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51.
Seagrass meadows are ecosystems of great ecological and economical value and their monitoring is an important task within coastal environmental management. In this paper, an acoustic mapping technique is presented using a profiling sonar. The method has been applied to three different sites with meadows of Zostera marina, Zostera noltii and Posidonia oceanica respectively, with the aim to test the method’s applicability. 相似文献
52.
Stefania Bilardi Richard T. Amos David W. Blowes Paolo S. Calabrò Nicola Moraci 《Ground Water Monitoring & Remediation》2013,33(1):97-104
MIN3P, a multicomponent reactive transport model for variably saturated porous media, is used to simulate the outputs of column tests carried out using zero valent iron (ZVI) for nickel contaminated groundwater remediation. The objective of this study is to investigate the main chemical reactions involved in contaminant removal and the main causes of the reactivity decline of ZVI over time. According to the results of the model the major causes of ZVI reactivity loss is identified in the mineral precipitation of α‐FeOOH on iron surface that probably caused ZVI passivation and led to a decline of the electron transfer rate. An existing empirical relationship between mineral precipitation and the reactivity loss of ZVI, included in the model, reproduced the changes in nickel removal observed during different laboratory column tests. 相似文献
53.
Christian Ferrarin Andrea Cucco Georg Umgiesser Debora Bellafiore Carl L. Amos 《Continental Shelf Research》2010
To describe the exchange of water and sediment through the Venice Lagoon inlets a 3-D hydrodynamic and sediment transport model has been developed and applied to a domain comprising Venice Lagoon and a part of the Adriatic Sea. The model has been validated for both current velocities and suspended particle concentration against direct observations and from observations empirically derived fluxes from upward-looking acoustic Doppler current profiler probes installed inside each inlet. The model provides estimates of the suspended sediment transport in the lower 3 m of the water column that is not detected by acoustic Doppler current profiler sensors. The bedload model prediction has been validated against measured sand transport rates collected by sand traps deployed in the Lido and Chioggia inlets. Results indicate that, in the Lido inlet, 87% of the total load is in suspension, while the rest moves as bedload. 相似文献
54.
This study fits into a wider research program from RWS RIKZ concerning the exchange of sediment between the coast and the tidal basins, Western Scheldt and Wadden Sea, which are the largest basins along the Dutch Coast, over different time-scales. For both basins, questions about the evolution of the import/export at the mouth recently arose. In case of the Western Scheldt, which is the subject of this study, mainly the uncertainty about the future developments after the change from import to export at the mouth was noticed in the 1990s, which necessitated a more detailed study of this area. 相似文献
55.
A long radiometrically dated oxygen isotopic record of continental climatic variations since the penultimate glaciation was obtained from a stalagmite deposited in a sealed cave in Jerusalem. This record shows that speleothems have the potential of assigning dates to long- and short-term climatic events, with possible refining of Milankovitch tuning of ice and marine records which themselves are not datable. Short-term (1000-yr) events are very significant in the region, reaching 50% of glacial/interglacial fluctuations. The Mediterranean Sea was the most probable source of local precipitation throughout the last glacial cycle. 相似文献
56.
57.
Devendra Lal Christina D. Gallup Loïc Vacher Anthony J.T. Jull Robert C. Speed Amos Winter 《Geochimica et cosmochimica acta》2005,69(24):5717-5728
We present results of measurements of cosmogenic 10Be, 26Al and 36Cl, and the indigenous (intrinsic) concentrations of the stable elements Be, Al and Cl in 120-200 kyr old corals from Barbados and Puerto Rico. The concentration levels of these radionuclides in the corals lie in the range 104 to 108 atoms/g. A comparison of the measured nuclide concentrations with those expected to be produced in the corals by nuclear interactions of energetic cosmic radiation shows that (i) the radionuclides 26Al and 36Cl are derived from in situ cosmic ray interactions in the corals after their formation, but that (ii) the radionuclide 10Be owes its provenance in the coralline lattice primarily due to incorporation of dissolved beryllium in seawater in the lattice structure of the corals. 相似文献
58.
Supply limited sediment transport in a high-discharge event of the tropical Burdekin River, North Queensland, Australia 总被引:1,自引:0,他引:1
Kathryn J. Amos Jan Alexander Anthony Horn† Geoff D. Pocock‡ Chris R. Fielding§ 《Sedimentology》2004,51(1):145-162
Interactions between catchment variables and sediment transport processes in rivers are complex, and sediment transport behaviour during high‐flow events is not well documented. This paper presents an investigation into sediment transport processes in a short‐duration, high‐discharge event in the Burdekin River, a large sand‐ and gravel‐bed river in the monsoon‐ and cyclone‐influenced, semi‐arid tropics of north Queensland. The Burdekin's discharge is highly variable and strongly seasonal, with a recorded maximum of 40 400 m3 s?1. Sediment was sampled systematically across an 800 m wide, 12 m deep and straight reach using Helley‐Smith bedload and US P‐61 suspended sediment samplers over 16 days of a 29‐day discharge event in February and March 2000 (peak 11 155 m3 s?1). About 3·7 × 106 tonnes of suspended sediment and 3 × 105 tonnes of bedload are estimated to have been transported past the sample site during the flow event. The sediment load was predominantly supply limited. Wash load included clay, silt and very fine sand. The concentration of suspended bed material (including very coarse sand) varied with bedload transport rate, discharge and height above the bed. Bedload transport rate and changes in channel shape were greatest several days after peak discharge. Comparison between these data and sparse published data from other events on this river shows that the control on sediment load varies between supply limited and hydraulically limited transport, and that antecedent weather is an important control on suspended sediment concentration. Neither the empirical relationships widely used to estimate suspended sediment concentrations and bedload (e.g. Ackers & White, 1973) nor observations of sediment transport characteristics in ephemeral streams (e.g. Reid & Frostick, 1987) are directly applicable to this river. 相似文献
59.
Amos Bein 《Organic Geochemistry》1986,10(4-6)
A sequence of alternating lacustrine marls, peat and basalts was penetrated in the Notera-3 well in the northern part of the Jordan Rift, Israel. The 2781 m thick sequence, ranges from Upper Miocene to Recent, reflects high sedimentation rate in the active continental rift associated with the Dead Sea Transform. The deep burial and the relatively high geothermal gradient (40°C km−1) compensate for the short time span so that coalification expressed by vitrinite reflectance consistently increases with depth, from about 0.32% Ro at 1040 m to 0.48% Ro at 2495 m.Analysis of the peat reveals that the O/C, S/C and δ13C of the humic acids (HA) and the heavy to light normal alkane ratios are the only parameters sensitive enough to express this slight maturation increase with depth. A sharp δ13C change from about − 18‰ prevailing in the uppermost meters to an average of − 27.5‰ at 15 m and deeper reflects a change in the higher plant source of the peat (from C4 to C3 plants) rather than an early diagenetic modification.The δ13C, O/C, S/C and N/C ratios are usually lower in the kerogens than in the corresponding HA. The decrease in the δ13C and the O/C ratios are explained by elimination of oxygen-containing functional groups during transformation and by polymerization effects. The gradual decrease in the 12C and the O/C of the HA with depth are attributed to decarboxylation coupled with kinetic effects. The N/C depletion during the transformation from HA to kerogens probably results from the breakdown of amino acids. The S/C ratio which decreases both during this transformation and also with maturation is most readily explained by the breakdown of ester sulfate-containing groups such as sulfated polysaccarids, which formed diagenetically during the humification process. 相似文献
60.
In the eastern Mediterranean the collision of the Erastosthenes and the Anaximander Seamounts with the Cyprus arc results in a unique tectonic setting due to the small size of the eastern Mediterranean basin. As a result of the collision, some of the motion between the African plate and the Eurasian plate is taking place by thrust faulting along the north African passive margin. It seems that the stress at the plate boundary along the Cyprus arc may be transmitted southward to cause the reactivation of a pre-existing fault zone along the passive margin of eastern north Africa.
Zusammenfassung Im östlichen Mittelmeerbecken hat die Kollision des Erastosthenes und des Anaximander Seamounts mit dem Cypern-Bogen eine spezielle tektonische Situation geschaffen, die durch den engen Raum dieses Beckens bestimmt wird. Als Ergebnis dieser Kollision erscheinen Überschiebungen der Afrikanischen Platte auf Eurasische Platte entlang des passiven nordafrikanischen Randes. Es erscheint möglich, daß das Streßfeld an der Plattengrenze entlang des Zypernbogens südwärts wirkt und dadurch die alte Störungszone entlang des passiven Kontinentrandes von Nordafrika reaktiert wird.
Résumé En Méditerrannée orientale, la collision des guyots Eratosthène et Anaximandre avec l'arc de Chypre a engendré une situation tectonique particulière, due à la faible dimension du bassin est-méditerrannéen. Cette collision a eu pour conséquence la production de charriages de la plaque africaine sur la plaque eurasiatique le long de la marge passive nord-africaine. Il semble que les contraintes règnant au bord de la plaque le long de l'arc de Chypre se soient transmises vers le Sud pour y provoquer la réactivation d'une zône failleuse préexistante le long de la marge passive du NE de l'Afrique.
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