.; Ehrmann, W. U.; Esper, O.

    2015-12-01

    The Amundsen Sea sector of the West Antarctic Ice Sheet (WAIS) is experiencing rapid mass loss and there is a pressing need to place the contemporary ice-sheet changes into a longer term context. The continental rise in this region is characterised by large sediment mounds that are shaped by westward flowing bottom currents and that resemble contouritic drifts existing offshore from the Antarctic Peninsula. Similar to the Antarctic Peninsula drifts, marine sediment cores from the poorly studied sediment mounds in the Amundsen Sea have the potential to provide reliable records of dynamical ice-sheet behaviour in West Antarctica and palaeoceanographic changes in the Southern Ocean during the Late Quaternary that can be reconstructed from their terrestrial, biogenic and authigenic components. Here we use multi-proxy data from three sediment cores recovered from two of the Amundsen Sea mounds to present the first high-resolution study of environmental changes on this part of the West Antarctic continental margin over the glacial-interglacial cycles of the Late Quaternary. Age constraints for the records are derived from biostratigraphy, AMS 14C dates and lithostratigraphy. We focus on the investigation of processes for drift formation, thereby using grain size and sortable silt data to reconstruct changes in bottom current speed and to identify episodes of current winnowing. Data on geochemical and mineralogical sediment composition and physical properties are used to infer both changes in terrigenous sediment supply in response to the advance and retreat of the WAIS across the Amundsen Sea shelf and changes in biological productivity that are mainly controlled by the duration of annual sea-ice coverage. We compare our data sets from the Amundsen Sea mounds to those from the well-studied Antarctic Peninsula drifts, thereby highlighting similarities and discrepancies in depositional processes and climatically-driven environmental changes.

  18. The natural sediment regime in rivers: broadening the foundation for ecosystem management

    USGS Publications Warehouse

    Wohl, Ellen E.; Bledsoe, Brian P.; Jacobson, Robert B.; Poff, N. LeRoy; Rathburn, Sara L.; Walters, David M.; Wilcox, Andrew C.

    2015-01-01

    Water and sediment inputs are fundamental drivers of river ecosystems, but river management tends to emphasize flow regime at the expense of sediment regime. In an effort to frame a more inclusive paradigm for river management, we discuss sediment inputs, transport, and storage within river systems; interactions among water, sediment, and valley context; and the need to broaden the natural flow regime concept. Explicitly incorporating sediment is challenging, because sediment is supplied, transported, and stored by nonlinear and episodic processes operating at different temporal and spatial scales than water and because sediment regimes have been highly altered by humans. Nevertheless, managing for a desired balance between sediment supply and transport capacity is not only tractable, given current geomorphic process knowledge, but also essential because of the importance of sediment regimes to aquatic and riparian ecosystems, the physical template of which depends on sediment-driven river structure and function.

  19. Quantifying Ozone Production throughout the Boundary Layer from High Frequency Tethered Profile Measurements during a High Ozone Episode in the Uinta Basin, Utah

    NASA Astrophysics Data System (ADS)

    Sterling, C. W.; Johnson, B.; Schnell, R. C.; Oltmans, S. J.; Cullis, P.; Hall, E. G.; Jordan, A. F.; Windell, J.; McClure-Begley, A.; Helmig, D.; Petron, G.

    2015-12-01

    During the Uinta Basin Winter Ozone Study (UBWOS) in Jan - Feb 2013, 735 tethered ozonesonde profiles were obtained at 3 sites including during high wintertime photochemical ozone production events that regularly exceeded 125 ppb. High resolution profiles of ozone and temperature with altitude, measured during daylight hours, showed the development of approximately week long high ozone episodes building from background levels of ~40 ppb to >150 ppb. The topography of the basin combined with a strong temperature inversion trapped oil and gas production effluents in the basin and the snow covered surface amplified the sun's radiation driving the photochemical ozone production at rates up to 13 ppb/hour in a cold layer capped at 1600-1700 meters above sea level. Beginning in mid-morning, ozone mixing ratios throughout the cold layer increased until late afternoon. Ozone mixing ratios were generally constant with height indicating that ozone production was nearly uniform throughout the depth of the cold pool. Although there was strong diurnal variation, ozone mixing ratios increased during the day more than decreased during the night, resulting in elevated levels the next morning; an indication that nighttime loss processes did not compensate for daytime production. Even though the 3 tethersonde sites were at elevations differing by as much as 140 m, the top of the high ozone layer was nearly uniform in altitude at the 3 locations. Mobile van surface ozone measurements across the basin confirmed this capped structure of the ozone layer; the vehicle drove out of high ozone mixing ratios at an elevation of ~1900 meters above sea level, above which free tropospheric ozone mixing ratios of ~50 ppb were measured. Exhaust plumes from a coal-fired power plant in the eastern portion of the basin were intercepted by the tethersondes. The structure of the profiles clearly showed that effluents in the plumes were not mixed downward and thus did not contribute precursor nitrogen

  20. Metal availability in a highly contaminated, dredged-sediment disposal site: field measurements and geochemical modeling.

    PubMed

    Lions, Julie; Guérin, Valérie; Bataillard, Philippe; van der Lee, Jan; Laboudigue, Agnès

    2010-09-01

    Two complementary approaches were used to characterize arsenic and metal mobilizations from a dredged-sediment disposal site: a detailed field study combined with hydrogeochemical modeling. Contaminants in sediments were found to be mainly present as sulfides subject to oxidation. Secondary phases (carbonates, sulfates, (hydr)oxides) were also observed. Oxidative processes occurred at different rates depending on physicochemical conditions and contaminant contents in the sediment. Two distinct areas were identified on the site, each corresponding to a specific contaminant mobility behavior. In a reducing area, Fe and As were highly soluble and illustrated anoxic behavior. In well-oxygenated material, groundwater was highly contaminated in Zn, Cd and Pb. A third zone in which sediments and groundwater were less contaminated was also characterized. This study enabled us to prioritize remediation work, which should aim to limit infiltration and long-term environmental impact.

  1. Towards in situ and high frequency estimates of suspended sediment properties

    NASA Astrophysics Data System (ADS)

    Martínez-Carreras, Núria; Schwab, Michael Peter; Klaus, Julian; Hissler, Christophe

    2016-04-01

    Sediment properties, including sediment-associated chemical constituents and sediment physical properties (as colour), can exhibit significant variations within and between storm runoff events. However, the number of samples included in suspended sediment studies is often limited by the time consuming and expensive laboratory procedures for suspended sediment analysis after stream water sampling. This, in turn, restricts high frequency sampling campaigns to a limited number of events and reduces accuracy when aiming to estimate fluxes and loads of sediment-associated chemical constituents. Our contribution addresses the potential for portable ultraviolet-visible (UV-VIS) light spectrometers (220-730 nm) to estimate suspended sediment properties in situ and at high temporal resolution. As far as we know, these instruments have primarily been developed and used to quantify solute concentrations (e.g. DOC and NO3-N), total concentrations of dissolved and particulate forms (e.g. TOC) and turbidity. Here we argue that light absorbance values can be calibrated to estimate solely sediment properties. For our proof-of-concept experiment, we measured light absorbance at 15-min intervals at the Weierbach catchment (NW Luxembourg, 0.46 km2) from December 2013 to January 2015. We then performed a local calibration using suspended sediment loss-on-ignition (LOI) measurements (n=34). We assessed the performance of several regression models that relate light absorbance measurements with the percentage weight LOI. The robust regression method presented the lowest standard error of prediction (0.48{%}) and was selected for calibration (adjusted r2 = 0.76 between observed and predicted values). This study demonstrates that spectrometers can be used to estimate suspended sediment properties at high temporal resolution and for long time spans in a simple, non-destructive and affordable manner. The advantages and disadvantages of the method compared to traditional approaches will be

  2. Determination of pentachlorophenol in water and aquifer sediments by high-performance liquid chromatography

    USGS Publications Warehouse

    Goerlitz, D.F.

    1981-01-01

    Methods for the determination of pentachlorophenol (PCP) in water and aquifer sediments are presented. Reverse-phase high-performance liquid chromotography employing ion suppression and gradient elution is used. PCP can be determined directly in water at a lower limit of detection Of 0.2 micrograms per liter. For extracts of sediment, PCP can be determined to a lower limit of 1.0 micrograms per kilogram.

  3. New evidence of Holocene atmospheric circulation dynamics based on lake sediments from southern Sweden: a link to the Siberian High

    NASA Astrophysics Data System (ADS)

    Muschitiello, F.; Schwark, L.; Wohlfarth, B.; Sturm, C.; Hammarlund, D.

    2013-10-01

    Oxygen (δ18O) and carbon (δ13C) isotope records of calcitic carbonate components (Chara sp. algal encrustations and Bithynia tentaculata gastropod opercula) from a lake-sediment succession on the Baltic Sea island of Gotland, south-eastern Sweden, have been obtained to investigate regional climate dynamics during the Holocene. The hydrological sensitivity of the small lake, particularly in terms of spring snowmelt contribution to the local water budget, provides a means of tracing past changes in the influence of snow-bearing easterly winds across the Baltic Sea Proper, which signifies the wintertime strength of the Siberian High. Repeated episodic depletions in 18O at the centennial scale correlate with events of increased potassium concentration in the GISP2 ice-core record from Greenland, which indicates a coupling to large-scale fluctuations in atmospheric circulation patterns. A corresponding correlation with simultaneous depletions in 13C suggests repeated responses of the local lake hydrology to snow-rich winters through decreasing water residence time, perhaps augmented by methanogenesis due to prolonged ice-cover seasons under the influence of an expanding Siberian High. Frequency analysis of the isotopic records reveals well-defined fluctuations at quasi-500-520-, 670-, 830- and 1430-yr periodicities, and a gradually stronger impact of Polar air outbreaks across the southern Baltic Sea region with time after ca 6000 cal. BP.

  4. High resolution analysis of northern Patagonia lake sediments

    NASA Astrophysics Data System (ADS)

    Jarvis, S. W.; Croudace, I. W.; Langdon, P. G.; Rindby, A.

    2009-04-01

    Sediment cores covering the period from the last glacial maximum through the Holocene to the present have been collected from sites in the Chacubuco valley, southern Chile (around 47°08'S, 72°25'W, to the east of the North Patagonian Icecap). Cores were taken from five lakes and one recently dried lake bed. Short cores (0.2 to 0.5m), covering approximately the last two hundred years, were taken from all the lakes. Additionally, long sequences were obtained from one of the lakes and from the dried lake bed, the latter sequence extending back to the last glacial maximum as indicated by thick clay at the base. Each of the lakes are small-medium sized and are open systems situated at 300-1000m above sea level. The shorter cores comprise predominantly clastic gyttja but show a number of distinct changes in colour and chemical composition that suggest major environmental changes over the period of sediment accumulation. This is also reflected in variations in the loss on ignition of samples from the cores and in elemental profiles produced by scanning the cores with the Itrax micro-XRF corescanner at 200μm resolution. The long sequence from the dried lake bed has very low organic content glacial clay at the base, interpreted as last glacial maximum basal clay following determination in the field that this layer exceeded 2m in thickness. Similar sediments occur within a stratigraphically discrete section of approximately 14cm and may relate to a stadial event. The latter section also shows a drop in organic content and appears to be glacial clay incorporating some coarse sandy components indicative of detrital input from the catchment. The second long sequence, from a carbonate lake, includes two mineral layers indicating increased detrital input from the catchment. The deeper and thicker of these layers appears similar to the 14cm layer in the first long sequence, while the upper layer comprises a fine grain size indicative of rock flour and hence also of glacial

  5. Sediment transport modeling using highly resolved Euler-Lagrange LES

    NASA Astrophysics Data System (ADS)

    Arolla, Sunil; Desjardins, Olivier

    2014-11-01

    We use an explicitly volume-filtered Euler-Lagrange large eddy simulation methodology to investigate the detailed dynamics of turbulent liquid-solid slurry flows through a horizontal pipe. A series of simulations have been performed by varying the superficial liquid velocity to be consistent with the available experimental data by Danielson (2007). From our numerical simulations, the critical deposition velocity below which a static sand bed starts forming is predicted and compared with the experiments. We discuss the dynamics of liquid-solid slurry flow in connection with the Shields diagram. Depending on the Shields number, patterns develop at the surface of the particle bed, in close analogy with patterns discussed in sediment transport research. We also present statistics extracted to evaluate and improve recently proposed RANS based closure modeling ideas in the context of Euler-Euler formalism.

  6. Composition of fluids expelled during compaction of Mississippi delta sediments

    NASA Astrophysics Data System (ADS)

    Hanor, Jeffrey S.

    1981-09-01

    Fluids discharged from subaerial springs along faults on a sediment diapir near the mouth of the Mississippi River are derived from buried marine pore waters which have been extensively altered chemically by processes of bacterial respiration, mineral precipitation and, possibly, by fractionation due to the presence of clays of high exchange capacity. Vertical mass transport of dissolved components in many shallow marine sediments is controlled by long-term compaction, diffusion and bioturbation. In areas of rapid sediment deposition, however, these processes can be overwhelmed by catastrophic episodes of sediment failure, vertical mixing and upward discharge of water, gas and dissolved species.

  7. Ammonia- and methane-oxidizing microorganisms in high-altitude wetland sediments and adjacent agricultural soils.

    PubMed

    Yang, Yuyin; Shan, Jingwen; Zhang, Jingxu; Zhang, Xiaoling; Xie, Shuguang; Liu, Yong

    2014-12-01

    Ammonia oxidation is known to be carried out by ammonia-oxidizing bacteria (AOB) and archaea (AOA), while methanotrophs (methane-oxidizing bacteria (MOB)) play an important role in mitigating methane emissions from the environment. However, the difference of AOA, AOB, and MOB distribution in wetland sediment and adjacent upland soil remains unclear. The present study investigated the abundances and community structures of AOA, AOB, and MOB in sediments of a high-altitude freshwater wetland in Yunnan Province (China) and adjacent agricultural soils. Variations of AOA, AOB, and MOB community sizes and structures were found in water lily-vegetated and Acorus calamus-vegetated sediments and agricultural soils (unflooded rice soil, cabbage soil, and garlic soil and flooded rice soil). AOB community size was higher than AOA in agricultural soils and lily-vegetated sediment, but lower in A. calamus-vegetated sediment. MOB showed a much higher abundance than AOA and AOB. Flooded rice soil had the largest AOA, AOB, and MOB community sizes. Principal coordinate analyses and Jackknife Environment Clusters analyses suggested that unflooded and flooded rice soils had relatively similar AOA, AOB, and MOB structures. Cabbage soil and A. calamus-vegetated sediment had relatively similar AOA and AOB structures, but their MOB structures showed a large difference. Nitrososphaera-like microorganisms were the predominant AOA species in garlic soil but were present with a low abundance in unflooded rice soil and cabbage soil. Nitrosospira-like AOB were dominant in wetland sediments and agricultural soils. Type I MOB Methylocaldum and type II MOB Methylocystis were dominant in wetland sediments and agricultural soils. Moreover, Pearson's correlation analysis indicated that AOA Shannon diversity was positively correlated with the ratio of organic carbon to nitrogen (p < 0.05). This work could provide some new insights toward ammonia and methane oxidation in soil and wetland sediment

  8. High bacterial biodiversity increases degradation performance of hydrocarbons during bioremediation of contaminated harbor marine sediments.

    PubMed

    Dell'Anno, Antonio; Beolchini, Francesca; Rocchetti, Laura; Luna, Gian Marco; Danovaro, Roberto

    2012-08-01

    We investigated changes of bacterial abundance and biodiversity during bioremediation experiments carried out on oxic and anoxic marine harbor sediments contaminated with hydrocarbons. Oxic sediments, supplied with inorganic nutrients, were incubated in aerobic conditions at 20 °C and 35 °C for 30 days, whereas anoxic sediments, amended with organic substrates, were incubated in anaerobic conditions at the same temperatures for 60 days. Results reported here indicate that temperature exerted the main effect on bacterial abundance, diversity and assemblage composition. At higher temperature bacterial diversity and evenness increased significantly in aerobic conditions, whilst decreased in anaerobic conditions. In both aerobic and anaerobic conditions, biodegradation efficiencies of hydrocarbons were significantly and positively related with bacterial richness and evenness. Overall results presented here suggest that bioremediation strategies, which can sustain high levels of bacterial diversity rather than the selection of specific taxa, may significantly increase the efficiency of hydrocarbon degradation in contaminated marine sediments.

  9. Analogies Between Colloidal Sedimentation and Turbulent Convection at High Prandtl Numbers

    NASA Technical Reports Server (NTRS)

    Tong, P.; Ackerson, B. J.

    1999-01-01

    A new set of coarse-grained equations of motion is proposed to describe concentration and velocity fluctuations in a dilute sedimenting suspension of non-Brownian particles. With these equations, colloidal sedimentation is found to be analogous to turbulent convection at high Prandtl numbers. Using Kraichnan's mixing-length theory, we obtain scaling relations for the diffusive dissipation length delta(sub theta), the velocity variance delta u, and the concentration variance delta phi. The obtained scaling laws over varying particle radius alpha and volume fraction phi(sub ) are in excellent agreement with the recent experiment by Segre, Herbolzheimer, and Chaikin. The analogy between colloidal sedimentation and turbulent convection gives a simple interpretation for the existence of a velocity cut-off length, which prevents hydrodynamic dispersion coefficients from being divergent. It also provides a coherent framework for the study of sedimentation dynamics in different colloidal systems.

  10. Factitious psychogenic nonepileptic paroxysmal episodes

    PubMed Central

    Romano, Alissa; Alqahtani, Saeed; Griffith, James; Koubeissi, Mohamad Z.

    2014-01-01

    Mistaking psychogenic nonepileptic paroxysmal episodes (PNEPEs) for epileptic seizures (ES) is potentially dangerous, and certain features should alert physicians to a possible PNEPE diagnosis. Psychogenic nonepileptic paroxysmal episodes due to factitious seizures carry particularly high risks of morbidity or mortality from nonindicated emergency treatment and, often, high costs in wasted medical treatment expenditures. We report a case of a 28-year-old man with PNEPEs that were misdiagnosed as ES. The patient had been on four antiseizure medications (ASMs) with therapeutic serum levels and had had multiple intubations in the past for uncontrolled episodes. He had no episodes for two days of continuous video-EEG monitoring. He then disconnected his EEG cables and had an episode of generalized stiffening and cyanosis, followed by jerking and profuse bleeding from the mouth. The manifestations were unusually similar to those of ES, except that he was clearly startled by spraying water on his face, while he was stiff in all extremities and unresponsive. There were indications that he had sucked blood from his central venous catheter to expel through his mouth during his PNEPEs while consciously holding his breath. Normal video-EEG monitoring; the patient's volitional and deceptive acts to fabricate the appearance of illness, despite pain and personal endangerment; and the absence of reward other than remaining in a sick role were all consistent with a diagnosis of factitious disorder. PMID:25667902

  11. Factitious psychogenic nonepileptic paroxysmal episodes.

    PubMed

    Romano, Alissa; Alqahtani, Saeed; Griffith, James; Koubeissi, Mohamad Z

    2014-01-01

    Mistaking psychogenic nonepileptic paroxysmal episodes (PNEPEs) for epileptic seizures (ES) is potentially dangerous, and certain features should alert physicians to a possible PNEPE diagnosis. Psychogenic nonepileptic paroxysmal episodes due to factitious seizures carry particularly high risks of morbidity or mortality from nonindicated emergency treatment and, often, high costs in wasted medical treatment expenditures. We report a case of a 28-year-old man with PNEPEs that were misdiagnosed as ES. The patient had been on four antiseizure medications (ASMs) with therapeutic serum levels and had had multiple intubations in the past for uncontrolled episodes. He had no episodes for two days of continuous video-EEG monitoring. He then disconnected his EEG cables and had an episode of generalized stiffening and cyanosis, followed by jerking and profuse bleeding from the mouth. The manifestations were unusually similar to those of ES, except that he was clearly startled by spraying water on his face, while he was stiff in all extremities and unresponsive. There were indications that he had sucked blood from his central venous catheter to expel through his mouth during his PNEPEs while consciously holding his breath. Normal video-EEG monitoring; the patient's volitional and deceptive acts to fabricate the appearance of illness, despite pain and personal endangerment; and the absence of reward other than remaining in a sick role were all consistent with a diagnosis of factitious disorder. PMID:25667902

  12. Erosion resistance and behaviour of highly organic in-sewer sediment.

    PubMed

    Seco, I; Gómez Valentín, M; Schellart, A; Tait, S

    2014-01-01

    Reliable prediction of time-varying pollutant loads in combined sewer systems during storm periods can aid better management of the release of pollution into natural environments as well as enhancing storage tank design. Better understanding of the behaviour of sewer sediments is crucial for the development of models that adequately describe the transport of in-sewer solids and accurately predict the changes in pollutant concentration within combined sewers during storm events. This paper reports on the results of a test programme to examine the erosion of highly organic sewer sediment under the application of time-varying shear stress. The tests were carried out with and without supplying oxygen, and varying simulated dry-weather periods. The aim was to investigate the behaviour of real in-sewer sediment with a high organic content (around 80%) in an attempt to improve prediction of the transport rates under the particular Mediterranean conditions of long dry-period/build-up and intense rainfall/wash-off, and understand how this environment affects the erosional resistance and subsequent sediment release. Results have been compared with previous work on lower organic content sewer sediments and artificial organic sediment.

  13. Characterization of near-bed sediment transport in air and water by high-speed video

    NASA Astrophysics Data System (ADS)

    Martin, C. S.; Hamm, N. T.; Cushman-Roisin, B.; Dade, W. B.

    2010-12-01

    Near-bed sediment transport comprises a large fraction of the total mass flux of environmental flows, yet is difficult to characterize at fine scales without disturbing the flow. Particle-tracking velocimetry by means of high-speed video has proven to be an effective technique for quantifying particle behavior under this constraint. We present here results of experiments examining: i) the vertical structure of mass and momentum and ii) initial properties of particle trajectories within a layer of sediment transport immediately above a bed of loose grains in channel flows. Observations were conducted in both air and water of test particles with the density of quartz and with median diameters that ranged from 30 µm to 600 µm. Analysis of such a wide range of sediment transport conditions by the same method permits an evaluation of the fundamental structure of the near-bed sediment transport layer, including particle concentration and particle velocity. With appropriate normalization, self-consistent structure is identified for all particles in air, medium sand in water, and fine sand and silt in water. The integral values by which the data were normalized are found to be consistent with the relevant physical properties of the sediment transporting flow. This study advances the use of high-speed videography as a method by which to investigate the detailed mechanics of particle motion in a near-bed boundary layer, which in turn, can provide boundary conditions used for modeling sediment transport in a variety of applications.

  14. Abnormal monsoon years and their control on erosion and sediment flux in the high, arid northwest Himalaya

    NASA Astrophysics Data System (ADS)

    Bookhagen, Bodo; Thiede, Rasmus C.; Strecker, Manfred R.

    2005-02-01

    The interplay between topography and Indian summer monsoon circulation profoundly controls precipitation distribution, sediment transport, and river discharge along the Southern Himalayan Mountain Front (SHF). The Higher Himalayas form a major orographic barrier that separates humid sectors to the south and arid regions to the north. During the Indian summer monsoon, vortices transport moisture from the Bay of Bengal, swirl along the SHF to the northwest, and cause heavy rainfall when colliding with the mountain front. In the eastern and central parts of the Himalaya, precipitation measurements derived from passive microwave analysis (SSM/I) show a strong gradient, with high values at medium elevations and extensive penetration of moisture along major river valleys into the orogen. The end of the monsoonal conveyer belt is near the Sutlej Valley in the NW Himalaya, where precipitation is lower and rainfall maxima move to lower elevations. This region thus comprises a climatic transition zone that is very sensitive to changes in Indian summer monsoon strength. To constrain magnitude, temporal, and spatial distribution of precipitation, we analyzed high-resolution passive microwave data from the last decade and identified an abnormal monsoon year (AMY) in 2002. During the 2002 AMY, violent rainstorms conquered orographic barriers and penetrated far into otherwise arid regions in the northwest Himalaya at elevations in excess of 3 km asl. While precipitation in these regions was significantly increased and triggered extensive erosional processes (i.e., debris flows) on sparsely vegetated, steep hillslopes, mean rainfall along the low to medium elevations was not significantly greater in magnitude. This shift may thus play an important role in the overall sediment flux toward the Himalayan foreland. Using extended precipitation and sediment flux records for the last century, we show that these events have a decadal recurrence interval during the present-day monsoon

  15. Critical peripheral ischemia precipitated by severe episode of Raynaud's phenomenon in a patient with aPL-positive systemic lupus erythematosus, upon high titer anti-RNP seroconversion.

    PubMed

    Levy, O; Maslakov, I; Vosco, S; Markov, A; Amit-Vazina, M; Tishler, M

    2015-03-01

    A 35-year-old female with long standing aPL-positive lupus without history of thromboembolic events, who has developed critical peripheral ischemia (CPI) is described. An episode of severe Raynaud's phenomenon rapidly progressed to an extensive digit-threatening ischemia, involving bilateral hands and feet. She was successfully treated with corticosteroids, anticoagulation, iloprost, sildenafil, and nifedipine. Her serological studies were remarkable for the emergence of high titer anti-RNP seroconversion and an increase in aPL titer, suggesting that these autoantibodies played a role in the pathogenesis of CPI. It is important to note that such observation should herald this potentially devastating complication of systemic lupus erythematosus.

  16. Unexpectedly high radioactivity burdens in ice-rafted sediments from the Canadian Arctic Archipelago.

    PubMed

    Cota, Glenn F; Cooper, Lee W; Darby, Dennis A; Larsen, I L

    2006-07-31

    Unexpectedly high specific activities of (137)Cs (1800-2000 Bq kg(-1) dry weight) have been detected in fine-grained sediments entrained in multi-year sea ice floes grounded in Resolute Bay near the center of the Northwest Passage through the Canadian Arctic Archipelago. These results are remarkable because: (1) the specific activities are about two orders of magnitude higher than average specific activities detected in previous studies of sea ice rafted sediments from the Arctic Ocean, (2) two independent observations of these unexpectedly high specific activities were made several years apart, (3) the sampling site is on the opposite side of the Arctic basin from potential radioactive sources such as disposal and weapons testing sites of the former Soviet Union and nuclear fuel reprocessing sites in western Europe, and (4) the closest compositional match to known geologic source regions is Banks Island, on the western edge of the Arctic Archipelago, although a smaller number of grains from one of the two samples were mineralogically matched to sediments in the Laptev Sea. Consequently, the sediments are probably not from a single distinct source and were likely mixed during sea ice transport. Coupled with previous observations of higher radionuclide specific activities in some sea ice rafted sediments relative to bottom sediments, these new observations indicate that comparatively high as well as variable radioactive contaminant burdens in ice rafted sediments must be common and geographically independent of proximity to known contaminant sources. The mechanisms that would facilitate these unexpected high radionuclide burdens in sea ice are not known and require additional study, as well as investigations of the implications for the transport and fate of contaminants in Arctic sea ice. PMID:16197983

  17. Unexpectedly high radioactivity burdens in ice-rafted sediments from the Canadian Arctic Archipelago.

    PubMed

    Cota, Glenn F; Cooper, Lee W; Darby, Dennis A; Larsen, I L

    2006-07-31

    Unexpectedly high specific activities of (137)Cs (1800-2000 Bq kg(-1) dry weight) have been detected in fine-grained sediments entrained in multi-year sea ice floes grounded in Resolute Bay near the center of the Northwest Passage through the Canadian Arctic Archipelago. These results are remarkable because: (1) the specific activities are about two orders of magnitude higher than average specific activities detected in previous studies of sea ice rafted sediments from the Arctic Ocean, (2) two independent observations of these unexpectedly high specific activities were made several years apart, (3) the sampling site is on the opposite side of the Arctic basin from potential radioactive sources such as disposal and weapons testing sites of the former Soviet Union and nuclear fuel reprocessing sites in western Europe, and (4) the closest compositional match to known geologic source regions is Banks Island, on the western edge of the Arctic Archipelago, although a smaller number of grains from one of the two samples were mineralogically matched to sediments in the Laptev Sea. Consequently, the sediments are probably not from a single distinct source and were likely mixed during sea ice transport. Coupled with previous observations of higher radionuclide specific activities in some sea ice rafted sediments relative to bottom sediments, these new observations indicate that comparatively high as well as variable radioactive contaminant burdens in ice rafted sediments must be common and geographically independent of proximity to known contaminant sources. The mechanisms that would facilitate these unexpected high radionuclide burdens in sea ice are not known and require additional study, as well as investigations of the implications for the transport and fate of contaminants in Arctic sea ice.

  18. A sediment record of barrier estuary behaviour at the mesoscale: Interpreting high-resolution particle size analysis

    NASA Astrophysics Data System (ADS)

    Clarke, David W.; Boyle, John F.; Chiverrell, Richard C.; Lario, Javier; Plater, Andrew J.

    2014-09-01

    At present, limited understanding of mesoscale (years-decades-centuries) back-barrier lagoon, barrier estuary behaviour is a critical shortcoming for resource managers and decision makers. In this paper, high-resolution particle size analysis of a sediment core from an intermittently open and closed barrier estuary is utilised to reconstruct a history of back-barrier environmental change at mesoscale temporal resolution. Sediments from Pescadero Marsh, California, were analysed for their particle size distribution at consecutive 2-mm intervals down-core. Site selection, informed by a time series of maps and aerial photographs coupled with a robust core chronology, ensured that the particle size data primarily reflect changing hydrodynamics of the back-barrier area over the European-American era (1850 to the present). Following more traditional plotting of particle size data and summary statistics, and statistical analysis of particle size end-members, visual analysis and categorisation of particle size distribution curves (PSDCs) provide an effective basis for the identification of recurring modal sizes and subpopulations. These particle size windows (PSWs) are interpreted as reflecting different modes of sediment transport and deposition, i.e., suspension and saltation loads, the varying prominence of which is interpreted as being modified by barrier integrity. When considered together, the down-core mean particle size (MPS) trend and individual PSDCs offer considerable insight into mesoscale system behaviour at subannual resolution over multiple years. This behaviour is expressed in the recurrence of characteristic barrier estuarine environments (closed lagoon, tidal lagoon, tidal marsh, and open estuary) and the overall barrier regime, and their persistence over the last c. 150 years. Subannual and multiannual fluctuations in back-barrier environmental configuration are seen to be superimposed on a longer-term quasi-stable barrier regime, demonstrating the value

  19. High virus-to-cell ratios indicate ongoing production of viruses in deep subsurface sediments.

    PubMed

    Engelhardt, Tim; Kallmeyer, Jens; Cypionka, Heribert; Engelen, Bert

    2014-07-01

    Marine sediments cover two-thirds of our planet and harbor huge numbers of living prokaryotes. Long-term survival of indigenous microorganisms within the deep subsurface is still enigmatic, as sources of organic carbon are vanishingly small. To better understand controlling factors of microbial life, we have analyzed viral abundance within a comprehensive set of globally distributed subsurface sediments. Phages were detected by electron microscopy in deep (320 m below seafloor), ancient (∼14 Ma old) and the most oligotrophic subsurface sediments of the world's oceans (South Pacific Gyre (SPG)). The numbers of viruses (10(4)-10(9) cm(-3), counted by epifluorescence microscopy) generally decreased with sediment depth, but always exceeded the total cell counts. The enormous numbers of viruses indicate their impact as a controlling factor for prokaryotic mortality in the marine deep biosphere. The virus-to-cell ratios increased in deeper and more oligotrophic layers, exhibiting values of up to 225 in the deep subsurface of the SPG. High numbers of phages might be due to absorption onto the sediment matrix and a diminished degradation by exoenzymes. However, even in the oldest sediments, microbial communities are capable of maintaining viral populations, indicating an ongoing viral production and thus, viruses provide an independent indicator for microbial life in the marine deep biosphere.

  20. High virus-to-cell ratios indicate ongoing production of viruses in deep subsurface sediments.

    PubMed

    Engelhardt, Tim; Kallmeyer, Jens; Cypionka, Heribert; Engelen, Bert

    2014-07-01

    Marine sediments cover two-thirds of our planet and harbor huge numbers of living prokaryotes. Long-term survival of indigenous microorganisms within the deep subsurface is still enigmatic, as sources of organic carbon are vanishingly small. To better understand controlling factors of microbial life, we have analyzed viral abundance within a comprehensive set of globally distributed subsurface sediments. Phages were detected by electron microscopy in deep (320 m below seafloor), ancient (∼14 Ma old) and the most oligotrophic subsurface sediments of the world's oceans (South Pacific Gyre (SPG)). The numbers of viruses (10(4)-10(9) cm(-3), counted by epifluorescence microscopy) generally decreased with sediment depth, but always exceeded the total cell counts. The enormous numbers of viruses indicate their impact as a controlling factor for prokaryotic mortality in the marine deep biosphere. The virus-to-cell ratios increased in deeper and more oligotrophic layers, exhibiting values of up to 225 in the deep subsurface of the SPG. High numbers of phages might be due to absorption onto the sediment matrix and a diminished degradation by exoenzymes. However, even in the oldest sediments, microbial communities are capable of maintaining viral populations, indicating an ongoing viral production and thus, viruses provide an independent indicator for microbial life in the marine deep biosphere. PMID:24430483

  1. Episodic future thinking.

    PubMed

    Atance, Cristina M.; O'Neill, Daniela K.

    2001-12-01

    Thinking about the future is an integral component of human cognition - one that has been claimed to distinguish us from other species. Building on the construct of episodic memory, we introduce the concept of 'episodic future thinking': a projection of the self into the future to pre-experience an event. We argue that episodic future thinking has explanatory value when considering recent work in many areas of psychology: cognitive, social and personality, developmental, clinical and neuropsychology. Episodic future thinking can serve as a unifying concept, connecting aspects of diverse research findings and identifying key questions requiring further reflection and study.

  2. In Situ, High-Resolution Profiles of Labile Metals in Sediments of Lake Taihu.

    PubMed

    Wang, Dan; Gong, Mengdan; Li, Yangyang; Xu, Lv; Wang, Yan; Jing, Rui; Ding, Shiming; Zhang, Chaosheng

    2016-01-01

    Characterizing labile metal distribution and biogeochemical behavior in sediments is crucial for understanding their contamination characteristics in lakes, for which in situ, high-resolution data is scare. The diffusive gradient in thin films (DGT) technique was used in-situ at five sites across Lake Taihu in the Yangtze River delta in China to characterize the distribution and mobility of eight labile metals (Fe, Mn, Zn, Ni, Cu, Pb, Co and Cd) in sediments at a 3 mm spatial resolution. The results showed a great spatial heterogeneity in the distributions of redox-sensitive labile Fe, Mn and Co in sediments, while other metals had much less marked structure, except for downward decreases of labile Pb, Ni, Zn and Cu in the surface sediment layers. Similar distributions were found between labile Mn and Co and among labile Ni, Cu and Zn, reflecting a close link between their geochemical behaviors. The relative mobility, defined as the ratio of metals accumulated by DGT to the total contents in a volume of sediments with a thickness of 10 mm close to the surface of DGT probe, was the greatest for Mn and Cd, followed by Zn, Ni, Cu and Co, while Pb and Fe had the lowest mobility; this order generally agreed with that defined by the modified BCR approach. Further analyses showed that the downward increases of pH values in surface sediment layer may decrease the lability of Pb, Ni, Zn and Cu as detected by DGT, while the remobilization of redox-insensitive metals in deep sediment layer may relate to Mn cycling through sulphide coprecipitation, reflected by several corresponding minima between these metals and Mn. These in situ data provided the possibility for a deep insight into the mechanisms involved in the remobilization of metals in freshwater sediments. PMID:27608033

  3. In Situ, High-Resolution Profiles of Labile Metals in Sediments of Lake Taihu

    PubMed Central

    Wang, Dan; Gong, Mengdan; Li, Yangyang; Xu, Lv; Wang, Yan; Jing, Rui; Ding, Shiming; Zhang, Chaosheng

    2016-01-01

    Characterizing labile metal distribution and biogeochemical behavior in sediments is crucial for understanding their contamination characteristics in lakes, for which in situ, high-resolution data is scare. The diffusive gradient in thin films (DGT) technique was used in-situ at five sites across Lake Taihu in the Yangtze River delta in China to characterize the distribution and mobility of eight labile metals (Fe, Mn, Zn, Ni, Cu, Pb, Co and Cd) in sediments at a 3 mm spatial resolution. The results showed a great spatial heterogeneity in the distributions of redox-sensitive labile Fe, Mn and Co in sediments, while other metals had much less marked structure, except for downward decreases of labile Pb, Ni, Zn and Cu in the surface sediment layers. Similar distributions were found between labile Mn and Co and among labile Ni, Cu and Zn, reflecting a close link between their geochemical behaviors. The relative mobility, defined as the ratio of metals accumulated by DGT to the total contents in a volume of sediments with a thickness of 10 mm close to the surface of DGT probe, was the greatest for Mn and Cd, followed by Zn, Ni, Cu and Co, while Pb and Fe had the lowest mobility; this order generally agreed with that defined by the modified BCR approach. Further analyses showed that the downward increases of pH values in surface sediment layer may decrease the lability of Pb, Ni, Zn and Cu as detected by DGT, while the remobilization of redox-insensitive metals in deep sediment layer may relate to Mn cycling through sulphide coprecipitation, reflected by several corresponding minima between these metals and Mn. These in situ data provided the possibility for a deep insight into the mechanisms involved in the remobilization of metals in freshwater sediments. PMID:27608033

  4. Concurrent low- and high-affinity sulfate reduction kinetics in marine sediment

    NASA Astrophysics Data System (ADS)

    Harder Tarpgaard, Irene; Røy, Hans; Jørgensen, Bo Barker

    Bacterial sulfate reduction in marine sediments generally occurs in the presence of high millimolar concentrations of sulfate. Published data indicate that low sulfate concentrations may limit sulfate reduction rates below 0.2-2 mM. Yet, high sulfate reduction rates occur in the 1-100 μM range in freshwater sediments and at the sulfate-methane transition in marine sediments. Through a combination of 35S-tracer experiments, including initial velocity experiments and time course experiments, we searched for different sulfate affinities in the mixed community of sulfate reducers in a marine sediment. We supported the radiotracer experiments with a highly sensitive ion chromatographic technique for sulfate with a detection limit of 0.15 μM SO 42- in marine pore water. Our results showed that high and low affinities for sulfate co-occur and that the applied experimental approach may determine the observed apparent half saturation constant, Km. Our experimental and model data both show that sulfate reduction in the studied marine sediment could be explained by two dominating affinities for sulfate: a low affinity with a mean half saturation constant, Km, of 430 μM SO 42- and a high affinity with a mean Km of 2.6 μM SO 42-. The high-affinity sulfate reduction was thermodynamically un-constrained down to <1 μM SO 42-, both in our experiments and under in situ conditions. The reduction of radio-labeled sulfate was partly reversible due to concurrent re-oxidation of sulfide by Fe(III) and possibly due to a reversibility of the enzymatic pathway of sulfate reduction. A literature survey of apparent Km values for sediments and pure cultures is presented and discussed.

  5. Brain structure in people at ultra-high risk of psychosis, patients with first-episode schizophrenia, and healthy controls: a VBM study.

    PubMed

    Nenadic, Igor; Dietzek, Maren; Schönfeld, Nils; Lorenz, Carsten; Gussew, Alexander; Reichenbach, Jürgen R; Sauer, Heinrich; Gaser, Christian; Smesny, Stefan

    2015-02-01

    Early intervention research in schizophrenia has suggested that brain structural alterations might be present in subjects at high risk of developing psychosis. The heterogeneity of regional effects of these changes, which is established in schizophrenia, however, has not been explored in prodromal or high-risk populations. We used high-resolution MRI and voxel-based morphometry (VBM8) to analyze grey matter differences in 43 ultra high-risk subjects for psychosis (meeting ARMS criteria, identified through CAARMS interviews), 24 antipsychotic-naïve first-episode schizophrenia patients and 49 healthy controls (groups matched for age and gender). Compared to healthy controls, resp., first-episode schizophrenia patients had reduced regional grey matter in left prefrontal, insula, right parietal and left temporal cortices, while the high-risk group showed reductions in right middle temporal and left anterior frontal cortices. When dividing the ultra-high-risk group in those with a genetic risk vs. those with attenuated psychotic symptoms, the former showed left anterior frontal, right caudate, as well as a smaller right hippocampus, and amygdala reduction, while the latter subgroup showed right middle temporal cortical reductions (each compared to healthy controls). Our findings in a clinical psychosis high-risk cohort demonstrate variability of brain structural changes according to subgroup and background of elevated risk, suggesting frontal and possibly also hippocampal/amygdala changes in individuals with genetic susceptibility. Heterogeneity of structural brain changes (as seen in schizophrenia) appears evident even at high-risk stage, prior to potential onset of psychosis.

  6. Respiratory health concerns in children at some strategic locations from high PM levels during crop residue burning episodes

    NASA Astrophysics Data System (ADS)

    Gupta, Sachin; Agarwal, Ravinder; Mittal, Susheel K.

    2016-07-01

    Particulate Matter (PM) levels in the ambient air of three urban sites of strategic importance in Punjab (second largest agricultural state of India) were monitored from September 2013 to June 2014 covering two seasons of crop residue burning episodes of rice and wheat, respectively. During both crop periods, the levels varied from 71 to 167 μgm-3(PM10) and 43-107 μgm-3 (PM2.5), which were observed to be much beyond the permissible limits of 100 μgm-3 for PM10 and 60 μgm-3 for PM2.5 set by state pollution control agencies. Simultaneously, Pulmonary Function Test (PFT) parameters of children (age group 10-16 years) residing at these sites were monitored. PFT parameters like Forced Vital Capacity (FVC) and Peak Expiratory Flow (PEF) were monitored on 50 healthy subjects at each site. The results indicated an alarming fall in FVC (5%-7%) and in PEF (4%-6%) parameters during the crop residue burning period's .The decrement was almost same for all age groups of children. The adverse effect was more on female subjects than male subjects. The impact of particulate matter pollution was more prominent in industrially important site (7%, SIS) as compared to historically (3%, HIS) and commercially (4%, CAS) important sites.

  7. Characterizing riverbed sediment using high-frequency acoustics 1: spectral properties of scattering

    USGS Publications Warehouse

    Buscombe, Daniel D.; Grams, Paul E.; Kaplinski, Matt A.

    2014-01-01

    Bed-sediment classification using high-frequency hydro-acoustic instruments is challenging when sediments are spatially heterogeneous, which is often the case in rivers. The use of acoustic backscatter to classify sediments is an attractive alternative to analysis of topography because it is potentially sensitive to grain-scale roughness. Here, a new method is presented which uses high-frequency acoustic backscatter from multibeam sonar to classify heterogeneous riverbed sediments by type (sand, gravel,rock) continuously in space and at small spatial resolution. In this, the first of a pair of papers that examine the scattering signatures from a heterogeneous riverbed, methods are presented to construct spatially explicit maps of spectral properties from geo-referenced point clouds of geometrically and radiometrically corrected echoes. Backscatter power spectra are computed to produce scale and amplitude metrics that collectively characterize the length scales of stochastic measures of riverbed scattering, termed ‘stochastic geometries’. Backscatter aggregated over small spatial scales have spectra that obey a power-law. This apparently self-affine behavior could instead arise from morphological- and grain-scale roughnesses over multiple overlapping scales, or riverbed scattering being transitional between Rayleigh and geometric regimes. Relationships exist between stochastic geometries of backscatter and areas of rough and smooth sediments. However, no one parameter can uniquely characterize a particular substrate, nor definitively separate the relative contributions of roughness and acoustic impedance (hardness). Combinations of spectral quantities do, however, have the potential to delineate riverbed sediment patchiness, in a data-driven approach comparing backscatter with bed-sediment observations (which is the subject of part two of this manuscript).

  8. Effects of cumulative stressful and acute variation episodes of farm climate conditions on late embryo/early fetal loss in high producing dairy cows

    NASA Astrophysics Data System (ADS)

    Santolaria, Pilar; López-Gatius, Fernando; García-Ispierto, Irina; Bech-Sàbat, Gregori; Angulo, Eduardo; Carretero, Teresa; Sánchez-Nadal, Jóse Antonio; Yániz, Jesus

    2010-01-01

    The aim of this study was to determine possible relationships between farm climate conditions, recorded from day 0 to day 40 post-artificial insemination (AI), and late embryo/early fetal loss in high producing dairy cows. Pregnancy was diagnosed by rectal ultrasonography between 28 and 34 days post-AI. Fetal loss was registered when a further 80- to 86-day diagnosis proved negative. Climate variables such as air temperature and relative humidity (RH) were monitored in the cubicles area for each 30-min period. Temperature-humidity indices (THI); cumulative stressful values and episodes of acute change (defined as the mean daily value 1.2 times higher or lower than the mean daily values of the 10 previous days) of the climate variables were calculated. The data were derived from 759 cows in one herd. A total of 692 pregnancies (91.2%) carried singletons and 67 (8.8%) carried twins. No triplets were recorded. Pregnancy loss was recorded in 6.7% (51/759) of pregnancies: 5.6% (39/692) in single and 17.9% (12/67) in twin pregnancies. Using logistic regression procedures, a one-unit increase in the daily cumulative number of hours for the THI values higher than 85 during days 11-20 of gestation caused a 1.57-fold increase in the pregnancy loss, whereas the likelihood of fetal loss increased by a factor of 1.16 for each additional episode of acute variation for the maximum THI values during gestation days 0-40. THI values higher than 85 and episodes of acute variation for the maximum THI values were only recorded during the warm and cool periods, respectively. The presence of twins led to a 3.98-fold increase in pregnancy loss. In conclusion, our findings show that cumulative stressful and episodes of acute variation of climatic conditions can compromise the success of gestation during both the cool and warm periods of the year. Twin pregnancy was confirmed as a main factor associated with pregnancy loss.

  9. Salinity drives archaeal distribution patterns in high altitude lake sediments on the Tibetan Plateau.

    PubMed

    Liu, Yongqin; Priscu, John C; Xiong, Jinbo; Conrad, Ralf; Vick-Majors, Trista; Chu, Haiyan; Hou, Juzhi

    2016-03-01

    Archaeal communities and the factors regulating their diversity in high altitude lakes are poorly understood. Here, we provide the first high-throughput sequencing study of Archaea from Tibetan Plateau lake sediments. We analyzed twenty lake sediments from the world's highest and largest plateau and found diverse archaeal assemblages that clustered into groups dominated by methanogenic Euryarchaeota, Crenarchaeota and Halobacteria/mixed euryarchaeal phylotypes. Statistical analysis inferred that salinity was the major driver of community composition, and that archaeal diversity increased with salinity. Sediments with the highest salinities were mostly dominated by Halobacteria. Crenarchaeota dominated at intermediate salinities, and methanogens were present in all lake sediments, albeit most abundant at low salinities. The distribution patterns of the three functional types of methanogens (hydrogenotrophic, acetotrophic and methylotrophic) were also related to changes in salinity. Our results show that salinity is a key factor controlling archaeal community diversity and composition in lake sediments on a spatial scale that spans nearly 2000 km on the Tibetan Plateau.

  10. Metal and Metalloid Size-Fractionation Strategies in Spatial High-Resolution Sediment Pore Water Profiles.

    PubMed

    Fabricius, Anne-Lena; Duester, Lars; Ecker, Dennis; Ternes, Thomas A

    2016-09-01

    Sediment water interfaces (SWIs) are often characterized by steep biogeochemical gradients determining the fate of inorganic and organic substances. Important transport processes at the SWI are sedimentation and resuspension of particulate matter and fluxes of dissolved materials. A microprofiling and micro sampling system (missy), enabling high resolution measurements of sediment parameters in parallel to a direct sampling of sediment pore waters (SPWs), was combined with two fractionation approaches (ultrafiltration (UF) and cloud point extraction (CPE)) to differentiate between colloidal and dissolved fractions at a millimeter scale. An inductively coupled plasma-quadrupole mass spectrometry method established for volumes of 300 μL enabled the combination of the high resolution fractionation with multi-element analyzes. UF and CPE comparably indicated that manganese is predominantly present in dissolved fractions of SPW profiles. Differences found for cobalt and iron showed that the results obtained by size-dependent UF and micelle-mediated CPE do not necessarily coincide, probably due to different fractionation mechanisms. Both methods were identified as suitable for investigating fraction-related element concentrations in SPW along sediment depth profiles at a millimeter scale. The two approaches are discussed with regard to their advantages, limitations, potential sources of errors, further improvements, and potential future applications. PMID:27504804

  11. Salinity drives archaeal distribution patterns in high altitude lake sediments on the Tibetan Plateau.

    PubMed

    Liu, Yongqin; Priscu, John C; Xiong, Jinbo; Conrad, Ralf; Vick-Majors, Trista; Chu, Haiyan; Hou, Juzhi

    2016-03-01

    Archaeal communities and the factors regulating their diversity in high altitude lakes are poorly understood. Here, we provide the first high-throughput sequencing study of Archaea from Tibetan Plateau lake sediments. We analyzed twenty lake sediments from the world's highest and largest plateau and found diverse archaeal assemblages that clustered into groups dominated by methanogenic Euryarchaeota, Crenarchaeota and Halobacteria/mixed euryarchaeal phylotypes. Statistical analysis inferred that salinity was the major driver of community composition, and that archaeal diversity increased with salinity. Sediments with the highest salinities were mostly dominated by Halobacteria. Crenarchaeota dominated at intermediate salinities, and methanogens were present in all lake sediments, albeit most abundant at low salinities. The distribution patterns of the three functional types of methanogens (hydrogenotrophic, acetotrophic and methylotrophic) were also related to changes in salinity. Our results show that salinity is a key factor controlling archaeal community diversity and composition in lake sediments on a spatial scale that spans nearly 2000 km on the Tibetan Plateau. PMID:26887660

  12. High methylmercury production under ferruginous conditions in sediments impacted by sewage treatment plant discharges.

    PubMed

    Bravo, Andrea G; Bouchet, Sylvain; Guédron, Stéphane; Amouroux, David; Dominik, Janusz; Zopfi, Jakob

    2015-09-01

    Sewage treatment plants (STPs) are important point sources of mercury (Hg) to the environment. STPs are also significant sources of iron when hydrated ferric oxide (HFO) is used as a dephosphatation agent during water purification. In this study, we combined geochemical and microbiological characterization with Hg speciation and sediment amendments to evaluate the impact of STP's effluents on monomethylmercury (MMHg) production. The highest in-situ Hg methylation was found close to the discharge pipe in subsurface sediments enriched with Hg, organic matter, and iron. There, ferruginous conditions were prevailing with high concentrations of dissolved Fe(2+) and virtually no free sulfide in the porewater. Sediment incubations demonstrated that the high MMHg production close to the discharge was controlled by low demethylation yields. Inhibition of dissimilatory sulfate reduction with molybdate led to increased iron reduction rates and Hg-methylation, suggesting that sulfate-reducing bacteria (SRB) may not have been the main Hg methylators under these conditions. However, Hg methylation in sediments amended with amorphous Fe(III)-oxides was only slightly higher than control conditions. Thus, in addition to iron-reducing bacteria, other non-SRB most likely contributed to Hg methylation. Overall, this study highlights that sediments impacted by STP discharges can become local hot-spots for Hg methylation due to the combined inputs of i) Hg, ii) organic matter, which fuels bacterial activities and iii) iron, which keeps porewater sulfide concentration low and hence Hg bioavailable.

  13. In situ two-dimensional high-resolution profiling of sulfide in sediment interstitial waters.

    PubMed

    DeVries, Christopher R; Wang, Feiyue

    2003-02-15

    A recently developed technique of diffusive gradients in thin films (D6T)-computer-imaging densitometry (CID) was improved to study in situ two-dimensional distributions of sulfide in sediment interstitial waters adjacent to the DGT device. The in situ profiler accumulates sulfide from the sediment interstitial water through a diffusive gel onto a AgI binding gel to form black Ag2S. The amount of sulfide bound in the binding gel is then determined from the gray scale density of the dried binding gel. New gel-making procedures were employed to produce stable, evenly dispersed AgI binding gels and to minimize the darkening of the AgI gel upon exposure to light The improved DGT-CID technique was used to profile the distribution of sulfide in sediment interstitial waters at Delta Marsh, a highly productive Prairie wetland on the south shore of Lake Manitoba, at a vertical and lateral resolution of < or = 0.4 mm. The in situ high-resolution microprofiles revealed unprecedented two-dimensional heterogeneity in sulfide concentrations in the sediment interstitial waters adjacent to the DGT device. The mosaic distribution of oxic and sulfidic microenvironments suggested not only the complexity and heterogeneity of the biogeochemistry of sulfur species and sulfide-binding metals (e.g., Cd, Cu, Pb, Hg, Zn) in sediments but also the capability of aquatic organisms for coping with the sulfidic environment

  14. Patients with first-episode, drug-naive schizophrenia and subjects at ultra-high risk of psychosis shared increased cerebellar-default mode network connectivity at rest

    PubMed Central

    Wang, Houliang; Guo, Wenbin; Liu, Feng; Wang, Guodong; Lyu, Hailong; Wu, Renrong; Chen, Jindong; Wang, Shuai; Li, Lehua; Zhao, Jingping

    2016-01-01

    Increased cerebellar-default mode network (DMN) connectivity has been observed in first-episode, drug-naive patients with schizophrenia. However, it remains unclear whether increased cerebellar-DMN connectivity starts earlier than disease onset. Thirty-four ultra-high risk (UHR) subjects, 31 first-episode, drug-naive patients with schizophrenia and 37 healthy controls were enrolled for a resting-state scan. The imaging data were analyzed using the seed-based functional connectivity (FC) method. Compared with the controls, UHR subjects and patients with schizophrenia shared increased connectivity between the right Crus I and bilateral posterior cingulate cortex/precuneus and between Lobule IX and the left superior medial prefrontal cortex. There are positive correlations between the right Crus I-bilateral precuneus connectivity and clinical variables (Structured Interview for Prodromal Syndromes/Positive and Negative Symptom Scale negative symptoms/total scores) in the UHR subjects. Increased cerebellar-DMN connectivity shared by the UHR subjects and the patients not only highlights the importance of the DMN in the pathophysiology of psychosis but also may be a trait alteration for psychosis. PMID:27188233

  15. Episodic acidification of small streams in the northeastern united states: ionic controls of episodes

    USGS Publications Warehouse

    Wigington, P.J.; DeWalle, David R.; Murdoch, Peter S.; Kretser, W.A.; Simonin, H.A.; Van Sickle, J.; Baker, J.P.

    1996-01-01

    As part of the Episodic Response Project (ERP), we intensively monitored discharge and stream chemistry of 13 streams located in the Northern Appalachian region of Pennsylvania and in the Catskill and Adirondack Mountains of New York from fall 1988 to spring 1990. The ERP clearly documented the occurrence of acidic episodes with minimum episodic pH ??? 5 and inorganic monomeric Al (Alim) concentrations >150 ??g/L in at least two study streams in each region. Several streams consistently experienced episodes with maximum Alim concentrations >350 ??g/L. Acid neutralizing capacity (ANC) depressions resulted from complex interactions of multiple ions. Base cation decreases often made the most important contributions to ANC depressions during episodes. Organic acid pulses were also important contributors to ANC depressions in the Adirondack streams, and to a lesser extent, in the Catskill and Pennsylvania streams. Nitrate concentrations were low in the Pennsylvania streams, whereas the Catskill and Adirondack study streams had high NO3- concentrations and large episodic pulses (???54 ??eq/L). Most of the Pennsylvania study streams also frequently experienced episodic pulses of SO42- (???78 ??eq/L), whereas the Adirondack and Catskill streams did not. High baseline concentrations of SO42- (all three study areas) and NO3- (Adirondacks and Catskills) reduced episodic minimum ANC, even when these ions did not change during episodes. The ion changes that controlled the most severe episodes (lowest minimum episodic ANC) differed from the ion changes most important to smaller, more frequent episodes. Pulses of NO3- (Catskills and Adirondacks), SO42- (Pennsylvania), or organic acids became more important during major episodes. Overall, the behavior of streamwater SO42- and NO4- is an indicator that acidic deposition has contributed to the severity of episodes in the study streams.

  16. Lidar Observations of the Vertical Structure of Ozone and Aerosol during Wintertime High-Ozone Episodes Associated with Oil and Gas Exploration in the Uintah Basin

    NASA Astrophysics Data System (ADS)

    Senff, C. J.; Langford, A. O.; Banta, R. M.; Alvarez, R. J.; Weickmann, A.; Sandberg, S.; Marchbanks, R. D.; Brewer, A.; Hardesty, R. M.

    2013-12-01

    The Uintah Basin in northeast Utah has been experiencing extended periods of poor air quality in the winter months including very high levels of surface ozone. To investigate the causes of these wintertime ozone pollution episodes, two comprehensive studies were undertaken in January/February of 2012 and 2013. As part of these Uintah Basin Ozone Studies (UBOS), NOAA deployed its ground-based, scanning Tunable Optical Profiler for Aerosol and oZone (TOPAZ) lidar to document the vertical structure of ozone and aerosol backscatter from near the surface up to about 3 km above ground level (AGL). TOPAZ, along with a comprehensive set of chemistry and meteorological measurements, was situated in both years at the Horse Pool site at the northern edge of a large concentration of gas producing wells in the eastern part of the Uintah Basin. The 2012 study was characterized by unusually warm and snow-free condition and the TOPAZ lidar observed deep boundary layers (BL) and mostly well-mixed vertical ozone profiles at or slightly above tropospheric background levels. During UBOS 2013, winter weather conditions in the Uintah Basin were more typical with snow-covered ground and a persistent, shallow cold-pool layer. The TOPAZ lidar characterized with great temporal and spatial detail the evolution of multiple high-ozone episodes as well as cleanout events caused by the passage of synoptic-scale storm systems. Despite the snow cover, the TOPAZ observations show well-mixed afternoon ozone and aerosol profiles up to about 100 m AGL. After several days of pollutant buildup, BL ozone values reached 120-150 ppbv. Above the mixed layer, ozone values gradually decreased to tropospheric background values of around 50 ppbv throughout the several-hundred-meter-deep cold-pool layer and then stayed constant above that up to about 3 km AGL. During the ozone episodes, the lidar observations show no indication of either vertical or horizontal transport of high ozone levels to the surface, thus

  17. Sedimentary processes in High Arctic lakes (Cape Bounty, Melville Island, Canada): What do sediments really record?

    NASA Astrophysics Data System (ADS)

    Normandeau, Alexandre; Lamoureux, Scott; Lajeunesse, Patrick; Francus, Pierre

    2016-04-01

    Lacustrine sedimentary sequences can hold a substantial amount of information regarding paleoenvironments, hydroclimate variability and extreme events, providing critical insights into past climate change. The study of lacustrine sediments is often limited to the analysis of sediment cores from which past changes are inferred. However, studies have provided evidence that the accumulation of sediments in lacustrine basins and their distribution can be affected by a wide range of internal and external forcing mechanisms. It is therefore crucial to have a good knowledge of the factors controlling the transport and distribution of sediments in lakes prior to investigating paleoenvironmental archives. To address this knowledge gap, the Cape Bounty Arctic Watershed Observatory (CBAWO), located on southern Melville Island in the Canadian High Arctic, was initiated in 2003 as a long term monitoring site with the aim of understanding the controls over sediment transport within similar paired watersheds and lakes. The East and West lakes have been monitored each year since 2003 to document the role of hydro-climate variability on water column processes and sediment deposition. Moorings recording water electrical conductivity, temperature, density, dissolved oxygen and turbidity, as well as sediment traps were deployed during the active hydrological period (generally May-July). These data were analyzed in combination with hydrological and climatic data from the watersheds. Additionally, a high-resolution bathymetric and sub-bottom survey was completed in 2015 and allowed imaging the lake floor and sub-surface in great detail. This combination of process and lake morphological data are unique in the Arctic. The morphostratigraphic analysis reveals two highly disturbed lake floors, being widely affected by subaqueous mass movements that were triggered during the last 2000 years. Backscatter intensity maps and the presence of bedforms on each delta foresets indicate that

  18. Model tracks sediment dynamics for highly curved meandering rivers

    NASA Astrophysics Data System (ADS)

    Schultz, Colin

    2013-07-01

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

  19. Evaluating Reduction of Sediment Pollution as a Strategy for Conservation of Coral Reef in High C02 World

    NASA Astrophysics Data System (ADS)

    Maina, J. M.; de Moel, H.; Mora, C.; Ward, P.; Watson, J.

    2014-12-01

    One of the key strategies for coral reef conservation in a high CO2 world is reduction of sediment and nutrient pollution. However, the reduction of sediment is a complicated planning issue as a result of the competing land uses from the demands to satisfy food production needs and from economic development, among others. Moreover, despite the significance of sedimentation as a threat to coral reefs, historical baseline and future estimates of sediment discharge on coral reefs remains poorly quantified. Therefore, the effectiveness of this strategy hinges upon (i) identifying the future sediment discharge on coral reefs relative to historical baseline, and (ii) on identifying spatially where sediment reduction actions are urgently needed and where they are likely to succeed. We provide this understanding by simulating sediment dynamics for historical and future time scales using models of land use and climate, for coastal watersheds adjacent coral reefs where they are found globally.

  20. Ligand-enhanced electrokinetic remediation of metal-contaminated marine sediments with high acid buffering capacity.

    PubMed

    Masi, Matteo; Iannelli, Renato; Losito, Gabriella

    2016-06-01

    The suitability of electrokinetic remediation for removing heavy metals from dredged marine sediments with high acid buffering capacity was investigated. Laboratory-scale electrokinetic remediation experiments were carried out by applying two different voltage gradients to the sediment (0.5 and 0.8 V/cm) while circulating water or two different chelating agents at the electrode compartments. Tap water, 0.1 M citric acid and 0.1 M ethylenediaminetetraacetic acid (EDTA) solutions were used respectively. The investigated metals were Zn, Pb, V, Ni and Cu. In the unenhanced experiment, the acid front could not propagate due to the high acid buffering capacity of the sediments; the production of OH(-) ions at the cathode resulted in a high-pH environment causing the precipitation of CaCO3 and metal hydroxides. The use of citric acid prevented the formation of precipitates, but solubilisation and mobilisation of metal species were not sufficiently achieved. Metal removal was relevant when EDTA was used as the conditioning agent, and the electric potential was raised up to 0.8 V/cm. EDTA led to the formation of negatively charged complexes with metals which migrated towards the anode compartment by electromigration. This result shows that metal removal from sediments with high acid buffering capacity may be achieved by enhancing the electrokinetic process by EDTA addition when the acidification of the medium is not economically and/or environmentally sustainable. PMID:26490900

  1. Physicochemical and sorption properties of thermally-treated sediments with high organic matter content.

    PubMed

    Pan, Bo; Huang, Ping; Wu, Min; Wang, Zhenyu; Wang, Peng; Jiao, Xingchun; Xing, Baoshan

    2012-01-01

    Sediment samples with high organic carbon contents (22.04% and 8.46%) were collected and thermally-treated using a method analogous to biochar production. The obtained thermally-treated sediments (TTSs) showed a much higher degree of carbon capture in comparison to biochar derived from common biomass, indicating potential use of TTSs in soil amendment and carbon sequestration. Their sorption with organic contaminants was also investigated using sulfamethoxazole (SMX) as a model sorbate. SMX sorption increased greatly with pyrolytic temperature. Desorption ratio of the adsorbed SMX in TTSs generally decreased with increased pyrolytic temperature and with decreased solid-phase concentrations. The thermodynamic analysis showed that the higher entropy increase (positive ΔS) was well related with the decreased desorption ratio with increased solid-phase concentration for the original sediments. The fate-controlling effect of contaminants in TTS application for soil amendment should be evaluated combining sorption/desorption and sorption thermodynamic studies. PMID:22033373

  2. Characterizing riverbed sediment using high-frequency acoustics 2: scattering signatures of Colorado River bed sediment in Marble and Grand Canyons

    USGS Publications Warehouse

    Buscombe, Daniel D.; Grams, Paul E.; Kaplinski, Matt A.

    2014-01-01

    In this, the second of a pair of papers on the statistical signatures of riverbed sediment in high-frequency acoustic backscatter, spatially explicit maps of the stochastic geometries (length- and amplitude-scales) of backscatter are related to patches of riverbed surfaces composed of known sediment types, as determined by geo-referenced underwater video observations. Statistics of backscatter magnitudes alone are found to be poor discriminators between sediment types. However, the variance of the power spectrum, and the intercept and slope from a power-law spectral form (termed the spectral strength and exponent, respectively) successfully discriminate between sediment types. A decision-tree approach was able to classify spatially heterogeneous patches of homogeneous sands, gravels (and sand-gravel mixtures), and cobbles/boulders with 95, 88, and 91% accuracy, respectively. Application to sites outside the calibration, and surveys made at calibration sites at different times, were plausible based on observations from underwater video. Analysis of decision trees built with different training data sets suggested that the spectral exponent was consistently the most important variable in the classification. In the absence of theory concerning how spatially variable sediment surfaces scatter high-frequency sound, the primary advantage of this data-driven approach to classify bed sediment over alternatives is that spectral methods have well understood properties and make no assumptions about the distributional form of the fluctuating component of backscatter over small spatial scales.

  3. Characterizing riverbed sediment using high-frequency acoustics: 2. Scattering signatures of Colorado River bed sediment in Marble and Grand Canyons

    NASA Astrophysics Data System (ADS)

    Buscombe, D.; Grams, P. E.; Kaplinski, M. A.

    2014-12-01

    In this, the second of a pair of papers on the statistical signatures of riverbed sediment in high-frequency acoustic backscatter, spatially explicit maps of the stochastic geometries (length and amplitude scales) of backscatter are related to patches of riverbed surfaces composed of known sediment types, as determined by georeferenced underwater video observations. Statistics of backscatter magnitudes alone are found to be poor discriminators between sediment types. However, the variance of the power spectrum and the intercept and slope from a power law spectral form (termed the spectral strength and exponent, respectively) successfully discriminate between sediment types. A decision tree approach was able to classify spatially heterogeneous patches of homogeneous sands, gravels (and sand-gravel mixtures), and cobbles/boulders with 95, 88, and 91% accuracy, respectively. Application to sites outside the calibration and surveys made at calibration sites at different times were plausible based on observations from underwater video. Analysis of decision trees built with different training data sets suggested that the spectral exponent was consistently the most important variable in the classification. In the absence of theory concerning how spatially variable sediment surfaces scatter high-frequency sound, the primary advantage of this data-driven approach to classify bed sediment over alternatives is that spectral methods have well-understood properties and make no assumptions about the distributional form of the fluctuating component of backscatter over small spatial scales.

  4. Turbulent behaviour of non-cohesive sediment gravity flows at unexpectedly high flow density

    NASA Astrophysics Data System (ADS)

    Baker, Megan; Baas, Jaco H.; Malarkey, Jonathan; Kane, Ian

    2016-04-01

    Experimental lock exchange-type turbidity currents laden with non-cohesive silica-flour were found to be highly dynamic at remarkably high suspended sediment concentrations. These experiments were conducted to produce sediment gravity flows of volumetric concentrations ranging from 1% to 52%, to study how changes in suspended sediment concentration affects the head velocities and run-out distances of these flows, in natural seawater. Increasing the volumetric concentration of suspended silica-flour, C, up to C = 46%, within the flows led to a progressive increase in the maximum head velocity. This relationship suggests that suspended sediment concentration intensifies the density difference between the turbulent suspension and the ambient water, which drives the flow, even if almost half of the available space is occupied by sediment particles. However, from C = 46% to C = 52% a rapid reduction in the maximum head velocity was measured. It is inferred that at C = 46%, friction from grain-to-grain interactions begins to attenuate turbulence within the flows. At C > 46%, the frictional stresses become progressively more dominant over the turbulent forces and excess density, thus producing lower maximum head velocities. This grain interaction process started to rapidly reduce the run-out distance of the silica-flour flows at equally high concentrations of C ≥ 47%. All flows with C < 47% reflected off the end of the 5-m long tank, but the head velocities gradually reduced along the tank. Bagnold (1954, 1963) estimated that, for sand flows, grain-to-grain interactions start to become important in modulating turbulence at C > 9%. Yet, the critical flow concentration at which turbulence modulation commenced for these silica-flour laden flows appeared to be much higher. We suggest that Bagnold's 9% criterion cannot be applied to flows that carry fine-grained sediment, because turbulent forces are more important than dispersive forces, and frictional forces start to

  5. Evolution of a high-latitude sediment drift inside a glacially-carved trough based on high-resolution seismic stratigraphy (Kveithola, NW Barents Sea)

    NASA Astrophysics Data System (ADS)

    Rebesco, Michele; Özmaral, Asli; Urgeles, Roger; Accettella, Daniela; Lucchi, Renata G.; Rüther, Denise; Winsborrow, Monica; Llopart, Jaume; Caburlotto, Andrea; Lantzsch, Hendrik; Hanebuth, Till J. J.

    2016-09-01

    Kveithola is a glacially-carved, E-W trending trough located in the NW Barents Sea, an epicontinental shelf sea of the Arctic Ocean located off northern Norway and Russia. A set of confined sediment drifts (the "Kveithola Drift") is located in the inner part of the trough. In general, drift deposits are commonly characterized by high lateral continuity, restricted occurrence of hiatuses and relatively high accumulation rates, and thus represent excellent repositories of paleo-environmental information. We provide for the first time a detailed morphological and seismostratigraphic insight into this sediment drift, which is further supported by some preliminary lithological and sedimentological analyses. The complex morphology of the drift, imaged by combining all available multibeam data, includes a main and a minor drift body, two drift lenses in the outer part of the trough, more or less connected drift patches in the innermost part and small perched sediment patches in a structurally-controlled channel to the north. The seismic (PARASOUND) data show that the main and minor drift bodies are mainly well-stratified, characterized by sub-parallel reflections of moderate to high amplitude and good lateral continuity. The reflectors show an abrupt pinch-out on the northern edge where a distinct moat is present, and a gradual tapering to the south. Internally we identify the base of the drift and four internal horizons, which we correlate throughout the drift. Two units display high amplitude reflectors, marked lensoidal character and restricted lateral extent, suggesting the occurrence of more energetic sedimentary conditions. Facies typical for contourite deposition are found in the sediment cores, with strongly bioturbated sediments and abundant silty/sandy mottles that contain shell fragments. These characteristics, along with the morphological and seismic information, suggest a strong control by a bottom current flowing along the moat on the northern edge of the

  6. High dynamic range optical scanning of sediments and rock samples: More than colour?

    NASA Astrophysics Data System (ADS)

    Klug, Martin; Fabian, Karl; Knies, Jochen

    2015-04-01

    An automated high dynamic range (HDR) scanning procedure for cores and single sediment samples has been developed based on the GeoTek core scanner equipped with a 3* 2048 pixel CCD array GeoScan colour line-scan camera and a Sigma AF 105mm F2.8 EX DG MACRO lens. Repeated colour line scans of the same core sequence using different illumination and exposure time settings, but equal aperture, can be combined into single HDR images. This yields improved colour definition especially if layers of highly variable brightness occur in the same sequence. Colour calibration is performed automatically during image processing based on synchronization of colour charts. Polarized light is used to minimize gloss on wet surfaces. Beyond improved colour detection, high resolution scans with pixel size down to 25 µm provide the possibility of quantifying fabric, texture, and colour contrast between mottle and matrix. We present examples from marine sediments, lake sediments, hard rock cores, and individual soil samples. Due to the high resolution in sediment sequences, the improved images provide important background information to interpret synchronous measurements of density, magnetic susceptibility, or X-ray fluorescence with respect to their respective measurement footprint. If for example an XRF measurement indicates a 2% increase in Fe at a location of a thin black layer of 1/10 of the XRF measurement footprint, within an otherwise homogenous sequence, it can be inferred that the real Fe abundance within the layer is probably 20% higher than in the surrounding sediment. HDR scanning can therefore help to provide high resolution informed interpolation and deconvolution of measurements with larger sensor footprints.

  7. Geomicrobiology of High Level Nuclear Waste-Contaminated Vadose Sediments at the Hanford Site, Washington State

    SciTech Connect

    Fredrickson, Jim K.; Zachara, John M.; Balkwill, David L.; Kennedy, David W.; Li, Shu-Mei W.; Kostandarithes, Heather M.; Daly, Michael J.; Romine, Margaret F.; Brockman, Fred J.

    2004-07-07

    Sediments from a high-level nuclear waste plume were collected as part of investigations to evaluate the potential fate and migration of contaminants in the subsurface. The plume originated from a leak that occurred in 1962 from a waste tank consisting of high concentrations of alkali, nitrate, aluminate, Cr(VI), 137Cs, and 99Tc. Investigations were initiated to determine the distribution of viable microorganisms in the vadose sediment samples, probe the phylogeny of cultivated and uncultivated members, and evaluate the ability of the cultivated organisms to survive acute doses of ionizing radiation. The populations of viable aerobic heterotrophic bacteria were generally low, from below detection to {approx}104 7 CFU g-1 but viable microorganisms were recovered from 11 of 16 samples including several of the most radioactive ones (e.g., > 10 ?Ci/g 137Cs). The isolates from the contaminated sediments and clone libraries from sediment DNA extracts were dominated by members related to known Gram-positive bacteria. Gram-positive bacteria most closely related to Arthrobacter species were the most common isolates among all samples but other high G+C phyla were also represented including Rhodococcus and Nocardia. Two isolates from the second most radioactive sample (>20 ?Ci 137Cs g-1) were closely related to Deinococcus radiodurans and were able to survive acute doses of ionizing radiation approaching 20kGy. Many of the Gram-positive isolates were resistant to lower levels of gamma radiation. These results demonstrate that Gram-positive bacteria, predominantly high G+C phyla, are indigenous to Hanford vadose sediments and some are effective at surviving the extreme physical and chemical stress associated with radioactive waste.

  8. Artificial soft sediment resuspension and high density opportunistic macroalgal mat fragmentation as method for increasing sediment zoobenthic assemblage diversity in a eutrophic lagoon.

    PubMed

    Martelloni, Tatiana; Tomassetti, Paolo; Gennaro, Paola; Vani, Danilo; Persia, Emma; Persiano, Marco; Falchi, Riccardo; Porrello, Salvatore; Lenzi, Mauro

    2016-09-15

    Superficial soft sediment resuspension and partial fragmentation of high density opportunistic macroalgal mats were investigated by boat to determine the impact on zoobenthic assemblages in a eutrophic Mediterranean lagoon. Sediment resuspension was used to oxidise superficial organic sediments as a method to counteract the effects of eutrophication. Likewise, artificial decay of macroalgal mat was calculated to reduce a permanent source of sediment organic matter. An area of 9ha was disturbed (zone D) and two other areas of the same size were left undisturbed (zones U). We measured chemical-physical variables, estimated algal biomass and sedimentary organic matter, and conducted qualitative and quantitative determinations of the zoobenthic species detected in sediment and among algal mats. The results showed a constant major reduction in labile organic matter (LOM) and algal biomass in D, whereas values in U remained stable or increased. In the three zones, however, bare patches of lagoon bed increased in size, either by direct effect of the boats in D or by anaerobic decay of the algal mass in U. Zoobenthic assemblages in algal mats reduced the number of species in D, probably due to the sharp reduction in biomass, but remained stable in U, whereas in all three areas abundance increased. Sediment zoobenthic assemblages increased the number of species in D, as expected, due to drastic reduction in LOM, whereas values in U remained stable and again abundance increased in all three zones. In conclusion, we confirmed that reduction of sediment organic load enabled an increase in the number of species, while the algal mats proved to be an important substrate in the lagoon environment for zoobenthic assemblages, especially when mat alternated with bare intermat areas of lagoon bed. Sediment resuspension is confirmed as a management criterion for counteracting the effects of eutrophication and improving the biodiversity of zoobenthic assemblages in eutrophic lagoon

  9. Artificial soft sediment resuspension and high density opportunistic macroalgal mat fragmentation as method for increasing sediment zoobenthic assemblage diversity in a eutrophic lagoon.

    PubMed

    Martelloni, Tatiana; Tomassetti, Paolo; Gennaro, Paola; Vani, Danilo; Persia, Emma; Persiano, Marco; Falchi, Riccardo; Porrello, Salvatore; Lenzi, Mauro

    2016-09-15

    Superficial soft sediment resuspension and partial fragmentation of high density opportunistic macroalgal mats were investigated by boat to determine the impact on zoobenthic assemblages in a eutrophic Mediterranean lagoon. Sediment resuspension was used to oxidise superficial organic sediments as a method to counteract the effects of eutrophication. Likewise, artificial decay of macroalgal mat was calculated to reduce a permanent source of sediment organic matter. An area of 9ha was disturbed (zone D) and two other areas of the same size were left undisturbed (zones U). We measured chemical-physical variables, estimated algal biomass and sedimentary organic matter, and conducted qualitative and quantitative determinations of the zoobenthic species detected in sediment and among algal mats. The results showed a constant major reduction in labile organic matter (LOM) and algal biomass in D, whereas values in U remained stable or increased. In the three zones, however, bare patches of lagoon bed increased in size, either by direct effect of the boats in D or by anaerobic decay of the algal mass in U. Zoobenthic assemblages in algal mats reduced the number of species in D, probably due to the sharp reduction in biomass, but remained stable in U, whereas in all three areas abundance increased. Sediment zoobenthic assemblages increased the number of species in D, as expected, due to drastic reduction in LOM, whereas values in U remained stable and again abundance increased in all three zones. In conclusion, we confirmed that reduction of sediment organic load enabled an increase in the number of species, while the algal mats proved to be an important substrate in the lagoon environment for zoobenthic assemblages, especially when mat alternated with bare intermat areas of lagoon bed. Sediment resuspension is confirmed as a management criterion for counteracting the effects of eutrophication and improving the biodiversity of zoobenthic assemblages in eutrophic lagoon

  10. Widespread distribution and high abundance of Rhizobium radiobacter within Mediterranean subsurface sediments.

    PubMed

    Süss, Jacqueline; Schubert, Karin; Sass, Henrik; Cypionka, Heribert; Overmann, Jörg; Engelen, Bert

    2006-10-01

    Eastern Mediterranean sediments are characterized by the occurrence of distinct, organic-rich layers, called sapropels. These harbour elevated microbial numbers in comparison with adjacent carbon-lean intermediate layers. A recently obtained culture collection from these sediments was composed of 20% of strains closely related to Rhizobium radiobacter, formerly classified as Agrobacterium tumefaciens. To prove and quantify the in situ abundance of R. radiobacter, a highly specific quantitative polymerase chain reaction (PCR) protocol was developed. To convert quantification results into cell numbers, the copy number of rrn operons per genome was determined. Southern hybridization showed that our isolates contained four operons. Finally, quantitative PCR was applied to 45 sediment samples obtained across the eastern Mediterranean. Rhizobium radiobacter was present in 38 of 45 samples indicating an almost ubiquitous distribution. In total, 25-40 000 cells per gram of sediment were detected, corresponding to 0.001-5.1% of the bacterial cells. In general, the relative and absolute abundance of R. radiobacter increased with depth and was higher in sapropels than in intermediate layers. This indicates that R. radiobacter forms an active population in up to 200 000 years old sapropels. The present study shows for the first time that a cultivated subsurface bacterium is highly abundant in this environment.

  11. Ineffectiveness of daily standard and high-dose antiviral therapy in preventing short episodes of genital HSV-2 reactivation: three randomized, open-label cross-over trials

    PubMed Central

    Johnston, Christine; Saracino, Misty; Kuntz, Steve; Magaret, Amalia; Selke, Stacy; Huang, Meei-li; Schiffer, Joshua T.; Koelle, David M.; Corey, Lawrence; Wald, Anna

    2012-01-01

    Background Recent studies indicate that short subclinical episodes of herpes simplex virus type 2 (HSV-2) are the predominant form of skin and mucosal viral shedding. We evaluated whether standard or high-dose antiviral therapy reduced the frequency of such shedding. Methods To determine whether short episodes of genital HSV shedding are suppressed on standard dose (SD) and high-dose (HD) antiviral therapy, HSV-2 seropositive, HIV seronegative persons in Seattle, WA were enrolled into three separate but complementary randomized, open-label, cross-over studies comparing 1) no medication to aciclovir 400 mg twice daily (SD-ACV), 2) valaciclovir 500 mg daily (SD-VAL) to aciclovir 800 mg three times daily (TID) (HD-ACV), and 3) SD-VAL to HD-VAL (1 gm TID). Study arms lasted 4–7 weeks, separated by one week wash-out. Participants obtained genital swabs four times daily for quantitative HSV DNA PCR. The primary endpoint was within-person comparison of shedding rate on each study arm. Results Of 113 participants randomized, 90 were eligible for analysis of the primary endpoint. Participants collected 23,605 swabs; of these 1272 (5·4%) had HSV detected. HSV shedding was significantly higher during the no medication arm (18·1% of swabs) compared with SD-ACV (1.2% of swabs, IRR=0·05, 95% CI=0·03–0·08). Breakthrough reactivations occurred on all doses (SD-ACV 1·2%, SD-VAL 5·2%, HD-ACV 4·2%, and HD-VAL 3·3% of swabs). HD-VAL was associated with less shedding compared with SD-VAL (IRR=0·54, 95% CI=0·44–0·66), likely due to more rapid clearance of mucosal HSV (4·7 logs/6 hours on HD-VAL vs. 4·4 logs/6 hours on SD-VAL, (p=0·02)). However, the annualized breakthrough episodes was similar on SD-VAL (22·6) and HD-ACV (20·2, p=0·54) and SD-VAL (14.9) and HD-VAL (16·5, p=0·34). Regardless of dose, breakthrough episodes were short (median 7–10 hours) and 80% were subclinical. Studies were not designed to make inter-trial comparisons between antiviral doses

  12. U-Pb geochronological constraints on the timing of episodic regional metamorphism and rapid high-T exhumation of the Grand Forks complex, British Columbia

    NASA Astrophysics Data System (ADS)

    Cubley, J. F.; Pattison, D. R. M.; Tinkham, D. K.; Fanning, C. M.

    2013-01-01

    The Grand Forks complex (GFC) is a fault-bounded metamorphic core complex in the southern Omineca Belt of British Columbia, Canada. It experienced prograde metamorphism ranging from upper-amphibolite to granulite facies conditions during the Mesozoic to early Tertiary compressional stage of the Cordilleran orogeny. Peak metamorphism was followed by multi-stage exhumation in the Early Eocene. This study provides U-Pb monazite and zircon constraints on the timing of metamorphic episodes in the GFC and subsequent high-T, amphibolite facies decompression in the Early Eocene. Monazite LA-ICP-MS ages from metapelitic gneisses record episodic metamorphism from the Late Jurassic to Paleocene, with peak metamorphism occurring between ~ 59 and 50 Ma. Peak metamorphism was followed by rapid, near-isothermal decompression of the GFC between ~ 52 and 50 Ma, and leucosome crystallization at ~ 50 Ma. Thermodynamic modeling of metapelites in the system MnNCKFMASHPYCe predicts that monazite was not stable at peak metamorphic conditions, consistent with the dominant population of ~ 59 Ma ages representing growth along the prograde path, most likely at subsolidus conditions. Growth of widespread high-Y monazite rims (~ 50 Ma) is predicted along suprasolidus decompression and cooling paths. Zircon SHRIMP ages from igneous bodies in the GFC and hanging wall of the bounding Kettle River fault (KRF) suggest ductile deformation related to high-T decompression of the GFC was ongoing at 51 Ma but had ceased by 50 Ma, truncated by post-kinematic granitoids. This high-T deformation predates subsequent greenschist facies extension on the overlying KRF. A pre-KRF, hanging wall ductile shear zone is constrained to ~ 59-51 Ma. It deforms 59 Ma Ladybird suite leucogranites and may be related to high-T exhumation of the core complex. Rapid, > 100 °C/Ma cooling rates are required to accommodate high-T (amphibolite facies) exhumation of the GFC at 52-50 Ma followed by low-T (greenschist facies

  13. Gravitational failure of sea cliffs in weakly lithified sediment

    USGS Publications Warehouse

    Hampton, M.A.

    2002-01-01

    Gravitational failure of sea cliffs eroded into weakly lithified sediment at several sites in California involves episodic stress-release fracturing and cantilevered block falls. The principal variables that influence the gravitational stability are tensional stresses generated during the release of horizontal confining stress and weakening of the sediment with increased saturation levels. Individual failures typically comprise less than a cubic meter of sediment, but large areas of a cliff face can be affected by sustained instability over a period of several days. Typically, only the outer meter or so of sediment is removed during a failure episode. In-place sediment saturation levels vary over time and space, generally being higher during the rainy season but moderate to high year-round. Laboratory direct-shear tests show that sediment cohesion decreases abruptly with increasing saturation level; the decrease is similar for all tested sediment if the cohesion is normalized by the maximum, dry-sediment cohesion. Large failures that extend over most or all of the height of the sea cliff are uncommon, but a few large wedge-shaped failures sometimes occur, as does separation of large blocks at sea cliff-gully intersections.

  14. Sediment dynamics in paired High Arctic lakes revealed from high-resolution swath bathymetry and acoustic stratigraphy surveys

    NASA Astrophysics Data System (ADS)

    Normandeau, A.; Lamoureux, S. F.; Lajeunesse, P.; Francus, P.

    2016-09-01

    High Arctic lakes are commonly used for paleoclimatic reconstructions because they are particularly sensitive to climate variability. However, the processes leading to sediment deposition and distribution in these lakes are often poorly understood. Here for the first time in the Canadian High Arctic, we present original data resulting from swath bathymetry and subbottom surveys carried out on two lakes at Cape Bounty, Melville Island. The results reveal the dynamic nature of the lakes, in which mass movement deposits and bedforms on the deltas reflect frequent slope instabilities and hyperpycnal flow activity. The analysis of the mass movement deposits reveals that small blocky debris flows/avalanches, debris flows, and a slide occurred during the Holocene. These mass movements are believed to have been triggered by earthquakes and potentially by permafrost thawing along the shoreline. Altogether, these mass movement deposits cover more than 30% of the lake floors. Additionally, the river deltas on both lakes were mapped and reveal the presence of several gullies and bedforms. The presence of gullies along the delta front indicates that hyperpycnal flows generated at the river mouth can transport sediment in different trajectories downslope, resulting in a different sediment accumulation pattern and record. The dynamic nature of these two lakes suggests that further analysis on sediment transport and distribution within Arctic lakes is required in order to improve paleoclimatic reconstructions.

  15. Sterols and Stanols Preserved in Pond Sediments Track Seabird Biovectors in a High Arctic Environment.

    PubMed

    Cheng, Wenhan; Sun, Liguang; Kimpe, Linda E; Mallory, Mark L; Smol, John P; Gallant, Lauren R; Li, Jinping; Blais, Jules M

    2016-09-01

    Seabirds are major vertebrates in the coastal ecosystems of the Canadian High Arctic, where they transport substantial amounts of marine-derived nutrients and pollutants from oceans to land by depositing guano and stomach oils to their nesting area, which often includes nearby freshwater ponds. Here we present novel indicators for evaluating the impact of seabirds on freshwater ecosystems. The ratio of cholesterol/(cholesterol + sitosterol) in pond sediments showed significant enrichment near a nesting colony of northern fulmars (Fulmarus glacialis) and was significantly correlated with ornithogenic enrichment of sediment as determined by sedimentary δ(15)N. The sterol ratio was also correlated with several bioaccumulative persistent organic pollutants (POPs), suggesting its usefulness in tracking biovector enrichment of contaminants. Human-derived epicoprostanol was also analyzed in the sediments, and its relationship with an abandoned, prehistoric camp was recorded, suggesting its potential as a tracer of prehistoric human activities in the Arctic. Sterols and stanols preserved in sediments appear to be useful geochemical tools that will inform our understanding of migratory species and the presence of prehistoric human populations in the Arctic, and possibly other animal populations. PMID:27409713

  16. Reservoir and contaminated sediments impacts in high-Andean environments: Morphodynamic interactions with biogeochemical processes

    NASA Astrophysics Data System (ADS)

    Escauriaza, C. R.; Contreras, M. T.; Müllendorff, D. A.; Pasten, P.; Pizarro, G. E.

    2014-12-01

    Rapid changes due to anthropic interventions in high-altitude environments, such as the Altiplano region in South America, require new approaches to understand the connections between physical and biogeochemical processes. Alterations of the water quality linked to the river morphology can affect the ecosystems and human development in the long-term. The future construction of a reservoir in the Lluta river, located in northern Chile, will change the spatial distribution of arsenic-rich sediments, which can have significant effects on the lower parts of the watershed. In this investigation we develop a coupled numerical model to predict and evaluate the interactions between morphodynamic changes in the Lluta reservoir, and conditions that can potentially desorb arsenic from the sediments. Assuming that contaminants are mobilized under anaerobic conditions, we calculate the oxygen concentration within the sediments to study the interactions of the delta progradation with the potential arsenic release. This work provides a framework for future studies aimed to analyze the complex connections between morphodynamics and water quality, when contaminant-rich sediments accumulate in a reservoir. The tool can also help to design effective risk management and remediation strategies in these extreme environments. Research has been supported by Fondecyt grant 1130940 and CONICYT/FONDAP Grant 15110017

  17. The sorption of heavy metals on thermally treated sediments with high organic matter content.

    PubMed

    Dong, Xudong; Wang, Chi; Li, Hao; Wu, Min; Liao, Shaohua; Zhang, Di; Pan, Bo

    2014-05-01

    A sediment sample with organic matter higher than 60% was thermally treated and the sorption of Cu(II), Cd(II), and Pb(II) was investigated and compared to evaluate the potential use of sediments with high organic matter content to produce biochar. Cu(II) and Cd(II) sorption generally decreased with increasing pyrolysis temperature, concurred with decreased oxygen-containing functional groups of the adsorbents. Sediment particles pyrolyzed at 400 and 500 °C showed higher sorption to Pb(II) than other temperatures. The small hydrated ionic radius of Pb(II) may enable its close contact with solid particles and thus facilitated the diffusion of Pb(II) into the pores and the formation of cation-π bond with aromatic structures generated by pyrolysis. The sorption of heavy metals in thermally treated sediment showed comparable sorption to or higher sorption than natural adsorbents and biochars from biomass, suggesting their possible significant impact on the transport and risk of heavy metals. PMID:24486102

  18. High fungal diversity and abundance recovered in the deep-sea sediments of the Pacific Ocean.

    PubMed

    Xu, Wei; Pang, Ka-Lai; Luo, Zhu-Hua

    2014-11-01

    Knowledge about the presence and ecological significance of bacteria and archaea in the deep-sea environments has been well recognized, but the eukaryotic microorganisms, such as fungi, have rarely been reported. The present study investigated the composition and abundance of fungal community in the deep-sea sediments of the Pacific Ocean. In this study, a total of 1,947 internal transcribed spacer (ITS) regions of fungal rRNA gene clones were recovered from five sediment samples at the Pacific Ocean (water depths ranging from 5,017 to 6,986 m) using three different PCR primer sets. There were 16, 17, and 15 different operational taxonomic units (OTUs) identified from fungal-universal, Ascomycota-, and Basidiomycota-specific clone libraries, respectively. Majority of the recovered sequences belonged to diverse phylotypes of Ascomycota (25 phylotypes) and Basidiomycota (18 phylotypes). The multiple primer approach totally recovered 27 phylotypes which showed low similarities (≤97 %) with available fungal sequences in the GenBank, suggesting possible new fungal taxa occurring in the deep-sea environments or belonging to taxa not represented in the GenBank. Our results also recovered high fungal LSU rRNA gene copy numbers (3.52 × 10(6) to 5.23 × 10(7)copies/g wet sediment) from the Pacific Ocean sediment samples, suggesting that the fungi might be involved in important ecological functions in the deep-sea environments.

  19. Mercury profiles in sediment from the marginal high of Arabian Sea: an indicator of increasing anthropogenic Hg input.

    PubMed

    Chakraborty, Parthasarathi; Vudamala, Krushna; Chennuri, Kartheek; Armoury, Kazip; Linsy, P; Ramteke, Darwin; Sebastian, Tyson; Jayachandran, Saranya; Naik, Chandan; Naik, Richita; Nath, B Nagender

    2016-05-01

    Total Hg distributions and its speciation were determined in two sediment cores collected from the western continental marginal high of India. Total Hg content in the sediment was found to gradually increase (by approximately two times) towards the surface in both the cores. It was found that Hg was preferentially bound to sulfide under anoxic condition. However, redox-mediated reactions in the upper part of the core influenced the total Hg content in the sediment cores. This study suggests that probable increase in authigenic and allogenic Hg deposition attributed to the increasing Hg concentration in the surface sediment in the study area.

  20. Mercury profiles in sediment from the marginal high of Arabian Sea: an indicator of increasing anthropogenic Hg input.

    PubMed

    Chakraborty, Parthasarathi; Vudamala, Krushna; Chennuri, Kartheek; Armoury, Kazip; Linsy, P; Ramteke, Darwin; Sebastian, Tyson; Jayachandran, Saranya; Naik, Chandan; Naik, Richita; Nath, B Nagender

    2016-05-01

    Total Hg distributions and its speciation were determined in two sediment cores collected from the western continental marginal high of India. Total Hg content in the sediment was found to gradually increase (by approximately two times) towards the surface in both the cores. It was found that Hg was preferentially bound to sulfide under anoxic condition. However, redox-mediated reactions in the upper part of the core influenced the total Hg content in the sediment cores. This study suggests that probable increase in authigenic and allogenic Hg deposition attributed to the increasing Hg concentration in the surface sediment in the study area. PMID:26797942

  1. High resolution characterization of uranium in sediments by DGT and DET techniques ACA-S-12-2197.

    PubMed

    Gregusova, Michaela; Docekal, Bohumil

    2013-02-01

    Diffusive equilibrium (DET) and diffusive gradient in thin film (DGT) techniques with an inductively coupled plasma mass spectrometry detection of elements were applied to characterize uranium, manganese, iron and (238)U/(235)U isotopic ratio depth profiles in sediment pore water at high spatial resolution and to monitor uranium uptake/remobilization processes in uranium spiked sediment core samples under laboratory, well controlled conditions. Modified constrained sediment DGT probes, packed with Spheron-Oxin(®) resin gel, were employed for selective uranium measurements. Spatially resolved DET and DGT responses were indicative of local redistribution of uranium in naturally uranium poor and rich sediments. PMID:23340286

  2. PROFILE: Management of Sedimentation in Tropical Watersheds.

    PubMed

    NAGLE; FAHEY; LASSOIE

    1999-05-01

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

  3. Impact of neighborhood biomass cooking patterns on episodic high indoor particulate matter concentrations in clean fuel homes in Dhaka, Bangladesh

    PubMed Central

    Salje, Henrik; Gurley, Emily S.; Homaira, Nusrat; Ram, Pavani K.; Haque, Rashidul; Petri, William; Moss, William J.; Luby, Stephen P.; Breysse, Patrick; Azziz-Baumgartner, Eduardo

    2013-01-01

    Exposure to particulate matter (PM2.5) from the burning of biomass is associated with increased risk of respiratory disease. In Dhaka, Bangladesh, households that do not burn biomass often still experience high concentrations of PM2.5 but the sources remain unexplained. We characterized the diurnal variation in the concentrations of PM2.5 in 257 households and compared the risk of experiencing high PM2.5 concentrations in biomass and non-biomass users. Indoor PM2.5 concentrations were estimated every minute over 24 hours once a month from April 2009 through April 2010. We found that households that used gas or electricity experienced PM2.5 concentrations exceeding 1000 μg/m3 for a mean of 35 minutes within a 24-hour period compared to 66 minutes in biomass burning households. In both households that used biomass and those that had no obvious source of particulate matter, the probability of PM2.5 exceeding 1000 μg/m3 were highest during distinct morning, afternoon and evening periods. In such densely populated settings, indoor pollution in clean fuel households may be determined by biomass used by neighbors, with the highest risk of exposure occurring during cooking periods. Community interventions to reduce biomass use may reduce exposure to high concentrations of PM2.5 in both biomass and non-biomass using households. PMID:24033488

  4. HALOE Observations of Perturbations in High Northern Latitude NO and O3 During the April 2002 Solar Storm Episode

    NASA Technical Reports Server (NTRS)

    Anderson, John; Jackman, C. H.; Russell, J. M., III

    2002-01-01

    The April 2002 solar storm event provides a unique opportunity to study the resulting effects on upper atmospheric constituents such as NO and O3. Two sources may perturb these constituents. For a magnetic-storm-source, energetic particles collide with and dissociate N2 in the lower thermosphere to produce excited nitrogen atoms which then combine with O to produce NO. The NO subsequently is transported down to lower altitudes where it reacts with and thus destroys mesospheric and possibly stratospheric ozone. For a solar-particle-event-source, high energy particles penetrate directly into the mesosphere, break apart N2 and water vapor, creating NOx and HOx to destroy ozone in the middle atmosphere. We present perturbations in high northern latitude NO and O3 as measured by the Halogen Occultation Experiment (HALOE) aboard the Upper Atmosphere Research Satellite between April 20-27. HALOE observations show an order of magnitude increase in mesospheric NO and a factor of approximately 2 decrease in mesospheric O3. We will also compare these observations with NASA GSFC 2D model computations.

  5. Sediment Characteristics of a High-Mountain Lake in South Central Anatolia, Turkey

    NASA Astrophysics Data System (ADS)

    Ataselim, Zeynep; Leroy, Suzanne; Gurbuz, Alper; Gurbuz, Esra; Onur Yucel, Tahsin; Yedek, Ozgur; Koc, Koray

    2016-04-01

    Lake Dipsiz is at the top of Mount Erenler, located 55 km west of Konya city in Central Anatolia, Turkey. Mount Erenler is the largest part of Central Anatolia Volcanic Province and consists of Miocene-Pliocene calc-alkaline lavas together with pyroclastic rocks and covers an area approximately 2000 km2. The peak of the Mount Erenler is at 1900 m while Lake Dipsiz is located at 1600 m altitude. Despite the small surface area (0.33 km2), the depth is relatively high (16 m). The drainage area of the lake is 8 km2. Although the topography of the lake points out to glacier presence, it formed as a landslide-dammed lake. Lake Dipsiz geographically is between mountainous Mediterranean region and Central Anatolia plateau. Climatically, the lake is in a transition zone between Taurids and Central Anatolia. In this study, we investigated sedimentation in a high altitude lake at a climatic transition. For this purpose, three cores (D1, D2 and D3) which are 50 cm length are taken with a hand corer from the coastline of the lake. D1 and D2 cores are sampled in every 2 cm and D3 core is samples in every 1 cm. Geochemical, total organic carbon, magnetic susceptibility and total carbonate analyses were performed on all sample sets. Lake sediments are brownish/green clay and silt in composition. Despite the proximity of the sediment source, no sand or more coarse grains were observed in the sedimentary filling. Organic matter content is between 2 - 28 %. According to one 14C date, the sequence indicates a Late Holocene age. δ13C isotope values are between -28.9 and -25.3 ‰ and it means that the sediment composed of terrestrial C3 organic matter. The detrital input in the lake has increased in the last 1000 years. Sedimentation rate was low between 3000 and cal. 1700 BP to the contrary of significant increasing from 250 BP to nowadays. Our data show that the sedimentation in this high altitude lake is more sensitive to other environmental conditions rather than climate.

  6. Fluvial suspended sediment characteristics by high-resolution, surrogate metrics of turbidity, laser-diffraction, acoustic backscatter, and acoustic attenuation

    NASA Astrophysics Data System (ADS)

    Landers, Mark Newton

    Sedimentation is a primary and growing environmental, engineering, and agricultural issue around the world. However, collection of the data needed to develop solutions to sedimentation issues has declined by about three-fourths since 1983. Suspended-sediment surrogates have the potential to obtain sediment data using methods that are more accurate, of higher spatial and temporal resolution, and with less manually intensive, costly, and hazardous methods. The improved quality of sediment data from high-resolution surrogates may inform improved understanding and solutions to sedimentation problems. The field experiments for this research include physical samples of suspended sediment collected concurrently with surrogate metrics from instruments including 1.2, 1.5, and 3.0 megahertz frequency acoustic doppler current profilers, a nephelometric turbidity sensor, and a laser-diffraction particle size analyzer. This comprehensive data set was collected over five storms in 2009 and 2010 at Yellow River near Atlanta, Georgia. Fluvial suspended sediment characteristics in this study can be determined by high-resolution surrogate parameters of turbidity, laser-diffraction and acoustics with model errors 33% to 49% lower than traditional methods using streamflow alone. Hysteresis in sediment-turbidity relations for single storm events was observed and quantitatively related to PSD changes of less than 10 microns in the fine silt to clay size range. Suspended sediment particle size detection (PSD) is significantly correlated with ratios of measured acoustic attenuation at different frequencies; however the data do not fit the theoretical relations. Using both relative acoustic backscatter (RB) and acoustic attenuation as explanatory variables results in a significantly improved model of suspended sediment compared with traditional sonar equations using only RB. High resolution PSD data from laser diffraction provide uniquely valuable information; however the size detection

  7. Mulch effects on runoff and sediment production at the hillslope scale in the High Park Fire, Colorado

    NASA Astrophysics Data System (ADS)

    Wilson, C.; Kampf, S. K.; Wagenbrenner, J. W.; MacDonald, L. H.; Gleason, H.

    2015-12-01

    The 2012 High Park Fire (HPF) burned 330 km2 of Front Range forests surrounding the Cache la Poudre River just upstream of the municipal water supply intakes for the cities of Fort Collins and Greeley. From 2012-2014, millions of dollars were spent on mulch treatments to stabilize burned soils and protect water supplies. The objective of this research is to evaluate how runoff and sediment production vary with precipitation (P) on two unmulched and two mulched hillslopes of the HPF during the 2014 summer thunderstorm season. The four hillslopes are moderate to severely burned zero-order catchments 0.2-0.4 ha in area. Sediment fences were installed at the base of each hillslope to collect bedload sediment; each fence was fitted with a V-notch weir and a series of flow splitters to collect proportional samples of runoff and suspended sediment. Runoff and sediment were captured during 3-7 events for the unmulched sites and 1-9 events for the mulched sites; some P events that produced bedload sediment did not produce measurable runoff. The 30-minute maximum P intensity thresholds for runoff and sediment production were lower for unmulched (10 mm hr-1) than mulched hillslopes (16 mm hr-1). Runoff ratios were similar for the unmulched (0.01-0.10) and mulched sites (0.00-0.08), but total sediment yield (bedload + suspended load; Mg ha-1) for the unmulched sites was up to three times greater (0.02-1.54) than the mulched sites (0.01-0.50. The ratio of suspended sediment to bedload was similar for the unmulched (0.24-1.97) and mulched sites (0.16-2.52). The results of this research suggest that (1) bedload sediment measurements under-represent hillslope sediment production, and (2) mulching may reduce sediment production in zero-order catchments, but the magnitude of the mulch effect varies by catchment and by rain event.

  8. Estimation of sediment transport with an in-situ acoustic retrieval algorithm in the high-turbidity Changjiang Estuary, China

    NASA Astrophysics Data System (ADS)

    Ge, Jian-zhong; Ding, Ping-xing; Li, Cheng; Fan, Zhong-ya; Shen, Fang; Kong, Ya-zhen

    2015-12-01

    A comprehensive acoustic retrieval algorithm to investigate suspended sediment is presented with the combined validations of Acoustic Doppler Current Profiler (ADCP) and Optical Backscattering Sensor (OBS) monitoring along seven cross-channel sections in the high-turbidity North Passage of the Changjiang Estuary, China. The realistic water conditions, horizontal and vertical salinities, and grain size of the suspended sediment are considered in the retrieval algorithm. Relations between net volume scattering of sound attenuation ( S v ) due to sediments and ADCP echo intensity ( E) were obtained with reasonable accuracy after applying the linear regression method. In the river mouth, an intensive vertical stratification and horizontal inhomogeneity were found, with a higher concentration of sediment in the North Passage and a lower concentration in the North Channel and South Passage. Additionally, The North Passage is characterized by higher sediment concentration in the middle region and lower concentration in the entrance and outlet areas. The maximum sediment flux rate, occurred in the middle region, could reach 6.3×105 and 1.5×105 t/h during the spring and neap tide, respectively. Retrieved sediment fluxes in the middle region are significantly larger than that in the upstream and downstream region. This strong sediment imbalance along the main channel indicates potential secondary sediment supply from southern Jiuduansha Shoals.

  9. Episodic coronal heating

    NASA Technical Reports Server (NTRS)

    Sturrock, P. A.; Dixon, W. W.; Klimchuk, J. A.; Antiochos, S. K.

    1990-01-01

    A study is made of the observational consequences of the hypothesis that there is no steady coronal heating, the solar corona instead being heated episodically, such that each short burst of heating is followed by a long period of radiative cooling. The form of the resulting contribution to the differential emission measure (DEM), and to a convenient related function (the differential energy flux, DEF) is calculated. Observational data for the quiet solar atmosphere indicate that the upper branch of the DEM, corresponding to temperatures above 100,000 K, can be interpreted in terms of episodic energy injection at coronal temperatures.

  10. High-resolution modeling of overland flow and sediment transport following wildfire: Insights into initiation mechanisms and sediment sources for runoff-generated debris flows

    NASA Astrophysics Data System (ADS)

    McGuire, L.; Kean, J. W.; Staley, D. M.; Rengers, F. K.

    2015-12-01

    Sediment transport in steep landscapes may be facilitated by both water-dominated flows and debris-flow processes. Given the differences in erosion potential and mobility possessed by runoff and debris flows, knowledge of the conditions that determine the runoff-to-debris-flow transition has important implications for hazard assessment as well as our understanding of the long-term evolution of steep bedrock channels. Debris flows in alpine areas and burned steeplands are frequently triggered by runoff following high-intensity rainfall, but the mechanics by which runoff generates a debris flow are not well understood. To examine the connections between runoff and debris flow initiation, we developed a numerical model that couples overland flow with sediment transport and debris-flow processes. We applied the model to study erosion and debris-flow initiation that occurred during a rainfall event that produced numerous debris flows within a burned drainage basin in the San Gabriel Mountains, CA, USA. Input data for the numerical model was constrained by rain gauges, stage measurements at the basin outlet, soil-moisture sensors, and high-resolution topographic data obtained using a terrestrial laser scanner (TLS). Numerical model predictions, which compare well with TLS-derived measurements of topographic change, indicate that hillslope erosion at our study site was primarily the result of raindrop-induced sediment transport. Further, results indicate that the majority of sediment eroded from the hillslopes was deposited within the channel system during the storm with only minor amounts being transported out of the basin in suspension. Based on model results, we hypothesize that numerous debris flows were generated from the mass failure of sediment dams that built up within the channel system throughout the storm. This study adds to our understanding of sediment transport in steep landscapes and provides insight into the topographic and hydrologic factors that

  11. A revised velocity-reversal and sediment-sorting model for a high-gradient, pool-riffle stream

    USGS Publications Warehouse

    Thompson, D.M.; Wohl, E.E.; Jarrett, R.D.

    1996-01-01

    Sediment-sorting processes related to varying channel-bed morphology were investigated from April to November 1993 along a 1-km pool-riffle and step-pool reach of North Saint Vrain Creek, a small mountain stream in the Rocky Mountains of northern Colorado. Measured cross-sectional areas of flow were used to suggest higher velocities in pools than in riffles at high flow. Three hundred and sixteen tracer particles, ranging in size from 16 mm to 256 mm, were placed in two separate pool-riffle-pool sequences and used to assess sediment-sorting patterns and sediment-transport competence variations. Tracer-particle depositional evidence indicated higher sediment-transport competence in pools than in riffles at high flow. Pool-riffle sediment sorting may be created by velocity reversals, and more localized sorting results from gravitational forces along the upstream sloping portion of the channel bed located at the downstream end of pools.

  12. Diversity and distribution of fungal communities in the marine sediments of Kongsfjorden, Svalbard (High Arctic)

    NASA Astrophysics Data System (ADS)

    Zhang, Tao; Fei Wang, Neng; Qin Zhang, Yu; Yu Liu, Hong; Yan Yu, Li

    2015-10-01

    This study assessed the diversity and distribution of fungal communities in eight marine sediments of Kongsfjorden (Svalbard, High Arctic) using 454 pyrosequencing with fungal-specific primers targeting the internal transcribed spacer (ITS) region of the ribosomal rRNA gene. Sedimentary fungal communities showed high diversity with 42,219 reads belonging to 113 operational taxonomic units (OTUs). Of these OTUs, 62 belonged to the Ascomycota, 26 to Basidiomycota, 2 to Chytridiomycota, 1 to Zygomycota, 1 to Glomeromycota, and 21 to unknown fungi. The major known orders included Hypocreales and Saccharomycetales. The common fungal genera were Pichia, Fusarium, Alternaria, and Malassezia. Interestingly, most fungi occurring in these Arctic sediments may originate from the terrestrial habitats and different basins in Kongsfjorden (i.e., inner basin, central basin, and outer basin) harbor different sedimentary fungal communities. These results suggest the existence of diverse fungal communities in the Arctic marine sediments, which may serve as a useful community model for further ecological and evolutionary study of fungi in the Arctic.

  13. Diversity and distribution of fungal communities in the marine sediments of Kongsfjorden, Svalbard (High Arctic)

    PubMed Central

    Zhang, Tao; Fei Wang, Neng; Qin Zhang, Yu; Yu Liu, Hong; Yan Yu, Li

    2015-01-01

    This study assessed the diversity and distribution of fungal communities in eight marine sediments of Kongsfjorden (Svalbard, High Arctic) using 454 pyrosequencing with fungal-specific primers targeting the internal transcribed spacer (ITS) region of the ribosomal rRNA gene. Sedimentary fungal communities showed high diversity with 42,219 reads belonging to 113 operational taxonomic units (OTUs). Of these OTUs, 62 belonged to the Ascomycota, 26 to Basidiomycota, 2 to Chytridiomycota, 1 to Zygomycota, 1 to Glomeromycota, and 21 to unknown fungi. The major known orders included Hypocreales and Saccharomycetales. The common fungal genera were Pichia, Fusarium, Alternaria, and Malassezia. Interestingly, most fungi occurring in these Arctic sediments may originate from the terrestrial habitats and different basins in Kongsfjorden (i.e., inner basin, central basin, and outer basin) harbor different sedimentary fungal communities. These results suggest the existence of diverse fungal communities in the Arctic marine sediments, which may serve as a useful community model for further ecological and evolutionary study of fungi in the Arctic. PMID:26494429

  14. Analysis of very high frequency propagation in sediments: Experimental results and modeling

    NASA Astrophysics Data System (ADS)

    Brothers, Richard; Page, Sarah; Heald, Gary; Leighton, Tim; Simpson, Matt; Dix, Justin

    2002-11-01

    A current QinetiQ study is investigating the propagation of sound waves into sediment at frequencies higher than 300 kHz. Previous work has found notable discrepancies between model predictions and experimental results and comparisons are inconsistent and unreliable. This new work package investigates the development of new scattering theories for frequencies ranging from 300 kHz to 1 MHz. In particular, the application of a pseudospectral time difference approached is analyzed. The model originally developed for lower frequency applications, is set up in various geometrical scenarios and for varying very high frequencies. Results show the received simulated pulses obtained for hydrophones placed within the sediment and source colocated. Furthermore, simulations are compared in tank experimental data. The controlled tank experiments were conducted by Southampton University and data are analyzed and discussed for various conditions and frequencies.

  15. Bedload monitoring under conditions of ultra-high suspended sediment concentrations

    NASA Astrophysics Data System (ADS)

    Liébault, F.; Jantzi, H.; Klotz, S.; Laronne, J. B.; Recking, A.

    2016-09-01

    The bedload response of the Moulin Ravine, a small alluvial system draining a very active Mediterranean badlands landscape entrenched into Jurassic black marls of the Southern French Prealps, has been investigated using an automatic Reid bedload slot sampler. This site is known for its exceptional sediment transport conditions thanks to a long-term monitoring program that started in the late 1980s, revealing a mean annual bedload yield of 2810 t km-2 yr-1, and suspended sediment concentrations (SSCs) during flow events commonly reaching 100 g L-1. With the deployment of the slot sampler, it has been possible to record instantaneous bedload fluxes during 10 s time increments and to investigate bedload response under flow conditions with ultra-high SSCs. Bedload records cover 4 flashy summer flow events induced by heavy convective storms including a 20-yr return period event. Due to the very high SSC conditions these events challenge bedload monitoring. Even if slot sampling has been recognized as insensitive to fine sediments (silts and clays), it has never been tested in such exceptional muddy flow conditions. The bedload slot sampler performed well in such conditions. A flow-invariant proportion of fines (∼15-20%) was captured in the slot sampler during flows. This proportion is equivalent to its content in the active bedload layer during summer flows, suggesting that fines enter the slot embedded with coarse particles. Instantaneous bedload fluxes recorded in the Moulin are amongst the highest hitherto reported values worldwide, providing evidence of the exceptional sediment transport conditions of marly alpine badlands. The dimensionless entrainment threshold is one order of magnitude higher than commonly reported for gravel-bed rivers, likely reflecting the cohesion effect of fines intruded in the channel surface and subsurface.

  16. Heavy haze episodes in Beijing during January 2013: Inorganic ion chemistry and source analysis using highly time-resolved measurements from an urban site.

    PubMed

    Han, Bin; Zhang, Rui; Yang, Wen; Bai, Zhipeng; Ma, Zhiqiang; Zhang, Wenjie

    2016-02-15

    The heavy air pollution that occurred in Beijing in January of 2013 attracted intense attention around the world. During this period, we conducted highly time-resolved measurements of inorganic ions associated with PM2.5 at an urban site of Beijing, and investigated ion chemistry and potential sources. Hourly concentrations of Cl(-), NO3(-), SO4(2-), Na(+), NH4(+), K(+), Mg(2+), and Ca(2+) were measured. Peak concentrations of SO4(2-) and NO3(-) were observed on the 10th-15th, 21st-24th, and the 26th-30th during this monitoring campaign. The percentages of SO4(2-) and NH4(+) in total ion concentration increased with the enhancement of PM2.5 concentrations, indicating that high concentrations of SO4(2-) and NH4(+) may play important roles in the formation of haze episodes. The ratio of [NO3(-)]/[SO4(2-)] was calculated, revealing that the sources of SO4(2-) would contribute more to the formation of PM2.5 than mobile sources. Diurnal variations of SO4(2-), NO3(-), NH4(+) (SNA) exhibited a similar pattern, with high concentrations at night and low levels during the day, revealing that meteorological conditions, such as mixing layer height, relative humidity, were likely to be responsible for high levels of SNA at night. The roles of meteorological conditions were further discussed in the formation of secondary inorganic ions. Relative humidity and temperature played key roles and exhibited positive correlations with secondary inorganic ions. An aerosol inorganics simulation model showed that SNA existed mainly in the aqueous phase during the sampling period. Furthermore, potential sources were identified by applying positive matrix factorization model. Secondary nitrate, secondary sulfate, coal combustion and biomass burning, as well as fugitive dust, were considered to be major contributors to total ions.

  17. Heavy haze episodes in Beijing during January 2013: Inorganic ion chemistry and source analysis using highly time-resolved measurements from an urban site.

    PubMed

    Han, Bin; Zhang, Rui; Yang, Wen; Bai, Zhipeng; Ma, Zhiqiang; Zhang, Wenjie

    2016-02-15

    The heavy air pollution that occurred in Beijing in January of 2013 attracted intense attention around the world. During this period, we conducted highly time-resolved measurements of inorganic ions associated with PM2.5 at an urban site of Beijing, and investigated ion chemistry and potential sources. Hourly concentrations of Cl(-), NO3(-), SO4(2-), Na(+), NH4(+), K(+), Mg(2+), and Ca(2+) were measured. Peak concentrations of SO4(2-) and NO3(-) were observed on the 10th-15th, 21st-24th, and the 26th-30th during this monitoring campaign. The percentages of SO4(2-) and NH4(+) in total ion concentration increased with the enhancement of PM2.5 concentrations, indicating that high concentrations of SO4(2-) and NH4(+) may play important roles in the formation of haze episodes. The ratio of [NO3(-)]/[SO4(2-)] was calculated, revealing that the sources of SO4(2-) would contribute more to the formation of PM2.5 than mobile sources. Diurnal variations of SO4(2-), NO3(-), NH4(+) (SNA) exhibited a similar pattern, with high concentrations at night and low levels during the day, revealing that meteorological conditions, such as mixing layer height, relative humidity, were likely to be responsible for high levels of SNA at night. The roles of meteorological conditions were further discussed in the formation of secondary inorganic ions. Relative humidity and temperature played key roles and exhibited positive correlations with secondary inorganic ions. An aerosol inorganics simulation model showed that SNA existed mainly in the aqueous phase during the sampling period. Furthermore, potential sources were identified by applying positive matrix factorization model. Secondary nitrate, secondary sulfate, coal combustion and biomass burning, as well as fugitive dust, were considered to be major contributors to total ions. PMID:26657378

  18. Neural correlates of aberrant emotional salience predict psychotic symptoms and global functioning in high-risk and first-episode psychosis.

    PubMed

    Modinos, Gemma; Tseng, Huai-Hsuan; Falkenberg, Irina; Samson, Carly; McGuire, Philip; Allen, Paul

    2015-10-01

    Neurobiological and behavioral findings suggest that psychosis is associated with corticolimbic hyperactivity during the processing of emotional salience. This has not been widely studied in the early stages of psychosis, and the impact of these abnormalities on psychotic symptoms and global functioning is unknown. We sought to address this issue in 18 patients with first-episode psychosis (FEP), 18 individuals at ultra high risk of psychosis (UHR) and 22 healthy controls (HCs). Corticolimbic response and subjective ratings to emotional and neutral scenes were measured using functional magnetic resonance imaging. The clinical and functional impact of corticolimbic abnormalities was assessed with regression analyses. The FEP and UHR groups reported increased subjective emotional arousal to neutral scenes compared with HCs. Across groups, emotional vs neutral scenes elicited activation in the dorsomedial prefrontal cortex, inferior frontal gyrus/anterior insula and amygdala. Although FEP and UHR participants showed reduced activation in these regions when viewing emotional scenes compared with controls, this was driven by increased activation to neutral scenes. Corticolimbic hyperactivity to neutral scenes predicted higher levels of positive symptoms and poorer levels of functioning. These results indicate that disruption of emotional brain systems may represent an important biological substrate for the pathophysiology of early psychosis and UHR states.

  19. High-resolution modelling of waves, currents and sediment transport in the Catalan Sea.

    NASA Astrophysics Data System (ADS)

    Sánchez-Arcilla, Agustín; Grifoll, Manel; Pallares, Elena; Espino, Manuel

    2013-04-01

    In order to investigate coastal shelf dynamics, a sequence of high resolution multi-scale models have been implemented for the Catalan shelf (North-western Mediterranean Sea). The suite consists of a set of increasing-resolution nested models, based on the circulation model ROMS (Regional Ocean Modelling System), the wave model SWAN (Simulation Waves Nearshore) and the sediment transport model CSTM (Community Sediment Transport Model), covering different ranges of spatial (from ~1 km at shelf-slope regions to ~40 m around river mouth or local beaches) and temporal scales (from storms events to seasonal variability). Contributions in the understanding of local processes such as along-shelf dynamics in the inner-shelf, sediment dispersal from the river discharge or bi-directional wave-current interactions under different synoptic conditions and resolution have been obtained using the Catalan Coast as a pilot site. Numerical results have been compared with "ad-hoc" intensive field campaigns, data from observational models and remote sensing products. The results exhibit acceptable agreement with observations and the investigation has allowed developing generic knowledge and more efficient (process-based) strategies for the coastal and shelf management.

  20. High abundance and diversity of archaea from deep-sea sediments of the South China Sea

    NASA Astrophysics Data System (ADS)

    Wang, P.; Li, T.; Hu, A.; Zhang, C.

    2009-12-01

    Archaea communities from two subseafloor sediment core MD05-2896 and MD05-2902 from the south china sea were evaluated by molecular analysis. Archaea abundances determined by FISH and DAPI were over 109 cells/gram along two cores and the portion of archaea to microbial community ranged from 29% to 57% in our study, indicating the important role of archaea in South China Sea. The most of Shannon index of two sites were over 1.5, indicating the high diversity of archaea in South China Sea. The phylogenetic analysis showed that the spatial community structure of two cores were different and the geographical position, TON were the main factors for the difference. A. Depth profiles of total prokaryotic cells in sediment cores. Open square (DAPI for MD05-2896), closed square (FISH: EUB338+ARC915 for MD05-2896); open triangle (DAPI for MD05-2902), closed triangle (FISH: EUB338+ARC915 for MD05-2902) B. Archaeal percentage of total prokaryotic cells (FISH: EUB338+ARC915) in sediment cores. Open circle (MD05-2896), closed circle (MD05-2902)

  1. Bioremediation of high organic load lagoon sediments: compost addition and priming effects.

    PubMed

    d'Errico, G; Giovannelli, D; Montano, C; Milanovic, V; Ciani, M; Manini, E

    2013-03-01

    Lagoons are often affected by eutrophication phenomena, due to their shallow nature, high productivity, weak hydrodynamism and anthropic exploitation. Bioremediation techniques have been widely used in the treatment of chemical pollution; however, no information is available on the use of bioremediation of organic-rich sediments. In the present study, we investigated the priming effects following compost addition to organic-rich lagoon sediments, and the effects of this compost addition on degradation and cycling of organic detritus, transfer of organic matter to higher trophic levels, and in situ prokaryotic community structure. There was a positive response to treatment, particularly during the first days after compost addition. The compost had a stimulating effect on degradation activity of the prokaryotic community. This occurred despite an increase in available organic matter, as the community was more efficient at removing it. These data are supported by the prokaryotic community structure analysis, which revealed no changes in the in situ community following compost addition. This priming effect enhancement through compost addition represents an efficient method to treat organic-rich sediments. PMID:23273326

  2. High-precision measurements of wetland sediment elevation. II The rod surface elevation table

    USGS Publications Warehouse

    Cahoon, D.R.; Lynch, J.C.; Perez, B.C.; Segura, B.; Holland, R.D.; Stelly, C.; Stephenson, G.; Hensel, P.

    2002-01-01

    A new high-precision device for measuring sediment elevation in emergent and shallow water wetland systems is described. The rod surface-elevation table (RSET) is a balanced, lightweight mechanical leveling device that attaches to both shallow ( 1 m in order to be stable. The pipe is driven to refusal but typically to a depth shallower than the rod bench mark because of greater surface resistance of the pipe. Thus, the RSET makes it possible to partition change in sediment elevation over shallower (e.g., the root zone) and deeper depths of the sediment profile than is possible with the SET. The confidence intervals for the height of an individual pin measured by two different operators with the RSET under laboratory conditions were A? 1.0 and A? 1.5 mm. Under field conditions, confidence intervals for the measured height of an individual pin ranged from A? 1.3 mm in a mangrove forest up to A? 4.3 mm in a salt marsh.

  3. Chemical analysis and genotoxicity of high molecular mass PAH in sediment samples and biota

    SciTech Connect

    McCarry, B.E.; Marvin, C.H.; Smith, R.W.; Bryant, D.W.

    1995-12-31

    A normal phase liquid chromatography (NPLC) method was used to fractionate the organic extracts of prepared from coal tar-contaminated sediments from hamilton Harbor in Ontario and from Sydney Harbor in Nova Scotia into molecular mass classes. Each PAH fraction up to 302 amu was analyzed by GC-MS and fractions containing PAH with molecular masses greater than 302 amu were analyzed by atmospheric pressure chemical ionization (APCI) LC-MS.Each fraction was also subjected to Ames bioassays using a TA100-like strain of Salmonella typhimurium (YG1025 + S9). The 300/302 amu, 326/328 and 350/352 amu PAH fractions accounted for 25% of the total genotoxic response of the extract; these PAH constitute a substantial genotoxic burden. A number of 300, 302, 326, 350, 374 and 400 amu PAH were identified using APCI LC-MS and comparison with authentic standards. The non-polar aromatic extracts of bottom sediments, suspended sediments and zebra mussels from Hamilton Harbor were also examined by GC-MS, APCI LC-MS and genotoxicity bioassays. The profiles of the priority and high mass PAH in these samples were identical showing that all PAH up to and exceeding 400 amu were readily bioavailable to biota such as Zebra mussels. In addition, the pseudo faeces of the Zebra mussels and amphipod detritivores which fed on the pseudo faeces had chemical profiles identical to the Zebra mussels. Since many sport fish prize amphipods as food, this observation demonstrates a pathway for organic contaminants adsorbed to suspended sediments to enter the food chain of non-bottom-feeding fish in areas infested by Zebra mussels.

  4. Trace metals and organochlorines in sediments near a major ocean outfall on a high energy continental margin (Sydney, Australia).

    PubMed

    Matthai, C; Birch, G F

    2000-12-01

    Sewage effluent from a large ocean outfall south of Sydney, southeastern Australia, is efficiently dispersed on this high energy continental margin. An enrichment of Ag, Cu, Pb and Zn is only detectable in the fine fraction (<62.5 microm) of sediment. Ag, Co, Cu, Ni, Pb and Zn in the bulk sample correlate strongly with the mud content of surficial sediment, making an identification of the anthropogenic trace metal source difficult using total sediment analyses. The concentrations of HCB and DDE in the total sediment are also slightly elevated near the outfall. In the vicinity of the outfall, the estimated sewage component in the fine fraction of sediment, using Ag, Cu and Zn in a conservative, two-endmember physical mixing model, is <5% and is <0.25% of the total sediment. A greater anthropogenic Pb component in the fine fraction (mean: 24.8%) of surficial sediment compared to Ag, Cu and Zn may suggest a source other than sewage to Sydney continental margin sediments.

  5. Linking Sediment Microbial Communities to Carbon Cycling in High-Latitude Lakes

    NASA Astrophysics Data System (ADS)

    Emerson, J. B.; Varner, R. K.; Johnson, J. E.; Owusu-Dommey, A.; Binder, M.; Woodcroft, B. J.; Wik, M.; Freitas, N. L.; Boyd, J. A.; Crill, P. M.; Saleska, S. R.; Tyson, G. W.; Rich, V. I.

    2015-12-01

    It is well recognized that thawing permafrost peatlands are likely to provide a positive feedback to climate change via CH4 and CO2 emissions. High-latitude lakes in these landscapes have also been identified as sources of CH4 and CO2 loss to the atmosphere. To investigate microbial contributions to carbon loss from high-latitude lakes, we characterized sediment geochemistry and microbiota via cores collected from deep and shallow regions of two lakes (Inre Harrsjön and Mellersta Harrsjön) in Arctic Sweden in July, 2012. These lakes are within the Stordalen Mire long-term ecological area, a focal site for investigating the impacts of climate change-related permafrost thaw, and the lakes in this area are responsible for ~55% of the CH4 loss from this hydrologically interconnected system. Across 40 samples from 4 to 40 cm deep within four sediment cores, Illumina 16S rRNA gene sequencing revealed that the sedimentary microbiota was dominated by candidate phyla OP9 and OP8 (Atribacteria and Aminicenantes, respectively, including putative fermenters and anaerobic respirers), predicted methanotrophic Gammaproteobacteria, and predicted methanogenic archaea from the Thermoplasmata Group E2 clade. We observed some overlap in community structure with nearby peatlands, which tend to be dominated by methanogens and Acidobacteria. Sediment microbial communities differed significantly between lakes, by overlying lake depth (shallow vs. deep), and by depth within a core, with each trend corresponding to parallel differences in biogeochemical measurements. Overall, our results support the potential for significant microbial controls on carbon cycling in high-latitude lakes associated with thawing permafrost, and ongoing metagenomic analyses of focal samples will yield further insight into the functional potential of these microbial communities and their dominant members.

  6. Comparison of the SAPRC07 and SAPRC99 photochemical mechanisms during a high ozone episode in Texas: Differences in concentrations, OH budget and relative response factors

    NASA Astrophysics Data System (ADS)

    Li, Jingyi; Zhang, Hongliang; Ying, Qi

    2012-07-01

    The latest SAPRC photochemical mechanism SAPRC07 (S07), an update from SAPRC99 (S99), is implemented into the Community Multi-scale Air Quality (CMAQ) model and applied to simulate a high ozone episode during the Texas Air Quality Study 2000 (TexAQS 2000). The results from the S07 mechanism are compared with those from the S99 mechanism. In general, the predicted O3 concentrations by S07 are lower than those of S99 with maximum difference as high as 20%. The two mechanisms also show significant differences in the predicted OH, HNO3, PAN and HCHO concentrations. S99 predicts higher OH concentration by 7-20%, higher PAN by approximately 20-25% and higher HCHO by approximately 15% than S07. OH budget analysis suggests that OH propagation factor (POH) is higher in urban and industrial areas but lower in rural areas. Although S07 generally predicts similar or higher POH, S99 predicts higher new OH formation rate from H2O + O(1D) and leads to higher OH and thus higher O3 in most part of the domain. OH reactions with VOCs and CO accounts for a majority part of reacted OH. Secondary VOCs photolysis is not a main path of regenerated OH. New OH mainly comes from H2O + O(1D) reaction. Although the two mechanisms predict different ozone concentrations, the relative response factor (RRF) of ozone at rural, urban and industrial sites under emission controls of anthropogenic NOx and VOC controls by factors 0.6-1.4 predicted by the two mechanisms are very similar. This suggests that although the absolute predictions are different, both models will provide nearly identical attainment assessment in regulatory applications.

  7. The Role of Episodic and Semantic Memory in Episodic Foresight

    ERIC Educational Resources Information Center

    Martin-Ordas, Gema; Atance, Cristina M.; Louw, Alyssa

    2012-01-01

    In this paper we describe a special form of future thinking, termed "episodic foresight" and its relation with episodic and semantic memory. We outline the methodologies that have largely been developed in the last five years to assess this capacity in young children and non-human animals. Drawing on Tulving's definition of episodic and semantic…

  8. Episodes, events, and models

    PubMed Central

    Khemlani, Sangeet S.; Harrison, Anthony M.; Trafton, J. Gregory

    2015-01-01

    We describe a novel computational theory of how individuals segment perceptual information into representations of events. The theory is inspired by recent findings in the cognitive science and cognitive neuroscience of event segmentation. In line with recent theories, it holds that online event segmentation is automatic, and that event segmentation yields mental simulations of events. But it posits two novel principles as well: first, discrete episodic markers track perceptual and conceptual changes, and can be retrieved to construct event models. Second, the process of retrieving and reconstructing those episodic markers is constrained and prioritized. We describe a computational implementation of the theory, as well as a robotic extension of the theory that demonstrates the processes of online event segmentation and event model construction. The theory is the first unified computational account of event segmentation and temporal inference. We conclude by demonstrating now neuroimaging data can constrain and inspire the construction of process-level theories of human reasoning. PMID:26578934

  9. Relatively high antibiotic resistance among heterotrophic bacteria from arctic fjord sediments than water - Evidence towards better selection pressure in the fjord sediments

    NASA Astrophysics Data System (ADS)

    Hatha, A. A. Mohamed; Neethu, C. S.; Nikhil, S. M.; Rahiman, K. M. Mujeeb; Krishnan, K. P.; Saramma, A. V.

    2015-12-01

    The objective of this study was to determine the prevalence of antibiotic resistance among aerobic heterotrophic bacteria and coliform bacteria from water and sediment of Kongsfjord. The study was based on the assumption that arctic fjord environments are relatively pristine and offer very little selection pressure for drug resistant mutants. In order to test the hypothesis, 200 isolates belonging to aerobic heterotrophic bacteria and 114 isolates belonging to coliforms were tested against 15 antibiotics belonging to 5 different classes such as beta lactams, aminoglycosides, quinolones, sulpha drugs and tetracyclines. Resistance to beta lactam and extended spectrum beta lactam (ESBL) antibiotics was considerably high and they found to vary significantly (p < 0.05) between heterotrophic and coliform bacteria. Though the coliforms showed significantly high level of antibiotic resistance against ESBL's extent and diversity of antibiotic resistance (as revealed by multiple antibiotic resistance index and resistance patterns), was high in the aerobic heterotrophic bacteria. Most striking observation was that isolates from fjord sediments (both heterotrophic bacteria and coliforms) in general showed relatively high prevalence of antibiotic resistance against most of the antibiotics tested, indicating to better selection pressure for drug resistance mutants in the fjord sediments.

  10. Mineralogic reservoirs for high-field strength elements in deeply subducted continental sediments

    NASA Astrophysics Data System (ADS)

    Rapp, R. P.; Shimizu, N.; Irifune, T.; Nishiyama, N.

    2013-12-01

    For more than 40 years now, mantle geochemists have interpreted the isotopic signature of ocean-island basalts (OIB) in terms of deeply recycled crustal lithologies, including terrigeneous sediments, being transported via subduction into the source region for mantle plumes, which reside in the transition zone (MTZ) and/or lower mantle. As such, continent-derived sediments in particular represent domains of extreme isotopic and trace-element heterogeneity relative to the deep primitive mantle (PM). In an effort to understand the extent to which the original geochemical signature of deeply subducted continental material is preserved, and to determine which mineral phases act as reservoirs for transporting key trace-elements (e.g., large-ion lithophile elements, LILE; high-field strength elements, HFSE) into the deep mantle, we have conducted a series of phase-equilibria multi-anvil experiments on natural terrigeneous sediments at pressures appropriate to the base of the MTZ and uppermost lower mantle. The starting materials for these experiments contain modest amounts of water, and a small carbonate component, and their major- and trace-element composition are a close approximation to that of average 'global subducting sediment' (i.e., GLOSS; Plank and Langmuir, 1998). Experiments were conducted over the pressure range ~15-23 GPa, and temperatures between ~1200-1800°C. Below ~22 GPa, the high-pressure phase assemblage consists of K-hollandite, majoritic garnet, stishovite, and depending on temperature, either a hydrous alumino-silicate (e.g., phase-EGG or δ-AlOOH), or kyanite or corundum. Stable accessory minerals at these conditions include rutile, and zircon, where much of the whole-rock complement of HFSE resides, and occasionally monazite. At higher pressure (>23 GPa), the breakdown of garnet produces a Fe-Al-Mg perovskite phase, which is exceptionally rich in TiO2 (up to 9 wt%), and the aforementioned accessory phases are no longer stable. The full phase

  11. The Prevalence and Diagnostic Validity of Short-Duration Hypomanic Episodes and Major Depressive Episodes.

    PubMed

    Miller, Shefali; Dennehy, Ellen B; Suppes, Trisha

    2016-03-01

    Current diagnostic criteria for a hypomanic episode, as outlined in both the fourth and fifth editions of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV and DSM-5), require a minimum duration of four consecutive days of symptoms of mood elevation. The 4-day criterion for duration of hypomania has been challenged as arbitrary and lacking empirical support, with many arguing that shorter-duration hypomanic episodes are highly prevalent and that those experiencing these episodes are clinically more similar to patients with bipolar disorder than to those with unipolar major depressive disorder. We review the current evidence regarding the prevalence, diagnostic validity, and longitudinal illness correlates of shorter-duration hypomanic episodes and summarize the arguments for and against broadening the diagnostic criteria for hypomania to include shorter-duration variants. Accumulating findings suggest that patients with major depressive episodes and shorter-duration hypomanic episodes represent a complex clinical phenotype, perhaps best conceptualized as being on the continuum between those with unipolar depressive episodes alone and those with DSM-5-defined bipolar II disorder. Further investigation is warranted, ideally involving large prospective, controlled studies, to elucidate the diagnostic and treatment implications of depression with shorter-duration hypomanic episodes. PMID:26830885

  12. Genetics Home Reference: episodic ataxia

    MedlinePlus

    ... Ebers GC. A genome-wide screen and linkage mapping for a large pedigree with episodic ataxia. Neurology. ... investigators. Primary episodic ataxias: diagnosis, pathogenesis and treatment. Brain. 2007 Oct;130(Pt 10):2484-93. Epub ...

  13. Investigation of the time evolved spatial distribution of urban PM2.5 concentrations and aerosol composition during episodic high PM events in Yuma, AZ

    NASA Astrophysics Data System (ADS)

    Holmes, Heather A.; Pardyjak, Eric R.; Tyler, Bonnie J.; Peterson, Richard E.

    An interdisciplinary field study designed to investigate the spatial and temporal variability of atmospheric aerosols during high particulate matter ( PM) events along the US-Mexico border near Yuma, AZ was run during the week of March 18, 2007. The experiments were designed to quantify chemical composition and physical phenomena governing the transport of aerosols generated from episodic high PM events. The field study included two micrometeorological monitoring sites; one rural and one urban, equipped with sonic anemometers, continuous particulate concentration monitors and ambient aerosol collection equipment. In addition to the two main monitoring sites, five additional locations were equipped with optical particle counters to allow for the investigation of the spatial and temporal distribution of PM2.5 in the urban environment. In this paper, the meteorological and turbulence parameters governing the distribution and concentration of PM2.5 in the urban environment for two high-wind erosion events and one burning event are compared. The interaction between local atmospheric conditions and the particulate distribution is investigated. Results indicate that a single point measurement in the urban area of Yuma may not be sufficient for determining the ambient PM concentrations that the local population experiences; all three high PM events indicated PM2.5 varied considerably with maximum urban concentrations 5-10 times greater than the measured minima. A comparison of inorganic and carbonaceous content of the aerosols for the three high PM events is presented. The comparison shows an increase in silicon during crustal dust events and an increase in elemental and organic carbon during the burn event. Additional surface chemistry analysis, using time-of-flight secondary ion mass spectrometry (ToF-SIMS), for aerosols collected at the urban and rural sites during the burn event are discussed. The surface chemistry analysis provides positive ion mass spectra of organic

  14. Quaternary sedimentation and diagenesis in a high-latitude reef, Houtman Abrolhos Islands, Western Australia

    SciTech Connect

    Rosen, M.R.; Collins, L.B. ); Wyrwoll, K.H.; Hatcher, B.G. )

    1990-05-01

    The Houtman Abrolhos reefs are located 80 km off the west coast of Australia between latitudes 28 and 29{degree} south. The islands are situated on three Pleistocene carbonate reef platforms which rise above the surrounding shelf. The modern coral reefs are close to the geographic limit for coral growth in the southern hemisphere and survive due to the presence of the Leeuwin current (a poleward-flowing warm stream). Two major shallow-water benthic communities coexist in the Abrolhos: a macroalgal-dominated community on the windward platform margins and a coral-dominated community on the leeward margins. These communities overlap-particularly in the platform lagoons, where competition between macroalgae and corals is intense. This interaction has been suggested as a major factor controlling the growth of cord reefs at high latitudes. The Holocene carbonate sediments lack nonskeletal components and are dominated by coral and coralline algal fragments with subordinate molluskan and echinoderm debris. The accumulations can be grouped into the following major facies: (1) coral framestone and coralline algal/serpulid boundstone, (2) submarine sand sheets, (3) subaerial coral storm ridges, (4-) peritidal to subtidal shingle and rubble veneers composed of dominantly coral debris, and (5) eolian dunes and beach sand. The Holocene sediment is a thin (< 2 m) veneer on the Pleistocene reef platform, which is emergent as small islands. The Pleistocene platform is composed of reef facies that can be directly related to the Holocene sediments. The platform is composed of framestone and boundstone facies (corals and coralline algal/serpulid facies), rudstones (submarine coral rubble facies), planar-bedded skeletal grainstones dipping 12-13{degree} (submarine sand sheet and peritidal shingle facies), and large 15-m-high eolianite dunes (eolian dune facies).

  15. Verlorenvlei - The first continuous Holocene high-resolution lake sediment record from the Winter Rainfall Zone of South Africa

    NASA Astrophysics Data System (ADS)

    Haberzettl, T.; Kasper, T.; Lederer, M.; Wündsch, M.; Frenzel, P.; Zabel, M.; Kirsten, K. L.; Meadows, M. E.; Quick, L. J.; St-Onge, G.; Maeusbacher, R.

    2015-12-01

    Verlorenvlei is a coastal lake in the Winter Rainfall Zone of the Western Cape Province of South Africa. Up to now several attempts have been made to recover sediment cores from this lake. However, no continuous high-resolution record covering large parts of the Holocene has been available so far. Within the project RAIN (Regional Archives for Integrated iNvestigations) it was possible to recover a 14.2 m paired parallel core from the central part of Verlorenvlei. Investigations on recent surface sediment distributions (elemental composition and grain sizes) indicate that this sediment core is very well suited for paleoenvironmental reconstructions. Using a set of 23 radiocarbon ages, a chronology for the past 9,000 cal BP was established which suggests continuous sedimentation over this period. Preliminary lithological and geochemical investigations show that this record can be used for sea level reconstructions as the lake was periodically inundated by the ocean during the past 9,000 cal BP. This is recorded in distinctly elevated Ca and Sr contents as well as the occurrence of marine indicator species (snail and mussel shells) in parts of the sediment core. Thin, pale grey layers of fine sediment occurring at various sediment depths seem to reflect event related deposits. In terms of lithology, geochemical and magnetic composition, the upper 50 cm clearly differ from the rest of the record and indicate increased sediment supply from the catchment, which is likely linked to anthropogenic farming activities. In conclusion, the newly recovered sediment record from Verlorenvlei offers excellent potential for a detailed, high-resolution reconstruction of sea level changes, climate variations and anthropogenic impact during the past 9,000 cal BP in an area in which natural archives are very scarce or poorly dated.

  16. Voxel-Based Morphometry in Individuals at Genetic High Risk for Schizophrenia and Patients with Schizophrenia during Their First Episode of Psychosis

    PubMed Central

    Bai, Chuan; Zhou, Qian; Wei, Shengnan; Jiang, Xiaowei; Geng, Haiyang; Zhou, Yifang; Tang, Yanqing; Wang, Fei

    2016-01-01

    Background Understanding morphologic changes in vulnerable and early disease state of schizophrenia (SZ) may provide further insight into the development of psychosis. Method Whole brain voxel-based morphometry was performed to identify gray matter (GM) regional differences in 60 individuals with SZ during their first psychotic episode (FE-SZ), 31 individuals at genetic high risk for SZ (GHR-SZ) individuals, and 71 healthy controls. Results Significant differences were found in several regions including the prefrontal cortex, parietal lobe, temporal lobe, hippocampus, occipital lobe, and cerebellum among the three groups (p<0.05, corrected). Compared to the HC group, the FE-SZ group had significantly decreased GM volumes in several regions including the cerebellum, hippocampus, fusiform gyrus, lingual gyrus, supramarginal gyrus, and superior, middle, and inferior temporal gyri and significantly increased GM volumes in the middle frontal gyrus and inferior operculum frontal gyrus (p<0.05). The GHR-SZ group had significant decreases in GM volumes in the supramaginal gyrus, precentral gyrus, and rolandic operculum and significant increases in GM volumes in the cerebellum, fusiform gyrus, middle frontal gyrus, inferior operculum frontal gyrus, and superior, middle, and inferior temporal gyri when compared to the HC group (p<0.05). Compared to the GHR-SZ group, the FE-SZ group had significant decreases in GM volumes in several regions including the cerebellum, fusiform gyrus, supramarginal gyrus, and superior, middle, and inferior temporal gyri (p<0.05). Conclusions The findings herein implicate the involvement of multisensory integration in SZ development and pathophysiology. Additionally, the patterns of observed differences suggest possible indicators of disease, vulnerability, and resiliency in SZ. PMID:27723806

  17. Attentional Episodes in Visual Perception

    ERIC Educational Resources Information Center

    Wyble, Brad; Potter, Mary C.; Bowman, Howard; Nieuwenstein, Mark

    2011-01-01

    Is one's temporal perception of the world truly as seamless as it appears? This article presents a computationally motivated theory suggesting that visual attention samples information from temporal episodes (episodic simultaneous type/serial token model; Wyble, Bowman, & Nieuwenstein, 2009). Breaks between these episodes are punctuated by periods…

  18. A study of the interrupted REM episode.

    PubMed

    Merica, H; Gaillard, J M

    1991-12-01

    Brief interruptions of REM sleep are considered to be part of the REM episode. The maximum allowable duration of such an interruption, which is used to define the end of the REM episode, is currently a matter of debate. Making measurements on individual REM cycles, inter-REM interval analysis was carried out to determine whether the generally adopted 15 minute empirical rule for this maximum needs to be extended to 25 minutes as suggested by several including Kobayashi et al. Our results show that there is no reason to alter the 15 minute rule and that measurements which do not take into account the time-of-night effect may be misleading. The proportion of interrupted REM episodes observed in our population of healthy adults is high. We have therefore also examined in some detail the phenomenology of the temporal evolution of the structure and content of the interrupted REM episodes. Both showed a definite change over the night: the interruptions in the earlier episodes tend to return the system to slow wave sleep while those in the later episodes tend to return it to wake. It is hypothesized that these interruptions reflect a measure of REM sleep pressure and its interaction with both slow wave sleep and wake pressures. PMID:1798770

  19. High Frequency Time-series of the Dynamic Sedimentation Processes on the Western Shelf of the Mississippi River Delta

    NASA Astrophysics Data System (ADS)

    Dail, M. B.; Corbett, D. R.; McKee, B.; Duncan, D.

    2004-12-01

    Rivers annually transport billions of tons of organic and inorganic sediment to coastal environments, making them an extremely important part of global biogeochemical cycles. However, the majority of the freshwater and suspended materials are delivered to the coastal ocean by only a few rivers. In these river-dominated ocean margins (RiOMar), sediments are deposited and re-suspended repeatedly before stable deposition. This sediment cycling is poorly understood and is critical to understanding how deltas and continental shelves, considered to be major repositories of organic carbon in marine sediments, manipulate the global carbon cycle and biogeochemical processes affecting coastal environments. During six cruises in the fall of 2003 (October, November, and December) and spring of 2004 (March, April, and May), on the shelf west of the Mississippi River Delta, sediment samples collected from cores were analyzed for particle reactive radionuclides (210Pb, 137Cs, and 234Th) to create a quantitative high frequency time-series of sediment deposition and erosion processes and evaluate the transport and fate of material on the shelf. Based on previous work completed by Corbett et al. (2004), seasonal variations in short-lived tracers could be explained by river flow and weather conditions. Inventories of the tracers collected during the fall cruises suggest increased deposition during the late summer months and that most sediment reworking and export occurs during the winter months, typically a period of low/increasing river discharge and increased weather forcing.

  20. Monochromatic multicomponent fluorescence sedimentation velocity for the study of high-affinity protein interactions

    PubMed Central

    Zhao, Huaying; Fu, Yan; Glasser, Carla; Andrade Alba, Eric J; Mayer, Mark L; Patterson, George; Schuck, Peter

    2016-01-01

    The dynamic assembly of multi-protein complexes underlies fundamental processes in cell biology. A mechanistic understanding of assemblies requires accurate measurement of their stoichiometry, affinity and cooperativity, and frequently consideration of multiple co-existing complexes. Sedimentation velocity analytical ultracentrifugation equipped with fluorescence detection (FDS-SV) allows the characterization of protein complexes free in solution with high size resolution, at concentrations in the nanomolar and picomolar range. Here, we extend the capabilities of FDS-SV with a single excitation wavelength from single-component to multi-component detection using photoswitchable fluorescent proteins (psFPs). We exploit their characteristic quantum yield of photo-switching to imprint spatio-temporal modulations onto the sedimentation signal that reveal different psFP-tagged protein components in the mixture. This novel approach facilitates studies of heterogeneous multi-protein complexes at orders of magnitude lower concentrations and for higher-affinity systems than previously possible. Using this technique we studied high-affinity interactions between the amino-terminal domains of GluA2 and GluA3 AMPA receptors. DOI: http://dx.doi.org/10.7554/eLife.17812.001 PMID:27436096

  1. Monochromatic multicomponent fluorescence sedimentation velocity for the study of high-affinity protein interactions.

    PubMed

    Zhao, Huaying; Fu, Yan; Glasser, Carla; Andrade Alba, Eric J; Mayer, Mark L; Patterson, George; Schuck, Peter

    2016-01-01

    The dynamic assembly of multi-protein complexes underlies fundamental processes in cell biology. A mechanistic understanding of assemblies requires accurate measurement of their stoichiometry, affinity and cooperativity, and frequently consideration of multiple co-existing complexes. Sedimentation velocity analytical ultracentrifugation equipped with fluorescence detection (FDS-SV) allows the characterization of protein complexes free in solution with high size resolution, at concentrations in the nanomolar and picomolar range. Here, we extend the capabilities of FDS-SV with a single excitation wavelength from single-component to multi-component detection using photoswitchable fluorescent proteins (psFPs). We exploit their characteristic quantum yield of photo-switching to imprint spatio-temporal modulations onto the sedimentation signal that reveal different psFP-tagged protein components in the mixture. This novel approach facilitates studies of heterogeneous multi-protein complexes at orders of magnitude lower concentrations and for higher-affinity systems than previously possible. Using this technique we studied high-affinity interactions between the amino-terminal domains of GluA2 and GluA3 AMPA receptors. PMID:27436096

  2. High-magnesium calcite dissolution in tropical continental shelf sediments controlled by ocean acidification.

    PubMed

    Haese, R R; Smith, J; Weber, R; Trafford, J

    2014-01-01

    Increases in atmospheric CO2 cause the oceanic surface water to continuously acidify, which has multiple and profound impacts on coastal and continental shelf environments. Here we present the carbonate mineral composition in surface sediments from a range of continental shelf seabed environments and their current and predicted stability under ocean acidifying conditions. Samples come from the following four tropical Australian regions: (1) Capricorn Reef (southern end of the Great Barrier Reef), (2) the Great Barrier Reef Lagoon, (3) Torres Strait, and (4) the eastern Joseph Bonaparte Gulf. Beyond the near-shore zone, these regions typically have a carbonate content in surface sediments of 80 wt % or more. The abundance of high-magnesium calcites (HMC) dominates over aragonite (Arag) and low-magnesium calcite (LMC) and constitutes between 36% and 50% of all carbonate. HMC, with a magnesium content larger than 8-12 mol %, is more soluble than both Arag and LMC, and the solubility of HMC positively correlates with its magnesium concentration. From the solubility data of Plummer and Mackenzie ( Am. J. Sci. 1974 , 274 , 61 - 83 ), 95% of HMC in the four regions is presently in metastable equilibrium relative to global mean tropical sea surface water. HMC is predicted to become destabilized in the four regions between 2040 and 2080 AD, with typical HMC decline rates between 2% and 5% per year. The range of respective estimated carbonate dissolution rates is expected to exceed current continental shelf carbonate accumulation rates, leading to net dissolution of carbonate during the period of HMC decline. In a geological context, the decline in HMC in tropical continental shelf environments is a global event triggered by reaching below-equilibrium conditions. The characteristic change in carbonate mineral composition in continental shelf sediments will serve as a geological marker for the proposed Anthropocene Epoch.

  3. Identifying climate forcing on suspended sediment transport in the high Pamir Mountains

    NASA Astrophysics Data System (ADS)

    Pohl, Eric; Andermann, Christoff; Gloaguen, Richard; Fuchs, Margret C.

    2016-04-01

    Climate, tectonics and erosion interact in a feedback loop to shape mountain ranges. The importance of individual aspects varies based on time-scale and regional settings. In rainfall-runoff dominated regions, like the southern margin of the Himalayas, rainfall is a good predictor for short-term erosion rates. This is because rainfall provides reliable estimates for river flow, which evacuates sediments out of the orogen. However, at geological time-scales, todays rainfall patterns often fail to explain regional erosion variability. Consequently, climatic forcing on erosion is assumed to play a subordinate role at such long time-scales. We present recent suspended sediment analyses based on historic time-series data in the Pamir Mountains. In this high mountain environment the dominance of winter precipitation causes extensive snow cover and glaciation. The resulting runoff regime is nival-glacial and shows a temporal decoupling of precipitation and runoff. With the aid of a hydrological model, we demonstrate 1) why mean annual precipitation and temperature are irrelevant climatological parameters for erosional studies in such an environment, and 2) why knowledge about intra-annual dynamics of climatological parameters are key to still utilize precipitation and temperature as surrogate for climate. The spatial information about melting and runoff processes from the hydrological model allows to discriminate the spheres of different erosional processes and their meaning for landscape evolution. Derived interactions between climate and sediment transport through the hydrological model might help illuminate the role of climate in regions, where the climate system in the past was like the one in the Pamirs today.

  4. High-magnesium calcite dissolution in tropical continental shelf sediments controlled by ocean acidification.

    PubMed

    Haese, R R; Smith, J; Weber, R; Trafford, J

    2014-01-01

    Increases in atmospheric CO2 cause the oceanic surface water to continuously acidify, which has multiple and profound impacts on coastal and continental shelf environments. Here we present the carbonate mineral composition in surface sediments from a range of continental shelf seabed environments and their current and predicted stability under ocean acidifying conditions. Samples come from the following four tropical Australian regions: (1) Capricorn Reef (southern end of the Great Barrier Reef), (2) the Great Barrier Reef Lagoon, (3) Torres Strait, and (4) the eastern Joseph Bonaparte Gulf. Beyond the near-shore zone, these regions typically have a carbonate content in surface sediments of 80 wt % or more. The abundance of high-magnesium calcites (HMC) dominates over aragonite (Arag) and low-magnesium calcite (LMC) and constitutes between 36% and 50% of all carbonate. HMC, with a magnesium content larger than 8-12 mol %, is more soluble than both Arag and LMC, and the solubility of HMC positively correlates with its magnesium concentration. From the solubility data of Plummer and Mackenzie ( Am. J. Sci. 1974 , 274 , 61 - 83 ), 95% of HMC in the four regions is presently in metastable equilibrium relative to global mean tropical sea surface water. HMC is predicted to become destabilized in the four regions between 2040 and 2080 AD, with typical HMC decline rates between 2% and 5% per year. The range of respective estimated carbonate dissolution rates is expected to exceed current continental shelf carbonate accumulation rates, leading to net dissolution of carbonate during the period of HMC decline. In a geological context, the decline in HMC in tropical continental shelf environments is a global event triggered by reaching below-equilibrium conditions. The characteristic change in carbonate mineral composition in continental shelf sediments will serve as a geological marker for the proposed Anthropocene Epoch. PMID:24972293

  5. Magnetite with anomalously high Cr2O3 as a fingerprint to trace upper Yangtze sediments to the sea

    NASA Astrophysics Data System (ADS)

    Yue, Wei; Liu, James T.; Zhang, Dan; Wang, Zhanghua; Zhao, Baocheng; Chen, Zhongyuan; Chen, Jing

    2016-09-01

    This paper examines geochemical properties of detrital magnetite, in order to link sediments in a Plio-Quaternary core taken in the delta area to their sources in the Yangtze River basin. A total of 40 sediment samples were collected from both the main river channel/tributaries and a sediment core from the Yangtze delta. The geochemical compositions of detrital magnetite in these sediments were analyzed by electron microprobe, including FeO, TiO2, CoO, MgO, Cr2O3, MnO, ZnO, Al2O3 and V2O3. The results revealed that the detrital magnetite grains with anomalously high Cr2O3 occurred exclusively in the upper reaches of the Yangtze (upstream of the Three Gorges Dam), where the E'mei Basalt block is located. This type of magnetite could therefore be considered a unique sediment proxy of the upper river basin to help identify sediment source in the delta area. Our analysis found such magnetite grains with high Cr2O3 occurring throughout the core depth above 186.5 m, in contrast to the extremely low Cr2O3 below this depth. The boundary between high and low Cr2O3 in magnetite grains of the core sediments was dated by paleomagnetism at ca. ~ 1.2-1.0 Ma, signifying that the linkage between the Yangtze River course and the sea was before ~ 1.2-1.0 Ma. This demonstrates that the sediment provenance of the Yangtze delta has experienced a change from local to distal Yangtze River, which took place with the uplift of the Tibetan plateau and coastal subsidence during the Plio-Quaternary.

  6. Characteristics of sediment transport at selected sites along the Missouri River during the high-flow conditions of 2011

    USGS Publications Warehouse

    Galloway, Joel M.; Rus, Dave L.; Alexander, Jason S.

    2013-01-01

    During 2011, many tributaries in the Missouri River Basin experienced near record peak streamflow and caused flood damage to many communities along much of the Missouri River from Montana to the confluence with the Mississippi River. The large runoff event in 2011 provided an opportunity to examine characteristics of sediment transport in the Missouri River at high-magnitude streamflow and for a long duration. The purpose of this report is to describe sediment characteristics during the 2011 high-flow conditions at six selected sites on the Missouri River, two in the middle region of the basin between Lake Sakakawea and Lake Oahe in North Dakota, and four downstream from Gavins Point Dam along the Nebraska-South Dakota and Nebraska-Iowa borders. A wider range in suspended-sediment concentration was observed in the middle segment of the Missouri River compared to sites in the lower segment. In the middle segment of the Missouri River, suspended-sediment concentrations increased and peaked as flows increased and started to plateau; however, while flows were still high and steady, suspended-sediment concentrations decreased and suspended-sediment grain sizes coarsened, indicating the decrease possibly was related to fine-sediment supply limitations. Measured bedload transport rates in the lower segment of the Missouri River (sites 3 to 6) were consistently higher than those in the middle segment (sites 1 and 2) during the high-flow conditions in 2011. The median bedload transport rate measured at site 1 was 517 tons per day and at site 2 was 1,500 tons per day. Measured bedload transport rates were highest at site 3 then decreased downstream to site 5, then increased at site 6. The median bedload transport rates were 22,100 tons per day at site 3; 5,640 tons per day at site 4; 3,930 tons per day at site 5; and 8,450 tons per day at site 6. At the two sites in the middle segment of the Missouri River, the greatest bedload was measured during the recession of the

  7. Modelling the landslide area and sediment discharge in landslide-dominated region, Taiwan

    NASA Astrophysics Data System (ADS)

    Teng, Tse-Yang; Huang, -Chuan, Jr.; Lee, Tsung-Yu; Chen, Yi-Chin; Jan, Ming-Young; Liu, Cheng-Chien

    2016-04-01

    Many studies have indicated the magnified increase of rainfall intensification, landsliding and subsequent sediment discharge due to the global warming effect. However, a few works synthesized the "chain reaction" from rainfall, landsliding to sediment discharge at the same time because of the limited observations of landslide area and sediment discharge during episodes. Besides, the sediment transport strongly depends on the sediment supply and stream power which interact conditionally. In this study, our goal is to build a model that can simulate time-series landslide area and subsequent sediment discharge. The synthesized model would be applied onto Tsengwen Reservoir watershed in southern Taiwan, where lots of landslides occur every year. Unlike other studies, our landslide model considers not only rainfall effect but also previous landslide status, which may be applied to landslide-dominated regions and explains the irrelevant relationship between typhoon rainfall and landslide area. Furthermore, our sediment transport model considers the sediment budget which couples transport- and supply-limited of sediment. The result shows that the simulated time-series landslide area and the sediment transport agree with the observation and the R2 are 0.88 and 0.56, respectively. Reactivated ratio of previous landslide area is 72.7% which indicates the high reoccurrence of historical landslide in landslide-dominated regions. We divided nine historical typhoons into three periods to demonstrate the effect of sediment supply/supply-limited condition upon sediment transport. For instance, the rainfall is smaller in period 3 than in period 1 but the sediment transport is higher in period 3 due to the catastrophic landslide (typhoon Morakot) during period 2. We argue that quantifying sediment transport should couple not only with water discharge but sediment budget, which is rarely considered in calculating sediment transport. Moreover, the parameterization of the controlling

  8. Sediments of Lake Van - a high-resolution archive of changing climate, volcanic events and seismic activity in Eastern Anatolia for the last 500'000 yrs

    NASA Astrophysics Data System (ADS)

    Stockhecke, M.; Anselmetti, F. S.; Sturm, M.; Paleovan Scientific Party

    2012-04-01

    record. The sub-mm thin laminated intervals as recovered from different interglacials/interstadials stand out prominently against the more banded lithologies of the remaining sections. From 168 to 189 meters below the lake floor a unit of major irregularities and accumulation of deformations were identified as a large-scale mega-event deposit. It overlies a unit of carbonate-poor diatomaceous mud and a gravel-rich unit containing fresh-water gastropods (Bithynia) and mussels. The gravel is interpreted to have been deposited under beach-like conditions and reflects the early transgressive state of the lakés history. The distinct and great variability of sediment types is indicative of highly and rapidly changing depositional conditions forced by lake level and other climate-driven changes and by tectonic events over the past 500'000 years. The annual laminated intervals reflect strong seasonal fluctuations in particle fluxes to the lake bottom and bottom water anoxia. The onset/cessation of theses episodically occurring laminations represent threshold crossings indicative for abrupt changes of climate (e.g. Dansgaard-Oeschger cycles) and tectonic activities. The partly varved lacustrine record enables, for the first time, to reconstruct the environmental and climate conditions captured during several glacial/interglacial cycles at a mid-latitudinal continental realm.

  9. Recurrent Episodes of Dissociative Fugue

    PubMed Central

    Angothu, Hareesh; Pabbathi, Lokeswar Reddy

    2016-01-01

    Dissociative fugue is rare entity to encounter with possible differentials of epilepsy and malingering. It is one of the dissociative disorders rarely seen in clinical practice more often because of the short lasting nature of this condition. This might also be because of organized travel of the individuals during the episodes and return to their families after the recovery from episodes. This is a case description of a patient who has experienced total three episodes of dissociative fugue. The patient has presented during the third episode and two prior episodes were diagnosed as fugue episodes retrospectively based on the history. Planned travel in this case by the patient to a distant location was prevented because of early diagnosis and constant vigilance till the recovery. As in this case, it may be more likely that persons with Dissociative fugue may develop similar episodes if they encounter exceptional perceived stress. However, such conclusions may require follow-up studies. PMID:27114633

  10. Exploring fungal diversity in deep-sea sediments from Okinawa Trough using high-throughput Illumina sequencing

    NASA Astrophysics Data System (ADS)

    Zhang, Xiao-Yong; Wang, Guang-Hua; Xu, Xin-Ya; Nong, Xu-Hua; Wang, Jie; Amin, Muhammad; Qi, Shu-Hua

    2016-10-01

    The present study investigated the fungal diversity in four different deep-sea sediments from Okinawa Trough using high-throughput Illumina sequencing of the nuclear ribosomal internal transcribed spacer-1 (ITS1). A total of 40,297 fungal ITS1 sequences clustered into 420 operational taxonomic units (OTUs) with 97% sequence similarity and 170 taxa were recovered from these sediments. Most ITS1 sequences (78%) belonged to the phylum Ascomycota, followed by Basidiomycota (17.3%), Zygomycota (1.5%) and Chytridiomycota (0.8%), and a small proportion (2.4%) belonged to unassigned fungal phyla. Compared with previous studies on fungal diversity of sediments from deep-sea environments by culture-dependent approach and clone library analysis, the present result suggested that Illumina sequencing had been dramatically accelerating the discovery of fungal community of deep-sea sediments. Furthermore, our results revealed that Sordariomycetes was the most diverse and abundant fungal class in this study, challenging the traditional view that the diversity of Sordariomycetes phylotypes was low in the deep-sea environments. In addition, more than 12 taxa accounted for 21.5% sequences were found to be rarely reported as deep-sea fungi, suggesting the deep-sea sediments from Okinawa Trough harbored a plethora of different fungal communities compared with other deep-sea environments. To our knowledge, this study is the first exploration of the fungal diversity in deep-sea sediments from Okinawa Trough using high-throughput Illumina sequencing.

  11. Bioaccumulation of highly hydrophobic organohalogen flame retardants from sediments: application of toxicokinetics and passive sampling techniques.

    PubMed

    Li, Huizhen; Zhang, Baozhong; Wei, Yanli; Wang, Fei; Lydy, Michael J; You, Jing

    2014-06-17

    Highly hydrophobic organohalogen flame retardants (HHOFRs) are found ubiquitously in the environment; therefore, a better understanding of their bioavailability is needed. In the current study, bioaccumulation testing using the oligochaete, Lumbriculus variegatus, and passive sampling (solid-phase microextraction (SPME)) were performed to study the bioaccumulation potential of HHOFRs, including decabromodiphenyl ether (deca-BDE), decabromodiphenyl ethane (DBDPE), and dechlorane plus (DP), in laboratory-spiked and field-collected sediments. The HHOFRs were bioavailable to L. variegatus even though their biota-sediment accumulation factors were low (0.016 ± 0.002 to 0.48 ± 0.082 g organic carbon/g lipid, syn-DP > anti-DP > deca-BDE > DBDPE). Hydrophobicity and stereoisomerism affected HHOFR bioavailability. Meanwhile, HHOFR concentrations on the SPME fibers (Cf) correlated with those in biota (Cb), suggesting the potential application of SPME in bioavailability prediction for those compounds. The log Cf to log Cb correlation for deca-BDE and DP had a greater intercept than that for polychlorinated biphenyls (data obtained from the literature) although the slopes were similar, while data for DBDPE fell on the regression line for PCBs, implying some uncertainty in application of SPMEs across chemical classes. The increasing sorptive ability of proteins for HHOFRs in comparison to the less-brominated BDEs suggested that protein-binding should be considered when estimating bioaccumulation potential of HHOFRs in benthic invertebrates.

  12. Monitoring stream sediment loads in response to agriculture in Prince Edward Island, Canada.

    PubMed

    Alberto, Ashley; St-Hilaire, Andre; Courtenay, Simon C; van den Heuvel, Michael R

    2016-07-01

    Increased agricultural land use leads to accelerated erosion and deposition of fine sediment in surface water. Monitoring of suspended sediment yields has proven challenging due to the spatial and temporal variability of sediment loading. Reliable sediment yield calculations depend on accurate monitoring of these highly episodic sediment loading events. This study aims to quantify precipitation-induced loading of suspended sediments on Prince Edward Island, Canada. Turbidity is considered to be a reasonably accurate proxy for suspended sediment data. In this study, turbidity was used to monitor suspended sediment concentration (SSC) and was measured for 2 years (December 2012-2014) in three subwatersheds with varying degrees of agricultural land use ranging from 10 to 69 %. Comparison of three turbidity meter calibration methods, two using suspended streambed sediment and one using automated sampling during rainfall events, revealed that the use of SSC samples constructed from streambed sediment was not an accurate replacement for water column sampling during rainfall events for calibration. Different particle size distributions in the three rivers produced significant impacts on the calibration methods demonstrating the need for river-specific calibration. Rainfall-induced sediment loading was significantly greater in the most agriculturally impacted site only when the load per rainfall event was corrected for runoff volume (total flow minus baseflow), flow increase intensity (the slope between the start of a runoff event and the peak of the hydrograph), and season. Monitoring turbidity, in combination with sediment modeling, may offer the best option for management purposes.

  13. Thermophilic nitrate-reducing microorganisms prevent sulfate reduction in cold marine sediments incubated at high temperature

    NASA Astrophysics Data System (ADS)

    Nepomnyashchaya, Yana; Rezende, Julia; Hubert, Casey

    2014-05-01

    Hydrogen sulphide produced during metabolism of sulphate-reducing microorganisms (SRM) is toxic, corrosive and causes detrimental oil reservoir souring. During secondary oil recovery, injecting oil reservoirs with seawater that is rich in sulphate and that also cools high temperature formations provides favourable growth conditions for SRM. Nitrate addition can prevent metabolism of SRM by stimulating nitrate-reducing microorganisms (NRM). The investigations of thermophilic NRM are needed to develop mechanisms to control the metabolism of SRM in high temperature oil field ecosystems. We therefore established a model system consisting of enrichment cultures of cold surface marine sediments from the Baltic Sea (Aarhus Bay) that were incubated at 60°C. Enrichments contained 25 mM nitrate and 40 mM sulphate as potential electron acceptors, and a mixture of the organic substrates acetate, lactate, propionate, butyrate (5 mM each) and yeast extract (0.01%) as potential carbon sources and electron donors. Slurries were incubated at 60°C both with and without initial pasteurization at 80°C for 2 hours. In the enrichments containing both nitrate and sulphate, the concentration of nitrate decreased indicating metabolic activity of NRM. After a four-hour lag phase the rate of nitrate reduction increased and the concentration of nitrate dropped to zero after 10 hours of incubation. The concentration of nitrite increased as the reduction of nitrate progressed and reached 16.3 mM after 12 hours, before being consumed and falling to 4.4 mM after 19-day of incubation. No evidence for sulphate reduction was observed in these cultures during the 19-day incubation period. In contrast, the concentration of sulphate decreased up to 50% after one week incubation in controls containing only sulphate but no nitrate. Similar sulfate reduction rates were seen in the pasteurized controls suggesting the presence of heat resistant SRM, whereas nitrate reduction rates were lower in the

  14. Sediment characterization of the highly impacted Augusta harbour (Sicily, Italy): modern benthic foraminifera in relation to grain-size and sediment geochemistry.

    PubMed

    Romano, Elena; Bergamin, Luisa; Magno, Maria Celia; Ausili, Antonella

    2013-05-01

    The Augusta harbour is affected by high anthropogenic impact due to intense harbour activity and a large chemical and petrochemical pole. Thirty-seven sediment samples were collected during an environmental characterization project and analyzed for grain size, chemical parameters (Al, As, Cd, Cr, Cu, Fe, Hg, Ni, Pb, Zn and V) and foraminifera, the last one generally being used as ecological indicators of environmental quality. Anthropogenic enrichment was recognized for As, Cu, Hg, Pb and Zn and, among these, Hg showed very high concentrations (up to 191 mg kg(-1) d.w.) often associated in the southern sector of the study area to very high PCB levels (up to 0.83 mg kg(-1)). In this area, an assemblage dominated by Rosalina bradyi and Quinqueloculina lata was recognized. This assemblage shows a clear decrease of foraminiferal density and diversity and, at the same time, increased dominance with respect to the assemblage characterizing the central and northern less polluted sectors, in which Miliolinella subrotunda prevails. Quinqueloculina lata was demonstrated to be a stress-tolerant species because it was not influenced by sediment texture, but positively correlated with the concentration of Hg, PCBs and PAHs. The environmental stress shown by the high-dominance of the Ammonia tepida assemblage was attributed mainly to the influence of stream mouths, which determine environmental instability. Foraminiferal assemblages showed a clear response to environmental degradation in the most polluted area but, at the same time, they demonstrated a high adaptation to pollution.

  15. Oak Forest Responses to Episodic-Seasonal-Drought, Chronic Multi-year Precipitation Change and Acute Drought Manipulations in a Region With Deep Soils and High Precipitation

    NASA Astrophysics Data System (ADS)

    Hanson, Paul J.; Wullschleger, Stan D.; Todd, Donald E.; Auge, Robert M.; Froberg, Mats; Johnson, Dale W.

    2010-05-01

    Implications of episodic-seasonal drought (extremely dry late summers), chronic multi-year precipitation manipulations (±33 percent over 12 years) and acute drought (-100 percent over 3 years) were evaluated for the response of vegetation and biogeochemical cycles for an upland-oak forest. The Quercus-Acer forest is located in eastern Tennessee on deep acidic soils with mean annual temperatures of 14.2 °C and abundant precipitation (1352 mm y-1). The multi-year observations and chronic manipulations were conducted from 1993 through 2005 using understory throughfall collection troughs and redistribution gutters and pipes. Acute manipulations of dominant canopy trees (Quercus prinus; Liriodendron tulipifera) were conducted from 2003 through 2005 using full understory tents. Regional and severe late-summer droughts were produced reduced stand water use and photosynthetic carbon gain as expected. Likewise, seedlings and saplings exhibited reduced survival and cumulative growth reductions. Conversely, multi-year chronic increases or decreases in precipitation and associated soil water deficits did not reduce large tree basal area growth for the tree species present. The resilience of canopy trees to chronic-change was the result of a disconnect between carbon allocation to tree growth (an early-season phenomenon) and late-season drought occurrence. Acute precipitation exclusion from the largest canopy trees also produced limited physiological responses and minimal cumulative growth reductions. Lateral root water sources were removed through trenching and could not explain the lack of response to extreme soil drying. Therefore, deep rooting the primary mechanism for large-tree resilience to severe drought. Extensive trench-based assessments of rooting depth suggested that ‘deep' water supplies were being obtained from limited numbers of deep fine roots. Observations of carbon stocks in organic horizons demonstrated accumulation with precipitation reductions and

  16. High-resolution sizing of monolayer-protected gold clusters by differential centrifugal sedimentation.

    PubMed

    Krpetić, Zeljka; Davidson, Adam M; Volk, Martin; Lévy, Raphaël; Brust, Mathias; Cooper, David L

    2013-10-22

    Differential centrifugal sedimentation (DCS) has been applied to accurately size ligand-protected gold hydrosols in the 10 to 50 nm range. A simple protocol is presented to correct for particle density variations due to the presence of the ligand shell, which is formed here by either polyethylene glycol-substituted alkane thiols (PEG-alkane thiols) of different chain length or oligopeptides. The method gives reliable data for all particle sizes investigated and lends itself to rapid routine sizing of nanoparticles. Unlike TEM, DCS is highly sensitive to small changes in the thickness of the organic ligand shell and can be applied to monitor shell thickness variations of as little as 0.1 nm on particles of a given core size.

  17. Improving NMR Diffusion Logs by Accounting for High Magnetic Susceptibility in Sediments

    NASA Astrophysics Data System (ADS)

    Fay, E. L.; Knight, R. J.

    2013-12-01

    Nuclear magnetic resonance (NMR) well-logging can be used to measure the apparent diffusion coefficient of fluids in the soil or rock around a well. NMR diffusion logs have several potential applications in the field of hydrogeophysics, such as improving estimates of permeability and characterizing LNAPL contamination. Near-surface environments, however, offer an added challenge to measuring diffusion with NMR due to the high variability in the magnetic mineral content of soils. In this work, we were able to improve the accuracy of diffusion measurements from an NMR log by accounting for the magnetic susceptibility of the sediments. NMR diffusion measurements have been used extensively both in laboratory and logging applications to measure the relative saturation of water, gas, and oil in reservoir rocks, due to the contrasting diffusion coefficients of these fluids. Laboratory diffusion measurements have also been used to study restricted diffusion in pore systems, which yields information on the pore size and the connectivity of the pore space, both critical to predicting the permeability of a material. NMR diffusion measurements rely on the application of an external magnetic field gradient across the measured volume. This magnetic field gradient is used to measure the displacement of fluid molecules during a specified diffusion time interval. The magnitude of the effective field gradient, i.e. the gradient experienced in the measured volume, must be known in order to calculate of the diffusion coefficient of the fluid from the NMR signal. Common practice in NMR logging is to assume that internal gradients are negligible and that the effective gradient is equal to the externally applied gradient, which is typically well characterized. In materials with low magnetic susceptibility, this is a valid assumption. Complications arise in materials with high magnetic susceptibility, because magnetic field gradients will be present within these materials before the

  18. Toxicity assessment of polycyclic aromatic hydrocarbons in sediments from European high mountain lakes.

    PubMed

    Quiroz, Roberto; Grimalt, Joan O; Fernández, Pilar

    2010-05-01

    Sediment quality guidelines and toxic equivalent factors have been used for assessment of the toxicity of sedimentary long-range atmospherically transported polycyclic aromatic hydrocarbons (PAHs) to the organisms living in high mountain European lakes. This method has provided indices that are consistent with experimental studies evaluating in situ sedimentary estrogenic activity or physiological response to AhR binding in fish from the same lakes. All examined lakes in north, central, west, northeast and southeast European mountains have shown sedimentary PAH concentrations that are above thresholds of no effect but only those situated in the southeast lakes district exhibited concentrations above the indices of probable effects. These mountains, Tatras, are also those having PAH concentrations of highest activity for AhR binding. Chrysene+triphenylene, dibenz[a]anthracene, benzo[k]fluoranthene and indeno[1,2,3-cd]pyrene are the main compounds responsible for the observed toxic effects.

  19. Power management systems for sediment microbial fuel cells in high power and continuous power applications

    NASA Astrophysics Data System (ADS)

    Donovan, Conrad Koble

    The objective of this dissertation was to develop power management systems (PMS) for sediment microbial fuel cells (SFMCs) for high power and continuous applications. The first part of this dissertation covers a new method for testing the performance of SMFCs. This device called the microbial fuel cell tester was developed to automatically test power generation of PMS. The second part focuses on a PMS capable of delivering high power in burst mode. This means that for a small amount of time a large amount of power up to 2.5 Watts can be delivered from a SMFC only generating mW level power. The third part is aimed at developing a multi-potentiostat laboratory tool that measures the performance at fixed cell potentials of microbial fuel cells so that I can optimize them for use with the PMS. This tool is capable of controlling the anode potential or cathode potential and measuring current of six separate SMFCs simultaneously. By operating multiple potentiostats, I was able to run experiments that find ideal operating conditions for the sediment microbial fuel cells, and also I can optimize the power management system for these conditions. The fourth part of the dissertation is targeting a PMS that was able to operate a sensor continuously which was powered by an SMFC. In pervious applications involving SMFCs, the PMS operated in batch mode. In this PMS, the firmware on the submersible ultrasonic receiver (SUR) was modified for use with my PMS. This integration of PMS and SUR allowed for the continuous operation of the SUR without using a battery. Finally, the last part of the dissertation recommends a scale-up power management system to overcome the linearity scale up issue of SMFCs as future work. Concluding remarks are also added to summarize the goal and focus of this dissertation.

  20. Groundwater penetrating radar and high resolution seismic for locating shallow faults in unconsolidated sediments

    SciTech Connect

    Wyatt, D.E. |; Waddell, M.G.; Sexton, B.G.

    1993-12-31

    Faults in shallow, unconsolidated sediments, particularly in coastal plain settings, are very difficult to discern during subsurface exploration yet have critical impact to groundwater flow, contaminant transport and geotechnical evaluations. This paper presents a case study using cross-over geophysical technologies in an area where shallow faulting is probable and known contamination exists. A comparison is made between Wenner and dipole-dipole resistivity data, ground penetrating radar, and high resolution seismic data. Data from these methods were verified with a cone penetrometer investigation for subsurface lithology and compared to existing monitoring well data. Interpretations from these techniques are compared with actual and theoretical shallow faulting found in the literature. The results of this study suggests that (1) the CPT study, combined with the monitoring well data may suggest that discontinuities in correlatable zones may indicate that faulting is present (2) the addition of the Wenner and dipole-dipole data may further suggest that offset zones exist in the shallow subsurface but not allow specific fault planes or fault stranding to be mapped (3) the high resolution seismic data will image faults to within a few feet of the surface but does not have the resolution to identify the faulting on the scale of our models, however it will suggest locations for upward continuation of faulted zones (4) offset 100 MHz and 200 MHz CMP GPR will image zones and features that may be fault planes and strands similar to our models (5) 300 MHz GPR will image higher resolution features that may suggest the presence of deeper faults and strands, and (6) the combination of all of the tools in this study, particularly the GPR and seismic may allow for the mapping of small scale, shallow faulting in unconsolidated sediments.

  1. Overview of selected surrogate technologies for high-temporal resolution suspended-sediment monitoring

    USGS Publications Warehouse

    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.

  2. Lateral and vertical heterogeneity of flow and suspended sediment characteristics during a dam flushing event, in high velocity conditions

    NASA Astrophysics Data System (ADS)

    Antoine, Germain; Cazilhac, Marine; Monnoyer, Quentin; Jodeau, Magali; Gratiot, Nicolas; Besnier, Anne-Laure; Henault, Fabien; Le Brun, Matthieu

    2015-04-01

    The dynamic of suspended sediments in highly turbulent and concentrated flow is an important issue to better predict the sediment propagation along mountain rivers. In such extreme environments, the spatial and temporal variability of hydraulic and sediment parameters are difficult to measure: the flow velocity and the suspended sediment concentration (SSC) could be high (respectively several m/s and g/l) and rapidly variable. Simple methods are commonly used to estimate water discharge and mean or punctual SSC. But no method has been used successfully in a mountain river to estimate during a whole event the spatial distribution of flow velocity and SSC, as well as sediment parameters like grain size or settling velocity into a river cross section. This leads to these two questions: in such conditions, can we calculate sediment fluxes with one sediment concentration measurement? How can we explain the spatial heterogeneity of sediment characteristics? In this study, we analyze sampled data from a very well instrumented river reach in the Northern French Alps: the Arc-Isère River system. This gravel-bed river system is characterized by large concentrations of fines sediments, coming from the highly erodible mountains around. To control the hydraulic, sedimentary and chemical parameters from the catchment head, several gauging stations have been established since 2006. Especially, several measurements are usually done during the flushing of the dams located on the upper part of the river. During the flushing event of June 2014, we instrumented the gauging station located just upstream the confluence between the Isere and the Arc River, at the outlet of the Arc River watershed. ADCP measurements have been performed to estimate the spatial distribution of the flow velocity (up to 3 m/s), and turbidimeters and automatic samplers have been used to estimate the spatial distribution of the SSC into the cross section (up to 6 g/l). These samples have been directly analyzed

  3. Stratification effects by fine suspended sediment at low, medium, and very high concentrations

    NASA Astrophysics Data System (ADS)

    Winterwerp, J. C.

    2006-05-01

    This paper describes results of the second part of a study on stratification effects by cohesive and noncohesive sediment. Winterwerp (2001) applied classical stratified flow theory implemented in a one-dimensional vertical numerical model (the 1DV POINT MODEL), showing that sediment-induced stratification effects may occur at already fairly small suspended sediment concentrations (i.e., a few 100 mg/L). We also discussed a basic difference between the behavior of cohesive and noncohesive sediment, which emerges as a result of the large water content of mud flocs. In this paper we elaborate further on the hydrodynamic description of the transport of fine suspended sediment by analyzing field and laboratory observations over a very large range of concentrations. We propose a sediment stability diagram to explain some features of hyperconcentrated flows, such as those observed in the Yellow River. We show that the behavior of hyperconcentrated flows is affected largely by hindered settling effects reducing the energy required to keep the sediment in suspension. The hydrodynamic description of sediment transport is used to predict capacity conditions as a function of a dimensionless stream power, i.e., U3/hgWs. This prediction agrees favorably with observations reported in literature covering four orders of magnitude in suspended sediment concentration.

  4. A new device for high precision in situ sediment temperature profile measurements at the seafloor

    NASA Astrophysics Data System (ADS)

    Feseker, T.; Wetzel, G.; Heesemann, B.

    2012-04-01

    In situ sediment temperature profile measurements at the seafloor provide valuable information on fluid seepage, hydrate stability, and ambient temperature of samples. In addition, it can be convenient to approximate other parameters such as concentrations of porewater constituents from temperature or temperature gradient using transfer functions if their distribution is controlled by the same processes and direct quantification involves time-consuming sampling and laboratory analyses. We present a new instrument that can be used to obtain precisely positioned sediment temperature profile measurements from the seafloor during ROV dives. Consisting of a 0.4 m-long sensor rod equipped with eight temperature sensors and a standard data logger, the new T-Stick can be operated by an ROV in a fully autonomous mode. The temperature range of the instrument is -5 °C to 35 °C and it can withstand pressures of up to 600 bar. Compared to previously used instruments, the smaller diameter of the new T-Stick reduces the thermal inertia of the lance and results in shorter equilibration times. Virtual measurements generated by a numerical model showed that the T-Stick provides highly accurate temperature profile measurements with a root mean square error of 0.0027 K for a wide range of thermal sediment properties. Modeled temperature gradients are representative of both normal deep sea settings and cold seep environments with elevated temperature gradients of up to three orders of magnitude above normal background values, which are the primary target areas for T-Stick measurements. Deviations from the true in situ temperature profiles are caused by disturbance of the temperature field by the probe itself and may lead to underestimation of gradients and curvature in the profiles. A first field test of the T-Stick was conducted at the Håkon Mosby mud volcano at 1250 m water depth on the Barents Sea slope, where the new instrument provided useful information about the origin and

  5. The evolution of episodic memory

    PubMed Central

    Allen, Timothy A.; Fortin, Norbert J.

    2013-01-01

    One prominent view holds that episodic memory emerged recently in humans and lacks a “(neo)Darwinian evolution” [Tulving E (2002) Annu Rev Psychol 53:1–25]. Here, we review evidence supporting the alternative perspective that episodic memory has a long evolutionary history. We show that fundamental features of episodic memory capacity are present in mammals and birds and that the major brain regions responsible for episodic memory in humans have anatomical and functional homologs in other species. We propose that episodic memory capacity depends on a fundamental neural circuit that is similar across mammalian and avian species, suggesting that protoepisodic memory systems exist across amniotes and, possibly, all vertebrates. The implication is that episodic memory in diverse species may primarily be due to a shared underlying neural ancestry, rather than the result of evolutionary convergence. We also discuss potential advantages that episodic memory may offer, as well as species-specific divergences that have developed on top of the fundamental episodic memory architecture. We conclude by identifying possible time points for the emergence of episodic memory in evolution, to help guide further research in this area. PMID:23754432

  6. Survival of Desulfotomaculum spores from estuarine sediments after serial autoclaving and high-temperature exposure

    PubMed Central

    O'Sullivan, Louise A; Roussel, Erwan G; Weightman, Andrew J; Webster, Gordon; Hubert, Casey RJ; Bell, Emma; Head, Ian; Sass, Henrik; Parkes, R John

    2015-01-01

    Bacterial spores are widespread in marine sediments, including those of thermophilic, sulphate-reducing bacteria, which have a high minimum growth temperature making it unlikely that they grow in situ. These Desulfotomaculum spp. are thought to be from hot environments and are distributed by ocean currents. Their cells and spores upper temperature limit for survival is unknown, as is whether they can survive repeated high-temperature exposure that might occur in hydrothermal systems. This was investigated by incubating estuarine sediments significantly above (40–80 °C) maximum in situ temperatures (∼23 °C), and with and without prior triple autoclaving. Sulphate reduction occurred at 40–60 °C and at 60 °C was unaffected by autoclaving. Desulfotomaculum sp. C1A60 was isolated and was most closely related to the thermophilic D. kuznetsoviiT (∼96% 16S rRNA gene sequence identity). Cultures of Desulfotomaculum sp. C1A60, D. kuznetsoviiTand D. geothermicum B2T survived triple autoclaving while other related Desulfotomaculum spp. did not, although they did survive pasteurisation. Desulfotomaculum sp. C1A60 and D. kuznetsovii cultures also survived more extreme autoclaving (C1A60, 130 °C for 15 min; D. kuznetsovii, 135 °C for 15 min, maximum of 154 °C reached) and high-temperature conditions in an oil bath (C1A60, 130° for 30 min, D. kuznetsovii 140 °C for 15 min). Desulfotomaculum sp. C1A60 with either spores or predominantly vegetative cells demonstrated that surviving triple autoclaving was due to spores. Spores also had very high culturability compared with vegetative cells (∼30 × higher). Combined extreme temperature survival and high culturability of some thermophilic Desulfotomaculum spp. make them very effective colonisers of hot environments, which is consistent with their presence in subsurface geothermal waters and petroleum reservoirs. PMID:25325382

  7. The Episodic Nature of Episodic-Like Memories

    ERIC Educational Resources Information Center

    Easton, Alexander; Webster, Lisa A. D.; Eacott, Madeline J.

    2012-01-01

    Studying episodic memory in nonhuman animals has proved difficult because definitions in humans require conscious recollection. Here, we assessed humans' experience of episodic-like recognition memory tasks that have been used with animals. It was found that tasks using contextual information to discriminate events could only be accurately…

  8. High-resolution multitemporal measurement of rockglacier dynamics and periglacial sediment storage in the eastern Alps, Austria

    NASA Astrophysics Data System (ADS)

    Dusik, Jana-Marie; Haas, Florian; Heckmann, Tobias; Hilger, Ludwig; Neugirg, Fabian; Leopold, Matthias; Becht, Michael

    2013-04-01

    High alpine environments are subject to rapid change due to melting glaciers and permafrost. As a consequence, rockwalls and moraines experience destabilization and increased mobilization of sediment. The work presented here is part of the joint project PROSA (High-resolution measurements of morphodynamics in rapidly changing PROglacial Systems of the Alps) which deals with the calculation and quantification of the sediment budget for an alpine catchment situated in the Kaunertal, Austrian Alps. Rockglaciers are frequently appearing landforms in the Kaunertal and represent large sediment storages. Usually the sediment flux of rockglaciers is rather small, depending on their activity status. All activity forms of rockglaciers (active, inactive and relict) are present in the catchment area. Besides the highly active and well-known Ölgrube rockglacier, this work deals especially with the examination of the Riffeltal rockglacier which is situated on the opposite valley side. The activity status of the Riffeltal rockglacier is assessed and compared to the Ölgrube rockglacier with respect to the local parameters aspect, altitude, existence/absence of glaciers, geology and catchment area. Furthermore sediment volumes of both rockglaciers, their rates of movement and therefore their contribution to the sediment budget of the Kaunertal-catchment area is estimated. The internal structure of the Riffeltal rockglacier was inferred from geophysical measurements (refraction seismics, ground penetrating radar and electrical resistivity tomography). Temperature loggers were placed on and around the rockglacier before the first snowfall to measure the bottom temperature of snowcover (BTS) once per hour during winter, and BTS measurements will be performed with a probe in February, March and April to infer permafrost probability. Rockglacier dynamics are identified with the analysis of multitemporal orthophotos and digital elevation models, derived from high-resolution airborne

  9. Physical resuspension and vertical mixing of sediments on a high energy continental margin (Sydney, Australia).

    PubMed

    Matthai, C; Birch, G F; Jenkinson, A; Heijnis, H

    2001-01-01

    Four sediment cores from the continental margin adjacent to Sydney were analyzed for 210Pb, 137Cs, trace metals (Ag, Cd, Co, Cu, Mn, Ni, Pb, Zn), iron, dry bulk density, mud and moisture content. The concentrations of trace metals in the total sediment are low at all sites, although slightly elevated concentrations of Ag, Cu, Pb and Zn are present in the fine fraction of sediment (< 62.5 microns) near a major ocean outfall. Concentrations of trace metals in the fine fraction of sediment are similar in the upper 10-15 cm, indicating strong vertical mixing of the sediments, whereas an upward coarsening grain size in the upper 1-3 cm of sediment supports physical resuspension during storms. Sediment accumulation rates on the middle shelf adjacent to Sydney were estimated from downcore profiles of 210Pb and 137Cs and range between 0.2 and 0.4 cm yr-1. Although the mass fluxes of Cu, Pb and Zn within a distance of 2 km from the outfall (up to 36.1, 30.8 and 86.2 micrograms cm-2 yr-1, respectively) are greater than 20 km north of the outfall (< 23.5 micrograms cm-2 yr-1), the low concentrations of trace metals in sediments near the outfall support an efficient dispersal of anthropogenic contaminants on this continental margin.

  10. The impact of high-frequency sedimentation cycles on stratigraphic interpretation

    SciTech Connect

    Perlmutter, M.A.; Radovich, B.J.; Matthews, M.D.

    1997-01-01

    Global cyclostratigraphy, a methodology that utilizes climate change to evaluate sediment flux, characterizes the impact of sediment cycles on stratigraphy. Climatic succession, sediment yield cycles, and the phase relationship of sediment cycles to eustatic cycles are all determined in the early stages of basin analysis. Sedimentologic information is then used to assist in sequence evaluations. Climatic successions are intrinsically associated with global position (paleogeography) and are not necessarily synchronous with glacioeustatic sea-level cycles. A preliminary evaluation of the effect of climate on sediment supply from modem river systems indicates that sediment yield may vary by well over two orders of magnitude during one climate cycle. Consequently, basins in different climatic belts can have distinctly different volumes and lithologies for systems tracts that have similar base-level changes. The stratigraphic computer program Sedpak was utilized to examine the possible impact of different sedimentation cycles on sequence interpretation and reservoir forecasts. The effect of sedimentation cycles on reservoir distribution in real world sequences is demonstrated with a comparison of the Miocene section of the Surma basin, Bangladesh, and the Plio-Pleistocene section of the Gulf of Mexico. In the Surma basin, reservoirs are most likely to occur in transgressive and highstand systems tracts, while reservoirs in the Gulf of Mexico are more likely in lowstand prograding complexes.

  11. Rift tectonics and limestone sedimentation: Jurassic of the central and eastern High Atlas, Morocco

    SciTech Connect

    Warme, J.E.; Hazlett, B.H.; Crevello, P.D.; Letsch, D.K.; Burke, R.B. )

    1988-08-01

    The central and eastern High Atlas ranges of southern Morocco represent deposition in an Early to Middle Jurassic rift which first collected continental basalts, red beds, and evaporites. Carbonate deposition was initiated by a euxinic phase, followed by a mosaic of normal marine limestones and marls controlled by regional subsidence and local differential fault-block movements and overprinted by global sea level changes. The High Atlas is now an en echelon series of high-angle reverse faults, creating abrupt and discontinuous fault-bounded ridges separated by broad synclines. Facies relationships of the Jurassic carbonates show that the faults were originally synrift normal faults, probably transtensional, now structurally reversed. Overlying Aalenian to Bajocian shelf limestones prograded into an axial seaway filled with thick marls, punctuated in the Bajocian by horizons of spectacularly exposed coralgal reefs which appear structurally isolated on separate fault blocks. Sedimentation eventually outpaced subsidence, culminating in continental deposits as the sea finally retreated in the mid-Dogger. Although abundant potential source rocks of this rift are thermally overmature, the basin serves as a well-exposed model for comparison with carbonate-filled rifts elsewhere.

  12. Tidal and meteorological forcing of sediment transport in tributary mudflat channels

    PubMed Central

    Ralston, David K.; Stacey, Mark T.

    2011-01-01

    Field observations of flow and sediment transport in a tributary channel through intertidal mudflats indicate that suspended sediment was closely linked to advection and dispersion of a tidal salinity front. During calm weather when tidal forcing was dominant, high concentrations of suspended sediment advected up the mudflat channel in the narrow region between salty water from San Francisco Bay and much fresher runoff from the small local watershed. Salinity and suspended sediment dispersed at similar rates through each tidal inundation, such that during receding ebbs the sediment pulse had spread spatially and maximum concentrations had decreased. Net sediment transport was moderately onshore during the calm weather, as asymmetries in stratification due to tidal straining of the salinity front enhanced deposition, particularly during weaker neap tidal forcing. Sediment transport by tidal forcing was periodically altered by winter storms. During storms, strong winds from the south generated wind waves and temporarily increased suspended sediment concentrations. Increased discharge down the tributary channels due to precipitation had more lasting impact on sediment transport, supplying both buoyancy and fine sediment to the system. Net sediment transport depended on the balance between calm weather tidal forcing and perturbations by episodic storms. Net transport in the tributary channel was generally off-shore during storms and during calm weather spring tides, and on-shore during calm weather neap tides. PMID:21499572

  13. High prevalence of multiple-antibiotic-resistant (MAR) Escherichia coli in river bed sediments of the Apies River, South Africa.

    PubMed

    Abia, Akebe Luther King; Ubomba-Jaswa, Eunice; Momba, Maggy Ndombo Benteke

    2015-10-01

    This study aimed at investigating the presence of antibiotic-resistant Escherichia coli in river bed sediments of the Apies River, Gauteng, South Africa, in order to better inform health management decisions designed to protect users of the river. Overall, 180 water and sediment samples were collected at 10 sites along the Apies River from January to February 2014. E. coli was enumerated using the Colilert® 18/Quanti-Tray® 2000 (IDEXX). Isolates were purified by streaking on eosin methylene blue agar followed by the indole test. Pure E. coli isolates were tested for resistance to nine antibiotics by the Kirby-Bauer disc diffusion method. Over 98% of the isolates were resistant to at least one of the antibiotics tested. The highest resistance was observed against nitrofurantoin (sediments) and ampicillin (water). Over 80% of all resistant isolates showed multiple antibiotic resistance (resistance to ≥3 antibiotics). The abundance of E. coli in the sediments not only adds to the evidence that sediments are a reservoir for bacteria and possibly other pathogens including antibiotic-resistant bacteria but also suggests that antibiotic-resistant genes could be transferred to pathogens due to the high prevalence of multiple-antibiotic-resistant (MAR) strains of E. coli observed in the sediment. Using untreated water from the Apies River following resuspension for drinking and other household purposes could pose serious health risks for users. Our results suggest that river bed sediments could serve as reservoirs for MAR bacteria including pathogens under different climatic conditions and their analysis could provide information of public health concerns.

  14. In situ high-resolution evaluation of labile arsenic and mercury in sediment of a large shallow lake.

    PubMed

    Wang, Chao; Yao, Yu; Wang, Peifang; Hou, Jun; Qian, Jin; Yuan, Ye; Fan, Xiulei

    2016-01-15

    The precise evaluation of arsenic (As) and mercury (Hg) bioavailability in sediment is crucial to controlling As and Hg contamination, but traditional ex situ measurements hamper comprehensive analysis of labile As and Hg in sediment. In this study, we characterized in situ labile As and Hg in sediment of Lake Hongze using the zirconium (Zr) oxide diffusive gradients in thin films (DGT) technique and 3-mercaptopropyl functionalized silica gel DGT, respectively. The concentrations of DGT-labile As and Hg in the sediment profiles were found to exhibit considerable variation, ranging from 0.15 to 4.15 μg L(-1) for As and from 0.04 to 1.35 μg L(-1) for Hg. As and Hg flux values, calculated based on the concentration gradients measured from the DGT profiles for both the overlying water and sediment close to the sediment-water interface, were used to determine the contamination status of As and Hg. Flux values of As and Hg were between -0.066 and 0.067 ng cm(-2)d(-1) and between -0.0187 and 0.0181 ng cm(-2)d(-1), respectively. The GNU's Not Unix R (GNU R) programming language was used to identify outliers of As and Hg at various depths at the sampling sites. The results indicate that the sites with the most outliers were all located in the regions that were seriously affected by contaminants from the Huai River. The DGT-labile As and Hg concentrations in the 0-30 mm layer were found to be significantly correlated with concentrations of labile As and Hg, total dissolved As and Hg, and total As and Hg in the overlying water, as indicated by ex situ measurements. Results show that DGT is a reliable and high-resolution technique that can be used for in situ monitoring of the labile fractions of As and Hg in sediment in fresh water bodies. PMID:26398454

  15. Shallow stratigraphy and sedimentation history during high-frequency sea-level changes on the central California shelf

    USGS Publications Warehouse

    Grossman, E.E.; Eittreim, S.L.; Field, M.E.; Wong, F.L.

    2006-01-01

    Analyses of high-resolution seismic-reflection data and sediment cores indicate that an extensive sediment deposit on the central California continental shelf is comprised of several late-Pleistocene to Holocene age facies. Offshore of the littoral zone, in water depths of 30-90 m, a 3-6 m thick veneer of fine sediment referred to as the mid-shelf mudbelt has formed along 50-100 km of the coast. The mudbelt drapes a parasequence characterized by prograding clinoforms that in places overlies a 1-3 m thick basal transgressive lag deposit. These facies overlie a prominent erosional unconformity that extends from the shore to the outer shelf. Eighteen calibrated 14CAMS ages of marine molluscs and terrestrial wood detritus sampled in cores range 15,800 yr BP to modern indicating a postglacial age for these sediments (one >55,000 yr BP represents relict sand). We model accumulation of these facies using (1) the topography of the underlying erosional unconformity interpreted from seismic reflection profiles, (2) observed sediment facies (grain size) distribution across the shelf (a proxy for wave/current sediment partitioning), and published estimates of (3) eustatic sea-level history, and (4) regional tectonics. Our model and data indicate that deposition of the transgressive lag began during early, slow postglacial sea-level rise and that a notable change in depositional environment occurred across an area of more than 200 km2 of the outer shelf likely in response to abrupt drowning during Meltwater Pulse 1B (11,500 yr BP). We propose that rapid progradation of clinoforms may have occurred during transgression because of the unique interaction of modest rates of sediment input and tectonic uplift, variable rates of eustatic sea-level rise and a complex stepped antecedent topography.

  16. In situ high-resolution evaluation of labile arsenic and mercury in sediment of a large shallow lake.

    PubMed

    Wang, Chao; Yao, Yu; Wang, Peifang; Hou, Jun; Qian, Jin; Yuan, Ye; Fan, Xiulei

    2016-01-15

    The precise evaluation of arsenic (As) and mercury (Hg) bioavailability in sediment is crucial to controlling As and Hg contamination, but traditional ex situ measurements hamper comprehensive analysis of labile As and Hg in sediment. In this study, we characterized in situ labile As and Hg in sediment of Lake Hongze using the zirconium (Zr) oxide diffusive gradients in thin films (DGT) technique and 3-mercaptopropyl functionalized silica gel DGT, respectively. The concentrations of DGT-labile As and Hg in the sediment profiles were found to exhibit considerable variation, ranging from 0.15 to 4.15 μg L(-1) for As and from 0.04 to 1.35 μg L(-1) for Hg. As and Hg flux values, calculated based on the concentration gradients measured from the DGT profiles for both the overlying water and sediment close to the sediment-water interface, were used to determine the contamination status of As and Hg. Flux values of As and Hg were between -0.066 and 0.067 ng cm(-2)d(-1) and between -0.0187 and 0.0181 ng cm(-2)d(-1), respectively. The GNU's Not Unix R (GNU R) programming language was used to identify outliers of As and Hg at various depths at the sampling sites. The results indicate that the sites with the most outliers were all located in the regions that were seriously affected by contaminants from the Huai River. The DGT-labile As and Hg concentrations in the 0-30 mm layer were found to be significantly correlated with concentrations of labile As and Hg, total dissolved As and Hg, and total As and Hg in the overlying water, as indicated by ex situ measurements. Results show that DGT is a reliable and high-resolution technique that can be used for in situ monitoring of the labile fractions of As and Hg in sediment in fresh water bodies.

  17. High prevalence of multiple-antibiotic-resistant (MAR) Escherichia coli in river bed sediments of the Apies River, South Africa.

    PubMed

    Abia, Akebe Luther King; Ubomba-Jaswa, Eunice; Momba, Maggy Ndombo Benteke

    2015-10-01

    This study aimed at investigating the presence of antibiotic-resistant Escherichia coli in river bed sediments of the Apies River, Gauteng, South Africa, in order to better inform health management decisions designed to protect users of the river. Overall, 180 water and sediment samples were collected at 10 sites along the Apies River from January to February 2014. E. coli was enumerated using the Colilert® 18/Quanti-Tray® 2000 (IDEXX). Isolates were purified by streaking on eosin methylene blue agar followed by the indole test. Pure E. coli isolates were tested for resistance to nine antibiotics by the Kirby-Bauer disc diffusion method. Over 98% of the isolates were resistant to at least one of the antibiotics tested. The highest resistance was observed against nitrofurantoin (sediments) and ampicillin (water). Over 80% of all resistant isolates showed multiple antibiotic resistance (resistance to ≥3 antibiotics). The abundance of E. coli in the sediments not only adds to the evidence that sediments are a reservoir for bacteria and possibly other pathogens including antibiotic-resistant bacteria but also suggests that antibiotic-resistant genes could be transferred to pathogens due to the high prevalence of multiple-antibiotic-resistant (MAR) strains of E. coli observed in the sediment. Using untreated water from the Apies River following resuspension for drinking and other household purposes could pose serious health risks for users. Our results suggest that river bed sediments could serve as reservoirs for MAR bacteria including pathogens under different climatic conditions and their analysis could provide information of public health concerns. PMID:26419380

  18. THE ELECTROMAGNETIC MODEL OF SHORT GRBs, THE NATURE OF PROMPT TAILS, SUPERNOVA-LESS LONG GRBs, AND HIGHLY EFFICIENT EPISODIC ACCRETION

    SciTech Connect

    Lyutikov, Maxim

    2013-05-01

    and interpret the prompt tail as an energetic long GRB (the supernova-less long burst GRB060505 and GRB060614 may belong to this category). We also demonstrate that episodic accretion onto the black hole of magnetized clouds that carry non-zero magnetic flux can be highly efficient in extracting the spin energy of the black hole, producing the electromagnetic outflows with power exceeding the average M-dot c{sup 2} accretion power and total energy exceeding the rest mass energy of the accreted mass. We identify the late time flares with such accretion events.

  19. Constraints from Field Geology for Numerical Modeling of the Crustal Overturn Processes During the Cretaceous High-Magma-Flux Episode in the Central and Southern Sierra Nevada, USA

    NASA Astrophysics Data System (ADS)

    Cao, W.; Paterson, S. R.; Kaus, B. J.; Anderson, J. L.; Memeti, V.

    2010-12-01

    Building on prior studies, recent fieldwork combined with geochronology, thermobarometry and geochemistry studies in the Cretaceous Sierra Nevada arc reveal the following arc-scale features: 1) The Middle to Late Cretaceous Sierra Nevada arc has a 30-35 km thick granodioritic to tonalitic upper-middle crust and may have had up to 30-35 km of mafic to ultramafic lower crust, including dehydrated amphibolitic residues. 2) Plutons emplaced during the ~20 myr long High-Magma-Flux Episode (HMFE, 105-85 Ma) include large batholiths (~1000 km2 at exposure level) with growth histories occurring over millions of years (e.g. ~9 myr for Tuolumne Batholith). Magma pulses creating such large intrusions could vary from up to 103 km3 in dimension depending on different growth models. 3) In the central Sierra Nevada, emplacement depths of the granitoid plutons during the HMFE are 7-15 km with shallow emplaced plutons’ solidi at usually ~700 -760 °C. 4) Plutons intruding only slightly older volcanic host rocks in the central and southern Sierra Nevada indicate that host rocks’ downward displacement of ~7-25 km depths occurred within 1-3 myr. This process is accompanied with the long-lived arc exhumation since at least middle Jurassic. 5) Steep syn-emplacement subsolidus lineations, rim monoclines, and plastic shear strain in pluton aureoles suggest ductile deformations of host rock materials. 6) Partial melting occurred along the margins of plutons and in the middle-lower crust, as represented in the more deeply exposed southern Sierra (30-45 km). 7) Magmatic to subsolidus foliations in plutons and ductile shear zones in host rocks indicate NW-trending transpressional tectonics during the HMFE. 8) Isotopic oxygen data and mass balance calculation indicate that crustal components provides more than 50% of the entire arc’s mass. Intra-crustal magma sources of the HMFE are sustained possibly by thickened crust due to contractional tectonics. These observations in the central

  20. Sediment yields in a thick loess region: The Missouri River basin

    SciTech Connect

    Bettis, E.A. III

    1995-12-31

    Sediment yields in the thick loess region of the Missouri River basin are among the highest in North America. The combination of high local relief, easily eroded loessal surficial deposits, entrenched stream systems, and a humid climate foster high erosion rates and sediment yields. Stratigraphic investigations in over twenty watersheds within the thick loess region have documented the magnitude of several episodes of Holocene sediment movement and storage. Spatial and temporal patterns of sediment storage vary within a given drainage basin, but are similar in like-size elements of different basins. These patterns suggest that intrinsic controls are as important a climate in the long-term behavior of this fluvial system. The magnitude and pattern of Holocene sediment accumulation during the Historic period is similar to that which occurred on at least one occasion during the prehistoric period when the landscape was little modified by human activity.

  1. Analysis of Coastal Sediment Plume Dynamics in Puerto Rico using MODIS/Terra 250-m Imagery

    NASA Astrophysics Data System (ADS)

    Otis, D. B.; Muller-Karger, F. E.; Mendez-Lazaro, P.; McCarthy, M.; Chen, F. R.

    2014-12-01

    Anomalous events of suspended sediments can degrade water quality in nearshore ecosystems by reducing light penetration, inhibiting primary production, and delivering pollutants associated with the sediment particles. Coral reefs, for example, are subject to stress by anomalous sediment loads. The island of Puerto Rico has a diverse topography, with steep mountain slopes, episodic high-intensity rainfall events, and weathered soils that lead to episodes of high sediment volumes being delivered to the coastal zone by rivers. We developed a time series of turbidity observations based on Moderate Resolution Imaging Spectroradiometer (MODIS) imagery for use in the coastal areas of Puerto Rico. The product uses remote-sensing reflectance (Rrs) of Band 1 (645 nm) at a spatial resolution of 250 m. These estimates were compared to in-situ turbidity measurements collected in San Juan Bay. Sediment plumes from the major rivers of Puerto Rico were assessed quantitatively and compared with time-series of meteorological and other parameters, including precipitation, river discharge, and wind velocity. The spatial extent of plumes, the timing and duration of plume events, and their potential impact on coral reefs are examined. Results show that plume events are episodic and short-lived, but that they may affect coral reefs located several kilometers offshore.

  2. Dispersal of river sediment in the Southern California Bight

    USGS Publications Warehouse

    Warrick, J.A.; Farnsworth, K.L.

    2009-01-01

    The rivers of Southern California deliver episodic pulses of water, sediment, nutrients, and pollutants to the region's coastal waters. Although river-sediment dispersal is observed in positively buoyant (hypopycnal) turbid plumes extending tens of kilometers from river mouths, very little of the river sediment is found in these plumes. Rather, river sediment settles quickly from hypopycnal plumes to the seabed, where transport is controlled by bottom-boundary layer processes, presumably including fluid-mud (hyperpycnal) gravity currents. Here we investigate the geographical patterns of river-sediment dispersal processes by examining suspended-sediment concentrations and loads and the continental shelf morphology offshore river mouths. Throughout Southern California, river sediment is discharged at concentrations adequately high to induce enhanced sediment settling, including negative buoyancy. The rivers draining the Western Transverse Range produce suspended-sediment concentrations that are orders of magnitude greater than those in the urbanized region and Peninsular Range to the south, largely due to differences in sediment yield. The majority of sediment discharge from the Santa Clara River and Calleguas Creek occurs above the theoretical negative buoyancy concentration (>40 g/l). These rivers also produce event sediment loading as great as the Eel River, where fluid-mud gravity currents are observed. The continental shelf of Southern California has variable morphology, which influences the ability to transport via gravity currents. Over half of the rivers examined are adjacent to shelf slopes greater than 0.01, which are adequately steep to sustain auto-suspending gravity currents across the shelf, and have little (<10 m) Holocene sediment accumulation. Shelf settings of the Ventura, Santa Clara, and Tijuana Rivers are very broad and low sloped (less than 0.004), which suggests that fluid-mud gravity currents could transport across these shelves, albeit slowly

  3. Late-Holocene climate variability and ecosystem responses in Alaska inferred from high-resolution multiproxy sediment analyses at Grizzly Lake

    NASA Astrophysics Data System (ADS)

    Tinner, Willy; Beer, Ruth; Bigler, Christian; Clegg, Benjamin F.; Jones, Richard T.; Kaltenrieder, Petra; van Raden, Ulrike J.; Gilli, Adrian; Hu, Feng Sheng

    2015-10-01

    The late-Holocene shift from Picea glauca (white spruce) to Picea mariana (black spruce) forests marked the establishment of modern boreal forests in Alaska. To understand the patterns and drivers of this vegetational change and the associated late-Holocene environmental dynamics, we analyzed radiocarbon-dated sediments from Grizzly Lake for chironomids, diatoms, pollen, macrofossils, charcoal, element composition, particle size, and magnetic properties for the period 4100-1800 cal BP. Chironomid assemblages reveal two episodes of decreased July temperature, at ca. 3300-3150 (ca -1 °C) and 2900-2550 cal BP (ca -2 °C). These episodes coincided with climate change elsewhere in the Northern Hemisphere, atmospheric reorganization, and low solar activity. Diatom-inferred lake levels dropped by ca. 5 m at 3200 cal BP, suggesting dry conditions during the period 3200-1800 cal BP. P. glauca declined and P. mariana expanded at ca. 3200 cal BP; this vegetational change was linked to diatom-inferred low lake levels and thus decreased moisture availability. Forest cover declined at 3300-3100, 2800-2500 and 2300-2100 cal BP and soil erosion as inferred from increased values of Al, K, Si, Ti, and Ca intensified, when solar irradiance was low. Plant taxa adapted to disturbance and cold climate (e.g. Alnus viridis, shrub Betula, Epilobium) expanded during these periods of reduced forest cover. This open vegetation type was associated with high fire activity that peaked at 2800 cal BP, when climatic conditions were particularly cold and dry. Forest recovery lagged behind subsequent climate warming (≤+3 °C) by ca. 75-225 years. Our multiproxy data set suggests that P. glauca was dominant under warm-moist climatic conditions, whereas P. mariana prevailed under cold-dry and warm-dry conditions. This pattern implies that climatic warming, as anticipated for this century, may promote P. glauca expansions, if moisture availability will be sufficiently high, while P. mariana may

  4. [Chemical characteristics in airborne particulate matter (PM10) during a high pollution spring dust storm episode in Beijing, Tianjin and Zhangjiakou, China].

    PubMed

    Liu, Qing-Yang; Liu, Yan-Ju; Zhao, Qiang; Zhang, Ting-Ting; Zhang, Mei-Gen; Wang, Cun-Mei

    2014-08-01

    Atmospheric particulate matter (PM10) was collected at sampling locations of Beijing, Tianjin and Zhangjiakou from April 1st to May 24th, 2012. The mass concentration of PM10 and concentrations of ions, elemental carbon (EC) and organic carbon (OC) in PM10 were determined. The results showed that average mass concentration of PM10 were 233.82 microg x m(-3) for Beijing, 279.64 microg x (-3) for Tianjin and 238.13 microg x m(-3) for Zhangjiakou, respectively. Backward trajectories results confirmed dust storm events occurred from 27th to 29th April. The maximum daily mass concentrations of PM10 were 755.54 microg x m(-3) for Beijing, 831.32 microg x m(-3) for Tianjin and 582.82 microg x m(-3) for Zhangjiakou during the dust storm episodes, respectively. Water-soluble ions (Na+, NH4+, Ca2+, K+, F-, Cl-, NO3-, SO4(2-)), organic carbon (OC) and elemental carbon (EC) were major aerosol components during the dust storm episodes, and their concentrations were higher than non-dust storm days. In addition, dust storm caused increases in NO3-, SO4(2-) and enrichment of secondary organic carbon (SOC) concentration relative to OC, suggesting that chemical reaction processes involving gas-particle conversion occurred during the long-distance transport of aerosol particles. PMID:25338350

  5. [Chemical characteristics in airborne particulate matter (PM10) during a high pollution spring dust storm episode in Beijing, Tianjin and Zhangjiakou, China].

    PubMed

    Liu, Qing-Yang; Liu, Yan-Ju; Zhao, Qiang; Zhang, Ting-Ting; Zhang, Mei-Gen; Wang, Cun-Mei

    2014-08-01

    Atmospheric particulate matter (PM10) was collected at sampling locations of Beijing, Tianjin and Zhangjiakou from April 1st to May 24th, 2012. The mass concentration of PM10 and concentrations of ions, elemental carbon (EC) and organic carbon (OC) in PM10 were determined. The results showed that average mass concentration of PM10 were 233.82 microg x m(-3) for Beijing, 279.64 microg x (-3) for Tianjin and 238.13 microg x m(-3) for Zhangjiakou, respectively. Backward trajectories results confirmed dust storm events occurred from 27th to 29th April. The maximum daily mass concentrations of PM10 were 755.54 microg x m(-3) for Beijing, 831.32 microg x m(-3) for Tianjin and 582.82 microg x m(-3) for Zhangjiakou during the dust storm episodes, respectively. Water-soluble ions (Na+, NH4+, Ca2+, K+, F-, Cl-, NO3-, SO4(2-)), organic carbon (OC) and elemental carbon (EC) were major aerosol components during the dust storm episodes, and their concentrations were higher than non-dust storm days. In addition, dust storm caused increases in NO3-, SO4(2-) and enrichment of secondary organic carbon (SOC) concentration relative to OC, suggesting that chemical reaction processes involving gas-particle conversion occurred during the long-distance transport of aerosol particles.

  6. Sediment resuspension and bed armoring during high bottom stress events on the northern California inner continental shelf: measurements and predictions

    USGS Publications Warehouse

    Wiberg, P.L.; Drake, D.E.; Cacchione, D.A.

    1994-01-01

    Geoprobe bottom tripods were deployed during the winter of 1990-1991 on the northern California inner continental shelf as part of the STRESS field experiment. Transmissometer measurements of light beam attenuation were made at two levels and current velocity was measured at four levels in the bottom 1.2 m of water. Intervals of high measured bottom wave velocity were generally correlated with times of both high attenuation and high attenuation gradient in the bottom meter of the water column. Measured time series of light attenuation and attenuation gradient are compared to values computed using a modified version of the Smith [(1977) The sea, Vol. 6, Wiley-Interscience, New York, pp. 539-577] steady wave-current bottom-boundary-layer model. Size-dependent transmissometer calibrations, which show significantly enhanced attenuation with decreasing grain size, are used to convert calculated suspended sediment concentration to light attenuation. The finest fractions of the bed, which are the most easily suspended and attenuate the most light, dominate the computed attenuation signal although they comprise only about 5-7% of the bed sediment. The calculations indicate that adjusting the value of the coefficient ??0 in the expression for near-bed sediment concentration cannot in itself give both the correct magnitudes of light attenuation and attenuation gradient. To supply the volumes of fine sediment computed to be in suspension during peak events, even with values of ??0 as low as 5 ?? 10-5, requires suspension of particles from unreasonably large depths in the bed. A limit on the depth of sediment availability is proposed as a correction to suspended sediment calculations. With such a limit, reasonable attenuation values are computed with ??0 ??? 0.002. The effects of limiting availability and employing a higher ??0 are to reduce the volume of the finest sediment in suspension and to increase the suspended volumes of the coarser fractions. As a consequence, the

  7. CRITICAL BODY RESIDUES FOR FRESHWATER AND SALTWATER AMPHIPODS EXPOSED TO SEDIMENT CONTAINING A MIXTURE OF HIGH KOW PAHS

    EPA Science Inventory

    Sediments were spiked with a mixture of 13 high log Kow (5.4-6.8) PAH compounds to determine critical body residues (CBR) in Hyalella azteca and Leptocheirus plumulosus. Hyalella were exposed for 28 d in a intermittent flow test and for 10 d in a static test to compare PAH uptake...

  8. A preliminary evaluation of Trinity river sediment and nutrient loads into Galveston Bay, Texas, during two periods of high flow

    USGS Publications Warehouse

    Lee, Michael T.

    2010-01-01

    Suspend-sediment and water-quality data were measured during two periods o high flow, one during April 20-23, 2009 and a second during September 22-November 3, 2009. On the basis of streamflow and continuous and discrete water-quality measurements, the two periods of high flow had different flood and nutrient loading characteristics. Some differences in the nature of these two periods of high flow were evident. Preliminary results indicate that it might be possible to better understand the extent of sediment and nutrient loading in Galveston Bay using selected measurements of discrete and continuous water-quality data. An apparent correlation was observed between the concentrations of selected nutrients and suspended sediment, and an apparent correlation was observed between suspended sediment and total nutrient concentration measured with in-situ turbidity measurements during periods of high flow in Trinity River at the Wallisville, Texas gage, about 3.5 miles upstream from where the Trinity River enters Galveston Bay. Additional data are needed to confirm these preliminary results.  

  9. Microbial Community Structure in Lake and Wetland Sediments from a High Arctic Polar Desert Revealed by Targeted Transcriptomics

    PubMed Central

    Stoeva, Magdalena K.; Aris-Brosou, Stéphane; Chételat, John; Hintelmann, Holger; Pelletier, Philip; Poulain, Alexandre J.

    2014-01-01

    While microbial communities play a key role in the geochemical cycling of nutrients and contaminants in anaerobic freshwater sediments, their structure and activity in polar desert ecosystems are still poorly understood, both across heterogeneous freshwater environments such as lakes and wetlands, and across sediment depths. To address this question, we performed targeted environmental transcriptomics analyses and characterized microbial diversity across three depths from sediment cores collected in a lake and a wetland, located on Cornwallis Island, NU, Canada. Microbial communities were characterized based on 16S rRNA and two functional gene transcripts: mcrA, involved in archaeal methane cycling and glnA, a bacterial housekeeping gene implicated in nitrogen metabolism. We show that methane cycling and overall bacterial metabolic activity are the highest at the surface of lake sediments but deeper within wetland sediments. Bacterial communities are highly diverse and structured as a function of both environment and depth, being more diverse in the wetland and near the surface. Archaea are mostly methanogens, structured by environment and more diverse in the wetland. McrA transcript analyses show that active methane cycling in the lake and wetland corresponds to distinct communities with a higher potential for methane cycling in the wetland. Methanosarcina spp., Methanosaeta spp. and a group of uncultured Archaea are the dominant methanogens in the wetland while Methanoregula spp. predominate in the lake. PMID:24594936

  10. Modeling glacial meltwater plume dynamics and sedimentation in high-latitude fjords

    NASA Astrophysics Data System (ADS)

    Mugford, R. I.; Dowdeswell, J. A.

    2011-03-01

    A model, SedPlume, has been developed to simulate marine sediment deposited by glacial meltwater plumes emerging from tidewater glaciers. Turbid meltwater emerging from beneath a glacier into a fjord rises as a buoyant forced plume due to density contrasts with the ambient fjord water. SedPlume assumes that meltwater discharge flows at a constant rate for long enough periods that the plume reaches a steady state. Entrainment of ambient fluid into the turbulent plume is assumed to occur at a rate proportional to the local velocity of the plume. Plume motion is considered in two dimensions: one horizontal dimension (perpendicular to the glacier front) and the vertical dimension. An integral model is formulated for the conservation equations of volume, momentum, buoyancy, and sediment flux along the path of a turbulent plume injected into stably stratified ambient fluid. Sedimentation occurs from the plume when the radial component of the sediment fall velocity exceeds the entrainment velocity. When the plume reaches the surface, it is treated as a radially spreading surface gravity current, for which exact solutions exist for the sediment deposition rate. Flocculation of silt and clay particles is modeled using empirical measurements of particle settling velocities in fjords to adjust the settling velocity of fine-grained sediments. SedPlume has been applied to McBride Inlet, Alaska, a temperate glaciated fjord where the majority of sedimentation originates from meltwater sources. SedPlume produces rates and patterns of sedimentation in good agreement with observations, with calculated peak ice-proximal annual sedimentation rates of approximately 22 m yr-1.

  11. Segment-scale volcanic episodicity: Evidence from the North Kolbeinsey Ridge, Atlantic

    NASA Astrophysics Data System (ADS)

    Yeo, I. A.; Devey, C. W.,; LeBas, T. P.; Augustin, N.; Steinführer, A.

    2016-04-01

    The upper oceanic crust is produced by magmatism at mid-ocean ridges, a process thought to be characterized by cyclic bouts of intense magmatic activity, separated by periods when faulting accommodates most or even all of the plate motion. It is not known whether there is a distinct periodicity to such magmatic-tectonic cycles. Here we present high-resolution sidescan sonar data from the neovolcanic zone of the North Kolbeinsey Ridge, a shallow slow-spreading ridge where high glacial and steady post-glacial sedimentation rates allow relative flow ages to be determined with a resolution of around 2 kyr using backscatter amplitude as a proxy for sediment thickness and hence age. We identify 18 lava flow fields covering 40% of the area surveyed. A group of 7 flow fields showing the highest (and similar) backscatter intensity are scattered along 75 km of axial valley surveyed, suggesting that at least this length of the segment was magmatically active within a 1.2 kyr time window. Based on conservative age estimates for all datable flows and estimated eruption volumes, the post-glacial volcanic activity imaged is insufficient to maintain crustal thickness, implying that episode(s) of enhanced activity must have preceded the volcanism we image.

  12. A colorimetric DET technique for the high-resolution measurement of two-dimensional alkalinity distributions in sediment porewaters.

    PubMed

    Bennett, William W; Welsh, David T; Serriere, Antoine; Panther, Jared G; Teasdale, Peter R

    2015-01-01

    Measurements of porewater alkalinity are fundamental to the study of organic matter mineralization in sediments, which plays an essential role in the global cycles of carbon and nutrients. A new colorimetric diffusive equilibration in thin film (DET) technique is described for measuring two-dimensional total alkalinity distributions in sediment porewaters at high resolution (1-2 mm(2)). Thin polyacrylamide hydrogel layers (0.8 mm) equilibrate with the porewater and, after removal, are immediately laid onto another hydrogel containing formic acid, which reacts with alkalinity-generating species, and the pH-indicator bromophenol blue. The resultant color change is quantified using computer-imaging densitometry. The lower limit of detection is 0.2 meq L(-1) and the upper measurement limit is 8 meq L(-1). Deployment in seagrass colonized sediment revealed high levels of spatial heterogeneity in the porewater alkalinity distribution, with concentrations ranging from 2.28 meq L(-1) in the overlying water to 5.13 meq L(-1) in some parts of the sediment. This is the first time that two-dimensional, high-resolution distributions of porewater alkalinity have been measured. PMID:25112581

  13. Culture-dependent and independent studies of microbial diversity in highly copper-contaminated Chilean marine sediments.

    PubMed

    Besaury, Ludovic; Marty, Florence; Buquet, Sylvaine; Mesnage, Valérie; Muyzer, Gerard; Quillet, Laurent

    2013-02-01

    Cultivation and molecular-based approaches were used to study microbial diversity in two Chilean marine sediments contaminated with high (835 ppm) and very high concentrations of copper (1,533 ppm). The diversity of cultivable bacteria resistant to copper was studied at oxic and anoxic conditions, focusing on sulfate-, thiosulfate-, and iron-reducing bacteria. For both sediments, the cultivable bacteria isolated at oxic conditions were mostly affiliated to the genus Bacillus, while at anoxic conditions the majority of the cultivable bacteria found were closely related to members of the genera Desulfovibrio, Sphingomonas, and Virgibacillus. Copper resistance was between 100 and 400 ppm, with the exception of a strain affiliated to members of the genus Desulfuromonas, which was resistant up to 1,000 ppm of copper. In parallel, cloning and sequencing of 16S rRNA was performed to study the total bacterial diversity in the sediments. A weak correlation was observed between the isolated strains and the 16S rRNA operational taxonomic units detected. The presence of copper resistance genes (copA, cusA, and pcoA) was tested for all the strains isolated; only copA was detected in a few isolates, suggesting that other copper resistance mechanisms could be used by the bacteria in those highly copper-contaminated sediments. PMID:22976340

  14. A method of measurement of (239)Pu, (240)Pu, (241)Pu in high U content marine sediments by sector field ICP-MS and its application to Fukushima sediment samples.

    PubMed

    Bu, Wenting; Zheng, Jian; Guo, Qiuju; Aono, Tatsuo; Tazoe, Hirofumi; Tagami, Keiko; Uchida, Shigeo; Yamada, Masatoshi

    2014-01-01

    An accurate and precise analytical method is highly needed for the determination of Pu isotopes in marine sediments for the long-term marine environment monitoring that is being done since the Fukushima Dai-ichi Nuclear Power Plant accident. The elimination of uranium from the sediment samples needs to be carefully checked. We established an analytical method based on anion-exchange chromatography and SF-ICP-MS in this work. A uranium decontamination factor of 2 × 10(6) was achieved, and the U concentrations in the final sample solutions were typically below 4 pg mL(-1), thus no extra correction of (238)U interferences from the Pu spectra was needed. The method was suitable for the analysis of (241)Pu in marine sediments using large sample amounts (>10 g). We validated the method by measuring marine sediment reference materials and our results agreed well with the certified and the literature values. Surface sediments and one sediment core sample collected after the nuclear accident were analyzed. The characterization of (241)Pu/(239)Pu atom ratios in the surface sediments and the vertical distribution of Pu isotopes showed that there was no detectable Pu contamination from the nuclear accident in the marine sediments collected 30 km off the plant site. PMID:24328266

  15. A method of measurement of (239)Pu, (240)Pu, (241)Pu in high U content marine sediments by sector field ICP-MS and its application to Fukushima sediment samples.

    PubMed

    Bu, Wenting; Zheng, Jian; Guo, Qiuju; Aono, Tatsuo; Tazoe, Hirofumi; Tagami, Keiko; Uchida, Shigeo; Yamada, Masatoshi

    2014-01-01

    An accurate and precise analytical method is highly needed for the determination of Pu isotopes in marine sediments for the long-term marine environment monitoring that is being done since the Fukushima Dai-ichi Nuclear Power Plant accident. The elimination of uranium from the sediment samples needs to be carefully checked. We established an analytical method based on anion-exchange chromatography and SF-ICP-MS in this work. A uranium decontamination factor of 2 × 10(6) was achieved, and the U concentrations in the final sample solutions were typically below 4 pg mL(-1), thus no extra correction of (238)U interferences from the Pu spectra was needed. The method was suitable for the analysis of (241)Pu in marine sediments using large sample amounts (>10 g). We validated the method by measuring marine sediment reference materials and our results agreed well with the certified and the literature values. Surface sediments and one sediment core sample collected after the nuclear accident were analyzed. The characterization of (241)Pu/(239)Pu atom ratios in the surface sediments and the vertical distribution of Pu isotopes showed that there was no detectable Pu contamination from the nuclear accident in the marine sediments collected 30 km off the plant site.

  16. High-resolution variations in terrigenous sediment sources and their sedimentation flux since the last glaciation in the northern South China Sea: clay mineralogical and grain-size investigations

    NASA Astrophysics Data System (ADS)

    Zhao, S.; Liu, Z.; CHEN, Q.; Wen, K.

    2013-12-01

    Terrigenous sediments in marginal seas of the low-latitude western Pacific provide excellent materials for paleoenvironmental studies because of their high sedimentation rate resulting from massive detrital input of Asian large rivers. A high-resolution temporal series study on terrigenous sediments and their accumulation history is very helpful for understanding how terrigenous materials respond to climate and environment changes in low latitudes. In this study, high-resolution clay mineralogy and grain-size distribution are analyzed at a Casq core MD12-3428 (20°08.48' N, 115°49.80' E, water depth 903 m), which was retrieved on the upper continental slope (off the Pearl River delta) of the northern South China Sea. The study aims to investigate temporal series changes of terrigenous sediment provenances, accumulation rate and flux, and their response to regional or global paleoenvironment changes. The age model reconstructed from planktonic foraminifera oxygen isotopes and AMS-14C datings will be combined with individual sediment components (terrigenous, biological carbonate, biological silica, and organic matters) and dry bulk density data to obtain individual accumulation rate and flux. Clay mineral assemblages will be implied to determine potential sources of fine-grained terrigenous sediments and their contribution in the northern South China Sea. Meanwhile, we also look forward to investigating the millennial-scale climate variability documented in the sedimentary core through combining clay mineralogical and grain size data, including how the sea level rise and abrupt climate change affect the sediment records.

  17. A varved lake sediment record from Finland: between the North Atlantic Oscillation and Siberian High Pressure Cell

    NASA Astrophysics Data System (ADS)

    Saarni, Saija; Saarinen, Timo

    2015-04-01

    Varved lake sediments are widely used for paleoclimatological and paleoenvironmental studies. The advantages of such records are precise time control, which enables high resolution studies of even seasonal scale, and the length of the records extending potentially beyond thousands of years. The clastic organic varved sediments from a small boreal Lake Kalliojärvi (area 0.15 km2, maximum depth 12 m) in Central Finland, record environmental change and snow accumulation history for more than two thousand years. The high quality sediments of the Lake Kalliojärvi are laminated until the present day and reflect the annual circulation of boreal zone. A single varve year consists of two laminae that are composed of i) minerogenic clasts and ii) amorphous organic matter and microfossils. Total varve thickness was measured, and the accumulation of minerogenic and organic matter were analyzed using digital image analysis. The major element composition of the lake sediments was also determined using micro X-ray fluorescence (µ-XRF). The clastic laminae are interpreted as a proxy for catchment erosion, reflecting spring floods triggered by snow melt. Qualitative comparison of minerogenic matter accumulation and reconstructed North Atlantic Oscillation (NAO) phases reveal correspondence between the two records. Positive NAO conditions occur simultaneously with increased minerogenic lamina thicknesses which suggest that the changes in snow accumulation are induced by NAO. However, there are indications that the strong Siberian High Pressure Cell (SHPC) prevailing on eastern Scandinavia may be important for Scandinavian climate via blocking the westerly winds. Strong SHCP potentially leads to colder winter temperatures in Finland and increased ice formation. Stronger and prolonged ice cover in lake environments cause prolonged water column stratification and increased oxygen deficiency which is related to an increased Fe/Mn ratio. This study discusses the importance of NAO and

  18. Geomicrobiology of High-Level Nuclear Waste-Contaminated Vadose Sediments at the Hanford Site, Washington State

    PubMed Central

    Fredrickson, James K.; Zachara, John M.; Balkwill, David L.; Kennedy, David; Li, Shu-mei W.; Kostandarithes, Heather M.; Daly, Michael J.; Romine, Margaret F.; Brockman, Fred J.

    2004-01-01

    Sediments from a high-level nuclear waste plume were collected as part of investigations to evaluate the potential fate and migration of contaminants in the subsurface. The plume originated from a leak that occurred in 1962 from a waste tank consisting of high concentrations of alkali, nitrate, aluminate, Cr(VI), 137Cs, and 99Tc. Investigations were initiated to determine the distribution of viable microorganisms in the vadose sediment samples, probe the phylogeny of cultivated and uncultivated members, and evaluate the ability of the cultivated organisms to survive acute doses of ionizing radiation. The populations of viable aerobic heterotrophic bacteria were generally low, from below detection to ∼104 CFU g−1, but viable microorganisms were recovered from 11 of 16 samples, including several of the most radioactive ones (e.g., >10 μCi of 137Cs/g). The isolates from the contaminated sediments and clone libraries from sediment DNA extracts were dominated by members related to known gram-positive bacteria. Gram-positive bacteria most closely related to Arthrobacter species were the most common isolates among all samples, but other phyla high in G+C content were also represented, including Rhodococcus and Nocardia. Two isolates from the second-most radioactive sample (>20 μCi of 137Cs g−1) were closely related to Deinococcus radiodurans and were able to survive acute doses of ionizing radiation approaching 20 kGy. Many of the gram-positive isolates were resistant to lower levels of gamma radiation. These results demonstrate that gram-positive bacteria, predominantly from phyla high in G+C content, are indigenous to Hanford vadose sediments and that some are effective at surviving the extreme physical and chemical stress associated with radioactive waste. PMID:15240306

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  20. High Diagnostic Accuracy of Nitrite Test Paired with Urine Sediment can Reduce Unnecessary Antibiotic Therapy

    PubMed Central

    Ferry, Sven A.; E. Holm, Stig; Ferry, B. Magnus; Monsen, Tor J.

    2015-01-01

    Background: Urinary tract infections (UTIs) are common bacterial infections dominated by lower UTI in women (LUTIW). Symptoms only are insufficient for diagnosis and accordingly, near patient diagnostic tests confidently confirming significant bacteriuria are desirable. The nitrite test (NIT) has low sensitivity, while bacterial and leukocyte counts disjunctively paired in urine sediment microscopy (SED) have high sensitivity. Similar symptomatic cure rates are found post antibiotic vs. placebo therapy in patients with negative cultures. Consequently, prescription on symptoms only implies unnecessary antibiotic therapy. Aims: to evaluate the diagnostic outcomes of NIT, SED and NIT disjunctively paired with SED (NIT+SED) vs. urine culture, with special focus on bladder incubation time (BIT), and to assess if NIT+SED can reduce unnecessary antibiotic therapy. Methods: A diagnostic, primary care, multicentre study including 1070 women with symptoms suggestive of lower UTI. Results: Significant bacteriuria was found in 77%. The BIT highly influenced the diagnostic outcomes and the optimal duration was ≥4h with sensitivity of 66, 90 and 95% for NIT, SED and NIT+SED, respectively. SED performed only in NIT negative specimens could reduce unnecessary antibiotics by 10% vs. prescription on symptoms only. The number needed to test with SED to reduce one unnecessary antibiotic course was five patients at BIT ≥4h and six patients at ≤3h or overall. Conclusion: The BIT highly influences the diagnostic outcomes with the highest accuracy of NIT+SED. Diagnosis of LUTIW with NIT+SED can reduce unnecessary antibiotic therapy and subsequently decrease antimicrobial resistance. Trial registration: The Swedish Medical Product Agency 1995 03 01:151:01783/94. PMID:26668667

  1. New climate archives from the high latitude North Atlantic Ocean: Preliminary results from IODP Exp 342, Newfoundland sediment drifts

    NASA Astrophysics Data System (ADS)

    Bailey, I.; Wilson, P. A.; Norris, R. D.; Blum, P.

    2014-12-01

    The geologic record holds a rich history of abrupt ecological and climate change events but our understanding of the ocean-atmosphere dynamics involved is not well developed, particularly for high CO2 warm climate states of the pre-Quaternary because the deep-sea records available typically come from low sedimentation rate (of 1-2 cm/kyr) sites that do not permit studies on times scales similar to or shorter than the ~1500 year mixing time of the ocean. The principle objective of IODP Expedition 342 (drilled summer, 2012) was to target sediment drifts off Newfoundland with unusually high rates of sedimentation in order to investigate, for the first time, the stability of the Cenozoic greenhouse and icehouse climate states on sub-orbital timescales. The sedimentary sequences drilled accumulated directly under the flow path of the Deep Western Boundary Current and are well-situated to provide an archive of changes in chemistry, flow history, and depth structure of waters exiting the Nordic seas and Arctic Ocean during the transition from ice-free peak Cenozoic warmth in the early Eocene to the onset of Arctic sea ice formation and the growth of major ice sheets on Antarctica. The sediment drift deposits drilled are characterized by high sedimentation rates and clay-rich lithologies hosting spectacularly well-preserved calcareous microfossils (benthic and planktic) and sand-sized lithic fragments. These remarkable archives present an exciting opportunity to address some long-standing questions of relevance to this session. For example: (1) How stable was the Eocene greenhouse climate state? (2) Is large amplitude suborbital variability in Earth's climate restricted to the late Pleistocene? (3) When and why did Earth shift to its present climate state with large ice sheets in both hemispheres? (4) How valid are suggestions of Eocene bipolar glaciation? (5) How and why did the carbonate chemistry (CCD) and circulation of the North Atlantic Ocean change in association

  2. Recent and Past High Resolution Organic Sedimentation in an Upwelling Cell of Humboldt Current System; Mejillones bay, Northern Chile.

    NASA Astrophysics Data System (ADS)

    Jorge, V.; Abdel, S.; Luc, O.; Gabriel, V.; Catherine, P.

    2005-12-01

    In this study, we present information of annual hydrographic variability, surface sediments distribution and one sedimentary core analyses to reconstruct the past 200 years of oceanographic history of Mejillones, focusing on the productivity and oxygenation factors. Spatial differences in surface water productivity were evaluated using periodical ^13C measurements of dissolved inorganic carbon. The organic composition of the superficial sediment, analyzed by statistical approach, reflects the three principal zones identified by their degree of bottom oxygenation. The oxic coastal zone preserves principally non-metabolizable organic matter with high Oxygen Index (OI) and low Hydrogen Index (HI), total carbon (TC), total organic carbon (TOC) and nitrogen content (NT). In this area, the organic fraction is dominated by dispersed amorphous organic matter. This suggests an environment where most of metabolizable organic matter has been degraded within the water column and/or at the benthic surface sediments. The microxic hemipelagic zone located deeper than 65 meters, is marked by low OI values and high HI, TC, TOC and NT values. Palynofacies study of sediments collected in this zone reveals the presence of abundant agglomerated amorphous organic matter. All these results suggest high primary productivity and increased flocculation (self-sedimentation) of organic matter, which partly permitted its preservation. The sedimentary organic matter deposited in the transitional disoxic zone, located between the costal and hemipelagic areas, is characterized by the same values of TC and NT than the microxic zone, but do not present the same petrographical parameters. Based on this calibration study, we identified three differents periods in the oceanographic evolution of the embayment, during the past 200 years. Before the nineteenth century, the sedimentary record suggests an enhanced oxygenation and/or depleted productivity Abrupt alternations of the two oceanographic state

  3. High-frequency time-series of the dynamic sedimentation processes on the western shelf of the Mississippi River Delta

    NASA Astrophysics Data System (ADS)

    Reide Corbett, D.; Dail, Michael; McKee, Brent

    2007-06-01

    Multiple box cores were collected on the continental shelf in the Mississippi Deltaic Region adjacent to Southwest Pass and analyzed for particle reactive radionuclides 234Th and 7Be to examine seasonal sediment dynamics associated with variations of river discharge and hydrodynamics. Three stations located along a line west of Southwest Pass were cored and reoccupied in October, November, and December of 2003 and March, April, and May of 2004. High-frequency sampling (˜monthly) comparable to the short half-life of the radiotracers ( 234Th t1/2=24.1 d; 7Be t1/2=53.3) enabled us to isolate the relative influence that various forcing agents (river discharge, waves, currents) had on sediment inventories of 7Be and 234Th. In addition, the primary source of 7Be (fluvial) differs from 234Th (marine), providing further insight into processes affecting sediment transport and supply. Monthly 7Be inventories showed a significant positive relationship to river discharge ( P=0.03) proximal to Southwest Pass. Sites further from Southwest Pass exhibited little to no relationship between 7Be inventories and river flow. At these sites, monthly 7Be inventories demonstrated a significant positive relationship with average wave orbital velocity ( P<0.01). During our sampling period, the transport of 7Be-rich sediments to sites located on the middle to outer shelf were dependent on sea conditions not river discharge. Relatively high wave orbital velocities potentially allow particles to remain in suspension longer and travel further distances before initial deposition. In addition, 234Th inventories showed evidence of sediment focusing during periods of high wave orbital velocities.

  4. Typology of potential high contribution areas in the sediment budget in the Upper Guil Catchment (Queyras, French Alps)

    NASA Astrophysics Data System (ADS)

    Lissak, Candide; Fort, Monique; Fassetta, Gilles Arnaud; Viel, Vincent; Carlier, Benoit

    2015-04-01

    transfers in the floodplain, (ii) assessment of slopes contribution to sediment supply with a main focus on lower slopes where lateral cutting and landslides provide huge quantities of material to the valley bottom. The semi-automatic methodology proposed here is based on data directly derived from remote sensing, GIS analysis (e.g. interpretation of aerial photographs, measurement from regional scale Digital Elevation Model (DEM), high-resolution DEM derived from airborne-based LiDAR) and field surveys. This study highlights spatial differences in sediment storage and redistribution areas grounded on quantitative and qualitative environmental parameters and index defined for 250 homogeneous sections (i.e. definition of morphological index, geometric measurement, rates and type of vegetation cover, hydraulic infrastructures location, urban development rates…). It also provides a useful classification of six distinct reach types and areas that will be susceptible to erosion, transport and deposition during the next flooding event (i.e. sediment production areas, temporary and permanent sediment storage areas, areas sensitive to erosion...).

  5. Hypoxic cyclicity in sediments of Soledad Basin, Baja Mexico: A record of high-frequency climate fluctuations?

    NASA Astrophysics Data System (ADS)

    Westman, A. E.; Brooks, G. R.; Lea, C.

    2007-05-01

    The sedimentary record in Soledad Basin, 45 km west of Baja, Mexico, shows high-frequency oscillations in hypoxia, which can be linked to fluctuations in climate. Soledad Basin, a semi-enclosed basin with a sill depth of 290m, has been shown to exhibit variable levels of hypoxia throughout the geologic past. Located at the intersection of the California Current and California Undercurrent, Soledad Basin is highly responsive to changes in current strength and upwelling, the combination of which creates fluctuations in hypoxia. During climatic cool periods, the California Current is weakened decreasing upwelling and biologic productivity along the Baja Borderland. This causes increased hypoxia in Soledad Basin. The California Undercurrent is also weakened during these cooler periods and brings less nutrients and oxygen to the basin further increasing hypoxia. Since Soledad Basin sediments are undisturbed and have accumulated rapidly, this is a prime location to study high frequency variations in hypoxia in the sedimentary record. The objective of this study was to examine how and to what extent hypoxic events have been recorded in the sedimentary record of Soledad Basin, and gain insight into what controls these events. Surface sediment samples and a single 1.1m gravity core were collected aboard the S.S.V. Robert C. Seamans on a SEA Semester cruise in October 2005. The core was taken at a depth of 490 m near the deepest point of the basin. The core contained laminated sediments consisting of >95% mud. Using 210Pb analysis, a sedimentation rate of 15 cm over the past 100 years was determined, which is consistent with previous research. Trace metal analyses were performed at the cm-scale on selected intervals between 0.34-0.44m and 0.78-0.92m. These intervals correspond to dark organic-rich (>15% organic content) laminations alternating with lighter layers containing less organic material (<15% organic content). All sediments were found to be enriched in Molybdenum

  6. A calendar savant with episodic memory impairments.

    PubMed

    Olson, Ingrid R; Berryhill, Marian E; Drowos, David B; Brown, Lawrence; Chatterjee, Anjan

    2010-06-01

    Patients with memory disorders have severely restricted learning and memory. For instance, patients with anterograde amnesia can learn motor procedures and retain some restricted ability to learn new words and factual information. However, such learning is inflexible and frequently inaccessible to conscious awareness. Here we present a case of patient AC596, a 25-year-old male with severe episodic memory impairments, presumably due to anoxia during a preterm birth. In contrast to his poor episodic memory, he exhibits savant-like memory for calendar information that can be flexibly accessed by day, month, and year cues. He also has the ability to recollect the exact date of a wide range of personal experiences over the past 20 years. The patient appears to supplement his generally poor episodic memory by using memorized calendar information as a retrieval cue for autobiographical events. These findings indicate that islands of preserved memory functioning, such as a highly developed semantic memory system, can exist in individuals with severely impaired episodic memory systems. In this particular case, our patient's memory for dates far outstripped that of normal individuals and served as a keen retrieval cue, allowing him to access information that was otherwise unavailable.

  7. A Calendar Savant with Episodic Memory Impairments

    PubMed Central

    Olson, Ingrid R.; Berryhill, Marian E.; Drowos, David B.; Brown, Lawrence; Chatterjee, Anjan

    2010-01-01

    Patients with memory disorders have severely restricted learning and memory. For instance, patients with anterograde amnesia can learn motor procedures as well as retaining some restricted ability to learn new words and factual information. However, such learning is inflexible and frequently inaccessible to conscious awareness. Here we present a case of patient AC596, a 25-year old male with severe episodic memory impairments, presumably due to anoxia during a preterm birth. In contrast to his poor episodic memory, he exhibits savant-like memory for calendar information that can be flexibly accessed by day, month, and year cues. He also has the ability to recollect the exact date of a wide range of personal experiences over the past 20 years. The patient appears to supplement his generally poor episodic memory by using memorized calendar information as a retrieval cue for autobiographical events. These findings indicate that islands of preserved memory functioning, such as a highly developed semantic memory system, can exist in individuals with severely impaired episodic memory systems. In this particular case, our patient’s memory for dates far outstripped that of normal individuals and served as a keen retrieval cue, allowing him to access information that was otherwise unavailable. PMID:20104390

  8. Episodic tremor triggers small earthquakes

    NASA Astrophysics Data System (ADS)

    Balcerak, Ernie

    2011-08-01

    It has been suggested that episodic tremor and slip (ETS), the weak shaking not associated with measurable earthquakes, could trigger nearby earthquakes. However, this had not been confirmed until recently. Vidale et al. monitored seismicity in the 4-month period around a 16-day episode of episodic tremor and slip in March 2010 in the Cascadia region. They observed five small earthquakes within the subducting slab during the ETS episode. They found that the timing and locations of earthquakes near the tremor suggest that the tremor and earthquakes are related. Furthermore, they observed that the rate of earthquakes across the area was several times higher within 2 days of tremor activity than at other times, adding to evidence of a connection between tremor and earthquakes. (Geochemistry, Geophysics, Geosystems, doi:10.1029/2011GC003559, 2011)

  9. Behind the Webb Episode 27

    NASA Video Gallery

    This episode of "Behind the Webb" explores the multi-tasking capabilities of one of the cameras on the Webb Space Telescope, the Near-Infrared Spectrograph. Newly designed technology known as "micr...

  10. Using geochemical indicators to distinguish high biogeochemical activity in floodplain soils and sediments.

    PubMed

    Kenwell, Amy; Navarre-Sitchler, Alexis; Prugue, Rodrigo; Spear, John R; Hering, Amanda S; Maxwell, Reed M; Carroll, Rosemary W H; Williams, Kenneth H

    2016-09-01

    A better understanding of how microbial communities interact with their surroundings in physically and chemically heterogeneous subsurface environments will lead to improved quantification of biogeochemical reactions and associated nutrient cycling. This study develops a methodology to predict potential elevated rates of biogeochemical activity (microbial "hotspots") in subsurface environments by correlating microbial DNA and aspects of the community structure with the spatial distribution of geochemical indicators in subsurface sediments. Multiple linear regression models of simulated precipitation leachate, HCl and hydroxylamine extractable iron and manganese, total organic carbon (TOC), and microbial community structure were used to identify sample characteristics indicative of biogeochemical hotspots within fluvially-derived aquifer sediments and overlying soils. The method has been applied to (a) alluvial materials collected at a former uranium mill site near Rifle, Colorado and (b) relatively undisturbed floodplain deposits (soils and sediments) collected along the East River near Crested Butte, Colorado. At Rifle, 16 alluvial samples were taken from 8 sediment cores, and at the East River, 46 soil/sediment samples were collected across and perpendicular to 3 active meanders and an oxbow meander. Regression models using TOC and TOC combined with extractable iron and manganese results were determined to be the best fitting statistical models of microbial DNA (via 16S rRNA gene analysis). Fitting these models to observations in both contaminated and natural floodplain deposits, and their associated alluvial aquifers, demonstrates the broad applicability of the geochemical indicator based approach. PMID:27145490

  11. Chemical characterization of Lake Constance sediments record by high resolution EDXRF

    NASA Astrophysics Data System (ADS)

    Rammlmair, D.; Wessels, M.

    2003-04-01

    Sediment-input into Lake Constance is mainly characterized by the Alpine Rhine River which drains some 12000 km2 in the Alps. Due to melting of snow in the catchment, the annual runoff and sediment input has a strong maximum in summer. This is superimposed by single events of heavy rain fall generating strong flood events and leads to annually laminated sediments along the northern slope of Lake Constance. These were used to reconstruct past environmental history and processes within the lake and its catchment, such as heavy metal contamination, eutrophication, and climate history. A typical core covering a time span of some 180 years during which the Lake and its catchment was heavily influenced by hydraulic engineering (end of 1800s), chemical pollution, and eutrophication and recovery since the 1990s was scanned for major and trace element contents with an EDXRF core scanner (Mo-tube, 45 kV, 30mA, slit capillary, 50 µm step size and 30 sec signal accumulation time). In our contribution, we present first results of selected elements which were used to characterize the sedimentary record according to - background-sediments deposited during years with low runoff and low allochthonous sediment accumulation influenced by anthropogenic heavy metal input (brownish-grey layers) - calcite precipitation within the lake (thin white layers) - individual flood-layers of tributaries to the Alpine-Rhine-River System (grey lamina) - other smaller tributaries draining the molasse catchment (brown and yellowish layers) - chemical gradation within a single layer.

  12. Potential accumulation of contaminated sediments in a reservoir of a high-Andean watershed: Morphodynamic connections with geochemical processes

    NASA Astrophysics Data System (ADS)

    Contreras, María. Teresa; Müllendorff, Daniel; Pastén, Pablo; Pizarro, Gonzalo E.; Paola, Chris; Escauriaza, Cristián.

    2015-05-01

    Rapid changes due to anthropic interventions in high-altitude environments, such as the Altiplano region in South America, require new approaches to understand the connections between physical and geochemical processes. Alterations of the water quality linked to the river morphology can affect the ecosystems and human development in the long term. The future construction of a reservoir in the Lluta River, located in northern Chile, will change the spatial distribution of arsenic-rich sediments, which can have significant effects on the lower parts of the watershed. In this investigation, we develop a coupled numerical model to predict and evaluate the interactions between morphodynamic changes in the Lluta reservoir, and conditions that can potentially desorb arsenic from the sediments. Assuming that contaminants are mobilized under anaerobic conditions, we calculate the oxygen concentration within the sediments to study the interactions of the delta progradation with the potential arsenic release. This work provides a framework for future studies aimed to analyze the complex connections between morphodynamics and water quality, when contaminant-rich sediments accumulate in a reservoir. The tool can also help to design effective risk management and remediation strategies in these extreme environments. This article was corrected on 15 JUNE 2015. See the end of the full text for details.

  13. Episodic memory in nonhuman animals

    PubMed Central

    Templer, Victoria L.

    2013-01-01

    Summary Episodic memories differ from other types of memory because they represent aspects of the past not present in other memories, such as the time, place, or social context in which the memories were formed. Focus on phenomenal experience in human memory, such as the sense of “having been there” has resulted in conceptualizations of episodic memory that are difficult or impossible to apply to nonhumans. It is therefore a significant challenge for investigators to agree on objective behavioral criteria that can be applied in nonhumans and still capture features of memory thought to be critical in humans. Some investigators have attempted to use neurobiological parallels to bridge this gap. However, defining memory types on the basis of the brain structures involved rather than on identified cognitive mechanisms risks missing the most crucial functional aspects of episodic memory, which are ultimately behavioral. The most productive way forward is likely a combination of neurobiology and sophisticated cognitive testing that identifies the mental representations present in episodic memory. Investigators that have refined their approach from asking the naïve question “do nonhuman animals have episodic memory” to instead asking “what aspects of episodic memory are shared by humans and nonhumans” are making progress. PMID:24028963

  14. A step decrease in sediment concentration in a highly modified tidal river delta following the 1983 El Niño floods

    USGS Publications Warehouse

    Hestir, Erin L.; Schoellhamer, David H.; Morgan-King, Tara; Ustin, Susan L.

    2013-01-01

    Anthropogenic activities in watersheds can have profound effects on sediment transport through river systems to estuaries. Disturbance in a watershed combined with alterations to the hydro-climatologic regime may result in changes to the sediment flux, and exacerbate the impacts of extreme events (such as large-magnitude floods) on sediment transport. In the San Francisco Estuary, suspended sediment has been declining over the past 30 years as a result of declining sediment supply, contributing to dramatic changes in the ecology and geomorphology of the estuary. However, the decline has not been gradual. Recent observations of an abrupt decrease in suspended sediments in the San Francisco Bay have been explained by a model that suggests that the step change has occurred due to exceedance of a sediment regulation threshold that triggered the change from a sediment transport regime to a supply-limited system. We investigated structural changes in the historical record of total suspended solids (TSS) concentration measured in the upper estuary to verify the model predictions. TSS in the upper estuary exhibited an abrupt step decrease in 1983 corresponding to the record-high winter and summer flows from the 1982 to 1983 El Niño event. After this step change, TSS concentrations had a significant declining trend despite subsequent near-record high flows. The abrupt change in TSS followed by the declining trend provides evidence for the hypothesis of sediment supply limitation in the San Francisco Estuary.

  15. Systems analysis approach to the disposal of high-level waste in deep ocean sediments

    SciTech Connect

    de Marsily, G.; Hill, M. D.; Murray, C. N.; Talbert, D. M.; Van Dorp, F.; Webb, G. A.M.

    1980-01-01

    Among the different options being studied for disposal of high-level solidified waste, increasing attention is being paid to that of emplacement of glasses incorporating the radioactivity in deep oceanic sediments. This option has the advantage that the areas of the oceans under investigation appear to be relatively unproductive biologically, are relatively free from cataclysmic events, and are areas in which the natural processes are slow. Thus the environment is stable and predictable so that a number of barriers to the release and dispersion of radioactivity can be defined. Task Groups set up in the framework of the International Seabed Working Group have been studying many aspects of this option since 1976. In order that the various parts of the problem can be assessed within an integrated framework, the methods of systems analysis have been applied. In this paper the Systems Analysis Task Group members report the development of an overall system model. This will be used in an iterative process in which a preliminary analysis, together with a sensitivity analysis, identifies the parameters and data of most importance. The work of the other task groups will then be focussed on these parameters and data requirements so that improved results can be fed back into an improved overall systems model. The major requirements for the development of a preliminary overall systems model are that the problem should be separated into identified elements and that the interfaces between the elements should be clearly defined. The model evolved is deterministic and defines the problem elements needed to estimate doses to man.

  16. The role of bay breezes and regional transport on a high surface ozone episode during the Houston, Texas DISCOVER-AQ field campaign

    NASA Astrophysics Data System (ADS)

    Loughner, C.; Follette-Cook, M. B.; Pickering, K. E.; Estes, M. J.

    2014-12-01

    The highest observed surface ozone concentrations in the Houston metropolitan area in 2013 occurred on September 25, which coincided with the Texas DISCOVER-AQ (Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality) field campaign. Surface ozone was elevated throughout the Houston metropolitan area. Maximum 8-hour average ozone peaked along the western shore of Galveston Bay, reaching 124 ppbv, almost 50 ppbv above the current EPA standard of 75 ppbv, at La Porte Sylvan Beach. Continental air pollution from the north and northeast was transported into the Houston metropolitan area where it mixed with locally generated emissions. A bay breeze circulation formed causing pollutants that were transported out over the water in the morning to recirculate back inland where they mixed with freshly emitted pollution near the bay breeze convergence zone. The highest surface ozone concentrations were reported near the bay breeze front at La Porte Sylvan Beach. This ozone episode will be presented using measurements made during the DISCOVER-AQ field campaign and WRF and CMAQ model simulations.

  17. The role of refinery flaring events and bay breezes on a high surface ozone episode during the Houston, Texas DISCOVER-AQ field campaign

    NASA Astrophysics Data System (ADS)

    Loughner, C.; Follette-Cook, M. B.; Fried, A.; Pickering, K. E.

    2015-12-01

    The highest observed surface ozone concentrations in the Houston metropolitan area in 2013 occurred on September 25, which coincided with the Texas DISCOVER-AQ (Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality) field campaign. Surface ozone was elevated throughout the Houston metropolitan area with maximum 8-hour average ozone peaking along the western shore of Galveston Bay, reaching 124 ppbv, almost 50 ppbv above the current EPA standard of 75 ppbv. The NASA P-3B aircraft observed plumes from refinery flares west and northwest of Galveston Bay that were transported over the water. Continental air pollution from the north was transported into the Houston metropolitan area where it mixed with locally generated emissions. A bay breeze circulation formed causing pollutants that were transported out over the water in the morning to recirculate back inland where they mixed with freshly emitted pollution near the bay breeze convergence zone. The highest surface ozone concentrations were reported near the bay breeze front. This ozone episode will be presented using measurements made during the DISCOVER-AQ field campaign and a CMAQ model simulation with integrated source apportionment, which tracks the contribution of emissions source groups and regions on ozone concentrations.

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

    USGS Publications Warehouse

    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.

  19. Brahmaputra sediment flux dominated by highly localized rapid erosion from the easternmost Himalaya

    NASA Astrophysics Data System (ADS)

    Stewart, R. J.; Hallet, B.; Zeitler, P. K.; Malloy, M. A.; Allen, C. M.; Trippett, D.

    2008-09-01

    The Brahmaputra River slices an exceptionally deep canyon throughthe eastern Himalaya. Fission-track and laser-ablation U-Pbages of detrital zircon grains from the river document veryrapid erosion from this region and its impact on sediment fluxesdownstream in the Brahmaputra. Downstream from the canyon, 47%of the detrital zircons in the river's modern sediment loadcomprise a fission-track age population averaging only 0.6 Ma.Equally young cooling ages are reported from bedrock in thecanyon through the Namche Barwa-Gyala Peri massif butare absent from riverbank sands of major tributaries upstream.Simple mixing models of U-Pb ages on detrital zircons from samplestaken above and below this massif independently suggest that45% of the downstream detrital zircons are derived from thebasement gneisses extensively exposed in the massif. Constraintson the extent of the source area provided by bedrock coolingages together with sediment-flux estimates at Pasighat, India,suggest exhumation rates averaging 7-21 mm yr-1in an area of ~3300 km2 centered on the massif. This rapid exhumation,which is consistent with the very young cooling ages of thedetrital zircons from this area, produces so much sediment that~50% of the vast accumulation in the Brahmaputra system at thefront of the Himalaya comes from only ~2% of its drainage. Thisextreme localization of rapid erosion, sediment evacuation,and bedrock cooling bear on (1) common assumptions in geodynamicand geochemical studies of the Himalaya about sources of sediment,and (2) plans for hydroelectric development and flood managementin southeastern Tibet and the heavily populated areas of easternIndia.

  20. Photosynthesis in sediments determined at high spatial resolution by the use of microelectrodes.

    PubMed

    Nakamura, Yoshiyuki; Satoh, Hisashi; Okabe, Satoshi; Watanabe, Yoshimasa

    2004-05-01

    The present study investigated photosynthetic rates and their regulation by light within the upper 5mm of sediment in a tidal area of Niida River in Hachinohe, Japan. Steady-state concentration profiles of O(2), NH(4)(+), NO(2)(-), H(2)S, and pH in the sediment were measured with microelectrodes. Microzonation of O(2) respiration, denitrification and SO(4)(2-) reduction was found in the sediment. When light intensities exceeded 1050 micromol photons/m(2)/s, net photosynthetic activity was detected in the upper 0.5mm of the microbial mat colonizing on the sediment surface in the tidal area. In contrast, gross photosynthetic activity was detected in the upper 1.0mm of the microbial mat at 1900 micromol photons/m(2)/s. As light intensity increased, the net photosynthetic rate and O(2) penetration depth increased. The maximal net photosynthetic rate and O(2) penetration depth were 6.1 micromol O(2)/cm(3)/h and 2.2mm, respectively, at 1900 micromol photons/m(2)/s. Net photosynthetic rates in the microbial mat in the tidal area were lower than in the upstream sediment. The analysis of continuous O(2) concentration measurements in different layers of the microbial mat during artificial light-dark cycles demonstrated that the photosynthetic activity response to changes in light intensity was extremely fast (a few seconds) and the O(2) concentration in the microbial mat became stable within 200s. The measurement of physical and chemical parameters in river water revealed that the study site was relatively polluted and sunlight intensity significantly fluctuated temporally. These results suggested that the in situ microbial processes occurring in the sediment fluctuated in accordance with periodic fluctuations in sunlight intensity. PMID:15142806

  1. Episodic plate tectonics on Venus

    NASA Technical Reports Server (NTRS)

    Turcotte, Donald

    1992-01-01

    Studies of impact craters on Venus from the Magellan images have placed important constraints on surface volcanism. Some 840 impact craters have been identified with diameters ranging from 2 to 280 km. Correlations of this impact flux with craters on the Moon, Earth, and Mars indicate a mean surface age of 0.5 +/- 0.3 Ga. Another important observation is that 52 percent of the craters are slightly fractured and only 4.5 percent are embayed by lava flows. These observations led researchers to hypothesize that a pervasive resurfacing event occurred about 500 m.y. ago and that relatively little surface volcanism has occurred since. Other researchers have pointed out that a global resurfacing event that ceased about 500 MYBP is consistent with the results given by a recent study. These authors carried out a series of numerical calculations of mantle convection in Venus yielding thermal evolution results. Their model considered crustal recycling and gave rapid planetary cooling. They, in fact, suggested that prior to 500 MYBP plate tectonics was active in Venus and since 500 MYBP the lithosphere has stabilized and only hot-spot volcanism has reached the surface. We propose an alternative hypothesis for the inferred cessation of surface volcanism on Venus. We hypothesize that plate tectonics on Venus is episodic. Periods of rapid plate tectonics result in high rates of subduction that cool the interior resulting in more sluggish mantle convection.

  2. The high-frequency backscattering angular response of gassy sediments: Model/data comparison from the Eel River Margin, California

    NASA Astrophysics Data System (ADS)

    Fonseca, Luciano; Mayer, Larry; Orange, Dan; Driscoll, Neal

    2002-06-01

    A model for the high-frequency backscatter angular response of gassy sediments is proposed. For the interface backscatter contribution we adopted the model developed by Jackson [et al.] [J. Acoust. Soc. Am. 79, 1410-1422 (1986)], but added modifications to accommodate gas bubbles. The model parameters that are affected by gas content are the density ratio, the sound speed ratio, and the loss parameter. For the volume backscatter contribution we developed a model based on the presence and distribution of gas in the sediment. We treat the bubbles as individual discrete scatterers that sum to the total bubble contribution. This total bubble contribution is then added to the volume contribution of other scatters. The presence of gas affects both the interface and the volume contribution of the backscatter angular response in a complex way that is dependent on both grain size and water depth. The backscatter response of fine-grained gassy sediments is dominated by the volume contribution while that of coarser-grained gassy sediments is affected by both volume and interface contributions. In deep water the interface backscatter is only slightly affected by the presence of gas while the volume scattering is strongly affected. In shallow water the interface backscatter is severely reduced in the presence of gas while the volume backscatter is only slightly increased. Multibeam data acquired offshore northern California at 95 kHz provides raw measurements for the backscatter as a function of grazing angle. These raw backscatter measurements are then reduced to scattering strength for comparison with the results of the proposed model. The analysis of core samples at various locations provides local measurements of physical properties and gas content in the sediments that, when compared to the model, show general agreement. copyright 2002 Acoustical Society of America.

  3. Sources, dispersal, and fate of fine sediment supplied to coastal California

    USGS Publications Warehouse

    Farnsworth, Katherine L.; Warrick, Jonathan A.

    2007-01-01

    We have investigated the sources, dispersal, and fate of fine sediment supplied to California coastal waters in a partnership between the U.S. Geological Survey (USGS) and the California Sediment Management Workgroup (CSMW). The purpose of this study was to document the rates and characteristics of these processes so that the State can better manage its coastal resources, including sediment. In this study, we made the following observations: - Rivers dominate the supply of fine sediment to the California coastal waters, with an average annual flux of 34 megatonnes (Mt). - Cliff and bluff erosion in central and southern California is a source of fine sediment, with a delivery rate of approximately 10 percent of river loads. In the southern most part of the State, however, where river-sediment loads are low, cliff and bluff erosion represent approximately 40 percent of the total fine-sediment flux. - Temporal variation in the sources of fine sediment is high. River floods and bluff erosion are episodic and dominated by winter storms, which supply most sediment flux to the coast. The magnitude of winter storms is generally related to the El Niño-Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO) climate cycles. - The three rivers that dominate fine-sediment flux to the California coast are the Eel, Salinas, and Santa Clara Rivers. Because the sediment delivery from these and all other California coastal watersheds is episodic, individual rivers discharge most of their annual loads over the course of only a few days per year. - Spatial variation in river-sediment discharge is high and generally related to such watershed characteristics as geology, precipitation, and drainage area. For example, the Transverse Range of southern California represents only 9 percent of the watershed-drainage area but 18 percent of the fine-sediment flux, a function of the young sedimentary bedrock and active tectonics of this region. The urban rivers of southern California

  4. Transfer of radionuclides from high polluted bottom sediments to marine organisms through benthic food chain in post Fukushima period

    NASA Astrophysics Data System (ADS)

    Bezhenar, Roman; Jung, Kyung Tae; Maderich, Vladimir; Willemsen, Stefan; de With, Govert; Qiao, Fangli

    2015-04-01

    A catastrophic earthquake and tsunami occurred on March 11, 2011 and severely damaged the Fukushima Daiichi Nuclear Power Plant (FDNPP) that resulted in an uncontrolled release of radioactivity into air and ocean. Around 80% of the radioactivity released due to the FDNPP accident in March-April 2011 was either directly discharged into the ocean or deposited onto the ocean surface from the atmosphere. A large amount of long-lived radionuclides (mainly Cs-137) were released into the environment. The concentration of radionuclides in the ocean reached a maximum in mid-April of 2011, and then gradually decreased. From 2011 the concentration of Cs-137 in water essentially fell except the area around the FDNPP where leaks of contaminated water are continued. However, in the bottom sediment high concentrations of Cs-137 were found in the first months after the accident and slowly decreased with time. Therefore, it should be expected that a time delay is found of sediment-bound radionuclides in marine organisms. For the modeling of radionuclide transfer from highly polluted bottom sediments to marine organisms the dynamical food chain model BURN-POSEIDON (Heling et al, 2002; Maderich et al., 2014) was extended. In this model marine organisms are grouped into a limited number of classes based on their trophic level and type of species. These include: phytoplankton, zooplankton, fishes (two types: piscivorous and non-piscivorous), crustaceans, and molluscs for pelagic food chain and bottom sediment invertebrates, demersal fishes and bottom predators for benthic food chain and whole water column predators feeding by pelagial and benthic fishes. Bottom invertebrates consume organic parts of bottom sediments with adsorbed radionuclides which then migrate through the food chain. All organisms take radionuclides directly from water as well as via food. In fishes where radioactivity is not homogeneously distributed over all tissues of the organism, it is assumed that radionuclide

  5. Exploring a semimechanistic episodic Langevin model for bed load transport: Emergence of normal and anomalous advection and diffusion regimes

    NASA Astrophysics Data System (ADS)

    Fan, Niannian; Singh, Arvind; Guala, Michele; Foufoula-Georgiou, Efi; Wu, Baosheng

    2016-04-01

    Bed load transport is a highly stochastic, multiscale process, where particle advection and diffusion regimes are governed by the dynamics of each sediment grain during its motion and resting states. Having a quantitative understanding of the macroscale behavior emerging from the microscale interactions is important for proper model selection in the absence of individual grain-scale observations. Here we develop a semimechanistic sediment transport model based on individual particle dynamics, which incorporates the episodic movement (steps separated by rests) of sediment particles and study their macroscale behavior. By incorporating different types of probability distribution functions (PDFs) of particle resting times Tr, under the assumption of thin-tailed PDF of particle velocities, we study the emergent behavior of particle advection and diffusion regimes across a wide range of spatial and temporal scales. For exponential PDFs of resting times Tr, we observe normal advection and diffusion at long time scales. For a power-law PDF of resting times (i.e., f>(Tr>)˜Tr-ν), the tail thickness parameter ν is observed to affect the advection regimes (both sub and normal advective), and the diffusion regimes (both subdiffusive and superdiffusive). By comparing our semimechanistic model with two random walk models in the literature, we further suggest that in order to reproduce accurately the emerging diffusive regimes, the resting time model has to be coupled with a particle motion model able to produce finite particle velocities during steps, as the episodic model discussed here.

  6. Investigation of detachment and transport processes of sediment using different sand mixtures in high precision rainfall simulations

    NASA Astrophysics Data System (ADS)

    Fister, Wolfgang; Mayer, Marius; Reichle, Elisabeth; Kinnell, Peter I. A.; Kuhn, Nikolaus J.

    2016-04-01

    Detachment and transport of sediment in the landscape are controlled by many different factors. Beside environmental factors such as soil surface properties, land management and vegetation cover, the dominant ones are rainfall and surface flow characteristics. In order to be able to investigate the change of sediment properties over transport distance and time, it is, therefore, necessary to understand the basic interactions between rainfall kinetic energy and amount, particle size and density as well as flow depth and velocity. So far, the mechanistic understanding of these principal physical interactions is mostly of empirical nature, obtained either under natural, highly complex and uncontrollable conditions, or with rainfall experiments that weren't able to control the conditions with high enough precision. The aim of this study was, therefore, to fill this gap of knowledge in our mechanical process understanding by conducting rainfall experiments on different sand mixtures. In this bottom-up approach, the highly controlled experimental conditions and the use of stable sand ensured that the number of variable factors was kept to a minimum. Thus, specific relations between sand-sizes, drop kinetic energy, force of flow, and resulting erosion rates could be obtained. Although the results are very promising and could lead to a better understanding of the erosion processes in the future, they clearly show that already straightforward sand mixtures behave in a very complex way. Further experiments with simple grain mixtures are, therefore, needed before experiments on more complex, instable sediments can or should be investigated.

  7. Multiple climatic signals inferred from the varved sediments of a coastal lake in the Canadian High Arctic

    NASA Astrophysics Data System (ADS)

    Amann, Benjamin; Lamoureux, Scott F.

    2016-04-01

    The Arctic is extremely sensitive to climate change, and an influential part of the global climate system. However, the assessment of climate change and impacts from the Arctic remains a challenge mainly due to short and sparse meteorological records. In this context, data from natural paleoclimate archives are fundamental to place climate variability into perspective and assess the sensitivity of Earth's climate to natural and anthropogenic forcings. In particular, Arctic lakes are excellent potential archives. They are sensitive to extreme seasonal variations in surface processes and have a limited direct human impact. Nevertheless, the study of Arctic lakes is an analytical and technical challenge because: (i) limnological information are often lacking due to difficult accessibility; (ii) 210Pb inventories are low and terrestrial macrofossils for 14C dating are rare, which limits the development of precise sediment chronologies; and (iii) sediment accumulation rates are often low, which may restrict the temporal resolution and length of the paleoclimate records. Here, we present a high-resolution record from the varved sediments (annual laminations) of a saline coastal lake located in the Canadian High Arctic (unofficial name Chevalier Lake; Melville Island, NT). The particular interest of this location is the catchment area: 152 times larger than the lake area (Ac = 350 km²; AL = 2.3 km²). This particularity generates high sedimentation rates, atypical of previously studied arctic lakes. Two sediment cores were recovered from the centre and a more proximal zone of the lake. We used microstratigraphy supported by X-ray fluorescence data (Zr/K for particle size, Fe/Rb for the winter clay cap distinction) to develop a precise and cross-dated varve chronology covering the last 400 years. Dating of the uppermost section could be validated with preliminary 137Cs data. Stratigraphical analysis reveals the presence of three sediment units within the meter

  8. In situ, high-resolution evidence for iron-coupled mobilization of phosphorus in sediments

    PubMed Central

    Ding, Shiming; Wang, Yan; Wang, Dan; Li, Yang Yang; Gong, Mengdan; Zhang, Chaosheng

    2016-01-01

    Reductive dissolution of phosphorus-bearing iron (Fe) (oxyhydr)oxides has been regarded as a primary mechanism responsible for the mobilization of phosphorus (P) in sediments for over 70 years. However, to date there is little in situ evidence to support this hypothesis. In this study, a total of 16 sites in the large eutrophic Lake Taihu were selected for investigation. Newly-developed diffusive gradients in thin films (ZrO-Chelex DGT) probes were deployed to simultaneously measure labile Fe and P mainly released from sediment solids at millimeter spatial resolution. Significantly positive correlations were observed between DGT-labile Fe and P at 14 sites, implying a release of P following reductive dissolution of Fe (oxyhydr)oxides. A coincident resupply of Fe(II) and P was observed from sediment solids to buffer their releases from DGT perturbance, further verifying the mechanism of Fe-coupled mobilization of P. The ratio of DGT-labile Fe/P was found to be positively correlated with the ratio of easily reducible (oxyhydr)oxide Fe to its associated P, indicating that this solid phase should retain P prior to its release. The results provide direct evidence for the coupling between Fe and P in sediments and further identify the easily reducible Fe (oxyhydr)oxide species involved in the coupling process. PMID:27087199

  9. Heat transfer from a high temperature condensable mixture. II. Sedimentation of fog condensate

    SciTech Connect

    Condiff, D.W.; Cho, D.H.; Chan, S.H.

    1985-01-01

    A kinematic wave analysis of fog sedimentation is employed to relate growth of a fog condensate deposit layer to radiation generated fog formation rates. The increase of surface radiation absorptivity with deposit layer thickness promotes a feedback mechanism for higher growth rates, which is evaluated in detail.

  10. Long-range transport of air pollutants originating in China: A possible major cause of multi-day high-PM10 episodes during cold season in Seoul, Korea

    NASA Astrophysics Data System (ADS)

    Oh, Hye-Ryun; Ho, Chang-Hoi; Kim, Jinwon; Chen, Deliang; Lee, Seungmin; Choi, Yong-Sang; Chang, Lim-Seok; Song, Chang-Keun

    2015-05-01

    Massive air pollutants originating in China and their trans-boundary transports are an international concern in East Asia. Despite its importance, details in the trans-boundary transport of air pollutants over East Asia and its impact on regional air quality remain to be clarified. This study presents an evidence which strong support that aerosols emitting in China play a major role in the occurrence of multi-day (≥4 days) severe air pollution episodes in cold seasons (October through March) for 2001-2013 in Seoul, Korea, where the concentration of PM10 (particulates with diameters ≤ 10 μm) exceeds 100 μg m-3. Observations show that these multi-day severe air pollution episodes occur when a strong high-pressure system resides over the eastern China-Korea region. In such weather conditions, air pollutants emitted in eastern China/southwestern Manchuria are trapped within the atmospheric boundary layer, and gradually spread into neighboring countries by weak lower tropospheric westerlies. Understanding of trans-boundary transports of air pollutants will advance the predictability of local air quality, and will encourage the development of international measures to improve air quality.

  11. Metabolically active microbial communities in marine sediment under high-CO(2) and low-pH extremes.

    PubMed

    Yanagawa, Katsunori; Morono, Yuki; de Beer, Dirk; Haeckel, Matthias; Sunamura, Michinari; Futagami, Taiki; Hoshino, Tatsuhiko; Terada, Takeshi; Nakamura, Ko-Ichi; Urabe, Tetsuro; Rehder, Gregor; Boetius, Antje; Inagaki, Fumio

    2013-03-01

    Sediment-hosting hydrothermal systems in the Okinawa Trough maintain a large amount of liquid, supercritical and hydrate phases of CO(2) in the seabed. The emission of CO(2) may critically impact the geochemical, geophysical and ecological characteristics of the deep-sea sedimentary environment. So far it remains unclear whether microbial communities that have been detected in such high-CO(2) and low-pH habitats are metabolically active, and if so, what the biogeochemical and ecological consequences for the environment are. In this study, RNA-based molecular approaches and radioactive tracer-based respiration rate assays were combined to study the density, diversity and metabolic activity of microbial communities in CO(2)-seep sediment at the Yonaguni Knoll IV hydrothermal field of the southern Okinawa Trough. In general, the number of microbes decreased sharply with increasing sediment depth and CO(2) concentration. Phylogenetic analyses of community structure using reverse-transcribed 16S ribosomal RNA showed that the active microbial community became less diverse with increasing sediment depth and CO(2) concentration, indicating that microbial activity and community structure are sensitive to CO(2) venting. Analyses of RNA-based pyrosequences and catalyzed reporter deposition-fluorescence in situ hybridization data revealed that members of the SEEP-SRB2 group within the Deltaproteobacteria and anaerobic methanotrophic archaea (ANME-2a and -2c) were confined to the top seafloor, and active archaea were not detected in deeper sediments (13-30 cm in depth) characterized by high CO(2). Measurement of the potential sulfate reduction rate at pH conditions of 3-9 with and without methane in the headspace indicated that acidophilic sulfate reduction possibly occurs in the presence of methane, even at very low pH of 3. These results suggest that some members of the anaerobic methanotrophs and sulfate reducers can adapt to the CO(2)-seep sedimentary environment; however

  12. Metabolically active microbial communities in marine sediment under high-CO2 and low-pH extremes

    PubMed Central

    Yanagawa, Katsunori; Morono, Yuki; de Beer, Dirk; Haeckel, Matthias; Sunamura, Michinari; Futagami, Taiki; Hoshino, Tatsuhiko; Terada, Takeshi; Nakamura, Ko-ichi; Urabe, Tetsuro; Rehder, Gregor; Boetius, Antje; Inagaki, Fumio

    2013-01-01

    Sediment-hosting hydrothermal systems in the Okinawa Trough maintain a large amount of liquid, supercritical and hydrate phases of CO2 in the seabed. The emission of CO2 may critically impact the geochemical, geophysical and ecological characteristics of the deep-sea sedimentary environment. So far it remains unclear whether microbial communities that have been detected in such high-CO2 and low-pH habitats are metabolically active, and if so, what the biogeochemical and ecological consequences for the environment are. In this study, RNA-based molecular approaches and radioactive tracer-based respiration rate assays were combined to study the density, diversity and metabolic activity of microbial communities in CO2-seep sediment at the Yonaguni Knoll IV hydrothermal field of the southern Okinawa Trough. In general, the number of microbes decreased sharply with increasing sediment depth and CO2 concentration. Phylogenetic analyses of community structure using reverse-transcribed 16S ribosomal RNA showed that the active microbial community became less diverse with increasing sediment depth and CO2 concentration, indicating that microbial activity and community structure are sensitive to CO2 venting. Analyses of RNA-based pyrosequences and catalyzed reporter deposition-fluorescence in situ hybridization data revealed that members of the SEEP-SRB2 group within the Deltaproteobacteria and anaerobic methanotrophic archaea (ANME-2a and -2c) were confined to the top seafloor, and active archaea were not detected in deeper sediments (13–30 cm in depth) characterized by high CO2. Measurement of the potential sulfate reduction rate at pH conditions of 3–9 with and without methane in the headspace indicated that acidophilic sulfate reduction possibly occurs in the presence of methane, even at very low pH of 3. These results suggest that some members of the anaerobic methanotrophs and sulfate reducers can adapt to the CO2-seep sedimentary environment; however, CO2 and p

  13. Floodplain development in engineered and natural settings determined with novel, high resolution 210-Pb geochronology: Insights from sedimentation studies along the lower Sacramento River, California

    NASA Astrophysics Data System (ADS)

    Aalto, R.; Singer, M. B.

    2008-12-01

    This presentation summarizes results from studies of floodplain sedimentation along the middle and lower Sacramento River that investigate processes using a new, high resolution methodology for 210Pb geochronology of 1-5 m floodplain cores. This approach accounts both for grain-size effects and radon ventilation and can resolve both deposition and erosional events. Therefore, it was possible to assess sedimentation over the past century within a wide array of sedimentary environments throughout the Sacramento Valley, where other techniques are limited. In particular, the Sacramento Valley has naturally low 210Pb activity due to its proximity to the Pacific Ocean, high rates of radon ventilation due to dry, porous floodplain sediment, and deposition of widely varying grain sizes - challenges that we have addressed with our enhanced methodology. The analytical approach affords a new ability to assess and directly compare dates and rates of sedimentation and erosion in disparate sedimentary environments throughout this complex fluvial dispersal system. We compare and contrast sediment deposition in engineered floodplains called bypasses, levied ancestral floodplains which serve as floodways during high flow, with sedimentation occurring in some remaining natural floodplains adjacent to the Sacramento River. We find that bypasses tend to accumulate sand and silt at their entrances, but that rates and textures decline rapidly with distance away from the channel. Essentially, a quasi-natural physical process of levee construction by advective overbank transport and deposition of sediment is operating (Singer and Aalto, ESPL, in press). These engineered floodways tend to siphon sediment out of the active channel, such that relatively low sedimentation rates prevail in floodplains and oxbow lakes within the active meander corridor that is bypassed. However, we document significant accumulation of fine-grained material in sedimentary sinks throughout floodplains upstream

  14. Impact of Highly Basic Solutions on Sorption of Cs+ to Subsurface Sediments from the Hanford Site, USA

    SciTech Connect

    Ainsworth, Calvin C.; Zachara, John M.; Wagnon, Ken B.; McKinley, Susan G.; Liu, Chongxuan; Smith, Steven C.; Schaef, Herbert T.; Gassman, Paul L.

    2005-11-28

    The effect of caustic NaNO3 solutions on the sorption of 137Cs to the Hanford site micaceous subsurface sediment was investigated as a function of time, temperature (10 C or 50 C), and NaOH concentration. At 100C and 0.1 M NaOH, the slow evolution of [Al]aq was in stack contrast to the rapid increase and subsequent loss of [Al]aq observed at 50 C (regardless of base concentration). At 50 C, dissolution of phyllosilicate minerals increased with [OH], at 1 and 3 M NaOH solutions, almost complete dissolution of clay-sized phyllosilicates occurred. At 0.1 M NaOH, a zeolite (tetranatrolite) precipitated after about 7 days, while an unnamed mineral phase (Na2Al2Si3O10?2H2O) precipitated after 4 and 2 days of exposure to 1 M and 3 M NaOH solutions. At 100C there was no conclusive evidence of secondary mineral precipitation. The effect of base dissolution on Cs+ sorption by the Hanford sediment was investigated via (1) Cs+ sorption over a large concentration range (10-9 ? 10-2 mol/L) to sediment after exposure to 0.1 M NaOH for 56, 112, and 168 days, (2) Cs+ sorption to sediment in the presence of NaOH (0.1 M, 1 M, and 3 M NaOH) at Cs+ concentrations selected to probe high affinity, transition, and low affinity cation exchange sites, and (3) the application of a two-site numeric ion exchange model (Zachara et al. 2002a). No effect on Cs+ sorption to the Hanford sediment was observed during the 168 days sediment was exposed to 0.1 M NaOH, at 10 C; Cs+ sorption in the presence of base was well described by the ion exchange model when enthalpy effects were considered. In contrast, at 50 C, there was a trend toward slightly lower (log {approx} 0.25) conditional equilibrium exchange constants over the entire range of surface coverage, and a slight loss of high affinity sites (15%) after 168 days of exposure to 0.1 M base solution. However, model simulations of Cs+ sorption to the sediment in the presence of 0.1 M base for 112 days were good at the lower Cs+ surface densities

  15. Bacterial Diversity and Bioremediation Potential of the Highly Contaminated Marine Sediments at El-Max District (Egypt, Mediterranean Sea)

    PubMed Central

    Amer, Ranya A.; Mapelli, Francesca; El Gendi, Hamada M.; Barbato, Marta; Goda, Doaa A.; Corsini, Anna; Cavalca, Lucia; Fusi, Marco; Borin, Sara; Daffonchio, Daniele; Abdel-Fattah, Yasser R.

    2015-01-01

    Coastal environments worldwide are threatened by the effects of pollution, a risk particularly high in semienclosed basins like the Mediterranean Sea that is poorly studied from bioremediation potential perspective especially in the Southern coast. Here, we investigated the physical, chemical, and microbiological features of hydrocarbon and heavy metals contaminated sediments collected at El-Max bay (Egypt). Molecular and statistical approaches assessing the structure of the sediment-dwelling bacterial communities showed correlations between the composition of bacterial assemblages and the associated environmental parameters. Fifty strains were isolated on mineral media supplemented by 1% crude oil and identified as a diverse range of hydrocarbon-degrading bacteria involved in different successional stages of biodegradation. We screened the collection for biotechnological potential studying biosurfactant production, biofilm formation, and the capability to utilize different hydrocarbons. Some strains were able to grow on multiple hydrocarbons as unique carbon source and presented biosurfactant-like activities and/or capacity to form biofilm and owned genes involved in different detoxification/degradation processes. El-Max sediments represent a promising reservoir of novel bacterial strains adapted to high hydrocarbon contamination loads. The potential of the strains for exploitation for in situ intervention to combat pollution in coastal areas is discussed. PMID:26273661

  16. High levels of methylmercury in guano and ornithogenic coral sand sediments on Xisha islands, South China sea.

    PubMed

    Chen, Qianqian; Liu, Xiaodong; Xu, Liqiang; Sun, Liguang; Yan, Hong; Liu, Yi; Luo, Yuhan; Huang, Jing

    2012-08-01

    This study determined the distribution and main source of methylmercury in ornithogenic coral sand sediments and pure guano collected from Guangjin and Jinqing islets of the South China Sea. Results showed that the levels of methylmercury (MeHg) and total mercury (THg), as well as the percentage of MeHg relative to THg (%MeHg), are high in both fresh and ancient guano samples. %MeHg in ancient guano exceeded 70 %, much greater than that in fresh seabird droppings (~45 %). These results suggest that excretion through feces likely plays an important role in the cycling of MeHg by seabirds. Guano has been identified as the major source of MeHg in the ornithogenic coral sand sediments in the Xisha Islands. The close relationship between MeHg and guano-derived phosphorus has weakened considerably since 1840 AD. This is probably caused by a significant increase in THg and MeHg in modern guano samples due to the recent increase of Hg pollution. %MeHg in the ornithogenic coral sand sediments is extremely high, ranging from 10 to 30 % (average 20 %).

  17. Linkage of sediment supply and transport processes in Miyagawa Dam catchment, Japan

    NASA Astrophysics Data System (ADS)

    Imaizumi, Fumitoshi; Sidle, Roy C.

    2007-09-01

    Linkages between sediment supply by episodic geomorphic processes (obtained from aerial photographs and field surveys) and sediment transport (estimated from changes in sediment deposition behind a large dam) were investigated in the Miyagawa Dam catchment, central Japan. A total of 6667 landslides were confirmed in the period from 1965 to 2000 on the basis of seven temporal pairs of aerial photographs. Both the occurrence of landslides and discharge into the dam lake affect sediment yield, indicating that fluvial systems in Miyagawa Dam catchment are supply limited with respect to sediment. Sediment yields are affected by not only the initial failed volume of landslides but also the mobility of landslides and debris flows. In Miyagawa Dam catchment, percentages of landslides reaching channels varied from 56% in 1997-2000 to 75% in 1976-1981 and were correlated with maximum hourly rainfall. In addition, the mobility of debris flows was higher during periods with high maximum instantaneous discharge compared to lower discharge, suggesting that the water content both in initially failed materials and transported sediment controlled their mobility. Topography also affected the mobility of landslides/debris flows. For catchments >0.1 km2, the percentage of channel network length impacted by debris flows decreased with increasing catchment area due to reduced channel gradient. Thus both the magnitude of rainfall-runoff events and the catchment topography affect how landslide sediment contributes to sediment yield at the large catchment scale.

  18. Episodic Memory: A Comparative Approach

    PubMed Central

    Martin-Ordas, Gema; Call, Josep

    2013-01-01

    Historically, episodic memory has been described as autonoetic, personally relevant, complex, context-rich, and allowing mental time travel. In contrast, semantic memory, which is theorized to be free of context and personal relevance, is noetic and consists of general knowledge of facts about the world. The field of comparative psychology has adopted this distinction in order to study episodic memory in non-human animals. Our aim in this article is not only to reflect on the concept of episodic memory and the experimental approaches used in comparative psychology to study this phenomenon, but also to provide a critical analysis of these paradigms. We conclude the article by providing new avenues for future research. PMID:23781179

  19. Episodic fresh surface waters in the Eocene Arctic Ocean

    USGS Publications Warehouse

    Brinkhuis, H.; Schouten, S.; Collinson, M.E.; Sluijs, A.; Damste, J.S.S.; Dickens, G.R.; Huber, M.; Cronin, T. M.; Onodera, J.; Takahashi, K.; Bujak, J.P.; Stein, R.; Van Der Burgh, J.; Eldrett, J.S.; Harding, I.C.; Lotter, A.F.; Sangiorgi, F.; Cittert, H.V.K.V.; De Leeuw, J. W.; Matthiessen, J.; Backman, J.; Moran, K.

    2006-01-01

    It has been suggested, on the basis of modern hydrology and fully coupled palaeoclimate simulations, that the warm greenhouse conditions that characterized the early Palaeogene period (55-45 Myr ago) probably induced an intensified hydrological cycle with precipitation exceeding evaporation at high latitudes. Little field evidence, however, has been available to constrain oceanic conditions in the Arctic during this period. Here we analyse Palaeogene sediments obtained during the Arctic Coring Expedition, showing that large quantities of the free-floating fern Azolla grew and reproduced in the Arctic Ocean by the onset of the middle Eocene epoch (???50 Myr ago). The Azolla and accompanying abundant freshwater organic and siliceous microfossils indicate an episodic freshening of Arctic surface waters during an ???800,000-year interval. The abundant remains of Azolla that characterize basal middle Eocene marine deposits of all Nordic seas probably represent transported assemblages resulting from freshwater spills from the Arctic Ocean that reached as far south as the North Sea. The termination of the Azolla phase in the Arctic coincides with a local sea surface temperature rise from ???10??C to 13??C, pointing to simultaneous increases in salt and heat supply owing to the influx of waters from adjacent oceans. We suggest that onset and termination of the Azolla phase depended on the degree of oceanic exchange between Arctic Ocean and adjacent seas. ?? 2006 Nature Publishing Group.

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

    NASA Astrophysics Data System (ADS)

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

    2003-12-01

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

  1. Assessment of aquatic wastewater pollution in a highly industrialized zone with sediment linear alkylbenzenes.

    PubMed

    Zhang, Kai; Wang, Ji-Zhong; Liang, Bo; Shen, Ru-Lang; Zeng, Eddy Y

    2012-04-01

    Forty-five sediment samples collected from Dongjiang River, which drains one of the most industrialized and urbanized regions in South China, were analyzed for 19 linear alkylbenzene (LAB) components. The sample dry weight-based concentrations of total LABs (ΣLAB) ranged from 1.5 to 410 ng/g. Comparison of the relative abundances of n-dodecylbenzenes (or C(12) -LABs) and internal to external ratio (I/E) values in riverine sediment, wastewater, and sediment samples from the outfalls of paper mills, as well as three brands of domestic detergents obtained from the present and previous studies, implicated the occurrence of untreated wastewater in the sampling sites. Levels of ΣLAB were significantly linear correlated with those of total organic carbon (TOC) but not with those of polycyclic aromatic hydrocarbons. Multiple linear regression integrated principal component analysis indicated that 56% of LABs in wastewater in the study area were treated, but the extent of degradation of LABs was low. Finally, it is proposed that ineffective law enforcement and loopholes in the current regulations for wastewater discharge account for the substantial amount (44%) of untreated wastewater discharged in the study region. PMID:22331642

  2. High abundance of small zoobenthos around biogenic structures in tidal sediments of the Wadden Sea

    NASA Astrophysics Data System (ADS)

    Reise, K.

    1981-12-01

    On the tidal flats of the island of Sylt (eastern part of the North Sea) the quantity of micro- and meiofauna associated with shoots of seagrass (Zostera noltii), with infaunal bivalves (Macoma balthica), and with tubes and burrows of polychaetes (Pygospio elegans, Pectinaria koreni, Nereis diversicolor, Nereis virens, Arenicola marina) was found to add up to 5 to 33 % of the overall abundance. These structures, taken together, account for 10 to 50 % of the faunal abundance on an average tidal flat at Sylt. The quantitative effect of biogenic structures at the sediment surface (casts and funnels) is small compared to that of tubes and burrows penetrating the anaerobic subsurface layer. In providing stable oxic microenvironments these elite structures frequently bring together more individuals than occur in the entire reducing sediment below surface. Faunal composition of irrigated dwellings of large infauna is different from that of the oxic surface sediment. The common denominator of all elite structures of the subsurface is an oxic halo. Burrows without such a halo are unattractive. There is no evidence that owners of burrows prey on their smaller inmates.

  3. Assessment of aquatic wastewater pollution in a highly industrialized zone with sediment linear alkylbenzenes.

    PubMed

    Zhang, Kai; Wang, Ji-Zhong; Liang, Bo; Shen, Ru-Lang; Zeng, Eddy Y

    2012-04-01

    Forty-five sediment samples collected from Dongjiang River, which drains one of the most industrialized and urbanized regions in South China, were analyzed for 19 linear alkylbenzene (LAB) components. The sample dry weight-based concentrations of total LABs (ΣLAB) ranged from 1.5 to 410 ng/g. Comparison of the relative abundances of n-dodecylbenzenes (or C(12) -LABs) and internal to external ratio (I/E) values in riverine sediment, wastewater, and sediment samples from the outfalls of paper mills, as well as three brands of domestic detergents obtained from the present and previous studies, implicated the occurrence of untreated wastewater in the sampling sites. Levels of ΣLAB were significantly linear correlated with those of total organic carbon (TOC) but not with those of polycyclic aromatic hydrocarbons. Multiple linear regression integrated principal component analysis indicated that 56% of LABs in wastewater in the study area were treated, but the extent of degradation of LABs was low. Finally, it is proposed that ineffective law enforcement and loopholes in the current regulations for wastewater discharge account for the substantial amount (44%) of untreated wastewater discharged in the study region.

  4. Marine protist diversity in European coastal waters and sediments as revealed by high-throughput sequencing.

    PubMed

    Massana, Ramon; Gobet, Angélique; Audic, Stéphane; Bass, David; Bittner, Lucie; Boutte, Christophe; Chambouvet, Aurélie; Christen, Richard; Claverie, Jean-Michel; Decelle, Johan; Dolan, John R; Dunthorn, Micah; Edvardsen, Bente; Forn, Irene; Forster, Dominik; Guillou, Laure; Jaillon, Olivier; Kooistra, Wiebe H C F; Logares, Ramiro; Mahé, Frédéric; Not, Fabrice; Ogata, Hiroyuki; Pawlowski, Jan; Pernice, Massimo C; Probert, Ian; Romac, Sarah; Richards, Thomas; Santini, Sébastien; Shalchian-Tabrizi, Kamran; Siano, Raffaele; Simon, Nathalie; Stoeck, Thorsten; Vaulot, Daniel; Zingone, Adriana; de Vargas, Colomban

    2015-10-01

    Although protists are critical components of marine ecosystems, they are still poorly characterized. Here we analysed the taxonomic diversity of planktonic and benthic protist communities collected in six distant European coastal sites. Environmental deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) from three size fractions (pico-, nano- and micro/mesoplankton), as well as from dissolved DNA and surface sediments were used as templates for tag pyrosequencing of the V4 region of the 18S ribosomal DNA. Beta-diversity analyses split the protist community structure into three main clusters: picoplankton-nanoplankton-dissolved DNA, micro/mesoplankton and sediments. Within each cluster, protist communities from the same site and time clustered together, while communities from the same site but different seasons were unrelated. Both DNA and RNA-based surveys provided similar relative abundances for most class-level taxonomic groups. Yet, particular groups were overrepresented in one of the two templates, such as marine alveolates (MALV)-I and MALV-II that were much more abundant in DNA surveys. Overall, the groups displaying the highest relative contribution were Dinophyceae, Diatomea, Ciliophora and Acantharia. Also, well represented were Mamiellophyceae, Cryptomonadales, marine alveolates and marine stramenopiles in the picoplankton, and Monadofilosa and basal Fungi in sediments. Our extensive and systematic sequencing of geographically separated sites provides the most comprehensive molecular description of coastal marine protist diversity to date.

  5. Earthquake-ponded sediments as a high-resolution archive of Anthropocene climate change on the Fuyun Fault (Xinjiang, China).

    NASA Astrophysics Data System (ADS)

    Chua, Stephen; Gouramanis, Chris; Etchebes, Marie; Klinger, Yann; Gao, Mingxing; Switzer, Adam; Tapponnier, Paul

    2016-04-01

    High-resolution, late-Holocene climate patterns in arid central Asia, in particular the behaviour of the Asian Monsoon and occurrences of precipitation events, are not yet fully understood. In particular, few high-resolution palaeoenvironmental and palaeoclimate studies are available from the Junggar-Altay region in the Xinjiang Province, northwestern China. This area is tectonically active and the last large earthquake (Mw 7.9) occurred along the Fuyun strike-slip fault in 1931, resulting in ˜6m of right-lateral movement. South of the epicentre at Karaxingar, this earthquake resulted in the construction of large scarp-bounded ponds (46o43'N, 89o55'E) now filled with sediment. Sediment samples were collected every centimetre at a two-meter deep trench where the main pond was the deepest. The majority of the AMS 14C ages of charcoal and plant fibre samples are modern (56±34 to 171±34 yr BP) with the exception of a few much older carbon (842±26 to 2017±26 yr BP) at the base of the trench. The post-1931 age of the pond is validated by the 137Cs and 210Pb age-depth chronology. Each sediment sample was analysed for organic, carbonate and clastic contents and particle-size. This high-resolution analysis revealed eleven upward-fining sequences, with three prominent grain size peaks at depths of 1.7m, 0.95m and 0.6m below ground surface, suggesting three major modern precipitation events. The 11 grain-size peaks since 1931 in the pond coincide with 11 periods of increased precipitation measured in high-elevation tree-ring records ˜50 km north of the pond. Thus, low-altitude post-seismic sedimentary depocentres provide excellent high-resolution palaeoclimate archives that can fill a significant data gap where other proxy records are not available.

  6. Effects of agricultural tillage and sediment accumulation on emergent plant communities in playa wetlands of the U.S. High Plains.

    PubMed

    O'Connell, Jessica L; Johnson, Lacrecia A; Daniel, Dale W; McMurry, Scott T; Smith, Loren M; Haukos, David A

    2013-05-15

    Identifying community assembly filters is a primary ecological aim. The High Plains, a 30 million ha short-grass eco-region, is intensely cultivated. Cultivation disturbance, including plowing and eroded soil deposition down-slope of plowing, influences plant composition in depressional wetlands, such as playas, within croplands. We evaluated influences of wetland cultivation and sediment deposition on plant composition in playas embedded within croplands (46 plowed and 32 unplowed) and native grasslands (79) across 6 High Plains' states. Sediment accumulation ranged from 7 to 78 cm in cropland and 1 to 35 cm in grassland playas. Deeper sediments and plowing each decreased wetland plant richness, 28% and 70% respectively in cropland wetlands. Sediment depth reduced richness 37% in small grasslands playas while it increased richness 22% in larger ones, suggesting moderate disturbance increased richness when there were nearby propagule sources. Sediment depth was unrelated to species richness in plowed wetlands, probably because plowing was a strong disturbance. Plowing removed perennial plants from vegetation communities. Sediment accumulation also influenced species composition in cropland playas, e.g., probability of Eleocharis atropurpurea increased with sediment depth, while probability of Panicum capillare decreased. In grassland playas, observed lighter sediment depths did not influence species composition after accounting for wetland area. Sediment accumulation and plowing shift wetland plant communities toward annual species and decrease habitat connectivity for wetland-dependent organisms in cropland playas over 39,000 and 23,400 ha respectively. Conservation practices lessening sediment accumulation include short-grass buffer strips surrounding wetlands. Further, wetland tillage, allowed under federal agricultural conservation programs, should be eliminated.

  7. Effects of agricultural tillage and sediment accumulation on emergent plant communities in playa wetlands of the U.S. High Plains.

    PubMed

    O'Connell, Jessica L; Johnson, Lacrecia A; Daniel, Dale W; McMurry, Scott T; Smith, Loren M; Haukos, David A

    2013-05-15

    Identifying community assembly filters is a primary ecological aim. The High Plains, a 30 million ha short-grass eco-region, is intensely cultivated. Cultivation disturbance, including plowing and eroded soil deposition down-slope of plowing, influences plant composition in depressional wetlands, such as playas, within croplands. We evaluated influences of wetland cultivation and sediment deposition on plant composition in playas embedded within croplands (46 plowed and 32 unplowed) and native grasslands (79) across 6 High Plains' states. Sediment accumulation ranged from 7 to 78 cm in cropland and 1 to 35 cm in grassland playas. Deeper sediments and plowing each decreased wetland plant richness, 28% and 70% respectively in cropland wetlands. Sediment depth reduced richness 37% in small grasslands playas while it increased richness 22% in larger ones, suggesting moderate disturbance increased richness when there were nearby propagule sources. Sediment depth was unrelated to species richness in plowed wetlands, probably because plowing was a strong disturbance. Plowing removed perennial plants from vegetation communities. Sediment accumulation also influenced species composition in cropland playas, e.g., probability of Eleocharis atropurpurea increased with sediment depth, while probability of Panicum capillare decreased. In grassland playas, observed lighter sediment depths did not influence species composition after accounting for wetland area. Sediment accumulation and plowing shift wetland plant communities toward annual species and decrease habitat connectivity for wetland-dependent organisms in cropland playas over 39,000 and 23,400 ha respectively. Conservation practices lessening sediment accumulation include short-grass buffer strips surrounding wetlands. Further, wetland tillage, allowed under federal agricultural conservation programs, should be eliminated. PMID:23500104

  8. RAGG - R EPISODIC AGGREGATION PACKAGE

    EPA Science Inventory

    The RAGG package is an R implementation of the CMAQ episodic model aggregation method developed by Constella Group and the Environmental Protection Agency. RAGG is a tool to provide climatological seasonal and annual deposition of sulphur and nitrogen for multimedia management. ...

  9. Measurement of sediment loads during flash flood events: 14 years of results from a six stream monitoring network on the southern Colorado Plateau

    NASA Astrophysics Data System (ADS)

    Griffiths, R. E.; Topping, D. J.

    2015-12-01

    In in arid and semi-arid environments, short-duration, high-intensity rainfall events—flash floods—are the primary driver of sediment transport in ephemeral streams. The spatial and temporal variability of these rainfall events results in episodic and irregular stream flow and resultant sediment transport. As a result of limited-flow durations, measuring discharge and collecting suspended-sediment samples on ephemeral streams in arid regions is difficult and time-consuming. Because of these limitations, few sediment-monitoring programs on ephemeral streams have been developed; some examples of sediment-monitoring gages and gaging networks constructed on arid ephemeral streams include Walnut Gulch, United States, Nahal Yael, Israel, and the Luni River Basin, India. The difficulty in making measurements of discharge and suspended-sediment concentration on arid ephemeral streams has led many researchers to use methods such as regional sediment-yield equations, sediment-rating curves, and peak discharge to total-sediment load relations. These methods can provide a cost-effective estimation of sediment yield from ungaged tributaries. However, these approaches are limited by, among other factors, time averaging, hysteresis, and differences in local and regional geology, rainfall, and vegetation. A monitoring network was established in 2000 on six ephemeral tributaries of the Colorado River in lower Glen and upper Marble canyons. Results from this monitoring network show that annual suspended-sediment loads for individual streams can vary by 5 orders of magnitude while the annual suspended-sediment load for the entire network may vary annually by 2 orders of magnitude, suspended-sediment loads during an individual flood event do not typically correlate with discharge, and local geology has a strong control on the sediment yield of a drainage basin. Comparing our results to previous estimates of sediment load from these drainages found that previous, indirect, methods

  10. Combination of high throughput cultivation and dsrA sequencing for assessment of sulfate-reducing bacteria diversity in sediments.

    PubMed

    Colin, Yannick; Goñi-Urriza, Marisol; Caumette, Pierre; Guyoneaud, Rémy

    2013-01-01

    Improving the knowledge on sulfate-reducing bacteria (SRB) diversity and ecophysiology will permit a better understanding on their key roles in aquatic ecosystems. Therefore, their diversity was evaluated in estuarine sediments by a polyphasic approach including dsrA gene cloning and sequencing (156 clones) and high-throughput isolations in 384-well microplates (177 strains). Using the related thresholds of 95% (DsrA amino acid sequences) and 97% (16S rRNA gene sequences) for sequence similarity, SRB were grouped into 60 and 22 operational taxonomic units, respectively. Both approaches poorly overlapped and rather complemented each other. The clone library was dominated by sequences related to the Desulfobacteraceae, while only one isolate belonged to this family. Most of the strains were affiliated to the genera Desulfopila and Desulfotalea within the Desulfobulbaceae. Desulfopila-related strains exhibited a high phylogenetic microdiversity and represented numerically significant populations. In contrast, Desulfovibrio isolates were less abundant but displayed a high phylogenetic diversity. Three hundred and eighty-four-well microplate isolations enhanced significantly the number of isolates handled. As a consequence, 15 new taxa sharing less than 98% sequence similarity (16S rRNA gene) with their closest relatives were obtained. This polyphasic approach allowed to obtain a high phylogenetic diversity and thus a better view of sulfate-reducing communities in intertidal sediments.

  11. High sulfate reduction efficiency in a UASB using an alternative source of sulfidogenic sludge derived from hydrothermal vent sediments.

    PubMed

    García-Solares, Selene Montserrat; Ordaz, Alberto; Monroy-Hermosillo, Oscar; Jan-Roblero, Janet; Guerrero-Barajas, Claudia

    2014-12-01

    Sulfidogenesis in reactors is mostly achieved through adaptation of predominantly methanogenic granular sludge to sulfidogenesis. In this work, an upflow anaerobic sludge blanket (UASB) reactor operated under sulfate-reducing conditions was inoculated with hydrothermal vent sediments to carry out sulfate reduction using volatile fatty acids (VFAs) as substrate and chemical oxygen demand (COD)/SO4 (-2) ratios between 0.49 and 0.64. After a short period of adaptation, a robust non-granular sludge was capable of achieving high sulfate reduction efficiencies while avoiding competence with methanogens and toxicity to the microorganisms due to high sulfide concentration. The highest sulfide concentration (2,552 mg/L) was obtained with acetate/butyrate, and sulfate reduction efficiencies were up to 98 %. A mixture of acetate/butyrate, which produced a higher yielding of HS(-), was preferred over acetate/propionate/butyrate since the consumption of COD was minimized during the process. Sludge was analyzed, and some of the microorganisms identified in the sludge belong to the genera Desulfobacterium, Marinobacter, and Clostridium. The tolerance of the sludge to sulfide may be attributed to the syntrophy among these microorganisms, some of which have been reported to tolerate high concentrations of sulfide. To the best of our knowledge, this is the first report on the analysis of the direct utilization of hydrothermal vent sediments as an alternate source of sludge for sulfate reduction under high sulfide concentrations.

  12. Cool-water Eocene-Oligocene carbonate sedimentation on a paleobathymetric high, Kangaroo Island, southern Australia

    NASA Astrophysics Data System (ADS)

    James, Noel P.; Matenaar, Joanne; Bone, Yvonne

    2016-07-01

    The Kingscote Limestone is a thin, biofragmental ~ 41 m thick Paleogene subtropical to cool-temperate carbonate interpreted to have accumulated in a seaway developed between a series of mid-shelf islands. It is a pivotal section that allows interpretation of a region in which there is little exposure of early Cenozoic shelf sediments. Sedimentation occurred on part of the shelf along the northern margin of an extensive Eocene embayment that evolved into a narrow Oligocene ocean following collapse of the Tasman Gateway. Eocene strata are subtropical echinoid-rich floatstones with conspicuous bryozoans, and mollusks, together with large and small benthic foraminifers. Numerous echinoid rudstone storm deposits punctuate the succession. Correlation with coeval Eocene strata across southern Australia supports a regional facies model wherein inner neritic biosiliceous spiculitic sediments passed outboard into calcareous facies. The silica was derived from land covered by a thriving subtropical forest and attendant deep weathering. Oligocene rocks are distinctively cooler cyclic cross-bedded bryozoan rudstones and floatstones with a similar benthic biota but dominated by bryozoans and containing no large benthic foraminifers. These deposits are interpreted as flood-dominated tidal subaqueous dunes that formed in a flood-tide dominated inter-island strait. Omission surfaces at the top of the Eocene and at the top of most Oligocene cycles are Fe-stained hardgrounds that underwent extensive multigeneration seafloor and meteoric diagenesis prior to deposition of the next cycle. Cycles in the Kingscote Limestone, although mostly m-scale and compositionally distinct are similar to those across the region and point to a recurring cycle motif controlled by icehouse eustasy and local paleogeography.

  13. High-resolution seismic-reflection interpretations of some sediment deposits, Antarctic continental margin: Focus on the western Ross Sea

    USGS Publications Warehouse

    Karl, Herman A.

    1989-01-01

    High-resolution seismic-reflection data have been used to a varying degree by geoscientists to interpret the history of marine sediment accumulations around Antarctica. Reconnaissance analysis of 1-, 3.5-, and 12-kHz data collected by the U.S. Geological Survey in the western Ross Sea has led to the identification of eight echo-character facies and six microtopographic facies in the sediment deposits that overlie the Ross Sea unconformity. Three depositional facies regions, each characterized by a particular assemblage of echo-character type and microtopographic facies, have been identified on the continental shelf. These suites of acoustic facies are the result of specific depositional processes that control type and accumulation of sediment in a region. Evidence of glacial processes and products is uncommon in regions 1 and 2, but is abundant in region 3. McMurdo Sound, region 1, is characterized by a monospecific set of acoustic facies. This unique assemblage probably represents turbidity current deposition in the western part of the basin. Most of the seafloor in region 2, from about latitude 77??S to 75??S, is deeper than 600 m below sealevel. The microtopographic facies and echo-character facies observed on the lower slopes and basin floor there reflect the thin deposits of pelagic sediments that have accumulated in the low-energy conditions that are typical of deep-water environments. In shallower water near the boundary with region 3, the signature of the acoustic facies is different from that in deeper water and probably indicates higher energy conditions or, perhaps, ice-related processes. Thick deposits of tills emplaced by lodgement during the most recent advance of the West Antarctic Ice Sheet are common from latitude 75??S to the northern boundary of the study area just south of Coulman Island (region 3). The signature of microtopographic facies in this region reflects the relief of the base of the grounded ice sheet prior to decoupling from the

  14. Sediment connectivity in the high-alpine valley of Val Müschauns, Swiss National Park - linking geomorphic field mapping with geomorphometric modelling

    NASA Astrophysics Data System (ADS)

    Messenzehl, Karoline; Hoffmann, Thomas; Dikau, Richard

    2014-09-01

    The efficiency of sediment routing through mountain sediment cascades is controlled by the connectivity of hillslopes to the main river system. A lack of connectivity may cause long-term sediment storage and exclude large fractions of a basin from the sediment routing for several thousand years. Here, we studied sediment dynamics in a small, formerly glaciated valley in the Swiss Alps. To characterise the sediment connectivity to the stream, we calculated a morphometric index using a GIS algorithm. The modelling results were tested against a field based geomorphic mapping of sediment storages, which were evaluated with respect to their state of (de)coupling. In accordance to the field diagnostics, the modelling results indicate very well that the present-day sediment flux is conditioned by the glacial valley morphometry inherited through Pleistocene glaciation. Especially in the upper hanging valleys, the connectivity index is reduced noticeably due to the glacial cirque morphology. Based on the field mapping, 30% of the hillslope sediment cascades are interrupted and 20% of the storage boundaries are currently affected by a lack of material transfer. As a consequence, ~ 29% of the basin surface is currently disconnected from the main river. Nevertheless, the GIS algorithm overestimates the connectivity within the basin, because it fails to calculate decoupling between neighbouring pixels in digital terrain models (DTMs). Around 35% of the basin surface, which has been mapped in the field as being decoupled, is related to relative high connectivity. Our study highlights the potential of morphometric GIS modelling for studying sediment connectivity, but additionally emphasises the indispensability of geomorphic field mapping for a holistic understanding of mountain cascading systems.

  15. Characterization of bacterial communities in sediments receiving various wastewater effluents with high-throughput sequencing analysis.

    PubMed

    Lu, Xiao-Ming; Lu, Peng-Zhen

    2014-04-01

    454 Pyrosequencing was applied to examine bacterial communities in sediment samples collected from a river receiving effluent discharge from rural domestic sewage (RDS) and various factories, including a tannery (TNS), clothing plant (CTS), and button factory (BTS), respectively. For each sample, 4,510 effective sequences were selected and utilized to do the bacterial diversity and abundance analysis, respectively. In total, 1,288, 2,036, 1,800, and 2,150 operational taxonomic units were obtained at 3% distance cutoff in TNS, CTS, BTS, and RDS, respectively. Bacterial phylotype richness in RDS was higher than the other samples, and TNS had the least richness. The most predominant class in the TNS, CTS, and BTS samples is Betaproteobacteria. Cyanobacteria (no_rank) is the most predominant one in the RDS sample. Circa 31% sequences in TNS were affiliated with the Rhodocyclales order. In the four samples, Aeromonas, Arcobacter, Clostridium, Legionella, Leptospira, Mycobacterium, Pseudomonas, and Treponema genera containing pathogenic bacteria were detected. Characterization of bacterial communities in sediments from various downstream branches indicated that distinct wastewater effluents have similar potential to reduce the natural variability in river ecosystems and contribute to the river biotic homogenization. PMID:24477925

  16. Evolution of a high-latitude sediment drift inside a glacially-carved trough based on high-resolution seismic stratigraphy (Kveithola, NW Barents Sea)

    NASA Astrophysics Data System (ADS)

    Rebesco, M.; Özmaral, A.; Urgeles, R.; Accettella, D.; Lucchi, R.; Rüther, D. C.; Winsborrow, M.; Llopart, J.; Caburlotto, A.; Lantzsch, H.; Hanebuth, T. J. J.

    2015-12-01

    Kveithola is a glacially-carved, E-W trending trough located in the NW Barents Sea. A set of confined sediment drifts (the "Kveithola Drift") is located in the inner part of the trough. We provide for the first time a detailed morphological, seismostratigraphic, lithological and sedimentological insight into this sediment drift. The PARASOUND data show that the drift is mainly well-stratified, characterized by sub-parallel reflections of moderate to high amplitude and good lateral continuity. The reflectors show an abrupt pinch-out on the northern edge where a distinct moat is present, and a gradual tapering to the south. Internally we identify the base of the drift and four internal horizons, which we correlate throughout the drift. Two units display high amplitude reflectors, marked lensoidal character and restricted lateral extent, suggesting a relatively larger contribution of gravity processes to the drift growth. Facies typical for contourite deposition are found in the sediment cores, with strongly bioturbated sediments and abundant silty/sandy mottles that contain shell fragments. These characteristics suggest a strong control by a bottom current flowing along the moat on the northern edge of the drift. Brine-enriched shelf water (BSW) produced during winter and flowing westward in the moat, is suggested to be responsible for the genesis of the Kveithola Drift. The formation of BSW is inferred to have started around 13 cal. ka BP, the onset of drift deposition, suggesting that conditions leading to atmospheric cooling of the surface waters and/or the presence of coastal polynyas and wind have persisted on the western Barents Shelf since that time. The units which formed under a larger influence of gravity processes (dated to the Younger Dryas and to 8.9-8.2 cal ka BP) indicate that bottom current activity was reduced during these two climatically colder periods, possibly due to expanded grounded and sea ice cover over the Barents Sea.

  17. Chemical characteristics and source apportionment of fine particulate organic carbon in Hong Kong during high particulate matter episodes in winter 2003

    NASA Astrophysics Data System (ADS)

    Li, Yun-Chun; Yu, Jian Zhen; Ho, Steven Sai Hang; Schauer, James J.; Yuan, Zibing; Lau, Alexis K. H.; Louie, Peter K. K.

    2013-02-01

    PM2.5 samples were collected at six general stations and one roadside station in Hong Kong in two periods of high particulate matter (PM) in 2003 (27 October-4 November and 30 November-13 December). The highest PM2.5 reached 216 μg m- 3 during the first high PM period and 113 μg m- 3 during the second high PM period. Analysis of synoptic weather conditions identified individual sampling days under dominant influence of one of three types of air masses, that is, local, regional and long-range transported (LRT) air masses. Roadside samples were discussed separately due to heavy influences from vehicular emissions. This research examines source apportionment of fine organic carbon (OC) and contribution of secondary organic aerosol on high PM days under different synoptic conditions. Six primary OC (POC) sources (vehicle exhaust, biomass burning, cooking, cigarette smoke, vegetative detritus, and coal combustion) were identified on the basis of characteristic organic tracers. Individual POC source contributions were estimated using chemical mass balance model. In the roadside and the local samples, OC was dominated by the primary sources, accounting for more than 74% of OC. In the samples influenced by regional and LRT air masses, secondary OC (SOC), which was approximated to be the difference between the total measured OC and the apportioned POC, contributed more than 54% of fine OC. SOC was highly correlated with water-soluble organic carbon and sulfate, consistent with its secondary nature.

  18. Terrestrial source to deep-sea sink sediment budgets at high and low sea levels: Insights from tectonically active Southern California

    USGS Publications Warehouse

    Covault, J.A.; Romans, B.W.; Graham, S.A.; Fildani, A.; Hilley, G.E.

    2011-01-01

    Sediment routing from terrestrial source areas to the deep sea influences landscapes and seascapes and supply and filling of sedimentary basins. However, a comprehensive assessment of land-to-deep-sea sediment budgets over millennia with significant climate change is lacking. We provide source to sink sediment budgets using cosmogenic radionuclide-derived terrestrial denudation rates and submarine-fan deposition rates through sea-level fluctuations since oxygen isotope stage 3 (younger than 40 ka) in tectonically active, spatially restricted sediment-routing systems of Southern California. We show that source-area denudation and deep-sea deposition are balanced during a period of generally falling and low sea level (40-13 ka), but that deep-sea deposition exceeds terrestrial denudation during the subsequent period of rising and high sea level (younger than 13 ka). This additional supply of sediment is likely owed to enhanced dispersal of sediment across the shelf caused by seacliff erosion during postglacial shoreline transgression and initiation of submarine mass wasting. During periods of both low and high sea level, land and deep-sea sediment fluxes do not show orders of magnitude imbalances that might be expected in the wake of major sea-level changes. Thus, sediment-routing processes in a globally significant class of small, tectonically active systems might be fundamentally different from those of larger systems that drain entire orogens, in which sediment storage in coastal plains and wide continental shelves can exceed millions of years. Furthermore, in such small systems, depositional changes offshore can reflect onshore changes when viewed over time scales of several thousand years to more than 10 k.y. ?? 2011 Geological Society of America.

  19. Culturable prokaryotic diversity of deep, gas hydrate sediments: first use of a continuous high-pressure, anaerobic, enrichment and isolation system for subseafloor sediments (DeepIsoBUG)

    PubMed Central

    Parkes, R John; Sellek, Gerard; Webster, Gordon; Martin, Derek; Anders, Erik; Weightman, Andrew J; Sass, Henrik

    2009-01-01

    Deep subseafloor sediments may contain depressurization-sensitive, anaerobic, piezophilic prokaryotes. To test this we developed the DeepIsoBUG system, which when coupled with the HYACINTH pressure-retaining drilling and core storage system and the PRESS core cutting and processing system, enables deep sediments to be handled without depressurization (up to 25 MPa) and anaerobic prokaryotic enrichments and isolation to be conducted up to 100 MPa. Here, we describe the system and its first use with subsurface gas hydrate sediments from the Indian Continental Shelf, Cascadia Margin and Gulf of Mexico. Generally, highest cell concentrations in enrichments occurred close to in situ pressures (14 MPa) in a variety of media, although growth continued up to at least 80 MPa. Predominant sequences in enrichments were Carnobacterium, Clostridium, Marinilactibacillus and Pseudomonas, plus Acetobacterium and Bacteroidetes in Indian samples, largely independent of media and pressures. Related 16S rRNA gene sequences for all of these Bacteria have been detected in deep, subsurface environments, although isolated strains were piezotolerant, being able to grow at atmospheric pressure. Only the Clostridium and Acetobacterium were obligate anaerobes. No Archaea were enriched. It may be that these sediment samples were not deep enough (total depth 1126–1527 m) to obtain obligate piezophiles. PMID:19694787

  20. Episodic transdermal delivery of testosterone.

    PubMed

    Malik, Ritu; Venkatesh, K S; Dwivedi, Anil Kumar; Misra, Amit

    2012-06-01

    Film-forming lotions, precast films and adhesive patches containing testosterone (T) were prepared by compounding vinylic, acrylic and cellulosic polymers with a variety of excipients in order to achieve distribution of T in domains of heterogeneity within multicomponent matrices. The feasibility of this approach in achieving episodic transdermal delivery of testosterone (T) was investigated. Composition-dependent differences in extent of in vitro drug release and periodicity were observed. Representative formulations showing the most pronounced episodic T release in vitro were tested in female rats. Whereas intravenously administered T decayed exponentially, three maxima of T in serum were observed upon application of selected formulations. Thus, peak serum concentrations of 240, 36, and 29 ng/dL were observed at 0.2, 5, and 16.8 h after application of the preferred lotion formulation, and 89, 65, and 64 ng/dL at 1, 16.4, and 48.8 h after patches. Deconvolution, noncompartment pharmacokinetic analysis and multiple peak fitting also indicated episodicity. These results suggest the feasibility of using transdermal systems for pulsatile T delivery in a variety of clinical applications, including hormone supplementation and male contraception.

  1. Methane Seep in Shallow-Water Permeable Sediment Harbors High Diversity of Anaerobic Methanotrophic Communities, Elba, Italy.

    PubMed

    Ruff, S Emil; Kuhfuss, Hanna; Wegener, Gunter; Lott, Christian; Ramette, Alban; Wiedling, Johanna; Knittel, Katrin; Weber, Miriam

    2016-01-01

    The anaerobic oxidation of methane (AOM) is a key biogeochemical process regulating methane emission from marine sediments into the hydrosphere. AOM is largely mediated by consortia of anaerobic methanotrophic archaea (ANME) and sulfate-reducing bacteria (SRB), and has mainly been investigated in deep-sea sediments. Here we studied methane seepage at four spots located at 12 m water depth in coastal, organic carbon depleted permeable sands off the Island of Elba (Italy). We combined biogeochemical measurements, sequencing-based community analyses and in situ hybridization to investigate the microbial communities of this environment. Increased alkalinity, formation of free sulfide and nearly stoichiometric methane oxidation and sulfate reduction rates up to 200 nmol g(-1) day(-1) indicated the predominance of sulfate-coupled AOM. With up to 40 cm thickness the zones of AOM activity were unusually large and occurred in deeper sediment horizons (20-50 cm below seafloor) as compared to diffusion-dominated deep-sea seeps, which is likely caused by advective flow of pore water due to the shallow water depth and permeability of the sands. Hydrodynamic forces also may be responsible for the substantial phylogenetic and unprecedented morphological diversity of AOM consortia inhabiting these sands, including the clades ANME-1a/b, ANME-2a/b/c, ANME-3, and their partner bacteria SEEP-SRB1a and SEEP-SRB2. High microbial dispersal, the availability of diverse energy sources and high habitat heterogeneity might explain that the emission spots shared few microbial taxa, despite their physical proximity. Although the biogeochemistry of this shallow methane seep was very different to that of deep-sea seeps, their key functional taxa were very closely related, which supports the global dispersal of key taxa and underlines strong selection by methane as the predominant energy source. Mesophilic, methane-fueled ecosystems in shallow-water permeable sediments may comprise distinct

  2. Methane Seep in Shallow-Water Permeable Sediment Harbors High Diversity of Anaerobic Methanotrophic Communities, Elba, Italy.

    PubMed

    Ruff, S Emil; Kuhfuss, Hanna; Wegener, Gunter; Lott, Christian; Ramette, Alban; Wiedling, Johanna; Knittel, Katrin; Weber, Miriam

    2016-01-01

    The anaerobic oxidation of methane (AOM) is a key biogeochemical process regulating methane emission from marine sediments into the hydrosphere. AOM is largely mediated by consortia of anaerobic methanotrophic archaea (ANME) and sulfate-reducing bacteria (SRB), and has mainly been investigated in deep-sea sediments. Here we studied methane seepage at four spots located at 12 m water depth in coastal, organic carbon depleted permeable sands off the Island of Elba (Italy). We combined biogeochemical measurements, sequencing-based community analyses and in situ hybridization to investigate the microbial communities of this environment. Increased alkalinity, formation of free sulfide and nearly stoichiometric methane oxidation and sulfate reduction rates up to 200 nmol g(-1) day(-1) indicated the predominance of sulfate-coupled AOM. With up to 40 cm thickness the zones of AOM activity were unusually large and occurred in deeper sediment horizons (20-50 cm below seafloor) as compared to diffusion-dominated deep-sea seeps, which is likely caused by advective flow of pore water due to the shallow water depth and permeability of the sands. Hydrodynamic forces also may be responsible for the substantial phylogenetic and unprecedented morphological diversity of AOM consortia inhabiting these sands, including the clades ANME-1a/b, ANME-2a/b/c, ANME-3, and their partner bacteria SEEP-SRB1a and SEEP-SRB2. High microbial dispersal, the availability of diverse energy sources and high habitat heterogeneity might explain that the emission spots shared few microbial taxa, despite their physical proximity. Although the biogeochemistry of this shallow methane seep was very different to that of deep-sea seeps, their key functional taxa were very closely related, which supports the global dispersal of key taxa and underlines strong selection by methane as the predominant energy source. Mesophilic, methane-fueled ecosystems in shallow-water permeable sediments may comprise distinct

  3. Methane Seep in Shallow-Water Permeable Sediment Harbors High Diversity of Anaerobic Methanotrophic Communities, Elba, Italy

    PubMed Central

    Ruff, S. Emil; Kuhfuss, Hanna; Wegener, Gunter; Lott, Christian; Ramette, Alban; Wiedling, Johanna; Knittel, Katrin; Weber, Miriam

    2016-01-01

    The anaerobic oxidation of methane (AOM) is a key biogeochemical process regulating methane emission from marine sediments into the hydrosphere. AOM is largely mediated by consortia of anaerobic methanotrophic archaea (ANME) and sulfate-reducing bacteria (SRB), and has mainly been investigated in deep-sea sediments. Here we studied methane seepage at four spots located at 12 m water depth in coastal, organic carbon depleted permeable sands off the Island of Elba (Italy). We combined biogeochemical measurements, sequencing-based community analyses and in situ hybridization to investigate the microbial communities of this environment. Increased alkalinity, formation of free sulfide and nearly stoichiometric methane oxidation and sulfate reduction rates up to 200 nmol g-1 day-1 indicated the predominance of sulfate-coupled AOM. With up to 40 cm thickness the zones of AOM activity were unusually large and occurred in deeper sediment horizons (20–50 cm below seafloor) as compared to diffusion-dominated deep-sea seeps, which is likely caused by advective flow of pore water due to the shallow water depth and permeability of the sands. Hydrodynamic forces also may be responsible for the substantial phylogenetic and unprecedented morphological diversity of AOM consortia inhabiting these sands, including the clades ANME-1a/b, ANME-2a/b/c, ANME-3, and their partner bacteria SEEP-SRB1a and SEEP-SRB2. High microbial dispersal, the availability of diverse energy sources and high habitat heterogeneity might explain that the emission spots shared few microbial taxa, despite their physical proximity. Although the biogeochemistry of this shallow methane seep was very different to that of deep-sea seeps, their key functional taxa were very closely related, which supports the global dispersal of key taxa and underlines strong selection by methane as the predominant energy source. Mesophilic, methane-fueled ecosystems in shallow-water permeable sediments may comprise distinct

  4. A diagnostic Study of a High Impact Weather Episode in the Western Mediterranean Region: IOP8 a HyMeX case

    NASA Astrophysics Data System (ADS)

    Khodayar, Samiro; Kalthoff, Norbert; Raff, Fritz

    2013-04-01

    Fall season heavy rainfall in the western Mediterranean region is one of the most threatening phenomena in the area. Devastating flash floods occur every year somewhere in eastern Spain resulting in a large amount of property losses, destruction of infrastructures, enormous agricultural losses and human fatalities. The forecast of the underlying HIW is a subject of special concern for local meteorologist because of its catastrophic nature. Within the framework of HyMeX (Hydrological cycle in the Mediterranean eXperiment) a HIW (High Impact Weather) event took place on the south and eastern part of the Spanish coast, particularly in Andalusia, Murcia, Valencia, Catalonia and less pronouncedly in the Balearic Islands, moving afterwards towards France southern coast. During this event casualties and important economic damage were registered. The amounts of precipitation locally overpassed 200 mm in 24 hours and a tornado occurred in Gandia (Valencia). The main objective of this work is to provide a comprehensive description of the physical atmospheric processes giving rise to the intense precipitation in this event and its movement along the Spanish coast. High-resolution COSMO-CLM model simulations supported by the analysis of observational data sets will be presented. The model simulations and observational data sets, such as a dense network of global positioning systems (GPS), raingauges, surface measurements and radiosoundings are analyzed to document in detail the evolution of the warm and wet air masses which fed the high precipitation event (HPE) systems, as well as the low-level convergence to which the main convective systems were associated.

  5. Reducing length of stay for acute diabetic foot episodes: employing an extended scope of practice podiatric high-risk foot coordinator in an acute foundation trust hospital

    PubMed Central

    2013-01-01

    Background To enhance the acute management of people with diabetic foot disease requiring admission, an extended scope of practice, podiatric high-risk foot coordinator position, was established at the Great Western Hospital, Swindon in 2010. The focus of this new role was to facilitate more efficient and timely management of people with complex diabetic foot disease. The aim of this project was to investigate the impact of the podiatric high-risk foot coordinator role on length of stay, rate of re-admission and bed cost. Method This study evaluated the difference in length of stay and rate of re-admission between an 11- month pre-pilot period (November 2008 to October 2009) and a 10-month pilot period (August 2010 to June 2011). The estimated difference in bed cost between the pre-pilot and pilot audits was also calculated. Inclusion criteria were restricted to inpatients admitted with a diabetic foot ulcer, gangrene, cellulitis or infection as the primary cause for admission. Eligible records were retrieved using ICD-10 (V9) coding via the hospital clinical audit department for the pre-pilot period and a unique database was used to source records for the pilot phase. Results Following the introduction of the podiatric high-risk foot coordinator, the average length of stay reduced from 33.7 days to 23.3 days (mean difference 10.4 days, 95% CI 0.0 to 20.8, p = 0.050). There was no statistically significant difference in re-admission rate between the two study periods, 17.2% (95% CI 12.2% to 23.9%) in the pre-pilot phase and 15.4% (95% CI 12.0% to 19.5%) in the pilot phase (p = 0.820). The extrapolated annual cost saving following the implementation of the new coordinator role was calculated to be £234,000 for the 2010/2011 year. Conclusions This audit found that the extended scope of practice coordinator role may have a positive impact on reducing length of stay for diabetic foot admissions. This paper advocates the role of a podiatric high-risk foot

  6. Planning Physical Education Lessons as Teaching "Episodes"

    ERIC Educational Resources Information Center

    Chatoupis, Constantine

    2016-01-01

    An "episode" is a unit of time within which teachers and students are working on the same objective and are engaged in the same teaching/learning style. The duration of each episode, as well as the number of them in a single lesson, may vary. Additionally, the multiple episodes of a lesson may have similar objectives, offer similar…

  7. Prediction of transition from ultra-high risk to first-episode psychosis using a probabilistic model combining history, clinical assessment and fatty-acid biomarkers

    PubMed Central

    Clark, S R; Baune, B T; Schubert, K O; Lavoie, S; Smesny, S; Rice, S M; Schäfer, M R; Benninger, F; Feucht, M; Klier, C M; McGorry, P D; Amminger, G P

    2016-01-01

    Current criteria identifying patients with ultra-high risk of psychosis (UHR) have low specificity, and less than one-third of UHR cases experience transition to psychosis within 3 years of initial assessment. We explored whether a Bayesian probabilistic multimodal model, combining baseline historical and clinical risk factors with biomarkers (oxidative stress, cell membrane fatty acids, resting quantitative electroencephalography (qEEG)), could improve this specificity. We analyzed data of a UHR cohort (n=40) with a 1-year transition rate of 28%. Positive and negative likelihood ratios were calculated for predictor variables with statistically significant receiver operating characteristic curves (ROCs), which excluded oxidative stress markers and qEEG parameters as significant predictors of transition. We clustered significant variables into historical (history of drug use), clinical (Positive and Negative Symptoms Scale positive, negative and general scores and Global Assessment of Function) and biomarker (total omega-3, nervonic acid) groups, and calculated the post-test probability of transition for each group and for group combinations using the odds ratio form of Bayes' rule. Combination of the three variable groups vastly improved the specificity of prediction (area under ROC=0.919, sensitivity=72.73%, specificity=96.43%). In this sample, our model identified over 70% of UHR patients who transitioned within 1 year, compared with 28% identified by standard UHR criteria. The model classified 77% of cases as very high or low risk (P>0.9, <0.1) based on history and clinical assessment, suggesting that a staged approach could be most efficient, reserving fatty-acid markers for 23% of cases remaining at intermediate probability following bedside interview. PMID:27648919

  8. Prediction of transition from ultra-high risk to first-episode psychosis using a probabilistic model combining history, clinical assessment and fatty-acid biomarkers.

    PubMed

    Clark, S R; Baune, B T; Schubert, K O; Lavoie, S; Smesny, S; Rice, S M; Schäfer, M R; Benninger, F; Feucht, M; Klier, C M; McGorry, P D; Amminger, G P

    2016-01-01

    Current criteria identifying patients with ultra-high risk of psychosis (UHR) have low specificity, and less than one-third of UHR cases experience transition to psychosis within 3 years of initial assessment. We explored whether a Bayesian probabilistic multimodal model, combining baseline historical and clinical risk factors with biomarkers (oxidative stress, cell membrane fatty acids, resting quantitative electroencephalography (qEEG)), could improve this specificity. We analyzed data of a UHR cohort (n=40) with a 1-year transition rate of 28%. Positive and negative likelihood ratios were calculated for predictor variables with statistically significant receiver operating characteristic curves (ROCs), which excluded oxidative stress markers and qEEG parameters as significant predictors of transition. We clustered significant variables into historical (history of drug use), clinical (Positive and Negative Symptoms Scale positive, negative and general scores and Global Assessment of Function) and biomarker (total omega-3, nervonic acid) groups, and calculated the post-test probability of transition for each group and for group combinations using the odds ratio form of Bayes' rule. Combination of the three variable groups vastly improved the specificity of prediction (area under ROC=0.919, sensitivity=72.73%, specificity=96.43%). In this sample, our model identified over 70% of UHR patients who transitioned within 1 year, compared with 28% identified by standard UHR criteria. The model classified 77% of cases as very high or low risk (P>0.9, <0.1) based on history and clinical assessment, suggesting that a staged approach could be most efficient, reserving fatty-acid markers for 23% of cases remaining at intermediate probability following bedside interview. PMID:27648919

  9. Estimating Bedrock Topography beneath Ice and Sediment Fillings in High Mountain Valleys: Preliminary Results from a Method Comparison Study

    NASA Astrophysics Data System (ADS)

    Mey, J.; Scherler, D.; Strecker, M. R.; Zeilinger, G.

    2012-12-01

    Knowledge about the thickness distribution of ice and sediment fillings in high mountain valleys is important for many applications in the fields of Hydrology, Geology, Glaciology, Geohazards and Geomorphology. However, direct geophysical measurements of ice/sediment thickness are laborious and require infrastructure and logistics that is often not available, particularly in remote mountain regions. In the past years, several methods have been developed to approximate the valley fill thicknesses primarily based on digital elevation data. In the case of sediment fillings, the thickness estimates are mostly based on simple morphometric considerations, whereas in the case of ice, more complex methods have been established using glacier mass balance and ice-flow dynamics. In this study we compare three of these methods that have been frequently applied in the past. These include a physically based approach for estimating ice-thickness distribution of valley glaciers using mass fluxes and flow mechanics. Further we adopt a method that uses the prediction capability of artificial neural networks (ANN) and we investigate a method that is based on the extrapolation of the slopes of the valley walls into the subsurface. We set up a test series in which all methods are applied to four glaciers and two sediment-filled valleys in the European Alps. The resulting bedrock topography derived from each method is checked against available ground truth data, comprising ground penetrating radar-, seismic reflection- and borehole measurements. Obviously, the method developed for estimation of ice-thickness is applicable only to the cases where valleys are occupied by ice, whereas the ANN approach and the slope extrapolation method are independent of the sort of valley fill. Thus a direct comparison is restricted to glacier settings. First results show that all methods can qualitatively reconstruct bedrock topography with typical overdeepenings and trough-shaped cross-profiles. Due to

  10. Ephemerality of discrete methane vents in lake sediments

    USGS Publications Warehouse

    Scandella, Benjamin P.; Pillsbury, Liam; Weber, Thomas; Ruppel, Carolyn; Hemond, Harold F.; Juanes, Ruben

    2016-01-01

    Methane is a potent greenhouse gas whose emission from sediments in inland waters and shallow oceans may both contribute to global warming and be exacerbated by it. The fraction of methane emitted by sediments that bypasses dissolution in the water column and reaches the atmosphere as bubbles depends on the mode and spatiotemporal characteristics of venting from the sediments. Earlier studies have concluded that hot spots—persistent, high-flux vents—dominate the regional ebullitive flux from submerged sediments. Here the spatial structure, persistence, and variability in the intensity of methane venting are analyzed using a high-resolution multibeam sonar record acquired at the bottom of a lake during multiple deployments over a 9 month period. We confirm that ebullition is strongly episodic, with distinct regimes of high flux and low flux largely controlled by changes in hydrostatic pressure. Our analysis shows that the spatial pattern of ebullition becomes homogeneous at the sonar's resolution over time scales of hours (for high-flux periods) or days (for low-flux periods), demonstrating that vents are ephemeral rather than persistent, and suggesting that long-term, lake-wide ebullition dynamics may be modeled without resolving the fine-scale spatial structure of venting.

  11. Ephemerality of discrete methane vents in lake sediments

    NASA Astrophysics Data System (ADS)

    Scandella, Benjamin P.; Pillsbury, Liam; Weber, Thomas; Ruppel, Carolyn; Hemond, Harold F.; Juanes, Ruben

    2016-05-01

    Methane is a potent greenhouse gas whose emission from sediments in inland waters and shallow oceans may both contribute to global warming and be exacerbated by it. The fraction of methane emitted by sediments that bypasses dissolution in the water column and reaches the atmosphere as bubbles depends on the mode and spatiotemporal characteristics of venting from the sediments. Earlier studies have concluded that hot spots—persistent, high-flux vents—dominate the regional ebullitive flux from submerged sediments. Here the spatial structure, persistence, and variability in the intensity of methane venting are analyzed using a high-resolution multibeam sonar record acquired at the bottom of a lake during multiple deployments over a 9 month period. We confirm that ebullition is strongly episodic, with distinct regimes of high flux and low flux largely controlled by changes in hydrostatic pressure. Our analysis shows that the spatial pattern of ebullition becomes homogeneous at the sonar's resolution over time scales of hours (for high-flux periods) or days (for low-flux periods), demonstrating that vents are ephemeral rather than persistent, and suggesting that long-term, lake-wide ebullition dynamics may be modeled without resolving the fine-scale spatial structure of venting.

  12. Studies on the diversity of arbuscular mycorrhizal fungi and the efficacy of two native isolates in a highly alkaline anthropogenic sediment.

    PubMed

    Oliveira, R S; Vosátka, M; Dodd, J C; Castro, P M L

    2005-12-01

    A field survey of the arbuscular mycorrhizal status of herbaceous plant species was conducted in a highly alkaline anthropogenic sediment resulting from the disposal of waste from an acetylene and polyvinyl chloride factory. Most plant species found at the site were mycorrhizal and the dominant mycotrophic plant species was Conyza bilbaoana. Fungal species richness was assessed by identification of spores extracted from the sediment and from continuously propagated trap pot cultures. All of the six species of arbuscular mycorrhizal fungi (AMF) found were from the genus Glomus. Glomus intraradices and G. mosseae were found in field-collected sediment samples and also occurred most frequently in trap cultures. To test the symbiotic effectiveness of these two fungi, seedlings of C. bilbaoana were inoculated with either native G. intraradices BEG163 or G. mosseae BEG198 and non-native G. intraradices BEG75 or G. mosseae BEG25 isolates in sterile and non-sterile sediment collected from the study site. All four isolates were able to colonise C. bilbaoana. However, AMF native to the target sediments were generally more effective than the non-native fungi in promoting plant establishment and growth under highly alkaline conditions. The non-native G. intraradices was, however, more effective than the non-native G. mosseae. The results of this study suggest the use of adapted AMF as inoculants for phytorestoration of alkaline anthropogenic-stressed sediments. PMID:16007472

  13. Episodic continental arc volcanism, tectonism and erosion recorded in stratigraphy and detrital zircon geochronology

    NASA Astrophysics Data System (ADS)

    Cao, W.; Paterson, S. R.

    2015-12-01

    Stratigraphic studies and detrital zircon geochronology of metamorphic host rock pendants of the Mesozoic Sierra Nevada arc in California show temporal correlations with episodic arc volcanism and tectonism, and have implications for our understanding of sources and sinks of recycled volcanic and sedimentary materials, as well as the paleo-geography and erosion history of an ancient continental arc. The Middle Triassic to Early Cretaceous stratigraphy of the metamorphic pendants shows alternating volcanic and sedimentary beds. The latter varies from rocks formed in high-energy terrestrial to low-energy shallow marine environments. Sedimentary textures also vary from poorly sorted volcanic-clast/breccia-rich to well-sorted fine-grained rocks and carbonates. We interpret these variations in stratigraphic records to reflect the waning and waxing of arc volcanism and tectonism, which controls erosion of source rocks, as well as elevation changes through isostastic balance. These in turn control the paleo-geography and depositional environments. Detrital zircon geochronology confirms our hypothesis. Detrital zircon ages of sedimentary rocks closely track the ages of volcanic/plutonic rocks formed immediately earlier and also include age signals of older igneous rocks and pre-arc basement, suggesting the erosion of igneous rocks of higher elevation during the magmatic flare-ups and deposition of these clasts afterwards. We conclude that episodic arc volcanism and tectonism play important roles on processes of surface erosion and sedimentation.

  14. Novel precipitated zirconia-based DGT technique for high-resolution imaging of oxyanions in waters and sediments.

    PubMed

    Guan, Dong-Xing; Williams, Paul N; Luo, Jun; Zheng, Jian-Lun; Xu, Hua-Cheng; Cai, Chao; Ma, Lena Q

    2015-03-17

    Water-sediment exchange is a fundamental component of oxyanion cycling in the environment. Yet, many of the (im)mobilization processes overlay complex spatial and temporal redox regimes that occur within millimeters of the interface. Only a few methods exist that can reliably capture these porewater fluxes, with the most popular being high-resolution diffusive gradients in thin films (HR-DGT). However, functionality of HR-DGT is restricted by the availability of suitable analyte binding agents within the sampler, which must be simple to cast and homogeneously distributed in the binding layer, exhibit adequate sorption capacities, be resistive to chemical change, and possess a very fine particle size (≤10 μm). A novel binding layer was synthesized to meet these requirements by in situ precipitation of zirconia into a precast hydrogel. The particle diameter≤0.2 μm of zirconia in this precipitated gel was uniform and at least 50-times smaller than the conventional molding approach. Further, this gel had superior binding and stability characteristics compared with the commonly used ferrihydrite HR-DGT technique and could be easily fabricated as an ultrathin gel (60 μm) for simultaneous oxygen imaging in conjunction with planar-optodes. Chemical imaging of anion and oxygen fluxes using the new sampler were evaluated on Lake Taihu sediments. PMID:25655234

  15. Identification of ambient PM 2.5 sources and analysis of pollution episodes in Detroit, Michigan using highly time-resolved measurements

    NASA Astrophysics Data System (ADS)

    Morishita, Masako; Keeler, Gerald J.; Kamal, Ali S.; Wagner, James G.; Harkema, Jack R.; Rohr, Annette C.

    2011-03-01

    Recent studies have indicated that the chemical composition of ambient PM 2.5, or fine particulate matter (aerodynamic diameter <2.5 μm), may be closely associated with the health effects induced by PM. Thus, identification of the sources of these components of PM 2.5 is critical to understanding source-specific health risks posed by PM 2.5. However, ambient PM measurements are typically 24-h average concentrations, masking the temporal variability of individual sources. These daily samples can limit our understanding of the associations between sources and observed heath effect parameters. In the present study, highly time-resolved sampling methods were utilized to characterize trace element concentrations and to obtain information on potential emission sources impacting a site in urban Detroit where a complex mixture of local point and mobile sources, as well as regional sources, is observed. Positive matrix factorization (PMF) was applied to 117 8-h PM 2.5 filter samples from which six major factors were extracted including secondary aerosol, gasoline-powered vehicles, iron and steel manufacturing, diesel-powered vehicles, refining, and sludge incineration. In addition, PMF was applied to 268 30-min PM 2.5 samples where six major source factors were identified including secondary aerosol, gasoline- and diesel-powered vehicles, iron and steel manufacturing, refining, sludge incineration, and cement/lime production. Contributions of various emission source factors and peak concentrations for each factor were characterized using detailed meteorology and, factor directionality analysis. Although some variations were observed between the 8-h integrated filter samples and the 30-min SEAS samples, the results from the two datasets are generally consistent, suggesting that 46% and 43% of ambient PM, respectively, is derived from local sources. These findings have advanced our understanding of temporal PM source-receptor relationships in a complex urban air shed.

  16. Variability of atmospheric aerosol and ozone concentrations at marine, urban, and high-altitude monitoring stations in southern Italy during the 2007 summer Saharan dust outbreaks and wildfire episodes.

    PubMed

    Bencardino, M; Sprovieri, F; Cofone, F; Pirrone, N

    2011-09-01

    In order to evaluate the spatial variation of aerosol (particulate matter with aerodynamic diameter < or = 10 microm [PM10]) and ozone (03) concentrations and characterize the atmospheric conditions that lead to 03 and PM10-rich episodes in southern Italy during summer 2007, an intensive sampling campaign was simultaneously performed, from middle of July to the end of August, at three ground-based sites (marine, urban, and high-altitude monitoring stations) in Calabria region. A cluster analysis, based on the prevailing air mass backward trajectories, was performed, allowing to discriminate the contribution of different air masses origin and paths. Results showed that both PM10 and 03 levels reached similar high values when air masses originated from the industrialized continental Europe as well as under the influence of wildfire emissions. Among natural sources, dust intrusion and wildfire events seem to involve a marked impact on the recorded data. Typical fair weather of Mediterranean summer and persisting anticyclone system at synoptic scale were indeed favorable conditions to the arrival of heavily dust-loaded air masses over three periods of consecutive days and more than half of the observed PM10 daily exceedances have been attributed to Saharan dust events. During the identified dust outbreaks, a consistent increase in PM10 levels with a concurrent decrease in 03 values was also observed and discussed.

  17. Comparison of three sequential extraction procedures for fractionation of arsenic from highly polluted mining sediments.

    PubMed

    Larios, Raquel; Fernández-Martínez, Rodolfo; Rucandio, Isabel

    2012-03-01

    Three sequential extraction procedures were evaluated for the study of fractionation of arsenic in environmental solid samples. The procedures considered were as follows: i) the standardized and widely recognised BCR procedure, conceived for the study of the partitioning of heavy metals; ii) the procedure developed by Manful, who adapted a phosphorus scheme for arsenic fractionation; and iii) a novel sequential extraction scheme especially devised for arsenic. The efficiency and suitability of these methods and the corresponding extraction steps for partitioning arsenic obtained from the most important solid forms were tested by application of the methods to real sediment samples heavily polluted by mining activity. Results showed the BCR scheme was inappropriate for arsenic fractionation. The procedure could, nevertheless, be a first approach for the assessment of arsenic partitioning, because its first extraction step can be regarded as adequate for the estimation of the most easily mobilizable arsenic. Although the Manful scheme results in a more differentiated arsenic pattern, some drawbacks arise from the lack of selectivity of some of the reagents used, for example overlapping of specific target phases, overestimation of adsorbed arsenate because of inadequate coprecipitation processes, and the inability to discriminate among amorphous and crystalline oxyhydroxides which are mainly responsible for arsenic retention. The novel procedure achieves the most suitable arsenic fractionation, because the main phases retaining arsenic are selectively targeted according to mobilization potential. In addition, the simplicity of its extraction steps would enable automation in a continuous flow scheme.

  18. A simple fiber-optic microprobe for high resolution light measurements: application in marine sediment

    NASA Technical Reports Server (NTRS)

    Jorgensen, B. B.; Des Marais, D. J.

    1986-01-01

    A fiber-optic microphobe is described which is inexpensive and simple to build and use. It consists of an 80-micrometers optical fiber which at the end is tapered down to a rounded sensing tip of 20-30-micrometers diameter. The detector is a hybrid photodiode/amplifier. The probe has a sensitivity of 0.01 microEinst m-2 s-1 and a spectral range of 300-1,100 nm. Spectral light gradients were measured in fine-grained San Francisco Bay sediment that had an undisturbed diatom coating on the surface. The photic zone of the mud was only 0.4 mm deep. Measured in situ spectra showed extinction maxima at 430-520, 620-630, 670, and 825-850 nm due to absorption by chlorophyll a, carotenoids, phycocyanin, and bacterio-chlorophyll a. Maximum light penetration in the visible range was found in both the violet and the red < or = 400 and > or = 700 nm.

  19. A simple fiber-optic microprobe for high resolution light measurements: application in marine sediment.

    PubMed

    Jorgensen, B B; Des Marais, D J

    1986-01-01

    A fiber-optic microphobe is described which is inexpensive and simple to build and use. It consists of an 80-micrometers optical fiber which at the end is tapered down to a rounded sensing tip of 20-30-micrometers diameter. The detector is a hybrid photodiode/amplifier. The probe has a sensitivity of 0.01 microEinst m-2 s-1 and a spectral range of 300-1,100 nm. Spectral light gradients were measured in fine-grained San Francisco Bay sediment that had an undisturbed diatom coating on the surface. The photic zone of the mud was only 0.4 mm deep. Measured in situ spectra showed extinction maxima at 430-520, 620-630, 670, and 825-850 nm due to absorption by chlorophyll a, carotenoids, phycocyanin, and bacterio-chlorophyll a. Maximum light penetration in the visible range was found in both the violet and the red < or = 400 and > or = 700 nm. PMID:11542043

  20. High-Magnitude (>Mw8.0) Megathrust Earthquakes and the Subduction of Thick Sediment, Tectonic Debris, and Smooth Sea Floor

    NASA Astrophysics Data System (ADS)

    Scholl, D. W.; Kirby, S. H.; von Huene, R.; Ryan, H. F.; Wells, R. E.

    2014-12-01

    INTRODUCTION: Ruff (1989, Pure and Applied Geophysics, v. 129) proposed that thick or excess sediment entering the subduction zone (SZ) smooths and strengthens the trench-parallel distribution of interplate coupling strength. This circumstance was conjectured to favor rupture continuation and the generation interplate thrusts (IPTs) of magnitude >Mw8.2. But, statistically, the correlation of excess sediment and high magnitude IPTs was deemed "less than compelling". NEW OBSERVATIONS: Using a larger and better vetted catalog of instrumental era (1899 through Jan. 2013) IPTs of magnitude Mw7.5 to 9.5 (n=176), and a far more accurate compilation of trench sediment thickness, we tested if, in fact, a compelling correlation exists between the occurrence of great IPTs and where thick (>1.0-1.5 km) vs thin (<1.0-0.5 km) sedimentary sections enter the SZ. Based on the new compilations, a statistically supported statement can be made that great megathrusts are most prone to nucleate at well-sedimented SZs. Despite the shorter (by 7500 km) global length of thick- (vs thin) sediment trenches, ~53% of all instrumental events of magnitude >Mw8.0, ~75% of events >Mw8.5, and 100% of IPTs >Mw9.0 occurred at thick-sediment trenches. No event >Mw9.0 ruptured at thin-sediment trenches, three super giant IPTs (1960 Chile Mw9.5, 1964 Alaska Mw9.2, and 2004 Sumatra Mw9.2) occurred at thick-sediment trenches. Significantly, however, large Mw8.0-9.0 events also commonly (n=23) nucleated at thin-sediment trenches. These IPTs are associated with the subduction of low-relief oceanic crust and where the debris of subduction erosion thickens the subduction channel separating the two plates. INFERENCES: Our new, larger, and corrected date compilations support the conjecture by Ruff (1989) that subduction of a thick section of sediment favors rupture continuation and nucleation of high magnitude Mw8.0 to 9.5 IPTs. This observation can be linked to a causative mechanism of sediment

  1. Predicting episodic memory formation for movie events

    PubMed Central

    Tang, Hanlin; Singer, Jed; Ison, Matias J.; Pivazyan, Gnel; Romaine, Melissa; Frias, Rosa; Meller, Elizabeth; Boulin, Adrianna; Carroll, James; Perron, Victoria; Dowcett, Sarah; Arellano, Marlise; Kreiman, Gabriel

    2016-01-01

    Episodic memories are long lasting and full of detail, yet imperfect and malleable. We quantitatively evaluated recollection of short audiovisual segments from movies as a proxy to real-life memory formation in 161 subjects at 15 minutes up to a year after encoding. Memories were reproducible within and across individuals, showed the typical decay with time elapsed between encoding and testing, were fallible yet accurate, and were insensitive to low-level stimulus manipulations but sensitive to high-level stimulus properties. Remarkably, memorability was also high for single movie frames, even one year post-encoding. To evaluate what determines the efficacy of long-term memory formation, we developed an extensive set of content annotations that included actions, emotional valence, visual cues and auditory cues. These annotations enabled us to document the content properties that showed a stronger correlation with recognition memory and to build a machine-learning computational model that accounted for episodic memory formation in single events for group averages and individual subjects with an accuracy of up to 80%. These results provide initial steps towards the development of a quantitative computational theory capable of explaining the subjective filtering steps that lead to how humans learn and consolidate memories. PMID:27686330

  2. Suspended-sediment dynamics in the tidal reach of a San Francisco Bay tributary

    USGS Publications Warehouse

    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.

  3. Suspended-sediment dynamics in the tidal reach of a San Francisco Bay tributary

    NASA Astrophysics Data System (ADS)

    Shellenbarger, Gregory G.; Downing-Kunz, Maureen A.; Schoellhamer, David H.

    2015-11-01

    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.

  4. Detrital zircons of deep-sea sediments of the Arctic ocean - key to the understanding of High Polar Arctic tectonics

    NASA Astrophysics Data System (ADS)

    Shokalsky, S.; Morozov, A.; Petrov, O.; Belyatsky, B.; Rekant, P.; Shevchenko, S.; Sergeev, S.

    2012-04-01

    appreciably different for Polar sample (200-450 Ma) and Geophysicists Spur (200, 300, 400-600 Ma). It is known, that formation of modern deep-sea sediments takes place mainly due to fluvial discharge (ca 90%), erosion of oceanic bedrocks and coastal beaches. Wind-borne component and extraterraneous dust are not significant (<1%). Transportation of continental material by icebergs (ice-rafted debris) is added to these sources in polar areas. Well-known Permian-Triassic sandstones of Arctic coast (including polar islands) are defined by the presence of Grenvillian age zircons - Canadian Arctic, Alaska, Greenland (Miller et al., 2006), while Jurassic-Cretaceous sandstones of the South Anjui Zone, Chukotka and New Siberian Islands of Russian Arctic (Miller et al., 2008) have clastic zircon with ages very similar to the obtained by us for deep-sea sediments. We suppose that modern deep-sea sediments were formed either due to ablation of these sandstones with distal transportation of detritus (highly unlikely), or due to weathering of similar rock of oceanic highs of Lomonosov Ridge. The last is more realistic because the similarity of the Lomonosov Ridge and north-east continental Arctic is proved by geophysical data (Jokat et al., 1992).

  5. Hypoxia in high-resolution sediment records: reconstructing the California Current Oxygen Minimum Zone on multi-decadal timescales

    NASA Astrophysics Data System (ADS)

    Moffitt, S. E.; Hill, T. M.

    2012-12-01

    The recent deglaciation event is an ideal laboratory to study the rapid expansion of Oxygen Minimum Zones (OMZs) and the ecological ramifications of such events. Santa Barbara Basin (SBB) sediments are high-resolution archives of seafloor ecosystems, recording both global-scale climate and regional-scale hydrographic events. Seafloor hypoxia in the California Current Ecosystem (CCE) is caused by OMZs in intermediate water depths (300-1200 m), and produces striking evidence in SBB sediment archives. We construct a vertical transect of proxies across SBB (34° 15'N, 119° 45'W) using a core from 418 m water depth (MV0811-15JC), and previously investigated cores from 440 m (MD02-2504) and 570 m (MD02-2503) water depths. Benthic foraminiferal assemblages and planktonic δ18O proxies were quantified at all three depths, while benthic invertebrate communities were quantified in the shallowest core at a 1-cm resolution (~10 years). This high-resolution invertebrate record provides a window into rapid, decadal-scale environmental change in continental margin ecosystems. Seafloor biodiversity is highly variable on 10-10^4 year timescales (across Protist, Mollusc, Arthropod and Echinoderm taxonomic groups), and is tightly coupled to both regional-scale environmental change and global-scale climate events. Additionally, we provide evidence that strongly hypoxic waters shoaled to <300 m water depth at Termination 1A (14.7 ka), implying that the upper boundary of the regional OMZ can expand >150 m on multi-decadal timescales. These data confirm that OMZs have rapidly expanded in the CCE during previous events of global-scale warming, and that continental margin seafloor biodiversity is variable on previously undescribed timescales.

  6. Branched glycerol dialkyl glycerol tetraethers in Arctic lake sediments: Sources and implications for paleothermometry at high latitudes

    NASA Astrophysics Data System (ADS)

    Peterse, Francien; Vonk, Jorien E.; Holmes, R. Max; Giosan, Liviu; Zimov, Nikita; Eglinton, Timothy I.

    2014-08-01

    Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are analyzed in different lakes of the Mackenzie (Canadian Arctic) and Kolyma (Siberian Arctic) River basins to evaluate their sources and the implications for brGDGT-based paleothermometry in high-latitude lakes. The comparison of brGDGT distributions and concentrations in the lakes with those in river suspended particulate matter, riverbank sediments, and permafrost material indicates that brGDGTs in Arctic lake sediments have mixed sources. In contrast to global observations, distributional offsets between brGDGTs in Arctic lakes and elsewhere in the catchment are minor, likely due to the extreme seasonality and short window of biological production at high latitudes. Consequently, both soil- and lake-calibrated brGDGT-based temperature proxies return sensible temperature estimates, even though the mean air temperature (MAT) in the Arctic is below the calibration range. The original soil-calibrated MBT-CBT (methylation of branched tetraethers-cyclisation of branched tetraethers) proxy generates MATs similar to those in the studied river basins, whereas using the recently revised MBT'-CBT calibration overestimates MAT. The application of the two global lake calibrations, generating summer air temperatures (SAT) and MAT, respectively, illustrates the influence of seasonality on the production of brGDGTs in lakes, as the latter overestimates actual MAT, whereas the SAT-based lake calibration accounts for this influence and consequently returns more accurate temperatures. Our results in principle support the application of brGDGT-based temperature proxies in high-latitude lakes in order to obtain long-term paleotemperature records for the Arctic, although the calibration and associated transfer function have to be selected with care.

  7. Episodic Memories in Anxiety Disorders: Clinical Implications

    PubMed Central

    Zlomuzica, Armin; Dere, Dorothea; Machulska, Alla; Adolph, Dirk; Dere, Ekrem; Margraf, Jürgen

    2014-01-01

    The aim of this review is to summarize research on the emerging role of episodic memories in the context of anxiety disorders (AD). The available literature on explicit, autobiographical, and episodic memory function in AD including neuroimaging studies is critically discussed. We describe the methodological diversity of episodic memory research in AD and discuss the need for novel tests to measure episodic memory in a clinical setting. We argue that alterations in episodic memory functions might contribute to the etiology of AD. We further explain why future research on the interplay between episodic memory function and emotional disorders as well as its neuroanatomical foundations offers the promise to increase the effectiveness of modern psychological treatments. We conclude that one major task is to develop methods and training programs that might help patients suffering from AD to better understand, interpret, and possibly actively use their episodic memories in a way that would support therapeutic interventions and counteract the occurrence of symptoms. PMID:24795583

  8. Fixation Mechanisms and Desorption Rates of Sorbed Cs in High-Level Waste Contaminated Subsurface Sediments: Implications to Future Behavior and In-Ground Stability

    SciTech Connect

    Zachara, John M.; McKinley, James P.; Ainsworth, Calvin C.; Serne, R. Jeff

    2001-06-01

    The high-yield fission product 137Cs is a major contaminant of the vadose zone at Hanford and other DOE sites. Over 100 kCi of 137Cs was discharged to the vadose zone in the S-SX tank farm at Hanford through the leakage of high-level waste from tanks SX-108 and SX-109. Although 137Cs is strongly sorbed by subsurface sediments, certain waste characteristics, such as high Na+, can expedite its migration and reduce its retardation to low values. This project is focused on defining the in-ground geochemistry of sorbed 137Cs released from high-level waste tanks, so that better future projections can be made of Cs mobility in the vadose zone. The project will study Cs-contaminated subsurface sediments from various Hanford tank farms to (1) determine the mineralogic and surface site residence of sorbed Cs in contaminated sediments varying in current Cs content and original waste composition, (2) establish geochemical factors and processes controlling Cs desorbability and desorption kinetics from contaminated sediment and Cs-enriched sediment particles, and (3) define and parameterize a kinetic model for Cs desorption that incorporates multi-site behavior and heterogeneous intraparticle Cs distribution.

  9. Effects of sediment and turbulence on alkaline phosphatase activity and photosynthetic activity of phytoplankton in the shallow hyper-eutrophic Lake Taihu, China.

    PubMed

    Ding, Yanqing; Qin, Boqiang; Xu, Hai; Wang, Xiaodong

    2016-08-01

    Sediments play important roles, as nutrient reservoir, especially in shallow lake ecosystem. The water column of large shallow lakes is often stable but also disturbed by turbulence causing resuspension of sediments. While considerable research has been carried out to investigate the influence of sediment resuspension on nutrient release, fewer studies have been done to understand the contribution of alkaline phosphatase activity (APA) in water as a response to the two conditions (turbulence and stability). Also, effects of the two lake conditions on photosynthetic efficiency of phytoplankton are still poorly understood. This study will evaluate the effect of these two conditions on photosynthetic efficiency and APA. Sediments used in the indoor experiments were collected from Zhushan Bay in Lake Taihu. Turbulence was generated by rotors to simulate the strong wind-induced disturbance in Lake Taihu. Results of the experiments showed that TN and TP in the stable and episodically turbulent conditions were not significantly different, with TN ranging from 1.34 to 1.90 mg/L and TP from 0.08 to 0.18 mg/L. Whereas, the soluble reactive phosphorus in the episodically turbulent condition was significantly higher than in the stable condition. Episodic turbulence could enhance P cycling by resuspending sediment-associated P, which alleviated algal P limitation. In stable conditions, P deficiency induced the production of high APA, which enhanced the availability of P. Although episodic turbulence could also cause increased algal biomass, photosynthetic efficiency of the algae was also affected not only by the nutrients but also by many other factors, especially light availability. Our results suggest that episodic turbulence is an important driver of biogeochemical cycling in large shallow hypertrophic lake ecosystem.

  10. Effects of sediment and turbulence on alkaline phosphatase activity and photosynthetic activity of phytoplankton in the shallow hyper-eutrophic Lake Taihu, China.

    PubMed

    Ding, Yanqing; Qin, Boqiang; Xu, Hai; Wang, Xiaodong

    2016-08-01

    Sediments play important roles, as nutrient reservoir, especially in shallow lake ecosystem. The water column of large shallow lakes is often stable but also disturbed by turbulence causing resuspension of sediments. While considerable research has been carried out to investigate the influence of sediment resuspension on nutrient release, fewer studies have been done to understand the contribution of alkaline phosphatase activity (APA) in water as a response to the two conditions (turbulence and stability). Also, effects of the two lake conditions on photosynthetic efficiency of phytoplankton are still poorly understood. This study will evaluate the effect of these two conditions on photosynthetic efficiency and APA. Sediments used in the indoor experiments were collected from Zhushan Bay in Lake Taihu. Turbulence was generated by rotors to simulate the strong wind-induced disturbance in Lake Taihu. Results of the experiments showed that TN and TP in the stable and episodically turbulent conditions were not significantly different, with TN ranging from 1.34 to 1.90 mg/L and TP from 0.08 to 0.18 mg/L. Whereas, the soluble reactive phosphorus in the episodically turbulent condition was significantly higher than in the stable condition. Episodic turbulence could enhance P cycling by resuspending sediment-associated P, which alleviated algal P limitation. In stable conditions, P deficiency induced the production of high APA, which enhanced the availability of P. Although episodic turbulence could also cause increased algal biomass, photosynthetic efficiency of the algae was also affected not only by the nutrients but also by many other factors, especially light availability. Our results suggest that episodic turbulence is an important driver of biogeochemical cycling in large shallow hypertrophic lake ecosystem. PMID:27151245

  11. The value of manual, event-based sediment sampling in local-scale sediment budget studies

    NASA Astrophysics Data System (ADS)

    Casagrande, J.; Watson, F.; Hager, J.; Anderson, T.; Newman, W.; Kozlowski, D.; Rocha, A.; Cole, W.; Larson, J.; Feikert, B.; Oakins, A.; Pierce, L.; Curry, B.

    2001-12-01

    Many contemporary sediment-budget studies lack two things: a first-hand understanding of the behavior of the system, and high-frequency data during storm events. In a study designed to understand sediment source areas, we have approach these deficiencies through manual sampling, almost exclusively during storm events. Manual sampling leads to better understanding. Frequently, the researcher finds oneself standing in streams observing phenomenon that contradict their a priori, desktop, or textbook-based perception of system behaviour. The case study we present reflects this in its observations of very high percolation rates, differing levels of land-stream connectivity under different sized events, and landowner intervention in water and sediment flux. In drier regions with episodic rainfall, event sampling is essential. During one season, we sampled 13 sites in a 316 km2 watershed about 50 times each. The sampling times were targeted to observe the start of the rising stage, many points immediately around the hydrograph peak, once or twice during the falling stage, and once after the return to pre-event conditions. The same number of samples spread over the year at regular intervals would lead to a grossly inaccurate representation of the system by the data. For example, event sampling permitted a reasonably accurate characterization of total annual load at each site. A simple, static model was then used to apportion total loads to different land use sources, and in-channel sources.

  12. Community Response to a Heavy Precipitation Event in High Temperature, Chemosynthetic Biofilms and Sediments

    NASA Astrophysics Data System (ADS)

    Meyer-Dombard, D. R.; Loiacono, S. T.; Shock, E.

    2012-12-01

    Coordinated analysis of the "Bison Pool" (BP) Environmental Genome and a complementary contextual geochemical dataset of ~75 parameters revealed biogeochemical cycling and metabolic and microbial community shifts in a Yellowstone National Park hot spring ecosystem (1). The >22m outflow of BP is a gradient of decreasing temperature, increasing dissolved oxygen, and changing availability of nutrients. Microbial life at BP transitions from a 92°C chemosynthetic community in the BP source pool to a 56°C photosynthetic mat community. Metagenomic data at BP showed the potential for both heterotrophic and autotrophic carbon metabolism (rTCA and acetyl-CoA cycles) in the highest temperature, chemosynthetic regions (1). This region of the outflow is dominated by Aquificales and Pyrococcus relatives, with smaller contributions of heterotrophic Bacteria. Following a 2h heavy precipitation event we observed an influx of exogenous organic material into the source pool supplied from the meadow surrounding the BP area. We sampled biomass and fluid at several locations within the outflow immediately following the event, and on several occasions for the next eight days. Elemental analysis and carbon and nitrogen isotopic analyses were conducted on biomass and sediment, and dissolved organic and inorganic carbon content and δ13C of fluids were analyzed. DNA and RNA were extracted, and following RT-PCR, nitrogen cycle functional gene expression was evaluated. Previous work at BP has shown that chemosynthetic biomass may carry isotopic signatures of fractionation during carbon fixation, via the acetyl-CoA and rTCA cycles (2). However, the addition of exogenous organic carbon during the rain event had an immediate and dramatic effect on the sediments and biofilms in the chemosynthetic zone of the outflow. Dissolved organic carbon was the highest measured in six years. Chemosynthetic biomass responded by incorporating the organic carbon. Carbon isotopic signatures in chemosynthetic

  13. A laboratory-incubated redox oscillation experiment to investigate Hg fluxes from highly contaminated coastal marine sediments (Gulf of Trieste, Northern Adriatic Sea).

    PubMed

    Emili, A; Carrasco, L; Acquavita, A; Covelli, S

    2014-03-01

    Mercury (Hg) mobility at the sediment-water interface was investigated during a laboratory incubation experiment conducted with highly contaminated sediments (13 μg g(-1)) of the Gulf of Trieste. Undisturbed sediment was collected in front of the Isonzo River mouth, which inflows Hg-rich suspended material originating from the Idrija (NW Slovenia) mining district. Since hypoxic and anoxic conditions at the bottom are frequently observed and can influence the Hg biogeochemical behavior, a redox oscillation was simulated in the laboratory, at in situ temperature, using a dark flux chamber. Temporal variations of several parameters were monitored simultaneously: dissolved Hg (DHg) and methylmercury (MeHg), O2, NH4 (+), NO3 (-) + NO2 (-), PO4 (3-), H2S, dissolved Mn(2+), dissolved inorganic and organic carbon (DIC and DOC). Under anoxic conditions, both Hg (665 ng m(2) day(-1)) and MeHg (550 ng m(2) day(-1)) fluxed from sediments into the water column, whereas re-oxygenation caused concentrations of MeHg and Hg to rapidly drop, probably due to re-adsorption onto Fe/Mn-oxyhydroxides and enhanced demethylation processes. Hence, during anoxic events, sediments of the Gulf of Trieste may be considered as an important source of DHg species for the water column. On the contrary, re-oxygenation of the bottom compartment mitigates Hg and MeHg release from the sediment, thus acting as a natural "defence" from possible interaction between the metal and the aquatic organisms.

  14. Episodic future thinking and episodic counterfactual thinking: Intersections between memory and decisions

    PubMed Central

    Schacter, Daniel L.; Benoit, Roland G.; De Brigard, Felipe; Szpunar, Karl K.

    2014-01-01

    This article considers two recent lines of research concerned with the construction of imagined or simulated events that can provide insight into the relationship between memory and decision making. One line of research concerns episodic future thinking, which involves simulating episodes that might occur in one’s personal future, and the other concerns episodic counterfactual thinking, which involves simulating episodes that could have happened in one’s personal past. We first review neuroimaging studies that have examined the neural underpinnings of episodic future thinking and episodic counterfactual thinking. We argue that these studies have revealed that the two forms of episodic simulation engage a common core network including medial parietal, prefrontal, and temporal regions that also supports episodic memory. We also note that neuroimaging studies have documented neural differences between episodic future thinking and episodic counterfactual thinking, including differences in hippocampal responses. We next consider behavioral studies that have delineated both similarities and differences between the two kinds of episodic simulation. The evidence indicates that episodic future and counterfactual thinking are characterized by similarly reduced levels of specific detail compared with episodic memory, but that the effects of repeatedly imagining a possible experience have sharply contrasting effects on the perceived plausibility of those events during episodic future thinking versus episodic counterfactual thinking. Finally, we conclude by discussing the functional consequences of future and counterfactual simulations for decisions. PMID:24373942

  15. Quantitative High-Pressure Liquid Chromatography-Fluorescence Determination of Some Important Lower Fatty Acids in Lake Sediments

    PubMed Central

    Hordijk, Kees A.; Cappenberg, Thomas E.

    1983-01-01

    For the quantitative determination of traces of fatty acids in pore water, several gas and liquid chromatographic methods were tested and discussed. Direct determination by gas-liquid chromatography with the use of formic acid-saturated carrier gas was found to be the least laborious method, but it is only recommended for the determination of volatile acids such as acetate and higher homologs. For the determination of lactate and formate, a derivatization procedure is necessary. The determination of these acids as phenacyl or benzyl esters was complicated by contaminants in the reagents. For this reason, a high-pressure liquid chromatography procedure with 4-bromomethyl-7-methoxycoumarin as a fluorescent labeling reagent is preferred. With this method, lactic, acetic, and formic acids could be demonstrated simultaneously at the nanogram level in 5-ml samples. Profiles of these acids in the sediment of Lake Vechten were measured, and they showed correlations with sulfate-reducing and methanogenic bacterial activities. PMID:16346362

  16. Depositional and structural evolution of the Middle Miocene depositional episode, east-central Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Combellas Bigott, Ricardo Ignacio

    Two widespread, transgressive deposits associated with the faunal top Amphistegina B (15.5 Ma) and Textularia W (12.1 Ma) define the Middle Miocene depositional episode. An extensive stratigraphic correlation framework established in this study allowed tracing of the middle Miocene sediment dispersal system from the shelf through the slope to the basin floor in the complex paleogeography of the east-central Gulf of Mexico. The Middle Miocene depositional episode is recorded in four genetic cycles (˜1 to 2 Ma), bounded by regional maximum flooding surfaces in the shelf and shelf margin setting, and three equivalent seismic sequences punctuated by condensed sections in the slope and basin floor. Two principal, long-lived extrabasinal fluvial/delta axes, the ancestral Mississippi and the Tennessee systems, provided the bulk of sediments that infilled the middle Miocene depocenters. Salt-related structural provinces controlled the configuration of the depocenters. Structural linked systems, dominated by gravity spreading, and a minibasin province, driven by differential subsidence, were established during the Middle Miocene depositional episode. Sediment supply coupled with wave energy flux, high-frequency sea-level changes, and salt tectonism determined the time and space distribution of progradation, aggradation, and retrogradation of system tracts. Middle Miocene shelf margins have prograded 20 to 40 miles from the relict lower Miocene shelf margin. Two depositional systems tracts characterize the constructional shelf margin: (1) a mixed-load fluvial-dominated platform delta/shelf-margin delta/delta-fed apron systems tract; and (2) a strandplain/shelf/muddy slope systems tract. However, the constructional, offlapping shelf margin systems were locally punctuated by a large-scale phase of retreat and erosion, named the Harang collapse system, in which a large volume of sediments bypassed the shelf margin to be deposited on the slope and basin floor. The Harang

  17. Association between impaired brain activity and volume at the sub-region of Broca's area in ultra-high risk and first-episode schizophrenia: A multi-modal neuroimaging study.

    PubMed

    Iwashiro, Norichika; Koike, Shinsuke; Satomura, Yoshihiro; Suga, Motomu; Nagai, Tatsuya; Natsubori, Tatsunobu; Tada, Mariko; Gonoi, Wataru; Takizawa, Ryu; Kunimatsu, Akira; Yamasue, Hidenori; Kasai, Kiyoto

    2016-04-01

    Recent studies have suggested that functional abnormalities in Broca's area, which is important in language production (speech and thoughts before speech), play an important role in the pathophysiology of schizophrenia. While multi-modal approaches have proved useful in revealing the specific pathophysiology of psychosis, the association of functional abnormalities with gray matter volume (GMV) here in subjects with an ultra-high risk (UHR) of schizophrenia, those with first-episode schizophrenia (FES), and healthy controls has yet to be clarified. Therefore, the relationship between cortical activity measured using functional near-infrared spectroscopy (fNIRS) during a verbal fluency task, and GMV in the Broca's area assessed using a manual tracing in magnetic resonance imaging (MRI), which considers individual structural variation, was examined for 57 subjects (23 UHR/18 FES/16 controls). The UHR and FES group showed significantly reduced brain activity compared to control group in the left pars triangularis (PT) (P=.036, .003, respectively). Furthermore in the FES group, the reduced brain activity significantly positively correlated with the volume in the left PT (B=0.29, P=.027), while significant negative association was evident for all subjects (B=-0.18, P=.010). This correlation remained significant after adjusting for antipsychotics dosage, and voxel-wise analysis could not detect any significant correlation between impaired cortical activity and volume. The significant relationship between neural activity and GMV in the left PT may reflect a specific pathophysiology related to the onset of schizophrenia. PMID:26873807

  18. Aquatic Sediments.

    ERIC Educational Resources Information Center

    Sanville, W. D.; And Others

    1978-01-01

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

  19. Influence of anthropogenic inputs and a high-magnitude flood event on metal contamination pattern in surface bottom sediments from the Deba River urban catchment.

    PubMed

    Martínez-Santos, Miren; Probst, Anne; García-García, Jon; Ruiz-Romera, Estilita

    2015-05-01

    The purpose of this study was to assess the influence of anthropogenic factors (infrastructure construction and industrial and wastewater inputs) and hydrological factors (high-magnitude flood events) on metal and organic contamination and on the source variability of sediments taken from the Deba River and its tributaries. The pollution status was evaluated using a sequential extraction procedure (BCR 701), enrichment factor, individual and global contamination factors and a number of statistical analysis methods. Zn, Cu and Cr were found to have significant input from anthropogenic sources, with moderately severe enrichment, together with an extremely high potential risk of contamination. The principal scavenger of Cu and Cr was organic matter, whereas Zn was uniformly distributed among all non-residual fractions. For Fe, the anthropogenic contribution was more obviously detected in bulk sediments (<2 mm) than in fine fractions (<63 μm). Finally, the recent construction of a rail tunnel traversing Wealden Facies evaporites, together with intense rainfalls, was the main reason for the change in the source variability of bottom sediments and metal distribution in headwaters. The occurrence of a high-magnitude flood event resulted in a washout of the river bed and led to a general decrease in fine-grained sediment and metal concentrations in labile fractions of channel-bottom sediments, and a consequent downstream transfer of the pollution.

  20. Influence of anthropogenic inputs and a high-magnitude flood event on metal contamination pattern in surface bottom sediments from the Deba River urban catchment.

    PubMed

    Martínez-Santos, Miren; Probst, Anne; García-García, Jon; Ruiz-Romera, Estilita

    2015-05-01

    The purpose of this study was to assess the influence of anthropogenic factors (infrastructure construction and industrial and wastewater inputs) and hydrological factors (high-magnitude flood events) on metal and organic contamination and on the source variability of sediments taken from the Deba River and its tributaries. The pollution status was evaluated using a sequential extraction procedure (BCR 701), enrichment factor, individual and global contamination factors and a number of statistical analysis methods. Zn, Cu and Cr were found to have significant input from anthropogenic sources, with moderately severe enrichment, together with an extremely high potential risk of contamination. The principal scavenger of Cu and Cr was organic matter, whereas Zn was uniformly distributed among all non-residual fractions. For Fe, the anthropogenic contribution was more obviously detected in bulk sediments (<2 mm) than in fine fractions (<63 μm). Finally, the recent construction of a rail tunnel traversing Wealden Facies evaporites, together with intense rainfalls, was the main reason for the change in the source variability of bottom sediments and metal distribution in headwaters. The occurrence of a high-magnitude flood event resulted in a washout of the river bed and led to a general decrease in fine-grained sediment and metal concentrations in labile fractions of channel-bottom sediments, and a consequent downstream transfer of the pollution. PMID:25647464

  1. The characteristics of Beijing aerosol during two distinct episodes: impacts of biomass burning and fireworks.

    PubMed

    Cheng, Yuan; Engling, Guenter; He, Ke-bin; Duan, Feng-kui; Du, Zhen-yu; Ma, Yong-liang; Liang, Lin-lin; Lu, Zi-feng; Liu, Jiu-meng; Zheng, Mei; Weber, Rodney J

    2014-02-01

    The chemical composition of Beijing aerosol was measured during summer and winter. Two distinct episodes were identified. Water-soluble potassium (K(+)) increased significantly during the firework episode in winter with an episode to non-episode ratio of 4.97, whereas the biomass burning (BB) episode in summer was characterized by high episode to non-episode ratios of levoglucosan (6.38) and K(+) (6.90). The BB and firework episodes had only a minor influence on the water-soluble OC (organic carbon) to OC ratio. Based on separate investigations of episode and non-episode periods, it was found that: (i) sulfate correlated strongly with both relative humidity and nitrate during the typical winter period presumably indicating the importance of the aqueous-phase oxidation of sulfur dioxide by nitrogen dioxide, (ii) oxalate and WSOC during both winter and summer in Beijing were mainly due to secondary formation, and (iii) high humidity can significantly enhance the formation potential of WSOC in winter.

  2. The characteristics of Beijing aerosol during two distinct episodes: impacts of biomass burning and fireworks.

    PubMed

    Cheng, Yuan; Engling, Guenter; He, Ke-bin; Duan, Feng-kui; Du, Zhen-yu; Ma, Yong-liang; Liang, Lin-lin; Lu, Zi-feng; Liu, Jiu-meng; Zheng, Mei; Weber, Rodney J

    2014-02-01

    The chemical composition of Beijing aerosol was measured during summer and winter. Two distinct episodes were identified. Water-soluble potassium (K(+)) increased significantly during the firework episode in winter with an episode to non-episode ratio of 4.97, whereas the biomass burning (BB) episode in summer was characterized by high episode to non-episode ratios of levoglucosan (6.38) and K(+) (6.90). The BB and firework episodes had only a minor influence on the water-soluble OC (organic carbon) to OC ratio. Based on separate investigations of episode and non-episode periods, it was found that: (i) sulfate correlated strongly with both relative humidity and nitrate during the typical winter period presumably indicating the importance of the aqueous-phase oxidation of sulfur dioxide by nitrogen dioxide, (ii) oxalate and WSOC during both winter and summer in Beijing were mainly due to secondary formation, and (iii) high humidity can significantly enhance the formation potential of WSOC in winter. PMID:24275313

  3. Cabergoline-induced manic episode: case report

    PubMed Central

    Yüksel, Rabia Nazik; Elyas Kaya, Zeynep; Dilbaz, Nesrin; Cingi Yirün, Merve

    2016-01-01

    Cabergoline is an orally administered synthetic dopamine agonist that is used for the treatment of hyperprolactinemia, Parkinson’s disease and antipsychotic-induced prolactin elevation. One of the main characteristics of cabergoline is its long duration of effect. It is highly effective in suppressing prolactin levels up to 21 days after a single 1 mg oral dose. The prolonged elimination half-life offers an advantage of once-daily dosing, but it might be a handicap in terms of washout of adverse effects such as psychosis. Cabergoline has been associated with adverse reactions consistent with other dopaminergic agonists including cardiovascular, gastrointestinal and neuropsychiatric effects. It is known that dopaminergic treatment is a remarkable risk factor for psychosis. A number of reports implicate dopamine agonists in the development of psychosis, but there is no knowledge in the literature of dopamine agonist-induced mania. In this case, we report the first manic episode occurring after cabergoline use for hyperprolactinemia treatment. In susceptible individuals, cabergoline can cause manic episodes and cabergoline should be used more carefully considering the risk–benefit ratio. PMID:27354910

  4. A bird-brain view of episodic memory.

    PubMed

    Rattenborg, N C; Martinez-Gonzalez, D

    2011-09-12

    In humans, the hippocampus plays a critical role in the formation of episodic memories. Although non-human animals are unable to report whether they also re-experience past events, at least some birds and mammals exhibit 'episodic-like' memory characterized by an ability to recall what happened where and when. In mammals, the hippocampus interacts closely with virtually the entire neocortex to form episodic-like memories. The hippocampus receives highly processed information from high-order association areas, and thereby the rest of the neocortex. Distinct neurophysiological hippocampal rhythms (theta and sharp-wave ripples) coordinate activity between the hippocampus and high-order association areas during the encoding and retrieval of information contributing to episodic-like memories. Although recent studies have demonstrated that food hoarding birds are able to remember what food they hid where and when, neuroanatomical and neurophysiological studies suggest that there may be a fundamental difference between episodic-like memory in birds and mammals. In contrast to the mammalian hippocampus, the avian hippocampus only receives visual and olfactory input; most high-order association areas in the avian brain involved in performing functions similar to those performed by neocortical association areas do not project to the hippocampus or structures providing it with direct input. Consistent with this neuroanatomical difference, mammalian-like rhythms involved in communicating between the hippocampus and neocortical high-order association areas have not been found in birds. Collectively, this suggests that information contributing to episodic-like memory is more limited and processed in a different manner in birds when compared to mammals.

  5. Relating the ability of mallards to ingest high levels of sediment to potential contaminant exposure in waterfowl

    USGS Publications Warehouse

    Heinz, Gary H.; Beyer, W. Nelson; Hoffman, David J.; Audet, Daniel J.

    2010-01-01

    When waterfowl feed from the bottom of bodies of water, they sometimes ingest sediments along with their food, and this sediment can be a major source of contaminants. Learning how much sediment waterfowl can consume in their diet and still maintain their health would be helpful in assessing potential threats from contaminants in sediment. In a controlled laboratory study the maximum tolerated percentage of sediment in the diet of mallards (Anas platyrhynchos) was measured. When fed a well-balanced commercial avian diet, 50, 60, or 70% sediment in the diet on a dry-weight basis did not cause weight loss over a two-week period. Ducks fed this same commercial diet, but containing 80 or 90% sediment, lost 8.6 and 15.6% of their body weight, respectively, in the first week on those diets. After factoring in the ability of the mallards to sieve out some of the sediment from their diet before swallowing it, we concluded that the mallards could maintain their health even when approximately half of what they swallowed, on a dry-weight basis, was sediment.

  6. Neural modeling of episodic memory: encoding, retrieval, and forgetting.

    PubMed

    Wang, Wenwen; Subagdja, Budhitama; Tan, Ah-Hwee; Starzyk, Janusz A

    2012-10-01

    This paper presents a neural model that learns episodic traces in response to a continuous stream of sensory input and feedback received from the environment. The proposed model, based on fusion adaptive resonance theory (ART) network, extracts key events and encodes spatio-temporal relations between events by creating cognitive nodes dynamically. The model further incorporates a novel memory search procedure, which performs a continuous parallel search of stored episodic traces. Combined with a mechanism of gradual forgetting, the model is able to achieve a high level of memory performance and robustness, while controlling memory consumption over time. We present experimental studies, where the proposed episodic memory model is evaluated based on the memory consumption for encoding events and episodes as well as recall accuracy using partial and erroneous cues. Our experimental results show that: 1) the model produces highly robust performance in encoding and recalling events and episodes even with incomplete and noisy cues; 2) the model provides enhanced performance in a noisy environment due to the process of forgetting; and 3) compared with prior models of spatio-temporal memory, our model shows a higher tolerance toward noise and errors in the retrieval cues.

  7. Maar Lake Sediments in the Mediterranean: High-Resolution Archives for Tephra Recording and Paleoenvironmental Reconstruction - a Case Study From Lago Grande di Monticchio (Southern Italy)

    NASA Astrophysics Data System (ADS)

    Negendank, J. F.; Wulf, S.; Brauer, A.; Mingram, J.

    2001-12-01

    Maar lake deposits with sedimentation rates of one or two order of magnitude higher than marine records are excellent archives for the preservation of annual laminations (varves) and thus make available information of the past with a high temporal resolution. In the Mediterranean, such archives are known from maar and crater lakes situated within Quaternary volcanic fields of the Italian Peninsula. Because of the vicinity to high-explosive volcanoes - most of them characterised by numerous tephra producing events during the Late Quaternary - sediments of these sites additionally provide considerable potential for tephrochronological and tephrostratigraphical studies. The maar lake Lago Grande di Monticchio (Mt. Vulture, Basilicata) has turned out to be one of the most suitable sites in Europe. On the one hand, intensive sedimentological, geochemical, palynological and palaeomagnetic studies on numerous laminated sediment cores spanning the last 101 kyr have demonstrated the great potential for palaeoenvironmental reconstruction. The results of these studies indicate a highly variable environment during the last glacial / interglacial cycle with numerous short and abrupt changes, that can be correlated to rapid climate changes recognized in ice-core and deep-sea records. For such comparisons independent chronologies are required. Regarding the sediment record of Lago Grande di Monticchio a varve-supported sedimentation rate chronology has been established based on the counting of annual laminations and interpolation of sedimentation rates for non-varved sections. This chronology has been confirmed by a high-resolution tephrochronology, numerous radiocarbon datings and three 40Ar/39Ar datings on prominent tephra layers. In addition to its value as a high-resolution palaeoclimatic archive, the Monticchio record has become a key position for inter-site correlation in the eastern Mediterranean. This is mainly due to the large number of intercalated tephra layers (n=344

  8. Spatial Distribution of Eukaryotic Communities Using High-Throughput Sequencing Along a Pollution Gradient in the Arsenic-Rich Creek Sediments of Carnoulès Mine, France.

    PubMed

    Volant, A; Héry, M; Desoeuvre, A; Casiot, C; Morin, G; Bertin, P N; Bruneel, O

    2016-10-01

    Microscopic eukaryotes play a key role in ecosystem functioning, but their diversity remains largely unexplored in most environments. To advance our knowledge of eukaryotic microorganisms and the factors that structure their communities, high-throughput sequencing was used to characterize their diversity and spatial distribution along the pollution gradient of the acid mine drainage at Carnoulès (France). A total of 16,510 reads were retrieved leading to the identification of 323 OTUs after normalization. Phylogenetic analysis revealed a quite diverse eukaryotic community characterized by a total of eight high-level lineages including 37 classes. The majority of sequences were clustered in four main groups: Fungi, Stramenopiles, Alveolata and Viridiplantae. The Reigous sediments formed a succession of distinct ecosystems hosting contrasted eukaryotic communities whose structure appeared to be at least partially correlated with sediment mineralogy. The concentration of arsenic in the sediment was shown to be a significant factor driving the eukaryotic community structure along this continuum.

  9. Spatial Distribution of Eukaryotic Communities Using High-Throughput Sequencing Along a Pollution Gradient in the Arsenic-Rich Creek Sediments of Carnoulès Mine, France.

    PubMed

    Volant, A; Héry, M; Desoeuvre, A; Casiot, C; Morin, G; Bertin, P N; Bruneel, O

    2016-10-01

    Microscopic eukaryotes play a key role in ecosystem functioning, but their diversity remains largely unexplored in most environments. To advance our knowledge of eukaryotic microorganisms and the factors that structure their communities, high-throughput sequencing was used to characterize their diversity and spatial distribution along the pollution gradient of the acid mine drainage at Carnoulès (France). A total of 16,510 reads were retrieved leading to the identification of 323 OTUs after normalization. Phylogenetic analysis revealed a quite diverse eukaryotic community characterized by a total of eight high-level lineages including 37 classes. The majority of sequences were clustered in four main groups: Fungi, Stramenopiles, Alveolata and Viridiplantae. The Reigous sediments formed a succession of distinct ecosystems hosting contrasted eukaryotic communities whose structure appeared to be at least partially correlated with sediment mineralogy. The concentration of arsenic in the sediment was shown to be a significant factor driving the eukaryotic community structure along this continuum. PMID:27535039

  10. An improved cell separation technique for marine subsurface sediments: applications for high-throughput analysis using flow cytometry and cell sorting.

    PubMed

    Morono, Yuki; Terada, Takeshi; Kallmeyer, Jens; Inagaki, Fumio

    2013-10-01

    Development of an improved technique for separating microbial cells from marine sediments and standardization of a high-throughput and discriminative cell enumeration method were conducted. We separated microbial cells from various types of marine sediment and then recovered the cells using multilayer density gradients of sodium polytungstate and/or Nycodenz, resulting in a notably higher percent recovery of cells than previous methods. The efficiency of cell extraction generally depends on the sediment depth; using the new technique we developed, more than 80% of the total cells were recovered from shallow sediment samples (down to 100 meters in depth), whereas ~50% of cells were recovered from deep samples (100-365 m in depth). The separated cells could be rapidly enumerated using flow cytometry (FCM). The data were in good agreement with those obtained from manual microscopic direct counts over the range 10(4)-10(8) cells cm(-3). We also demonstrated that sedimentary microbial cells can be efficiently collected using a cell sorter. The combined use of our new cell separation and FCM/cell sorting techniques facilitates high-throughput and precise enumeration of microbial cells in sediments and is amenable to various types of single-cell analyses, thereby enhancing our understanding of microbial life in the largely uncharacterized deep subseafloor biosphere. PMID:23731283

  11. An improved cell separation technique for marine subsurface sediments: applications for high-throughput analysis using flow cytometry and cell sorting

    PubMed Central

    Morono, Yuki; Terada, Takeshi; Kallmeyer, Jens; Inagaki, Fumio

    2013-01-01

    Summary Development of an improved technique for separating microbial cells from marine sediments and standardization of a high-throughput and discriminative cell enumeration method were conducted. We separated microbial cells from various types of marine sediment and then recovered the cells using multilayer density gradients of sodium polytungstate and/or Nycodenz, resulting in a notably higher percent recovery of cells than previous methods. The efficiency of cell extraction generally depends on the sediment depth; using the new technique we developed, more than 80% of the total cells were recovered from shallow sediment samples (down to 100 meters in depth), whereas ∼ 50% of cells were recovered from deep samples (100–365 m in depth). The separated cells could be rapidly enumerated using flow cytometry (FCM). The data were in good agreement with those obtained from manual microscopic direct counts over the range 104–108 cells cm−3. We also demonstrated that sedimentary microbial cells can be efficiently collected using a cell sorter. The combined use of our new cell separation and FCM/cell sorting techniques facilitates high-throughput and precise enumeration of microbial cells in sediments and is amenable to various types of single-cell analyses, thereby enhancing our understanding of microbial life in the largely uncharacterized deep subseafloor biosphere. PMID:23731283

  12. Analysis of estrogens in sediment from a sewage-impacted urban estuary using high-performance liquid chromatography/time-of-flight mass spectrometry.

    PubMed

    Reddy, Sharanya; Brownawell, Bruce J

    2005-05-01

    We describe a highly selective and sensitive method for determination of estrone (E1) and beta-estradiol (E2) in sediments, using high-performance liquid chromatography/time-of-flight (HPLC-ToF) mass spectrometry. The method involved sequential cleanup of sediment extracts over solid phase extraction cartridges, normal phase HPLC, and immunoaffinity extraction, which combine to remove coeluting matrix interferences. Resulting method detection limits (0.03 and 0.04 ng/g for E1 and E2, respectively) are sufficient to determine E1 and E2 in estuarine sediments collected from sewage-impacted Jamaica Bay (New York, NY, USA). The ToF analyzer has a higher resolution (>6,000) than quadrupole mass analyzers and can provide accurate mass estimation to within 2 mDa, which helped in distinguishing steroids from isobaric matrix interferences. The E1 and E2 were internally mass calibrated with respect to their coeluting surrogate standards, and the mass measurement error was between 1.1 and 1.4 mDa. The levels of E1 and E2 ranged between 0.07 to 2.52 and 0.05 to 0.53 ng/g, respectively. The measured concentrations of steroids in sediments correlated closely with other wastewater tracers. Despite the low concentrations of sediment-associated estrogens, their predicted estrogenic potency exceeds that of other measured estrogenic contaminants. PMID:16110980

  13. Ultra-high-resolution paleoenvironmental records via direct laser-based analysis of lipid biomarkers in sediment core samples

    PubMed Central

    Wörmer, Lars; Elvert, Marcus; Fuchser, Jens; Lipp, Julius Sebastian; Buttigieg, Pier Luigi; Zabel, Matthias; Hinrichs, Kai-Uwe

    2014-01-01

    Marine microorganisms adapt to their habitat by structural modification of their membrane lipids. This concept is the basis of numerous molecular proxies used for paleoenvironmental reconstruction. Archaeal tetraether lipids from ubiquitous marine planktonic archaea are particularly abundant, well preserved in the sedimentary record and used in several molecular proxies. We here introduce the direct, extraction-free analysis of these compounds in intact sediment core sections using laser desorption ionization (LDI) coupled to Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). LDI FTICR-MS can detect the target lipids in single submillimeter-sized spots on sediment sections, equivalent to a sample mass in the nanogram range, and could thus pave the way for biomarker-based reconstruction of past environments and ecosystems at subannual to decadal resolution. We demonstrate that ratios of selected archaeal tetraethers acquired by LDI FTICR-MS are highly correlated with values obtained by conventional liquid chromatography/MS protocols. The ratio of the major archaeal lipids, caldarchaeol and crenarchaeol, analyzed in a 6.2-cm intact section of Mediterranean sapropel S1 at 250-µm resolution (∼4-y temporal resolution), provides an unprecedented view of the fine-scale patchiness of sedimentary biomarker distributions and the processes involved in proxy signal formation. Temporal variations of this lipid ratio indicate a strong influence of the ∼200-y de Vries solar cycle on reconstructed sea surface temperatures with possible amplitudes of several degrees, and suggest signal amplification by a complex interplay of ecological and environmental factors. Laser-based biomarker analysis of geological samples has the potential to revolutionize molecular stratigraphic studies of paleoenvironments. PMID:25331871

  14. Sediment accumulation rates and high-resolution stratigraphy of recent fluvial suspension deposits in various fluvial settings, Morava River catchment area, Czech Republic

    NASA Astrophysics Data System (ADS)

    Sedláček, Jan; Bábek, Ondřej; Kielar, Ondřej

    2016-02-01

    We present a comprehensive study concerning sedimentary processes in fluvial sediment traps within the Morava River catchment area (Czech Republic) involving three dammed reservoirs, four meanders and oxbow lakes, and several natural floodplain sites. The objective of the study was to determine sediment accumulation rates (SAR), estimate erosion rates, calculating these using a combination of the 137Cs method and historical data. Another purpose of this study was to provide insight into changing erosion and accumulation rates over the last century. Extensive water course modifications were carried out in the Morava River catchment area during the twentieth century, which likely affected sedimentation rates along the river course. Other multiproxy stratigraphic methods (X-ray densitometry, magnetic susceptibility, and visible-light reflectance spectrometry) were applied to obtain additional information about sediment infill. Sediment stratigraphy revealed distinct distal-to-proximal patterns, especially in reservoirs. Granulometrically, silts and sandy silts prevailed in sediments. Oxbow lakes and meanders contained larger amounts of clay and organic matter, which is the main difference between them and reservoirs. Pronounced 137Cs peaks were recorded in all studied cores (maximum 377 Bq·kg- 1), thus indicating Chernobyl fallout from 1986 or older events. Calculated sediment accumulation rates were lowest in distal parts of reservoirs (0.13-0.58 cm/y) and floodplains (0.45-0.88 cm/y), moderately high rates were found in proximal parts of reservoirs and oxbow lakes (2.27-4.4 cm/y), and the highest rates in some oxbow lakes located near the river (6-8 cm/y). The frequency of the inundation still can be high in some natural areas as in the Litovelské Pomoraví protected area, whereas the decreasing frequency of the inundation in other modified parts can contribute to a lower sedimentation rate. The local effects such as difference between SARs in oxbow lakes and

  15. Upper Mississippi River Floods During Late Holocene Warm Episodes: Implications for the 21st Century

    NASA Astrophysics Data System (ADS)

    Knox, J. C.

    2002-12-01

    Instrument records for the Upper Mississippi River (UMR) show that the mean and variance of annual maximum flood magnitudes increased during the late 20th century in relation to their long-term average values for the period from about 1880 to present. These increases parallel an observed global warming trend over the same period and the similarity supports the idea that global warming enhances the hydrologic cycle of the UMR watershed. However, a longer perspective from geologic evidence shows a more complex relationship between UMR floods and warm climate episodes whereby large floods tend to be especially frequent at the beginning of warm episodes and/or during short duration warm episodes. A proxy record of floods representing the last few thousand years is retained in the alluvial sedimentary record that underlies low terraces and the floodplain of the UMR. The bed sediments of the UMR and its floodplain secondary channels are dominated by sand,whereas large volumes of silt and clay are transported as suspended load,especially during floods.Turbulent energy of floods delivers sediment onto floodplain and low terraces resulting in vertical strata of various mixtures of sand, silt, and clay that reflect the specific energy of the floods and define individual flood depositional units. Deposits associated with periods of small floods normally are finer textured and are associated with relatively higher magnitudes of organic carbon than deposits associated with large floods. Application of radiocarbon dating to alluvial deposits of the UMR on Wisconsin's western border indicates that exceptionally large floods occurred about 4700, 2500-2200, 1800-1500, 1280, 1000-750, and 600-300 calendar years B.P. These ages, in many cases, are broadly similar to the ages of about 4800-4300, 1750-1580, 1250-1050, 950-750, and 550-450 calendar years B.P. that other researchers have recognized as times of relative warming and major droughts for nearby areas marginal to the UMR

  16. Late Quaternary sapropel sediments in the eastern Mediterranean Sea: Faunal variations and chronology

    NASA Astrophysics Data System (ADS)

    Muerdter, David R.; Kennett, James P.; Thunell, Robert C.

    1984-05-01

    Distinctive planktonic foraminiferal assemblages which characterize particular late Quaternary sapropel layers in deep basin sediments from the eastern Mediterranean Sea have been identified using cluster analysis. Three distinct clusters allow for identification and intercore correlation of the nine sapropels deposited during the last 250,000 yr. Cluster 1, representing sapropel layers S1 and S9, exhibits low abundances of Neogloboquadrina dutertrei and high abundances of Globigerinoides ruber; Cluster 2, which groups S3, S5, and S7, contains high abundances of G. ruber, N. dutertrei, and Globigerina bulloides, and Cluster 3, which includes samples from S4, S6, and S8, is marked by extremely abundant N. dutertrei and G. bulloides, and rare G. ruber. Analysis of sedimentation rates in 14 cores reveals the following approximate ages for the sapropel layers: S2 = 52,000 yr B.P.; S3 = 81,000-78,000 yr B.P.; S4 = 100,000-98,000 yr B.P.; and S5 = 125,000-116,000 yr B.P. As previously suggested, sedimentation rates on the Mediterranean Ridge were determined to be relatively constant during the last 127,000 yr. In contrast, basin sedimentation rates have fluctuated markedly from lower rates during interglacial stage 5 to higher rates during the last glacial episode. These glacial/interglacial differences are most pronounced in the northern Ionian Basin, because of increased terrigenous sediment deposition during glacial episodes. Unusually high biogenic sedimentation rates occurred in an arc south of Crete during the deposition of sapropel S5, probably due to higher productivity in this region.

  17. Heavy metals in benthic foraminifera from the highly polluted sediments of the Naples harbour (Southern Tyrrhenian Sea, Italy).

    PubMed

    Rumolo, Paola; Manta, Daniela Salvagio; Sprovieri, Mario; Coccioni, Rodolfo; Ferraro, Luciana; Marsella, Ennio

    2009-10-15

    A systematic investigation evaluated the concentrations of a selected number of trace elements (Cd, Co, Cu, Li, Ni, Pb, V and Zn) in carbonates of the benthic foraminifera Ammonia tepida collected from surface sediments of the highly polluted harbour of Naples. Application of cleaning procedures, combined with Scanning Electron Microscopy investigation (SEM) of the analysed shells allowed reliable quantification of the elements in the carbonate lattice. Adoption of biogenic carbonate/seawater distribution coefficients reported in the literature provided the ranges of variability of total dissolved trace elements in the studied marine environment. Very high concentrations of Zn, Cd, and Cu calculated in seawater (from 100 to 10,000 times higher than those reported for uncontaminated Mediterranean seawaters) testify to intense effects of anthropogenic impact on the harbour mainly related to the industrial and commercial activities carried out in the neighbouring area. The ensemble of the obtained results emphasizes the high potential of measurements of trace elements in the biogenic carbonates of benthic foraminifera as tracers of anthopogenic pollution of seawater and reliable proxies of potentially bioavailable forms (as free ions and/or more labile organic complexes) of seawater dissolved metals. PMID:19647291

  18. Episodic acidification and associated fish and aquatic invertebrate responses in four Catskill Mountain streams: An interim report of the Episodic Response Project. Open File Report

    SciTech Connect

    Murdoch, P.S.; Bonitz, C.E.; Eakin, K.W.; Ranalli, A.J.; Witt, E.C.

    1991-07-01

    The Episodic Response Project is a multidisciplinary research project designed to assess the role of storm and snowmelt runoff in stream acidification and the associated responses of fish and invertebrates. Four streams in the Catskill region of eastern New York were selected to represent the following conditions: (1) high acid-neutralizing capacity (ANC) with no acidic episodes annually, (2) high ANC with few acidic episodes, (3) moderate to low ANC with few acidic episodes, and (4) low ANC with frequent acidic episodes. Results of the first 9 months of research in the Catskill region indicate that storm and snowmelt runoff are associated with short periods of stream acidification that, if sufficiently severe, lead to fish mortality or migration away from acidic reaches. Increased discharge coincided with decreased pH and increased total aluminum concentrations in all four streams.

  19. Mechanisms of surface wave energy dissipation over a high-concentration sediment suspension

    NASA Astrophysics Data System (ADS)

    Traykovski, Peter; Trowbridge, John; Kineke, Gail

    2015-03-01

    Field observations from the spring of 2008 on the Louisiana shelf were used to elucidate the mechanisms of wave energy dissipation over a muddy seafloor. After a period of high discharge from the Atchafalaya River, acoustic measurements showed the presence of 20 cm thick mobile fluid-mud layers during and after wave events. While total wave energy dissipation (D) was greatest during the high energy periods, these periods had relatively low normalized attenuation rates (κ = Dissipation/Energy Flux). During declining wave-energy conditions, as the fluid-mud layer settled, the attenuation process became more efficient with high κ and low D. The transition from high D and low κ to high κ and low D was caused by a transition from turbulent to laminar flow in the fluid-mud layer as measured by a Pulse-coherent Doppler profiler. Measurements of the oscillatory boundary layer velocity profile in the fluid-mud layer during laminar flow reveal a very thick wave boundary layer with curvature filling the entire fluid-mud layer, suggesting a kinematic viscosity 2-3 orders of magnitude greater than that of clear water. This high viscosity is also consistent with a high wave-attenuation rates measured by across-shelf energy flux differences. The transition to turbulence was forced by instabilities on the lutocline, with wavelengths consistent with the dispersion relation for this two-layer system. The measurements also provide new insight into the dynamics of wave-supported turbidity flows during the transition from a laminar to turbulent fluid-mud layer.

  20. The residues, distribution, and partition of organochlorine pesticides in the water, suspended solids, and sediments from a large Chinese lake (Lake Chaohu) during the high water level period.

    PubMed

    Liu, Wen-Xiu; He, Wei; Qin, Ning; Kong, Xiang-Zhen; He, Qi-Shuang; Ouyang, Hui-Ling; Xu, Fu-Liu

    2013-04-01

    The levels of organochlorine pesticides (OCPs) in the water, suspended solids, and sediments from Lake Chaohu during the high water level period were measured by a solid-phase extraction gas chromatograph-electron capture detector. The spatial distributions of the three phases and the water/suspended solids and sediment/water partition coefficients were analyzed. The results showed the following: (1) The mean contents of OCPs in the water, suspended solids, and sediments were 132.4 ± 432.1 ng/L, 188.1 ± 286.7 ng/g dry weight (dw), and 13.7 ± 9.8 ng/g dw, respectively. The dominant OCP components were isodrin (85.1%) for the water, DDTs (64.4%) for the suspended solids, and both isodrin (48.5%) and DDTs (31.8%) for the sediments. (2) β-HCH was the primary isomer of HCHs in the water and sediments, and the proportions were 61.7 and 41.3%; γ-HCH was the primary isomer in the suspended solids, accounting for 49.3%; p,p'-DDT was the dominant content of DDTs in the water and suspended solids, whereas p,p'-DDD was the main metabolite of DDTs in the sediments. (3) The concentrations of contaminants in the water from the western lake were greater than those from the eastern lake, but the concentrations in the suspended solids from the western lake were less than those from the eastern lake. (4) There was no significant correlation between the water-suspended solids partition coefficient Kd and the n-octanol-water partition coefficient Kow, and between the sediment-water organic-C weighted sorption coefficients Koc and Kow.

  1. Reduced diversity and high sponge abundance on a sedimented Indo-Pacific reef system: implications for future changes in environmental quality.

    PubMed

    Powell, Abigail; Smith, David J; Hepburn, Leanne J; Jones, Timothy; Berman, Jade; Jompa, Jamaluddin; Bell, James J

    2014-01-01

    Although coral reef health across the globe is declining as a result of anthropogenic impacts, relatively little is known of how environmental variability influences reef organisms other than corals and fish. Sponges are an important component of coral reef fauna that perform many important functional roles and changes in their abundance and diversity as a result of environmental change has the potential to affect overall reef ecosystem functioning. In this study, we examined patterns of sponge biodiversity and abundance across a range of environments to assess the potential key drivers of differences in benthic community structure. We found that sponge assemblages were significantly different across the study sites, but were dominated by one species Lamellodysidea herbacea (42% of all sponges patches recorded) and that the differential rate of sediment deposition was the most important variable driving differences in abundance patterns. Lamellodysidea herbacea abundance was positively associated with sedimentation rates, while total sponge abundance excluding Lamellodysidea herbacea was negatively associated with rates of sedimentation. Overall variation in sponge assemblage composition was correlated with a number of variables although each variable explained only a small amount of the overall variation. Although sponge abundance remained similar across environments, diversity was negatively affected by sedimentation, with the most sedimented sites being dominated by a single sponge species. Our study shows how some sponge species are able to tolerate high levels of sediment and that any transition of coral reefs to more sedimented states may result in a shift to a low diversity sponge dominated system, which is likely to have subsequent effects on ecosystem functioning.

  2. Distribution of PAHs and the PAH-degrading bacteria in the deep-sea sediments of the high-latitude Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Dong, C.; Bai, X.; Sheng, H.; Jiao, L.; Zhou, H.; Shao, Z.

    2014-09-01

    Polycyclic aromatic hydrocarbons (PAHs) are persistent organic pollutants, which can be transferred to a long distance and tend to accumulation in marine sediment. However, PAHs distribution and natural bioattenuation is less known in open sea, especially in the Arctic Ocean. In this report, sediment samples were collected at four sites from the Chukchi Plateau to Makarov Basin in the summer of 2010. PAH composition and total concentrations were examined with GC-MS, we found that the concentrations of 16 EPA-priority PAHs varied from 2.0 to 41.6 ng g-1 dry weight in total and decreased with sediment depths and as well as from the southern to northern sites. Among the targeted PAHs, phenanthrene was relatively abundant in all sediments. To learn the diversity of bacteria involved in PAHs degradation in situ, the 16S rRNA gene of the total environmental DNA was analyzed with Illumina high throughput sequencing (IHTS). In all the sediments, occurred the potential degraders including Cycloclasticus, Pseudomonas, Halomonas, Pseudoalteromonas, Marinomonas, Bacillus, Dietzia, Colwellia, Acinetobacter, Alcanivorax, Salinisphaera and Shewanella, with Dietzia as the most abundant. Meanwhile on board, enrichment with PAHs was initiated and repeated transfer in laboratory to obtain the degrading consortia. Most above mentioned bacteria in addition to Hahella, Oleispira, Oceanobacter and Hyphomonas, occurred alternately as a predominant member in enrichment cultures from different sediments, as revealed with IHTS and PCR-DGGE. To reconfirm their role in PAH degradation, 40 different bacteria were isolated and characterized, among which Cycloclasticus and Pseudomonas showed the best degradation capability under low temperature. Taken together, PAHs and PAH-degrading bacteria were widespread in the deep-sea sediments of the Arctic Ocean. We propose that bacteria of Cycloclasticus, Pseudomonas, Pseudoalteromonas, Halomonas, Marinomonas and Dietzia may play the most important role

  3. Distribution of PAHs and the PAH-degrading bacteria in the deep-sea sediments of the high-latitude Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Dong, C.; Bai, X.; Sheng, H.; Jiao, L.; Zhou, H.; Shao, Z.

    2015-04-01

    Polycyclic aromatic hydrocarbons (PAHs) are common organic pollutants that can be transferred long distances and tend to accumulate in marine sediments. However, less is known regarding the distribution of PAHs and their natural bioattenuation in the open sea, especially the Arctic Ocean. In this report, sediment samples were collected at four sites from the Chukchi Plateau to the Makarov Basin in the summer of 2010. PAH compositions and total concentrations were examined with GC-MS. The concentrations of 16 EPA-priority PAHs varied from 2.0 to 41.6 ng g-1 dry weight and decreased with sediment depth and movement from the southern to the northern sites. Among the targeted PAHs, phenanthrene was relatively abundant in all sediments. The 16S rRNA gene of the total environmental DNA was analyzed with Illumina high-throughput sequencing (IHTS) to determine the diversity of bacteria involved in PAH degradation in situ. The potential degraders including Cycloclasticus, Pseudomonas, Halomonas, Pseudoalteromonas, Marinomonas, Bacillus, Dietzia, Colwellia, Acinetobacter, Alcanivorax, Salinisphaera and Shewanella, with Dietzia as the most abundant, occurred in all sediment samples. Meanwhile, enrichment with PAHs was initiated onboard and transferred to the laboratory for further enrichment and to obtain the degrading consortia. Most of the abovementioned bacteria in addition to Hahella, Oleispira, Oceanobacter and Hyphomonas occurred alternately as predominant members in the enrichment cultures from different sediments based on IHTS and PCR-DGGE analysis. To reconfirm their role in PAH degradation, 40 different bacteria were isolated and characterized, among which Cycloclasticus Pseudomonas showed the best degradation capability under low temperatures. Taken together, PAHs and PAH-degrading bacteria were widespread in the deep-sea sediments of the Arctic Ocean. We propose that bacteria of Cycloclasticus, Pseudomonas, Pseudoalteromonas, Halomonas, Marinomonas and Dietzia may

  4. Reduced Diversity and High Sponge Abundance on a Sedimented Indo-Pacific Reef System: Implications for Future Changes in Environmental Quality

    PubMed Central

    Powell, Abigail; Smith, David J.; Hepburn, Leanne J.; Jones, Timothy; Berman, Jade; Jompa, Jamaluddin; Bell, James J.

    2014-01-01

    Although coral reef health across the globe is declining as a result of anthropogenic impacts, relatively little is known of how environmental variability influences reef organisms other than corals and fish. Sponges are an important component of coral reef fauna that perform many important functional roles and changes in their abundance and diversity as a result of environmental change has the potential to affect overall reef ecosystem functioning. In this study, we examined patterns of sponge biodiversity and abundance across a range of environments to assess the potential key drivers of differences in benthic community structure. We found that sponge assemblages were significantly different across the study sites, but were dominated by one species Lamellodysidea herbacea (42% of all sponges patches recorded) and that the differential rate of sediment deposition was the most important variable driving differences in abundance patterns. Lamellodysidea herbacea abundance was positively associated with sedimentation rates, while total sponge abundance excluding Lamellodysidea herbacea was negatively associated with rates of sedimentation. Overall variation in sponge assemblage composition was correlated with a number of variables although each variable explained only a small amount of the overall variation. Although sponge abundance remained similar across environments, diversity was negatively affected by sedimentation, with the most sedimented sites being dominated by a single sponge species. Our study shows how some sponge species are able to tolerate high levels of sediment and that any transition of coral reefs to more sedimented states may result in a shift to a low diversity sponge dominated system, which is likely to have subsequent effects on ecosystem functioning. PMID:24475041

  5. Episodic memory--from brain to mind.

    PubMed

    Ferbinteanu, Janina; Kennedy, Pamela J; Shapiro, Matthew L

    2006-01-01

    Neuronal mechanisms of episodic memory, the conscious recollection of autobiographical events, are largely unknown because electrophysiological studies in humans are conducted only in exceptional circumstances. Unit recording studies in animals are thus crucial for understanding the neurophysiological substrate that enables people to remember their individual past. Two features of episodic memory--autonoetic consciousness, the self-aware ability to "travel through time", and one-trial learning, the acquisition of information in one occurrence of the event--raise important questions about the validity of animal models and the ability of unit recording studies to capture essential aspects of memory for episodes. We argue that autonoetic experience is a feature of human consciousness rather than an obligatory aspect of memory for episodes, and that episodic memory is reconstructive and thus its key features can be modeled in animal behavioral tasks that do not involve either autonoetic consciousness or one-trial learning. We propose that the most powerful strategy for investigating neurophysiological mechanisms of episodic memory entails recording unit activity in brain areas homologous to those required for episodic memory in humans (e.g., hippocampus and prefrontal cortex) as animals perform tasks with explicitly defined episodic-like aspects. Within this framework, empirical data suggest that the basic structure of episodic memory is a temporally extended representation that distinguishes the beginning from the end of an event. Future research is needed to fully understand how neural encodings of context, sequences of items/events, and goals are integrated within mnemonic representations of autobiographical events.

  6. Established time series measure occurrence and frequency of episodic events.

    NASA Astrophysics Data System (ADS)

    Pebody, Corinne; Lampitt, Richard

    2015-04-01

    Established time series measure occurrence and frequency of episodic events. Episodic flux events occur in open oceans. Time series making measurements over significant time scales are one of the few methods that can capture these events and compare their impact with 'normal' flux. Seemingly rare events may be significant on local scales, but without the ability to measure the extent of flux on spatial and temporal scales and combine with the frequency of occurrence, it is difficult to constrain their impact. The Porcupine Abyssal Plain Sustained Observatory (PAP-SO) in the Northeast Atlantic (49 °N 16 °W, 5000m water depth) has measured particle flux since 1989 and zooplankton swimmers since 2000. Sediment traps at 3000m and 100 metres above bottom, collect material year round and we have identified close links between zooplankton and particle flux. Some of these larger animals, for example Diacria trispinosa, make a significant contribution to carbon flux through episodic flux events. D. trispinosa is a euthecosome mollusc which occurs in the Northeast Atlantic, though the PAP-SO is towards the northern limit of its distribution. Pteropods are comprised of aragonite shell, containing soft body parts excepting the muscular foot which extends beyond the mouth of the living animal. Pteropods, both live-on-entry animals and the empty shells are found year round in the 3000m trap. Generally the abundance varies with particle flux, but within that general pattern there are episodic events where significant numbers of these animals containing both organic and inorganic carbon are captured at depth and therefore could be defined as contributing to export flux. Whether the pulse of animals is as a result of the life cycle of D. trispinosa or the effects of the physics of the water column is unclear, but the complexity of the PAP-SO enables us not only to collect these animals but to examine them in parallel to the biogeochemical and physical elements measured by the

  7. Geochemistry of highly aluminiferous Vendian-Cambrian sediments of the Tunka Bald Mountains, East Sayan

    NASA Astrophysics Data System (ADS)

    Shkol'Nik, S. I.; Barash, I. G.; Belichenko, V. G.; Letnikova, E. F.

    2011-01-01

    This paper presents comprehensive geochemical characteristics of highly aluminiferous schists discovered in the Tunka Bald Mountains and associated with the Vendian-Cambrian cover of the Tuva-Mongolian Microcontinent. The Al2O3 content varies within a wide range, the maximum being up to 36.11 wt. %. A specific feature of the geochemical composition of these rocks is the simultaneously high contents of Cr (up to 1400 ppm), V (up to 2700 ppm), and Zr (up to 800 ppm). The origin has been interpreted, and the conditions in which the highly aluminiferous rocks formed have been considered. Based on geochemical data, it is assumed that the main origin could be weathering crusts formed after ultramafic and mafic rocks, with a felsic source playing a secondary role.

  8. Sediment Dynamics Affecting the Threatened Santa Ana Sucker in the Highly-modified Santa Ana River and Inset Channel, Southern California, USA

    NASA Astrophysics Data System (ADS)

    Minear, J. T.; Wright, S. A.

    2015-12-01

    In this study, we investigate the sediment dynamics of the low-flow channel of the Santa Ana River that is formed by wastewater discharges and contains some of the last remaining habitat of the Santa Ana Sucker (Catostomus santaanae). The Santa Ana River is a highly-modified river draining the San Bernardino Mountains and Inland Empire metropolitan area east of Los Angeles. Home to over 4 million people, the watershed provides habitat for the federally-threatened Santa Ana Sucker, which presently reside within the mainstem Santa Ana River in a reach supported by year-round constant discharges from water treatment plants. The nearly constant low-flow wastewater discharges and infrequent runoff events create a small, approximately 8 m wide, inset channel within the approximately 300 m wide mainstem channel that is typically dry except for large flood flows. The sediment dynamics within the inset channel are characterized by constantly evolving bed substrate and sediment transport rates, and occasional channel avulsions. The sediment dynamics have large influence on the Sucker, which rely on coarse-substrate (gravel and cobble) for their food production. In WY 2013 through the present, we investigated the sediment dynamics of the inset channel using repeat bathymetric and substrate surveys, bedload sampling, and discharge measurements. We found two distinct phases of the inset channel behavior: 1. 'Reset' flows, where sediment-laden mainstem discharges from upstream runoff events result in sand deposition in the inset channel or avulse the inset channel onto previously dry riverbed; and 2. 'Winnowing' flows, whereby the sand within the inset channel is removed by clear-water low flows from the wastewater treatment plant discharges. Thus, in contrast to many regulated rivers where high flows are required to flush fine sediments from the bed (for example, downstream from dams), in the Santa Ana River the low flows from wastewater treatment plants serve as the flushing

  9. Relationship of Sensory Modality to Retention of Episodic Memory.

    PubMed

    Morris, Jeri; Woodworth, Craig; Swier-Vosnos, Amy; Rossini, Edward; Jackson, Ilana

    2015-01-01

    This study investigated the difference between episodic memory for verbal information presented in an oral format versus equivalent material presented in a written format. The study utilized the Logical Memory subtest of the Wechsler Memory Scales-Fourth Edition and the recently validated Morris Revision-IV Paragraphs. In a sample of 97 normal participants, auditory and visual memory performances were found to be significantly correlated (r = .651, p < .001). Post-hoc analysis revealed a slight though not clinically significant preference for retention in the visual modality. The results demonstrate a high-degree correlation for retention of episodic memory for these two sensory modalities in normal participants. PMID:25372988

  10. Relationship of Sensory Modality to Retention of Episodic Memory.

    PubMed

    Morris, Jeri; Woodworth, Craig; Swier-Vosnos, Amy; Rossini, Edward; Jackson, Ilana

    2015-01-01

    This study investigated the difference between episodic memory for verbal information presented in an oral format versus equivalent material presented in a written format. The study utilized the Logical Memory subtest of the Wechsler Memory Scales-Fourth Edition and the recently validated Morris Revision-IV Paragraphs. In a sample of 97 normal participants, auditory and visual memory performances were found to be significantly correlated (r = .651, p < .001). Post-hoc analysis revealed a slight though not clinically significant preference for retention in the visual modality. The results demonstrate a high-degree correlation for retention of episodic memory for these two sensory modalities in normal participants.

  11. Neural correlates of metacognitive monitoring during episodic and semantic retrieval.

    PubMed

    Elman, Jeremy A; Klostermann, Ellen C; Marian, Diane E; Verstaen, Alice; Shimamura, Arthur P

    2012-09-01

    Activity in the posterior parietal cortex (PPC) has been shown to be a strong correlate of successful recognition performance. We assessed the degree to which the PPC mediates metacognitive judgments by assessing the feeling of knowing (FOK) for recently learned (episodic) and well-learned (semantic) facts (e.g., "The sport that is associated with Wimbledon is . . ."). Activity in ventral regions of the PPC was observed for strong FOKs for both sets of facts, although greater activity was observed for episodic than for semantic facts. Strong semantic FOKs activated anterior temporal regions. Weaker FOK ratings, when contrasted with strong FOKs, activated dorsal parietal regions, a finding that parallels contrasts during explicit tests in which low-confident responses were compared with high-confident responses. These findings demonstrate retrieval-related parietal activity during metacognitive judgments. Furthermore, they show that the ventral PPC is particularly engaged during context-specific, episodic retrieval, as compared to semantic retrieval. PMID:22562436

  12. OBSERVING EPISODIC CORONAL HEATING EVENTS ROOTED IN CHROMOSPHERIC ACTIVITY

    SciTech Connect

    McIntosh, Scott W.; De Pontieu, Bart E-mail: bdp@lmsal.co

    2009-11-20

    We present the results of a multi-wavelength study of episodic plasma injection into the corona of active region (AR) 10942. We exploit long-exposure images of the Hinode and Transition Region and Coronal Explorer spacecraft to study the properties of faint, episodic, 'blobs' of plasma that are propelled upward along coronal loops that are rooted in the AR plage. We find that the source location and characteristic velocities of these episodic upflow events match those expected from recent spectroscopic observations of faint coronal upflows that are associated with upper chromospheric activity, in the form of highly dynamic spicules. The analysis presented ties together observations from coronal and chromospheric spectrographs and imagers, providing more evidence of the connection of discrete coronal mass heating and injection events with their source, dynamic spicules, in the chromosphere.

  13. Comparing InSAR observations of incremental fault growth in the 2005-2010 Dabbahu (Ethiopia) rifting episode with cumulative displacement-length measurements from high-resolution LiDAR

    NASA Astrophysics Data System (ADS)

    Hofmann, B.; Wright, T.; Paton, D. A.; Rowland, J. V.; Vye, C.

    2012-12-01

    It has long been recognized that faults develop as a result of a series of successive slip events but direct observations of growth are few and far between. Published fault growth models are therefore commonly based on statistical properties of cumulative fault displacement patterns. Here we use InSAR observations of fault slip during the 2005-2010 Dabbahu (Afar) rifting episode to test fault growth models directly. The recent Dabbahu rifting episode, which commenced in 2005 within the Afar Depression, has provided a unique opportunity to study progressive fault growth. The initial dike intrusion caused deformation along the entire length (60 km) of the segment comprising horizontal opening of up to 8 m, subsidence of up to 3 m in a 2-3 km wide graben and uplift on the flanks of up to 1 m. Displacements during the initial event and the subsequent 13 smaller dike intrusions have been observed with InSAR using data from ENIVISAT, with 4 of the dikes also being imaged by ALOS. InSAR measurements can provide accurate maps of surface deformation over large areas (10s of km) with a precision in the range of mm and a spatial resolution of meters to tens of meters. For dike intrusions the majority of the deformation is centered above the dike in the area of extensive faulting where unwrapping of the short (5.6 cm) wavelength C-band ENVISAT interferograms is very challenging. We have therefore focused our analysis on the 4 dike intrusions observed by the longer (23.6 cm) wavelength L-band ALOS. However, without precise local digital elevation models (DEM) relating this deformation to individual surface features is impossible. We therefore combine the ALOS InSAR data with a high-resolution DEM, derived from an airborne LiDAR survey, to process the ALOS data at full resolution and reduce the error caused by the relative large baseline between the ALOS acquisitions and to precisely locate slip on individual surface faults. The high-resolution airborne LiDAR survey was carried

  14. Fixation Mechanisms and Desorption Rates of Sorbed Cs in High-Level Waste Contaminated Subsurface Sediments: Implications to Future Behavior and In-Ground Stability

    SciTech Connect

    Zachara, John M.; McKinley, James P.; Ainsworth, Calvin C.; Serne, R. Jeff

    2002-06-01

    Research is investigating mineralogic and geochemical factors controlling the desorption rate of 137Cs+ from subsurface sediments on the Hanford Site contaminated with different types of high level waste. The project will develop kinetic data and models that describe the release rates of 137Cs+ from contaminated sediments over a range of potential geochemical conditions that may evolve during waste retrieval from overlying tanks, or in response to meteoric water infiltration. Scientific understanding and computational techniques will be established to predict the future behavior of sorbed, in-ground 137Cs+.

  15. ChemCam First Discovery of High Silica Sediments in Gale Crater

    NASA Astrophysics Data System (ADS)

    Frydenvang, J.; Gasda, P. J.; Wiens, R. C.; Newsom, H. E.; Bridges, J.; Gasnault, O.; Maurice, S.; Forni, O.; Mangold, N.; Cousin, A.; Payré, V.; Anderson, R. B.; Mitrofanov, I. G.; Jun, I.; Rice, M. S.; Milliken, R.; Edwards, P.; Vaniman, D. T.; Morris, R. V.; Blake, D. F.; Gellert, R.; Thompson, L. M.; Clark, B. C.; Hurowitz, J.; Sumner, D. Y.; Ehlmann, B. L.; Fraeman, A.; Kinch, K. M.; Madsen, M. B.; Calef, F.; Grotzinger, J. P.; Vasavada, A. R.

    2015-12-01

    On sol 991, The Curiosity rover ascended a steep slope to Marias Pass in Gale Crater. Close to the top, ChemCam analyzed the rock target Elk from an apparent bright unit. Utilizing the new elemental calibration implemented for ChemCam in the summer of 2015, four of five points on Elk were measured to contain 76-82 wt% SiO2 and >3 wt% TiO2, whereas the last point showed elevated CaSO4. The Elk target is identified to be part of the Murray formation, and hence related to the Pahrump area mudstones that were subjected to intensive studies by the Curiosity rover team over the sols 758-948. While the Murray formation west of Elk did show elevated SiO2 (~65 wt%) compared to the Pahrump area, no targets with similarly high SiO2 wt% as Elk were observed, thus prompting - together with detection of anomalously high DAN H signals in the same area - the Curiosity rover to return to the Elk target area for additional analyses. This return led to numerous additional high Si observations (targets Pistol, Mary, Shepard, Dublin Gulch and Frog) that all corroborated the initial high Si observation at Elk. Additionally, the Alpha Particle X-ray Spectrometer (APXS) analyzed the target Lamoose and found SiO2 content in excess of 72 wt% and moderately elevated TiO2. Considering the difference in footprint (1.7 cm for APXS vs ~400μm for ChemCam) and the fact that the target couldn't be brushed, this is considered a good corroboration of the very high Si observed with ChemCam. These targets suggest that the Elk-area targets represent an end-member of the Murray formation, but there are multiple working hypotheses for the origin of the high SiO2 and TiO2 in these: 1. primary precipitates from the water column of a lake, 2. a post-depositional leaching/weathering front and 3. a hydrothermal silica precipitate.

  16. Occurrence of polycyclic aromatic hydrocarbons in surface sediments of a highly urbanized river system with special reference to energy consumption patterns.

    PubMed

    Zhang, Kai; Wang, Ji-Zhong; Liang, Bo; Zeng, Eddy Y

    2011-06-01

    Sediment samples collected from downstream of the Dongjiang River, a highly urbanized river network within the Pearl River Delta of South China, were analyzed for 28 polycyclic aromatic hydrocarbons (PAHs). Total concentrations of 28 PAHs, 16 priority PAHs designated by the United States Environmental Protection Agency (USEPA) and the seven carcinogenic PAHs classified by the USEPA ranged from 480 to 4600, 100 to 3400 and 10 to 1700 ng/g dry weight, respectively. Principal component analysis-based stepwise multivariate linear regression showed that sediment PAHs were predominantly derived from coal combustion, refined fossil fuel combustion and oil spills, accounting for 37%, 32% and 23%, respectively, of the total loading. The levels of sediment PAHs remained steady from 2002 to 2008, during which fossil fuel consumption had doubled, probably reflecting efforts to control PAH emissions from fossil fuel combustion. Finally, use of natural gas and liquefied petroleum gas in automobiles should be encouraged to improve environmental quality. PMID:21470730

  17. Coupled Wave-Sediment Dynamics on the Atchafalaya shelf, Louisiana, USA

    NASA Astrophysics Data System (ADS)

    Jaramillo, S.; Sheremet, A.; Allison, M.

    2006-12-01

    We present a set of field observations of wave, current and sediment dynamics on the muddy, shallow (less than 5-m water depth) inner Atchafalaya shelf, Louisiana, USA. Two instrumented platforms were deployed for over two months in Spring 2006, a period of the year characterized by transient, relatively energetic sea states associated with cold front passages. The platforms collected high-resolution measurements of wave, current, and sediment motion (e.g. downward-looking PC- ADPs sampled the velocity in the first 50 cm above the bottom at 2 Hz, in 17 3-cm bins). Suspended sediment concentration was monitored using optical backscatter sensors (OBS) and laser devices (LISST). Lutocline formation and the position of the bottom was monitored using the PC-ADP bottom-tracker beam and acoustic backscatter sensors (ABS). Episodic fluid mud layers are observed to form during and in the wake of, energetic wave events. Observations of bottom position and vertical current velocity structure suggest that high density sediment suspension (fluid mud) layers can be generated both through direct liquefaction of the bottom sediment by energetic swell, and by increased sediment concentration due to a combination of advection and sediment settling processes. Even though the bottom gradient in the area is very low (less than 0.001), in some instances the direction of the flow within the fluid mud layer was seaward, opposite to the direction of the upper water-column current, suggesting that the origin of the layer might be a gravitational flow. Surface wave dissipation is strongly correlated to fluid-mud layer formation, increasing from negligible values in relatively calm weather to about 60% wave energy loss over about 10 km in the presence of fluid muds. The observations suggest a significant coupling between wave, current, and sediment dynamics during energetic events. Continuous data analysis work focuses on the study of near-bottom wave nonlinearities, turbulence, and modeling

  18. Autobiographically significant concepts: more episodic than semantic in nature? An electrophysiological investigation of overlapping types of memory.

    PubMed

    Renoult, Louis; Davidson, Patrick S R; Schmitz, Erika; Park, Lillian; Campbell, Kenneth; Moscovitch, Morris; Levine, Brian

    2015-01-01

    A common assertion is that semantic memory emerges from episodic memory, shedding the distinctive contexts associated with episodes over time and/or repeated instances. Some semantic concepts, however, may retain their episodic origins or acquire episodic information during life experiences. The current study examined this hypothesis by investigating the ERP correlates of autobiographically significant (AS) concepts, that is, semantic concepts that are associated with vivid episodic memories. We inferred the contribution of semantic and episodic memory to AS concepts using the amplitudes of the N400 and late positive component, respectively. We compared famous names that easily brought to mind episodic memories (high AS names) against equally famous names that did not bring such recollections to mind (low AS names) on a semantic task (fame judgment) and an episodic task (recognition memory). Compared with low AS names, high AS names were associated with increased amplitude of the late positive component in both tasks. Moreover, in the recognition task, this effect of AS was highly correlated with recognition confidence. In contrast, the N400 component did not differentiate the high versus low AS names but, instead, was related to the amount of general knowledge participants had regarding each name. These results suggest that semantic concepts high in AS, such as famous names, have an episodic component and are associated with similar brain processes to those that are engaged by episodic memory. Studying AS concepts may provide unique insights into how episodic and semantic memory interact.

  19. Terrestrial Sediment and Nutrient Discharge, and Their Potential Influence on Coral Reefs, Puerto Rico

    NASA Astrophysics Data System (ADS)

    Larsen, M. C.; Webb, R. M.; Warne, A. G.

    2004-12-01

    Sediment and nutrient discharge to the insular shelf of Puerto Rico (18 degrees latitude), augmented by anthropogenic activity, is believed to have contributed to widespread degradation of coral reefs of Puerto Rico during the 20th century. Sediment deposition degrades coral reefs because it reduces the area of sea floor suitable for growth of new coral, diminishes the amount of light available for photosynthesis by symbiotic algae that live within individual coral animals, and in extreme cases, buries coral colonies. Land-use history and data from 30 water-discharge, 9 daily and 15 intermittent sediment-concentration, and 24 water-quality gaging stations were analyzed to investigate the timing and intensity of terrestrial sediment and nutrient discharge into coastal waters. Watersheds in Puerto Rico generally are small (10's to 100's of square km), channel gradients are steep, and stream valleys are deeply incised and narrow. Major storms are usually brief (<24 h) but intense such that the majority of the annual sediment discharge occurs in a few days. From 1960 through 2000 the highest mean daily discharge for a water year (October - September) accounted for 20 to 60 percent of the total annual sediment discharge. Major storms, with a return frequency of approximately a decade, were capable of discharging up to 30 times the median annual sediment-discharge volume. Prior to agricultural and industrial development, coastal waters are believed to have been relatively transparent, with strong currents and seasonal high-energy swells assisting corals in the removal of minor amounts of sediment deposited after storms. Land clearing and modification, first for agriculture and later for urban development, have increased sediment and nutrient influx to the coast during the 19th and 20th centuries. Although forest cover has increased to approximately 30 percent of the surface of Puerto Rico during the past 60 years, sediment eroded from hillslopes during the agricultural

  20. Understanding processes controlling sediment transports at the mouth of a highly energetic inlet system (San Francisco Bay, CA)

    USGS Publications Warehouse

    Elias, Edwin P.L.; Hansen, Jeff E.; Barnard, P.L.; Jaffee, B.E.; Schoellhamer, D.H.

    2013-01-01

    San Francisco Bay is one of the largest estuaries along the U.S. West Coast and is linked to the Pacific Ocean through the Golden Gate, a 100 m deep bedrock inlet. A coupled wave, flow and sediment transport model is used to quantify the sediment linkages between San Francisco Bay, the Golden Gate, and the adjacent open coast. Flow and sediment transport processes are investigated using an ensemble average of 24 climatologically derived wave cases and a 24.8 h representative tidal cycle. The model simulations show that within the inlet, flow and sediment transport is tidally dominated and driven by asymmetry of the ebb and flood tides. Peak ebb velocities exceed the peak flood velocities in the narrow Golden Gate channel as a result of flow convergence and acceleration. Persistent flow and sediment gyres at the headland tips are formed that limit sediment transfer from the ebb-tidal delta to the inlet and into the bay. The residual transport pattern in the inlet is dominated by a lateral segregation with a large ebb-dominant sediment transport (and flow) prevailing along the deeper north side of the Golden Gate channel, and smaller flood dominant transports along the shallow southern margin. The seaward edge of the ebb-tidal delta largely corresponds to the seaward extent of strong tidal flows. On the ebb-tidal delta, both waves and tidal forcing govern flow and sediment transport. Wave focusing by the ebb-tidal delta leads to strong patterns of sediment convergence and divergence along the adjacent Ocean Beach.

  1. Surprising abundance of Gallionella-related iron oxidizers in creek sediments at pH 4.4 or at high heavy metal concentrations

    USGS Publications Warehouse

    Fabisch, Maria; Beulig, Felix; Akob, Denise M.; Küsel, Kirsten

    2013-01-01

    We identified and quantified abundant iron-oxidizing bacteria (FeOB) at three iron-rich, metal-contaminated creek sites with increasing sediment pH from extremely acidic (R1, pH 2.7), to moderately acidic (R2, pH 4.4), to slightly acidic (R3, pH 6.3) in a former uranium-mining district. The geochemical parameters showed little variations over the 1.5 year study period. The highest metal concentrations found in creek sediments always coincided with the lowest metal concentrations in creek water at the slightly acidic site R3. Sequential extractions of R3 sediment revealed large portions of heavy metals (Ni, Cu, Zn, Pb, U) bound to the iron oxide fraction. Light microscopy of glass slides exposed in creeks detected twisted stalks characteristic of microaerobic FeOB of the family Gallionellaceae at R3 but also at the acidic site R2. Sequences related to FeOB such as Gallionella ferruginea, Sideroxydans sp. CL21, Ferritrophicum radicicola, and Acidovorax sp. BrG1 were identified in the sediments. The highest fraction of clone sequences similar to the acidophilic “Ferrovum myxofaciens” was detected in R1. Quantitative PCR using primer sets specific for Gallionella spp., Sideroxydans spp., and “Ferrovum myxofaciens” revealed that ~72% (R2 sediment) and 37% (R3 sediment) of total bacterial 16S rRNA gene copies could be assigned to groups of FeOB with dominance of microaerobic Gallionella spp. at both sites. Gallionella spp. had similar and very high absolute and relative gene copy numbers in both sediment communities. Thus, Gallionella-like organisms appear to exhibit a greater acid and metal tolerance than shown before. Microaerobic FeOB from R3 creek sediment enriched in newly developed metal gradient tubes tolerated metal concentrations of 35 mM Co, 24 mM Ni, and 1.3 mM Cd, higher than those in sediments. Our results will extend the limited knowledge of FeOB at contaminated, moderately to slightly acidic environments.

  2. High resolution sparker evidence of sediment transport patterns and Late Quaternary structures between the islands of Sylt and Rømø, SE. Northsea

    NASA Astrophysics Data System (ADS)

    Boldreel, L. O.; Kuijpers, A.; Madsen, E. B.; Hass, C.; Rasmussen, R.; Lindhorst, S.; Bartholdy, J.

    2009-04-01

    The off-shore northern part of the barrier island Sylt in the southeastern North Sea has been investigated using high-resolution sparker seismics. Bedforms identified in the seismic data reveal the postglacial sedimentary regime and actual sediment dynamics. The area can be divided into three parts. The North Sea sector of the area is characterized by northward sediment bypass as a result of strong long-shore (tidal) currents heading towards the Lister Deep, the tidal inlet between Sylt and the Danish island of Rømø. The Lister Deep is characterized by a major dune field with up to 8 m heigh dunes with a wavelength of 270 m indicative of easterly sediment transport (flood dominated). Further to the northwest in the outer delta a dune field suggesting westerly sediment transport is found. The northern part of the Lister Deep is formed by a marked erosion channel with a depth of 30-40 msec. The two dune fields are separated by minor structures. East of Sylt the area is characterized by presence of dunes of smaller dimensions than those observed in the Lister Deep. In the eastern and western part of the channel system present here, the dunes indicate sediment transport towards south (flood dominated), whereas in the central part of the area northward transport is indicated. Based on the bedform pattern a general current regime can be described. Northward sediment transport along the westcoast of Sylt following the coastline leads into the Lister Deep, where under the influence of the coastal configuration and Coriolis effect a major dune field has been formed along the north coast of Sylt. The outgoing (ebb) current comes from the Wadden Sea area towards the east and enters the northern part of the Lister Deep, where the erosion channel is found. Here the current is responsibly for the formation of the west migrating dunefield in the Lister Deep and towards the outer delta the current turns north and large amounts of sediments are likely deposited. Thus the model

  3. Surprising abundance of Gallionella-related iron oxidizers in creek sediments at pH 4.4 or at high heavy metal concentrations

    PubMed Central

    Fabisch, Maria; Beulig, Felix; Akob, Denise M.; Küsel, Kirsten

    2013-01-01

    We identified and quantified abundant iron-oxidizing bacteria (FeOB) at three iron-rich, metal-contaminated creek sites with increasing sediment pH from extremely acidic (R1, pH 2.7), to moderately acidic (R2, pH 4.4), to slightly acidic (R3, pH 6.3) in a former uranium-mining district. The geochemical parameters showed little variations over the 1.5 year study period. The highest metal concentrations found in creek sediments always coincided with the lowest metal concentrations in creek water at the slightly acidic site R3. Sequential extractions of R3 sediment revealed large portions of heavy metals (Ni, Cu, Zn, Pb, U) bound to the iron oxide fraction. Light microscopy of glass slides exposed in creeks detected twisted stalks characteristic of microaerobic FeOB of the family Gallionellaceae at R3 but also at the acidic site R2. Sequences related to FeOB such as Gallionella ferruginea, Sideroxydans sp. CL21, Ferritrophicum radicicola, and Acidovorax sp. BrG1 were identified in the sediments. The highest fraction of clone sequences similar to the acidophilic “Ferrovum myxofaciens” was detected in R1. Quantitative PCR using primer sets specific for Gallionella spp., Sideroxydans spp., and “Ferrovum myxofaciens” revealed that ~72% (R2 sediment) and 37% (R3 sediment) of total bacterial 16S rRNA gene copies could be assigned to groups of FeOB with dominance of microaerobic Gallionella spp. at both sites. Gallionella spp. had similar and very high absolute and relative gene copy numbers in both sediment communities. Thus, Gallionella-like organisms appear to exhibit a greater acid and metal tolerance than shown before. Microaerobic FeOB from R3 creek sediment enriched in newly developed metal gradient tubes tolerated metal concentrations of 35 mM Co, 24 mM Ni, and 1.3 mM Cd, higher than those in sediments. Our results will extend the limited knowledge of FeOB at contaminated, moderately to slightly acidic environments. PMID:24385973

  4. A 13000-year, high-resolution multi-proxy record of climate variability with episodes of enhanced atmospheric dust in Western Asia: Evidence from Neor peat complex in NW Iran

    NASA Astrophysics Data System (ADS)

    Sharifi, O.; Pourmand, A.; Canuel, E. A.; Peterson, L. C.

    2011-12-01

    The regional climate over West Asia, extending between Iran and the Arabian Peninsula to the eastern Mediterranean Sea, is governed by interactions between three major synoptic systems; mid-latitude Westerlies, the Siberian Anticyclone and the Indian Ocean Summer Monsoon. In recent years, a number of paleoclimate studies have drawn potential links between episodes of abrupt climate change during the Holocene, and the rise and fall of human civilizations across the "Fertile Crescent" of West Asia. High-resolution archives of climate variability from this region, however, are scarce, and at times contradicting. For example, while pollen and planktonic data from lakes in Turkey and Iran suggest that dry, continental conditions prevailed during the early-middle Holocene, oxygen isotope records indicate that relatively wet conditions dominated during this interval over West Asia. We present interannual to decadal multi-proxy records of climate variability from a peat complex in NW Iran to reconstruct changes in moisture and atmospheric dust content during the last 13000 years. Radiocarbon dating on 20 samples from a 775-cm peat core show a nearly constant rate of accumulation (1.7 mm yr-1, R2=0.99) since 13356 ± 116 cal yr B.P. Down-core X-ray fluorescence measurements of conservative lithogenic elements (e.g., Al, Zr, Ti) as well as redox-sensitive elements (e.g., Fe, K, Rb, Zn, Cu, and Co) at 2 mm intervals reveal several periods of elevated dust input to this region since the early Holocene. Down-core variations of total organic carbon and total nitrogen co-vary closely and are inversely correlated with conservative lithogenic elements (Al, Si, Ti), indicating a potential link between climate change and accumulation of organic carbon in the Neor peat mire. Major episodes of enhanced dust deposition (13000-12000, 11700-11200, 9200-8800, 7000-6000, 4200-3200, 2800-2200 and 1500-600 cal yr B.P) are in good agreement with other proxy records that document more arid

  5. Geochemical Modeling of pH Neutralization of High Alkaline-Saline Waste Fluids in Unsaturated Sediments

    NASA Astrophysics Data System (ADS)

    Zhang, G.; Zheng, Z.

    2004-12-01

    Leakage of high alkaline-saline fluids, such as those stored in Hanford, a site of the U.S. Department of Energy (DOE) in Washington State, has raised attention of scientific community. These fluids have unique thermodynamic and physical properties. Chemical components in the fluids are incompletely dissociated, especially those containing divalent or polyvalent ions. A number of laboratory experiments through injecting synthetic high alkaline-saline fluids (up to 10M of sodium nitrate, pH >12) into the sediments sampled from the DOE Hanford site were conducted to study the reactive transport processes of the fluids in subsurface environments. The experimental results observed show that the composition of the high alkaline sodium nitrate fluids can be drastically changed due to fluid-rock interactions, and eventually lead to pH neutralization of the fluid in the plume front. The dominant fluid-rock interactions are cation exchanges (Na+-K+-Ca+2-Mg+2-H+), precipitation of calcium and magnesium minerals, and dissolution of silica. In order to precisely model the reactive transport of these processes, a coupling of the Pitzer's ion-interaction geochemical model and a flow and transport model would be highly needed. The extended existing reactive geochemical transport code, BIO-CORE2Dc, incorporating a comprehensive Pitzer ion-interaction model, is capable of predicting the experimental observations. In addition, the developed model was tested against two reported cases. In both cases, the measured mean ionic activity coefficients were well reproduced by our model, while the Debye-Hückel model, usually used to calculate aqueous species activities in dilute solutions, was unable to predict the experimental data. Finally, modeling study based on our laboratory column experiment was performed. Our simulation is able to capture the observed pH trends, changes in exchangeable cations such as Ca+2, Mg+2, and formation of secondary precipitation phases in the plume front.

  6. Glacial-interglacial sedimentation rates and turbidite frequency in the Bahamas: a clear case of carbonate shedding during high sea level stands

    SciTech Connect

    Droxler, A.W.; Schlager, W.

    1985-01-01

    Vail's sea level curve is built on a basic principle that siliciclastic continental shelves and implicitly carbonate platforms mainly export sediment toward the surrounding basins during sea level low stands. The authors late Quaternary Bahamian data demonstrate however, that sediment export from carbonate banks is just the opposite. Five, 8-13 m long, piston cores were studied from the southern Tongue of the Ocean, a 1300 m deep flat-floored basin in the Bahamas, surrounded on its three sides by wide shallow carbonate banks. Turbidite layers were visually distinguished from intervening periplatform ooze. Glacial cyclic variations of aragonite content in the periplatform ooze, along with nannoplankton stratigraphy were used to identified the last two glacial and interglacial intervals, low and high stand situations respectively. On average, turbidite frequency and accumulation rates were much higher, 14 times and 45 to 22 times respectively, during interglacial than glacial stages. The Bahamian carbonate banks export therefore more material during sea level high stands when the platform tops are flooded and produce sediment. This is in direct opposition with siliciclastic ocean margins, where sediment is stored on the inner shelf during high stands and passed on to continental rises and abyssal plains during low stands. In addition, aragonite dissolution as postulated by Droxler et al. (Geology April 1983) is working in phase with the input signal by removing material during glacial intervals.

  7. Chemical composition and microstructure of uroliths and urinary sediment crystals associated with the feeding of high-level cottonseed meal diet to water buffalo calves.

    PubMed

    Wang, X; Huang, K; Gao, J; Shen, X; Lin, C; Zhang, G

    1997-01-01

    The chemical composition and microstructure of seven uroliths and four urinary sediment samples associated with the feeding of high-level cottonseed meal diet to buffalo calves were examined by chemical qualitative analyses, scanning electron microscopy (SEM), X-ray diffraction, and X-ray energy dispersive spectrometry (EDS). Struvite was a major component of kidney stones and of some bladder stones. The kidney stone sample appeared cracked under low power under SEM, aggregated into tiny balls under high power, and as a blade-like structure under even higher power. The bladder stone samples appeared finely granular or granular with various forms of prismatic crystals. The urinary sediments were prismatic crystals, with granules. The newly found prismatic crystals, which were rich in potassium and similar to struvite in crystal structure, were identified as potassium magnesium phosphate (KMgPO4.6H2O) in some bladder stones and urinary sediments. However, crystals which contained Mg and P only, which had been used for struvite identification, were not found by EDS examination in urinary sediments from fresh urine samples of buffalo calves fed the high-level cottonseed meal diet.

  8. Design and maintenance of a network for collecting high-resolution suspended-sediment data at remote locations on rivers, with examples from the Colorado River

    USGS Publications Warehouse

    Griffiths, Ronald E.; Topping, David J.; Andrews, Timothy; Bennett, Glenn E.; Sabol, Thomas A.; Melis, Theodore S.

    2012-01-01

    instruments have been constructed and verified by using either equal-discharge-increment (EDI) or equal-width-increment (EWI) measurements of the velocity-weighted suspended-sediment concentration and grain-size distribution. The suspended-silt-and-clay concentration parts of these calibration relations have also included information from EDI- or EWI-calibrated samples collected by automatic pump samplers. Three of the monitoring stations are equipped with two-way satellite broadband telemetry systems that operate once a day to remotely monitor and program the instruments and download data. Data from these stations are typically downloaded twice per month; data from stations without satellite-telemetry systems are downloaded during site visits, which occur every 2 months or semiannually, depending on the remoteness of the site. Upon downloading and processing, suspended-silt-and-clay concentration, suspended-sand concentration, and suspended-sand median grain size are posted on the World Wide Web. Satellite telemetry in combination with the high-resolution sediment surrogate measurements can generate near-real-time suspended-sediment-concentration and grain-size data (limited only by the time required to download the instruments and process the data). The approach for measuring suspended-sediment concentration and grain size using this monitoring network is more practical, and can be done at a much lower cost and with higher temporal resolution, than any other method.

  9. Characterization of aerosol episodes in the greater Mediterranean Sea area from satellite observations (2000-2007)

    NASA Astrophysics Data System (ADS)

    Gkikas, A.; Hatzianastassiou, N.; Mihalopoulos, N.; Torres, O.

    2016-03-01

    An algorithm able to identify and characterize episodes of different aerosol types above sea surfaces of the greater Mediterranean basin (GMB), including the Black Sea and the Atlantic Ocean off the coasts of Iberia and northwest Africa, is presented in this study. Based on this algorithm, five types of intense (strong and extreme) aerosol episodes in the GMB are identified and characterized using daily aerosol optical properties from satellite measurements, namely MODIS-Terra, Earth Probe (EP)-TOMS and OMI-Aura. These aerosol episodes are: (i) biomass-burning/urban-industrial (BU), (ii) desert dust (DD), (iii) dust/sea-salt (DSS), (iv) mixed (MX) and (v) undetermined (UN). The identification and characterization is made with our algorithm using a variety of aerosol properties, namely aerosol optical depth (AOD), Ångström exponent (α), fine fraction (FF), effective radius (reff) and Aerosol Index (AI). During the study period (2000-2007), the most frequent aerosol episodes are DD, observed primarily in the western and central Mediterranean Sea, and off the northern African coasts, 7 times/year for strong episodes and 4 times/year for extreme ones, on average. The DD episodes yield 40% of all types of strong aerosol episodes in the study region, while they account for 71.5% of all extreme episodes. The frequency of occurrence of strong episodes exhibits specific geographical patterns, for example the BU are mostly observed along the coasts of southern Europe and off the Atlantic coasts of Portugal, the MX episodes off the Spanish Mediterranean coast and over the Adriatic and northern Aegean Sea, while the DSS ones over the western and central Mediterranean Sea. On the other hand, the extreme episodes for all but DD aerosol display more patchy spatial patterns. The strong episodes exhibit AOD at 550 nm as high as 1.6 in the southernmost parts of central and eastern Mediterranean Sea, which rise up to 5 for the extreme, mainly DD and DSS, episodes. Although more

  10. A Transactional Approach to Transfer Episodes

    ERIC Educational Resources Information Center

    Jornet, Alfredo; Roth, Wolff-Michael; Krange, Ingeborg

    2016-01-01

    In this article we present an analytical framework for approaching transfer episodes--episodes in which participants declare or can be declared to bring prior experience to bear on the current task organization. We build on Dewey's writings about the continuity of experience, Vygotsky's ideas of unit analysis, as well as more recent developments…

  11. Training Lessons Learned from Peak Performance Episodes.

    ERIC Educational Resources Information Center

    Fobes, James L.

    A major challenge confronting the United States Army is to obtain optimal performance from both its human and machine resources. This study examines episodes of peak performance in soldiers and athletes. Three cognitive components were found to enable episodes of peak performance: psychological readiness (activating optimal arousal and emotion…

  12. Tracking the Construction of Episodic Future Thoughts

    ERIC Educational Resources Information Center

    D'Argembeau, Arnaud; Mathy, Arnaud

    2011-01-01

    The ability to mentally simulate possible futures ("episodic future thinking") is of fundamental importance for various aspects of human cognition and behavior, but precisely how humans construct mental representations of future events is still essentially unknown. We suggest that episodic future thoughts consist of transitory patterns of…

  13. Police Response to Family Abduction Episodes.

    ERIC Educational Resources Information Center

    Plass, Peggy S.; And Others

    1995-01-01

    Examines role of police in responding to family abduction episodes using data from a national survey. Addresses questions concerning frequency of police involvement, how abductions to which police respond differ from those to which they don't, actions taken by police, and the effects of their actions on episode outcomes. (LKS)

  14. Reconstruction of a high-resolution late holocene arctic paleoclimate record from Colville River delta sediments.

    SciTech Connect

    Schreiner, Kathryn Melissa; Lowry, Thomas Stephen

    2013-10-01

    This work was partially supported by the Sandia National Laboratories, Laboratory Directed Research and Development (LDRD) fellowship program in conjunction with Texas A&M University (TAMU). The research described herein is the work of Kathryn M. Schreiner (Katie) and her advisor, Thomas S. Bianchi and represents a concise description of Katies dissertation that was submitted to the TAMU Office of Graduate Studies in May 2013 in partial fulfillment of her doctorate of philosophy degree. High Arctic permafrost soils contain a massive amount of organic carbon, accounting for twice as much carbon as what is currently stored as carbon dioxide in the atmosphere. However, with current warming trends this sink is in danger of thawing and potentially releasing large amounts of carbon as both carbon dioxide and methane into the atmosphere. It is difficult to make predictions about the future of this sink without knowing how it has reacted to past temperature and climate changes. This project investigated long term, fine scale particulate organic carbon (POC) delivery by the high-Arctic Colville River into Simpsons Lagoon in the near-shore Beaufort Sea. Modern POC was determined to be a mixture of three sources (riverine soils, coastal erosion, and marine). Downcore POC measurements were performed in a core close to the Colville River output and a core close to intense coastal erosion. Inputs of the three major sources were found to vary throughout the last two millennia, and in the Colville River core covary significantly with Alaskan temperature reconstructions.

  15. Hydrology, sediment circulation and long-term morphological changes in highly urbanized Shenzhen River estuary, China: A combined field experimental and modeling approach

    NASA Astrophysics Data System (ADS)

    Zhang, Shiyan; Mao, Xian-zhong

    2015-10-01

    The Shenzhen River estuary is a small estuary in highly urbanized regions between Shenzhen and Hong Kong, China. An increasing amount of sediment has been observed to accumulate in the estuary, imposing a severe impact on the ecological environment. In this study we utilized a series of hydrographic and bathymetry surveys to study the hydrology, sediment transport and morphological processes in the estuary. Flow and sediment circulation patterns in different seasons were inferred using current velocity, salinity and suspended sediment concentration (SSC) time series collected in the hydrographic surveys in conjunction with fathometer profiles in bathymetry surveys. Historical time series at two stations were also analyzed by Mann-Kendall test for possible trends of the driving forces for estuarine morphological processes. The two-dimensional depth-averaged DELFT numerical model was employed to simulate the flow, salinity and SSC fields during the synchronous surveys and to predict the long-term morphological processes in the estuary. A bimodal SSC distribution was observed with two high-SSC zones separated by a low-SSC zone near the central bay, which cannot be explained by the conventional nongravitational transport theory of Postma (1967). It is hypothesized that sediment circulation in the estuary can be separated into two different systems: the "tidal zone" is under the influence of marine sediment from the Pearl River estuary, whereas the "fluvial zone" is mainly affected by terrestrial sediment from the river. Sediment mass exchange between the two systems is limited due to the presence of the low-SSC zone, the location of which could vary with the relative strengths of river flow and tides. The trend analysis of historical time series shows that the river discharge and the mean sea level are increasing and the flood tide range and the ebb tide range are decreasing. These trends are closely related to the intense human activities in the urbanization of

  16. Integrating high-resolution mapping of the seafloor with sediment-transport measurements to understand coastal erosion in northern South Carolina

    NASA Astrophysics Data System (ADS)

    Barnhardt, W.; Baldwin, W.; Denny, J.; Schwab, W.; Paul, G.; Driscoll, N.; Warner, J.; Voulgaris, G.

    2006-12-01

    Shoreline behavior along the coast of Long Bay, South Carolina is dictated by waves, tidal currents, and sediment supply that act within the overall constraints of the regional geologic setting. This study examined the influence of the geologic framework on coastal evolution through the interpretation of high-resolution geophysical data (swath bathymetry, sidescan-sonar imagery, seismic-reflection profiles), bottom samples and cores. Interpreted geophysical data were used to form conceptual models of sediment flux in the nearshore area, which are being tested by conducting site-specific sediment transport and oceanographic measurements and modeling. The inner shelf of Long Bay extends from the shoreface to about 10 km offshore (5-15 m water depth). It is underlain by coastal-plain strata of Cretaceous/Tertiary age that are incised by large fluvial channels formed during the Pliocene and Pleistocene. The indurated coastal-plain and channel-fill deposits are exposed as hardgrounds over large expanses of the inner shelf, and locally overlain by a discontinuous veneer of sandy Holocene sediment generally less than 1-m thick. A regional unconformity, thought to represent erosion during the most recent marine transgression, coincides with the seafloor in these areas of sparse sediment. Minor bathymetric highs occur where relatively thicker accumulations of Holocene sediment lie above the low- relief, transgressive unconformity. One of the thickest accumulations of Holocene sediment is contained within an anomalous, shore-oblique sand body that lies 3 km offshore of Myrtle Beach and is not associated with a modern tidal inlet. The lobate deposit is approximately 11-km long, 3-km wide, and up to 3-m thick. Cores show that the shoal is a marine deposit less than 5000 years old with a gravelly lag at the base representing the transgressive surface. It contains an estimated volume of 26 million m3 of sediment, largely consisting of fine to medium, well sorted quartz sand and

  17. Sedimentary infill dynamic and associated trace element temporal trends in a dam reservoir: evidence of high polluted sediment storage after major flood events (Upper Loire river, France)

    NASA Astrophysics Data System (ADS)

    Dhivert, Elie; Grosbois, Cécile; Desmet, Marc; Coynel, Alexandra; Lefevre, Irène

    2014-05-01

    The Villerest Dam, was built in the Upper Loire river during the early 1980's, 80 km downstream of the most important industrial and coal mining area of the basin. It constitutes an important trap of sediments and associated pollutants since its operation in 1984. A 154 cm long core was sampled in 2010, in a former channel levee in the reservoir. This study highlights (i) important sediment accumulation rate during flood events in the reservoir, (ii) the influence of high discharge events in sedimentary infill in terms of stored sediment quality, geochemical markers and anthropogenic sources influence. Coupling sedimentological analyses and 137Cs datation allows to define 3 sedimentary units in this core. The deepest unit corresponds to transported and/or reworked fluvial sediments undated, the uppermost unit to lacustrine sediments post 1984 and between, to a transition unit resulting from the reservoir water infilling in 1983-1984. In addition, the upper unit shows 3 turbiditic-like layers (of 6, 20 and 13 cm thick) corresponding respectively to 1996, 2003 and 2008 major flood events (more than 20-year flood average daily outflow). These flood sequences result from underflow sedimentary inputs and contribute to 43% of the 151 kg/m² of accumulated sediments since 1984. Over the 1984-2010 period, sediments show a general contamination decrease but major flood events transport highly impacted sediments (highest enrichment factor > 20 for Hg and >10 for Cd and Bi), never reached during interflood periods. During these events, trace elements (TE) are mostly associated to organic fraction and clays. Rich-TE solid sources appear to be only solicited, and/or severely amplified, during important flood events over the recording period. In addition to these pollutants inputs, floods also bring an important detrital fraction, diluting anthropogenic TE signal. In details, flood deposits show variations of sedimentological and geochemical signals delimiting two distinct

  18. Sympathetic Activation and Baroreflex Function during Intradialytic Hypertensive Episodes

    PubMed Central

    Rubinger, Dvora; Backenroth, Rebecca; Sapoznikov, Dan

    2012-01-01

    Background The mechanisms of intradialytic increases in blood pressure are not well defined. The present study was undertaken to assess the role of autonomic nervous system activation during intradialytic hypertensive episodes. Methodology/Principal Findings Continuous interbeat intervals (IBI) and systolic blood pressure (SBP) were monitored during hemodialysis in 108 chronic patients. Intradialytic hypertensive episodes defined as a period of at least 10 mmHg increase in SBP between the beginning and the end of a dialysis session or hypertension resistant to ultrafiltration occurring during or immediately after the dialysis procedure, were detected in 62 out of 113 hemodialysis sessions. SBP variability, IBI variability and baroreceptor sensitivity (BRS) in the low (LF) and high (HF) frequency ranges were assessed using the complex demodulation technique (CDM). Intradialytic hypertensive episodes were associated with an increased (n = 45) or decreased (n = 17) heart rate. The maximal blood pressure was similar in both groups. In patients with increased heart rate the increase in blood pressure was associated with marked increases in SBP and IBI variability, with suppressed BRS indices and enhanced sympatho-vagal balance. In contrast, in those with decreased heart rate, there were no significant changes in the above parameters. End-of- dialysis blood pressure in all sessions associated with hypertensive episode was significantly higher than in those without such episodes. In logistic regression analysis, predialysis BRS in the low frequency range was found to be the main predictor of intradialytic hypertension. Conclusion/Significance Our data point to sympathetic overactivity with feed-forward blood pressure enhancement as an important mechanism of intradialytic hypertension in a significant proportion of patients. The triggers of increased sympathetic activity during hemodialysis remain to be determined. Intradialytic hypertensive episodes are associated

  19. Minimum recruitment frequency in plants with episodic recruitment.

    PubMed

    Wiegand, Kerstin; Jeltsch, Florian; Ward, David

    2004-10-01

    There is concern about the lack of recruitment of Acacia trees in the Negev desert of Israel. We have developed three models to estimate the frequency of recruitment necessary for long-term population survival (i.e. positive average population growth for 1,000 years and < 10% probability of extinction). Two models assume purely episodic recruitment based on the general notion that recruitment in arid environments is highly episodic. They differ in that the deterministic model investigates average dynamics while the stochastic model does not. Studies indicating that recruitment episodes in arid environments have been overemphasized motivated the development of the third model. This semi-stochastic model simulates a mixture of continuous and episodic recruitment. Model analysis was done analytically for the deterministic model and via running model simulations for the stochastic and semi-stochastic models. The deterministic and stochastic models predict that, on average, 2.2 and 3.7 recruitment events per century, respectively, are necessary to sustain the population. According to the semi-stochastic model, 1.6 large recruitment events per century and an annual probability of 50% that a small recruitment event occurs are needed. A consequence of purely episodic recruitment is that all recruitment episodes produce extremely large numbers of recruits (i.e. at odds with field observations), an evaluation that holds even when considering that rare events must be large. Thus, the semi-stochastic model appears to be the most realistic model. Comparing the prediction of the semi-stochastic model to field observations in the Negev desert shows that the absence of observations of extremely large recruitment events is no reason for concern. However, the almost complete absence of small recruitment events is a serious reason for concern. The lack of recruitment may be due to decreased densities of large mammalian herbivores and might be further exacerbated by possible changes

  20. Anomalously high radon concentrations in dwellings located on permeable glacial sediments.

    PubMed

    Sundal, A V; Jensen, C L; Anestad, K; Strand, T

    2007-09-01

    Indoor radon concentrations were measured in different seasons in 104 dwellings located on a highly permeable ice-marginal moraine in Kinsarvik, Western Norway. The measurements revealed the highest indoor radon levels ever detected in Norway and extreme variations in seasonal and short-term indoor radon levels. Annual average indoor radon concentrations up to 56 000 Bq m(-3) and a mean value of 4340 Bq m(-3) for the whole residential area are reported. By using the ICRP conversion factors to effective dose, these indoor radon values correspond to a total annual effective dose of 930 mSv and 72 mSv, respectively. By using the conversion as recommended by UNSCEAR, the effective doses would be about 50% higher. The indoor radon concentrations are found to be strongly influenced by thermally induced flows of radon-bearing soil air directed towards the upper part of the ice-marginal deposit in winter and towards the area of lowest elevation in summer. The pattern of seasonal variations observed suggests that in areas where thermal convection may occur, annual average indoor radon levels should be derived from measurements performed both in summer and in winter.

  1. Self-templated synthesis of TiO2 hierarchical structure photocatalyst with high efficiency and good sedimentation property

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoning; Sang, Yuanhua; Yu, Xin; Liu, Baishan; Liu, Hong

    2016-10-01

    The balance between highly efficient photocatalysis and a good emulsion/water extraction property is crucial for the practical application of TiO2 photocatalysts. The TiO2 hierarchical structure was synthesized via a hydrothermal treatment of H2Ti3O7 nanobelts with TiF4. The hydrolysis of TiF4 supplies the TiO2 nucleus, and HF, which is derived from the hydrolysis process, acts as a corrosive to etch the H2Ti3O7 nanobelt, resulting in a dynamic dissolution and precipitation process. The etching process resulted in self-generated TiF4 and initiated hydrolysis to generate new TiO2 primary particles. Induced by F etching process, Ti3+ defects were formed in the hierarchical structures, which was beneficial to the photocatalytic property. This hydrolysis-etching-hydrolysis process allows for template dissolution and self-assembly of anatase TiO2 nanobelts to form the TiO2 hierarchical structures. This process balances the nanominiaturization and sedimentation property requirements by the photocatalytic and emulsion/water extraction properties. This simple hydrolysis-etching-hydrolysis process can be applied to the synthesis of many other hierarchical structures.

  2. Aluminum forms in stream sediment: Relation to bedrock geology and water chemistry

    SciTech Connect

    Turner, R.R.; Bogle, M.A.; Zeiler, M.A.; Mulholland, P.J.; Elwood, J.W.; Cook, R.B.

    1987-01-01

    Longitudinal gradients in sediment and water chemistry were characterized in a high elevation stream in the southern Appalachian Mountains, USA, to elucidate the geochemical behavior of aluminum across gradients in pH (4.5 to 6.5) and elevation (1120 to 1895 m). Observed gradients are driven in part by the presence of pyritic bedrock, which occurs at higher elevations and yields acidity when exposed to oxidation by landslide activity. Exchangeable Al in sediment (estimated using potassium chloride) varied in response to monomeric Al in streamwater and thus decreased downstream. Organic Al in sediment (estimated using sodium pyrophosphate) did not vary in proportion to the organic carbon content of sediment. Amorphous Al in sediment (estimated as the difference between oxalate- and pyrophosphate-extractable Al) and Al extractable with acidified streamwater (pH 4.5) was lowest at the more acidic sites. These results suggest that increases in soluble Al in downstream reaches during episodic pH depressions could be due in part to the release of adsorbed and/or precipitated Al in sediment.

  3. Hydrothermal fluid effects on sediment column in Middle Valley, Juan de Fuca Ridge (northeast Pacific)

    SciTech Connect

    Al-Aasm, I.S.; Blaise, B.

    1987-05-01

    Core PAR 85-34, located near a high heat flow area in Middle Valley, northern Juan de Fuca Ridge, contains carbonate nodules of various sizes (less than or equal to 1-5 cm in length). Sedimentological, geochemical, and isotopic results allow us to understand the origin of these concretions and the effects of hydrothermal activity from nearby sulfide vents on the sediment column. The mineralogy of the olive-gray surface sediment (0-15 cm) is identical to unaffected hemipelagic sediments in the region except for a concentration of barite crystals (up to 1 cm) at the water-sediment interface. In the clay, mud fraction, and bulk sediment, the FeO, S, Ba, Cu, Ni, Pb, Zn and As are more enriched than in normal hemipelagic sediment in the area due to hydrothermal activity. Petrographic and SEM analysis of the nodules reveal iron calcite and barite minerals in cracks and on the outside part of the nodules with mineralogical and textural variations downcore. Stable isotope curves of these nodules appear to demonstrate the effects of both bacterial sulfate reduction and microbiological methane generation, with consequent extreme /sup 13/C-depletion in the precipitated carbonate. The curves also demonstrate that the hydrothermal fluid entering the system may have caused the negative shift in oxygen isotopes downcore, although this effect may have been of cyclic or episodic nature.

  4. Are high p-wave velocity sediments on thin Tethyan crust, deep-water carbonates?

    NASA Astrophysics Data System (ADS)

    Gutscher, Marc-Andre; Graindorge, David; Klingelhoefer, Frauke; Dellong, David; Kopp, Heidrun; Sallares, Valenti; Bartolome, Rafael; Gallais, Flora

    2016-04-01

    Seismic reflection profiles from the Central Mediterranean and Gulf of Cadiz regions indicate the widespread presence of a seismic unit, marked by strong continuous reflectors, directly overlying the basement. Seismic velocity analysis from seismic reflection and refraction studies indicate high p-wave velocities of 3.5 - 4.5 km/s in this layer. These same seismic studies image a thin crust, typically 6-9 km thick, in most cases thought to be oceanic in nature and related to the Tethys oceanic domain separating Africa (Gondwana) from Laurussia. We interpret this 2-3 km thick reflective layer to be carbonates, deposited in the late Triassic, Jurassic and early Cretaceous in the Tethys Ocean, in deep marine basins. Few drilling studies have penetrated into this layer. In one case (DSDP site 135, drilled at 4152 m water depth on Coral Patch Ridge in the western Gulf of Cadiz), Aptian (early Cretaceous) marls and limestone were drilled (560-689 m sub-seafloor depth). The Calcite compensation depth during the Jurassic to Early Cretaceous was about 4000 m to 3500 m according to compilations from the Atlantic and Indian Oceans and is consistent with deposition of deep-water carbonates. For the NW Moroccan margin (Mazagan transect near El Jadida) there is a 2 km thick sedimentary layer with p-wave velocities of 4.0 - 4.5 km/s at the base of a 4 - 6 km thick sedimentary section. This layer extends from seafloor thought to be oceanic crust (west of the West African Coast magnetic anomaly) across a domain of thin/transitional crust with abundant Triassic salt diapirs to the foot of the margin. This reflective basal layer is also observed in reflection and refraction profiles from the Seine abyssal plain, below the toe of the Cadiz accretionary wedge (S. Algarve margin), in the Ionian abyssal plain and below the toe of the Calabrian accretionary wedge, all regions floored by this thin Tethyan crust. Work is in progress to determine the exact nature of this crust.

  5. Bridging the Gap between Brain and Behavior: Cognitive and Neural Mechanisms of Episodic Memory

    ERIC Educational Resources Information Center

    Eichenbaum, Howard; Fortin, Norbert J.

    2005-01-01

    The notion that non-human animals are capable of episodic memory is highly controversial. Here, we review recent behavioral work from our laboratory showing that the fundamental features of episodic memory can be observed in rats and that, as in humans, this capacity relies on the hippocampus. We also discuss electrophysiological evidence, from…

  6. Aquatic sediments

    SciTech Connect

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

    1990-06-01

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

  7. A unique memory process modulated by emotion underpins successful odor recognition and episodic retrieval in humans

    PubMed Central

    Saive, Anne-Lise; Royet, Jean-Pierre; Ravel, Nadine; Thévenet, Marc; Garcia, Samuel; Plailly, Jane

    2014-01-01

    We behaviorally explore the link between olfaction, emotion and memory by testing the hypothesis that the emotion carried by odors facilitates the memory of specific unique events. To investigate this idea, we used a novel behavioral approach inspired by a paradigm developed by our team to study episodic memory in a controlled and as ecological as possible way in humans. The participants freely explored three unique and rich laboratory episodes; each episode consisted of three unfamiliar odors (What) positioned at three specific locations (Where) within a visual context (Which context). During the retrieval test, which occurred 24–72 h after the encoding, odors were used to trigger the retrieval of the complex episodes. The participants were proficient in recognizing the target odors among distractors and retrieving the visuospatial context in which they were encountered. The episodic nature of the task generated high and stable memory performances, which were accompanied by faster responses and slower and deeper breathing. Successful odor recognition and episodic memory were not related to differences in odor investigation at encoding. However, memory performances were influenced by the emotional content of the odors, regardless of odor valence, with both pleasant and unpleasant odors generating higher recognition and episodic retrieval than neutral odors. Finally, the present study also suggested that when the binding between the odors and the spatio-contextual features of the episode was successful, the odor recognition and the episodic retrieval collapsed into a unique memory process that began as soon as the participants smelled the odors. PMID:24936176

  8. Potential effects of runoff, fluvial sediment, and nutrient discharges on the coral reefs of Puerto Rico

    USGS Publications Warehouse

    Larsen, M.C.; Webb, R.M.T.

    2009-01-01

    Coral reefs, the foundation and primary structure of many highly productive and diverse tropical marine ecosystems, have been degraded by human activity in much of the earth's tropical oceans. To contribute to improved understanding of this problem, the potential relation between river sediment and nutrient discharges and degradation of coral reefs surrounding Puerto Rico was studied using streamflow, suspended-sediment, and water-quality data. Mean annual runoff for the 8711 km2 island is 911 mm, about 57% of mean annual precipitation (1600 mm). Mean annual suspended-sediment discharge from Puerto Rico to coastal waters is estimated at 2.7-9.0 million metric tonnes. Storm runoff transports a substantial part of sediment: the highest recorded daily sediment discharge is 1-3.6 times the mean annual sediment discharge. Hurricane Georges (1998) distributed an average of 300 mm of rain across the island, equivalent to a volume of about 2.6 billion m3. Runoff of more than 1.0 billion m3 of water and as much as 5 to 10 million metric tonnes of sediment were discharged to the coast and shelf. Nitrogen and phosphorous concentrations in river waters are as much as 10 times the estimated presettlement levels. Fecal coliform and fecal streptococcus concentrations in many Puerto Rico rivers are near or above regulatory limits. Unlike sediment discharges, which are predominantly episodic and intense, river-borne nutrient and fecal discharge is a less-intense but chronic stressor to coral reefs found near the mouths of rivers. Negative effects of riverderived sediment and nutrient discharge on coral reefs are especially pronounced on the north, southwest, and west coasts.

  9. Sediment distribution and transport along a rocky, embayed coast: Monterey Peninsula and Carmel Bay, California

    USGS Publications Warehouse

    Storlazzi, C.D.; Field, M.E.

    2000-01-01

    Field measurements of beach morphology and sedimentology were made along the Monterey Peninsula and Carmel Bay, California, in the spring and summer of 1997. These data were combined with low-altitude aerial imagery, high-resolution bathymetry, and local geology to understand how coastal geomorphology, lithology, and tectonics influence the distribution and transport of littoral sediment in the nearshore and inner shelf along a rocky shoreline over the course of decades. Three primary modes of sediment distribution in the nearshore and on the inner shelf off the Monterey Peninsula and in Carmel Bay were observed. Along stretches of the study area that were exposed to the dominant wave direction, sediment has accumulated in shore-normal bathymetric lows interpreted to be paleo-stream channels. Where the coastline is oriented parallel to the dominant wave direction and streams channels trend perpendicular to the coast, sediment-filled paleo-stream channels occur in the nearshore as well, but here they are connected to one another by shore-parallel ribbons of sediment at depths between 2 and 6 m. Where the coastline is oriented parallel to the dominant wave direction and onshore stream channels are not present, only shore-parallel patches of sediment at depths greater than 15 m are present. We interpret the distribution and interaction or transport of littoral sediment between pocket beaches along this coastline to be primarily controlled by the northwest-trending structure of the region and the dominant oceanographic regime. Because of the structural barriers to littoral transport, peaks in wave energy appear to be the dominant factor controlling the timing and magnitude of sediment transport between pocket beaches, more so than along long linear coasts. Accordingly, the magnitude and timing of sediment transport is dictated by the episodic nature of storm activity. (C) 2000 Elsevier Science B.V.

  10. Current-use pesticides and organochlorine compounds in precipitation and lake sediment from two high-elevation national parks in the Western United States

    USGS Publications Warehouse

    Mast, M.A.; Foreman, W.T.; Skaates, S.V.

    2007-01-01

    Current-use pesticides (CUPs) and banned organochlorine compounds (OCCs) were measured in precipitation (snowpack and rain) and lake sediments from two national parks in the Western United States to determine their occurrence and distribution in high-elevation environments. CUPs frequently detected in snow were endosulfan, dacthal, and chlorothalonil in concentrations ranging from 0.07 to 2.4 ng/L. Of the OCCs, chlordane, hexachlorobenzene, and two polychlorinated biphenyl congeners were detected in only one snow sample each. Pesticides most frequently detected in rain were atrazine, carbaryl, and dacthal in concentrations from 3.0 to 95 ng/L. Estimated annual deposition rates in one of the parks were 8.4 ??g/m2 for atrazine, 9.9 ??g/m2 for carbaryl, and 2.6 ??g/m2 for dacthal, of which >85% occurred during summer. p,p'-DDE and p,p'-DDD were the most frequently detected OCCs in surface sediments from lakes. However, concentrations were low (0.12 to 4.7 ??g/kg) and below levels at which harmful effects for benthic organisms are likely to be observed. DDD and DDE concentrations in an age-dated sediment core suggest that atmospheric deposition of DDT and its degradates, and possibly other banned OCCs, to high-elevation areas have been decreasing since the 1970s. Dacthal and endosulfan sulfate were present in low concentrations (0.11 to 1.2 ??g/kg) and were the only CUPs detected in surface sediments. Both pesticides were frequently detected in snow, confirming that some CUPs entering high-elevation aquatic environments through atmospheric deposition are accumulating in lake sediments and potentially in aquatic biota as well. ?? 2007 Springer Science+Business Media, Inc.

  11. Current-use pesticides and organochlorine compounds in precipitation and lake sediment from two high-elevation national parks in the Western United States.

    PubMed

    Mast, M A; Foreman, W T; Skaates, S V

    2007-04-01

    Current-use pesticides (CUPs) and banned organochlorine compounds (OCCs) were measured in precipitation (snowpack and rain) and lake sediments from two national parks in the Western United States to determine their occurrence and distribution in high-elevation environments. CUPs frequently detected in snow were endosulfan, dacthal, and chlorothalonil in concentrations ranging from 0.07 to 2.4 ng/L. Of the OCCs, chlordane, hexachlorobenzene, and two polychlorinated biphenyl congeners were detected in only one snow sample each. Pesticides most frequently detected in rain were atrazine, carbaryl, and dacthal in concentrations from 3.0 to 95 ng/L. Estimated annual deposition rates in one of the parks were 8.4 microg/m2 for atrazine, 9.9 microg/m2 for carbaryl, and 2.6 microg/m2 for dacthal, of which >85% occurred during summer. p,p'-DDE and p,p'-DDD were the most frequently detected OCCs in surface sediments from lakes. However, concentrations were low (0.12 to 4.7 microg/kg) and below levels at which harmful effects for benthic organisms are likely to be observed. DDD and DDE concentrations in an age-dated sediment core suggest that atmospheric deposition of DDT and its degradates, and possibly other banned OCCs, to high-elevation areas have been decreasing since the 1970s. Dacthal and endosulfan sulfate were present in low concentrations (0.11 to 1.2 microg/kg) and were the only CUPs detected in surface sediments. Both pesticides were frequently detected in snow, confirming that some CUPs entering high-elevation aquatic environments through atmospheric deposition are accumulating in lake sediments and potentially in aquatic biota as well.

  12. Wild chacma baboons (Papio ursinus) remember single foraging episodes.

    PubMed

    Noser, Rahel; Byrne, Richard W

    2015-07-01

    Understanding animal episodic-like memory is important for tracing the evolution of the human mind. However, our knowledge about the existence and nature of episodic-like memory in non-human primates is minimal. We observed the behavio