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41.
Pietro Vittorio Curzi Enrico Dinelli Marianna Ricci Lucchi Stefano Claudio Vaiani 《Geological Journal》2006,41(5):591-612
Accumulation of continental, deltaic and shallow‐marine sediments in the Po River coastal plain preserves a record of the Late Quaternary sea‐level changes and shoreline migrations. The palaeoenvironmental evolution of this area and the changes in composition and provenance of sediments have been investigated through integrated sedimentological, micropalaeontological (mainly foraminifers) and geochemical analyses of core S1, from the southern part of the Po River delta, within a chronological framework supported by radiocarbon dating and correlations with adjacent core sequences. Eleven lithofacies, grouped into five facies associations, and four palaeontological assemblages provide the basis to define the palaeoenvironmental reconstruction of this succession consisting, from the base to the top, of: (i) continental sediments accumulated during the Late Pleistocene; (ii) back‐barrier sediments marking the onset of Holocene sea‐level rise; (iii) transgressive sands deposited during the rapid landward migration of a barrier‐lagoon system; (iv) shallow‐marine and prodelta sediments with faunal associations indicating a gradual approach to the Po River mouth; and (v) sub‐recent delta front sands that form a considerable portion of the present coastal plain. Bulk chemical composition of sediments shows remarkable relationships with palaeoenvironments and locally improves facies characterizations. For example, they reveal carbonate leaching that emphasizes the occurrence of palaeosols in continental deposits or record enrichments in loss on ignition, S and Br, diagnostic of organic‐rich layers in back‐shore sediments. Selected geochemical elements (e.g. Mg and Ni) are particularly effective for the recognition of sediment provenances from the three main source areas observed in the subsurface deposits of the Po River coastal plain (e.g. Apenninic rivers, North Adriatic rivers and Po River). An Apenninic provenance is observed in continental and back‐barrier sediments. A North Adriatic provenance characterizes the transgressive sands and the shallow‐marine deposits; a significant Po River provenance is recorded in sediments related to the onset of the prodelta environment, confirmed by foraminiferal assemblages indicating remarkable increase in fluvial influxes. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
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Ocean Dynamics - Effects of the viscosity, Earth rotation, and sphericity (beta-effect) on the long-wave dynamics are investigated based on the linear model. The basic equation for the complex... 相似文献
43.
Uncertainty in applying the linear poroelasticity model to field situations as a result of periodic loading in heterogeneous aquifers 
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下载免费PDF全文 The solid Earth's surface frequently experience changes in total stresses as a result of periodic loading. When the fluid‐saturated porous media deform in response to changes in stress, the induced variations in pore volume affect the pore water pressure. The fluid flow therefore occurs in response to the gradient in the induced excess pore water pressure. This work aims at quantifying the spatial variability in excess pressure head produced by the periodic loading accounting for the variation of log hydraulic conductivity (lnK). It is important for the rational management of groundwater resources. A closed‐form expression is developed by the nonstationary spectral approach to analyse the influence of the statistical properties of lnK process, the hydraulic parameters, and the spatial position. The general stochastic framework outlined in this work provides a basis for assessing the impact of statistical properties of input aquifer parameters on the output variability (or uncertainty). Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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Ricardo Cesar Marianna Silva Juan Colonese Edison Bidone Silvia Egler Zuleica Castilhos Helena Polivanov 《Environmental Earth Sciences》2012,66(8):2281-2292
The toxicity and potential bioavailability of heavy metals were studied in sewage sludge-amended ferralsols and chernosols, using bioassays with earthworms (Eisenia andrei). Acute toxicity tests and avoidance assays were performed according to standard protocols. Potentially bioavailable concentrations of heavy metals were estimated by quantifying their concentrations in tissues of survival earthworms. The results revealed that soil properties played an important role in the toxicity and bioavailability of heavy metals. In this respect, higher levels of toxicity were detected for the ferralsol. The abundance of 2:1 clay minerals, high fertility and more basic values of pH seem to be very important in the reduction of toxicity levels for earthworms. Organisms exposed to the chernosols were able to uptake higher amount of metals. In that case, higher contents of nutrients in chernosols may have influenced such bioavailability processes. Avoidance responses were the most sensible indicator of toxicity. In the near future, such data can subsidize the establishment of toxic reference concentrations able to reflect the characteristics of important tropical pedological occurrences, supporting the definition of sustainable indicators for using sewage sludge in the tropical agriculture. 相似文献
46.
Marianna V. Ivashina Jan Simons Jan Geralt Bij De Vaate 《Experimental Astronomy》2004,17(1-3):149-162
In this paper we demonstrate the practical analysis of a dense Focal Plane Array (FPA) for a deep dish radio telescope. The analytical model is used to optimize efficiency and bandwidth of deep dish system by varying design parameters such as feed size and FPA aperture field. A prototype FPA was evaluated on the Westerbork Synthesis Radio Telescope (WSRT) and the resulting efficiency is discussed. 相似文献
47.
Antonio Santo Giuseppe Di Crescenzo Giovanni Forte Raffaele Papa Marianna Pirone Gianfranco Urciuoli 《Landslides》2018,15(1):63-82
In the last 20 years, major efforts have been made to investigate shallow flow-type landslides. Such phenomena are usually rainfall-induced and in the geological context of Campania (Southern Italy) occur in pyroclastic soils resting on steep slopes mainly constituted by carbonate or volcanic bedrock and by flysch deposits. They are generally complex landslides with an early soil slide and a subsequent flow evolution. In this paper, a database of flowslides occurring in recent years within the flysch deposits of Avellino (Campanian Apennines) is first discussed and then the case study of Bosco de’ Preti landslide on March 4, 2005, is described. The geological and geotechnical characteristics of the soils involved are described and the monitoring of the groundwater heads collected over 1 year from June 2005 to June 2006 is also shown. The last part of the paper illustrates the results of numerical modelling of the landslide triggering to gain insights into such phenomena. Slope stability analyses are preceded by hydrological modelling of the slope based on the monitoring data. Numerical analysis demonstrated that the rainfall during the 2 months preceding the event was able to fully saturate the pyroclastic cover and to establish positive pore water pressure at the depth of the surface of rupture, a soil condition never witnessed in carbonatic contexts. Hence, a combination of antecedent (predisposing factors) and single rainfall events (triggering factors) led to slope failure, as usually happens in pyroclastic soils in carbonatic and volcanic contexts. Finally, analysis of the historical landslides together with detailed investigation of the Bosco de’ Preti case study permitted comparison between flow-type landslides in pyroclastic soils on carbonatic/volcanic bedrock and those on flysch. 相似文献
48.
Preparation and characterization of antibacterial silver/vermiculites and silver/montmorillonites 总被引：1，自引：0，他引：1
Marta Valášková Marianna Hundáková Jana Seidlerová Erich Pazdziora Martin He?mánek David Rafaja 《Geochimica et cosmochimica acta》2010,74(22):6287-6300
The reason for the preparation and characterization of the novel antibacterial silver/vermiculites (Ag/V) together with the silver/montmorillonites (Ag/M) was that the information on the vermiculite structure change and stability of Ag/V in water as well as its effect on bacteria are sporadic. The vermiculite (V), (Si3.02Al0.98)IV (Mg2.27Al0.12Ti0.07)VI O10(OH)2 Ca0.09Na0.21K0.50 from West China and montmorillonite (M), (Si3.96Al0.04)IV (Al1.20Mg0.42Ti0.02)VI O10 (OH)2Ca0.15Na0.14K0.08 from Ivan?ice (Czech Republic), fraction <0.4 μm were the starting clay materials for sample preparation. The samples V1 and M1 were prepared via reaction of the V and M with the 0.01 mol L−1 AgNO3 aqueous solution. The samples V2 and M2 were treated with the aqueous solution of AgNO3 for two times. The cation exchange and reduced metallic silver on M1 and V1 evoked the specific surface area (SSA) diminution, the mean particle-size diameter extension and appearance of micropores with radius (<0.4 nm). Repeated silver cation exchange in M2 and V2 reduced particle size, increased slightly SSA and micropores with radius of 0.4-0.5 nm. Samples Ag/V and Ag/M showed higher content of pores with radius 0.5-1.0 nm than original V and M. The Ag concentration was found higher in Ag/V than in Ag/M and higher in repeatedly treated samples: 0.9 wt.% Ag in V1, 1.4 wt.% Ag in V2, 0.6 wt.% Ag in M1 and 1.0 wt.% Ag in M2. Vermiculite structure consisting of the hydrated interstratified phases and the mica-like phase changed to the cation-one-zero layer hydrate interstratification structure in V1 and to the random of two-one layer hydrate interstratifications in V2. Infrared and Mössbauer spectroscopy revealed no changes in the structure of the clay minerals that could be related directly to the sorption and crystallization of silver. Transmission electron microscopy showed that the silver nanoparticles size distribution was much narrower for the samples Ag/M than for Ag/V. The mean size of the Ag particles was between 40 and 50 nm. Although the Ag nanoparticles did not adhere sufficiently at the clay minerals surface and migrated moderately into water, all samples under study were approved to be effective inhibitors of the bacterial growth persisting for the whole testing period of 6 days. Silver/vermiculite was antimicrobial more efficient against Klebsiella pneumoniae and Pseudomonas aeruginosa than silver/montmorillonite. 相似文献
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Recent studies have shown that many natural systems display temporal fluctuations with long-range power-law correlations, suggesting a fractal geometry of the underlying dynamical system. Four geoelectrical time series, measured in a seismic area of Southern Italy, are investigated by means of spectral tools in order to evidence the existence of power-law correlations. Results show the scaling behaviour for all the signals recorded, pointing to the presence of fractal features expressing a long-term correlation with scaling exponents which indicate stabilizing mechanisms. Furthermore, our findings suggest an observational evidence of correlations between the variation of parameters describing the temporal fluctuations of geoelectrical signals and earthquakes that occurred in the area investigated. 相似文献
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The stabilisation of deep landslides is still a challenge for geotechnical engineers, mainly due to the high cost of structural control works that generally lead engineers to opt for drain systems. Unfortunately there are operative difficulties affecting excavation of deep drain trenches in soils dislocated by landslides (especially as regards the provisional support of the excavation walls). Small- and medium-diameter wells are a valid alternative in deep landslides, being less expensive than large-diameter wells equipped with horizontal pipes and simpler to construct than deep trenches. However, no technical procedures for their proper design are reported in the literature: design criteria commonly used in practice are derived from pumping problems and are largely inadequate, being based on Dupuit’s hypothesis that presumes stream lines to be horizontal. This paper presents numerical solutions obtained from three-dimensional seepage and consolidation analyses of a slope drained by small- and medium-diameter wells, arranged according to various positions, showing that the efficiency of the well system decreases as the depth of the landslide slip surface increases. Comparison is also made between well systems and deep trenches occupying the same draining volume in the landslide body, showing that the former attains much greater efficiency than the latter. Non-dimensional abaci for the square grid of wells (which is the most effective arrangement) are reported herein to be used for practical purposes.
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