Initial assessment of the infiltration and overland flow for different rainfall events in land constituted of sandstones of the Botucatu Formation (Guarani Aquifer), State of São Paulo, Brazil   总被引：1，自引：0，他引：1  

Lázaro Valentin Zuquette  Janaina Barrios Palma  Osni José Pejon 《Environmental Geology》2006,50(3):371-387

This study was carried out in the Córrego do Vaçununga basin constituted of eolic sandstones of Botucatu Formation and residual unconsolidated materials (>90%), considered the most important unconfined aquifer in Brazil, in the city of Luiz Antonio, State of São Paulo, Brazil. Laboratory and in situ tests were performed to characterize the unconsolidated materials in terms of basic physical properties, potential infiltration rate, suction and hydraulic conductivity. The results for infiltration and overland flow depths were obtained according to Morel-Seytoux and Khanji (Water Resour Res 10(4):795–800, 1976) and Chu (Water Resour Res 14(3):461–466, 1978) adaptation of the Green and Ampt [J Agr Sci 4(Part 1):1–24, 1911] model for steady and transient rainfalls, respectively. Rainfall data were collected from January of 2000 to December of 2002, and 12 scenarios were defined considering the intensity and durations. Rather than high homogeneity in terms of the texture of unconsolidated materials, the infiltration and overland flow ratio depends on the type of land use and associated management practices. The results showed that rainfall with high intensity and short duration do not produce high overland flow ratio as we have observed for transient scenarios with long duration and low intensities.  相似文献   

Temporal Variability of Dark Carbon Fixation and Bacterial Production and Their Relation with Environmental Factors in a Tropical Estuarine System     

Camila N. Signori  Jean L. Valentin  Ricardo C. G. Pollery  Alex Enrich-Prast 《Estuaries and Coasts》2018,41(4):1089-1101

Dark carbon fixation (DCF) is considered an important energy source in aquatic environments, although it has been neglected for a long time. DCF is known to be relevant in ecosystems associated with redoxclines, shallow-water sulfide-rich habitats, deep-sea vents, cold seeps, and even in coastal waters associated with upwelling events. The aim of this study was to evaluate the relative importance of DCF in relation to heterotrophic bacterial production (BP), as well as how these rates affect each other, and how they are influenced by the environmental factors. This study was conducted monthly during 2 years in a tropical eutrophic bay (Guanabara Bay), where two stations were sampled and compared. DCF and BP were measured by ¹⁴C-bicarbonate and ³H-leucine incorporation, respectively, and incubations in the dark. Our results showed that DCF is not a quantitatively relevant process in this estuarine system, when compared to heterotrophic BP, and possibly occurred via anaplerotic reactions. Relatively higher DCF rates were associated with less oxygenated waters at the more polluted station and during the wet summer-spring, when the water column is more stratified. BP rates presented clear spatial patterns, according to pollution and depth gradients, with higher rates in more polluted areas, and also at surface waters. The hydrodynamics combined with other environmental conditions (precipitation, temperature, dissolved organic carbon, and nutrients) may control the distribution of DCF and BP over space and time. The allochthonous inputs of organic matter are more important than DCF-derived organic carbon to bacterioplankton in this polluted and eutrophic bay, where the heterotrophic metabolism prevails.  相似文献   

Characterization of groundwater in the hydrogeological network of Lom River basin in eastern Cameroon using a DC electrical method     

Gouet  Daniel Herv&#;  Kana  Janvier Domra  Oya  Valentin  Ewembe  Fontama Yuka 《Hydrogeology Journal》2022,30(4):1055-1069

Hydrogeology Journal - Lom River basin, associated with outflow from the Lom River system, is located in the East Region of Cameroon. The geology of the basin comprises Precambrian crystalline and...  相似文献   

Phase equilibria in the KFeS<Subscript>2</Subscript>–Fe–S system at 300–600 °C and bartonite stability     

Valentin?O.?OsadchiiEmail authorView author&#;s OrcID profile  Mikhail?V.?Voronin  Alexander?V.?Baranov 《Contributions to Mineralogy and Petrology》2018,173(5):44

The article deals with phase relations in the KFeS₂–Fe–S system studied by the dry synthesis method in the range of 300–600 °C and at a pressure of 1 bar. At the temperature below 513?±?3 °C, pyrite coexists with rasvumite and there are pyrite–rasvumite–KFeS₂ and pyrite–rasvumite–pyrrhotite equilibria established. Above 513?±?3 °C pyrite and rasvumite react to form KFeS₂ and pyrrhotite, limiting the pyrite–rasvumite association to temperatures below this in nature. The experiments also outline the compositional stability range of the copper-free analog of murunskite (K _x Fe_2?yS₂) and suggest that mineral called bartonite is not stable in the Cl-free system, at least at atmospheric pressure and the temperature in the experiments. Chlorbartonite could be easily produced after adding KCl in the experiment. Possible parageneses in the quaternary K–Fe–S–Cl system were described based on the data obtained in this research and found in the previous studies. The factors affecting the formation of potassium–iron sulfides in nature were discussed.  相似文献   

The magma plumbing system for the 1971 Teneguía eruption on La Palma,Canary Islands     

Abigail?K.?BarkerEmail author  Valentin?R.?Troll  Juan?Carlos?Carracedo  Peter?A.?Nicholls 《Contributions to Mineralogy and Petrology》2015,170(5-6):54

The 1971 Teneguía eruption is the most recent volcanic event of the Cumbre Vieja rift zone on La Palma. The eruption produced basanite lavas that host xenoliths, which we investigate to provide insight into the processes of differentiation, assimilation and magma storage beneath La Palma. We compare our results to the older volcano magmatic systems of the island with the aim to reconstruct the temporal development of the magma plumbing system beneath La Palma. The 1971 lavas are clinopyroxene-olivine-phyric basanites that contain augite, sodic-augite and aluminium augite. Kaersutite cumulate xenoliths host olivine, clinopyroxene including sodic-diopside, and calcic-amphibole, whereas an analysed leucogabbro xenolith hosts plagioclase, sodic-augite-diopside, calcic-amphibole and hauyne. Mineral thermobarometry and mineral-melt thermobarometry indicate that clinopyroxene and plagioclase in the 1971 Teneguía lavas crystallised at 20–45 km depth, coinciding with clinopyroxene and calcic-amphibole crystallisation in the kaersutite cumulate xenoliths at 25–45 km and clinopyroxene, calcic-amphibole and plagioclase crystallisation in the leucogabbro xenolith at 30–50 km. Combined mineral chemistry and thermobarometry suggest that the magmas had already crystallised, differentiated and formed multiple crystal populations in the oceanic lithospheric mantle. Notably, the magmas that supplied the 1949 and 1971 events appear to have crystallised deeper than the earlier Cumbre Vieja magmas, which suggests progressive underplating beneath the Cumbre Vieja rift zone. In addition, the lavas and xenoliths of the 1971 event crystallised at a common depth, indicating a reused plumbing system and progressive recycling of Ocean Island plutonic complexes during subsequent magmatic activity.  相似文献   

The Black Sea Ecosystem Changes Related to the Introduction of New Mollusc Species   总被引：1，自引：0，他引：1  

Valentin  Zolotarev 《Marine Ecology》1996,17(1-3):227-236

Abstract. The unintentional introduction of the new mollusc species Rupunu rhomasiuna, Mya arenaria , and Scuphurcu inaequivulvis has become a significant reason for modern transformations of certain bottom biocoenoses in the Black Sea. These molluscs have been passed across natural barriers in fouling of ships or in ship seawater ballast and have successfully acclimatized in the new region, forming communities with a high density and biomass. The resulting changes in the structure of the bottom biocoenoses after these introductions are in many cases comparable with or exceed the consequences of other episodic environmental events and other kinds of anthropogenic activity. The intense spreading of the introduced species in the new area is the result of their high adaptive capability and the instability of the Black Sea ecosystem, the latter being due to its few species, low level of competitive interactions, and constant growth of diverse anthropogenic loads.  相似文献   

Population parameters of Pleopis polyphemoides (Crustacea, Cladocera) in a tropical bay     

Andrea Marazzo  Jean Louis Valentin   《Estuarine, Coastal and Shelf Science》2003,57(5-6):1015-1021

Populations of Pleopis polyphemoides were studied in Guanabara Bay, southeastern Brazil, to assess temporal variations in density and population parameters. The abundance of P. polyphemoides varied widely during summer, and collapsed in fall–winter. These variations probably resulted from the combined effects of water temperature and predation pressure. It is assumed that the planktonic population began by hatching from resting eggs, while the collapse of the planktonic population in April seemed to be related to lower temperatures and high densities of predatory chaetognaths.  相似文献   

Reply to: Bonev N,Spikings R and Marchev P (2016) Comment on Georgiev et al. “Structure and U–Pb zircon geochronology of an Alpine nappe stack telescoped by extensional detachment faulting (Kulidzhik area,Eastern Rhodopes,Bulgaria)”     

Neven Georgiev  Nikolaus Froitzheim  Zlatka Cherneva  Dirk Frei  Valentin Grozdev  Silke Jahn-Awe  Thorsten J. Nagel 《International Journal of Earth Sciences》2016,105(7):2171-2173

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Some Observations on the Determination of Gold and the Platinum-Group Elements in Black Shales   总被引：2，自引：0，他引：2  

Valentin N. Mitkin  Alexander A. Galizky  Tamara M. Korda 《Geostandards and Geoanalytical Research》2000,24(2):227-240

This research compares various ways of applying oxidative chemical decomposition to the analysis of gold-bearing black shale ores from the Russian Natalka and Sukhoj Log deposits. This study was conducted as part of the certification program for the Russian candidate black shale reference materials SLG-1 and SCHS-1 and also because of the paucity of data available on the determination of the platinum group elements (PGE) in analogous sample types. We report direct evidence of PGE volatilisation from black shale materials when processed in the presence of oxygen. We also developed a comprehensive analytical scheme for the quantitative determination of PGE in all phases (gaseous and ash) produced during slow combustion of carbonaceous materials in oxygen.
This study has shown that during combustion in oxygen at 600 °C, PGE contained in the Natalka black shale ores are lost as gaseous reaction products. Thus, the volatilized PGE (recovered in traps) account for up to 14% Pt, 40% Pd, 40% Ru and 10 % Ir relative to their total concentrations in a carbonaceous concentrate. It was also established that in the process of combustion, Au quantitatively remains in the ash cake.
In order to avoid the deleterious effects of oxygen on the volatility of the PGE, we propose a new comprehensive sample decomposition method based on the application of fluoroxidants such as BrF₃ and KBrF₄. This method was validated using samples of black shale ores and their processing products by comparing our results with those obtained independently using sealed autoclave processing of the same materials. It was shown that PGE in black shale ores and their processing products not only exist in commercially exploitable quantities but that a small proportion of PGE compounds are soluble in alcohol. We propose that in gold-bearing black shale ores, PGE are present as organometallic compounds.  相似文献   

Detection of point scatterers using diffraction imaging and deep learning     

Valentin Tschannen  Norman Ettrich  Matthias Delescluse  Janis Keuper 《Geophysical Prospecting》2020,68(3):830-844

Diffracted waves carry high-resolution information that can help interpreting fine structural details at a scale smaller than the seismic wavelength. However, the diffraction energy tends to be weak compared to the reflected energy and is also sensitive to inaccuracies in the migration velocity, making the identification of its signal challenging. In this work, we present an innovative workflow to automatically detect scattering points in the migration dip angle domain using deep learning. By taking advantage of the different kinematic properties of reflected and diffracted waves, we separate the two types of signals by migrating the seismic amplitudes to dip angle gathers using prestack depth imaging in the local angle domain. Convolutional neural networks are a class of deep learning algorithms able to learn to extract spatial information about the data in order to identify its characteristics. They have now become the method of choice to solve supervised pattern recognition problems. In this work, we use wave equation modelling to create a large and diversified dataset of synthetic examples to train a network into identifying the probable position of scattering objects in the subsurface. After giving an intuitive introduction to diffraction imaging and deep learning and discussing some of the pitfalls of the methods, we evaluate the trained network on field data and demonstrate the validity and good generalization performance of our algorithm. We successfully identify with a high-accuracy and high-resolution diffraction points, including those which have a low signal to noise and reflection ratio. We also show how our method allows us to quickly scan through high dimensional data consisting of several versions of a dataset migrated with a range of velocities to overcome the strong effect of incorrect migration velocity on the diffraction signal.  相似文献