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排序方式: 共有341条查询结果,搜索用时 203 毫秒
121.
Juciene Andrade Figueiredo Eldemar Albuquerque Menor Maria Teresa Taboada-Castro Maria Mercedes Taboada-Castro Luís Drude Lacerda 《Applied Geochemistry》2012
This paper presents a method based on hydrogeochemical signatures for the identification of flow components, from the descending limb to the baseflow, without the direct support of hydrographs. The proposed model was built using chemical analysis of waters from a small agro-forestry catchment having a temperate climate. The sampling was performed every 15 days at the Corbeira stream outlet, from 2004 to 2008. A statistical approach was used with particulate P/dissolved P (PP/DP) values, resulting in a global histogram, within which mini-Gaussian distributions were highlighted. The mean of each group of highlighted PP/DP values, as well as all other selected analytical parameters, were calculated and plotted in Cartesian diagrams. The results showed the hydrogeochemical signatures of the Corbeira stream in the descending limb to baseflow conditions. Scatterplots of the migration of particulate matter showed linear regressions forming α ≠ 0 to the X-axis, while dissolved compounds showed parallel linearity (α = 0) in relation to the same axis. Deflections in the linear behavior point to significant changes in the chemical concentrations from different types of aqueous inputs. Flow components in the descending limb show distinct ranges along the X-axis: the mean PP/DP values. The ranges varying from 3.3 to 2.0 correspond to its upper phases from 2.0 to 0.9 suggests mixtures between inflows and from 0.9 to 0.3 denote subsurface flow dominance. Finally, PP/DP < 0.3 indicates exclusive baseflow conditions. These intervals are specific to the Corbeira catchment as a consequence of its geographical characteristics and should be numerically different from the proposed method if applied to other catchments. However, this method remains valid for application in other small catchments as the PP/DP ranges in the descending limb are defined by the relative behavior between the linear correlations from the hydrogeochemical concentrations plotted in a Cartesian diagram. 相似文献
122.
Non‐Metabolic Uptake of Al3+ by Dead Leaves of Rubus ulmifolius: Comparison With Metabolic Bioaccumulation Data
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123.
Jim Braun Jon Dumm Francesco De Palma Chad Finley Albrecht Karle Teresa Montaruli 《Astroparticle Physics》2008,29(4):299-305
Neutrino telescopes are moving steadily toward the goal of detecting astrophysical neutrinos from the most powerful galactic and extragalactic sources. Here we describe analysis methods to search for high energy point-like neutrino sources using detectors deep in the ice or sea. We simulate an ideal cubic kilometer detector based on real world performance of existing detectors such as AMANDA, IceCube, and ANTARES. An unbinned likelihood ratio method is applied, making use of the point spread function and energy distribution of simulated neutrino signal events to separate them from the background of atmospheric neutrinos produced by cosmic ray showers. The unbinned point source analyses are shown to perform better than binned searches and, depending on the source spectral index, the use of energy information is shown to improve discovery potential by almost a factor of two. 相似文献
124.
John L. Daniels Gautham P. Das Maria Teresa Serrano Hernandez Sunyoung Bae 《Marine Georesources & Geotechnology》2013,31(3):183-191
The Taiwan Strait region has many miles of coastline, and the Taiwan Straits Tunnel (TST) project faces many potential pollution problems as construction proceeds through sensitive areas. Conventional approaches for pollution mitigation require further examination. The recent development of nanoscale particle technology has shown distinct advantages for contaminant attenuation and ground improvement. This paper is focused on trace metals and is part of the overall effort to develop the nanoscale particle technology. Trace metals in ground and surface waters represent a continued threat to human and ecological health. One of the difficulties in removing toxic concentrations of trace metals from solution is the variable oxidation state and amphoteric nature of multiple constituents. In particular, while cationic metals (e.g., Pb2+, Cd2+, Ni2+) may be rendered less mobile under high pH conditions, anionic metals (e.g., AsO4 3?, CrO4 2?, SeO4 2?)may become more mobile. The objective of this research was to evaluate the sorption of both cationic and anionic trace elements, including arsenic (As), cadmium (Cd), chromium (Cr) and selenium (Se) under batch conditions. Mixtures of a local residual soil were tested alone and in combination with lime and zero valent iron. It was hypothesized that lime would raise the pH and precipitate positively charged metals while zero valent iron would create reducing conditions favorable to the immobilization of negatively charged metals. Results indicate that the use of lime and/or zero valent iron can increase the sorption capacity of soil. Compared to the baseline soil, sorption capacity increased with addition of lime for arsenic and cadmium while it decreased for chromium and selenium. In the case of zero valent iron addition, sorption capacity increased for cadmium, chromium and selenium, while showing no change for arsenic. When both lime and zero valent iron were used, the sorption capacity increased for all metals tested. These results suggest that the combined use of lime and zero valent iron may serve as an alternative treatment technology for removing trace metals from contaminated water systems. 相似文献
125.
Gaetano Robustelli Federica Luc Fabio Corbi Teresa Pelle Francesco Dramis Giandomenico Fubelli Fabio Scarciglia Francesco Muto Domenico Cugliari 《Geomorphology》2009,106(3-4):165-179
In this paper we present the results of an integrated geomorphological, pedological and stratigraphical study carried out along the Ionian coast of northern Calabria (southern Italy). This area is characterised by the occurrence of five orders of alluvial terraces that are striking features of the landscape, where large and steep catchments debouch from the mountain front to the hilly coastal belt.Field investigations indicate that the deposits of all five terraces are suggestive of shallow gravel-bed braided streams.On the basis of the age of the Pleistocene substratum and morphostratigraphic correlation with marine terraces cropping out in the nearby areas, each order has been associated to specific marine oxygen isotope stages.Consequently, we focused on the interplay of allocyclic factors influencing stream aggradation/degradation. Soil features and other climatic proxies suggest that climate didn't play an important role with respect to tectonic and base-level changes in controlling fluvial dynamics.In particular, we recognised that during the middle Pleistocene the study area experienced a period of subaerial landscape modelling, as suggested by the thick and complex alluvial sequence of the highest terrace (T1). The onset of regional uplift marks a change in the geomorphic scenario, with tectonic and eustatically driven changes in base-level working together in causing switches in fluvial aggradational/erosional phases (T2–T5 terraces). Because of the uplift, river dissection occurred during phases of sea level fall, whereas aggradation phases occurred during periods of climate amelioration (sea level rise) just before highstands were attained.As a consequence, the stepped terraces in the study area reflect the interplay between tectonics (uplift) and sea level changes, in which terraces define episodes of relative sea level fall during the late Quaternary. 相似文献
126.
The 2013 eruption of Pavlof Volcano, Alaska began on 13 May and ended 49 days later on 1 July. The eruption was characterized by persistent lava fountaining from a vent just north of the summit, intermittent strombolian explosions, and ash, gas, and aerosol plumes that reached as high as 8 km above sea level and on several occasions extended as much as 500 km downwind of the volcano. During the first several days of the eruption, accumulations of spatter near the vent periodically collapsed to form small pyroclastic avalanches that eroded and melted snow and ice to form lahars on the lower north flank of the volcano. Continued lava fountaining led to the production of clastogenic lava flows that extended to the base of the volcano, about 3–4 km beyond the vent. The generation of fountain-fed lava flows was a dominant process during the 2013 eruption; however, episodic collapse of spatter accumulations and formation of hot spatter-rich granular avalanches was a more efficient process for melting snow and ice and initiating lahars. The lahars and ash plumes generated during the eruption did not pose any serious hazards for the area. However, numerous local airline flights were cancelled or rerouted, and trace amounts of ash fall occurred at all of the local communities surrounding the volcano, including Cold Bay, Nelson Lagoon, Sand Point, and King Cove. 相似文献
127.
Lateglacial and Holocene palaeohydrology in the western Mediterranean region: The Lake Estanya record (NE Spain) 总被引:3,自引:0,他引:3
Mario Morelln Blas Valero-Garcs Teresa Vegas-Vilarrúbia Penlope Gonzlez-Sampriz
scar Romero Antonio Delgado-Huertas Pilar Mata Ana Moreno Mayte Rico Juan Pablo Corella 《Quaternary Science Reviews》2009,28(25-26):2582-2599
The multi-proxy analysis of sediment cores recovered in karstic Lake Estanya (42°02′ N, 0°32′ E; 670 m a. s. l., NE Spain), located in the transitional area between the humid Pyrenees and the semi-arid Central Ebro Basin, provides the first high-resolution, continuous sedimentary record in the region, extending back the last 21 000 years. The integration of sedimentary facies, elemental and isotopical geochemistry and biogenic silica, together with a robust age model based on 17 AMS radiocarbon dates, enables precise reconstruction of the main hydrological and environmental changes in the region during the last deglaciation.Arid conditions, represented by shallow lake levels, predominantly saline waters and reduced organic productivity occurred throughout the last glacial maximum (21–18 cal kyrs BP) and the lateglacial, reaching their maximum intensity during the period 18–14.5 cal kyrs BP (including Heinrich event 1) and the Younger Dryas (12.9–11.6 cal kyrs BP). Less saline conditions characterized the 14.5–12.6 cal kyrs BP period, suggesting higher effective moisture during the Bölling/Allerød. The onset of more humid conditions started at 9.4 cal kyrs, indicating a delayed hydrological response to the onset of the Holocene which is also documented in several sites of the Mediterranean Basin. Higher, although fluctuating, Holocene lake levels were punctuated by a mid Holocene arid period between 4.8 and 4.0 cal kyrs BP. A major lake-level rise occurred at 1.2 cal kyrs BP, conducive to the establishment of conditions similar to the present and interrupted by a last major water level drop, occurring around 800 cal yrs BP, which coincides with the Medieval Climate Anomaly.The main hydrological stages in Lake Estanya are in phase with most Western Mediterranean and North Atlantic continental and marine records, but our results also show similarities with other Iberian and northern African reconstructions, emphasizing peculiarities of palaeohydrological evolution of the Iberian Peninsula during the last deglaciation. 相似文献
128.
Guidelines on the use of inverse velocity method as a tool for setting alarm thresholds and forecasting landslides and structure collapses 总被引:4,自引:4,他引:0
Tommaso Carlà Emanuele Intrieri Federico Di Traglia Teresa Nolesini Giovanni Gigli Nicola Casagli 《Landslides》2017,14(2):517-534
Predicting the time of failure is a topic of major concern in the field of geological risk management. Several approaches, based on the analysis of displacement monitoring data, have been proposed in recent years to deal with the issue. Among these, the inverse velocity method surely demonstrated its effectiveness in anticipating the time of collapse of rock slopes displaying accelerating trends of deformation rate. However, inferring suitable linear trend lines and deducing reliable failure predictions from inverse velocity plots are processes that may be hampered by the noise present in the measurements; data smoothing is therefore a very important phase of inverse velocity analyses. In this study, different filters are tested on velocity time series from four case studies of geomechanical failure in order to improve, in retrospect, the reliability of failure predictions: Specifically, three major landslides and the collapse of an historical city wall in Italy have been examined. The effects of noise on the interpretation of inverse velocity graphs are also assessed. General guidelines to conveniently perform data smoothing, in relation to the specific characteristics of the acceleration phase, are deduced. Finally, with the aim of improving the practical use of the method and supporting the definition of emergency response plans, some standard procedures to automatically setup failure alarm levels are proposed. The thresholds which separate the alarm levels would be established without needing a long period of neither reference historical data nor calibration on past failure events. 相似文献
129.
The Calatabiano landslide (southern Italy): preliminary GB-InSAR monitoring data and remote 3D mapping 总被引:1,自引:1,他引:0
Luca Lombardi Massimiliano Nocentini William Frodella Teresa Nolesini Federica Bardi Emanuele Intrieri Tommaso Carlà Lorenzo Solari Giulia Dotta Federica Ferrigno Nicola Casagli 《Landslides》2017,14(2):685-696
On 24 October 2015, following a period of heavy rainfall, a landslide occurred in the Calatabiano Municipality (Sicily Island, Southern Italy), causing the rupture of a water pipeline supplying water to the city of Messina. Following this event, approximately 250,000 inhabitants of the city suffered critical water shortages for several days. Consequently, on 6 November 2015, a state of emergency was declared (O.C.D.P. 295/2015) by the National Italian Department of Civil Protection (DPC). During the emergency management phase, a provisional by-pass, consisting of three 350-m long pipes passing through the landslide area, was constructed to restore water to the city. Furthermore, on 11 November 2015, a landslide remote-sensing monitoring system was installed with the following purposes: (i) analyse the landslide geomorphological and kinematic features in order to assess the residual landslide risk and (ii) support the early warning procedures needed to ensure the safety of the personnel involved in the by-pass construction and the landslide stabilization works. The monitoring system was based on the combined use of Ground-Based Interferometric Synthetic Aperture Radar (GB-InSAR) and terrestrial laser scanning (TLS). In this work, the preliminary results of the monitoring activities and a remote 3D map of the landslide area are presented. 相似文献
130.
José R. Martínez Catalán Ricardo Arenas Jacobo Abati Sonia Sánchez Martínez Florentino Díaz García Javier Fernández Suárez Pablo González Cuadra Pedro Castiñeiras Juan Gómez Barreiro Alejandro Díez Montes Emilio González Clavijo Francisco J. Rubio Pascual Pilar Andonaegui Teresa E. Jeffries James E. Alcock Rubén Díez Fernández Alicia López Carmona 《Comptes Rendus Geoscience》2009,341(2-3):114-126
Ophiolites of different Paleozoic ages occur in North-West (NW) Iberia in a rootless suture representing the remnants of the Rheic Ocean. Associated allochthonous terranes in the hanging- and foot-walls of the suture derive from the former margins, whereas the relative autochthon corresponds to the Paleozoic passive margin of northern Gondwana. The Paleozoic tectonic evolution of this part of the circum-Atlantic region is deduced from the stratigraphical, petrological, structural and metamorphic evolution of the different units and their ages. The tectonic reconstruction covers from Cambro-Ordovician continental rifting and the opening of the Rheic Ocean to its Middle to Upper Devonian closure. Then, the Variscan Laurussia–Gondwana convergence and collision is briefly described, from its onset to the late stages of collapse associated with the demise of the orogenic roots. 相似文献